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GEOLOGICA CARPATHICA, AUGUST 2007, 58, 4, 353—366

www.geologicacarpathica.sk

Late Miocene sequence stratigraphy of the Pannonian Basin

fill (Kiskunhalas—Mélykút region, Hungary):

how core, electric log and seismic data fit together?

ÁGNES TÓTH-MAKK

Geological Institute of Hungary, Stefánia út 14, 1143 Budapest, Hungary;  makk@mafi.hu

(Manuscript received April 18, 2006; accepted in revised form December 7, 2006)

Abstract: In the area of the Danube—Tisza Interfluve, Pannonian Basin, Hungary, sedimentological, paleontological
and well log interpretations of fully cored boreholes made it possible to establish the sequence stratigraphic subdivi-
sion of the Upper Miocene lacustrine and fluvial sections of boreholes Kaskantyú Kas-2, Jánoshalma J-1 and Bácsalmás
Bá-1, of which Kas-2 is paleomagnetically dated. 8 sequences were determined in borehole Kas-2 and 6—6 ones in the
boreholes J-1 and Bá-1 respectively. The correlation of the sequences was made along two independent composite
seismic lines with the help of cross seismic profiles and well logs of 29 boreholes. 11 sequences were marked out in the
Upper Miocene basin fill. The areal distribution of the sequences reflects the NW—SE direction of the sediment
transport. By the time of maximum flooding surface (MFS) 2, the area was almost completely flooded. The oldest 4
sequences were identified in a seismically observable thickness in the NE Kiskunhalas depression. Their condensed
layers are present in the well Bá-1 in the SE part of the area, revealed by dinoflagellates. Sequences 5 to 11 are present
in well-observable thickness in the study area. The thickest part of the successive sequences is shifting towards the SE.
Sequences 8 and 10 are developed only in the eastern part of the area. The basin evolution had two major phases: from
10.2 Ma to approximately 7.6 Ma the sequences 1—4 were characterized by local sediment accumulation despite their
complete water cover, while between 7.6 and 6.6 Ma (sequences 5—10) regional sedimentation occurred.

Key words: Upper Miocene, Pannonian Basin, paleogeography, biostratigraphy, magnetostratigraphy, sequence
stratigraphy, delta progradation.

Introduction and research history

The Late Neogene Pannonian Basin and its subbasins has
been in the centre of interest of stratigraphers, sedimentol-
ogists and paleontologists for decades. Being an approxi-
mately 12—13 million-year-old disconnected Paratethyan
depository, the facies dependent and low diversity brack-
ish water endemic fauna has caused serious correlation
problems both in the basin, and in the remaining connect-
ed parts of the Paratethys. In the present era of integrated
stratigraphy however, many former unanswered questions
turned out to be less important, for example, the overem-
phasized elaboration and refinement of the Paratethyan
(local) Late Miocene stages and substages or the urge to
find more and more – not properly supportable – bios-
tratigraphic subdivisions in the Pannonian Basin.

After the decades governed by the concept of static and

basin-wide contemporaneous lacustrine infilling, a model
of fluvial-dominated delta systems prograding mainly from
NW to SE has been established offering a new explanation
for the development of the infilling of the Pannonian Basin
(Bérczi & Phillips 1985). Magnetostratigraphic data proved
the protracted character of the infilling and the duration of
the whole process was determined (Elston et al. 1985, 1990,
1994; Csató 1993; Juhász E. et al. 1997).

By the second half of the 1980s, many papers were pub-

lished on the seismic facies of the different deep Pannon-
ian subbasins of medium size. Later, using composite

seismic sections, sequences according to the concept of
Vail and co-authors (e.g. Posamentier & Vail 1988) were
outlined and correlated to the ‘global’ system (Mattick et
al. 1985; Pogácsás & Völgyi 1987; Pogácsás & Révész
1987; Pogácsás et al. 1987, 1988, 1989, 1992; K. Juhász
Gy. et al. 1989; Korpás-Hódi et al. 1992; Csató 1993). In
the early 1990s a new generation of seismic stratigraphers
as well as sedimentologists made an effort to complete the
missing parts and construct a unified system both in space
and time (Vakarcs & Várnai 1991; Tari et al. 1992;
Vakarcs et al. 1993, 1994).

