Extremely High Methane Concentration in Bottom Water and Cored Sediments from Offshore Southwestern Taiwan
Resource
Terrestrial, Atmospheric and Oceanic Sciences 17 (4): 903-920
Journal
Terrestrial, Atmospheric and Oceanic Sciences
Journal Volume
17
Journal Issue
4
Pages
903-920
Date Issued
2006
Date
2006
Author(s)
Chuang, Pei-Chuan
Yang, Tsanyao-Frank
Lee, Hsiao-Fen
Lan, Tefang F.
Hong, Wei-Li
Chen, Ju-Chin
Wang, Yun-Shuen
Abstract
It has been found that Bottom Simulating Reflections (BSRs), which infer the existence of potential gas hydrates underneath seafloor sediments, are widely distributed in offshore southwestern Taiwan. Fluids and gases derived from dissociation of gas hydrates, which are typically methane enriched, affect the composition of seawater and sediments near venting areas. Hence, methane concentration of seawater and sediments become useful proxies for exploration of potential gas hydrates in a given area. We systematically collected bottom waters and sedimentary core samples for dissolved and pore-space gas analyses through five cruises: ORI-697, ORI-718, ORII-1207, ORII-1230, and ORI-732 from 2003 to 2005 in this study. Some sites with extremely high methane concentrations have been found in offshore southwestern Taiwan, e.g., sites G23 of ORI-697, N8 of ORI-718, and G96 of ORI-732. The methane concentrations of cored sediments display an increasing trend with depth. Furthermore, the down-core profiles of methane and sulfate reveal very shallow depths of sulfate methane interface (SMI) at some sites in this study. It implies sulfate reduction being mainly driven by the process of anaerobic methane oxidation (AMO) in sediments; thus indicating that there is a methane-enriched venting source, which may be the product of dissociation of gas hydrates in this area.
Subjects
Anaerobic methane oxidation; Gas hydrate; Methane; Sulfate methane interface
SDGs
Other Subjects
bottom water; gas hydrate; marine sediment; methane; seawater; sediment chemistry; sediment core; Asia; Eurasia; Far East; Taiwan
Type
journal article
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