Paleogene Basin Research Articles

Szemelvények az elmúlt két évtized ELTE-n végzett, medenceléptékű hidrogeológiai kutatásaiból

Az Eötvös Loránd Tudományegyetem (ELTE) Általános és Alkalmazott Földtani Tanszékének hidrogeológiai kutató és oktatócsoportja (Tóth József és Erzsébet Hidrogeológia Professzúra) tevékenységének középpontjában a felszínalatti vízáramlásoknak és kapcsolódó jelenségeknek a hidraulikus folytonosság alaptételére épülő medenceléptékű és rendszer szemléletű megközelítése áll. A jelen tanulmány e megközelítést történeti felvezetéssel és a korábbi, rétegtani (hidrosztratigráfiai) alapú „artézi” paradigmával szembeállítva mutatja be. A folyamatosan fejlesztett medenceléptékű hidrogeológiai kutatási módszertant röviden tárgyaljuk, a technikai részletek helyett kiemelve az alkalmazott módszertani megközelítések magyarázatát. Ezek közül legnagyobb jelentőséggel a kutakban mérhető hidraulikai adatok medenceléptékű, azaz medencehidraulikai elemzése bír, amelynek eredménye a „valós vízáramlási rendszermodell” felállítása. Ennek megfelelően kutatás történetünkből a medenceléptékű és különösen a medencehidraulikai eredményeket szemlézzük a továbbiakban, említve az ezekáltal összefüggésrendszerbe helyezett és egyéb módszerekkel vizsgált jelenségeket is. Az ország területének nagyrészét lefedő kutatásaink domborzattól és kőzettípustól (sziliciklasztos vagy karbonátos) függetlenül kimutatták a kőzetváz hidraulikus folytonosságát és a gravitáció vezérelte regionális felszínalatti vízáramlási rendszerek jelenlétét. Ezek medenceléptékben fedetlen, csapadékvízből utánpótlódó és közel hidrosztatikus nyomásrezsimű tartománya alatt a mélymedencékben abnormális nyomásrezsimek (túlnyomásos vagy alulnyomásos) fedett, és nem vagy csak korlátozottan utánpótlódó tartományai találhatók. E komplex hidraulikai helyzettel és a felszínalatti víz áramlások földtani és környezeti hatótényező szerepével számos felszíni (szikesedés, felszín alatti víztől függő ökoszisztémák, FAVÖKO-k stb.), és felszín alatti (hipogénbarlangképződés, szénhidrogén csapdázódás stb.) jelenség és folyamat nyert magyarázatot.

Last scene in the large scale rotations of the Western Carpathians as reflected in paleomagnetic constraints

This paper provides an overview of the paleomagnetic results which constrain the post-Paleogene tectonic development of the Western Carpathians. A group of these results are relevant to the last stage of the Tertiary folding and thrusting of the Silesian, Dukla and Magura nappes of the Outer Western Carpathian and were obtained from Paleogene-Lower Miocene flysch sediments. Both the pre- and post-folding remanences indicate about 50° CCW vertical axis rotation with respect to the present orientation. This is about a 60° rotation relative to stable Europe. It follows that the general orientation of the Silesian and more internal nappes were NW-SE, at least until the mid-Miocene. The CCW vertical axis rotation was co-ordinated with that of the Central Carpathian Paleogene Basin. The termination of the rotation can be estimated from the paleomagnetic data available from the Pieniny andesites which intruded the Pieniny Klippen Belt and the southern part of the Magura Nappe as well as from those obtained for the Neogene intramontane basins which opened up in the Outer and in the Central Western Carpathians. The paleomagnetic vectors for the andesites form two groups. The first group suggests about 45° CCW rotation relative to north, while the second shows no rotation. At the present stage of our knowledge it seems likely that some of the andesite bodies were intruded around 18 Ma, which is the oldest isotope age for the intrusions of the Wżar Mts, while some other bodies could have been emplaced after the rotation, around 11 Ma, which is the youngest isotope age for the Brijarka quarry. Vertical axis CCW rotation was also observed on sediments older than 11.6 Ma in the Orava-Nowy Targ Intramontane Basin which saddles the Magura Nappe and the Central Carpathian Paleogene Basin. However, this rotation was related to fault zone activity and was not attributed to the general rotation of the Outer Western Carpathian nappe system. Paleomagnetic results from the Nowy Sącz Intramontane Basin, which opened over the Magura Nappe, and those for the Central Western Carpathian Turiec Intramontane Basin do not indicate vertical axis rotation. In the first case, the loosely controlled age limit of the termination of the rotation is around 12 Ma. Well constrained results from the second basin imply that the rotation was definitely over by 8 Ma. Based on the above observations, and aware of the problem of often loose age control on the formation and deformation of the deposits of the intramontane basins, it is tentatively concluded that the large scale CCW rotation of the Central Western Carpathians, together with the Magura, Dukla and Silesian nappes, must have started after 18 Ma and terminated around 11 Ma.

