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К стратиграфии аптского яруса Ульяновского Поволжьястатья
- Авторы: Барабошкин Е.Ю., Гужиков А.Ю., Лееревельд Х., Дундин И.А.
- Сборник: Труды Научно - исследовательского института геологии Саратовского государственного университета
- Серия: новая серия
- Том: 1
- Год издания: 1999
- Место издания: Изд. Государственного учебно - научного центра "Колледж" Саратов
- Первая страница: 44
- Последняя страница: 64
- Аннотация: Recent complex (bio- and magnetostratigraphy) reinvestigation of sections provided the opportunity to propose a new biostratigraphic zonation for the Aptian deposits of the region. The Barremian/Aptian boundary is defined by the paleomagnetic data (MO chron), the disappearance of the belemnite Oxyteuthis (Validoteuthis) lahuseni and paleobotany data. The basal Aptian does not contain any index macrofauna. It is overlain Lower Aptian Zones: the Deshayesites forbesi Zone (its stratigraphical range in the River Volga basin was determined for the first time), the Deshayesites deshayesi Zone, the Deshayesites grandis Zone, the Tropaeum (T.) bowerbanki Zone. It was possible to recognize only one ammonite Zone, the Aconeceras nisus Zone, in the Middle Aptian. The Upper Aptian cannot be characterised by means of ammonites because of the near-shore origin. The uppermost of the section is characterized by magnetozon of reverse polarity. Most probably, the zone recognized is analogous to the ISEA chron. It is overlain disconformably by the Upper Albian with a sharp basal contact. The succession is very similar to that in England. The section is characterized by chiefly normal polarity, with three magnetozones of reverse sign against its background: one of them is associated with the base of the Aptian stage, the other two are situated in the uppermost of the section. In the geophysical aspect, the data obtained from the Ulyanovsk section, confirm the point of view, stating that the regime of the Aptian normnal field after the epoch of reverse polarity MO, was repeatedly complicated by reversals.
- Добавил в систему: Барабошкин Евгений Юрьевич