Many problems and questions arose during this 20 years

of manifold studies, for example regarding synchronism of
the sea-level (SL) rise-and-fall and the water-level chang-
es in a detached part of a previously interconnected brack-
ish water sea system (Paratethys), the ordering (3

rd

, 4

th

 or

5

th

-6

th

) of the independent sequences (Juhász E. et al.

1994a, 1996), finding out whether these sequences are
mostly climatic or tectonics related (Juhász E. et al. 1997)
or whether they are the results of complex and/or feed-
back-type mechanisms.

By the middle of the 1990s, each working group estab-

lished a series of sequences coherent to their disciplines
but not matching the others. The aim of this paper is to
give an example for gathering multidisciplinary (sedimen-
tological, ecological, lithological and seismic) data in a
study area of the eastern central part of the Pannonian Ba-
sin to evaluate them in their interdependence.

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354

TÓTH-MAKK

Summarizing the above mentioned facts, the infill model

of the Pannonian Basin has been developed from a static
one – lower finer grained and upper cyclically sandy series
– through a lithostratigraphic one – based on the moving
delta facies-system – to a recent sequence stratigraphic
model based on the relative lake level changes and the bal-
ance between the overall subsidence and sediment influx.
According to this model, ca. 6—12 elongated sigmoid-
shaped bodies, piled on each other and slipped by their
geometric centre toward the accumulation direction, consti-
tute the Upper Miocene infilling of the basin. This model,
by its geometry, certainly outlines the possible direct corre-
lation of conductive coarser grained sand bodies important
from the underground streaming fluids (water, oil and gas)
and fluid movement modelling points of view.

The study area

The study area lies in the central and southern part of the

Danube—Tisza Interfluve, where three fully cored boreholes
were drilled in the 1980s (Kaskantyú Kas-2, Jánoshalma J-1
and Bácsalmás Bá-1) cutting through the whole Upper Mi-
ocene (Fig. 1). There are paleomagnetic data from Kas-2,
and biostratigraphic data based on dinoflagellates from
Kas-2 and Bá-1 available. Due to former hydrocarbon ex-
ploration, the area was properly investigated and a large
number of seismic lines were shot, however, no seismic
lines go exactly through the wells J-1 and Bá-1.

All of the studied boreholes are situated above base-

ment highs. The composite seismic sections are going
through the Kiskunhalas depression located SE of Kas-2
and E of J-1. The Mélykút depression lies between the
wells J-1 and Bá-1. Both depressions are relatively shal-
low parts of the basin system with undulating paleotopog-
raphy that link to the Makó—Hód Trough E and SE of the
Tisza river.

The cores of Kas-2, J-1 and Bá-1 were described minutely

resulting in dm-scale resolution of the sedimentological,
ecological and biostratigraphical data, while the 2D correla-
tion of the seismic sections reflects 30—50 m resolution of
the acoustic waves. Since the Upper Miocene formations
here have a relatively limited thickness (400—1500 m)
compared to the 5000—6000 m of those in the deepest
basins to the SE (Makó—Hód Trough, Békés Basin)
(Bérczi & Philips 1985; Bérczi 1988; Révész et al. 1989),
the use of all the advantages of disciplines besides
seismics was necessary.

Methods

In order to gain at least two series of data, two different

composite sections were compiled, a shorter one near the
shallower part of the sub-basin and a longer one closer to
the deeper areas crossing or approaching local basement
highs. To improve the results 12 additional crossing seismic
sections were used (from ‘a’ to ‘l’, in Fig. 1). Close to the
borehole Jánoshalma J-1 the two composite sections are

running together. The necessary number of the sections was
determined by the reliable tracing of the systems tracts.

Between 1992 and 1996 the detailed sedimentological

supervision of the cores and data available of the fully
cored boreholes was carried out in the course of the Basin
Analysis Project of the Geological Institute of Hungary
(MÁFI) (Juhász E. et al. 1993, 1994b, 1996). This work
was completed in the framework of a joint Hungarian—US
governmental project between 1994 and 1997 by the
USGS and the MÁFI (U.S.—Hungarian Science & Technol-
ogy Joint Fund, JFNo. 329. Juhász E. et al. 1997, 1999, fi-
nal report: Juhász E. & Phillips 1998). As a part of this
project, the sedimentological data sheets of these three
boreholes were also completed by detailed environmental
interpretation. The ecological interpretation of the mol-
lusc fauna was made by Pál Müller (personal communica-
tion), the biostratigraphic zonation from the wells Kas-2
and Bá-1 was performed by Sütő-Szentai (1982, 1983,
1991, 2003 pers. comm.). All these data were evaluated to
establish sequences and systems tracts. Well log (electric
and nuclear) interpretations were made to complete the
sedimentological framework regarding cyclicity (“parase-
quences”) and upward coarsening or fining trends of the
series. On Fig. 2 a part of the data sheet of the well Bács-
almás Bá-1 demonstrates the elaboration.

