The thick Lake Pannon sedimentary record provides insights into the downdip and lateral development of stratigraphic surfaces through the analysis of the basin-scale clinoform progradation. The ...clinoform architecture from the eastern part of the Drava Basin (Pannonian Basin System) was interpreted to reflect the base-level changes. A major downlap surface interpreted as a flooding event followed by rejuvenation of slope progradation was recognized on 2D seismic sections. Detailed 3D seismic interpretation combined with well data revealed that the large sigmoidal and the overlying small oblique clinoform sets that downlap the large one only apparently produce the geometry of a maximum flooding surface. Instead, the 3D mapping revealed the influence of two competing slope systems arriving from the north and northwest. Lateral switching of sediment input, similar to many recent deltaic systems. e.g., Danube and Po rivers led to the variability of stratigraphic surfaces, lithology, and thickness, which resulted in non-uniform shelf-edge migration. These observations were supported by forward stratigraphic modeling simulating different scenarios, which led to the generation of the depositional architecture with an apparent maximum flooding surface. This study also implies the potential pitfalls in basin analysis based only on scarce 2D seismic and emphasizes the role of lateral variations in sediment input controlling the depositional architecture.
Soil gas measurements of radon (222Rn), CO2, and hydrocarbon concentrations, as well as gamma-ray spectrometry, were conducted at two separate locations to estimate the measurement results for known ...locations of hydrocarbon accumulations in the subsurface and oil seepage on the surface. The aim of the study was to confirm the applicability of the method for identifying migration pathways (e.g., faults) and to detect possible seepages of hydrocarbons to the surface as well as to investigate possible health issue potential about the soil gas analysis results. Site A investigations were performed with a large number of sampling points to provide sufficient spatial coverage to capture the influence of subsurface lithologic variability as well as the influence of the migration pathway on the measured parameters. For the investigation of site B, sampling points were positioned to reflect the situation between the area above producing hydrocarbon fields and areas with no confirmed accumulation. The results presented show that it is possible to distinguish the near-surface lithology (gamma-ray spectrometry), characterize the migration pathway, and indicate the area of oil seepage at the surface. Areas above the known hydrocarbon accumulations generally have elevated radon concentrations and detectable heavier hydrocarbons with sporadic methane in soil gas, which contrasts with the lower radon levels and lack of detectable heavier hydrocarbons in soil gas in the area with no confirmed hydrocarbon accumulation in the subsurface.
Upper Miocene to Pliocene (Pannonian) sediments of the Pannonian Basin System accumulated in the brackish Lake Pannon and the fluvial feeder systems, between 11.6-2.6 Ma. Their stratigraphic ...subdivision has been problematic for a long time due to the laterally prograding architecture of the basin fill and the historically independently evolving stratigraphic schemes of the neighbouring countries. We correlated the lithostratigraphic units of the Lake Pannon deposits between Hungary and Croatia in the Drava Basin, using lithological, sedimentological and palaeontological data from boreholes and outcrops, and seismic correlation. The Croatica and Medvedski breg formations in Croatia correspond to the Endrőd Fm. in Hungary, comprising shallow to deep water, open lacustrine, calcareous to argillaceous marls. The Andraševec fm. in Croatia corresponds to the Szolnok and Algyő Fms. in Hungary, consisting of sandstones and siltstones of turbidite systems and of clay marls deposited on the shelf-break slope. The Nova Gradiška fm. in Croatia is an equivalent of the Újfalu Fm. in Hungary, built up of a variety of lithologies, including sand, silt, clay and huminitic clay, deposited in deltaic environments. The Pluska fm. in Croatia corresponds to the Zagyva Fm. in Hungary, consisting of variegated clays, silts, sands and lignites, deposited in alluvial and fluvial environments. Coarse-grained (sand, gravel) basal layers are assigned to the Kálla and Békés Fms. and the Sveti Matej member of the Croatica fm. Coarse-grained intercalations within the deep-water marls belong to the Dorozsma Member of the Endrőd Fm. in Hungary, and to the Bačun member of the Medvedski breg fm. in Croatia. Sediment transport and lateral accretion of the shelf edge in the Drava Basin took place from the N, NW, and W, to the S, SE, and E, respectively. According to the biostratigraphic and chronostratigraphic analyses, the oldest shelf-break slopes in the Mura Basin are more than 8 Ma old, whereas the youngest ones in the southeasternmost part of the Drava Basin may be Pliocene in age (younger than 5.3 Ma). Thus, the 180 km long and at least 700 m deep Drava Basin was transformed into a fluvial plain during the last 3.5 million years of the Miocene.
