Integrated biostratigraphy of the Upper Cretaceous Abderaz Formation of the East Kopet Dagh Basin (NE Iran)

Abstract

Based on planktonic foraminifera, inoceramids and echinoids, we present a detailed biostratigraphic analysis of the Abderaz Formation at the 606 m thick Padeha section, NE Iran. This sequence consists mainly of gray shales and marls with four levels of chalky limestones intercalated. The lower boundary of the Abderaz Formation with the Aitamir Formation is a paraconformity, while the upper boundary with the Abtalkh Formation represents a gradual transition. Fifty four species of planktonic foraminifera from 15 genera were identified, and five zones were recognized, namely: Whiteinella archaeocretacea (Bolli) Partial-Range-Zone; Helvetoglobotruncana helvetica (Sigal) Total-Range-Zone; Marginotruncana schneegansi (Dalbiez) Interval-Range-Zone; Dicarinella concavata (Brotzen) Interval-Range-Zone; and Dicarinella asymetrica (Sigal) Total-Range-Zone. Based on these data, the age of the Abderaz Formation is determined as earliest Turonian to earliest Campanian. Inoceramid bivalves Cremnoceramus walterdorfensis walterdorfensis (Andert) and Cremnoceramus deformis deformis (Meek) were identified in the uppermost Turonian and in the middle part of the early Coniacian, respectively. Echinocorys ex. gr. scutata and Cordiceramus sp. were recorded near the Coniacian/Santonian boundary.