Changes in the fossil mammal faunas of Western Transbaikalia during the Pliocene-Pleistocene boundary and the Early-Middle Pleistocene transition

摘要

The faunal variations, sedimentary evolution and successive changes in vegetation during the Late Pliocene through the Middle Pleistocene of the Western Transbaikal area were analyzed to ascertain the main events on the Pliocene-Pleistocene boundary and to trace the Early-Middle Pleistocene transition. The evolutionary development of the main characteristic small mammals and their phyletic lineages involved replacement of the Itantsinian fauna by the Dodogolian assemblage. In the West Transbaikalia, the Pliocene-Pleistocene boundary is recognized between the Late Pliocene Itantsinian and the Early Pleistocene Dodogolian faunas. Biostratigraphic studies on small mammals have revealed that the Early-Middle Pleistocene transition can be placed at the Brunhes-Matuyama paleomagnetic boundary (0.78 Ma) which is determined in the middle sequence of the Tologoi key section, between the latest Early Pleistocene fauna of the Tologoi 2.1 and 2.2 and Middle Pleistocene fauna of Tologoi Complex (Tologoi 2.4 and 2.5).