青藏高原北缘新生代早期构造运动——来自酒西盆地始新世-渐新世的沉积学约束

位于青藏高原北缘的酒西盆地,出露有完整的晚始新世地层,真实地记录了周缘构造的运动,使其成为研究高原北缘新生代构造活动的最佳场所之一.基于酒西盆地11条沉积剖面的沉积相、重矿物和古水流研究,建立了火烧沟组-白杨河组高精度的沉积格架,识别出盆地在晚始新世主要为走滑盆地,沉积形态主要受阿尔金断裂左行走滑作用控制.阿尔金断裂强烈的走滑作用受到北部阿拉善地体的阻挡,在酒西盆地北部形成一个前锋带.随后,高原内部强烈的南-北向挤压作用沿酒西盆地的刚性基底向南传递到北祁连断裂,形成了新近纪早期酒西前陆盆地的雏形.

Early tectonic evolution of the northern margin of the Tibetan Plateau: Constraints from the sedimentary evidences in the Eocene-Oligocene of the Jiuxi basin

The Jiuxi basin, bounded by the Altyn Tagh fault and northern Qilian fault located in the northern margin of the Tibetan Plateau, is the perfect area to study the Early Cenozoic tectonic action, because the tectonic events of the two faults were recorded in the Late Eocene sediments. In this paper, an integrated research of sedimentary facies, heavy minerals, and paleocurrents on eleven sedimentary sections from the Jiuxi basin provides a detailed record of the early tectonic evolution of the northern margin of the Tibetan Plateau since the Late Eocene. Then these data indicate the sedimentary frame of the earliest sediments records, the Huoshaogou Formation, in the Jiuxi basin was constrained by the left-slip motion along the northern part of the Altyn Tagh fault. However, the Altyn Tagh fault could not extend beyond the Tibetan Plateau within the Alxa block because of the rigid nature of the Alxa block. Hence this strong crustal extrusion from the Altyn Tagh fault had to southwardly transform to the northern Qilian fault to south which resulted Early Cenozoic thrusting of the northern Qilian fault while the foreland basin stage of the Jiuxi basin had been formed.