| Title | Chemostratigraphy of the Shaler Supergroup, Victoria Island, NW Canada: a record of ocean composition prior to the Cryogenian glaciations |
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| Author | Thomson, D; Rainbird, R H ; Planavsky, N; Lyons, T W; Bekker, A |
| Source | Precambrian Research vol. 263, 2015 p. 232-245, https://doi.org/10.1016/j.precamres.2015.02.007 |
| Image |  |
| Year | 2015 |
| Alt Series | Earth Sciences Sector, Contribution Series 20140479 |
| Publisher | Elsevier BV |
| Document | serial |
| Lang. | English |
| Media | on-line; digital |
| File format | pdf |
| Province | Northwest Territories |
| NTS | 87G; 87H; 88A |
| Area | Victoria Island; Minto Inlet; Wynniatt Bay |
| Lat/Long WENS | -119.0000 -110.0000 73.0000 70.5000 |
| Subjects | stratigraphy; geochemistry; geochronology; stratigraphic analyses; stratigraphic correlations; carbon isotopes; iron geochemistry; molybdenum geochemistry; vanadium geochemistry; uranium geochemistry;
uranium lead dates; glaciation; sedimentary environment; sulphur isotope ratios; geochemical interpretations; isotopic studies; diagenesis; sea water geochemistry; methane; basin analyses; basin evolution; biostratigraphy; lithostratigraphy;
biogeochemistry; Minto Inlier; Shaler Supergroup; Bitter Springs stage; Amundsen Basin; Cryogenian glaciation; Proterozoic |
| Illustrations | geological sketch maps; photographs; isotopic analyses |
| Program | GEM: Geo-mapping for Energy and Minerals PGE/Base Metals - Victoria Island (NWT and Nunavut) |
| Released | 2015 07 01 |
| Abstract | A new d13Ccarb curve combined with d13Corg values is presented for the upper Shaler Supergroup (~900 to ~720 Ma), Amundsen Basin, northwestern Canada. The dataset fills gaps in the existing
stratigraphic record and makes correlations with adjacent basins more robust. There is a pronounced negative d13C excursion in the Wynniatt Formation that can be correlated with a putative worldwide negative carbon isotope excursion, namely the
Bitter Springs stage. However, in the Amundsen Basin, the d13Ccarb excursion drops to anomalously negative values (-14 per mil), which we attribute to local overprints wherein isotopically light carbon in pore waters, released by oxidation of methane
and organic matter during sulphate and iron reduction, was incorporated into authigenic carbonate cement. We document basin euxinia and anoxia during the same time interval using a multi-proxy approach; specifically, Fe-speciation and redox-sensitive
trace metal data. Patterns of pronounced enrichment in Mo, V, and U concentrations in euxinic black shales suggest that the Bitter Springs stage was a transitional period in Earth's redox evolution, from the more reduced global oceans during the
mid-Proterozoic to the more oxygenated oceans during the Phanerozoic. |
| Summary | (Plain Language Summary, not published)
C isotope values for the upper Shaler Supergroup, Amundsen Basin, northwestern Canada fill gaps in the existing stratigraphic record and makes
correlations with adjacent basins more robust. Data provides support for correlation with the global ~800 Ma Bitter Springs stage. Markedly negative C-isotope values are attributed to local overprints caused by oxidation of methane and organic matter
during sulphate and iron reduction. We document basin euxinia and anoxia from Fe-speciation, pyrite sulphur isotope composition, and redox-sensitive trace metal data. Patterns of pronounced Mo, V, and U enrichment in euxinic black shales suggest
that the Bitter Springs stage was a transitional period in Earth¿s redox evolution, from the more reduced global oceans during the mid-Proterozoic to the more oxygenated oceans during the Phanerozoic. |
| GEOSCAN ID | 295946 |
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