山东半岛南部近岸海域晚第四纪以来有孔虫和介形类化石群落分布特征及古环境演化

在山东半岛南部近岸海域QDZ03孔16.2m的沉积记录中,通过有孔虫和介形类化石群落的定量分析,探讨了研究区晚第四纪氧同位素(MIS)4期以来古沉积环境演变。在距今6万年前后开始的黄海海退期(相当于MIS4期),发育了有多次沉积间断的第1层(孔深16.2~12.0m)陆相地层。进入玉木亚间冰期(相当于MIS3)后,由于海平面的震荡上升,发育了第2层—第5层的滨岸弱海相—陆相沉积层,其中第5层上部可能包含部分MIS2期的产物,而MIS2期绝大部分沉积地层缺失。在距今12 000—11 000年前,海水逐渐由黄海入侵到青岛地区,发育了第6层下段(孔深9.1—8.6m)的海陆过渡相沉积层;在全新世最大洪泛面MFS来临之前(距今约11.0—9.0ka期间),海平面进一步上升,钻孔中发育了第6层中段(孔深8.6—7.7m)的滨岸相沉积层。随着距今6 000年前南黄海最大海泛面出现,后降至现今水平,并基本保持稳定状态,在黄河、近岸短源河流以及海岸带基岩侵蚀物等物质联合贡献下完成了南黄海中部泥质沉积体在近岸的延伸(7.7m以上),其中顶部约4.8m以上粒度粗化及与之相关的较多含量胶结壳有孔虫化石的出现,可能与约3 000—2 000年以来海岸带地区人类活动的加剧有关。

LATE QUATERNARY DISTRIBUTION CHARACTERS OF FORAMINIFERA AND OSTRACODA IN THE OFFSHORE AREA OF SOUTHERN SHANDONG PENINSULA AND PALEOENVIRONMENTAL EVOLUTION

The paleoenvironmental evolution off the southern Shandong Peninsula since the Marine Isotope Stage(MIS)4is studied based on the quantitative analyses of foraminifera and ostracoda communities sampled from a 16.2-meter sedimentary record of core QDZ03.The first terrestrial layer with several depositional gaps(depth 16.2—12.0m)was estimated to be formed during the Yellow Sea Regression Stage at 60ka BP(equal to MIS4)approximately.Due to the dramatic sea-level rise in Yumu interglacial stage(equal to MIS3),a littoral to terrestrial environment were dominated in the second to fifth layer.Part of sediment in MIS2was probably located above the upper part of the fifth layer,and most of the deposits in MIS2were lost.In 12—11ka BP,the littoral deposit in the upper part of the sixth layer(depth 9.1—8.6m)was formed in the process of seawater intrusion from the Yellow Sea into Qingdao area.Before the Maximum Flooding Surface(MFS)in Holocene(11.0—9.0ka BP,approximately),the midst of sixth layer(depth 8.6—7.7m)was formed under a nearshore environment with the further sea-level rising.As the sea-level reached its maximum at 6ka BP and then declined to the present level with stable characters,sediments of the mud clinoform extended by 7.7meter along the coast of South Yellow Sea as a result of the combined contributions made by Yellow River,small rivers and proximal coastal sediments of the Shandong Peninsula.The top 4.8-meter sediments with coarser sandy deposits and more abundant agglutinated foraminifera were probably related to the enhanced anthropogenic activities in coastal area since the last 3—2ka.