内蒙古额济纳旗地貌特征及其构造、气候事件

Tectonic and Climatic Events Recorded by Morphologic Units in Ejin Qi, Inner Mongolia

根据遥感卫星影像解译及野外地质实地调查,将内蒙古额济纳旗地区的地貌单元划分为中低山区、冲—洪积平原、湖积盆地及风成地貌。根据不同地貌单元组成的沉积物年龄测定和分析,初步认为上新世—早更新世的构造抬升形成苏泊淖尔级湖积阶地;早更新世末(750±60kaBP),发生一次明显的构造抬升活动,形成东、西居延海间的台地;另一次明显的构造抬升记录发生在中更世末—晚更新世初,即149±60kaBP之后,形成黑城冲湖积台地;苏泊淖尔级阶地形成于全新世早、中期,属气候干旱湖泊萎缩形成的气候阶地,阶地沉积物中保存的古风成砂丘,表明晚更新世末—全新世早期气候一度恶化。天鹅湖湖积阶地的形成表明5000a之后一段时间,气候相对适宜;全新世中后期,气候波动强烈,1200aBP出现一次丰水期。

The basin and morphologic units aeolian landform of by Ejin Qi can be divided into middle-low mountain, geologic investigation and interpretation of remote fluvial-pluvial plain, lake sense picture. Landform feature and sediment age dating can distinguish some of the tectonic and climatic events. The second grade terrace of Sogo Nuer Lake formed in Pliocene or Early Pleistocene epoch by sporopollen analysis. The terrace between Sogo Nuer and Gaxun Niir Lake was formed by tectonic uplift at the end of Early Pleistocene. The age of sediment is 750±60 ka BP. Another obvious tectonic uplift, which formed the alluvial-lacustrine terrace of Heicheng, occurred at the end of Middle Pleistocene or the beginning of Late Pleistocene according to the sediment dating age, 149±60 ka BP. The first grade terrace of Sogo Nuer formed mainly of climatic arid and lake shrinking at early-middle period of Holocene. Harsh climate is showed by the dune relics in section of terrace from early to middle Holocene. The climate was humid from 7360±135a BP to 4740±60 a BP, when sediment of Swan Lake terrace deposited. The climate fluctuated violently during the period or middle-late Holocene. A period abundant in rainfall appeared at 1200 a BP.