Ján Soták

Sedimentology and hydrocarbon habitat of the submarine-fan deposits of the Central Carpathian Paleogene Basin (NE Slovakia)

Abstract The Central Carpathian Paleogene Basin accommodates a subsiding area of the destructive plate-margin. The basin history comprises marginal faulting and alluvial fan accumulation (E 2 ); transgressive onlap by shoreface sediments and carbonate platform deposits (E 2 ); glacio-eustatic regression induced by cooling (Terminal Eocene Event); forced regression, tectonic subsidence and growth-fault accumulation of basin-floor and slope fans (E 3 ); decelerating subsidence, aggradation and sea-level rising during the mud-rich deposition (O 1 ); high-magnitude drop in sea-level (Mid-Oligocene Event), retroarc backstep of depocenters and lowstand accumulation of sand-rich fans and suprafans (O 2 –M 1 ); subduction-related shortening and basin inversion along the northern margins affected by backthrusting and transpressional deformation (O 2 –M 1 ). The basin-fill sequence has poor (TOC≤0.5%) to fair (TOC

Late Tertiary paleogeographic evolution of the Western Carpathians

Abstract The evolution of the Tertiary basins in the Western Carpathians was closely connected with the evolution of the Carpathian orogenic belt. During the Oligocene, the sea of the Outer Carpathian flysch troughs became for the first time part of the Paratethys regime due to isolation from the Mediterranean Tethys. Oblique collision between the North European Platform and the overriding West Carpathian Plate during the Early Miocene led to the development of the outer accretionary wedge, built up mainly from flysch nappes, and the formation of a foredeep. Intramontane basins developed in transpressional regime along the northern margin of the Early Alpine consolidated Central Carpathians, from where the sea also invaded the hinterland of the orogenic mountain chain. Progradation of the Alpine nappes gradually closed the Early Miocene (stage Eggenburgian) seaway in front of the Alps which led again to the isolation of the basins inside the West Carpathian segment. The marine connection with the Mediterranean started to open again through the West Carpathian hinterland at the end of the Early Miocene (stage Karpatian). In the Middle Miocene, the Outer Carpathian accretionary wedge obtained its present position, followed by the eastward migration of foredeep depocentres. Inside the orogenic belt large transtensional basins opened. The final closure of the marine connections (stage Badenian) led to a gradual decrease of salinity during the Late Miocene. The sedimentation in the Vienna, Danube (Little Hungarian plain) and East Slovakian (Transcarpathian) basins during the Late Miocene and Pliocene was influenced mainly by the thermal subsidence of the Pannonian domain.

Paleoenvironmental changes across the Eocene-Oligocene boundary: insights from the Central-Carpathian Paleogene Basin

Paleoenvironmental changes across the Eocene-Oligocene boundary: insights from the Central-Carpathian Paleogene Basin The sedimentary sequence of the Central-Carpathian Paleogene Basin provides proxy records of climatic changes related to cooling events at the Eocene/Oligocene boundary (TEE). In this basin, climatic deterioration is inferred from the demise of the carbonate platform and oligotrophic benthic biota in the SBZ19 and from the last species of warm-water planktonic foraminifers in the E14 Zone. Upper Eocene formations already indicate warm-temperate to cool-temperate productivity and nutrient-enriched conditions (Bryozoan Marls, Globigerina Marls). Rapid cooling during the earliest Oligocene (Oi-1 event) led to a temperature drop (~11 °C), humidity, fresh water influx and continental runoff, water mass stratification, bottom water anoxia, eutrofication, estuarine circulation and upwelling, carbonate depletion, sapropelitic and biosiliceous deposition, H2S intoxication and mass faunal mortality, and also other characteristics of Black Sea-type basins. Tectonoeustatic events with the interference of TA 4.4 sea-level fall and the Pyrenean phase caused basin isolation at the beginning of the Paratethys. The Early Oligocene stage of Paratethyan isolation is indicated by a stagnant regime, low tide influence, endemic fauna development, widespread anoxia and precipitation of manganese deposits. The episodic rise in the sea-level, less humid conditions and renewed circulation is marked by calcareous productivity, nannoplankton blooms and the appearance of planktic pteropods and re-oxygenation. Paleogeographic differentiation of the Carpatho-Pannonian Paleogene basins resulted from plate-tectonic reorganization during the Alpine orogenesis.