Sedimentology of mixed siliciclastic-carbonate system in a structurally constrained Paleogene basin: Eocene Musawa Formation in Eastern Oman Mountains

The Middle Eocene sedimentary succession in Abat Basin contains a thick mixed siliciclastic and carbonate sequence belonging to the upper member of the Musawa Formation. Over 300 m thick deltaic sediments of the Bartonian to Priabonian upper member of the Musawa Formation show two main facies successions over ten km distance, grading from a proximal delta-plain to a distal delta-front succession. Four major lithofacies associations based on their depositional significance are identified in the basin, namely the conglomerate, sandstone, mudstone, and carbonate. Each of these lithofacies associations is further divided into several individual lithofacies based on their depositional characteristics. The lithofacies association assemblage represents fluvially-dominated deltaic sediments that accumulated as a local siliciclastic feature in a carbonate dominated tropical environment. The conglomerate and sandstone lithofacies associations were deposited by channels and shoreface processes, whereas coastal processes in delta-plain setting deposited mudstone lithofacies association (including coal). The carbonate lithofacies association was deposited in an open marine shelf conditions during transgressive events associated with highstands of sea level and delta-lobe switching. The occurrence of thick siliciclastic sediments is interpreted as the result of activation of the North Ja'alan Fault resulting in a transtensional basin during the Middle to Late Eocene.

Control of the Paleogene sedimentary record of the Anglo-Paris Basin by both the Iceland mantle plume and the Massif Central hotspot

We test here an earlier hypothesis of ours that the Massif Central hotspot, combined with the Iceland mantle plume, exercised first-order control of the Paleogene sedimentary record in the Anglo-Paris Basin. The Anglo-Paris Basin formed a southwestern arm of the Paleogene North Sea. Correlation of Paleogene depositional sequences across the North Sea Basin suggests that control of the sedimentary record in the Anglo-Paris Basin was exercised by both hotspots. The Cretaceous chalk in the basin was uplifted in two main episodes during the early and middle Paleocene. Also during the Paleocene, there was broadly synchronous vertical uplift of the unconformably underlying Mesozoic rocks on both the northwest and southeast flanks of the Anglo-Paris Basin. The resulting opposed regional dips are still obvious at the present day. This regional tilting of the Mesozoic into the Paleogene basin was caused by uplift by the early Iceland plume to the northwest, and by uplift associated with the inception of the early Massif Central hotspot to the southeast. Crustal shortening played a minor role in these hotspot-created vertical movements. In the Paleocene-early Eocene, high-frequency changes in relative regional sea-level in the Anglo-Paris Basin were controlled by apparently synchronous time-dependent behaviour of the Iceland and Massif Central hotspots. In contrast, from the early Eocene onwards, control of sea-level appears to have been exercised separately, with the two hotspots pulsing at different times.

