|
ИСТИНА |
Войти в систему Регистрация |
Интеллектуальная Система Тематического Исследования НАукометрических данных |
||
Late Cretaceous of Southwestern Crimea (Ukraine): Biostratigraphy, sea level changes and tectonostratigraphyтезисы доклада
- Автор: Ludmila Kopaevich
- Сборник: 8th International Symposium on the Cretaceous System, Plymouth University, 6-12 September 2009, Plymouth, Abstract Volume
- Тезисы
- Год издания: 2009
- Место издания: Plymouth
- Первая страница: 827
- Последняя страница: 827
- Аннотация: The Upper Cretaceous strata of the Southwestern Crimea comprise 700 meters of carbonate sediments. Diagnostic fauna are confined to a few levels only: ammonites for Upper Albian–Lower Cenomanian; inoceramids for Coniacian; ammonites and belemnites for the Campanian and Maastrichtian. The Late Santonian level is dated by crinoids of Marsupites. Microfossils are quite abundant in Crimean Upper Cretaceous rocks. For age determination purposes, the standard planktonic foraminifer zonation may be used (Robaszynski, Caron, 1995). The benthic foraminifer zonation of the Russian Platform can be used for the interpretation of Crimean shallow-water forams, for instance, Lower Cenomanian and Upper Maastrichtian (Beniamovskii, Kopaevich, 1998). From the Late Albian untill the end of the Maastrichtian stage, this area was influenced by transgressions with short-term regressions, in the region of the Southern Crimea, the Upper Albian formations comprise mainly transgressive (TST) and high stand system tracts (HST). An erosional boundary is present between Albian and Cenomanian. The top of the Lower Cenomanian is truncated by the erosion surface. Within the SW Crimea, the Cenomanian comprises three full sequences, and the fourth sequence corresponds to the late Cenomanian and early Turonian (Gale and al., 1999). Near the Cenomanian–Turonian boundary, a discontinuous “black shale” horizon is present. In the Turonian sequence two parts were distinguished. The chalky limestones and marls with minor chert nodules constitute the lower part. The upper part consists of pure limestones with brachiopods, inoceramids and echinoids. Coniacian strata are lithologically identical with Turonian ones. The Cenomanian–Coniacian rocks represent the single sedimentary sequence. The maximum of basin deepening corresponds with the Cenomanian–Turonian boundary and this could result not from the eustatic sea level change, but also from the tectonic subsidence. Between the Coniacian and Late Santonian, this area was partially exposed, and some submarine erosion took place. The pre-Campanian vertical movements were likely caused by the short-term tectonic compression (the Subhercynian tectonic phase of Western Europe). At the base of the new sequence, the hard-ground surface and traces of erosion are observed. Chalky marls and limestones with belemnites present Campanian succession. All Campanian interval coincides with TST and HST of 3th order. The Maastrichtian is an example of a regressive phase. This succession presents an example of a fast regression record, with sediments indicative of a transition from an open shelf to a coastal environment. This is proved not only by sedimentological data, but also by assemblages of foraminifers and shallow-marine bivalves. The HST was followed by LST. The youngest unit of Maastrichtian indicates a short-term transgression, with smooth pectinids and planktonic foraminifers. This transgression and warming seem to be not local, but could correspond to a global-scale event. At the top of the Maastrichtian a well expressed hard ground is ubiquitous. The overlying bed is rich in glauconite, and contains reworked Maastrichtian fossils.
- Добавил в систему: Копаевич Людмила Федоровна