Citation: | Bin Liu, Jiang-xin Chen, Syed Waseem Haider, Xi-guang Deng, Li Yang, Min-liang Duan, 2020. New high-resolution 2D seismic imaging of fluid escape structures in the Makran subduction zone, Arabian Sea, China Geology, 3, 269-282. doi: 10.31035/cg2020027 |
Seabed fluid escape is active in the Makran subduction zone, Arabian Sea. Based on the new high-resolution 2D seismic data, acoustic blanking zones and seafloor mounds are identified. Acoustic blanking zones include three kinds of geometries: Bell-shaped, vertically columnar and tilted zones. The bell-shaped blanking zone is characterized by weak and discontinuous reflections in the interior and up-bending reflections on the top, interpreted as gas chimneys. Vertically columnar blanking zone is interpreted as side-imaged gas chimneys associated with focused fluid flow and topped by a seafloor anomaly expressed as a localized reflection discontinuity, which may together serve as a vent structure. Tilted acoustic blanking zone could be induced by accretionary thrust activity and rapid sedimentation surrounding slope. Seafloor mounds occur at the sites of bell-shaped acoustic blanking zone and may be associated with the material intrusion. Bottom simulating refectors (BSRs) are widely distributed and exhibit a series of characteristics including diminished amplitude, low continuity as well as local shoaling overlapping with these acoustic blanking zones. The large amount of gases dissociated from the gas hydrates migrated upwards and then arrived at the near-seafloor sediments, followed by the formation of the gas hydrates and hence the seafloor mound.
[1] | Andresen K. 2012. Fluid flow features in hydrocarbon plumbing systems: What do they tell us about the basin evolution? Marine Geology, 332–334, 89–108. |
[2] | Baba K, Yamada Y. 2004. BSRs and associated reflections as an indicator of gas hydrate and free gas accumulation: An example of accretionary prism and forearc basin system along the Nankai Trough, off Central Japan. Resource Geology, 54, 11–24. doi: 10.1111/j.1751-3928.2004.tb00183.x |
[3] | Bahk JJ, Kim JH, Kong GS, Park Y, Lee H, Park Y, Park K. 2009. Occurrence of near-seafloor gas hydrates and associated cold vents in the Ulleung Basin, East Sea. Geosciences Journal, 13(4), 371–386. doi: 10.1007/s12303-009-0039-8 |
[4] | Baraza J, Ercilla G. 1996. Gas-charged sediments and large pockmark-like features on the Gulf of Cadiz slope (SW Spain). Marine and Petroleum Geology, 13, 253–261. doi: 10.1016/0264-8172(95)00058-5 |
[5] | Barnes P, Lamarche G, Bialas J, Henrys S, Pecher I, Netzeband G, Greinert J, Mountjoy J, Pedley K, Crutchley G. 2010. Tectonic and geological framework for gas hydrates and cold seeps on the Hikurangi Subduction Margin, New Zealand. Marine Geology, 272, 26–48. doi: 10.1016/j.margeo.2009.03.012 |
[6] | Berndt C. 2005. Focused fluid flow on continental margins. Philosophical Transactions Series A, Mathematical, Physical, and Engineering Sciences, 363, 2855–2871. doi: 10.1098/rsta.2005.1666 |
[7] | Bohrmann G. 2008. Report and preliminary results of R/V METEOR Cruise M74/3, Fujairah-Male, 30 October–28 November 2007. Cold Seeps of the Makran Subduction Zone (Continental Margin of Pakistan). Berichte Fachbereich Geowissenschaften, Universitat Bremen, 266, 1–161. http://elibsuubuni-bremende/ip/docs/00010636pdf. |
[8] | Cartwright J, Aplin A, Huuse M. 2007. Seal bypass system. AAPG Bulletin, 91, 1141–1166. doi: 10.1306/04090705181 |
[9] | Clayton C, Hay S. 1994. Gas migration mechanisms from accumulation to surface. Bulletin of the Geological Society of Denmark, 41, 12–23. |
