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Dynamic Mechanism of Formation of Dustpan Subsidence,Northern Jiangsu

CHEN An-ding   

  1. Geological Research Institute,JOECO, SINOPEC, Jiangsu Yangzhou 225009,China
  • Received:2001-12-20 Revised:2001-12-20 Online:2001-12-20 Published:2001-12-20

Abstract: Subei Basin is composed of several smal1 subbasin shaped like dustpan. Many authors had previously explained the origin of Subei Basin on the theory, of pull apart basin or rifting basin. However, seismic information suggests that wedges of the Palaeogene strata formed mainly through imbalance uplifting and erosion beside the sedimentary reason. In fact, Suhei Basin is a residual basin in the Palaeogene period. The tectonic phenomena happened in the Cenozoic are caused by both of the continuity of the Mesozoic tectonic processes and the complexity of Cenozoic stress field During the end of Indosinian to middle Yanshan movement, eastern China was only effected by Pacific-Kula plate, then the strata were deform ed strongly, and with the single di1ection of stress field, bearing the NW -NWW compression direction or the left-lateral shearing, lots of thrust-nappe tectonics were formed in eastern China. Since the Eocene the compression force caused by collision of India Plate to Eurasia has been added to this region. Subei Basin is in alter native-variable dualstic dynamic environment because of different move velocity for two plates. As the force source from India plate dominated, the force couple of right-lateral twist emerged and led to the reverse faults of early-middle Yanshan period to be reacted and reversed The sedimentation dominated in this region, while the raising dominated in western continental of China. But as the force source from Pacific Plate dominated, the couple force of left-lateral transpression appeared, then the whole uplifting of the basin occured, the slope and heave underwent erosion so that the dustpan structure got enhanced. Alternation of two force sources on the time and space completed a whole “fault subsidence-depression-uplift”, i.e. the sedimentary-erosion tectonic cycle.