Central Italy

Transcription

Central Italy

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RENDICONTI Online
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Società Geologica Italiana
Volume 20 - Luglio 2012
X Congresso GEOSED
“Associazione Italiana per la Geologia del sedimentario”
Feltre 2-6 Luglio 2012
NOTE BREVI E RIASSUNTI
A cura di: Valeria Bianchi, Giovanni Gattolin & Manuel Rigo
ROMA
SOCIETÀ GEOLOGICA ITALIANA
2012
www.socgeol.it
X Congresso GEOSED
“Associazione Italiana per la Geologia del sedimentario”
Feltre 2-6 Luglio 2012
COMITATO ORGANIZZATORE
Anna Breda
Valeria Bianchi
Giovanni Gattolin
Massimiliano Ghinassi
Nereo Preto
Manuel Rigo
Cristina Stefani
Massimiliano Zattin
© Società Geologica Italiana, Roma 2012
INDICE
Premessa........................................................................................................................................................................................
5
AMOROSI A. - The occurrence of glaucony in the stratigraphic record: Distribution patterns and sequence-stratigraphic
significance................................................................................................................. .......................................................
6
BAR ALE L., BERTOK C., D TR I A., DOMINI G., MARTIRE L. & PIANA F. Cretaceous-Lower Eocene hydrothermal
dolomitization in the Maritime Alps (NW Italy)................................................................................................................
7
BER NARDI E., DELA PIERR E F., GENNARI R., LOZAR F. & VIOLANTI D. - Astrochronologiacal calibration and
paleoenvironmental reconstruction of the Messinian events at the Northern edge of the Mediterranean: the Govone
section (Tertiary Piedmont Basin)......................................................................................................................................
10
BER SEZIO R., FELLETTI F. & VALENTE A. - Turbidite facies changes in a base of slope basin setting (Langhe Basin, Lower
Cengio Turbidite System, Oligocene, Tertiary Piedmont Basin).....................................................................................
12
BIANCHI V.,GHINASSI M., ALDINUCCI M., BOAGA J. & DEI ANA R. - Tectonic control on fluvial aggradation: the PlioPleistocene Ambra valley-fill succession (Tuscany, Italy)............................................................................................. ....
15
BILLI P. - Sedimentology and sediment transport processes in a few ephemeral streams of the Horn of Africa.........................
17
BRANDANO M., TOMASSETTI L. & RONCA S. - Depositional processes of the carbonate-siliciclastic rhodolith rich deposits
...........................................................
20
BRANDANO M., GUARINI G., PETRUNGARO R., VELOCC I L., MELONI D., MASC ARO G. & L IPPARINI L. - Digital 3D modelling
of submarine dune field by laser scanning technique (Bolognano Formation, Majella)....................................................
21
BURATTI N, BARC HI M. R., BERTINI A., CIRILLI S., GASPERINI L., MARC HEGIANO M. & PAZZAGLIA F. - Lacustrine organic
facies and pollen analysis from the Trasimeno lake (Central Italy): a preliminary note....................................................
22
CAGGIATI M., B REDA A., GIANOLLA P., RIGO M. & ROGHI G. - Depositional systems of the Eastern Southern Alps (NE Italy,
W Slovenia) during the late Carnian..................................................................................................................................
24
COZZI A. - Identifying plays and prospects in carbonates............................................................................................................
28
D' ALPAOS A., CARNIELLO L., STEFANON L. & RINALDO A. - Modeling tidal network dynamics in response to changes in the
environmental forcings....................................................................................................... ................................................
29
ALB ERTO L. & GIORDANO D. - Jurassic extensional faulting at the Trento platform Belluno basin margin sedimentary
and tectonic.........................................................................................................................................................................
32
DE MURO S., KALB C., BRAM BILLA W. & IBBA A. - Sedimentological, geomorfological and geochemical evidence of the last
marine ingression in central Magellan Straits-southernmost Chile...................................................................................
33
DI CAPUA A., GROPPELLI G. & VEZZOLI G. - Stratigraphic trend evolution of the sedimentary pulses of Val d'Aveto
Formation........................................................................................................................................................................
35
FIDOLI NI F. & ANDREETTA A. - Sedimentological and pedological study of some pedogenized intervals of the PlioPleistocene Upper Valdarno Basin.....................................................................................................................................
38
GATTOLIN G., FRANCESCHI M., BREDA A. & PRETO N. - Facies and geometries of carbonate platforms of the Dolomites after
the Carnian Pluvial Event (CPE)......................................................................................................................................
41
GRILLENZONI C., CONTI S., FONTANA D. & TURCO E. - Seep-carbonates as indicators of global cooling events (Miocene,
northern Apennines)..........................................................................................................................................................
42
IADANZA A., SAMPALMIER I G, FRIJIA G., CIPOLLARI P., COSENTINO D. & MOLA M. - The subsurface record of hydrocarboncharged fluids migrating through the Messinian sedimentary column (Maiella Basin, Central Italy)..............................
LONGHITANO S.G. - The role of the Backshore/Foreshore length ratio in short-term beach monitoring studies..........................
44
46
MARCHETT I L., SANTI G. & AVANZINI M. - The problem of small footprints in paleoichnology related to extramorphologies:
new data from the Early Permian Erpetopus.....................................................................................................................
48
MARIN E., TER UGGI L.B., MAROCCHI NO E. & VACC ARO C. - Geochemical characterization of sediment quality in the river
basin of the Rio Grande Quequén (Argentina).................................................................................. ...............................
51
MARIN E., NAC HITE D., NAJIH M., ANFUSO G., MAROCCHINO E. & VACC ARO C. - The lagoon of Nador (Morocco):
geochemical and petrographic analysis of sediments and environmental conditions.......................................................
53
MARTINI I. & SANDR ELLI F. - Facies analysis and sequence stratigraphic interpretation of sandy deposits in the central part
of the Siena Basin (Italy)................................................................................................... ................................................
55
MAZZUCCHI A. & TOMASSETTI L. - Coral patch reef in a Burdigalian mixed carbonate-siliciclastic coastal system (Cala
Paraguano, Corsica)..........................................................................................................................................................
57
MIETTO P. & MANFRIN S. - Mysterious Triassic ammonoids of Recoaro area: state of art........................................................ ..
59
MONEGATO G. & STEFANI C. - Upper Miocene Lower Pliocene provenance changes in the Venetian Foreland......................
60
MOSCON G. - Provenance of the Pleistocene fluvial deposits of the Ambra valley (central Tuscany): implication for palaeodrainage evolution.............................................................................................................................................................
63
PALLADINO G. & PROSSER G. - Study and interpretation of some uncertain Triassic lithosomes at the base of the Lagonegro
Basin succession: a key for a correct reconstruction of the Monte Facito Formation (Basilicata, southern Italy)...........
64
PASCUCCI V., ANDREUCCI S. & FRULIO G. - New estimation of the post Little Ice Age sea level rise..........................................
67
PIOVAN S., STEFANI C. & MOZZI P. - Late Holocene palaeohydrography in central and southern Venetian Plain: the role of
petrographical sand analysis..............................................................................................................................................
68
RAGAZZI E., AVANZINI M., DIENI I., ROGHI G. & STEFANI C. - New amber findings in Northeastern Italy: suggestions for an
integrated view on fossil resin
71
ROSSATO S., MOZZI P., MONEGATO G., CUCATO M., GAUDIOSO B. & MIOLA A. - Connections between glacial and fluvial
systems in the lower Astico Valley and the piedmont plain (NE Italy).............................................................................
76
Rend. Online Soc. Geol. It., Vol. 20 (2012), p. 5.
Premessa
La decima riunione annuale del Gruppo di Geologia del Sedimentario GEOSED organizzata dal Dipartimento di Geoscienze
a Feltre tra il 2 e il 6 luglio 2012. Il convegno è stato ospitato presso il Campus
Universitario della
.
nelle
piattaforme triassiche delle
-miocenica veneta. Per i
giovani è stato inoltre organizzato un corso breve sui processi ed architetture deposizionali in sistemi torbiditici.
I contriburi scientifici presentati nel corso del congresso hanno affrontato una significativa molteplicità di aspetti della geologia
del sedimentario, e sono stati raccolti in questo volume sotto forma di note brevi o riassunti.
Il comitato organizzatore desidera ringraziare tutti i partecipanti e gli enti patrocinatori che hanno contribuito alla buona riuscita
della manifestazione.
Anna Breda, Valeria Bianchi, Giovanni Gattolin, Massimiliano Ghinassi, Nereo Preto, Manuel Rigo, Cristina Stefani e
Massimiliano Zattin.
The occurrence of glaucony in the stratigraphic record: Distribution
patterns and sequence-stratigraphic significance
ALESSANDRO AMOROSI (*)
Key words: Glaucony, Glauconite, Sequence stratigraphy,
Condensed section, Maximum flooding surface.
Glaucony is traditionally regarded as an indicator of low
sedimentation rate and represents one of the most reliable
stratigraphic markers within marine sediments. An integrated
sedimentological,
mineralogical
and
geochemical
characterization of about 250 glaucony-bearing horizons from 41
sites in Western Europe provides a comprehensive framework for
the definition of the sequence-stratigraphic significance of
glauconitic minerals.
Autochthonous glaucony follows predictable trends in
abundance and maturity, with positive correlation between
potassium content and proportion of green grains in the host
rock. Three basic types of condensed horizons are differentiated:
i) simple omission surfaces, containing < 20% (poorly-evolved)
glaucony, ii) condensed sections, including 20-50% (evolved)
glaucony, and iii) mega-condensed sections, with > 50% (highlyevolved) glaucony. By contrast, glauconitic grains of
_________________________
(*) University of Bologna, Dipartimento di Scienze della Terra e
geologico-Ambientali, Via Zam boni 67, 40127 Bologna, Italy.
E-mail: [email protected]
allochthonous origin do not exhibit any peculiar trend in
abundance and maturity. High amounts of parautochtonous
(intrasequential) glaucony are relatively common in the
stratigraphic record, whereas a detrital (extrasequential) origin
for the green grains accounts for anomalously low concentrations
of highly-evolved glaucony.
In terms of sequence stratigraphy, simple omission surfaces
correspond to marine flooding surfaces at parasequence
boundaries. These surfaces span intervals of time in the order of
104 years and are expected to have low correlation potential.
Condensed horizons represent basin -wide stratigraphic markers
that may either bracket the TST/HST boundary (i.e., the
model) or comprise a significant portion of the TST (105 years).
Mega-condensed sections imply huge stratigraphic condensation,
spanning from systems tracts to third-order depositional
sequences with episodicities of 106 years. Mega-condensed
sections are likely to be correlative on a global scale.
Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 7-9, 2 figs.
Cretaceous-Lower Eocene hydrothermal dolomitization in the
Maritime Alps (NW Italy)
LUC A BARALE (*), CARLO BERTOK (*), ANNA D
TRI (*), GABRIELE D OM INI (**),
LUC A M ARTIRE (*) & FABRIZIO PIANA (°)
Key words: Hydrothermal dolomitization, Jurassic limestones,
Maritime Alps, Provençal-Dauphinois Domain.
INTRODUCTION
Hydrothermal dolomitization has recently become
argument of broad interest and debate. According to the widely
accepted definitions of MACHEL & LONNEE (2002) and DAVIES
& SMITH (2006), a proper hydrothermal dolomitization is
characterized by a fluid temperature at least 5-10 °C higher
than that of the host limestone.
In the Provençal-Dauphinois and Subbriançonnais Domains
of the Maritime Alps, the Jurassic carbonate succession is
locally characterized by a diffuse dolomitization. The
stratigraphic framework, the geometric and petrographic
features of the dolomitized bodies, together with preliminary
data from stable isotope analysis and fluid inclusion
microthermometry, allowed to define timing and modes of
dolomite formation process. Dolomitization of the Jurassic
limestones occurred in the Early Cretaceous-Early Eocene
interval, in a very shallow burial environment, and was due to
fluids significantly hotter than the host limestone.
Thus, the study case represents a straightforward example
of hydrothermal dolomitization, perfectly fitting with the above
definition, and has important regional implications for the
tectono-sedimentary evolution of this part of the passive
European Tethyan margin.
GEOGRAPHIC AND GEOLOGICAL SETTING
The study area lies in the eastern Maritime Alps (North
_________________________
(*) Dipartimento di Scienze della Terra, Università di Torino, 10125
Torino, Italy.
(**) Strada M arentino 2, 10020 Andezeno (TO), Italy.
(°) CNR-Istituto Geoscienze e Georisorse, 10125 Torino, Italy
Lavoro eseguito con il contributo finanziario di GeoSed (Contributo Ricerca
GeoSed giovani 2011, assegnato a Luca Barale).
Western Italy), between the Sabbione Valley to the west and
the Vermenagna Valley to the east. This sector is composed of
several tectonic units, superimposed along NW-SE striking
Alpine tectonic contacts, classically attributed to ProvençalDauphinois and Subbriançonnais paleogeographic domains of
the Alpine Tethys European paleomargin (CARRARO et alii,
1970). The Mesozoic succession is characterized by the
presence of a thick limestone succession of Middle?-Upper
Jurassic age and by the marked reduction or total absence of
Cretaceous deposits. The top of the Mesozoic succession is
truncated by a regional unconformity corresponding to a hiatus
spanning the Cretaceous-Early Eocene. Above the
unconformity, the Alpine Foreland Basin succession consists of
the Middle Eocene Nummulitic Limestone, followed by the
hemipelagic Upper Eocene Globigerina Marl and by the Upper
Eocene-Lower Oligocene
turbidites (SINC LAIR,
1997).
The occurrence of dolomitization affecting the Jurassic
limestones in the study area was already pointed out
(CAM PANINO STURANI, 1967; CARRARO et alii, 1970;
M ALARODA , 1970). However, apart from the mere reporting,
no description of the dolomitization features was given and no
explanation was proposed regarding its genesis.
DOLOMITIZATION FEATURES
Host rocks
Dolomitization affects the Jurassic limestones of both
Provençal-Dauphinois and Subbriançonnais units. They are
composed of a 200-300 m thick succession, which mainly
consists of mudstones to packstones with echinoderm
fragments, dubitatively attributed to the Middle -Late Jurassic
(CARRARO et alii, 1970). The uppermost interval of this
succession, made up of bioclastic packstones to rudstones and
coral-stromatoporid boundstones, is
dated to the
Kimmeridgian-Tithonian (CAM PANINO STURANI, 1967). The
stratigraphically highest dolomitized beds are locally
represented by charophyte-rich wackestones, which could have
8
BARALE ET ALII
dolomite, occurring both as replacive and as void-filling
cement.
18
O values (ranging from -4 to -6
fluids. Quantitative paleotemperature data from preliminary
primary fluid inclusion microthermometry on saddle dolomite,
indicate fluid temperatures ranging from 170 to 220 °C.
Reworked dolomite
Fig. 1 Upper portion of the partially dolomitized Jurassic limestones: note
the juxtaposition of cm-wide bands of rock with randomly oriented dolomitecemented veins and of subvertical tabular bodies of dolomite-cemented
breccias .
a Berriasian age for comparison with the adjacent successions
of the Nice Arc.
The basal interval of the Nummulitic Limestone, made up
of conglomerate and arenite beds, locally contains abundant
mm- to dm-sized clasts of dolostones. The occurrence of such
clasts was already reported by CAM PREDON (1972) who,
however, did not investigate their origin. Petrographic features
of the dolostone clasts clearly document their provenance from
the dolomitized Jurassic limestones.
DISCUSSION AND CONCLUSIONS
Timing of dolomitization
Dolomite features
Dolomite-bearing rocks show a great heterogeneity in the
study area. They range from partly dolomitized limestones with
only scattered dolomite crystals, to quite homogeneous
medium to coarsely crystalline dolostones; the majority of
dolomitized rocks, however, shows intermediate degrees of
dolomitization with respect to these two end-members.
Dolomitization, both partial and complete, affects discrete rock
masses that are randomly distributed in the host limestone.
Dolomitization frequently develops along a more or less
close network of veins (100
- to 2 mm-thick), locally
closely spaced and arranged along sub-vertical, cm- to dmwide, channels (Fig. 1). Mm- to cm-sized dissolution cavities,
filled up with dolomite and calcite cements, can locally be
observed between the veins.
Tabular breccia bodies also occur within the dolomitized
rocks, randomly distributed with respect to the bedding. They
are clast-supported, with heterometric clasts, centimetric to
decimetric in size and subrounded to angular in shape. Breccias
are either polymictic or monomictic, and clasts include
partially or totally dolomitized limestones, undolomitized
limestones, and dolomite vein fragments. A fine matrix is
rarely present; more commonly voids are filled up with mmthick rims of a coarsely crystalline whitish dolomite cement,
followed by a dark sparry calcite cement (Fig. 2).
Thin section observations allowed to distinguish two
dolomite types. The first is a finely- to medium-crystalline,
very turbid, replacive dolomite, whereas the second is a less
turbid, well-zoned, coarsely- to very coarsely-crystalline saddle
The age of dolomite formation can be inferred on the basis
of solid stratigraphic evidence. Dolomitization can not be
younger than the Early Eocene, as showed by the occurrence of
clasts of the dolomitized limestones in the basal levels of the
Middle Eocene Nummulitic Limestone. On the other hand, the
top of the dolomitized succession has a Tithonian-Berriasian?
age, and thus dolomitization can not be older. It can be
therefore stated that dolomitization occurred in the Early
Cretaceous-Early Eocene interval.
Fig. 2 Clas t-supported breccia with fully dolomitized clasts coated by a mmthick rim of whitish dolomite cement. Remaining voids are plugged by a
sparry, grey to black, calcite cem ent. Pencil tip for scale, on the left, is 1.5 cm
long.
CRETACEOUS-LOWER EOCENE HYDROTEHERM AL DOLOMITIZATION
Dolomitization process
The geometry of dolomitized bodies, cross-cutting the host
limestone bedding, their close relation with vein networks, and
the common occurrence of saddle dolomite (pointing to
temperatures higher than about 60 °C; RADKE & M ATHIS ,
1980) indicate a dolomitization process related to the
circulation of hot fluids through fracture and vein networks.
This hypothesis is actually confirmed by preliminary data from
stable isotopes ( 18 O lower than and fluid inclusion
microthermometry (homogenization temperatures around 200
°C).
The reduced thickness or even absence of Cretaceous to
Lower Eocene deposits in the stratigraphic succession of the
study area, along with their complete lack as clasts in the
transgressive Middle Eocene conglomerates, indicates that if a
Cretaceous-Lower Eocene sediment package had been
deposited, it was thin enough to be completely removed before
the Middle Eocene transgression. A very shallow burial setting
can thus be argued for the Jurassic limestones in the Early
Cretaceous-Early Eocene.
From the above considerations, it follows that the
dolomitizing fluids were significantly warmer than the host
rocks, and thus may be properly referred as hydrothermal fluids
(sensu M ACHEL & LONNEE , 2002; DAVIES & SMITH, 2006).
The wide occurrence, in the dolomitized rocks, of breccia
bodies and vein networks, indicates that the hydrothermal
system was characterized by repeated hydrofracturing events.
These were probably due to the cyclic abrupt expulsion of
overpressured fluids along main fluid-flow pathways, likely
represented by high-angle faults and related fracture systems.
Regional implications
The recognized hydrothermal dolomitization indirectly
documents a fault activity during the Early Cretaceous-Early
Eocene interval in this sector of the Alpine Tethys European
paleomargin. Evidence of tectonic activity since Early
Cretaceous has been indeed recently recognized also in the
adjacent External Ligurian Briançonnais Domain (BERTOK et
alii, 2012) that is locally affected by an Upper Jurassic
dolomitization.
Such
faultand
fracture-controlled
9
hydrothermal dolomitization thus appears as the evidence of a
major syndepositional deformation zone cutting transversally
across at least three paleogeographical units (Briançonnais,
Subbriançonnais, Provençal-Dauphinois domains).
REFERENCES
BERTOK C., M ARTIRE L., PEROTTI E., D TRI A. & P IANA F.
(2012) - Kilometre-scale palaeoescarpments as evidence
for Cretaceous synsedimentary tectonics in the External
Briançonnais domain (Ligurian Alps, Italy). Sediment.
Geol., 251-252, 58-75.
CAM PANINO S TURANI F. (1967) - Sur quelques Nérinées du
Malm des Alpes Maritimes (couverture sédimentaire de
iées du Col de Tende). Rend.
Acc. Naz. Lincei, 8, 42, 527-529.
CAM PREDON R. (1972) - Les formations paléogènes des AlpesMaritimes franco-italiennes. PhD Thesis, Univ. de Nice,
539 p.
CARRARO F., DAL PIAZ G.V., FRANCESCHETTI B., M ALARODA
R., STURANI C. & ZANELLA E. (1970) - Note Illustrative
scala 1: 50.000. Mem. Soc. Geol. Ital., IX, 557-663.
D AVIES G.R. & SMITH L.B. JR. (2006) - Structurally controlled
hydrothermal dolomite reservoir facies: An overview.
AAPG Bull., 90, 11, sp. issue, 1641-1690.
M ACHEL H.G. & LONNEE J. (2002) - Hydrothermal dolomite-a
product of poor definition and imagination. Sediment.
Geol., 152, 163-171.
M ALARODA R. (1970) - Carta Geologica del Massiccio
1: 50.000. Mem. Soc. Geol. Ital.,
IX.
RADKE B.M. & MATHIS R.L. (1980) - On the formation and
occurrence of saddle dolomite. J. Sediment. Res., 50, 11491168.
S INCLAIR H.D. (1997) - Tectonostratigraphic model for
underfilled peripheral foreland basins: an Alpine
perspective. GSA Bull., 109, 3, 324-346.
Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 10-11.
Astrochronological calibration and paleoenvironmental
reconstruction of the Messinian events at the Northern edge of the
Mediterranean: the Govone section (Tertiary Piedmont Basin)
ELISA BERNARDI (*), FRANCESCO D ELA P IER RE (*), ROCCO GENNARI (**),
F RANCESCA LOZAR & DONATA VIOLANTI (*)
Key words: Astrochronological calibration, Biostratigraphy,
Foraminifera, Mediterranean, Messinian, Paleoecology,
Tertiary Piedmont Basin.
The Tertiary Piedmont Basin (TPB) preserves the
northernmost record of the Messinian salinity crisis (MSC); in
this basin the lateral transition between marginal and deep
water successions can be reconstructed in detail (DELA PIERRE
et alii, 2011). As a matter of fact up to 14 cycles of primary
sulphate evaporites (Primary Lower Gypsum unit = PLG;
ROVERI et alii, 2008), consisting of laminated shale-gypsum
couplets, were deposited in marginal settings. Conversely, in
the more distal part of the basin, the lower gypsum cycles are
transitional to cyclic muddy sediments, that are well exposed in
the Govone section. This section comprises the entire
Messinian succession and starts with the marine sediments of
the
Marl (the object of this study),
composed of a rhythmic alternation of laminated mudstonehomogeneous marl. This unit is overlain by the PLG unit that is
here composed of nine lithologic cycles consisting of laminated
shale/gypsum cumulite couplets. The PLG is sharply followed
by clastic gypsum facies and chaotic bodies (Resedimented
Lower Gypsum= RLG; ROVERI et alii, 2008) and finally by
fluvio-deltaic deposits with Lago-Mare fossil assemblages in
the upper part (Cassano Spinola Conglomerates).
Cyclostratigraphic and quantitative micropaleontological
analyses were performed on the
Marl, in
order to constrain the onset of the MSC and to define the
paleoenvironmental changes heralding this Mediterraneanscale palaeoceanographic event. The lithologic cyclicity of this
unit is reflected by regular fluctuation of microbiological
_________________________
(*)
Dipartimento di Scienze della Terra
Valperga Peluso, 35, 10125, Torino
- Università di Torino, via
(**) Dipartimento di Scienze della Terra - Università di Parma, Parco Area
delle Scienze 157A - 43100, Parma
assemblages, testifying to the influence of precessioncontrolled climatic changes. Several bioevents (Last Abundant
Occurrence of G. miotumida, First Abundant Occurrence of T.
multiloba, Neogloboquadrinids S/D coiling change, influxes of
G. scitula, Last Recovery of foraminifers and calcareous
nannofossils) were recognised in the section; their integration
with magnetostratigraphic data has been used as the starting
point for the astrochronologial calibration of the succession:
each cycle was tuned to 65°N summer insolation and
precession indexes of the La2004 astronomical solution
( LASKAR et alii, 2004). The results of this study allowed an
accurate bed to bed correlation of the Govone section with
other reference sections from both Western (Abad composite;
SIERRO et alii, 2001), Southern (Falconara Gibliscemi; BLANC VALLERON et alii, 2002), and Eastern (Pissouri; KRIJGSMANN et
alii, 2002) Mediterranean as well as with the Atlantic record
(An el Beida section; KRIJGSMANN et alii, 2004). The phase
relations between the lithologic cycles and astronomical curves
since 6.60 Ma (dating for the base of the Govone section) was
defined. Moreover, this study allowed to precisely constrain the
main paleoenvironmental changes at the northernmost edge of
the Mediterranean sea immediately before the onset of the
MSC, in a time interval between 6.60 Ma and 5.96 Ma. The
progressive impoverishment of the foraminiferal assemblages,
that become poorly diversified and dominated by stress tolerant
taxa upward, suggests a decrease of bottom water oxigenation
and/or increase of water column stratification. The
establishment of restricted conditions heralding the onset of
MSC was dated at Govone at 6.20 Ma, approximately 200 Kyr
later than in other Mediterranean sections (Cyprus e.g.
K OUWENOVEN et alii, 2006; Northern Apennines e.g.
K OUWENOVEN et alii, 1999; DI STEFANO et alii, 2010) in which
the final increase of basin restriction occurred at around 6.4
Ma.
Finally the results of this study allowed to recognize that
the onset of the MSC has not sedimentological and lithological
evidence and is placed within a barren succession of euxinic
shale/marl couplets, six sedimentary cycles (i.e. approximately
120 kyr) below the first primary gypsum bed. These barren
ASTROCHRONOLOGIC AL CALIBRATION AND PALEOENVIRONMENTAL OF THE M ESSINIAN GOVONE SECTION
sediments represent the deep water counterparts of the lower
PLG cycles deposited in the marginal part of the basin.
REFERENCES
BLANC -VALLERON M.M, PIER RE C., CAULET J.P., CARUSO A.,
ROUCHY J.M., CAESPUGLIO G., S PROVIERI R., PESTREA S.
& D I S TEFANO E. (2002) - Sedimentary, stable isotope and
micropaleontological records of paleoceanographic change
in the Messinian Tripoli Formation (Sicily, Italy).
Palaeogeogr., Palaeoclim., Palaeoecol., 185, 255-286.
DELA PIERRE F., BERNARDI E., CAVAGNA S., CLARI P.A.,
GENNARI R., I RACE A., LOZAR F., LUGLI S., M ANZI V.,
NATALICCHIO M., ROVERI M. & V IOLANTI D. (2011) - The
record of the Messinian salinity crisis in the Tertiary
Piedmont Basin (NW Italy): The Alba section revisited.
DI STEFANO A., V ERDUCCI M., LIRER F., FERRARO L.,
IACCARINO S.M., H USING S.K. & H ILGEN F.J. (2010) Paleoenvironmental conditions preceding the Messinian
Salinity Crisis in the Central Mediterranean: Integrated
data from the Upper Miocene Trave section (Italy).
LASKAR J., ROBUTEL P., JOUTELL F., G ASTINEAU M., CORREIA
A.C.M. & LEVRARD B. (2004) - A longterm numerical
solution for the insolation quantities of the Earth. Astron.
Astrophys. 428, 261 285.
11
K OUWENHOVEN T.J., SEIDENKRANTZ M.S. & VAN DER ZWAAN
G.J. (1999) - Deep-water changes: the near-synchronous
disappearance of a group of benthic foraminifera from the
late Miocene Mediterranean. Palaeogeogr., Palaeoclim.,
Palaeoecol., 152, 259 281.
K OUWENHOVEN T.J., SMORIGI C., N EGRI A., GIUNTA S.,
KRIJGSMAN
W.
& ROUCHY
J.M. (2006)
Palaeoenvironmental
evolution
of
the
eastern
Mediterranean during the Messinian: constraints from
integrated microfossil data of the Pissouri Basin (Cyprus).
Mar. Micropalaeont. 60, 17-44.
K RIJGSMAN W., BLANC -VALLERON M.M., FLEC KER R., HILGEN
F.J., KOUWENHOVEN T.J., MERLE D., O RSZAG-SPERBER F.
& ROUCHY J.M. (2002) - The onset of the Messinian
salinity crisis in the Eastern Mediterranean (Pissouri
Basin, Cyprus). EPSL, 194, 299-310.
K RIJGSMAN W., G ABOARDI S., HILGEN F.J., IACCARINO S.M.,
DE K AENEL E. & VAN DER LAAN E. (2004) - Revised
astrochronology for the Ain el Beida section (Atlantic
Morocco): no glacio eustatic control for the onset of the
Messinian Salinity Crisis. Stratigraphy, 1, 87 101.
ROVERI M., LUGLI S., MANZI V., & SCHREIBER B.C. (2008) The Messinian Sicilian stratigraphy revisited: new insights
for the Messinian Salinity Crisis. Terra Nova, 20, 483-488.