Data for: The Na Duong Basin: a key for understanding Paleogene basin evolution in relation to the left-lateral Cao Bang-Tien Yen Fault (North Vietnam)

Data for: The Na Duong Basin: a key for understanding Paleogene basin evolution in relation to the left-lateral Cao Bang-Tien Yen Fault (North Vietnam)

Paleoenvironmental evolution of Central Paratethys Sea and Lake Pannon during the Cenozoic

Deep wells penetrated Cenozoic sedimentary record of two different basins: 1) Oligocene retro-arc basin which is buried under the 2) Miocene back-arc Danube Basin. This study is focused on biotic and abiotic proxies discussed in terms of existing biostratigraphical, paleoenvironmental and sedimentological data. Biotic proxies are represented by palynofacies and biomarkers (palynomorphs, AOM, phytoclasts, TOC, Pr/Ph ratio, steranes). Abiotic proxies are represented by inorganic geochemistry (e.g., CIA, Sr/Ba, Ga/Rb, Th/U, SiO2/Al2O3, Corg/P and enrichment factors). The biotic and abiotic proxies helped to refine the knowledge about the changes in redox conditions, salinity, depositional system, and paleoclimate. In the study area five temporally different environments are observed: 1) Sedimentation in the Oligocene fragment of the retro-arc Hungarian Paleogene Basin that took place on a highly proximal part of the shelf. A major dysoxic event connected with humid marsh environment is documented within (last Rupelian transgression; Ru4/Ch1–Ch2). 2) After a hiatus the Danube Basin initiated with early Badenian (Langhian) stable oxic to slightly dysoxic shelf with minor salinity changes (Lan2/Ser1-Ser2 transgression). 3) Late Badenian (early Serravallian) dysoxic deposition, similar in all basins of the Central Paratethys, was influenced by upwelling connected with the Ser2-Ser3 transgression. 4) Sarmatian (late Serravallian) dysoxic event associated with subsequent flooding (Ser3-Ser4/Tor1), which created shallow marginal marine environment. 5) Pannonian (Tortonian-Messinian) sedimentation took place on an oxic shelf of the Lake Pannon near a fluvio-deltaic source, most likely represented by the paleo-Danube delta system.

BIOSTRATIGRAPHY OF PALEOGENE THE SOUTHERN UKRAINE BY SMALL BENTHIC FORAMINIFERA: RETROSPECTIVE VIEW

The article deals with history of small benthic foraminifera biostratigraphy of Paleogene deposits the southern Ukraine. The significance of O.K. Kaptarenko-Chernousova, A.M. Voloshina, M.V. Yartseva, Ye.Ya. Kraeva, A.P. Pechenkina, N.G. Savenko and I.D. Konenkova’s works on study foraminifera is shown. Due to their investigarions the sequence and space-time relationships of Paleogene small benthic foraminifera assemblages have been determined in the southern Ukraine. Comparison foraminifera assemblages of Paleogene the southern Ukraine with intergerional benthic foraminifera zones of the Crimea-Caucasus Region is given. The article provides full references to previous literature on Paleogene foraminiferal biostratigraphy of the northern Peri-Black Sea Region and the southern slope of Ukrainian Shield. Up to the beginning the seventies years of the last century the researchers had distinguished and had described foraminifera assemblages characterizing Series and regional units of Paleogene the southern Ukraine. Taxonomic composition of benthic foraminifera assemblages was defined. Their spreading in Paleogene section of the northern Peri-Black Sea Region, the southern slope of Ukrainian Shield and adjacent part the Azov Crystalline Massif was studied. For some foraminifera assemblages the regional significance has been proved. Other assemblages are important for characterizing and dating suites, members, stratum and beds of the local stratigraphic schemes. Foraminifera associations of relatively deep-water depositional environments of the south of the northern Peri-Black Sea Region include species of zonal assemblages of interregional benthic foraminifers zones the Crimea-Caucasus Region. The most of distinguished benthic foraminifera assemblages are characteristic for shallow- and marginal-marine sediments of Paleogene basin in the northern Peri-Black Sea Region and its peripheral facies within depressions the southern slope of Ukrainian Shield. The space-time relations of benthic foraminifera assemblages are defined for Paleogene regional stages of the southern Ukraine section.