Lower cretaceous shallow marine buildups in the Western Carpathians and their relationship to pelagic facies

The scarcity of Lower Cretaceous shallow marine sediments in the Western Carpathians is in apparent contradiction to the abundance of these rocks in the pebbles of younger conglomerates, hence the increased importance of transitional facies (olistolites, slope debris, slumped bodies, near-slope fans, fluxoturbidites etc.) which contain redeposited shallow marine carbonates in pelagic sediments. In the Outer Carpathians, latest Jurassic carbonate platforms, including the famous Stramberk reef, were destroyed during Early Cretaceous basinal development. On the other hand, late Hauterivian to early Albian carbonate platforms, mostly connected by elevated crustal blocks, developed in the Central Carpathians. Subsequently, they were mostly destroyed by erosion following tectonic uplift.

Evolution of Late Cretaceous–Palaeogene synorogenic basins in the Pieniny Klippen Belt and adjacent zones (Western Carpathians, Slovakia): tectonic controls over a growing orogenic wedge

Ab stract: The Pieniny Klippen Belt and neigh bour ing zones of the West ern Carpathians rep re sent an an cient accretionary wedge that de vel oped dur ing the meso-Alpidic (Coniacian–Eocene) tec tonic ep och. Af ter an over view of the ex ten sive lit er a ture data, the au thors pres ent an in ter pre ta tion of the synorogenic sed i men tary re cord of these zones as be ing re lated to var i ous en vi ron ments of the fore land ba sin sys tem con sist ing of the trench-foredeep and wedge-top depositional ar eas. The pe riph eral trench-foredeep depozones mi grated from the South PenninicVahic oce anic realm to wards the Oravic con ti nen tal frag ment in an intra-Penninic po si tion, where the synorogenic de pos its were laid down with coars en ingand thick en ing-up ward trends be fore be ing overthrust by the prop a gat ing orogenic wedge tip. The de vel op ment of wedge-top, pig gy back bas ins (Gosau Supergroup) was con trolled by the dy nam ics of the un der ly ing wedge, com posed of fron tal el e ments of the Fatric and Hronic cover nappe sys tems of the Cen tral West ern Carpathians (Austroalpine units). Sev eral compressional and extensional events are doc u mented in the com plex sed i men tary and struc tural rock re cords within the wedge and re lated bas ins. The suc ces sive transgressive-regressive depositional cy cles and cor re spond ing de for ma tion stages are in ter preted in terms of a dy namic accretionary wedge that main tained the crit i cal taper only tran siently. The super criti cal taper states are re flected in re gres sion, shallowing and ero sion in the wedge-top area, while the trench was sup plied with large amounts of clastics by var i ous grav ity-flow types. On the other hand, the col lapse stages tend ing to subcritical wedge taper are in di cated by wide spread ma rine trans gres sions or in gres sions in the wedge-top area and a gen eral deep en ing of all bas ins to bathyal con di tions. Ac cord ingly, the evo lu tion of the en tire trench-foredeep and wedge-top ba sin sys tems was prin ci pally con trolled by the com plex in ter play of the re gional tec tonic evo lu tion of the Al pine-Carpathian orogenic sys tem, lo cal wedge dy nam ics and eustatic sea-level fluc tu a tions.

