GEOLOGICA CARPATHICA, APRIL 2005, 56, 2, 103112
Geophysical and structural characteristics of the pre-Tertiary
basement of the Mura Depression (SW Pannonian Basin,
Environmental Agency of the Republic of Slovenia, Dunajska 47, SI-1000 Ljubljana, Slovenia; firstname.lastname@example.org
University of Ljubljana, Faculty of Natural Sciences and Engineering, Akerèeva 12, SI-1000 Ljubljana, Slovenia
(Manuscript received January 7, 2004; accepted in revised form June 16, 2004)
Abstract: The Mura Depression is located at the SW border of the Pannonian Basin in the transition zone to the Eastern
Alps. The Periadriatic Lineament, Labot, Ljutomer and Raba faults govern its structural characteristics. Ridges trending
in the NEESWW direction divide the depression into three sub-basins. Therefore, the thickness of Miocene to Quater-
nary sediments varies considerably. The greatest depth to the Paleozoic metamorphic rocks is over 5500 m in the Ptuj-
Ljutomer synform. The structure of the pre-Tertiary basement is well resolved by seismic reflection, gravity and mag-
netic investigations, as well as by drilling for hydrocarbons and thermal water exploration. The main tectonic units of the
Mura Depression were correlated by using geophysical data to the structures outcropping at its western and southern
rims. A compiled structural map of the pre-Tertiary basement is presented and geophysical and structural characteristics
of main geotectonic units discussed. Beside minor production of oil and gas, the Mura Depression is an important
geothermal area. Some locations were also explored as promising for the construction of an underground gas storage
facility in aquifers.
Key words: Pannonian Basin, Mura Depression, seismic reflection, gravity, magnetic, geothermal.
The Mura Depression is one of the deep depressions of the
Pannonian Basin system, and is situated at its SW rim. The
largest part of the Mura Depression is located in NE Slovenia
(Fig. 1), but it also extends into Austria, Hungary and Croatia.
The Mura Depression is not a uniform sedimentary basin, but
is divided into at least three sub-basins, by ridges trending in
the NEESWW direction (Voncina 1965; Kisovar 1977). In
Slovenia, the following tectonic units are distinguished
(Fig. 2), listed from NW to SE: Rdeci breg, Radgona de-
pression, Murska Sobota massif, Ptuj-Ljutomer syn-
form, Ormoz-Selnica antiform.
South-east from the Ormoz-Selnica antiform, the Cakovec
depression is located within the Croatian territory (Mioc &
Markovic 1998). The greatest depth to the pre-Tertiary meta-
morphic basement is over 5500 m, located west of Lendava in
the Ptuj-Ljutomer synform (Plenicar 1970). The Mura Depres-
sion is an important geothermal area (Kralj & Kralj 2000),
while the current production of oil and gas is rather low (Mioc
& Znidarcic 1996). Some localities in the Mura Depression
have potential for the development of an underground storage
facility of natural gas in aquifers. Geophysical investigations
related to this project are described in separate article in Gosar
In this article, an overview of geophysical data available for
the Mura Depression, including gravity, magnetic, geothermal
and seismic reflection data, is given. On the basis of these data
sets and using borehole information, a structural map of the
pre-Tertiary basement is presented. Geophysical and structural
characteristics of the main geotectonic units are described and
their correlation to the structures outcropping west and south
of the Mura Depression is discussed. The interpretation of two
seismic reflection profiles together with gravity and magnetic
profiles from the NW part of the Mura Depression are present-
ed, to put in a regional context a detailed seismic reflection in-
vestigation performed for underground storage of gas in aqui-
fers of the Pecarovci and Dankovci structures located on the
Murska Sobota massif.
Fig. 1. Location map of the Mura Depression. Dark areas out-
crops of the pre-Tertiary basement.
GEOPHYSICAL AND STRUCTURAL CHARACTERISTICS OF THE MURA DEPRESSION 105
The Mura Depression is situated in the transition zone be-
tween the Alps, the Dinarides and the Pannonian Basin. This
results in its quite complex structural pattern (Haas et al.