[10] | Collett TS, Wendlandt RF. 2000. Formation evaluation of gas hydrate-bearing marine sediments on the Blake Ridge with downhole geochemical log measurements, in Proceedings of the Ocean Drilling Program, Scientific Results, 164, 199–215, Texas A&M University, CollegeStation, Texas, Ocean Drilling Program. |
[11] | Crutchley G, Fraser D, Pecher I, Gorman A, Maslen G, Henrys S. 2015. Gas migration into gas hydrate-bearing sediments on the southern Hikurangi margin of New Zealand: Gas migration, Hikurangi margin. Journal of Geophysical Research: Solid Earth, 120, 725–743. doi: 10.1002/2014JB011503 |
[12] | Delisle G, Rad U, Andruleit H, Daniels CH, Tabrez A, Inam A. 2002. Active mud volcanoes on- and offshore eastern Makran, Pakistan. International Journal of Earth Sciences, 91, 93–110. doi: 10.1007/s005310100203 |
[13] | DeMets C, Gordon R, Argus D, Stein S. 1990. Current Plate Motions. Geophysical Journal International, 101, 425–478. doi: 10.1111/j.1365-246X.1990.tb06579.x |
[14] | Dimitrov L. 2002. Mud volcanoes-the most important pathway for degassing deeply buried sediments. Earth-Science Reviews, 59, 49–76. doi: 10.1016/S0012-8252(02)00069-7 |
[15] | Ding F, Spiess V, Fekete N, Murton B, Brüning M, Bohrmann G. 2010. Interaction between accretionary thrust faulting and slope sedimentation at the frontal Makran accretionary prism and its implications for hydrocarbon fluid seepage. Journal of Geophysical Research, 115(8), 1–16. |
[16] | Dong DD, Wu SG, Sun YB, Wang XJ. 2008. Analysis of fluid potential in the Qiongdong-nan basin and its implication to gas hydrate formation. Marine Geology&Quaternary Geology, 28, 93–100 (in Chinese with English abstract). |
[17] | Etiope G, Milkov A, Derbyshire E. 2008. Did geologic emissions of methane play any role in Quaternary climate change? Global and Planetary Change, 61(1–2), 79–88. |
[18] | Feng D, Qiu JW, Hu Y, Peckmann J, Guan HX, Tong HP, Chen C, Chen JX, Gong SG, Li N, Chen DF. 2018. Cold seep systems in the South China Sea: An overview. Journal of Asian Earth Sciences, 168, 3–16. doi: 10.1016/j.jseaes.2018.09.021 |
[19] | Fischer D, Mogollón J, Strasser M, Pape T, Bohrmann G, Fekete N, Spiess V, Kasten S. 2013. Subduction zone earthquake as potential trigger of submarine hydrocarbon seepage. Nature Geoscience, 6(8), 647–651. doi: 10.1038/ngeo1886 |
[20] | Fruehn J, White R, Minshull T. 1997. Internal deformation and compaction of the Makran accretionary wedge. Terra Nova, 9, 101–104. doi: 10.1046/j.1365-3121.1997.d01-13.x |
[21] | Garcia-Gil S, Vilas F, Garcia-Garcia A. 2002. Shallow gas features in incised-valley fills (Ría de Vigo, NW Spain): A case study. Continental Shelf Research, 22(16), 2303–2315. doi: 10.1016/S0278-4343(02)00057-2 |
[22] | Gay A, Lopez M, Berndt C, Séranne M. 2007. Geological controls on focused fluid flow associated with seafloor seeps in the Lower Congo Basin. Marine Geology, 244, 68–92. doi: 10.1016/j.margeo.2007.06.003 |
[23] | Gay A, Lopez M, Cochonat P, Séranne M, Levaché D, Sermondadaz G. 2006. Isolated seafloor pockmarks linked to BSRs, fluid chimneys, polygonal faults and stacked Oligocene-Miocene turbiditic palaeochannels in the Lower Congo Basin. Marine Geology, 226, 25–40. doi: 10.1016/j.margeo.2005.09.018 |
[24] | Golonka J. 2004. Plate tectonic evolution of the Southern Margin of Eurasia in the Mesozoic and Cenozoic. Tectonophysics, 381(1–4), 235–273. |
[25] | Gong JM, Liao J, Sun J, Yang CS, Wang JQ, He YJ, Tian RC, Cheng QS, Chen ZQ. 2016. Factors controlling gas hydrate accumulation in Makran accretionary wedge off Pakistan. Marine geology frontiers, 32(12), 10–15 (in Chinese with English abstract). |
