罗布泊东阿奇克谷地雅丹地貌与库姆塔格沙漠形成的关系

阿奇克谷地位于罗布泊洼地之东, 93°E以西, 东西长约150km, 南北宽20~30km。为新生代北山与阿尔金山之间的地堑凹地的一部分, 与东面河西走廊的地堑凹地相通。根据出露的雅丹地层河湖相沉积样品所作的ESR测年(2272~10094kaBP)和本区的地质地貌特征可将阿奇克谷地演化与库姆塔格沙漠的发育史归纳为4个时期。①早更新世至中更新世罗布泊古湖扩大时期, 东部湖湾宽约50~60km, 向东延伸至93°15′E或更东; ②中更新世晚期山地上升与古湖湾退缩消失时期, 距今30万年前左右, 青藏高原强烈隆升, 阻挡了海洋水汽的进入, 亚洲内陆加速变干, 由于阿尔金山的左旋向东滑动, 在北面古湖区地层发生了与阿尔山斜交的羽毛状断裂谷群, 并因东北向的断裂上升与东西向的河西地堑谷地斜交, 阻断了疏勒河水不再向西流入罗布泊, 使东部湖湾向西退缩并逐步消失; ③中更新世晚期至晚更新世初, 暴雨径流与强烈的风蚀作用时期, 阿奇克谷地北部的洪积湖相沉积台地支沟口形成雅丹土丘群, 谷地南面库姆塔格沙漠北面羽毛状断裂谷群形成雅丹垄脊和风蚀谷, 谷地中央呈现出季节性的盐碱沼泽和零星雅丹土丘; ④晚更新世末至全新世库姆塔格沙漠扩大, 向北埋没了羽毛状断裂谷(风蚀谷)和雅丹垄脊, 形成了世界上独特的羽毛状沙丘。

The Yardang Landform of Aqik Valley in the East of Lop-Nor and its Relationship with the Evolution of the Kumtagh Desert

The Aqik Valley is located between the Lop-Nor depression and longitude 93°E. It is about 150 km long and 20~30 km wide. It is a part of the Neogene graben depression between the Aljin Mountains and the Baishan Hill. Its east end is adjoined to the Hexi Corridor depression. Based on the ESR dating of the Yarding strata and regional geomorphological features, the evolution history of the Aqik Valley and the Kumtagh Desert can be divide into four stages:(1) The big lake stage of Lop-Nor. This stage is from early Pleistocene to middle Pleistocene. The east side of the lake is at about longitude 93°15′E or more far, and the east part of the lake had 50~60 km wide.(2) The mountain uplift and lake retreat stage. During late middle Pleistocene(about 300 ka BP), the strong uplift of the Qinghai-Tibetan Plateau formed a barrier for the maritime air mass, and this caused the climate of Central Asia to be drier. In the north of the Aljin Mountains, plumetic fault valley group occurred in the strata of old lakes. The reason is that Aljin Mountains is moving eastward. In this region, there are two groups of faults(one EW direction, the other NE direction). So, the water of Shule River doesn't flow into the Lop-Nor. Its east lake valley is dried up gradually.(3) The rainstorm erosion and strong wind erosion stage. During the late Middle Pleistocene and the early Late Pleistocene, there are many Yardang groups at the branch river mouth of the north part of Aqik Valley. In the southern side of the valley, there are many NE direction, paralleled Yardang ranges and wind-eroded valleys. In the middle of the Aqik valley, there are seasonal salt marsh and isolated Yardang.(4) The expanding stage of Kumtagh Desert at the end of Late Pleistocene and Holocene. In this stage, the dunes expanded northward and covered up the plumetic fault valleys. Hence, wind erosion valleys and Yardang ranges became the most incredible plumetic sand dunes in the world.