The most recent major earthquake series struck near Petrinja (December 29th 2020 M 6.2), and triggered extensive ground failures in the wider area of Petrinja, Sisak and Glina. Coseismic ground ...failures including subsidence dolines, liquefaction and landslides have been documented over a large area by various experts and teams. These data are stored in the newly created inventory, which is openly presented in this paper. This inventory is administered and updated by the Croatian Geological Survey, and will be available online via a Web Map Service (WMS) (www.hgi-cgs.hr). The aim of the inventory is to not only provide data for the development of susceptibility maps and more detailed exploration for possible remediation measures, but also to define the priorities for immediate action. The earthquake triggered the rapid development of dropout dolines which endanger the local populations of the villages of Mečenčani and Borojevići. This is still an ongoing process in the vicinity of the houses and therefore in-situ exploration started immediately. Liquefaction related to alluvial sediments of the Sava, Kupa and Glina rivers occurred almost exclusively in loose and pure sands, and was accompanied by sand boils, subsidence and lateral spreading. Liquefaction also presents a greater hazard because settlement of houses and river embankments occurred. Lateral spreading caused failures of river flood embankments and natural river banks. According to the data known to date, the majority of the coseismic landslides were reactivated with minor displacements. Despite that, it has been recognised that houses at the edge, or in landslide colluvium suffered greater damage than other houses located outside the landslide impact zone.
The overall geometry of sedimentary basins is driven by a complex interplay between subsidence, water-level variations, sedimentation rates and basin-margin topography. Seaward movement of the ...shoreline is driven by either high sediment input or by base-level drop. The influence of the specific driving mechanisms is often overwritten by subsequent burial and compaction effects or it is below the resolution of observational data. Our main aim is to describe and discuss the influence of these internal and external forcing factors and demonstrate their sedimentary response, particularly the related unconformities and clinoform geometries in a deep lacustrine setting. To this aim, 3D numerical simulations were performed using DionisosFlow stratigraphic forward modeling software. Models are constrained by seismic and well data from the Drava Basin part of the SW Pannonian Basin, Central Europe. A wide range of parameters, such as subsidence rates, lake-level curves and sedimentation rates were compared and analyzed. Post-rift subsidence and inversion of the basin have been simulated together with the main sedimentary transport routes. Our calculation infers that paleo-water depth could have reached ca. 1300 m in the deepest parts of the basin. Furthermore, our models show that differential compaction, subsidence and lateral variations of the sediment supply result in apparently descending shelf-edge trajectories and onlapping clinoform surfaces that are often misinterpreted as base-level drops. By analyzing the sedimentary response to different climatic variations, we argue that there is no direct indication of a major base-level drop in the Drava Basin, which was much larger than the seismic resolution, i.e. 40–50 m. Modeling also infers that autoretreat and autocyclic variations are more effective at low sediment supply and higher amplitude lake-level variations.
•Forced and normal regression in analyzed in 3D models.•Kilometer-scale palaeo-water depth variations in Lake Pannon.•Tectonic motions and differential compaction overwrite clinoform geometries.•Lateral variability of sediment input rates creates pronounced unconformities.•Higher frequency climatic variations enhance the effect of autocyclic processes.