Large-volume gravity flow deposits in the Central Carpathian Paleogene Basin (Orava region, Slovakia): evidence for hyperpycnal river discharge in deep-sea fans

Abstract The deep-water clastic systems of the Central Carpathian Paleogene Basin contain megabeds, which are developed in distinctive stratigraphic horizons and can be traced over long distances. These beds are characterized by great individual thickness (4-13 m), uniform lithology and internal structures. On the basis of their lithology, sedimentary structures and sequence development, the megabeds are characterized by 15 individual facies and interpreted from the viewpoint of flow hydrodynamics. The grain-size distribution and internal structures of the megabeds point to their deposition from uniform turbulent flows. The main controlling factor for generation of such large voluminous flows is inferred in the sea-level changes, when a relative rising of sea level during the Eocene/Oligocene boundary was responsible for long-lasting accumulation of the clastic supply at the basin margins. The large volume of detritus from river discharge and ravinement surfaces of flooded land was accumulated on the shore and in the conduit heads where the sediment was remobilized by other triggers. The flows generated by catastrophic floods during the early Rupelian sea-level lowstand are thought to be the most probably triggering mechanism. The large highly erosive hyperpycnal flows from flooding rivers could erode accumulated deposits in the conduit or on steeper basin-margin slopes and could cause progressive increase of the sand volume in the flow. Conduit flushing appears to be the most probable source of sediment for the very large voluminous flows that were responsible for deposition of the Orava megabeds

Markov Chain analysis of turbiditic facies and flow dynamics (Magura Zone, Outer Western Carpathians, NW Slovakia)

Markov Chain analysis of turbiditic facies and flow dynamics (Magura Zone, Outer Western Carpathians, NW Slovakia) Methods based on the Markov Chains can be easily applied in the evaluation of order in sedimentary sequences. In this contribution Markov Chain analysis was applied to analysis of turbiditic formation of the Outer Western Carpathians in NW Slovakia, although it also has broader utilization in the interpretation of sedimentary sequences from other depositional environments. Non-random facies transitions were determined in the investigated strata and compared to the standard deep-water facies models to provide statistical evidence for the sedimentological interpretation of depositional processes. As a result, six genetic facies types, interpreted in terms of depositional processes, were identified. They comprise deposits of density flows, turbidity flows, suspension fallout as well as units which resulted from syn- or post-depositional deformation.

A Middle Triassic pachypleurosaur (Diapsida: Eosauropterygia) from a restricted carbonate ramp in the Western Carpathians (Gutenstein Formation, Fatric Unit): paleogeographic implications

Abstract An eosauropterygian skeleton found in the Middle Triassic (upper Anisian) Gutenstein Formation of the Fatric Unit (Demänovská dolina Valley, Low Tatra Mountains, Slovakia) represents the earliest known occurrence of marine tetrapods in the Western Carpathians. The specimen represents a partly articulated portion of the postcranial skeleton (nine dorsal vertebrae, coracoid, ribs, gastral ribs, pelvic girdle, femur and one zeugopodial element). It is assigned to the Pachypleurosauria, more precisely to the Serpianosaurus–Neusticosaurus clade based on the following combination of features: (1) small body size; (2) morphology of vertebrae, ribs and femur; (3) tripartite gastral ribs; and (4) microanatomy of the femur as revealed by μCT. Members of this clade were described from the epicontinental Germanic Basin and the Alpine Triassic (now southern Germany, Switzerland, Italy), and possibly from Spain. This finding shows that pachypleurosaur reptiles attained a broader geographical distribution during the Middle Triassic, with their geographical range reaching to the Central Western Carpathians. Pachypleurosaurs are often found in sediments formed in shallow, hypersaline carbonate-platform environments. The specimen found here occurs in a succession with vermicular limestones in a shallow subtidal zone and stromatolitic limestones in a peritidal zone, indicating that pachypleurosaurs inhabited hypersaline, restricted carbonate ramps in the Western Carpathians.