On the figure, two seguence boundaries can be seen. The lower

one is characterized by gradual upward coarsening of the deposited
material, with a definite m-scale thick sandy bed, littoral clams to-
gether with slight upward coarsening trend visible on gamma and
resistivity logs, followed by a sharp decrease in the average grain
size of the sediment. The transgressive systems tract is dominanted
by silts. Some sublittoral faunal elements show the deepening of the
water cover. The maximum flooding surface is below the horizon
where the upward coarsening trend of the cyclicity of fourth- or
fifth-order occurs together with littoral shell fragments. The shal-
lowing of the facies may also be indicated by the disappearance of
the dinoflagellates. Approaching the upper sequence boundary the
lagoonal fossils also disappear. At the top root casts, calcareous
concretions and variegated sediment colour are also characteristic.

Results and discussion

Correlation of the sequence stratigraphic units

Sequence stratigraphic outline

The Upper Miocene series was divided into sequences

in all the three boreholes. In the deepest Kas-2 well 8 com-
plete sequences appear, while in the shallower wells (J-1
and Bá-1) 5-5 can be identified. In Fig. 3 the general out-
line of the systems tracts can be seen. At the base there is a
basin-wide erosional contact between the Middle Mi-
ocene and Upper Miocene series with significant time gap
in the study area. At the top there is a subaerial unconfor-
mity between the Pliocene and Miocene strata.

Figure 3 also illustrates the following most common fea-

tures of the Upper Miocene series on the Great Hungarian
Plain: the monotonous, cyclic alternation of sandy and
muddy layers, the shallowing and/or upward coarsening

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LATE MIOCENE SEQUENCE STRATIGRAPHY OF THE PANNONIAN BASIN (HUNGARY)

Fig. 1. Location map with the three cored wells, composite seismic sections #1 and #2, additional crossing seismic sections above the
thickness contour map of the Upper Miocene (Pannonian) series.

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356

TÓTH-MAKK

character of the complete Upper Miocene series (see also
Juhász E. et al. 1996) and the significant (here: 150—200 m)
thickness of the basal silty clay—clayey silt set of strata
regardless of the relative closeness of the elevated
background or the thickness of the covering littoral sedi-
ments. The development of this fine-grained basin unit is
primarily the result of the quick and significant incipient
deepening of the Pannonian Basin (starving basin era).
The rapid infilling process here could have been started
not before 9.8 Ma (see Fig. 3, Kas-2 well).

Fig. 2. Sedimentological chart of Bácsalmás-1 borehole section and systems tracts interpretation (sedimentology: Juhász et al. 1994b;
molluscs: Müller P. in Juhász et al. 1994b and pers. comm. 2002; dinoflagellates: Sütőné Szentai M. 1982, 2003, pers. comm.).

Correlation

The location of the already performed fully cored wells

limited the possibility of choosing seismic sections with
numerous diagnostic terminations of the reflectors. To
make a well-established net of sequence stratigraphic hori-
zons, the well logs of 29 additional hydrocarbon explora-
tion wells were also used (see Fig. 1). In order to correlate
these logs with the pattern of the systems tracts detected
along the seismic sections, the general upward coarsening

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357

LATE MIOCENE SEQUENCE STRATIGRAPHY OF THE PANNONIAN BASIN (HUNGARY)

Fig. 3. Sequences and systems tracts in Kas-2, J-1 and Bá-1 cored wells
(interpretation was based on lithology, sedimentology, electric log inter-
pretation, sedimentary environment and paleoecology of the fossils). Age
data: Lantos in Juhász E. et al. (1996).

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TÓTH-MAKK

or fining trends of the approximately 100 m thick bedsets,
parasequence sets were depicted, thus improving the reli-
ability of the comparison. In Fig. 4 a well log of a bore-
hole located in the Mélykút local depression is presented.
With the help of the crossing seismic sections, stepping
from well to well on the composite seismic lines of  # 1 and
# 2 , the correlation of the sequence stratigraphic units was
successfully achieved.

