НОВЫЕ СВЕДЕНИЯ ПО ФОРАМИНИФЕРАМ И БИОСТРАТИГРАФИИ ВЕРХНЕГО СЕНОМАНА СЕВЕРНОГО РАЙОНА ЗАПАДНОЙ СИБИРИ

• Main Author: Подобина, Вера
• Format: Text
• Language: unknown
• Published: Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Национальный исследовательский Томский государственный университет" 2012
• Subjects: УВАТСКИЙ ГОРИЗОНТ; ВЕРХНИЙ СЕНОМАН; ФОРАМИНИФЕРЫ; ЗАПАДНАЯ СИБИРЬ; Arctic; Foraminifera*; Siberia
• Online Access: http://cyberleninka.ru/article/n/novye-svedeniya-po-foraminiferam-i-biostratigrafii-verhnego-senomana-severnogo-rayona-zapadnoy-sibiri; http://cyberleninka.ru/article_covers/13981085.png

Исследованы комплексы фораминифер и литологический состав верхней части уватского горизонта по разрезам семи скважин Ван-Еганской площади северного района Западной Сибири. Виды фораминифер сравнивались с одновозрастными Северной Канады и Северной Аляски (Канадская провинция). Среди них описаны 10 видов, из них 8 новые. Foraminifers and biostratigraphy of the Upper Cenomanian of the northern district of Western Siberia were first studied with the use of materials from seven newly bored holes on the territory of the Van-Yeganskaya area. Two foraminiferal zones (the Lower Saccammina micra Ammomarginulina sibirica and the Upper Trochammina wetteri tumida Verneuilinoides kansasensis) were established in the Upper Cenomanian by the change in the species composition of the foraminiferal assemblages and the lithology of the enclosing rocks of seven studied borehole sections. The beds with Gaudryinopsis nanushukensis elongatus were traced within the lower part of the upper zone. The change in the species composition and the rocks lithology results from the depth variations in the spread of the advancing Boreal transgression. The significant difference of facies (the alternation of the relatively deep-water and shallow facies) is observed not only within the section of the Uvatskian Horizon (the Upper Cenomanian), but also laterally, especially in its uppermost strata. Hence, in some borehole sections of the Van-Yeganskaya area, in the upper strata of the Uvatskian Horizon, the marine facies of dark-gray clays were distinguished, to which the well-preserved foraminiferal assemblages of the upper zone were assigned. The similar well-preserved assemblages had previously been distinguished from the dark-grey, almost black clays of the top of the Uvatskian Horizon within the borehole sections of the Tazovskaya and Purpeyskaya areas. In the lower deposits of the Uvatskian Horizon, within the investigated seven borehole sections of the Van-Yeganskaya area, the foraminiferal tests, not sufficiently well preserved, were discovered having principally coarse-grained quartz-siliceous wall. The comparison of the Late Cenomanian foraminiferal assemblages from the West Siberian and Canadian provinces was made within the whole Arctic paleobiogeographical Realm. Thereby, the common species, vicariants and geographical subspecies were established. Owing to this comparison, the detailed correlation and refinement of the age of West-Siberian foraminiferal zones and beds of the Upper Cenomanian stratons were performed. In the present paper, ten species are described, eight of them are new. They are assigned to the following orders: Ammodiscida (the superfamily Haplophragmiidea the families Haplophragmoididae and Haplophragmiidae), Textulariida (the family Textulariidae). All the described species are illustrated on three paleontological plates. These taxa are of great importance for the subsequent determinative works for the study of foraminifers and biostratigraphy of the Cenomanian deposits of Western Siberia.