engleski

Reinterpretation of the biostratigraphy and sedimentology of the Upper Permian and Lower Triassic strata of the Masore section, Western Slovenia

Upper Permian and lowermost Triassic strata of the Masore section in western Slovenia have been restudied by means of bio- and lithostratigraphy. The section is mainly characterized by a carbonate succession of the Bellerophon Formation deposited in a shallow ramp environment that was located in the western part of the Palaeo-Tethys. Four types of microfacies have been differentiated in the Bellerophon Formation and microfacies indicate deposition on the well inhabited inner ramp and the reworking of primary biomicrites in the vicinity of small biostromes. Deposition of the bioclast-rich Bellerophon Formation abruptly ceased and was overlain by fossil-poor microbial deposits of the Permian-Triassic boundary (PTB) transition marked by laminated microbialites – stromatolites. The microbial facies was deposited in the mid-part of an unrimmed ramp around a fair-weather wave break. The conodont elements recovered enabled the recognition of the Hindeoduspraeparvus Zone (Late Changhsingian) in the Bellerophon Formation. Gondolellids are documented in the PTB transitional interval with microbial microfacies, whereas the Isarcicellaisarcica Zone (EarlyGriesbachian) is recognized in the tectonically separated Werfen Formation just above the microbial deposit of the section. The conodont faunas are characterized by dominant Hindeodus-Isarcicella populations indicating restricted marine environments. The PTB transitional interval beds are marked also by the presence of Clarkinasuggesting a good communication with the open sea, possibly in a deeper part of an extensive ramp.The recovery of gondolellid elements from the PTB interval of Slovenia has significant global correlation potential. Foraminifers from the Upper Permian Bellerophon Formation are abundant, diverse, and consist of species characteristic for the Upper Permian, of many regions of the Palaeo-Tethys. Foraminifers from the PTB transitional interval are very scarce and represented by the agglutinated species Ammodiscuskalhori and Hyperamminadeformis, with rare representatives of the Late Permian calcareous genera Geinitzina, Tristix and Globivalvulina, probably holdover taxa trying to survive in a stressful environment after the mass extinction of calcareous foraminifers.

Upper Permian, Lower Triassic, Dinarides, Wester Slovenia, Biostratigraphy, Sedimentology

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