PRELIMINARY ANALYSIS OF SEDIMENTARY ENVIRONMENT FROM CAMBRIAN “TSINGHSUTUNG FORMATION”IN BALANG AREA,JIANHE COUNTY,GUIZHOU PROVINCE—CASE STUDY OF SONGSHAN SECTION FROM BALANG VILLAGE,JIANHE COUNTY
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Abstract:
The Cambrian "Tsinghsutung Formation"crops out extensively in eastern Guizhou,it is perfectly exposed in the Songshan section at the Balang Village,Jianhe County. "Tsinghsutung Formation"is 272 m thick.Lithologically,the"Tsinghsutung Formation ", dominated by limestones, mudstones and dolomites can be subdivided into four members in ascending order:Thin-bedded to medium-bedded biodetritus pelmicrite(Member I);Thin-bedded to mediumbedded pelmicrite(Member Ⅱ);Thin-bedded to medium-bedded biodetritus pelmicrite(MemberⅢ); Thin-bedded to medium-bedded pelmicrite with algae underlaying fine-crystal dolostones(Member Ⅳ).What's more,silt mudstone from the upper part of the "Tsinghsutung Formation"contains a Burgess shale-type Lagersta¨tte,known as the Jianhe biota. Based on detailed field investigation, microfacial analysis and palaeontological evidence,we proposed that the limestone-dominated "Tsinghsutung Formation"was deposited at the edge of deep shelf or deep shelf, which refers to a low water energy environment with high oxygen,normal salinity and good light conditions.Specifically,the Lagersta¨tte in the mid-upper part of the "Tsinghsutung Formation"indicates a rapid-burial event.In general, the sea level regarding the entire Tsinghsutung succession changes corresponding to three shallowing periods and two deepening periods,respectively.Our study also indicates that the MemberⅢ may have been deposited nearby the redox surface,whereas the members I,ⅡandⅣ were probably deposited above the redox surface.