S IER RO F.J., H ILGEN F.J., K RIJGSM AN W. & F LORES J.A. (2001)
- The Abad composite (SE Spain): a Messinian reference
section for the Mediterranean and the APTS. Palaeogeogr.,
Palaeoclim., Palaeoecol., 168, 141 169.
Turbidite facies changes in a base of slope basin setting (Langhe Basin, Lower
Cengio Turbidite System, Oligocene, Tertiary Piedmont Basin)
RICCARDO BERSEZIO (**), F ABRIZIO FELLETTI (*) & ALBERTO V ALENTE (***)
Key words: Cengio turbidite system, Oligocene, slope basins,
Langhe Basin, Tertiary Piedmont Basin, turbidites.
FOREWORD
The Langhe Basin is the major depocenter of the Tertiary
Piedmont Basin, an episutural basin set upon a complex of
nappes of the Liguria - Piemonte Western Alps. The basin hosts a
more than 4000-m-thick Oligo-Miocene succession (GELATI &
GNACCOLINI, 1998, 2003). Late Oligocene normal and strike -slip
faulting, related to the opening of the Ligure Provençal Gulf
(FORCELLA et alii, 1999, with references therein) resulted in the
establishment of deep-water conditions in the Langhe basin. This
led to deposition of an hemipelagic mudstone wedge with several
lenticular bodies of sandstone and conglomerates (Rocchetta
Monesiglio Fm.; Early Oligocene - Burdigalian), one of which is
the Cengio Turbidite System (CTS; CAZZOLA et alii, 1981; 1985;
BERSEZIO et alii, 2005; 200 9). Extension and transpression
during the Oligocene delineated the complex and irregular shape
of the southwestern marginal slope of the Langhe basin that
included several slope and base-of-slope depressions which could
accommodate a number of sparse turbidite lenses. As a
consequence of the latest Oligocene - Early Burdigalian rifting
and drifting of the Ligure - Provençal Gulf the basin widened and
deepened, assuming an about E-W elongation during Late
Burdigalian - earliest Langhian time (GELATI & GNACCOLINI,
2003). The entire TPB was lately involved by Apennine
tectonics, hence it was uplifted and eroded, giving birth to the
present day almost homoclinal N-wards dipping structure of its
remnants.
The lower part of the CTS, the Lower Cengio Turbidite
_________________________
(*) Dipartim ento Scienze della Terra, Università di Milano, via Mangiagalli
34, 20133 I-Milano
(**) CNR
IDPA, via M angiagalli 34, 20133 I-Milano
(***) Present Address: Baker Hughes S.p.A.
System (LCTS; Membro delle Arenarie di Bertulla, Carta
Geologica d'Italia, Foglio 228 - Cairo Montenotte), is the widest
of the mentioned group of slope to base of slope clastic lenses
that fill local depressions and/or minor depocenters close to, or
above the western and eastern marginal slopes of the Langhe
Basin. The LCTS is preserved over an area of about 16 km2 at its
south-western margin in the Bormida di Millesimo valley. Its
architectural features attracted our attention because some
evidences of facies segregation due to basin irregularities were
evident, suggesting to compare these features to those of some
slope basins, as are described for instance in the Gulf of Mexic o
among many others (P RATHER, 2003 with references). Hence we
carried on a traditional study based on 1:10.000 and 1:5.000
geological and facies mapping for physical stratigraphy
reconstruction, bed-by-bed measurement and facies analysis of
20 sedimentological logs, statistical analysis of facies changes
and bed thickness distribution.
BASIN SETTING OF THE LCTS
The western slope of the Langhe Basin in the Cengio
Millesimo area consists of a complex wedge of hemipelagic
mudstones that envelopes at least 7 lens-shaped, small clastic
bodies, that are mostly formed by turbiditic sandstones and only
in one case by conglomerates and sandstones. They developed
under control of syn-sedimentary tectonics and slope instability,
during the Rupelian Chattian deepening of the former coast and
shelf depositional setting of the top Molare Fm. (GELATI &
G NACCOLINI, 2003). The LCTS (GELATI & GNACCOLINI, 1980;
CAZZOLA et alii, 1981; 1985) is the uppermost body within this
group. It is up to 35 m thick and is formed by two stacked
sandstone-mudstone bodies separated by a hemipelagic m-thick
interval. The LCTS has the shape of a concave-up lens, framed
by hemipelagic mudstones, up to 40 m thick below its base and
by an about 15 m thick interval of mudstones with thin to
medium sandstone beds, above its top. The upper part of the CTS
(CAZZOLA et alii, 1981; 1985; BERSEZIO et alii, 2005; 2009) lies
above these mudstones, pinching out onto the western and
TURBIDITE FAC IES CHANGES IN A BASE OF SLOPE BASIN SETTING
northern slopes, spreading out over a progressively wider area
and sealing the former morphology to which the LCTS
deposition was constrained.
Geological and facies mapping provided the following
features: i) the LCTS is confined to the West and North by slope
mudstones, onto which onlap terminations are preserved and
exposed; ii) the eastern margin is not preserved in outcrops but
its presence is documented by regional termination of all the
sedimentary bodies to the east; iii) an intrabasinal mudstone
relief, that branches from the regional western slope and shows a
present day E-W strike, subdivides the LCTS depositional area
into two laterally connected sectors (southern and northern). Both
the sandstone bodies of the LCTS lap-out onto this relief; iv)
palaeocurrent measurements document that sediments were
supplied from the S and SW, hence the sector North of the
mudstone relief was located downcurrent with respect to the
southern one. Deflection of palaeoflows, towards SE-NW and
SW-NE occurs close to the mudstone relief; v) the upper CTS
seals the separation between the two LCTS sub-basins, laying
directly above the top of the mudstone relief.
TURBIDITE FACIES CHANGES IN THE LCTS BASE OF
SLOPE SETTING
The two sandstone-mudstone bodies of the LCTS are formed
by different associations of 10 turbidite l.s. facies: graded to
massive pebbly sandstones and sandstones; graded to massive
then laminated sandstone-mudstone and mudstone-sandstone
couplets; laminated pebbly sandstones, sandstones and
sandstone-mudstone couplets; mudstone-sandstone couplets with
Bouma sequences; complex sandstone and sandstone-mudstone
beds with repetitive parallel and oblique laminated divisions;
siltstone-mudstone couplets with Td-e Bouma sequence; massive
to laminated mudstones; disturbed and chaotic beds with variable
grain-size.
All of these facies can be recognized in the lower body of the
LCTS, that is formed by stacked minor genetic units with fining
upwards or stationary trends separated by mudstone intervals,
with a general fining and thinning upwards trend. The upper
body is thinner than the lower one and is characterized by the
prevalence of the graded to massive and laminated sandstone
facies. This vertical evolution can be related either to
progradation of the turbidite bodies or to changes of the basin
configuration and of the parent flows through time. The analysis
of the facies changes from the up-current sector (South) to the
down-current area (North), and the statistical analysis of facies
distribution provide a key also to this interpretation.
We computed univariate statistics to quantify the distribution
of bed thicknesses, the sand/mud ratio, the grain-size at the base
of the beds, the amalgamated beds percentage, the clay chips
abundance, the individual facies abundance, and the distribution
of the ratios between specific internal divisions of the beds
(massive or graded vs. total divisions, graded vs. massive
13
divisions, laminated vs. total divisions and laminated vs. graded
plus massive divisions), comparing the two sub-units and the two
sub-areas. A bivariate analysis was computed comparing two
distribution has been studied also computing the exceedence bed
thickness cumulative plots, for the entire LCTS, the two subunits and the two sub-areas.
In synthesis the results of qualitative and statistical facies
analysis show that the coarsest grained beds, the highest
sand/mud ratio, the highest abundance of graded and massive
sandstone divisions, the highest thicknesses of the sandstone beds
are all typical of the lower unit into the up -current area, South of
the intrabasinal relief. The down-current area shows an opposite
statistical distribution, the lower body of LCTS being
characterized by abundance of fine-grained turbidites,
mudstones, laminated divisions, clay chips and of the complex
beds facies. Even if sandier and generally thicker-bedded than the
lower one, the upper body shows quite similar trends from S to
N.
In addition to these features, the percentage of bed
amalgamation, the abundance of massive divisions and the
sand/mud ratio have been shown to increase in correspondence of
the western and northern onlaps as well as all around the
intrabasinal mudstone relief, for both the lower and upper bod ies
of the LCTS.
The cumulative bed thickness distribution plots for both the
sandstone divisions and the total thickness of beds appears of the
convex upwards type (CARLSON & GROTZINGER, 2001;
S INCLAIR & COWIE, 2003). This pattern is quite similar to a log
normal distribution that could result from a random combination
of several factors, like depositional flow patterns, grain size of
clastic input, basin configuration (TALLING, 2001). In any case
no aggradational patterns imputable to total ponding of parent
flows are shown by the curves.
The brief summary of the outstanding features of the LCTS
base of slope basin permits to draw some observations:
1) the LCTS sandstone bodies were deposited within two
along-current connected depressions at the, or close to, the base
of the marginal slope of the Langhe Basin in the Cengio area;
2) the mudstone divide between the two sub areas acted to
force facies segregation from the southern (up-current) to the
northern (down-current) sectors;
3) during deposition of the lowermost body of the LCTS the
effect of this basin configuration was the trapping of most of the
sand in the up -current sub-basin and the by-pass, either
-grained fraction that was collected by the
down-current sub-basin. This p
process described by several authors (WINKER, 1996;
P RATHER, 2003; T ONIOLO et alii, 2006) for slope mini-basins of
different regions and after flume experiments. The same process
could explain also the peculiar abundance of the complex beds
facies in the down-current northern sub-basin, considering that it
14
BERSEZIO ET ALII
could derive from repetitive cycles of re-concentration of a
parent flow that suffered a hydraulic jump, was temporarily
ponded, released the coarsest fraction in the southern sub-basin
then thickened and spilled over the mudstone relief towards the
northern sub-basin where the repetitive laminated beds were
deposited;
4) the slope physiography determined also the other facies
changes that we observed: approaching the marginal slopes,
deposition of amalgamated sandstone beds was promoted,
together with the increase of the sand/mud ratio, that are the
fingerprints of the onlaps of the LCTS. The internal mudstone
divide acted also deflecting the palaeoflows, forcing expansion of
the spilling over turbidites so promoting deposition of
amalgamated sandstone beds along the up-current termination of
LCTS within the northern sub-basin, and lastly providing the
abundant clay chips that are another peculiar feature of this
down-current area.
REFERENCES
BERSEZIO R., FELLETTI F. & M ICUCCI L. (2005) - Statistical
analysis of stratal patterns and facies changes at the
terminations of turbiditic sandstone bodies: the Oligocene
Cengio Unit (Tertiary Piedmont Basin). Geoacta, 4, 83-104.
BERSEZIO R., FELLETTI F., RIVA S.& M ICUCCI L. (2009) - Bed
thickness and facies trends of turbiditic sandstone bodies:
unravelling the effects of basin confinement, depositional
processes and modes of sediment supply. In: B. Kneller & B.
Mc Caffrey (Eds.) -Water
- Special Publication. 92, 303321.
CARLSON, J. & GROTZINGER, J.P. (2001). Submarine fan
environment inferred from turbidite thickness distribution.
Sedimentology, 48, 1331-1351.
CARTA G EOLOGIC A D'I TALIA 1:50.000,
Cairo
Montenotte http://www.isprambiente.gov.it/, in press.
CAZZOLA C., F ONNESU F., MUTTI E., RAM PONE G., SONNINO M.
& VIGNA B. (1981) - Geometry and facies of small, faultcontrolled deep-sea fan systems in a transgressive depositional
setting (Tertiary Piedmont Basin, Northwestern Italy). In: F.
Ricci Lucchi (Ed.)
IAS, 2 nd European Regional Meeting
Excursion Guidebook, Bologna, 7- 53.
CAZZOLA C., M UTTI E. & V IGNA B. (1985) - Cengio Turbidite
System, Italy. In: A. Bouma, W.R. Normark and N.E. Barnes
(Eds.) - Submarine fans and related turbidite systems. Springer
Verlag, 179-183.
F ORCELLA F., GELATI R., GNACCOLINI M., ROSSI P.M. &
BERSEZIO R. (1999) - Il Bacino Terziario Ligure-Piemontese
tra il Monregalese e la valle del T.Lemme: stato delle
ricerche e prospettive future. In: Orombelli G. (Ed.) - Studi
geografici e geologici in onore di Severino Belloni, Brigatti,
Genova, 339-365.
G ELATI R. & GNACCOLINI M. (1980) - Significato dei corpi
arenacei di conoide sottomarina (Oligocene
Miocene
-sedimentaria del Bacino
Terziario
Ligure-Piemontese.
Rivista
Italiana
di
Paleontologia e Stratigrafia, 87, 167-186.
G ELATI R. & G NACCOLINI M. (1998) - Synsedimentary tectonics
and sedimentation inthe Tertiary Piedmont Basin,
Northwestern Italy. Rivista Italiana di Paleontologia e
Stratigrafia, 98, 425-452.
G ELATI R & G NACCOLINI M. (2003) - Genesis and evolution of
the Langhe Basin, with emphasis on the Latest Oligocene
Earliest Miocene and Serravallian. Atti Ticinesi di Scienze
della Terra, 44, 3 18, Pavia.
P RATHER B.E. (2003) - Controls on reservoir distribution,
architecture and stratigraphic trapping in slope settings.
Marine and Petroleum Geology, 20, 529 545.
SINCLAIR H.D. & COWIE. P.A. (2003) - Basin floor topography
and the scaling of turbidites. Journal of Geology, 111, 277299.
T ALLING P. (2001) - On the frequency distribution of turbidite
thickness. Sedimentology, 48, 1297-1329.
T ONIOLO H., LAM B M. & PARKER G. (2006)
Depositional
turbidity currents in diapiric minibasins on the continental
slope: formulation and theory. Journal of Sedimentary
Research, 76, 783-797.
W INKER C. D. (1996) - High resolution seismic stratigraphy of a
late Pleistocene submarine fan ponded by salt-withdrawal
mini-basins on the Gulf of Mexico Continental slope. Proc.
1996 Offshore Technology Conference, paper OTC 8024
(May 6 9, 1996, Houston, Texas), 619-628.
Tectonic control on fluvial aggradation: the Plio-Pleistocene Ambra
valley-fill succession (Tuscany, Italy).
VALERIA BIANCHI (*), M ASSIM ILIANO GHINASSI (*), MAURO ALDINUCCI (°), JACOPO BOAGA (*), RITA DEIANA (**)
Key words: non-marine valley-fill, epeirogenic movements,
Northern Appennines, alluvial sedimentation.
Even if most of incised-valleys documented in the
stratigraphic record have been filled in response to downstream
relative sea/lake-level changes, few authors highlight the
importance of tectonic and climatic upstream control on valleyfill aggradation (SHANLEY & M CCABE , 1994; H OLBROOK , 2001;
BLUM & TORNQVIST, 2000). In addition, the presence of sinsedimentary tectonic warping can cause a modification of fluvial
patterns, along with erosion or aggradation, with consequent
development of heterogeneous valley-fill architectures. The
effects of sin-sedimentary tectonic warping are known in a
modern setting (S CHUMM, 1986) or laboratory experiments
(O UCHI, 1985), whereas study cases from fossil record are almost
missing. The present study focuses on a fluvial, valley-fill
succession (Ambra River valley) exposed along the Northern
margin of the Chianti Mounts (Northern Apennines).
The Plio-Pleistocene deposits of the Ambra River valley are
located along the southern margin of the Chianti Mounts
(Tuscany, Italy). This ridge separates the Siena and Upper
Valdarno Basin, two depressions belonging to the external sector
of the Northern Apennines (MARTINI AND S AGRI, 1993). The
valley drained toward SW and was cut both on pre-neogene
bedrock (northern valley reach) and Pliocene marine to
transitional deposits of the Siena Basin (southern valley reach) as
consequence of a Middle Pliocene regional forced regression
(A LDINUCCI et alii, 2007). This valley fill is an example of a
fluvial valley-fill uninfluenced by relative sea-level changes
(A LDINUCCI et alii, 2007), due to the considerable elevation and
several rocky shoulders between paleo-coastline and the valley.
The valley fill consists of two intervals separated by an
_________________________
(*) Dipartimento di Geoscienze, Università degli Studi di Padova, via G.
Gradenigo, 6, 35131 Padova, Italy ([email protected]).
erosive surface. The upper interval is cut in the lower one in the
northern and southern part of the study area, whereas they are
offset in the central part. The lower interval (40 m thick) is
mainly made of gravels and has been the focus of pre vious
studies, which emphasized the role of tectonic and climate in
controlling accumulation of the alluvial deposits. The upper
interval, which is the focus of the present study, is about 35 m
thick and deposited across a sin-sedimentary normal fault dipping
toward NE (i.e. upstream) which is still affected by intense CO2
emissions (BROGI et alii, 2002). The present study focuses on the
upper interval and aims at unraveling the role of a tectonic
warping on valley-fill aggradation.
The normal fault divides the upper valley-fill interval into two
segments: the downvalley and the upvalley portion. Downvalley
deposits consist of cross- to plane-parallel stratified gravels with
subordinate sands. These deposits are commonly organized into
form set (2-4 m thick) of large scale inclined beds, which are
interpreted as channel bars developed in a gravel-bed river
setting. The correlative upvalley deposits have been mainly
analyzed through integration of ERT (Electrical Resistivity
Tomography) lines and well -core data. These deposits consist of
organic-rich mud containing isolated, erosive-based sand bodies
(2-4 m thick), which are interpreted as the active infill of fluvial
channels.
The heterogeneity of the study vallive deposits is ascribed to
a sin-depositional activity of the normal fault, which is also
attested by tectonic deformations in the lower valley-fill deposits.
Tectonic upwarping caused a decrease in transport capability in
the upstream reaches of the paleovalley, manifested by the
aggradation of poorly-drained floodplain deposits. In parallel,
downstream of the upwarping area, aggradation was promoted by
the increase in sediment supply due to erosion of the uplifted
area. The fault activity is also thought to be the cause of the local
offset typifying the upper and lower valley fill deposits in the
central part of the study area.
REFERENCES
(°)Weatherford Petroleum Consultants AS, 5147 Bergen, Norway.
(**) Dipartim ento di Beni Culturali, Università degli Studi di Padova,
Palazzo Liviano, Piazza Capitaniato 7, 35139 Padova.
A LDINUCCI M., GHINASSI M. AND S ANDRELLI F. (2007) Climatic and tectonic signature in the fluvial infill of a late
16
BIANCHI ET ALII
Pliocene valley (Siena Basin, Northern Appennines, Italy).
SEPM, Journal of Sedimentary Research, 77, 398-414.
BLUM, M.D., TORNQVIST, T.E. (2000) - Fluvial response to
climate and sea-level change: a review and look forward.
Sedimentology 47, 1 48 (Supplement).
BROGI A., COSTANTINI A., LAZZAROTTO A. (2002) - Structural
setting of Rapolano Trequanda ridge (Southern Tuscany,
Italy). Boll. Soc. Geol. It. Vol. sp. 1, 757-767.
HOLBROOK, J.M. (2001) - Origin, genetic interrelationships, and
stratigraphy over the continuum of fluvial channel -form
bounding surfaces: An illustration from middle Cretaceous
strata, southeastern Colorado. Sedimentary Geology, 124,
202 246.
M ARTINI AND SAGRI (1993) - Tectono-sedimentary
characteristics of Late Miocene-Quaternary extensional
basins of the Northern Appennines, Italy. Earth-Science
Reviews, 34, 197-233.
O UCHI S., (1985) - Response of alluvial rivers to slow active
tectonic movement. Geological Society of America Bulletin,
96, 504-515.
S CHUMM, S. A. (1986) - Alluvial river response to active
tectonics. Active Tectonics, 80 94.
S HANLEY K.W. AND M CCABE P.J. (1991) - Predicting facies
architecture through sequence stratigraphy an example from
the Kaiparowits Plateau, Utah. Geology, 19, 742-745.
Sedimentology and sediment transport processes in a few ephemeral
streams of the Horn of Africa
PAOLO BILLI (*)
Key words: Bedload sheets, distributary system, ephemeral
streams, hyperconcentrated flow, plane bed.
Ephemeral streams are a main geomorphologic feature in
many drylands of the planet. In the last decades these rivers
have attracted the attention of geomorphologists and
sedimentologists for the flash flood hazards connected with
their impulsive nature and for providing a modern equivalent
of depositional characteristics and diagnostic tools to interpret
old arid river deposits as potential reservoirs in oil and gas
fields exploration (N ORTH & TAYLOR, 1996). In this
presentation. channel morphology, bedforms, sedimentary
structures and sediment transport processes of the distributary
system and the main stem of ephemeral streams in the
structural basin of Kobo (northern Ethiopia) and the Samoti
plain (Eritrean Danakil) are described and analysed through
field observations and measurements.
The distributary systems of the study ephemeral stream
show peculiar characteristics differentiating them from
floodouts (TOOTH , 2000) and terminal fans (PARKASH et alii,
1983; KELLY & O LSEN , 1993). The main channel is rectangular
in cross-section with almost vertical banks and has an almost
straight morphology recalling that of the American arroyos.
Channel width expands rapidly just beyond the headwater
gorge, is constant along the main stem as far as its most
downstream reach (upstream of the distributary system) where
widths tends to decrease in response to transmission losses.
(BILLI, 2007). Bird-foot type distributary
systems consist of five reach units, with different
morphological,
sedimentological
and
hydrological
characteristics. They are: 1) main feeder channel; 2) primary
distributary reach; 3) flow expansion reach; 4) accretionary
front; 5) run out channel. In the expansion reach, partly
_________________________
(*) Dipartimento Scienze della Terra, Università di Ferrara.
Lavoro eseguito n
transport in the ephemeral streams of the Kobo
contributo finanziario di National Geographic e
con il
unconfined flow expands and the depositi on of coarse gravel
particles takes place forming an accretionary front. This is the
only site where a conspicuous accumulation of coarse material
is found in the whole fluvial system making that as a
distinctive feature of the study distributary systems in
comparison with the terminal fans and floodouts described in
the literature (PARKASH et alii, 1983; KELLY AND OLSEN,
1993). The lobate distributary systems are less common and
morphologically similar to TOOTH S (2005) splays but are fed
by upstream runoff and tends to become wider in a downstream
direction due to flow expansion caused also by the roughnes
provided by shrub vegetation.
The streambed of all the sandy study rivers is flat, devoid
of any bedform and punctuated by individual particles.
Horizontal, planar bedding is by far the prevailing sedimentary
structure in the main feeder channel as well as in the
distributary reaches. The fast transit of the floods may also
account for a depositional aftermath consisting only of
horizontal planar laminae. A typical internal bed arrangement,
consisting of four main divisions is found and a schematic
model is presented (BILLI , 2008). From bottom to top it
consists of: 1) the basal reversely graded or massive, fine grained division; 2) the core coarse division; 3) the horizontally
laminated sandy and grainy division and 4) the receding flood
flow mud and sandy mud drape. This division association
model conforms very well to the vertical shear stress
distribution postulated by SOHN (1997) for hyperconcentrated
flows: the coarse core division coincides with the highest value
of shear stress that is predicted to decrease both downward in
the basal massive or reverse graded division and upward in the
horizontally laminated division, near the top of the collisiona l
zone. By this model it is possible to account for the
characteristics and origin of horizontal laminae that are the
most common sedimentary feature of ephemeral streams. The
upward fining of the natural horizontal laminae and their
position in the division association model indicates these
bedforms are to be interpreted as thin bedload sheets rather
than as generated by the migration of low amplitude bed waves
as postulated by BEST & BRIDGE (1992). However, since in the
upper part of the collision zone, Froude numbers higher than
18
BILLI ET ALII
one were measured in the field during floods, an origin for
horizontal laminae associated with plane bed to antidune
transition, as reported by ALEXANDER et alii (2001), cannot be
excluded.
The large, individual boulders punctuating the streambed
of the study rivers have their roots in the coarse core division
and protrude though the overlaying massive sand and fine
gravelly sand with rare flow perturbation features such as
poorly developed undulated lamination in the boulder vicinity.
The flow energy at bankfull discharge was found to be capable
of entraining such large particles, but the lack of flow
disturbance around them and the erosionless transition of the
coarse core division, in which they are rooted, to the lower
massive or reversely graded division and to the overlaying
horizontally laminated division indicate large and small
particles are subjected to conditions of almost equal mobility
leading to the conclusion that, though buoyancy forces may be
active on boulders, en masse bed material transport is the
prevailing bedload process.
The theory of GRANT (1997) that high-gradient sand to
boulder bed streams achieve an equilibrium adjustment
between flow, sediment transport and channel morphology at
critical flow through the dissipation of the available energy by
the development of bedforms and flow structures seems to
apply well to the study ephemeral streams in which energy is
dissipated to sustain hyperconcentrated flows and flow
resistance is provided by outsize boulders transported on top of
gradient of the study rivers, which is remarkably high for
sandbed channels (0.014-0.044), can be accounted for.
Field measurements of bed and suspended load transport in the
Gereb Oda, a sandbed ephemeral stream of the Kobo basin,
proved that during floods Froude number was constantly higher
than one and supercritical flow conditions occurred also at
shallow flow depths (BILLI, 2011). The variation of Froude
number with discharge follows a counter-clockwise hysteresis
curve. The suspended sediment concentration was very high
(as much as 136 gl-1) leading close to hyperconcentrated flow
conditions. The grain size of bedlaod is commonly finer than
bed material. However, as discharge increases bedload
coarsens (its median size becomes larger than that of bed
material) as a larger proportion of fine bed particles is
conveyed into suspension, contributing to increase the density
of the water-sediment mixture. The sandy streambed of Gereb
Oda is punctuated by large boulders of about 0.3-0.4 m. They
were observed to be entrained and transported at discharge near
to or slightly higher than banbkfull and shallow flows as deep
as their size.
The only bedforms observed on the stream bed of Gereb
Oda are leaf-shaped, thin sand sheet. Their thickness is similar
to that of bedload sheets as calculated from the bedload
samples and by the KARIM AND K ENNEDY (1983) equation. The
development of the leaf-shaped bedforms can be associated
with the onset of bedload flux and confirms the hypothesis of
BILLI (2008) about the role of sheet-like bedload transport for
the wide occurrence of horizontally laminated sediment and the
lack of small scale bedforms on steep, sand-bed ephemeral
streams.
The streambed morphology of coarse-grained, boulder bed
ephemeral streams is similar to that of braided rivers in more
humid environments as it consists of longitudinal and lateral
bars and anabranching of shallow channels. The bars have a
more or less elongated, rhomboidal shape, but they commonly
have sharp margins and do not show any feature associated
with depositional processes such as accretionary fronts,
foresets and a fine tail. Bars and channel deposits are hardly
discernible and have common features such as subtle bedding,
lack of erosive surfaces, are very coarse grained, imbricated,
massive with poorly defined inner divisions and, subordinately,
reversely graded, and sand is present in the pockets among the
large particles, on the higher bar top, as patches on the braided
channel bed or, in places, as a massive 20-30 cm thick deposits
in apparent pools. The overall sedimentological characteristics,
in association with some morphological peculiarities such as
the lack of well developed riffle and pool sequences, lead to
interpret the streambed deposits of the Golina (Kobo basin) and
Dandero (Eritrean Danakil) study reach as resulting from the
emplacement of 1.0-1.5 m thick cobble to boulder, bedload
sheets (WHITING et al., 1988) and the braided channel
morphology as originated by their dissection during the
receding flood flows. This depositional model well matches the
meorphological and sedimentological characteristics and
structure of a very coarse-grained, ephemeral streams as it
accounts for : a) the lack of the accretionary front, foresets and
fine deposits in the downstream side of bars as instead
commonly generated by flow separation in perennial braided
river bars; b) the lack of riffle and pool sequences, replaced by
short and steep glides, originated from the backward reworking
of the bedload sheet front, and by apparent pools marked by
fine, mainly sandy material; c) bar and channel deposits
sharing the same sedimentological structures consisting of
horizontal, tabular, subtle stratification of clast-supported and
matrix filled about 2-3D84 thick bedload sheets (BILLI, 2011).
REFERENCES
A LEXANDER, J., BRIDGE , J.S., CHEEL, R.J., & LEC LAIR, S.F.
(2001) - Bedforms and associated sedimentary structures
formed under supercritical water flows over aggrading
sand beds. Sedimentology, 48, 133-152.
BEST, J., BRIDGE, J. (1992) - The morphology and dynamics of
low amplitude bedwaves upon upper stage plane beds and
the preservation of planar laminae. Sedimentology, 39,
737-752.
BILLI, P. (2007) - Morphology and sediment dynamics of
ephemeral streams terminal reaches in the Kobo basin
(northern Welo, Ethiopia). Geomorphology, 85, 98-113.
BILLI, P. (2008) - Flash floods, sediment transport and
bedforms in the ephemeral streams of Kobo basin,
northern Ethiopia. CATENA, 75 (1), 5-17.
SEDIMENTOLOGY AND SEDIMENT TRANSPORT PROCESSES IN A FEW EPHEMERAL STREAMS OF THE HORN OF AFRIC A
BILLI, P. (2011) - Flash flood sediment transport in a steep
sand-bed ephemeral stream. Int. Jour. Sediment, Res.,
26(2), 193-209.
