www.geologicacarpathica.sk
GEOLOGICA CARPATHICA, AUGUST 2010, 61, 4, 341—352 doi: 10.2478/v10096-010-0020-5
Introduction
For decades, the Neogene Pannonian Basin has been in the
centre of interest of stratigraphers, sedimentologists, struc-
tural geologists, geophysicists, and paleontologists. Hydro-
carbon explorations resulted in an enormous amount of data
about the structure, sedimentary fill and evolutionary history
of the Pannonian Basin. Most of the important results from
the southern, Serbian part of the Pannonian Basin, however,
regretfully remained unpublished. The highlight of this pa-
per is to present new data on the stratigraphy and tectonics of
the Čoka area, in northern Banat of Serbia (Fig. 1), obtained
by subsurface geological methods (reflection seismics, well
logs, cores, cuttings, etc.). The Čoka structure represents an
anticline, which resulted from the Middle-Late Miocene inver-
sion of an earlier extensional structure (within basin high)
covered by Middle Miocene to Quaternary sediments.
Geological setting
The Pannonian Basin was formed due to continental colli-
sion and subduction of the European Plate under the African
(Apulian) Plate during the late Early to Late Miocene times
(Horváth & Royden 1981; Royden 1988; Tari et al. 1992; Hor-
váth 1995; Kováč et al. 1998; Pavelić 2002; Fodor et al. 2005).
The Pannonian Basin was bordered by the mountain chains of
the Alps, Carpathians and Dinarides (Schmid et al. 2008).
Late Early Miocene subsidence and sedimentation as a
consequence of the syn-rift extensional phase resulted in the
Geology of the Čoka structure in northern Banat
(Central Paratethys, Serbia)
DEJAN RADIVOJEVIĆ
1
, LJUPKO RUNDIĆ
2
and SLOBODAN KNEŽEVIĆ
2
1
NIS Naftagas, Narodnog fronta 12, 21000 Novi Sad, Serbia; dejan.radivojevic@nis.rs
2
Department of Geology, Faculty of Mining and Geology, University of Belgrade, Kamenička 6, P.O. Box 227, 11000 Belgrade, Serbia;
rundic@rgf.bg.ac.rs; knezevic.slobodan@gmail.com
(Manuscript received July 8, 2009; accepted in revised form March 11, 2010)
Abstract: The Čoka structure is a fault-bounded anticline in northern Banat, in the southern part of the Neogene Pannonian
Basin. The structure and its vicinity were explored by 24 wells. In addition to well logs, paleontological, sedimentological
and petrological analyses of cores and 27 seismic sections with different parameters of acquisition and processing were
used for geological investigation of the area. The E-SE dipping pre-Neogene basement consists of Lower Triassic clastics
and, in the NW part of the study area, Paleozoic greenschists. Thin Middle Miocene (Badenian) sediments unconformably
overlie the basement and pinch out towards the elevated NW part of the study area. They are also missing in some wells on
the apex of the Čoka structure, probably due to erosion. Badenian sediments were deposited in a shallow marine environment.
The late Middle Miocene (Sarmatian) strata are missing and the Badenian is directly overlain by Upper Miocene (Pannonian)
sediments. The latter also pinch out towards the NW but in contrast to Badenian sediments, they are present in all boreholes
on the Čoka structure. Pannonian deposition took place in a caspibrackish environment of Lake Pannon, with predominance
of marls and fine-grained clastics. Pannonian sediments are conformably overlain by latest Miocene (Pontian) and Pleistocene
lacustrine, alluvial and terrestrial sediments.
