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Constraints on Early Paleozoic Deep-Ocean Oxygen Concentrations From the Iron Geochemistry of the Bay of Islands Ophiolite

Stolper, Daniel A. and Pu, Xiaofei and Lloyd, Max K. and Christensen, Nikolas I. and Bucholz, Claire E. and Lange, Rebecca A. (2022) Constraints on Early Paleozoic Deep-Ocean Oxygen Concentrations From the Iron Geochemistry of the Bay of Islands Ophiolite. Geochemistry, Geophysics, Geosystems, 23 (7). Art. No. e2021GC010196. ISSN 1525-2027. doi:10.1029/2021gc010196.

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The deep ocean is generally considered to have changed from anoxic in the Precambrian to oxygenated by the Late Paleozoic (∼420–400 Ma) due to changes in atmospheric oxygen concentrations. When the transition occurred, that is, in the Early Paleozoic or not until the Late Paleozoic, is less well constrained. To address this, we measured Fe³⁺/ΣFe of volcanic rocks, sheeted dykes, gabbros, and ultramafic rocks from the Early Paleozoic (∼485 Ma) Bay of Islands (BOI) ophiolite as a proxy for hydrothermal alteration in the presence or absence of O₂ derived from deep marine fluids. Combining this data with previously published data from the BOI indicates that volcanic rocks are oxidized relative to intrusive crustal rocks (0.35 ± 0.02 vs. 0.19 ± 0.01, 1 standard error), which we interpret to indicate that the volcanic section was altered by marine-derived fluids that contained some dissolved O₂. We compare our results directly to the Macquarie Island and Troodos ophiolites, drilled oceanic crust, previously compiled data for ophiolitic volcanic rocks, and newly compiled data for ophiolitic intrusive rocks. These comparisons show that the BOI volcanic (but not intrusive) rocks are oxidized relative to Precambrian equivalents, but are less oxidized relative to Late Paleozoic to modern equivalents. We interpret these results to indicate that the Early Paleozoic ocean contained dissolved O₂, but at concentrations ∼2.4× lower than for the Late Paleozoic to today.

Item Type:Article
Related URLs:
URLURL TypeDescription Information S1 Set S1 Set S2 Set S3 produced and compileddatafor this paper associated with Stolper and Keller (2018)
Stolper, Daniel A.0000-0003-3299-3177
Pu, Xiaofei0000-0003-2120-7054
Lloyd, Max K.0000-0001-9367-2698
Christensen, Nikolas I.0000-0003-2956-040X
Bucholz, Claire E.0000-0001-5332-8278
Lange, Rebecca A.0000-0003-0309-6178
Additional Information:© 2022 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. Issue Online: 05 July 2022; Version of Record online: 05 July 2022; Accepted manuscript online: 02 June 2022; Manuscript accepted: 17 May 2022; Manuscript revised: 24 February 2022; Manuscript received: 04 October 2021. DAS acknowledges support from an Esper Larsen Jr. Research Grant. MKL acknowledges support from the Agouron Institute Geobiology Postdoctoral Fellowship. XP and RAL acknowledge support from University of Michigan discretionary research funds. DAS thanks N Swanson-Hysell for helpful discussions on the paleogeography of Early Paleozoic landmasses. Data Availability Statement: The newly produced and compiled data for this paper are contained in the text, figures and Supporting Information and are also archived externally at Data associated with Stolper and Keller (2018) are available from
Funding AgencyGrant Number
Esper Larsen Jr. FundUNSPECIFIED
Agouron InstituteUNSPECIFIED
University of MichiganUNSPECIFIED
Subject Keywords:oxygen; ophiolites; iron redox; Earth history; hydrothermal
Issue or Number:7
Record Number:CaltechAUTHORS:20220606-735977000
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Official Citation:Stolper, D. A., Pu, X., Lloyd, M. K., Christensen, N. I., Bucholz, C. E., & Lange, R. A. (2022). Constraints on Early Paleozoic deep-ocean oxygen concentrations from the iron geochemistry of the Bay of Islands ophiolite. Geochemistry, Geophysics, Geosystems, 23, e2021GC010196.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115024
Deposited By: George Porter
Deposited On:07 Jun 2022 19:21
Last Modified:15 Jul 2022 22:58

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