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Study on Sinian Geologic Events in Xuzhou-Suzhou Area and Discussion on Their Origin

PAN Guo-qiang, LIU Jia-run, KONG Qing-you, WU Qun-qi, ZHANG Qing-long, ZENG Jia-hu, LIU Dao-zhong   

  1. Department of Earth Sciences, Nanjing University, Nanjing 210093, China
  • Received:2000-12-20 Revised:2000-12-20 Online:2000-12-20 Published:2000-12-20

Abstract: The Sinian strata in Xuzhou-Suzhou area are deposits of the epicontinental sea. They are mainly referred to the carbonate platform facies. In the supratidal to subtidal low-energy sedimental environments, sudden, violent high -energy sedimentation occasionally occur, which are often associated with some abn ormal sedimentary structures. These structures along with step-like small faul ts may indicate the ancient seismic traces. In the studied area, the Sini an seismic traces mainly include densely-spaced veins of micritic calcites, strongly scouring and erosion structures of "bag gutter" like, plastic rudites, eart hquake breccias, inter-formation folds and step-like small faults. Five disti ng uished stratomeres with closely-spaced seismic traces represen- ting five ear thqua kes phases have been recognized, which might include dozens, even hundreds of st rong earthquakes. At least two phases of hypabyssal to subsurface basic magmatic intrusions can be distinguished, occurring respectively in the early and late Sinian period. The seismic events, magmatic intrusions and sea-level changes a r e related in origin. Frequent, strong earthquake activities caused the sea-lev e l rise. The magmatic intrusions occurred in the interval between tow seismic ph ases and in the sea-level fall times.   The research results showed that the Sinian geologic events in the studied area might be controlled by extensional structures. The ages of these events ar e 738.6-604Ma, corresponding to the breakup times (780-600Ma) of global superc ontinent Rodinia. Therefore it is deduced that the origin of the Sinian geologi c events in Xuzhou-Suzhou area might relate to the breakup processes of Rodinia . The area from "Plaeo-Tanlu zone" to the north of boundary fault zone in the northern side of North Qinling Mountains might be the breakup zone within the North China Plate margin.