桑沟湾周边海域晚更新世以来的层序地层

    Sequence stratigraphy around Sanggou Bay since the Late Pleistocene

    • 摘要: 通过桑沟湾周边海域高分辨率浅地层剖面的地质解译,结合典型钻孔沉积地层的对比分析,揭示了研究区晚更新世以来的层序地层序列。研究表明,桑沟湾周边海域晚更新世以来的地层上覆于基岩之上,自下而上识别出了具有层序意义的3个声学地层单元(SU2、SU1-2、SU1-1),与钻孔的3个沉积地层单元(DU2、DU1-2、DU1-1)对应性良好。桑沟湾周边海域晚更新世以来的层序序列,形成于末次冰盛期低海面时期及早—中全新世高海面以来,自下而上包括低水位体系域(河流-河道充填相沉积)、海侵体系域(潮流沙脊与滨海相沉积)、高水位体系域(浅海相沉积)。研究区低水位体系域受河流下切侵蚀作用,沉积厚度变化较大,介于0~15 m;海侵体系域的沉积厚度普遍介于4.5~5.5 m,分布广泛;高水位体系域由岸向海,自西南至东北沉积厚度逐渐增加,最厚处超过30 m。

       

      Abstract: High-resolution seismic reflection data and depositional stratigraphy of typical cores were studied in detail to determine the sequence stratigraphy since the Late Pleistocene around the Sanggou Bay off Rongcheng in Shandong Peninsula. Results show that the Late Pleistocene strata above bedrock in the study area could be subdivided into three seismic units (SU2, SU1-2, SU1-1 in descending order), and they are well corresponded to three depositional units (DU2, DU1-2, DU1-1) of borehole. The sediment sequence covered deposits during the sea-level lowstand of LGM and the sea-level highstand of early-middle Holocene, comprising lowstand systems tract (LST) (deposits of fluvial to incised-channel filling facies), transgressive systems tract (TST) (deposits of tidal sand ridges and littoral facies); and the highstand systems tract (HST) (deposits of neritic facies since). The LST varies considerably in thickness of 0~15 m due to river erosion, while the TST is widely distributed in the thickness of 4.5~5.5 m, and the HST gradually thickens seaward from SW to NE with a maximum thickness of more than 30 m in the study area.

       

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