Biostratigraphy and palaeogeography of Late Ordovician and Early Silurian chitinozoans from the Zagros Basin, Southern Iran

Abstract

Investigation of 200 surface samples from the Kuh‐e‐Faraghun area of the Zagros Basin has permitted recognition 42 chitinozoan taxa, upon which six successive assemblage zones are based. Assemblage zones I‐III occur in the Late Ordovician Seyahou Formation and IV‐VI occur in the Early Silurian Sarchahan Formation. The chitinozoans Plectochitina persica sp. nov. and Plectochitina khosravii sp. nov. are described from the Sarchahan Formation. A hiatus, encompassing the Middle and Late Silurian and possibly corresponding to the Caledonian Orogeny, is recognized between the Sarchahan Formation and the Faraghan Formation (Devonian). Diverse chitinozoan and acritarch assemblages suggest a marine environment for the two formations. Comparison of chitinozoans from the Zagros Basin with those from other parts of the world indicates that the Zagros Basin was part of North Gondwanaland during the Late Ordovician and Early Silurian.