Preprints
https://doi.org/10.5194/bg-2021-204
https://doi.org/10.5194/bg-2021-204

  02 Aug 2021

02 Aug 2021

Review status: this preprint is currently under review for the journal BG.

The influence of lateral transport on sedimentary alkenone paleoproxy signals

Blanca Ausín1,2, Negar Haghipour2,3, Elena Bruni1, and Timothy Eglinton1 Blanca Ausín et al.
  • 1Geology Department, Salamanca University, Salamanca, 37008, Spain
  • 2Earth Sciences Department, ETH Zurich, Zurich, 8092, Switzerland
  • 3Laboratory of Ion Beam Physics, ETH Zurich, Zurich, 8092, Switzerland

Abstract. Alkenone signatures preserved in marine sedimentary records are considered one of the most robust paleothermometers available, and are often used as a proxy for paleoproductivity. However, important gaps remain on the provenance and fate of alkenones, and their impact on derived environmental signals in marine sediments. Here, we analyze the abundance, distribution, and radiocarbon (14C) age of alkenones in bulk sediments and corresponding grain-size fractions in surficial sediments from seven continental margin settings in the Pacific and Atlantic Oceans in order to evaluate the impact of organo-mineral associations and hydrodynamic sorting on sedimentary alkenone signals. We find that alkenones preferentially reside within fine-grained mineral fractions of continental margin sediments, with the preponderance of alkenones residing within the fine silt fraction (2–10 µm), and most strongly influencing alkenone 14C age, and SST signals from bulk sediments as a consequence of their proportional abundance and higher degree of OM protection relative to other fractions. Our results demonstrate that selective association of alkenones with mineral surfaces and associated hydrodynamic mineral sorting processes can alter alkenone signals encoded in marine sediments (14C age, content, and distribution) and confound corresponding proxy records (productivity and SST) in the spatial and temporal domain.

Blanca Ausín et al.

Status: open (extended)

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  • RC1: 'Comment on bg-2021-204', Anonymous Referee #1, 28 Aug 2021 reply

Blanca Ausín et al.

Blanca Ausín et al.

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Short summary
The preservation and distribution of alkenones -organic molecules produced by marine algae- in marine sediments allows to reconstruct past variations in sea surface temperature, primary productivity and CO2. Here, we explore the impact of remobilization and lateral transport of sedimentary alkenones on their fate in marine sediments. Our results demonstrate the pervasive influence of these processes on alkenone-derived environmental signals, compromising the reliability of related paleorecords.
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