PROVENANCE AND SEDIMENTARY FEATURES OF THE DIAMICTITE UNIT IN THE NANHUAN SIZHOUSHAN FORMATION IN THE NORTHWESTERN MARGIN OF THE CATHAYSIA BLOCK AND ITS CORRELATION
Correlation of the Nanhuan System between the northwestern margin of the Cathaysia Block and the southeastern margin of the Yangtze Block affects our understanding of the regional tectonic background.In this work,the macro-and micro-sedimentary textures/structures of the lower diamictite unit of the early Nanhuan Sizhoushan Formation distributing in the northwestern margin of the Cathaysia Block,detrital zircon U-Pb ages of the basal quartz sandstone and the above-mentioned diamictite unit,and the origin of the diamictite unit and its provenance,were studied comprehensively.It could be concluded that the lower diamictite unit was resulted from glaciation and its maximum deposition age is 730-740 Ma,which is consistent to the Chang'an Formation in the southeastern part of the Yangtze Block.The provenance of the bottom layer of the Sizhoushan Formation is characteristic of pro-Yangtze type,and the provenance of upper diamictite unit is the mixture of pro-Cathaysia and pro-Yangtze types.A northwestwards progradation of the pro-Cathaysia type provenance during the late Neoproterozoic to early Paleozoic could be demonstrated based on the results of this study and other published data.The southeastern area of Hunan Province could be the transitional area for sedimentary correlation between the Yangtze and Cathaysia blocks.The results provide new insights for tectonic research of South China Block during the Nahuan.