FN Archimer Export Format
PT J
TI U-Th isotope constraints on gas hydrate and pockmark dynamics at the Niger delta margin
BT 
AF BAYON, Germain
   HENDERSON, Gideon M.
   ETOUBLEAU, Joel
   CAPRAIS, Jean-Claude
   RUFFINE, Livio
   MARSSET, Tania
   DENNIELOU, Bernard
   CAUQUIL, Eric
   VOISSET, Michel
   SULTAN, Nabil
AS 1:1;2:2;3:1;4:3;5:1;6:1;7:1;8:4;9:1;10:1;
FF 1:PDG-REM-GM-LGM;2:;3:PDG-REM-GM-LGM;4:PDG-REM-EEP-LEP;5:PDG-REM-GM-LGM;6:PDG-REM-GM-LES;7:PDG-REM-GM-LES;8:;9:PDG-REM-GM-CTDI;10:PDG-REM-GM;
C1 IFREMER, Unite Rech Geosci Marines, F-29280 Plouzane, France.
   Univ Oxford, Dept Earth Sci, Oxford OX1 3PR, England.
   IFREMER, Unite Rech Etud Ecosyst Profonds, F-29280 Plouzane, France.
   TOTAL, F-92069 Paris, France.
C2 IFREMER, FRANCE
   UNIV OXFORD, UK
   IFREMER, FRANCE
   TOTAL, FRANCE
SI BREST
SE PDG-REM-GM-LGM
   PDG-REM-EEP-LEP
   PDG-REM-GM-LES
   PDG-REM-GM-CTDI
   PDG-REM-GM
IN WOS Ifremer jusqu'en 2018
   copubli-france
   copubli-europe
IF 2.503
TC 54
UR https://archimer.ifremer.fr/doc/00286/39708/41518.pdf
LA English
DT Article
CR NERIS 1
   NERIS 2
BO Le Suroît
   L'Atalante
DE ;Gas hydrates;Pockmarks;U-series;Authigenic carbonates;Niger delta
AB The application of uranium-thorium dating methods to authigenic carbonates provides unique constraints on the temporal evolution of methane seeps at ocean margins. In this study, we report U-Th isotope measurements for carbonate breccias collected from within a hydrate-bearing pockmark located at the Niger Delta margin. These concretions were extracted from a carbonate-rich layer in the upper two meters of a sediment core (N2-KS-44; ~ 1200 m water depth), well above the present-day sulphate-methane transition zone (about 3 m depth) and the presence of gas hydrates in the sediment. The stratigraphy of core N2-KS-44 was established by tuning its downcore Al/Ti profile to a well-dated nearby reference core, and carbonate 230Th/U ages were calculated using isochron methods.  Our results indicate that a major event of aragonite precipitation occurred between about 13 and 2.5 ka at the studied location. Comparison of sediment accumulation rates at both core N2-KS-44 and the nearby reference site suggests that the initial stage of carbonate precipitation, between 13 and 10 ka, was associated with sediment winnowing, probably related to intense fluid seepage. In contrast, our data indicate that sedimentation rates rapidly increased within the pockmark after 7 ka. In agreement with the presence of carbonate breccias exhibiting U-Th ages older than their corresponding stratigraphic age, this observation would suggest that sediment reworking took place after that time, possibly caused by erosion of the surrounding sediment within the pockmark.  We hypothesize that the period of carbonate formation between 13 and 2.5 ka was related to an upward migration of gas-hydrate reservoirs to the near seafloor environment. After this pulse of enhanced fluid flow, the diminution of methane fluxes at the base of the local gas-hydrate occurrence zone would have led to hydrate dissolution in sub-surface sediments and pockmark formation, thereby explaining the progressive increase in sedimentation rates, the absence of recent carbonate concretions and the deepening of the sulphate-methane transition zone at site N2-KS-44 inferred from pore water data. Overall, these results provide further constraints about the relationship between gas hydrate dynamics and the evolution of pockmarks at ocean margins through time.
PY 2015
PD DEC
SO Marine Geology
SN 0025-3227
PU Elsevier Science Bv
VL 370
UT 000366233500008
BP 87
EP 98
DI 10.1016/j.margeo.2015.10.012
ID 39708
ER

EF