The Study Of Sedimentary Environment And Chronology Of The Gaojiashan Member Of The Dengying Formation In Ning Qiang,Hanzhong

Gao jiashan member of Ningqiang County in Hanzhong is located in northwest margin of the Yangtze plate. The period of Dengying is the marina shallow sea sedimentary system,The Dengying Formation of the Ediacaran in this region has been well-developed, but was less stuied on sedimentsry environmental.The sedimentology, chronology and resources of the sediments of Gaojiashan member of Dengying Formation are studied in detail by method of field measured profile and indoor microscopic identification and analysis of the sample.That Dengying Formation of the Ediacaran is identified as shore-neritic sedimentary system according to the facies markers of the rock type, rock fabric and sedimentary structures. The neritic subfacies of Gaojiashan member can be distinguished further as proximal tempestite microfacies and distal tempestite microfacies. The member of algal dolomite and Beiwang member are distinguished as the sub-tidal micro-facies. Through zircon U-Pb Chronology of the debris zircon from the bottom and top of the Gaojiashan member, combined with previous experiment data, I think that the age of Gaojiashan member is about551Ma-543Ma. According to (CL) image and Th/U ratio,the detrital zircons of these two samples are consided as from magma with ages maily in800-1000Ma, which is connected with Provenance mainly from neoproterozoic basement.Comparing Gaojiashan member from Biewan-Niuluokeng profile with Shizikou profile, I think that Biewan-Niuluokeng profile was closer to carbonate platform, where the water depth is relatively shallow.