GEOLOGICA CARPATHICA, 53, 4, BRATISLAVA, AUGUST 2002
NEO-ALPINE LINEAR DENSITY BOUNDARIES (FAULTS)
DETECTED BY GRAVIMETRY
, MICHAL KOVÁČ
, IVAN KUČERA
, PAVOL MICHALÍK
and JOZEF HÓK
Geophysical Institute of the Slovak Academy of Sciences, Dúbravská cesta 9, 842 28 Bratislava, Slovak Republic; firstname.lastname@example.org
Department of Geology and Paleontology, Faculty of Science, Comenius University, Mlynská dolina G, 842 15 Bratislava, Slovak Republic
Relix Ltd., Staré grunty 61, 841 04 Bratislava, Slovak Republic
EQUIS, Ltd., 831 02 Bratislava, Slovak Republic
State Geological Institute of Dionýz Štúr, Mlynská dolina 1, 817 04 Bratislava, Slovak Republic
(Manuscript received July 24, 2001; accepted in revised form December 13, 2001)
Abstract: The use of gravimetry, as one of the geophysical methods for identification of brittle deformations – faults
active during the neo-Alpine development of the Western Carpathians, confirmed its role in research of the orogene
geodynamic evolution. The study of several sites in the western part of the Western Carpathians documents the fact, that
the maps obtained by means of different effective gravimetric methods of transformations and visualization of gravity
(potential field) data can be correlated well with the age, and thus also with the depth of the faults. The map of the total
Bouguer gravity anomaly displays faults without distinguishing their age and depth. In such case the use of the Linsser
method is proper for the detection of faults or density boundaries. While the derived maps, such as the vertical and
horizontal gradients, and the residual anomaly maps, document the faults depending on the type of transformation and
visualization of the input computation parameters. The results and interpretation indicate, that the map of residual anomalies
displays mainly the deep faults of the initial rifting and of the synrift stage of the back-arc basin development and the
map of the vertical gradient displays most of all the young shallow marginal faults and faults linked with the postrift
thermal subsidence stage and tectonic inversion of the basin.
Key words: neo-Alpine tectonics, Western Carpathians, brittle deformations, linear density boundaries, gravimetry.
Gravimetry can be used, in an applied form, for investigation
of the geological pattern of the region, which means also for
detecting the brittle tectonic deformations – faults (e.g. Lins-
ser 1967a,b; Nettleton 1971; Garland 1979; Griffiths & King
1981; Fusán et al. 1987; Šefara et al. 1987; Murata & Noro
1994; Langenheim 1995; Wybraniec 1999; Nemesi et al.
The gravity gradients most often separate the boundaries of
units, which vary in petrographic and/or density, and are the
major indicators of tectonics on a gravimetric map. Their in-
tensity is proportional to the density difference, the amplitude
of the step, and the slope of the fault. For practical application,
the density boundary (fault) is approximated by a simple geo-
metric body (two-dimensional), the dimension of which along
the fault is infinite (Nettleton 1971; Linsser 1967a,b; Pick et
al. 1973; Griffiths & King 1981).
The principle of the method lies in calculation of the gradi-
ent function based on taking the derivative of the measured
gravity data (V
) either with respect to the x and y axes (hori-
zontal gradient – V
(HG)), or the z axis (vertical gra-
dient – V
(VG)). The derivatives may be calculated by fi-
nite differences. The resulting maps are portrayed either in
positions of the inflex points (by localizing the maxima of the
amplitude of the gravity field gradient) or by isolines of the
gradient moduli (Parasnis 1967; Pick et al. 1973; Lillie 1999;
The main goal of this study is to test the use of gravimetry as
one of the geophysical methods for investigation of the neotec-
tonics in the western part of the Western Carpathians (Fig. 1).
Fig. 1. Schematic tectonic map of the Eastern Alpine—Western
Carpathian—Pannonian basin region (modified after Lillie et al.
