FN Archimer Export Format
PT J
TI Shallow gas hydrate accumulations at a Nigerian deep‐water pockmark ‐ Quantities and dynamics
BT 
AF Pape, Thomas
   Ruffine, Livio
   Hong, Wei‐Li
   Sultan, Nabil
   Riboulot, Vincent
   Peters, Carl A.
   Kölling, Martin
   Zabel, Matthias
   Garziglia, Sebastien
   Bohrmann, Gerhard
AS 1:1;2:2;3:3,4;4:2;5:2;6:1,5,6;7:1;8:1;9:2;10:1;
FF 1:;2:PDG-REM-GM-LCG;3:;4:PDG-REM-GM-LAD;5:PDG-REM-GM-LAD;6:;7:;8:;9:PDG-REM-GM-LAD;10:;
C1 MARUM – Center for Marine Environmental Sciences, University of Bremen Bremen ,Germany
   IFREMER, Département Ressources physiques et Ecosystèmes de fond de Mer (REM), Unité des Géosciences Marines Plouzané ,France
   CAGE ‐ Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geology, UiT The Arctic University of Norway Tromsø ,Norway
   Geological Survey of Norway, Marine Geology Trondheim ,Norway
   Ocean Frontier Institute, Dalhousie University Halifax Nova Scotia, Canada
   Tefnut Consulting Halifax Nova Scotia ,Canada
C2 UNIV BREMEN MARUM, GERMANY
   IFREMER, FRANCE
   UNIV ARCTIC UIT NORWAY, NORWAY
   GEOL SURVEY NORWAY, NORWAY
   UNIV DALHOUSIE, CANADA
   TEFNUT CONSULTING, CANADA
SI BREST
SE PDG-REM-GM-LCG
   PDG-REM-GM-LAD
IN WOS Ifremer UPR
   copubli-europe
   copubli-int-hors-europe
IF 3.848
TC 9
UR https://archimer.ifremer.fr/doc/00643/75491/76344.pdf
   https://archimer.ifremer.fr/doc/00643/75491/76345.pdf
   https://archimer.ifremer.fr/doc/00643/75491/76346.avi
LA English
DT Article
CR GUINECO-MEBO
BO Pourquoi pas ?
DE ;pockmark;gas hydrate;methane;MeBo;pressure coring;pore water modeling
AB The evolution of submarine pockmarks is often related to the ascent of fluid from the subsurface. For pockmarks located within the gas hydrate stability zone, methane oversaturation can result in the formation of gas hydrates in the sediment. A ca. 600 m‐wide sea floor depression in deep‐waters offshore Nigeria, Pockmark A, was investigated for distributions and quantities of shallow gas hydrates, origins of hydrocarbons and time elapsed since the last major fluid ascent event. For the first time, pressure coring of shallow sediments and drilling of more than 50‐m‐long cores with the sea floor drill rig MARUM‐MeBo70 were conducted in this pockmark. Unusually high hydrate saturations of up to 51% of pore volume in the uppermost 2.5 meters of sediment in the pockmark center substantiate that deep‐water pockmarks are a relevant methane reservoir. Molecular and stable C and H isotopic compositions suggest that thermogenic hydrocarbons and secondary microbial methane resulting from petroleum biodegradation are injected into shallower sediments and mixed with primary microbial hydrocarbons. Two independent pore water chloride and sulfate modeling approaches suggest that a major methane migration event occurred during the past one to two centuries. A rough sea floor topography within the pockmark most likely results from combined sediment removal through ascending gas bubbles, hydrate clogging and deflection of migration pathways, gas pressure build‐up, and hydrate sea floor detachment. This study shows for the first time the chronological interrelationship between gas migration events, hydrate formation and sea floor shaping in a deep‐sea pockmark. 
PY 2020
PD SEP
SO Journal Of Geophysical Research-solid Earth
SN 2169-9313
PU American Geophysical Union (AGU)
VL 125
IS 9
UT 000577119500012
DI 10.1029/2019JB018283
ID 75491
ER

EF