Key words: Miocene, Central Paratethys, Serbia, Northern Banat, tectonics, stratigraphy.
formation of numerous grabens filled with relatively thin
syn-rift marine and brackish deposits (Horváth & Royden
1981; Tari 1994; Tari & Pamić 1998; Lučić et al. 2001;
Pavelić 2001). The Late Miocene (pre-Pannonian) unconfor-
mity is a result of the first early post-rift phase of basin inver-
sion that occurred during the Sarmatian (the latest Middle
Miocene; Horváth & Tari 1999). After that, a quiet and slow
thermal subsidence took place, combined with an uplift and
erosion of the surrounding mountain belt (Horváth & Royden
1981; Schmid et al. 2008). That post-rift sinking was com-
pensated by intensive sedimentation in the “caspibrackish”
Lake Pannon during the Late Miocene (Juhász 1991; Magyar
et al. 1999; Rundić 2000; Fodor et al. 2005). As a result,
huge amounts of sediment were supplied, via large fluvial to
deltaic systems, into Lake Pannon. The final result is succes-
sions of several thousand meters of post-rift sediments
(Bérczi et al. 1988; Szentgyörgyi & Juhász 1988; Juhász
1991, 1994; Vakarcs G. et al. 1994; Magyar et al. 1999;
Fodor et al. 2005; Tóth-Makk 2007).
At about the Miocene-Pliocene boundary, and locally even
more intensively in the Quaternary, another compressive phase
took place in the Pannonian Basin (Jamičić 1995; Horváth &
Cloetingh 1996; Prelogović et al. 1998; Márton et al. 2002). It
reactivatied earlier normal faults, into reverse faults, and also
resulted in folding of Neogene strata (Saftić et al. 2003; Fodor
et al. 2005; Horváth et al. 2006; Marović et al. 2007).
The southern part of the Pannonian Basin is underlain by
the Tisza Unit. During the Early and Middle Miocene exten-
sion of this unit was synchronous with that of the ALCAPA
(Alpine-Carpathian-Pannonian) unit in the north (Saftić et al.
342
RADIVOJEVIĆ, RUNDIĆ and KNEŽEVIĆ
2003; Fodor et al. 2005). From the end of
the Karpatian (end of Early Miocene) sub-
sidence of Tisza was coupled with east-
ward motion and possible clockwise
rotation under a transtensive stress field
(Csontos et al. 1992, 2002; Csontos 1995;
Saftić et al. 2003; Horváth et al. 2006).
The pre-Neogene basement of the
northern Banat of Serbia, is tectonically
bordered by the Trans-Banat-Bačka Dislo-
cation belt, a complex E-W striking, re-
gional dextral strike-slip fault zone that
separates two major tectonic units in the
pre-Neogene basement: the Vardar Zone
and the Tisza-Dacia block to the south and
north, respectively (Fig. 2). West of the
Tisa River, the area is bordered by the
North Bačka High with pre-Neogene
basement at depth between —500 to
—1000 m below the surface. It is an iso-
metric plateau formed during younger
Miocene tectonic events. The major Neo-
gene tectonic features of the northern
Banat are shown in Fig. 2 and include the
North Banat and Mako Grabens, which
are bounded by NW-SE to N-S striking
normal faults. The pre-Neogene basement
is downthrown to a depth between 2000
and 3500 meters with a relatively elevated
(2000—2500 m) Kikinda-Szeged High
which trends NE—SW. The Čoka structure
is located on the western flank of the
North Banat Graben (Fig. 2).
The Miocene sediments of the northern
Banat unconformably overlie strongly
deformed Paleozoic-Mesozoic basement
of magmatic, metamorphic and sedi-
mentary rocks.
Materials and methods
The geological model of the Čoka area
presented here is based on seismic sur-
veys, well logs, and paleontological, petro-
logical, and sedimentological analyses of
core samples.
The Čoka structure and its vicinity were
explored by 24 wells. The seismic data-
base consisted of 27 profiles with different
parameters of acquisition and processing,
the most recent made in 2005.
Our geological model was built in three
steps: data analysis, interpretation, and
synthesis of results. The first step included
analyses of all available data and checking
of their quality. Data quality was also
controlled (well diameters, and well log
interpretation).
Fig. 1. Location of the study area within the Pannonian Basin System.
Fig. 2. Top pre-Neogene basement structure contour map of northern Banat (Marović et
al. 2007 – modified).
