Miniaturized biosignature analysis reveals implications for the formation of cold seep carbonates at Hydrate Ridge (off Oregon, USA)

Abstract

Abstract. Methane-related carbonates from Hydrate Ridge typically show several macroscopically distinguishable mineral phases, namely whitish aragonite, lucent aragonite, and gray micrite. The relationship of these phases to particular microorganisms or biogeochemical processes is as yet unclear. We used a miniaturized biomarker technique on mg samples, combined with factor analysis and subsequent electron microprobe analysis, to study lipid biomarkers and chemical compositions of the individual phases. This allows us to identify particular mechanisms involved in the formation of the different carbonate precipitates. Our combined analysis of biomarkers and petrographic traits shows that most of the lipids related to the anaerobic oxidation of methane (>90% by weight) are concentrated within only a minor compartment (∼20% by volume) of the Hydrate Ridge carbonates, the whitish aragonite. The patterns indicate that the whitish aragonite represents fossilized biofilms of methanotrophic consortia containing mainly archaea of the ANME-2 group and sulfate reducing bacteria, whereas the precipitation of the lucent aragonite may have lacked the immediate proximity of microorganisms during formation. By contrast, the gray micrite formed by incorporation of allochthonous organic and inorganic matter during carbonate precipitation induced by the anaerobic oxidation of methane involving ANME-1 archaea.

Seep-carbonate lamination controlled by cyclic particle flux

“…15) as the dominant carbon source and agree with sulphate-dependent anaerobic oxidation of methane (AOM: CH 4  + SO 4 2−  → HCO 3 −  + HS −  + H 2 O; e.g., ref. 17) – the biogeochemical key process inducing carbonate precipitation at methane seeps (e.g., refs 1, 2, 3, 4). Inside the build-up, upward flow of gaseous methane was facilitated by the porous carbonate framework (permeability ~1.088 * 10 −9  m 2 ; porosity between 5–16 vol.%; Fig.…”

“…Carbonate build-ups develop at areas of seafloor methane venting where microbially mediated sulphate-dependent anaerobic oxidation of methane produces alkalinity, thus facilitating precipitation of seep-carbonates1234. Seep-carbonates recently gained attention as geological archives, recording past methane release events56 and comprising significant sinks in the carbon cycle78.…”

Patterns of carbonate authigenesis at the Kouilou pockmarks on the Congo deep-sea fan

“…For example, ANME-1 groups occur at sites of lower methane concentrations (Nauhaus et al, 2005) and greater depths within the sediment than ANME-2, which are often reported to be dominant near the sediment-water interface at high methane flux sites Knittel et al, 2005;Niemann et al, 2005). Biomarkers enclosed in seep carbonates archive such differences (Leefmann et al, 2008;Stadnitskaia et al, 2008). Accordingly, the formation of calcitic nodules such as GeoB 8212-2a was taking place deeper within the sediment and at moderate methane fluxes based on the predominance of diagnostic biomarkers of ANME-1 archaea.…”

Biomarkers from individual carbonate phases of an Oligocene cold-seep deposit, Washington State, USA

“…Until now, however, mostly bulk samples have been analysed for biomarkers, whereas only a few studies on modern seep deposits have so far attempted to retrieve information preserved in individual seep carbonate horizons and/or mineral phases (Aloisi et al. 2002; Leefmann et al. 2008; Stadnitskaia et al.…”

“…2010). On a mm‐scale, a highly selective distribution of lipid biomarkers was found within modern seep carbonate phases from Hydrate Ridge (off Oregon, USA; Leefmann et al. 2008).…”