Jozef Hók

Cretaceous—Quaternary tectonic evolution of the Tatra Mts (Western Carpathians): constraints from structural, sedimentary, geomorphological, and fission track data

Abstract The Tatra Mts area, located in the northernmost part of Central Western Carpathians on the border between Slovakia and Poland, underwent a complex Alpine tectonic evolution. This study integrates structural, sedimentary, and geomorphological data combined with fission track data from the Variscan granite rocks to discuss the Cretaceous to Quaternary tectonic and landscape evolution of the Tatra Mts. The presented data can be correlated with five principal tectonic stages (TS), including neotectonics. TS-1 (~95-80 Ma) is related to mid-Cretaceous nappe stacking when the Tatric Unit was overlain by Mesozoic sequences of the Fatric and Hronic Nappes. After nappe stacking the Tatric crystalline basement was exhumed (and cooled) in response to the Late Cretaceous/Paleogene orogenic collapse followed by orogen-parallel extension. This is supported by 70 to 60 Ma old zircon fission track ages. Extensional tectonics were replaced by transpression to transtension during the Late Paleocene to Eocene (TS-2; ~80-45 Ma). TS-3 (~45-20 Ma) is documented by thick Oligocene-lowermost Miocene sediments of the Central Carpathian Paleogene Basin which kept the underlying Tatric crystalline basement at elevated temperatures (ca. > 120 °C and < 200 °C). The TS-4 (~20-7 Ma) is linked to slow Miocene exhumation rate of the Tatric crystalline basement, as it is indicated by apatite fission track data of 9-12 Ma. The final shaping of the Tatra Mts has been linked to accelerated tectonic activity since the Pliocene (TS-5; ~7-0 Ma).

Tertiary extension development and extension/compression interplay in the West Carpathian mountain belt

Abstract This paper describes palaeostresses calculated from fault-striae data, the inferred palaeostrain patterns and determines the inter-relation of the compression and extension during the Tertiary development of the West Carpathians. The calculated stress and inferred strain patterns for the Palaeogene–Burdigalian indicate that the ancestral West Carpathians formed a more-or-less straight orogenic belt. This belt underwent contraction and uplift in its narrow frontal zone, stretching along its strike during the Paleocene–Chattian, and regional contraction and uplift during the Chattian–Burdigalian. The strain/stress pattern is similar to the collision-related pattern known from the Eastern Alps for the Paleocene–Burdigalian. During the Burdigalian–Tortonian, the calculated and inferred West Carpathian stress and strain patterns indicate narrow frontal contractional and lateral sinistral transpressional zones in the orogenic front and broad extensional and dextral transtensional zones in the orogenic interior. The stress/strain pattern is similar to the subduction-related pattern known from areas such as the Hellenic or Sunda/Banda Arcs.

Neogene and Quaternary development of the Turiec Basin and landscape in its catchment: a tentative mass balance model

Neogene and Quaternary development of the Turiec Basin and landscape in its catchment: a tentative mass balance model The development of the Turiec Basin and landscape evolution in its catchment has been reconstructed by methods of geological research (structural geology, sedimentology, paleoecology, and geochronological data) as well as by geophysics and geomorphology. The basin and its surrounding mountains were a subject of a mass balance study during periods of tectonic activity, accompanied by considerable altitudinal differentiation of relief and also during quiet periods, characterized by a development of planation surfaces in the mountains. The coarse clastic alluvial fans deposited beneath the offshore pelitic sediments document the rapid Middle Miocene uplift of mountains on the margin of the Turiec Basin. The Late Miocene finegrained sedimentation represents the main fill of this basin and its origin was associated with the formation of planation surfaces in the surrounding mountains. The rapid uplift of the western and northern parts of the catchment area during the latest Miocene and Early Pliocene times further generated the deposition of coarse-grained alluvial fans. The Late Pliocene basin inversion, due to uplift of the whole Western Carpathians mountain chain, was associated with the formation of the Early Quaternary pediment and ultimately with the formation of the Turiec river terrace systems.

Pliocene to Quaternary tectonics in the Horná Nitra Depression (Western Carpathians)