GRANT, G.E. (1997) - Critical flow constraints flow hydraulic
in mobile-bed streams: A new hypothesis. Water
Resources Research, 33 (2), 349-358.
KARIM M. F., KENNEDY J. F. (1983) - Computer-based
predictors for sediment discharge and friction factor of
alluvial streams. Proc. Sec. Intl. Symp. on River
Sedimentation, Nanjing, China, Paper A18.
19
P ARKASH, B., AWASTHI, A.K. & G OHAIN, K. (1983) Lithofacies of the Markanda terminal fan, Kurukshetra
district, Haryana, India. In: J.D. Collinson and J. Lewin,
(Eds.) - Modern and Ancient Fluvial Systems. Spec. Publs.
Int. Ass. Sediment., 6, 337-344.
S OHN, Y.K. (1997) - On traction-carpet sedimentation. Jour.
Sedim. Res., 67 (3), 502-509.
T OOTH, S. (2000) - Process, form and change in dryland
rivers: a review of recent research. Earth-Sci. Rev., 51,
67-107.
KELLY , S.B., O LSEN, H. (1993) - Terminal fans a review with
reference to Devonian examples. Sediment. Geology, 85,
339-374.
T OOTH, S. (2005) - Splay formation along the lower reaches of
ephemeral rivers on the Northern Plains of arid Central
Australia. Jour. Sedim. Research, 75,636-649.
NORTH, CP., TAYLOR , KS. (1996) - Ephemeral-fluvial deposits:
Integrated outcrop and simulation studies reveal
complexity. AAPG Bulletin, 80 (6), 811-830.
W HITING, P.J., DIETRICH , W.E., LEOPOLD , L.B., DRAKE & T.G,
S HREVE, R.L. (1988) - Bedload sheets in heterogeneous
sediment . Geology, 16, 105-108.
Depositional processes of the carbonate-siliciclastic rhodolith rich
deposits in the Saint Florant Basin (Burdigalian
Formation, Corsica)
M ARCO BRANDANO (*), LAURA TOM ASSETTI (*) & S ARA RONCA (*)
Key words: Rhodolith, Miocene,
carbonate-siliciclastic mixing.
Corsica,
lithofacies,
Many sedimentary processes may lead to the formation of
carbonate-siliciclastic sediments in shallow shelf environments.
The Miocene Saint Florant Basin (Corsica), and in particular
rhe Monte S. Angelo Formation, offers the possibility to
analyses coarse mixed sediments produced by erosion of rocky
coast, fluvial input and shallow water carbonate production.
The Miocene succession of Saint Florent unconformably
overlies the Nebbio tectonic unit and it consists of 4
stratigraphic units. The first unit is knowns as Fium Albino
Formation, and it is up to 60 m thick. The unit crops out locally
in erosional depressions cut into the underlying Nebbio nappe
and consists of continental deposits pebble conglomerate and
very coarse- to coarse-grained sandstone. This unit is overlaid
by the Torra Formation that is 50m thick and made up of
massive medium- to coarse-grain ned sandstone and pebble
conglomerate with abundant skeletal remain (mollusk,
echinoids and bryozoans). The
up to 250m in thick, conformably overlies the Torra Formation
and is overlain by the Farinole Formation.
_________________________
(*) Dipartimento di Scienze della Terra, Sapienza Università di Roma.
Piazzale Aldo M oro, 5 00185, Roma.
E-mail: [email protected]
bioclastic detritus with varying amounts of siliciclastic detritus.
The skeletal assemblages of this unit is dominated by bivalves,
bryozoans and foraminifera corallinacean red algae that form
rhodoliths. The Farinole Formation is about 80 m thick and is
dominated by pelagic components.
Three main rhodolith rich facies have bee n recognized in the
Monte S. Angeolo Formatiion The F1 is a rhodolith rudstone
with lithoclasts organized in 2-3 m thick beds, dominated by
laminar rhodoliths with elliptical shape. The F2 is a chanellized
conglomerate with rhodoliths. In this lithofacies rhodoliths are
ellipsoidal to subsherical in shape and show a prevalent
laminar structure. The F3 is a rhodolith rudstone to floatstone
with laminar, branching and columnar rhodoliths characterized
ellipsoidal to subspherical shape. The nucleus of rhodoliths in
all three facies is made up of lithoclasts or bryozoan colonies.
The red algal assemblages is dominated by the oligophotic
melobesioids and sporolithacens. Euphotic genera are only
accessory. The rhodolith facies alternated with cross bedded
calcarenites that were interpreted as large subacqueous dunes.
The rhodolith rich deposits represent the accumulation on the
distal sector of an infra-littoral prism.
Digital 3D modelling of submarine dune field by laser scanning
technique (Bolognano Formation, Majella)
M ARCO BRANDANO (*,$), G IORGIO G UARINI (**), RENZO PETRUNGARO (**), LUC A VELOCCI (**),
DEM ETRIO MELONI (*), G AIA MASCARO (*) & LORENZO LIPPARINI (°)
Key words: Laser scan, submarine dune, Oligocene, Majella,
carbonate ramp.
To study a sedimentary structures the prerequisite is the
availability of 3D outcrop. Sedimentary structures reproductions
may be based on drawings, supplied by photographs. However
drawings and photographs present and cause different problems,
for examples the accuracy of drawings as well as photographs are
dependent on the direction and intensity of light.
Laser sc
giving an accurate
and precise three dimensional representation of a considered
target. Terrestrial laser scanner has been used in order to obtain a
model of the trampled area taking in account that terrestrial laser
scanner allows a highly detailed geometric characterization also
on target situated at distances up to tens of meters.
The acquisition has been performed with Riegl VZ 400 laser
scanner from a distance of approximately 90 m, setting a mean
point to point spacing of 0,005 m . The 3D digital modelling was
performed on the sedimentary structures of the Chattian
Lepidocyclina limestone of Majella (Formazione di Bolognano)
along a 200 m long transect. The depositional profile of the
Lepidocyclina Limestone is consistent with a high energy
carbonate ramp, where most of the sediments appear to be
parautochthonous in the middle ramp environment and
autochthonous dominated in the outer ramp environment. the
sediment as transported along the ramp by downslope currents
that were able to form submarine dunes field. In this work it will
be presented the result of the 3D modelling of the sedimentary
structures of
the sigmoidal cross-bedded grainstone that
represent the record of submarine dune migration in the middle
ramp environment.
.
_________________________
(*) Dipartimento di Scienze della Terra, La Sapienza, Università di Roma
(**) Pet ra Geo Scan s .n.c., www.petrageoscan.it
(°) Medoilgas Italia s pa
($) IGAG-CNR Area della Ricerca di Rom a 1
Lacustrine organic facies and pollen analysis from the Trasimeno lake
(Central Italy): a preliminary note
N ICOLETTA BURATTI (*), M ASSIM ILIANO R. BARCHI (*), ADELE BERTINI A. (°), S IMONETTA CIRILLI (*),
LUC A GASPERINI (^), MARTA M ARCHEGIANO (*), & FAUSTO PAZZAGLIA (*)
Key words: paleoclimate,
Pleistocene, Trasimeno.
palynofacies,
pollen
analysis,
In the frame of a multidisciplinary project, aimed to
reconstruct the palaeoenvironmental and paleoclimatic evolution
of Trasimeno lake during the Pleistocene, one core (175 m long)
was drilled along the south-eastern coast of the lake, by the
Regione Umbria Geological Survey.
In this first approach the aim of this study was to reconstruct
vegetation changes within the catchment area, from fossil pollen
assemblages, and to identify the relative contributions of the
different sources of organic debris delivered to the lacustrine
sediments.
Sediments are the product of lake life and can be regarded as
a bank of information about environmental changes occurring in
both the water body and in the catchment area (de Vicente et al.,
2006). The primary source of organic matter to lake sediments is
mainly from the particulate detritus of plants, degraded to various
degrees, and deriving from both autochthonous and
allochthonous sources (Meyers & Lallier-Vergès, 1999). As the
plant life in and around lakes change, the composition and
amount of organic matter delivered to lake sediments changes.
Optical examination of palynofacies, coupled with a
preliminary pollen analysis was performed. Although a careful
interpretation of the results will require a comparison with
sedimentology, complete pollen record and a well-constrained
sediment chronology, some reliable conclusions can be achieved.
The Trasimeno lake (Umbria, Central Italy) is a mesoeutrophic, shallow (<6 m deep) lake with a large extension (~120
km2), characterized by a water balance strongly affected by the
_________________________
(*)(*) Dipartimento di Scienze della Terra, Università di Perugia
(°) Dipartimento di Scienze della Terra, Università di Firenze
(^) Istitut o di Scienze Marine
Bologna
Consiglio Nazionale delle Ricerche,
Geologico e Sismico della Regione Umbria e il CNR-ISMAR di Bologna.
pluviometric regime (Dragoni, 2004). As is common in shallowwater ecosystems, climate change plays a fundamental role in
their evolution and functioning. Today the hydrological, thermal
and hydrochemical regime of Trasimeno lake are deeply
influenced by climatic variations (Ludovisi & Gaino, 2010).
Most of the organic production originates from t he macrophyte
community, which mainly consists of submerged plants,
distributed from the shore to the center of the lake and
subordinately of semi-emerged plants, growing around the lake.
The lake is located between two extensional basins, the
Valdichiana to the west and the Valtiberina to the east. Its onset
probably started in the Early Pleistocene, as evolution of a lateral
branch of the Valdichiana basin. Seismic reflection data
(Gasperini et alii, 2010) show below the lake floor almost 600 m
of sediments overlying a deeply eroded Miocene bedrock.
The geological data of the surrounding area (Barchi &
Marroni, 2007; Aruta et alii, 2004) and the litology of the core
suggest this evolution for the Trasimeno area: a) Early Piocene
deposition of marine clays and sands in the Valdichiana basin; b)
Pleistocene deposition of (fluvio?)-lacustrine clays, sandy clays
in the Trasimeno basin.
Quantitative analysis of organic constituents was carried out
in Trasimeno sediments, within a palynologically productive
interval, comprised between 15 m and 30 m. Palynofacies types
were identified on the basis of visual evaluation of the relative
abundances of organic constituents and then integrated by cluster
analysis, in order to test group consistency.
Three main palynofacies assemblages (A, B, C) and three
sub -assemblages (A1, B1, C1) were recognized. Palynofacies A
was dominated by poorly preserved woody remains, partially
degraded in aerobic conditions (soil) before deposition,
associated with relatively abundant translucent, well preserved
woody remains, still maintaining tracheidal structure and cuticles.
The rest of the palynofacies was composed by highly diversified
pollen assemblages, gelified debris, accessory fungal remains,
and framboidal pyrite. Much of the organic matter characteristic
of palynofacies A was represented by fluvially or wind
transported allochthonous remains. The relative abundance and
good preservation of this material, which comprises numerous
LACUSTRINE ORGANIC FACIES AND POLLEN ANALYSIS FROM THE TRASIM ENO LAKE
centimeter-size plant remains, imply short transport distances.
The organic matter would thus originate from higher plants that
grew within the basin or in its immediate vicinity, as testified by
the great sporomorphs diversity in palynological residues.
Palynofacies B has a transitional nature between A and C. It
was characterized by an analogous contribution from both
allochthonous and authocthnous organic debris. As in
palynofacies A, very low amount of amorphous organic matter
revealed a good oxygenation of the depositional environment.
Palynofacies C was almost completely composed of gelified
debris, relatively abundant framboidal pyrite and amorphous
organic matter. This palynofacies was dominated by an
authocthnous organic fraction, produced in the lake itself.
Gelified material could represent the result of submerged and
semi-emerged macrophyte degradation within the water column
(Siffedine et alii, 1995; Martín-Closas et alii, 2005). Low
percentages of the allochthonous fraction could suggest a reduced
plant cover and /or a very low land supply. The occurrence of
dark brown, amorphous organic flakes and framboidal pyrite
suggested reducing conditions in the depositional environment.
Data obtained from the petrographic study of sedimentary
organic matter will be integrated by organic geochemistry
analysis (TOC, 13C, 15N, C/N), providing additional valuable
information on organic matter sources and paleoproductivity.
Pollen analysis revealed a vegetation landscape considerably
different from the present one, for the presence of a number of
taxa today extinct in Europe (e.g. Carya, Pterocarya, Tsuga),
living in North America and Asia (Bertini, 2003, 2010; Magri,
2010).
An interglacial cycle marked by the presence of a mixed -oak
forest (mainly deciduous Quercus, Ulmus/Zelkova, Carpinus,
Corylus and Fagus) followed by Juglandaceae (Carya,
Pterocarya and Juglans) and then by conifers (P. diploxylontype, Cedrus, Abies, Picea, Tsuga, and Cupressaceae) has been
detected in the central portion of the succession. At its base the
end of a glacial is testified by the pollen of grasses and other
herbs. At its top an interglacial/glacial transition as well as the
start of a new glacial phase are expressed by the increase
respectively of altitudinal coniferous taxa and Artemisia, Poaceae
and Chenopodiaceae typical taxa of steppe phases.
Such pollen record is significant to discuss the stratigraphical
position of this part of the Trasimeno core (from 19 m to 21,5 m)
in absence of chronological constrains. In fact the peculiar floral
composition as well as the evaluation of the relative percentages
of each pollen taxon (e.g. presence of Carya, Pterocarya, Tsuga
and Cedrus; absence of Taxodium type, Liquidambar) permit to
attempt a correlation with the Glacial/interglacial cycles within
the Early/ Middle Pleistocene transition.
Pollen analyses though still in progress seem to represent a
valuable starting point for biostratigraphic correlations with other
Italian palynological records (starting from the geographically
closer ones) and for adding new information about the
distributi
Central Italy during the Early-Middle Pleistocene.
23
REFERENCES
A RUTA G., BOR GIA A., BRUNI P., CECCHI G., CIPRIANI N.,
TREDICI Y. (2004) - Pliocene and Pleistocene unconformity
bounded stratigraphic units (UBSU) in Val di Chiana. In
Morini D. and Bruni P. (editors): The "Regione Toscana"
Project of Geological Mapping, case histories and data
acquisition, Regione Toscana, 133-136.
BARCHI M.R. & MARRONI M. (2007) - Note illustrative del
Foglio 310, Passignano sul Trasimeno. Progetto CARG
(CARtografia Geologica), ISPRA.
BERTINI A. (2010) - Pliocene to Pleistocene palynoflora and
vegetation in Italy: State of the art. Quaternary International,
225, 5-24.
BERTINI A. (2003) - Early to Middle Pleistocene changes of the
Italian flora and vegetation in the light of a
chronostratigraphic framework. Il Quaternario, 16, (1bis),
19-36.
D E V ICENTE I., AMORES V. & CRUZ-PIZARRO L. (2006) Instability of shallow lakes: A matter of the complexity of
factors involved in sediment and water interaction?
Limnetica, 25, (1-2), 253-270.
D RAGONI W. (2004) - Il Lago Trasimeno e le Variazioni
Climatiche
Difesa Idraulica, pp. 60, Perugia.
G ASPERINI L., BARCHI M.R., BELLUCCI L.G., BORTOLUZZI G.,
LIGI M. & PAUSELLI C. (2010). Tectonostratigraphy of Lake
Trasimeno (Italy) and the geological evolution of the
Northern Apennines. Tectonophysics, 492, 164-174.
LUDOVISI A. & GAINO E. (2010) - Meteorological and water
quality changes in Lake Trasimeno (Umbria, Italy) during
the last fifty years. J. Limnol., 69, (1), 174-188.
M AGRI D. (2010) - Persistence of tree taxa in Europe and
Quaternary climate changes. Quaternary International 219,
145-151.
M ARTÍN -CLOSAS C., PERM ANYER A. & VILA M.J. (2005) Palynofacies distribution in a lacustrine basin. Geobios, 38,
197-210.
M EYERS P.A. & LALLIER-VERGÈS E. (1999) - Lacustrine
sedimentary organic matter records of Late Quaternary
paleoclimates. Journal of Paleolimnology, 21, 345-372.
S IFEDDINE A., LAGGOUN -D EFAR GE F., LALLIER-VERGES E.,
DISNAR J.R., W ILLIAMSON D., G ASSE F. & GIBER T E. (1995) La sédimentation organique lacustre en zone tropicale sud au
cours des 36 000 dernières années (Lac Tritrivakely,
Madagascar). Comptes Rendus de l'Académie des Sciences
Paris, Series IIa, 321, 385-391.
Depositional systems of the Eastern Southern Alps (NE Italy, W
Slovenia) during the late Carnian
M ARCELLO CAGGIATI (*), ANNA BREDA (**), P IER O G IANOLLA (*), M ANUEL RIGO (**) & G UIDO ROGHI (°)
Key words: Upper Triassic, Southern Alps, carbonate platforms,
paleoenvironments, paleogeography.
INTRODUCTION
During the early Late Triassic, the Eastern Southern Alps
(SA) were characterized by widespread flattening of the
paleotopography. Mostly during the so called Carnian Pluvial
Event (CPE, late Julian) a marked pulse of siliciclastics or mixed
sediments filled the inherited basins and an important shift of the
coastline toward N and NE occurred. As a consequence of the
flattening, a general low gradient topography is documented in
all the SA from latemost Julian. Typically depositional systems
span from mixed carbonate-siliciclastic deposits representing
ramp/lagoon environments in the late Julian-early Tuvalian (e.g.
Heiligkreuz and Travenanzes Fms.) to mainly carbonate peritidal
facies of the Dolomia Principale (DP) close to the
Carnian/Norian boundary. The main goal of this contribution is
to analyze in detail the SA palaeo-envinronmental evolution in
order to better understand the start-up of the Dolomia Principale,
the widest epicontinental carbonate platform of western Tethys,
which lasted for over 20 million years.
The paleogeographic reconstruction of the eastern sector of
the SA has been possible because of the increase, in the last
years, of the stratigraphic resolution: physical stratigraphy
(mapping geology, lithostratigraphy, sequence stratigraphy,
facies analysis) and biostratigraphy (palinomorphs, conodonts
and ammonoids). Nevertheless, it is complicated by the complex
structural arrangement of the area, due to the polyphasic Alpine
tectonics (Fig. 1).
_________________________
(*) Dipartimento di Scienze della Terra, Università di Studi di Ferrara, Via
Saragat 1, 44122 Ferrara, Italy.
(**) Dipartimento di Geoscienze, Università degli Studi di Padova, Via G.
Gradenigo 6 , 35131 Padova, Italy.
(°) Istituto di Geoscienze e Georis orse, CNR. Via G. Gradenigo 6, 35131
Padova, Italy.
PALEOENVIRONMENT RECONSTRUCTION
Lower Tuvalian
In the Recoaro and Trento areas, as well as in the Venetian
Alps, south to the Valsugana Fault System (VFS) and in the
western Dolomites, an erosional gap on top of Ladinian and
lower Carnian units (e.g. Cassian Dolomite) does not allow to
define lower Tuvalian sedimentation patterns. The same gap is
also documented by wells from successions currently under the
Venetian Plain and Adriatic Sea.
First evidences of lower Tuvalian lithofacies can be observed
in the southern Belluno Dolomites, south of the VFS (S IORPAES
& G IANOLLA , 1991; GIANOLLA et alii, 1998). Mixed terrigenouscarbonate facies from the top of Heiligkreuz Fm. (HKS), can be
referred to a carbonate-lagoon depositional environment, close to
a terrigenous coastline and hence characterized by frequent
coarse-grained input.
Significant and abrupt facies variation occurred northwards,
in the Central Dolomites, marked by the presence of an oolitic
shoal (ca W-E oriented) characterized by oolitic-bioclastic and
hybrid calcarenites (HKS, Lagazuoi mb., NER I et alii, 2007;
BREDA et alii, 2009). Locally, tidal inlets dissecting the barrier
are present, infilled by high energy tidal deposits with
herringbone cross-stratification (HKS, Falzarego mb., NERI et
alii, 2007; BREDA et alii, 2009).
Moving to the East, a similar framework is observed in
eastern Cadore and western Carnia regions, where a lagoon
environment is denoted by marly limestones and marls (nearby of
Passo Mauria, Ampezzo and Degano valley; cf. V ENTURINI et
alii, 2006) switching laterally to more carbonate terms, like well
stratified dolostones (eastern Marmarole massif; cf. CASATI et
alii, 1982; P ICOTTI & PROSSER , 1987), or gradually passing to a
thick dolomitized body, referable to a shallow carbon ate ramp
setting, and lithostratigraphically correlable to the top of HKS.
The former unit is a lithomarker traceable for several kilometers
CARULLI et alii, 1987; Portella dolomite in D E
ZANCHE et alii, 2000), and testifies the almost complete
DEPOSITIONAL SYSTEMS OF THE EASTERN SOUTHERN ALPS
disappearing of the terrigenous component in the easternmost
SA.
Northeastwards, a rapid transition from the southern
carbonate ramps and oolitic shoals to carbonate peritidal cycles
representing a tidal flat environment, is locally documented both
in Northeastern Dolomites (PRETO & HINNOV, 2003) and in
Slovenian Julian Alps (uppermost Razor limestone in Ramovs,
1987).
The top of this interval, all over in the SA, is characterized by
karst surfaces, paleosols and other diagenetic features related to a
long lasting emersion due to a pronounced sea level fall, well
developed on inner ramp and peritidal facies (NER I et alii, 2007).
Upper Tuvalian
The first Carnian units from cores in the Venetian Plain and
Adriatic Sea are characterized by the alternation of dolostones,
anhydrites and fine red siliciclastics, referable to mud flats and/or
sabkha environments. However, the paleogeographic framework
of the upper Carnian in this area should be more complex: while
sedimentation is recorded north of Vicenza (Villaverla well),
near Udine (Cargnacco well) and in the offshore (Amanda 1 bis
well), the area in between is still characterized by non deposition.
A similar situation is also present in the Recoaro area, with
exposed sectors facing terrigenous-evaporitic lagoons to the
Fig. 1
25
south (D E ZANCHE & MIETTO , 1975). Shallow lagoon to peritidal
carbonate facies with less terrigenous input have been
documented also in the area west of Trento (Gola and Vela
Valleys). Moving to the east, in the Western Dolomites and in the
region south of the VFS, the upper Tuvalian units are not
exposed, but hints can be obtained in the Passo Duran and
Cibiana area, where an alluvial plain environment can be
deduced by the presence of meandering-channel conglomerates
and fine-grained red beds of Travenanzes Fm. (BREDA & PRETO,
2011). This fluvial system passes northwards (Cortina area) to a
distal alluvial plain, where unconfined ephemeral streams splay
onto the coastal mudflat. The TVZ is not cropping out in the
most of the Western Dolomites, but where it is present (e.g.
Sciliar massif or Mendola area), it is characterized by very thin
alluvial plain successions. Alluvial facies pass northeastwards to
flood basin mudstones and coastal sabkha evaporites. The two
environments are irregularly distributed along a WNW-ESE belt
and well correlate with upper Carnian evaporites of upper
Tagliamento Valley (Passo Mauria), laterally passing to
multicolored mudstones (Forni di Sotto).
A transition from tidal flats to shallow lagoons is testified in
northeastern Dolomites by alternations of aphanitic dolostones
and multicolored mudstones. A similar shifting to shallow,
coastal, low-energy environments is documented also in eastern
Simplified structural scheme of the Southern Alps, with main localities and position of profiles shown in Fig. 2. Modified after Castellarin et alii (2006).
26
CAGGIATI ET ALII
Carnia by the northern transition from gypsum evaporites
(CARULLI et alii, 1998) to shallow water dolostones, limestones
and dark shale (lower part of Monticello Fm.) that directly
overlie the top of the previous massive dolomitized unit, lower
Tuvalian in age.
While in Dolomites and in Carnia evidences of upper
Tuvalian deposition are mainly continental to marginal marine, in
the S. Stefano di Cadore area marls and calciturbidites
identifying a basinal setting (belonging to ammonoid subullatus
and anatropites subzones) is documented (G EYER, 1900),
testifying the presence of a shelf break and a carbonate margin.
In the Julian Alps the shallow lagoon environment passes
northwards to a margin-slope-basin system. In particular, in the
Cave del Predil area, back-reef facies are interfingered with a
massive serpulid/microbial bioconstructed margin referable to the
Dolomia Principale (GIANOLLA et alii, 2003). Breccia bodies at
the toe of slope are interfingered with marly basinal limestones of
Carnizza Fm., documented in the whole Slovenian Julian Alps
(Martuljek group, CELARC & K OLAR-J
, 2008).
DISCUSSION
Despite the structural complexity affecting the Southern Alps,
regional patterns of the paleoenvironmental evolution in the early
l ate Triassic are recognizable and some interesting topics can be
debated.
Starting from the depicted paleoenvironmental reconstruction,
a simplified paleogeographic scheme can be obtained. Despite
few data are available about the shortening due to the alpine
major fault systems, we can here consider the main direction of
faulting of different thrusts. In particular, region north of the VFS
should be restored several kilometers to the north-northwest,
whereas Carnia and Julian Alps must be expanded in a S-N
direction, with increasing shifting amount moving to the east
(CASTELLARIN et alii, 2006; VENTURINI et alii., 2006). The
resulting paleogeographic scheme shows a main framework
structured in NW-SE oriented environmental belts, with a general
transition from southwestern facies with most continental
affinity, to northeastern facies related to more open carbonate
environments (Fig. 2). Furthermore, other local changes can be
related to sin-sedimentary tectonics, sea level oscillations and
climate, and to the presence/absence of southern deltaic bodies.
After the complete flattening of the topography during the
latemost Julian, in the lower Tuvalian it can be noted that deeper
environments were concentrated in the central b elt. These more
subsiding areas were probably related with the presence of
Fig. 2 SW- NE s chematic sections showing lateral paleoenvironmental changes in the lower (A) and upper (B) Tuvalian. Symbols in legend: a) exposed land; b)
alluvial plain; c) flood basin; d) mud flat and evaporitic; e) mainly terrigenous lagoon/ramp; f) mainly carbonate lagoon/ramp; g) peritidal h) slope i) basin. Purple
dotted lines indicate schematic sin-sedimentary faults. Vertical scale is exaggerated.
DEPOSITIONAL SYSTEMS OF THE EASTERN SOUTHERN ALPS
27
underlying thick basinal successions. Differently, in the upper
Tuvalian, especially in the Dolomites, the central area constituted
a connection between a southern emerged belt and a northern
shallow lagoon region (Fig. 2). An analogue pattern seems to be
configured in Julian Alps and Carnia, even if the central area
records again high subsidence patterns (thick succession of
evaporites and shallow marine sediments).
Due to the same northeasternwards environment transition
observed in Julian Alps and Dolomites, it can be suggested that
the margin-to-basin complex shad to be somewhere present also
northward of the shallow lagoon facies of northern Dolomites.
The S. Stefano di Cadore basinal succession could be interpreted
as belonging to this northern domain, later displaced to the south
by the Alpine orogeny which shortening should have been
particularly strong in the Cadore area (see the convergence of
thrusts of the VFS in Fig. 1).
The DP margin system was a sort of energy barrier, which
protected the inner platform area from the sudden marine
ingression, characterizing the transgression (TST) of Car 4 of
GIANOLLA et alii (1998). Basinwards, in the northeastern part of
the Southern Alps, a general drowning of peritidal sediments
occurred leading to the deposition of a basinal succession
(LIEBERMAN, 1978; SCHLAF , 1996).
CELARC B. & KOLAR-J
T. (2008)
The CarnianNorian basin- platform system of the Martuljek Mountain
Group (Julian Alps, Slovenia): progradation of the Dachstein
carbonate platform. Geologica Carpathica 59 (3), 211-224.
REFERENCES
LIEBERMAN H.M. (1978) Carnitza Formation. Mitt. Ges. Geol.
Bergbaustud. Österr. 25, 35-60.
BREDA A. & PRETO N. (2011) - Anatomy of an Upper Triassic
continental to marginal-marine system: the mixed
siliciclastic carbonate Travenanzes Formation (Dolomites,
Northern Italy). Sedimentology, 58, 1613-1647.
BREDA A., PRETO N., ROGHI G., FURIN S. et al. (2009) The
Carnian Pluvial Event in the Tofane area (Cortina
). Geo.Alp, 6, 80-115.
CARULLI G.B., FANTONI R., M ASETTI D., PONTON M., et al.
(1998) Analisi di facies e proposta di revisione stratigrafica
del Triassico Superiore del Sudalpino orientale. Atti Tic. Di
Sc. Della Terra, 7 (serie sp.), 159-183.
CARULLI G.B., FRIZZO P., LONGO SALVADOR G., SEM ENZA E., et
al. (1987) La geologia della zona tra il T. Chiarzò e il F.
Fella (Alpi Carniche). Giornale di Geologia, 49 (1), 1-32.
CASATI P., JADOUL F., NICORA A., MARINELLI M., et al.(1982)
Geologia della Valle dell Ansiei e dei gruppi M. Popera- Tre
Cime di Lavaredo. Riv. It. Pal. Strat., 87, 371-498.
CASTELLARIN A., N ICOLICH R., FANTONI R., CANTELLI L., SELLA
M. & SELLI L. (2006) Structure of the lithosphere beneath
the Eastern Alps (southern sector of the TRANSALP
transect). Tectonophysics, 414, 259 282.
