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Constraints on Earth system functioning at the Paleocene-Eocene Thermal Maximum from the marine silicon cycle

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doi: 10.1029/2020PA003873
Authors:Fontorbe, Guillaume; Frings, Patrick J.; De La Rocha, Christina L.; Hendry, Katharine R.; Conley, Daniel J.
Author Affiliations:Primary:
Lund University, Department of Geology, Lund, Sweden
Other:
German Research Centre for Geosciences, Germany
University of Bristol, United Kingdom
Volume Title:Paleoceanography and Paleoclimatology
Source:Paleoceanography and Paleoclimatology, 35(5). Publisher: John Wiley & Sons, International. ISSN: 1944-9186
Publication Date:2020
Note:In English. 153 refs.; illus., incl. 1 table, sketch map
Summary:The Paleocene-Eocene Thermal Maximum (PETM, ca. 56 Ma) is marked by a negative carbon isotope excursion (CIE) and increased global temperatures. The CIE is thought to result from the release of 13C-depleted carbon, although the source(s) of carbon and triggers for its release, its rate of release, and the mechanisms by which the Earth system recovered are all debated. Many of the proposed mechanisms for the onset and recovery phases of the PETM make testable predictions about the marine silica cycle, making silicon isotope records a promising tool to address open questions about the PETM. We analyzed silicon isotope ratios (δ30Si) in radiolarian tests and sponge spicules from the Western North Atlantic (ODP Site 1051) across the PETM. Radiolarian δ30Si decreases by 0.6 ppm from a background of 1 ppm coeval with the CIE, while sponge δ30Si remains consistent at 0.2 ppm. Using a box model to test the Si cycle response to various scenarios, we find the data are best explained by a weak silicate weathering feedback, implying the recovery was mostly driven by nondiatom organic carbon burial, the other major long-term carbon sink. We find no resolvable evidence for a volcanic trigger for carbon release, or for a change in regional oceanography. Better understanding of radiolarian Si isotope fractionation and more Si isotope records spanning the PETM are needed to confirm the global validity of these conclusions, but they highlight how the coupling between the silica and carbon cycles can be exploited to yield insight into the functioning of the Earth system. Abstract Copyright (2020), . The Authors.
Subjects:Cenozoic; Chemical composition; Geochemical cycle; Isotope ratios; Isotopes; Marine environment; Microfossils; Ocean Drilling Program; Paleo-oceanography; Paleocene-Eocene Thermal Maximum; Paleoclimatology; Paleoenvironment; Paleogene; Porifera; Radiolaria; Si-30/Si-28; Silicates; Silicon; Spicules; Stable isotopes; Tertiary; Volcanism; Weathering; Atlantic Ocean; Blake Nose; Blake Plateau; Leg 171B; North Atlantic; ODP Site 1051; Silicon cycle
Coordinates:N300311 N300311 W0762128 W0762128
Record ID:882897-3
Copyright Information:GeoRef, Copyright 2020 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom
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