Abstract:

Based on the recognition and redefinition of regional angular unconformities, staggered evolution of tectonic subsidence, impulsive activities of growth faults and the change of structural framework, the episodic rifting process and its characteristics of Paleogene in Qiongdongnan basin were revealed. Ulteriorly, the controlling of episodic rifting on the generation and evolution of sedimentary sequences was elucidated systematically in association with the comprehensive analysis on sequence stratigraphy and sedimentary filling of Paleogene. The results show that there are three rifting episodes during the rifting period of Paleogene, namely rifting episodeⅠ(S₁₀₀-S₈₀), rifting episodeⅡ(S₈₀-S₇₀) and rifting episodeⅢ(S₇₀-S₆₀), corresponding to the initial faulted period, the main faulted period and the transition faulted period respectively. The evolutionary trend of rifting activities went from weak to strong and to weak，which is characterized by intense differential subsidence of fault blocks in the early stage of rifting period, while gradually replaced by homogeneous subsidence which was controlled by a combination of regional depression and weak activities of growth faults in the later. Because of the profound influences on accommodation space, tectonic subsidence rate, synsedimentary faulting activity and palaeostructural frameworks, the multistage episodic rifting and differences of tectonic activities among different rifting episodes controlled the development of sequence stratigraphy units and sedimentary cycles at various levels, and the spatial-temporal distribution of depositional and subsidence centers as well as the composition and configuration of depositional system tracts in the sequence stratigraphic frameworks.

Key words: Qiongdongnan basin, Paleogene, episodic rifting, sedimentary filling, stratigraphy, South China Sea