关键词: 柴达木盆地, 嗷唠山, 三叠系, 碎屑锆石U－Pb年代学, 物源

Abstract: A dispute whether there was Triassic sedimentation or not in Qaidam Basin and its later evolution are continuous as yet. Via systematic analysis of detrital zircon geochronometry, rock assemblages and regional stratigraphic correlation on the Triassic
strata from Aolaoshan area, in the west section of north Qaidam Basin, this study aiming at providing evidence for the Triassic stratigraphic framework in the northern margin of Qaidam. The average age of young zircons in the lower part of Tb Triassic Formation is 248 Ma. Considering paleontological data from the underlying Ta strata, the deposition time limit of the Aolaoshan Triassic deposits was Early to Middle Triassic. The detrital zircon U-Pb ages were between 243-260 Ma, 414-538 Ma, 678-857 Ma, 1064-1642 Ma and 1700-2836 Ma. Respectively, indicating that the sedimentary materials may derived from Indosinian magmatic rocks, Upper Devonian recycle material, North Qaidam tectonic belt, Shaliuhe Group and Dakendaban Group. The study area has the same sedimentary characteristics as the Triassic in the Huaitousala area, and they both are markedly different from the Triassic stratigraphic division in Qilian and West Qinling areas. It is suggested that a series of continuous or intermittent sedimentary strata were developed in the northern margin of the Qaidam Basin during the Triassic period. In the early Triassic, influenced by the subduction of the Zongmurong Ocean to the south, the northern margin of the Qaidam Basin began to uplift rapidly. Several sets of sedimentary strata and crystalline basement in the early period were rapidly denudated, and the sedimentary strata dominated by alluvial and alluvial facies were formed near the source fault depression. In the Middle Triassic, the activity intensity of the peripheral tectonic belt tended to be stable on the whole, and the northern margin of the Qaidam basin was in the shallow sea shelf platform sedimentary system with thick-bedded limestone as the main deposits. Until the late Triassic, with the strong continental collision between East Kunlun and Qaidam terrane, the whole Qaidam Basin was rapidly uplifted, and the weakly consolidated Triassic in the basin was large-scale denudated. Some of the weakly consolidated Triassic in the basin was transported eastward to Gonghe Basin, and only part of the depressions were preserved. 

Key words: Qaidam Basin, Aolaoshan area, Triassic strata, detrital zircon U-Pb geochronology, provenance