Ostracod turnover during the Carnian Pluvial Episode (Late Triassic) in the Western Neotethys.

The Carnian Pluvial Episode (CPE) caused a biotic crisis and turnover in terrestrial and marine ecosystems in the Western Neotethyan realm. The expansion of deltaic systems on land and the increased siliciclastic input affected the distribution of benthic ostracods, both nearshore and offshore. Diversity changes of Carnian ostracod faunas from seven successions in the Transdanubian Range (TR), Western Hungary tracked the effects of the CPE, despite its distal hemipelagic depositional setting and position within an intraplatform basin. At the onset of CPE in the early Julian 2, the composition of the studied benthic ostracod assemblage was similar to that of the late Julian 1 communities albeit with decreased abundance of smooth bairdiids and healdiids. The ratio of healdiids and smooth bairdiids is likely related to the detrital supply with bairdiids colonizing primarily in intervals with decreased terrestrial input and carbonate platform progradation. During the maximum expansion of CPE in late Julian 2, the predominance of platycopid Bektasia indicates a shallowing trend, infilling of the Carnian basins and stressed environment due to clastic input and salinity stress. The Julian–Tuvalian boundary is characterized by high extinction rates among marine invertebrates simultaneously with the occurrence of a unique low diversity but abundant brackish water ostracod community with Simeonella and Renngartenella that can be traced along the entire Western Neotethys and northern Gondwana shelf. The appearance of this community is primarily linked to salinity variations during the CPE and the formation of restricted basin habitats in the TR with water stratification where the special community lived or was transported there with storms or river outflow. During the Tuvalian, fully open marine conditions were re-established with increased carbonate productivity in the platforms, favouring the colonization of stable shallow marine habitats with the appearance of ornate bairdiids in the ostracod faunas. • Ostracod response to environmental changes during the CPE in the Western Neotethys. • Diversity drop at the onset of the CPE with mainly healdiids and smooth bairdiids. • Significant turnover at the Julian–Tuvalian boundary with monogeneric faunas. • Widespread crisis fauna is linked to brackish conditions, stratification and storms. • Tuvalian return of stable marine conditions and shallowing with ornate bairdiids. [ABSTRACT FROM AUTHOR]