1. Signs of crustal extension in Lower Jurassic carbonates from central SloveniaLuka Gale, Boštjan Rožič, 2024, original scientific article Abstract: The Lower Jurassic Podbukovje Formation represents a succession of shallow marine carbonate rocks deposited on the former Southern Tethyan Megaplatform and one of its successors, the Adriatic Carbonate Platform. Several outcrops of the Podbukovje Formation from central Slovenia (southern margin of the Ljubljana Moor) are presented, bearing possible evidence of Early Jurassic extensional tectonics. Peritidal facies of the lowermost, Hettangian – Sinemurian, part of the Podbukovje Formation locally interfingers with bodies of matrix supported pervasively dolomitized polymictic breccia, several metres to tens of metres thick and is locally cut by neptunian dykes some few decimetres to metres wide. The same or slightly younger part of the formation locally contains grabens/half-grabens metres to tens of metres deep and filled with poorly sorted pervasively dolomitized matrix supported polymictic breccia. Small miliolid foraminifera are present within the clasts and in the matrix. Finally, partly dolomitized blocky breccia tens of metres thick locally overlies the Pliensbachian – lowermost Toarcian limestone with lithiotid bivalves. Besides completely and partly dolomitized clasts, the breccia contains a variety of limestone clasts and preserves common radial ooids and some bioclasts within the partially dolomitized matrix.
The Hettangian-Sinemurian breccias and dykes are presumably related to the early, diffused rifting stage of the Penninic (Alpine Tethys) Ocean, whereas Toarcian breccias relate to the main, focused rifting stage. Together with evolving biota and changing paleo-oceanographic conditions, the extensional tectonics may have been an important factor behind the facies changes observed within the Podbukovje Formation
Keywords: carbonate platform, External Dinarides, Early Jurassic, Podbukovje Formation, neptunian dyke, breccia
Published in DiRROS: 09.07.2024; Views: 11; Downloads: 2
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2. Upper Triassic–to Lower Cretaceous Slovenian Basin successions in the northern margin of the Sava FoldsBenjamin Scherman, Boštjan Rožič, Ágnes Görög, Szilvia Kövér, László Fodor, 2023, original scientific article Abstract: The evolution of the Slovenian Basin southern margin is currently interpreted based on the successions outcropping in the surroundings of Škofja Loka, on the Ponikve Plateau and in the foothills of the Julian Alps in western Slovenia, as well as from the valley of the Mirna River in south-eastern Slovenia. However, no extensive research on this paleogeographic unit has been carried out in the northern part of the Sava Folds region. Recent field observations permitted the recognition of Upper Triassic to lowermost Cretaceous successions of the Slovenian Basin, including the recently described Middle Jurassic Ponikve Breccia Member of the Tolmin Formation. Based on reambulation-type geological mapping, macroscopic facies observations supported by microfacies analysis and biostratigraphy, three stratigraphic columns were constructed showcasing Slovenian Basin formations on the northern flank of the Trojane Anticline (Sava Folds region). These newly described successions encompass Upper Triassic (Bača Dolomite Formation) and Jurassic–lowermost Cretaceous resedimented limestones and pelagic formations, while the attribution of the Pseudozilian Formation is complex. Based on facies characteristics these successions are similar to those preserved in the Podmelec Nappe (lowermost thrust unit of the Tolmin Nappe) in western Slovenia. The connection between the western and the eastern Slovenian Basin during the Late Triassic-Early Cretaceous interval could be thus recognised.
Keywords: Southern Alps, Sava Folds, Slovenian Basin, Jurassic, Ponikve Breccia, stratigraphy, foraminifera
Published in DiRROS: 15.01.2024; Views: 363; Downloads: 156
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3. Depositional environment of the Middle Triassic Strelovec Formation on Mt. Raduha, Kamnik-Savinja Alps, northern SloveniaPrimož Miklavc, Bogomir Celarc, 2022, original scientific article Abstract: The Raduha section represents a continuation of the research of the Anisian Strelovec Formation in the Kamnik-Savinja Alps. The Strelovec Formation was deposited during the Anisian on a drowned section of the Serla Dolomite carbonate platform in a restricted probably outer ramp environment associated with an intraplatform basin. The base of the section is represented by dolostone breccia containing angular carbonate lithoclasts of shallow-marine origin. This is followed by alternations of laminated and homogenous hemipelagic limestones deposited in a restricted and anoxic environment. Hemipelagic sedimentation was occasionally interrupted by clay input and deposition of sediments from gravity mass flows. Slow filling of the basin lead to a gradual cessation of anoxic conditions and sedimentation of bedded shallow-marine limestones. After shallow water conditions were established, bioclastic dolostone of the Contrin Formation was deposited.