[26] | Gong JM, Liao J, Yun WH, Zhang L, He YJ, Sun ZL, Yang CS, Wang JQ, Huang W, Meng M, Cheng HY. 2018. Gas hydrate accumulation models of Makran accretionary wedge, northern Indian Ocean. Marine Geology&Quaternary Geology, 38(2), 148–155 (in Chinese with English abstract). |
[27] | Grando G, McClay K. 2007. Morphotectonics domains and structural styles in the Makran accretionary prism, offshore Iran. Sedimentary Geology, 196, 157–179. doi: 10.1016/j.sedgeo.2006.05.030 |
[28] | Granli J, Arntsen B, Sollid A, Hilde E. 1999. Imaging through gas-filled sediments using marine shear-wave data. Geophysics, 64, 668–677. doi: 10.1190/1.1444576 |
[29] | Graue K. 2000. Mud volcanoes in deepwater Nigeria. Marine and Petroleum Geology, 17, 959–974. doi: 10.1016/S0264-8172(00)00016-7 |
[30] | Hansen J, Cartwright JA, Huuse M, Clausen O. 2005. 3D seismic expression of fluid migration and mud remobilization on the Gjallar Ridge, Offshore Mid-Norway. Basin Research, 17, 123–139. doi: 10.1111/j.1365-2117.2005.00257.x |
[31] | Himmler T, Bach W, Bohrmann G, Peckmann J. 2010. Rare earth elements in authigenic methane-seep carbonates as tracers for fluid composition during early diagenesis. Chemical Geology, 277(1–2), 126–136. |
[32] | Hosseini MA, Maleki AB, Mokhtari M. 2018. Splay faults in the makran subduction zone and changes of their transferred coulomb stress. Journal of the Earth and Space Physics, 43(4), 1–10. |
[33] | Fang YX, Lu JA, Liang JQ, Kuang ZG, Cao YC, Chen DF. 2019. Numerical studies of gas hydrate evolution time in Shenhu area in the northern South China Sea. China Geology, 2, 49–55. doi: 10.31035/cg2018054 |
[34] | Foucher JP, Westbrook GK, Boetius A, Ceramicola S, Dupré S, Mascle J, Mienert J, Pfannkuche O, Pierre C, Praeg D. 2009. Structure and Drivers of Cold Seep Ecosystems. Oceanography, 22, 93–109. |
[35] | Jensen J, Bennike O. 2009. Geological setting as background for methane distribution in Holocene mud deposits, Arhus Bay, Denmark. Continental Shelf Research, 29(5–6), 775–784. |
[36] | Judd AG. 2003. The global importance and context of methane escape from the seabed. Geo-Marine Letters, 23(3–4), 147–154. doi: 10.1007/s00367-003-0136-z |
[37] | Judd AG, Hovland M. 1992. The evidence of shallow gas in marine sediments. Continental Shelf Research, 12, 1081–1095. doi: 10.1016/0278-4343(92)90070-Z |
[38] | Judd AG, Hovland M. 2007. Seabed Fluid Flow: The Impact on Geology, Biology and the Marine Environment. Cambridge, Cambridge University Press. |
[39] | Karstens J, Berndt C. 2015. Seismic chimneys in the Southern Viking Graben-Implications for palaeo fluid migration and overpressure evolution. Earth and Planetary Science Letters, 412, 88–100. doi: 10.1016/j.jpgl.2014.12.017 |
[40] | Kong L, Zhang ZF, Yuan QM, Liang QY, Shi YH, Lin JQ. 2018. Multi-factor sensitivity analysis on the stability of submarine hydrate-bearing slope. China Geology, 1, 367–373. doi: 10.31035/cg2018051 |
[41] | Kopp C, Fruehn J, Flueh ER, Reichert C, Kukowski N, Bialas J, Klaeschen D. 2000. Structure of the Makran subduction zone from wide-angle and reflection seismic data. Tectonophysics, 329, 171–191. doi: 10.1016/S0040-1951(00)00195-5 |
[42] | Kukowski N, Schillhorn T, Huhn K, Rad U, Husen S, Flueh E. 2001. Morphotectonics and mechanics of the central Makran accretionary wedge off Pakistan. Marine Geology, 173(1−4), 1–19. doi: 10.1016/S0025-3227(00)00167-5 |
