ПРЕОБЛАДАНИЕ ПРИМИТИВНЫХ ФОРАМИНИФЕР ПРИ ОТСТУПЛЕНИИ ТРАНСГРЕССИЙ В МЕЗОЗОЕ И КАЙНОЗОЕ ЗАПАДНОЙ СИБИРИ

• Main Authors: Подобина, Вера, Татьянин, Геннадий
• Format: Text
• Language: unknown
• Published: Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Национальный исследовательский Томский государственный университет" 2011
• Subjects: ФОРАМИНИФЕРЫ; ТРАНСГРЕССИЯ; МЕЗОЗОЙ; КАЙНОЗОЙ; ЗАПАДНАЯ СИБИРЬ; Yenisey; khatanga; Siberia
• Online Access: http://cyberleninka.ru/article/n/preobladanie-primitivnyh-foraminifer-pri-otstuplenii-transgressiy-v-mezozoe-i-kaynozoe-zapadnoy-sibiri; http://cyberleninka.ru/article_covers/14004318.png

Обмеление бассейнов Западной Сибири в поздневолжское время, раннем кампане и позднем эоцене привело к обеднению систематического состава фораминифер и преобладанию примитивно устроенных раковин. Это объясняется активным воздействием восходящих тектонических движений в указанные периоды, приведших в среднем кампане и позднем эоцене к выведению слоев на дневную поверхность и их размыву. In the Mesozoic and Cenozoic of Western Siberia the assemblages dominated by primitively arranged forms are assigned to the final stages of transgressions. These assemblages are commonly met in shallow and probably desalted basins, thus indicating the ascending tectonic movements in this region. In the Late Volgian the emergence of the Ammodiscus veteranus Evolutinella volossatovi is noted, which is dominated by planispiral forms of the Ammodiscus Genus and more complicated Evolutinella. These foraminifers confined to the top of the Bazhenovskian Horizon succeeded the Middle Volgian Dorothia tortuosa Spiroplectammina vicinalis Assemblage of a more diverse systematic composition and of a more complicated arrangement of tests. In the uppermost beds of the Bazhenovskian Horizon, in the Jurassic/Cretaceous transition, the systematic composition of the benthic foraminifers is significantly changed. The Trochammina rosaceaformis Assemblage is most often distinguished and occurring in the bottom of the Berriassian. Here trochamminas are abundant, Western Siberia and the Yenisey-Khatanga depression this assemblage is not traced, but the alternative Gaudryinopsis gerkei Assemblage is known, which is also characterized by the predominance of morphologically complicated tests. The upper boundary between the Jurassic and Cretaceous passes within almost monotonous clayey rocks of the top Bazhenovskaya Suite and other coeval suites. This boundary is not established by the lithological characteristics and from the logs. It may be only traced by the disappearance of the Late Volgian foraminifers of the Ammodiscus veteranus Evolutinella volossatovi Zone and the emergence of the Berriassian forms. In the Late Cretaceous epoch the shallowing of the basin is observed in the beginning of the Campanian Age from the accumulation of the top of the Slavgorodskaya Suite. Here the Late Santonian Cribrostomoides exploratus Ammomarginulina crispa Assemblage composed mostly of agglutinated quartz-siliceous foraminifers is followed by the Early Campanian Bathysiphon vitta, Recurvoides magnificus Assemblage predominated by the primitive forms. If compared with the Campanian foraminiferal zones of the East-European Platform, in Western Siberia the omission of a number of middle zones from the section is noted in the boundary between the lowermost and uppermost beds of the Campanian. A similar phenomenon is known from the Upper Eocene top of the Lyulinvorskaya Suite. The Reophax subfusiformis R. dentaliniformis Assemblage with the impoverished foraminiferal composition was distinguished from the more complete sections (Podobina, 1998). When comparing with the Paleogene benthic foraminifers scale of the East-European Platform and Central Asia, the analogues of the Upper Eocene zones were not discovered in Western Siberia. The change in the transgression direction resulted in the omission of a number of foraminiferal zones corresponding to substages and some other subunits of the general stratigraphic scheme in the Cretaceous and Paleogene.