Upper Triassic–to Lower Cretaceous Slovenian Basin successions in the northern margin of the Sava Folds

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.