Boreskov

PP‐32by the ammonite Arctocephalites arcticus (Newton). These sediments are overlain by theBathonian Arcticoceras ishmae Zone, also containing cephalopods of Arctic origin. Thus, ithas been established that the beginning of the first Boreal transgression onto the territory ofCentral Russia is dated as the bed of the Bajocian. At the beginning of the Bathonian, Borealwaters reached far south, reaching the latitude of Saratov. Importantly, migrations ofvarious groups of molluscs, including cephalopods, were asynchronous. Paradoxically, themigration of belemnoids (and apparently bivalves), was more rapid than that of ammonoids.The new studies allow the geochronological correlation of the Boreal and Tethyan strata atthe Bajocian‐Bathonian boundary and recognition of the paleobiogeographical features ofthis interval of geological time.01122).The study is supported by the Russian Foundation for Basic Research (project no. 11‐05‐References[1]. Callomon J.H. The ammonite succession in the Middle Jurassic of East Greenland // Bull. geol. Soc.Denmark. 1993. V. 40. P. 83‐113.[2]. Meledina S.V. Boreal Middle Jurassic of Siberia. Novosibirsk: Nauka, 1994. 180 p.[3]. Mitta V.V., Barskov I.S., Gründel J., et al. The Upper Bajocian and Lower Bathonian in the section nearSaratov // VM‐Novitates. 2004. N 12. 39 p.[4]. Mitta V.V., Seltzer V.B. The discovery of Arctocephalitinae (Ammonoidea) in the Jurassic of the southeasternRussian Platform, and correlation of the Boreal Bathonian Stage with the standard scale // Trudy.Nauch. Issled. Geol. Institute, Saratov State Univ. N.S. V. 10. 2002. P. 12‐39.191