O - Università degli studi di Cagliari.

Transcription

SUBCOMMISSION on
SILURIAN
STRATIGRAPHY in
SARDINIA
S4
Fieldmeeting
4 - 11 June 2009
Time and life in the Silurian: a multidisciplinary approach
Rendiconti
della
Società Paleontologica Italiana
SUPPLEMENTO AL BOLLETTINO DELLA SOCIETÀ PALEONTOLOGICA ITALIANA, VOL. 48, N. 1
TIME AND LIFE IN THE SILURIAN:
A MULTIDISCIPLINARY APPROACH
Subcommission on Silurian Stratigraphy Field Meeting 2009
Abstracts
SOCIETÀ PALEONTOLOGICA ITALIANA
MODENA - 2009
Rendiconti della Società Paleontologica Italiana
3
(III)
Time and Life in the Silurian:
a multidisciplinary approach
Subcommission on Silurian Stratigraphy Field Meeting 2009
Sardinia, June 4-11, 2009
Abstracts
Edited by
Maria G. Corriga
Sergio Piras
Società Paleontologica Italiana
2009
I
REFERENCES TO THIS VOLUME
It is recommended that reference to the whole or part of this volume be made in one of
the following forms, as appropriate:
CORRIGA M.G. & PIRAS S., eds. (2009). Time and Life in the Silurian: a multidisciplinary approach.
Abstracts. Rendiconti della Società Paleontologica Italiana, 3 (3): 106 pp.
BARRICK J.E., KLEFFNER M.A., GIBSON M.A., PEAVEY F.N. & KARLSSON H.R. (2009). The Lau
Primo-Secundo Oceanic Event and Mid-Ludfordian Isotope Excursion (Ludlow, Silurian) in
Southern Laurentia. In Corriga M.G. & Piras S. (Eds.), Time and Life in the Silurian: a
multidisciplinary approach. Abstracts. Rendiconti della Società Paleontologica Italiana, 3
(3): 267-268.
EDITORS ADDRESSES
Maria G. Corriga
Dipartimento di Scienze della Terra, Università di Cagliari
via Trentino 51, I-09127 Cagliari (Italy); [email protected]
Sergio Piras
Dipartimento di Scienze della Terra, Università di Cagliari
via Trentino 51, I-09127 Cagliari (Italy); [email protected]
THE ITALIAN PALAEONTOLOGICAL SOCIETY
The Association named Società Paleontologica Italiana was founded in 1948 to promote
research in palaeontology and related sciences. Membership is open to institution and to anyone
is interested in palaeontology, wheather as a professional scientist or as amateur. Membership
fees for year 2009 are:
Ordinary membership (European Union) 35 Euro
Ordinary membership (extra E.U.)
45 Euro
Junior membership (under 30)
21 Euro
Istitutional membership
70 Euro
Since 1960 the Society publishes the Bollettino della Società Paleontologica Italiana, an
international journal with scientific papers dealing on any branch of palaeontology. In year 2000,
it also started to publish PaleoItalia, a half-yearly booklet written in Italian, mainly addressed
to amateur palaeontologists.
The Rendiconti della Società Paleontologica Italiana is a series of volumes grouping
documents of scientific meetings (abstracts and proceedings) and field trips guidebooks.
For further informations: www.spi.unimo.it
II
Time and life in the Silurian: a multidisciplinary approach
Subcommission on Silurian Stratigraphy field meeting 2009
Sardinia, June 4-11, 2009
ORGANIZING COMMITTEE
Carlo Corradini
Annalisa Ferretti
Petr Storch
Sebastiano Barca
Maria G. Corriga
Myriam Del Rio
Maurizio Gnoli
Kathleen Histon
Francesco Leone
Alfredo Loi
Gian Luigi Pillola
Sergio Piras
Paola Pittau
Paolo Serventi
Università di Cagliari, Italy
Università di Modena e Reggio Emilia, Italy
Czech Academy of Sciences, Czech Republic
SCIENTIFIC COMMITTEE
Stanley Finney
Michael J. Melchin
Juan Carlos Gutiérrez-Marco
Charles H. Holland
Jiri Kriz
Peep Männik
Florentin Paris
Jiayu Rong
Hans Peter Schönlaub
Enrico Serpagli
Jacques Verniers
California State University Long Beach, Long Beach, CA, U.S.A.
St. Francis Xavier University, Antigonish, Canada
Universidad Complutense de Madrid, Madrid, Spain
Trinity College, Dublin, Ireland
Czech Geological Survey, Prague, Czech Republic
Tallinn Technical University, Tallin, Estonia
Université de Rennes 1, Rennes, France
Chinese Academy of Sciences, Nanjing, China
Austrian Academy of Sciences, Vienna, Austria
Università di Modena and Reggio Emilia, Modena, Italy
Ghent University, Ghent, Belgium
III
IV
Università degli Studi
di Cagliari
Università degli Studi
di Modena e Reggio Emilia
UNDER THE PATRONAGE OF
Il Magnifico Rettore dell’Università degli Studi di Cagliari
Il Magnifico Rettore dell’Università degli Studi di Modena e Reggio Emilia
Il Preside della Facoltà di Scienze MM.FF.NN., Università di Cagliari
Il Presidente della Società Paleontologica Italiana
SPONSORING INSTITUTIONS
Università di Cagliari
Università di Modena e Reggio Emilia
Facoltà di Scienze MM.FF.NN., Università di Cagliari
Comune di Goni
Comune di Silius
V
VI
Rendiconti della Società Paleontologica Italiana, 3 (3), 2009: 267-268
Time and Life in the Silurian: a multidisciplinary approach
Sardinia, Italy - June 4-11, 2009
The Lau Primo-Secundo Oceanic Event and MidLudfordian Isotope Excursion (Ludlow, Silurian) in
southern Laurentia
JAMES E. BARRICK, MARK A. KLEFFNER, MICHAEL A. GIBSON, F. NICOLE PEAVEY,
HARALDUR R. KARLSSON
J.E. Barrick - Department of Geosciences, Texas Tech University, Lubbock, TX 79409-1053 (U.S.A.); [email protected]
M.A. Kleffner - School of Earth Sciences, Division of Geological Sciences, The Ohio University at Lima, Lima, OH
45804 (U.S.A.).
M.A. Gibson - Department of Geology, Geography & Physics, University of Tennessee at Martin, Martin, TN 382385039 (U.S.A.).
F.N. Peavey - Texas Tech University, Lubbock, TX 79409-1053 (U.S.A.).
R.H. Karlsson - Texas Tech University, Lubbock, TX 79409-1053 (U.S.A.).
The Lau Primo-Secundo Oceanic Event and the mid-Ludfordian Isotope Excursion
have been recognized in three regions in southern Laurentia: the Arbuckle Mountains in
southern Oklahoma (2 sections), the western Illinois Basin in eastern Missouri (1 section),
and the western valley of Tennessee (5 sections).
Pre-Lau strata in southern Oklahoma comprise the brownish argillaceous, silty
wackestones and shales with poorly preserved graptolites of the lower Henryhouse
Formation. A diverse Dapsilodus-dominated fauna includes species characteristic of the
Havdlem Primo Episode in moderate abundance: Polygnathoides siluricus, Oulodus
siluricus, Ozarkodina confluens, Walliserodus sp., Kockelella sp. and Panderodus
recurvatus. These species disappear at a bedding surface, to be replaced by a fauna
characterized by Ozarkodina snajdri and abundant Wurmiella excavata and Dapsilodus.
Clay and silt content declines abruptly at the faunal break and more resistant skeletal
wackestones appear slightly higher, with Pedavis latialata and O. auriformis. Values of
δ13C dip from +1 to –0.5‰ below the faunal break, rise to near +4.0‰ in the W. excavata
fauna, and fall to +1.0‰ in the overlying resistant wackestones. The lower Henryhouse
silty wackestones and shales have been removed by erosion over much of southern
Oklahoma, and the post-Lau skeletal wackestones lie at the base of the Henryhouse
Formation at many sections.
In eastern Missouri, pre-Lau strata of the Bainbridge Formation comprise mottled red
argillaceous wackestones and shales yielding a Panderodus equicostatus-dominated fauna,
with P. recurvatus, less common O. confluens, Walliserodus, and rare Polygnathoides
siluricus. Above this lies a thin, >1 m, argillaceous greenish gray carbonate mudstone
from which only a few elements of Pseudooneotodus have been recovered. Above this
mudstone are interbedded reddish shales and thin limestones, in which an abundant
Dapsilodus and W. excavata fauna appears. This is overlain by a clean, more resistant
skeletal wackestone with O. snajdri and O. auriformis. Values of δ13C dip from +1.0 to
–3.5‰ in the base of the greenish-gray mudstone, rise to near +5.0‰ in the top of the
mudstone, and fall to +1.0‰ in the shale and thin limestones below the resistant wackestone
unit.
267
Subcommission on Silurian Stratigraphy field meeting 2009 - Abstract book
Pre-Lau strata in the Brownsport Formation in western Tennessee comprise green to
brown fossiliferous shales and argillaceous skeletal wackestones of the Beech River
Member, which may grade upward into an echinoderm grainstone facies, the Bob Member.
The Beech River and Bob members are characterized by a sparse Panderodus equicostatus/
P. recurvatus conodont fauna that includes small numbers of O. confluens, P. siluricus,
and rare other species. In the more western sections, darker gray argillaceous carbonate
mudstones, packstones and shales overlie the Beech River-Bob section, near the base of
which the mid-Ludfordian Excursion appears, which extends through 5 m of section and
reaches values of δ13C greater than +6‰. In the more eastern sections, however, the
Excursion appears near the base of, and ranges through a 4- to 5-m section of, coarsegrained echinoderm grainstones that rest directly on Beech River-Bob lithofacies. Maximum
values of δ13C reach only as high as +5‰ in these grainstones. The pre-Lau Panderodusdominated conodont fauna disappears as the values of δ13C start to rise from a short
interval of negative values in both areas. At the base of the grainstones, a conodont fauna
with W. excavata, Dapsilodus, Decoriconus, and rare O. snajdri is present, with rare P.
recurvatus. In both areas, strata that comprise the Mid-Ludfordian Excursion yield only a
few isolated elements of W. excavata, Dapsilodus or Pseudooneotodus. The Lobelville
Member, the upper shaly member of the Brownsport with a unique coral fauna, is postLau in age in its type area in the east, but may include the Lau Event at its base to the
west.
The Lau Event and mid-Ludfordian Excursion in southern Laurentia represent an
interval of time during which a major reorganization of conodont faunas occurred, but
with few lineage extinctions. The major rearrangement of shallow water lithofacies in
western Tennessee, shifts in deeper water carbonate lithofacies in eastern Missouri and in
Oklahoma, and an erosional unconformity in Oklahoma all indicate the presence of a
significant sequence boundary that was the product of a major middle Ludfordian fall and
rise in eustatic sea level.
268
Early Palaeozoic palaeogeography of Severnaya
Zemlya, Arctic Russia (with new data on the Silurian)
OLGA K. BOGOLEPOVA, ALEXANDER P. GUBANOV
O.K. Bogolepova - CASP, Cambridge University, 18 a Huntingdon Road, Cambridge, CB3 0DH (United Kingdom);
[email protected]
A.P. Gubanov - CASP, Cambridge University, 18 a Huntingdon Road, Cambridge, CB3 0DH, (United Kingdom);
[email protected]
Our research in recent years has been focused on the palaeontology, biostratigraphy
and palaeogeography of the Severnaya Zemlya Archipelago of Arctic Russia. This area,
together with northern Taimyr, belongs to the Kara Terrane, palaeogeography of which
during the early Palaeozoic remains problematic; it may have been an independent
microcontinent, a part of separate microcontinent Arctida, or contiguous with Baltica
(Gee & Pease, 2004; Metelkin et al., 2005, and references therein).
The Cambrian trilobites, brachiopods, molluscs and microfossils of Severnaya Zemlya
show affinity to Baltica and Siberia (Bogolepova et al., 2001). The Ordovician macroand microfossil assemblages contain elements typical of both Siberian and Baltic biotic
provinces (Bogolepova et al., 2006).
New data on the Silurian faunas provide some unique information on their similarities
to those of Baltica and Laurentia. The evidence from the ostracodes Entomozoe aff. E.
tuberosa indicates connection between Severnaya Zemlya and eastern North Greenland
(Siveter & Bogolepova, 2006). One more example of these affinities can be shown with
regard to conodonts, which occur commonly in the Early Silurian successions of Severnaya
Zemlya). Several taxa characteristic of the Telychian faunas of the eastern (Timan-Pechora)
and western (Estonia) parts of Baltica (e.g. Apsidognathus cf. milleri, Distomodus cf.
staurognathoides and Pterospathodus eopennatus) were found in the region for the first
time. Moreover, on Severnaya Zemlya, Pterospathodus eopennatus occurs together with
Aspelunda aff. expansa and Ozarcodina broenlundi, known from Peary Land of eastern
North Greenland (Männik et al., 2009).
Thus, a probable palaeogeographic scenario is that the Kara Terrane was located
between Baltica and Siberia during the Late Cambrian and Ordovician. The entire region
was covered by shallow seas, with no deep-water seaways, allowing easy faunal exchange
between Baltica and Siberia. The presence of common benthic taxa throughout the
Cambrian suggests that Iapetus was a rather narrow seaway even when it reached its
maximum size during the Early Ordovician (Gubanov & Tait, 1998). The Iapetus Ocean
began to narrow through the rest of the Ordovician and was closed in late Silurian by
relatively orthogonal collision between Laurentia and Baltica (Roberts & Gee, 1985); this
gave an increasing number of taxa of the Laurentian affinity into Kara.
REFERENCES
BOGOLEPOVA O.K., GUBANOV A.P. & RAEVSKAYA E.G. (2001). The Cambrian of Severnaya Zemlya Archipelago,
Russia. Newsletters on Stratigraphy, 39 (1): 73-91.
269
BOGOLEPOVA O.K., GUBANOV A.P. & PEASE V. (2006). The Ordovician of Severnaya Zemlya Archipelago.
Newsletters on stratigraphy, 42 (1): 1-21.
GEE D.G. & PEASE V.L. eds. (2004). The Neoproterozoic Timanide Orogeny of Eastern Baltica. Geological
Society, London, Memoirs, 30, 249 pp.
GUBANOV A.P. & TAIT J. (1998). Maclurites (Mollusca) and Ordovician palaeogeography. Schriften des
Staatlichen Museums für Mineralogie und Geologie zu Dresden, 9: 140-142.
MÄNNIK P., BOGOLEPOVA O.K., POLDVERE A. & GUBANOV A.P. (2009). New data on Ordovician-Silurian conodonts
and stratigraphy of the Severnaya Zemlya Archiopelago, Russian Arctic. Geological Magazine [in
press]
METELKIN D.V., VERNIKOVSKY V.A., KAZANSKY A.YU., BOGOLEPOVA O.K. & GUBANOV A.P. (2005). Paleozoic
history of the Kara microcontinent and its relation to Siberia and Baltica: paleomagnetism, palaeogeography
and tectonics. Tectonophysics, 398: 225-243.
ROBERTS D. & GEE D.G. (1985). An introduction to the structure of the Scandinavian Caledonides. In: Gee
D.G., Sturt B.A. (Eds.),The Caledonide Orogen - Scandinavia and Related Areas. Wiley, Chichester, 55–
68
SIVETER D.J. & BOGOLEPOVA O.K. (2006). The myodocope ostracod Entomozoe from the early Silurian of
Severnaya Zemlya, Russian Arctic. Norwegian Journal of Geology, 86: 51-58.
270
Trilobites from the Scyphocrinites limestone (Pridoli)
of the Sierra Norte of Seville Natural Park, southern
Spain
RODRIGO CASTAÑO, ISABEL RÁBANO, GRACIELA N. SARMIENTO
R.Castaño - Instituto Geológico y Minero de España (Spanish Geological Survey); Avda. Real 1, 24006 León (Spain);
[email protected]
I. Rábano - Instituto Geológico y Minero de España (Spanish Geological Survey); Ríos Rosas, 23, 28003 Madrid
(Spain); [email protected]
G.N. Sarmiento - Instituto de Geología Económica (CSIC-UCM), Ciudad Universitaria s/n, 28040 Madrid (Spain);
[email protected]
Two of the more complete and representative Silurian sections of the Ossa-Morena
Zone of the SW Iberian Massif are located in the Sierra Norte of Seville Natural Park
within the cores of the Valle and Cerrón del Hornillo synclines (Robardet & GutiérrezMarco, 2004). The Silurian succession of this area has a reduced thickness and displays a
tripartite stratigraphy reminiscent of the “Thuringian triad” of the northern margin of
Gondwana, being composed of graptolitic black shales with an intermediate carbonate
unit, the “Scyphocrinites limestone” (Jaeger & Robardet, 1979).
The “Lower graptolitic shales” represent a complete succession of Llandovery, Wenlock
and Ludlow age, recorded by 20 graptolitic biozones (Jaeger & Robardet, 1979; Robardet
& Gutiérrez-Marco, 2004).
The “Scyphocrinites limestone” consists of 10-15 meters of alternating dark limestones
and calcareous shales with abundant scyphocrinoid remains (columnals, crowns and loboliths
of Scyphocrinites and Camarocrinus), as well as some brachiopods, trilobites, cephalopods,
bivalves, gastropods, ostracods, cornulitids, hyolitids, machaeridians, solitary corals,
graptolites, conodonts and siliceous sponge spicules.
The “Upper graptolitic shales” of latest Pridoli to Lochkovian age contains in its basal
5-6 meters calcareous nodules with latest Silurian graptolites and molluscs and, according
to Oczlon (1989), also the trilobite Cromus aff. bohemicus (Barrande), not relocated by
us.
The trilobite assemblage reported here was collected from marly intercalations of the
“Scyphocrinites limestone” and includes the following taxa: Cromus cf. krolmusi Chlupác,
C. aff. leirion Šnajdr, Cromus n. sp. 1, Cromus n. sp. 2, Crotalocephalus cf. transiens
(Bou´ek), Bohemoharpes (Unguloharpes) sp., Denkmanites sp. and Leonaspis sp. This
association has a distinct Bohemian character, but Cromus n. sp. 1 resembles Cromus
rialpensis von Gaertner, which occurs in Ludlow strata in the Pyrenees.
The “Scyphocrinites limestone” correlates entirely with the Pridoli. The graptolites of
the lower part of this unit belong to the lower Pridoli Neocolonograptus parultimus- N.
ultimus Biozone, and those from the top of the limestone, as well as those recorded from
the calcareous nodules at the base of the “Upper graptolitic shales”, indicate correlation
with the uppermost Pridoli Istrograptus transgrediens Biozone (Piçarra et al., 1998).
The conodont assemblages found in the same beds of both formations belong to the
271
Ozarkodina remscheidensis interval Zone (Pridoli), as indicated by the occurrence of
Oulodus elegans (Walliser), Pseudooneotodus beckmanni (Bischoff & Sannemann),
“Ozarkodina” remscheidensis (Ziegler), “O.” confluens (Branson & Mehl),“O.”
eosteinhornensis (Walliser) and “O.” excavata (Branson & Mehl).
Of paleogeographic importance is the close affinity of the trilobite association of the
“Scyphocrinites limestone” with Bohemian faunas, so far unknown in the coeval
“Ockerkalk” of the typical Thuringian facies from Germany and southeastern Sardinia.
In addition to SW Iberia, some of the Bohemian trilobite taxa are geographically widespread,
occurring in Pridolian limestones of an intermediate Thuringian-Bohemian facies, as
indicated by its possible occurrence in several localities of N Africa and the Pyrenees.
This work is a contribution to the PATRIORSI project (CGL2006-07628/BTE) of the
Spanish Ministry of Science and Innovation.
REFERENCES
JAEGER H. & ROBARDET M. (1979). Le Silurien et le Dévonien basal de la Province de Séville (Espagne).
Geobios, 12: 687-714.
OCZLON M. (1989). Fazies und fauna im Silur und Devon des “Valle” (Provinz Sevilla, SW-Spanien).
Diplomarbeit Universität Heidelberg. 86 pp. (Unpublished).
PIÇARRA, J.M., GUTIÉRREZ-MARCO, J.C., LENZ, A.C., ROBARDET, M. (1998). Pridoli graptolites from the Iberian
Peninsula: a review of previous data and new records. Canadian Journal of Earth Sciences, 35: 65-75.
ROBARDET M. & GUTIÉRREZ-MARCO J.C. (2004). The Ordovician, Silurian and Devonian rocks of the OssaMorena Zone (SW Iberian Peninsula, Spain). Journal of Iberian Geology, 30: 73-92.
272
Looking for a late Silurian Standard Conodont
Zonation: still a long way to go
CARLO CORRADINI
C. Corradini - Dipartimento di Scienze della Terra, Università di Cagliari, via Trentino 51, I-09127 Cagliari (Italy);
[email protected]
In the last forty years several conodont zonation schemes were proposed for the
Silurian, but none has been widely accepted up to now.
The first conodont zonation for the Silurian was proposed by Walliser (1964), who
based his scheme primarily on the Cellon Section (Carnic Alps, Austria), taking in account
also data from Bohemia and Spain. The author defined twelve successive appearance
zones spanning the Silurian and the lowermost Devonian. Several of these zones have
been widely recognized, but the difficulties of applying the complete scheme in other
parts of the world have led to the development of many local zonations, mainly for the
Llandovery, which is not completely exposed in Cellon.
Aldridge & Schönlaub (1989), considering all the available data, provided a new scheme,
which is a “step on the path to the development of a reference biozonation” (p. 275).
Their global zonation has been reported also in the Newsletter of the Subcommission of
Silurian Stratigraphy (Silurian Times n°1; 1993). Two years later, a new Conodont Global
Zonation chart appeared (Silurian Times n°3; Nowlan, 1995), significantly different from
the others, but never fully justified or discussed.
Corradini & Serpagli (1998, 1999) proposed a new scheme, based on Sardinian data:
the authors proved that the Sardinian conodont zonation is widely usable worldwide and
claimed that it is “of practical use for Silurian biostratigraphy, and therefore more generally
useful than extremely detailed schemes, sometimes based on not yet defined or endemic
taxa” (Corradini & Serpagli, 1999, p. 270). Following these considerations, the same
authors (Corradini & Serpagli, 2000) proposed their scheme as a Standard Silurian
Conodont Zonation for the Wenlock-Pridoli time span.
Finally, Ogg et al. (2008) published a scheme intermediate between those introduced
by Nowlan (1995) and Corradini & Serpagli (1999), but with some problems still open,
mainly the occurrence of a “not zoned” interval in the lower Ludlow.
Other unsolved problems arose recently from the taxonomic revision of some
Ozarkodinids carried on by a few authors in the last five years (Murphy et al., 2004;
Carls et al., 2005, 2007), who left without a home several morphotypes previously identified
as Oz. remscheidensis. We agree that those taxa may represent several different species
within the Genus Zieglerodina, but it is necessary to conclude soon the revision at a
species level (and not at genus level), in order to avoid the big taxonomic chaos that we
can observe now. All specimens figured by different authors in the last decades should be
included and discussed in this revision. In fact, it is not acceptable simply to write that
several previous taxonomic determinations and all previous biostratigraphic schemes for
the Pridoli are wrong (Carls et al., 2007), without providing any alternative.
273
Fig. 1 - Comparison of main late Silurian conodont zonation schemes.
The proposal by Corriga & Corradini (2009) and Corriga et al. (2009) to rename the
former “remscheidensis interval Zone” as “eosteinhornensis s.l. interval Zone” without
changing the meaning of the zone and the definition of its boundaries is a temporary
solution and can be accepted only until that taxonomic work will be concluded. Then, a
new zonation for the Pridoli should be proposed.
REFERENCES
ALDRIDGE R.J. & SCHÖNLAUB H.P. (1989). Conodonts. In Holland C.H. & Bassett M.G. (Eds.), A Global
Standard for the Silurian System. National Museum of Wales, Geological Series, 9: 274-279.
CARLS P., SLAVIK L. & VALENZUELA-RIOS J.I. (2005). A new Ludlow (Late Silurian) Spathognathodontidae
(Conodonta) from Bohemia with incipient alternating denticulation. Neues Jahrbuch für Geologie und
Paläontologie Monatshefte, 2005-H9: 547-565.
CARLS P., SLAVIK L. & VALENZUELA-RIOS J.I. (2007). Revision of conodont biostratigraphy across the SilurianDevonian boundary. Bulletin of Geosciences, 82 (2): 145-164.
CORRADINI C. & SERPAGLI E. (1998). A Late Llandovery-Pridoli (Silurian) conodont biozonation in Sardinia. In
Serpagli E. (Ed.), Sardinia Field-trip Guide-book, ECOS VII. Giornale di Geologia, 60, Spec. Issue: 8588.