The sequence stratigraphy of the study area

As a result of correlation 11 complete sequences were

traced (Fig. 5). The previously stated (Bérczi & Phillips
1985; Mattick et al. 1985; Pogácsás & Révész 1987;
Bérczi 1988; Juhász Gy. 1992; Vakarcs et al. 1994) NW—SE
direction of accumulation also governs the sedimenta-
tion here. The area of the successive sequences advances to
the SE and the position of their greatest thickness
progresses into the same direction. In the vicinity of
Kaskantyú and in the Kiskunhalas local depression the
sequences 1—7 are fully developed. The bulk of the material
of the first 4 sequences was deposited in the northeastern
Kiskunhalas depression (see Fig. 5). The fifth sequence is
the first such sequence with a thickness greater than the
average resolving power of the seismics in the whole
study area; nevertheless it is eroded near Kas-2 by

sequence boundary (SB) 6. Sequence 8
is also missing in the relatively flat,
gently dipping indented rim of the ele-
vated western part of the Danube—Tisza
Interfluve (see Fig. 1). The possible rea-
sons for this absence are to be discussed
in the next part.

Paleogeography of the sequences

The area of the individual successive

sequences reveals the main NW—SE di-
rection of the accumulation at the inves-
tigated sites. In Fig. 6 the area of
maximum flooding surface (MFS) 1 and
MFS2 show the steps of the flooding
process while the area of SB1 and SB2
show the maximum extent of sediment
accumulation detectable by acoustic
waves. Notice that in the well J-1 and in
its vicinity, as well as to the SE, near the
crossing of the f and g lines (f/g crossing
point, see also Fig. 1) there is an area
without sedimentation due to elevated
position and/or underwater erosion.

The water cover of the area is also con-

firmed and dated by the dinoflagellate
data since the Spiniferites bentorii-ob-
longus and the Pontiadinium pecsva-
radensis Biozones are also present in the
near bottom layers of the wells Kas-2
and Bá-1 (Sütő-Szentai 1991; Magyar et
al. 2001).

The infilling process was continuing slowly; Fig. 7 shows

the area of the 3—5 sequences. As it can also be seen in Fig. 5,
the bulk of the material of the first 4 sequences was kept in
the Kiskunhalas depression, thus the areas of these sequences
do not differ significantly. Note that sequence 5 is missing in
Kaskantyú-2 and in its close vicinity probably due to the ero-
sive character of sequence 6 in this small region.

Sequences 6, 7 and 9 are thick and widely extended all

over the whole area (see Fig. 5). In accordance with the
NW—SE accumulation direction, the thicknesses of se-
quence 5 and 6 are greater in the NW (Kiskunhalas de-
pression) while sequences 7 and 9 are thicker in the SE
(Mélykút depression).

The area of sequences 8 and 10 is somewhat different

from all the others (Fig. 8). Both are mainly developed in
the eastern part of the Kiskunhalas depression according
to composite line  # 2 and the crossing a—g lines. Since the
thickness of these two sequences is gradually decreasing
towards the W and S, their absence in the three cored wells
can be explained rather by reworking during the next
transgression than by underwater erosion and removal.
The simplest explanation could be the actual change of
the direction of the feeding channel.

In Table 1 the identified sequences are listed in the

three master-cored wells with the thicknesses of the indi-
vidual systems tracts.

Fig. 4. The electric logs (GR and resistivity) of well numbered 1.12 along seismic sec-
tion  # 2. Sequence boundaries, top lowstand surfaces and maximum flooding surfaces
were identified and correlated with joint interpretation of well log shapes and seismic re-
flection configuration.

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LATE MIOCENE SEQUENCE STRATIGRAPHY OF THE PANNONIAN BASIN (HUNGARY)

Fig. 5. Composite master seismic line  # 1, and sequence stratigraphic interpretation. On the left magnetostratigraphic data from Kaskantyú-2
borehole (the breaks of the systems tracts’ boundaries mark the position of the faults which were not illustrated because of the significant
vertical exaggeration).

