The Features and Geneticdiscussion of Carbonate Autochthonous Tempestite in Wumishan Formation in the Jixian

It grows a group of the autochthonous storm deposits in the Wumishan formation of the middle - late Proterozoic in the Jixian area. The complete depositional sequence character is: the bottom unit is the silex striped fine - powdery graded dolomitite. The lower unit A has two types, one is the autochthonous storm-fringe deposits, it's the silex striped dolomitite and fine graded dolomitite, there is a hummocky stirring bedding in the strate, the other is the autochthonous storm-center deposits, it's hummpcky breccia, the tabular breccias of silex and dolomitite show vertical fan, radiating, sheaf, radiator arrangement in the section and triangle trellis arrangement on the surface. The middle unit B is the white and black streaking powery -fine graded dolomitite with corrugated bedding. The upper unit C is the silex striped asphaltic fine graded dolorm-lite with horizontal bedding. The top unit D is the silex striped stromatolites dolomitite with thick -massive bedding. The uncomplete depositional sequence is: the unit B or C often absent, only it's the A that is a mark to identify the autochthonous storm deposits. During the deposition of the Wumishan formation of the middle -late Proterozoic, the platform of the Jixian area was in Pacific Ocean, the palaeolatitude was 1°-10°N, the depth of seawater was less in the basin. The sedimentary environment was shallow sea. It was the same as the area of 5°-20°N latitude of the modern storm movement. There must were storm moving here during the Wumishan formation. A strong vortices storm whirled the seawater highly during the storm event. The strom wave base was deepened to get to 200m depth, the seabed geted huge shearing stress U which can be resloved into horizontal U1 and vertical U2. When weak storm, U2 was a little force which couldn't cut out anything on the seabed, U1 pulled the sediments of seabed to go to vortes point, hummocky stirring bedding was shapeed. This is the autochthonous storm -fringe deposits. When stron storm, U1 pulled and U2 cut off the carbonate sediments on seabed. Breccia was shaped. Under the vortices flows action, breccias were moving to vortex center. At last, breccias showed vertical fan, radiating, sheaf, radkator arrangement in the section and triangle trellis arrangement on the surface. This is the autochthonous storm -cneter deposits. In late storm, the seawater flows turned the upper flow regime vortex into the lower flow regime. The coarse grade loose carbonate sediments were confused by storm and redeposited to make corrgated bedding, and the fine graded redeposited to get horizontal bedding in the lower flow regime of storm end. In fair weather, the fine sun. prosperous organisms, rich sediments, the thick-massive was made. There weren't the tsunami during the deposition of the Wumishan formation, because the mark of the earthquake and the vulcenicity has been not discovered in the strata of the Wumishan formation. There only is the autochthonous storm deposits cf storm direct action, it's different from the storm gravity flows and the pattern showing autochlonstorm sedimentary on ramp.