CORRADINI C. & SERPAGLI E. (1999). A Silurian conodont zonation from late Llandovery to end Pridoli in
Sardinia. Bollettino della Società Paleontologica Italiana, 38 (2-3): 255-273.
CORRADINI C. & SERPAGLI E. (2000). A new (standard?) Silurian conodont zonation. Silurian Times, 8: 25-28.
CORRIGA M.G. & CORRADINI C. (2009). Upper Silurian and Lower Devonian conodonts from the Monte Cocco
II Section (Carnic Alps, Italy). Bulletin of Geosciences, 84 (1): 155-168.
CORRIGA M.G., CORRADINI C. & FERRETTI A. (2009). Silurian conodonts from Sardinia: an overview. Rendiconti
della Società Paleontologica Italiana 3 (1): 95-107.
MURPHY M.A., VALENZUELA-RIOS J.I. & CARLS P. (2004). On Classification of Pridoli (Silurian)-Lochkovian
(Devonian) Spathognathodontidae (Conodonts). University of California, Riverside Campus Museum
Contribution, 6: 1-25.
NOWLAN G.S. (1995). Left Hand Column for Correlation Charts: Silurian Times, 3: 7-8.
OGG J.G., OGG G. & GRADSTEIN F.M. (2008). The Concise Geologic Time Scale. 177 pp., Cambridge University
Press.
W ALLISER O. (1964). Conodonten des Silurs. Abhandlungen des Hessischen Landesamtes für
Bodenforschung zu Wiesbaden, 41: 1-106.
274
Rendiconti della Società Paleontologica Italiana, 3 (3), 2009: 275
Silurian-Lower Devonian conodonts from the Rifugio
Lambertenghi Fontana III Section (Carnic Alps, Italy)
MARIA G. CORRIGA, CARLO CORRADINI
M.G. Corriga - Dipartimento di Scienze della Terra, Università di Cagliari, via Trentino 51, I-09127 Cagliari (Italy);
[email protected]
C. Corradini - Dipartimento di Scienze della Terra, Università di Cagliari, via Trentino 51, I-09127 Cagliari (Italy);
[email protected]
The Carnic Alps, located at the Italian-Austrian border, expose one of the most complete
Palaeozoic sedimentary successions, documenting almost continuously a Late Ordovician
to Permian Age.
Silurian and Lower Devonian sediments are irregularly distributed within the Carnic
Chain from the Monte Cocco area, at the East, to Lake Wolayer, at the West.
The Rifugio Lambertenghi Fontana III (RLF III) Section is located just South of Lake
Volayer. The area is well known for the abundant Silurian and Devonian sediments exposed
in the area.
The RLF III Section, recently discovered, exposes about 15 m of grey-reddish
“Orthoceras limestones”. The abundant macrofauna, mainly crinoids, brachiopods,
nautiloids and trilobites, indicates a shallow water environment.
In order to achieve a precise age placing for the section, seventeen conodont samples
were collected and processed with the conventional formic acid technique. All the
investigated levels were productive and about 1200 conodont elements were recovered.
The state of preservation is generally quite good, even if a few elements are broken or
slightly deformed. In general the Silurian part of the section is richer (up to 96 elements/
kg), whereas abundance strongly decreases in the upper part, in connection with a shallowing
depositional environment. The conodont colour is dark brown, corresponding to a Color
Alteration Index of 3.5-4. Twenty taxa, belonging to ten genera (Belodella, Coryssognathus,
Dapsilodus, Icriodus, Oulodus, Ozarkodina, Panderodus, Pseudooneotodus, Wurmiella
and Zieglerodina) were discriminated. Wurmiella excavata and Panderodus unicostatus
are very abundant in the lower part of the section. Belodella, both B. anomalis and B.
resima are constantly present.
It is difficult to precisely locate the Silurian/Devonian Boundary, due to the scarcity of
the fauna in the upper part of the section. Icriodus hesperius, the taxon normally used to
indicate a Devonian age, occurs only at very top of the section; however, it is possible to
suppose that the boundary is about 3.5 m below, between the last occurrence of Ozarkodina
confluens and the entry of Zieglerodina remscheidensis.
275
276
Integrated high-resolution chronostratigraphy of the
Telychian and Sheinwoodian stages: conodonts,
graptolites, isotopes, and the future of Paleozoic
chronostratigraphy
BRADLEY D. CRAMER, DAVID K. LOYDELL, CHRISTIAN SAMTLEBEN, AXEL MUNNECKE,
DIMITRI KALJO, PEEP MÄNNIK, TÕNU MARTMA, LENNART JEPPSSON, MARK A.
KLEFFNER, JAMES E. BARRICK, MATTHEW R. SALTZMAN
B.D. Cramer - Division of Geological Sciences, School of Earth Sciences, The Ohio State University, Columbus, Ohio
43210 (U.S.A.).
D K. Loydell - School of Earth and Environmental Sciences, University of Portsmouth, Portsmouth P01 3QL (United
Kingdom).
C. Samtleben - Institut für Geowissenschaften, Universität Kiel, D-24118 Kiel (Germany).
A. Munnecke - GeoZentrum Nordbayern, Fachgruppe Paläoumwelt, Universität Erlangen, D-91054 Erlangen
(Germany).
D. Kaljo - Institute of Geology at Tallinn University of Technology, 19086 Tallinn (Estonia).
P. Männik - Institute of Geology at Tallinn University of Technology, 19086 Tallinn (Estonia).
T. Martma - Institute of Geology at Tallinn University of Technology, 19086 Tallinn (Estonia).
L. Jeppsson - Department of Geology, GeoBiosphere Science Centre, Lund University, SE-223-62 Lund (Sweden).
M A. Kleffner - Division of Geological Sciences, School of Earth Sciences, The Ohio State University at Lima, Lima,
Ohio 45804 (U.S.A.).
J.E. Barrick - Department of Geosciences, Texas Tech University, Lubbock, Texas 79409 (U.S.A.).
M.R. Saltzman - Division of Geological Sciences, School of Earth Sciences, The Ohio State University, Columbus,
Ohio 43210 (U.S.A.).
The resolution and reliability of global chronostratigraphy is directly related to the time
period under investigation. Whereas Cenozoic strata can often be correlated with a precision
of a few thousand to a few hundred thousand years, Paleozoic global chronostratigraphic
correlation is frequently practiced with error bars of ±1 million years or worse. The
general lack of Paleozoic deep-sea sediments and orbitally-tuned data series combined
with the incomplete epicontinental stratigraphic record have engendered a prevailing wisdom
among the comparatively small Paleozoic community that suggests resolving the Paleozoic
timescale to the level achieved for the Cenozoic was either impractical or simply impossible.
Here we integrate conodont and graptolite biostratigraphic and carbonate carbon isotopic
data from seven of the chronostratigraphically best-constrained sections from Baltica,
Avalonia and Laurentia, and demonstrate global chronostratigraphic control for upper
Llandovery through middle Wenlock (Telychian-Sheinwoodian) strata with precision
approaching 100 kyr. Some intervals require further study to delineate such small time
slices, but this study helps demonstrate that it is possible to produce a Paleozoic timescale
comparable to that of younger eras.
277
278
Late Silurian Ostracodes from the Hazro Anticline (SE
Turkey)
CLAUDIA DOJEN
C. Dojen - Westfälische Wilhelms-University, Institute for Geology and Palaeontology, Corrensstr. 24, D-48149 Muenster
(Germany); [email protected]
A new ostracode fauna recently has been discovered from the Fetlika Valley in the
Hazro Anticline (SE Turkey), some 75 km northeast of the city of Diyarbakir. The area is
situated south of the Assyrian suture, at the northern border of the Arabian platform.
Here, adjacent to the northern margin of Gondwana, late Silurian to early Devonian
sediments of the Dadas and Hazro Formation were deposited in a marine shoreline
environment. The base of the Dadas Formation consists of biocalcarentic limestones
deposited in a mid to outer shelf position.
The studied ostracodes are taken around the transition between the middle and upper
Dadas Formation, where the Silurian/Devonian boundary was supposed. But according
to Stolle (2008) palynomorph records indicate a late Silurian age for the lower part of the
upper Dadas Formation, which corresponds well with the ostracodes.
The ostracode associations consist mainly of beyrichioids represented by several new
taxa of the subfamily Amphitoxitidinae. The occurring taxa resemble strongly genera such
as Hobergiella, Juviella, Hemsiella, and Macrypsilon which are well known from the
late Silurian from Gotland and partly also from South America. Thus far, no certain
identification of these beyrichioids was possible as very few heteromorphs have been
found. Additionally, the ostracodes specimens show only comparatively small sizes for
beyrichioids (between 0.5 an 1.0 mm), indicating that only larval stages are represented.
Due to the outer shelf position, a turbiditic deposit is suggested. Besides these beyrichioids
some new beyrichiomorph and primitiopsiomorph taxa, e.g., with affinities to
Limbinariella, as well as some new binodicope and podocope taxa have been found.
The occurrence of beyrichioid ostracodes at the northern border of Gondwana in Late
Silurian times is remarkable, as the distribution of this ostracode group and their assumed
absence from Gondwana before the Emsian has been one of the main arguments for the
Rheic Ocean. However, the pre-Emsian occurrence of beyrichioids not only on the Arabian
platform, but also in South America and most probably in North Africa evidence against a
mature ocean which separates Gondwana from Baltica-Avalonia from the late Silurian
onward. Other possibilities like island hoping, dispersal via other marine hosts, or transport
by whirlwinds is unlikely because of the assumed large distances between the land masses.
Recent palaeogeographic reconstructions consider for the late Silurian a width of about
2500 km of the Rheic Ocean, with no rifting anymore but subduction zones, which would
function as a barrier for benthic faunas. Other palaeontological evidence such as the
distribution of shallow marine brachiopods corroborate the opinion of a wide shallow
marine area instead of alare Rheic ocean.
279
ACKNOWLEDGEMENT
I am thankful to David Siveter (University of Leicester, Great Britain) and Roger Schallreuter (University
Greifswald, Germany) for many information concerning the ostracode fauna.
REFERENCES
STOLLE E. (2008). Upper Silurian to Middle Devonian stratigraphy of the Dada_ section, Hazro area, SE
Turkey. In: Königshof, P. & Linnemann, U. (Eds.), From Gondwana and Laurussia to Pangea: Dynamics
of Oceans and Supercontinents. 20th International Senckenberg-Conference and 2nd Geinitz-Conference.
Final Meeting of IGCP 497 and IGCP 499. Abstract & Programme: 39-40.
280
Conodonts of the Silurian-Devonian boundary beds in
Podolia, Ukraine
DANIEL DRYGANT, HUBERT SZANIAWSKI
D. Drygant - State Museum of Natural History, National Academy of Sciences of Ukraine, Teatralna 18, Lviv 79008
(Ukraine); [email protected]
H. Szaniawski - Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warszawa (Poland);
[email protected]
Upper Silurian and Lower Devonian sediments are well exposed at many localities
along the banks of Dniester and its tributaries. They are composed of continuous marine
sedimentary sequence formed since the late Llandovery to the late Lochkovian. Thickness
of the Silurian deposits is about 340 m. and of the marine Devonian (Lochkovian) about
500 m. The marine Lochkovian pass gradualy into terrigenous Old Red facies.
Lower part of the Pridoli series (50 m.) is composed of limestones of various lithologic
type with the bioherms and biostroms, as well as dolomites and dolomitic marls. Conodonts
are rare; represented mainly by Ozarkodina typica and some wide-spread species of
Panderodus. Upper part of the series (20 m.) is build mainly of nodular limestone with
rich assemblages of fauna. The limestone is rich also in conodonts. Comparatively abundant
are: Ozarkodina typica, Parazieglerodina eosteinhornensis, Wurmiella excavata and
Panderodus unicostatus. Rarely occur also Delotaxis detorta and Belodella resima
(Drygant 1984). Some of the species are important for identification of the S/D boundary.
O. typica and W. excavata curvata do not occur higher than 1,4 m. below the boundary
and P. eosteinhornensis disappear just below the boundary. The boundary is established
on the first occurence of graptolite Monograptus uniformis angustidens, which is known
in Podolia from the outcrops in the villages Dinstrove (Volkovtsy) and Rashkiv (Nikiforova
Predtechenskij 1968). The lowermost part of the Lochkovian stage, the Khudykivtsi
Formation (57 m), is developed in form of the clayey limestones interbedded with shales.
40 cm below the S/D boundary appears Zieglerodina remscheidensis and 60 cm above it
the first representative of the genus Caudicriodus, the C. hesperius. We can not confirm
the earlier reports about occurence of Caudicriodus specimens below the boundary.
Higher part of the Lochkovian – the Mytkiv Fm. (about 125 m) is composed of dark
shales with rare and thin lenses of coquilla limestone, composed mainly of the brachiopod
shells. Occurrences of graptolites, Monograptus uniformis uniformis at 55 to 130 m
above the S/D boundary and M. uniformis brevis at 160 m above the boundary (Koren
1973), correlates well with the distribution of conodonts. Caudicriodus hesperius and
Zieglerododina remscheidensis disappear on about the same level as the graptolites. It
suggest that stratigraphic range of the conodont horizon C. hesperius corresponds to the
range of the graptolite horizon M. uniformis.
REFERENCES
DRYGANT D. (1984). Correlation and conodonts of the Silurian - Lower Devonian deposits of Volyn and
Podolia. Naukova Dumka, Kiev, pp. 1-192 (in Russian).
281
KOREN T.( 1973). Lower Devonian biostratigraphy of Pai-Khoi, Polar Urals and Podolia on Graptolites.
Stratigrafija nizhniego i sredniego devona. Trudy III Mezhdunarodnogo simpoziuma po granice silura i
devona i stratigrafii nizhniego i sredniego devona (in Russian). T. 2. Nauka, Leningrad: 142-148.
NIKIFOROVA O.I., PREDTECHENSKIJ N.N. (1968). A guide to the geological excursion on Silurian and Lower
Devonian deposits of Podolia (Middle Dniestr River). In: Proceedings of the 3rd international symposium
on Silurian-Devonian boundary and Lower and Middle Devonian stratigraphy. Leningrad: 1-58.
282
Geobiodiveristy Database and its application in
graptolite research
JUNXUAN FAN, DAN GOLDMAN, FENG CHEN, HUA ZHANG
J. Fan - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology,
Chinese Academy of Sciences, Nanjing 210008 (China); [email protected]
D. Goldman - Department of Geology, University of Dayton, Dayton (U.S.A.); [email protected]
F. Chen - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology,
H. Zhang - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology,
The Geobiodiversity Database (GBDB) Project (http://www.geobiodiversity.com) is
dedicated to the construction and maintenance of a web-enabled taxonomic, stratigraphic,
and geographic database for information gathered from the fossil record. Its goal is to
facilitate regional and global scientific collaborations focused on studying the history,
diversity, geography, and environmental context of life on Earth. The key elements of
GBDB are data, analyzing tools and web services.
The GBDB is structured around several independent subsets or tables, such as
bibliographic reference, geography (locality or section), taxonomy (fossil classification),
stratigraphy, and fossil collection. Each record of these subsets can be linked to a record
or records in other subsets. For example, one reference may contain several sections,
each containing a lithostratigraphic description and hundreds of fossil collections. The
reference subset is compatible with Endnote and has the available function of uploading a
standardized reference list (text format, such MS word or rtf). In the taxonomy subset,
the user can input general taxonomic information from the rank of phylum down to
species or subspecies. In the collection subset, the user can relate geographic,
chronostratigraphic, lithostratigraphic, or taxonomic information as well as the isotopic
age and paleogeographic information of any fossil collection by simply searching in different
subsets.
The GBDB also provides a powerful text-searching engine. For example, the user can
search collection subsets by using any combination of 22 fields, such as fossil name,
locality and biozone. Results are viewable on present-day geographic and satellite maps at
present. The statistical tools and related functions, such as data visualization (e.g.,
rangechart, data visualization on reconstruction maps), diversity statistics (e.g., diversity
curve, origination and extinction rates), and linkage to Geographic Information Systems
(GIS) software will be soon be available. The integration of GBDB with GIS will provide
powerful tools for the analysis of spatial data from the fossil record. The server of GBDB,
which is hosted in the State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing
Institute of Geology and Palaeontology, Chinese Academy of Sciences, is supported by
the institute and the laboratory, and will provide stable, long-term, free access.
The GBDB online database is an important tool in graptolite research, facilitating
studies on paleogeographic distribution, biodiversity trends, systematics, and regional and/
or global correlations. A preliminary study on the biogeographic evolution of graptolite
283
faunas in South China during the Late Ordovician to Early Silurian extinction and recovery
interval was recently conducted with the graptolite data from the GBDB. A stepwise
shrinking of graptolite distribution from the pre-Hirnantian to the early Hirnantian followed
by a subsequent expansion in the earliest Silurian can be recognized – a pattern that
seems to coincide with simultaneous icesheet and sea-level changes.
284
Biostratigraphy and geography of the OrdovicianSilurian Lungmachi black shales in South China
JUNXUAN FAN, MICHAEL J. MELCHIN, XU CHEN, YI WANG, YUANDONG ZHANG, QING
CHEN, FENG CHEN
J. Fan - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and
Palaeontology, Chinese Academy of Sciences, Nanjing 210008 (China); [email protected]
M. J. Melchin - Department of Earth Sciences, St. Francis Xavier University, Antigonish, Nova Scotia
B2G 2W5 (Canada); [email protected]
X. Chen - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and
Y. Wang - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and
Y. Zhang - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and
Q. Chen - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and
F. Chen - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and
Based on the new material of seven sections investigated recently, together with
previously published data, the authors analyze the tempo and spatial distributions of the
Lungmachi black shales, a key petroleum source bed widely distributed in South China.
The Lungmachi black shales range in age from the Normalograptus persculptus Biozone
of the uppermost Ordovician to the Spirograptus guerichi Biozone of the lower Telychian,
and ten graptolite biozones can be recognized within this unit (Fig. 1). The basal and
upper contacts of the Lungmachi black shales are diachronous. The basal contact ranges
from the N. persculptus to the Coronograptus cyphus biozones, a span of five graptolite
biozones over two stages. The upper contact ranges from the D. pectinatus-M. argenteus
Fig. 1 - Temporal and spatial distribution of the Lungmachi black shales in South China.
285
Biozone to the Spirograptus guerichi Biozone, which spans four graptolite biozones
over two stages.
The Yichang Uplift resulted in the formation of the Hunan-Hubei Submarine High in
the border area of Hubei, Hunan, and Chongqing. This is supported by a break in
sedimentation in this area spanning all or part of the Hirnantian, and in many areas
extending into the underlying Katian and overlying Rhuddanian. Comparison of the
distribution of the Katian to Rhuddanian strata in this area indicates a growth and subsequent
reduction in area of the Hunan-Hubei Submarine High particularly in the Hirnantian to
early Rhuddanian, which may partly represent the influence of the process of formation
and melting of ice sheet in Ordovician South Pole and consequent sea level change.
286
Cephalopod limestone biofacies in the Silurian of the
Carnic Alps, Austria
ANNALISA FERRETTI, KATHLEEN HISTON
A. Ferretti - Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia, largo S. Eufemia 19, I-41100
Modena (Italy); [email protected]
K. Histon - Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia, largo S. Eufemia 19, I-41100
Cephalopod limestones represent one of the most peculiar biofacies that developed in
Silurian times along the northern margin of Gondwana. The presence and relative
abundance of fossils, clearly visible in the field, enabled a taxonomic study of the main
fossil groups since the end of the eighteenth century. Together with the most evident
cephalopods, also bivalves, brachiopods and trilobites were studied in detail in different
times. A good stratigraphic assignment either with graptolites or with conodonts was
made of most sections. Paleoecological studies, on the contrary, were not so definite.
Cephalopod limestones from North Gondwana are often referred to as a single unit, and
the same paleoecologic-environmental conclusions driven in an area are borrowed and
extended to other regions.
Key-stratigraphic sections (Rauchkofel Boden, Cellon, Rauchkofel Boden torl, Valentin
Törl, Seewarte, Seekopf) representing distinctive paleogeographic/paleoenvironmental
settings were taken into consideration and studied in detail in this work, paying particular
attention to observe taphonomical information (abundance, dimension, orientation, colour,
preservation, etc.) of all organisms composing the fauna. The study aimed to fit even the
Carnic Alps cephalopod limestone biofacies into a more general picture of the Silurian. In
particular, a precise depositional environment and an improved sequence-stratigraphical
frame for the Silurian of the Carnic Alps in Austria based on a sedimentological,
lithostratigraphical, biostratigraphical and microfacial approach was achieved (Brett et al.,
in press).
Furthermore, analysis of “ooidal pockets” and “stromatolite-like” structures within the
Pt. celloni – Pt. a. amorphognathoides conodont zones is also discussed with regard to
their paleoenvironmental implications. Similar studies in other sectors (Oggiano & Mameli,
2006 from the Ordovician/Silurian of northern Sardinia), for this stratigraphical interval
highlight that knowledge to date regarding these peculiar carbonate facies is still quite
limited. In-depth studies in key areas to recognise these markers may shed light on the
relative positions of microterranes along the North Gondwana margin.
REFERENCES
BRETT C., FERRETTI A., HISTON K., SCHÖNLAUB H.P. Silurian Sequence Stratigraphy of the Carnic Alps, Austria.
Palaeogeography, Palaeoclimatology, Palaeoecology (in press).
OGGIANO G., MAMELI P. (2006). Diamictite and oolitic ironstones, a sedimentary association at Ordovician–
Silurian transition in the north Gondwana margin: New evidence from the inner nappe of Sardinia Variscides
(Italy). Gondwana Research, 9: 500-511.
287
288
Palaeozoic black shales: how much should we trust the
Recent to reconstruct the Past?
ANNALISA FERRETTI, ALESSANDRA NEGRI, THOMAS WAGNER, PHILIP A. MEYERS
Annalisa Ferretti - Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia, largo S. Eufemia 19,
I-41100 Modena (Italy); [email protected]
Alessandra Negri - Dipartimento di Scienze del Mare, Università Politecnica delle Marche, Via Brecce Bianche, I60131 Ancona (Italy); [email protected]
Thomas Wagner - School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, NE1
7RU (United Kingdom); [email protected]
Philip A. Meyers - Department of Geological Sciences, The University of Michigan, Ann Arbor, Michigan 48109-1005
(U.S.A.); [email protected]
Organic-carbon-rich sediments were widely deposited during multiple intervals of
Mesozoic and Palaeozoic time or even earlier; on the contrary, sediments rich in organic
carbon are today restricted to small areas along continental margins and have rarely
accumulated during the Cenozoic. Global marine deposits document that episodes of
accumulation of OC-rich sediments occurred in different regions and at different times.
These episodes were linked to climatic and palaeoceanographic perturbations that resulted
in massive fluctuations in hydrologic and nutrient cycles and in ocean chemistry and that
recurred throughout geologic time.
The whole Palaeozoic is punctuated by a profusion of episodes of black shale deposition
that represent a common and not unusual sediment for that time. Furthermore, the
abundance of organic matter does not, per se, imply black shales. The Palaeozoic, in fact,
is also characterized by fossiliferous OC-rich limestones, e.g. the Silurian–Devonian
“Orthoceras limestones” bordering northern Gondwana. However, the paucity of surviving
Palaeozoic and earlier black shale sections makes it difficult to impossible to recognize
the internal structure of global events that are common in younger OC-rich sedimentary
sequences. Going ever deeper into the past, in fact, two factors appear playing a more
and more fundamental role: preservation and time resolution. OC-rich sediments, either
in form of black shales or limestones, do not necessarily reflect periods of elevated
deposition of high organic matter but may paradoxically simply represent times of better
organic matter preservation. Then, even well-dated sequences do not offer the highresolution records needed to fully document or delineate short-time processes. In the
Palaeozoic the length of individual biozones is generally on the order of millions of years,
which is in the same range as third-order sea-level changes. Thus, an important question
in Palaeozoic sequences is whether episodes occur at different scales or belong to cycles
of diverse order.
Also according to this premise, too often was exasperate the use of the uniformitarianism
principle in which models or opinions derived from recent examples are simplistically
applied to any of the older “timeboxes”. In actuality, physical and biological conditions
(e.g., oxygen and CO2) have strongly varied through time. Palaeozoic black shales were
clearly deposited in a CO2-dominated setting (see Berner, 1994, 1998), whereas younger
deposits reflect a lower concentration of the same gas. Again, the nature of primary
producers is not yet completely defined for pre-Jurassic production of organic matter.