Pliocene to Quaternary tectonics in the Horná Nitra Depression (Western Carpathians) The Horná Nitra Depression is an Upper Miocene-Quaternary intramontane sedimentary basin. This N-S elongated half-graben structure is rimmed from the west by the marginal Malá Magura fault which is the most distinctive fault in the Horná Nitra Depression, traditionally considered as an active fault during the neotectonic phase. This dislocation is attended by contrasting landforms and their parameters. The low S-index of about 1.10, at least two generations of well-preserved faceted slopes along this fault, and longitudinal river valley profiles point to the presence of a low-destructed actual mountain front line, which is typical for the Quaternary active fault systems. Comparison with known normal fault slip rates in the world makes it possible to set an approximate vertical slip rate between 0.3-1.1 m · kyr-1. The present-day fault activity is considered to be normal, steeply dipping towards the east according to structural and geophysical data. The NNW-SSE present-day tectonic maximum horizontal compressional stress SH and perpendicular minimum horizontal compressional stress Sh was estimated in the Horná Nitra region. The Quaternary activity of the Malá Magura fault is characterized by irregular movement. Two stages of important tectonic activity along the fault were distinguished. The first stage was dated to the Early Pleistocene. The second stage of tectonic activity can by dated to the Late Pleistocene and Holocene. The Malá Magura fault is permeable for gases because the soil atmosphere above the ca. 150 meters wide fault zone contains increased contents of methane and radon.

3D gravity interpretation of the pre-Tertiary basement in the intramontane depressions of the Western Carpathians: a case study from the Turiec Basin

Abstract New results related to the thickness and density of the sedimentary fill of the Turiec Basin allowed us to construct the first original stripped gravity map for this typical intramontane Neogene depression of the Western Carpathians. The stripped gravity map of the Turiec Basin represents the Bouguer gravity anomalies corrected for the gravity effect of the density contrast of its Quaternary-Tertiary sedimentary basin fill. It means that the map reflects the gravity effects of the density inhomogeneities which are located beneath the sedimentary basin fill. This map is therefore suitable for the interpretation of the structure and composition of the pre-Tertiary basement. Based on the new data analysis, two different density models of the sedimentary fill were constructed. The 3D density modelling was used to calculate the gravity effect of the density models. The stripped gravity maps were produced by subtracting the density model gravity effects from Bouguer anomalies. The regional trend was also removed from the stripped gravity maps. The residual stripped gravity maps were consequently used for geological interpretation of the pre-Tertiary basement of the Turiec Basin. The pre-Tertiary basement of the Turiec Basin can be divided into northern and southern parts due to its gravity characteristics. Furthermore the northern part can be split into two domains: western and eastern. The crystalline basement of the western domain is probably formed by the Hercynian crystalline basement of the Tatric Unit. In the eastern domain the basement could consist mostly of the Mesozoic complexes of the Fatric Unit. The southern part of the pre-Tertiary basement of the Turiec Basin is built predominantly by Mesozoic complexes of the Hronic Unit. It is suggested that the Hronic Unit also forms the bedrock of the volcano-sedimentary complex of the Kremnické vrchy Mts. The resultant stripped gravity maps and the map of total horizontal gravity gradients have also proven to be very useful for the interpretation of faults or fault systems in the study area. Various faults, particularly of NNE-SSW and NW-SE directions were discovered. The analysis of the faults indicates clearly that the contact of the Turiec Basin with the Malá Fatra Mts and the Veľká Fatra Mts is tectonic.

The Alpine tectonic evolution of the Danube Basin and its northern periphery (southwestern Slovakia)

Abstract The tectonic evolution of the pre-Cenozoic basement, as well as the Cenozoic structures within the Danube Basin (DB) and its northern periphery are presented. The lowermost portion of the pre-Cenozoic basement is formed by the Tatricum Unit which was tectonically affected by the subduction of the Vahicum / Penninicum distal continental crust during the Turonian. Tectonically disintegrated Tatricum overlaid the post-Turonian to Lower Eocene sediments that are considered a part of the Vahicum wedge-top basin. These sediments are overthrust with the Fatricum and Hronicum cover nappes. The Danube Basin Transversal Fault (DBTF) oriented along a NW–SE course divided the pre-Neogene basement of the DB into two parts. The southwestern part of the DB pre-Neogene basement is eroded to the crystalline complexes while the Palaeogene and Mesozoic sediments are overlaid by the Neogene deposits on the northeastern side of the DBTF. The DBTF was activated as a dextral fault during the Late Oligocene – Earliest Miocene. During the Early Miocene (Karpatian – Early Badenian) it was active as a normal fault. In the Middle – Late Miocene the dominant tectonic regime with NW – SE oriented extension led to the disintegration of the elevated pre-Neogene basement under the simple and pure shear mechanisms into several NE – SW oriented horst and graben structures with successive subsidence generally from west to east. The extensional tectonics with the perpendicular NE – SW orientation of the Shmin persists in the Danube Basin from the ?Middle Pleistocene to the present.