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GEOLOGY OF THE ČOKA STRUCTURE (SERBIA)
The second phase included determination of lithology and
stratigraphy for each well on the basis of cores, cuttings and
well logs, computation of a synthetic seismogram, structural
and stratigraphic interpretation of the seismic sections, and
construction of structural maps, geological cross-sections and
thickness maps. Well logs were calibrated with core data and
used for qualitative lithological interpretation where the cores
were missing. The main lithology suggested by the mud log
was correlated horizontally with gamma ray and spontaneous
potential logs, then to other types (resistivity, sonic and neu-
tron), and finally to sidewall cores and cuttings. In cases
where the lithological interpretation of logs was ambiguous,
we returned to the checking of log quality. Stratigraphic inter-
pretation was based on paleontological analysis of core sam-
ples (molluscs, ostracods, foraminifers, and palynomorphs).
Lithological-stratigraphic columns were compiled for each
well. The nearest well where checkshots were measured was
about 11—12 km east of the Čoka locality; therefore a synthet-
ic seismogram based on the sonic and density logs of C-9 was
created in order to convert time-structural interpretations into
the depth domain. Three structural maps were produced based
on interpretation of all seismic sections of the investigated
area. Three geological cross-sections, intersecting each other
at C-10, were drawn on the basis of the structural maps. Two
thickness maps focused on the Čoka structure were construct-
ed according to borehole data; the thickness of Neogene strata
in this area was below seismic resolution.
The final step in geological model generation was synthesis
of the results obtained in the second phase.
Results
Stratigraphy
In the study area, several boreholes reached the basement of
the Neogene deposits (Fig. 3). The basement consisted of
breccias, sandstones, clays and dolomitic limestones. Fossils
in these sediments are rare, so their age is determined by cor-
relation to other localities in northern Banat and northern
Bačka. The occurrence of the foraminifer Meandrospira pusilla
indicates their Early Triassic age.
Fig. 3. Lithostratigraphic columns of representative boreholes of the Čoka area. The interpretation is based on well logs and paleontologi-
cal, sedimentological and petrological analyses of cores and cuttings. Location of the wells is indicated in Figs. 5—7 and 9—13.
344
RADIVOJEVIĆ, RUNDIĆ and KNEŽEVIĆ
In the C-1, the basement was
metamorphic (greenschist).
In most of the wells, the Neogene
succession starts with biogenic
limestones of Badenian age. These
include light-grey to white bio-
sparudites
and
biomicrosparites
made up of microsparite matrix and
small sparicalcite microfossil shells
(detritus made up of molluscs, bryo-
zoans, hydrozoas, corallinacean al-
gae (Lithothamnion, Lithophylum,
etc.), annelids, cidaroids, ostra-
codes, microgastropods, and vari-
ous benthic foraminifera, such as
Asterigerinata planorbis, Rosalina
dubia, Elphidium crispum, E. fich-
telianum, E. flexuosum, Borelis
melo, Virgulina schreibersiana,
Quinqueloculina
partschii,
Q.
heidingeri, Q. contorta, Q. longi-
rostra, Q. heidingerii, Adelosina
longirostra, Hansenisca soldanii,
Cibicidoides ungerianus, Ammonia
beccarii, Globulina gibba, Glan-
dulina laevigata and Sphaeroidina
bulloides. Palynological investiga-
tions revealed the presence of
spores and pollen grains of gymno-
sperms and angiosperms, such as
Sporites sp., Polypodiaceoisporites
sp., Laevigatosporites haardti, Ca-
thayapollenites div. sp., Pinuspolle-
nites labdacus, Cathayapollenites
div. sp., Monocolpopollenites tran-
quillus, Triatriopollenites
cory-
phaeus,
Alnipollenites
verus,
Caryapollenites
simplex,
Poly-
poropollenites
stellatus,
Tri-
colpopollenites liblarensis and T.
cingulum.
In addition to reef limestones,
there are light-grey arkoses, carbon-
ate sandstones and siltstones with
the forams Globigerinoides trilo-
bus, G. quadrilobatus, Elphidium
crispum, Globigerina bulloides, G.
concinna, Heterolepa dutemplei,
Cibicidoides pseudoungerianus, C.
floridanus, Pullenia bulloides, Uvi-
gerina semiornata, U. pygmoides,
U. aculeata, Sphaeroidina bul-
loides, Textularia gramen, T. pala,
Gyroidinoides soldanii, Martinot-
tiella communi and Glandulina lae-
vigata present.
