海底麻坑的构型、特征、演化及成因——以西非木尼河盆地陆坡为例
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摘要
基于高分辨率三维地震数据,研究了西非木尼河盆地海底麻坑的构型、演化模式及成因机制。海底麻坑分为孤立麻坑和条带状麻坑(简称麻坑带),麻坑带由较多的单个麻坑呈条带状排列聚集而成,单个麻坑的面积在0.2~0.6km2,麻坑深度约20~60 m。过孤立麻坑或横切麻坑带的地震剖面上,麻坑及其之下地层具有U形反射特征,显示麻坑之下有气烟囱发育,并具有振幅增强、同相轴下拉的特征;顺麻坑带走向的地震剖面具有脊-槽相间的地形特征。研究区的麻坑带受古深水水道控制,麻坑带与古水道的平面分布相吻合。由古水道控制形成麻坑带的演化模式可以划分为四个阶段:古水道超压形成、古水道超压释放、麻坑物质冲洗、麻坑形成。海底麻坑的成因机制具有多样性,但基本上都是由海底地层中的流体发生渗漏或喷发所形成的。
Based on high-resolution 3D seismic data,the seabed pockmarks can be divided into isolated pockmarks and pockmark belts by their distribution in Rio Muni Basin,West Africa.Pockmark belts are distributed along meandering bands on seafloor.A single seabed pockmark can be in a range from 0.2 to 0.6 km2 in area and from 20 to 60m in depth.The seismic profiles across the isolated pockmarks or seabed pockmark belts illustrate U-shaped reflection characters of them an d the underlaying beds with increasing amplitudes and pulling-down seismic events,which implies the existence of gas chimneys under these seabed pockmarks,The seafloor along the strikes of the seabed pockmark belts is characterized by a ridge-by-swale topography.The distribution of the seabed pockmark belts are controlled by the palaeochannels so that the distribution of pockmark belts is coherent with that of alaeochannels in plane.The evolution of the seabed pockmark belts that are controlled by palaeochannels can be divided into four stages:overpressure build-up stage,overpressure release stage,pockmark sediments expulsion stage and pockmark formation stage.The genesis of pockmarks is relative to some geological conditions but all of pockmarks have been associated with fluids seepage or expulsion in sea floor strata.
Based on high-resolution 3D seismic data,the seabed pockmarks can be divided into isolated pockmarks and pockmark belts by their distribution in Rio Muni Basin,West Africa.Pockmark belts are distributed along meandering bands on seafloor.A single seabed pockmark can be in a range from 0.2 to 0.6 km2 in area and from 20 to 60m in depth.The seismic profiles across the isolated pockmarks or seabed pockmark belts illustrate U-shaped reflection characters of them an d the underlaying beds with increasing amplitudes and pulling-down seismic events,which implies the existence of gas chimneys under these seabed pockmarks,The seafloor along the strikes of the seabed pockmark belts is characterized by a ridge-by-swale topography.The distribution of the seabed pockmark belts are controlled by the palaeochannels so that the distribution of pockmark belts is coherent with that of alaeochannels in plane.The evolution of the seabed pockmark belts that are controlled by palaeochannels can be divided into four stages:overpressure build-up stage,overpressure release stage,pockmark sediments expulsion stage and pockmark formation stage.The genesis of pockmarks is relative to some geological conditions but all of pockmarks have been associated with fluids seepage or expulsion in sea floor strata.
引文
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[15]Hovland M,Gardner J V,Judd A G.The significance of pockmarks to understanding fluid flow processes and geohazards[J].Geofluids,2002,2(2):127-136.
[16]王健,邱文弦,赵俐红.天然气水合物发育的构造背景分析.地质科技情报,2010,29(2):100-106.
[17]Brothers L L,Kelley J T,Bellknap D F,et al.Shallow stratigraphic control on pockmark distribution in north temperate estuaries[J].Marine Geology,2012,329-331(1):34-45.
[18]罗敏,吴庐山,陈多福.海底麻坑研究现状及进展[J].海洋地质前沿,2012,28(5):33-42.
[19]Andresen K J,Huuse M,Schodt N H,et al.Hydrocarbon plumbing systems of salt minibasins offshore Angola revealed by three-dimensional seismic analysis[J].AAPG Bulletin,2011,95(6):1039-1065.
[20]Gay A,Lopez M,Cochonat P,et al.Sinuous pockmark belt as indicator of a shallow buried turbiditic channel on the lower slope of the Congo Basin,West African Margin//Van Rensbergen P,Hillis R R,Maltman A J,et al.Subsurface sediment mobilization.London:Geological Society of London,2003:173-189.
[21]Jobe Z R,Lowe D R,Uchytil S J.Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea[J].Marine and Petroleum Geology,2010,28(3):843-860.
[22]Ondeas H,Olu K,Fouquet Y,et al.ROV study of a giant pockmark on the Gabon continental margin[J].Geo-Marine Letters,2005,25(5):1-26.
[23]Chaduteau C,Philippe J B,Fourre E,et al.Helium transport in sediment pore fluids of the Congo-Angola margin[J].Geochemistry Geophysics Geosystems,2009,10(1):1-12.
