鄂西建始中更新世高海拔砾石层的发现及意义

在鄂西建始李家湾长江、清江分水岭处发现残留的中更新世河流相砾石层,砾石层及河谷地貌特征反映其可能为NNE向古水系即"古马水河"所残留的"高阶地",从而指示"古马水河"可能为一条顺NNE向构造线向SW方向流的大河,说明长江水系在不断向南袭夺清江水系,分水岭不断南移。对砾石层两个样品的ESR年龄测定结果分别为728±72 kaBP和789±78 kaBP,属中更新世早期。与长江三峡阶地的年代对比表明砾石层与长江三峡第五级阶地为同时期形成,这可能指示在三峡地区已不存在多级夷平面,目前所存在的剥夷面可能形成于早更新世。

Discovery of high-elevation gravel during middle Pleistocene in Jianshi area and its significance

We report the middle Pleistocene gravel on the watershed of the Qingjiang and Yangtze Rivers in Jianshi area,west Hubei Province.Features of gravel and valley geomorphic show that the gravel bed may be the high terrace of the NNE ancient river Old Mashui River;therefore,the Old Mashui river might be the great river along the NNE tectonic line flowing southwest,indicating that the Yangtze River captures the Qingjiang River continuously,and the watershed moved southward accordingly.The ESR dates of two sample...