Stratigraphy and Geochemistry of the Vossenveld Formation

The Winterswijkse Steengroeve quarry complex in the east of the Netherlands exposes a ~ 40 m thick sedimentary sequence of intertidal and shallow marine deposits of the Vossenveld Formation dated as Anisian (early Middle Triassic). Here, we present a detailed stratigraphic and sedimentological description combined with geochemical data (carbonate content, spectral gamma ray, magnetic susceptibility, stable isotopes) of the sedimentary sequence in the Winterswijkse Steengroeve. Stable isotope ratios point to paleotemperatures in the range of 25 to 35 °C. These high temperatures in combination with the shallow enclosed character and proximity to the equator made the environment particularly susceptible to substantial evaporation and likely very saline. The concentration of predominantly isolated skeletal fossils resulted from storm activity. Unexpected is the overall increasing salinity in combination with the occurrence of larger sauropterygians in the top 10 m, accompanied by the halophytic bivalve Neoschizodus orbicularis. A subsequent literature study of the distribution of the sauropterygian genera described from the Vossenveld Formation sheds light on their deposition and burial conditions. The combined isotopic, geochemical, and sedimentological study on the Vossenveld Formation elucidates the depositional environment in which the rich fossil assemblage of Winterswijk is preserved. The obtained information on the preservation and paleoenvironment is pivotal in understanding the mode and pacing of the biotic recovery after the end-Permian mass extinction.