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dc.contributor.authorTosca, Nicholas J.
dc.contributor.authorJohnston, David T
dc.contributor.authorMushegian, Alexandra Arcadievna
dc.contributor.authorRothman, Daniel H.
dc.contributor.authorSummons, Roger E.
dc.contributor.authorKnoll, Andrew Herbert
dc.date.accessioned2010-04-13T14:35:16Z
dc.date.issued2010
dc.identifier.citationTosca, Nicholas J., David T. Johnston, Alexandra Arcadievna Mushegian, Daniel H. Rothman, Roger E. Summons, and Andrew Herbert Knoll. 2010. Clay mineralogy, organic carbon burial, and redox evolution in Proterozoic oceans. Geochimica et Cosmochimica Acta 74(5): 1579-1592.en_US
dc.identifier.issn0016-7037en_US
dc.identifier.urihttp://nrs.harvard.edu/urn-3:HUL.InstRepos:3934551
dc.description.abstractClay minerals formed through chemical weathering have long been implicated in the burial of organic matter (OM), but because diagenesis and metamorphism commonly obscure the signature of weathering-derived clays in Precambrian rocks, clay mineralogy and its role in OM burial through much of geologic time remains incompletely understood. Here we have analyzed the mineralogy, geochemistry and total organic carbon (TOC) of organic rich shales deposited in late Archean to early Cambrian sedimentary basins. Across all samples we have quantified the contribution of 1M and 1Md illite polytypes, clay minerals formed by diagenetic transformation of smectite and/or kaolinite-rich weathering products. This mineralogical signal, together with corrected paleo-weathering indices, indicates that late Archean and Mesoproterozoic samples were moderately to intensely weathered. However, in late Neoproterozoic basins, 2M1 illite/mica dominates clay mineralogy and paleo-weathering indices sharply decrease, consistent with an influx of chemically immature and relatively unweathered sediment. A late Neoproterozoic switch to micaceous clays is inconsistent with hypotheses for oxygen history that require an increased flux of weathering-derived clays (i.e., smectite or kaolinite) across the Precambrian–Cambrian boundary. Compared to previous studies, our XRD data display the same variation in Schultz Ratio across the late Neoproterozoic, but we show the cause to be micaceous clay and not pedogenic clay; paleo-weathering signals cannot be recovered from bulk mineralogy without this distinction. We find little evidence to support a link between these mineralogical variations and organic carbon in our samples and conclude that modal clay mineralogy cannot by itself explain an Ediacaran increase in atmospheric oxygen driven by enhanced OM burial.en_US
dc.description.sponsorshipOrganismic and Evolutionary Biologyen_US
dc.language.isoen_USen_US
dc.publisherElsevieren_US
dc.relation.isversionofdoi:10.1016/j.gca.2009.12.001en_US
dash.licenseOAP
dc.subjectorganic carbonen_US
dc.subjectProterozoicen_US
dc.subjectoxygenen_US
dc.subjectclayen_US
dc.subjectmineralogyen_US
dc.subjectsedimentary geochemistryen_US
dc.titleClay Mineralogy, Organic Carbon Burial, and Redox Evolution in Proterozoic Oceansen_US
dc.typeJournal Articleen_US
dc.description.versionAccepted Manuscripten_US
dc.relation.journalGeochimica et Cosmochimica Actaen_US
dash.depositing.authorKnoll, Andrew Herbert
dc.date.available2010-04-13T14:35:16Z
dc.identifier.doi10.1016/j.gca.2009.12.001*
dash.contributor.affiliatedMushegian, Alexandra Arcadievna
dash.contributor.affiliatedJohnston, David
dash.contributor.affiliatedKnoll, Andrew


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