Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 1

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: International Chronostratigraphic Chart

Sortuj według:

Ogranicz wyniki do:

New data on boundary-stratotype (limitotype) of the Vyatkian stage, Upper Permian, East European Platform

Zhokina M. A.

Geology, Geophysics and Environment

2014

Vol. 40, no. 1

150--151

The International Chronostratigraphic Chart (ICC) of the Permian system is based on marine sections. The Middle and the Upper Permian deposits in Russia are mainly represented by continental sediments, and that fact complicates the usage of the ICC because of global problems of detailed correlation of the marine and the continental deposits. The general stratigraphic scale (GSS) is used for subdivision and correlation of the Permian system in Russia. It is based on sections on the East European platform (Fedonkin et al. 2013). The most numerous and widespread group of fossil organisms from the Permian continental deposits of the East European platform is represented by freshwater ostracods. Active research on this group has been carried out by Russian micropaleontologists for more than 80 years. As a result, a huge material on ostracods was collected (Molostovskaya & Lukin 1998). At this point revision of all this materials was conducted. Specific, generic and familial features were marked. Sexual dimorphism, ostracod ontogeny and phylogeny were studied. The stages of ostracod development were reconstructed. On this basis the Middle and the Upper Permian deposits were subdivided into six Assemblage Zones that form the baseline for the determination of stages and substages of the GSS (Molostovskaya 2005). The boundary between the Severodvinian and Vyatkian stages of the Upper Permian (Tatarian) was fixed at the base of the Wjatkellina fragilina - Dvinella cyrta Assemblage Zone. Section Mutovino on the Sukhona River (Vologda region) was selected as the boundary-stratotype (limitotype) of the above-mentioned boundary. We obtained new data on the ostracod distribution in the boundary deposits of the Severodvinian and Vyatkian stages of this section. Prasuchonella stelmachovi (Spizharskyi, 1939), Pr. ex gr. stelmachovi (Spizharskyi, 1939), Suchonellina parallela Spizharskyi, 1939, S. cf. parallela Spizharskyi, 1939, S. inornata Spizharskyi, 1939, Sinusuella vjatkensis (Posner, 1948) were found just below the boundary. Prasuchonella cf. stelmachovi (Spizharskyi, 1939), Pr. cf. stelmachovi var. ovalis (Kotschetkova, 1970), Suchonella cf. blomi Molostovskaya, 2001, S. ex gr. auriculata (Schneider, 1948), Suchonella sp., Suchonellina inornata Spizharskyi, 1939, S. cf. inornata Spizharskyi, 1939, S. cf. parallela Spizharskyi, 1939, Darwinuloides cf. svijazhicus (Sharapova, 1948), Sinusuella vjatkensis (Posner, 1948) occur at the base of the Vyatkian. The occurrence of Prasuchonella stelmachovi and Suchonella blomi is particularly noteworthy because these species are the members of an evolutionary lineage of Prasuchonella nasalis - P. sulacensis - P. stelmachovi - Suchonella blomi - S. auriculata - S. typica. Thus, the lower boundary of the Vyatkian stage which was established as a boundary of an assemblage zone could be fixed by the first appearance of Suchonella blomi which is an element of the evolutionary lineage.