The Kvarner area is located in the Northern Adriatic Sea, between the south-east Istrian Swell, the Rijeka coast and the Croatian sea boundary. It includes several islands, representing the ...outcropping parts of anticlines produced by the compressional/transpressional deformation of the External Dinaric Chain. An extensive 2D seismic dataset, acquired for hydrocarbon exploration and calibrated by wells, allowed us to reconstruct the time structural maps in Kvarner and unravel its regional fault pattern. The Dinaric compressional phase affected the area in the Late Cretaceous, with both thin- and thick-skinned tectonics related to Adriatic Carbonate Platform (AdCP) succession rigidity. Structural highs facing the Kvarner offshore from the Istrian inland continue through the Kvarner and Rijeka bays and outcrop in the islands. These anticlines, originating from the pre-Messinian Dinaric thrust system, were reactivated by the post-Messinian transpression, as testified by flower structures. Several sharp valleys represent two main low structural lineaments, developed between the anticlines and partially incised during the Messinian. They were observed throughout the entire studied area, specifically in the western part of the bays, where the lineament continues through the valleys and penetrates the SW-Istria land. Data show that the Messinian erosional effect and sedimentation patterns were influenced and driven by the morphology of older structures produced by the Dinaric compressional phase.
•Thin-and thick-skinned tectonics is present in the External Dinarides.•Structures of Kvarner Islands continue in the Istrian peninsula through Kvarner offshore.•Sharp valleys are filled by a prograding clinoform system bounded by two major unconformities.•Older tectonic structures played an important role in recent geodynamics of External Dinarides.
Within the Croatian part of the Pannonian Basin System, there are several depressions and subdepressions. A geostatistical analysis was performed in the Bjelovar Subdepression, which is part of the ...larger Drava Depression. Data for the analysis were obtained from structural maps of the subdepression, previously made by hand interpolation. Square grid cells (2 × 2 km) were laid over the maps. The analysis of cell data included a sufficient number of data (>700 per map) and the semivariogram analyses after which experimental and theoretical semivariograms were made. Consequently a new map set was interpolated by the Ordinary Kriging technique including the pre-Neogene palaeorelief border ('Tg') and e-log markers ('Rs7' and 'Rs5'). New maps were subsequently compared with the older, hand-interpolated maps. It was shown that the method of transferring non-computer into computer interpolated maps via/using an artificial, regular grid of point data is an effective way of 'digitizing' older paper-based maps, preserving almost all of the regional information.
At the beginning of the 20th century, the middle section of the Sava River in Croatia was unaffected by major human activities and rich in ichthyofauna. The Sava River was important for commercial ...and recreational fishing for the local population, which still remains today. However, the 1920s mining industry was established in Slovenia, which emitted carbon dust into the Sava River. At the same time, the construction of embankments to mitigate flooding started in the middle section. Furthermore, in the 1980s, the Krško nuclear power plant (NPP), and in the 2010s, the Krško hydropower plant (HPP) were built in Slovenia. These activities could have an impact on the composition of fish communities downstream from the major sources of disturbances. Therefore, the main aim of this paper were to analyze the changes in fish assemblages of the Sava River from 1978 to 2017, prior to and after the construction of Krško NPP and HPP at the Medsave site on the Sava River, 20 km downstream from the major construction operations. Collected data were divided into four sampling periods (SP): SP1, from 1978 to 1980; SP2, from 1991 to 1994; SP3, from 2001 to 2006, and SP4 from 2011 to 2017. Besides alien fish species, water quality and hydromorphological modifications were identified as significant stressors. In SP1 and SP2 limnophilic and eurytopic fish groups were predominant, and 26 different fish species were identified, but in SP3 and SP4 rheophilic fish groups become dominant, and the diversity has declined to 21 species. Threatened species blageon, Telestes souffia seems to be missing from the main course of the Sava River in last 20 years. It can be concluded that disturbances in the fish assemblage pattern have coincided with the presence of multiple stressors of human origin.
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•Variations in fish assemblages of the Sava River from 1978 to 2017 were analyzed.•Limnophilic and eurytopic types of fish group were predominant from 1978 to 1980.•Four alien fish species recorded 1978–1991, of which three remained until today.•Changes in species composition and decline in diversity has been noted after 2001.•Threatened Telestes souffia appears to be missing from the Medsave site.
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