289
Furthermore, palaeogeographic scenarios reveal completely different worlds in terms of
land masses, oceans, palaeolatitudes, etc. According to this, any attempt to model the
deposition of OC-rich sediments through the Phanerozoic must necessarily be tuned with
all these variables. Another relevant point is that some of the Phanerozoic OC-rich sediments
are defined as global events, like the Cretaceous OAE1a and OAE2, but some others
appear to have had a more restricted and even localized significance. These differences
require the application of different approaches in search of possible interpretations and
perhaps diverse mechanisms leading to the deposition of OC-rich sequences.
Finally, many of the most significant black shale episodes in the Palaeozoic strictly
match with major crises in the history of life. Understanding what drives global diversity
may be used to explain processes, such as mass extinctions, that control diversity and
turnover at a variety of geographic and temporal scales.
The main issues described here need to be further investigated and are certainly worth
answering. The Scientific Community must come to a multiple-time scale approach and
to a constructive dialogue that better integrates data and models in order to be even more
successful. These efforts, with an emphasis on the upscaling/downscaling of processes
and effects/feedbacks, will lead to the identification of methodologies that may be used
uniformly in the Palaeozoic, Mesozoic and Cenozoic. In that case the scientific community
will be able to test the validity of processes in the recent as well as its application in the
past, to obtain real progress in the knowledge of OC-rich sediments, and to gain credibility
for delineating true perspectives for the future.
REFERENCES
BERNER R.A. (1994). GEOCARB II: a revised model for atmospheric CO2 over Phanerozoic time. American
Journal of Science, 294: 56-91.
BERNER R.A. (1998). The carbon cycle and CO2 over Phanerozoic time: the role of land plants. Philosophical
Transactions of the Royal Society of London, B 353: 75-82.
NEGRI A., FERRETTI A., WAGNER T. & MEYERS P.A. (2009). Organic-carbon-rich sediments through the
Phanerozoic: Processes, progress, and perspectives. Palaeogeography, Palaeoclimatology,
Palaeoecology, Special Issue, 273 (3-4): 197 pp.
290
Nautiloid Cephalopods from the Silurian of the Carnic
Alps – New evidences
MAURIZIO GNOLI, PAOLO SERVENTI, LUCA SIMONETTO
M. Gnoli - Dipartimento di Scienze della Terra , Università di Modena e Reggio Emilia, Largo Sant’Eufemia 19, I41100 Modena, (Italy); [email protected]
P. Serventi - Dipartimento del Museo di Paleobiologia e dell’Orto Botanico, Università di Modena e Reggio Emilia,
via Università 4, I-41100 Modena (Italy); [email protected]
L. Simonetto - Museo Friulano di Storia Naturale, via Marangoni 39-41, I-33100 Udine (Italy); [email protected]
Nautiloid Cephalopods from the Carnic Alps are the most frequent macrofossils found
in Silurian limestones. They have been described by Italian, German and Austrian
paleontologists since the 18th century (see Frech, 1888; Gortani & Vinassa de Regny,
1909; Heritsch, 1929). After the Second World War, apart from Ristedt’s (1968) taxonomic
revision on the Order Orthocerida and on juvenile stages and protoconchs, in the nineties
researches were resumed mainly revising Universities and Museums major collections
(Gnoli & Histon, 1998, Histon, 1999, Gnoli et al., 2000). The reviewed fauna is dominated
by orthoconic shells belonging to the Order Orthocerida (Families Orthoceratidae,
Geisonoceratidae and Pseudorthoceratidae), but also Orders Oncocerida and Barrandeocerida (Families Oncoceratidae, Barrandeoceratidae, Uranoceratidae and Lechritrochceratidae).
The present research deals with new material collected during several field trips, thanks
to the cooperation between the Museum of Natural History of Udine and the University
of Modena and Reggio Emilia. The new genus and species Serpaglioceras forojuliense
has been created (Gnoli & Serventi, 2008). The new taxon presents a very characteristic
grid-like outer adornment and “actinoceroid-type” recumbent septal necks, but the lack
of the endosiphuncular system does not allow the attribution to the Order Actinocerida.
Taxa belonging to the Order Actinocerida had been described on the basis of their
characteristic inner features, even if the poor state of preservation does not permit a
definitive specific attribution; the species identified are: Huroniella? sp. ind.; Ormoceras
sp. ind. A; Elrodoceras sp. ind. A. Furthermore, the species Nucleoceras cf. obelus is
found for the first time outside Bohemia, its type-area.
REFERENCES
F RECH F. 1888. Uber das Devon des Ostalpen, nebst Bemerkungen uberdas Silur und einem
paläontologischen Anhang. Zeitschrift Deutsche Geophysikalische Gesellschaft, Berlin: 659-738.
GORTANI M. & VINASSA DE REGNY P. 1909. Fossili neosilurici del Pizzo di Timau e dei Pal nell’Alta Carnia.
Memorie della Reale Accademia dell’Istituto di Scienze, Bologna: 183-217.
GNOLI M. & HISTON K. 1998. Silurian Nautiloid cephalopods from the Carnic Alps: a preliminary investigation.
Bollettino della Società Paleontologica Italiana, 36: 311-330.
GNOLI M. & SERVENTI P. 2008. A new Cephalopod from the early Silurian of the Carnic Alps (Italian side).
Rivista Italiana di Paleontologia e Stratigrafia, 114 (2): 171-178.
GNOLI M., HISTON K. & SERVENTI P. 2000. Revision of Silurian cephalopods from the Carnic Alps: the Gortani
and Vinassa de Regny collection, 1909. Bollettino della Società Italiana, 39 (1): 3-12.
HERITSCH F. 1929. Faunen aus dem Silur der Ostenalpen. Abhandlungen der Geologischen Bundesanstalt,
23(2): 1-183.
291
HISTON K. 1999. Revision of Silurian nautiloid Cephalopods from the Carnic Alps (Austria) - The Heritsch
(1929) Collection in the Geological Survey of Austria. Abhandlungen der Geologischen Bundesanstalt,
56 (1): 229-258.
R ISTEDT H. 1968. Zur Revision der Orthoceratidae. Abhandlungen der MathematischNaturwissenschaftlichen. Akademie der Wissenschaften und Literatur in Mainz, Klasse, 68 (4): 212287.
292
The Silurian of the southern Siberian Platform
ALEXANDER P. GUBANOV, OLGA K. BOGOLEPOVA, JAMES P. HOWARD,
MELISE B. HARLAND, MARCELA GOMEZ-PEREZ
A.P. Gubanov - CASP, Cambridge University, 18 a Huntingdon Road, Cambridge, CB3 0DH (United Kingdom);
[email protected]
O.K. Bogolepova - CASP, Cambridge University, 18 a Huntingdon Road, Cambridge, CB3 0DH (United Kingdom);
[email protected]
J.P. Howard - CASP, Cambridge University, 18 a Huntingdon Road, Cambridge, CB3 0DH (United Kingdom);
[email protected]
M.B. Harland - previously CASP, now GETECH, Leeds (United Kingdom); [email protected]
M. Gomez-Perez - CASP, Cambridge University, 18 a Huntingdon Road, Cambridge, CB3 0DH (United Kingdom).
The Silurian rocks of the southern part of Siberian Platform are poorly exposed and
studied.
During fieldwork in 2008 in the Tayshet Region of East Siberia, previously unknown
Silurian exposures of the Kezhem Formation were described and sampled for
palaeontology, petrography and provenance studies. At these new localities the strata are
represented by siliciclastic rocks. The succession does not contain fossils that will enable
dating of the strata, but by lithological comparison with the type section on Kezhem River
(Komarevsky & Zhukov, 1966) and the section on Chuna River (Tesakov et al., 2000),
we suggest a preliminary correlation of these strata. The Kezhem River sequence is up to
100 m thick and lies conformably on Late Ordovician strata. It consists of basal
conglomerate, and quartz sandstone interbedded with claystone. The Chuna River
siliciclastic sequence yields lingulids, gastropods, cephalopods, acanthodians and thelodonts
of Early Silurian age. The sequence is interpreted as inshore to lagoonal deposits.
A detailed paleogeography of this region will be presented.
REFERENCES
KOMAREVSKY V.T. & ZHUKOV N.V. (1966). Explanatory notes to the geological map 1961, sheet N-47-II.
Moscow, Nedra,:1-73 (in Russian)
TESAKOV YU.I., PREDTECHENSKY N.N., LOPUSHINSKAYA T.V., KROMYCH V.G., BAZAROVA L.S., BERGER A.YA., &
KOVALEVSKAYA E.O. (2000). Stratigraphy of Oil and Gas Basins of Siberia. Silurian of Siberian Platform.
403 pp. GEO, Novosibirsk (in Russian with English summary).
293
294
Upper Silurian nautiloid faunas from the Eggenfeld
section (Graz, Austria)
KATHLEEN HISTON, BERNHARD HUBMANN
B. Hubman - Institute for Earth Sciences (Geology & Palaeontology), University of Graz, Heinrichstrasse 26, A-8010
Graz (Austria); [email protected]
The preliminary results of a systematic investigation of the nautiloid faunas from the
Upper Silurian (Pridoli) sections of the Graz Palaeozoic are presented. The aim of the
present study is to add a further contribution to the systematic description of Silurian
nautiloid cephalopods within a well defined biostratigraphic framework in order to elaborate
their use as a tool for biostratigraphic correlation and palaeobiogeographic reconstructions.
The presence of the common Circum Mediterranean ‘Orthoceras’ Limestone and
Scyphocrinites Communities (Vai 1999) and the Dualina nigra-Patrocardia bivalve
subcommunity (Kriz 1999) within the latest Pridoli of the Carnic Alps sections demonstrates
that faunal exchange was taking place during this interval between the North Gondwana
terranes and Baltica.
Unfortunately there are few age comparable faunas described for considering exchange
of the nautiloid faunas between the North Gondwana terranes during the Pridoli as
systematic revision, particularly of the Bohemian fauna, is still lacking. Gnoli (1990) has
shown links between the Sardinian and Bohemian Silurian nautiloid faunas within a broad
stratigraphic framework while Histon (2002) concluded that the more shallow water facies
restricted nautiloid species described from the Carnic Alps were common to both areas
possibly reflecting closeness to Bohemia where these forms are common in the Ludlow /
Pridoli series while the more pelagic faunas in common reflected the exchange between
the various North Gondwana terranes, Baltica and the Urals due to currents.
The preliminary data presented for the faunas from the Graz Palaeozoic
- increase and add to the existing documentation of Silurian nautiloid faunas and thus
make a further contribution towards the palaeobiogeographic knowledge of the position
of this fragment of the North Gondwana terranes at a precise stratigraphic interval, the
latest Pridoli.
- provide more data in support of the idea of faunal exchange between North Gondwana
terranes such as the Carnic Alps and Sardinia, and Baltica.
- are of great importance as they place the the nautiloid faunas from the Graz Silurian
within a global scenario. The results of the proposed study of the systematics and
paleobiogeography of the fossil nautiloids will provide important information on regional
paleogeography and possible migrational pathways for pelagic organisms. This will yield
further insights into the positioning of paleocontinents and paleooceangraphy during the
Silurian.
295
REFERENCES
GNOLI M. (1990). New evidence of faunal links between Sardinia and Bohemia in Silurian time on the basis of
nautiloids. Bollettino della Societé Paleontologica Italiana, 29 (3): 289-307.
HISTON K. (2002). A nautiloid assemblage from the Upper Silurian (Pridoli) of the Carnic Alps, Austria. In:
Wyse Jackson P.N., Parkes M.A. & Wood R. (eds), Studies in Palaeozoic Palaeontology and biostratigraphy
in honour of Charles Hepworth Holland, Special Papers in Palaeontology, 67: 115-133.
KRIZ J. (1999). Silurian and Lowermost Devonian Bivalves of Bohemian Type from the Carnic Alps. In
Lobitzer and Grecula (eds) Geologie ohne grenzen - Festschrift 150 Jahre Geologische Bundesanstalt.
Abhandlungen der Geologische Bundesanstalt, 56: 259-316.
VAI G.B. (1999). Wenlockian to Emsian communities of the Carnic Alps (Austria and Italy). In Boucot A.J.
& Lawson J.D. (eds) Paleocommunities - a case study from the Silurian and Lower Devonian: 282-304.
296
The Cellon Section: a Review of the Stratotype Section
for the Southern Alps (1894-2009)
KATHLEEN HISTON, HANS PETER SCHÖNLAUB, ANNALISA FERRETTI
H.P. Schönlaub - Austrian Academy of Science, Center for Geosciences, Vienna (Austria); [email protected]
A. Ferretti - Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia, largo S. Eufemia 19, I-41100
Among the many geological sections located in the Central and Southern Alps the
Cellon Section represents one of the most important as it serves as a reference section for
the Upper Ordovician and the Silurian. There is no other profile which has beed visited so
often or has attracted so many Earth scientists for basic or comparative studies. In fact,
the long lasting history of research started with a mapping report of the area by Geyer
(1894) which served as a basis for further studies. Geyer correlated the section with the
upper Silurian in the former terminology of the 19th century. After the Great War scientists
from both Austria and Italy worked in the area. Of particular importance is the
comprehensive study carried out by von Gaertner who focused his work on the Cellon
section and introduced a formal lithostratigraphic subdivision which has partly been in use
until the present. In the late 1950s Otto H. Walliser studied the conodont biostratigraphy
for the Upper Ordovician, Silurian and lowermost Devonian portion of the Cellon Section.
Based on more than 250 samples he collected almost 35,000 conodont elements which he
assigned to 11 Silurian conodont zones. This zonation (Walliser, 1964) has served for
many years as a standard for global correlation of Silurian strata. An Hirnantian conodont
fauna has also now been documented (Ferretti & Schönlaub, 2001). In recent times,
however, some additions and amendments from other sections have provided a more
detailed zonation. Other studies on chitinozoans (Priewalder, 1997) and graptolites (Jaeger,
1975: Storch pers. comm. - presence of Glyptograptus persculptus) have added further
important data so the section is now fully defined biostratigraphically using three
standardarized zonations. Over the last four decades a variety of systematic palaeontological
research by diverse authors has been carried out in the Cellon Section, e.g. on bivalves,
brachiopods, nautiloids, graptolites, agglutinated foraminifers, ostracods, acritarchs,
chitinozoans, trilobites and most recently even corals. Detailed studies have been done of
the microfacies and faunal taphonomy in addition to studies of the sedimentology,
geochemistry and application of C and O isotope analysis methods for the whole section.
More recently, bentonite-bearing horizons in the Late Ordovician, upper Llandovery and
Wenlock have been correlated with coeval occurrences in other parts of Europe. The ash
layers originated from a subduction-related volcanism of an active plate margin and was
dominated by calcalcalic mafic lavas of a volcanic arc setting with andesitic-rhyodacitic/
dacitic magmatism, data of important significance with relation to geodynamics and
palaeogeographical reconstructions of the Peri-Gondwanan terranes (Histon et al., 2007).
Finally, sequence stratigraphic methods were applied to the Silurian part of the Cellon
297
Section by a team headed by Carl Brett which highlighted eustatic changes which may be
traced across four palaeocontinents (Brett et al., in press).
Present and Future - A valuable multidisciplinary data set is now available with regard
to the Cellon Section which may be used for subdivision, to discriminate minute timelapses and to recognize short or long-lasting events in Earth’s history which occur
simultaneously in other parts of the world. A short overview of the research done to date
and present/future projects regarding faunal response to eustatic changes will be presented
so as to highlight the still outstanding importance of this standard section.
REFERENCES
BRETT C.E., FERRETTI A., HISTON K. & SCHÖNLAUB H.P. (in press). Silurian sequence stratigraphy of the
Carnic Alps (Austria). Palaeogeography, Palaeoclimatology, Palaeoecology.
FERRETTI A. & SCHÖNLAUB H.P. (2001). New conodont faunas from the Late Ordovician of the Central
Carnic Alps, Austria. Bollettino della Società Paleontologica Italiana, 40: 3-15.
HISTON K., KLEIN P., SCHÖNLAUB H.P. & HUFF W.D. (2007). Lower Paleozoic K-bentonites from the Carnic
Alps, Austria. Austrian Journal of Earth Sciences, 100: 26-42.
JAEGER H. (1975). Die Graptolithenführung im Silur/Devon des Cellon-Profils (Karnische Alpen). Carinthia
II, 165 (85): 111-126.
PRIEWALDER H. (1997). The distribution of the chitinozoans in the Cellon section (Hirnantian – lower Lochkovian)
- A preliminary report. Berichte der Geologischen Bundesanstalt, 40: 74-85.
W ALLISER O.H. (1964). Conodonten des Silurs. Abhandlungen des Hessischen Landesamtes für
Bodenforschung, 41: 1-106.
298
Does “Lilliput Effect” of brachiopod exist in South
China after the late Ordovician mass extinction?
BING HUANG, DAVID A. T. HARPER, JIAYU RONG, RENBIN ZHAN
B. Huang - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology,
D.A.T. Harper - Geological Museum, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen (Denmark);
[email protected]
J. Rong - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology,
Chinese Academy of Sciences, Nanjing 210008 (China).
R. Zhan - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology,
Body size is a key morphological parameter that has many implications for the behaviour,
ecology and morphological development of an animal. In the immediate aftermath of
mass extinction fossil organisms are typically much smaller at species level than those of
pre-event times. This evolutionary phenomenon is termed “Lilliput Effect” (Urbanek,
1993).
The Lilliput Effect describes significant size reduction within species-level taxa that
survive the extinction events and is usually a temporary phenomenon confined to the
survival interval. However the continued discovery of new miniaturized faunas has
expanded the definition of the Lilliput Effect far beyond Urbanek’s (1993) original concept.
Recently, two types of the Lilliput Effect have been recognized through a series of detailed
case studies: 1) a specific effect, following the original definition which affects species
level taxa, related to deteriorated environments, and 2) a more general effect, apparent in
higher rank above the species level (e.g. Twtichett, 2007).
To date, case studies of the Lilliput Effect have concentrated mainly on the aftermath
of the end Permian event. The body size change of brachiopods across the end Ordovician
mass extinction is poorly known. In this study, the body sizes of brachiopods from southeast
China through the Ordovician and Silurian transition (late Katian, Hirnantian, earliest
Rhuddanian) are compared at generic, superfamilial, ordinal, and class levels.
Implicit in the Lilliput model is that the miniaturized faunas are in some way dwarfed
or stunted. To avoid this, the size frequency and survivorship curves for Levenea and
Leptaena were produced, and results of both genera from different taxonomic classes can
be compared with the normal population of the brachiopod Lepidocyclus capax from
Ordovician strata.
To focus on macroevolutionary trends within a defined environmental setting, all fossil
collections were restricted to BA3, which include normally-oxygenated, shallow-water
environments. Analyses were also limited to the assemblages from silty mudstones or
mudstones. The width and length of all complete and nearly complete specimens (juvenile
specimens are excluded from the analyses) were measured. Instead of the traditional 90%
or 95% confidence interval estimate, the IQR (Inter Quartile Range) which more
representative than the standard deviation (Hampel, 1974) is adopted for estimates of the
spread of the body size data.
299
Some preliminary conclusions are as follows.
1) Trends in the fluctuations of body size of taxa at lower taxonomic ranks are highly
variable, which is more in line with Urbanek’s (1993) original definition and very different
from the Lilliput Effect occurred after the end Permian mass extinction. A possible
explanation is that the intensity of the terminal Ordovician extinction event was much less
than that of the end Permian mass extinction.
2) Representatives of Orthida and Strophomenida both increased their body sizes during
the latest Ordovician extinction but suffered significant losses after the crisis; but those of
Pentamerida and Rhynchonellida, which decreased their body size, diversified rapidly
after the extinction in the earliest Silurian. These contrasting trends in body size change at
the ordinal level and dominance suggest that these two major groups adopted quite different
survival strategies.
REFERENCES
HAMPEL F.R. (1974). The influence curve and its role in robust estimation. Journal of the American Statistical
Association, 69: 383-393.
TWITCHETT R.J. (2007). The Lilliput effect in the aftermath of the end-Permian extinction event.
Palaeogeography, Palaeoclimatology, Palaeoecology, 252: 132-144.
URBANEK A. (1993). Biotic crises in the history of Upper Silurian graptoloids: a palaeobiological model. Historical
Biology, 7: 29-50.
300
Origin and diversification of the Early Silurian
virgianid brachiopods
JISUO JIN, PAUL COPPER
J. Jin - Department of Earth Sciences, University of Western Ontario, London, Ontario N6A 5B7 (Canada); [email protected]
P. Copper - Department of Earth Sciences, Laurentian University, Sudbury, Ontario P3E 2C6 (Canada);
[email protected]
Late Ordovician virgianid brachiopods (Order Pentamerida), which developed
conspicuously large shells and thrived in the shallow tropical seas of Laurentia, Baltica,
Kazakhstan, Siberia, North China, South China, and their surrounding microplates and
terranes, virtually disappeared during the latest Ordovician (Hirnantian) mass extinctions.
Only two Late Ordovician genera of the Suborder Pentameridina survived into the Early
Silurian: Holorhynchus which originated in the latest Katian, and Brevilamnulella in the
Hirnantian.
During the earliest Silurian, the virgianids constituted a major component of the postextinction recovery brachiopod faunas in the paleocontinents of North America (including
Greenland), Siberia, Baltica, and Kazakhstan. But the origin of the large-shelled virgianids
(as well as the stricklandiids and clorindids) during the earliest Silurian (Rhuddanian) has
been a puzzle because neither Holorhynchus nor Brevilamnulella appear to have been
likely ancestors on the basis of previously known fossil record.
A series of intermediate forms between Brevilamnulella and Virgiana has now been
found in the lower Rhuddanian (basal Llandovery) carbonate strata of Anticosti Island,
strongly suggesting that either the Virgiana lineage originated from Brevilamnulella, or
that the two lineages were sister groups. Several morphological modifications have been
observed in a morpho-series from the Hirnantian Brevilamnulella to the early Rhuddanian
Viridita and then to the middle-late Rhuddanian Virgiana.
1. Shell size and shape (outline and convexity). Increasing shell size, from
equidimensional to elongate; from nearly equibiconvex to strongly ventribiconvex. In
Viridita lenticularis, shells are slightly wider than long, and transversely subelliptical.
Some shells may become equidimensional with equal length and width. The strongly
transverse shell of Viridita becsciensis appears to be a rare and extreme case among the
various forms of genus on Anticosti Island. A more advanced but yet undescribed form
(Viridita n. sp.) from the upper Fox Point Member of the Becscie Formation is intermediate
between typical Viridita lenticularis and early Virgiana barrandei in its larger, more
strongly convex shell, with some specimens showing a tendency towards accelerated
longitudinal growth.
2. Umbonal height. In relatively small shells of V. lenticularis, the ventral and dorsal
umbones are low (1-2 mm above hinge line) and of similar height, with the ventral umbo
slightly higher in larger specimens.
3. Shell costae. Brevilamnulella has a largely smooth shell. In Viridita, the shells
change from quasi-smooth in small forms to weakly costate antero-medially in adults.
Contrary to common belief, Virgiana barrandei, the type species of mid-Rhuddanian
301
age, is only faintly costate, with the ribs clearly visible only with the help of coating and
proper lighting in some specimens. Stronger and distinct costae are not developed until
the late Rhuddanian, in such species as V. mayvillensis.
4. Fold and sulcus. Brevilamnulella of Hirnantian age lacks a fold and sulcus. This is
true also for the early growth stage (up to 5 mm length) of Viridita lenticularis in the
early Rhuddanian. At later growth stages, a ventral sulcus and a dorsal fold of variable
strength are developed and extend to the anterior margin to produce a uniplicate
commissure. In Viridita n. sp., the fold and sulcus have a tendency to become flattened
near the anterior margin, concomitant with the a moderate increase in shell size and
convexity. The result is a rectimarginate anterior commissure, although the coarse costae
make the margin denticulate.
A flattening of the dorsal valve and development of an antero-medial depression,
together with a notable shell elongation, mark the origin of the true Virgiana, represented
by Virgiana barrandei that first appears in early middle Rhuddanian strata of the Becscie
Formation. In V. barrandei, the uniformly convex state (or the Brevilamnulella state),
without a fold or sulcus, is confined to apical 2 mm. From 2 mm to about 20 mm length,
a dorsal fold and a ventral sulcus are well defined, usually with a single costa in the
sulcus. This can be referred to as the Viridita state. The fold and sulcus disappear more
anteriorly – the dorsal fold inverts into a gentle medial depression that broadens towards
the anterior margin, whereas the corresponding antero-medial carina in the ventral valve
is usually less well delimited than the medial depression of the dorsal valve. The result is
a weakly sulciplicate anterior commissure in relatively large shells of V. barrandei. With
ontogeny, therefore, the anterior commissure of a Virgiana shell may change from
rectimarginate to uniplicate, to rectimarginate, and then to gently sulciplicate.
302
Tracking Silurian eustasy: Alignment of empirical
evidence or pursuit of deductive reasoning?