1994). The studied area is shown by a frame.
And Alpine Flysch
C a r
236 BIELIK et al.
That is also why we will deal only with those gravity field in-
terpretation methods, that can contribute most to the indication
of linear structures of the gravity field. In this paper, effective
mapping methods of gravity data are described. The total Bou-
guer gravity anomaly map in combination with its transformed
and visualized gravity data help us to understand the interde-
pendent nature of the relationships of geological phenomena
(Meskó 1985; Šefara 1989; Bielik 1982).
The total Bouguer gravity anomaly is a superposition of the
gravity effects of all the density inhomogeneities that are
present under the surface of the studied region. The effect of
inhomogeneities depends on their size, differential density,
and the distance from the observation point (e.g. Torge 1989).
In practice it often happens that the gravity effect of the anom-
alous body under our interest (here – the linear density
boundary – fault) is partly or totally concealed by effects of
other anomalous masses. This implies that the quality of the
interpretation substantially depends on the quality of separat-
ing the gravity effect of the investigated fault from the Bougu-
er gravity anomalies. Generally, the anomaly may be divided
at each point into two components: the regional and the residu-
al. The regional (residual) component of the gravity is charac-
terized by long-wavelength (short-wavelength) anomalies.
Linear form of the Bouguer gravity anomaly (density bound-
ary) produces a couple of positive/negative residual anomalies
and the density boundary is going between them.
In gravimetry, the transformed maps (the derived or convo-
lution maps) differ from the original maps of total Bouguer
gravity anomalies by having the components of the original
field, that concern us, pronounced (e.g. Ku et al. 1971; Meskó
1985; Pick et al. 1973; Šefara et al. 1987; Bielik 1982; Blakely
1996). Any transformation cannot bring a basically new infor-
mation, it may, however, somehow extract and amplify what is
already contained within the original map.
The use of the transformation method depends mainly on
whether we deal with a shallow fault or a deep fault. When
searching for shallow (deep-seated) faults, the interpreter must
apply such transformation method, which pronounces the
anomalies with short (long) wavelengths. The residual anoma-
ly at the point of calculation was defined as the mean value of
the anomaly on the surface of a circle (Griffin 1949; Pick et al.
1973). Digitization of gravity data for all transformed maps
were performed in a grid of 200 m. When the radius for com-
puting the mean is chosen suitably, it is possible, on the basis
of the character of the anomalies of the gravity field of the
transformed map, to find out at least indirectly, whether we are
dealing with a shallow or a deep fault structure, and to esti-
mate its depth.
The Linsser method (Linsser 1967a,b) has also been used
for indicating the density boundaries. It is based on filtering
the anomalous field by means of a comparison of a pre-deter-
mined theoretical anomalous effect of a certain model in the
measured gravity field (Šefara 1973, 1989). When solving the
directional characteristics of the anomalous gravity field, we
follow a model of the vertical density boundary (massive half-
space), which appears the most suitable for approximating lin-
ear geological structures. The defined indications of the verti-
cal density boundaries are the output data. If these indications
fall into certain lines, we can essentially interpret them as the
vertical, or slanted density boundary of a linear shape – fault.
If these indications on the maps are non-linear, then they fea-
ture more probably the presence of three-dimensional bodies.
The maps of the vertical or horizontal gradient represent
a significant group of transformed maps suitable for solving
the structural-tectonic relationships. In the vertical gradient
(VG) maps we find a pair of bands of opposite sign values
over the sub-vertical density boundaries. The excess masses
feature negative anomalies in the VG while the masses defi-
cient feature positive VG anomalies, (opposite to the input of
the total Bouguer gravity anomaly map). The vertical gradient
of the total Bouguer gravity anomaly is generally sensitive to
shallower density inhomogeneities, compared to the horizontal
gradient. The paths of the signatures of tectonics need be
drawn on the boundary separating positive and negative anom-
aly bands. The VG responds to the density fill of the shallow
volumes with anomalies of signs opposite to those of the input
total Bouguer gravity anomaly map or the local anomaly map.
