祁连山南部地区三叠纪弧后前陆盆地——基于沉积填充与大地构造的证据

本文通过对祁连山南部地区三叠纪沉积充填特征的研究，建立了盆地形成过程中沉积充填与区域构造演化的关联。依据沉积充填特征、构造接触关系及区域地质背景，认为祁连山南部地区三叠纪盆地具有弧后前陆盆地的构造属性；综合分析年代学、沉积物性和盆地内部填充单元的差异划分出与柴达木岛弧带和祁连山南部弧后前陆盆地相关的区域大地构造单元。认为早三叠世-中三叠世中期，南部遭受俯冲作用持续向北挤压推覆导致盆地挠曲沉降；中三叠世中期-晚三叠世中期发生弧(东昆仑-柴北缘)-陆(巴颜喀拉地块)碰撞，祁连山南部盆地挠曲沉降增大，其间形成区域性断裂和不整合等盆地记录的地质事件；晚三叠世晚期祁连山南部盆地发生过补偿陆相填充，弧后前陆盆地消亡。

Triassic retroarc foreland basin in southern Qilian area: Evidence from sedimentary filling and tectonics

Based on the sedimentary filling characteristics of the Triassic basin in southern Qilian area, the relationship between the basin formation and the regional tectonic backgrounds is rebuilt, which demonstrates that this Triassic basin has a tectonic affinity of retroarc foreland basin. A comprehensive analysis of the chronology, sedimentary properties, and the differences in the filling units within this basin disclosed that the formation of the regional tectonic units are related to the evolution of the Qaidam island arc and the retroarc foreland basin in the southern Qilian area. It is believed that during the Early-Middle Triassic, the southern Qilian area suffered from subduction and continued to squeeze and nappe to the north, which caused the basin flexural settlement. In the Middle Triassic to the Late Triassic, an arc (Eastern Kunlun-Northern Qaidam)-continent (Bayan Har Block) collision occurred, and the flexural subsidence of the southern basin in Qilian area increased, and regional faults and unconformities formed during the period. In the Late Triassic, the southern basin of the Qilian area had an over-compensated filling process, which resulted in the disappearance of the retroarc foreland basin.