Abstract:

As an important transition domain between the last identifiable extended continent crust and the first true oceanic crust, the oceancontinent transition (OCT) zone preserved a wealth of information on the processes of lithospheric extension and breakup. In this paper, considering OCT as a key to understanding the mechanism of the lithospheric extension and breakup, we try to show the geological nature of the OCT, and its geological and geophysical identification based on an integrated analysis of a rich subsurface data, including borehole data and newly released geological and geophysical data collected by marine geological survey and hydrocarbon exploration and development. We are also to elucidate the continental lithosphere configuration and its overlying sedimentary basins tectonostratigraphic framework in the different tectonic units on the continental margin. It is noteworthy that we will compare the structures, major tectonic boundaries and tectonic sequences in the sediment fillings of the basins, which will explore the information during the processes of the continental margin extension, exhumation, breakup and oceanic spreading. In addition, we will study the largescale detachment faults and their controls on the lithospheric thinning and continental mantle exhumation. We will investigate where the lithosphere of continent margin concentrated, and how the deformtion migrated and superimposed, and further construct the model of lithospheric extension and breakup. OCT is the area where the lithospheric deformation and final breakup occurred. Therefore, Our research will better improve our understanding of the birth of the oceanic crust and symmetric conjugate structures in the South China Sea, and has a great significance for economic exploration(hydrocarbon) in the deepwater/ultradeepwater area of South China Sea.

Key words: South China Sea, oceancontinent transition, detachement fault, exhumation, breakup sequence