QUATERNARY GLACIAL REMNANTS IN THE ZANDA BASIN AND ITS PERIPHERAL HIGH MOUNTAIN AREAS, TIBET, AND DIVISION AND CORRELATION OF GLACIAL STAGES

Quaternary glacial remnants in the Zanda basin and its peripheral high mountain areas,Tibet,are widespread and continuously developed and have a complete range of types.The main glacial-eroded remnants include U-shaped valleys,knife-edge crests,horns(pyramidal peaks),firn basins,cirques,ice-scoured hills and bedrock drumlins;the till remnants are moraines,outwash deposits,glacial erratic boulders,terminal moraines,lateral moraines and medial moraines.The characteristic morainic and outwash geomorphologies include outwash plains and platforms,morainic hills.The remnants of compressional structures are folds,faults,epigenetic structures formed by faulting,press pits,pressure fractures and deformed gravels.ESR dating of moraines gives a maximum age of 2.33 Ma.According to the features,distribution and ages of the morainic and outwash deposits,seven glacial stages,six interglacial stages and one neoglacial stage of regional glacial development may be distinguished from older to younger.The Zanda basin and its peripheral high mountain areas,Tibet,are now known as a region where the most Quaternary glacial remnants are found and Quaternary glacial remnants are most completely preserved and most continuously developed on the Qinghai-Tibet Plateau.This study provides important data and grounds for the study of the Quaternary glacier evolution,division and correlation glacial stages and study of the paleoclimate and paleoenvironment in this area and the Qinghai-Tibet Plateau.