[43] | Langhi L, Strand J, Ross AS. 2016. Fault-related biogenic mounds in the Ceduna Sub-basin, Australia. Implications for hydrocarbon migration. Marine and Petroleum Geology, 74, 47–58. doi: 10.1016/j.marpetgeo.2016.04.006 |
[44] | Lee G, Kim D, Kim HJ, Jou HT, Lee Y. 2005. Shallow gas in the central part of the Korea Strait shelf mud off the southeastern coast of Korea. Continental Shelf Research, 25(16), 2036–2052. doi: 10.1016/j.csr.2005.08.008 |
[45] | Lee M, Collett T. 2006. Gas hydrate and free gas saturations estimated from velocity logs on hydrate ridge, offshore oregon, U.S.A. Proceedings of the Ocean Drilling Program. Scientific Results, 204, 1–25. |
[46] | Lee M, Dillon W. 2001. Amplitude blanking related to the pore-filling of gas hydrate in sediments. Marine Geophysical Researches, 22, 101–109. doi: 10.1023/A:1010371308699 |
[47] | Liu X, Flemings P. 2006. Passing gas through the hydrate stability zone at southern Hydrate Ridge, offshore Oregon. Earth and Planetary Science Letters, 241, 211–226. doi: 10.1016/j.jpgl.2005.10.026 |
[48] | Løseth H, Gading M, Wensaas L. 2009. Hydrocarbon leakage interpreted on seismic data. Marine and Petroleum Geology, 26, 1304–1319. doi: 10.1016/j.marpetgeo.2008.09.008 |
[49] | Løseth H, Wensaas L, Arntsen B, Hanken NM, Basire C, Graue K. 2011. 1000 m Long Gas Blow-out Pipes. Marine and Petroleum Geology, 28, 1047–1060. doi: 10.1016/j.marpetgeo.2010.10.001 |
[50] | Løvlie R, Hanken NM. 2002. Conglomerate test of non-lithified Plio-Pleistocene marine sediments and rock magnetic constrains suggests pDRM type remagnetisation. Physics and Chemistry of the Earth, 27, 1121–1130. doi: 10.1016/S1474-7065(02)00107-9 |
[51] | Macelloni L, Lutken CB, Ingrassia M, D’Emidio M, Pizzi M. 2016. Mesoscale biogeophysical characterization of Woolsey Mound (northern Gulf of Mexico), a new attribute of natural marine hydrocarbon seeps architecture. Marine Geology, 380, 330–344. doi: 10.1016/j.margeo.2016.03.016 |
[52] | Maestrelli D, Iacopini D, Jihad AA, Bond C, Bonini M. 2017. Seismic and structural characterization of fluid escape pipes using 3D and partial stack seismic from the Loyal Field (Scotland, UK): A multiphase and repeated intrusive mechanism. Marine and Petroleum Geology, 88, 489–510. doi: 10.1016/j.marpetgeo.2017.08.016 |
[53] | Mazumdar A, Peketi A, Dewangan P, Badesab F, Ramprasad T, Ramana M, Patil D, Dayal A. 2009. Shallow gas charged sediments off the Indian west coast: Genesis and distribution. Marine Geology, 267(1–2), 71–85. |
[54] | Milkov A. 2000. Worldwide distribution of submarine mud volcanoes and associated gas hydrates. Marine Geology, 167, 29–42. doi: 10.1016/S0025-3227(00)00022-0 |
[55] | Minshull T, White R. 1989. Sediment compaction and fluid migration in the Makran Accretionary Prism. Journal of Geophysical Research, 94(B6), 7387–7402. doi: 10.1029/JB094iB06p07387 |
[56] | Moss J, Cartwright J. 2010. 3D seismic expression of Km-scale fluid escape pipes from offshore Namibia. Basin Research, 22, 481–501. doi: 10.1111/j.1365-2117.2010.00461.x |
[57] | Paull C, Normark W, Ussler B, Caress D, Keaten R. 2008. Association among active seafloor deformation, mound formation, and gas hydrate growth and accumulation within the seafloor of the Santa Monica Basin, offshore California. Marine Geology, 250, 258–275. doi: 10.1016/j.margeo.2008.01.011 |
[58] | Pecher I, Henrys S, Wood W, Kukowski N, Crutchley G, Fohrmann M, Kilner J, Senger K, Gorman A, Coffin R, Greinert J, Faure K. 2010. Focussed fluid flow on the Hikurangi Margin, New Zealand-Evidence from possible local upwarping of the base of gas hydrate stability. Marine Geology, 272, 99–113. doi: 10.1016/j.margeo.2009.10.006 |
