Study On The Late Neoproterozoic Sedimentary Facies And Chronostratigraphy In South Hanzhong Area, Shannxi

Located in northwestern margin of the Yangtze Platform, Nanzheng-Ningqiang area of Shannxi is the part of the South Hanzhong area. It yield the complete and continuous strata of Late Neoproterozoic sedimentary sequences, include Liantuo Formation and Nantuo Formation of Nanhua Period, and the Doushantuo Formation and Dengying Formation of Sinian Period. Bases on the analysis of the facies markers such as rock types, rock structure, sedimentary structure and sedimentary sequence, the article explored the Late Neoproterozoic sedimentary facies of this area in detail, and carry out research into the U-Pb dating on detrital zircons from the lower Gaojiashan member of the Dengying formation in Gaojiashan area. Besides that, after the collation and study of the Ice age date from the Guozigou section and Linkuanggou section, Xinjiang and Hanlilu section, Nanzheng, we came to a new understanding about the sequence division and correlation of the Ice age in the relevant region:1. The late Neoproterozoic strata in the study area are mainly the terrigenous clastic and carbonatite sedimentary system with the granitic crystalline basement outcrop on the surface in the Gangchang, Nanzheng area. The glacial deposit of Liantuo formation and Nantuo formation of Nanhua Period include moraine deposit and proglacial deposites of glacial ice. Developing carbonatite and clastic depositions, the Siniansystem is an association of littoral-neritic carbonate rocks. The Doushantuo formation is the littoral to marine-terrigenous facies, while the Dengying formation is the tideland and shallow storm sedimentary facies.2. The new U-Pb dating date on detrital zircons from the lower Gaojiashan member of the Dengying formation in Gaojiashan area is 547±9Ma, and that is to say the formation age over this stratum is later than 547Ma, and we can theorize that the pyritized soft-bodied fossils in Gaojiasan should formed from 547Ma-542Ma.3. Based on the data from the Hanlilu section and the Guozigou section, we can draw a conclusion with previous detrital zircon ages that the age range of the Talisayi formation tillite is from 575.5±3.2Ma to 550.6±6.0Ma, which belongs to the Sinian System. The Talisayi formation can also be made a stratigraphy comparison with the Hangerqiaok formation in the Kuruktag area and Gaskiers Ice age. The Nantuo formation in the Hanlilu area can be made a stratigraphy comparison with the Sturitan Ice age.