MARKES E. JOHNSON
M.E. Johnson - Department of Geosciences, Williams College, Williamstown, Massachusetts 01267 (U.S.A.);
[email protected]
Sea level is not static, but liable to fluctuations due to addition or subtraction of water
in the world’s oceans, as well as changes to the shape and holding capacity of ocean
basins. Relative changes in sea level are well supported by the rock record on a regional
scale. Whether or not global (eustatic) changes are evident and how frequently they
occurred during any given interval of time is a matter of contention among stratigraphers.
Opinions have evolved over the last century with arguments based on refinements in
biostratigraphy, chemostratigraphy, radiometric dating, and conceptual advances in sequence
stratigraphy derived from technological advances in seismic stratigraphy. The Pulsation
Theory of A.W. Grabau (1936) attributed to Paleozoic strata a global history of 11
highstands distributed through a sequence with 21 subdivisions. In 1977, Peter Vail and
associates from the Exxon Production Research Company independently interpreted a
similar Paleozoic history showing 10 second-order highstands but distributed over 19
subdivisions. The approach of Vail et al. (1977) was model-based and followed a deductive
path, while Grabau’s was based on inductive reasoning. Recent refinements in a Paleozoic
sea-level curve by Haq & Schutter (2008) are based on the same deductive approach
taken by the Vail group, but pinned to patterns in sequence stratigraphy. Drawing on the
Silurian System as a Paleozoic sample, this contribution compares the timing, frequency,
and magnitude of sea-level highstands deduced by Haq & Schutter (2008) with those
promulgated by the author from the mid-1980s onward using empirical evidence more in
line with Grabau’s methodology (Johnson 2006). Both apply the concept of geographic
reference areas, but Haq & Schutter (2008) identify many more Silurian highstands over
an interval lasting 27.7 million years. Eight out of 10 Silurian highstands identified by this
author (Johnson 2006) match or overlap 8 out of 15 highstands recognized by Haq &
Schutter (2008). At issue is which, if any, qualify as eustatic signals with respect to
current databases for biostratigraphic and chemostratigraphic correlation. Evaluation is
based on paleontological and biostratigraphic evidence reviewed from Iowa, New York,
Norway, Estonia, and Austria in the paleogeographic context of three separate Silurian
continents. All sequences are compared using the Silurian time scale and biostratigraphic
zonations from Ogg et al. (2008).
REFERENCES
GRABAU A.W. (1936). Oscillation or pulsation?. International Geological Congress, Report of the 16th session,
United States of America 1933, 1: 539-553.
HAQ B.U. & SCHUTTER S.R. (2008). A chronology of Paleozoic sea-level changes, Science, 322: 64-68.
JOHNSON M.E. (2006). Relationship of Silurian sea-level fluctuations to oceanic episodes and events, GFF,
128: 115-121.
303
OGG J.G., OGG G. & GRADSTEIN F.M. (2008). The Concise Geologic Time Scale. Cambridge University Press,
Cambridge, UK, 177 pp.
VAIL P.R., MITCHUM R.M., JR. & THOMPSON S., III (1977). Seismic stratigraphy and global changes of sea
level, Part 4: Global cycles of relative changes of sea level. In Payton C.E. (Ed.), Seismic Stratigraphy –
Applications to Hydrocarbon Exploration, American Association of Petroleum Geologists Memoir, 26:
83-97.
304
Additions to the carbon isotope trend of Podolia
(Ukraine) with a summary and evaluation of the
Silurian chemostratigraphy
DIMITRI KALJO, VOLODYMIR GRYTSENKO, TÕNU MARTMA
D. Kaljo - Institute of Geology, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); [email protected]
V. Grytsenko - Geological Museum of State Natural History Museum of National Academy of Sciences, 15 B. Khmelnitsky
Str., 01030 Kyiv (Ukraine); [email protected]
T. Martma - Institute of Geology, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia);
[email protected]
Silurian chemostratigraphy has been progressing rather rapidly during the last two
decades. Many papers have been published concerning Silurian carbon isotope trends
mainly of Baltica and Laurentia, but also Australia, China, Avalonia and Barrandia. Our
team at the Institute of Geology started these studies in the mid-1990s, in later years
involving colleagues from elsewhere. Since then we have been publishing about Ordovician
and Silurian carbon isotope chemostratigraphy, mainly of the Baltic area sensu stricto
(Estonia, Latvia and Lithuania), but also of Gotland, Norway and Podolia. Here only the
Silurian is discussed.
Podolia is known as a classical area of Silurian rocks. The succession begins with the
topmost Llandovery, ranging up to the very end of the Pridoli and continuing into the
lower Devonian. In Kaljo et al. (2007) three global δ13C excursions were revealed in the
lower and upper Wenlock and upper Ludlow of Podolia. The Pridoli was left out of that
study. Recently, however, we took a series of samples from a drill core made in the
Ternopil area at Katuzhiny village. The drilling partly penetrated very shallow water
facies (upper Ludlow to lower Pridoli), represented by dolomitic rocks with gypsum
interbeds and obvious gaps. Higher in the Pridoli facies became gradually more marine,
as evidenced by limestones, marlstones and even argillites with graptolites appearing in
the lowermost Devonian. It means that after a sea level low stand in the late Ludlow/
earliest Pridoli, later during the latter epoch the Podolian basin experienced a continued
transgression and deepening. The Grinchuk Formation (Fm.), lying just below the midLudfordian δ13C excursion, shows in the Katuzhiny section the same plateau of values
around 0‰ as observed earlier in outcrops. The mid-Ludfordian peak is missing in the
Isakovtsy and lower Prigorodok Fms of the core; instead there occurs a large negative
excursion with a maximum value (–5‰) measured in the lowermost Pridoli (lower Varnitsa
Fm.). Higher in the Varnitsa Fm. values remain below 0‰, and in the Trubchin Fm.
around 0, but below 1‰ except in a few samples at the top. These samples show the
beginning of a new δ13C excursion with the highest value of 4.5‰ in the Dzwinogorod
Fm. The falling limb of this excursion is rather steep and may refer to a gap at this level.
A new recovery of the curve reaches a value of 2.8‰ in the lowermost Devonian (Taina
Fm.).
Summarizing the new Podolian data, we note a major δ13C excursion in the upper
Pridoli and a medium one at the very beginning of the Devonian on the background of
305
relatively low values and several gaps in the section. Comparing these data with the Baltic
ones, we see several minor coincidences in trends, but none of the positive excursions
noted above is observed due to specificity of these sections. However, Andrew et al.
(1994) found a major δ13C shift at the bottom of the Devonian in Australia, proving a
global value of this excursion.
The topmost Ordovician major δ13C excursion, peaking in the mid-Hirnantian slightly
below the O/S boundary, is a good starting point for discussions about Silurian
chemostratigraphy. Some negative δ13C excursions might appear to be very characteristic,
but here we consider only positive shifts of medium and major sizes, which are most
trusted in chemostratigraphy. The following seven excursions have been established: midAeronian and early Telychian in the Llandovery, early Sheinwoodian and late Homerian
in the Wenlock, late Gorstian (?) and mid-Ludfordian in the Ludlow, and one excursion in
the late Pridoli. The Silurian/Devonian boundary is marked by a clear shift as described
above. Most of these excursions are well defined also biostratigraphically and are thus
highly useful for Silurian stratigraphy.
The study was partly supported by the Estonian target funding projects SF 0140020s08
and 320080s07.
REFERENCES
ANDREW A.S., HAMILTON P.J., MAWSON R., TALENT J.A. & WHITFORD, D.J. (1994). Isotopic correlation tools in
the mid-Paleozoic and their relation to extinction events. Australian Petroleum Exploration Association
Journal, 34: 268-277.
KALJO D., GRYTSENKO V., MARTMA T. & MÕTUS M.A. (2007). Three global carbon isotope shifts in the Silurian
of Podolia (Ukraine): stratigraphical implications. Estonian Journal of Earth Sciences, 56: 205-220.
306
Silurian sea level variations based on SiO2/Al2O3 and
K2O/Al2O3 ratios from Priekule drill core section,
Latvia, and comparison with redox conditions
carbonate precipitation and global δ13C changes
TARMO KIIPLI, ENLI KIIPLI, DIMITRI KALJO
T. Kiipli - Institute of Geology, Tallinn University of Technology, Ehitajate 5, 19086 Tallinn (Estonia); [email protected]
E. Kiipli - Institute of Geology, Tallinn University of Technology, Ehitajate 5, 19086 Tallinn (Estonia); [email protected]
D. Kaljo - Institute of Geology, Tallinn University of Technology, Ehitajate 5, 19086 Tallinn (Estonia); [email protected]
Eustatic sea level responds sensitively to the climatic changes due to the growth and
retreat of continental ice sheets at high latitudes (McKerrow, 1979). Long range variations
in global sea level may be caused by plate tectonic processes and global distribution of
continents (Haq & Shutter, 2008). These sea level falls and rises can be read from the
facies movements, breaks in sedimentation and changes in benthic faunal communities in
sedimentary sections on stable platforms (Johnson, 1996).
Here we propose independent method for establishing sea level high and low stands by
the SiO2/Al2O3 and K2O/Al2O3 ratios. This bases on aluminium concentration preferably
in clay minerals forming the major part of fine grained pelitic fraction of terrigenous
material. In contrary, silicon and potassium concentrate in quartz and potassium feldspar,
which are abundant in coarser fractions. Therefore these element ratios reflect grain size
of siliciclastic material depending on the intensity of water movement and sea depth. The
West-Latvian Priekule drill core section from the Silurian deep shelf was investigated.
Deep shelf environment is favourable for study of sea level fluctuations by this method
because of steady sedimentation without breaks. Specific aspect, compared with shallow
water sections, is that only large changes in sea level are recorded. Correlation of section
bases on finds of zonal graptolites, and the published δ13C curve (Kaljo et al., 1997).
In more than 400 m thick shale and marlstone section from Telychian to Ludfordian
the SiO2/Al2O3 ratio is 3.4 in average. In Lower Sheinwoodian, Upper Homerian and
Lower Ludfordian the ratio rises to the 3.8–4.0. This corresponds to the content of 40–
50% of coarse silt fraction and indicates sea level fall. Probably the fall leads to sea
depths less than 120 m, the depth of surface mixing zone in shelves open to the ocean.
Lower values of the SiO2/Al2O3 ratio (2.7–3.3) are characteristic to the Telychian, Middle
Wenlock, Gorstian and Upper Ludfordian indicating greater sea depths than mixing zone.
K2O/Al2O3 ratio behaves similarly to SiO2/Al2O3 confirming these depth changes. Positive
δ13C excursions identified in many studies worldwide reflect global events. Good correlation
of increased values of SiO2/Al2O3 and K2O/Al2O3 ratio with positive δ13C excursions
indicates that they all correspond to the global sea level changes. Changes in redox conditions
in sediments can be described on the basis of sulphur content. Sulphur fixation into
sediment depends on the reduction of sulphate in pore water, depending on organic matter
content. Higher sulphur contents in the Priekule section exceeding 1% occur in the intervals
of sea level low stand. Enhanced flux of organic matter into sediments can be caused by
307
about two times decrease of water depth, although contribution from higher bioproductivity
is also possible. Higher contents of carbonates occur in the intervals corresponding to the
sea level low stands as well. This can be caused by shifting of sedimentation area from
suboxic pH minimum zone to the shallower seawater mixing zone during the fall of sea
level. All five described geochemical signatures correlate in general, but at different levels
may have temporal differences: e. g. some sea level low stands start earlier and last
longer, than δ13C positive excursions.
Three lowstands and four highstands described herein in deep shelf Priekule section
reflect large most important changes in sea level. Present study suggests that the amplitude
of many sea level changes recorded in previous more detailed studies needs to be reestimated.
REFERENCES
HAQ B.U. & SHUTTER S.R. (2008). A chronology of Paleozoic sea level changes. Science, 322: 64-68.
JOHNSON M. E. (1996). Stable cratonic sequences and a standard for Silurian eustasy. In Witzke B.J., Ludvingson
G.A. & Day J.E. (Eds.), Paleozoic Sequence Stratigraphy: Views from the North American Craton.
Geological Society of America Special Paper, 306: 203-211.
KALJO D., KIIPLI T. & MARTMA T. (1997). Carbon isotope event markers through the Wenlock-Pridoly sequence
at Ohesaare (Estonia) and Priekule (Latvia). Palaeogeography, Palaeoclimatology Palaeoecology,
132: 211-223.
MCKERROW W.C. (1979). Ordovician and Silurian changes in sea level. Journal of the Geological Society
London, 136: 137-145.
308
Aeronian and lower Telychian retiolitid graptolites,
Arctic Canada
ALFRED LENZ, MICHAEL MELCHIN, ANNA KOZLOWSKA
A. Lenz - Department of Earth Sciences, University of Western Ontario, London, Ontario N6A 5B7 (Canada);
[email protected]
M. Melchin - Department of Earth Sciences, St. Francis Xavier University, Antigonish, Nova Scotia B2G 2W5 (Canada);
[email protected]
A. Kozlowska - Institute of Paleobiology, Polish Academy of Sciences, 51/55 ul. Twarda, PL-00 818 Warszawa (Poland);
[email protected]
Aeronian and lower Telychian retiolitid graptolites have been relatively poorly known
or understood, due largely to their morphologic complexity and mode of preservation.
The recovery of isolated, uncompressed and beautifully preserved material from Arctic
Canada contributes to a much better understanding of their morphology and the
evolutionary development of retiolitids as a whole. Retiolitids, first represented by
Pseudoretiolites, appeared in the basal Aeronian, and by mid-Aeronian (convolutus
Biozone) at least six species of retiolitids were in existence. The earliest members of the
genus Pseudoretiolites, presumably the ancestors to later-appearing members, but of
which no complete specimen has yet been recovered, preserve a complete sicula as well
as a partially preserved theca 11. By contrast, the sicular preservation of those occurring
in the convolutus Biozone ranges from a complete metasicula, partial metasicula, prosicula
only, or non-preservation. This variation exists even within the same species, although
most representatives of each species preserve at least the prosicula. Two other taxa,
Eorograptus and “Eorograptus” also occur in the convolutus Biozone; both possess a
shallow, bowl-shaped ancora umbrella that is weakly spiralled, and both generally preserve
at least a prosicula. The former genus possesses pleural lists but no thecal ventral lists,
whereas the latter, most probably a new genus and species, possesses no pleural lists, but
complete thecal ventral lists; the latter taxon is similar to the younger (early Telychian)
genus Rotaretiolites in possessing complete thecal ventral lists. Rotaretiolites and
Pseudoplegmatograptus occur in the earliest Telychian guerichi Biozone. The apparent
proliferation of retiolitid taxa in the convolutus Biozone and to a lesser extent in the
guerichi Biozone appear to be real in that the underlying and overlying biozones, with the
exception of the sedgwickii Biozone, have yielded ample occurrences other graptolites,
and furthermore, the diversification surges in retiolitids correspond to global peaks in
other graptolites (Melchin et al., 1998).
REFERENCE
MELCHIN M.J., KOREN’ T. N. & STORCH P. (1998). Global diversity and survivorship patterns of Silurian graptoloids.
In Landing E. & Johnson M.E. (Eds.), Silurian Cycles. New York State Museum Bulletin 491: 165-182.
309
310
Occurrence and 3D-preservation of Llandovery
graptolites in the Criadero Quartzite of the Almadén
mining district (Spain)
SATURNINO E. LORENZO, JUAN C. GUTIÉRREZ-MARCO
S.E. Lorenzo - Departamento de Ingeniería Geológica y Minera, Escuela Universitaria Politécnica, Universidad de
Castilla-La Mancha, E-13400 Almadén (Ciudad Real) (Spain); [email protected]
J.C. Gutiérrez-Marco - Instituto de Geología Económica (CSIC-UCM), José Antonio Novais 2, E-28040 Madrid
The Criadero Quartzite is one of the most distinctive Paleozoic formations of the
Iberian Massif because it hosts the famous mercury mineralization of Almadén (CentralIberian Zone), where mining started more than 2,000 years ago and has since accounted
for one third of the cumulative world mercury production (Ortega Gironés & Hernández
Sobrino, 1992). The Criadero Quartzite has been traditionally considered as “basal Silurian”,
correlating with the entire Llandovery or possibly the Llandovery and Wenlock. However,
a low-diversity Hirnantia Fauna indicates that its basal part spans the Ordovician/Silurian
boundary (García Palacios et al., 1996; Villas et al., 1999). Previously, graptolites possibly
of Aeronian age were reported from the uppermost beds of a lateral equivalent of the
Criadero Quartzite, located east of the Almadén syncline (Gutiérrez-Marco & Pineda
Velasco, 1988; García Palacios et al., 1996).
The Criadero Quartzite displays important variations in thickness and lithologies in the
southern flank (65-70 m) of the Almadén syncline in comparison with sections in the
northern flank (0-30 m), which have been related to shallower environments of blanket
sandstones deposited by tidal currents prevailing in the south (Gallardo-Millán et al.,
1994).
The graptolite locality described here lies in the upper part of the Criadero Quartzite
on the northern flank of the syncline, about 11 Km NE of the Almadén mine. The
graptolites occur in an alternating sequence (7-8 m thick) of dark micaceous sandstones
and shales from a bed of sandstone with weathered pyrite nodules that is 4 m above the
top of the coquinoid quartzite bearing the Late Ordovician Hirnantia Fauna described by
Villas et al. (1999). The monospecific assemblage comprises abundant specimens of a
biserial graptolite provisionally identified here as Normalograptus scalaris (Hisinger),
which is a widespread species ranging from the middle Aeronian Pribylograptus leptotheca
or Lituigraptus convolutus biozones to the lowest Spirograptus turriculatus Biozone
(lower Telychian). The most interesting aspect is, however, the extraordinary threedimensional preservation of the specimens, which occur as empty rhabdosomes with the
periderm apparently replicated by iron-oxides and with a minor proportion of phyllosilicates.
This preservation may be explained by multiphase pyritization of the graptolites, similar
to some samples described by Underwood & Bottrell (1994). In this sense, the framboidal
pyrite that mineralized the periderm during very early diagenesis was remarkably resilient
not only to subsequent deformation, but also to the differential weathering of the massive
overpyrite that constitute the nodules that wholly enclosed rhabdosomes.
311
The occurrence of pyrite nodules within the Criadero Formation was reported by
Saupé (1971) from a single horizon of black quartzites at the base of the Upper Quartzite
member (8-10 m). This basal horizon of the San Francisco ore body, may be even a
lateral equivalent of the bed here studied on the northern flank of the syncline, which a
further search of graptolites at the Almadén mine could clarify.
This work is a contribution to the project CGL2006-07628/BTE of the Spanish Ministry
of Science and Innovation.
REFERENCES
GALLARDO-MILLÁN J.L., HIGUERAS P. & MOLINA J.M. (1994). Análisis estratigráfico de la “Cuarcita de Criadero”
en el Sinclinal de Almadén. Boletín Geológico y Minero, 105: 135-145.
GARCÍA PALACIOS A., GUTIÉRREZ-MARCO J.C. & HERRANZ ARAÚJO P. (1996). Edad y correlación de la “Cuarcita
de Criadero” y otras unidades cuarcíticas del límite Ordovícico-Silúrico en la Zona Centroibérica meridional
(España y Portugal). Geogaceta, 20: 19-22.
GUTIÉRREZ-MARCO J.C. & PINEDA VELASCO A. (1988). Datos bioestratigráficos sobre los materiales silúricos del
subsuelo de El Centenillo (Jaén). Comunicaciones II Congreso Geológico de España, Granada, 1: 91-94
ORTEGA GIRONÉS E. & HERNÁNDEZ SOBRINO A. (1992). The mercury deposits of the Almadén syncline, Spain.
Chronique de la Recherche Minière, 506: 3-24.
SAUPÉ F. (1971). Stratigraphie et pétrographie du «Quartzite du Criadero» (Valentien) à Almadén (province de
Ciudad Real, Espagne). Mémoires du Bureau des Recherches Géologiques et Minières, 73: 139-147.
UNDERWOOD C.J. & BOTTRELL S.H. (1994). Diagenetic controls on multiphase pyritization of graptolites. Geological
Magazine, 131: 315-327.
VILLAS E., LORENZO S. & GUTIÉRREZ-MARCO J.C. (1999). First record of a Hirnantia Fauna from Spain, and its
contribution to the Late Ordovician palaeogeography of northern Gondwana. Transactions of the Royal
Society of Edinburgh: Earth Sciences, 89: 187-197.
312
Silurian geoheritage of the Almadén Mining Park
(central Spain)
SATURNINO E. LORENZO, JUAN C. GUTIÉRREZ-MARCO, ISABEL RÁBANO
S.E. Lorenzo - Departamento de Ingeniería Geológica y Minera, Escuela Universitaria Politécnica, Universidad de
Castilla-La Mancha, E-13400 Almadén (Ciudad Real) (Spain); [email protected]
J.C. Gutiérrez-Marco - Instituto de Geología Económica (CSIC-UCM), José Antonio Novais 2, E-28040 Madrid
I. Rábano - Museo Geominero, Instituto Geológico y Minero de España, Ríos Rosas 23, E-28003 Madrid (Spain);
[email protected]
The Almadén mining district (Central-Iberian Zone of the Iberian Massif) constitutes
the largest geochemical mercury anomaly in the Earth’s crust. Mercury ore bodies are
hosted by uppermost Ordovician, Silurian and Upper Devonian sedimentary and volcanic
rocks. In the Almadén-type mineralization, cinnabar and native Hg stratabound orebodies
are distributed throughout the uppermost Ordovician to lower Silurian Criadero Quartzite.
The Almadén mine ceased operation in 2001 after having produced approximately 200,000
metric tons of mercury during more than 2,000 years of uninterrupted mining by Romans,
Arabs and Christians. The mine were transferred to the Spanish crown in the 16th century
when mercury became a strategic metal used in the amalgamation of the gold and silver
produced in the American territories of the Spanish Empire.
With the great decrease international market price because of declined use of mercury
due to its environmental problems, the Almadén mine is now a legacy, yet it retains
notable interest from the geological, paleontological and mining perspective. Operative
since 2006, the Almadén Mining Park transformed the mining enclosures, the underground
mine and the metallurgical facilities into an area for culture, education and quality tourism,
where visitors can enjoy the magnificent scientific, industrial and technological heritage of
one of the oldest mines in the world adapted to modern times through centuries of
technological innovation.
Also planned for the Almadén Mining Park is an Interpretation Centre for understanding
the geology and mining activities in the district, which will include information on the
stratigraphy and paleontology of the Silurian succession and also on the probable deepseated (mantle derived mafic magma) source of mercury.
Before the mining activities ended, the present authors (helped by Petr Storch, J.M.
Piçarra and F. Palero) collected graptolites between the 10th and 12th floors of the
underground mine (about -300 m) from black shales directly above the Criadero Quartzite.
A big part of the graptolite collection belongs to the Monoclimacis griestoniensis and
Torquigraptus tullbergi biozones (mid-Telychian) with abundant specimens (other than
the named species) of Metaclimacograptus flamandi (Legrand), Parapetalolithus
meridionalis Legrand, Monograptus priodon (Bronn), M. juancarlosi Storch and
Cochlograptus veles (Richter), a.o. Older Telychian beds belonging to the Rastritest
linnaei Biozone are known through old samples coming from the mine, now preserved in
museums, as well from a number of outcrops located north and south of the Almadén
mine that expose the contact among the Criadero Quartzite and the basal graptolite shales.
313
Silurian graptolites were discovered in the Almadén mine by Kuss (1878) and Malaise
(1897), and after the work of Hernández Sampelayo (1926) and Haberfelner (1931) the
mining district became a classical reference for Silurian paleontology in central Spain with
some widespread species defined there (for instance Parapetalolithus hispanicus).
Besides the projected museum displays on Silurian fossils within the Almadén Mining
Park, we are proposing a Silurian geo-route for further demonstration of the stratigraphy
and paleontology of the area. Starting at the Interpretation Centre, it will lead visitors to
selected Silurian outcrops in the vicinity of the mining park (Lápiz stream, Chillón railway,
El Entredicho open pit).
This work is a contribution to the project CGL2006-07628/BTE of the Spanish Ministry
of Science and Innovation.
REFERENCES
HABERFELNER E. (1931). Eine Revision der Graptolithen der Sierra Morena (Spanien). Abhandlungen der
senckenbergischen naturforschenden Gesellschaft, 43: 19-66.
HERNÁNDEZ SAMPELAYO P. (1926). Yacimientos de graptolítidos en la zona de Almadén. Boletín de la Real
Sociedad Española de Historia Natural, 26: 251-262.
KUSS H. (1878). Mémoire sur les mines et usines d’Almadén. Annales des Mines [7], 13: 39-151.