[59] | Plaza-Faverola A, Bünz S, Mienert J. 2010. Fluid distributions inferred from P-wave velocity and reflection seismic amplitude anomalies beneath the Nyegga pockmark field of the mid-Norwegian margin. Marine and Petroleum Geology, 27, 46–60. doi: 10.1016/j.marpetgeo.2009.07.007 |
[60] | Platt JP, Leggett JK, Young J, Raza H, Alam S. 1985. Large-scale sediment underplating in the Makran accretionary prism, southwest Pakistan. Geology, 13, 507–511. doi: 10.1130/0091-7613(1985)13<507:LSUITM>2.0.CO;2 |
[61] | Rad UV, Berner U, Delisle G, Doose-Rolinski H, Fechner N, Linke P, Lückge A, Roeser HA, Schmaljohann R, Wiedicke M. 2000. Gas and fluid venting at the Makran accretionary wedge off Pakistan. Geo-Marine Letters, 20, 10–19. doi: 10.1007/s003670000033 |
[62] | Riedel M, Novosel I, Spence G, Hyndman R, Chapman R, Solem R. 2006. Geophysical and geochemical signatures associated with gas hydrate-related venting in the northern Cascadia margin. Geological Society of America Bulletin, 118, 23–38. doi: 10.1130/B25720.1 |
[63] | Riedel M, Spence G, Chapman R, Hyndman R. 2002. Seismic investigations of a vent field associated with gas hydrates, offshore Vancouver Island. Journal of Geophysical Research, 107(B9), 2200. |
[64] | Römer M, Sahling H, Pape T, Spiess V, Bohrmann G. 2012. Gas bubble emission from submarine hydrocarbon seeps at the Makran continental margin (offshore Pakistan). Journal of Geophysical Reseach, 117, C10015. |
[65] | Ryu BJ, Collett T, Riedel M, Kim G, Chun JH, Bahk J, Lee JY, Kim JH, Yoo DG. 2013. Scientific results of the Second Gas Hydrate Drilling Expedition in the Ulleung Basin (UBGH2). Marine and Petroleum Geology, 47, 1–20. doi: 10.1016/j.marpetgeo.2013.07.007 |
[66] | Sager W, Lee C, Macdonald I, Schroeder W. 1999. High-frequency near-bottom acoustic reflection signatures of hydrocarbon seeps on the Northern Gulf of Mexico continental slope. Geo-Marine Letters, 18, 267–276. |
[67] | Sain K, Minshull T, Singh S, Hobbs RW. 2000. Evidence for a thick free gas layer beneath the bottom simulating reflector in the Makran accretionary prism. Marine Geology, 164, 3–12. doi: 10.1016/S0025-3227(99)00122-X |
[68] | Sanchez-Guillamón O, Vázquez JT, Palomino D, Medialdea T, Fernández-Salas LM, León R, Somoza L. 2018. Morphology and shallow structure of seafloor mounds in the Canary Basin (Eastern Central Atlantic Ocean). Geomorphology, 313, 27–47. doi: 10.1016/j.geomorph.2018.04.007 |
[69] | Schlüter H, Prexl A, Gaedicke C, Roeser H, Reichert C, Meyer H, Daniels C. 2002. The Makran accretionary wedge: Sediment thicknesses and ages and the origin of mud volcanoes. Marine Geology, 185, 219–232. doi: 10.1016/S0025-3227(02)00192-5 |
[70] | Schroot B, Klaver G, Schüttenhelm R. 2005. Surface and subsurface expressions of gas seepage to the seabed−Examples from the Southern North Sea. Marine and Petroleum Geology, 22, 499–515. doi: 10.1016/j.marpetgeo.2004.08.007 |
[71] | Schwalenberg K, Wood W, Pecher I, Hamdan L, Henrys S, Jegen M, Coffin R. 2010. Preliminary interpretation of electromagnetic, heat flow, seismic, and geochemical data for gas hydrate distribution across the Porangahau Ridge, New Zealand. Marine Geology, 272, 89–98. doi: 10.1016/j.margeo.2009.10.024 |
[72] | Shedd W, Boswell R, Frye M, Godfriaux P, Kramer K. 2012. Occurrence and nature of “bottom simulating reflectors” in the northern Gulf of Mexico. Marine and Petroleum Geology, 34, 31–40. doi: 10.1016/j.marpetgeo.2011.08.005 |
