塔西北柯坪剪切挤压构造

塔里木西北的柯坪地区存在着再变形的逆冲岩席。研究表明塔里木盆地西北边界断层－阿合奇断层为一巨型左行走滑断层。它在新生代的总走滑量达３０４ｋｍ，具有与塔里木盆地东南边界阿尔金断层相同量级的走滑量。阿合奇断层与阿尔金断层造成了阿合奇－西昆仑－西南塔里木－阿尔金断层剪切挤压构造系统。

ON THE KALPIN TRANSPRESSION TECTONICS OF NORTHWEST TARIM

Located on the northwest margin of the Tarim basin, the Kalpin Ranges are totally composed of thrust sheets, which comprise from Cambrian to Permian stata generally dipping to north. The Cambrian strata at the basal part of the sheets thrust over the Permian strata of the top part of further south thrust sheets. Therefore the verging direction of the thrusting is southward obviously. These thrust sheets arrange parallelly with the length of 30 to 150 km for a single sheet. The valleys between two sheets are usually filled with present alluvial fans. The paleogene and early Neogene which sometimes appear above the Permian strata are the top of the thrust sheet. These Tertiary sediments lie on the Permian parallelly or with angles only a few degrees, suggesting that the thrusts emplaced after or during Miocene deposition. The Miocene Kanchun formation exhibits non-marine sandstones, mudstones and gradually grows into the Pliocene Kuqa formation exhibits massif sandstones and conglomerates. The sedimentary features of these two formations as uniform mollase deposits indicate the uplifting and the thrusting during the Neogene time. There is no Mesozoic in Kalpin area except minor Cretaceous strata in the west, most of Kalpin Ranges, suggesting that the Kalpin area uplifted during Mesozoic and exhibited as a plateau untill Neogone. The Tianshan mountains reacted since Miocene and started the mollase deposition and the thrusting in Kalpin area. In the Kalpin Ranges there are six rows of thrust sheets, but in some places only two. They were aranged straight or curved forming special small orocline pattern in the map view. Using the strata polarity of the thrust sheet, considering the long itudinal strike ship faulting along the thrust sheets, the mystical structure pattern of Kalpin Range is solved clearly. In Kalpin Ranges, there are two longitudinal strike slip faults F1 and F2, two strike slip faults bend contortion (A)and (C)and one strike slip fault propagation contortion (B) of asymmetric type structurtes of strika slip fault related contortion. ENE trending Aheqi fault zone starts from Kalakuaili, passing Heiyingshan, Wushi County, Aheqi town, to north of Wuqa, then extends into Kirghizstan. As a boundary fault zone it separates the Mesozoic and Cenozoic strata and structures of Tarim basin from those of south Tianshan mountains. It is northwest boundary fault zone of Tarim basin. In the point view of the stress field and deformation mechanism, Aheqi fault zone is a broad fault zone, and the structures of Kalpin are involved into the Aheqi fault system. The strike of Aheqi fault zone is N60°E. According to slip line field caused by the India-Tibetan collision,the Aheqi fault zone falls into the position of sinistral strike slip line. Closely located to the south of Aheqi fault zone, the Kalpin Range faults get their E-W strike in their western part. Therefore the Kalpin Range faults fall in the transpression or restraining fault bend. The transpression resulted in the southward thrusting in Kalpin Ranges. The amount of sinistral strike slip (304 km) of Aheqi fault zone closely coincides with the 300 km slip (Tapponnier et a1. 1986) of Altyn fault.