The Permian of the Transbaikal region, eastern Russia: Biostratigraphy, correlation and biogeography

Abstract

Permian deposits in the Transbaikal region within the Mongol–Okhotsk belt and adjacent areas have been studied. The characteristics of the Permian marine and continental formations are documented, and our present understanding of the stratigraphy is presented. The constitution of the regional stratigraphic units, or horizons, is specified, and their paleontological characteristics are stated. The correlation of the horizons with the Permian global chronostratigraphical scale is rather tentative, and has been made possible only by comparison with the well-characterized sections of Northeast Russia. Incomplete faunal distribution in the sections of the Transbaikal region makes it difficult to distinguish uninterrupted zonal sequences. However, the presence of characteristic associations and often, of index-species of biozones recognized outside the Transbaikal region, makes it possible to trace and date these biostratigraphic units. The contradiction between paleobiogeographic and paleomagnetic evidence is noted, the Permian biota being represented by Boreal faunas and Angaran floras suggestive of temperate latitudes, while paleomagnetic data seem to indicate tropical latitudes for the Transbaikal Region during the Permian.