MALAISE C. (1897). Découverte de graptolithes à Almaden, province de Ciudad Real, Espagne. Bulletin de la
Société Géologique de Belgique, 24: 26.
314
Nitrogen Isotopes in Paleozoic Chemostratigraphic
Studies: Contrasting Examples from the Hirnantian
and early Wenlock
MICHAEL J. MELCHIN, CHRIS HOLMDEN
M. J. Melchin - Department of Earth Sciences, St. Francis Xavier University, PO Box 5000, Antigonish, Nova Scotia
B2G 2W5 (Canada); [email protected]
C. Holmden - Saskatchewan Isotope Laboratory, Department of Geological Sciences, University of Saskatchewan,
114 Science Place, Saskatoon, Saskatchewan S7N 5E (Canada); [email protected]
Integrated paleoenvironmental and bioevent studies in the Ordovician and Silurian
systems have commonly employed O and C isotopes for chemostratigraphic analysis,
although isotopes of Sr, S, Os, and Nd are also leading to valuable insights. LaPorte et al.
(in press) showed that variations in N isotopes from organic matter in Late Ordovician
strata in Nevada may be interpreted in terms of changes in ocean state and patterns of Ncycling from pre-Hirnantian into Hirnantian, peak glacial times. Their model proposes
that during times of greenhouse climate, development of widespread denitrification zones
in the world’s oceans resulted in a low upwelling flux of recycled ‘fixed’ nitrogen to the
photic zone. Algal productivity then depended on the presence of a significant biomass of
nitrogen-fixing cyanobacteria within the photic zone, leading to relatively low δ15N values
in the produced organic matter. In contrast, during glacial times, increased oceanic ventilation
resulted in reduction in the oceanic dentrification zones and an increased supply of fixed
nitrogen transported to the surface waters, which could be directly utilized by algal plankton.
This would lead to higher δ15N values in organic matter. The LaPorte et al. (in press)
model was developed using data from a section that preserved only the preglacial to
Hirnantian glacial rise in δ15N values; postglacial strata were not preserved at that section.
The present study provides new δ15N data on organic matter from two sections in
Arctic Canada that span the pre-Hirnantian to post-Hirnantian stratigraphic succession.
The Hirnantian glacial interval in these sections has already been well characterized in
terms of biostratigraphy, lithostratigraphy, and C-isotope chemostratigraphy (Melchin &
Holmden, 2006). Both sections show a strong (~3‰), positive δ15N excursion that is
restricted to the strata representing the Hirnantian glacial interval, providing strong support
for the Laporte et al. model. Our interpretation of these new data suggests that prior to
the Hirnantian interval of peak glaciation, substantial denitrification zones were widespread
around the paleotropical margins of Laurentia during late Katian times but were dramatically
reduced by glacially-induced oceanic ventilation during the early Hirnantian. In addition,
the end of the glacial episode saw a rapid return to preglacial conditions of oceanic
denitrification. The coincidence of the change in δ15N values with dramatic drops in
graptoloid biodiversity and abundances during the early Hirnantian supports the widely
accepted hypothesis that the preferred graptoloid habitat was closely linked with the
presence of oceanic denitrification zones.
The lower Wenlock strata in Arctic Canada show a significant, positive carbon isotope
excursion in both the organic and inorganic carbon fractions of the sediments (the Ireviken
315
Event). Although the Ireviken Event shows many similarities with the early Hirnantian
glacial event, there are some important differences. Most notably, this sequence shows
continuous deposition of graptolite-bearing black shales through the C-isotope excursion
interval, which is generally not the case for the Hirnantian interval in similar facies
worldwide. Moreover, we have found no significant positive shift in δ15N values. Together,
these lines of evidence suggest that Ireviken excursion was not accompanied by a profound
increase in ocean ventilation and reduction in denitrification, at least on the northern
margin of Laurentia. This suggests that the Ireviken and Hirnantian events may have
been significantly different in terms of the scale and/or nature of the processes that were
responsible for the observed paleoenvironmental and biodiversity changes.
REFERENCES
LAPORTE D.F., HOLMDEN C. PATTERSON W.P., LOXTON J.D., MELCHIN M.J., MITCHELL C.E., FINNEY S.C. & SHEETS
H.D. (in press). Carbon and nitrogen cycling during the Hirnantian glaciation: implications for epeiric sea
gradients, productivity and calcite dust deposition. Palaeogeography, Palaeoclimatology,
Palaeoecology.
MELCHIN,M.J. & HOLMDEN C. (2006). Carbon isotope chemostratigraphy in Arctic Canada: sea-level forcing
of carbonate platform weathering and implications for Hirnantian global correlation. Palaeogeography,
Palaeoclimatology, Palaeoecology, 234: 186-200.
316
The Upper Ordovician to lower Silurian Tihange
sections, Condroz Inlier: a litho- and biostratigraphical
study with chitinozoans combined with carbon isotopes
JAN MORTIER, DAVID A.T. HARPER, JAN A. ZALASIEWICZ, PHILIPPE CLAEYS,
JACQUES VERNIERS
J. Mortier - Research Unit Palaeontology, Department of Geology and Soil Science, Ghent University, Krijgslaan 281
building S8, B-9000 Ghent (Belgium); [email protected]
D.A.T. Harper - Natural History Museum of Denmark (Geological Museum), University of Copenhagen, Øster Voldgade
5-7, DK-1350 Copenhagen K (Denmark); [email protected]
J.A. Zalasiewicz - Department of Geology, University of Leicester, University Road, Leicester LE1 7RH (United
Kingdom); [email protected]
P. Claeys - Department of Geology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels (Belgium);
[email protected]
J. Verniers - Research Unit Palaeontology, Department of Geology and Soil Science, Ghent University, Krijgslaan
281 building S8, B-9000 Ghent (Belgium); [email protected]
Five lithostratigraphical units, exposed in a series of outcrops in Tihange (central Condroz
Inlier, Belgium) range from the middle Upper Ordovician to the lowermost Silurian. Two
are only known from these outcrops. One newly discovered unit may be dated by
brachiopods and another is dated using graptolites. Forty seven samples from the five
units in a 112 m thick composite section contain chitinozoans, but these are often longranging forms. Preliminary results from carbon isotope studies on the organic material
will be presented.
The lowest unit, the Vitrival-Bruyère Formation consists of dark grey, medium grained
siltstone. It belongs to the Rue de Courrière Member (uppermost member of the VitrivalBruyère Formation) although the facies is slightly different from the type area. It was
deposited during the Burrelian to middle Streffordian (Caradoc, upper Sandbian to lower
Katian) based on the occurrence of Spinachitina bulmani, Desmochitina juglandiformis
and possibly Desmochitina nodosa.
The following Bois de Presles Member (lower member of the Fosses Formation)
contains brownish grey siltstone and limestone nodules. It was probably deposited during
the Pusgillian to early Rawtheyan (middle Ashgill, upper Katian) based on lithostratigraphical
correlation with the type area of that member, where it was dated by chitinozoans.
The Faulx-les-Tombes Member (middle member of the Fosses Formation) consists of
greyish green to grey, fine siltstone with characteristic, dark grey, fusiform to elliptic
bioturbation traces of a few mm diameter (“schistes mouchetés” in litteris ). Towards
the top, it becomes darker grey with the appearance of small rusty spheres to ellipses
(maximum 1 mm in diameter). It is thought to have been deposited during the Rawtheyan
(middle Ashgill, upper Katian) based on lithostratigraphical correlation with the type area
of that member, where it was dated with chitinozoans.
The Tihange Member (the new upper member of the Fosses Formation) can be divided
into two. The lower part consists of dark grey, fine siltstone with millimetric rusty spheres
to ellipses prominent and larger in comparison with the top of the underlying unit. Its age
317
probably ranges from latest Rawtheyan to Hirnantian. The upper part consists of light
grey, fine siltstone that quickly coarsens upwards into coarse siltstone with laminations
and irregular yellow patches (possibly caused by weathering). This is followed by a rapid
fining upwards into fine siltstone with a slightly darker colour and the occurrence of rusty
spheres to ellipses identical to those in the lower part of the member. This newly discovered
member, only occurring in the eastern Condroz Inlier, has correlated with the Hirnantian
based on a newly discovered brachiopod fauna: the first evidence of this stage in the
Condroz Inlier.
The highest unit, the Bonne Espérance Formation (a new name) consists of dark
green to dark grey, finely laminated shales with the occurrence of white clayey layers of
possibly volcanic origin. It is deposited during the middle Rhuddanian based on the
occurrence of graptolites belonging to the upper part of the Parakidograptus acuminatus
biozone and the Atavograptus atavus biozone. The occurrence of Belonechitina
postrobusta is in agreement with this age.
318
New biostratigraphic and chemostratigraphic data
from the lower Chicotte Formation (Llandovery) on
Anticosti Island (Quebec, Canada)
AXEL MUNNECKE, PEEP MÄNNIK
A. Munnecke - GeoZentrum Nordbayern, Fachgruppe Paläoumwelt, Loewenichstr. 28, D-91054 Erlangen Germany);
[email protected]
P. Männik - Institute of Geology, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia);
[email protected]
The sequence on Anticosti with its excellent coastal-cliff and river-valley outcrops
represents one of the best-preserved exposures of upper Ordovician–lower Silurian shallowwater carbonates. The youngest rocks exposed on Anticosti are represented by the 8090m thick Chicotte Formation, which consists of crinoidal limestones, interpreted as innerramp shoal deposits, and reefs. The formation is considered to be Llandovery in age.
Conodonts of the I. inconstans and lowermost P. a. amorphognathoides zones have
been identified from the lower part of the formation (Uyeno and Barnes 1983). Earlier
stable isotope data from Anticosti Island did not show much variation in the δ13C values
in Llandovery, and scatter around +1‰ (Azmy et al. 1998). An increase is observed from
ca. +0.5‰ in the upper part of the Jupiter Formation to about 1.5‰ in the overlying
Chicotte Formation.
Recently, 19 brachiopod shells and 7 micrite samples from the lower part of the
Chicotte Formation (below the major unconformity reported by Desrochers 2006) were
measured for stable isotopes and four samples were processed for conodonts. Based on
our studies, the mean δ13C values show an increase from about 1.0‰ in the uppermost
Jupiter Formation (upper part of Pavillon Member) to 2.8‰ in the lower part of the
Chicotte Formation, with peak values of > 3.1‰. In the youngest sample studied the
values decrease back to around 1.4‰. Similar small positive δ13C excursion was recognized
in the Viki core section, western Estonia (Kaljo et al. 2003; our new data). In the last
section the δ13C values increase from ca. 0.1‰ in the lower Rumba Formation (? uppermost
Aeronian) up to values between 2 and 3‰ in the interval spanning the uppermost P.
eopennatus ssp. n. 1 Zone to the lower Upper P. eopennatus ssp. n. 2 Subzone (lower
Velise Formation). Towards the top of the P. eopennatus ssp. n. 2 Zone the values of
˜ 13C decrease gradually and remain +/- constant around 2‰ in the lower part of the
succeeding P. a. angulatus Zone.
The conodont data available suggest that the δ13C excursions recognized in the lower
Chicotte Formation on Anticosti and in the lower Velise Formation in the Viki core section
are of the same age. Also on Anticosti Island the δ13C values reach maximum below the
appearance of P. a. angulatus in the sequence. In summary, the stratigraphic position of
the lower part of the Chicotte Formation (below the major unconformity) ranges from the
P. eopennatus ssp. n. 1 Zone to the P. a. angulatus Zone. This time interval is not only
represented by a minor extinction period for conodonts (Valgu Event, Männik 2007) but
is also characterised by significant changes in depositional environments. In the Viki core,
319
the interval spanning the isotope excursion shows frequent intercalations of micritic
limestones, marls and claystones with reddish or brownish colours, and on Anticosti
Island the Chicotte Formation is built by pure crinoidal limestones and reefs.
REFERENCES
AZMY K., VEIZER J., BASSETT M.G. & COPPER P. (1998). Oxygen and carbon isotopic composition of Silurian
brachiopods: Implications for coeval seawater and glaciations. GSA Bulletin, 110 (11): 1499-1512.
DESROCHERS A. (2006). Rocky shoreline deposits in the Lower Silurian (upper Llandovery, Telychian) Chicotte
Formation, Anticosti Island, Québec. Canadian Journal of Earth Sciences, 43: 1205-1214.
KALJO D., MARTMA T., MÄNNIK P. & VIIRA V. (2003). Implications of Gondwana glaciations in the Baltic late
Ordovician and Silurian and a carbon isotopic test of environmental cyclicity. Bulletin de la Societe
Geologique de France, 174: 59-66.
MÄNNIK P. (2007). Some comments on the Telychian-Early Sheinwoodian conodont faunas, Events and
stratigraphy. Acta Palaeontologica Sinica, 46: 305-310.
UYENO T.T. & BARNES C.R. (1983). Conodonts of the Jupiter and Chicotte formations (lower Silurian), Anticosti
Island, Québec. Geological Survey of Canada Bulletin, 355: 49 pp.
320
Silurian of the Barrancos-Hinojales domain of SW
Iberia: a contribution to the geological heritage of the
Barrancos area (Portugal) and the Sierra de AracenaPicos de Aroche Natural Park (Spain)
JOSÉ M. PIÇARRA, JUAN C. GUTIÉRREZ-MARCO, GRACIELA N. SARMIENTO,
ISABEL RÁBANO
J.M. Piçarra - Laboratório Nacional de Energia e Geologia, Ap. 104, P-7801-902 Beja (Portugal);
[email protected]
J.C. Gutiérrez-Marco - Instituto de Geología Económica (CSIC-UCM,) José Antonio Novais 2, E-28040 Madrid
G.N. Sarmiento - Instituto de Geología Económica (CSIC-UCM,) José Antonio Novais 2, E-28040 Madrid (Spain);
[email protected]
I. Rábano - Museo Geominero, Instituto Geológico y Minero de España, Ríos Rosas 23, E-28003 Madrid (Spain);
[email protected]
Fossiliferous Silurian strata crop out extensively in the Barrancos-Hinojales region of
the Ossa-Morena Zone (SW Iberia), where the structural complexity often makes precise
stratigraphic studies difficult. The Silurian succession of this region differs from the
Thuringian-like facies of the eastern Ossa-Morena areas (Sierra Norte of Seville) by the
absence of the “Scyphocrinites limestone”, the greater lateral variation of clastic units,
the relatively less diverse graptolite record and by the scarcity of benthic faunas.
The localities of Barrancos in Portugal, and of Encinasola and Hinojales river in Spain,
are the sections more complete and representative of the Silurian stratigraphic and
palaeontological development in the studied domain. All of them lie in natural areas protected
by regional laws; such is the case of the Sierra de Aracena-Picos de Aroche Natural Park
for the Spanish localities.
The Silurian of Barrancos corresponds to a condensed succession (80 m) of lydites,
black shales and dark shales and siltstones. Within it, 19 graptolite biozones ranging from
the lower Rhuddanian Parakidograptus acuminatus Biozone to the Pridoli Monograptus
bouceki Biozone have been recognized (Piçarra in Robardet et al., 1998).
The Encinasola sections, direct extensions of the outcrops at Barrancos, also have
abundant Rhuddanian to Gorstian graptolites, but post-Ludlow strata are virtually
unfossiliferous (Giese et al., 1994).
The Silurian strata of the Hinojales area are middle Aeronian to lower Sheinwoodian
graptolite black shales; Wenlock-Ludlow strata lack graptolites and are identify by
palynomorphs (Mette, 1987, 1989).
These sections characterize a unique Silurian realm unknown in other parts of the
Iberian Peninsula that are important for the paleogeographic reconstruction of northern
Gondwana. Also the partly continuous graptolite succession documents critical episodes
on marine life related with global climatic changes (Gutiérrez-Marco et al., 1996).
Therefore, these Silurian sections should be recognized as important geosites that
generate added value for the natural areas to which belong and which were originally
321
established to protect biodiversity in their original ecosystems and landscapes. But at the
moment this geological heritage is not appreciated as a scientific resource of international
interest by the local government agencies.
In our opinion, these Silurian geosites should be reserved for scientific study because
of their rarity and fragility, although the dissemination of scientific information in Barrancos
could be provided by an interpretation center such as that being planned by the town hall,
or by the new walking track created as a georoute by the private Noudar Nature Park in
the same area.
This work is a contribution to the PATRIORSI project (CGL2006-07628/BTE) of the
Spanish Ministry of Science and Innovation.
REFERENCES
GIESE U., HOEGEN R. VON, HOLLMANN G. & WALTER R. (1994). The Palaeozoic of the Ossa Morena Zone north
and south of the Olivenza-Monesterio Anticline (Huelva province, SW Spain). Neues Jahrbuch für
Geologie und Paläontologie, Abhandlungen, 192: 293-331.
GUTIÉRREZ-MARCO J.C., LENZ A.C., ROBARDET M. & PIÇARRA J.M. (1996). Wenlock-Ludlow graptolite
biostratigraphy and extinction: a reassessment from the southwestern Iberian Peninsula (Spain and Portugal).
Canadian Journal of Earth Sciences, 33: 656-663.
METTE W. (1987). Geologische und biostratigraphische Untersuchungen im Altpaläozoikum westlich
von Cala, westliche Sierra Morena. Diplomarbeit Institut und Museum für Geologie und Paläontologie,
Universität Göttingen, 174 p. (unpublished).
METTE W. (1989). Acritarchs from Lower Paleozoic rocks of western Sierra Morena, SW-Spain and
biostratigraphic results. Geologica et Palaeontologica, 23: 1-19.
ROBARDET M., Piçarra J.M., Storch P., Gutiérrez-Marco J.C. & Sarmiento G.N. (1998). Ordovician and
Silurian stratigraphy and faunas (graptolites and conodonts) in the Ossa Morena Zone of the SW Iberian
Peninsula (Portugal and Spain). Temas Geológico-Mineros, ITGE, 23: 289-318.
322
Silurian stratigraphy and paleontology of the Valongo
anticline and Arouca-Tamames syncline, CentralIberian Zone (Portugal and Spain)
JOSÉ M. PIÇARRA, ARTUR A. SÁ, PETR STORCH, JUAN C. GUTIÉRREZ-MARCO
[email protected]
A.A. Sá - Departamento de Geologia, Universidade de Trás-os-Montes e Alto Douro, Ap. 1013, P-5001-801 Vila Real,
(Portugal); [email protected]
P. Storch - Institute of Geology, Academy of Sciences of the Czech Republic, Rozvojova 269, 165 02 Praha 6, Czech
Republic; [email protected]
J.C. Gutiérrez-Marco - Instituto de Geología Económica (CSIC-UCM) José Antonio Novais 2, E-28040 Madrid
Silurian rocks crop out intermittently in a narrow belt, 320 km long, extending from
the NW corner of Portugal to south of Salamanca, Spain. Although graptolitic shales have
been known from many localities since the 19th Century, detailed knowledge on their
stratigraphy and fossils is very limited and comes mainly from the classical Valongo and
Tamames areas. The Silurian succession comprises three units that, in ascending order,
are: a) ca. 100 m of black shales and lydites (lower “Xistos Carbonosos”); b) dark shales
with alternating siltstones and lydites (upper “Xistos Carbonosos”, of unknown thickness)
and c) about 200 m of sandstones and siltstones (Sobrado Formation). The highest unit
may include the Silurian-Devonian boundary or may be entirely Devonian on the basis of
the Middle Devonian age of El Castillo volcanic rocks in the Spanish outcrops (GutiérrezAlonso et al., 2008).
Published graptolite data (Thadeu, 1956; Waterlot, 1965; Romariz, 1962, 1969 and
references cited therein) allowed the lower black shales to be correlated to the Llandovery
and the upper dark shales to the Wenlock. However, available graptolite lists show a
remarkable inconsistency by the identification of some Aeronian, Telychian, Sheinwoodian
or even Ordovician graptolite species from the same horizons, and sometimes associated
on a single slab. The Wenlock graptolite assemblages of the upper shale unit were related
to the so-called “Sardic faunas”; among them, 25 new species and “varieties” were
described in the Valongo region (Monograptus duriensis, Monoclimacis lusitanica,
Pristiograptus valongensis, a.o.: Romariz, 1962; Waterlot, 1965). This “Sardic fauna”
was later reviewed by Piçarra and Gutiérrez-Marco (2001), who showed that all these
local taxa are based upon highly deformed graptolites, unrecognizable at specific or even
generic level.
The present authors examined most of the original material collected by the earlier
workers from the Valongo and Tamames regions, as well as new localities sampled in the
Arouca Geopark. Our results allow the preliminary identification of the Aeronian
Demirastrites pectinatus-D. triangulatus, Lituigraptus convolutus and ?Stimulograptus
sedgwickii biozones, as well as the Telychian Rastrites linnaei, ?Monoclimacis
griestoniensis, ?Torquigraptus tullbergi and ?Oktavites spiralis biozones within the lower
“Xistos Carbonosos”. However, the best material comes from old localities presently
323
inaccessible (closed mines, urbanized areas). A good fossiliferous section needs to be
located.
Graptolite-rich beds from the upper “Xistos Carbonosos” have also yielded, other
than the unrecognizable “Sardic faunas”, some assemblages indicating the presence of
the Sheinwoodian Cyrtograptus rigidus-Monograptus belophorus Biozone and Homerian
Cyrtograptus lundgreni Biozone including its Cyrtograptus radians Subzone without
any doubt. The youngest graptolite records are of imprecise Gorstian age, as indicated by
the occurrence of Bohemograptus bohemicus in the Tamames area.
This work is a contribution to the projects CGL2006-07628/BTE (Spain) and PTDC/
CTE-GEX/64966/2006 (Portugal).
REFERENCES
GUTIÉRREZ-ALONSO G., MURPHY J.B., FERNÁNDEZ-SUÁREZ J. & HAMILTON M.A. (2008). Rifting along the northern
Gondwana margin and the evolution of the Rheic Ocean: A Devonian age for the El Castillo volcanic
rocks (Salamanca, Central Iberian Zone). Tectonophysics, 461: 157-165.
PIÇARRA J.M. & GUTIÉRREZ-MARCO J.C. (2001). Revisão preliminar dos graptólitos silúricos portugueses de
tipo “sardo”. Publicaciones del Seminario de Paleontología de Zaragoza, 5: 434-440.
ROMARIZ C. (1962). Graptolitos do Silúrico Português. Revista da Faculdade de Ciências de Lisboa, 2ª
Série C, 10: 115-312.
ROMARIZ C. (1969). Graptolitos silúricos do Noroeste Peninsular. Comunicações dos Serviços Geológicos
de Portugal, 53: 107-155.
THADEU D. (1956). Note sur le silurien beiro-durien. Boletim da Sociedade Geológica de Portugal, 12: 138.
WATERLOT G. (1965). Découverte d’une faune graptolitique géante dans le Llandovérien et le Tarannonien
inférieur des environs de Porto (Portugal). Annales de la Société Géologique du Nord, 85 : 159-169.
324
New data on Silurian graptolites from the Rio Ollastu
valley (SE Sardinia)
SERGIO PIRAS
S. Piras - Dipartimento di Scienze della Terra, Università di Cagliari, via Trentino 51, I-09127 Cagliari (Italy);
[email protected]
The Silurian graptolites in southeastern Sardinia are well documented from the Lower
Graptolitic Shales, an informal lithostratigraphic unit recognized in the “Sarrabus tectonic
Unit” and in the “Gerrei tectonic Unit”. A series of graptolite biozones ranging from lower
Llandovery to lower Ludlow are documented in the unit (Storch & Piras, 2009).
The Riu Ollastu valley is located in the Sarrabus subregion (SE Sardinia), between
Burcei and San Vito villages. Helmcke (1973) and Barca & Jaeger (1990) reported graptolites
from the Lower Graptolitic Shales in this area and brought evidence on the following
graptolite biozones of the zonal scheme presented by Storch & Piras (2009): ascensusacuminatus, vesiculosus, cyphus, triangulatus-pectinatus, lepthotheca-convolutus,
linnaei, turriculatus-crispus, tullbergi, spiralis, lundgreni-testis, ludensis-gerhardi and
nilssoni-colonus.
New field researches in the Rio Ollastu valley revealed a few, previously unstudied
outcrops of the Lower Graptolitic Shales. Among those, the one at Sarcilloni locality is of
particular importance. Two highly fossiliferous levels of black siliceous and argillaceous
shales, rich in graptolites of Cyrt. lapworthi and Cyrt. insectus biozones, have been
detected in this outcrop. Graptolite association includes: Retiolites angustidens Elles &
Wood, Monograptus pseudocultellus Boucek, Monoclimacis geinitzi (Boucek), Oktavites
spiralis (Geinitz), Oktavites falx? (Suess) and Cyrtograptus lapworthi (Tullberg) in the
lapworthi Biozone, and Retiolites geinitzianus (Barrande), Pristiograptus largus (Perner),
Mediograptus cf. vittatus Storch, Mediograptus ?morleyae Loydell & Cave, Mediograptus
sp., Monograptus priodon (Bronn), Monograptus praecedens Boucek, Monograptus
pseudocultellus Boucek, Monoclimacis geinitzi (Boucek), Cyrtograptus insectus Boucek
and Barrandeograptus pulchellus (Tullberg) in the insectus Biozone.