2000). To the west, the Mura Depression is confined by the
Boc, Pohorje and Kozjak Mountains (Fig. 2) and to the south
by the Donacka gora, Ravna gora, Ivanscica and Kalnik
Mountains in Croatia. To the north and north-east, the border
is represented by outcrops of Paleozoic rocks at Gleichenberg
in Austria and at Közag in Hungary. From the Steiermark de-
pression, towards the NW, it is separated by the structural
height of Burgenland (Kroell et al. 1988) and from the Drava
depression towards the SE, it is separated by the Inka massif.
Separation from the Zala depression in the NE is not so clearly
evident. Therefore, some authors (e.g. Márton et al. 2002)
consider both depressions collectively as the Mura-Zala Basin.
The total area of the Mura Depression is 3300 km
which 2460 km
belongs to Slovenia.
The Mura Depression was formed due to a ENEWSW
trending crustal extension in the late Early Miocene (Márton
et al. 2002). Firstly, marine sedimentation took place. Later,
during thermal subsidence, deltaic and fluvial sediments were
deposited. The main deformation took place in the latest Mi-
ocenePliocene as a result of NNWSSE compression, which
caused folds, reverse and strike-slip faults (Márton et al.
2002). The tectonic background is controlled by major faults,
such as the Periadriatic Lineament, Rába, Labot and Donat
faults (Fodor et al. 2002). The eastern continuation of the Peri-
adriatic Lineament is most probably related to the Ljutomer
fault and the mid-Hungarian line. These tectonic lines separate
areas with different Paleogene and Early Miocene sedimenta-
tion (Sachsenhofer et al. 2001). The Ljutomer fault was
formed in late Early Miocene as a normal fault and was reacti-
vated in post-Miocene times as a reverse fault. It separates the
Ptuj-Ljutomer synform filled with more than 5000 m thick
Neogene sediments from the Ormoz-Selnica antiform (Fig. 2).
Basin inversion, younger than the steep dipping Late Miocene
sediments (Sachsenhofer et al. 2001), and the formation of an-
ticlines is caused by rotation of blocks north of the Ljutomer
fault and by dextral movements along the Labot fault (Fodor
et al. 1998) situated at the SW rim of the Pohorje Mountain.
Pre-Tertiary basement. In the deep boreholes drilled within
the Mura Depression, mainly Paleozoic metamorphic rocks
were found beneath the Tertiary sediments. They outcrop in
the western and southern border of the depression and in Rde-
ci breg. They are composed of quartz-sericite schists, phyllite
and phyllite schists, amphibolites, pyroxenite and gneiss. In
some places, on the top of the metamorphic rocks, Mesozoic
rocks (limestone, dolomite and, also locally, lime marl and
breccia) were found. In some places, their thickness is only
tens of meters, but in others up to several hundred meters.
During Tertiary and Quaternary, the basement was faulted and
thrusted, leaving fractures that were widened in some places
by dissolution (Rajver et al. 2002).
Neogene sediments. In the Mura Depression Miocene clays,
sands, marls, sandstones and conglomerates as well as
Pliocene clayey sediments prevail. Correlation of lithostrati-
graphic and chronostratigraphic units in the Mura Depression
was presented by Znidarcic & Mioc (1989) and for the whole
Pannonian Basin by Horváth & Pogácsas (1988). The Neo-
gene sediments are divided into the Murska Sobota, Lendava
and Mura Formations. The Murska Sobota Formation is up to
2000 m thick and comprises Lower and Middle Miocene
units, including Eggenburgian (M
, average thickness is
400 m), Ottnangian (M
, 300 m), Karpatian (M
, 300 m), Bad-
, 350 m) and Sarmatian (M
, 300 m) stages accord-
ing to Central Paratethys divisions (Steininger et al. 1988).
The Lendava Formation is up to 1500 m thick and consists of
Upper Miocene and possibly Lower Pliocene rocks, including
the Pannonian (M
, 300 m) and Pontian (M
, 650 m)
stages. The youngest Mura Formation is up to 1500 m thick
and corresponds in its entirety to Pliocene rocks of the Dacian
) to Romanian (Pl
) stages (Turk 1993). Upper
Pliocene volcaniclastic sediments and alkali basalts related to
basaltic volcanism in the neighbouring Styrian Basin are
found in the central part of the Radgona depression (Kralj
Quaternary sediments. Quaternary sediments cover the
whole Mura Basin, the Drava-Ptuj Lowland and large areas in
Goricko, Slovenske gorice and Haloze. The Pleistocene cover
is composed of sandy clay with lenses of gravel and sandy
gravel in fluvial terraces. These sediments are up to 35 m
thick. The Holocene layers are composed mainly of marsh
sediments, deluvium, proluvium and alluvium deposits up to
15 m thick.
