The morphological characteristics of glacial deposits during the Last Glaciation, taking the Parlung Zangbo River Basin as an example

Abstract

Moraine morphology is a mark of climate change.Previous field investigations have found that the moraine of last glacial has a uniform pattern.Ten glacial deposits in the Parlung Zangbo River basins,southeast Tibetan Plateau,were selected to study the deposit characteristics of the Last Glaciation,to reveal the climate change process reflected by the glaciation.It is found that a huge moraine ridge deposited by ancient glacier in MIS(marine isotope state) 2 of the last glacial,which can be mentioned as the main moraine ridge.The main moraine ridge indicates that it was formed under a longtime sustained and stable climate.There are at least two but smaller moraine ridges in external extension or in the bottom of the main moraine ridge,which indicate that climate of the ice age before MIS 2 was more severe but the duration was relatively short.These phenomena may reflect the climate in the ice age of MIS 4 and / or MIS 3.In the valley between the inside of the main moraine ridge and the modern glacier there are many moraine ridges usually,of which the scale is small as compared with the main moraine.Some of the moraine ridges may be recessional moraine,but the influence of Younger Dryas or Heinrich t events should be noteworthy.The moraine ridges of Neoglaciation and Little Ice Age can be identified near the terminus of modern glacier.With high-precision system dating,one can restore the curve of climate change by studying the shape,scope and scale characteristics of glacial deposits in southeastern Tibet,which is helpful to understand the relationship between global oxygen isotope curve and climate change.