塔里木西南喀什凹陷几个地质问题的新认识

NEW KNOWLEDGE ON GEOLOGY OF KASHI DEPRESSION IN SOUTHWEST TARIM

喀什凹陷的主要构造样式为逆冲推覆构造,喀什凹陷南部前震旦系结晶基底于前锋带呈飞来蜂形式产出.喀什凹陷南部石炭系——下二叠统有4种沉积类型,并可建立塔西南C—PI有限洋盆—克拉通边缘深坳陷—克拉通内部坳陷碳酸盐岩沉积相模式.以构造相变、同位素、古生物化石等为依据,认为前人所划T3或T3—J大多为J,T3仅为零星分布.以区域构造、沉积作用及沉积相带展布等为依据,对白垩纪—古近纪喀什凹陷原型盆地进行了分析;上新世以来帕米尔地块强烈向北逆冲,分割了曾经相互连通的塔里木—卡拉库姆地块.

The Kashi depression is dominated by thrust-nappe structure which led to the formation of outlier of pre-Sinian crystalline basement in the fronter zone. Four sedimentary types for the Carboniferous-Lower Permian strata are differentiated in southern Kashi depression and adjacent Qimgen area. Sedimentary facies model of the carbonate rocks is built up for C-P1, i.e. limited ocean basin-craton marginal deep depression-craton interior depression. Proofs are thus provided for the lateral extension of the Kashi depression during the late Paleozoic.The evidences from structure, facies change, isotopic data and fossils show that the late Triassic of Kashi depression only has a small exposure, implying that the Kashi depression was uplifted during the time. The prototype basin during the Cretaceous-Paleogene in Kashi depression is also discussed in terms of regional tectonics. It is regarded that Pamir block has thrust northward and disconnected Tarim block from Karakum block.