remains of fossiliferous rocks similar to those characteristic of the

ACTA PALAEONTOLOGICA ROMANIAE V. 6 (2008), P. 339-343.
REMAINS OF FOSSILIFEROUS ROCKS SIMILAR TO THOSE
CHARACTERISTIC OF THE ARJANA NAPPE AS PART OF THE EXOTIC
MATERIAL ASSOCIATED TO THE UPPER CRETACEOUS OLISTOSTROME OF
THE CERNA UNIT:
DANUBIAN - SOUTHERN CARPATHIANS
Ion STĂNOIU1
Abstract: within the Mehedinţi Formation (Upper Cretaceous) in the Cerna Unit (Danubian Realm) there have
been separated the remains rocks (Kimmeridgian – Neocomian fossiliferous limestones, basalts and trachytes)
similar to those characteristic of the Arjana Nappe.
Key words: Upper Cretaceous, Mehedinţi Formation, Kimmeridgian – Neocomian exotic material, Cerna Unit,
Arjana Nappe.
In the Mesosoic stratigraphic succession of
the Cerna Unity (Cerna zone; Codarcea, 1940),
one distinguishes (Stanoiu, 1997), two
distinctive
stratigraphic
intervals
which
superpose one another: the Jurassic - Lower
Cretaceous stratigraphic succession of the
Cerna Basin and the Upper Cretaceous s. s. of
the D anubian Trench Basin.
The sector of Cenomanian-Middle Turonian
begins with the Nadanova Formation and ends
with the Mehedinti Formation of Upper
Turonian-Maastrichtian age. The Mehedinti
Formation has been defined as representing the
Mededinti Flysch (Upper Cretaceous), and
characterizing the Coşuştea and Cerna zone
(Codarcea, 1940).
Stanoiu (2000),
has emended the
denomination of Mehedinti Formation by
restricting its constituency to the stratigraphic
succession of the Cerna Unity (Upper TuronianLower Maastrichtian). Consequently, when the
matter came to the synchronic stratigraphic
succession of the Coşuştea Unity he employed
other denominations (Stănoiu, 1996).
The stratigraphic succession of Mehedinti
Formation has been described by Draghici
(1962), as being a chaotic flysch, wildflysch or
olistostrome. Characteristic of its content is a
sandstone-argillaceous
lithology
and
is
constituted of some flyschoid intervals in
alternance with sequences of olistostrome type.
In many situations and especially at the contact
with the Postaustrian Getic Megastructure (the
Second Phase Getic Nappe: Codarcea, 1940),
this succession is highly deformed and exhibits
an appearance of wildflysch.
Divided in two lithostratigraphic entities
(Stanoiu, 1982), the resulted boundary is rather
an arbitrary one. Thus the Jghiabu Member
stands in its lower part where there are an
abundance of olistolithes with Urgonian
limestones, whereas the Titirlesti Member that
develops in the upper part is characterized by an
abundance of exotic material similar to the
1
Sinaia and Azuga Beds. The age of Titirleşti
Member has been appreciated on the base of its
parallelization with the fosiliferous Upper
Cretaceous lithostratgraphic units of the
Coşuştea Nappe (Stanoiu, 1996), as Middle
Campanian-Lower Maastrichtian.
Within the suite of olistostrome-like
sequences from the upper half of the Titirlesti
Member on the Brebina Valley (fig. 1), Mededinti
Plateau, and at two stratigraphic levels placed at
about 100 m (of stratigraphic thickness) one
from the other, there are fragments and boulder
stones of basalts, trachytes (our colleagues
Nicolae Istrate, Stefan Avram and Doina RussoSandulescu, helped us with the petrographic
diagnosis), and limestones often in a breccious
form (Bratilovu Breccia). In some instances the
calcareous fragments are enclaved within the
magmatic rocks previously mentioned. These
ones exhibit re-crystallization processes and
include siliciclastic particles. The material of
exotic origin also encompasses fragments of
crystalline schists (micaschists, paragneisses,
and siliciclastic rocks).
Other calcareous fragments show a micritic
character being of reddish colour and includes
fossiliferous
remains
such
as:
Parastomiosphaera
malmica
(Borza),
Colomisphaera
carpathica
(Borza),
C.
minutissima (Colom), Globochete alpina
Lombard, foraminifers, and numerous pieces of
Sacoccoma sp. plus Aptychus (pl. I, pl. II).Both
the fossil rests and lithofacies parallelizations
reflect the Kimmeridgian-Lower Tithonian age.