Stratigraphic and tectonic control of deep-water scarp accumulation in Paleogene synorogenic basins: a case study of the Súľov Conglomerates (Middle Váh Valley, Western Carpathians)

Abstract The Súľov Conglomerates represent mass-transport deposits of the Súľov-Domaniža Basin. Their lithosomes are intercalated by claystones of late Thanetian (Zones P3 - P4), early Ypresian (Zones P5 - E2) and late Ypresian to early Lutetian (Zones E5 - E9) age. Claystone interbeds contain rich planktonic and agglutinated microfauna, implying deep-water environments of gravity-flow deposition. The basin was supplied by continental margin deposystems, and filled with submarine landslides, fault-scarp breccias, base-of-slope aprons, debris-flow lobes and distal fans of debrite and turbidite deposits. Synsedimentary tectonics of the Súľov-Domaniža Basin started in the late Thanetian - early Ypresian by normal faulting and disintegration of the orogenic wedge margin. Fault-related fissures were filled by carbonate bedrock breccias and banded crystalline calcite veins (onyxites). The subsidence accelerated during the Ypresian and early Lutetian by gravitational collapse and subcrustal tectonic erosion of the CWC plate. The basin subsided to lower bathyal up to abyssal depth along with downslope accumulation of mass-flow deposits. Tectonic inversion of the basin resulted from the Oligocene - early Miocene transpression (σ1 rotated from NW-SE to NNW-SSE), which changed to a transpressional regime during the Middle Miocene (σ1 rotated from NNE-SSW to NE-SW). Late Miocene tectonics were dominated by an extensional regime with σ3 axis in NNW-SSE orientation.

Oligocene-Early Miocene Planktonic Microbiostratigraphy and Paleoenvironments of the South Slovakian Basin (Lučenec Depression)

Abstract Oligocene and Lower Miocene sediments of the Lučenec Depression were studied to demonstrate the planktonic bioevents and climatic proxies from the Číž Formation (Rupelian) and Lučenec Formation (Chattian-Aquitanian) on the basis of quantitative analyses of foraminifers and calcareous nannofossils. The oldest nannofossil assemblages of the Číž Formation belonged to the NP23 Zone and were dominated by Reticulofenestra ornata known for preference of temperate eutrophic water conditions. An increase in bioproductivity was documented by abundant large-sized planktonic foraminifers (e.g. Turborotalia ampliapertura, Paragloborotalia nana, Subbotina gortanii) and epifaunal to shal-low-infaunal benthic species. The middle part of the Číž Formation reveals a lowstand progradation of deltaic sediments of the Rapovce Member. There, the planktonic foraminifers are impoverished in both size and diversity, containing mostly tenuitellid and cassigerinellid species, probably as a result of decreased salinity and increased anoxia in the Tard Clay. Contrary of this, the benthic foraminifers are rich, mainly the infaunal forms of uvigerinid species. They probably proliferated due to a high organic flux from riverine input. Open marine conditions were restored in the upper part of the Číž Formation above the lowest occurrence (LO) of Cyclicargolithus abisectus on the NP23-NP24 zone boundary. The transitional interval between the Číž and Lučenec formations (O5/O6 - NP24/25) was approximated by the HOs of Paragloborotalia opima and Sphenolithus distentus and the LOs of Globigerinoides primordius and Pontosphaera enormis. Benthic foraminifera of the Lučenec Formation indicate a high productivity and oxygen-deplected environ-ments. The Oligocene-Miocene boundary in the Lučenec Formation was appointed by the HOs of Helicospahera recta and Dictyococcites bisectus. Foraminiferal markers of this boundary were established from the HO of Globigerina ciperoensis and the LO of G. ottnangiensis. The highest nannofossil dating in the Lučenec Formation is recorded by the LOs of Helicosphaera mediterranea (NN1 Zone) and Discoaster druggi (NN2 Zone). The uppermost part of the Lučenec Formation contained many Paratethys benthic foraminifera, such as Uvigerina posthantkeni.