Extremely high methane concentration in bottom water and cored sediments from offshore southwestern Taiwan

Pei Chuan Chuang, Tsanyao Frank Yang, Saulwood Lin, Hsiao Fen Lee, Tefang F. Lan, Wei Li Hong, Char Shine Liu, Ju Chin Chen, Yunshuen Wang

Research output: Contribution to journalArticlepeer-review

63 Scopus citations

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.

Original languageEnglish
Pages (from-to)903-920
Number of pages18
JournalTerrestrial, Atmospheric and Oceanic Sciences
Volume17
Issue number4
DOIs
StatePublished - Dec 2006

Keywords

  • Anaerobic methane oxidation
  • Gas hydrate
  • Methane
  • Sulfate methane interface

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