修沟-玛沁断裂

修沟-玛沁断裂,南北两侧地块都自西北向东南运移,所不同的是晚期南侧比北侧移动快,故似具反扭性质。断裂两侧三叠纪地层上的石炭-二叠纪地层体,是古三叠纪海中的半岛和孤岛,其形成、展布与修沟-玛沁断裂没有直接的成因联系。 修沟-玛沁断裂是昆仑纬向体系与巴颜喀拉山北西-南东向扭动体系之间的过渡性构造,它的形成、演化标志着古生代昆仑纬向体系历史的结束与中生代青藏高原东北部新体系的诞生。

THE XUGUI-MAQIN FAULT

The Xiugou-Maqen fault in central Qinhai Province has attracted interest of the Chinese and foreign geologists for many years.Based on previous research results and the author's field investigation this artiele provides a summary in three aspects of the fault,including its geomorphologic features, activity and relation with the Kunlun latitudinal system.The Xiugou-Maqen fault appears as a wide valley geomorphologically. The early and late stages of the activity of the faultmay be distinguished. In the early stage, the north wall of the fault moved towards the southeast relative to the south wall, while in the late stage, the south wall moved towards the southeast, accompanied by extension and down faulting.As to the relation between the Xiugou-Maqen fault and the Kunlun latitudinal system, the author believes that:l) the presence of the Permo-Carboniferous rocks within the Triassic strata in the Buqing-Anymaqing Mountain has no necessary connection with the formation of the Xiugou-Maqen fault; and 2) the Xiugou-Maqen fault is a transitional zone between the Kunlun latitudinal system and the Bayan Har NW-trending shear system, and its formation and evolution marked the end of the history of the Paleozoic Kunlun latitudinal system and the birth of the Mesozoic shear system in the northeastern part of the Qinghai-Xizang Plateau.