Radiolarians of the Kungurian Stage of the Lower Permian in the South Urals of Russia

Abstract

Kungurian radiolarians from the Lower Permian sections Alegazovo on the Ai River and Mechetlino on the Yuryuzan River on the western slope of the South Urals were studied. The distribution of 23 radiolarian species in the studied sections was analyzed, enabling the recognition of two new radiolarian ecozones: Astroentactinia mirifica of the Saraninian Regional Substage in the Neostreptognathodus pnevi conodont Zone and Alexialeks uralicus–Octatormentum permicum of the Irenian Regional Substage, corresponding to the Neostreptognathodus imperfectus conodont Zone. The ecozones are based on the quantitative ratio of high-ranking taxa (classes). The use of the method of correlation of taxa of higher rank at the class level as an indicator of changes in paleoenvironments shows the inversion of the taxonomic composition of radiolarian associations of new ecozones of the Saraninian and Irenian regional substages indicating a change in the radiolarian habitats due to the shallowing of the basin. The taxonomic compositions of the radiolarian associations of the basinal and shelf environment are shown to be different. Three new radiolarian species from the Kungurian Stage of the South Urals are described: Astroentactinia mirifica Afanasieva, sp. nov., Helioentactinia parvispina Afanasieva, sp. nov., and H. venusta Afanasieva, sp. nov.