Lower Berriasian of Southern Primorye (Far East Russia) and the problem of Boreal–Tethyan correlation

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.