Sedimentary rocks of Pennsylvanian age outcrop at several regions in Croatia. Most of these rocks were deposited in a marine environment, in different tectonic units: Karst (External) Dinarides, ...Internal Dinarides and Tisia. Pennsylvanian deposits contain a significant amount of terrestrial debris, related to the uplift of the Hercynian mountain belt and its intense erosion. Remnants of land flora are not common, but are present at almost all localities. The most diverse and the best preserved Pennsylvanian land flora in Croatia was discovered on the Velebit Mt. and in the Lika Region. It was dominated by ferns, pteridosperms and cordaitales. The fossil flora from Banovina is less diverse, with pteridosperms, scarce ferns, horsetails and lycopods. The sporadic occurrence of lycopods and horsetails was reported from the mountains of NW Croatia. In the Gorski Kotar Region only plant detritus was observed. Ferns and pteridosperms from Papuk Mt. were discovered in older, Mississippian deposits. Palaeobotanical data reopen the discussion about the palaeogeographic position of the research areas.
(1) The ancient Paratethys Sea was a spacious inland salt-water basin, extending from the Alps, over Central Europe, to Central Asia. The southwestern part of its central area, the Croatian part of ...the Pannonian Basin System (CPBS), is generally known for shallow-water deposition and biota. The main purpose of this paper is to emphasize the significance of its less widespread deeper-water deposits in environmental and applied geology. (2) The authors consulted the previously published data, combined with their own results, obtained from the paleontological and sedimentological research, seismic stratigraphy and well-log analyses. (3) During our research in the CPBS, we noticed the connection between the tectonic structures and deep marine canyons and depressions within the Paratethyan shallows. Such structures can be recognized on well-logs and seismic or surface outcrops. They are situated along the faults, and deposits are characterized by the domination of pelagic over the benthic biota, sometimes with visible selective dissolution of aragonite/calcite tests. (4) Studied sedimentary sequences from these structures proved to be a precious source of data on the transgressive-regressive cycles, ancient migrations, modes of deposition and hydrocarbon formation during the Miocene Epoch in the CPBS.
Geological probability calculation was applied to the Northern Croatian Neogene deposits in the western Sava Depression. Structures “A” and “B” (with sandstone hydrocarbon reservoirs inside the ...Kloštar Ivanić Formation, Upper Miocene) were analyzed using two different Probability of Success (POS) methodologies. The classical POS approach showed that, in such play and wider areas of selected two structures, the probability for discovering the new HC reservoirs is 42.18%. This is valid for minimum of 500,000 m
3
of geological reserves. The modified POS approach has been used for calculation of waterflooding efficiency in selected structures “A” and “B.” The probability value of 56.25% indicates that future flooding would result in increased recovery.
Stable isotopes of carbonates (δ
13C
carb, δ
18O
carb), organic matter (δ
13C
org, δ
15N
org) and major, trace and rare earth element (REE) compositions of marine carbonate rocks of Late Permian to ...Early Triassic age were used to establish the position of the Permian–Triassic boundary (PTB) at two continuous sections in the Velebit Mountain, Croatia. The chosen sections — Rizvanuša and Brezimenjača — are composed of two lithostratigraphic units, the Upper Permian Transitional Dolomite and the overlying Sandy Dolomite. The contact between these units, characterized by the erosional features and sudden occurrence of ooids and siliciclastic grains, was previously considered as the chronostratigraphic PTB. The Sandy Dolomite is characterized by high content of non-carbonate material (up to ~
30
wt.% insoluble residue), originated from erosion of the uplifted hinterland. A relatively rich assemblage of Permian fossils (including
Geinitzina,
Globivalvulina,
Hemigordius, bioclasts of gastropods, ostracods and brachiopods) was found for the first time in Sandy Dolomite, 5
m above the lithologic boundary in the Rizvanuša section. A rather abrupt negative δ
13C
carb excursion in both sections appears in rocks showing no recognizable facies change within the Sandy Dolomite, −2‰ at Rizvanuša and −1.2‰ at Brezimenjača, 11
m and 0.2
m above the lithologic contact, respectively. This level within the lower part of the Sandy Dolomite is proposed as the chemostratigraphic PTB. In the Rizvanuša section, the δ
13C
org values decline gradually from ~
−25‰ in the Upper Permian to ~
−29‰ in the Lower Triassic. The first negative δ
13C
org excursion occurs above the lithologic contact, within the uppermost Permian deposits, and appears to be related to the input of terrigenous material. The release of isotopically light microbial soil-biomass into the shallow-marine water may explain this sudden decrease of δ
13C
org values below the PTB. This would support the hypothesis that in the western Tethyan realm the land extinction, triggering a sudden drop of woody vegetation and related land erosion, preceded the marine extinction. The relatively low δ
15N
org values at the Permian–Triassic (P–Tr) transition level, close to ≈
0‰, and a secondary negative δ
13C
org excursion of −0.5‰ point to significant terrestrial input and primary contribution of cyanobacteria. The profiles of the concentrations of redox-sensitive elements (Ce, Mn, Fe, V), biogenic or biogenic-scavenged elements (P, Ba, Zn, V), Ce/Ce* values, and normalized trace elements, including Ba/Al, Ba/Fe, Ti/Al, Al/(Al
+
Fe
+
Mn) and Mn/Ti show clear excursions at the Transitional Dolomite–Sandy Dolomite lithologic boundary and the chemostratigraphic P–Tr boundary. The stratigraphic variations indicate a major regression phase marking the lithologic boundary, transgressive phases in the latest Permian and a gradual change into shallow/stagnant anoxic marine environment towards the P–Tr boundary level and during the earliest Triassic.
