UPPER TURONIAN FORAMINIFERAL ZONE- BOUNDARY DEPOSITS OF WEST SIBERIAN MIDDLE CRETACEOUS

Turonian Foraminifera have been established in Kusnetzovskian Horizon of West Siberian province as two assemblages: Gaudryinopsis angustus (lower) and Pseudoclavulina hastata (upper). Layers with these assemblages have been distinguished in two of the same name zones. The Pseudoclavulina hastata zone is the boundary between Turonian and Coniacian stages offering to Middle Order of Cretaceous system. The Turonian foraminifera of two assemblages consist of agglutinated kwartz-siliceous shells of the similar systematic composition. Several characteristic species as Ammoscalaria antis Podobina, Trochammina arguta Podobina and others belong to upper turonian substage. The Pseudoclavulina hastata zone have spread almost on the all territory of the West Siberian province. The new data about this zone have been known in the northern paleobiogeographical district - Van-Eganskaya, South-Russkaya and Vyngapurovskaya areas. More various composition species have been known from section well 700 Vyngapurovskaya area, where upper Turonian foraminifera have been established in rocks from deeps 966,81 and 966,07 m. Summery assemblage from these deeps consist of 20 species: Psammosphaera laevigata White; Saccammina complanata (Franke); Thurammina papillata Brady; Reophax inordinatus Young; Labrospira fraseri (Wickenden) stata Podobina; L. collyra (Nauss); Haplophragmoides rota Nauss sibiricus Zaspelova; H. crickmayi Stelck et Wall; Recurvoidella sewellensis (Olsson) parvus (Belousova); Ammobaculites agglutinoides Dain; Ammoscalaria antis Podobina; Trochammina arguta Podobina; T. wetteri Stelck et Wall; T. subbotinae Zaspelova; Miliammina manitobensis Wickenden; Pseudobolivina contorta Bulatova; Gaudryinopsis angustus Podobina; Asarotammina antisa Podobina; Pseudoclavulina hastata (Cushman); Cibicides westsibiricus Balakhmatova. Paleont. tab. I-VI. This assemblage consisting of different systematic composition have habited in more deep water basin, above Coltogorsky-Urengoisky megathrouph in regen-erative living conditions. Due to similar assemblages of West Siberian and Canadian provinces the age of Kusnetsovskian horizon have been confirmed as Turonian. These provincies with similar foraminiferal systematic composition have been offered to one Arctic paleobiogeographical realm.

Automated summary

Turonian Foraminifera in West Siberian province have been divided into two assemblages: Gaudryinopsis angustus (lower) and Pseudoclavulina hastata (upper). These assemblages have been found in two distinct zones. The Pseudoclavulina hastata zone marks the boundary between the Turonian and Coniacian stages. The foraminifera in the Turonian consist of agglutinated quartz-siliceous shells.