Sequence architecture and depositional evolution of Eocene to Oligocene, synrift to early postrift strata in the Baiyun Sag, South China Sea

The Pearl River Mouth Basin (PRMB), located on the northern continental margin of the South China Sea, underwent a complex evolution during the Paleogene. We have focused on the Baiyun Sag in the PRMB with the goal of constructing the architecture and depositional evolution of the Eocene–Early Oligocene synrift stage to the Late Oligocene early postrift stage of basin evolution. Based on analysis of 3D seismic data complemented by well logs and cores, the Paleogene basin fills can be classified into three composite sequences bounded by regional unconformities and 14 sequences bounded by local unconformities. We identify seismic facies on the basis of different internal reflection configurations, external shapes, and contact relationships. The distribution of seismic facies and lithologies interpreted from gamma-ray curves reveal that the synrift basin fill consists mainly of fan delta deposits adjacent to the southern fault scarp, braid delta deposits on the adjacent hanging-wall blocks, and lacustrine mudstones and sublacustrine fan deposits in the center of the basin. The overlying early postrift stage is dominated by shelf and shelf-slope environments, with widespread developed southward-prograding deltas and submarine fans. Tectonics is the principal controlling factor on the development and distribution of depositional systems during the synrift stage. In contrast, sea-level changes superimposed on long-term subsidence related to thermal cooling determined the stacking patterns of sequences during the postrift stage. The results provide new insights on synrift and early postrift tectonics and sedimentation patterns along an evolving passive margin.

Amber and organic matter from the late Oligocene deep-water deposits of the Central Western Carpathians (Orava–Podhale Basin)

The occurrence of amber in the Central Carpathian Paleogene Basin is reported here for the first time. The amber has been analyzed by means of optical microscopic methods, infrared spectroscopy, gas chromatography/mass spectrometry, and pyrolysis-gas chromatography/mass spectrometry to understand the amber composition, origin, taphonomy, alteration, and diagenesis. Organic petrographic and reflectance analyses of organic matter from amber-bearing sediment was carried out to get information about paleoenvironment and maturity of sedimentary rock.Analyses confirmed polylabdane structure associated with Class Ib -type of amber and its possible origin from the conifer family Araucariaceae. It is characterized by a high degree of maturity, where both temperature and exogenic processes have participated in its conversion. Heterogeneity of reflectance values in the resinite suggests that amber was not redeposited from an older and more mature sedimentary unit. The discrepancy between the maturity of the amber and amber-bearing sedimentary rock, along with abundant char and inertinite macerals indicates a probability of thermal alteration of the amber under the influence of heat from a wildfire and increased maturity occurring before its ultimate burial in a deep-sea environment. The assemblage of terrigenous macerals and numerous char and inertinite particles which were found in amber-bearing sediment, as well as in the amber crust, suggest forest-swamp type vegetation affected by wildfires. The presence of amber and predominantly terrigenous organic matter, besides mud rip-up clasts derived from freshwater sediments in deep-marine deposits, indicates a direct connection of terrestrial environments to the deep-water depositional system.

Muricidae (Neogastropoda) from the Middle Eocene of the Hungarian Paleogene Basin

A Middle Eocene (Lutetian–Early Bartonian) muricid assemblage with eight species is described and illustrated from the Hungarian Paleogene Basin. Th ree species and one genus are newly recorded in Hungary, and two new species are described: Paziella (Flexopteron) zsoldosi n. sp. and Harmatia tokodensis n. sp. With 31 figures.

Cenozoic basin evolution of the central Tibetan plateau as constrained by U-Pb detrital zircon geochronology, sandstone petrology, and fission-track thermochronology