D E ZANCHE V., GIANOLLA P. & ROGHI G. (2000)
Carnian
stratigraphy in the Raibl/Cave del Predil area (Julian Alps,
Italy). Ecl. Geol. Helv., 93, 331-347.
D E ZANCHE V. & MIETTO , P. (1975) Il Carnico nelle Prealpi
Vicentine. Bol. Soc. Geol. It., 94, 1573-1593.
G EYER G. (1900) Ueber die Verbreitung und stratigraphische
Stellung der schwarzen Tropites-Kalke bei Sau Stefano in
Cadore. Verhandlungen der k.k. Geologischen Reichsanstalt,
15/16, 355-370.
G IANOLLA P., D E ZANCHE V. & M IETTO P. (1998) Triassic
Sequence Stratigraphy in the Southern Alps (Northern Italy):
definition of sequences and basin evolution. In P.C. de
Gracianscky, J. Hardenbol, T. Jacquin, P.R. Vail, and D.
Ulmer-Scholle (Eds)
Mesozoic-Cenozoic Sequence
Stratigraphy of European Basins, SEPM Sp. Pub., 60, 723751.
G IANOLLA P., DE ZANCHE V. & ROGHI G. (2003) An Upper
Tuvalian (Triassic) Platform-Basin System in the Julian Alps:
the Start-up of the Dolomia Principale (Southern Alps, Italy).
Facies, 49, 135-150.
N ER I C., G IANOLLA P., FUR LANIS S., CAPUTO R., BOSELLINI A. et
al. (2007) Note Illustrativscala 1:50000, Foglio 29 Cortina
d Ampezzo. A.P.A.T., , 1-202.
P ICOTTI V. & PROSSER G. (1987) - Studio geologico dell'area
compresa tra Lozzo di Cadore e il gruppo delle Marmarole
(Dolomiti, Alpi Meridionali). Giorn. Geol., 49 (1), 33-50.
P RETO N. & HINNOV L.A. (2003) Unraveling the origin of
carbonate platform cyclothems in the Upper Triassic
Dürrenstein Formation (Dolomites, Italy). J. Of Sed. Res., 73
(5), 774-789.
R
A. (1987)
Ausbildung der Karn-Stufe im östlichen
Teil der nördlichen Julischen Alpen. Geologija, 30, 67-82.
S CHLAF J. (1996) - Ein obertriadisches Intraplattformbecken aus
den Südkarawanken (Kärnten, Österreich). Mitt. Ges. Geol.
Berg. Österr., 39/40, 1-14.
S IORPAES C. & GIANOLLA P. (1991) - Stratigrafia triassica del
versante settentrionale delle cime di San Sebastiano
(Dolomiti orientali). Rendiconti S.G.I., 114 (1), 155-156.
V ENTURINI C. (2006) - Note illustrative della Carta Geologica
d'Italia alla scala 1:50.000. Foglio 031 Ampezzo. APAT, 1232.
Identifying plays and prospects in carbonates
ANDREA COZZI (*)
Key words: Ammonoid fauna, ceratitoid, Recoaro area, German
basin, Alpine basin,.
ABSTRACT
Carbonate rocks host ~60% of the world hydrocarbon discovered
reserves and still hold 3,000 billion barrels of oil and 3,000
trillion cubic feet of gas in place. Carbonate reservoirs are
affected in their rock properties by syn- and post-depositional
mechanical (tectonics) and chemical (diagenesis) processes. The
occurrence and distribution through the rock record of
_________________________
(*) IEOC
Egypt Branch, No. 1, Rd. 204 - Degla Square, Maadi, Cairo
Egypt P.O. Box 52 - New Maadi 11742,
email: [email protected]
Hydrocarbon-bearing Carbonate reservoirs varies according to
their original depositional setting (ramps, shelves, buildups) or to
post-depositional tectonic settings. Eni has been producing from
Carbonate rocks for more than 50 years around the globe, some
of these fields stand out as Giant and Super Giant (e.g., South
Pars, Khashagan, Zubair, Perla). Carbonate reservoirs and plays
are highly complex and require a thorough understanding of the
interaction between depositional, mechanical and c hemical
controlling factors. The continuous advances in cutting-edge
technology applications will have a vital role to continue
exploring, finding and exploiting Hydrocarbon accumulations
hosted by Carbonate rocks.
Modeling tidal network dynamics in response to changes in the
environmental forcings
ANDREA
LPAOS
(*), LUC A CARNIELLO (**), LUANA S TEFANON (**) & ANDREA RINALDO (***)
Key words: Tidal landscape, Tidal networks, Drainage Density,
Tidal Prism
INTRODUCTION
Channel networks are ubiquitous morphological features of
the tidal landscape that control to a large extent water, sediment,
and nutrient fluxes within tidal systems. Despite their importance
in landscape evolution, tidal networks have received less
attention when compared to their fluvial counterparts (e.g.,
HOWARD et alii, 1994) particularly in terms of the chief processes
governing their initiation and evolution, and their response to
changes in the external forcings (e.g., RINALDO et alii, 1995). A
classical and fascinating question in geomorphology is whether
the morphological features of a given landscape retain signatures
of past climates or are in equilibrium with current ones (e.g.,
LEOPOLD , 1964). In particular, within tidal landscapes, improving
our understanding of network dynamics in response to variations
in Relative Mean Sea Level (RMSL) is theoretically and
practically relevant for the key role exerted by tidal networks on
the morphodynamic evolution of tidal systems (e.g. FAGHERAZZI
& OVEREEM , 2007).
Recently, several mathematical models have been developed
to describe the morphogenesis and development of tidal networks
(see e.g. FAGHERAZZI et alii, 2012 for a detailed review). Some
of these models have also addressed tidal network response to
RMSL changes (D'ALPAOS et alii, 2007; K IRWAN & M URRAY,
2007), However, the effects of cyclic variations in RMSL on the
characteristics and structure of tidal networks remain poorly
understood, and the possibility of detecting signatures of past
_________________________
(*) Dipartimento di Geoscienze, Università di Padova.
(**) Dipartimento ICEA, Università di Padova.
(***)Laboratory of Ecohydrology, ECHO/IEE/ENAC, Ècole Polytechnique
Fèdèrale Lausanne, Lausanne, Switzerland.
conditions imprinted on the landscape justifies analyses of the
type proposed herein.
Here we present the results obtained from the analysis of tidal
network response to changes in the landscape-forming tidal prism
(i.e., the total volume of water exchanged through the inlet
between low water slack and the following high water slack),
triggered by RMSL variations (S TEFANON et alii, 2012), on the
basis of laboratory experiments over timescales which would
preclude network monitoring through field observations. The use
of a controlled laboratory environment (see Fig. 1 and STEFANON
et alii, 2010, for a detailed description of the experimental
apparatus) allows us to isolate the effects of RMSL changes on
landscape evolution, among those of the other physical and
biological processes which shape the tidal landscape.
The experimental results show that changes in RMSL
immediately affect the tidal prism, and the tid al prism rapidly and
strongly influences channel cross-sectional areas, network
structure and its drainage density as a measure of network
efficiency in draining the landscape. We have in fact observed
that a decrease in the tidal prism leads to network retreat and
contraction of channel cross sections. Conversely, an increase in
the tidal prism promotes network re-incision and re-expansion of
channel cross sections: Network retreat and expansion tend to
occur wit hin the same planar blueprint (see Fig. 2). Our results
show that the drainage density of tidal channels is linearly related
to the landscape-forming prism, although this relation is
speculated to hold with reasonable approximation as a statistical
tendency rather than as a pointwise, instantaneous adaptation.
Changes in the tidal prism rapidly influence network efficiency
in draining the intertidal platform and the related transport of
water, sediments, nutrients and pollutants (STEFANON et alii,
2012).
These results bear significant practical implications on the
predictability of the long -term eco-morphodynamics of tidal
landscapes and may help refining our understanding of tidal
network dynamics in response to changes in RMSL and of the
extent of the imprinting of such changes in the landscape.
30
D ALPAOS ET ALII
Fig. 1 Sketch of the experimental apparatus. The plan view (a) and the section A-A (b) show the lagoon basin (5.3m long and 4.0m wide) and the sea (1.6m
long and 4.0m wide), connected by the lagoon inlet (0.20m wide) opened through a barrier of wooden panels. Water level measured at the sea through the
ultrasonic probes are used continuously correct the motion of the weir, allowing one to generate a sinusoidal tide of fixed amplitude and period, oscillating
around MWL. The laser s ys tem which measures bottom elevations has a 300 m resolution and is characterized by an accuracy of ± 1mm and a plan imetric
resolution of 1cm × 1cm (from S TEFANON et alii, 2012).
Fig. 2 Distribution of bottom elevations for different network configurations during the experiment of cyclic RMSL changes: (a) initial configuration; (b) 288
cycles; (c) 1752 cycles; (d) 9351 cycles; (e) 9631 cycles; (f) 11355 cycles; (g) 12459 cycles; (h) 13063 cycles ; (h) 13063 cycles. Elevations are referred to the
initial mean sea level.
MODELING TIDAL NETWORK DYNAMICS
REFERENCES
D'ALPAOS A., LANZONI S., MARANI M., & RINALDO A. (2007) Landscape evolution in tidal embayments: Modeling the
interplay of erosion, sedimentation, and vegetation dynamics,
Journal of Geophysical Research, 112, F01008,
doi:10.1029/2006JF000537.
FAGHERAZZI S. & OVEREEM I. (2007) - Models of deltaic and
inner continental shelf landform evolution, Annual Review of
Earth Planetary Sciences, 35, 685 715.
FAGHERAZZI S., ET AL. (2012) - Numerical models of salt marsh
evolution: Ecological, geomorphic, and climatic factors,
Reviews
of
Geophysics,
50,
RG1002,
doi:10.1029/2011RG000359.
HOWARD A., D IETRICH W. & SEIDL M. (1994) - Modeling fluvial
erosion on regional to continental scales, Journal of
Geophysical Research, 99(B7), 13,971 13,986.
31
K IRWAN M. & M URRAY B. (2007) - A coupled geomorphic and
ecological model of tidal marsh evolution, Proceedings of the
National Academy of Sciences. U.S.A., 104(15), 6118 6122.
LEOPOLD L.B., WOLMAN M.G., & M ILLER J.P. (1964) - Fluvial
Processes in Geomorphology, W. H. Freeman (Eds), New
York.
RINALDO A., DIETRICH W.E., V OGEL G., RIGON R., &
RODRIGUEZ-ITURBE I. (1995) - Geomorphological signatures
of varying climate; Nature, 374, 632 636.
S TEFANON L., CARNIELLO L., D'ALPAOS A., & LANZONI S.
(2010) - Experimental analysis of tidal network growth and
development; Continental Shelf Research, 30, 950 962,
doi:10.1016/j.csr.2009.08.018.
S TEFANON L., CARNIELLO L., D'ALPAOS A., & RINALDO A.
(2010) - Signatures of sea level changes on tidal
geomorphology: Experiments on network incision and
retreat, Geophysical Research Letters, 39.
Jurassic extensional faulting at the
Trento platform - Belluno basin margin
LUC IO
LBERTO & D ANILO GIORDANO
basin, Alpine basin.
The Jurassic paleogeography in the Venetian Prealps is
composed of the Friuli Platform, the Belluno trough and the
Trento plateau. The reconstrution of this paleogeographic settings
is recognizable by the presence and thickness of some
formations.
On the Trento plateau sedimented a condensed section (Calcari
Grigi Group, RAV, Maiolica p.p.) with some hiatus intervals in
it. The Belluno trough instead was filled with various formations
in relationship to the distance from the platform margins and to
the opening stage of the basin: Soverzene Formation, Igne
Formation, Lower and Upper Rosso Ammonitico, Vaiont
Limestone, Fonzaso Formation, Maiolica p.p..
Various studies have described and defined the stratigraphy of
the margin Trento Platform - Belluno Basin mostly of the M.
Grappa, Asiago Plateau, Schiara Mountain. Less work has been
done in the Vette Feltrine area (BECCARO et alii, 2002;
KOLCKMANN , 1992; DAL PIAZ, 1907).
_________________________
(*)
[email protected]
Feltre (BL);
(*)
The purpose of this note is to correlate data from previous works
with new observations to trace better the margin evolution and its
importance reflected in the deformation during the Alpine
Orogenic events. The area we are focusing on belongs to the Alpi
Feltrine range and in more details for the Canzoi Valley.
At the head of the Canzoi Valley, deep into the Vette Feltrine
range, we found some tens of meters of Vaiont Limestone that
belongs to the Belluno Basin stratigraphy. Its location in the
valley seems to follow the major faults alignment. Associated to
this unit there are also some black shales of Toarcian age. At the
entrance and in the surroundings of the valley it is possible to
recognize different stratigraphic sections some with a more
platform condensed sequence others with more basinal facies.
From all these data we suggest that, during the Jurassic, the
Canzoi Valley was a lateral engul fing area of the Belluno Basin
connected also with the dolomitic realm partially raised and in
erosion. Later the Alpine orogeny reactivated the same faults as
lateral ramps during the compression and growth of the Alpi
Feltrine. This reactivation created also some changes at the
Belluno and Neva thrusts with changes in orientation and
formation of secondary faults with lateral movement.
Sedimentological, geomorfological and geochemical evidence of the
last marine ingression in central Magellan Straits-southernmost Chile
SANDRO DE M URO , CLAUDIO K ALB, W ALTER BRAM BILLA & ANGELO IBBA (*)
Key words: Holocene, Magellan Straits, Periantartic Areas,
Quaternary Geology, Sedimentology.
ABSTRACT
Research along the coastal belt of the Magellan Straits was
carried out in detail with mapping of morphological units.
Attention was given to the study of palaeo-shorelines and
different terrace orders (Fig. 1) of presumed marine and
transitional origin (BRAM BATI & DE M URO , 2004; BRAM BATI et
alii, 2004a; D E MURO et alii, 2000).
On the basis of sedimentological , geological and
geomorphological results obtained, we made a zoning of the
coastal belts along the Atlantic opening of the Straits which
enabled us to print three sheets on a scale of 1:200,000
(BRAM BATI et alii, 2004b; DE M URO et alii, 2004a; D I G RANDE
et alii, 2004a).
Detailed studies and mapping (scale 1:50,000) of the
terraced sequences linked to Holo-Pleistocene glacio-eustatic
variations are in course. An atlas of 12 maps topographically
based on 28 sections of 1:50,000 scale maps (sheets 35, 50, 53,
67, 68, 69, 70, 84, 86, 101, 103 of the Chilean IGM), was made
also using the preliminary cartography by Empresa Nacional de
Petroleo (ENAP) and the Chilean IGM, aerial photos by Servicio
Aerofotogrammetrico Fuerza Aerea de Chile (SAF) and TM and
MSS Landsat satellite images (DE MURO et alii, 2004b, c, d, e;
DE M URO & D I GRANDE , 2004b; DI GRANDE et alii, 2004b).
The Atlas provides a zoning of the area distribution of the
most significant deposits processes and forms relating to the
coastal belt between Punta Dungeness and Cabo Froward (Fig.
2).
Morphogenesis of the area was strictly controlled by the
_________________________
(*) Departm ent of Chemical and Geological Sciences - OCEANS,
University of Cagliari, Italy, Email: dem [email protected];
processes associated with the advance and retreat of the
Magellano Glacier (CLAPPERTON , 1992) and, subordinately, by
the main morphodynamic event represented by post deglaciation
marine ingression. The Holocene paleogeographic evolutionary
Fig. 1 - Strait of M agellan, Bahia Iutil (Tierra del Fuego). Three orders of
terraces recognizable.
picture of the Patagonia-Tierra del Fuego area is mainly
controlled by the imposing phenomenon of glacio-isostasy,
though it cannot beruled out that the morphogenesis subsequenct
to deglaciation may have been affected by mild neo -tectonic
movements. As previously observed, relative marine ingressions
that produced terracing of the coasts and backland presumably
depend on prevalently positive movements of the whole coastal
system, related to the final deglaciation of the region.
It is deduced that following deglaciation, a strong parallel
uplift of the mean sea level was produced with initally
transgressive stratigraphic effects. Isostatic rebound, that
probably occurred rather late compared to post-glacial
transgression, is superimposed with very complex and articulate
phenomena, that are under study at present and will be the
subject of future works.
34
DE M URO ET ALII
(Holocene) and geomorphological map of the coastal area of
Península Juan Mazía, Tierra del Fuego, Straits of Magellan,
Chile (1:50,000 scale map). Map n. Proc. 2/12. 32nd
International Geological Congress - Florence, Italy - August
20-28, 2004.
D E M URO S., D I G RANDE A. & BRAM BATI A. (2004c) Distribution of the marine and transitional terraces
(Holocene) and geomorphological map of the coastal area
between Punta Paulo and Porvenir, Tierra del Fuego, Straits
of Magellan, Chile (1:50,000 scale map). Map n. 3/12. Proc.
32nd International Geological Congress - Florence, Italy August 20-28, 2004.
Fig. 2 Puerto Percy, Tierra del Fuego. Second-Order terrace deposits with
bilvaves and gasteropods.
REFERENCES
BRAM BATI A. & DE M URO S. (2004) ingression in central Magellan Straits, southernmost Chile:
- Proc.
-28
Agosto 2004, Firenze.
BRAM BATI A., D E MURO S. & D I GRANDE A. (2004a) the Marine and Transitional Terraces in the Magellan Straits
- Proc.
-28 Agosto 2004,
Firenze. 9/12 maps, 353.
BRAM BATI A., D E MURO S., DI GRANDE A. (2004b)
Distribution of marine and transitional terrace (Holocene)
and geomorphological map of the coastal area between
Bahia San Felipe and Paso Ancho Strait of Magellan
(1:200.000 scale map). Map B. Proc. 32nd
20-28, 2004.
CLAPPERTON C. M. (1992) - La ultima glociacion y deglaciacion
en el Estrecho de Magallanes: implicacíones para el
poblamiento de Tierra del Fuego Ans. Ins. Pat., Ser. Cs. Hs.,
Punta Arenas (Chile), 21, 113-128.
DE M URO S., BRAM BATI A., DI G RANDE A. (2004a)
Punta Dungeness and Bahía San Felipe, Strait of Magellan
Chile
(1:200.000 scale map). Map A. Proc. 32nd
20-28, 2004.
DE MURO S., DI G RANDE A. & BRAM BATI A. (2004b) -
D E MURO S., D I G RANDE A., BRAM BATI A. & G. FONTOLAN
(2004d) terraces (Holocene) and geomorphological map of the Punta
Catalina, Tierra del Fuego, Straits of Magellan, Chile
(1:50,000 scale map). Map n. 4/12. Proc. 32nd International
Geological Congress - Florence, Italy - August 20-28, 2004.
D E M URO S., D I G RANDE A. & BRAM BATI A. (2004e) Distribution of the marine and transitional terraces
(Holocene) and geomorphological map of the coastal area of
Primera Angostura, Patagonia, Tierra del Fuego, Straits of
Magellan, Chile (1:50,000 scale map). Map n. 5/12. Proc.
D E MURO S. & DI G RANDE A. (2004) - Distribution of the
marine and transitional terraces (Holocene) and
geomorphological map between Punta Arenas And Rio
Quema Angusta, Peninsula Brunswick, Patagonia, Straits of
Magellan, Chile . (1:50,000 scale map) Map n. 6/12. Proc.
32nd International Geological Congress - Florence, Italy August 20-28, 2004
D E MURO S., D I G RANDE A., FONTOLAN G. & BRAM BATI A.
(2000) postglacial evolutionary framework. Map n. 4/12 of the
Geomorphological Atlas of the Coasts of the Strait of
- Terra Antartica Reports, 4, 55-62, ISSN: 17237211 ISBN 88-900221-7-5
D I GRANDE A., D E M URO S., BRAM BATI A. (2004a)
Punta Dungeness and Bahía San Felipe, Strait of Magellan
(1:200.000
scale map). Map C. Proc. 32nd
20-28, 2004.
D I G RANDE A., S. DE M URO & BRAM BATI A. (2004b) Distribution of the marine and transitional terraces
(Holocene) and geomorphological map of the coastal area
between Porvenir and Puerto Yartoù, Patagonia, Straits of
Magellan, Chile (1:50,000 scale map). Map n. 1/12. Proc.
Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 35-37, 2 figs., 3 graphs.
Stratigraphic trend evolution of the sedimentary pulses of
Val d'Aveto Formation
ANDREA DI CAPUA (*), GIANLUCA G ROPPELLI (**) & GIOVANNI VEZZOLI (*)
Key words: Alpine Chain, Apennines, petrographic counting,
stratigraphic trend's evolution, Val d'Aveto Formation, Tertiary
clastic sequences.
main aim is to characterize the stratigraphic trend evolution of
the turbidity sequences of Val d'Aveto Formation (M UTTI &
RICCI LUCCHI , 1972).
METHODS
INTRODUCTION
The Tertiary clastic sequences bordering the SouthAlpine front
and the Apennines provide fundamental information about the
evolution of the Alpine chain between Eocene and Miocene
Fig. 1 - Fig. 1
A detailed geological/structural map at 1:5000 scale has been
realized. Val d'Aveto Formation is composed of five members: 1)
basal calcareous-arenitic member; 2) pelitic- arenitic silicoclastic
member with two para-conglomerates interbedded; 3)
volcanoclastic para-conglomerate member; 4) volcanoclastic
sandstone member; 5) calcareous sandstone member, with a paraconglomerate interbedded.
Conglomerate facies of Val d'Aveto Formation
(MUTTI & RICCI LUCCHI, 1972; G ELATI et alii, 1988; BERSEZIO
et alii, 1993; ELTER et alii, 1999; SCIUNNACH & TREM OLADA,
2004; GARZANTI & M ALUSÀ, 2008; M ALUSÀ et alii, 2010). Our
_________________________
(*) Dipartim ento di Scienze Geologiche e geotecnologie
studi di M ilano Bicocca.
(**) Istituto per la Dinamica dei Processi Am bientali
CNR.
Università degli
Sezione di Milano,
Fig. 2
Folds in the calcareous
arenitic member
On eight conglomerate bodies, three of which in the pelitic arenitic member, five in the conglomerate member and the last
one in the upper calcareous sandstones member, statistical
counting pebbles were concentrated. Statistical method has been
used, which contemplates a counting of over a hundred of
36
DI C APUA ET ALII
Gr aph. 1 Fieldwork counting results. Note that counting on the same bodies are shown as a single value derived from an average of counts. Bottom of
stratigraphical sequence = 123; top of stratigraphical sequence = 175 + 176.
pebbles in a 1.5 m² area. Fieldwork counting results are shown in
Graph.1
with metamorphic minerals, in particular garnets, while heavy
minerals from A41 sample is mainly composed of abundant
associations epidote and light mineral (usually quartz), garnet
Pebbles analysis has been integrated by two thin sections of
samples collected into two microconglomerate levels (A1 and
A2) located in the upper part of the pelitic-arenitic silicoclastic
member and by heavy minerals analysis of the paraconglomerate' matrix (A41) interbedded in the upper calcareous
sandstones. Results of the thin sections and heavy mineral
analysis are shown in Graph. 2 and 3.
DISCUSSION AND CONCLUSION
The petrographical signal underlines a preponderant presence
of metamorphic rocks, in particular quarzite, followed by gneiss
and micaschists, and a constant presence of calcareous clasts,
with two main pulses with an increasing trend of volcanoclastisc
material and a very weak pulse of plutonic rock. Moreover, thin
sections A1 and A2 show a preponderant content of
plutonic/ortogneiss fragments plus feldspar and quartz fragments,
Gr aph. 2
Thin section counting results.
STRATIGRAPHIC TREND EVOLUTION OF THE SEDIM ENTARY PULSES OF VAL D AVETO FORMATION
35,0
Zircone incolore
Rutilo giallo
30,0
CATANZARITI R., FERONI A. C., O TTR IA G. & LEVI N. (2009)
The contribution of calcareous nannofossil biostratigraphy in
Apatite incolore
Apatite rosa
25,0
R.F. apatite inc+bt+L
R.F. apatite rosa+TiO2+L
20,0
Epidoto incolore
15,0
Pistacite
Epidoto granulare
10,0
Zoisite
R.F. epidoto+L
5,0
R.F. epidoto+L+bt
Granato incolore
0,0
R.F. granato+ti+L
Miocene foredeep of the northern Apennines (Italy ), SEPM
Special Pubblication 93, 309-321.
E LTER P., CATANZATIRI R., GHISELLI F., M ARRONI M., M OLLI G.,
OTTRIA G. & PANDOLFI L. (1999)
L'Unità Aveto
(Appennino settentrionale): caratteristiche litostratigrafiche,
biostratigrafia, petrografia delle areniti e assetto strutturale.
Boll Soc Geol It. 118, 41 63.
G ARZANTI E. &. M ALUSÀ. M. G. (2008) The Oligocene Alps:
Domal unroofing and drainage development during early
orogenic growth. Earth and Planetary Science Letters 268,
487 500.
R.F. granato+epidoto
HM
Gr aph. 3
37
G ELATI R., NAPOLITANO A. & V ALDISTURLO A., (1988)
A41 heavy minerals' content on percentage
and epidote, and single crystals of epidote and apatite.
To trace a plausible source area our results have been
integrated available data available in literature (E LTER et alii,
1999, CATANZAR ITI et alii, 2009, MATTIOLI et alii, 2012). In
particular M ATTIOLI et alii (2012) suggests a local Apennine
source area, even if a detailed study of the sedimentary fraction
of Aveto Formation is however highly needed to completely
exclude or not the possibility derivation of the sedimentary
succession from the Alpine chain.
This work is still in progress: next steps will be the
stratigraphical and petrological study of both the foredeep and
Molassa Alpine Tertiary Formations, and to compare them with a
modern and active case.
La
pino . Rivista Italiana di
Paleontologia e Stratigrafia, 94, 285-332.
M ALUSÀ M. G. & GARZANTI E. (2012) Actualistic snapshot of
the early Oligocene Alps: the Alps-Apennines knot detangled.
Terra Nova doi: 10.1111/j.1365-3121.2011.01030.x
M ALUSÀ M. G., V ILLA I. M., VEZZOLI G. & GARZANTI E. (2011)
Detrital geochronology of unroofing magmatic complexes
and the slow erosion of Oligocene volcanoes in the Alps.
Earth and Planetary Science Letters, 301(1-2), 324-336.
Elsevier B.V. doi:10.1016/j.epsl.2010.11.019
M ATTIOLI M., LUSTRINO M., RONCA S. & BIANCHINI G. (2012)
Alpine geochimical petrographic constrains and geodynmic
implication from Early Oligocene Aveto
Petrignacola
Formatio (Italy). Lithos 134-135, 201 220
REFERENCES
M UTTI E. & RICCI LUCCHI F. (1972) Le torbiditi dell'Appennino
settentrionale: introduzione all'analisi di facies. Mem. Soc.
Geol. It., 11, 161 199, 30 ff., 1 tab.
BERSEZIO R., FORNAC IARI M., G ELATI R., N APOLITANO A. &
V ALDISTURLO, A. (1993)
The significance of the Upper
Cretaceous to Miocene clastic wedges in the déformation
history of the Lombardian southern Alps. Géologie Alpine,
1993, L 69, p. 320
S CIUNNACH D. & TREM OLADA F. (2004)
The Lombardian
Gonfolite Group in central Brianza (Como and Milano
Province, Italy): calcareous nannofossils biostratigraphy and
sedimentary record of neo alpine tectonics. Eclogae Geol.
Helv., 97, 119-131, Basel.
Sedimentological and pedological study of some pedogenized
intervals of the Plio-Pleistocene Upper Valdarno Basin
FRANCESCO F IDOLINI (*) & ANNA ANDREETTA (**)
Key words: facies analysis, palaeosols, sedimentary
environments, Upper Valdarno basin, Plio-Pleistocene.
INTRODUCTION
The study of palaeosols, coupled with the classical methods
of process sedimentology, is increasingly being recognized as an
effective tool for evaluating landscape stability and evolution.
The intrinsic complementarity of these two methods, which
record the effects of processes developing over different periods
of time, allows improving the information gained from
palaeoenvironmental reconstruction.
Even if the Upper Valdarno basin is one of the best-studied
Plio-Quaternary continental basins of the Northern Apennines,
only few works that include palaeopedological investigations
have been published (M ANCINI & ROM AGNOLI , 1966; BERTINI et
alii, 2010).
The objective of this study was to document the existence of
some important pedogenised stratigraphic intervals in the Upper
Valdarno basin and to characterise their morphological features,
with the aim to improve the understanding of landscape evolution
in the basin by integrating stratigraphic and sedimentological
data with palaeosol properties.
We selected four representative stratigraphic intervals bearing
pedogenised horizons, which are considered particularly useful to
a complete palaeoenvironmental reconstruction in key phases of
basin-fill accumulation.
elongated in a NW-SE direction and drained by the Arno River,
which flows to NW parallel to the main axis of the basin. The
depression, which is widely interpreted as a half-graben with the
main normal fault system located along the NE margin, is filled
by 550 m of alluvial and lacustrine deposits accumulated during
the Plio-Pleistocene.
