Response between relative sea-level change and the Pearl River deep-water fan system in the South China Sea
Response between relative sea-level change and the Pearl River deep-water fan system in the South China Sea
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作者：
Pang Xiong
根据微体古生物分析建立的第三纪相对海平面变化曲线表明，南海北方边缘珠江口盆地（PRMB）发育了与全球古生物旋回一致的三级旋回，但与全球古生物旋回的二级旋回不同。三级层序的形成导致了各层序体系域在陆棚和陆坡之间的迁移。层序地层学研究表明，珠江口外斜坡深水区广泛发育珠江深水扇体系，第三系多层序叠置。区域构造作用导致了太平洋盆地二级海平面变化与全球海平面变化的差异。与全球海退海平面旋回相反的海侵海平面曲线在此发育。白云凹陷自32 Ma B. P.南海扩张以来，经历了三次受相对海平面变化控制的海侵事件，现处于斜坡深水区。发育阶式退积层序组，表现为向上变细的沉积层序。因此，在23.8Ma B. P.之前，表现为浅三角洲-滨岸砂泥岩沉积组合的特征，23.8~ 10.5Ma B. P.为深水扇砂泥岩沉积组合，10.5Ma B. P.以来的远源变细沉积。
A Tertiary relative sea-level change curve built from micropaleontological analysis demonstrates that the Pearl River Mouth Basin (PRMB) in the northern margin of the South China Sea developed the third order cycle which is the same as that of global eustasy, however, the second order cycle is different. The third order eustasy led to a system tract shift of each sequence between the broad shelf and slope. Sequence stratigraphy shows that the Tertiary multi-sequences overlapped the Pearl River deep-water fan system which developed broadly in the slope deep-water area outside of the Pearl River Mouth. Regional tectonism resulted in the differences between PRMB second order sea-level change and the change of global eustasy. The transgressive sea-level curve was developed here, which is opposite to the global regressive eustatic cycle. Baiyun Sag, now sitting on the slope deep-water area went through three step transgressive events controlled by the relative sea-level change, since the expansion of the South China Sea at 32 Ma B.P.. Stepping retrogradation sequence sets were developed and display upward-fining depositional sequence. Consequently, it shows the characteristics of shallow delta-littoral sand-shale depositional assemblage before 23.8 Ma B.P., of a deep-water fan sand-shale depositional assemblage during 23.8～10.5 Ma B.P., and of distal fining deposition since 10.5 Ma B.P..