M.N. Urazaeva
Kazan Federal University, Kazan, 420008 Russia
E-mail: Milyausha.Urazaeva@kpfu.ru
Abstract
Four stages (Late Urzhumian-Early Severodvinian, Late Severodvinian, Terminal Severodvinian-Early Vyatkian, Late Vyatkian) have been established in the evolution of Permian non-marine bivalve fauna from continental deposits of the Severnaya Dvina River Basin. These stages have been singled out based on estimation of the number of autochthonous cosmopolitan, endemic, and allochthonous generic taxa in the assemblages of bivalves. The Late Urzhumian-Early Severodvinian stage is characterized by the dominance of the Angarian genus Prilukiella. The cosmopolitan subgenus Palaeomutela (Palaeomutela) has a subordinate significance. The Late Severodvinian stage is distinguished by the dominance of the cosmopolitan genus Palaeomutela s.1. Representatives of the endemic genus Opokiella appear in the beginning of this stage. The Terminal Severodvinian-Early Vyatkian stage is characterized by a sharp increase in the number of endemic genera and the appearance of rare representatives of the Angarian genus Concinella. The cosmopolitan genus Palaeomutela s.1. has a predominant significance during the Late Vyatkian stage. The number of endemic genera decreases in this stage. It has been assumed that the disappearance of Angarian non-marine bivalves is caused by the relative warming as evidenced by the general direction of the positive excursions of carbon and oxygen isotopes on the isotope curves.
Keywords: stratigraphy, non-marine bivalves, Permian system, Severnaya Dvina River basin
Acknowledgments. The author thanks M.P. Arefiev and V.K. Golubev for providing materials on the stratigraphy of the region studied and their advice on interpretation of data of isotope geochemistry.
This study was supported by the Russian Foundation for Basic Research (project no. 16-04-01062).
Figure Captions
Fig. 1. Paleozoogeographical regions of the Permian Stage (paleogeographical reconstruction of the Late Permian according to Ziegler et al (1997) and Rees (2002)).
Fig. 2. Distribution of non-marine bivalves in the Permian continental deposits of the Dvina-Mezen Basin. Green color – species of the Angarian fauna; yellow color – species of the endemic genera; pink color – species of the cosmopolitan genus Palaeomutela s.l. ------ – the boundaries of development stages of non-marine bivalves, – the boundaries of zones for Opokiella, – the boundaries of zones for Palaeomutela, – the boundaries of layers with Prilukiella fauna. Composite section and carbon and oxygen isotope curves given according to [12].
References
For citation: Urazaeva M.N. Evolution of Permian non-marine bivalve fauna from continental deposits of the Severnaya Dvina River Basin. Uchenye Zapiski Kazanskogo Universiteta. Seriya Estestvennye Nauki, 2016, vol. 158, no. 3, pp. 468–477. (In Russian)
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