东海陆架全新统高分辨率层序地层学研究

在高分辨率１４Ｃ测年、岩石、生物、化学、同位素、气候及磁性地层学研究成果基础上，通过不同沉积背景典型钻孔的沉积学分析，运用层序地层学理论，对东海陆架全新统进行了高分辨率层序划分及对比；建立了全新世层序地层格架及海平面变化过程；提出了相应的层序成因模式。研究结果表明，东海陆架全新统相当于一个发育中的六级（１～１０ｋａ）层序，可进一步划分为３个七级（０．１～１ｋａ）层序和若干个更次级层序。代表１个六级或３个七级周期相对海平面变化过程中叠加有若干更次级的海平面波动，它们与地球旋回谱系中的太阳带、历法带密切相关。七级层序具有与三级层序相近的内部构型和成因格架。在东海陆架全新世沉积演化过程中，长江三角州至少有３次不同程度地越过东海陆架进入冲绳海槽，并滞留有至少３层海侵改造“残积砂”沉积。在东海陆架全新世海平面变化期间，最大海平面时期为约距今６～５ｋａ，大致高于现今海平面２～４ｍ，最低海平面在距今１０ｋａ左右，大约低于现今海平面１３０ｍ。目前，由于温室效应的影响，海平面仍呈小幅度波浪式上升。事实证明，层序地层学不仅丰富了现代海洋沉积学的内容，而且解决了许多海洋沉积学未能解决的问题。

High-resolution sequence stratigraphy of the Holocene strata on the East China Sea shelf

The high-resolution sequence stratigraphic division and correlation of the Holocene strata on the East China Sea shall are made on the sequence stratigraphic theory dnd¹⁴C dating, litho-, bio-, chemo-, isotopic-, weather-, and magneto-stratigraphy, in conjunction with sedimentological analysis of typical boreholes in different sedimentary settings,result-ing in the construction of the sequence stratigraphic framework and sea-level curves and associated sequence stratigraphic model. The Holocene strata on the East China Sea shelf, which correspond to a sixth-order (1-10ka) sequence, may be divided into three seventh-order (0.1-1 ka)sequences and many lower-order sequences, representing one sixth-order or three seventh-order cycles of relative sea-level changes influenced by lower-order sea-level fluctuations. The seventh-order sequences exhibit internal architectures and genetic framework similar to those of third-order sequences. During the sedimentary evolution of the East China Sea shelf in the Holocene, the Yangtze River (delta) once extended at least for three times through the East China Sea shelf into the Okinawa Trough, and brought about three beds of transgressive reworked "eluvial sand" sediments. During the Holocene, the maximum sea level in the East China Sea occurred between 6 and 5 ka B.P., 2 to 4m higher than the present-day sea level;the minimum sea level appeared about 10ka B. P., 130 m lower than the present-day sea-level. Moreover the sea level is still rising with a small margin because of the "greenhouse" effects. The fact is that sequence stratigraphy has contribute a lot to the refinement of oceanic sedimentology and better resolution of un-resolved problems in oceanic sedimentology.