Gravity, magnetic, geothermal and seismic reflection data
acquired in the Mura Depression during more than 50 years
were compiled from different published and unpublished
sources. Potential filed data were mainly acquired in the
1950s and 1960s and are preserved in the archives of Geoin-
zeniring and Geological Survey of Slovenia in Ljubljana.
The Bouguer anomaly gravity map of the Mura Depression
shown in Fig. 3 was constructed from 3700 points measured
with an average density of 1.5 points/km
using Worden grav-
ity meter (Urh 1956; Plenicar 1970). Bouguer anomalies were
calculated using reference density values between 1.9 and
derived from several profiles using the Nettleton
method. Data were reduced to the datum plane of 150 m a.s.l.
which is very close to the lowest elevation of the surface in the
area. Terrain corrections were computed in a radius of 10 km
using segmentation by concentric circles and radial division
A magnetic map of the Mura Depression (Fig. 4) was ex-
tracted from the regional map of the vertical component of the
magnetic field in Slovenia (Ravnik et al. 1995a). This is based
on the surface magnetic measurements with an average densi-
ty of 2 points/km
using balance magnetometer Ruska and tor-
sion magnetometer Askania (Novak 1959; Miklic 1969).
Therefore, the vertical component of the magnetic field is pre-
sented in the Fig. 4. Normal geomagnetic field was removed
according to Bock (1959) with coefficients extrapolated for
the epoch 1969. Smaller parts of the Mura Depression were
later surveyed for the project of underground gas storage also
with proton precession magnetometer. There was no aeromag-
netic survey performed in this region yet.
The Mura Depression is an important geothermal area char-
acterized by increased heat flow density in comparison to the
other parts of Slovenia. Heat flow density is in the range of 80
to 120 mW/m
(Fig. 5). The highest values were detected be-
tween Lenart, G. Radgona and Murska Sobota within the
Murska Sobota massif and on the SE flank of the Radgona de-
pression (Ravnik et al. 1995b). The most important geother-
mal aquifers are Pliocene and/or Upper Miocene sands within
the Mura Formation. They have an effective maximum thick-
ness of 60 m, dipping from the surface down to the depths of
1500 m (Kralj & Kralj 2000). The thermal waters have tem-
peratures of up to 80 °C. Mineralization (17 g/l) is mainly
dependent on CO
content. Fig. 5 shows the temperature dis-
tribution in the Mura Depression at the depth of 1000 m (Ra-
jver et al. 2002). Temperature gradually increases from the
south-west part of the Mura Depression towards the Murska
Altogether, more than 2000 km of reflection seismic pro-
files (Djurasek 1988; Gosar 1995) have been acquired to date
within the Mura Depression, mainly due to hydrocarbon pros-
Fig. 3. Bouguer anomaly map of the Mura Depression (after Urh 1956). AA indicates cross-section shown in Fig. 6.
pecting. The density of seismic profiles varies considerably.
The densest coverage is close to the Lendava in the SE Mura
Depression, where the oil and gas fields of Petisovci and Doli-
na are still producing, and near Dobrovnik, where the Filovci
field has already been closed. Most of the profiles were re-
corded by Geofizika Zagreb using line explosive sources
(Geoflex and Primacord). The distance between geophone
groups was 3040 m and CMP (common-midpoint) coverage
24 or 30 fold. Some newer profiles were recorded using the
Vibroseis source. Data processing, using standard processing
flow was performed mainly by INA-Naftaplin in Zagreb
Structure of the pre-Tertiary basement
The structural map of the pre-Tertiary basement was con-
structed using the interpretation of seismic reflection profiles
and the data from about 40 exploration boreholes that reached
the basement. In the area NE of the Mura river it is based on
the map drawn by Djurasek (1989), which does not cover oth-
er parts of the depression. This part of the map was also modi-
fied according to newly acquired data and using improved
seismic velocity information from reflection profiling and
measurements in boreholes, which allowed more accurate
time to depth conversion (Gosar 2005). The main tectonic
GEOPHYSICAL AND STRUCTURAL CHARACTERISTICS OF THE MURA DEPRESSION 107
Fig. 4. Map of the vertical component of the magnetic field in the Mura Depression (after Miklic 1969 and Ravnik et al. 1995a). AA
indicates the cross-section shown in Fig. 6.