Chronostratigraphic calibration of the sequences

Biochronostratigraphy: Dinoflagellate biozones

In the wells Kas-2 and Bá-1, Sütő-Szentai (1982,

1983) has carried out detailed investigations referring
to the dinoflagellate flora and summarized them to-
gether with the available data from the boreholes of
the whole Pannonian Basin, differentiating biozones,
subzones, as well as associations and correlating them
to the flora of the Mediterranean Late Miocene (Sütő-
Szentai 1991; Magyar et al. 2001). Sütő-Szentai up-
dated the biostratigraphic subdivision of these two
boreholes in 2003 (pers. comm.). These data are
shown in Fig. 9 together with the latest version of the
sequence stratigraphic division. There are two bio-
zones, A: Spiniferites bentorii and B: Spiniferites
balcanicus present in the time spans represented by
the samples. The boundary between the two biozones
is situated near the base of the thick, oldest clayey
sediments of both boreholes, thus zone B covers al-
most the whole series. Regarding biozones, the corre-
lation is perfect, however considering subzones the
partly unfavourable ecological conditions are reflect-
ed in the changes of the frequency and the number of
the species so strongly, that ecological Dinoflagella-
ta-Zygnemataceae assemblages (marked by D-Z 1, -2,
-3 in Fig. 9) break the succession of the subzones.
This also means that the boundaries of the Spiniferites

Fig. 6. Area of SB1, MFS1, SB2 and MFS2. Note the missing sequences
in the vicinity of well J-1 and crossing point f/g.

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TÓTH-MAKK

Subzones can be extended probably through the D-Z
zones (dashed lines on Fig. 9).

The correlations of the 4 subzones are as follows:

Spiniferites paradoxus’ is good but the upper bound-
ary is too high in Bá-1, Galeacysta etrusca’ is ap-
proximately acceptable, while Spiniferites validus
and  Sp. tihanyensis Subzones are uncorrelatable.
Nevertheless the thicknesses of the zones in Kaskan-
tyú-2 show excellently that the sedimentation rate
was higher here in the first 4 sequences than during
the sequences 6 and 7. Up to now, the contradictory
results have not been solved.

One possible cause of the contradictions is the sig-

nificantly elevated synsedimentary position of the
place exposed by borehole Bá-1, so the thicknesses of
the developed individual sequences are near or partly
below the seismic resolution of the acoustic waves.
Therefore below SB5 all the sequence boundaries
must be considered here as approximations. As men-
tioned above, the bottom layers of the Upper Miocene
in vast territory of the Pannonian Basin are rather fine-
grained, as it can be seen in Fig. 2, so this lithology is
unfavourable for distinguishing sequences both from
seismic and sedimentological aspects.

Radioisotope data

In the borehole Bácsalmás-1, at a depth of 485 m,

9.6 ± 1 Ma age was measured on biotites of dacite tuff
forming a few cm thick layer (Balogh 1983). In the
Kiskunhalas region (Kiha-Ny-3 well) below the fine-
grained sediments belonging to the Spiniferites para-
doxus Dinoflagellate Subzone, radioisotope ages
ranging from 9.35 ± 0.68 to 9.77 ± 0.71 Ma (4 samples)
were determined from basalts (Cserepes-Meszéna
1978; Balogh et al. 1986).

Magnetostratigraphy

Vertically oriented samples were taken from every

0.5—1 m, for magnetic measurements, from the well
Kaskantyú-2. The polarity zones were correlated to
the polarity/time scale of Berggren et al. (1985) (El-
ston et al. 1990). As Kas-2 was the first section mea-
sured for paleomagnetic purposes in the Pannonian
Basin, its magnetic profile may hold more uncertain-
ties than the younger ones (Elston et al. 1990,
pp. 113, 116) due to sampling methods and the rate
of demagnetization. Lantos (in Juhász E. et al. 1996)
adjusted the polarity zonation of numerous wells in-
cluding Kas-2, to the new polarity/time scale of Berg-
gren et al. (1995).

For dating the sequence stratigraphic units of the

study area, mainly the paleomagnetic data of the well
Kas-2 were used. The ages of SB2, 3, 4, 6, 7 and 9 are
linearly interpolated from the next two ages of the re-
versals, SB1 is extrapolated (as the first measurable
reversal was the C5n to C4Ar at the age of 9.74 Ma).
The obtained data are listed in Table 2.

Fig. 7. Area of SB3, SB4 and SB5. Note the relatively slow advance of
the sedimented material in seismically observable thickness.

Fig. 8. Area of sequence boundaries 8 and 10. Note their similar contours
and the absence or thinning out of their sediments toward the West and South.

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LATE MIOCENE SEQUENCE STRATIGRAPHY OF THE PANNONIAN BASIN (HUNGARY)

Table 1: Depth position and thickness of the systems tracts in the cored wells.