REFERENCES
BARCA S. & JAEGER H., (1990). New geological and biostratigraphical date on the Silurian in the SE-Sardinia.
Close affinity with Thuringia. Bolletino della Società Geologica Italiana 108, 565-580.
HELMCKE D. (1973). Schichtgebundene NE-Metall- und F-Ba-Lagerstätten im Sarrabus-Gerrei-Gebiet, SESardinien. II. Bericht: Zur Stratigraphie des Silur und Unterdevon der Lägerstättenprovinz SarrabusGerrei. Neues Jahrbuch für Geologie und Paläontologie. Monatshefte 1973, 529-544.
STORCH P. & PIRAS S. (2009). Silurian graptolites of Sardinia: assemblages and biostratigraphy. Rendiconti
della Società Paleontologica Italiana, 3 (1), 77-93.
325
326
Silurian chitinozoan biostratigraphy of Sardinia
PAOLA PITTAU, MYRIAM DEL RIO
P. Pittau - Dipartimento di Scienze della Terra, Università di Cagliari, via Trentino 51, I-09127 Cagliari (Italy);
[email protected]
M. Del Rio - Dipartimento di Scienze della Terra, Università di Cagliari, via Trentino 51, I-09127 Cagliari (Italy);
[email protected]
Silurian chitinozoan assemblages and biozones of southeastern Sardinia are well
calibrated against graptolite biozones, whereas those deriving from isolated blocks of the
Fluminimaggiore Fm of southwestern Sardinia have less precise biochronologic constraints.
An attempt to arrange, into a regional frame, the up to now known chitinozoan
assemblages according to the stratigraphic significance of index species, allow to discriminate
eight biozones from Llandovery to lowermost Lochkovian; however not all the time
intervals are documented. One biozone, Conochitina emmastensis, is recognized in the
Aeronian - Telychian of the Rio Ollastu section. Three chitinozoan biozones: C. goniensisC. subcyatha, Sphaerochitina jaegeri, S. serpaglii are correlated from the belophorousrigidus to the lundgreni-testis graptolite biozones. One chitinozoan biozone, C.
pachycephala, calibrated against vulgaris-gerhardi graptolite biozone and fitting
ecostratigraphically within the Cardiola docens-C. donigala bivalves community.
Angochitina cf. elongata biozone ecostratigraphycally encompassing the Cardiola docens
community; Urnochitina urna and Eisenackitina bohemica ecostratigraphically correlating
respectively with Cheiopteria-Patrocardia-Cardiolinka, Patrocardia evolvens evolvensPanenka bivalves communities and Pterinopecten-Cybele nesiotes and Patrocardia
evolvens evolvens-Panenka communities that encompass Pridoli and Lochkovian.
327
328
Wenlock bentonites from the Midland Platform,
England: geochemistry, sources and correlation
DAVID RAY
D. Ray - School of Earth & Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road,
Portsmouth PO1 3QL (United Kingdom); [email protected]
Forty-two bentonites have been sampled from the Wenlock Series (Silurian) strata of
the Eastnor Park and Lower Hill Farm boreholes, and from outcrops at Coates Quarry,
Harley Hill (Wenlock Edge, Shropshire) and Wren’s Nest Hill (Dudley, West Midlands).
The composition of the sand and clay size fractions of each bentonite has been established
by XRD, heavy liquid separation and microscopy. In addition primary volcanogenic apatite
grains have proven sufficiently abundant in fifteen bentonites to allow for chemical
fingerprinting. Based upon the rare earth element (REE) and yttrium concentrations of
these apatite grains the chemical similarity between ash fall events and the nature of the
source magma has been established. The REE compositions of the bentonites indicate an
evolving subduction related magmatic source that becomes increasingly granitic within
decreasing age. Furthermore comparisons with Wenlock bentonites from Gotland, Sweden
indicate a close affinity with samples SW10, SW11 and SW12 (Batchelor & Jeppsson
1999), possibly reflecting the same source region. Finally two bentonite horizons, constrained
by five samples, have been shown to be regionally traceable. The lower of the bentonite
horizons occurs within the uppermost Woolhope Limestone and Buildwas Formation
(Eastnor Park and Lower Hill Farm boreholes) and is probably contained within the
lower riccartonensis Biozone (Ray 2007). The upper bentonite occurs in the Much
Wenlock Limestone Formation at Coates Quarry, Harley Hill and Wren’s Nest Hill and is
contained within the ludensis Biozone. Such correlations provide important Wenlock
Series time-lines between the type area and the remainder of the Midland Platform.
REFERENCES
BATCHELOR R. A. & JEPPSSON L. (1999). Wenlock metabentonites from Gotland, Sweden: geochemistry,
sources and potential as chemostratigraphic markers. Geological Magazine, 136 (6): 661-669
RAY D.C. (2007). The correlation of Lower Wenlock Series (Silurian) bentonites from the Lower Hill Farm
and Eastnor Park boreholes, Midland Platform, England. Proceedings of the Geologists’ Association.
118 (2): 175-185.
329
330
Sequence stratigraphy of the Wenlock Series of the
Midland Platform, England
DAVID RAY, OWEN SUTCLIFFE
D. Ray - Neftex Petroleum Consultants Ltd. 97 Milton Park, Abingdon, Oxfordshire OX14 4RY (United Kingdom);
[email protected]
O. Sutcliffe - Neftex Petroleum Consultants Ltd. 97 Milton Park, Abingdon, Oxfordshire OX14 4RY (United Kingdom);
[email protected]
The Wenlock Series of the Midland Platform, England has been studied via borehole
records and a limited number of outcrops. Based upon new data and a re-evaluation of
lithological and palaeontological data from the Lower Hill Farm borehole and outcrops
within the type Wenlock area (Bassett et al., 1975; Swire 1993) an assessment of relative
sea-level change has been made. Broadly the Wenlock Series consists of two shallow
water carbonates separated by terrigenous sediments. Within this framework two major
depositional sequences have been recognised along with higher-order cycles. The sequence
boundary of sequence-1 straddles the Llandovery-Wenlock boundary (amorphognathoides
conodont Biozone) and probably represents a depositional hiatus. The overlying strata
initially consists of argillaceous sediment with the basal limestones of the Wenlock
(Buildwas, Woolhope and Barr Limestone formations) becoming established (centrifugus
Biozone) and prograding during a minor regressive-transgressive cycle. As the rate of
transgression increased limestone production was halted giving way to the deposition of
the Coalbrookdale Formation and highest relative level-sea (dubius Biozone of Zalasiewicz
and Williams, 1998). Sequence-2 is characterised a gradual infilling of the accommodation
space by argillaceous sediments followed by extensive limestone development. Within the
argillaceous portion of sequence-2 are two additional transgressive-regressive cycles that
are associated with the deposition of sandstones within the southern Midland Platform
(rigidus-lundgreni biozones of Zalasiewicz and Williams, 1998). The maximum regressive
surface of sequence-2 is within the upper lundgreni Biozone and is identified by the
maximum progradation of sandstones. The overlying transgressive-regressive cycle is
characterised by the gradual reestablishment of limestone production culminating in the
onset of the Much Wenlock Limestone and Farley Member (of the Coalbrookdale
Formation) (uppermost lundgreni Biozone). The limestones of sequence-2 are characterised
by the development of two prominent limestone bands separated by a more nodular and
argillaceous interval associated with the maximum flooding surface (nassa Biozone). An
additional minor regression is also widely identifiable at the top of the lower limestone
(nassa Biozone). The upper sequence boundary is contained within the uppermost Much
Wenlock Limestone Formation (uppermost ludensis Biozone) and is overlain by
transgressive limestones and then argillaceous sediments marking the base of the Ludlow
Series.
REFERENCES
BASSETT M.G., COCKS L.R.M., HOLLAND C.H., RICKARDS R.B. & WARREN P.T. (1975). The type Wenlock Series. Institute of
Geological Sciences Report no. 75/13: 1-19.
331
SWIRE P.H. (1993). The palynology of the Lower Wenlock of the Wenlock type area, Shropshire, England. Palaeontology,
48: 97-109.
ZALASIEWICZ J. & WILLIAMS M. (1998). Graptolite biozonation of the Wenlock Series (Silurian) of the Builth Wells district,
central Wales. Geological Magazine, 136: 263-283
332
Discovery of a latest Ordovician deep water
brachiopod fauna at Yuhang, Hangzhou, Zhejiang,
East China
JIAYU RONG, RENBIN ZHAN, BING HUANG, DAVID A.T. HARPER
J.Rong - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology,
R. Zhan - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology,
B.Huang - State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology,
D.A.T. Harper - Geological Museum, University of Copenhagen, Copenhagen (Denmark).
The formation of the continental glaciations in northern Africa during the Hirnantian
(latest Ordovician) caused a dramatic drop of global sea level and the widespread of cool
and shallow water benthic regimes within which benthic shelly faunas are well-developed
and essentially different from those of pre-Hirnantian. Most of the documented Hirnantian
shelly faunas around the world are shallow water in nature, and little is known about the
deep water benthic faunas of this time interval. During the field seasons of 2007 and
2008, a moderately diverse brachiopod and trilobite assemblage, the LeangellaDalmanitnia (Songxites) Assemblage, was found in the upper Yankou Formation
(Hirnantian, probably equivalent to the top Normalograptus persculptus Biozone) at
Shizi Hill, Yuhang, west of Hangzhou, northern Zhejiang, East China. The brachiopods
are moderately rich in abundance, characterized by minute, thin shells with small body
cavities (mostly less than 8 mm in width), preserved in silty mudstone as external and
internal moulds. Preliminary study reveals that the taxonomic composition of this
assemblage includes Paracraniops sp., Skenidioides sp., Dolerorthis sp., Ravozetina
sp., dalmanellid indet., ?Jezercia sp., Epitomyonia sp., Aegiromena planissima (Reed),
Anisopleurella sp., Eoplectodonta sp., Leangella cf. scissa (Davidson), Brevilamnulella
sp., and ?Alispira sp. Taking into account of those accompanied fossils (e.g., trilobites
Dalmanitina (Songxites) cf. wuningensis (Lin) and Niuchangella sp., gastropods Holopea
sp., machaeridid Lepidocoleus, cystoids, and stems of crinoids), sedimentary features of
the rocks and the regional geology of this area, this unique brachiopod fauna may have
inhabited quiet, deep-water and dysaerobic slope environments with low levels of nutrients,
equivalent to Benthic Assemblage 5. Most genera were adapted for life in deep water.
The slope environments were recolonised from outer shelf and upper slope communities
during the early Hirnantian after the first phase of the end Ordovician mass extinctions.
Relatively isolated biotas may have survived in deeper-water habitats by reducing their
individual size, population size and diversity during the crisis. The Leangella-Dalmanitina
(Songxites) Assemblage, slightly younger than most of the representatives of the HirnantiaDalmanitina Fauna, provides a unique Hirnantian window through which we can monitor
the changes in the deep-water biofacies following the first phase of the extinctions. It
bridges the gap between the normal Hirnantia Fauna and the earliest Silurian shelly
333
Fig. 1 - Correlation chart showing the stratigraphic position of the Leangella-Dalmanitina
(Songxites) Assemblage and its coeval strata.
faunas (Fig. 1). Significantly, it may indicate that parts of the deep water marine
environments may have survived the end Ordovician mass extinctions.
334
P-rich nodules and “hollow graptolites” in the upper
Silurian of the Moncorvo synclinorium, north Portugal
ARTUR A. SÁ, JOSÉ M. PIÇARRA, JUAN C. GUTIÉRREZ-MARCO,
GRACIELA N. SARMIENTO
A.A. Sá - Departamento de Geologia, Universidade de Trás-os-Montes e Alto Douro, Ap. 1013, P-5001-801 Vila Real
(Portugal); [email protected]
[email protected]
J.C. Gutiérrez-Marco - Instituto de Geología Económica (CSIC-UCM,) José Antonio Novais 2, E-28040 Madrid
G.N. Sarmiento - Instituto de Geología Económica (CSIC-UCM,) José Antonio Novais 2, E-28040 Madrid (Spain);
[email protected]
The Moncorvo synclinorium in the Trás-os-Montes region of N Portugal is located in
the northern Central-Iberian Zone. The core of the synclinorium includes a 300-600 m
thick Silurian succession of strongly tectonized and sparsely fossiliferous shales with
some limestone intercalations. Sarmiento et al. (1999) described the Silurian succession
as a relatively condensed sequence that is much thinner and stratigraphically similar to
Silurian successions of the Ossa-Morena Zone, SE Sardinia and parts of north Africa.
Their distal shelf characteristics resemble the “Thuringian triad” by the presence, towards
the upper part, of a Ludlow-Pridoli scyphocrinoid limestone correlated by conodonts.
We report here the graptolite taphonomy of silico-phosphatic nodules (up to 15 cm in
diameter) found ESE from Moncorvo in a metric bed of alum shale below the
scyphocrinoid limestone. From these nodules we recorded a Sheinwoodian assemblage of
3D-specimens of Pristiograptus dubius (Suess), Monograptus cf. flemingii (Salter),
Monoclimacis cf. flumendosae (Gortani), and Retiolites sp. They occur as “hollow”
Fig. 1 - A) Equatorial section of a nodule, showing concentric rims (x 0.7); B) detail of phosphate
grains (x 2.7); C) longitudinal sections of rhabdosomes (x 2.1); D) transverse sections of
rhabdosomes (x 2.4); E) pseudo-stalactites of phosphatic minerals inside a rhabdosome (x
11.3); F) phosphatic overgrowth in both sides of the graptolite periderm (hollow space, arrowed)
(x 116); G) geopetal silica (arrowed) at the base of an interthecal septum (x 66).
335
moulds in a siliceous matrix with coarse phosphatic grains. The organic periderm is not
preserved, but features such as the fusellar tissue are finely replicated by phosphatic
overgrowths that coated the inner and outer surfaces of the rhabdosome. Occasional
“stalactites” of phosphatic minerals and colloidal silica partially occupied the empty spaces.
A later alteration of the dispersed iron sulphides favoured the ferruginous impregnation of
some rhabdosomes.
Our results corroborate the correlation between these Wenlock strata and the beds
with “phosphoritknollen” that occur towards the middle part of the Lower Graptolitic
Shales in Thuringia and SE Sardinia (Jaeger, 1976), being restricted to these Thuringian
facies developed in offshore settings in northern Gondwana.
This work is a contribution to the projects CGL2006-07628/BTE (Spain) and PTDC/
CTE-GEX/64966/2006 (Portugal).
REFERENCES
JAEGER H. (1976). Das Silur und Unterdevon vom thüringischen Typ in Sardinien und seine regionalgeologische
Bedeutung. Nova Acta Leopoldina, n.F., 45, 224: 263-299.
SARMIENTO G.N., PIÇARRA J.M., REBELO J.A., ROBARDET M., GUTIÉRREZ-MARCO J.C., STORCH P. & RÁBANO I.
(1999). Le Silurien du synclinorium de Moncorvo (NE du Portugal): biostratigraphie et importance
paléogéographique. Geobios, 32: 749-767.
336
Howellellid branches at the Silurian/Devonian
boundary interval and their importance for
delthyridoid spiriferid evolution
MENA SCHEMM-GREGORY
M. Schemm-Gregory - Senckenberg Forschungsinstitut und Naturmuseum, Paläozoologie III, Senckenberganlage
25, D-60325 Frankfurt am Main (Germany); [email protected]
The cosmopolitan genus Howellella Kozlowski, 1946 is regarded as the root of several
branches of delthyridoid spiriferids, a group of coarsely plicated and mostly alate
brachiopods. During the Silurian and Early Devonian taxa of Howellella were globally
distributed and closely related to each other. Within the Early Devonian faunal isolation
began resulting in endemic brachiopod provinces and realms each with its own evolutionary
branch of brachiopods. Extinctions events followed by re-settlements of brachiopod
communities characterised each region.
The type species of Howellella, H. elegans Muir-Wood, 1925, occurs in the Wenlock
of Gotland, Sweden, and is characterized by a very small specimens with two to three
ribs on each flank and a fimbriate micro-ornamentation consisting of single rows of microspines at the edge of each growth lamella. Younger species, however, show an increase in
size and amount of ribs as well as development of other forms of micro-ornamentation,
capillate with and without micro-spines or fimbriate with more than one row of microspines at the edge of each growth lamella.
Several phylogenetic lineages are recognisable coming out of Howellella, e.g., the
vanuxemi-cycloptera-murchisoni lineage in eastern North America or the cortazarisalicamensis-arduennensis-mosellanus lineage in Western and Central Europe.
All taxa of Howellella seem very similar on first sight but already Carls (1985) and
Carls et al. (1993) showed that Howellella can be subdivided into subspecies in Europe.
It is remarkable that all lineages under consideration are characterized by an increase
in size of specimens, one of the most spectacular example is the ratio of size in Howellella
and Euryspirifer Wedekind, 1926. However, it is remarkable that with Quiringites Struve,
1992 a Howellella-like morphotype occured for a short time again within the Eifelian
(early Middle Devonian).
According to Johnson & Hou (2006) in the revised “Treatise on Invertebrate
Paleontology”, descendants of Howellella survived until the early Middle Devonian in
Asia with the genus Xenospirifer Hou & Xian, 1975. After detailed comparison with
other delthyridoid spiriferids it has turned out that Xenospirifer belongs to a different and
new family within the Delthyridoidea of the “Asian delthyridoid spiriferid clade” (SchemmGregory 2009), but originating also from Howellella.
REFERENCES
CARLS P. (1985). Howellella (Hysterohowellella) knetschi (Brachiopoda, Spiriferacea) aus dem tiefen UnterGedinnium Keltiberiens. Senckenbergiana lethaea, 65: 297-326.
337
CARLS P., MEYN H. & VESPERMANN J. (1993). Lebensraum, Entstehung und Nachfahren von Howellella
(Iberohowellella) hollmanni n. sg., n. sp. (Spiriferacea; Lochkovium, Unter-Devon). Senckenbergiana
lethaea, 73: 227-267.
JOHNSON J.G. & HOU H. (2006). Delthyridoidea. In Kaesler R.L. (Ed.), Treatise on Invertebrate Paleontology,
Part H, Brachiopoda 5 (revised). Geological Society of America & University of Kansas, Lawrence,
Kansas: 1825-1847.
KOZLOWSKI R. (1946). Howellella, a new name for Crispella Kozlowski, 1929. Journal of Paleontology,
20: 295.
MUIR-WOOD H.M. (1925). Notes on the Silurian braciopod genera Delthyris, Uncinulus, and Meristina.
Annals and Magazine of Natural History, series 9, 15: 83-95.
SCHEMM-GREGORY M. (2009). A new spiriferid genus and ist phylogenetic position within the Delthyridoidea
(Brachiopoda, Lower Devonian). Neues Jahrbuch für Geologie und Paläontologe, 252: 53-70.
STRUVE W. (1992). Neues zur Stratigraphie und Fauna des rhenotypen Mittel-Devon. Senckenbergiana
lethaea, 71: 503-624.
WEDEKIND R. (1926). Die devonische Formation. In Salomon W. (Ed.), Grundzüge der Geologie 2,
Erdgeschichte. Schweizerbart’sche Verlagsbuchhandlung (Nägele), Stuttgart: 194-226.
338
The Silurian of the Goldsteintal (Rheinisches
Schiefergebirge, Germany)
MENA SCHEMM-GREGORY, ULRICH JANSEN
M. Schemm-Gregory - Senckenberg Forschungsinstitut und Naturmuseum, Paläozoologie III, Senckenberganlage
25, D-60325 Frankfurt am Main (Germany); [email protected]
U. Jansen - Senckenberg Forschungsinstitut und Naturmuseum, Paläozoologie III, Senckenberganlage 25, D-60325
Frankfurt am Main (Germany); [email protected]
At the classic locality in the idyllic Goldsteintal (“Golden Stone Valley”) near Wiesbaden
in the Taunus Hills of the southern Rheinisches Schiefergebirge and at other localities
nearby, the Kellerskopf Formation (= Graue Phyllite or „Grey Phyllites“ in former works)
crops out yielding a small fauna consisting of corals, brachiopods, trilobites, crinoidal
remains, bryozoans, and bivalves (Struve, 1973). Due to strong tectonic deformation and
even gentle metamorphosis of this succession during the Variscan orogeny, most of the
fossils are poorly preserved. Accordingly, the age of this stratum has been controversal
for a long time; it has been dated either as late Silurian (Dahmer, 1946) or earliest Devonian
(Fuchs, 1929; Shirley, 1962; Struve, 1973). New finds confirm the identification of the
brachiopod Dayia shirleyi Alvarez & Racheboeuf, 1986, allowing a correlation with the
lowermost Noulette Formation of Artois (France), the Köbbinghausen Formation of the
Ebbe Anticline (N Rheinisches Schiefergebirge, Germany) and the lower Muno Formation
of the Ardennes (cp. Godefroid, 1995; Godefroid & Cravatte, 1999). As for these strata,
a late Silurian (Pridolian) age is suggested for the faunas of the Kellerskopf Formation, as
the genus Dayia has never been observed to cross the Silurian/Devonian boundary. The
presence of Quadrifarius dumontianus (de Koninck, 1876) and Shaleria rigida (de
Koninck, 1876) support this assignment, whereas the presence of Platyorthis would
rather plead for an Early Devonian age. The two taxa mentioned first allow a correlation
with the Weismes Formation (= Grès de Gdoumont) of the Hautes Fagnes and the Silberg
Formation of the Müsen Horst (N Rheinisches Schiefergebirge). The finds in the
Goldsteintal fit well in a scenario of a vast “dumontianus Shelf” (Carls, 2001) during
Pridolian time, representing the first transgression after the Caledonian orogeny in the
Rheinisches Schiefergebirge and marking the onset of the Variscan cycle.
REFERENCES
ALVAREZ F. & RACHEBOEUF P.R. (1986). Sous-famille Dayiinae Waagen 1883. In Racheboeuf P.R. (Ed.), Le
Groupe de Liévin. Pridoli-Lochkovien de L‘Artois (N. France). Sédimentologie - Paléontologie Stratigraphie - Biostratigraphie du Paléozoique, 3: 128-131.
C ARLS P. (2001). Kritik der Plattenkinematik um das Rhenohercynikum bis zum frühen Devon.
Braunschweiger geowissenschaftliche Arbeiten, 24: 27-108.
DAHMER G. (1946). Gotlandium mit Dayia navicula im Taunus. Seine Beziehungen zu den Köbbinghäuser
(Dayia-) Schichten des Ebbe- und Remscheider Sattels und zu den Schichten von Weismes.
Senckenbergiana, 27: 76-84.
FUCHS A. (1929). Die unteren Gedinneschichten der Gegend von Wiesbaden. Jahrbuch des Nassauischen
Vereins für Naturkunde, 80 (2): 74-86.
339
GODEFROID J. (1995). Dayia shirleyi Alvarez & Racheboeuf, 1986, un brachiopode silurien dans les ”Schistes
de Mondrepuis” à Muno (sud de la Belgique). Bulletin de l’Institut Royal des Sciences Naturelles de
Belgique: Sciences de la Terre, 65: 269-272.
GODEFROID J. & CRAVATTE T. (1999): Les brachiopodes et la limite Silurien/Dévonien à Muno (sud de la
Belgique). Bulletin de l’Institut Royal des Sciences Naturelles de Belgique: Sciences de la Terre, 69: 526.
KONINCK L. (1876). Notice sur quelques fossiles recueillis par G. Dewalque dans le système Gédinnien de A.
Dumont. Annales (le la Société géologique de Belgique, 3: 25-52.
SHIRLEY J. (1962). Review of the correlation of the supposed Silurian strata of Artois, Westphalia, the Taunus
and Polish Podolia. In Erben H.K. (Ed.), Symposium Silur/Devon-Grenze 1960: 234-242.
STRUVE W. (1973). Die ältesten Taunus-Fossilien. Natur und Museum, 103: 349-359.
