The Neoproterozoic Late Tonian stratum (the Xiajiang Group and its time-equivalent stratum) is well exposed in the Hunan-Guizhou-Guangxi area. It is an important research subject for studying the evolution of the rift basin in South China after the collision between the Yangtze Craton and the Cathaysia Block. Here, we report the zircon U-Pb ages of the tuffs and tuffite in the upper part of the Qingshuijiang Formation and the bottom and middle parts of the Pinglue Formation in the Wanshan area, Tongren City, Guizhou Province to be 763.8±5.5 Ma (N=24, MSWD=0.29), 760.2±4.1 Ma (N=25, MSWD=0.39), and 759.1±3.9 Ma (N=26, MSWD=0.38), respectively. By compiling the area's volcanic, volcanic-sedimentary and tuffeous rock ages, we further determined the deposition periods of the Xiajiang Group and its equivalence to be around 822-715 Ma. We propose that the basalt within the Sanmenjie Formation of the Danzhou Group in northern Guangxi formed in an extensional setting after the Wuling movement, as a result of maximum extension of the Hunan-Guizhou-Guangxi rift basin. A large amount of volcanic materials in the Qingshuijiang and Pinglue Formations are mainly sourced from the intermediate-acidic extrusive rocks (800-760 Ma) in the eastern section of the Jiangnan Orogen. Combined with regional stratigraphy, lithology and geochronology, we restore the Neoproterozoic Late Tonian evolutionary history of the Hunan-Guizhou-Guangxi basin and propose to establish the Xiajiang System. © 2020, Editorial Office of Earth Science Frontiers. All right reserved.
