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Evolution of the planktonic foraminifers and radiolarians across the Cretaceous crises boundariesтезисы доклада
- Авторы: Ludmila Kopaevich, Valetina Vishnevskaya
- 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 first major radiations of planktonic foraminifers occurred during the Cretaceous. The latest Aptian-early Albian and Cenomanian-Turonian corresponded with Oceanic Anoxic Events (OAE) 1 and 2, respectively and dynamic of paleoceanographic changes controlled the course of planktonic foraminiferal evolution. Brief decline in planktonic foraminiferal diversity occured during latest Cenomanian–earliest Turonian time. This interval is characterized by extinction of the genus Rotalipora, sharp absence of other keeled morphotypes at many localities, and abundance of large, relatively simple taxa of the genus Whiteinella. The other feature this interval is obvious prevalence of non-keeled small forms belonging to genera Hedbergella, Schackoina and Heterohelix. The middle part of Turonian coincides with rapid development and diversification of the keeled taxa of the genera Marginotruncana and Dicarinella. At the same time Praeglobotruncana declined rapidly. Representatives of this group have a double keeled test with an multiple aperture. The primary aperture is usually covered by portici, and also infralamimal accessory apertures also existed. These forms represent a new evolutionary lineage in development of planktonic foraminifers, which originated from the genus Praeglobotruncana and reached maximal diversity in the ConiacianSantonian. The genus Globotruncana was derived from Marginotruncana group by migration of the extra-umbilical-umbilical primary aperture towards an umbilical position and the replacement of the portici by tegilla. The evolution took place during Santonian, when Marginotruncana, Globotruncana and intermediate forms coexisted. The evolution of the genus Globotruncanita can be summarized as follows: at the end of the Santonian the primary aperture becomes umbilical in position, although the umbilical system remains composed of portici (in contrast with that of Globotruncana). The double keel was replacement step by step the typical for Globotruncanita a single keel. An explosion of planktonic foraminiferal diversity occurred during all Campanian –Maastrichtian interval and especially at the terminal Maastrichtian. The planktonic foraminiferal assemblages are very scarce at the interval just below K/T boundary and at the base of the Danian. In Radiolaria the extinction datum of Family Parvicingulidae takes place in the late Barremian - early Aptian and also corresponds to OAE 1. An intense speciation of the radiolarian genus Crolanium with first appearance in the late Barremian and last occurrences of its most species, the index species C. cuneatum included, was characteristic of the terminal Albian. Spheroid and discoid radiolarians were dominant in the Cenomanian. This event is in good correlation with OAE 2. Turonian was marked by intense development of all the radiolarian morphotypes. The strong change of radiolarian assemblages took place at Santonian-Campanian boundary: more warm the late Santonian Pseudoaulophacus floresensis assemblages change by cold water early Campanian Prunobrachium crassum. Cretaceous – Paleogene boundary as typical crisis level (inside of early Paleocene) also is characterized by dominant of only primitive spherical tests (Basov, Vishnevskaya, 1998; Hollis 1997; Vishnevskaya, 1997; Vishnevskaya et al., 2006.
- Добавил в систему: Копаевич Людмила Федоровна