The basin-fill succession is subdivided into three synthems
GEOLOGICAL OUTLINE
The Upper Valdarno basin (Fig. 1) is a 15 km wide tectonic
depression bounded by the Chianti Mountains and the
Pratomagno Ridge, about 35 km SE of Florence. The basin is
_________________________
(*) Dipartimento di Scienze della Terra, Università degli Studi di Firenze,
Via G. La Pira 4, 50121, Firenze.
(**) Dipartimento di Scienze delle Produzioni Vegetali, del Suolo e
delle Cascine 15, 50144, Firenze.
Fig. 1 Geological sketch map of the Upper Valdarno basin and location of
the studied s ections (m odified from F IDOLINI & ANDREETT A, in press).
39
FIDOLINI & ANDREETTA
(F IDOLINI et alii, in press), that are, from bottom up: Castelnuovo
dei Sabbioni (CSB), Montevarchi (VRC) and Torrente Ciuffenna
(UFF) synthems. A fourth one, Fosso del Salceto Synthem
(OLC) is exposed only in the Palazzolo sub-basin and is partly
coeval with the VRC Synthem.
The four studied sections are distributed within the fill
deposits as follows (Fig. 2):
The San Cipriano section, hosting the oldest pedogenised
deposits recognized in the basin, belongs to the youngest
unit of the CSB Synthem.
The Ricasoli section is located at the base of the VRC
Synthem.
Palaeosols found in this section are weakly developed and
polygenic, locally incorporating erosional surfaces. The presence
of Fe-oxide coatings around pores and the low chroma of the soil
matrix suggest their classification as Gleysols or Infragleysols,
developed in poorly drained conditions.
Ricasoli section
This section is made of vertically stacked, tabular sandy and
muddy beds cut by subordinate sand lenses. Tabular beds
represent overbank deposits and consist of sandy beds (5-40 cm)
produced by expanding, turbulent flows during flood events and
muddy intervals (20-100 cm), containing root traces and
pedogenic evidence, accumulated by suspension settling in flood
generated ponds. Sand lenses, which represent channel-fill
deposits, may contain gravels and mud clasts at the base as lag
deposits and are internally made of gently inclined or convexupward bedsets, made of plane-parallel or cross stratified beds,
accumulated by lateral and longitudinal bars respectively. The
overall palaeotransport direction is from SW (i.e. Chianti
margin).
Palaeosols are differ in the development of ped structure,
showing abundant Mn-Fe spherical concretions and can be
classified as Cambisols or Infracambisols. They show evidence
of transitory waterlogging and periodical changes from poorly- to
well-drained conditions.
Francalanci pit section
Fig. 2
Stratigraphic scheme for the Upper Valdarno basin. The
stratigraphic position of the four studied sections is reported (from
F IDOLINI & A NDREETT A, in press).
The Francalanci pit section covers the mid part of the VRC
Synthem.
The Acquaborra pit section exposes gravelly to sandymuddy deposits of the UFF Synthem.
STUDIED SECTIONS
San Cipriano section
It consists of sandy channelized deposits (up to 2 m thick and
8-12 m wide) incised into horizontally bedded floodplain mud,
bearing root traces and pedogenic features, with sandy interbeds.
Sandy channels, locally floored by lag deposits made of pebblesized gravels and mud clasts, consist of sets of gently inclined
(10°-15°) beds (up to 20 cm thick) accumulated by the lateral
migration of bars. Floodplain deposits consist of mud
accumulated by suspension settling in flood-generated ponds, and
sandy interbeds, which are up to 30 cm thick, representing
deposition of crevasse splays.
It consists of alternating, laterally persistent muddy and sandy
tabular beds cut by subordinate sand lenses, which are more
common in the lowermost and uppermost parts of the section,
resulting in a fining-to-coarsening-upward trend. Tabular beds
are commonly bioturbated and pedogenised, and consist of
muddy layers (up to 3 m thick) accumulated by sediment fallout
in standing water bodies developed after flood episodes, and
sheet-like sandy beds (5-30 cm) representing overbank deposits
produced by turbulent, unconfined flows expanding out of the
channels. Dark grey muds (30 cm thick) with abundant fresh
water bivalves, accumulated in small lakes, are locally present.
Sand lenses, internally made of sets of gently inclined beds (5-40
cm thick) accumulated by the lateral migration of bars, represent
channel deposits. Palaeotransport direction is mainly from SW
(i.e Chianti margin).
A composite soil located in the mid part of the section has
been studied. It shows the co-occurrence of carbonate
accumulation, vertic and hydromorphic pedofeatures, suggesting
successive phases of soil development characterised by different
conditions in terms of draining. It can be classified as a Calcic
Gleyc Vertisol or Pedocalcic Infragleyc Vertisol.
Acquaborra pit section
This section shows a clear fining-upward trend, passing from
gravelly to sandy and muddy deposits. Gravelly amalgamated
PEDOGENIZED INTERVALS OF THE PLIO-PLEISTOCENE UPPER VALDARNO BASIN
bodies (up to 6 m thick and tens of m wide), occurring in the
lower part, represent fluvial channels and consist of wedgeshaped units made of large-scale inclined beds accumulated by
the lateral migration of bars. In the upper part of the section,
tabular beds represent floodplain deposits, consisting in muddy
intervals (up to 3.5 m thick) accumulated by suspension fallout
after floods, and sandy beds (20-150 cm thick) deposited by
unconfined, turbulent flows as crevasse splays. Sand lenses (4-6
m thick and tens of m wide) cutting tabular deposits represent
fluvial channels, made of large-scale inclined bedsets
accumulated by the lateral migration of bars.
Palaeosols occurring in this section are characterised by the
coexistence in the same horizon of features that generally
develop in different soil environments, and thus they are
polygenic. Soils occurring in the lower part of the section show
carbonate accumulation within argic horizons, testifying a
transition from warm conditions, with alternating dry and wet
seasons, to temporary hydromorphic and reducing conditions.
Soils occurring in the upper part of the section are characterised
by the presence of hydromorphic features superposed on vertic
ones.
40
development, interrupted by depositional episodes, coherent with
the vicinity to active channels.
According to overall palaeotransport direction and
sedimentary features, deposits exposed in the Francalanci pit can
be referred to a transitional environment located between the
distal portion of alluvial fans sourced by the Chianti Mountains
and the lateral reaches of the axial floodplain. The superposition
of gleyc features over carbonate accumulation and vertic features
accounts for a significant stability of soil surface through time,
possibly related to sediment starving and low accommodation
Deposits exposed in the Acquaborra pit are referred to a
fluvial environment developed under changing draining
conditions. The lowermost part of the section represents a
relatively sinuous, gravelly fluvial system, while the upper part
represents a sinuous, mainly sandy fluvial system. Palaeosols
show stagnic or gleyic features, superimposed on carbonate
accumulation horizons and/or vertic features. These
characteristics are more evident in the uppermost part of the
pedostratigraphic sequence, in which channels appear to be more
isolated and entrenched within floodplain deposits.
REFERENCES
RESULTS
The main results of the study can be summarized as follows.
According to the collected data, deposits exposed in the San
Cipriano section can be referred to a fluvial environment
characterised by overall poorly drained conditions. Pedological
data attest for a general weak development of soils belonging to
this stratigraphic interval. The presence of compound truncated
sets and composite soils is coherent with unsteady depositional
conditions (KRAUS , 1999), characterized by episodes of sediment
accumulation and possible erosion and phases of soil
development. Redoximorphic features indicate overall
waterlogged conditions.
Sedimentary features, architecture and palaeotransport
direction suggest that deposits belonging to the Ricasoli section
can be referred to a distal alluvial fan setting characterised by
episodes of waterlogging. Palaeosols are weakly developed and
show evidence of weak oxidized conditions, with weathered
topmost horizons containing sparse organic matter. These
characteristics attest for relatively short periods of soil
BERTINI A., M AGI M., MAZZA P.A. & FAUQUETTE S. (2010)
Impact of short-term climatic events on latest Pliocene land
settings and communities in Central Italy (Upper Valdarno
basin). Quat. Int., 225, 92-105.
F IDOLINI F. & ANDREETTA A. (in press)
Integrating
sedimentological
and palaeopedological data
for
palaeoenvironmental reconstruction: examples from the PlioPleistocene Upper Valdarno basin (Northern Apennines). It.
J. Geosc.
F IDOLINI F., G HINASSI M., M AGI M., P APINI M. & S AGRI M. (in
press) - The Plio-Pleistocene Upper Valdarno Basin (Central
Italy): stratigraphy and basin fill evolution. It. J. Geosc.
K RAUS M.J. (1999)
Paleosols in sedimentary rocks: their
geologic applications. Earth Sc. Rev., 47, 41-70.
M ANCINI F. & ROM AGNOLI L. (1966) - Primo contributo alla
Geo-morfologia ed alla Paleopedologia del Valdarno
superiore. Boll. Soc. Geol. It., 84 (7), 169-185.
Facies and geometries of carbonate platforms of the Dolomites after
the Carnian Pluvial Event (CPE).
G IOVANNI GATTOLIN (*), MARCO FRANCESCHI (**), ANNA BREDA (*) & NEREO P RETO (*)
Key words: carbonate platform, Carnian Pluvial Event,
depositional geometries, Dolomites, facies.
Depositional geometries can be decisive in identifying the
origin of sedimentary bodies because their spatial characters can
be linked to the conditions in which sedimentation took place.
We here present preliminary results of an ongoing quantitative
study that aims at understanding the link between changes in
depositional architectures and the processes of shallow water
carbonate precipitation across the Carnian Pluvial Event (CPE).
During Middle Triassic, the Western Tethys displayed a
complex paleogeography, featuring isolated carbonate platforms
and carbonate-siliciclastic deep basins. This complexity
disappeared as a late Early Carnian global climatic event (CPE)
increased significantly the terrigenous input to marginal basins
and determined their infilling, leading to the formation of a
epeiric sea where the large Dolomia Principale (DP) carbonate
platform, deposited developing depositional geometries on the
scale of hundreds to thousands of kilometers. The transition from
isolated carbonate buildups to the epeiric DP platform is
apparently abrupt, and seems to imply a major crisis of carbonate
platform-depositional systems, during which the mode of
carbonate precipitation changed dramatically.
To investigate more in detail this transition, three dimensional
acquisition techniques (laser scanner and photogrammetry) were
applied to capture depositional geometries of sedimentary bodies
deposited
during
and
after
the
Carnian
crisis.
Contemporaneously, facies analysis was carried out to relate
changes in depositional geometries to facies variations.
The Early Carnian interval was surveyed on the southern walls
of the Tofana di Rozes (Dolomites, Falzarego valley - Cortina
d'Ampezzo, BL), that exposes a platform-to-basin transect of preand post-crisis platforms, and at Dibona hut where a ~ 30 m thick
prograding carbonate body deposited during the Carnian crisis
crops out. The Norian interval is being surveyed on the DP
margin and slope cropping out at Portella Pass (Dolomites, Cave
_________________________
(*) Dipartimento di Geoscienze, Università degli Studi di Padova, via
Gradenigo 6, 35137 - Padova
(**) Museo delle Scienze, via Calepina 14, 38122 - Trento
del Predil, Tarvisio, UD). In these outcrops both depositional
geometries and facies are preserved and consequently
observations from larger to finer scale can be done.
At the Tofana di Rozes, photogrammetric modeling of
topography permitted positioning and visualization of geological
features observed in the field into a three dimensional frame that
was used to define a conceptual sedimentological model for the
basal part of the Heiligkreuz Fm. (HK). It consists of numerous
carbonate mounds, tens to hundreds of meter in size, grown on a
pre-existing inclined surface, and intercalated with an alternation
of skeletal carbonates (grainstones and packstones) and siltitesarenites. This system soon evolved into a carbonate-clastic ramp.
A 3D model of the clinostratified body at Dibona was then
realized on the basis of LiDAR and petrographic analysis to test
if it fits in the larger scale conceptual model. The original
inclination of clinoforms ( ~ 25°) and their amplitude ( ~ 30 m)
point to a deltaic environment, deposited in a narrow passage
between mounds. Facies (mainly mixed carbonate siliciclastic
grainstones) are in agreement with this interpretation.
These observations on depositional architectures and facies
analysis seem to testify that a phase of complex intermediate
sedimentation in which carbonate mounds and detrital processes
coexisted, characterized the turnover of carbonate factory across
the CPE. This implies that, at least in terms of carbonate factories
turnover, the event has not to be considered strictly abrupt.
Preliminary results presented in this work seem to point out
that an integrated approach relying both on 3D characterization
of geometries and facies analysis could greatly help to shed light
on this critical interval of Late Triassic history.
Facies mapping and geometry acquisition via photogrammetry
are now being applied to the DP margin and slope at Portella
Pass. Preliminary results suggest that microbialites might be the
main character at play for the onset of the DP.
ACKNOWLEDGEMENTS
M. I. Sotton provided help during fieldwork, L. Tauro and E. Masiero realized
thin sections. Thanks to G. Teza for GPS data elaboration, M. Belvedere, S.
Castelli, F. Menna and 3DOM unit of FBK for basics on photogrammetry, G.
Roghi and J. Dal Corso for discussion.
foundation granted) with the financial contribution of
Seep-carbonates as indicators of global cooling events
(Miocene, northern Apennines).
CLAUDIA G RILLENZONI (°), STEFANO CONTI (°), D ANIELA FONTANA (°) & ELENA TURCO (*)
Key words: cooling events, Miocene, northern Apennines, seep carbonates.
Recent studies in dating seep-carbonates suggest that their
occurrence is controlled by climatic changes (TEICHERT et alii
2003). KIEL (2009) suggests that this correlation exists from
the late Jurassic to Recent, and shows a statistically relevant
correlations between the frequency of seep-carbonates in the
past 150 Ma and low deep-water temperature and low sealevels. In the Miocene of the northern Apennines, the
abundance and the extent of the seep-carbonates from different
tectonic-sedimentary settings, foredeep to satellite basins,
provide a rare opportunity to study the tectonic and/or climatic
controls on seepage (CONTI & F ONTANA, 1999).
The Vicchio outcrop in the Tuscan Apennines contains
excellent exposures of a Miocene seep-system (more than 80
Fig. 1- carbonate body enclosed in marly sediments of the Vicchio Fm.
_________________________
(°) Department of Earth Sciences, University of Modena and Reggio Emilia,
Largo Eufemia, 19, 41121, M odena
(*) Department of Earth Sciences , University of Parma, Parco Area delle
Scienze, 157A, 43100 Parma
carbonate bodies) enclosed in marly sediments (Fig. 1).
A detailed stratigraphic and biostratigraphic study of
carbonates and enclosing marls indicates that the stratigraphic
horizon bearing seep-carbonates lies between the T. cf. T.
quinqueloba AE (13.75 Ma) and the P. siakensis A1B (13.32
Ma) encompassing a time interval of about 400.000 years.
Since the AE of T. cf. T. quinqueloba approximates the midMiocene global cooling event, we infer that the beginning of
the seep-carbonate precipitation in the Vicchio Marls seems to
be related to this climatic event (Fig. 2). We assume that the
ascent and emission of methane-rich fluids may have been
triggered by the pressure drop due to the eustatic fall associated
with the Mi3b event, estimated in about 60 m (H ILGEN et alii,
2009). A drop of the hydraulic pressure on the plumbing
system during sea level lowering in glacial phase could
increase methane flows at seeps, inducing carbonate
precipitation.
SEEP-CARBONATES AS INDIC ATORS OF GLOBAL COOLING EVENTS
43
Fig. 2 - Geological map of the studied area showing the distribution of carbonate bodies and relationships with the Acme End (AE) of the T. cf T. quinqueloba.
REFERENCES
CONTI S. & FONTANA D. (1999) - Miocene chemoherms of the
northern Apennines (Italy). Geology, 27, 927-930.
HILGEN F.J., A BELS H.A., I ACCARINO S., KRIJ GSMAN W., RAFFI
I., S PROVIERI R., TURCO E. & ZACHARIASSE W.J. (2009) The Global Stratotype Section and Point (GSSP) of the
Serravallian Stage (Middle Miocene). Episodes, 32, 152166.
KIEL S. (2009) - Global hydrocarbon seep-carbonate
precipitation correlates with deep-water temperatures and
eustatic sea-level fluctuations since the Late Jurassic. Terra
Nova, 21, 279-284.
TEICHERT B.M.A., EISENHAUER A., BOHRMANN G., H AASESCHRAMM A., BOCK B. & LINKE P. (2003) - U/Th Systematics
and ages of authigenic carbonates from Hydrate Ridge,
Cascadia Margin: Recorders of fluid flow variations.
Geochimica et Cosmochimica Acta, 67, 3845-3857.
Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 44-45, 1 fig.
The subsurface record of hydrocarbon-charged fluids migrating
through the Messinian sedimentary column (Maiella Basin,
Central Italy)
ANNALISA I ADANZA (*), G IANLUCA SAM PALMIERI (*), GIANLUCA FRIJIA (**), PAOLA CIPOLLARI (*, °),
D OM ENICO COSENTINO (*, °), M ARCO MOLA (°)
Key words: Messinian, Maiella basin, fluid migration pathways,
brecciated buildups.
INTRODUCTION
During the Messinian Salinity Crisis of the Mediterranean Sea
(MSC), the Western Mediterranean margins recorded a fluid
migration event, possibly triggered by a major event of
dissociation of gas hydrates (P IER RE & ROUCHY , 2004; CLARI et
al., 2009; RYAN , 2009). In the Maiella Basin (Central Italy), in a
marginal foreland setting, similar seep-related phenomena took
place soon after the development of the Messian Erosional
Surface (MES), as evidenced by the informal Brecciated
Limestones unit, representing the early post-evaporitic (p-ev1)
record in the basin.
The investigation of the Brecciated Limestones unit was
performed using a suite of sedimentological and geochemical
techniques. The methodological approach chiefly encountered:
facies analyses, carried out at the outcrop scale and on polished
thin sections by means of optical, cathodoluminescence and
electronic microscopic devices; compositional analyses (Ca, Mg,
Mn, Fe, Sr); and stable isotopes analyses ( 13 C; 1 8O).
The main seep-related geobodies in the study area, resting
above the MES, are represented by: 1) widespread highly
brecciated buildups (intraformational breccias) and concretions;
2) minor patchy concretions embedded in the surrounding host
anoxic sediment; 3) localized metric fluid migration pathways
(while cemented chimneys were detected only at the microscale
in the host sediment). The fluid migration therefore presumably
developed with major fluxes along neoformed channels and
seepage through microchimneys in the host sediment.
The brecciated bodies are bedding-retentive, devoid of gravity
segregation and show scale-invariant brecciation. The related
_________________________
(*) Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre
(**) Institut für Erd- und Umweltwissenschaften, Universität Potsdam
(°) Istituto di Geologia Am bientale e Geoingegneria (IGAG-CNR), Area
della Ricerca Roma 1, Montelibretti.
limestones consist of pyrite bearing clotted microbialites,
microbrecciated at places, tar bearing (tar plagues and porefilling microtar), and accompanied by celestite.
Along with the most remarkable fluid migration features
represented by fluid migration pathways and microchimneys, the
integrated microfacies analysis also revealed the occurre nce of
fluidal microtextures and cross-cutting relationships.
The main fluid migration pathways are commonly typified by
channels filled by fluidized pelites. Nonetheless, the most
spectacular fluid migration structure, observed in a quarry
(Abbateggio Limestones Quarry, Fig. 1), is made up by
carbonates. There, within a major brecciated buildup, a
meandering brownish channelway mounding upward, at places
impregnates laterally and upwardly the surrounding host rock, at
other places cuts the main body. A single cylindrical calcitic
concretion collected from this channelway, yielding remarkable
microscale heterogenities and a complex history of cementation
and localized microbrecciation, was chosen to perform chemical
analyses, by microdrilling the most representative subsamples. Its
facies framework at a first glance is made up by two portions, a
pale cream core and a dark brown impregnated rim, separated by
a milling impregnation front: on one hand, the dark brown
impregnated portion is constituted by microbial fragments and
fluid microchannels, on the other hand, the pale cream portion is
typified by microbial fragments and pseudomorphs after gypsum
affected by corrosion-reaction rims. The resulting fabric put in
evidence that the brecciation event developed in multiple phases,
accompanied by oil impregnation. Compositional analyses of this
sample yielded preliminary results chiefly indicating: 1) a general
strong Sr enrichment (up to 10340 ppm), possibly pointing to
pristine aragonite phases or testifying the occurrence of Srenriched diagenetic fluids; 2) a local enrichment in Fe and Mg in
correspondence to cemented microveins.
The genetic relation of the Messinian Brecciated Limestones
in the Maiella area with a hydrocarbon seep paleoenvironment is
13
also definitely stressed by w
C data
(down to Their presumable origin from the
subsurface, within the sedimentary column, is herein inferred by
the occurrence of widespread autobrecciation accompanied by
fluid channels, together with the absence of chemosynthesisbased paleocommunities.
HYDROCARBON-CHARGED FLUIDS M IGRATING THROUGH THE MESSINIAN SEDIM ENTARY COLUMN
45
Fig. 1 - Fluid m igration pathway (Brecciated Lim estones unit; Abbateggio Limestones Quarry, Maiella Basin)
REFERENCES
CLARI P., DELA PIER RE F., M ARTIRE L. & CAVAGNA S. (2009) The Cenozoic CH4-derived carbonates of Monferrato (NW
Italy): A solid evidence of fluid circulation in the sedimentary
column. Marine Geology, 265, 167 184.
P IER RE C. & ROUCHY J.M. (2004) - Isotopic compositions of
diagenetic dolomites in the Tortonian marls of the Western
Mediterranean margins: Evidence of past gas hydrate
formation and dissociation. Chemical Geology, 205, 469-484.
RYAN W.B.F. (2009) - Decoding the Mediterranean salinity
crisis. Sedimentology, 56, 95 136.
Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 46-47, 2 figs., 1 tab.
The role of the Backshore/Foreshore length ratio in short-term
beach monitoring studies
SERGIO G. LONGHITANO (*)
Key words: beach equilibrium profile, backshore, foreshore.
INTRODUCTION
A straightforward conceptual method is proposed to
quantitatively assess the inter-annual tendency of retreatment or
advancement on microtidal beaches by using the
backshore/foreshore length ratio. This method is based on
measuring the profile of a beach when it passes through the
'transitional state' that separates the high- from the low-energy
season, period during which the morphological characteristics of
the beach are as similar as possible to its equilibrium profile.
The B/F length ratio method postulates that foreshore and
backshore lengths are equivalent in beaches that approximate to
their state of morphodynamic equilibrium (B/F~1) (Fig. 1A). A
backshore length exceeding the foreshore length is indicative of a
state of beach recession, with a B/F length ratio >1 (Fig. 1b).
When the foreshore length is greater than the backshore
length, the shoreline is advancing or, alternatively, it is
developing in a state of morphological confinement, i.e. due to
the presence of a sea cliff, with a B/F<1 (Fig. 1c). This empirical
method has been applied on a number of sand and gravel
microtidal beaches from the coasts of Basilicata, southern Italy.
The various beach states have been synthesised into seven
classes (I-VII), each identified from specific value intervals of
the B/F length ratio (Tab. 1).
RESULTS
The beach examples analysed in the present study pertain to
two very different coastlines, including sand, gravel and mixed
beaches. All these beaches lie in states of retreatment,
advancement or stability depending on highly varying local
conditions of sediment supply, morphological confinement and
exposure to dominant winds and waves (Fig. 2).
Fig. 1
Theoretical beach profiles defined on the basis of their respective
backshore and foreshore lengths.
_________________________
(*) Dipartimento di Scienze Geologiche, Università degli Studi della
E-Mail: [email protected]
Fig. 2 Beach profiles measured along the Tyrrhenian (a-c) and Ionian (d-g)
coas tline of Basilicata.
THE ROLE OF THE BACKSHORE/FORESHORE LENGHT RATIO IN SHORT-TERM BEACH MONITORING STUDIES
The Tyrrhenian beaches are confined or semi-confined
systems whose correspondent profiles have shown beaches that
nearly approximate to the equilibrium. This state is confirmed by
convex-up profile shapes and B/F lengt
indicate that backshore and foreshore have quasi equivalent
lengths (e.g., Acquafredda beach; fig. 2a). Profiles with B/F
length ratio <1 indicate advancing beaches or back-confined
evelop
if compared to the foreshore (e.g., Cersuta and Spiaggia Nera
beaches; figs. 2b and 2c). Thus, the beaches observed along the
Tyrrhenian coastline are included in the classes III and IV of the
Table 1.
In the Ionian examples, the B/F ratio increases from the
southern to the northern beaches, ranging from 1.75 to 4.11. The
advancing
receding
lower values, somewhat >1, express quasi -equilibrium states, and
this condition is also supported by the compound (concave- to
convex-up) 2D profiles of the Policoro and Terzo Cavone
beaches (Figs. 2f and 2g). These systems are in fact the bestpreserved beaches observed along the Ionian coast of Basilicata
where, although the shoreline is generally affected by a long-term
retreat, some beaches show short -term local advancement, due to
their position adjacent to river mouths. B/F ratios >>1 indicates
an extremely reduced foreshore and thus strong erosion for the
Metaponto and Lido Quarantotto beaches (Figs. 2d and 2e),
whose profiles maintain concave-up shapes also during the
transitional state from the winter to the summer season. The
beaches documented along this coastline are therefore included in
the classes V, VI and VII of the subdivision proposed in Table 1.
class
beach state
I
II
III
st r on g l y ad van ci n g
mo d erat el y ad v anci n g
sl i g ht l y ad v anci n g
stable
(neither advancing nor receding)
sl i g ht l y r e c e d in g
mo d erat el y rec edi n g
st r on g l y reced i n g
IV
V
VI
VII
47
B/F length
ratio
<0.5
0.5 0.8
0.8 - 1
1
1 -2
2 -3
>3
Tab. 1 - Subdivision into seven classes of advancing, receding and stable beaches on the base of their respective value
intervals of B/F length ratio.
FINAL REMARKS
SIGNIFICANCE OF THE B/S RATIO
The subdivision between backshore and foreshore detected in
the subaerial beach on the base of their genetic significance and
bi-dimensional volume, allow assessing quantitatively the state of
equilibrium or disequilibrium at the time of the profile
acquisition. Advancing, receding and stable beaches are
identified into seven classes of beach states on the base of their
respective values, or value intervals, of the B/F length ratio (Tab.
1
th
(Tab. 1).
The subaerial part of microtidal, wave-dominated beaches is
thus considered as key in the short-term evaluation of their state
of morpho-dynamic equilibrium. During the passage from the
high-energy to the lower-energy season, a beach crosses through
-equilibrium profile
whose shape lies between the two endpoints of the winter and
summer profiles. This intermediate state reflects more faithfully
the mean dynamics of a beach that results in the dimension of its
physical components forming the subaerial sector. Thus,
backshore and foreshore, if properly detected and bi dimensionally measured, can be consistently related to the state
of beach retreatment or advancement at the momen t of the
observation.
This very quick and low-cost method thus requires only one
profile measurement per year, which has to be strategically
acquired during the late spring, when a beach is expected to be in
preserve the tracks
of the advancing/retreating trend.
The problem of small footprints in paleoichnology related to
extramorphologies: new data from the Early Permian Erpetopus
LORENZO MARCHETTI (*), G IUSEPPE SANTI (**) & MARCO AVANZINI (°)
Key words: critical size, Early Permian, extramorphologies,
footprints, Erpetopus
but the use of new techniques and the discovery of new well
preserved specimens of this taxa in Italian Early Permian allow
us to bring new important data on this matter.
DISCUSSION
INTRODUCTION
The study of small footprints has always been difficult in
paleoichnology, because small size seems to be more strictly
linked to extramorphologies which could modify the true
morphology of footprints.
These extramorphologies have different origins and could be
caused by granulometry and wetness of sediment, or by different
kind of locomotion of trackmakers, so diagnostical characters
could be misunderstood.
Because of this, paleoichnolgists instituted a critical size (20
mm). Footprints smaller are too much affected by
extramorphologies to allow reliable data.
This fact, united with the technical difficulties to make
drawings and measures on these specimens explains the lack of
serious studies on footprints of this size, justifying in this way the
institution of ichnotaxa with very poor data.
In Early Permian paleoichnology this is the case of ichnotaxa
Erpetopus willinstoni (MOODIE, 1929), firstly described by the
ichnofauna of Castle Peak (Texas).
The lack of data brought some confusion, especially when
compared with the similar Camunipes cassinisi (CEOLONI et alii,
1987), found in Northern Italy.
Italian ichnologists justified the separation from Erpetopus
with a more distinctive rotation of V digit in Camunipes (S ANTI,
2007). American ichnologists rejected this supposition,
considering it only an extramorphological feature, frequent for
footprints under the "critical size".
This discussion appears to be "philosophical", because
reliable data to support one of the other hypothesis don't exist,
_________________________
(*) Dipartimento di Geoscienze, Università degli Studi di Padova, via
Gradenigo 6, 35131 Padova
(**) Dipartimento di Scienze della Terra
Studi di Pavia, via Ferrata 1, 27100 Pavia
, Unirsità degli
(°) Museo Tridentino di Scienze Naturali, via Calepina 14, 38100 Trento
A real problem in the study of footprints smaller than 20 mm
is the difficulty to find well-preserved specimen, with all the
features of footprints displayed.
