塔里木盆地腹地第四纪沉积物粒度特征及其沉积环境

Grain-size characteristics and sediment environment of Quaternary sediments in the central Tarim basin

利用MS-2000型激光粒度仪及相关软件,对位于塔里木盆地腹地的塔中KT2号钻孔进行粒度测试与分析,绘制频率曲线图、概率累计曲线图等,结合其他测试数据、资料,进行沉积环境分析。结果表明塔里木盆地在早更新世以河湖相沉积为主,其晚期出现了风成相沉积;中更新世早期以洼地湖泊相沉积为主,但风成相沉积作用明显加强,至中更新世晚期,发展成为以风成相为主,经晚更新世到全新世,沙漠大规模形成,并逐步发展。气候总体由温暖湿润变为寒冷干旱。

Tazhong KT2 hole locates at hinterland of Tarim Basin, Xinjiang, with depth of 885.99m, revealed the Quaternary stratum. The test results were illustrated as protracted frequency graph, probability cumulative graph, and other datum with Mastersizer - 2000 Laser Grain-size analyzer. The rock core is mainly made of silt sand, siltfine sand, fine sand. A few coarse sand, multilayer claypan, average grain diameter are in the range of 2.5 - 6.2φ, the deposition environment was in comparative stabilization. Frequency graph and probability accumulative graph reflect borderlines at 130 m and 650 m, including three groups from end to top. The first group corresponds to d-Pleistocene, climate became cold and dry, rives transformed to lake and marsh, basin settled rapidly, alluvium and diluvium developed broadly. The second groups corresponds to early Pleistocene, sediment mainly shows as river-lake phase, alluvium and diluvium appear by turns. Climate change frequently, cold and dry, change of temperature has evidence gyre character, Aeolian product appear at late, show the desert came into being. The third group corresponds to middle-late Pleistocene. At initial stage, it mainly includes rive-lake phase, then develop to eolian form, desert formed completely and started to expand. According to rock stratum, age measure datum and pollen information, Tarim Basin was mainly at river-lake sediment phase in early Pleistocene, later appeared eolianform phase deposition. At the beginning of middle-Pleistocene, marsh and lake phase deposition dominate the form, but eolian-form enforced distinctly, to later middle-Pleistocene, eolian-form phase deposition taked the main form from later Pleistocene to Pleistocene, desert formed cosmically and developed gradually. Climate changed from warm and wetness to cold and dry generally.