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TitleShale and pyrite Re-Os ages from the Hornby Bay and Amundsen basins provide new chronological markers for Mesoproterozoic stratigraphic successions of northern Canada
AuthorRainbird, R HORCID logo; Rooney, A D; Creaser, R A; Skulski, T
SourceEarth and Planetary Science Letters vol. 548, 116492, 2020 p. 1-10,
Alt SeriesNatural Resources Canada, Contribution Series 20200341
PublisherElsevier B.V.
Mediapaper; on-line; digital
File formatpdf; html
NTS86J; 86K; 86L; 86M; 86N; 86O
Lat/Long WENS-119.6500 -114.7247 68.1386 66.1247
SubjectsScience and Technology; stratigraphy; osmium; Amundsen Basin; Hornby Bay Basin; Elu Basin; Dismal Lakes Group; Shaler Supergroup; Proterozoic
Illustrationslocation maps; stratigraphic columns; tables
ProgramGEM2: Geo-mapping for Energy and Minerals Mackenzie Corridor
Released2020 08 05
AbstractHere we present Re-Os geochronological data from two carbonaceous shale units from the Hornby Bay and Amundsen basins that provide important chronological markers for Mesoproterozoic stratigraphic successions within northern Canada. Shale from the basal Escape Rapids Formation yields a robust depositional age of 1067.3 ± 13.5 Ma for the lowermost Shaler Supergroup of Amundsen basin with a remarkably unradiogenic initial 187Os/188Os value (0.15), implying that it derived from weathering of juvenile source material, such as basalt. Sedimentological features, indicative of large basin conditions, suggest deposition within an extensive epeiric sea that was intermittently mixed with waters from an exterior ocean. This age, and the 720 Ma age of the uppermost Shaler Supergroup, constrain deposition of the ~4 km-thick succession to a period of approximately 350 myr, recording sedimentation through a complete supercontinent cycle - amalgamation through to break-up of Rodinia. Further, it indicates that the Amundsen basin formed at the same time as the Borden, and Fury and Hecla basins on northern Baffin Island, and the Thule basin in northwestern Greenland, and that these basins were perhaps connected as part of a much larger basin situated in the interior of Rodinia. Diagenetic pyrite from sandstone dykelets in carbonaceous shales of the Fort Confidence Formation yielded a Re-Os model age of 1438 ± 8 Ma, providing a minimum age for deposition of the lower Dismal Lakes Group of the Hornby Bay basin. This age strengthens proposed regional correlation of the Hornby Bay basin with the large intracontinental Athabasca and Thelon basins, located on the Rae craton to the southeast, and is evidence for a Laurentia-wide marine flooding episode ca. 1500 Ma. Both new ages place important constraints on newly discovered eukaryotic microfossils from the Shaler Supergroup and Dismal Lakes Group and calibration points for critical chemostratigraphic data.
Summary(Plain Language Summary, not published)
Presents two new ages for Precambrian sedimentary rocks (black shales) from the Coppermine area of northern Canada. The ages were determined at two different labs that specialize in Re-Os geochronology. The ages provide important new calibration points for stratigraphic sections that previously were undated. The results allow us to make suggestions about how these strata correlate with other rocks of this age in Canada and globally. They also provide us with a more precise age for newly discovered microfossils, including Earth's oldest fossil fungi.

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