Characterization of Tempestite Sediments of the Neoproterozoic Zhaowei Formation in Xuzhou Area, Jiangsu Province

The Neoproterozoic Zhaowei Formation in Xuzhou consists of 4 units,i.e.,oolitic unit,tempestite unit,stromatolitic unit and dolomite unit.The stromatolitic unit was subdivided into A and B parts.The tempestites,which abate from early to later stages,alternate with non-tempestites in the vertical section.Some typical sedimentary symbols of tempestite sediments were developed in this zone such as hummocky cross stratification(HCS),flush-filling structure,cut structure,organic reef-cutting structures,calcrudites,graded bed and so on.Four kinds of tempestites sequences were summarized according to the vertical sequence types,structures and sediment characteristics.The distribution of tempestites was also summarized.The discovery of tempestites is helpful to interpret the sedimentary environment.According to the distribution of tempestites and the lithologic characteristics,the authors suggest that the sedimentary environments the Zhaowei Formation were successively shoals-landward shallow subtidal zone-open carbonate platform-restricted carbonate platform-tidal flat or lagoon and the climate during the deposition was warm and arid.Frequent storms occurred due to the relatively low palaeolatitude during the deposition.