Biostratigraphy, facies analysis of Upper Cretaceous–Lower Paleocene strata in south Zagros basin (southwestern Iran)

Abstract

In this study, two stratigraphic sections of the Tarbur Formation named Kuh-e Gadvan and Kuh-e Tir were selected. The thicknesses of the whole sediments of the sections studied are about 1100 m of which 400 thin sections were studied. Two biozones are determined in Kuh-e Gadvan and three biozones are described in Kuh-e Tir section. According to established biozones, the age of Tarbur Formation of Kuh-e Gadvan section is assigned to Campanian-Maastrichtian and Tarbur Formation age determination shows relation to Maastrichtian-Lower Paleocene in Kuh-e Tir section.Seven major lithofacies are distinguished along two studied stratigraphic columns which are foraminifer-bioclast wackestone, algal-foraminifer- intraclast wackestone, rudist biclast wackestone, bioclast packstone, bioclast-intraclast grainstone, coral and rudist boundstone. According to the recognized lithofacies, paleoenvironment of the Tarbur formation consists of lagoon, open margin of the reef landward, margin of the reef, flat reef, and seaward margin of the reef. Comparison of studied sections allows that geologic setting had been controlled biostratigraphy and facies change.