MIDDLE DEVONIAN AND FRASNIAN SEAS OF SIBERIA

Abstract

The paleolandscape schemes for the Eifelian, Givetian and Frasnian seas of Siberia are considered for the first time in the present work. On the basis of sediment lithology, composition of benthic communities, their habitat environments, and sedimentation conditions, the territory of Siberia is divided into fourteen Eifelian paleolandscapes comprising twelve particular regions, twenty one Givetian paleolandscapes divisible into four regions, and fifteen Frasnian paleolandscapes also subdivided into four regions. The paleolandscapes are characterized by data on their geographic position, size, sedimentation trends, relief and substratum of sea bottom, hydrodynamics, water salinity and temperature, tectonic regime, and volcanic activity. The comprehensive analysis of benthic populations provided grounds to conclude that the distinguished marine basins of Siberia were freely connected with nearby and distant seas, and this was favorable for migration of various organisms. It is also established that the widespread biohermal and reefal buildups extended like a wide belt from the Altai and Salair seas across the Nyurol'ka-Var'egan paleolandscape to the north of the West Siberian sea. In general, the considered seas were shallow, located in the past subtropical zone. Western and easternmost areas of the West Siberian sea were involved into intense tectonic movements accompanied by submarine eruptions of basic to intermediate lavas in the west and of intermediate to acidic lavas in the southeast.