340
Silurian Nautiloid Cephalopods from the Cabrières
area (Montagne Noire, France): a preliminary report
PAOLO SERVENTI, RAYMUND FEIST
R. Feist - Institut des sciences de l’évolution, Université Montpellier 2 – CNRS, Place Eugène Bataillon, F-34095
Montpellier (France); [email protected]
This preliminary report deals on a nautiloid cephalopod fauna collected on the northern
slope of the Plateau de Falgairas, a few km south of Cabrières. The Silurian-Lower
Devonian succession of the area mainly consists of isolated exposures (Feist, 2002) and
was described by Feist & Schönlaub (1974). Biostratigraphic data were provided on the
basis of conodonts (Feist & Schönlaub, 1974) and chitinozoans (De Bock, 1982).
Silurian nautiloid cephalopods from the Montagne Noire were illustrated by Ristedt
(1968), who described five taxa from this area.
The studied material have been collected from some blocks along the path from La
Roquette to Col de l’Orte. The association consists of four species: Orthocycloceras?
fluminese (Meneghini), Michelinoceras (Michelinoceras) michelini (Barrande),
Arionoceras submoniliforme (Meneghini) and Arionoceras canonicum (Meneghini).
Several protoconchs referable to subfamily Michelinoceratinae, have been collected, too.
Some specimens have been dated to Pridoli, thanks to conodonts found in the nautiloidbearing blocks.
REFERENCES
DE BOCK F. (1982). Présence de chitinozaieres dans le passage siluro-dévonien de la Montagne Noire sudorienatale. Geobios, 15 (6): 845-871.
FEIST R. (2002). The Palaeozoic of the Montagne Noire, Southern France. ECOS VIII Guidebook to the
Field Excursion: 85 pp.
FEIST R. & SCHÖNLAUB H.P. (1974). Zur Silur/Devon-Grenze in der östlichen Montagne Noire Süd-Frankreichs.
Neues Jahrbuch für Geologie und Paläontologie Monatshefte, 1974-H4: 200-219.
R ISTEDT H. 1968. Zur Revision der Orthoceratidae. Abhandlungen der MathematischNaturwissenschaftlichen. Akademie der Wissenschaften und Literatur in Mainz, Klasse, 68(4): 212287.
341
342
Gondwanan tectonics and European events in the
Silurian of Australasia
LAWRENCE SHERWIN
L. Sherwin - Geological Survey of New South Wales, Dept of Primary Industries, Locked Bag 21, Orange, New South
Wales 2800 (Australia); [email protected]
Silurian biostratigraphic events defined in north-west Europe correspond with intervals
of marked tectonic activity in Australasia (north-east Gondwana) but the accuracy in
correlation is not such that a European biostratigraphic event can be tied to a specific
Australasian tectonic event. Problems remain in a strict application of European Silurian
zonation schemes in Australasia (Strusz, 2007). In the eastern margin of Australasia the
earlier part of the Silurian (Llandovery - early Wenlock?) is represented mostly by deep
water siliciclastic sediments with few calcareous beds in the Lachlan Fold Belt (LFB).
Events of any kind are difficult to recognise within the Llandovery in the eastern part of
the LFB near Goulburn because of later structural complications, particularly the
imbrication of Late Ordovician and Early Silurian fault slices which nonetheless have
very similar lithologies.
Silurian strata are structurally simpler in the western part of the LFB near Forbes
where the pre Wenlock is represented by fairly uniform laminate quartzose siltstone of
the Cotton Formation. Here, the graptolitic sedgwickii bioevent coincides with a minor
change in lithology that results in sedgwickii and guerichi graptolite faunas (Sherwin,
1974; Loydell et al., 1993) being associated with distinctly more prominent outcrops.
Above the guerichi fauna the base of the Forbes Group is marked by a poorly dated
polymictic carbonate cemented cobble conglomerate (Bocobidgle Conglomerate),
succeeded by approximately 300m of generally massive olive grey silty mudstone
(Mumbidgle Formation). About the middle of this unit is an horizon with a ludensissherrardae fauna but without any marked change in lithology from the remainder of the
Mumbidgle Formation. The marked change in lithology from the Cotton Formation to the
Forbes Group is associated with an hiatus of uncertain duration but is interpreted as
encompassing the lapworthi and murchisoni graptolitic bioevents and the Ireviken, Boge
and Valleviken conodont bioevents. This hiatus is also apparent in the eastern part of the
LFB in the Yass and Goulburn districts (Thomas & Pogson, in press). The Forbes Group
is overlain with a low angle unconformity by the non graptolitic Derriwong Group. The
basal unit of the Derriwong Group is a pebbly sandstone lacking age diagnostic fossils but
overlying the sandstone is a felsic volcanic sequence with interbedded limestones which
contain a remscheidensis zone conodont fauna, although one sample indicates a possible
crispa zone age (Pickett & Ingpen, 1990). The indicated hiatus thus spans much of the
Ludlow and overlaps with the timespan covering the Linde and Lau conodont bioevents.
In the eastern part of the LFB there is more or less continuous sedimentation, with
notable olistostromes in the Pridoli (Sherwin, 1971, Thomas & Pogson, in press),
corresponding to the hiatus during the Ludlow in the western LFB.
Published with the permission of the Director, Geological Survey of New South Wales.
343
REFERENCES
LOYDELL D.K., STORCH P. & MELCHIN M.J. (1993). Taxonomy, evolution and biostratigraphical importance of
the Llandovery graptolite Spirograptus. Palaeontology, 36, 909-926.
PICKETT J.W. & INGPEN I.A. (1990). Ordovician and Silurian strata south of Trundle, New South Wales.
Geological Survey of New South Wales, Quarterly Notes, 100, 1-7.
SHERWIN L. (1971). Stratigraphy of the Cheesemans Creek district, New South Wales. Geological Survey of
New South Wales, Records, 13, 199-237.
SHERWIN L. (1974). Llandovery graptolites from the Forbes district, New South Wales. Special Papers in
Palaeontology, 13, 149-175.
STRUSZ D.L. (2007). The Silurian timescale – an Australian perspective. Memoirs of the Association of
Australasian Palaeontologists, 34, 157-171.
THOMAS O.D. & POGSON D.J. (in press). Goulburn 1:250000 Geological Sheet, 2nd edition. Explanatory
Notes. Geological Survey of New South Wales, Maitland.
344
Problematic fossil remains from the Silurian Kok
Formation in the type area (Carnic Alps, Italy)
LUCA SIMONETTO, PAOLO SERVENTI, MONICA PONDRELLI, CARLO CORRADINI
L. Simonetto - Museo Friulano di Storia Naturale, via Marangoni 39-41, I-33100 Udine (Italy); [email protected]
M. Pondrelli - International Research School of Planetary Sciences, Dipartimento di Scienze, Università d’Annunzio,
viale Pindaro 42, I-65127 Pescara (Italy); [email protected]
C.Corradini - Dipartimento di Scienze della Terra, Università di Cagliari, via Trentino 51, I-09127 Cagliari (Italy);
[email protected]
This report is one of the outcomes of a broader research project which aim is to
survey the geology of the Silurian Orthoceras Limestone cropping out in the Italian side
of the Carnic Alps (North-Eastern Italy). The former researches on this subject date in
fact from the first half of the twentieth century.
The Silurian Orthoceras Limestone crop out through all the Carnic Alps, but the
complex tectonic assemblage of the area, due to compressional as well as extensional
deformative phases, makes the unravelling of the depositional setting quite complex.
Moreover, this unit is generally only few meters thick. As a consequence the outcrops are
usually small and scattered.
A revision of the macrofossils preserved in the Silurian limestone of the study area has
been undertaken. The Carnic Alps, in fact, have been known since the end of the nineteenth
century for the abundance and variety of Silurian fossils. Orthoconic cephalopods are,
doubtless, the most frequent remains, followed by trilobite fragments (usually isolated
pygidiums and cephalons), bivalves, gastropods and crinoids; the latter are quite frequent
as isolated articles, forming at places true encrinite levels. Brachiopods, corals and ostracods
remains are rarer.
In the eastern part of the chain Silurian fossils are particularly abundant in the Monte
Cocco area, North of Ugovizza village. Important mining activities have been documented
in this area, since sixteenth century, digging out iron and manganese from cephalopod
limestone. The mined non-mineralized limestone was spread outside the gallery entrances;
as a consequence, a lot of fossiliferous rocks are available in spite of the relative scarcity
of wide outcrops, most of which being hidden by wood or debris.
Large collections of Silurian fossils from Monte Cocco are stored in the Museo Friulano
di Storia Naturale, in Udine. That material and newly collected samples from the late
Llandovery-lower Ludlow Kok Formation have been investigated in order to obtain new
data on the Silurian faunas of the Carnic Alps. Conodonts allow to date most of these
remnants at the amorphognathoides Zone.
Beside representatives of common fossil groups, the study of thousands of samples
evidenced the presence of several small-sized remains whose interpretation turn out to be
difficult, although having characteristic shape. Beside other less common shapes, three
different morphologies are relatively abundant in the examined material: a sub-triangular
with sigmoidal ornamentation (Fig. 1a), a subcircular with a concentric ornamentation
345
Fig. 1 - Problematic fossil microremains from Monte Cocco. Both from block “Tamer-BK 1”
(amorphognathoides Zone). a) Subtriangular plate with sigmoidal ornamentation. b) Subcircular
plate with a irregular concentric ornamentation.
(Fig. 1b) and an elongate with chessboard thin costae. It should be noted that representatives
of these morphs are constant is size.
Moreover, a few fossil fragments can be ascribed to the artropods but have no trilobite
features. We hypothesize that these samples could be parts of eurypterids but the remains
are so poorly preserved that the determination is quite tricky. Furthermore, eurypterids
remains have never been reported in literature for this area, so their eventual detection
must be carefully evaluated.
346
Carbon isotope data and graptolite record in the lower
Silurian (Llandovery) of northern peri-Gondwana –
exemplified by Barrandian area, Czech Republic
PETR STORCH, JIRI FRYDA
P. Storch - Institute of Geology, Academy of Sciences of the Czech Republic, Rozvojova 269, 165 02 Praha 6 (Czech
Republic); [email protected]
J. Fryda - Czech Geological Survey, Klarov 3, 118 21 Praha 1, and Faculty of Environmental Sciences, CULS, 165 21
Praha 6 (Czech Republic); [email protected]
Late Ordovician and Silurian carbon isotope record exhibits a series of positive excursions
which coincide with sea-level changes and mass faunal extinctions. The δ13Corg values
from the uppermost Hirnantian to lower Telychian strata of the Barrandian area are
compared with data on graptolite faunal dynamics based on a high resolution graptolite
biostratigraphy.
Significant negative shift in δ13Corg from late Hirnantian baseline values to ca. 31 ‰ is
associated with graptolite-rich black shale that appears just below the base of the Silurian
Akidograptus ascensus Biozone. Further increase in the organic carbon content coincides
with a magnificent adaptive radiation among graptolites and gradual increase of δ13Corg.
This trend extends from A. ascensus, through Parakidograptus acuminatus to Cystograptus
vesiculosus biozones in Repy and Hlasna Treban sections. A prominent gap in
sedimentation, embracing upper A. ascensus – Coronograptus cyphus biozones, was
documented in Radotin tunnel section. A sequence boundary expressed by this stratigraphic
unconformity (Storch, 2006) coincides with a sudden rise in organic carbon content and
minor positive shift in δ13Corg in Radotin tunnel. The δ13Corg values fluctuate between 28
and 30 ‰ during early and middle Aeronian Demirastrites triangulatus – Lituigraptus
convolutus biozones, whereas maximum TOC values of the late Rhuddanian C. cyphus
Biozone and early Aeronian D. triangulatus Biozone decline through to the lower part of
late Aeronian Stimulograptus sedgwickii Biozone. Rich and diverse mid-Aeronian graptolite
fauna vanished from the black shale at about the top of the convolutus Biozone, hence
the lower part of the sedgwickii Biozone, remarkable by silty fraction and abundant
pyrite, exhibits few graptolite rhabdosomes.
Pyrite-rich interval is overlain by a heavily mottled, silty/sandy-micaceous bed. Rapid
sea-level drawdown, supposed by Loydell (1998) manifests itself by increased input of
the silty/sandy-micaceous fraction, that correlates with a gap in sedimentation elsewhere
in Barrandian and abroad. Siliciclastic signal is compatible with low organic content and
heavy bioturbation in this particular level and further coincides with a strong positive
carbon isotope excursion. Positive excursion, recorded also in Dob‘s Linn, Scotland and
Cornwallis Island of Arctic Canada (Melchin & Holmden, 2006), is rather short-term,
perhaps incomplete in the Barrandian area. It clearly postdates, however, the major phase
of graptolite extinction known as sedgwickii Event. Lithology, sequence architecture,
organic carbon content, isotope record, as well as graptolite faunal dynamics, are consistent
with a conception of short term advance in continental glaciation in Gondwana.
347
The level with positive δ13C excursion is overlain by micaceous black shale characterized
by a rapid return to normal δ13Corg values, rapid increase in TOC, and rapid proliferation
of low diversity-high abundance graptolite fauna belonging to the middle part of the S.
sedgwickii Biozone.
Though the anoxic black shale is intercalated with pale-coloured marlstones in the
succeeding lowermost Telychian Rastrites linnaei and Spirograptus turriculatus biozones,
and TOC values fluctuate, the δ13Corg record is steady.
REFERENCES
LOYDELL D.K. (1998). Early Silurian sea-level changes. Geological Magazine, 135: 447-471.
MELCHIN M.J. & HOLMDEN C. (2006). Carbon isotope chemostratigraphy of the Llandovery in Arctic Canada:
implications for global correlation and sea-level change. GFF, 128: 173-180.
STORCH P. (2006). Facies development, depositional settings and sequence stratigraphy across the OrdovicianSilurian boundary: a new perspective from the Barrandian area of the Czech Republic. Geological
Journal, 41: 163-192.
348
Paleoenvironment of the Siluro-Devonian sequence in
southern Burgenland (Austria)
THOMAS J. SUTTNER
T.J. Suttner - Commission for the Palaeontological and Stratigraphical Research of Austria c/o University of Graz,
Institute of Earth Sciences (Geology and Palaeontology), Heinrichstrasse 26, A-8010 Graz (Austria);
[email protected]
Late Silurian to Lower Devonian deposits of southern Burgenland (Austria) are known
from an ancient quarry south of the village of Kirchfidisch and near Sulz, where a several
tens of meters thick sequence is exposed (Pollak, 1962). From the base to the top, the
unit consists of phyllitic shale (8 m), white carbonaceous marl (8 m), laminated limestone
(17.5 m), even bedded serpulid tube-bearing limestone which is intercalated by thin silt
layers (2 m), and dolomitic limestone and dolomite (4 m). Due to the evidence that only
the upper 6 meters of the unit yield fossils, geochemical analysis were used to gain
additional information on the rock composite for a better interpretation of the deposits
according to paleoenvironmental conditions and settings. In general the fauna consists of
spiculae, gastropods, serpulids, ostracods, brachiopods, crinoids and conodonts (Suttner
& Lukeneder, 2004).
Until now it is not clear, whether the basal phyllitic shale is overlain by the marls
conformably or if a hiatus separates them. The development above the shale seems to be
more or less continuous. According to the facies, different lithologies like dark bituminous
laminated limestones, dolomites or the serpulid bearing limestones, hint to shallow marine
conditions. This is supported by the conodont fauna, which is dominated by icriodontids
(Suttner, 2009). Earlier speculations that the ancient serpulid-tube build ups were related
to cold seeps could be disproved as geochemical data of carbon isotopes and trace elements
do not show values distinctive for such environments.
Taphonomic analyses of serpulid bearing limestone beds conclude allochthonous
deposition. The accumulated trochospiral and helical tubes are not erected within the
limestone beds. Single tubes and re-deposited tube-aggregates show no orientation; they
are ‘floating’ in the limestone matrix. Fragmentation of tubes and accompanying fauna is
low which suggests that the accumulated tubes must have been deposited proximal to the
ancient build up. An in situ serpulid bioherm which was constructed by similar tubemorphotypes is known from Devonian strata of Arizona (Beus, 1980). In dolomitic
limestones above the serpulid bearing beds, thin shell layers alternate with fine laminated
limestone layers, which finally are overlain by unfossiliferous dolomite. From the dolomitic
limestone beds some fused conodont clusters are known.
In general, shallow to subtidal settings are proposed to be dominating paleoenvironment,
where calm periods (indicated by the growth of microbial mats, or deposition of thin
brownish silt layers) alternate with more turbulent, possibly storm induced periods resulting
in accretion of serpulid tubes or shell layers. Even though the serpulid beds and the
preservation of conodont clusters might hint to special conditions for this interval - how
far can it justify whether this small outcrop accords to restricted lagoonal deposits or not?
349
Additionally it remains unclear whether this sequence was deposited during temperate
cool or subtropical warm conditions.
REFERENCES
BEUS S.S. (1980). Devonian serpulid bioherms in Arizona. Journal of Paleontology, 54: 1125-1128.
POLLAK W. (1962). Untersuchungen über Schichtfolge, Bau und tektonische Stellung des österreichischen
Anteils der Eisenberggruppe im südlichen Burgenland. 108 pp. unpublished Ph.D. thesis, University of
Vienna.
SUTTNER T.J. (2009). Lower Devonian conodonts of the “Baron von Kottwitz” quarry (Southern Burgenland,
Austria). In Over D.J. (Ed.) Conodont Studies Commemorating the 150th Anniversary of the First Conodont
Paper (Pander, 1856) and the 40th Anniversary of the Pander Society, Palaeontographica Americana,
62: 75-87.
SUTTNER T. & LUKENEDER A. (2004). Accumulations of Late Silurian serpulid tubes and their palaeoecological
implications (Blumau-Formation; Burgenland; Austria). Annalen des Naturhistorischen Museums in
Wien, 105 A: 175-187.
350
Siluro-Devonian biodiversification of trilete spores and
cryptospores from Tunisia: palaeophytogeographic and
palaeoclimatic implications
MARCO VECOLI, AMALIA SPINA
M. Vecoli - Université Lille 1, UMR 8157 “Géosystèmes” CNRS, F-59655 Villeneuve d’Ascq (France).
A. Spina - Dipartimento di Scienze della Terra, Università di Perugia, I-06124 Perugia (Italy).
A detailed study on miospore assemblages from Ludlow-Lochkovian time interval in
Southern Tunisia (MG-1 borehole, Ghadamis Basin) permits a comparison with coeval
associations from other Gondwanan and Euramerican localities and to better define the
palaeoclimatic changes across this time span.
Four palynological assemblages have been established and assigned respectively to
upper Gorstian-Ludfordian, Ludfordian-lower Pridoli, Pridoli and Lochkovian. The
Gorstian-Ludfordian assemblage is mainly characterised by the presence of patinate forms
with verrucate sculpture (e.g., S. verrucatus), and laevigate trilete spores with equatorial
crassitude such as Ambitisporites avitus, and occurrence of retusoid spores (Retusotriletes
warringtonii). The Ludfordian-lower Pridoli assemblage mainly consists of abundant
ornamented trilete spores such as Chelinospora poecilomorpha, Amicosisporites
splendidus, Synorisporites libycus, and less abundant cryptospores. The Pridoli association
is mainly characterised by interradial tripapillate spores recorded both in Gondwana and
Laurussia domains, co-occurring with laevigate trilete spores (i.e. Archeozonotriletes,
Ambitisporites, etc.), present in all Silurian record. In the upper part of the assemblage,
the microflora is characterized by a bloom of Aneurospora spp., abundantly present also
in the overlying Lochkovian assemblage. Most cryptospore and trilete spore species first
appearing during the Pridoli, range through the Silurian-Devonian boundary and commonly
occur during the Lochkovian. This pattern is recognized in Gondwanan as well as in
Euramerica. In addition, Lochkovian assemblages are characterized by the appearance
and diversification of tripapillate spores, distally sculptured with grana, coni, and spinae,
such as Streelispora newportensis, which appears to be palaeogeographically widespread
during the Early Devonian. These data suggest that the Silurian-Devonian transition is not
characterised by pronounced floristic turnover. With the exception of some minor local
differences probably due to the endemism of some species, the close similarities of
microflora recorded both from Gondwana and Europe reflect palaeogoegraphical proximity
as well as broadly uniform climatic conditions between Gondwana and Laurussia during
the Silurian-Devonian transition.
The diversification of cryptospores and trilete spores from MG-1 borehole has been
compared with that recorded from Gondwana and Euramerica. Over 60 selected
publications have been used to draw a trilete spores and cryptospores biodiversity curve
for the Wenlock-Lochkovian time interval of both Gondwanan and Euramerican domain.
Trilete spore and cryptospore have been plotted as average diversity per geologic stage.
The cryptospores biodiversity curve shows the same trend for both Euramerican and
351
Gondwanan domain, although in this latter they are less diversified. In comparison with
the trilete spores, generally the cryptospores disappear progressively from the WenlockLudlow to Lochkovian, although they are slightly more abundant in the Early Devonian
than in the Pridoli. On the contrary, the diversification of trilete spore continues from
Wenlock to Lochkovian. Nevertheless, the Euramerican trilete spores are less diversified
than those from Gondwana. The MG-1 biodiversity curve shows the same trend recorded
in Gondwana. The biodiversity of these sporomorphs could be correlated with the
transgressive-regressive trend recorded in both domains from Wenlock to Lochkovian.
352
Discovery of a new Llandovery-Wenlock boundary
section in Bajiaokou, Ziyang, China
JIAN WANG, LI-PU FU, YONG MENG, RONG-SHE LI, HONG-PING HUANG
J. Wang - Xi’an Institute of Geology and Mineral Resoures; Xi’an 71005 (China); [email protected]
L.-P. Fu - Xi’an Institute of Geology and Mineral Resoures; Xi’an 71005 (China); [email protected]
Y. Meng - Xi’an Institute of Geology and Mineral Resoures; Xi’an 71005 (China); [email protected]
R.-S Li - Xi’an Institute of Geology and Mineral Resoures; Xi’an 71005 (China); [email protected]
H.-P. Huang - Xi’an Institute of Geology and Mineral Resoures; Xi’an 71005 (China).
A biostratigraphic study of the Silurian sections of Ziyang was carried out in the course
of 1:50000 scale geological mapping. A new, highly fossiliferous section with particularly
well developed Llandovery-Wenlock boundary interval was encountered in Bajiaokou.
Great numbers of complete rhabdosomes of Cyrtograptus insectus Boucek and C.
centrifugus Boucek have been collected in this section. Present material of the former
zonal index species originated from 9 different beds, material of the latter species came
from 6 beds. Five graptolite biozones were identifiend in the section, in the ascending
order: C. sakmaricus Biozone 1.16 m above the base of the section, C. insectus Zone
1.16-3.10 m above the base, C. centrifugus Zone at 3.1-6.3 m, C. murchisoni Zone at
6.3-11.1 m, and Monograptus riccartonensis Zone at 11.1 m above the base.
353
354
The Silurian-Devonian Boundary in West Qinling of
South China – Evidence from Chemostratigraphy and
microvertebrate remains across the Silurian/Devonian
transition
WEN-JIN ZHAO, ULRICH HERTEN, NIAN-ZHONG WANG, ULRICH MANN, MIN ZHU,
ANDREAS LÜCKE
W.-j. Zhao - Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and
Paleoanthropology (IVPP), Chinese Academy of Sciences, PO Box 643, Beijing 100044 (China);
[email protected]
U. Herten - Institute of Chemistry and Dynamics of the Geosphere ICG-V: Sedimentary Systems, Research Center
Juelich GmbH, D-52425 Juelich (Germany); [email protected]
N.-z. Wang - Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and
[email protected]
U. Mann - Institute of Chemistry and Dynamics of the Geosphere ICG-V: Sedimentary Systems, Research Center
M. Zhu - Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and
[email protected]
A. Lücke - Institute of Chemistry and Dynamics of the Geosphere ICG-V: Sedimentary Systems, Research Center
Many biostratigraphic attempts have been made so far to define the exact level of the
Silurian/Devonian (S/D) Boundary in West Qinling of South China (XIGMR and NIGPAS,
1987; Rong et al., 1987). Because the comparisons to the S/D index fossils like the
graptolite Monograptus uniformis and the trilobite Warburgella rugulosa rugosa or diagnostic
chitinozoans from the GSSP Klonk (Czech Republic) are not feasible in the Putonggou
and Yanglugou sections, there exist many issues regarding the biostratigraphy of the Upper
Silurian – Lower Devonian in West Qinling, the S/D Boundary in particular. The first
isotope curve based on organic carbon for the SDB sequence from GSSP (Mann et al.,
2001) shows the distinct positive excursion of δ13Corg from uppermost Silurian to lowermost
Devonian is directly related to the high bioproductivity, mass burial of organic carbon and
transgression - regression of 3rd order, and represents a global bioproductivity event.