Keywords: Southern Alps, bituminous limestones, restricted basin, intraformational breccia, Anisian, facies analysis
Published in DiRROS: 18.01.2023; Views: 827; Downloads: 287
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4. A glimpse of the lost Upper Triassic to Middle Jurassic architecture of the Dinaric Carbonate Platform margin and slopeBoštjan Rožič, Luka Gale, Primož Oprčkal, Astrid Švara, Tomislav Popit, Lara Kunst, Dragica Turnšek, Tea Kolar-Jurkovšek, Andrej Šmuc, Aljaž Iveković, Jan Udovč, David Gerčar, 2022, original scientific article Abstract: In the southernmost outcrops of the Slovenian Basin the Middle Jurassic coarse-grained limestone breccia (mega)beds are interstratified within a succession that is otherwise dominated by hemipelagites and distal turbidites. In this paper, these beds are described as the Ponikve Breccia Member of the Tolmin Formation. We provide descriptions of the studied sections with detailed geological maps and analysis of the breccia lithoclasts. From the latter, a non-outcropping margin of the Dinaric Carbonate Platform is reconstructed. In the Late Triassic the platform margin was characterized by a Dachstein-type marginal reef. After the end-Triassic extinction event, the platform architecture remained, but the reefs were replaced by sand shoals characterized by ooids. In the late Early Jurassic and/or early Middle Jurassic a slope area might have been dissected by normal faults and a step-like paleotopography was formed. In the Bajocian, during a period of major regional geodynamic perturbations, extensional or transtensional tectonic activity intensified and triggered the large-scale collapses of the Dinaric Carbonate Platform margin producing the limestone breccias described herein. This may in turn have caused a backstepping of the platform margin, as is evident from the occurrence of Late Jurassic marginal reefs that are installed directly above the Upper Triassic and Lower Jurassic inner platform successions.
Keywords: Slovenian Basin, Dinaric Carbonate Platform, Middle Jurassic, limestone breccia, debris-flow, stratigraphy, Ponikve breccia
Published in DiRROS: 18.01.2023; Views: 654; Downloads: 468
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5. Sedimentological and paleontological analysis of the Lower Jurassic part of the Zatrnik Formation on the Pokljuka plateau, SloveniaLuka Gale, Duje Kukoč, Boštjan Rožič, Anja Vidervol, 2021, original scientific article Abstract: The uppermost Ladinian to Lower Jurassic Zatrnik Formation is the lithostratigraphic unit of the Mesozoic deeper marine Bled Basin. The uppermost part of the Zatrnik Formation and the transition into the overlying Ribnica Breccia was logged at the Zajamniki mountain pasture on the Pokljuka mountain plateau in the Julian Alps. The lowermost part the section belongs to the “classical” Zatrnik Formation and is dominated by beige micritic limestone and fine-grained calcarenite. Foraminifers Siphovalvulina, ?Everticyclammina, ?Mesoendothyra and ?Pseudopfenderina are present, indicating Early Jurassic age. The beige limestone is followed by light pink limestone of the uppermost Zatrnik Formation. Slumps are common in this interval, and crinoids are abundant. Alongside some species already present in beds lower in the succession, Meandrovoluta asiagoensis Fugagnoli & Rettori, Trocholina sp., Valvulinidae, small Textulariidae, Lagenida, and small ?Ophthalmidium alsooccur in this interval. Resedimented limestone predominates through the studied part of the Zatrnik Formation, indicating deposition on the slope or at the foot of the slope of the basin. The switch to crinoid-rich facies within the slumped interval of the Zatrnik Formation may reflect accelerated subsidence of the margins of the Julian Carbonate Platform in the Pliensbachian. The Zatrnik Formation is followed by the formation of the Pliensbachian (?) Ribnica Breccia. Impregnations of ferromanganese oxides, violet colour, and an increase in clay content are characteristic. The foraminiferal assemblage consists of Lenticulina, small elongated Lagenida, and epistominids. Individual beds of the Ribnica Breccia were deposited via debris flows. Enrichments in ferromanganese oxides point to slower sedimentation.
Keywords: Lower Jurassic, Bled Basin, Pokljuka Nappe, stratigraphy, foraminifer, Hierlatz facies, Ribnica Breccia, Zajamniki
Published in DiRROS: 09.03.2022; Views: 791; Downloads: 344
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