Permian ammonoid associations of the Verkhoyansk Region, Northeast Russia

On the basis of a study of the majority of Permian ammonoids known in Verkhoyansk Region, and an analysis of their age distribution, seven associations and four subassociations are established. These ammonoid associations are the Khorokyt, Arkachan, Endybal, Mysovy, Orol, Takamkyt, Delendzha and Post-Sverdrupites associations, in ascending order. The majority of these associations and subassociations include some complementary ammonoid Beds. The ammonoid associations and subassociations are considered as biostratigraphic divisions of regional stratigraphic extent and are useful for dating and correlating the Permian sedimentary sequences of the Verkhoyansk Region. The geographical and stratigraphic distributions of 360 Permian ammonoid shells in the Verkhoyansk Region permits us to not only diagnose each ammonoid association with specific index species, but also to elucidate the biogeographic connections and migration patterns of the Verkhoyansk ammonoid faunas in relation to these spreading throughout the entire Boreal Realm.