Sedimentary Evolution of Mesozoic Era in Kuche Depression, Tarim Basin

Key words: 
• sedimentary facies /
• sedimentary evolution /
• Mesozoic Era /
• Kuche Depression Tarim Basin /

Abstract: 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, fandeltas 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.