We conduct sandstone-composition analysis, U-Pb detrital-zircon dating, and apatite fission-track thermochronology to determine how basin development was associated with the Cenozoic deformation across central Tibet. Our results are consistent with a two-stage basin development model: first a single fluvial-lacustrine system formed (i.e., Paleo-Qaidam basin) in between two thrust belts (i.e., the Fenghuoshan and Qilian Shan thrust belts) in the Paleogene, which was later partitioned into two sub-basins in the Neogene by the Kunlun transpressional system and its associated uplift. The southern sub-basin (i.e., Hoh Xil basin) strata have detrital-zircon age populations at 210–300 Ma and 390–480 Ma for the Eocene strata and at 220–310 Ma and 400–500 Ma for the early Miocene strata; petrologic analysis indicates that the late Cretaceous-Eocene strata were recycled from the underlying Jurassic rocks. The northern sub-basin (i.e., Qaidam basin) strata yield detrital-zircon age clusters at 210–290 Ma and 370–480 Ma in the Eocene, 220–280 Ma and 350–500 Ma in the Oligocene, 250–290 Ma and 395–510 Ma in the Miocene, and 225–290 Ma and 375–480 Ma in the Pliocene. Proterozoic ages of the detrital zircon are most useful for determining provenance: the pre-Neogene Hoh Xil and Qaidam strata all contain the distinctive age peaks of ~1800 Ma and ~2500 Ma from the Songpan-Ganzi terrane south of the Kunlun fault, whereas detrital zircon of this age is absent in the Neogene Qaidam strata suggesting the emergence of a topographic barrier between the two basins. This inference is consistent with our fission-track thermochronological data from the Eastern Kunlun Range that suggest rapid cooling within the range did not start until after 30–20 Ma. Our new data support the Paleo-Qaidam hypothesis that requires the Hoh Xil and Qaidam basins were parts of a single Paleogene basin bounded by the Qilian Shan and Fenghuoshan thrust belts.

PALEONTOLOGICAL HERITAGE RESOURCES FOR TOURISM IN BULGARIA

A specific approach is needed based on a comprehensive study of both tourist resources and habitats / natural findings of fossils for develop a successful tourist product targeting customers who have interests in paleontology. The aim of the study is to evaluate the possibilities of modeling paleontological destinations in the country using leaf imprints and fossils. Fossils have their unique origins. They are formed at a certain point in geological development and in a specific geographic location. In this respect, by their genesis and common character, they are non-renewable resources of high scientific, educational, commercial and amateur value, which can be considered as a tourist resource. Two different paleontological outcrops have been studied: the Lovech Urgonian Group in Northern Bulgaria and the Smolyan Palaeogene Basin in the Western Rhodopes. Destination Lovech Urgonian Group: sampling rocks with finds of Orbitolina, Foraminifera, Algae, coral, Gastropoda, Bivalvia associated with coral reefs in the sedimentary rocks of the Lovech Urgonian Group are situated in the region of Veliko Tarnovo and Lovech. They are connected to a Urgonian paleo Sea, whose age is Low Cretaceous.Destination Smolyan Paleogene basin: different leaf imprints are found in the sedimentary rocks, representatives of the families Platanacea, Fagacaea, Lauraceae, Pinaceae, Podocarpaceae and others with different ecological characteristics. The paleo-floristic diversity shows a dynamic climatic situation through the Paleogene period in this region. The tourists accessibility to the natural revelations of paleo-reefs in North Bulgaria and of the palaeoflora outcrops in the Smolyan region is assessed. An assessment of the tourist infrastructure, the existence of geological landscapes, panoramic views and paleontological museum expositions has been made. The specialized paleontological museums in the country are limited in number. And the offering of paleontological tourist destinations is the opportunity for tourists with interests in the natural history and the live evolution to find a suitable form for satisfying their special interests.

