engleski

New paleontological and lithological evidence at the Permian-Triassic boundary in Slovenia (NW Dinarides)

This work represents new results from Permian-Triassic Boundary (PTB) interval sections in Slovenia located in the northwestern part of the External Dinarides. The Late Permian and Early Triassic beds are characterized by carbonate succession deposited on a shallow rampof the western Palaeotethys. The boundary transition is marked by malinated microbial stromatolites that appeared at the very biginning of Early Triassic as a characteristic microfacies pointing to worldwide known stressful conditions around the PTB. The alteraiton of laminae represents a distinct change of depositional conditions that favored microbial growth (sphere cluster and threads) and accumulations of a detrital calcitic component (microsparitic calcite, fine grained bioclasts and peloids). Among the laminae there is also a thicker one composed od peculiar micrispheres of unclear origin. The biota of the studied sections is marked by microfossil associations, but lack ammonoids. The main interest of this biostratigraphic study was to establish the presence of conodonts in order to introduce a conodont biozonation. The PTB interval in the Lukač section is represented by Hindeodus-Isarcicella population and the faunas present enabled the recognition of the following conodont biozones: preaparvus, parvus, lobata, isarcica, postparvus and anceps. Therefore, the Lukač seciton serves as a standard for the development of the PTB in the Dinarides. A recenet biostratigraphic study based on conodonts revealed the presence of neogondolellids in the boundary transitional strata. Their presence is interpreted to reflect a ramp with a clear communication with the open sea and possibly also a somewhat deeper environment as evidenced by new paleontologic data. A new report on the presence of neogondolellids in the PTB interval beds of NW Dinarides is important for making palaeoenvironmental reconstruction

PT boundary; external Dinarides

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