[73] | Shoar BH, Javaherian A, Farajkhah NK, Arabani MS. 2014. Reflectivity template, a quantitative intercept-gradient AVO analysis to study gas hydrate resources−A case study of Iranian deep sea sediments. Marine and Petroleum Geology, 51, 184–196. doi: 10.1016/j.marpetgeo.2013.12.007 |
[74] | Smith A, Flemings P, Liu X, Darnell K. 2014. The evolution of methane vents that pierce the hydrate stability zone in the world’s oceans. Journal of Geophysical Research: Solid Earth, 119, 6337–6356. doi: 10.1002/2013JB010686 |
[75] | Smith G, McNeill L, Henstock T, Arraiz D, Spiess V. 2014. Fluid generation and distribution in the highest sediment input accretionary margin, the Makran. Earth and Planetary Science Letters, 403, 131–143. doi: 10.1016/j.jpgl.2014.06.030 |
[76] | Smith G, McNeill L, Henstock T, Bull J. 2012. The structure and fault activity of the Makran accretionary prism. Journal of Geophysical Research (Solid Earth), 117, B07407. |
[77] | Suess E. 2014. Marine cold seeps and their manifestations: geological control, biogeochemical criteria and environmental conditions. International Journal of Earth Sciences, 103, 1889–1916. doi: 10.1007/s00531-014-1010-0 |
[78] | Sultan N, Bohrmann G, Ruffine L, Pape T, Riboulot V, Colliat JL, Alexis dP, Dennielou B, Garziglia S, Himmler T, Marsset T, Peters C, Rabiu A, Wei J. 2014. Pockmark formation and evolution in deep water Nigeria: Rapid hydrate growth versus slow hydrate dissolution: Pockmark formation and evolution. Journal of Geophysical Research: Solid Earth, 119, 2679–2694. doi: 10.1002/2013JB010546 |
[79] | Tamaki M, Fujii T, Suzuki K. 2017. Characterization and Prediction of the gas hydrate reservoir at the second offshore gas production test site in the eastern nankai trough, Japan. Energies, 10(10), 1678. doi: 10.3390/en10101678 |
[80] | Van Weering TCE, De Haas H, De Stigter HC, Lykke-Andersen H, Kouvaev I. 2003. Structure and development of giant carbonate mounds at the SW and SE Rockall Trough margins, NE Atlantic Ocean. Marine Geology, 198, 67–81. doi: 10.1016/S0025-3227(03)00095-1 |
[81] | Wang JL, Sain K, Wang XJ, Satyavani N, Wu SG. 2014. Characteristics of bottom-simulating reflectors for Hydrate-filled fractured sediments in Krishna-Godavari basin, eastern Indian margin. Journal of Petroleum Science and Engineering, 122, 515–523. doi: 10.1016/j.petrol.2014.08.014 |
[82] | Wang JL, Wu SG, Kong X, Ma BJ, Li W, Wang DW, Gao JW, Chen WL. 2018a. Subsurface fluid flow at an active cold seep area in the Qiongdongnan Basin, northern South China Sea. Journal of Asian Earth Sciences, 168, 17–26. doi: 10.1016/j.jseaes.2018.06.001 |
[83] | Wang JL, Wu SG, Yao YJ. 2018b. Quantifying gas hydrate from microbial methane in the South China Sea. Journal of Asian Earth Sciences, 168, 48–56. doi: 10.1016/j.jseaes.2018.01.020 |
[84] | Wang XD, Huang HW, Sun YD, Li N, Hu Y, Feng D. 2017. Recent progress on submarine cold seep activity of the northern Indian Ocean. Journal of tropical oceanography, 36(6), 82–89 (in Chinese with English abstract). |
[85] | Wang XJ, Wu SG, Dong DD, Gong YH, Chai C. 2008. Characteristics of gas chimney and its relationship to gas hydrate in Qiongdongnan Basin. Marine Geology&Quaternary Geology, 28, 103–108 (in Chinese with English abstract). |
[86] | Wenau S, Spiess V, Pape T, Fekete N. 2015. Cold seeps at the salt front in the Lower Congo Basin Ⅱ: The impact of spatial and temporal evolution of salt-tectonics on hydrocarbon seepage. Marine and Petroleum Geology, 67, 880–893. doi: 10.1016/j.marpetgeo.2014.09.021 |
[87] | White R, Klitgord K. 1976. Sediment deformation and plate tectonics in the Gulf of Oman. Earth and Planetary Science Letters, 32, 199–209. doi: 10.1016/0012-821X(76)90059-5 |