Other fragments of fine and micritic
limestones of grey colour include remains of
Colomisphaera
cf.
lapidosa
(Vogler),
Globochete alpina Lombard, Crassicollaria
brevis Remane, Calpionella alpina Lorenz,
Tintinopsella cf. longa (Colom), Calpionellopsis
simplex (Colom), which indicate the Upper
Tithonian-Neocomian
(Berriasian)
chronostratigraphic interval (pl. II).
Geological Institute of Romania, 1 Caransebeş; Str., Bucharest, Romania. e-mail: [email protected]
I. STĂNOIU
Figure 1 – Geological map of the Baia de Aramă – Mărăşeşti region (Mehedinţi Plateau)
I – Quaternary: a –alluvial plain; b – tearces. II – Postaustrian Getic Megastructure (the II-d phase
Getic Nappe: Codarcea, 1940): A – Godeanu Nappe (Austrian Getic Megatructure = the I-d phase Getic
Nappe: Codarcea, 1940; without the Obârşia Unit); B – Obârşia Unit. III – Cerna Unit. C – Nehedinţi
Formation (Upper Turonian – Lower Maastrictian): a and b – olistolithes (a – Upper Jurasic – Lower
Cretaceous limestones; b – Sinaia and Azuga Beds); c – Bratilovu Breccia. D – Nadanova Formation
(Cenomanian – Middle Turonian). E – Upper Jrasic – Lower Cretaceous limestones. IV – lithologic
boundary. V – unconformity boundary. VI – fault. VII – Austrain overthrust plane. VIII – Laramian and
Subhercynian overthrust plane. IX – localities: 1 – Baia de Aramă, 2 – Brebina, 3 – Titirlesti; 4 – Bratilovu;
5 – Mărăşeşti.
The lithologic aspects plus the reflected age
of the organic rests as found in the limestones
fragments, on the one hand, and the already
mentioned magmatic rocks, on the other hand,
as well as the relationships existing between
them are characteristic of the volcanosedimentary series (Lower Jurassic –
Neocomian) of the Arjana Nappe.
The presence of basaltic rocks within the
Mehedinti Formation has been also remarked
and discussed in some previous studies.
Therefore, Draghici (1962), Stanoiu (in: Pop
et al, 1975), Stanoiu (1982), have considered
them as being of allochthonuous source.
Stanoiu (in: Stanoiu et al, 1980), has admitted
that at least a part out of these rocks suggest
an ambiguous startigraphic position. Draghici
340
(1962), showed that the respective basalts
may document the existence of an andesiticbasaltic volcanism of Upper Cretaceous age,
in the Cerna zone. Savu (1985), stated that
they are also the product of a magmatic arcrelated volcanism of the same age expressed
as a result of subduction processes, while the
Moesia Microplate went under that of South
Carpathians.
Within the exotic material associated to the
Campanian – Early Maastrichtian stratigraphic
series (of flysch and olistostroma facies) of the
Cerna Unit, there occur roks of the Sinaia –
Azuga Beds type, as well as of the type
characteristic to the Arjana Nappe, a setting
which corroborated to additional information
(stanoiu , 1997) suggests the following: the
REMAINS OF FOSSILIFEROUS ROCKS SIMILAR TO THOSE CHARACTERISTIC OF THE ARJANA
NAPPE AS PART OF THE EXOTIC MATERIAL ASSOCIATED TO THE UPPER CRETACEOUS
OLISTOSTROME OF THE CERNA UNIT: DANUBIAN – SOUTHERN CARPATHIANS
generation
of
Postaustrian
Getic
Megastructure, as well as the generation of the
Danubian Nappes have started as a result of
the Sub-Hercynic Tectogenesis and have been
completed as a result of the Early Laramic
Tectogenesis; during the Campanian – Early
Maastrichtian,
the
Postaustrian
Getic
Megastructure (if not entirely, some of its
sections at least) reached a position adjacent
to the Cerna Unit (the Outward Danubian
Domain); the final part of the Campanian –
Early Maastrichtian stratigraphic series within
the Inward Danubian Domain is incomplete.
