FN Archimer Export Format
PT J
TI Methane-flow system within the Nyegga pockmark field, offshore mid-Norway
BT 
AF Dupré, Stéphanie
   Foucher, Jean-Paul
   Pierre, Catherine
   Decker, Carole
   Westbrook, Graham
   Ker, Stephan
   OLU - LE ROY, Karine
   Donval, Jean-Pierre
   Charlou, Jean-Luc
   Blanc-Valleron, Marie-Madeleine
   NOUZE, Herve
AS 1:1;2:1;3:2;4:3;5:4;6:1;7:3;8:1;9:1;10:5;11:1;
FF 1:PDG-REM-GEOOCEAN-ALMA;2:PDG-REM-GM-LGG;3:;4:PDG-REM-EEP-LEP;5:;6:PDG-REM-GEOOCEAN-ALMA;7:PDG-REM-BEEP-LEP;8:PDG-REM-GEOOCEAN-CYBER;9:PDG-REM-GM-LGM;10:;11:;
C1 UMR GEO-OCEAN, IFREMER, Plouzané, France
   UMR LOCEAN, Sorbonne Université, Paris, France
   UMR BEEP, IFREMER, Plouzané, France
   School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
   UMR-CR2P, CNRS-MNHN, Paris, France
C2 IFREMER, FRANCE
   UNIV SORBONNE, FRANCE
   IFREMER, FRANCE
   UNIV BIRMINGHAM, UK
   MNHN, FRANCE
SI BREST
SE PDG-REM-GEOOCEAN-ALMA
   PDG-REM-GM-LGG
   PDG-REM-EEP-LEP
   PDG-REM-BEEP-LEP
   PDG-REM-GEOOCEAN-CYBER
   PDG-REM-GM-LGM
UM BEEP-LM2E
   GEO-OCEAN
IN WOS Ifremer UMR
   DOAJ
   copubli-france
   copubli-europe
   copubli-univ-france
IF 2.9
TC 0
UR https://archimer.ifremer.fr/doc/00857/96866/105497.pdf
   https://archimer.ifremer.fr/doc/00857/96866/105498.docx
LA English
DT Article
CR HYDRATECH
   VICKING
BO Le Suroît
   Pourquoi pas ?
DE ;Norwegian margin;gas chimneys;pockmarks;seeps;authigenic carbonates;chemosynthesis-based communities;gas hydrate;dissolved methane
AB We investigated fluid seepage within the Nyegga pockmark field (600–900 m water depths) off mid-Norway from Remotely Operated Vehicle dives at the so-called CNE sites (CNE01 to CNE17). The seafloor morphology of some of these features corresponds to pockmarks and adjacent ridges, with the latter being the focus of present seepage activity. These structures are underlain by chimneys above a gas-charged zone with, in some cases, a substantial body of hydrate-invaded sediment (down to 1.3 s in two-way travel time at CNE03). Present-day methane-rich fluid seepage through the seabed is indicated by chemosynthetic fauna, in particular Siboglinidae polychaetes (Oligobrachia haakonmobiensis webbi and Sclerolinum contortum), microbial mats and associated Rissoidae gastropod (Alvania sp.) grazers, and confirmed by measured in situ bottom-water methane anomalies, up to 2,130 nL/L. No free-gas bubble emissions were observed or acoustically identified. The presence of authigenic carbonates reveals past seepage with very low δ13C values (down to −58‰) indicating that the major source of carbon was methane carried by the venting fluids. The ages of major periods of methane venting are provided by vesicomyid bivalve shells (Isorropodon nyeggaensis) present in two sedimentary layers, 14,930 and 15,500 14C yr BP (ca. 17,238 and 17,952 cal yr BP), respectively, corresponding to the time of Melt Water Pulse IA. The seafloor morphology and pattern of seepage -chemosynthetic fauna and microbial mat distribution and dissolved methane concentration-are remarkably heterogeneous. Pore-water chemistry profiles in a gravity core taken only 40 m from major seepage sites indicate no seepage and anaerobic methane oxidation at a sub-bottom depth of about 2 m. Present-day seepage from the studied pockmark-chimney fluid-flow system charged with gas hydrate is dominated by the advection of methane solution in pore water. Some of this methane could result from the dissolution of hydrate in the chimney, most of which would have formed during an earlier period (post-LGM times) of history of the chimney, when it was venting free gas. However, the presence of free gas beneath this chimney is probably why the water entering the chimney is already saturated with methane and the process of hydrate formation in the chimney continues today. 
PY 2023
PD OCT
SO Frontiers In Earth Science
SN 2296-6463
PU Frontiers Media SA
VL 11
UT 001091479200001
DI 10.3389/feart.2023.1250619
ID 96866
ER

EF