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TitleOn the Statherian-Callymian paleogeography of northwestern Laurentia
AuthorRainbird, R HORCID logo; Davis, W JORCID logo
SourceJournal of the Electrochemical Society vol. 179, 2022 p. 1-20,
Alt SeriesNatural Resources Canada, Contribution Series 20210475
PublisherThe Geological Society of London
Mediapaper; on-line; digital
File formatpdf
Subjectssurficial geology/geomorphology; paleogeography
Illustrationslocation maps
ProgramGEM-GeoNorth: Geo-mapping for Energy and Minerals GEM Program Coordination
Released2022 05 06
AbstractThe ~1.75 to 1.27 Ga Hornby Bay intracontinental basin, exposed in northwestern Canada, northeast of Great Bear Lake, includes the Big Bear, Mountain Lake and Dismal Lakes groups. The Big Bear group comprises mainly immature clastic rocks deposited by high-energy rivers in restricted fault-bounded basins formed during the late-stage assembly of supercontinent Nuna. Detrital zircon analysis of the Big Bear group suggests provenance from a combination of local sources including recycling of sedimentary rocks, which were originally derived from sources further east, such as the Thelon orogen. The overlying Mountain Lake group was deposited by westerly flowing rivers over a much broader region, with less evidence for syndepositional faulting, suggestingthermal subsidence. It displays provenance via recycling of strata from the proximal Coronation Supergroup and the more distal and correlative Goulburn Supergroup of
Kilohigok Basin. Following tectonic uplift and erosion, basal clastic rocks of the Dismal Lakes group were deposited in fluvial and then shallow marine to paralic environments. Detrital zircon from these strata display prominent late Archean peaks demonstrating provenance from adjacent rocks of the Slave craton and recycling of the Mountain Lake group. Detrital zircon geochronology of sandstones from the Hornby Bay basin supports stratigraphic correlation with the Wernecke Supergroup in the Wernecke Mountains and the Muskwa assemblage, located further southward along the ancient western margin of Laurentia. Our data, along with Nd and C isotopes from corresponding shale and carbonate units, provide robust evidence for a paleogeographic model whereby these successions represent the terrestrial and marine components of a west-facing, passivemargin clastic wedge, considered the westward extension of an Amazon-scale, braided fluvial system that originated in the foreland of the Trans-Hudson orogen, to the east. Elements of this system have been identified from inliers in northeastern Australia, which was attached to northwestern Laurentia prior to the break-up of supercontinent Nuna.
Summary(Plain Language Summary, not published)
The Hornby Bay sedimentary basin, located on Canada's northwestern arctic coastal region, represents a missing link in a continent-scale sediment-delivery system that originated from an extensive mountain range that traversed ancestral North America nearly 2 billion years ago. Zircon sand grains from samples of sandstone collected from this basin yield U-Pb ages that tell us that rivers which deposited these sand grains eroded rocks that lay more than one thousand kilometres to the east of the Hornby Bay basin. This basin represents a small but integral piece of a huge geologic jigsaw puzzle that depicts the early evolution of ancestral North America. Data for this study was collected over many years and informed by previous studies of the Athabasca and Thelon basins by the GSC in the 1960s, 1990s and 2000s. All of these basins are important repositories for Uranium, so understanding how they formed is an important aspect of assessing their mineral endowment.

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