Integrated Geophysical and Geological Investiga-tions of Karst Structures in Komberek, Slovakia

A complex of geophysical methods were used to investigate a small karst area aimed at the production of detailed geological mapping, to confirm geological localization of known sinkholes, and to find possible continuations of caves and voids below the surface. The dipole electromagnetic profiling and radiometric mapping (the gamma-ray spectrometry method) were applied to determine the spatial distribution of hard carbonate rocks and weathered valley-fill sediments. Detailed high-definition magnetometry was carried out at selected sites in the studied region with the aim of distinguishing between sinkholes and man-made lime-kilns, pits where limestone was heated and transformed into lime. The microgravity and the electrical-resistivity tomography (ERT) methods were used to create high-resolution images of the underground cave. The results of ERT and the geological survey were used as an initial model for gravity modeling. Subsurface cavities of various sizes are contrasting geophysical objects, and the electrical resistivity can range from very conductive to relatively resistive depending on the composition of the filling materials. The interpretation of resistivity properties is not always straightforward. We must distinguish air-filled (high-resistivity) and loamy water-filled (low-resistivity) cavities and fractures. The combined geophysical methodology permits us to determine a more accurate near-surface geological model, in our case the parallel interpretation of a strong conductive anomaly in the ERT inversion and a predominant density decrease in the gravity modelling yield the presence of cavities at depths approximately of 50 to 60 m below the surface.

Results of the gravity field interpretation in the Turčianska Kotlina Basin

Results of the gravity field interpretation in the Turčianska Kotlina Basin The paper deals with the quantitative interpretation of the gravity field in the Turčianska Kotlina Basin. The interpretation was done by means of the application of the 2D density modelling method using the GM-SYS software. Geophysical constraints of the density models are represented by the existing geophysical measurements and interpretations. The Turčianska Kotlina Basin in the picture of the regional gravity field is characterized by the local gravity low with amplitude of about 12 mGal. The source of this gravity low is low density Tertiary sediments, which fill the basin. From the Tertiary sediments the Neogene sediments play dominant role in observed gravity, because their gravity effects are considerably larger in comparison with the gravity effects of the Paleogene sediments. The contacts between the Malá Fatra and Veľká Fatra Mts., and the Turčianska Kotlina Basin are characterized by the significant gravity gradients. They reflect tectonic contact between the basin and crystalline core mountains. In the Turčianska gravity low we can see along the Profile TK-AL three local gravity lows. The highest local gravity low is explained by the largest thickness of the Tertiary sediments. Another two local gravity lows are also characterised by thicker layers of the Tertiary sediments. Density models assume that the eastern (western) part of the basin basement is built by the Mesozoic (crystalline) rocks. In the central part of the Profile TK-BL the thick Paleogene sedimentary filling (more than 1 km) compensates the deepest part of the Pretertiary basement. Density model along the Profile TK-BL does not suggest a presence of the Paleogene sediments in the basin filling. It is also indicated that the Mesozoic rocks underlie the Tertiary sediments. The Pretertiary basement was interpreted in the depths from 0 km up to the 2 km. Note that all geological structures (blocks) are sliding from the East to the West. The dipping of the Malá Fatra Mts. is steeper than in a case of the Veľká Fatra Mts. The anomalous bodies observed on the western part of the basin result from the alluvial and detrital cones. Their presence and gravity effect can be observed mainly on the eastern slope of the Malá Fatra Mts.

The resistivity image of the Upper Cretaceous Horné Belice Group: a case study from the Hranty section (Považský Inovec Mts., Western Carpathians)

Abstract The Tatricum crystalline basement in the northern Považský Inovec Mts. contains several narrow tectonic slices with different rock composition. Some of them composed of the Upper Cretaceous mass flow deposits (the Horné Belice Group) are considered unique within the framework of the Internal Western Carpathians and particularly within the Tatricum. Tectonic interpretation of their structural position is longer a matter of debate. Contrasting resistivity properties of the Hercynian mica schists and the Upper Cretaceous sandstones and shales were confirmed by the parametric geophysical measurements. The Hranty section, the structurally highest and most internal Upper Cretaceous tectonic slice was investigated by the electric resistivity tomography. Two longitudinal and two transverse resistivity profiles were measured and combined into a 3D image which suggests that the low resistivity Upper Cretaceous rocks form relatively shallow and flat lying structures folded and deformed between the crystalline basement slices.

A seismic source zone model for the seismic hazard assessment of Slovakia

Abstract We present a new seismic source zone model for the seismic hazard assessment of Slovakia based on a new seismotectonic model of the territory of Slovakia and adjacent areas. The seismotectonic model has been developed using a new Slovak earthquake catalogue (SLOVEC 2011), successive division of the large-scale geological structures into tectonic regions, seismogeological domains and seismogenic structures. The main criteria for definitions of regions, domains and structures are the age of the last tectonic consolidation of geological structures, thickness of lithosphere, thickness of crust, geothermal conditions, current tectonic regime and seismic activity. The seismic source zones are presented on a 1:1,000,000 scale map.