米仓山前缘震旦纪沉积古地理分异及其基底组成:来自沉积序列和碎屑锆石年代学的约束OA

With oil and gas exploration expanding into deeper stratigraphic levels,understanding the evolution of marine prototype basins and their paleogeography in the deep layers of the Sichuan Basin is increasingly a crucial constraint on the deep oil and gas exploration.Based on a regional comparison of sedimentary sequences,this study focuses on the chronological characteristics of detrital zircons from the Sinian Guanyinya Formation and Dengying Formation in the frontal region of the Micangshan.The result shows that the detrital zircons of the Guanyinya Formation are mainly derived from early to middle Neoproterozoic episodic volcanic-magmatic activities,and the sources of the middle Paleoproterozoic or older basements are scarce.Regional comparison reveals that the detrital zircons of both the Guanyinya Formation and the Dengying Formation at the frontal region of the Micangshan do not share a uniform source area,indicating a distinct Sinian sedimentary-paleogeographic differentiation that was different from the common depositional features of passive continental margins.Meanwhile,the Guanyinya Formation unconformably overlies the Huodiya Group.Combined with our recent research on the Huodiya Group,it is not difficult to speculate that the Huodiya Group in the Micangshan area was deposited during the early Neoproterozoic,rather than representing a mid-Paleoproterozoic basement as traditionally interpreted.This conclusion is important for reconstructing the Neoproterozoic sedimentary paleogeography along the northwest margin of the Yangtze Block.