On the Statherian-Calymmian paleogeography of northwestern Laurentia
Posted on 23.05.2022 - 15:29
Abstract: The ~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, suggesting thermal 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, passive-margin 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.
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Rainbird, R. H.; Davis, W. J. (2022): On the Statherian-Calymmian paleogeography of northwestern Laurentia. Geological Society of London. Collection. https://doi.org/10.6084/m9.figshare.c.5980940.v2
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R. H. Rainbird
W. J. Davis
suggesting thermal subsidencepaleogeographic model wherebymuch broader regionmargin clastic wedgefollowing tectonic upliftdismal lakes groupsdismal lakes groupbounded basins formedancient western marginproximal coronation supergroupcorrelative goulburn supergroupwesterly flowing riversprovide robust evidencebasal clastic rocksdetrital zircon geochronologydetrital zircon analysismountain lake groupgreat bear lakenorthwestern laurentia priornorthwestern laurentia abstractbraided fluvial systemdetrital zirconmountain lakewernecke supergroupnorthwestern canadaless evidenceenergy riversbig bearsedimentary rocksadjacent rockswestward extensionwernecke mountainsthelon orogensyndepositional faultingsupercontinent nunasuccessions representstage assemblyslave cratonshallow marinerestricted faultparalic environmentsoriginally derivednortheastern australiamuskwa assemblagemarine componentskilohigok basinhudson orogencorresponding shalecarbonate unitscalymmian paleogeographyc isotopes