MIS3中期以来北黄海中部陆架古环境演化

通过对北黄海中部陆架DLC70-2孔的岩性、粒度、微体古生物以及AMS14C年代学的分析,探讨了研究区MIS3中期以来的古环境演化。研究表明,北黄海中部陆架MIS3中期以来的沉积环境演化与海平面变化存在良好的对应关系,具有明显的阶段性特征:岩芯22.89~18.50 m段(43 639~42 558 cal yr B.P.)对应MIS3中期海平面上升过程中形成的河口湾相,与上覆地层之间存在明显的沉积间断;随着海平面的逐渐上升,海水自14 602 cal yr B.P. 开始侵入研究区,形成了18.50 m以上的沉积地层,自下而上可划分为末次冰盛期以来海平面上升过程中的河口充填相(18.50~10.02 m,14 602~12 602 cal yr B.P.)-新仙女木事件中晚期海平面停滞期间的河流泛滥平原相(10.02~5.10 m,12 602~10 357 cal yr B.P.)-全新世早中期海平面上升过程中的滨海、浅海相(5.10~0 m,10 357~4 913 cal yr B.P.)。岩芯10.02~5.10 m段(12 602~10 357 cal yr B.P.)记录的源自河流泛滥平原沉积的硬质黏土层与新仙女木事件的全球效应密切相关,可作为新仙女木事件在北黄海陆架响应的一个重要证据。

Paleo-environmental Evolution in the Central Shelf of the North Yellow Sea Since mid-MIS3

The North Yellow Sea is a typical semi-enclosed epicontinental sea and is characterized by strong land-sea interaction and paleoenvironmental changes during the Late Quaternary with sea-level fluctuations. In this study, based upon analysis of lithology, grain-size, micropaleontology and AMS14C dating for Core DLC70-2, located in the central shelf of the North Yellow Sea (NYS), the paleo-environmental evolution can be ascertained. The study suggests that the sedimentary environmental evolution in the central shelf of NYS since mid-MIS3, which was well corresponding to the relative sea level changes, shows prominent multistage characteristics. From 22.89 m to 18.50 m (43 639~42 558 cal yr B.P.), an estuarine facies, developed by sea level rise in the middle of MIS3, and there exists an apparent sedimentary hiatus between the facies and its overlying strata. The seawater arrived at the study area since 14 602 cal yr B.P. and a 18.50 m thick sediment formed from then on, which can be divided into estuarine filling facies (18.50~10.02 m, 14 602~12 602 cal yr B.P.), riverine floodplain facies (10.02~5.10 m, 12 602~10 357 cal yr B.P.)and littoral- neritic facies (5.10~0 m, 10 357~4 913 cal yr B.P.) from the bottom up, corresponding to the process of sea level rising since Last Glacial Maximum, the short stagnated period of sea level during the Younger Dryas event, and the process of sea level rising during the early-middle Holocene, respectively. The section from 10.02 m to 5.10 m (12 602~10 357 cal yr B.P.), a hard clay, the result of the riverine floodplain, may be closely correlated with the global impact of Younger Dryas event and can be regard as a significant evidence of the response of the NYS area to it.