Lower Berriasian of Southern Primorye (Far East Russia) and the problem of Boreal–Tethyan correlation
Abstract Jurassic/Cretaceous boundary deposits in the Far East of Russia are characterized by fauna of a mixed type, including Tethyan ammonites and Boreal species of Buchia . In the north of the region (Western Okhotsk area), the middle Volgian deposits comprise the upper Tithonian Durangites . In Southern Primorye, the lower Berriasian ammonites Pseudosubplanites cf. grandis , P . aff. combesi , Berriasella ex gr. jacobi , Dalmasiceras etc. occur on the Ussuri Bay coast, together with upper Volgian Buchia species. Hence, the notion of non-correspondence between the Tithonian and Volgian is confirmed, as well as that a part of the Volgian belongs to the Cretaceous. A description of the lower Berriasian ammonites and the upper Volgian Buchia is given, including one new ammonite species: Dalmasiceras orientale sp. nov.