THE STRUCTURE AND DEVELOPMENT OF THE BAIKAL RIFT DEPRESSION

Abstract

The Baikal rift depression, located in southeastern Siberia, is one of the best investigated intra-continental rift structures in the world. In addition to being the site of comprehensive studies by Russian geo-scientists for decades, the Baikal depression is now the subject of new international investigations using advanced technical means and technologies. The present paper summarizes the principal results concerning the morphostructure of the Baikal rift, the stratigraphy of the Cenozoic deposits and the stages of the Baikal depression development. Based on cross-sections which exhibit the impact of both tectonic and climatic processes, the development of the Baikal depression occurred through two stages: (i) the pre(crypto)-rift stage of the Late Cretaceous-Eocene and (ii) active rifting of the Oligocene-Recent. The second stage is divided into several steps and substeps separated by tectonic phases. Formation of the Baikal rift zone appears to be related to the Indo-Eurasian plate collision related to a model of passive rifting. The uplifted shoulders of the depression have a complex morphostructure overlain by Cenozoic deposits which are thin and restricted in area. The near-marginal zones of the rift are largely defined by the system of longitudinal blocks of different width. Surfaces of the blocks are inclined either to the uplifted shoulder of the rift bound by listric faults typical for western edges of the depression or to the axis of the depression. Cenozoic deposits on the blocks consist of accumulative plains composed primarily of thick lacustrine sequences.