PALEONTOLOGICAL HERITAGE RESOURCES FOR TOURISM IN BULGARIA

A specific approach is needed based on a comprehensive study of both tourist resources and habitats / natural findings of fossils for develop a successful tourist product targeting customers who have interests in paleontology. The aim of the study is to evaluate the possibilities of modeling paleontological destinations in the country using leaf imprints and fossils. Fossils have their unique origins. They are formed at a certain point in geological development and in a specific geographic location. In this respect, by their genesis and common character, they are non-renewable resources of high scientific, educational, commercial and amateur value, which can be considered as a tourist resource. Two different paleontological outcrops have been studied: the Lovech Urgonian Group in Northern Bulgaria and the Smolyan Palaeogene Basin in the Western Rhodopes. Destination Lovech Urgonian Group: sampling rocks with finds of Orbitolina, Foraminifera, Algae, coral, Gastropoda, Bivalvia associated with coral reefs in the sedimentary rocks of the Lovech Urgonian Group are situated in the region of Veliko Tarnovo and Lovech. They are connected to a Urgonian paleo Sea, whose age is Low Cretaceous.Destination Smolyan Paleogene basin: different leaf imprints are found in the sedimentary rocks, representatives of the families Platanacea, Fagacaea, Lauraceae, Pinaceae, Podocarpaceae and others with different ecological characteristics. The paleo-floristic diversity shows a dynamic climatic situation through the Paleogene period in this region. The tourists accessibility to the natural revelations of paleo-reefs in North Bulgaria and of the palaeoflora outcrops in the Smolyan region is assessed. An assessment of the tourist infrastructure, the existence of geological landscapes, panoramic views and paleontological museum expositions has been made. The specialized paleontological museums in the country are limited in number. And the offering of paleontological tourist destinations is the opportunity for tourists with interests in the natural history and the live evolution to find a suitable form for satisfying their special interests.

„Depositional setting of the Oligocene sequence of the Western Carpathians in the Polish Spisz region – a reinterpretation based on integrated palynofacies and sedimentological analyses” – Reply

The research on the Oligocene succession of the Central Carpathian Paleogene Basin (CCPB) in the Kacwin region focused on sedimentological and palynofacies analyses. Observations were carried out in natural exposures along three streams flowing in the Polish Spisz: Kacwinianka, Łapszanka and Kacwinski. Three main groups of lithofacies have been distinguished: coarse-grained, mixed and sandy-grained, and fine-grained. The lithofacies are characterized by variable sedimentary structures, e.g. massive structure, horizontal lamination, ripple cross-lamination, hummocky cross-stratification, deformation structure. Sedimentological analyses showed that structures typical for turbidity currents and those characteristic of relatively shallow deposition (HCS, wave ripples) could coexist in the investigated succession interpreted as typical for turbidity currents influenced by storm waves. This indicates relatively shallow-water environments. The palynofacies analysis enabled identification of the following components: black wood, brown wood, cortex, resin, sporomorphs, cuticle, algae, dinoflagellates and AOM. A high proportion of black wood and low diversity of components point to an origin related to turbidity currents. Furthermore, results of the palynofacies analysis have allowed determining that, during the deposition of the CCPB sediments in the Polish Spisz area, the distance between the deposition area and the source area became relatively large. The biostratigraphic analysis of dinoflagellate cysts from the Podhale Basin (Szaflary, Zakopane, and lower Chocholow beds) indicates an Early Rupelian age. Moreover, kerogen analysis in the UV was applied for the first time to study the CCPB succession. As a result, reworking was documented, so far unrecognized by other methods, and the mutual verification of the obtained results was possible

New data on the age of the sedimentary infill of the Orava-Nowy Targ Basin – a case study of the Bystry Stream succession (Middle/Upper Miocene, Western Carpathians)

The Neogene sedimentary succession of the Orava-Nowy Targ Basin directly overlies the Central Carpathian Paleogene Basin deposits, the Magura Unit, and the Pieniny Klippen Belt. It provides an excellent geological record that postdates the main Mesoalpine structural and geomorphological processes in the Western Carpathians. Sedimentological, petrographical and geochronological investigations have allowed for the re-examination of pyroclastic material, zircon dating, and a discussion on the relation of the Orava-Nowy Targ Basin to the exhumation of the Tatra Massif. The Bystry Stream succession is composed of NNW-inclined freshwater siltstones, sandstones and conglomerates. A few small, sometimes discontinuous, light grey intercalations of pyroclastic deposits and a single 1–2 m thick tuffite layer occur in the upper part of the succession. The tuffite contains an admixture of organic matter and siliciclastic grains (e.g., mica), suggesting that the volcanic ash fall was accompanied by normal deposition from weak currents. Sedimentation of deposits of the Bystry Stream succession took place in terrestrial settings, predominantly on floodplains and in rivers, in the vicinity of a hilly area supplying the basin with eroded material. The age of the tuffite layer from the Bystry Stream succession was determined at 11.87 +0.12/–0.24 Ma. The source of volcanogenic material in the tuffite was probably volcanic activity in the Inner Carpathians-Pannonian region, where effusive and volcanoclastic silica-rich rocks were being produced by extrusive and explosive activity ~12 Ma. Obtained result connects the development of the Orava-Nowy Targ Basin at ~12 Ma with the late stage of the main episode of the Tatra Massif exhumation between ~22–10 Ma.

