High resolution planktonic foraminiferal biostratigraphy of the Gurpi Formation, K/Pg boundary of the IZEH zone, SW Iran

Abstract

Planktonic foraminiferal biostratigraphy of the Gurpi Formation at the Danial section in northeast Izeh, the Zagros Basin, Iran, provides improved age resolution and good biostratigraphic control for late Cretaceous to Paleocene strata. The section was examined based on biostratigraphy, geochemistry, and lithology. The recorded fauna are of open marine forms, and most of the Late Cretaceous-Paleocene standard tropical/subtropical planktonic foraminiferal zones are represented. The high biostratigraphic resolution represented by Plummerita hankeninoide for the Late Maastrichtian and Guembelitria cretacea for the Early Danian, together with the Ir anomaly, represent a continuous Cretaceous-Paleogene (K-Pg) succession in the studied area. The sudden extinction of 42 out of 53 species at the K-Pg boundary, especially in globotruncanids and large heterohelicids, indicates a sudden change in tropical-subtropical deep photic sea water under the mesotrophic conditions of the Late Maastrichtian. On the other hand, planktonic foraminifera experienced relatively high stress conditions during this time as indicated by the low species richness and low abundance of globotruncanids simultaneously with blooms of the disaster opportunist Guembelitria species. © 2013 by the Sociedade Brasileira de Paleontologia.