The influence of lateral transport on sedimentary alkenone paleoproxy signals

[摘要] Alkenone signatures preserved in marine sedimentary records areconsidered one of the most robust paleothermometers available and are oftenused as a proxy for paleoproductivity. However, important gaps remainregarding the provenance and fate of alkenones, as well as their impact on derivedenvironmental signals in marine sediments. Here, we analyze the abundance,distribution and radiocarbon ( 14 C) age of alkenones in bulk sedimentsand corresponding grain-size fractions in surficial sediments from sevencontinental margin settings in the Pacific and Atlantic oceans to evaluatethe impact of organo-mineral associations and hydrodynamic sorting onsedimentary alkenone signals. We find that alkenones preferentially residewithin fine-grained mineral fractions of continental margin sediments, withthe preponderance of alkenones residing within the fine-silt fraction (2–10  µ m) and most strongly influencing alkenone- 14 C age and seasurface temperature (SST) signals from bulk sediments as a consequence oftheir proportional abundance and higher degree of organic matter protectionrelative to other fractions. Our results provide further evidence for thekey role of selective association of alkenones with mineral surfaces andassociated hydrodynamic mineral sorting processes on the reliability ofalkenone signals encoded in marine sediments ( 14 C age, content anddistribution) and the fidelity of corresponding proxy records (productivityand sea SST) in the spatial and temporal domain.

[学科分类] 大气科学