柴达木盆地达布逊湖北雅丹剖面沉积特征及其环境意义

摘要

柴达木盆地达布逊湖北盐湖构造发育一组NWW向雅丹地貌.对雅丹剖面沉积年代、总有机碳和粒度等进行测试,综合分析了影响因素与环境气候的关系.结果表明:雅丹剖面主要经历了中更新世(约740 ka)干旱→潮湿→干旱的气候波动过程;剖面可以划分为757.5~758.0、741.6~757.5、732.8~741.6 ka等3个气候变化相对明显的时期,分别对应干旱、潮湿、干旱阶段;剖面中沉积物总有机碳、粒径中值等可以较好地反映三湖坳陷北斜坡盐湖构造在中更新世(约740 ka)的气候环境演变,并且结合剖面具有典型的河流三角洲相和湖相沉积特点可以体现中更新世及其以后经构造运动挤压抬升一直处于风化剥蚀的状态;剖面底部为河流相沉积环境,上部为湖相沉积环境,经历了水进和水退的过程;剖面反映了内陆封闭湖泊在暖湿期水量充沛,沉积物中总有机碳较高以及粒径中值较小的特点.%NWW-direction Yadan geomorphology develops in the salt lake tectonic of the northern Dabsun Lake,Qaidam Basin.The sedimentary age,total organic carbon and particle size of Yadan profile were analyzed, and the relationship between the influencing factor and environmental climate was discussed.The results show that Yadan profile experiences Middle Pleistocene (~740 ka)climatic fluctuation process from dry to wet,and then to dry;the profile can be divided into three periods of 757.5-758.0,741.6-757.5,732.8-741.6 ka according to the relative obvious climatic change,corresponding to the stages of dry,wet and dry,respectively;the total organic carbon and median particle size of the profile show Middle Pleistocene (~740 ka) climatic-environmental changes in salt lake tectonic of the north slope,Sanhu depression,and reflect the weathering denudation of profile under the extrusion and uplift of tectonic movement in Middle Pleistocene and later,combined with the characteristics of typical fluvial delta facies and lacustrine facies of the profile;the bottom of the profile is fluvial facies sedimentary environment, and the top is lacustrine facies sedimentary environment,and experiences the water transgression and dereliction;the profile reflects that inland closed lakes have abundant water in warm-wet period,and have the characteristics of higher total organic carbon and smaller median particle size.