BIOGEOGRAPHY OF PERMIAN RADIOLARIANS AND AMMONOIDS OF RUSSIA

In the Permian of Russia ammonoids and radiolarians are present in the Urals, PreCaspian basin, North-East and Far East regions, all of which were located in different paleobiogeographic areas. The most rich and diverse Early Permian (Cisuralian) assemblages of Radiolaria and Ammonoidea are widespread in deposits of the western slope of the Southern Urals. Significantly less diverse assemblages are found in the Middle and Northern Urals. The most northern Early Permian radiolarians occur in Novaya Zemlya, but their taxonomic composition is not diverse. The diversity of the Southern Urals radiolarian and ammonoid assemblages is connected with the low-latitude position of the basin in the Early Permian where connections between the Uralian marine basin and the Tethyan ocean remained stable during this time as is evidenced by the presence of common ammonoid and radiolarian taxa at least on the generic level. Toward the end of the Early Permian, connections between the Uralian and Tethyan basins were completely disrupted as a result of tectonic movements. Later, marine transgressions into the Urals area occurred from the north basin of the PaleoArctic province. Middle Permian (Guadalupian) ammonoids are represented by Roadian (Kazanian) assemblages from deposits of the Volga-Urals basin and Novaya Zemlya, and these communities have a distinct boreal character and are well correlated with coeval assemblages of the Russian North-East and Arctic Canada. Currently there are no reliable data on the presence of radiolarians in Middle Permian deposits of the Urals. The PreCaspian basin is the deepest sedimentary paleobasin of suboceanic type; and the Asselian-Artinskian epoch of its development is characterized by the formation of bioherms. Radiolarians are found in slope deposits of the Karachaganak reef massif. Permian ammonoids and radiolarians are widespread in the eastern regions of Russia. Ammonoids of the Russian North-East (Verkhoyansk, the Okhotsk-Omolon mountain range) are typical of the PaleoArctic province and are found in eight biostratigraphic levels in the Lower and Middle Permian. Ammonoids of the Far East have a Tethyan origin and are present at ten levels in the second half of the Permian. The Permian biostratigraphic scale of the Sikhote-Alin comprises 11 radiolarian biozones.