The maps of the horizontal gradient (HG) normally have
maxima over the subvertical density boundaries, which origi-
nate, for instance, above the margins of sedimentary basins or
above contacts of intrusive bodies (suppose these are not hori-
zontal), as well as above fault systems, along which blocks
with varied density evolution were trapped next to each other
as a result of tectonic movements. The shape of the gravita-
tional effects of such density boundaries implies that the abili-
ty of the HG to respond to such effect must be high for various
depth ratios of the boundaries. The boundaries may (or may
not) be visible already on the surface of the earth and may (or
may not) continue to great depths exceeding the radius of the
analysed area of the computation point. Usually the HG maxi-
ma arrange themselves on the map into bands. The paths of
such bands are identical with the paths of centres of surfaces
of the subvertical density boundaries. The minima on the HG
maps represent blocks, in which the density changes are pre-
sented only in a vertical direction, if at all.
Detection of linear density boundaries
The suitability of the individual interpretation methods was
reviewed on a gravimetric and database file from the area of
western Slovakia, namely at the eastern margin of the Vienna
Basin, Malé Karpaty Mts horst, in the Danube Basin, the
Považský Inovec Mts and the Tribeč Mts horsts (Fig. 2). For
detecting the regionally significant fault systems we have used
the map scale 1:500,000 (Fig. 2). To verify the details of the
geological pattern of the area of the Zohor-Plavec Trough that
is superposed over the system of the Leitha faults (Fig. 2) and
in the area of the Považie fault system (Figs. 3, 4) we have
originally used the map scale of 1:100,000.
NEO-ALPINE LINEAR DENSITY BOUNDARIES 237
Linear density inhomogeneities indicated by various types
of regional gravimetric maps
Map of total Bouguer gravity anomalies
The figure 3A documents the distribution of the linear gravi-
ty elements, as well as of the low-density and high-density
masses in the western part of the Western Carpathians. The
NE-SW trending eastern margin of the Vienna Basin is particu-
larly pronounced at the boundary with the Malé Karpaty Mts
horst, as are the boundaries of the Malé Karpaty Mts horst and
the Považský Inovec Mts horst against the Danube Basin. The
ENE-WSW oriented margin of the southern and northern
boundary of the Blatné Depression of Danube Basin (transver-
sal Cífer fault and the Kátlovce fault, of the same direction as
the Brezová and Dobrá Voda fault system), as well as the fault
system at the boundary between the Rišňovce Depression of
the Danube Basin and the Bánovce Depression are also appar-
Fig. 2. The main structural and tectonic features of the western part of the Western Carpathians. The background of the figure is a scheme
of the residual gravity map (R = 12,000 m with a grid of 200 m). Red colour represents positive values of gravity anomalies. Blue repre-
sents negative values.
238 BIELIK et al.
NEO-ALPINE LINEAR DENSITY BOUNDARIES 239
ent (Fig. 2). The picture of the southern part of the territory
documents the presence of high-density masses in the Koláro-
vo anomaly area, whereby the effect of the Transdanubian
Range Unit is pronounced only to the east of Komárno (the
Komárno block sensu Hrušecký 1999).
Map of indications of vertical density boundaries – Linsser
This map (Fig. 3A) well documents the deep and the shal-
low boundaries, the linear course of which entitles us to inter-
pret them as neo-Alpine brittle deformations – faults. The
fault boundary of the Malé Karpaty Mts horst with respect to
the Vienna Basin (the Leitha fault system) and the Blatné De-
pression of the Danube Basin (the Malé Karpaty fault) are eas-
ily observable. Next, the Považie and Ripňany faults are clear-
ly visible and mark the eastern and western slopes of the
Považský Inovec Mts horst. In the western part of the Gabčík-
ovo Depression, the NNE-SSW oriented systems of Cífer
faults dipping towards the west are particularly pronounced, as
well as the Galanta faults dipping towards the east and they
represent margins of the Ú any elevation (sensu Hrušecký
1999). Towards the south, in the Hungarian part of the basin,
we assume a connection to the Mihályi elevation which is
bounded by the Répce fault system (sensu Tari et al. 1992).
