Age of Sulfate Methane Transition Zone Determined by Modelling Barium Sulfate Growth
Abstract
Methane seep to the sediment/water interface could initiate anaerobic methane oxidation (AOM) with subsequent build up of chemosynthetic community, carbonate, pyrite and a number of other authigenic mineral formation. Determination the duration, sequence and time of methane seeps are keys to understand how methane seep to the environment and degree of alteration to the vicinity area. However, limited method existed in defining time of methane seep since there are some known problems involving typical dating methods, i.e. old carbon on C14 of fossil test or authigenic carbonate, thorium from surrounding matrix on U/Th authigenic carbonate dating. In this study, we have employed barium determination method (Dickens, 2001) to model timing of methane seep at two locations in the South China Sea. Our objective is to compare timing of the barium accumulation near the sulfate methane transition zone (SMTZ) on these two different locations and to seek if a similar mechanism driving the methane seep at two locations far apart. Dissolved barium, total sediment barium and aluminum were measured as well as pore water sulfate, and sediment pyrite concentrations. Time for the barium sulfate accumulation is calculated by: T = C/F, C= ∫ I x p x (1-Ø) Our results show that SMTZ is stabilized at each site for a duration of about 4000-5000 years. AOM process have been active at both sites at about the same time. In conjunction, pyrite also accumulated at a depth near the SMTZ as a result of methane oxidation. This result show that AOM could stay at the SMTZ for a relatively long period of time, on a scale of thousands of years.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMOS53C1232L
- Keywords:
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- 3004 Gas and hydrate systems;
- MARINE GEOLOGY AND GEOPHYSICS;
- 4805 Biogeochemical cycles;
- processes;
- and modeling;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL;
- 4815 Ecosystems;
- structure;
- dynamics;
- and modeling;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL;
- 4219 Continental shelf and slope processes;
- OCEANOGRAPHY: GENERAL