Sedimentary features of the Doushantuo Formation in Siduping, northwestern Hunan Province and their paleogeographical significance

The Doushantuo Formation in Siduping, northwestern Hunan Province, has long been regarded as one important boundary marker of the slope facies zone in South China. However, in this study we found that the Doushantuo Formation in the Siduping area was not deep-water deposition, based on comprehensive analyses of tectonic and sedimentary features, stratigraphic sequence and lithology. The percolation structure in ‘cap dolomite’ of lower stratigraphic sequence and the oncolite newly discovered from the upper Formation suggests that the stratigraphic sequence and sedimentary feature in this area is basically consistent with that in the northern margin of the Yangtze Platform, being suggestive of carbonate platform intercalated with subtidal depression setting. Additionally, this study discusses the differences between the carbonate platform front facies and gravity-flow deposits in a slope setting, and redefines the lithofacies paleogeography of South China.