The Tribeč Mts horst boundary is also well documented, by
the Ve ké Zálužany fault system in the west and by the
Mojmírovce fault system in the east (Fig. 2). The Komjatice
Depression boundary is formed by the Mojmírovce faults in
the north-east and by the Šurany fault system in the south-east,
in the continuation of which the Kolárovo faults are located in
the Gabčíkovo Depression, with the same NW dip (Hók &
Ivanička 1996). The picture of the eastern part of the Danube
Basin is unclear. In the prolongation of the Ács-Komárno fault
system, there are faults limiting the eastern margin of the
Kolárovo—Pozba horst of the NE—SW direction (Hrušecký
1999). The Hurbanovo fault, or the northern margin of the
Transdanubian Range Unit are only partly visible.
Map of residual anomalies
The residual anomaly map with the radius of taking the
mean 4 km (Fig. 3B) documents the deep fault boundary of the
eastern margin of the Vienna Basin with respect to the Malé
Karpaty Mts horst, characterizing the boundary between the
Eastern Alpine and Western Carpathian units along the left-
lateral shear zone – the Leitha fault system (sensu Marko &
Next we easily trace the pronounced boundary at the eastern
slopes of the core mountains horsts: Malé Karpaty Mts,
Považský Inovec Mts and Tribeč Mts (Malé Karpaty,
Rišňovce and Mojmírovce fault systems). Unpronounced are
the fault systems in the basement below the Danube Basin fill.
The elevation structures of the Ú any and Kolárovo-Pozba
(Hrušecký 1999) are indicated only partly, like as the Trans-
danubian Range Unit in the eastern part of the basin. One
could conclude, that the map pronounces the deep-seated Neo-
gene faults at the eastern slopes of the core mountains com-
pensating the movement along the listric décollement at the
boundary of the rigid and ductile part of the crust during the
Danube Basin opening (the Wernike’s model used for the for-
mation of the Danube Basin sensu Horváth 1993; Lankreijer et
al. 1995). The prolongation of these faults in the central part of
the basin is indistinguishable, clearly due to the disturbing ef-
fect of the sedimentary fill of the Danube Basin, which reach-
es thickness of up to 8 km (Kilényi & Šefara 1989).
Map of vertical gradients
On the map of vertical gradients with a mean radius of 3 km
(Fig. 3C) there are linear inhomogeneities – faults indicated
by the contact of negative and positive anomalies. On the map,
the boundary at the eastern margin of the Vienna Basin is dem-
onstrated with a pronounced signature of the Leitha faults in
the area of the Zohor—Plavec graben at the western margin of
the Malé Karpaty Mts horst. The next very pronounced con-
tact represents the fault boundary of the western margin of the
Považský Inovec Mts horst (Považie faults) and the western
margin of the Tribeč Mts horst (Ve ké Zálužany fault). The
Malé Karpaty and Ripňany fault system at the eastern margin
of the core mountains is less clearly (Fig. 2).
On the other hand, the NW—SE oriented linear elements of
the same intensity multiply; these can be interpreted as
a documentation of structural deformations (faults, flexures)
known only in the youngest sediments of the Danube Basin
(Hók et al. 1999). The projection of the margin of the Trans-
danubian Range Unit onto the surface is apparent with the
same intensity in the area of the Hurbanovo fault zone. If the
map of the residual anomalies is compared with the map of the
vertical gradient, it seems that the vertical gradient documents
much better the younger and shallower faults and structural
deformations (flexures due to compaction of sediments of var-
ious grain size) in the sedimentary fill of the Vienna and
Danube Basins in Slovak territory, that is the tectonics of the
Upper Miocene to Pliocene-Pleistocene age.
