Glacial Cycles Influence Marine Methane Hydrate Formation. Issue 2 (26th January 2018)

• Record Type: Journal Article
• Authors: Malinverno, A.; Cook, A. E.; Daigle, H.; Oryan, B.
• Is Part Of: Geophysical research letters. Volume 45:Issue 2(2018)
• Page Start: 724
• Page End: 732
• Publication Date: 2018-01-26
• Subjects: methane hydrates -- Pleistocene glacial cycles -- microbial methanogenesis; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL075848
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Methane hydrates in fine‐grained continental slope sediments often occupy isolated depth intervals surrounded by hydrate‐free sediments. As they are not connected to deep gas sources, these hydrate deposits have been interpreted as sourced by in situ microbial methane. We investigate here the hypothesis that these isolated hydrate accumulations form preferentially in sediments deposited during Pleistocene glacial lowstands that contain relatively large amounts of labile particulate organic carbon, leading to enhanced microbial methanogenesis. To test this hypothesis, we apply an advection‐diffusion‐reaction model with a time‐dependent organic carbon deposition controlled by glacioeustatic sea level variations. In the model, hydrate forms in sediments with greater organic carbon content deposited during the penultimate glacial cycle (~120–240 ka). The model predictions match hydrate‐bearing intervals detected in three sites drilled on the northern Gulf of Mexico continental slope, supporting the hypothesis of hydrate formation driven by enhanced organic carbon burial during glacial lowstands. Plain Language Summary: Natural methane hydrates, ice‐like compounds of water and methane, are widespread in continental margin sediments. We show here evidence for the hypothesis that methane hydrates form preferentially in sediments deposited during glacial periods, which contain more organic matter that is converted to methane by microbes. Key Points: Methane hydrates within continental slope sediments often occupy isolated depth intervals Hydrate‐bearing intervals may be formed by enhanced methanogenesis in organic carbon‐rich sediments deposited during glacial lowstands Modeling driven by higher organic carbon deposition during lowstands matches hydrate‐bearing intervals observed in Gulf of Mexico boreholes