Preprints
https://doi.org/10.5194/egusphere-2023-3087
https://doi.org/10.5194/egusphere-2023-3087
03 Jan 2024
 | 03 Jan 2024

Cenozoic pelagic accumulation rates and biased sampling of the deep sea record

Johan Renaudie and David B. Lazarus

Abstract. Global weathering is a primary control of the earth's climate over geologic time scales: converting atmospheric pCO2 into dissolved bicarbonate; with carbon sequestration by marine plankton as carbonate and organic carbon on the ocean floor. The accumulation rate of pelagic marine biogenic sediments are thus a measure of weathering history. Previous studies of Cenozoic pelagic sedimentation have yielded contrasting results, though most show a dramatic rise (up to 6 times) in rates over the Cenozoic. This contrasts with model expectations for approximate steady state in weathering, pCO2, and sequestration over time. Here we show that the Cenozoic record of sedimentation recovered by deep sea drilling has a strong, systematic bias towards lower rates of sedimentation with increasing age. When this bias is removed accumulation rates are shown to actually decline by ca 2 times over the Cenozoic. When accumulation area however is adjusted for changes in available deposition area, global weathering is shown to have nearly doubled at the Eocene-Oligocene boundary, but was otherwise essentially constant. Compilations of other metrics correlated to sedimentation rate (e.g. productivity, biotic composition) also must have a strong age bias, which will need to be considered in future paleoceanographic studies.

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Johan Renaudie and David B. Lazarus

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-3087', Adriana Dutkiewicz, 27 Jan 2024
    • AC1: 'Reply on RC1', Johan Renaudie, 14 Mar 2024
  • RC2: 'Comment on egusphere-2023-3087', Sophie Westacott, 14 Feb 2024
    • AC2: 'Reply on RC2', Johan Renaudie, 14 Mar 2024
  • RC3: 'Comment on egusphere-2023-3087', Jakub Witkowski, 20 Feb 2024
    • AC3: 'Reply on RC3', Johan Renaudie, 14 Mar 2024
Johan Renaudie and David B. Lazarus
Johan Renaudie and David B. Lazarus

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Short summary
We provide a new compilation of rates at which sediments deposited in the deep sea over the last 70 million years. We highlight a bias, linked to the drilling process, that makes it more likely for high rates to be recovered for younger sediments than for older ones. Correcting for this bias, the record show, contrary to previous estimates, a more stable history, thus providing some insights on the past mismatch between physico-chemical model estimates and observations.