Map of the horizontal gradient
The horizontal gradient map (Fig. 3D), as was already noted
in the methodology, contains mainly the maxima above the ap-
pearances of subvertical density boundaries situated near the
margins of sedimentary basins in the western part of the West-
ern Carpathians. The map ignores the depth reached by faults
(and thus indirectly also their age and causes). All faults on the
peripheries of the core mountains are clearly visible: the Lei-
tha, the Malé Karpaty, the Považie, the Rišňovce, the Ve ké
Zalužany and the Mojmírovce fault systems separating the
partial depocentres of the Danube Basin: the Blatná, the
Rišňovce, and the Komjatice depression (Vass et al. 1990; Hók
et al. 1999). The interesting elements include the N-S running
of subvertical boundaries (depressions) in the central part of
the basin that can be compared to the direction of the Cífer
and Galanta faults, and the boundary of NE—SW direction
comparable with the Čertovica-Mojmírovce fault system
240 BIELIK et al.
Linear density inhomogeneities indicated by various types
of local gravimetric maps
The Zohor-Plavec graben area
As on the regional gravimetric maps (Fig. 3A—D), the sig-
nificant element on the detailed (local) gravimetric maps is the
Leitha faults of NE-SW direction (Fig. 4A—C). On the map of
indications of density boundaries – Linsser (Fig. 4C), as well
as on the residual anomaly map (Fig. 4A), however, we also
find the crosswise physical boundaries interpreted as older
faults of the NW-SE direction activated during the early neo-
tectonic stage of development of the studied region. The inter-
esting elements also include the boundaries located in the up-
Fig. 4. Local gravimetric maps in the Zohor-Plavec graben area
A – map of residual anomalies (R = 2000 m with a grid of 200 m,
the values of gravity anomalies vary from —1.4 to +1.6 mGal, a
step of isolines is 0.2 mGal), B – map of vertical gradient (R =
2000 m with a grid of 200 m, the values of gravity anomalies
vary from —1200 to +2500 E, the step of isolines is 200 E), C –
map of indications of vertical density boundaries [Linsser, h =
1000 m and
= 100 kg.m
; the grid of gravity values is 200 m,
size of marks is in accordance with the size of parameters E and C
defined by Linsser (1967a,b) and Šefara (1973)]. The background
of the map is the map of total Bouguer gravity anomalies (after Še-
fara et al. 1987, the values of gravity anomalies vary from —33 to
+24 mGal, the step of isolines is 3 mGal).
NEO-ALPINE LINEAR DENSITY BOUNDARIES 241
per left half of the figure, probably representing the structural
pattern (folds) of the Northern Calcareous Alp nappes in the
pre-Neogene basement of the Vienna Basin (Fig. 4C). The re-
sidual anomaly map (Fig. 4A) best documents the tectonic
components within the graben (division into partial depres-
sions), whereas the vertical gradient map (Fig. 4B) indicates,
the presence of young tectonic structures with an ENE-WSW
direction, as well as the presence of the NE-SW faults.
The Považie fault system
The dominant elements on the local gravimetric maps (Fig.
5A—C) are the inhomogeneties in the N-S and NNE-SSW di-
rection (the Považie fault). These inhomogeneities – faults
are accompanied also by faults of the NW-SE to ENE-WSW
direction. The most pronounced is the Koplotovce fault, which
is located in the continuation of the Kátlovce fault system.