The age of these shallow marine
and reef sediments is Badenian (ear-
ly and middle Middle Miocene,
Fig. 4. Chronostratigraphic position of the Neogene to Quaternary succession of the Čoka area
(time scale, magnetic polarity zones and chronostratigraphic division of the Neogene after
Gradstein et al. 2004; Piller et al. 2007 and Harzhauser & Mandić 2008).
345
GEOLOGY OF THE ČOKA STRUCTURE (SERBIA)
Fig. 4), as indicated by the presence of Asterigerinata
planorbis, Elphidium crispum, E. aculeatum, Borelis melo
etc. The maximum thickness of the Badenian in the selected
wells is 19 m (C-8; Fig. 3).
The Badenian is overlain by compact marlstone and marly
limestones with fragments of ostracods, such as Amplocypris
sp., Hemicytheria sp., Candona (Lineocypris) trapezoidea,
Candona (Caspiolla) labiata, Loxoconcha schweyeri and
Leptocythere sp. In light-grey compact marlstones, there is
an association of molluscs including Gyraulus praeponticus,
G. dubius, Radix croatica, Micromelania striata, Velutinopsis
velutina, Limnocardium sp. and Orygoceras sp., as well as
associations of spores and microplankton with Cathayapol-
lenites div. sp., Pinuspollenites labdacus and Sporites sp.
These ostracods and molluscs were endemic to the brackish
Lake Pannon and indicate the Pannonian (Late Miocene) age
of these sediments (Fig. 4). In some of the boreholes (C-2
and C-10) the Pannonian layers directly overlie the Triassic
basement. The maximum thickness of the Pannonian in the
selected wells is 87 m (C-8; Fig. 3).
The Pannonian sediments and the pre-Neogene basement,
where they former are missing (e.g. at C-1 and C-24), are
overlain by marls with thin intercalations of sandstone and
black clays containing rare ostracods such as Pontoleberis
pontica, Loxoconcha schweyeri, Leptocythere andrusovi,
Candona (Caspiocypris) labiata, Candona (Caspiocypris)
alta, Candona (Lineocypris) trapezoidea, Candona (Ponto-
niella) paracuminata, Bacunella dorsoarcuata, B. abchazica,
Hemicytheria pejinovicensis and the camoebians, including
Silicoplacentina majzoni, S. hungarica, and S. inflata. This
Fig. 5. Structure contour map of the base of the Neogene with location of wells, seismic
profiles and geological cross-sections.
unit is considered to be of Early Pontian
age in the sense of Stevanović et al.
(1990) and Rundić (1997) (Fig. 4). Its
maximum thickness in the selected wells
is 361 m (C-4; Fig. 3). The overlying
sediments are represented by sand-marly
clays with coals, thin sandstone layers and
grey-greenish marls with the molluscs
Paradacna cf. abichi and Lymnocardium
sp., ostracods Candona (Pontoniella)
paracuminata and Candona sp., and the
camoebians Silicoplacentina majzoni, S.
hungarica and S. inflata. These belong to
the Upper Pontian sensu Stevanović et al.
(1990), reaching a thickness of 303 m
(C-4; Fig. 3).
Further chronostratigraphic bound-
aries, like the Pliocene—Quaternary, have
not been determined, because there is lit-
tle material for correct stratigraphic cor-
relation. The post-Pontian formations are
represented by fluvial, lacustrine, marsh
and terrestrial sediments including fine-
grained sandstones and gravels, sandy
clays with coals, marly-clayey sand-
stones with the molluscs Gyraulus sp.,
Lythoglyphus sp., Pisidium sp., and eo-
lian sediments (Figs. 3, 4). Their maxi-
mum thickness is 886 m in C-10.