►Biogeochemical study of two sections across the Permian–Triassic boundary (PTB) in Croatia. ►A negative δ13Ccarb excursion in both sections appears in rocks showing no facies change. ►The chemostratigraphic excursions are compared with data from PTB sections worldwide. ►The results of this study are consistent with the development of water column anoxia–euxinia. ►This study filled a gap in the knowledge on the PTB in Croatia and wider region of SE Europe.
Interpolation is a procedure that depends on the spatial and/or statistical properties of the analysed variable(s). It is a particularly challenging task for small datasets, such as in those with ...less than 20 points of data. This problem is common in subsurface geological mapping, i.e., in cases where the data is taken solely from wells. Successful solutions of such mapping problems depend on interpolation methods designed primarily for small datasets and the datasets themselves. Here, we compare two methods, Inverse Distance Weighting and the Modified Shepard’s Method, and apply them to three variables (porosity, permeability, and thickness) measured in the Neogene sandstone hydrocarbon reservoirs (northern Croatia). The results show that cross-validation itself will not provide appropriate map selection, but, in combination with geometrical features, it can help experts eliminate the solutions with low-probable structures/shapes. The Golden Software licensed program Surfer 15 was used for the interpolations in this study.
An abundant and diverse Late Carboniferous brachiopod fauna from Velebit Mt. (Croatia) comprises 63 brachiopod taxa dominated by Productida and Spiriferida. The Spiriferinida, Athyridida, ...Orthotethida and Rhynchonellata are less common, while the Orthida, Dictyonellida and Terebratulida occur in very small numbers. Brachiopods are mostly preserved as casts and moulds in shales, limestones and sandstones. Associated fusulinid foraminifera and calcareous algae indicate a Kasimovian to Gzhelian age for the brachiopod-bearing deposits. The global biogeographic distribution of brachiopod taxa indicates the probable seaways and brachiopod migration routes, along the Euramerican shelves.
Middle and Late Miocene palynological biozonation of the south-western parts of Central Paratethys (Croatia) is presented based on organic-walled phytoplankton. Nine characteristic palynozones of ...regional palynostratigraphic range are recognized, e.g. Early Badenian (Langhian) Cribroperidinium tenuitabulatum (Cte), Badenian (Late Langhian - Earliest Serravallian) Unipontidinium aquaeductum (Uaq), Late Badenian (Early Serravallian) Cleistosphaeridium placacanthum (Cpl), Sarmatian (Middle and Late Serravallian) Polysphaeridium zoharyi - Lingulodinium machaerophorum (Pzo-Lma), early Early Pannonian s.l. Mecsekia ultima - Spiniferites bentorii pannonicus (Mul- Spa), middle Early Pannonian s.l. Spiniferites bentorii oblongus (Sob), late Early Pannonian s.l. Pontiadinium pecsvaradensis (Ppe), early Late Pannonian s.l. Spiniferites validus (Sva), and late Late Pannonian s.l. Galeacysta etrusca (Get). As inferred from the regional palynostratigraphic correlation, the signals of two transgressions after the isolation of Paratethys during the Sarmatian are recognised: the first one in the late Early Pannonian, when Mediterranean dinoflagellates migrated into the Pannonian Basin, and the second one in the Late Pannonian, when endemic Paratethyan taxa migrated into the Mediterranean.
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