The Consummate Geoscientist: A Celebration of the Career of Maarten de Wit
CONTAINS OPEN ACCESS

Papers in this special publication mirror Maarten's career as a leading expert on Gondwana evolution and Archean tectonics. Maarten also contributed to our understanding of Archean life, African erosional history and South African shale-gas development, and was a vigorous supporter of the advancement of South African students from varied backgrounds.
Extent and significance of the Racklan–Forward Orogen in Canada: far-field interior reactivation during Nuna assembly Available to Purchase
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Published:October 04, 2023
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CiteCitation
Sally Pehrsson, Bruce Eglington, Robert Rainbird, Daniele Regis, Paul Ramaekers, Charlie Jefferson, 2023. "Extent and significance of the Racklan–Forward Orogen in Canada: far-field interior reactivation during Nuna assembly", The Consummate Geoscientist: A Celebration of the Career of Maarten de Wit, A. J. Hynes, J. B. Murphy
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Abstract
Mesoproterozoic orogenesis is well established on the western and southern flanks of Laurentia in the well-known Racklan–Forward and Mazatzal orogens, but its significance within the previously assembled interior of the supercontinent Nuna has not been established. We examine regional isotopic and structural evidence for Mesoproterozoic deformation in the c. 1.7–1.63 Ga Hornby Bay, Elu, Thelon and Athabasca intracontinental basins, and present evidence for Mesoproterozoic reactivation of Paleoproterozoic structures in the Wopmay and Trans-Hudson orogens. The Racklan–Forward Orogeny in the interior of north Laurentia comprises north–south-trending, high-angle, east-vergent folds and thrusts that occur across a region 1660 km wide and over 1000 km long, stretching from the Yukon to near Hudson Bay and from Banks Island to below the Western Canada Sedimentary Basin. The structures progress from ductile amphibolite and greenschist facies in the Racklan type area to sub-greenschist facies and ultimately brittle or brittle-ductile in the far foreland, showing a predominant thick-skinned style typical of many intracontinental orogens. We present compiled low-temperature thermochronological data, including ages of spatially associated uraninite mineralization, to characterize the scope of reactivation of basement structures in the Archean Rae craton in Nuna's interior. We compare the nature of widespread far-field reactivation in the Racklan–Forward Orogen with other orogens of Nuna's assembly to show it is unusual for Nuna's peripheral margin. We suggest that c. 1.6 Ga continent–continent collision of North Australia with NW Laurentia propagated stresses far into the interior as a result of combined favourable pre-existing structural grain and a weak subcontinental lithospheric mantle in the Rae craton due to repeated episodes of refertilization across 500 Ma of accretion and intrusion. Cratons that experience the complex, two-sided collision and protracted upper plate setting during supercontinent assembly noted herein may be particularly susceptible to extensive foreland propagation of peripheral orogens.
- basement
- basins
- Canada
- Columbia Supercontinent
- deformation
- facies
- fold and thrust belts
- greenschist facies
- intracontinental belts
- Laurentia
- Mazatzal Orogeny
- Mesoproterozoic
- metamorphic rocks
- orogeny
- Paleoproterozoic
- plate boundaries
- plate collision
- plate tectonics
- Precambrian
- Proterozoic
- reactivation
- sedimentary basins
- structural analysis
- supercontinents
- tectonics
- thermochronology
- thick-skinned tectonics
- topography
- upper Precambrian
- Racklan-Forward Orogeny