Calcareous nannofossil communities during Late Triassic Mass Extinction and Early Jurassic recovery in the NW Tethys: evidence from Slovakia, Western Carpathians

Abstract

The first calcareous nannoplankton extinction and recovery close to the Triassic/Jurassic boundary (TJB) were studied in two Tatra Mountains sections of Kardolína and Furkaska. The studied sediments were deposited in an intra-shelf depression of the Tethyan shelf (the Zliechov Basin). Rare nannofossil assemblages were discovered in both sections. Rhaetian nannofossils are characterized by the dominance of Prinsiosphaera triassica and by episodic increases in the abundance of small-sized coccoliths. Coccoliths belonging to Calyculus? kardolinae sp. nov. were found on tops of the bedding planes. Triassic index species Eoconusphaera aff. hallstattensis was also recovered, it is rare though, probably due to the marginal or relatively high-latitudinal position of the area. The uppermost Triassic is characterized by a significant reduction in nannofossil abundance accompanied by the presence of organic matter in the rock, which was significant especially in the Kardolína section. The signal of the last occurrence of Prinsiosphaera triassica is overwritten by the reworking of Upper Triassic material into Jurassic strata within the boundary clay interval. The presence of representatives of Watznaueriaceae in the Jurassic Kopieniec Formation is surprising and might indicate hiatus in the TJB in the studied sections. We are also presenting the results of a newly developed method for the extraction of calcareous nannofossils from indurated rocks.

Keywords

• calcareous nannofossils
• biostratigraphy
• taphonomy
• rheatian
• hettangian
• tatra mountains