units of the Mura Depression are shown in the structural map
of the pre-Tertiary basement (Fig. 2), in gravity (Fig. 3), mag-
netic (Fig. 4) and temperature/heat flow density (Fig. 5) maps,
and in a regional cross-section Rdeci breg-Cakovec (Fig. 6).
The topography of the pre-Tertiary basement is well reflect-
ed in the map of Bouguer anomalies (Figs. 3 and 6) which
shows the main structures stretching in a SWNE direction.
Axes of antiform structures correspond fairly well with the
gravity maximums, while there is a discrepancy between the
axes of synform structures (Radgona depression, Ptuj-Lju-
tomer synform) and gravity minimums. The observed shifts
are discussed later. The main tectonic units are not so well re-
flected in a magnetic map (Fig. 4) as in gravity data, especially
in the SE part of the Mura Depression. It seems that lateral
variations in susceptibility or deeper structures have greater
influence on the magnetic anomalies than the topography of
the metamorphic rocks. Since the metamorphic basement was
drilled only in a few boreholes, the boundaries between differ-
ent lithological units are only roughly known. Moreover,
metamorphic rocks are covered with Mesozoic carbonates and
clastic sediments in the Radgona depression, the SE part of the
Ptuj-Ljutomer synform and the Ormoz-Selnica antiform.
Rdeci breg. Outcrops of quartz-sericite schists and phyllite
at the border between Slovenia and Austria are the only out-
crops of the metamorphic rocks inside the Mura Depression.
They are expressed as prominent positive magnetic (+150 nT)
and gravity (+46 mGal) anomalies. The latter continues to the
SW into the Cmurek anticline (+18 mGal). Both are the east-
ward continuation of the Kozjak Metamorphic Complex.
There is a strong fault separating Rdeci breg from the Radgo-
na depression (Poljak 1984). It can be correlated with the
Kungota fault to the SW (Znidarcic & Mioc 1989) and to the
Rába fault, or a fault parallel to it, to the NE, in Hungary.
Radgona depression. The Radgona depression is located
south of the structural height of Burgenland, which separates
the Mura Depression from the Steiermark depression. It is a
continuation of the Ribnica-Selnica tectonic graben located
between the Kozjak and Pohorje Mountains (Znidarcic &
Mioc 1989). The pre-Tertiary bedrock dips in a NE direction
from the depth of 1700 m at Cankova to 4500 m at Dolenci.
The NW slope of the depression towards the Rdeci breg is
quite steep, producing a lateral gravity gradient of 57 mGal/
km. Radgona depression has two closed minimum areas:
+5 mGal between Lenart and G. Radgona and 5 mGal at
Cankova, pointing to two smaller sub-basins. The third mini-
mum to the NE has at Salovci a value of 0 mGal, but continues
further into Hungary. The axis of gravity minimums is shifted
to the SE with respect to the axis of the basement topography
in the depression as is derived from seismic reflection data.
Since only a few boreholes were drilled in the area through the
Mesozoic carbonates and clastic sediments to the metamor-
phic rocks, there is not yet enough data about the lateral extent
of individual lithological units and their densities to give an
explanation for this observation. In the magnetic data the
Radgona depression is expressed in its SW part as elongated
negative anomaly (25 nT). The small circular positive anom-
aly (+75 nT) NW of Mackovci is related to the Upper Pliocene
basalts and basaltic tuffs.
Murska Sobota massif. This structure represents a direct
continuation of the Pohorje Metamorphic Complex below the
Neogene sediments of the Pannonian Basin. It is very clearly
reflected in gravity and magnetic data. At Krog, it is split into
two ridges: the northern one is the Murska Sobota ridge and
the southern the Martjanci ridge. In-between is the Martjanci
gulf. In the SW part of the massif, the depth to the basement
is between 400 and 500 m, while at the Murska Sobota it is in
the range of 11001200 m. The Murska Sobota massif is cut
by several minor faults with maximum displacements of sev-
eral tens of meters. In the gravity map the Murska Sobota mas-
sif is expressed as a clear elongated positive anomaly with two
maximums (+13 and +12 mGal). East of the Murska Sobota
there is a wide plateau (+6 mGal) related to the Martjanci gulf.
