Preserved organic matter in a fossil Ocean Continent Transition in the Alps: the example of Totalp, SE Switzerland

Mateeva, Tsvetomila ORCID: 0000-0002-6155-8687, Wolff, George A ORCID: 0000-0002-9380-1039, Manatschal, Gianreto, Picazo, Suzanne, Kusznir, Nick J and Wheeler, John ORCID: 0000-0002-7576-4465 (2017) Preserved organic matter in a fossil Ocean Continent Transition in the Alps: the example of Totalp, SE Switzerland. SWISS JOURNAL OF GEOSCIENCES, 110 (2). pp. 457-478.

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Abstract

Evidence from ultraslow spreading mid-ocean ridges and both fossil and present-day Ocean–Continent Transitions (OCT) demonstrates that mantle serpentinization resulting from the interaction of mantle rock and water during tectonic exhumation is widespread. Observations at white smokers in modern ocean settings suggest that methane produced by serpentinization can support methanotrophic bio-systems, which use methane as the only source of carbon. An important question is whether such bio-systems are more generally pervasive in their association with serpentinized mantle in the subsurface. In this study, we examined whether there is evidence for such a methanotrophic system in exhumed serpentinized mantle at a magma-poor rifted continental margin, by probing for characteristic biological markers in these and associated sedimentary rocks in the Totalp unit of SE Switzerland. This unit represents a remnant of the former OCT of the southern Alpine Tethyan margin and was chosen because of its mild Alpine tectonic and low-grade metamorphic overprint during Alpine orogeny, hence giving potential for the preservation of indigenous organic matter (OM). Totalp samples are characterized by low organic carbon contents of 11–647 ppm. The majority of the samples contain hydrocarbons in the form of n-alkanes in the range C17–C36. Some sediments contain isoprenoids, for example pristane and phytane and a suite of steranes that are consistent with a marine origin for the OM preserved in the rocks. Traces of marine planktonic and bacterial OM are preserved in the serpentinized mantle and overlying sediments of this ancient Tethyan OCT, but there is no evidence that the OM has been generated from methanotrophic bio-systems.

Item Type:	Article
Uncontrolled Keywords:	Serpentinization, Organic matter, Totalp unit, Biogeochemistry, Ocean Continent Transition (OCT)
Depositing User:	Symplectic Admin
Date Deposited:	15 Mar 2017 10:55
Last Modified:	19 Jan 2023 07:12
DOI:	10.1007/s00015-017-0266-3
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3006402