龙门山构造带印支期构造递进变形与变形时序

据盆山耦合关系,以四川盆地西缘须家河组沉积特点,推演出龙门山在印支期的变形分为三期,自北而南发生幕式递进冲断推覆构造。印支早幕发生在须二时期,构造变形局限于龙门山北段的北部后龙门山;印支中幕发生在须四时期,构造变形域局限于龙门山中段以北地区;印支晚幕发生在须家河期末,是本区变形强度大,波及范围最广的一期。四川盆地西部普遍缺失瑞替期沉积,并有不同程度的变形。

Indosinian progressive deformation and its chronogenesis in Longmengshan structural belt

According to the coupling relationship between basins and mountains and the depositional characteristics of the Xujiahe Formation in the western margin of Sichuan basin, it is deduced that Indosinian deformation occurred in three episodes in Longmengshan,with episodic progressive overthrust nappes developed from north to south. The early Indosinian episode happened during the deposition of the second member of Xujiahe Formation when the deformation was confined to the north section of Longmengshan; the middle Indosinian episode was within the deposition of the fourth member of Xujiahe Formation when the deformation was limited on the north part of the middle section of the mountain;and the late Indosinian episode was at the end of deposition of the Xujiahe Formation when the deformation was the strongest and most extensive in the study area. It is also noted that the Rhaetian deposits are generally absent in the western Sichuan basin with deformation of various degrees.