On the other hand, in the magnetic map there is a prominent
positive anomaly (+150 nT), which is clearly shifted towards
the SE with respect to the structural height of the Murska So-
bota massif. Since in the NE part of the Murska Sobota massif
all the boreholes were stopped in the Mesozoic carbonates and
clastic sediments overlying the metamorphic rocks, it is not
Fig. 5. Geothermal map of the Mura Depression. Temperatures (°C) at 1000 m depth (after Rajver et al. 2002) and heat flow density
) (after Ravnik et al. 1995b).
possible to make any estimation on lateral lithological varia-
tions in the metamorphic rocks to cause this discrepancy. The
measured susceptibility of the amphibolites, pyroxenite and
gneiss prevailing in the area also cannot explain the relatively
high amplitude of this anomaly. Therefore, it is most probably
that it is caused by a deeper unknown structure comprised of
metamorphic rocks with higher susceptibility. Within the
Murska Sobota massif the highest values (70 °C) of tempera-
ture at 1000 m depth in the whole Mura Depression were mea-
sured near Murska Sobota and between Lenart and Radenci.
At the same time this is the area of highest heat flow density
). Within the Murska Sobota massif, two struc-
tures (Pecarovci and Dankovci) having potential for under-
ground storage of gas in aquifers were also explored (Gosar
Ptuj-Ljutomer synform. This is the deepest sub-basin of the
Mura Depression, which continues into the Zala depression in
Hungary. It is separated from the Ormoz-Selnica antiform by
the prominent Ljutomer fault. Gravity measurements covered
only the NE part of the Ptuj-Ljutomer synform, but there is a
clear shift of the gravity minimum observed between Ljutomer
and Beltinci (5 mGal) towards the NW with respect to the
deepest part of this synform (5500 m) located between Lju-
tomer and Mostje. In the area between Ljutomer, Mostje and
Lendava the metamorphic rocks are covered with Mesozoic
carbonates and clastic rocks. On the other hand, between Bel-
GEOPHYSICAL AND STRUCTURAL CHARACTERISTICS OF THE MURA DEPRESSION 109
Fig. 6. Regional cross-section across the Mura Depression showing the topography of the pre-Tertiary basement, gravity and magnetic
tinci, Dobrovnik and Domanjsevci there are amphibolites and
pyroxenites laying directly under the Neogene sediments. The
variation of lithology and density of the pre-Tertiary basement
is therefore not sufficiently known to explain the observed
shift of the gravity minimum, which can be caused also by
deeper structures. In spite of the fact that the strong positive
magnetic anomaly (+150 nT) is also shifted from the Murska
Sobota massif towards the Ptuj-Ljutomer synform, there is a
clear minimum in the magnetic anomaly (25 nT) related to
the deepest part of the Ptuj-Ljutomer synform. Quite low tem-
peratures (40 °C) were encountered in the transition zone be-
tween the Murska Sobota massif and the Ptuj-Ljutomer syn-
form near Beltinci and Dobrovnik.
Ormoz-Selnica antiform. This structure is strongly de-
formed in longitudinal and transversal directions and confined
by the Ljutomer and Selnica faults. In the gravity data, the Or-
moz-Selnica antiform is expressed as a strong positive anoma-
ly (+20 mGal) which diminishes towards the NE. This is in
agreement with the dipping of the bedrock from 2500 m in the
central part of the antiform to the depth of 4000 m on the bor-
der with Hungary. Gravity data show that the northern limb of
the structure towards the Ptuj-Ljutomer synform is steeper
than the southern limb dipping towards the Cakovec depres-
sion. Only the small part of the Ormoz-Selnica antiform which
belongs to Slovenia is covered by the magnetic data. The max-
imum value of the magnetic anomaly is +75 nT. In the NE part
of this unit, there are oil and gas fields at Petisovci and Dolina.