[24]Pilcher R,Argent J.Mega-pockmarks and linear pockmark trains on the West African continental margin[J].Marine Geology,2007,244(1/4):15-32.
[2]Hovland M,Talbot M R,Qvale H,et al.Methane-related carbonate cements in pockmarks of the North-Sea[J].Journal of Sedimentary Petrology,1987,57(5):881-892.
[3]Kelley J T,Dickson S M,Belknap D F,et al.Giant seabed pockmarks:Evidence for gas escape from Belfast Bay,Maine[J].Geology,1994,22(1):59-62.
[4]Gay A,Lopez M,Cochonat P,et al.Isolated seafloor pockmarks linked to BSRs,fluid chimneys,polygonal faults and stacked Oligocene-Miocene turbiditic palaeochannels in the Lower Congo Basin[J].Marine Geology,2006,226(1/2):25-40.
[5]Forwick M,Baeten N J,Vorren T O.Pockmarks in Spitsbergen fjords[J].Norwegian Journal of Geology,2009,89(1/2):65-77.
[6]Moss J L,Cartwright J,Cartwright A,et al.The spatial pattern and drainage cell characteristics of a pockmark field,Nile deep sea fan[J].Marine and Petroleum Geology,2012,35(1):321-336.
[7]Somoza L,Medialdea T,Leon R,et al.Structure of mud volcano systems and pockmarks in the region of the Ceuta contourite depositional system[J].Marine Geology,2012,332-334(1):4-26.
[8]邸鹏飞,黄华谷,黄保家,等.莺歌海盆地海底麻坑的形成与泥底辟发育和流体活动的关系[J].热带海洋学报,2012,31(5):26-36.
[9]Bertoni C,Cartwright J,Hermanrud C.Evidence for largescale methane venting due to rapid drawdown of sea level during the Messinian Salinity Crisis[J].Geology,2013,41(3):371-374.
[10]Taviani M,Angeletti L,Ceregato A,et al.The Gela Basin pockmark field in the strait of Sicily(Mediterranean Sea):Chemosymbiotic faunal and carbonate signatures of postglacial to modern cold seepage[J].Biogeosciences Discussions,2013,10(1):967-1009.
[11]Sahling H,Bohrmann G,Spiess V,et al.Pockmarks in the Northern Congo Fan area,SW Africa:Complex seafloor features shaped by fluid flow[J].Marine Geology,2008,249(3/4):206-225.
[12]Salmi M S,Johnson H P,Leifer I,et al.Behavior of methane seep bubbles over a pockmark on the Cascadia continental margin[J].Geosphere,2011,7(6):1273-1283.
[13]Kasten S,Nohen K,Hensen C,et al.Gas hydrate decomposition recorded by authigenic barite at pockmark sites of the northern Congo Fan[J].Geo-Marine Letters,2012,32(5/6):373-378.
[14]Sultan N,Marsset B,Ker S,et al.Hydrate dissolution as a potential mechanism for pockmark formation in the Niger delta[J].Journal of Geophysical Research,2010,115(B8):1-33.
[15]Hovland M,Gardner J V,Judd A G.The significance of pockmarks to understanding fluid flow processes and geohazards[J].Geofluids,2002,2(2):127-136.
[16]王健,邱文弦,赵俐红.天然气水合物发育的构造背景分析.地质科技情报,2010,29(2):100-106.
[17]Brothers L L,Kelley J T,Bellknap D F,et al.Shallow stratigraphic control on pockmark distribution in north temperate estuaries[J].Marine Geology,2012,329-331(1):34-45.
[18]罗敏,吴庐山,陈多福.海底麻坑研究现状及进展[J].海洋地质前沿,2012,28(5):33-42.
[19]Andresen K J,Huuse M,Schodt N H,et al.Hydrocarbon plumbing systems of salt minibasins offshore Angola revealed by three-dimensional seismic analysis[J].AAPG Bulletin,2011,95(6):1039-1065.
[20]Gay A,Lopez M,Cochonat P,et al.Sinuous pockmark belt as indicator of a shallow buried turbiditic channel on the lower slope of the Congo Basin,West African Margin//Van Rensbergen P,Hillis R R,Maltman A J,et al.Subsurface sediment mobilization.London:Geological Society of London,2003:173-189.
[21]Jobe Z R,Lowe D R,Uchytil S J.Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea[J].Marine and Petroleum Geology,2010,28(3):843-860.
[22]Ondeas H,Olu K,Fouquet Y,et al.ROV study of a giant pockmark on the Gabon continental margin[J].Geo-Marine Letters,2005,25(5):1-26.
[23]Chaduteau C,Philippe J B,Fourre E,et al.Helium transport in sediment pore fluids of the Congo-Angola margin[J].Geochemistry Geophysics Geosystems,2009,10(1):1-12.
[24]Pilcher R,Argent J.Mega-pockmarks and linear pockmark trains on the West African continental margin[J].Marine Geology,2007,244(1/4):15-32.
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