Eruption history of the Columbia River Basalt Group constrained by high-precision U-Pb and 40Ar/39Ar geochronology

Kasbohm, J., Schoene, B., Mark, D. F. , Murray, J., Reidel, S., Szymanowski, D., Barfod, D. and Barry, T. (2023) Eruption history of the Columbia River Basalt Group constrained by high-precision U-Pb and 40Ar/39Ar geochronology. Earth and Planetary Science Letters, 617, 118269. (doi: 10.1016/j.epsl.2023.118269)

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Large igneous province volcanism of the Columbia River Basalt Group (CRBG) has been suggested to play a causal role in elevated global temperatures and atmospheric carbon dioxide levels of the Miocene Climate Optimum (MCO). However, assessing the connection between volcanism and warming is dependent upon an accurate and precise chronology for the timing and duration of CRBG emplacement. Building on our previous work (Kasbohm and Schoene, 2018), we present fifteen new high-precision ages, using CA-ID-TIMS U-Pb on zircon and multi-collector 40Ar/39Ar on basaltic groundmass, to provide a detailed dual-chronometer timeline for CRBG eruptions. We use both sets of new ages and precise stratigraphic positions of our samples in an integrated Markov Chain Monte Carlo model to calculate average long-term emplacement rates for main-phase CRBG volcanism of 0.2-0.9 km3/a, with a high likelihood of one prominent hiatus of 60-120 kyr duration occurring after main-phase emplacement. We analyzed trace elements and hafnium isotopes of each dated zircon from CRBG interbeds. The compositions are consistent with both Cascades subduction volcanism and evolved syn-CRBG volcanism proximal to the depositional area. Our age model also yields ages for all magnetic field reversals during the main phase of CRBG emplacement, which can be used to improve calibrations of Miocene paleoclimate records. We find that main-phase CRBG emplacement is coincident with the greatest sustained warmth of the MCO in astronomically-tuned records. Our work shows the power of using both U-Pb and 40Ar/39Ar geochronology in an integrated stratigraphic context to assess data reliability and develop the most robust age model possible for large igneous province emplacement.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Mark, Professor Darren and Barfod, Dr Dan
Authors: Kasbohm, J., Schoene, B., Mark, D. F., Murray, J., Reidel, S., Szymanowski, D., Barfod, D., and Barry, T.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Earth and Planetary Science Letters
ISSN (Online):1385-013X
Published Online:23 June 2023
Copyright Holders:Copyright © 2023 Elsevier B.V.
First Published:First published in Earth and Planetary Science Letters 617: 118269
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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