巴丹吉林沙漠及其高大沙山研究评述

亚洲内陆干旱化是国际古环境研究的热点问题。巴丹吉林沙漠是亚洲内陆第二大流动沙漠,拥有世界最高大的风积地貌——沙山,是亚洲内陆干旱化研究的重要载体。沙山的形成演化与其所在沙漠的环境变迁有关,且真实地记录了区域与全球的气候变化。沙山形成过程研究应从区域地质和环境演化入手。本文从地质演化、环境演化、沙漠沉积、沙漠水文、沙山地貌和沙山形成发育等6个方面阐述了有关巴丹吉林沙漠的高大沙山、沙漠湖泊和沙漠自身的形成演化。认为构造-气候事件是亚洲内陆干旱化的一级控制,地球运行轨道变化是二级控制。自新构造运动始至其趋缓,构造-气候事件始终是巴丹吉林沙漠环境气候的主控因素,地球运行轨道变化也起很大的作用。此时西风环流是中国北方沙漠带环境气候的主要驱动力。新构造运动趋缓后,地球运行轨道变化是中国北方沙漠带环境气候的主控因素,青藏高原对大气环流的影响逐渐显现,东亚季风环流是该地区环境气候的主要驱动力。古水说可以很好地解释沙漠湖泊水的来源问题,沙漠湖泊是通过浅层的地下水路依靠保存在地下的古水来相互补给的。宏观上沙漠湖泊是风蚀湖,高大沙山的维持与沙漠湖泊之间不存在必然的因果关系。风成说可以较好地解释沙山的成因。未来的重要研究方向之一是将沙山、沙漠及其演化一同进行研究,重建沙山和沙漠的演化历史,并探讨它们之间的关系。

A review of the Badain Jaran Sand Sea and its megadune

The inland aridification in Asia is a hot topic in paleoenvironmental research. The Badain Jaran Sand Sea is the second largest mobile sand sea in the Asian inland. It has the world′s highest aeolian landforms—megadune. Thus, it is an important carrier for the study of inland aridification in Asia. The formation and evolution of megadune are related to the environmental changes of the sand sea where they are located. Megadune recorded the regional and global climate changes. Therefore, the study on the formation and development of megadune should start from regional geology and environmental evolution. This paper expounded the formation and evolution of megadune, lakes and the sand sea itself in the Badain Jaran Sand Sea from six aspects: geological evolution, environmental evolution, sedimentology, hydrology, megadune landforms, and the formation and development of megadune. It is considered that for inland aridification in Asia tectonic/climatic events are the primary factor and the Earth′s orbital changes are the secondary factor. From the beginning of the neotectonic movement to its slowing down, tectonic/climatic events had always been the main factor controlling the climate in the Badain Jaran Sand Sea, and the Earth′s orbital changes had also played a significant role. At that time, the westerly circulation was the main driving force of the climate for these areas. After the moderating of neotectonic movement, the Earth′s orbital changes were the main controlling factor of climate in the sand sea belt of northern China. The influence of the Qinghai-Tibet Plateau on atmospheric circulation had gradually emerged. The East Asian monsoon circulation was the main driving force of climate in this region. In addition, effective moisture was controlled by summer monsoon, while winter monsoon dominated aeolian activities. These were different from the unified model under the action of westerly circulation. The paleo-source recharge hypothesis can better explain the origin of lake water. Lakes are replenished by the ancient water preserved underground through shallow underground waterways. On the macro level, lakes are wind-eroded lakes. Thus, there is no inevitable causal relationship between lakes and the maintenance of megadune. The aeolian hypothesis can better explain the formation of megadune. One of the important researches in the future will be to reconstruct the evolutionary history of megadune and sand seas and to explore the relationship between them.