Pore water geochemistry at two seismogenic areas in the Sea of Marmara

Type Article
Date 2015-07
Language English
Author(s) Ruffine Livio1, Germain Yoan1, Polonia Alina2, De Prunele Alexis1, Croguennec Claire1, Donval Jean-Pierre1, Pitel-Roudaut Mathilde1, Ponzevera Emmanuel1, Caprais Jean-Claude3, Brandily Christophe3, Grall Celine1, 4, 5, Bollinger Claire6, Geli LouisORCID1, Gasperini Luca2
Affiliation(s) 1 : IFREMER, Dept REM, Unite Geosci Marines, F-29280 Plouzane, France.
2 : CNR, Ist Sci Marine Geol Marina, IT-40129 Bologna, Italy.
3 : IFREMER, Dept REM, Unite Ecosyst & Environm Profonds, F-29280 Plouzane, France.
4 : Aix Marseille Univ, Coll France, CEREGE, CNRS, F-13545 Aix En Provence, France.
5 : Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA.
6 : Inst Univ Europeenne Bretagne, UBO, CNRS, UMR 6538, F-29280 Plouzane, France.
Source Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2015-07 , Vol. 16 , N. 7 , P. 2038-2057
DOI 10.1002/2015GC005798
WOS© Times Cited 15
Keyword(s) anaerobic oxidation of methane, North Anatolian Fault, pore water geochemistry, Sea of Marmara, seismic activity
Abstract Within the Sea of Marmara, the highly active North Anatolian Fault (NAF) is responsible for major earthquakes (Mw>=7), and acts as a pathway for fluid migration from deep sources to the seafloor. This work reports on pore water geochemistry from three sediment cores collected in the Gulfs of Izmit and Gemlik, along the Northern and the Middle strands of the NAF, respectively. The resulting data set shows that anaerobic oxidation of methane (AOM) is the major process responsible for sulfate depletion in the shallow sediment. In the Gulf of Gemlik, depth concentration profiles of both sulfate and alkalinity exhibit a kink-type profile. The Sulfate Methane Transition Zone (SMTZ) is located at moderate depth in the area. In the Gulf of Izmit, the low concentrations observed near the seawater-sediment interface for sulfate, calcium, strontium, and magnesium result from rapid geochemical processes, AOM, and carbonate precipitation, occurring in the uppermost part of the sedimentary column and sustained by free methane accumulation. Barite dissolution and carbonate recrystallization have also been identified at deeper depth at the easternmost basin of the Gulf of Izmit. This is supported by the profile of the strontium isotope ratios (87Sr/86Sr) as a function of depth which exhibits negative anomalies compared to the modern seawater value. The strontium isotopic signature also shows that these carbonates had precipitated during the reconnection of the Sea of Marmara with the Mediterranean Sea. Finally, a first attempt to interpret the sulfate profiles observed in the light of the seismic activity at both sites is presented. We propose the hypothesis that seismic activity in the areas is responsible for the transient sulfate profile, and that the very shallow SMTZ depths observed in the Gulf of Izmit is likely due to episodic release of significant amount of methane.
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Ruffine Livio, Germain Yoan, Polonia Alina, De Prunele Alexis, Croguennec Claire, Donval Jean-Pierre, Pitel-Roudaut Mathilde, Ponzevera Emmanuel, Caprais Jean-Claude, Brandily Christophe, Grall Celine, Bollinger Claire, Geli Louis, Gasperini Luca (2015). Pore water geochemistry at two seismogenic areas in the Sea of Marmara. Geochemistry Geophysics Geosystems, 16(7), 2038-2057. Publisher's official version : https://doi.org/10.1002/2015GC005798 , Open Access version : https://archimer.ifremer.fr/doc/00272/38339/