QUATERNARY MAGNETOSTRATIGRAPHY OF THE GONGHE BASIN ON THE NORTHEASTERN OF THE QINGHAI-TIBETAN PLATEAU

Study of the Quaternary magnetostratigraphy in the Gonghe basin on the northeastern margin of the Qinghai-Tibetan Plateau shows that four normal paleomagnetic polarity intervals and three reverse paleomagnetic polarity intervals are recorded in the Quaternary section and that the deposition of the section began at~2.11 MaB.P..Based on the magnetostratigraphic study,combined with an analysis of the sedimentary characteristics and features of available Quaternary,sporopollen assemblages of the section,the authors think that the section records the paleoclimatic evolution in the basin since 2.11 MaB.P.and that the major epochs of paleoclimatic transition occurred at about 1.92,1.75,1.40,1.02 and 0.87 MaB.P.respectively.This is mainly the result of the long-distance effect of the strong uplift of the Qinghai-Tibet Plateau.Therefore,the establishment of the time sequence of paleoclimatic changes in the Gonghe basin should have certain significance for the study of the uplift of the Qinghai-Tibetan Plateau and its environmental effect,as well as the development of the Yellow River.