Tectonics
The structure and thickness of individual stratigraphic units
are presented in structure contour maps (Figs. 5—7), seismic
profiles (Figs. 8, 9), geological cross-sections (Figs. 10—12),
and thickness maps (Figs. 13, 14).
Within the study area, the Neogene basement generally dips
from northwest to southeast and east in a monoclinal manner
(Figs. 5, 8, 10—12). The deepest part of the basement lies at a
depth of —1800 m in the eastern part of the research area, where-
as the shallowest part is in its northwestern corner at a depth of
—1040 m in C-1 (Fig. 5). The inclination of monocline is gentle
in the NW and becomes steeper in the SE, where the basement
starts to sink steeply into the North Banat Graben (Fig. 2).
The basement of the Neogene is mainly represented by
Lower Triassic clastics and, in the northwestern part of the
study area, by Paleozoic greenschists (Figs. 5, 8). The meta-
morphic rocks were hit only by C-1 (Fig. 10). The contact be-
tween the two rock types is interpreted to be tectonic in the
south, whereas the Lower Triassic depositionally or erosional-
ly pinches out on the elevated Paleozoic basement in the west
and east (Fig. 5).
The Čoka structure is a fault-bounded anticline, situated on
the basement slope (Fig. 5). This structure is shallowest at the
location of C-10 at —1393 m (Figs. 8, 10). The high is accentu-
ated on its west by two clearly recognizable paleodepressions
in the southern and central parts of the study area, respective-
ly, at a basement depth of —1500 m (Fig. 5). These depressions
are expressed on structure contour map of the top Badenian
and top Pannonian horizons (Figs. 6, 7).
346
RADIVOJEVIĆ, RUNDIĆ and KNEŽEVIĆ
position of the Pontian sediments on geological
cross-sections support this statement.
The Badenian strata pinch out towards the
north and west (Figs. 6, 8, 10, 11). They are the
shallowest at the pinch-out point (at about
—1250 m), while in the eastern part of the re-
search area, they are at a depth of —1800 m.
Over the entire Čoka area they are thin and are
missing from the top of the Čoka structure (in
C-2 and C-10; Fig. 13). Here, their thickness is
below the seismic resolution and thus could not
be distinguished from the top Triassic reflector
(Fig. 9). On the top Badenian structure contour
map, normal faults with north-south and north-
west-southeast direction can be noted (Fig. 6).
All the faults have small throw (few meters to a
few tens of meters).
The Pannonian sediments pinch out to the
northwest and deepen to the east down to
—1750 m (Fig. 7). They are the shallowest near
the pinch-out, near C-24 at about —1100 m
(Fig. 11). Unlike the Badenian, they are found in
all wells above the Čoka structure (Fig. 14). The
faults have a small gravitational movement and
most of them have a north-south direction. In the
western part of the area, there is a large E-W
trending normal fault (Fig. 7).
Interpretation and discussion
In the Čoka area, the Badenian represents the
oldest Neogene unit; its sediments transgressive-
ly overlie the Lower Triassic (Radivojević 2008).
The distribution and thickness of the Badenian
sediments, including their lack in C-2, C-10, C-22
and C-23, suggest that the Badenian was proba-
bly exposed to erosional processes for some
time. This interpretation is strongly supported by
the complete lack of the subsequent Sarmatian
sediments in the studied boreholes.
According to Kemenci (1991), the entire Mid-
dle Miocene (Badenian and Sarmatian) can be
characterized by significant expansion of the
aquatic environments in the southern Pannonian
Basin; only restricted areas (the highest parts of
the paleorelief) escaped marine flooding. If this
interpretation is correct, then the lack of the Sar-
matian and eroded nature of the Badenian in the
Čoka area is probably due to the tectonic inver-
sion that took place in the Late Sarmatian or Ear-
ly Pannonian and resulted in a widespread
pre-Pannonian unconformity (Horváth & Tari
Fig. 6. Structure contour map of the top Badenian with location of wells, seismic
profiles and geological cross-sections.
Fig. 7. Structure contour map of the top Pannonian with location of wells, seismic
profiles and geological cross-sections.
