莱州湾南岸全新世相对海平面变化重建

Reconstruction of the Holocene relative sea level change for the south coast of Laizhou Bay

在对莱州湾南岸8个钻孔沉积物沉积结构及有孔虫特征分析基础上,识别相关海面标志层位,辅以加速器质谱AMS14C测年,重建了全新世相对海面变化历史,并讨论了海面变化的沉积响应及控制因素。约9200cal BP以前,海面快速上升,研究区海侵时海面于-21.5m左右;9200~8400cal BP海面上升速率减缓至约2mm/a;8400~8000cal BP海面由-14m快速上升至-5.5m,速率约为33mm/a;8000~7600cal BP,海面持续数百年停滞或微弱下降;7600~7000cal BP海面由-5.5m快速上升至0m以上,速率至少约为13mm/a;7000~6000cal BP海面缓慢上升至+2^+3m位置,速率约为3mm/a;约6000cal BP以后海面缓慢下降至现今水平。约9200cal BP以前、8400~8000cal BP、7600~7000cal BP时期的3次海面快速上升,是MWP-1C融水脉冲、诱发8.2ka冷事件的融水脉冲,以及MWP-2融水脉冲的中纬度地区响应。中全新世全球冰融趋于停滞后,由于研究区沉积盆地沉降速度较慢,在冰川均衡调整效应下,使+2^+3m的相对高海面得以呈现。

On the basis of accelerator mass spectrometry （AMS） ,4C ages of eight Holocene core sediment samples from the south coast of Laizhou Bay, along with the analyses of sedimentary structure and foraminifera characteristics, the authors identified the sea level indicators and, on such a basis, reconstructed the Holocene relative sea level changes. The rapid sea level rise before ca. 9200cal BP probably resulted in the local postglacial flooding when the relative sea level reached -21.5m, followed by the decrease of sea lev-el rise to 2mm/a from 9200cal BP to 8400cal BP. During 8400～8000cal BP or so relative sea rose rapidly from -14m to -5.5m with a rate of 33mm/a. A stagnation or slight decline of the sea level was found which lasted hundreds of years from 8000cal BP to 7600cal BP. After 7600cal BP, this equilibrium was again interrupted by the rapid sea level rise of more than 13mm/a, and the relative sea lev-el passed over the moder^i elevation at around 7000cal BP with more than 5m rise magnitude. After about 7000cal BP, the relative sea level rose slowly at the rate of 3mm/a, and reached its high stand of 2～3m height at around 6000cal BP. And then it fell slowlydown to the present level. There were three times of rapid rise in Early Holocene, probably corresponding to three meltwater pulse events of MWP-1C, 8.2ka event and MWP-2, respectively. The global ice melting tended to be stagnant in the Middle Holocene; in virtue of the slow rate of local basin subsidence, the sea level highstand of ＋2？ -＋3m was presented under the effect of Glacial Isostat-ic Adjustment （GIA）.