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TitleA reappraisal of the Nonacho Basin (Northwest Territories, Canada): record of post-orogenic collapse and marine flooding in the Palaeoproterozoic of the Rae Craton
AuthorIelpi, A; Martel, E; Fischer, B; Pehrsson, S J; Tullio, M; Neil, B J C
SourcePrecambrian Research vol. 358, 106140, 2021 p. 1-22,
Alt SeriesNatural Resources Canada, Contribution Series 20210003
PublisherElsevier B.V.
Mediapaper; on-line; digital
File formatpdf; html
ProvinceNorthwest Territories
Lat/Long WENS-110.6667 -108.5000 62.3333 60.8333
Subjectssedimentology; Science and Technology; stratigraphy; basin analysis; craton; Nonacho Basin; Laurentia; Precambrian
Illustrationslocation maps; stratigraphic sections; photographs; tables; diagrams
ProgramGEM2: Geo-mapping for Energy and Minerals GEM Synthesis
Released2021 03 19
AbstractThe synoptic analysis of coeval orogens and sedimentary basins is crucial to our understanding of Earth's crustal and surface processes. The Nonacho Group (Northwest Territories, Canada) is a major and yet enigmatic clastic sedimentary unit part of a basin system preserved over >2300 km along its original continental-sloping direction. This basin system records crustal sagging, relaxation, and flexure at ~2.3-1.9 Ga in the Rae Craton, one of the main building blocks of ancestral North America. Correlations between the Nonacho Group and coeval supracrustal assemblages in the Rae Craton has posed challenges. The group has been hitherto related to continental deposition at ~1.9 Ga, in a regime of sinistral strike-slip linked to the collision of the Rae and adjoining Slave cratons. We reappraise the Nonacho Group by means of facies analysis, stratigraphic logging, and palaeocurrent-data collection at key sites. Record of marine deposition is inferred based on the cumulative thickness of shoreface strata, an inference corroborated by sedimentological indicators such as wave- and bimodal-ripple, hummocky-cross, and flaser stratification. The alluvial to marine stratigraphy of the lower and middle parts of the Nonacho Group records basin inception and expansion in a regime of crustal relaxation. Topographic rejuvenation and deposition of younger alluvial to marine strata floored by an unconformity (upper Nonacho Group) followed in a regime of crustal flexure and renewed extension. These stratigraphic trends are tentatively related to broadly contemporaneous tectono-depositional events in the Rae Craton, including crustal thickening and ensuing extensional collapse of the bounding Thelon-Taltson and Snowbird orogens. By these means, we provide new testable hypotheses of a pan-continental tectono-sedimentary system developed during the Palaeoproterozoic amalgamation of the Canadian Shield.
Summary(Plain Language Summary, not published)
This paper presents a new field based interpretation of the depositional setting of the 1.9 billion year old Nonacho basin, Northwest Territories. Measured sections, facies analysis and spot observations are integrated to demonstrate an alluvial to nearshore or inner shelf marine setting for deposition of its sandstone-mudstone -conglomerate packages. New testable hypotheses for sedimentary-tectonic drivers at this period of Canadian Shield evolution are presented and discussed.

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