K-Pg transition in neritic limestones: Deciphering the first bio/chemo-stratigraphic records and tectono-sedimentary evolution, eastern Neotethys (NE Türkiye)

Abstract

Interestingly, the K-Pg transition from the Cretaceous to the Paleogene is the closest to our time and, from today's perspective, the most dramatic extinction that has ever occurred on Earth. Using different methods and lithologies, K-Pg transition records have been identified in different areas around the Earth. In this study, the neritic carbonate successions in the arc sedimentary cover of eastern Neotethys (Eastern Sakarya Zone, NE Türkiye) were studied using high-resolution bio-chemo/stratigraphy and sedimentary geology methods. The Ziyarettepe Formation, which is the subject of this study, is characterized by its neritic and hemipelagic sedimentary features. Notwithstanding, the clastic and irregular distribution of macro- and microfossils in the Ziyarettepe Formation was realized in parallel with sea level changes, regional tectonism, and global event effects. As a result of these events, the shell structure of the fossils shows the processes of transport from shallow habitats, transport to the platform-platform edge-slope edge, and deposition under these conditions. On the other hand, the neritic and hemipelagic limestones of the Ziyarettepe Formation allow the study of benthic and planktonic foraminifera biostratigraphy, as well as other fossil groups in the stratigraphic interval around the K-Pg transition. According to the results, the stratigraphic age of the Ziyarettepe Formation is given as late Campanian-Thanetian, both chemostratigraphically and biostratigraphically (mainly foraminifera). The Ziyarettepe Formation (Tosunlu Tunnel) stratigraphic section was examined for stable δ¹³C and δ¹⁸O isotopes, rare earth elements, and whole rock carbonate geochemistry records within the Ziyarettepe Formation. Geochemical trends across the K-Pg transition are distinguished by anomalies resulting from many impact signals, including mainly the Deccan Traps and the Chicxulub Impact. The geochemical profile of the K-Pg transition was influenced by paleoenvironmental impacts, as in this example of a neritic succession in the eastern Neotethys. Together with multi-chemostratigraphic analyses, it could be shown for the first time that the K-Pg transition was also recorded in this basin. According to the tectono-sedimentary evolution in the region, these neritic successions were deposited in a back-arc environment during the northward subduction of the northern branch of Neotethys.