Since, apart from the presence of the NNE-SSW faults, the
vertical gradient map (Fig. 5A—B) also indicates, the presence
of structures with the ENE-WSW direction, clearly visible on
the map of density boundary indications – Linsser (Fig. 5C),
we consider that they are associated with the Pliocene-Quater-
Neo-Alpine development of the Western Carpathians
as indicated by means of different transformed gravity
maps – a discussion
The neo-Alpine development of the Western Carpathians
and the adjacent part of the Pannonian back arc basin is char-
acterized by several stages of development:
A – In the Early Miocene the oblique collision of the West-
ern Carpathian orogen with the Bohemian Massif played the
key role. The compression initiated the northward movement
of the ALCAPA microplate (ALCAPA – Alpine-Carpathian-
Pannonian block assemblage) eastern segment and caused
fold—nappe tectonics with formed the accretionary prism of the
Outer Carpathians. Dextral shears with an ENE—WSW direc-
tion were activated in the same stress field. In the area of the
Fig. 5. Local gravimetric maps in the Považie fault system region. A – map of residual gravity anomalies (R = 2000 m with a grid of 200 m,
the values of gravity anomalies vary from —1.4 to +3 mGal, the step of isolines is 0.3 mGal), B – map of vertical gradient (R = 2000 m with
a grid of 200 m, the values of gravity anomalies vary from —3400 to +6000 E, the step of isolines is 600 E), C – map of indications of verti-
cal density boundaries [Linsser, h = 1000 m and
= 100 kg.m
; the grid of gravity values is 200 m, size of marks is in accordance with
the size of parameters E and C defined by Linsser (1967a,b) and Šefara (1973)]. The background of the map is the map of total Bouguer
gravity anomalies (after Šefara et al. 1987, the values of gravity anomalies vary from —6 to +21 mGal, the step of isolines is 3 mGal).
242 BIELIK et al.
Central Western Carpathians, they led to opening of sedimenta-
ry basins of wrench fault furrow type (Kováč et al. 1989; Kováč
& Márton 1998; Kováč et al. 1997, 1998). These tectonic struc-
tures can be compared with the oldest detected linear density in-
homogeneities – faults in the studied area (the Brezová and
Dobrá Voda, Kátlovce and the transversal Cífer fault systems),
the activity of which is assumed from the Eggenburgian to Kar-
patian. They are manifested in the total Bouguer gravity anoma-
ly map, in the vertical density boundary map – Linsser and par-
tially in the residual anomaly map (Figs. 2, 3).
B – At the end of the Early and beginning of the Middle
Miocene the ALCAPA microplate extruded eastward (Ratsch-
bacher et al. 1991a,b). The disintegration of the microplate
was accompanied by the separation of the Western Carpathian
units moving in the NE direction from the Alpine units. The
zone of the Leitha faults at the eastern margin of the present
Vienna Basin is regarded as the boundary between the units of
the Eastern Alps and Western Carpathians. The extrusion was
accompanied by initial rifting, mostly by opening of pull-apart
type depocentres in the Vienna Basin and in the Blatné De-
pression of the Danube Basin (Royden 1993; Fodor 1995;
Lankreijer et al. 1995; Kováč et al. 1997; Hrušecký 1999).
The area of the left lateral shears (transform system of the
Leitha faults) makes up for a pronounced physical boundary
between the Eastern Alpine and Western Carpathian units,
which is well documented by all gravimetric maps. Its amplifi-
cation in the vertical gradient map indicates at the same time
its recent activity documented also by other geological and
geophysical methods (Gutdeutsch & Aric 1988; Hók et al.
2000). It is well known, that here we are dealing with one of
the most pronounced geophysical anomalous zones – discon-
tinuities in the crust of the Western Carpathians (Labák &
Brouček 1996; Šefara et al. 1998; Hók et al. 2000).