Table 2: Paleomagnetic ages of the sequences detected in well Kaskantyú-2.

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TÓTH-MAKK

Fig. 9. The dinoflagellate biozones of Kaskantyú Kas-2 and Bácsalmás Bá-1
wells after Sütő-Szentai (1991 and pers comm. 2003) (for the full names of the
zones see text). The environment in the time of the D—Z (Dinoflagellata—Zygne-
mataceae) zones was unfavourable for high diversity microflora. The boundaries
of the biozones are indistinctive in these cases.

The order of the sequences

The age calibration of the sequence boundaries implies

a possible duration of the confined sequences. As Table 2
shows, the duration of the individual sequences lies be-
tween 300 and 800 kyr. According to the original defini-
tions of Mitchum et al. (1977) and Van Wagoner et al.

(1990), the formation of the third-order sea-level change
sequences lies between 10

5

 to (1—2) 10

6

 years, the thick-

ness varies between 20 to 400 m. The 4

th

-order sequences

are of 10

4

 to (1—4) 10

5

 years, the average thickness varies

between 10 to 100 m (by order of magnitude). In our case
it means, that sequences 6 to 11 can be regarded as fourth-
order, sequences 1—6 can be regarded as third-order se-

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LATE MIOCENE SEQUENCE STRATIGRAPHY OF THE PANNONIAN BASIN (HUNGARY)

quences on the basis of their duration and thickness. Tak-
ing into account that the larger values: 500 kyr, 600 kyr
and 800 kyr, belong to the older sequences where either
the seismic or the sedimentological evidence is weak,
there is an increased possibility of finding one or two un-
differentiated sequences.

Vakarcs (1997) evaluated the order of the Upper Mi-

ocene sequences all over the Hungarian part of the Pan-
nonian Basin. The sequence boundaries at 10.8 (Pa2), 9.15
(Pa3), 6.85 (Pa4) and 4.4 (Pa5) were marked as 3

rd

-order

ones by him. There are several 4

th

-order sequences build-

ing up the 3

rd

-order ones. The number of these sequences

varies between 3 and 15.

In the Vienna Basin Harzhauser et al. (2004) marked as

third-order SB the one at the Serravallian/Tortonian
boundary at 11.6 Ma, and considered that the whole Lower
and Middle Pannonian lake deposits belong to one 3

rd

-or-

der sequence.

Kováč et al. (1998) marked one 3

rd

-order SB near the

base of the Pannonian series in the northern Vienna Basin,
and a second one near the top of the D zone sensu Papp.
Kováč et al. (2006) approved a 3

rd

-order sequence bound-

ary of SB1 type at Late Serravalian to Early Tortonian
(Sarmatian to Early Pannonian) at the northwestern basin
margin. The next 3

rd

-order cycle belonging to the Middle

Tortonian is characterized there by caspibrackish Lake
Pannon sequences. The last Late Pannonian (Late Torto-
nian) 3

rd

-order cycle includes freshwater lake and alluvial

plain deposits and are characterized by SB1 and SB2 type
sequence boundaries. Correlation of the Danube Basin cy-
cles of relative water level changes with global sea-level
fluctuations (sensu Haq et al. 1988 and Hardenbol et al.
1998) documents an indirect connection of the Lake Pan-
non with the world sea during the Pannonian time interval.

Juhász Gy. et al. (2006) underline the role of tectonics

in the formation of the 3

rd

-order sequences on the Great

Hungarian Plain.

In a detached part of a former inland sea (Paratethys)

mainly climate and tectonics can cause water level fluctu-
ations. The  ~ 400 kyr periodicity of the identified cycles
in the study area suggests climatically driven cyclicity in
Late Miocene time. This idea was first published concern-
ing the Hugarian part of the Pannonian Basin by Juhász E.
et al. (1996). Sacchi & Müller (2004) reported 400 kyr cy-
clicity in the Upper Miocene of the Transdanubian part of
the Pannonian Basin. Juhász Gy. et al. (2006) regard 4

th

-

and higher order cycles driven by large-scale climatic cy-
cles of the Milanković band (100, 200 and 400 kyr) or
their multiples.

Harzhauser & Piller  (2004) identified and documented

400 kyr period time cyclicity in the Sarmatian series of the
Western Central Paratethys.

