High-resolution stratigraphy of the Changhsingian (Late Permian) successions of NW Iran and the Transcaucasus based on lithological features, conodonts and ammonoids

The Permian–Triassic boundary sections in north-western Iran belong to the most complete successions, in which the largest mass extinction event in the history of the Earth can be studied. We investigated the Changhsingian stage in six sections in the area of Julfa (Aras Valley) for their lithology, conodonts and ammonoids. Revision of the biostratigraphy led to the separation of 10 conodont zones (from bottom to top Clarkina orientalis– C.subcarinata interval zone, C. subcarinata, C. changxingensis, C.bachmanni, C.nodosa, C. yini, C.abadehensis, C.hauschkei, Hindeoduspraeparvus– H.changxingensis and Merrilinaultima– Stepanovites ? mostleri zones) and 8 ammonoid zones (from bottom to top Iranitestranscaucasius– Phisonites triangulus, Dzhulfitesnodosus, Shevyrevites shevyrevi, Paratirolites trapezoidalis, P. waageni, Stoyanowites dieneri, Abichites stoyanowi and Arasella minuta zones). The new ammonoid genera Stoyanowites and Arasella are described.