The Albian Stage in West Siberia

The problem of the Albian Stage in West Siberia is considered. Its presence is supported by findings of ammonites Arcthoplites (Subarcthoplites), Cleo niceras, and Pseudopulchellia and inocerams Inoceramus anglicus Woods in th e Khanty-Mansiisk and Yarong Formations. The Lower Albian, corresponding to the Lower Khanty-Mansiisk Subformation, is recognized by ammonites Arcthop lites (Subarcthoplites), "Cleoniceras cf. bicurvatoides (Sinz.)" and forami nifers Ammosiphonia nonionioides (an analog of beds with Gaudryina tailleur i). The subformation is made up of dark-gray mudstone-like clays with rare interbeds of silts, clayey limestones, and siderites. Remains of marine inv ertebrates occur throughout the subformation: ammonites, bivalves (particul arly in the lower part), foraminifers, ostracodes, and fragments of fish sk eletons. Traces of vital activity are observed at the bottom of the subform ation. Beds with foraminifers Ammobaculites fragmentarius-Ammosiphonia bere soviensis are attributed to the uppermost Lower Albian. The Middle Albian i s likely to correspond to beds with Pseudopulchellia sp, ind. and Inoceramu s anglicus (foraminifer beds with Verneuilinoides borealis assanoviensis be resoviensis), corresponding to the lower member of the Upper Khanty-Mansiis k Subformation. This member consists of sills and stift gray sands with int erbeds of dark-gray, sometimes gray silty clays. The age of the upper membe r (foraminifer beds with Verneuilinoides borealis assanoviensis-Ammosiphoni a jamalica), made up of dark-gray, sometimes gray, substantially silty clay s with interbeds of gray silts and sands, is uncertain. Judging from findin gs of Inoceramus anglicus Woods, it belongs to the Upper or, possibly, Midd le Albian. In the overlying part of the section of the Khanty-Mansiisk Form ation, beds with foraminifers Verneuilinoides borealis assanoviensis, Milia mmina ischnia, acid Saccammina divulgata are recognized. Albian key macro- and microfossils are described.