南黄海太阳沙西侧海域晚第四系地震层序和沉积环境演变

在南黄海太阳沙西侧潮流脊槽海域进行了密集网格的高分辨率浅地震勘探,测线间距主要为120 m和200 m。沉积物穿透厚度最大约80~90 m,划分为2个地震层序(SQ1和SQ2),细分为5个亚层(U1~U5)。位于下部的层序1(U1)为晚更新世陆相沉积,上部的层序2(U2~U5)以全新世海相沉积为主。根据地震相特征研究了各亚层的沉积环境,从晚更新世晚期以来,研究区经历了三角洲辫状河流—河流刻蚀—古河道充填—河口滨海—三角洲滨浅海—现代潮流脊槽的沉积环境演变过程。在早全新世中期,研究区发育了一条窄河口型潮流沙脊,并随海平面的快速上升而被掩埋。现代潮流沙脊形成于末次高海面后,与古潮流沙脊没有继承关系,与晚更新世古地形也没有关系,受控于潮流系统。

Seismic sequences and sedimentary environment evolution of Late Quaternary west of Taiyangsha Ridge in the South Yellow Sea

High resolution shallow seismic exploration with dense grids,line intervals of mostly 120 m and 200 m, was carried out in tidal ridges and troughs area west of Taiyangshan Ridge in the South Yellow Sea. The maximum sediment penetration was about 80~90 m. Two seismic sequences(SQ1 and SQ2) were identified and further divided into five sub-sequences (U1~U5). The underlain Sequence 1(U1) consisted of land sediments of Late Pleistocene, while the upper Sequence 2(U2~U5) was mainly formed by marine sediments of Holocene. Sedimentary environments of each sub-sequence were studied based on seismic facies characteristics. Since the later period of Late Pleistocene, the study area has been mainly undergone sedimentary environment evolution of delta distributaries—river incision—paleo-river channel fill—estuary offshore—delta offshore-shallow sea —present tidal ridges and troughs. A tidal sand ridge in narrow river mouth was developed during the middle Early Holocene in the study area, but afterwards were buried due to fast sea level rise. Present tidal sand ridges were formed after the last high sea level. They did not have any inherited relationship with paleo-tidal sand ridges, nor with paleo-topography of Late Pleistocene, but were controlled by tidal current system.