[88] | Wiedicke M, Neben S, Spiess V. 2001. Mud volcanoes at the front of the Makran accretionary complex, Pakistan. Marine Geology, 172, 57–73. doi: 10.1016/S0025-3227(00)00127-4 |
[89] | Wood W, Hart P, Hutchinson D, Dutta N, Snyder F, Coffin R, Gettrust J. 2008. Gas and gas hydrate distribution around seafloor seeps in Mississippi Canyon, Northern Gulf of Mexico, using multi-resolution seismic imagery. Marine and Petroleum Geology, 25(9), 952–959. doi: 10.1016/j.marpetgeo.2008.01.015 |
[90] | Zhang RW, Lu JA, Wen PF, Kuang ZG, Zhang BJ, Xue H, Xu YX, Chen X. 2018. Distribution of gas hydrate reservoir in the first production test region of the Shenhu area, South China Sea. China Geology, 1, 493–504. doi: 10.31035/cg2018049 |
Overview maps of the Makran subduction zone. a–location of the study area; b–bathymetric map of the study area with the distribution of the seismic lines, indicated in red lines. Yellow lines indicate the sites where the acoustic blanking zones and the seafloor mounds are identified. Note that all the blanking zones are at the mid slope province; c–seafloor mounds SM1 and SM2 on the bathymetric data.
Seismic acquisition. a–the research vessel “Haiyangdizhi shi hao”; b–cartoon showing the 2D seismic survey; c–GI gun array used as the source; d–streamers used to record the seismic wave.
Bell-shaped acoustic blanking zones and induced seafloor mounds in the eastern study area. The five blanking zones (BZ1–BZ5) are at the structure high of the ridge with an almost continuous BSR beneath. The trend of BSR is consistent with that of seafloor topography, beneath which chaotic reflections and phase transition are observed in the western part and eastern part, respectively. Black arrow below BZ1 points to the partial enhanced BSR. Absolute absences of seismic reflections are indicated by dotted circles.
Columnar acoustic blanking zone in the central study area. A bell-shaped zone with reduced amplitude outlined by black dots occurs directly below the columnar blanking zone. Seafloor anomaly and the internal structure of the columnar blanking zone are shown at the zoomed view. A strong BSR separates the columnar blanking zone and the lower bell-shaped zone, with partial breakage at the connection.
Tilted acoustic blanking zone on the line 18 profile. BZ refers to the blanking zone. The blanking zone obliquely inserts into the crest of the ridge along the boundary of slope sediments, occurring at the landward. The intermittent BSR transects the blanking zone and the slope sediments, where the part that is in contact with the blanking zone becomes shallower.
Tilted acoustic blanking zone on the line 19 profile. BZ refers to the blanking zone. The blanking zone obliquely inserts into the crest of the ridge along the boundary of slope sediments, occurring at the landward and the seaward. The intermittent BSR transects the blanking zone and the slope sediments, where the part that is in contact with the blanking zone became shallower.
Seafloor mounds (SM1 and SM2) in the eastern study area. a–partial seismic image of line 23, showing the locations of the two seafloor mounds. A undulating, broken BSR crosscuts the sedimentary reflectors. SM1 and SM2 are located on either side of the central structural high with a similar conical shape. b–zoomed view of SM1, illustrating the spatial relationship between the chaotic reflections beneath SM1 and that at the lower right of SM1. c–zoomed view of SM2, showing the significantly disturbed reflections and a high amplitude reflection direct below SM2.