Foraminiferal δ18O reveals gas hydrate dissociation in Arctic and North Atlantic ocean sediments

Type Article
Date 2020-08
Language English
Author(s) Dessandier Pierre-Antoine1, Borrelli Chiara1, 2, Yao Haoyi1, Sauer Simone1, 3, Hong Wei-Li1, 4, Panieri Giuliana
Affiliation(s) 1 : Department of Geosciences, CAGE–Centre for Arctic Gas Hydrate, Environment and Climate, UiT The Arctic University of Norway in Tromsø, Tromso, Norway
2 : Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY, USA
3 : IFREMER-Institut Français de Recherche pour l’Exploitation de la Mer, Plouzane, France
4 : Geological Survey of Norway, Trondheim, Norway
Source Geo-marine Letters (0276-0460) (Springer Science and Business Media LLC), 2020-08 , Vol. 40 , N. 4 , P. 507-523
DOI 10.1007/s00367-019-00635-6
WOS© Times Cited 5
Keyword(s) Foraminiferal stable isotopes, Gas hydrates, Authigenic carbonates Arctic Ocean, North Atlantic Ocean
Abstract

Paleoceanographic investigations in the Arctic and north Atlantic are crucial to understanding past and current climate change, in particular considering amounts of pressure-temperature sensitive gas stored in marine sediments of the region. Many paleoceanographic studies are based on foraminiferal oxygen and carbon stable isotope compositions (δ18O, δ13C) from either planktonic specimens, benthic specimens or both. However, in seafloor regions promixal to high upward methane fluxes, such as where seafloor gas emission and shallow gas hydrate-bearing sediment occur, foraminiferal δ18O and δ13C display a wide range of values. Our study focuses on foraminiferal stable isotope signatures in shallow sediment at core sites in the Arctic and North Atlantic affected by significant upward flow of methane. This includes cores with shallow sulfate methane transitions that are adjacent to seeps and containing gas hydrate. We place emphasis on potential effects due to gas hydrate dissociation and diagenesis. Gas hydrate dissociation is known to increase pore-water δ18O, but our results indicate that precipitation of methane-derived authigenic carbonate (MDAC) also affects the foraminiferal δ18O of both planktonic and benthic species. In addition to this post-depositional overprint, we investigate the potential bias of the stable isotope record due to ontogenetic effects. Our data show that the size fraction does not impact the isotopic signal of planktonic and benthic foraminifera.

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