PROGRESS ON THE SECOND EPISODE OF HIMALAYA MOVEMENT AND PRIMARY DISCUSSION ON THE EXISTING PROBLEMS IN BASINS OF EASTERN CHINA

The change of subsidence model in Cenozoic petroliferous basins of Eastern China which goes from rifting subsidence stage in the Late Oligocene to whole thermal subsidence in the Early Miocene was caused by the second episode of Himalaya Movement.This movement resulted in some typical structure phenomena which are characterized by extensive unconformity in Eogene/Neogene strata,by the formations of secondary faults,and by the positive reverse structures in local areas.Accordingly,it caused the change of sedimentary systems in the up and down strata of E/N unconformity which was characterized by shore-shallow lacustrine facies,alluvial fan and fluvial-deltaic facies in the Oligocene to alluvial fan and braided fluvial facies in the Miocene.Four key problems were mainly discussed to elucidate the movement entirely,including the active period constraints,the denudation degrees,the effect on hydrocarbon reservoirs and its dynamic mechanism.Note that denudation degree research is the most important problem to this movement.Multiple methods(e.g.apatite fission track technique,vitrinite reflectance and acoustic time method) can be effectively used to reconstruct the denudation thickness of the second episode of Himalaya Movement.About this movement,there are chiefly two possible dyna-mic mechanisms.One is the transpressional mechanism related to the collision of plates;the other is the rebound mechanism of lithosphere.