Naslov
Mesozoic basins on the Adriatic continental margin - a cross-section through the Dinarides in Montenegro

Autori
Goričan, Špela ; Đaković, Martin ; Baumgartner, Peter O., Gawlick, Hans-Jurgen ; Cifer, Tim ; Djerić, Nevenka ; Horvat, Aleksander ; Kocjančić, Anja ; Kukoč, Duje ; Mrdak, Milica

Izvornik
Folia biologica et geologica (1855-7996) 63 (2022), 2; 85-149

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Dinarides, Neotethys ; radiolarites ; continental margin ; ophiolitic mélange

Sažetak
The Dinarides, together with the Albanides and Hellenides, preserve stratigraphic successions derived from the eastern margin of the Adriatic microplate and remnants of ophiolites obducted from the Maliac-Vardar branch of the Neotethys Ocean. The main stages in the Mesozoic geodynamic history are: 1) rifting leading to opening of the Maliac Ocean in the Late Anisian, 2) onset of an east-dipping intraoceanic subduction in the Early-Middle Jurassic and seafloor spreading in a supra-subduction setting (Vardar Ocean), 3) formation of ophiolitic mélanges in trench-like basins, westward obduction of young supra-subduction ophiolites in the Middle-Late Jurassic and accumulation of flysch-type deposits in foreland basins in the latest Jurassic to Early Cretaceous, 4) subaerial exposure of the newly formed nappes followed by middle to Late Cretaceous transgression, and 5) continental collision in the Maastrichtian and Paleogene. On the continental margin, the Middle Triassic to Early Jurassic extension created a complex horstand-graben geometry that is apparent in the stratigraphic record. The present day NW-SE striking tectonic units are in rough accordance with the Mesozoic paleogeography. Hence, the inferred configuration for the most complete SW to NE transect through Montenegro and Serbia is as follows:The Dalmatian Carbonate Platform, the Budva Basin, the High Karst Carbonate Platform, the Bosnian Basin, the Durmitor High, the Lim Basin, the Drina-Ivanjica High, and the deep-marine distal continental-margin domain. We present a short description of the stratigraphy for these tectonic/paleogeographic units and discuss their possible connection with other units of the Dinarides and Hellenides. The field guide focuses on deep-water deposits, in which radiolarians are the crucial tool for dating. We describe the complete Mesozoic succession of the Budva Zone, the Middle Triassic pelagic episode of the High Karst Zone, the Upper Triassic and Jurassic pelagic rocks of the Lim Zone and two localities with radiolarites associated with ophiolites. The largest part of the guide is devoted to the Budva Zone, a deeply rifted trough in the continuation of the Pindos Basin. The Budva Zone with its external location in the Dinaric orogen was a site of continuous pelagic sedimentation from the Middle Triassic to the end Cretaceous. Radiolarites characterize the Middle Triassic, Hettangian–Sinemurian, Aalenian to Tithonian, and Hauterivian–Barremian to lower Turonian ; pelagic limestones prevail in the Upper Triassic, Berriasian–Valanginian and upper Turonian to Maastrichtian. Calcareous turbidites from the adjacent High Karst Carbonate Platform are interstratified in all units and completely replace radiolarites in the Pliensbachian. Pelagic sequences also occur in the High Karst Zone, but are confined to the Middle Triassic syn- and early postrift deposits. A 20 m thick unit of Middle Triassic nodular limestone and radiolarite within shallow-water carbonates is a typical example. More internally, the western Ćehotina Subzone of the Lim Zone records pelagic sedimentation from the Middle Triassic to early Cretaceous, when synorogenic mixed carbonate-siliciclastic deposition began. This zone has been less investigated than the Budva Zone. A 100 m thick Norian to Rhaetian succession of limestone with chert nodules is dated with conodonts. A Callovian-early Oxfordian age of lime free cherts is determined with radiolarians. The Mihajlovići Subzone that may have been part of the Drina-Ivanjica paleogeographic unit shows Triassic shallow-water carbonates and a Jurassic deepening upward sequence ending with Oxfordian radiolarites. The last two field-trip stops show upper Bathonian-lower Callovian radiolarites in an ophiolitic mélange and upper Anisian radiolarites in direct contact with basalt. These ages, obtained in the south-westernmost ophiolite remnants of the Dinarides, agree with previously documented ophiolite ages in the wider region. In comparison with the Southern Alps and the Apennines, pelagic deposits of the Dinarides are characterized by an earlier onset and considerably higher proportions of silica with respect to carbonate throughout the Mesozoic. The Dinaric basins were connected with the central Neotethys, where the high fertility of surface waters enabled radiolarite formation since the oceanisation (Anisian or earlier) until the early Late Cretaceous, when planktonic foraminifera and calcareous nannoplankton began to dominate worldwide.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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