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TitleTerrestrial sources as the primary delivery mechanism of mercury to the oceans across the Toarcian Oceanic Anoxic Event (Early Jurassic)
AuthorThem, T R, II; Jagoe, C H; Caruthers, A H; Gill, B C; Grasby, S EORCID logo; Gröcke, D R; Yin, R; Owens, J D
SourceEarth and Planetary Science Letters vol. 507, 2018 p. 62-72, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20180336
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf; html
AreaBighorn Creek; Dotternhausen; Canada; Canada; Germany
Lat/Long WENS-180.0000 180.0000 90.0000 -90.0000
Subjectstectonics; geochemistry; stratigraphy; paleontology; Lower Jurassic; Toarcian; paleogeography; source areas; sea water geochemistry; mercury geochemistry; geochemical anomalies; tectonic setting; volcanism; biogeochemistry; paleoenvironment; depositional environment; marine environments; nearshore environment; isotopic studies; biostratigraphy; core samples; Toarcian Oceanic Anoxic Event; Panthalassa; Dotternhausen Quarry; Karoo-Ferrar Large Igneous Province; Tethys Ocean; Phanerozoic; Mesozoic; Jurassic
Illustrationsgeoscientific sketch maps; bar graphs; flow diagrams; profiles; lithologic sections; schematic cross-sections
ProgramGEM2: Geo-mapping for Energy and Minerals Western Arctic, High Arctic LIP
Released2018 12 06
AbstractThis study evaluates the utility of sedimentary mercury (Hg) contents as a proxy for fingerprinting ancient massive volcanism, which is often associated with biogeochemical perturbations. Herein we present new Hg geochemical data from anoxic marine basins across the Toarcian Oceanic Anoxic Event (T-OAE; ~183 Ma) as a test of the complex Hg cycle. The T-OAE was likely initiated by the main eruptive phase of the Karoo-Ferrar large igneous province, which caused a subsequent cascade of environmental perturbations and resulting mass extinction. At present the leading interpretation of sedimentary Hg anomalies has been volcanogenic outgassing as the primary source. Our study and compilation results suggest, however, that Hg/TOC anomalies were restricted to shallow-water, and/or proximal environments, while deep-water, more distal depositional settings document no significant Hg-related anomalies. Furthermore, asynchronous stratigraphic deviations in Hg enrichments favor terrestrially sourced materials and local redox variability, rather than direct volcanogenic emissions, as a primary control mechanism. Additionally, Hg isotope signatures from our only study site documenting an Hg anomaly are also consistent with a terrestrial Hg origin during the T-OAE. Therefore, our results suggest that Hg anomalies in the geological record need to be re-evaluated as a 'smoking gun' proxy that only infers volcanogenic inputs.
Summary(Plain Language Summary, not published)
This study examines tools developed by GSC scientists to test for signatures of massive volcanic eruptions that have occurred through geologic time to be able to assess the impact this had on Earth climate and environment. Results help to further refine methods and use of these tools.

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