Another is the measure of parameters, too small measures
tend to increase human errors.
In order to add reliable data on the knowledge of Erpetopus,
the study of well-preserved trackways was improved by the use
of photos and laser scanner techniques.
Imprints clearly modified by extramorphological effects were
not taken in account.
The study was focused on the re-examination of the holotype
of Camunipes cassinisi (specimen 10 pal_67, stored at Museum
Fig. 1 Particular of trackway 3 (specimen 12465). To notice the high and
regular divarication of digits, due to the soft mud. Scale bar 2 cm.
of Natural Sciences of Brescia) and an exceptional new specimen
with four complete trackways of Erpetopus (specimen 12465,
stored at Museum of Natural Sciences "E. Caffi" of Bergamo )
(Figs. 1, 2).
The holotype shows all the features of Erpetopus, plus
marked divarication between digits IV-V (65° in manus, 82° in
49
NEW DATA FROM THE EARLY PERM IAN ERPETOPUS
Fig. 2
Drawing of specimen 12465 (stored at Museum of Natural Sciences "E.Caffi", Bergam o). Scale bar 10 cm .
pes) and I-V (181° in manus, 161° in pes). Pes appears parallel to
midline and with central digits close to each other.
These features appear also in the specimen 12465, in
trackways 1 and 4, where we observe high divergences between
digits IV and V (51-72° in manus, 99° in pes) and digits I and V
(182-198° in manus, 193° in pes), and pes almost parallel to
midline.
This similitude appears to be not due to extramorphologies,
because we observe the same characteristics in different
substrates (silt in 10_pal 67 and mud in 12465), and in reptiles
with different speed of locomotion (trackmaker of the holotype is
slower) and size (holotype is bigger).
On the contrary, trackways 2 and 3 seems to vary their
features with speed of locomotion and wetness of substrate. The
high total divergence in trackway 3 (184° in manus and 180° in
pes) seems to be related with the difficult locomotion of the
reptile, which opened the digits to have more grip on the
ground. Trackway 2 instead has faster locomotion and appears
more digitigrade: this probably caused the very low total
divergence (76-89°) and low divergence between digits IV-V
(15-37°).
All these trackways seem to represent well the ichnotaxa
Erpetopus willinstoni, but distinctive features not related with
extramorphologies or ontogenetical stages are possible
(trackways 1-4 of 12465 and 10 pal_67). These features may be
due to different skeletal structures, in this case the presence of
Camunipes would be confirmed, but we need further data.
We can also see significant variations of parameters with
characteristics of substrate and speed in trackways 2-3, this
represents an extramorphological effect.
All these new data improve our knowledge on footprints
smaller than the critical size, proving that extramorphological
features are recognizable but not so striking to prevent serious
studies on footprints parameters, in particular for well-preserved
and long trackways.
REFERENCES
A VANZINI M., CEOLONI P., CONTI M.A., LEONARDI G., MANNI
R., MARIOTTI N., MIETTO P., M URARO C., NICOSIA U.,
SACCHI E., SANTI G. & SPEZZAM ONTE M. (2001) - Permian
and Triassic tetrapod ichnofaunal units of Northern Italy,
potential contribution to continental biochronology. Natura
Bresciana, Monografia, 25, 89-107.
BERNARDI M. & AVANZINI M. (2011) - Locomotor behavior in
early reptiles: insight from an unusual Erpetopus trackway.
Journal of Paleontology, 85 (5).
50
MARCHETTI ET ALII
CEOLONI P., CONTI M.A., MAR IOTTI N., M IETTO P. & N ICOSIA U.
(1987) - Tetrapod footprints from Collio Formation
(Lombardy, Northern Italy). Memorie di Scienze Geologiche,
39, 213-233.
HAUBOLD H. (1971) - Ichnia Amphibiourum et Retpiliorum
fossilium. Enciclopedia of Palaeoherpetology, 18, 1-124.
HAUBOLD H. (2000) - Tetrapodenfahrten aus dem Perm Kenntnisstand und progress 2000. Hallesches Jahrbuch für
Geowissenschaften, 22, 1-16.
HAUBOLD H. & LUCAS S.G. (2001) - Die Tetrapodenfährten der
Choza Formation (Texas) und das Artinsk-Alter der Redbed
Ichnofaunen des Unteren Perm. Hallesches Jahrbuch für
Geowissenschaften, 23, 79-108.
HAUBOLD H. & LUC AS S.G. (2003) - Tetrapod footprints of the
Lower Permian Choza Formation. Paläontologische
Zeitschrieft, 77, 247-261.
LEONARDI G. (1987) - Glossary and Manual of Tetrapod
Footprint Palaeoichnology. Depart. Nacional. Producao
Mineral, Brasilia. 117 pp.
M OODIE R. L. (1929) - Vertebrate footprints from the red bed of
Texas. American Journal of Science, 97, 352-368.
M OODIE R. L. (1930) - Vertebrate footprints from the red bed of
Texas II. Journal of Geology, 38, 548-565.
S ANTI G. & K RIEGER C. (2006) - A possible philetic relationship
between Camunipes and Erpetopus, ichnogenera of the
Lower Permian of Europe and North America. Giornate di
Paleontologia 2006, Trieste.
S ANTI G. (2007) - A short critique of the Ichnotaxonomic
Dualism Camunipes-Erpetopus, Lower Permian Ichnogenera
from Europe and North America. Ichnos, 14, 185-191.
S ARJEANT W.A.S. (1971) - Vertebrate tracks from the Permian
of Castle Peak, Texas Texas Journal of Science, 22, 344-366.
Geochemical characterization of sediment quality in the river
basin of the Rio Grande Quequén (Argentina)
EMANUELA M ARIN (*), LILIANA BEATRIZ TERUGGI (°), ELENA M ARROCCHINO (*) & CARM ELA VACCARO (*)
Key words: heavy metals, Rio Quequén Grande, river sediments,
XRF.
ABSTRACT
The hydrographic basin of Rio Quequén Grande (Argentine)
occupies 10.000 Km2 of the south-east area of the Buenos Aires
province, in the area "pampeana bonaerense", located in the
bigger area of Argentine loess, between latitude 20° and
40°South. The area of the basin is for the 97,5 % flat and, thanks
to the abundance of water resources and the fertility of the soil, it
has been interested by the intensification of agriculture which
made of it, in the last decades, one of the greater areas of food
supplying on worldwide scale (FARENGA et alii, 2005;
ROM ANELLI et alii, 2009; TERUGGI et alii, 2005b).
Through sedimentological, chemical and petrographic
analysis, this study provides data on the quality of river
sediments, from source to mouth of Rio Quequén Grande. A
comparison of the results with those obtained in the 2002
campaign, has allowed an assessment, after some time, about
problems of pollution due to storage of heavy metals such as Pb,
V and Zn, and salinity phenomena.
Geochemical analysis were obtained by X-ray fluorescence
(XRF) model ARL Advant'X spectrometer, while the
development took advantage of the use of GIS mapping, with use
of ArcGIS software, version 9.3.
Chemical data reflect the uniformity of the river sediments
derived by the rearrangement of aeolian sediments (loess
Quaternary Argentines) in an area prevalently flat and not
subject, from Mesozoic, to tectonic deformation events.
Despite this macro-uniformity, on scale of detail, it can be
observed variations in chemical and mineralogy composition, not
only due to the presence of the sequence of carbonate horizons,
_________________________
(*) Univers ità degli Studi di Ferrara, Dipartimento di Scienze della Terra,
Via Saragat 1, 44121 Ferrara (Fe)
(°)Università degli Studi di Firenze, Dipartimento di Ingegneria Civile ed
Ambientale, Via di Santa M arta 3, 50139 Firenze (Fi)
caliche, deposited during dry periods and persisted over time, due
to the precipitation of carbonate waters, but also for the
contributions of local deposits derived from the dismantling of
the Paleozoic basement, that outcrops on the edge of the basin in
the northern sector. Finally, some sediment samples, taken in the
vicinity of the greater built -up areas of the centers of Necochea,
Loberia and Quequén, showed an increase in metals that however
are included widely within the limits recommended by the
directives UNI and the Worldwide Organization of the Health.
Rio Quequén Grande morphology
From an environmental point of view, the impermeable beds
of caliche (Fig. 1) represent aquitards that, confining the
permeable sandy horizons, allow the development of the multi aquiferous system of the Pampa (TERUGGI et alii, 2005a).
Fig. 1
Carbonate beds, caliche.
These water resources serve not only for water supply, but also
for the development of internal marshy areas with fresh and
brackish waters, where protected plant and animal species can
find hospitality, including migratory birds (Fig. 2).
In Fig.3 we can see where, from the landscape of Argentine
loess, particularly in the north west area, are visible outcrops of
ancient Paleozoic basement.
52
MARIN ET ALII
REFERENCES
F ARENGA M.,TOM ÁS M., BERNASCONI M.V. & TERUGGI L.B.
(2005) - Implementación de un Sistema de Información
Geográfica en la Cuenca del Río Quequén Grande, Provincia
de Buenos Aires, Argentina: Desde la Generación de la
Cartografía Base hasta el Modelo Digital del Terreno.
Revista Cartogràfica, 80/81, 107-115. Instituto Panamericano
de Geografía e Historia, México.
Fig.2 - Flock of flamingos in a marshy area of the Argentina Pampas on the Rio
Quequén Grande.
ROM ANELLI A., QUIROZ LONDOÑO O.M., MARTINEZ D.E. &
BOCANEGRA E. (2009). - Caracterización hidrogeoquímica e
isotópica de la laguna La Salada y su relación con el
acuífero pampeano (Partido de Necochea, Provincia de
Buenos Aires). VI Congreso Nacional de Hidrogeología y IV
Seminario Hispano-Latinoamericano sobre temas actuales de
la Hidrología Subterránea, Actas, II, 601-610.
T ERUGGI L.B., M ARROCCHINO E., RAPTI-CAPUTO D. & V ACCARO
C. (2005a) - Geochemical characterization of bed sediments
of the Rio Quequén Grande Grande catchemnt, Argentina.
Geologica Romana, 38, 19 - 23.
T ERUGGI L.B., M ARTINEZ G.A, BILLI P. & PRECISO E. (2005b) Geomorphology and sediment transport in a very low relief
catchment:
R.
Quequén
Grande,
Argentina.
Geomorphological Processes and Human Impacts in River
Basins. IAHS Publ. 299, 154-160.
Fig.3 - Outcrops of the old basement.
The lagoon of Nador (Morocco): geochemical and petrographic
analysis of sediments and environmental conditions
EMANUELA MARIN (*), D RISS N ACHITE (**), MOHAM ED N AJ IH (°), G IORGIO ANFUSO (°°),
ELENA M ARROCCHINO (*) & CARM ELA V ACCARO (*)
Key words: ArcGis 9.3, anthropogenic pollution, lagoon of
Nador, heavy metals, XRF.
ABSTRACT
The Nador lagoon is one of the most important ports on the
coast of Morocco, and the second lagoon in North Africa by
extension (1115Km2). The lagoon is bordered to the north-west
by the volcanic products of the Gourougou volcano complex
(887 m asl) and south-east by the Jurassic carbonate succession
of marine environment belonging to the Complex of Kebdana
(932 m asl); the rest of the area around the lagoon is flat and is
characterized by arenaceous-pelitic deposits linked to the
Miocene and Quaternary magmatic activities.
The rocks outcropping in the hinterland are generally
characterized by low concentrations of metals, and are no
exception most of the volcanic rocks of the Gourougou Complex,
constituted mainly by latitic tuffs and trachytes, and rare basalts
and andesite of the promontory of Atalayoum that are not
volumetrically significant. A natural potentially impacting source
of heavy metals is located in the northwestern part of the lagoon,
where outcrops skarn with magnetite mineralization, widely
exploited since ancient times (EL ALAMI et alii, 1998; EL RHAZI
& H AYASHI, 2002; G ILLA et alii, 2004).
To fully describe the quality of Nador lagoon sediments, 49
samples along the banks and on the bottom of the lagoon were
gathered and their distribution was analysed and compared with
the patterns of water circulation in the lagoon.
The samples were subjected to petrographic and geochemical
characterization by x-ray Fluorescence (XRF) by means of an
ARL Advant X Spectrometer model. Furthermore, data
distribution was obtained using GIS tools (ArcGis software,
________________________
(*) Università degli studi di Ferrara, Dipartimento di Scienze della Terra, Via
Saragat 1, 44121 Ferrara (Italy)
(**) Faculté Polydisciplinaire de Larache. BP 745 Poste Principale, 92004,
Larache (M orocco)
(°) Centre régional de l'INRH à Nador B.P. 493 Nador principal, Nador
(M orocco)
version 9.3) and thematic maps were created.
The data showed that, despite the prevalence of contributions
from the Miocene-Quaternary sedimentary sequences,
characterized by low content of heavy metals, the samples
contained high quantities of heavy metals, evidencing diffuse
human related pollution problems.
Since sediments are predominantly composed by quartz and
carbonate, the content in metals is extreme ly low and the only
natural source of pollution is attributable to the mobilization of
metals contained in ancient iron mines dumps located along the
banks of the Gourougou Complex. Such sediments are exposed
to weathering and leaching processes that produce in nearby
areas the largest observed concentrations of iron, in this sense
enhancing the importance of the anthropogenic pollution versus
the natural one. Specifically, the points with higher rates in
metals are found near the town of Nador, the main urban centre
in the area. High concentrations are also observed south of
Nador, close to the plain of Bou Areg, densely tilled and devoted
to agricultural purposes carried out using massive quantities of
fertilizers and unpurified wastewater for irrigation. It is not clear
however if the Promontory of Atalayoum, located in the north of
the lagoon, constitutes a natural supply area of heavy metals. In
this sense, further investigation should be carried out to fully
understand the role of basic volcaniclastic deposits in the
pollution linked to Cr, Ni, V and Co. However, it is possible to
state that the main anomalies concern Cu, Fe, Pb and Zn, whose
contributions are typical of human impact. Along the banks of
the Nador lagoon, are also located the towns of Beni Enzar and
Kariet Arkmane, characterized by a dramatic increase in
population over the past 30 years, because of the opportunities
offered by the business linked to the construction of summer
houses, hotels, etc. as well as to the enlargement of the local port.
The rapid increase in population was not accompanied by the
realization of services and, most importantly, there are no
appropriate treatment facilities for wastewater, with the
associated environmental problems.
In addition, analyzing the obtained maps using a geochemical
point of view, two distinct areas are observed and linked to water
circulation patterns within the lagoon. It is possible to observe a
preferential current along the banks and a secondary current that
splits into two parts in the middle of the lagoon, this being related
54
MARIN ET ALII
Fig. 1
Distribution of Pb concentrations in the lagoon of Nador: map was created using IDW interpolation and software ArcGIS 9.3.
to the very specific geomorphologic characteristics of the lagoon;
it may be also noticed that neither the streams that flow into the
lagoon nor the inlet to the Mediterranean Sea create appreciable
convective motions.
The internal flows of the lagoon have low intensity; this fact
and the shallow water depths determine an insufficient water
supply and oxygenation (BLOUNDI et alii, 2008). For this reason,
in recent years, it was started the building of an artificial inlet
with the Mediterranean Sea. Specifically, the main aim of the
construction of the Canal is to improve the water quality of some
parts of the lagoon and mitigate the environmental problems,
which were confirmed by the presented investigations. It would
be useful, in a near future, to carry out further researches to
evaluate the effects of the new inlet on water circulation and
associated environmental problems.
In conclusion, the study outlines how the quality of bottom
sediments of Nador lagoon is deeply affected by the increasing
anthropogenic pressure and the geochemical intrinsic
characteristics of local sediments rich of heavy metals.
FIGURES
In Fig.1 example of thematic map describing the distribution of
elements in the Nador lagoon: the areas characterized by a
greater amount of Pb are located close to the cities of Nador and
Beni Anzari and in the northern area along the banks of
Gourogou Complex. Furthermore, the distribution of the
presented element reflects the geomorphologic characteristics
and the water current patterns in the lagoon.
REFERENCES
BLOUNDI M.K., FAURE P. & D UPLAY J. (2008) - Organic
contamination identification in sediments from a
Mediterranean coastal ecosystem: The case of the Nador
lagoon (Eastern Morocco). C. R. Geoscience, 340, 840 - 849.
E L A LAMI M., M AHJOUBI R., D AM NATI B., KAM EL S., ICOLE M.
& TAIEB M. (1998) - Sédimentologie et géochimie organique
des sédiments superficiels de la lagune de Nador (Maroc
nord oriental). J. Africain Earth Sci., 26, 249 -259.
E L RHAZI M. & HAYASHI K.(2002) - Mineralogy, Geochemistry,
and Age Constraints on the Beni Bou Ifrour Skarn Type
Magnetite Deposit, Northeastern Morocco. Resource
Geology, 52, 25 - 39.
G ILLA R.C.O., APARIC IO A., EL AZZOUZIC M., HERNANDEZD J.,
THIRLWALLA M.F., BOURGOISE J. & MARRINERA G.F. (2004)
- Depleted arc volcanism in the Alboran Sea and shoshonitic
volcanism in Morocco: geochemical and isotopic constraints
on Neogene tectonic processes. Lithos, 78, 363 - 388.
Facies analysis and sequence stratigraphic interpretation of sandy
deposits in the central part of the Siena Basin (Italy)
I VAN MARTINI & F ABIO SANDRELLI (*)
Key words: deltaic deposits, nearshore, Siena basin, sequence
stratigraphy
The Siena Basin is one of the post-collisional basins of the
inner Northern Apennines, a collisional belt formed during the
Cenozoic in response to the interaction between the Adria and
the Corso-Sardinian microplates (CARM IGNANI et alii, 2001
and references therein). The structural origin and evolution of
this basin is still a matter of debate (see BROGI, 2011 for a
comprehensive review). Regardless of its structural origin, the
Siena Basin was interested by a continental and marine
sedimentation during Miocene and Pliocene time. In detail, the
Pliocene marine succession is represented by nearshore marine
deposits (sands and conglomerates) passing basinward to
offshore silty clays. These deposits are generally considered as
the expression of a single transgressive-regressive cycle (early
Zanclean-late Piacenzian), characterized by a diachronous
transgression from the southern to the northern sectors of the
basin (BOSSIO et alii, 1992).
A striking feature of the Siena Basin is the presence of thick
(up to 80-100 m) sand-dominated bodies cropping out in its
central sector. They were interpreted by the first authors who
studied the Siena Basin (PANTANELLI , 1880; SIGNORINI, 1966)
as the expression of a generic nearshore deposition. GANDIN &
SANDRELLI (1992) reinterpreted the same deposits as turbiditic
lobes related to the re-sedimentation of nearshore sands
through gravity-driven processes, caused by sin-depositional
tectonic activity.
In this contribution these sandy bodies have been
investigated focusing on component sedimentary facies and
architectural geometries, integrated with micropalaeontological
investigations in order to establish their depositional age and
the palaeo-environmental conditions.
The obtained results show that they are organized in
coarseningand
shallowingupward
successions,
_________________________
(*) Dipartim ento di Scienze della Terra, Università di Siena, via Laterina 8,
53100, Siena.
representative of a deltaic deposition (i.e. shallow-water
deltas). A typical sequence is composed of basal offshore mud,
transitionally passing to alternations of muddy and sandy beds
overlaid by thick sand bedsets. The latter are d ominantly
composed of ungraded, structureless or plane-parallel
laminated fine-grained sands. Subordinate normal graded
(medium to fine-grained) sand beds, characterized by slight
erosional bases, are also present. Continental plant fragments
are common in both facies, testifying the genetic relation with
land-derived flows. The sandy beds show tabular or slightly
convex-up geometries at outcrop scale; lateral pinching-out and
compensational stacking patterns are locally present.
These deltaic deposits are the expression of two phases of
deltaic deposition (the first one during the late Zanclean, the
second one in the Piacenzian) separated by transgressive
offshore mud. Therefore, they can be interpreted as lowstand
deltas formed in response to two base-level falls. The same
subaerial unconformities bounding depositional sequences
(MARTINI et alii, 2010, 2011), thus allowing large scale
correlations across the basin.
REFERENCES
BOSSIO A., CERR I R., COSTANTINI A., GANDIN A.,
LAZZAROTTO A., M AGI M., M AZZANTI R., M AZZEI R.,
SAGRI M., SALVATOR INI G. & SANDRELLI F. (1992) I Bacini
distensivi Neogenici e Quaternari della Toscana. In: 76a
Riunione
Estiva
SGI-Convegno
SIMP,
Guida
Società Geologica Italiana, 198-227
BROGI A. (2011) - Bowl-shaped basin related to low-angle
detachment during continental extension: The case of the
controversial Neogene Siena Basin (central Italy, Northern
Apennines). Tectonophysics, 499 (1-4), 54-76.
CARM IGNANI L., D EC ANDIA F.A., DISPERATI L., FANTOZZI P.L.,
KLIGFIELD R., LAZZAROTTO A., LIOTTA D. & MECCHERI M.
(2001) - Inner Northern Apennines. In: G.B. Vai & I.P.
Martini (Eds) - Anatomy of an Orogen. The Apennines and
Adjacent Mediterranean Basins, 197-214.
56
MARTINI & SANDRELLI
GANDIN A. & S ANDRELLI F. (1992) - Caratteristiche
sedimentologiche dei corpi sabbiosi intercalate nelle
argille plioceniche del Bacino di Siena. Giornale di
Geologia, 54, 55-65.
(2010) The Pliocene deposits of the southeastern Siena
Basin (
-Montisi area, Tuscany, Italy)
revised through allostratigraphy. In: Abstract book GeoSed
2010, Torino, 47.
MARTINI I., ALDINUCCI M., F ORESI L.M., M AZZEI R. &
SANDRELLI F. (2011) - Geological map of the Pliocene
succession of the Northern Siena Basin (Tuscany, Italy).
Journal of Maps, 193-205, doi:10.4113/jom.2011.1176.
P ANTANELLI D. (1880)
Gli strati litorali e salmastri del
Pliocene inferiore in Toscana. Atti Soc. Tosc. Sc. Nat.,
Proc. Verb. Vol. II, Pisa.
MARTINI I., ARRAGONI S., A LDINUCCI M. & SANDRELLI F.
S IGNORINI R. (1966) I terreni neogenici del Foglio Siena.
Boll. Soc. Geol. It., LXXXV, Roma.
Coral patch reef in a Burdigalian mixed carbonate-siliciclastic
coastal system (Cala Paraguano, Corsica)
ANDREA M AZZUCCHI & LAURA TOM ASSETTI (*)
Key words: Burdigalian, coastal system, corals, carbonatesiliciclastic mixing, Corsica.
This study concerns facies analysis of a Burdigalian coralrich mixed carbonate-siliciclastic system developed in the
western part of the Bonifacio Basin (Cala Paraguano, southern
Corsica). The Miocene marine sediments of this basin are
divided in two formations: Cala di Labra Fm. and Bonifacio
Fm. (F ERRANDINI et alii, 2002). The deposits of Cala di Labra,
related to the Burdigalian transgression, overly the hercynian
basement and are characterized by different coral-rich episodes
(GALLONI et alii, 2001; FERRANDINI et alii, 2002). Cala di
Labra Fm., cropping out at Cala Paraguano, shows a very good
exposure and offers the opportunity to report an example of
coral patch reef development in costal settings, dominated by a
mixed carbonate-siliciclastic sedimentation.
At Cala Paraguano, the sea-cliff exposure allowed us to
trace the stratigraphic surfaces, and identify stratal and coral
bioconstruction geometries. The description of coral
bioconstructions follows the terminology proposed by
INSALACO (1998). Thin section analysis permitted a better
definition of the biotic constituents. Finally, the carbonate
content of the samples was determined through gasometric
analysis using a Dietrich-Fruhling calcimeter.
This deposits were assigned to four sedimentary facies: a)
coral rudstone to floatstone in a siliciclastic matrix, b) coral
floatstone, c) coral domestone, d) maerl.
The coral rudstone to floatstone in a siliciclastic matrix is a
roughly bedded facies gently dipping (up to 10°) to SW. Coral
colonies are abundant in this facies, although they are mostly
not in life position. Corals are predominantly small in size,
with massive-globular morphology, although subordinate plate
_________________________
(*) Dipartimento di Scienze della Terra, La Sapienza Università di Roma, P.
Aldo M oro 5, I-00185 Roma.
[email protected]
and rare branching forms are also present. The inter-coral
sediment is a hybrid sandstone with bivalves, ec hinoids and
subordinate small benthic foraminifera, red algae and
gastropods.
The coral floatstone facies shows a massive to crude
stratification, and locally a slightly ondulate lamination. Coral
colonies are both in life position and reworked, often dispersed
in the sediment, which is a grainstone-packstone consisting of
abundant geniculate and non geniculate red algae fragments
and subordinate bioclastic constituents.
Coral domestone facies is characterized by coral colonies
(Porites, subordinate Tarbellastrea and faviids) in living
position. The dominant massive-globular and the less common
platy colonies grow close one over another forming a dense
bioconstruction, which results in a build-up of up to 5 m in
height. The inter-coral sediment is represented by a
moderately-poorly sorted bioclastic floatstone to packstone.
The main components are red algae, bivalves, echinoids and
larger benthic foraminifera (Miogypsina and subordinate
Amphistegina).
The maerl facies consists of poorly sorted floatstone to
rudstone, in a packstone matrix, composite parallel beds,
characterized by planar to slightly ondulate internal
stratification. Red algae (Spongites, Sporolithon and
melobesoids), often intensively bored by clionid sponges, are
the major constituents of thi s facies. Other components include
bryozoans, pectinids, serpulids, larger benthic foraminifera
(Miogypsina, Amphistegina and rare Heterostegina) and
echinoids.
The reconstructed depositional model shows a wedgeshaped profile along the downdip direction. The coral rudstone
to floatstone in a siliciclastic matix facies developed in a highly
energetic environment under elevated terrigenous input,
whereas the coral domestone facies was originated by small
size patch reef in a moderate energetic and well-lit zone. These
coral bioconstruction pass basinward to the coral floatstone
facies. The more distal facies is represented by the maerl
facies, which indicates deeper and less energetic environment
in oligophotic condition.
58
MAZZUCCHI & TOMASSETTI
REFERENCES
FERRANDINI M., GALLONI F., BABINOT J.F. & MARGEREI J.P.
(2002) - La plateforme carbonatée burdigalienne de
Bonifacio
(Corse
du
Sud):
microfaunes
et
paléoenvironnements. Revue de Micropaleontologie, 45,
57-68.
G ALLONI F., CORNEE J.J., REBELLE M. & F ERRANDINI M.
(2001) - Sedimentary anatomies of early Miocene coral
reefs in South Corsica (France) and South Sardinia.
Géologie Mediterranéenne, 28, 73-77.
I NSALACO E. (1998) - The descriptive nomenclature and
classification of growth fabrics in fossil scleractinian reefs.
Sedimentary Geology, 118, 159-186.
Mysterious Triassic ammonoids of Recoaro area: state of art
PAOLO MIETTO , STEFANO MANFRIN (*)
basin, Alpine basis.
During the 1800 and the beginning of 1900, several germanspeaking geologists (such as Beyrich, Mojsisovics, Tornquist)
studied the Recoaro area, describing important ammonoid fauna
characterized also by peculiar species of the Germanic B asin.
This fauna, most of which is coming from the Nodosus
Formation, consists in problematic species that are affected by
provincialism and thus difficult to interpret under the taxonomic
and biostratigraphic point of view. Unfortunately, most of the
collected materials have been destroyed during the II World War,
precluding a modern taxonomic revision. One of the unravelled
_________________________
(*) Dipartimento di Geoscienze, Università degli Studi di Padova, via G.
Gradenigo, 6, 35131 Padova
[email protected]
questions was related to the presence of a german ceratitoids in
the alpine ammonoid association. Recent field work in the
Recoaro area tried to complete the lost collection but only not
well preserved specimens have been collected. Fortunately, an
unexpected ammonoid fauna from the Recoaro area has been
found in a small and old collection stored at the Museo
Geologico e Paleontologico of the University of Padova. This
small collection permitted to solve the open question since a
typical species belonging to the Germanic Muschelkalk has been
documented within the Alpine Basin. This finding is important
for the Triassic ammonoid taxonomy and biostratigraphy, and
plays an important role for the Triassic sequence stratigraphy.
Upper Miocene Lower Pliocene provenance changes in the
Venetian Foreland
G IOVANNI MONEGATO (*) & CRISTINA STEFANI (**)
Key words: Provenance, alluvial deposits, Venetian Basin,
Upper Miocene.
INTRODUCTION
The Upper Miocene clastic wedge of the Venetian Basin
represents a regressive foreland succession recording the
Neoalpine phase of the eastern Southalpine Chain, during the
Serravallian-Messinian time bracket (CASTELLARIN et alii,
2006). The succession encompasses the Vittorio Veneto
sandstone, related to offshore environment, and the Montello
conglomerate, mostly made of continental sedimentary units
(M ASSARI, 1975; MASSARI et alii, 1986); the latter is
interpreted as the filling of the foreland during the acme of the
Neoalpine tectonic phase (M ELLERE et alii, 2000). The facies
associations, as well as the stratigraphy of the succession, was
recently reviewed (STEFANI et alii, 2010) in order to delineate a
better chronology of the sedimentary wedge and the correlation
with comparable sedimentary units outcropping in the Friulian
piedmont plain (ZANFERRARI et alii, 2008).
