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The role of mat-forming diatoms in the formation of Mediterranean sapropels

Kemp, Alan E. S., Pearce, Richard B., Koizumi, Itaru, Pike, Jennifer ORCID: and Rance, S. Jae 1999. The role of mat-forming diatoms in the formation of Mediterranean sapropels. Nature 398 (6722) , pp. 57-61. 10.1038/18001

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The origins of sapropels (sedimentary layers rich in organic carbon) are unclear, yet they may be a key to understanding the influence of climate on ocean eutrophication, the mechanisms of sustaining biological production in stratified waters and the genesis of petroleum source rocks1, 2, 3. Recent microfossil studies of foraminifera1 and calcareous nannofossils2 have focused attention on a deep chlorophyll maximum as a locus for the high production inferred3 for sapropel formation, but have not identified the agent responsible. Here we report the results of a high-resolution, electron-microscope-based study of a late Quaternary laminated sapropel in which the annual flux cycle has been preserved. We find that much of the production was by diatoms, both mat-forming and other colonial forms, adapted to exploit a deep nutrient supply trapped below surface waters in a stratified water column. Reconstructed organic-carbon and opal fluxes to the sediments are comparable to those at high-productivity sites in today's oceans, and calculations based on diatom Si/C ratios suggest that the high organic-carbon content of sapropels may be entirely accounted for by sedimenting diatoms. We propose that this style of production may have been common in ancient Palaeogene and Cretaceous seas, environments for which conventional appeals to upwelling-driven production to account for the occurrence of diatomites, and some organic-carbon-rich sediments, have never seemed wholly appropriate.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Environmental Sciences
Subjects: Q Science > QE Geology
Q Science > QR Microbiology
Publisher: NPG
ISSN: 0028-0836
Last Modified: 18 Oct 2022 12:21

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