Transient mobilization of subcrustal carbon coincident with Palaeocene–Eocene Thermal Maximum

Gernon, Thomas M., Barr, Ryan, Fitton, J. Godfrey, Hincks, Thea K., Keir, Derek, Longman, Jack, Merdith, Andrew S., Mitchell, Ross N. and Palmer, Martin R. (2022) Transient mobilization of subcrustal carbon coincident with Palaeocene–Eocene Thermal Maximum. Nature Geoscience, 15 (7). pp. 573-579. ISSN 1752-0894

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Plume magmatism and continental breakup led to the opening of the northeast Atlantic Ocean during the globally warm early Cenozoic. This warmth culminated in a transient (170 thousand year, kyr) hyperthermal event associated with a large, if poorly constrained, emission of carbon called the Palaeocene–Eocene Thermal Maximum (PETM) 56 million years ago (Ma). Methane from hydrothermal vents in the coeval North Atlantic Igneous Province (NAIP) has been proposed as the trigger, though isotopic constraints from deep sea sediments have instead implicated direct volcanic carbon dioxide (CO2) emissions. Here we calculate that background levels of volcanic outgassing from mid-ocean ridges and large igneous provinces yield only one-fifth of the carbon required to trigger the hyperthermal. However, geochemical analyses of volcanic sequences spanning the rift-to-drift phase of the NAIP indicate a sudden ~220 kyr-long intensification of magmatic activity coincident with the PETM. This was likely driven by thinning and enhanced decompression melting of the sub-continental lithospheric mantle, which critically contained a high proportion of carbon-rich metasomatic carbonates. Melting models and coupled tectonic–geochemical simulations indicate that >104 gigatons of subcrustal carbon was mobilized into the ocean and atmosphere sufficiently rapidly to explain the scale and pace of the PETM.

Item Type: Article
Additional Information: Funding Information: This study was supported by a Natural Environment Research Council (NERC) grant (NE/R004978/1) to T.M.G., which also supported T.K.H. T.M.G. and T.K.H. received funding from The Alan Turing Institute under the EPSRC grant EP/N510129/1. J.L. was supported by NERC grant NE/K00543X/1 awarded to M.R.P. and T.M.G. T.M.G. acknowledges the Distinguished Geologists’ Memorial Fund of the Geological Society of London to sample the Rockall tuffs at the International Ocean Discovery Program (IODP) Bremen Core Repository (BCR). R.N.M. was supported by a National Natural Science Foundation of China grant (41888101) and a Key Research Programme of the Institute of Geology & Geophysics, Chinese Academy of Sciences (CAS), grant (number IGGCAS-201905). A.S.M. was supported by the Deep Carbon Observatory, Richard Lounsbery Foundation and MCSA Fellowship NEOEARTH, project 893615. We are grateful to the staff of the BCR, especially W. Hale, for their assistance, and to M. Cooper, A. Michalik and A. Milton (University of Southampton) for laboratory assistance. We thank G. Hincks for illustrating the Late Palaeocene northeast Atlantic ridge (Fig. 4). Funding Information: The first author has been supported by the Australian Research Council DECRA DE180100957 “PDEs, free boundaries and applications”. The second author is supported by the fellowship INdAM DP COFUND 2015 “INdAM Doctoral Programme in Mathematics and/or Applications Cofunded by Marie Sklodowska-Curie Actions”, Grant 713485. The third author has been supported by the Australian Laureate Fellowship FL190100081 “Minimal surfaces, free boundaries and partial differential equations”. Part of this work has been completed during a very pleasant visit of the second author to the University of Western Australia, that we thank for the warm hospitality.
Subjects: F800 Physical and Terrestrial Geographical and Environmental Sciences
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: Rachel Branson
Date Deposited: 17 Feb 2023 14:38
Last Modified: 17 Feb 2023 14:45

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