Subsequently, the distinct positive shifts in the isotopic composition of organic carbon
across SDB were confirmed at several global locations including the sections from Ukraine,
Turkey, USA, Morocco and Poland (Mann et al., 2001; Buggisch & Mann, 2004; Herten
et al., 2004). This distinct change trend from the isotopic composition of organic carbon
across SDB potentially offers a good means to exactly correlate and define the SDB from
different sedimentary facies. In addition, the study on microvertebrate remains since the
performing of IGCP328 showed that microvertebrates have played an important role in
the Silurian-Devonian Stratigraphy. The detailed geochemical analyses, as well as the
research of microvertebrate assemblage sequences, may throw new lights on the study of
the S/D Boundary in West Qinling. Recently, we focused on the two sections in West
Qinling, and applied the Chemostratigraphy (including the content of carbonate and total
355
organic carbon, stable isotopic ratios of carbonate and organic carbon versus depth, etc.)
and Biostratigraphy (including microvertebrate assemblage sequences) as a tool to identify
the Silurian/Devonian Boundary and set up the accurate Late Silurian – Lower Devonian
sequence framework in the region. Our newest results suggested that the variations of
δ13Corg exhibited at SDB in two sections from West Qinling can be correlated to the
representative curve of the SDB at Klonk in Czech Republic (GSSP), and in spite of the
absence of some index fossil, the exact level of the Silurian/Devonian (S/D) Boundary in
West Qinling can be located at the upper part of Yanglugou Formation (between ZY-06
and ZY-07) in Yanglugou Section and the lower part of Xiaputonggou Formation (between
ZP-09 and ZP-10) in the Putonggou section, which helped to study the early diversification
of vertebrates and land plants, and explore the interaction between the geosphere and the
biosphere.
REFERENCES
BUGGISCH W. & MANN U. (2004). Carbon isotope stratigraphy of Lochkovian to Eifelian limestones from the
Devonian of central and southern Europe. International Journal of Earth Science, 93: 521-541.
HERTEN U., MANN U. & YALÇIN M.N. (2004). Chemostratigraphic localization of the Silurian/Devonian Boundary
in the Palaeozoic of Istanbul (Esenyali, pendik-Istanbul) by stable carbon isotope composition. Proceedings
of International Symposium on Earth System Sciences 2004, Istanbul – Turkey: 321-334.
MANN U., HERTEN U., KRANENDONCK O., POELCHAU H.S., STROETMANN J., VOS H., WILKES H., SUCHÝ V., BROCKE
R., WILDE V., MULLER A., EBERT J., BOZDOGAN N., SOYLU C. EL-HASSANI A. & YALÇIN M.N. (2001).
Dynamics of the Silurian/Devonian boundary sequence: sedimentary cycles vs. organic matter variation.
Terra Nostra, (4): 44-48.
RONG J.Y., ZHANG Y. & CHEN X.Q. (1987). Pridolian and Lochkovian brachiopods from Luqu-Tewo area of
West Qinling Mts., China. In Xi’an Institute of Geology and Mineral Resources (XIGMR) & Nanjing
Institute of Geology and Palaeontology, Chinese Academy Sciences(NIGPAS) (eds.), Late SilurianDevonian strata and fossils from Luqu-Tewo area of west Qinling Mountains, China, Vol. 2: 1-94.
Xi’an Institute of Geology and Mineral Resources (XIGMR) & Nanjing Institute of Geology and Palaeontology,
Chinese Academy Sciences(NIGPAS), eds. (1987). Late Silurian-Devonian strata and fossils from LuquTewo area of west Qinling Mountains, China, Vol. 1. 305pp. Nanjing University Press, Nanjing.
356
The Xiaoxiang Fauna (Ludlow, Silurian) - a window to
explore the early diversification of jawed vertebrates
MIN ZHU, WEN-JIN ZHAO
M. Zhu - Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and
[email protected]
W.-j. Zhao - Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and
[email protected]
Gnathostomes, or jawed vertebrates, can be divided into four major clades: the
Placodermi, the Acanthodii, the Chondrichthyes (cartilaginous fishes) and the Osteichthyes
(actinopterygians and sarcopterygians). Despite the earliest record of gnathostomes possibly
extends to the Late Ordovician, the Silurian gnathostome remains had been few and
fragmentary for a long time, thus leaving the early evolutionary history of jawed vertebrates
enigmatic.
The Xiaoxiang Fauna, characterized by the early diversification of gnathostomes, is
known from the Ludlow of Qujing, Yunnan Province, southwestern China. The marine
Silurian strata in Qujing are subdivided into four formations in ascending order, the
Yuejiashan, Kuanti, Miaokao and Yulungssu formations (Ting & Wang, 1937; Fang et al.,
1985; Rong et al., 1990). Early fishes (mainly microremains) are recorded from the
sequence in association with rich invertebrates such as corals, brachiopods, cephalopods,
ostracods, bryozoans and trilobites (Fang et al., 1985), and include Psarolepis and an
indeterminable osteichthyan from the Yulungssu Formation (Gagnier et al., 1989; Zhu
and Schultze, 1997) and two “actinopterygians” Naxilepis gracilis and Ligulalepis
yunnanensis from the Miaokao and Kuanti formations (Wang & Dong, 1989). From the
muddy limestone of the Kuanti Formation immediately beneath the first appearance point
of Ozarkodina crispa (Walliser & Wang, 1989; Wang, 2001) at a locality near Xiaoxiang
Reservoir in the suburb of Qujing, we have recently found rich fish remains including the
oldest near-complete jawed vertebrate Guiyu oneiros (Zhu et al., 2009). The discovery
of Guiyu, with the accurate dating based on Silurian conodont zonation (Walliser &
Wang, 1989), provides not only the near-complete restoration of a primitive fish with
mosaic gnathostome characters, but also a new minimum date for the sarcopterygian –
actinopterygian split. In addition to Guiyu and other osteichthyan forms, the Xiaoxiang
Fauna includes agnathan galeaspids and diversified placoderms and acanthodians under
study. The research on the Xiaoxiang Fauna will significantly improve our understanding
of early diversification of gnathostomes, and the rise of osteichthyans from other primitive
gnathostomes in particular.
REFERENCES
FANG R.-S., JIANG N.-R., FAN J.-C., CAO R.-G. & LI D.-Y., et al. (1985). The Middle Silurian and Early
Devonian Stratigraphy and Palaeontology in Qujing District, Yunnan. 171 pp. Yunnan People’s Publishing
House, Kunming.
357
GAGNIER P.Y., JAHNKE H. & SHI Y. (1989). A fish fauna of the Lower Yulongsi Formation (Upper Silurian) of
Qujing (E. Yunnan, S. W. China) and its depositional environment. Courier Forschungsinstitut
Senckenberg, 110: 123-135.
RONG J.-Y., CHEN X., WANG C.-Y., GENG L.-Y., WU H.-J., DENG Z.-Q., CHEN T.-E. & XU J.-T. (1990). Some
problems concerning the correlation of the Silurian rocks in South China. Journal of Stratigraphy, 14:
161-177.
TING V.-K. & WANG Y.-L. (1937). Cambrian and Silurian Formations of Malung and Chutsing Districts,
Yunnan. Bulletin of the Geological Society of China, 16: 1-28.
WALLISER O.H. & WANG C.-Y. (1989). Upper Silurian stratigraphy and conodonts from the Qujing District,
East Yunnan, China. Courier Forschungsinstitut Senckenberg, 110: 111-121.
WANG C.-Y. (2001). Age of the Guandi Formation in Qujing District, E. Yunnan. Journal of Stratigraphy, 25:
125-127.
WANG N.-Z. & Dong Z.-Z. (1989). Discovery of Late Silurian microfossils of Agnatha and fishes from
Yunnan, China. Acta Palaeontologica Sinica, 28: 192-206.
ZHU M. & SCHULTZE H.P. (1997). The oldest sarcopterygian fish. Lethaia, 30: 293-304.
ZHU M., ZHAO W.-J., JIA L.-T., LU J., QIAO T. & QU Q.-M. (2009). The oldest articulated osteichthyan reveals
mosaic gnathostome characters. Nature. (doi: 10.1038/nature07855) (To be published on March 26,
2009).
358
Stable oxygen isotope stratigraphy using conodont
biogenic apatite from the Pridolof the Baltic Basin
ZIVILE ZIGAITE, MICHAEL M. JOACHIMSKI, OLIVER LEHNERT
Z. Zigaite - University of Lille 1, Laboratory of Palaeozoic Palaeontology and Palaeogeography, CNRS UMR 8014,
F-59655 Villeneuve d’Ascq cedex (France) and Department of Geology and Mineralogy, Vilnius University,
M.K.Ciurlionio 21/27, Vilnius (Lithuania); [email protected]
M.M. Joachimski - Institute of Geology and Mineralogy, University of Erlangen-Nurnberg, Schlossgarten 5, D-91054
Erlangen (Germany); [email protected]
O. Lehnert - Institute of Geology and Mineralogy, University of Erlangen-Nurnberg, Schlossgarten 5, D-91054 Erlangen
(Germany); [email protected]
Phosphatic conodont microfossils, originating from Upper Silurian (Pridolian) sections
of Lithuania, have been studied for their oxygen isotope composition. The 18O/16O ratios
of conodont apatite have been measured in order to obtain Silurian seawater
palaeotemperatures, if the phosphates are well-preserved and not alterated by diagenetic
processes. Diagenetic overprinting of the isotopic record has been aimed to be avoided by
selecting conodonts of less than 1.5 colour alteration index, which was the case for the
material examined, reflecting minor thermal alteration of the Upper Silurian strata in this
part of the Baltic Basin.
ä 18Oapatite values obtained ranged from 17.7 to 19.2‰ V-SMOW, perfectly fitting in
the general Silurian conodont apatite ä 18O value range of 17.5 to 19.5‰ V-SMOW,
proposed by Joachimski et al. (2003). Therefore the ä18O record appeared to be applicable
for the palaeobasin seawater temperatures reconstructions. The proper conodont apatite
ä 18O record also provides supplementary evidence for the low diagenetic alteration of the
Silurian strata of the Baltic Basin.
We present the first ä18Oapatite curve from a Pridolian section in the eastern Baltic
Basin (Gëluva-99 borehole), which is located in the central facies belt of the Silurian of
Lithuania. The position of a positive shift in the curve perfectly matches a facies change
between the lower Pridoli (Vievis Fm.), and the upper Pridoli (Lapës Fm.). The positive
excursion, indicating drop of palaeoseawater temperature, also corresponds to the
lithologically recorded and interpreted as an abrupt sea level drop in between Vievis and
Lapës Formations, in the middle Pridoli of the Baltic Basin (Paskevicius, 1997; Lazauskiene
et al., 2003). This formation boundary has been also recorded biostratigraphically, following
the significant change in faunal composition (Karatajute-Talimaa & Brazauskas, 1994).
Regarding this new chemostratigraphical ä18Oapatite record of conodont apatite, the formation
boundary can now be supported. Palaeoenvironmental climate interpretations of ä18O
data might indicate a cooling event (Lehnert et al., 2007) associated with this middle
Pridoli sea level drop in the Baltic Basin.
REFERENCES
JOACHIMSKI M.M., HORACEK S., BREISIG S. & BUGGISCH W. (2003). The oxygen isotopic composition of biogenic
apatite - no evidence for a secular change in seawater ä18O. European Geophysical Society, Geophysical
Research Abstracts, 5: 10792.
359
KARATAJUTE-TALIMAA V. & BRAZAUSKAS A. (1994). Distribution of vertebrates in the Silurian of Lithuania.
Geologija, 17: 106-114.
LAZAUSKIENE J., SLIAUPA S., BRAZAUSKAS A. & MUSTEIKIS P. (2003). Sequence stratigraphy of the Baltic Silurian
succession: tectonic control on the foreland infill. In McCann T. & Saistot A. (eds.). Tracing Tectonic
Deformation Using the Sedimentary Record. Geological Society, London, Special Publications, 208:
95-115.
LEHNERT O., ERIKSSON M.J., CALNER M., JOACHIMSKI M.M. & BUGGISH W. (2007). Concurrent sedimentary and
isotopic indications for global climatic cooling in the Late Silurian. Acta Palaeontologica Sinica, 46
(Suppl.): 249-255.
PASKEVICIUS J. (1997). The Geology of the Baltic Republics. Geological Survey of Lithuania, Vilnius, pp.
387.
360
Index of authors
Kiipli Enli
Kiipli Tarmo
Kozlowska Anna
Kleffner Mark A.
307
307
309
267, 277
Lenz Alfred
Lehnert Oliver
Li Rong-she
Lorenzo Saturnino E.
Loydell David K.
Lucke Andreas
309
359
353
311, 313
277
355
Mann Ulrich
Mannik Peep
Martma Tonu
Melchin Michael J.
Meng Yong
Meyers Philip A.
Mortier Jan
Munnecke Axel
355
277,
277,
285,
353
289
317
277,
Negri Alessandra
289
Barrick James E.
Bogolepova Olga K.
267, 277
269, 293
Castano Rodrigo
Chen Feng
Chen Qing
Chen Xu
Claeys Phillippe
Copper Paul
Corradini Carlo
Corriga Maria G.
Cramer Bradley D.
271
283, 285
285
285
317
301
273, 275, 345
275
277
Del Rio Myriam
Dojen Claudia
Drygant Daniel
327
279
281
Fan Junxuan
Feist Raymund
Ferretti Annalisa
Fryda Jiri
Fu Li-pu
283, 285
341
287, 289, 297
347
353
Gibson Michael A.
Gnoli Maurizio
Goldman Dan
Gomez-Perez Marcela
Grytsenko Volodymir
Gubanov Alexander. P.
Gutierrez-Marco Juan C.
Peavey F. Nichole
267
Picarra Josè
291
Piras Sergio
283
Pittau Paola
293
Pondrelli Monica
305
269, 293
311, 313, 321, 323, Ray David
Rabano Isabel
335
Rong Jiayu
293
Sa Artur. A.
299, 317, 333
Saltzman Matthew R.
355
Samtleben Christian
287, 295, 297
Sarmiento Graciela. N.
315
Schemm-Gregory Mena
293
Schönlaub Hans Peter
299, 333
Serventi Paolo
353
Sherwin Lawrence
295
Simonetto Luca
Spina Amalia
339
Storch Petr
277
Sutcliffe Owen
301
Suttner Thomas J.
359
Szaniawski Hubert
303
Vecoli Marco
Verniers Jacques
277, 305, 307
267
Harland Melise B.
Harper David A.T.
Herten Ulrich
Histon Kathleen
Holmden Chris
Howard James P.
Huang Bing
Huang Hong-ping
Hubmann Bernhard
Jansen Ulrich
Jeppsson Lennart
Jin Jisuo
Joachimski Michael M.
Johnson Markes E.
Kaljo Dimitri
Karlsson Haraldur R.
319
305
309, 315
319
267
321, 323, 335
325
327
345
329, 331
271, 313, 321
299, 333
323,
277
277
271,
337,
297
291,
343
291,
351
323,
331
349
281
351
317
335
321, 335
339
341, 345
345
347
361
Wagner Thomas
Wang Jian
Wang Nian-zhong
Wang Yi
289
353
355
285
Zalasiewicz Jan. A.
317
362
Zhan Renbin
Zhang Hua
Zhang Yuandong
Zhao Wen-jin
Zhu Min
Zigaite Zivile
299, 333
283
285
355, 357
355, 357
359
Table of contents
J.E. BARRICK, M.A. KLEFFNER, M.A. GIBSON, F.N. PEAVEY, H.R. KARLSSON - The Lau
Primo-Secundo Oceanic Event and Mid-Ludfordian Isotope Excursion (Ludlow,
Silurian) in Southern Laurentia .................................................................................... p. 267
O.K. BOGOLEPOVA, A.P. GUBANOV - Early Palaeozoic palaeogeography of Severnaya
Zemlya, Arctic Russia (with new data on the Silurian) ............................................... p. 269
R. CASTAÑO, I. RÁBANO, G.N. SARMIENTO - Trilobites from the Scyphocrinites
limestone (Pridoli) of the Sierra Norte of Seville Natural Park, southern Spain ..... p. 271
C. CORRADINI - Looking for a late Silurian Standard Conodont Zonation: still a long
way to go ....................................................................................................................... p. 273
M.G. CORRIGA, C. CORRADINI - Silurian-Lower Devonian conodonts from the
Rifugio Lambertenghi Fontana III Section (Carnic Alps, Italy) .................................. p. 275
B.D. CRAMER, D.K. LOYDELL, C. SAMTLEBEN, A. MUNNECKE, D. KALJO, P. MÄNNIK,
T. MARTMA, L. JEPPSSON, M.A. KLEFFNER, J.E. BARRICK, M.R. SALTZMAN Integrated High-Resolution Chronostratigraphy of the Telychian and
Sheinwoodian Stages: Conodonts Graptolites, Isotopes, and the Future of
Paleozoic Chronostratigraphy ..................................................................................... p. 277
C. DOJEN - Late Silurian Ostracodes from the Hazro Anticline (SE Turkey) .................. p. 279
D. DRYGANT, H. SZANIAWSKI - Conodonts of the Silurian-Devonian boundary beds
in Podolia, Ukraine ...................................................................................................... p. 281
J. FAN, D. GOLDMAN, F. CHEN, H. ZHANG - Geobiodiveristy Database and its
application in graptolite research ................................................................................ p. 283
J. FAN, M.J. MELCHIN, X. CHEN, Y. WANG, Y. ZHANG, Q. CHEN, F. CHEN - Biostratigraphy and geography of the Ordovician-Silurian Lungmachi black shales
in South China .............................................................................................................. p. 285
A. FERRETTI, K. HISTON - Cephalopod limestone biofacies in the Silurian of the
Carnic Alps, Austria ...................................................................................................... p. 287
A. FERRETTI, A. NEGRI, T. WAGNER, P.A. MEYERS - Palaeozoic black shales: how much
should we trust the Recent to reconstruct the Past? ................................................... p. 289
M. GNOLI, P. SERVENTI, L. SIMONETTO - Nautiloid Cephalopods from the Silurian of
the Carnic Alps – New evidences ................................................................................ p. 291
A.P. GUBANOV, O.K. BOGOLEPOVA, J.P. HOWARD, M.B. HARLAND, M. GOMEZ-PEREZ The Silurian of the southern Siberian Platform .......................................................... p. 293
K. HISTON, B. HUBMANN - Upper Silurian Nautiloid Faunas from the Eggenfeld
Section (Graz, Austria) ................................................................................................. p. 295
K. HISTON, H.P. SCHÖNLAUB, A. FERRETTI - The Cellon Section: a Review of the
Stratotype Section for the Southern Alps (1894-2009) ............................................. p. 297
B. HUANG, D.A.T. HARPER, J. RONG., R. ZHAN - Does “Lilliput Effect” of brachiopod
exist in South China after the late Ordovician mass extinction? ................................ p. 299
J. JIN, P. COPPER - Origin and diversification of the Early Silurian virgianid
brachiopods .................................................................................................................. p. 301
363
E.M. JOHNSON - Tracking Silurian eustasy: Alignment of empirical evidence or
pursuit of deductive reasoning? ................................................................................... p. 303
D. KALJO, V. GRYTSENKO, T. MARTMA - Additions to the Carbon Isotope trend
of Podolia (Ukraine) with a summary and evaluation of the Silurian
chemostratigraphy ........................................................................................................ p. 305
T. KIIPLI, E. KIIPLI, D. KALJO - Silurian sea level variations based on SiO2/Al2O3 and
K2O/Al2O3 ratios from Priekule drill core section, Latvia, and comparison with
redox conditions carbonate precipitation and global δ13C changes ........................... p. 307
A. LENZ, M. MELCHIN, A. KOZLOWSKA - Aeronian and lower Telychian retiolitid
graptolites, Arctic Canada ............................................................................................ p. 309
S.E. LORENZO, J.C. GUTIÉRREZ-MARCO - Occurrence and 3D-preservation of
Llandovery graptolites in the Criadero Quartzite of the Almadén mining district
(Spain) .......................................................................................................................... p. 311
S.E. LORENZO, J.C. GUTIÉRREZ-MARCO, I. RÁBANO - Silurian geoheritage of the
Almadén Mining Park (central Spain) ......................................................................... p. 313
M. J. MELCHIN, C. HOLMDEN - Nitrogen Isotopes in Paleozoic Chemostratigraphic
Studies: Contrasting Examples from the Hirnantian and early Wenlock ................... p. 315
J. MORTIER, D.A.T. HARPER, J. A. ZALASIEWICZ, P. CLAEYS, J. VERNIERS - The Upper
Ordovician to lower Silurian Tihange sections, Condroz Inlier: a litho- and
biostratigraphical study with chitinozoans combined with carbon isotopes ............. p. 317
A. MUNNECKE, P. MÄNNIK - New biostratigraphic and chemostratigraphic data from
the lower Chicotte Formation (Llandovery) on Anticosti Island (Quebec, Canada) . p. 319
J.M. PIÇARRA, J.C. GUTIÉRREZ-MARCO, G.N. SARMIENTO, I. RÁBANO - Silurian of the
Barrancos-Hinojales domain of SW Iberia: a contribution to the geological
heritage of the Barrancos area (Portugal) and the Sierra de Aracena-Picos de
Aroche Natural Park (Spain) ........................................................................................ p. 321
J.M. PIÇARRA, A.A. SÁ, P. STORCH, J.C. GUTIÉRREZ-MARCO - Silurian stratigraphy and
paleontology of the Valongo anticline and Arouca-Tamames syncline, CentralIberian Zone (Portugal and Spain) ............................................................................... p. 323
S. PIRAS - New data on Silurian graptolites from the Rio Ollastu valley (SE Sardinia) .. p. 325
P. PITTAU, M. DEL RIO - Silurian chitinozoan biostratigraphy of Sardinia ....................... p. 327
D. RAY - Wenlock bentonites from the Midland Platform, England: geochemistry,
sources and correlation ................................................................................................ p. 329
D. RAY, O. SUTCLIFFE - Sequence stratigraphy of the Wenlock Series of the Midland
Platform, England ......................................................................................................... p. 331
J. RONG, R. ZHAN, B. HUANG, D.A.T. HARPER - Discovery of a latest Ordovician deep
water brachiopod fauna at Yuhang, Hangzhou, Zhejiang, East China .......................... p. 333
A.A SÁ, J.M. PIÇARRA, J.C. GUTIÉRREZ-MARCO, G.N. SARMIENTO - P-rich nodules
and “hollow graptolites” in the upper Silurian of the Moncorvo synclinorium,
north Portugal ............................................................................................................... p. 335
M. SCHEMM- GREGORY - Howellellid branches at the Silurian/Devonian Boundary
interval and their importance for Delthyridoid Spiriferid evolution ......................... p. 337
M. SCHEMM-GREGORY, U. JANSEN - The Silurian of the Goldsteintal (Rheinisches
Schiefergebirge, Germany) .......................................................................................... p. 339
364
P. SERVENTI, R. FEIST - Silurian Nautiloid Cephalopods from the Cabrières area
(Montagne Noire, France): a preliminary report ........................................................ p. 341
L. SHERWIN - Gondwanan tectonics and European events in the Silurian of
Australasia .................................................................................................................... p. 343
L. SIMONETTO, P. SERVENTI, M. PONDRELLI, C. CORRADINI - Problematic fossil
remains from the Silurian Kok Formation in the type area (Carnic Alps, Italy) ........ p. 345
P. STORCH, J. FRYDA - Carbon isotope data and graptolite record in the lower Silurian
(Llandovery) of northern peri-Gondwana – exemplified by Barrandian area,
Czech Republic ............................................................................................................. p. 347
T.J. SUTTNER - Paleoenvironment of the Siluro-Devonian sequence in southern
Burgenland (Austria) .................................................................................................... p. 349
M. VECOLI, A. SPINA - Siluro-Devonian biodiversification of trilete spores and
cryptospores from Tunisia: palaeophytogeographic and palaeoclimatic
implications .................................................................................................................. p. 351
J. WANG, L. FU, Y. MENG, R.S. LI, H.P. HUANG - Discovery of a Llandovery-Wenlock
boundary section in Bajiaokou, Ziyang, China ............................................................ p. 353
W.J. ZHAO, U. HERTEN, N.Z WANG, U. MANN, M. ZHU, L. ANDREAS - The SilurianDevonian Boundary in West Qinling of South China – Evidence from Chemostratigraphy and microvertebrate remains across the Silurian/Devonian transition .. p. 355
M. ZHU, W.J. ZHAO - The Xiaoxiang Fauna (Ludlow, Silurian) - a window to explore
the early diversification of jawed vertebrates ............................................................. p. 357
Z. ZIGAITE, M.M. JOACHIMSKI, O. LEHNERT - Stable oxygen isotope stratigraphy using
conodont biogenic apatite from the Pridolof the Baltic Basin .................................. p. 359
Index of Authors ................................................................................................................. p. 361
365

O - Università degli studi di Cagliari.

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