TECTONIC SEQUENCE AND ITS SEDIMENTARY FILLING PROCESS OF THE SHUANGFENGNAN SLOPE IN NORTHERN SOUTH CHINA SEA

Based on high-resolution seismic profile and well logging data, tectonic sequence and its depositional characteristics of the ShuangFengNan slope in northern South China Sea was studied. The stratigraphy sequence can be divided into three tectonic sequences:upper tectonic sequence、middle tectonic sequence and lower tectonic sequence in studied areas, according to the seismic reflect unconformity、the structural development characteristics and the stratigraphic assemblage characteristics. The results show that the factors, such as tectonism、spreading of the basin、changing of relative sea level、volcanic activity、provenance supply et al., controlled the sedimentary filling process and its evolution of the each tectonic sequence commonly in different stages. The lower tectonic sequence(T_g-T₆) deposited in the lacustrine sedimentary environment, the depositional system was dominated by the major syndepositional faults obviously, it has developed the depositional systems of alluvial fan-fan delta-semi-deep lake mainly; The middle tectonic sequence(T₆-T₄) deposited under the tectonic background of the slow subsidence stage of the northwest sub-basin, under the influence of the slope subsidence and the eruption of the volcano, it created a special slope geometry structure, which were the main controlling factors for the developing of the depositional systems. it has developed the depositional system of the shelf-margin delta in up-midland, deepwater slope fan and related depositional system in the studied slope area. The upper tectonic sequence (T₄-T₀) deposited under the background of the relative sea level rising and the rapid subsidence stage of the northwest sub-basin. The sedimentation was mainly controlled by the supply of source and the deep-water deposition, it has developed the deep water depositional which characterized by the deepwater channel and the slump body.