罗布泊干盐湖第四纪环境演变研究进展

Research Progress of Quaternary Environmental Evolutionin Lop Nor Playa

罗布泊干盐湖作为塔里木盆地唯一的尾闾湖,经历了淡水湖—微咸水湖—咸水湖—盐湖—干盐湖的演化历程,是亚洲内陆环境演化及全球气候变化研究的天然实验室。简要概述罗布泊第四纪沉积特征及环境变化过程,并对未来研究提出展望。罗布泊早更新世主要为河流三角洲—滨浅湖—湖泊等沉积环境,是罗布泊盆地第四纪时期最为湿润的时期。自早更新世末期进入以含石膏粉砂黏土为主的咸水湖沉积阶段,中更新世中期罗北凹地进入巨量钙芒硝沉积阶段,干旱程度加剧,指示常年性盐湖亚环境。罗布泊全新统底部发育含石膏黏土、砂岩,表层广泛发育石盐壳,指示全新世伊始,罗布泊气候经历了一个相对湿润期,其北部逆向演化至咸水湖阶段,波动至半干旱气候,而后又向极端干旱气候转变,最终演化为干盐湖环境。展望未来,罗布泊古环境研究主要有以下几方面的内容需要进一步深入:①Ca-Cl型卤水对盐湖沉积亚环境综合判别的影响研究;②高精度地层时代框架;③可替代性环境演化载体;④定量化环境演变研究。

As the only terminal lake of the Tarim Basin,Lop Nor has experienced the evolution of freshwater lake-brackish lake-saline lake-playa.It is a natural laboratory for the study of environmental changes of Inner Asia even global climate change.In this report,we briefly summarize the Quaternary sedimentary and process of environmental changes in Lop Nor,furthermore bring up future research expectation.Early Pleistocene is dominated by sedimentary facies such as river deltas-shallow lakes and lakes,which is the wettest period in the Lop Nor Basin.In the end of the Early Pleistocene,Lop Nor entered the gypsum-bearing silt clay deposition stage which indicate enter brackish lake stage.In the mid-Middle Pleistocene,the Luobei depression entered the stage of massive glauberite deposition,indicating the perennial saline lake subenvironment and the degree of drought intensified.The Lower Holocene in Lop Nor developed gypsum-bearing clay and sandstone,and the surface layer developed salt crust,indicating it was in the playa stage,which means that at the beginning of the Holocene,the environment is wetter,the northern Lop Nor reversely evolved to the brackish lake stage,fluctuating to a semi-arid climate,and then turned to an extreme arid climate,and eventually evolved into a playa.Looking forward to the future,there are at least four aspects should be further studied:①the study on the influence of Ca-Cl brine on the comprehensive research of salt lake sedimentary subenvironment;②highprecision stratigraphic era framework;③alternative environmental index;④quantification environmental evolution research.