塔里木盆地库车坳陷中生代沉积演化

塔里木盆地库车坳陷中生代为一前陆坳陷,其内沉积了一套厚度巨大的冲积-湖泊碎屑沉积体,可识别出5种相类型、15种亚相及38种微相。坳陷呈北陡南缓的箕状,沉积体北厚南薄,沉降中心与沉积中心发生明显的错位。中生代,坳陷内湖泊经历了深陷-充填-变浅加宽的过程;三叠纪为深陷期,沉积区范围小;早、中侏罗世为充填期;晚侏罗世至白垩纪湖泊变浅加宽。气候变化总体趋势为:干旱-潮湿-干旱;早、中三叠世为干旱气候;晚三叠世至中侏罗世气候潮湿,煤系地层广泛发育;晚侏罗世至白垩纪气候转为干燥,沉积物皆呈红色

Sedimentary Evolution of Mesozoic Era in Kuche Depression, Tarim Basin

Kuche Depression, situated in the northern part of Tarim Basin, was a foreland depression and there was a set of extremely thick, alluvial lake classic deposits in it in Mesozoic Era. Five facies(meandering river facies, fan deltas facies, braided river deltas facies, meandering river deltas facies and lacutrine facies), fifteen subfacies and thirty eight microfacies are recognised. Kuche Depression was a "dustpan" shape depression with steep slope in the north side and gentle slope in the south side. Deposits are thicker in the north side than in the south and the depocenter did not coordinate with the center of subsidence. The lake in Kuche Depression went through a period from deep subsidence lacustrine (Triassic Period, fan deltas and braided river deltas sediments are dominant) to filling lacustrine (early and middle Jurassic, braided river deltas is dominant) to broad and shallow lacustrine (late Jurassic and Cretaceous Period, coastal lake and shallow lake sediments are dominant). From Triassic Period to middle Jurassic, Kuche Depression was an isolated basin and area was small, not joining with Tarim Basin because there was a provenance in its south side. Beginning from late Jurassic, the southern provenance vanished and Kuche Depression joined with Tarim Basin as a part of it. Palaeoclimate change was very clear in Kuche Depression. It was an arid climate in early and middle Triassic, a damp climate from late Triassic to middle Jurassic because many seam are discovered, back to an arid climate from late Jurassic because all sediments have red color.