In the Čoka area, several, N-S and E-W trending normal
faults with small movement have been interpreted. All faults
present in the Čoka area were probably reactivated during the
Pontian as inverted faults which is indicated on seismic and
geological cross-sections (Figs. 8—12). Reflectors above the
top Pannonian horizon which are also nicely folded and the
1999). Tectonic inversion is obvious both, on seismic lines
(Figs. 8, 9) and geological cross-sections (Figs. 10—12). All
reflectors above the top Pannonian horizon are nicely folded
and some inverted earlier normal faults are present. Position
of Pontian sediments on geological cross-sections also indi-
cates basin inversion.
347
GEOLOGY OF THE ČOKA STRUCTURE (SERBIA)
Fig. 8. Seismic profile 1 across the Čoka area. The strong reflector to the left of shot point 250 corresponds to the top of the Paleozoic hori-
zon. The large difference in the velocity between the Pontian sediments (Triassic, Badenian and Pannonian sediments are completely miss-
ing) and the schists caused appearance of a multiple under the top Paleozoic. For location of the profile see Figs. 5—7.
Fig. 9. Seismic profile 2 across the Čoka structure. The Pannonian sediments have a low reflective response over almost the entire study
area. The top of the Pannonian on the right side of the profile, however, has a well-defined reflection. This is a typical feature of the top
Pannonian in northern Banat. For location of the profile see Figs. 5—7.
348
RADIVOJEVIĆ, RUNDIĆ and KNEŽEVIĆ
Fig. 10. Geological cross-section A—B (for location see Figs. 5—7). Note the pinch-out trend of the Badenian and Pannonian towards C-1.
The Badenian is missing at C-10, probably due to erosion.
Fig. 11. Geological cross-section C—D (for location see Figs. 5—7). The Badenian and Pannonian pinch out towards C-24.
The Sarmatian-Pannonian boundary, roughly corresponding
to the Middle-Late Miocene boundary, was marked by a major
regression, which isolated the Central Paratethys from the glo-
bal sea, and transformed it into the large, long-lived, brackish
water body of Lake Pannon (Magyar et al. 1999). The cause of
this regression is still highly debated (Săndulescu 1988;
Vakarcs et al. 1994; Horváth & Cloething 1996; Harzhauser &
Piller 2004).
A lake-level rise during the Pannonian caused flooding of
previously emerged regions in northern Banat (Kemenci
349
GEOLOGY OF THE ČOKA STRUCTURE (SERBIA)
Fig. 12. Geological cross-section E—F (for location see Figs. 5—7).
Fig. 13. Thickness map of Badenian sediments above the Čoka structure (based on
well data). The Badenian is missing from the most elevated parts of the structure.
1991), thus the Pannonian strata are transgres-
sive at the base and deposited above an uncon-
formity over a greater part of the area. The
Pannonian sediments in northern Banat have a
wider distribution than the Badenian; they
overlie Paleozoic schists and magmatites, Tri-
assic, Badenian, and Sarmatian sediments.
In general, the Pannonian is represented by
thin sandstones with carbonate matrix in the lit-
toral facies, by pelites with presence of micrite
in the sublittoral facies, and by marls in the
deep-basin facies. The lithology as well as the
molluscan fauna with Radix croatica and Gy-
raulus praeponticus in the Čoka boreholes
point to a sublittoral facies that was widespread
in the region (Stevanović 1977; Knežević et al.
1994) and represents a transitional zone be-
tween the sandy littoral and clayey deep basinal
facies. The Pannonian associations of flora and
fauna indicate a low-salinity caspibrackish en-
vironment characteristic of Lake Pannon
(Steininger et al. 1988; Rögl 1996). Data from
Čoka area correspond to recent isotope trends
studies which indicate that Lake Pannon was a
simple system of an alkaline lake with steadily
declining salinity (Harzhauser & Piller 2007;
Harzhauser et al. 2007).
350
RADIVOJEVIĆ, RUNDIĆ and KNEŽEVIĆ
Progradation of deltaic clastic systems, shallowing and fi-
nally infilling of the basin during Pontian times was proba-
bly caused by deceleration of basin subsidence (Fodor et al.
