Stratigraphic and Structural Differences and Their Controls in the Shenhu Submarine Canyon,Northern South China Sea

doi:10.19657/j.geoscience.1000-8527.2018.04.17

Abstract

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.

Key words: Shenhu area, sedimentation-driven stratigraphic boundary, subsidence-driven stratigraphic boundary, sedimentary pattern, structural controls

CLC Number:

TE121.3

FU Chao, YU Xinghe, HE Yulin, LIANG Jinqiang, KUANG Zenggui, DONG Yisi, JIN Lina. Stratigraphic and Structural Differences and Their Controls in the Shenhu Submarine Canyon,Northern South China Sea[J]. Geoscience, 2018, 32(04): 807-818.

Figures/Tables 9

References 37

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	物源驱动型层序演化模式	沉降驱动型层序演化模式
体系域组成	低位域+海侵域+高位域	低位域+海侵域+高位域+海退域
海平面变化幅度	海平面变化明显(层序Ⅳ)、海平面变化不明显(层序Ⅲ)同时存在	海平面变化不明显(层序Ⅴ和层序Ⅳ)
层序界面	具有明显的峡谷侵蚀界面作为初始洪泛面(FS);最大海泛面(MFS)反射较弱,但连续性强	具有较明显的峡谷侵蚀界面作为初始洪泛面(FS);最大海泛面(MFS)反射较强,中部有明显错断;海泛面上部发育较为整齐的前积体底界面为最大海退面(MRS)
主控因素	物源供给、海平面变化、气候	物源供给、海平面变化、气候,基底构造运动
沉积单元	斜坡扇、盆地扇(低位域);沉积物波,水道体系(高位域和海侵域)	斜坡扇、海底扇(低位域);沉积物波,水道体系、斜坡扇(高位域和海侵域)
识别标志	同相轴内部连续性较好,顶部有明显的峡谷侵蚀	同相轴内部存在明显错断,侵蚀面上下均可见整齐同相轴前积

	物源驱动型层序演化模式	沉降驱动型层序演化模式
体系域组成	低位域+海侵域+高位域	低位域+海侵域+高位域+海退域
海平面变化幅度	海平面变化明显(层序Ⅳ)、海平面变化不明显(层序Ⅲ)同时存在	海平面变化不明显(层序Ⅴ和层序Ⅳ)
层序界面	具有明显的峡谷侵蚀界面作为初始洪泛面(FS);最大海泛面(MFS)反射较弱,但连续性强	具有较明显的峡谷侵蚀界面作为初始洪泛面(FS);最大海泛面(MFS)反射较强,中部有明显错断;海泛面上部发育较为整齐的前积体底界面为最大海退面(MRS)
主控因素	物源供给、海平面变化、气候	物源供给、海平面变化、气候,基底构造运动
沉积单元	斜坡扇、盆地扇(低位域);沉积物波,水道体系(高位域和海侵域)	斜坡扇、海底扇(低位域);沉积物波,水道体系、斜坡扇(高位域和海侵域)
识别标志	同相轴内部连续性较好,顶部有明显的峡谷侵蚀	同相轴内部存在明显错断,侵蚀面上下均可见整齐同相轴前积