These are the single hydrocarbon accumulations in the Mura
Depression, which are still in production.
Interpretation of two regional seismic reflection
In the next section, the interpretation of two regional seis-
mic reflection profiles recorded in the NW part of the Mura
Depression is presented, together with gravity and magnetic
profiles, and correlated with the profile recorded approximate-
ly 20 km to the NE, within the Zala Basin situated in Hungary.
The seismic reflection profiles, Dan-3-90 and Pec-2-90
(Fig. 7), are located in a NWSE direction 4 km apart, across
three tectonic units which spread in a SWNE direction: Rdeci
breg, the Radgona depression and the Murska Sobota massif
(Fig. 2). The profiles are 15 and 14 km long respectively. The
basic structural characteristics of both profiles are similar. In
the NW, the pre-Tertiary metamorphic bedrock is approaching
Fig. 7. The line drawing interpretation of two regional seismic profiles, Dan-3-90 (a) and Pec-2-90 (b), with gravity and magnetic profiles.
The KB horizon corresponds to the boundary between the Badenian and Sarmatian sediments and the Pt horizon to the pre-Tertiary bedrock.
Mz Mesozoic, M4 Badenian, M5 Sarmatian, M6 Pannonian, M7 Pontian, Pl Pliocene.
the surface, as it is outcropping in the continuation of the Pec-
2-90 profile within the Rdeci breg. In the transition zone be-
tween the Rdeci breg and the Radgona depression, there is a
stronger unnamed fault, which can be correlated to the Kungo-
ta fault to the SW and to the Rába fault, or a fault parallel to it,
to the NE, in Hungary. It should be stressed however, that the
appearance of this fault is different in both profiles considered.
In the Dan-3-90 profile, there are two parallel normal faults
GEOPHYSICAL AND STRUCTURAL CHARACTERISTICS OF THE MURA DEPRESSION 111
clearly displacing the pre-Tertiary basement (Pt horizon), but
without visible displacement of Neogene sediments. In the
Pec-2-90 profile, a single listric normal fault is interpreted in
the basement, which also cuts the KB horizon (discordant top
boundary of Badenian layers) and Middle Miocene strata. It
is accompanied by a clear antithetic fault. In the maps present-
ed by Djurasek (1989) and Poljak (2000), this fault is shown
as a normal fault. Rumpler & Horváth (1988) have interpreted
more faults related to the regional Rába fault in the profile Zi-
108 from the Zala Basin. According to their interpretation, this
fault expresses oblique displacement but it has a much greater
strike slip component than a dip-slip component. On the other
hand, Znidarcic & Mioc (1989) suppose for the Kungota fault
(SW continuation of this fault system in the Slovenske gorice)
a reverse character. Despite incomplete information about the
lithology on both sides of the fault in the Mura Depression, a
strike-slip fault with an important dip-slip component seems
to be more realistic.
The maximum depth to the pre-Tertiary basement within the
Radgona depression is on the Dan-3-90 profile around 2800 m
and on the Pec-2-90 profile around 2500 m. From the deepest
point, towards the SE, the basement gradually rises towards
the Murska Sobota ridge, which is the northern branch of the
Murska Sobota massif. In this area, two structures (Pecarovci
and Dankovci) were investigated for possible underground
storage of gas in aquifers. Two boreholes, Pec-1 and Dan-1,
were drilled in this area down to the pre-Tertiary basement and
one, Dan-3, down to the KB horizon. The metamorphic rocks
are here overlaid by layer of Mesozoic carbonates up to 100 m
a thick. On the SE side of both structures, a normal fault with a
minor dip-slip was interpreted in both seismic profiles. A
more detailed image of the faults in this area was obtained by
extensive reflection profiling carried out for the project related
to underground gas storage (Gosar 2005). A smaller sub-basin
is located in the SE part of the Dan-3-90 profile. The depth to
the pre-Tertiary basement at its SE termination is calibrated by
the Mt-3 borehole. The topography of the pre-Tertiary base-
ment is also well reflected in the gravity anomalies (Fig. 7),
while magnetic profiles seem to be more sensitive to lateral
variations in the magnetic susceptibilities of metamorphic
rocks, but a clear correlation with the basement topography is
Tectonic and kinematic characteristics of the
The structural characteristics of the Mura Depression de-
rived from geophysical data and presented in this paper can be
related to the results of structural-geological investigations in
the border areas and to the larger structural context of the SW
part of the Pannonian Basin (Royden et al. 1983; Horváth
1993). According to these studies the Mura Depression was
formed due to the ENEWSW trending crustal extension in
the late Early Miocene. The main deformation took place in
the latest MiocenePliocene as a result of NNWSSE com-
pression, which formed folds, reverse and strike-slip faults
(Márton et al. 2002). The formation of anticlines separating
the Mura Depression into more sub-basins is caused by the ro-
tation of blocks north of the Ljutomer fault and by dextral
movements along the Labot fault situated SW of the Pohorje
Mountain (Fodor et al. 1998).
