塔里木盆地西北缘柯坪冲断带构造变形特征

Structural deformation characteristics of the Kalpin thrust belt, NW Tarim

柯坪冲断带位于塔里木盆地西北缘，是新生代南天山褶皱冲断系的一部分。本文根据野外实际考察和地震剖面解释，总结了该冲断带的构造变形特征。它是发育于古生界中且以中寒武统膏盐层为主滑脱面的薄皮构造，是内部结构相对简单的叠瓦状冲断，因更新世才定型而具暴露式冲断前锋，有断层传播褶皱发育但已遭强烈剥蚀，前展式冲断。上新世晚期的冲断曾控制了磨拉石盆地发育（西域组砾岩），但该盆地已遭更新世的冲断推覆作用破坏。根据平衡剖面恢复，柯坪冲断带南部3排冲断层的总构造缩短量为29.1%～40.7%。

The Kalpin thrust belt or Kalpin fold-and-thrust belt, located in the northwestern margin of the Tarim Basin, is a part of the South Tianshan fold-and-thrust system. On the basis of field investigation and seismic section interpretation, the main features of the Kalpin thrust belt could be summerized as the follows. 1 ）Only the Paleozoic rocks were involved into the thrusting, which meant that the major detachment fault was gypsum-salt layer in the Middle Cambrian. 2）The belt was characterized by imbricated thrusting, with a relatively simple inner texture. 3）The belt had an exposed thrust front, since it did not create till Pleistocene. 4）The fault-propagation folds once occurred, which were experienced violently denuded. 5）The belt was a piggyback one, with the thrusting expanded southwards. 6） A molasse basin once occurred during Pliocene, with the geological records being conglomerate of the Xiyu Formation, but the basin had been disrupted by the Pleistocene thrusting-nappe structuring. The Kalpin thrust belt consisted of the northern fold sub-belt and the southern thrust-nappe structural subbelt, and for the latter, the balanced section analysis revealved the minimal shortening rate being 29.1% to 40.7%.