摘要
通过对渤海海峡1096 km高分辨率单道地震剖面进行解译,并结合钻孔岩心资料,探讨渤海海峡地区地层结构及第四纪环境演化过程.根据地震反射特征在单道地震剖面上共识别出7个地震反射界面,划分出7个地震反射单元,组成5套地震层序.其中,层序Ⅰ由U1组成,为一套强振幅、连续性较好的平行、亚平行反射波组成,厚度为0~30 m,为晚更新世和全新世沉积层;层序Ⅱ由U2组成,为低振幅、连续性较差的平行、亚平行反射波组,部分为声学透明或半透明反射层,厚度为0~50 m,为中更新世沉积层;层序Ⅲ由U3-U5组成,上部为低振幅的杂乱反射,部分为声学透明或半透明反射层,中部为连续性较好的强反射单元,下部以杂乱反射为主,最大厚度超过300 m,为早更新世沉积层;层序Ⅳ由U6组成,以杂乱反射为主,局部褶皱变形,仅在老铁山水道地区残留;层序Ⅴ由U7组成,为渤海海峡沉积地层的基底,由一套弱振幅、低连续、成层性差的地震反射单元组成.研究表明,渤海海峡第四纪以来经历多期环境变迁,并在地震剖面上表现出不同的反射特征.早更新世早期-中期,地震反射以杂乱反射为主,连续性较差、反射弱,指示陆相沉积;早更新世晚期,声学透明或半透明反射结构指示海侵开始;中更新世以来,地震反射特征以平行、亚平行的反射结构为主,指示海相沉积占主导地位.高分辨率地震剖面揭示渤海海峡地区活动断裂广泛发育,大部分断裂活动时间终止于中更新世,少数断裂晚更新世以来继续活动,这对海底工程建设严重不利.本次研究揭示了渤海海峡地区第四纪沉积地层结构和活动断裂的展布特征,为渤海海峡跨海通道工程建设的论证提供了新的基础地质支撑.
Seismic stratigraphy study is an effective method to analyze stratigraphic structure, establishes geochronological framework and reconstruct the evolution processing of paleoenvironment in the Bohai Straits. Here, the interpretation of 1096 km high-resolution single channel seismic profiles in Bohai Straits and core data has been carried out, and discussed the stratigraphic structure and Quaternary environmental evolution of the Bohai Straits. Through tracing, comparing, closing and interpreting to characteristic reflected waves of seismic profiles, we identified 7 seismic reflected waves, divided 7 seismic reflected units, and constituted 5 large seismic sequences. Sequence Ⅰ is composed of U1, and it consists of a set of parallel or subparallel reflection waves with strong amplitude and good continuity. This sequence is varying with the fluctuation of seafloor topography, with a thickness of 0~30 m, which represent the Late Pleistocene and Holocene sedimentary strata. Sequence Ⅱ including the U2, it consists of a group of low amplitude, poor continuity parallel or sub parallel reflection wave, some part is acoustic transparent or translucent reflection layer, with a thickness of 0~50 m. the sequence is on behalf of Middle Pleistocene sedimentary strata. Sequence Ⅲ is composed of U3~U5, the upper part is characterized by chaotic reflection with low amplitude, some part is part is acoustic transparent or translucent reflection layer;the middle part is a strong reflection unit with good continuity, the lower part is characterized by chaotic reflection with low amplitude. the sequence is on behalf of Early Pleistocene sedimentary strata with the maximum thickness is more than 300 m. Sequence Ⅳ including the U6, characterized by chaotic reflection, with fold deformation in some part. The sequence is only remnant in the Laotieshan channel. Sequence Ⅴ is composed of U7, which is the basement of the Bohai Strait sedimentary stratum. The results show that Bohai Strait has met multiple environmental changes because of the periodic climate changes since the Quaternary, and has different reflection characteristics on the high-resolution single channel seismic profile. In the early-middle of Early Pleistocene, the seismic profile was characterized by low amplitude, medium-weak reflection with poor continuity, the unit inferred was a continental deposit. In the late Early Pleistocene, the acoustic transparent or translucent reflection layer inferred that the transgression began to occurred in the Bohai Strait area. Since the Middle Pleistocene,the seismic reflection was mainly characterized by parallel or subparallel reflection structure,indicating that marine sediments are dominant. The active faults were widely developed in the Bohai Strait area,distributed in NE and NW directions,most of active faults end in the Middle Pleistocene,a few of them continue to active since the late Pleistocene,which is seriously detrimental to the construction of seabed engineering. This study reveals the Quaternary sedimentary stratigraphic structure and the distribution of active faults in the Bohai Straits,which provides the basic geological data support for the demonstration of the proposed bridge-tunnel path system across the Bohai Straits.
作者
刘长春
李攀峰
孙军
侯方辉
褚宏宪
祁江豪
杨源
陈珊珊
LIU Chang-chun;LI Pan-feng;SUN Jun;HOU Fang-hui;CHU Hong-xian;QI Jiang-hao;YANG Yuan;CHEN Shan-shan(Qingdao Institute of Marine Geology,China Geological Survey,Qingdao 266071,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266071,China;School of Ocean Sciences,China University of Geosciences(Beijing),Beijing 100083,China)
出处
《地球物理学进展》
CSCD
北大核心
2020年第6期2373-2383,共11页
Progress in Geophysics
基金
中国地质调查局项目(DD20190365,DD20190377,DD20191003,DD20190208,DD20189503)
国家自然科学基金(41706069,41606083,41776081)联合资助。
关键词
渤海海峡
地震层序
活动断裂
第四纪环境演化
跨海通道
Bohai Strait
Seismic stratigraphy
Active faults
Quaternary environmental evolution
Bohai Sea-Crossing Passage
