渤海东部潮流沉积特征及MIS4以来的沉积环境演化

Characteristics of the Tidal Sedimentation in the Eastern Bohai Sea and the Environmental Evolution since MIS4

渤海东部发育了典型的潮流沉积,由老铁山水道冲刷槽、辽东浅滩沙脊和渤中浅滩沙席组成。该文基于中国海洋地质调查最新获取的高分辨率单道地震数据,与水深变化进行对比,将该区的潮流沉积特征与其地震相特征进行精细分析,同时结合晚第四纪CD5孔的岩性、14C测年和层序地层划分,识别出晚更新世以来的四期层序地层,分别是MIS4以细砂为主的陆相地层、MIS3以粉砂和黏土为主的滨浅海相沉积地层、MIS2末次盛冰期形成的以粉砂质粘土和细砂质粉砂为主的陆相沉积地层和全新世(MIS1)发育的以粉砂质黏土和细砂组成的海相沉积地层。其中全新世地层分别由早期的滨海相沉积、中期的浅海沉积和晚期的潮流沉积组成。通过这四期层序的研究,揭示了该区MIS4期以来的沉积环境演化。

The typical tidal sedimentations have been discovered in the eastern of the Bohai Sea,which consists of the Laotieshan Channel,the Liaodong Shoal tidal sand ridges,and the Bozhong Shoal tidal sand sheets.In this paper,the sedimentary features and the seismic reflections of the tidal bodies in eastern Bohai Sea are analyzed based on the new high-resolution seismic data from the marine geological survey and the comparison with water depth changes.Combined with the lithology,14C age data,and stratigraphy of borehole CD5,four stratigraphic sequences have been identified,including the fine sand strata of land facies of MIS4,the silt and clay strata of nearshore facies of MIS3,the silty clay and fine sandy silt strata of land facies of MIS2,and the sand strata of marine facies of Holocene.Furthermore,the sedimentary facies of the Holocene strata can be divided into nearshore,neritic,and tidal environment.The analysis of the four sedimentary facies reveals the evolution of sedimentary environment since MIS4.