Klippen Belt, Flysch Belt and Inner Western Carpathian Paleogene Basin Relations in the Northern Slovakia by Magnetotelluric Imaging

The paper presents the interpretation of magnetotelluric measurements along the SW–NE profile near Stara Ľubovňa (Northern Slovakia). The profile passes through the Outer Carpathian Flysch Belt, Klippen Belt and ends in the Inner Western Carpathians Paleogene NW from Ružbachy horst structure. The interpretation of the older measurements from profile Mt4 was utilized and, moreover, the 3-D geoelectrical model of studied region was constructed. The magnetotelluric data interpretations verified the northern inclination of Flysch belt structures and their smaller thickness out of Klippen Belt in direction to the Carpathian electrical conductivity zone axis. We consider this as a consequence of the flower structure—more precisely the southern branch of the suture zone related to mentioned conductivity zone. Northerly from this zone the thickness of the Outer Carpathian Flysch Belt increases and the structures have inclination to the south, i.e. to the subduction zone. The contact of Flysch Belt with Klippen Belt has a fault character and it is subvertical, slightly inclined to the North. The southern boundary between Klippen Belt and Inner Western Carpathians has also fault character and is very steep. We detect the continuation of the Ružbachy horst to the NE in the basement of Inner Western Carpathian Paleogene. The structural discordance between this horst and Klippen Belt direction is a result of younger tectonic processes. According to our results the depth distribution of the pre-Tertiary basement below the Inner Western Carpathian units is non-uniform; the basement is broken to a number of partial blocks—horsts and grabens.

Evaluation of the trends of secondary and tertiary hydrocarbon migration processes based on oil density–reservoir depths relationship in Hungary

Depth of reservoirs of Hungarian oil fields and related oil density data were collected from the database of the Hungarian Mineral Resource Inventory. The purpose of the investigation was to point out the correlation between oil density and reservoir depth in some of the Hungarian hydrocarbon productive regions. Oil density related to reservoir depth in a particular area is generally linked to the migration mechanism. Zala Basin trends show a different migration process regionally and locally; tertiary migration by overflow mechanism can be supposed for the latter case. In the case of the Szeged–Kiskunsag region, locally and regionally, migration along carrier beds through semipermeable sediments is present, with faults playing a significant role. In the Nagykunsag region, the migration processes are similar to those in Zala, but the presence of faults seems more important. At depths below 2,000 m, the Bihar region trends are similar to those of the Szeged–Kiskunsag region. In the shallower zone, hydrodynamic effects are recognizable. In two studied regions, the Battonya–Pusztafoldvar High and the Hungarian Paleogene Basin, the density of crude oil data does not show any significant variability and trend. Biodegradation and water washing were recognizable in the depth sections shallower than 2,000 m below surface. In karstic reservoirs of the Zala Basin (Nagylengyel, Savoly), alteration is presumed at greater depths due to the karst water flow. The presented results show several trends of oil migration in the explored areas, which can be used for future estimation of the hydrocarbon potential in the Hungarian part of the Pannonian Basin.

