Siliciclastics in the Upper Triassic dolomite formations of the Krížna Unit (Malá Fatra Mountains, Western Carpathians): constraints for the Carnian Pluvial Event in the Fatric Basin

Abstract

Siliciclastics in the Upper Triassic dolomite formations of the Krížna Unit (Malá Fatra Mountains, Western Carpathians): constraints for the Carnian Pluvial Event in the Fatric Basin The Upper Triassic carbonates of the Krížna Unit in the eastern part of the Krivánska Malá Fatra Mts contain the unique siliciclastic interbeds. They are developed between the Ramsau Dolomite Formation and the Hauptdolomite Formation, and comprise alternating dark grey shales and pale grey dolomites. Such a shaly-dolomite formation is unknown from the Upper Triassic formations of the Krížna Unit, which makes it possible to define a new lithostratigraphic unit (Tržinovo Formation). The Ramsau Dolomites beneath the Tržinovo Formation contain microfauna of Carnian foraminifers. Therefore, the Carnian age has also been constrained for the Tržinovo Formation, which by the reduced carbonate productivity and enhanced terrigenous influx could be related to the Reingraben Event. This event related to the "Carnian Pluvial Episode" is also inferred in the Tržinovo Formation by the presence of lingulide brachiopods (Lingularia) and spinicaudatan crustaceans (Euestheria). This fauna provides evidence of not fully marine conditions of the Tržinovo Formation, influenced by continental freshwater influx and humid climate.