C – In the Middle Miocene a large back-arc extension took
place, which is manifested by a synrift stage of the Vienna and
Danube Basins development (Lankreijer et. al. 1995; Lankreijer
1998; Kováč 2000). On the basis of the seismic picture, in the
Slovak part of the Danube Basin (Hrušecký 1999), as in its Hun-
garian part (Tari et al. 1992; Horváth 1993) the core mountain
blocks tilting mechanism is applied above a deep zone of de-
tachment (Wernicke’s model of simple shear (Wernicke 1985;
Lankreijer 1998)). We regard the brittle deformations at the
eastern margin of the core mountains as the main normal faults,
their respective pair systems being the faults at the western
boundary of the Považský Inovec Mts horst, the Ú any elevation
and the Tribeč Mts horst. These, however, do not have such
a deep reach into the pre-Neogene basement.
The linear structures of the gravity field – identical with
the course of the main faults of the synrift stage in the studied
region are the Malé Karpaty, the Ripňany and Galanta faults,
and the Mojmírovce faults systems. Their effect is clearly visi-
ble in the residual anomaly map, where, however, the prolon-
gation of the Ripňany faults into the Galanta fault system is
not manifested, because the Galanta fault system is covered by
the very thick fill of the Danube Basin, as in the case of the
prolongation of the Mojmírovce fault system into the Koláro-
vo system (Figs. 2, 3).
D – During the Late Miocene to Pliocene, in period of the
postrift thermal subsidence the function of faults was pro-
nounced at the margins of the rising core mountains (generally
of NNE-SSW to NE—SW directions). In the Pliocene to Qua-
ternary, the period of tectonic inversion of the back-arc basin
(Horváth 1993; Bada 1999) a new group of tectonic structures
entered the game. These fault’s are limited to the Pliocene—
Quarternary sedimentary area of the Slovak part of the Danube
Basin (flexures, shallow faults). The Pliocene and the Early
Pleistocene stress field can be characterized by extension in
the NW—SE direction. Following the Early Pleistocene an ex-
tension of the NE—SW direction takes place (Hók et al. 2000;
Kováč et al. in press).
The pronounced activity of faults at the margins of the core
mountains is well documented by the horizontal gradient map
(Fig. 3D). On the contrary, the vertical gradient map (Fig. 3C)
pronounces faults that were active in the Pliocene-Quarternary
period. The function of these faults is significantly manifested
at the western margin of the core mountains (the Leitha, In-
ovec, Ve ké Zálužie faults).
Gravimetric methods can be used effectively to indicate lin-
ear density boundaries, which can be interpreted as rigid defor-
mations – faults of the neo-Alpine period of orogen forma-
tion (complemented by other geophysical and geological
The map of indications of vertical density boundaries –
Linsser, and the horizontal gradient map (Fig. 3A) pronounces
all fault boundaries independently of age and depth. Its advan-
tage is that it also documents the faults that are covered by
a thick sedimentary fill of the Neogene basins.
The residual anomaly map (Fig. 3B) pronounces the Neo-
gene (Miocene) faults reaching greater depths, they originated
in the stage of the initial rifting and in the synrift stage of basin
formation in the western part of the Carpathians (Vienna and
The vertical gradient map documents younger and shallower
faults at the margins of the core mountains, as well as structur-
al deformations (flexures caused by compaction of sediments
of various grain size) in the sedimentary fill of the Vienna and
Danube Basins in the territory of Slovakia. There faults repre-
sent the tectonics of the Late Miocene to Pliocene-Pleistocene
Acknowledgments: The authors are grateful to the Ministry
of Education of the Slovak Republic (MŠ SR) for the financial
support in terms of the trilateral project of the Austrian—Slo-
vak—Hungarian co-operation: The neo-Alpine formation of the
Alpine—Carpathian—Pannonian region and its influence on en-
vironmental risks. The VEGA Grants No.: 2/7060/20, 1/7087/
20, 2/7215/20 and 2/7068/20 are acknowledged too. The au-
thors are also grateful to J. Šefara, D. Plašienka and S. Wyb-
raniec, whose valuable comments helped us to improve the
presentation of our results.
NEO-ALPINE LINEAR DENSITY BOUNDARIES 243
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