Miocene transpression effects at the boundary of Central Carpathian Paleogene Basin and Pieniny Klippen Belt: examples from Polish-Slovakian borderland

A geological structural study has been conducted along the tectonic contact zone of the Central Carpathian Paleogene Basin (CCPB) and Pieniny Klippen Belt (PKB) in the eastern Podhale and western Spisska Magura areas. It concerned mostly the Central Carpathian Paleogene flysch strata and, to a lesser degree, the Upper Cretaceous rocks of the PKB. Tectonic deformation structures genetically related to the important tectonic boundary in question occur within a c. 1.5–2 km-wide strip of the Paleogene flysch rocks adjacent from the south to the PKB. Two parallel structural domains have been distinguished within this strip: the contact zone proper in the north and the peri-Pieniny monocline in the south. Most of the minor faults documented in the Paleogene flysch bear a record of dextral motion parallel to the contact zone. Some dextral-reverse oblique slip faults of NE-SW and W-E trends have also been recognized. Discrepancies in the orientation and sense of movement on strike-slip faults in the Paleogene flysch rocks and those in marlstones of the “klippen envelope” of the PKB were encountered. They probably reflect differences in the structural history of both the adjacent rock complexes, as the Upper Cretaceous deposits of the PKB must have experienced more deformation events and, in general, were affected by much more intense strain than those of the CCPB. Contractional structures, such as south-vergent reverse faults and recumbent folds which point to ca N-S tectonic shortening, have also been found in the Paleogene rocks. The entirety of the structural features found in the CCPB is characteristic of a transpressional regime. The regionally consistent coexistence of structures resulting from strike-slip movements and tectonic shortening, as well as features pointing directly to a transpressional regime, prove the transpressional dextral nature of the contact between the CCPB and PKB.

Crimea–Kopet Dagh zone of concentrated orogenic deformations as a transregional late collisional right-lateral strike-slip fault

It is shown that the Crimea, Caucasus, and Kopet Dagh fold systems make up a single whole unified by a lithospheric strike-slip fault zone of concentrated dislocations. The strike-slip fault that dissects the sedimentary cover and consolidated crust is rooted in subcrustal layers of the mantle. The notions about strike-slip dislocations in the structure of the Crimea–Kopet Dagh System are considered. Comparative analysis of structure, age, and amplitude of strike-slip fault segments is carried out. The effect of strike-slip faulting on the deep-seated and near-surface structure of the Earth’s crust is considered. Based on estimation of strike-slip offsets, the paleogeography of Paleogene basins is refined; their initial contours, which have been disturbed and fragmented by slipping motion strike-slip displacement, have been reconstructed.

CHARACTERIZATION AND DFN MODELLING OF THE FRACTURE NETWORK IN A MESOZOIC KARST RESERVOIR: GOMBA OILFIELD, PALEOGENE BASIN, CENTRAL HUNGARY

Reservoir rocks at Gomba oilfield, located in the Hungarian Paleogene Basin, include fractured and karstified Triassic carbonates with significant fluid storage potential. However little information is available about the fracture network in these carbonates which has led to production problems at Gomba. The purpose of this study is to investigate the relationship between the spatial distribution of high porosity zones in the carbonates and the microfracture system. For this evaluation, individual fractures were studied and used in a discrete fracture network (DFN) modelling exercise at two wells, Gomba‐1 and Gomba‐3. The investigation took place at two different scales. Fracture length and aperture distributions were derived at the micro‐scale (mm to cm), whereas fracture density and fracture orientation data were investigated at the reservoir scale. The results of both investigations were taken into consideration in the modelling. The results of the fracture network models were compared to reservoir lithologies which ranged from fractured carbonates to collapse breccias.Based on the results, it appears that the porosity associated with a significant proportion of the fractures was increased as a result of dissolution. Fracture distribution was not uniform along the studied well paths, and fracture orientation was chaotic at particular depth intervals. On the basis of the DFN models, three different fractured zones are predicted to occur in the reservoir, but only two of the zones have significant fracture porosity.Comparing these results with petrographic observations, an epigene karst phase is proposed which is older than (or the same age as) the time of hydrocarbon migration; karst‐related voids were therefore important pathways for fluid migration. The void system and karst caverns partly collapsed during subsequent burial, resulting in karst‐related traps. By analogy with modern cave systems, the karst cavern zones at Gomba probably extend horizontally rather than vertically, and are oriented NE‐SW parallel to major structural lineaments.