克里雅河河谷地貌与塔里木盆地早-中更新世大湖环境

Geomorphological features of the Keriya River valley and the early-middle Pleistocene great lake environment of the Tarim basin

克里雅河谷现今的地貌特征是其1.09Ma以来演化的结果,记录了构造-气候综合作用下的地表过程。在克里雅河流出西昆仑山山前的支流吾格也克河至克里雅河主支的康苏拉克河段,河谷地貌清楚地分为早期的宽阔河谷地貌和其后明显窄小的峡谷地貌。克里雅河近50年来的平均年径流量约为7.345×108m3,早期宽阔河谷发育阶段的河水年径流量推测值不小于146.9×108m3。这表明当时克里雅河的河水流量远比现今的观测值要高得多,当时上游来水、区域降水远比现在多,塔里木盆地的古气候环境与现今塔里木盆地的荒漠环境迥异。在邻区策勒河西域砾岩中观察到的泥石流沉积表明,早更新世及略早一些,西昆仑山有可观的季节性洪水,那时的克里雅河河谷更加宽阔。因此,早—中更新世塔里木盆地应当存在相当可观的大湖。

The present geomorphological features of the Keriya River valley are the results of evolution since 1.09 Ma BP and record the surface processes controlled by combined structural and climatic effects. Geomorphologically, the valley may be divided notably in- to the early-stage broad valley and the late-stage narrow and small deep-incised valley from the Wugeyeke River--a tributary of the Keriya River flowing out of the piedmont of the Kunlun Mountaim--to the Kangsulake River of the main branch of the Keriya Riv- er. During the past five decades, the mean annual runoff has been ~734.5 million m3, and the mean annual runoff in the early broad valley development stage is estimated to be more than 14.69 billion m3. It reveals that at that time the runoff of the Keriya River was by far higher than the present observation values, which suggests that the water from the upstream and regional precipitation were much more than nowadays, and that the paleoclimate and paleoenvironment of the Tarim basin were utterly different from the desert environment of the present Tarim basin. The mudflow deposits observed in the Xiyu conglomerate along the Qira River in the adja- cent area suggest that there was substantial seasonal flood in the West Kunlun Mountains in the early Pleistocene and slightly earlier, when the valley of the Keriya River was much broader. Therefore it is thought that a ＂great lake＂ should exist in the Tarim basin in the early-mid Pleistocene