22 - The N/Q boundary in Asian Russia and Tadjikistan

Summary

Introduction

On the Siberian Platform (i.e., the region extending from the Urals eastward to the Pacific Ocean), biostratigraphic, radiometric, and paleomagnetic scales have been applied to Pliocene and Pleistocene deposits to correlate them not only with the stratotype sequence of Vrica but also with key sequences of the European part of the former USSR and in Europe.

Stratigraphic summary

Nine areas are particularly helpful in studying the Plio–Pleistocene succession of this region. These are western Siberia, Transbaikalia, Olkhon Island in Lake Baikal, the upper basin of the Lena River, central Yakutia, the Kolyma Basin, Kamchatka, and the Primorie/Priamurie region (i.e., the Pacific coast provinces), all in eastern Russia, and the Tadjik Depression of Tadjikistan (Figures 22.1 and 22.2). There are difficulties, however, including the unequal extent of exploration, inadequate exposures, and the vast area of territory in Siberia affected by permafrost. As a result, few sequences are adequately known.

Western Siberia

The Plio–Pleistocene deposits of southwestern Siberia, around the headwaters of the Ob River, can be considered of paramount importance, as they include faunistic complexes that support extensive biostratigraphic correlations. The Kochkov Formation, which covers the Upper Pliocene and Eopleistocene, from about 2.4 Ma to 0.6 Ma, contains a series of sediments with four faunal complexes (Figure 22.2). The layers of Betekian age at the base contain remains of Hipparion sp., Paracamelus gigas, Paracamelus praebactrianus, Trogontherium minor, Promimomys gracilis, Mimomys polonicus, Mimomys hintoni, Villanyia petenyii, Villanyia steklovi, and so on (Zazhigin, 1980).