Rumpler & Horváth (1988) have provided analysis of a re-
gional stress field based on the structural interpretation of se-
lected reflection seismic profiles from the Pannonian Basin.
According to their analysis, the tectonic activity culminated in
the Middle Miocene, but locally minor activities have contin-
ued until recent times. For the most of the transition zone be-
tween the Alps, the Dinarides and the Pannonian Basin, two
sets of conjugate strike-slip faults are characteristic: NESW
strike faults are left-lateral and NWSE strike faults are right-
lateral. Areas of extension and normal faulting are associated
with discontinuous or divergent strike-slip faults and with
fragmentation in zones bounded by two major strike-slip
faults. Locally thrust faults and folds are also present. In the
Mura Depression, a similar tectonic style is observed, gov-
erned by the main regional faults which are: Periadriatic Lin-
eament, Rába, Labot and Donat faults. The development of
compressional and extensional structures occurred at about the
same time. Rumpler & Horváth (1988) think that separate pe-
riods characterized by contrasting styles of deformation can-
not be distinguished in the Pannonian Basin for the period be-
tween the Miocene and Quaternary. In spite of the fact that
some temporal variations in the stress field may have oc-
curred, the spatial variation seems to have been more impor-
tant. Analysis of geophysical data and the structural character-
istics of the Mura Depression has shown that this is also valid
for this depression located at the junction between the Eastern
Alps and the Pannonian Basin.
The structure of the Mura Depression was analysed on the
basis of the compilation of older gravity and magnetic data
and newer seismic reflection, borehole and geothermal data.
The presented structural map of the pre-Tertiary basement is
constructed from the interpretation of seismic reflection pro-
files using new seismic velocity information and data from
boreholes. In the major part of the depression the correlation
of this map with potential filed data is rather good, but in some
parts there are important discrepancies between the topogra-
phy of the basement and gravity or magnetic anomalies. Since
in the areas under discussion only a few boreholes have
reached the metamorphic basement, covered mainly by Meso-
zoic carbonates and clastic sediments, in general it was not
possible to explain the source of observed shifts. The strongest
positive magnetic anomaly (+150 nT) in the depression, ob-
served between Beltinci, Murska Sobota and Dobrovnik,
which is shifted with respect to the structural height of the
Murska Sobota massif, is most probably caused by a deeper
structure. Gravity and magnetic modelling can give some ad-
ditional insight into these questions, but in-situ data on the
density and magnetic susceptibility of the metamorphic rocks
from the basement is too sparse for reliable conclusions. Nev-
ertheless, it was possible to correlate the established structures
with the outcrops of the metamorphic complexes to the west
of the Mura Depression.
The interpretation of two regional seismic reflection profiles
measured from the Rdeci breg, across the Radgona Depression
to the Murska Sobota massif has shown that also the interpre-
tation of major faults in the Mura Depression cannot always
be unique. Two alternative interpretations of the strong fault
in the transition zone between Rdeci breg and the Radgona de-
pression, which can be related to the Rába fault towards the
NE and to the Kungota fault towards the SW, are therefore
The presented structural characteristics based on the geo-
physical data are in agreement with the results of structural-
geologic investigations in the border areas and with the struc-
tural context of the SW part of the Pannonian Basin. A more
detailed seismic reflection investigation performed for under-
ground storage of gas in aquifers of the Pecarovci and Dank-
ovci structures located on the Murska Sobota massif is pre-
sented in a separate article in Gosar (2005).
Acknowledgments: The author is grateful to M. Bielik, P.
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