The Upper Miocene succession of the Venetian Basin
reflected the uplift and the progradation of the chain at its back,
so changes in the drainage network within the chain are marke d
by variations in sedimentary supply and provenance in the
fluvial deposits of the related the foreland basin. Early analyses
on pebbles (MASSAR I et alii, 1974) and on sandstones
(STEFANI , 1987) were realized in the Montello conglomerate
separating the unit between the Tortonian interval from the
Messinian one, according to M ASSARI (1975) age boundary;
only in M ASSAR I et alii (1994) a rough analysis on pebbles
was performed along a composed stratigraphic section. The
present study provides a new analysis on sandstones realized
considering four main stratigraphic sections (marked in Fig.
1), in which some different units have been distinguished in
the Tortonian-Messinian interval (STEFANI et alii, 2010).
These analyses yielded a more detailed reconstruction on the
drainage network feeding the Venetian Basin during the
cited interval, compared also with samples of Pliocene age.
METHODS
Fig. 1
Sketch of the study area
_________________________
(*) CNR - Istituto di Geoscience e Georisorse, Torino
(**) Dipartimento di Geoscience, Università degli Studi di Padova
This work is part of the Post-doc project CPR095351/09, Università degli
Studi di Padova.
One hundred and five suitable sandstone and sand
samples were studied for quantitative analyses. They are
relative to four stratigraphic sections, while data for present
rivers have been included for comparison after MONEGATO
et alii (2010).
The entire sandy fraction (0.0625-2 mm) was examined.
It was split and impregnated in an epoxy resin according to the
methodology described by GAZZI et alii (1973). Thin sections
were stained with alizarine-red solution for the determination
of the carbonate phases. Sandstone and sand point counts were
carried out following Gazzi -Dickinson procedures (INGERSOLL
et alii, 1984). For each sandstone section 500 points were
counted, 300 for the sand ones, using 0.5 mm grid spacing. In
UPPER MIOCENE
61
LOWER PLIOCENE PROVENANCE CHANGES IN THE VENETIAN FORELAND
order to improve the information, a separate count of almost
200 rock fragments was performed on each sample. The results
were plotted in ternary diagrams and compared with the
existent databases (GAZZI et alii, 1973; G ARZANTI et alii, 2006;
MONEGATO et alii, 2010).
RESULTS
5) The more recent Pliocene deposits, making group 5, are
mostly related to the western sector and the composition points
to an increase of fine-grained lithic fragments. Compared to
the present day rivers, the analyses indicate that from the
exhumation of the Southalpine basement onwards, the Brenta
River catchment became to take shape, as shown by the
comparison to the present sediments (G ARZANTI et alii, 2006;
M ONEGATO et alii, 2010). In the eastern sector, the lack of a
The results were plotted in ternary diagrams (Fig. 2), which
evidence petrofacies clusters. Five groups were distinct from
the stratigraphic succession, after STEFANI et alii (2010), and
represented in figures 2 and 3.
1) The oldest of Tortonian age related to the Vittorio
M
10 0
1
2
3
4
5
Brenta
Piave
25
75
Q+F
Q+F
50
10 0
1
2
3
4
5
Brenta
Piave
25
75
1
2
3
4
5
50
75
25
50
10 0
50
10 0
75
50
25
V
S
75
25
10 0
10 0
L
75
50
25
CE
L
CE
Fig. 2 Ternary diagram of s andstone samples. Q: quartz, F: feldspars, L:
fine-grained
lithic
fragments;
CE carbonate
fragments.
1: m, iddle
Fig. 2 Ternary
diagram
of sandstone
samples. lithic
Q: quartz,
F: feldspars
L:
Tortonian;
upperfragments;
TortonianCE
keycarbonate
level; 3: upper
Tortonian; 4: M essinian; 5:
fine-grained2:lithic
lithic fragments.
Pliocene (see text for details).
Veneto sandstone and the basal Montello conglomerate, in this
the petrofacies is well defined despite samples collected in
different locations.
2) The second group is related to the horizon in which
clasts of the Southalpine basement appear. This is well defined
in the western portion of the study area, interested by an
important supply from the basement outcrop area (M ONEGATO
et alii, 2010), while it is smoothed towards the east.
3) The third group is related to a series of fluvial
sedimentary bodies interbedded with transitional of marine
facies. In this group differentiations in distinct source areas
become clearer. The western source is distinguishable for the
higher content in quartz and fine-grained lithic fragments.
4) The subdivision is maintained in the fourth group, which
is related to the spread of the alluvial fans in the piedmont
plain. A palaeoBrenta provenance is related to a different
petrofacies (Fig. 2), rich in quartz and fine-grained lithic
fragments.
Fig. 3 Ternary diagram of the lithic component. M: metam orphic rock
fragments , V: volcanic r.f., S: sedimentary r.f.. (see caption of figure 2 for
color legend).
clear trend and the overlapping to the present composition of
the Piave River suggest a steady catchment within the
Dolomitic area.
Taking into consideration the lithic fragments (Fig. 3),
these show how the boundary area between modern Brenta and
Piave catchments had an independent development during the
Messinian-Pliocene time. Actually, the presence of acidic
volcanic fragments (Permian rhyolites) together with low-grade
basement rocks points to the similarity to the present Cismon
Stream. This can be observed in pebble composition in the
correspondence of the modern outlet of the Piave valley.
REFERENCES
CASTELLARIN A., N ICOLICH R., F ANTONI R., CANTELLI L.,
SELLA M. & SELLI L. (2006) - Structure of the lithosphere
beneath the Eastern Alps (southern sector of the
TRANSALP transect). Tectonophysics, 414, 259-282.
G ARZANTI E., ANDÒ S. & VEZZOLI G. (2006) - The continental
crust as a source of sand (Southern Alps cross section,
northern Italy). J. Geol., 114, 533 554.
62
MONEGATO ET ALII
GAZZI P., ZUFFA G.G., G ANDOLFI G. & PAGANELLI L. (1973) Provenienza e dispersione litoranea delle sabbie delle
inquadramento regionale. Mem. Soc. Geol. It., 12, 1 37.
INGERSOLL R.V., BULLARD T.F., FORD R.L., GRIM M J.P.,
P ICKLE J.D. & SARES S.W. (1984) - The e ect of grain size
on detrital modes: a test of the Gazzi Dickinson pointcounting method. J. Sediment. Petrol., 54, 103 116.
(Italy). In: M. Marzo and C. Puigdefabregas (Eds) Alluvial Sedimentation Spec. Publ. Int. Ass. Sediment., 17,
501-520.
M ELLERE D., STEFANI C. & ANGEVINE (2000) - Polyphase
tectonics through subsidence analysis: the Oligo-Miocene
Venetian and Friuli Basin, north-east Italy. Basin Res., 12,
159-182.
MASSARI F. (1975) Sedimentazione ciclica e stratigrafia del
Tortoniano superiore Messiniano tra Bassano e Vittorio
Veneto. Mem. Ist. Geol. Min. Univ. di Padova, 31, 1-56.
M ONEGATO G., STEFANI C. & ZATTIN M. (2010) - From
present rivers to old terrigenous sediments: the evolution of
the drainage system in the eastern Southern Alps. Terra
Nova, 22, 218-226.
MASSARI F., ROSSO A. & RADICCHIO E . (1974) - Paleocorrenti
e composizione dei conglomerati tortoniano-messiniani
compresi tra Bassano e Vittorio Veneto. Mem. Ist. Geol.
Min. Univ. di Padova, 31, 1-20.
S TEFANI C. (1987) - Composition and provenance of arenites
from the Chattian to Messinian clastic wedges of the
Venetian foreland basin (Southern Alps, Italy). Giornale di
Geologia, 49, 155-166.
MASSARI F., GRANDESSO P., STEFANI C. & JOBSTRAIBIZER,
P.G. (1986) - A small polyhistory foreland basin evolving in
a context of oblique convergence: the Venetian basin
(Chattian to Recent, Southern Alps, Italy). In: P.A. Allen
and P. Homewood, (Eds) - Foreland Basin Spec. Publ. Int.
Ass. Sediment., 8, 141-168.
S TEFANI C., M ONEGATO G., GRANDESSO P. & FORNAC IARI E.
(2010) - Reconciling the Tortonian-Messinian stratigraphy
of the Venetian foothills (NE Italy). GeoSed 2010, Torino,
19-25 settembre 2010.
MASSARI F., MELLERE D. & DOGLIONI C. (1994) - Cyclicity in
non-marine foreland-basin sedimentary fill: the Messinian
conglomerate-bearing succession of the Venetian Alps
ZANFERRARI A, AVIGLIANO R, G RANDESSO P, MONEGATO G,
PAIERO G, POLI ME & STEFANI C. (2008) - Note illustrative
APATRegione Autonoma Friuli Venezia Giulia.
Provenance of the Pleistocene fluvial deposits of the Ambra valley
(central Tuscany): implication for palaeo-drainage evolution
G IORGIA MOSCON (*)
Key words: fluvial deposits, provenance analysis, Northern
Appennines, Pleistocene .
ABSTRACT
The Plio-Pleistocene evolution of the most main Tuscan rivers
has been outlined in 1981 by Bartolini and Pranzini. Those
Authors showed as the Chianti Ridge at the boundary between
the Siena and Upper Valdarno B asin (central Tuscany) was a key
area for the Arno River drainage evolution. During the Middle
Pliocene the Arno River flowed almost southward, from the
Casentino to the Val di Chiana Basin. Subsequently, between
Pliocene and Pleistocene, the Upper Valdarno Basin subsidence
induced a piracy of the Arno river, which started to flow toward
NE along the present-day tract. Recent studies (ALDINUCCI et
alii, 2007; BOSCAINI 2011) showed the Chianti Ridge at the
boundary between the Siena and Upper Valdarno Basin was
drained by a Plio-Pleistocene southward -flowing fluvial system
hosted in a N-S trending valley. Palaeohydrological studies
(RONER, 2011) showed that the paleo-discharge of this river was
comparable to that of the modern Arno River.
The present study focuses on the composition of sandy and
gravelly fluvial deposits, and aims at defining the meaning of this
fluvial system in the frame of the paleodrainage evolution of the
area.
The study paleovalley was cut both on pre-Neogene bedrock
forming the Chianti Ridge and Pliocene marine to transitional
deposits of the Siena Basin. The infill have been dated at PlioPleistocene through regional geological evidences and fossil
content (ALDINUCCI et alii, 2007).
The valley fill consists of two intervals separated by an
erosive surface. The upper interval is cut in the lower one in the
northern and southern part of the study area. The lower interval
(40 m thick) is mainly made of gravels. The upper interval is
about 35 m thick and deposited across a sin-sedimentary normal
fault dipping toward NE (i.e. upstream). This interval consists of
organic-rich mud containing isolated channels passing
downstream into channelized gravels.
_________________________
(*) Dipartimento di Geoscienze, Università degli Studi di
Padova, via G. Gradenigo, 6, 35131 Padova, Italy
The present study focuses on the composition of sandy and
gravelly deposits of the upper interval.
Both these fractions appear to be rich in calcareous
lithologies, which are relatively poorly exposed along the Chianti
Ridge. In particular, the sandy fraction, which belongs to the
sensu FOLK, 1974; ZUFFA , 1980) is rich in
calcareous and marly clasts. Such a composition is very similar
to that of the sand forming the Pleistocene terraces of the Arno
River in the Upper Valdarno Basin.
Compositional data highlight that the study paleovalley
probably drained an area which was significantly wider than the
Chianti Ridge. A preliminary hypothesis would suggest a
correlation between the study drainage and the Paleo-Arno
system, which passed through the study area before to enter the
Upper Valdarno Basin.
REFERENCES
A LDINUCCI M., GHINASSI M. AND S ANDRELLI F. (2007) Climatic and tectonic signature in the fluvial infill of a late
Pliocene valley (Siena Basin, Northern Appennines, Italy).
SEPM, Journal of Sedimentary Research, 77, 398-414.
BARTOLINI C., P RANZINI G. (1981) - Plio-Quaternary evolution of
the Arno basin drainage. Z. Geomorph. N.F., 40, 77 91.
BOSCAINI N. (2011) - I depositi plio-pleistocenici di valle incisa
del Torrente Ambra (Toscana, Italia: interazione tra tettonica
e sedimentazione). Master Thesis, unpublished.
CIPRIANI C . (1961) - Ricerche sulle arenarie:III. La composizione
mineralogica di una serie di rocce della Formazione del
Macigno. Period. Mineral. 30, 23 59.
F OLK R.L. (1974) - The petrology of sedimentary rocks. Austin,
Tx, Hemphill Publishing Co. 182.
RONER M. (2011) - I depositi ghiaiosi pleistocenici del paleoArno (Toscana centrale, Italia): facies sedimentarie ed
architetture deposizionali. Master Thesis, unpublished.
ZUFFA G.G. (1980) - Hybrid arenites: their composition and
classification. Jour. Sed. Petrology, 50, 21-29.
Study and interpretation of some uncertain Triassic lithosomes at the base of
the Lagonegro Basin succession: a key for a correct reconstruction of the
Monte Facito Formation (Basilicata, southern Italy)
GIUSEPPE PALLADINO & GIACOM O PROSSER (*)
Key words: Gravity-induced deposits, Lagonegro Basin, Monte
Facito Formation, southern Italy.
discuss the tectono-stratigraphic significance of the Monte Facit o
Formation.
THE MONTE FACITO FORMATION
INTRODUCTION
In passive margins gravity-induced deposits are usually
recognized at the hangingwall of the main extensional faults.
These sediments often form thick bodies mostly composed of
breccia and conglomerates, olistoliths, submarine slides etc.
Commonly, after these rocks are incorporated into the orogens,
their sedimentary nature is difficult to recognize due to the
tectonic overprinting taking place during thrust activity. In fact,
intense deformation in the correspondence of the main
detachment levels may completely obliterate the original
sedimentary fabric producing rock bodies with a block-in-matrix
structure, interpreted as mélanges, broken formations,
olistostromes, etc.. Consequently, discrimination of gravitydriven structures from those induced by later contractional
tectonics is difficult. These problems are commonly encountered
when a complete stratigraphic reconstruction of the Monte Facito
Formation is attempted. This Triassic unit, largely cropping out
at the base of the Lagonegro Basin succession, was deposited
during the first stages of the Africa-Europe continental separation
and later, during Miocene, was affected by contractional
deformation during the development of the southern Apennine
chain. As a consequence of this complex tectono-sedimentary
history, the Monte Facito Formation consists of a series of
equivocal, deformed lithosomes that can be interpreted to have
either a tectonic or sedimentary origin. A significant example of
this is provided by the genesis of pebbly mudstones,
(paraconglomerate in the current literature), that have been
interpreted both as Triassic gravity-flow deposits or as sheared
levels related to contractional Miocene shear zones. A detailed
study performed in well-exposed series of the Monte Facito
Formation gave us the opportunity to document the
sedimentological nature of these uncertain lithosomes and to
_________________________
(*) Università degli Studi della Basilicata, Dipartimento di Scienze
Geologiche, via dell'Ateneo Lucano, 10 - 85100 POTENZA
The Monte Facito Formation represent a very peculiar
stratigraphic unit of the southern Apennine thrust -belt. It records
the first stages of the Africa -Europe continental rifting of EarlyMiddle Triassic age (SCANDONE , 1967; DONZELLI & CRESCENTI ,
1970, WOOD, 1981; CIARAPICA et alii, 1990; P ANZANELLI
F RATONI, 1991; MARSELLA et alii, 1993; CIARAPICA & PASSERI ,
2000) (Fig 1). In particular, following Wood (1981), the
deposition of the Monte Facito Formation records the initial
break-up and the late extensional collapse of a previously
emerged basement. Following this evolutionary scheme, the
Monte Facito deposits can be subdivided, at first approximation,
into two informal categories of lithofacies:
- the first consists of Scithian to Anisian shallow-water
lithofacies, essentially made up of massive carbonate build-ups,
shelf rythmites and wave influenced shoreface sands
(SCANDONE , 1967; DONZELLI & CRESCENTI , 1970, WOOD , 1981;
CIARAPICA et alii, 1990; PANZANELLI FRATONI, 1991; CIARAPICA
& PASSERI , 2000);
- the second consists of deep-water lithofacies, made up of
gravity-induced deposits alternating with-fine-grained sediments
settled by fall -out mechanisms. In particular, most of the deepwater succession has been referred to a Ladinian olistostrome or
mélange containing up to hectometric -sized carbonate olistoliths,
breccias, conglomerates, etc. (W OOD, 1981; M ICONNET, 1988;
M ARSELLA et alii, 1993; CIARAPICA & P ASSERI, 2000).
The shallow-water lithofacies can be related to the first stage
of basin opening, whereas the deep-water lithofacies testify the
onset of a marked basin subsidence occurring after the
continental collapse.
In the field, the frequent occurrence of older shallow-water
lithofacies juxtaposed on younger deep-water beds (PANZANELLI
F RATONI, 1991) has been related to the presence of closely
spaced thrust planes. Following this view CIARAPICA & PASSER I
(2000) interpreted the paraconglomerate as resulting from
fragmentation of more competent beds within a contractional
shear zone. Alternatively, the paraconglomerate is regarded as
the product of sedimentary processes as well as gravity-flow
65
RECONSTRUCTION OF THE MONTE FACITO FORMATION
events occurred during the Triassic continental break-up (WOOD,
1981; PANZANELLI FRATONI , 1991).
This work provides new field data indicating the sedimentary
origin of some uncertain lithosomes in the Monte Facito
Formation, improving the knowledge on the tectono-stratigraphic
evolution of the southern tethyan domain during the Middle
Triassic time.
DESCRIPTION OF UNCERTAIN LITHOSOMES
In this work two categories of uncertain lithosomes,
respectively represented by folded slabs and pebbly mudstones
(paraconglomerate) are considered.
Folded slabs
This lithosome consist of slabs made up of thinly-bedded
Fig. 1
Folded strata slab consisting in a limestones /shale alternance.
calcarenite/shale couplets, typical of the Early Triassic shallow water lithofacies (Fig.1). Slabs are generally isolated in a
radiolaritc matrix. Internal structures include folds, normal faults
and boudinaged beds. Commonly, limestone/shale slabs overlie a
marked surface in the proximity of which deformation of the
strata increases.
We refer folded slabs to large slide bodies, consisting of
exotic,
semi-consolidate well-bedded material, along a planar basal shear
surface, emplaced during the Middle Triassic extensional phase.
A series of evidences support this hypothesis:
i) folded slabs are commonly recognized in association with
other gravity-driven deposits;
ii) folded slabs are imbedded within a scarcely deformed
Ladinian radiolarite host. Abrupt termination of individual slabs,
their chaotic distribution and orientation, together with the close
association with boulders, pebbles and cobbles of identical rock
types as constituents of the adjacent gravity-driven deposits,
indicate that the allochthonous masses have been emplaced by
sedimentary processes;
iii) the lack of structures typical of tectonic deformation, such as
evidence of folding by flexural slip processes.
Pebbly mudstones (Paraconglomerate)
They consist of massively-bedded, matrix-supported, polygenic
conglomerates and breccias. Clasts, very isolated in the matrix,
vary in size from few centimeters to some decimetres. Isolated
metre-scale blocks are also present. Often clasts exhibit a tabular
shape. Angular to well-rounded clasts have also been recognized.
A weak layer-parallel clast preferred orientation has been
sometimes observed. Clasts mainly consist of massive or crossbedded calcarenites, micaceous arenites and quartzarenites
deriving from Early Triassic shallow-water lithofacies. Matrix is
commonly made up of brown-greenish shale. Pebbly mudstone
bodies usually show irregularly-shaped geometries with a marked
erosional basal surface and a convex - up geometry in the upper
part. They may vary in thickness from few meters to some tens of
Fig. 2 Lens -shaped pebbly mudstone body alternating to red
radiolarites. Note at the base the undulating erosional surface.
coloured
meters.
The accurate study of well-outcropping successions of the
Monte Facito Formation reveal that pebbly mudstones are
regularly alternated to relatively undisturbed Ladinian radiolarite
deposits (Fig. 2).
The above characters lead us to interpreted the pebbly
mudstones as strongly dismembered slide masses or as debris
flows. The observed pebbly mudstone/ radiolarite alternation is
interpreted as a series of catastrophic events alternating with to
quiet periods during which only fallout sedimentation took place.
DISCUSSION
Within the Monte Facito Formation, folded slabs and pebbly
mudstone bodies are intimately associated everywhere. Often,
packages of well-stratified folded strata gradually become
brecciated laterally and vertically, resembling pebbly mudstones.
Starting from these considerations we interpret the pebbly
mudstones as the result of the progressive transformation of an
66
PALLADINO & PROSSER
supported conglomerate with poorly-sorted tabular-shaped clasts.
Only a slight imbrication can locally be observed. The massive
interval is interpreted to derive by progressive deformation and
fluidization of the overturned flank of the fold along a slide shear
surface. Fig. 4 illustrates a carbonate breccia from the Monte
Facito area. It should be noted that the original limestone strata
have been plastically deformed and fragmented into cm-sized
clasts.
MAIN STRATIGRAPHIC IMPLICATIONS
Fig. 3
portion.
Calcarenite/shale folded slab showing a brecciated basal
initially well-bedded calcarenite/shale slab during downslope
sliding. In fact, it is well known that slides can initiate their
downslope movements as coherent masses, successively evolving
into debris flows (SPENCE & TUCKER, 1997). This process is
particularly efficient when thin-bedded limestone/shales
alternations are involved. Initially slide masses are folded,
without exceeding their internal shear strength. Successively, the
initially well-bedded masses progressively lose their cohesion
because of the establishment of internal deformation mechanisms
consequent to the outpacing of the shear strength. As a
consequence, shale tends to make up a fluidized matrix, whereas
single strata are broken into a series of isolated tabular clasts. The
ultimate deposits produced through this process consist of a
matrix-supported, poorly-sorted, flat-pebble conglomerates with
clasts that exhibit both random or subparallel orientation.
The above described process can be often documented in the
field. If we analyze the folded slab in the Fig. 3, it is possible to
separate a well-bedded upper portion from a nearly massive
lower portion. In particular, this latter consist of a matrix-
Fig. 4 Breccia deriving from the progressive folding and fragmentation
of laminated calcarenite strata.
Early Triassic lithosomes, widely recognized in the Monte
Facito Formation, are here considered as gravity-induced
sedimentary bodies produced during the Early-Middle Triassic
extensional stages leading to the Africa-Europe continental
separation. This interpretation can easily explain the observed
older on younger contact s frequently recognized in the Monte
Facito Formation. Concluding, the upper part of the Monte Facito
Formation is made up of early Triassic rock bodies and clasts
included in a Ladinian radiolarite matrix.
REFERENCES
CIARAPICA G., CIRILLI S., M ARTINI R., RETTOR I R., SALVINI
BONNARD G. & ZANINETTI L. (1990) - Carbonate buildups
and associated facies in the Monte Facito Fm. (Southern
Apennines). Boll. Soc. Geol. It., 109 (1), 151-164.
CIARAPICA G. & PASSER I L. (2000) - Le facies del Triassico
inferiore e medio (Fm. di Monte Facito Auctt.) nelle aree di
Sasso di Castalda e di Moliterno (Basilicata). Boll. Soc.
Geol. It., 119 (2), 339-378.
D ONZELLI G. & CRESCENTI U. (1970) - Segnalazione di una
microbio facies permiana, probabilmente rimaneggiata, nella
Formazione di M. Facito (Lucania Occidentale). Boll. Soc.
Natur. Napoli,79, 13-19.
M ARSELLA E., KOZUR H. & ARGENIO B. (1993) - Monte Facito
Formation (Schitian-middle Carnian). A deposit of the
ancestral Lagonegro Basin in the Southern Apennines. Boll.
Serv. Geol. It., 110, 1991, 225-248.
M ICONNET P. (1988) - Evolution mesozoique du secteur de
Lagonegro. Mem. Soc. Geol. It., 41, 321-330.
P ANZANELLI FRATONI R. (1991) - Analisi stratigrafica della
«Formazione del M. Facito» Auctt. (serie di LagonegroAppennino Meridionale). Proposta di istituzione del Gruppo
di Monte Facito. Tesi di Dottorato in Scienze della Terra,
Università degli Studi di Perugia, 215 pp., Perugia.
S CANDONE P. (1967) - Studi di geologia lucana: la serie
calcareo-silico-marnosa. Boll. Soc. Natur. Napoli, 76, 1-75.
S PENCE G. H. & TUCKER M. E. (1997) Genesis of limestone
megabreccias end their significance in carbonate sequence
stratigraphy model: a review. Sedimentary Geology, 112,
163-193.
W OOD A.W. (1981) - Extensional tectonics and the Birth of the
LagonegroBasin (Southern Italian Apennines). N. Jb. Geol.
Palaont. Abh., 161 (1), 93-131.
Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 67.
New estimation of the post Little Ice Age sea level rise
V INCENZO PASCUCCI (*), S TEFANO ANDREUCCI (*) & GABRIELA FRULIO (**)
Key words: Little Ice Age, Medieval warm, late Pleistocene
sandstones, Dimension stones, Maunder, Sardinia, Alghero.
STATE OF ART
Sea level rise is one of the main effects of climate changes.
It is worldwide accepted that not only natural events have
driven this processes, but also humans. Holocene is considered
a high stand related to an Interglacial Stage. However climate
and, therefore, sea level have experienced several fluctuations.
It is well known that during the warm Medieval Period (9501350 AD) Vikings landed in Greenland and sailed through the
NW passage. This warm time was followed by a relative cold
one known as the Little Ice Age (LIA). During LIA, it has been
estimated that temperature (N hemisphere) dropped down of at
least 1 °C and that climate condition in Europe deteriorated to
increase glaciers. This period started at about 1350 AD and
ended 1850 AD and had three well defined minima
temperatures associated to low solar activity: Wolf (12801350), Sporer (1450-1550) and Maunder (1645 1715). The
new modern relative warm period started at about 1850 and is
continuing now. Because of the strong emission of CO 2 due to
industrial activities and related atmospheric pollution, it is not
simple to discriminate which are normal from induced effects
on this new climate warming.
AIM
Aim of this paper is to bring new information on the amount
of post Little Ice Age sea level rise. We hope that the
comparison of the emerged data with those relative to previous
warming times (i.e. Medieval) may discriminate the amount of
human contribution on climate changes.
THE SPANISH QUARRIES
The study area is located in NW Sardinia Island (Italy),
_________________________
* DIPNET, Università di Sassari, Via Pandanna 4, 07100, Sassari, Italy,
[email protected]
** TEXNH Project & Consulting, via Is M aglias 31, 09122 Cagliari, Italy
Mediterranean Sea. Sardinia is considered stable since the late
Pliocene with a negligible subsidence of about 0.01 mm/y. It is
therefore normally used to reconstruct the Pleistocene and
Holocene sea level curves. Our research focusses on the seafacing city of Alghero that since the 1353 to 1720 was under
the Spanish government. During this time the city was
renovated and new buildings edified. Dimension stones were
quarried all around Alghero both in the nearby inland and
along the coast. Coastal quarries were considered the most
suitable both for rock quality and the easy way to transport the
exploited material by boat.
The quarried rocks are late Pleistocene dune and beach
sandstones developed during the last Interglacial Stage (MIS5
Eemian). Sandstones crop out from few cm to 3m above the
present sea level and underwent to several consolidation
processes related to loading and marine weathering. This last
favoured dissolution and circulation of calcium carbonate who
cemented the rocks. It is reported that Spanish were looking for
characteristics. Coastal quarries were active during the entire
Spanish time. No documents indicate active costal quarries
after the 17 th Century. Different rules were adopted through
time for the size of dimension stones and this has allowed us to
establish a quarry exploitation chronology. For example
Alghero Cathedral dated at 1505-1593.
Nowadays most of the coastal Spanish quarries are some
centimetres below the minimum tide sea level (tidal range is 30
cm) and our measures have indicated that: 1) during low tide
the max water high is of 20 cm; 2) during high tide the max
water high is of 50 cm.
CONCLUSIONS
Data presented let us to infer that sea level from the apex of
the Little Ice Age rose at least of 50 cm with an estimated rate
of about 3 mm/y. If this were true and considering that sea
level rise during Medieval warm period was of 0.6 mm/y over
a period of about 400y, we may deduct that human influence is
so strong to allow sea level rise five times higher than previous
warm periods.
Late Holocene palaeohydrography in central and southern Venetian
Plain: the role of petrographical sand analysis
SILVIA PIOVAN (*), CRISTINA S TEFANI (**) & PAOLO MOZZI (**)
Key words: sand, petrography, palaeohydrography.
Recent studies of M OZZI et alii (2010) and PIOVAN et alii
(2010) focused on the Late Holocene palaeohydrographical
reconstruction of Padua surrounding areas (Fig. 1) and Adige-Po
alluvial plain, respectively (Fig. 2). These works were based on
remote sensing and DTM analysis (in particular, for DEMs
_________________________
(*)University of Padua, Department of History, Padua, 35123, Italy
(** ) University of Padua, Department of Geoscience, Padua, 35123, Italy
analysis of Padua, see also N INFO et alii, 2011) and
chronostratigraphical investigations.