The fact that rocks characteristic of the
Arjana Nappe are also present in the exotic
material belonging to the terminal part of the
Mehedinti Formation (Cerna Unity), as well as
other data has greatly contributed to
demonstrate the hypothesis (Stanoiu, 1997),
according to which the collision between the
Getic Plate and the Danubian Plate took place
during the Campanian (most probably in its
middle interval), at the same time when the
Danubian Nappes-forming processes has
begun, being also synchron with the starting of
Postaustrian subduction on to the palaeoplate
developed between these two plates.
The currently available information points to
the fact that the Firizu Unit (Nappe) and the
Obarsia Unit (Pseudo-nappe) never constituted
together an independent tectonic unit
(structure) (The Severin Nappe). Additionally,
there isn’t available any piece of information
which would suggest an independent tectonic
displacement of the Obarsia Unit (Pseudonappe), the latter being displaced together with
the Austrian and Post-Austrian Getic Nappe
(Megastructure), during the Sub-Hercynic and
Laramic Tectogeneses, at the bottom part of
the Getic Nappe.
The Postaustrian Getic Megastructure
thrust plane importance is also highlighted by
the occurrence of certain tectonic “fingerings”
(imbrications) and of severely tectonically
disturbed zones, frequently several hundreds
of meters thick, between the Getic Nappe
rocks (especially the Sinaia and the Azuga
Beds rocks and the Obarsia Complex rocks)
and the underlying rocks of the Danubian Unit
(especially the flysch and olistostroma facies
Late Cretaceous rocks of the Danubian Trench
Basin).
REFERENCES
Codarcea Al. (1940), Vues nouvelles sur la
tectonique du Banat et du Plateau de
Mehedinţi, An. Inst. Geol. Rom., XX,
Bucureşti.
Drăghici C. (1962), Structura geologică a
Platoului Mehedinţi între IsvernaCloşani-Padeş-Baia de Aramă, D.S.
Inst. Geol. Rom., XLVIII, Bucureşti
Pop. Gr., Marinescu Fl., Stănoiu I., Hârtopan I.
(1975) Harta Geologică a R.S.România,
sc. 1:50.000, Foaia Tismana, Inst. Geol.
Geofiz., Bucureşti
Savu H. (1985), Tectonic position and origin of
alpine ophiolites in the Mehedinţi
Plateau (South Carpathians), D.S. Inst.
Geol. Geofiz., LXIX/5, Bucureşti
Stănoiu I. (1982), Orizontarea formaţiunii
neocratice de tip olistostramă din partea
nord-vestică a Podişului Mehedinţi, D.S.
Inst Geol. Geofiz., LXVII/5, Bucureşti
Stănoiu I. (1996), Geology of the Domogled
Cerna Valley National Parc Avea, An
Inst. Geol. Rom. , 69/1, Bucureşti
Stănoiu I. (1997), The Mehedinţi Plateau
stratigraphy, Int. Symp. Geol. of the
Danube Gorges, Yugoslavia and
Romania, Belgrade – Bucharest.
Stănoiu I. (2000), Noul model paleogeografic,
stratigrafic şi facial al Bazinului Cerna
(Danubian – Carpaţii Meridionali), Stud.
Cerc. Geol., 45, Acad. Rom.
Stănoiu I., Hârtopanu I., Berza T., Iancu V.,
Hârtopanu P. (1980) Harta Litologică a
R.S.R., sc. 1:25.000, Foaia Călugăreni,
machetă, Inst. Geol. Geofiz., Bucureşti
PLATE CAPTIONS
Plate I: fig. 1-12. Sacoccoma sp., X70.
Plate II: fig.1, Calpionella alpina Lombard, x250; fig. 2 Globochaete alpina Lombard, x400; fig.3, 5,
Colomisphaera carpathica (Borza), x280; fig. 4, 6, Carpathomiphaera borzai (Naggy), x600; fig.
7, 9, Colomisphaera cf. lapidosa (Vogler), x280; fig. 10, Calpionellopsis simplex (Colom), x250;
fig. 11, Calpionella alpina Lorenz and Crassicollaria brevis Remane, x80; fig. 12, Tintinopsella
cf. longa (Colom), x280
341
I. STĂNOIU
342
PLATE I
I. STĂNOIU
PLATE II
343