南海北部神狐海域峡谷层序结构差异与控制因素
Stratigraphic and Structural Differences and Their Controls in the Shenhu Submarine Canyon，Northern South China Sea

摘要： 南海北部陆坡神狐海域峡谷作为我国水合物首次试采区，其沉积层序特征控制和影响着富含水合物沉积体的展布。海域峡谷区沉积作用复杂，影响因素较多，对比难度较大一直是全球深海沉积研究的难题之一。研究采用井震综合分析的方法识别出层序界面，并结合峡谷侵蚀—充填过程，刻画出不同级次的层序界面在空间上的展布。研究划分出6个四级层序，但是各层序内部同相轴发育特征不同：层序Ⅲ和层序Ⅳ的底界可见明显的下切谷和峡谷定向迁移现象，层序Ⅴ和层序Ⅵ层序可见明显的同相轴错断现象。依据层序结构样式存在的差异，将研究区层序类型分成物源驱动型层序和沉降驱动型层序。然后统计层序Ⅰ—Ⅳ内部的沉积参数，根据陆坡滨岸线的演化过程将物源驱动型层序和沉降驱动型层序进行体系域划分。最后将两种类型的层序进行解剖并提出对应的演化模式：物源驱动型层序可以再划分成3个体系域，即低位域、海侵域和高位域，整体物源供给较充足，沟谷侵蚀现象明显，陆坡滨岸线多呈上超结构；沉降驱动型层序划分成4个体系域，即低位域、海侵域、高位域和海退域，其中海退体系域为最大海泛面和峡谷侵蚀面间的规则前积体，层序发育过程伴随断裂沉降，陆坡滨岸线多呈S型结构。
Abstract: The northern continental slope of the South China Sea (SCS) is the first gas hydrate producing trial region in the SCS,and its stratigraphy would influence the distribution of gas hydratebearing sediments. The complex canyon sedimentation and varying stratigraphic styles have hampered stratigraphic correlations in the SCS deepsea sedimentology study. This study integrated the corelogseismic data into the stratigraphic boundary identification. Integrating the canyon development stages, we distinguished six fourorder stratigraphic boundaries: Sequence (SQ) Ⅲ and SQ Ⅳ were developed with apparent incised valley, and SQ Ⅴ and SQ Ⅵ were influenced by synsedimentary faults. Consequently, we classified the stratigraphic boundaries into two main types: sedimentationdriven and subsidencedriven. Sedimentdriven sequences can be divided into three system tracts: LST (low stand system tract), TST (transgression system tract) and HST (high stand system tract).This stratigraphic type with abundant sediment supply swashed the basement and formed apparent incised valley. The slopeline trajectory has shown overlapping structures. Subsidencedriven sequence can be divided into four system tracts: LST, TST, HST and RST (regression system tract), and the RST can be distinguished as the regular seismic package between the MFS (Maximum Flood Surface) and incised valley.This stratigraphic type with synsedimentary fault development can be shown in the “S” structure in the slopeline trajectory