黄河三角洲软弱层变形和刺穿作用
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摘要
黄河三角洲刺穿体分布在废弃三角洲叶瓣水下斜坡的下部,成因与密西西比三角洲有很大差别,其形成与软弱层变形(内因)和海洋侵蚀(外因)密切相关。高分辨率黄河三角洲典型的地震地层和解释地层剖面、浅地层剖面和钻孔资料联合解释表明,海底刺穿的发源层来自于河口沙坝下部的前三角洲相软弱层变形。三角洲特有的地层结构造成软弱层上覆的物质压力分布不均,普遍存在一个沿三角洲斜坡下部分布的低压异常带,三角洲堆积过程中,软弱层在低压异常带中的变形已经存在,形成前三角洲上部的凸出地形。黄河口摆动后,海底快速冲刷,在最大冲刷中心也是最大压力释放中心刺穿体形成,随着海洋侵蚀速率减缓,刺穿作用将逐渐减弱,最终将被冲刷消亡。软弱层变形及刺穿对海洋工程设施危害极大。类似这种三角洲特有的地层压力结构在平原海岸地区广泛存在,深入研究软弱层变形机理,对近海工程意义重大。
Diapir bodies are distributed in the lower slope of the abandoned delta lobe in the north of the Yellow River delta,the formation mechanism of which is related to the marine erosion and greatly different from that in the Mississippi delta.The interpretation of a typical sub-bottom profile reveals that the diapir of the Yellow River delta resulted from the interior deformation of soft prodelta layers at the delta front.The special stratification structure leads to the existing of a low-pressure zone on the soft layers,which contributes partly to the protuberant topography of the upper prodelta.After the river channel shifted,the discharging center of pressure was generated from the seabed erosion,on which the diapir came into being.As the seabed erosion rate decreases,the diapir shrinks gradually and disappears finally due to the erosion.The deformation of the soft strata and diapir will do great harm to the marine engineering especially in the delta region with such special stratification structures.
Diapir bodies are distributed in the lower slope of the abandoned delta lobe in the north of the Yellow River delta,the formation mechanism of which is related to the marine erosion and greatly different from that in the Mississippi delta.The interpretation of a typical sub-bottom profile reveals that the diapir of the Yellow River delta resulted from the interior deformation of soft prodelta layers at the delta front.The special stratification structure leads to the existing of a low-pressure zone on the soft layers,which contributes partly to the protuberant topography of the upper prodelta.After the river channel shifted,the discharging center of pressure was generated from the seabed erosion,on which the diapir came into being.As the seabed erosion rate decreases,the diapir shrinks gradually and disappears finally due to the erosion.The deformation of the soft strata and diapir will do great harm to the marine engineering especially in the delta region with such special stratification structures.
引文
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[11]Li Guangxue,Zhuang Kelin,Wei Helong.Sedi mentation in the Yellow River delta,part III:seabed erosion and diapirism in the abandoned subaqueous delta lobe[J].Marine Geology,2000,152:129-144.
[12]Wright L D,Wiseman WJ.Processes of marine dispersal and deposition of suspended silts off the modern mouth of the Huanghe(Yellow River)[J].Continental Shelf Research,1990,10(1):1-40.
[2]杨作升,王涛.埕岛油田勘探开发海洋环境[M].青岛海洋大学出版社,1993:641-872.[YANG Zuo-sheng,WANG Tao.Exploration and Development of Marine Environments in Chengdao Oilfield Area[M].Qingdao:Ocean University of Qingdao Press,1993:641-872.]
[3]杨作升,Keller G H,陆念珠.现代黄河水下三角洲地形及其不稳定性[J].青岛海洋大学学报,1990,20(1):1-7.[YANG Zuo-sheng,Keller G H,LU Nian-zhu.Unstability of undersea topography of the modern Yellow River Delta[J].Journal of Ocean University of Qingdao,1990,20(1):1-7.]
[4]Li Guangxue,Liu Shouquan,Jiang Yuchi,et al.Pri mary stud-y to the diapir in the north of the Yellow River Delta[J].Sci-ence in China(Series D),1999,42(2):153-159.
[5]Morgan J P.Mudslumps at the mouth of the Mississippi River[J].Genesis and Conservation Geology Bulletin,1961,35:1-116.
[6]Morgan J P,Coleman J M.Mudslumps at the mouth of South Pass,Mississippi River[C]//Sedi mentology,Paleontology,Structure,Origin,and Relationto Deltaic Processes.Louisana State University,Baton Rouge,Coastal Studies Series,1963,10:190.
[7]Morgan J P.Mudslumps:diapiric structuresin Mississippi del-ta sedi ments[C]//Diapirismand Diapirs:1968:145-161.
[8]Coleman J M,Garrison L E.Geological aspects of marine slope stability,northwestern Gulf of Mexico[J].Marine Geol-ogy,1977,2:9-44.
[9]周良勇,刘健,刘锡清,等.现代黄河三角洲滨浅海区的灾害地质[J].海洋地质与第四纪地质[J].2004,24(3):19-27.[ZHOU Liang-yong,LI UJian,LI U Xi-qing,et al.Geohazards in coastal areas of the modern Yellow River delta[J].Marine Geology and Quaternary Geology,2004,24(3):19-27.]
[10]成国栋.现代黄河三角洲的演化与结构[J].海洋地质与第四纪地质,1987,7(增刊):7-18.[CHENG Guo-dong.Evolution and structure of the modern Yellow River delta[J].Marine Geology and Quaternary Geology,1987,7(Supplement):7-18.]
[11]Li Guangxue,Zhuang Kelin,Wei Helong.Sedi mentation in the Yellow River delta,part III:seabed erosion and diapirism in the abandoned subaqueous delta lobe[J].Marine Geology,2000,152:129-144.
[12]Wright L D,Wiseman WJ.Processes of marine dispersal and deposition of suspended silts off the modern mouth of the Huanghe(Yellow River)[J].Continental Shelf Research,1990,10(1):1-40.
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