Padua lies on the Brenta River megafan (FONTANA et alii,
2008) and is encased within two meanders occupied, in the
modern age, by the minor Bacchiglione River.
The most ancient Holocene channel belt recognized in the
study area is the Mestrino -Rubano (MR) one, which incised the
alluvial plain formed during the Last Glacial Maximum. It was
formed by the Brenta River between the Lateglacial and 6300 cal
B
stretch of 13 km in the northeastern part of the Padua alluvial
plain; it probably was the last active river bed in the MR channel
belt, between 8400 and 6300 cal BP. The present Bacchiglione
Fig. 1 Geomorphological sketch of the alluvial plain around Padua with the location of petrography sand samples (m odified from Mozzi et alii, 2010).
LATE HOLOCENE PALAEOHYDROGRAPHY IN CENTRAL AND SOUTHERN VENETIAN PLAIN
Fig. 2
69
Geomorphological sketch of the Adige-Po alluvial plain with the location of petrography sand samples (m odified from Piovan et alii, 2010).
River follows another, more recent, Brenta River channel belt,
named Veggiano-Selvazzano (VS) channel belt. The meanders in
the city centre of Padua most probably belong to this channel belt
(M OZZI et alii, 2011). In the Padua southern area MiddleHolocene Brenta River deposits are present. In spite of the
detailed stratigraphical information presented, the attribution of
these channel bodies to a particular fluvial system has supported
only by geomorphological and, for more recent times, by
historical evidences.
More to the south, the Brenta River megafan is bounded by
the Adige-Po sedimentary system. This latter is characterized by
a complex network of alluvial ridges pertaining to the Po and
Adige rivers, which intersect and overlie one to another. These
alluvial ridges are formed by the aggradation of sandy and silty
channel deposits, natural levees and minor, proximal crevasse
splays. Between them, that of
the early Middle Ages. Another important alluvial ridge is the socalled
direction to the southern Venice Lagoon (PIOVAN et alii, 2010).
The Montagnana-Este alluvial ridge divides, near Pernumia, in
three minor branches: Terrassa, Bagnoli and Conselve alluvial
ridges. These two latter seem to join the Saline-Cona alluvial
ridge in Agna and Concadalbero, respectively. Around 3000 cal
BP the Saline-Cona was no more active but, in its distal part, the
aggradation continued until Roman times due to sedimentation of
the Bagnoli and Concadalbero palaeochannel (P IOVAN et alii,
2011). In particular, P IOVAN et alii (2010), thanks to
petrographical sand analysis, linked the Fratta and Saline-Cona
alluvial ridge to the Po basin, comparing the results with the data
obtained from the modern Adige alluvial ridge in Pettorazza
Grimani.
Here we present new data from petrographical sand analysis
performed on samples extracted by different corings located in
the Padua city centre and its surrounding: among them, those
from La Storta palaeochannel, Middle -Holocene Brenta River
deposits, VR channel belt and from the modern Bacchiglione
riverbed. A comparison of the results with those of PIOVAN et
alii, (2010) and those recalculated from G AZZI et alii (1973) and
S CETTRI (1991) has been carried out.
The main objective of this contribution is to describe the
results of petrographical analysis and to attempt a first attribution
of channel belts in Padua alluvial plain to the appropriate fluvial
basin (i.e. Brenta R. vs. Bacchiglione R .).
The ternary plot (Fig. 3) evidences three clusters of samples,
defined as petrofacies. All the Padua samples are in the lithic area
while the Po samples shifted more to the quartz vertex. Sands
from the modern Adige palaeomeander of Pettorazza Grimani
seems to have an intermediate content of lithic grains compared
to the other two clusters. In particular, Adige sands are
characterized by a larger amount of carbonate and acidic volcanic
rock fragments than the Po ones. Thanks to a different geological
setting of the drainage areas, the Po sands are distinguishable
from Adige ones also because the heavy mineral content, among
which the glaucophane is regarded as diagnostic (GAZZI et alii,
1973). The modern Bacchiglione sands seems to have a very high
70
PIOVAN ET ALII
content of lithic and carbonate grains but these data are not
sufficient to distinguish them from the other sand bodies in Padua
alluvial plain. However, their higher volcanic acid grain and
heavy minerals content suggest that these latter could be related
to the Brenta fluvial system.
The composition of modern Adige, Po (G AZZI et alii, 1973)
and
Brenta
rivers
sands
is
reported
for
comparison.
REFERENCES
F ONTANA A., MOZZI P. & BONDESAN A. (2008) - Alluvial
megafans in the Venetian-Friulian Plain (northeastern Italy):
Evidence of sedimentary and erosive phases during Late
Pleistocene and Holocene. Quaternary International 189, 7190.
G AZZI, P., ZUFFA, G.G., G ANDOLFI, G., & PAGANELLI, L. (1973) Provenienza e dispersione litoranea delle sabbie delle
Inquadramento regionale. Memorie Società
Italiana, 12, 1-37.
Geologica
M OZZI P., P IOVAN S., ROSSATO S., CUC ATO M., ABBÀ T. &
FONTANA A. (2010) - Palaeohydrography and early
settlements in Padua. Il Quaternario - Italian Journal of
Quaternary Sciences, 23(2bis), 387-400.
N INFO A., FERRARESE F., MOZZI P. & FONTANA A. (2011) - High
resolution DEMs for the analysis of fluvial and ancient
anthropogenic, landforms in the alluvial plain of Padua
(Italy). Geografia fisica e dinamica quaternaria, 34, 95-104.
P IOVAN S., M OZZI P. & STEFANI C. (2010) - Bronze Age
palaeohydrography of the Southern venetian plain.
Geoarcheology, 25(1), 6-35.
P IOVAN S., M OZZI P. (2010) - Recognizing avulsion events in the
Adige River alluvial system. Il Quaternario - Italian Journal of
Quaternary Sciences, 21, 120-122.
Fig.3 Gross composition of the analyzed sands. Modern Po (green circle)
and Adige (light blu circle) data are recalculated from Gazzi et alii, 1973. Q
represents total quartz; F represents felds pars; L+CE represents fine-grained
rock fragments and extrabasinal carbonates.
S CETTRI F. (1991) - Studio geomorfologico e sedimentologico
della pianura a Sud di Padova. Tesi di Laurea, Università
degli Studi di Padova.
New amber findings in Northeastern Italy: suggestions for an
integrated view on fossil resin
EUGENIO RAGAZZI (*), M ARCO AVANZINI (°), I GINIO D IENI (**), GUIDO ROGHI (°°) & CRISTINA S TEFANI (**)
Key words: Amber, Eocene, fossil resins, FTIR
INTRODUCTION
New amber findings in the Northeastern Italy increase
the palaeobotanical documentation of fossil resin occurrence in
this part of Italy and confirm the Early Eocene as a particular
"amber prolific" time interval. In Italy finds of amber have
been reported since long time, from Tertiary rocks of the
Northern Apennines (SKALSKI & VEGGIANI, 1990) and
especially of Sicily, where the fossil resin simetite has been
found near the river Simeto.
From the Southern Alps, since recent times, the
occurrence of amber has been cited only sporadically. Among
first records is a letter, dated 1827, where Catullo informed
Brugnatelli about a fossil forest, including fossil resin,
discovered in a valley near Roana, on the Asiago Plateau
(CATULLO, 1827). Stoppani (STOPPANI , 1886) reported that
amber was collected from the Chattian beds at the base of the
Monte Brione Formation, near Riva del Garda (Trento
province). Anecdotal reports of amber from the Triassic of the
Dolomites were from Koken (KOKEN , 1913), Zardini
(ZARDINI, 1973) and Wendt & Fürsich (WENDT & FÜRSICH,
1980), but no thorough study was performed before 1998
(G IANOLLA et alii, 1998).
During the last decade, more comprehensive
investigations on amber findings in Italy have been conducted
under geological and physico-chemical contexts. Here follows
a list of these reports:
1. near Redagno and Pietralba (Bolzano province) some
millimetric granules of amber from the Arenarie della Val
Gardena Formation, Upper Permian (M AFFI & MAFFI, 1992);
_________________________
(*) Departm ent of Pharmaceutical and Pharmacological Sciences, University of
Padova, largo E. M eneghetti 2, I-35131 Padova (Italy).
[email protected]
(**) Department of Geosciences, University of Padova.
(°) Trento M useum of Sciences, Geology section, Trento.
(°°) CNR Department of Geosciences and Georesources, Padova.
Badia (Bolzano province) amber from the Heiligkreuz
Formation, Upper Triassic (Carnian) (GIANOLLA et alii,
1998; RAGAZZI et alii, 2003; ROGHI et alii, 2006; SCHM IDT et
alii, 2006);
3. at Vernasso (Udine province) and at Ra Stua (near Cortina
Santonian) and Lower Cretaceous (Albian) sites, respectively
(ROGHI et alii, 2004);
4. at Cava Rossi quarry, Monte di Malo (Vicenza province),
some centimetric amber nodules from the marly limestones
of the Lower-Middle Eocene (BOSCARDIN & V IOLATI
TESCARI, 1996; TREVISANI et alii, 2005);
5. amber from the world -famous fossil-Lagerstätte of Pesciara
di Bolca (Verona province) in Lower Eocene sediments
(TREVISANI et alii, 2005); this amber presents a strict
similarity with Cava Rossi amber (TREVISANI et alii, 2005).
On the basis of the physico chemical and palynological
analysis of the site, some hypotheses were proposed about the
palaeobotanical origin of the fossil resin. The close
resemblance of the physico chemical properties of amber
from Bolca with that of Monte di Malo (mainly FTIR spectra
and thermal analysis behaviour), together with the
biostratigraphical correlation obtained by means of larger
foraminiferal biozones, permitted to hypothesize that the two
amber layers are substantially isochronous (Middle Cuisian,
Early Eocene), although with palaeoenvironmental
differences;
6. in the Chiavon stream, near Salcedo (Vicenza province)
some millimetric granules of amber from Oligocene beds
(RAGAZZI & ROGHI, 2003);
7. similar fragments were collected also from the Upper
Oligocene (Chattian) of Sedico (Belluno province) (RAGAZZI
& ROGHI, 2003); in Belluno province some fragments of
amber had been described by Arduino (ARDUINO , 1818),
within fossil wood in molar stone quarries, possibly close to
Tisoi church. Also Catullo (CATULLO, 1834, 1838, 1840)
quoted some samples of amber together lignite in blue marl
located in the Ardo river valley. Again Catullo (CATULLO,
1863-1864) described amber among lignite found within
Tertiary molasses dug in quarries from Fregona (Treviso);
similar sediment was found near Lamosano and Alpago
church (loc. Pissa), Belluno Province;
72
RAGAZZI ET ALII
8. most recently, TREVISANI et alii (2011) published a note
about amber found in the Eocene Belluno Flysch (Cuisian).
Based on Infra-red spectroscopical analysis, the fossil resin
was assigned to an Araucariacean source, possibly Agathis
genus, not recorded during Eocene in the Northern
hemisphere; therefore it should be older that Tertiary,
suggesting an origin of the material from an older sediment
(Cretaceous - Paleocene?).
NEW AMBER FINDINGS
The scenario of amber findings among different
geological sites in the Northeastern Italy has been further
expanded by three new samples (see map of Fig. 1) of which
we aimed to present the main characteristics.
Fig. 2
Image of the amber sample found near Pont village.
FTIR ANALYSIS
Fig. 1 Map of the area of discovery of the new amber samples. A) from
flysch sediment of M ujè stream, near the village of Frisanco, Pordenone
Province; B) from Pont village, Belluno Province; C) from Doss, Trento
city.
The new ambers are:
A. some small and very fractured samples of fossil resin
from Pordenone Province, found within flysch
sediment of Mujè stream, near the village of Frisanco,
in geological strata belonging to Eocene; this amber
has been already quoted by RIMOLI & DREON (1998)
but it still has not been fully investigated;
B. a centimeter-sized amber (Fig. 2) from Belluno
Province, near Pont village, belonging to Early
Eocene, found by one of us (C.S.) during
This fossil resin comes from the lowermost part of the
flysch succession corresponding to the Discoaster
lodoensis Nannoplancton Zone (GRANDESSO , 1976);
C. some fractured samples of fossil resin from Doss
Trento, (Trento city) (found by M.A.) in the Calcare di
Chiusole formation, Early Eocene in age.
The samples were analyzed under the physico-chemical
point of view. The characteristics were typical of fossil resins
(external aspect, color, hardness 2.5-3 of Mohs scale, no
appreciable surface solubility in alcohol or acetone). A Fourier
Transform Infrared Spectroscopy (FTIR) analysis (performed
on powdered samples included in potassium bromide pellets
with a Perkin Elmer 1600 series spectrophotometer) permitted
to observe the pattern of absorption typical of amber (Fig. 3),
although the spectra of both Trento and Mujè samples were
very few informative due to low intensity of most bands,
probably because of high degree of diagenetic alteration, as
already observed with Belluno Flysch Eocene amber
(TREVISANI et alii, 2011; see also Fig. 3).
The sample from Pont village produced a very clear
spectrum (Fig. 3). Among the several absorption bands
detected, some are present in all fossil resin spectra, such as
those around 3.5 µm (due to stretching of C -H bonds), 6.8 and
7.3 µm (due to bending of C-H bonds) and 5.8 µm (the
of C=O double bonds). The
bands in the upper region of the spectrum between 8 and 10 µm
chemical structures of the resin, but are more useful than those
in the lower region, since the former reflect changes in
composition (LANGENHEIM & BECK, 1965) and may represent
a comparison tool among different samples. As underlined by
73
NEW AMBER FINDINGS IN NORTHEASTERN ITALY
LANGENHEIM & BECK (1965), identity of spectra can never be
expected, even for samples obtained from a single specimen,
since resins are very highly complex and heterogeneous
mixtures of high molecular weight components. However, the
presence of similarities, in particular in the "fingerprint" region
of the spectrum, can suggest a structural similarity in terms of
major constituents.
DISCUSSION AND CONCLUSIONS
FTIR spectrum of Pont amber did not show the typical
the presence of succinic acid, although it is mostly in combined
form: TONIDANDEL et alii, 2009) which presents the so called
preceded by a flat shoulder, attributed to absorption of ester
groups (see Fig. 3).
The morphology of the fingerprint region of the spectrum
of Pont amber however, although with differences in the
intensity of absorption bands, presents similarities with that of
Bolca and Monte di Malo amber (Fig. 3), which are of Eocene
epoch as well, suggesting a common palaeobotanical origin.
Also a close similarity can be detected with spectra of Sedico
and Salcedo amber (RAGAZZI & ROGHI, 2003; see also Fig. 3),
although belonging both to Oligocene epoch.
Regarding the spectra of the other two samples of amber,
found at Trento and in proximity of the Mujè stream, as above
mentioned, the pattern of absorption bands is quite poor, and
therefore no sure comparisons can be made. However, a
similarity with a Belluno Flysch sample previously
investigated (TREVISANI et alii, 2011, reported also in Fig. 3) is
quite evident.
Considering that it is difficult to attribute any
palaeobotanical affinity to a fossil resin based only on infrared
spectra, and in absence of an association with identified vegetal
remains, however we might suggest that the newly investigated
fossil resins can belong to a unique general cluster. A similarity
with the spectrum produced by resins of the Araucariaceae
family genus Agathis (LANGENHEIM & BECK, 1968;
KOSM OWSKA -CER ANOWICZ , 1999) may suggest a link to this
conifer group, as already suggested for the Belluno Flysch
sample (Trevisani et alii, 2011). However, some features of the
spectra (discussed in TREVISANI et alii, 2005, 2011), suggest
that a link with an Angiosperm-type resin-producing plant
cannot be excluded, but at present the key signatures are too
scarce to provide a valuable palaeobotanical attribution.
As suggested for Bolca amber (TREVISANI et alii, 2005),
some similarity can be observed also with the spectrum of
glessite
(KOSM OWSKA -CERANOWICZ
et
alii,
1993;
KOSM OWSKA -CER ANOWICZ , 1994, 2001), a dark-brown fossil
resin found in Germany (Bitterfeld mine, Saxony-Anhalt, and
Lusatia), which has been attributed to the family Burseraceae,
and with fossil resin found in Borneo, attributed to the family
Dipterocarpaceae (KOSM OWSKA -CERANOWICZ, 1994), but all
remains in terms of speculation.
However, it is of interest to underline the fact that amber in
Italy has been found in many sediments of different geological
age, dating from Mesozoic to Cenozoic. Amber occurrence
during a strict time-interval in the Triassic (ROGHI et alii,
2006), presenting peculiar climate shifts, has suggested that
amber production might be linked to climate-induced plant
stress, documented also by palynological/palaeobotanical
evidences. The occurrence of amber findings, although
occasional, here reviewed, might suggest similar considerations
regarding the process of amber production also during the
Early Eocene in Italian area.
In conclusion, the three new amber samples permitted to
expand the knowledge concerning Northern Italy fossil resins
of geological interest, and suggest to take into account the role
of amber as a possible paleoclimatic/paleoenvironmental
indicator.
ACKNOWLEDGEMENTS
The authors thanks to Dr. Angelo Leandro Dreon for providing
the Mujè stream amber sample, and Dr. Giovanni Marzaro
(Padova University) for performing FTIR spectra.
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CATULLO T.A. (1834)
- Osservazioni sopra i terreni
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CATULLO T.A. (1838) - Trattato sopra la costituzione
geognostico-fisica dei terreni alluvionali o postdiluviani
delle provincie Venete. Sicca, Padova, p. 57.
CATULLO T.A. (1840) - Osservazioni geognostico-zoologiche
sopra due scritti pubblicati nel tomo terzo delle Memorie
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saggi della Imperiale Regia Accademia di Scienze Lettere
ed Arti in Padova, Sicca, Padova, vol. V, p. 230.
CATULLO T.A. (1863-1864) - Discorrimenti sopra alcuni
importanti fatti geognostico-paleozoici meritevoli di essere
Veneto di Scienze, Lettere ed Arti, Antonelli, Venezia, p.
473.
CATULLO T.A. (1827) - Scoperta di una foresta fossile.
Squarcio di lettera del Prof. Catullo al Prof. Brugnatelli.
Giornale di Fisica, Chimica, Storia Naturale Medicina ed
Arti, Decade II, Tomo X, p.151.
74
RAGAZZI ET ALII
Baltic
Belluno
Flysch
Sedico
Trento
Salcedo
Mujè
Bolca
Pont
Monte di
Malo
Fig. 3. - FTIR spectra (absorption mode) of amber
samples from Northeastern Italy; the spectrum of
Baltic amber is also shown for comparison. Some
of the reported spectra have been published in
previous papers (RAGAZZI & ROGHI , 2003;
TREVISANI et alii, 2005, 2011).
NEW AMBER FINDINGS IN NORTHEASTERN ITALY
GIANOLLA , P., RAGAZZI, E., & ROGHI, G. (1998) - Upper
Triassic amber from the Dolomites (Northern Italy). A
paleoclimatic indicator? Rivista Italiana di Paleontologia e
Stratigrafia 104, 381 390.
GRANDESSO P,. (1976) - Biostratigrafia delle formazioni
terziarie del Vallone Bellunese. Bollettino della società
Geologica Italiana, 94, 1323 1348.
KOKEN E. (1913) - Kennitnis der Schichten von Heiligenkreuz
(Abteital, Südtirol). Abhandlungen der KaiserlichKöniglichen Geologischen Reichsandstalt 16, 1 43.
KOSM OWSKA -CER ANOWICZ B. (1994) - Bursztyn z Borneo .
Geologiczny, 7, 576 578, 604.
KOSM OWSKA -CER ANOWICZ B. (2001) - Wie Bernstein entsteht.
In: Krumbiegel, G. & Krumbiegel, B. Eds., Faszination
Bernstein. 17 35. Goldschneck-Verlag.
KOSMOWSKA -CER ANOWICZ B., KRUM BIEGEL G. & V AVRA N.
(1993) - Glessit, ein tertiäres Harz von Angiospermen der
Familie Burseraceae. Neues Jahrbuch für Geologie und
Paläontologie 187, 299 324.
KOSM OWSKA -CER ANOWICZ B. (1999) - Succinite and some
other fossil resins in Poland and Europe (deposits, finds,
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Ciencias Naturales de Alava, 14 (Num. Esp. 2), 73-117.
LANGENHEIM J.H., BECK C.W. (1965) - Infrared spectra as a
means of determining botanical sources of amber. Science,
149, 52 55.
LANGENHEIM J.H. & BECK C.W. (1968) - Catalogue of
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Museo Civico G. Zannato, Montecchio Maggiore, 19 22.
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dell'area del Pordenonese con particolare riguardo ai
minerali della Val Cellina e della Val Colvera. Boll. Soc.
Naturalisti "Silvia Zenari" Pordenone, 22, 45-62.
ROGHI G., RAGAZZI E. & FEDELE P. (2004) delle Dolomiti e delle Prealpi Giulie (Italia). Giornate di
Paleontologia
S. P. I., Meeting of the Italian
Palaeontological Society, Bolzano (Italy) 21-23 May 2004,
Abstract book, p. 52.
ROGHI G., RAGAZZI E. & G IANOLLA P. (2006) - Triassic Amber
of The Southern Alps (Italy). Palaios, 21, 143-154.
S CHM IDT A.R., RAGAZZI E., COPPELLOTTI O. & ROGHI G.
(2006) - A microworld in Triassic amber. Amber as old as
the first dinosaurs captured the diversity of microbial life
220 million years ago. Nature, 444, 835.
S KALSKI A. & V EGGIANI A. (1990). Fossil resin in Sicily and
the Northern Apennines: Geology and organic content.
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Europa. Fratelli Dumolard editori, Milano.
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spectrometry in the characterization of Ambers. II. Free
succinic acid in fossil resins of different origin. Rapid
Communications in Mass Spectrometry, 23, 403-408.
TREVISANI E., RAGAZZI E. & ROGHI G. (2011) - First report of
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Alps, Northern Italy). Boll. Soc. Paleontologica It., 50, 2328.
TREVISANI E., P APAZZONI C.A., RAGAZZI E. & ROGHI G.
(2005) - Early Eocene amber from the Pesciara di Bolca
(Lessini Mountains, Northern Italy). Palaeogeography,
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.
Connections between glacial and fluvial systems in the lower Astico
Valley and the piedmont plain (NE Italy)
SANDRO ROSSATO (*), PAOLO M OZZI (*), G IOVANNI M ONEGATO (°), M AURIZIO CUCATO (^),
BARBARA G AUDIOSO & ANTONELLA M IOLA
Key words: glacial collapse, glacial transfluence, Last Glacial
Maximum, plain evolution, south-eastern Prealps, Venetian
Plain.
INTRODUCTION
This work concerns the Late Quaternary evolution of the
Astico Valley, with a focus on the relations between the glacial
complex hosted in the terminal valley tract and the piedmont
alluvial fans.
The Astico valley is located in the Venetian Prealps
(eastern-southern Alps), NW of the city of Vicenza (Italy).
The Astico River flows into this valley, initially N/S and
then NW/SE. This river has its source between the Sommo
Alto and the Plaut peaks and flows on the valley bottom as far
as the town of Piovene Rocchette, where it enters a narrow and
50-m deep gorge until reaching the Venetian alluvial plain,
about 10 km downstream.
The valley incise mostly limestones and dolostones
(Triassic to Cretaceous) and volcanic rocks (Triassic and
Cenozoic). The Cenozoic lithologies can be found in the final
tract of the valley, which is carved almost entirely in
Oligocenic volcanic rocks, both intrusive and effusive.
The whole area is interested by two main deformative
systems, related to the neoalpine tectonic phase (CASTELLARIN
& CANTELLI
SE/NW), which cuts the previous one with a left-strike-slip
cinematic. In addition, a third system (oriented roughly E-W) is
_________________________
(*) University of Padua, Departm ent of Geoscience, Padua, 35123, Italy
(°) National Research Council, Institute for Geoscience and Earth
Resources, Turin, 10123, Italy
(^) Province of Bolzano, Geology and material tests Office, 39053, Cardano
(BZ), Italy
(
University of Padua, Department of Biology, Padua, 35131, Italy
related to the thrust propagation front of the eastern Southern
Alps towards SSE.
The stratigraphy of the Quaternary successions at the outlet
of the Astico Valley shows different sedimentary episodes,
including glacial advances, related to the Middle and Late
Pleistocene (BARTOLOMEI, 1976; 1984; CUCATO, 2001; 2007).
Three distinct glacial events are considered here.
The last event created the terminal moraine system of
Cogollo del Cengio, whose outwash apron filled the lower part
of the Astico Valley and built a fan in the piedmont plain. Two
incised sandur channels are still recognizable in front of the
outer terminal moraine (BARTOLOMEI, 1976). This glacial
advance is attributed to the Last Glacial Maximum (LGM).
BARTOLOMEI (1976) and CUCATO (2001) report various
small outcrops of glacial deposits (lodgment and ablation till
and erratics) at various elevations on both valley flanks of the
lower Astico valley. These glacial deposits belong to lateral
moraines of a glacier whose front was further downstream of
the Cogollo del Cengio end moraines, and relate them to a preLGM glaciation.
The presence of a lodgement till about 5.5 km downstream
of the terminal LGM moraines, along with some pollen
analyses run on lacustrine deposits outcropping along the
fluvial scarp of the present Astico River, point to another preLGM glaciation.
Along the upper Astico Valley and at the margins of
surrounding plateaus, several glacial deposits have been
recognized and related to the glacial transfluence of the Adige
glacier through several saddles; these sediments are ascribed to
different glaciations, according to their weathering degree and
geomorphological position (CUCATO , 2007). Local glacial units
in the Sette Comuni Plateau were also described and mapped
(TREVISAN , 1939; BARTOLOMEI, 1984) according to CUCATO
(2007)
During the LGM these minor glaciers remained separated
from the Astico glacier.
Remote sensing, field survey, stratigraphic measurements
and reconstructions, sand petrography, radiocarbon datings and
pollen analyses confirmed the attribution of the last glaciation
CONNECTION BETWEEN GLACIAL AND FLUVIAL SYSTEMS IN THE LOWER ASTICO VALLEY AND THE PIEDIMONT PLAIN
to the LGM, the previous one probably to the MIS 6 and the
oldest to an undefined glaciation during the Middle
Pleistocene. Sand petrography analyses confirm that all these
glacial deposits contain rock fragments that reach the Astico
Valley through a transfluence of the Adige glacier. During
LGM, this glacial stream entered the Astico Valley from the
North through the Carbonare saddle (1075 m a.s.l.), as it
probably happened also in previous major glaciations. The
chronostratigraphy of two cores drilled near the towns of
77
Vicenza and Villaverla shows that the outwash stream changed
its way to the piedmont plain at the end of LGM, as a response
to rapid glacial collapse. This switch led to the deactivation of
the north-western sector of the plain (Thiene fan) in favour of
the south-eastern one (Sandrigo fan). The lower and middle
Astico Valley preserved significant evidence of minor glacial
fluctuations during the LGM in response of subtle climatic
changes, namely an early glacial withdrawal at 23-24 cal ka,
which may be difficult to distinguish in major Alpine glaciers.
Fig. 1 Evolution of the m iddle-lower Astico Valley since the M iddle Pleistocene; PR: Piovene Rocchette; Ca: Caltrano, I: M IS 6 (?), maximum advance; II:
MIS 6 (?), initial of the withdrawal; III: interglacial; IV: LGM, maxim um advance; V: LGM: glacial pulse; VI: LGM: the glacial transfluence stops; VII: pre sent
situation) (source: R OSSATO et alii, 2012).
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TREVISAN L. (1939) dei Sette Comuni (Vicenza). Bollettino del Comitato
Glaciologico Italiano, 19, 1-19.
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superiore 2,5 cm, margine inferiore 2,5, testo iustificato a
sinistra e non giustificato a destra, intestazione 1,25 cm
dal bordo. Evitare accuratamente di mettere trattini di
unione in fine di rigo.
Ogni pagina deve essere dattiloscritta soltanto sulla prima
faccia e deve essere numerata.
Nella intestazione, di non più di una riga, vanno indicati:
titolo sintetico (corrente) del lavoro, Autore di
riferimento, n. di pagina (8 pt, Arial o Helvetica).
iferimento, con il recapito
comprensivo di posta elettronica). In una nota a piè di
pagina saranno indicati gli indirizzi degli Autori e/o quello
Stile per le citazioni bibliografiche
SPAKMAN W. (1986) . Geologie en
Mijnbouw, 65,145-153.
BARCHI M., MINELLI G. & PIALLI G. (1998)
Mem. Soc. Geol. It 52, 383400.
RAMSAY J.G. & HUBER M. (1987) . Volume 2: Folds and
Fractures. Academic Press, London.
SUHADOLC P. & PANZA G.F. (1989)
. In: Boriani A., Bonafede M.,
Piccando G.B. & Vai G.B. Eds., The lithosphere in
ltaly. Advances in Earth Science Research., 15-40. Acc.
Naz. Lincei.
Figure
a e quello in italiano in
coda.
grafici).
Le dimensioni massime sono 185x244 (pagina) o 90x244
(colonna).

Central Italy

Transcription

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