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dc.contributor.authorStueeken, Eva E.
dc.contributor.authorJones, Simon
dc.contributor.authorRaub, Timothy D.
dc.contributor.authorPrave, Tony
dc.contributor.authorRose, Catherine V.
dc.contributor.authorLinnekogel, Stella
dc.contributor.authorCloutier, Jonathan
dc.identifier.citationStueeken , E E , Jones , S , Raub , T D , Prave , T , Rose , C V , Linnekogel , S & Cloutier , J 2020 , ' Geochemical fingerprints of seawater in the Late Mesoproterozoic Midcontinent Rift, North America : life at the marine-land divide ' , Chemical Geology , vol. 553 , 119812 .
dc.identifier.otherPURE: 269735193
dc.identifier.otherPURE UUID: 89c3cb05-625b-4f13-add9-3e3faec10860
dc.identifier.otherScopus: 85089107109
dc.identifier.otherORCID: /0000-0002-4614-3774/work/79226710
dc.identifier.otherORCID: /0000-0002-9432-9880/work/79226895
dc.identifier.otherORCID: /0000-0001-6861-2490/work/79226930
dc.identifier.otherORCID: /0000-0001-8149-0977/work/79226942
dc.identifier.otherWOS: 000575085100009
dc.identifier.otherORCID: /0000-0003-4513-2245/work/84315180
dc.description.abstractThe 1.1 Ga Midcontinent Rift (MCR) is a thick volcanic-sedimentary succession that forms a curvilinear belt through central North America and crops out along its northern apex around Lake Superior. Sedimentary units of the MCR have been long interpreted as fluvial-lacustrine and invited a number of studies on the early evolution of life in non-marine habitats. One of the key units is the siliciclastic Nonesuch Formation, thought to record deposition in a large lake. However, recent sedimentological observations indicate the presence of marine incursions. To further test this interpretation, we analysed trace element abundances in a broad suite of samples from multiple drill cores through the Nonesuch Formation. We aimed to differentiate geochemical influences of sediment provenance from post-depositional hydrothermal overprint and thereby identify authigenic enrichments in fluid-mobile elements that are indicators of primary environmental conditions. Our results reveal discrete enrichments in Mo and U in organic- and sulphide-rich horizons, which are most parsimoniously interpreted as marine signatures. This conclusion is supported by Sr/Ba ratios, which suggest mixing between freshwater and saltwater, and by rare cm-thick gypsum in the upper Copper Harbor Formation immediately below the Nonesuch rocks. The gypsum displays δ34S values of +25.9 ± 0.6‰, consistent with input of marine sulphate at least during parts of the basin's history. Collectively, our geochemical data support the sedimentological interpretation that this portion of the MCR archives a marine-influenced estuarine system. Although this conclusion rules out that microbial life documented from the MCR was living in exclusively freshwater habitats, the Nonesuch Fm and associated rocks still hold important clues about organisms that were capable of withstanding salinity gradients and bridging the gap between the marine and non-marine environments of the mid-Proterozoic.
dc.relation.ispartofChemical Geologyen
dc.rightsCopyright © 2020 Elsevier B.V. All rights reserved. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at
dc.subjectGE Environmental Sciencesen
dc.titleGeochemical fingerprints of seawater in the Late Mesoproterozoic Midcontinent Rift, North America : life at the marine-land divideen
dc.typeJournal articleen
dc.contributor.institutionUniversity of St Andrews.School of Earth & Environmental Sciencesen
dc.contributor.institutionUniversity of St Andrews.St Andrews Centre for Exoplanet Scienceen
dc.contributor.institutionUniversity of St Andrews.Marine Alliance for Science & Technology Scotlanden
dc.contributor.institutionUniversity of St Andrews.Scottish Oceans Instituteen
dc.contributor.institutionUniversity of St Andrews.St Andrews Sustainability Instituteen
dc.contributor.institutionUniversity of St Andrews.St Andrews Isotope Geochemistryen
dc.description.statusPeer revieweden

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