Sequence stratigraphic correlations

It is possible to compare the results of this study with

previously published data and results of Pogácsás et al.
(1988), Vakarcs (1997), Vakarcs et al. (1997) and Sacchi et
al. (1999, 2004). Without having a common data set, the

comparison can only involve the number, the order and
the age of the sequences.

Ages of sequence boundaries were first published from

the Late Miocene of the Pannonian Basin by Pogácsás et
al. (1988). These data were based on radioisotope and pa-
leomagnetic data. In Fig. 10 the available data with the
reference scales of Berggren et al. (1985, 1995) can be
seen. Since Vakarcs (1997) studied the latest filled and
deepest two sub-basins (Békés and Makó Grabens), his
data involve the youngest ages. Nevertheless, in the ma-
jority of the territory of the Pannonian Basin, in the Late
Miocene, sedimentation occurred between 10.8 and
6.3 Ma. Older strata were deposited in the deepest subba-
sins and marginal subbasins (due to tectonic reasons;
Vakarcs et al. 1993). Strata younger than 5.4 Ma occur
only in the SE part of the Great Hungarian Plain.

SB2 at 9.7 Ma of the study area may coincide with

Vakarcs’s (1997) Pa3 at 9.15 Ma. Kiskunhalas—Mélykút
region being a “starving basin” in the time of SB2 the de-
posited sediments were condensed and as a consequence,
on the seismic sections, the surfaces SB2 and MFS2 can-
not be distinguished, they are represented by the same
seismic event. Moreover, the extension of sequence 1 is
much more limited than the area of sequence 2 (see Fig. 6).
This fact underlines the significance of SB2, and gives an
intention to correlate it with a 3

rd

-order SB of Vakarcs

(1997) Pa3, 9.15 Ma. MFS2 of the study area at 9.3 Ma
and MFS2 of Sacchi & Müller (2004) at 9.075 Ma also
seems to be correlative.

The first hiatus of Pogácsás et al. (1988) was dated be-

tween 7.6 and 7.9 Ma. Projecting it to the Berggren (1995)
scale, this SB (or boundaries) can be correlated to either
SB3 (8.8 Ma) or SB4 (8.2 Ma) of the study area. One of
them can be compared to Pan2 at 8.75 Ma (Sacchi & Müller
2004). The big hiatus in the Messinian, involving perhaps
more than one sequence boundary between 5.7—6.8 Ma
(Pogácsás et al. 1988), can be correlated to Pa4 of Vakarcs
(1997) at 6.85 Ma and to SB6 of the study area at 7.4 Ma.
Fig. 5 and Fig. 6 show the significance of this surface all
over the study area. Note the erosive character of this sur-
face in relation to SB5.

The reason to connect MFS3 of Sacchi et al. (1999) at

7.455 Ma and MFS6 of the study area at 7.2 Ma is that both
are situated above a significant, correlated SB (see also
Fig. 6) and both can be traced well in their study areas.

Conclusions

This work is an attempt to make a synopsis of seismic,

well log and fully cored borehole investigations in a par-
ticular study area in order to match the results of different
disciplines.

In the area of the Danube—Tisza Interfluve sedimento-

logical, paleoecological and well log interpretations of
fully cored boreholes enabled the establishment of a se-
quence stratigraphic subdivision of the Upper Miocene
(Pannonian s.l.) section of the boreholes Kaskantyú Kas-2,
Jánoshalma J-1 and Bácsalmás Bá-1. Not considering the

background image

364

TÓTH-MAKK

Fig. 10. Chronology correlation chart of sequences, established by authors for different subbasins of the Pannonian Basin system. Age
data of Pogácsás et al. (1988) were correlated to Berggren et al. (1985) time scale (on the left) all the others are related to Berggren et
al. (1995) time scale (on the right). For discussion see text.

unconformity at the base of the Pliocene Nagyalföld For-
mation (sensu Császár 1997, which is present in all of the
three studied boreholes), 8 complete sequences were iden-
tified in the Kaskantyú Kas-2 borehole and 5—5 sequences
in the Jánoshalma (J-1) and the Bácsalmás (Bá-1) bore-
holes.

On the basis of joint interpretation of two independent

composite seismic lines, 12 cross seismic profiles and well
logs of 29 boreholes, sequence stratigraphic units were
correlated along the composite seismic lines between the
master cored boreholes. 11 sequences were observed in the
Upper Miocene basin fill complex of the study area, apart
from the regional erosional unconformity at the base of
the Upper Miocene.

