利用盐沼泥炭重建长江三角洲北部全新世中期海平面

根据对长江三角洲北部海安地区4个钻孔标志性沉积物(潮上带盐沼泥炭、高潮滩沉积)的年龄测定和高程测量,以及沉积物压实沉降量的分析研究,重建了本研究区全新世中期8.1～7.3 cal kyr BP和5.6～5.4 cal kyr BP的相对海平面位置。结果显示,8.1～7.3 cal kyr BP海平面缓慢上升1.46m,上升速率仅为0.2cm/yr, 与三角洲南部全新世早期海平面的快速上升(2cm/yr)形成鲜明对比,验证了冰盖控制下的全球海平面阶段性波动上升模式。对比长江三角洲地区海平面曲线发现,三角洲北部海平面曲线较南部低5～6m,长江三角洲海平面曲线与世界各地海平面曲线也存在明显差异,分析认为主要是由长江口地区的差异性沉降和中国东部边缘海的水均衡作用两个因素引起的。

Mid-Holocene sea-level of northern Yangtze River delta reconstructed by salt marsh peat

This study presents a mid-Holocene sea-level change curve during 8.1～7.3 cal kyr BP and 5.6～5.4 cal kyr BP for Hai′an area in Jiangsu Province,on the northern Yangtze River delta by using radiocarbon-dated and elevation-measured samples of supratidal salt marsh peat and high tidal flat sediments from 4 boreholes, and sediment compaction settlement analysis. The result indicated that the local relative sea level rose, about 1.46m during 8.1～7.3 cal kyr BP. This rate (0.2 cm/yr) contrasted to the rapid sea level rise in early-Holocene (2cm/yr) on the southern Yangtze River delta, which suggested a step-like global sea level rise controlled by the melting of ice sheets. The difference in relative sea-level between the northern and southern Yangtze River delta and other areas in the world indicated the effect of differential subsidence of the Yangtze River coastal region and the hydro-isostasy of the eastern China marginal sea.