2005; Horváth et al. 2006). The sedimentary complex depos-
ited during the Pannonian, Pontian and later, in northern and
central Banat is very thick, locally it may exceed 4000 m
(the Pannonian ranging from several m to several hundred m).
In the surrounding areas, such as the southern Banat, Fruška
Gora Mts, and most of Bačka, this complex is much thinner
(Kemenci 1991; Radivojević 2008).
The stratigraphic position of the oldest post-Pannonian
sediments that were treated in this paper is quite question-
able. Basic lithostratigraphic and paleontological parameters
indicate the presence of the Pontian s.str., which is known in
the Eastern Paratethys where they represent a regional stage
(Stevanović et al. 1990). From the paleogeographic point of
view, it should be emphasized that area of Eastern Serbia
corresponds to the Miocene and Pliocene development
which exists in Dacian Basin and further to the east, includ-
ing the Pontian in such development. In earlier references
there are data which confirm these correlations, similarities
and differences between the Pontian of these basins. Howev-
er, as in the past 20 years, few results from these areas that
are internationally recognized were published, the question
of Pontian (none) existence in the Pannonian part of Serbia
should be seriously revised, and verified on outcrops. The
validity of the model which is applicable for the western part
of Central Paratethys can only be tested with direct field ob-
servations. In that sense, the adjusted Miocene-Pliocene
Fig. 14. Thickness map of Pannonian sediments above the Čoka structure (based on
well data).
scheme, which includes both the Pannonian
and Dacian Basins is used in this paper as a
compromise (Harzhauser & Mandic 2008).
Conclusions
The basement of the Neogene succession
in the Čoka area is mainly represented by
Triassic sediments, except in the northwest-
ern corner of the study area where it is repre-
sented by Paleozoic schists. The paleorelief
subsided along normal faults from the North
Bačka High in the northwest to the North Ba-
nat Graben in the southeast and east. The
Čoka structure, which was initiated as a
within-basin high and later inverted into the
fault-bounded anticline is neighboured by
two local paleodepressions in the central and
southern parts of the study area.
The shallow marine Badenian sediments
were deposited transgressively on the Paleo-
zoic-Triassic basement. They pinch out at the
most elevated northwestern part and were
eroded from the top of the Čoka structure, as
indicated by their small thickness (up to a
few tens of meters) and by the lack of Sarma-
tian deposits.
The sublittoral Pannonian sediments are
present in all wells testing the Čoka struc-
ture, but they also pinch-out towards the west. They are
thicker than the erosionally truncated Badenian sequence (up
to 100 m). The overlying Pontian to Quaternary succession,
represented by lacustrine to alluvial and terrestrial deposits,
is thick (1000—1800 m) and uniform over the entire area.
Acknowledgments: We owe great gratitude to NIS Naftagas
for allowing unlimited access to all data. The authors are
grateful to Imre Magyar (MOL, Budapest) who greatly im-
proved the paper by his comments and suggestions. We wish
to thank Vladimir Muškinja and Zoran Stojanovski for the
graphic outfit of the paper. In addition, we owe great grati-
tude to colleagues: Jordan Kukavica who helped about the
location of pinch-out of the Badenian and Pannonian sedi-
ments, Rastko Pešalj and Snežana Marjanović for the given
material and Zorica Đokić who helped with the interpreta-
tion of the well log measurements. We are also grateful to
NIS Naftagas employees: Predrag Cvijić, Goran Bogićević
and Vladislav Gajić who helped with the stratigraphical and
petrological determination. Many thanks to Marianna
Kováčová (Comenius University, Bratislava) for reviewing
the list of pollen grains and spores. We also want to thank
Csaba Krézsek (OMV/Petrom, Bucharest) for critical com-
ments on the manuscript. Fruitful discussions and comments
of three anonymous reviewers improved the final version
significantly. A part of this paper represents the results of the
Project No. 146009 supported by the Ministry of Science
and Technological Development of the Republic of Serbia.
351
GEOLOGY OF THE ČOKA STRUCTURE (SERBIA)
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