西藏晚三叠世北羌塘前陆盆地构造层序及充填样式

晚三叠世北羌塘前陆盆地为处于金沙江缝合带南缘的周缘前陆盆地,其中充填了厚度大于2 500 m的晚三叠世肖茶卡群,自南向北可分出4个沉积相带,显示为北厚南薄的楔形沉积体,具双物源、双古流向以及沉降中心和沉积中心不一致性等特点,以不整合面为界可将其分为2个构造层序,下部构造层序以诺利期复理石建造为特征,上部构造层序以瑞替期磨拉石建造为特征.

TEVTONIC SEQUENCE AND FILL MODELS OF LATR TRIASSIC MORTHERN QIANGTANG FORELAND BASIN IN XIZANG,CHINA

The Late Triassic Northern Qiangtang Foreland Basin is a peripheral one situated to the south of the Jinshajiang suture zone, to the south of the basin is a forebulge (center uplift). The basin was filled with Late Triassic Xiaochaka group, in thickness more than 2 500 m, which could be divided into two tectonic sequences bounded by unconformities. In a transverse section there is a wedge|shaped sedimentary body with thicker in the north and thinner in the south with double paleocurrents and double provenances: the Hoh Xil thrust belt in the north and the forebulge in the south. The depocenter was located in north part of the basin . The sedimentary and tectonic evolution of the basin can be divided into two phases by stratigraphic signatures. The early one was flysch phase, characterized with the carbonate ramp developing along the north slope of the forebulge and the turbidite occurring along the south margin of the Hoh Xil thrust belt respectively. This phase should be coincident with subduction of the Jinshajiang Ocean and initial collision. The second one was molasse phase, during which the delta system developed along the north slope of the forebulge and the molasse deposits (alluvial apron as well as delta system) developed along the south margin of the Hoh Xil thrust belt respectively. This phase should be coincident with the collision followed the Jinshajiang ocean's closure.