The oldest four sequences were identified in a seismically

observable thickness only in the borehole Kaskantyú Kas-2
and in its surroundings. Its condensed layers were identi-
fied in the borehole Bácsalmás Bá-1 on the basis of
micropaleontological studies (Sütőné Szentai 1982). Se-
quences 5, 6 and 7 are widespread in the study area. Se-
quence 5 is eroded along SB6 near the borehole Kas-2, at
the northern margin of the Kiskunhalas sub-basin. Se-
quences 8 and 10 are well-developed in the eastern and

south-eastern part of the area. According to the cross-sec-
tions, they gradually thin towards the West and North.

In the study area sequence 6 is the most important. It lev-

elled off significant differences in basin topography. It has
a considerable thickness in the majority of the study area,
its lower sequence boundary is a remarkable onlap surface,
and it erosionally truncates sequence 5 in the North.
Sequence 7 displays similar features, however, its thickness
is significant only in the South and south-east.

The time duration of the sequences ranges between 0.3

and 0.8 Myr, older sequences 0.8 to 0.6 Myr, while young-
er sequences were deposited during a shorter period, of 0.3
to 0.4 Myr. Most of the observed sequences are in the
range of the 4

th

-order sequences based on their duration,

thickness and extension. The longer periods may hide un-
differentiated cycles due to condensed sedimentation in
the silty-marly lithofacies.

According to the sequence stratigraphic subdivision, es-

tablished in this work, the basin evolution had two major
phases. The first phase terminates with sequence 4 (the top
is identical with SB5). Despite the total water coverage
(known from dinoflagellate zones), this first phase was
characterized by local sediment accumulation, in which

background image

365

LATE MIOCENE SEQUENCE STRATIGRAPHY OF THE PANNONIAN BASIN (HUNGARY)

sediments were not able to fill the available accommoda-
tion space completely but they were trapped in the Kisku-
halas depression. The second phase of basin development
(sequences 5—10 between 7.8 and 6.6 Ma) was character-
ized by a regional, widespread sedimentation. Moreover,
sequences 1—4 have similar thickness in the basin areas
and above basement highs, which shows a uniform subsid-
ence. On the contrary, sequences younger than sequence 5
are thicker in the depressions. This may reflect to differen-
tial basin subsidence.

The dated sequence boundaries of this work have been

compared to previous results of other authors as well. It is
quite likely, that the hiatus between 5.7 and 6.8 Ma, de-
scribed by Pogácsás et al. (1988) can be identified with
the Pa4 sequence boundary of Vakarcs (1997) at 6.85 Ma
and also with SB6 at 7.4 Ma of this work. Based on the
previously listed evidence and endorsing Vakarcs’s
(1997) classification, this SB can be regarded as a 3

rd

-or-

der one. The hiatus between 7.6 and 7.9 Ma of Pogácsás et
al. (1988) can be identified with the SB4 at 8.2 Ma or SB3
at 8.8 Ma of this work (Fig. 10).

Considering that SB2 (9.7 Ma) and its maximum flood-

ing surface (9.3 Ma) can be followed in an extended area
from Kaskantyú to Bácsalmás, it could be identified with
the Pa3 3

rd

-order sequence boundary at 9.15 Ma of

Vakarcs (1997), despite the age differences. In the study
area this can also be classified as a 3

rd

-order one.

Sacchi followed and dated primarily the maximum

flooding surfaces in his sections. The age of the maxi-
mum flooding surface of sequence 2 in the borehole Kas-2
at 9.3 Ma, and the 7.2 Ma age of the maximum flooding
surface of sequence 6, can be correlated with the MFS
ages of Sacchi & Müller (2004) at 9.075 and 7.455 Ma
respectively.

The extension of the study area, the location of the fully

cored boreholes, the relative scarcity of fossils, and thick-
ness variability of the observed sequences did not allow
further conclusions based on evidence referring to syn-
chronism with the global sequence stratigraphic system.

Acknowledgments: I would like to express my personal
thanks for fruitful discussions to Orsolya Sztanó, my PhD
thesis supervisor. Mária Sütő Szentai and Pál Müller kind-
ly provided their paleontological results. I would like to
thank Imre Magyar, György Pogácsás and Györgyi Juhász
for revising the manuscript. I am also grateful to the Geo-
logical Institute of Hungary and to the Hungarian Scientif-
ic Research Fund (OTKA) T-035168 for financial support.

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