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TitleCenozoic exhumation history of the eastern margin of the northern Canadian Cordillera
AuthorMcKay, R; Enkelmann, E; Hadlari, TORCID logo; Matthews, W; Mouthereau, F
SourceTectonics vol. 40, issue 4, e2020TC006582, 2021 p. 1-18, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20210041
Mediapaper; on-line; digital
File formatpdf; html
ProvinceYukon; British Columbia; Northwest Territories
NTS106M/09; 106M/10; 106M/11; 106M/12; 106M/13; 106M/14; 106M/15; 106M/16; 107B/03; 107B/04; 107B/05; 107B/06; 107B/11; 107B/12; 116P/09; 116P/10; 116P/11; 116P/12; 116P/13; 116P/14; 116P/15; 116P/16; 117A/01; 117A/02; 117A/07; 117A/08; 117A/09; 117A/10
AreaRichardson Mountains
Lat/Long WENS-138.0000 -134.0000 68.7500 67.5000
Subjectstectonics; geochronology; Science and Technology; Nature and Environment; Neogene; Paleogene; tectonic history; deformation; thermal history; burial history; bedrock geology; lithology; sedimentary rocks; clastics; fission-track dates; zircon dates; apatite; modelling; structural trends; Canadian Cordillera; Phanerozoic; Cenozoic
Illustrationslocation maps; stratigraphic columns; plots; diagrams; charts
ProgramGEM2: Geo-mapping for Energy and Minerals Western Arctic-Beaufort-Northern Yukon
Released2021 02 18
AbstractNew low-temperature thermochronology data from clastic sedimentary rocks in the northern Richardson Mountains, Canada, indicate significant exhumational cooling during late Eocene-early Oligocene time. Apatite (U-Th-Sm)/He (AHe) data were collected from 19 Proterozoic-Paleocene rocks across a 115 km transect. Eighty-eight single-grain AHe dates range from 16-300 Ma and are generally younger than stratigraphic ages, indicative of thermal resetting by burial. Additionally, zircon (U-Th)/He (ZHe) datesfrom two Proterozoic-Cambrian rocks range from 49-123 Ma and suggest burial to >160°C. In contrast, ZHe dates from Jurassic sandstones are older than the stratigraphic age, which limits maximum burial to <160°C.Thermal history modeling reveals three phases of cooling, during the Paleocene-early Eocene (>65-50 Ma), late Eocene-early Oligocene (40-30 Ma), and late Oligocene-early Miocene (30-15 Ma). Most samples were sensitive to cooling during the first and second phases, whereas the third phase is less well constrained. In general, most rocks were below the sensitivity of AHe analysis since the early-middle Miocene. The results suggest a previously unrecognized phase of inferred deformation in the northern Richardson Mountains between 40-30 Ma. Our findings contribute to previous work that recognizes Late Cenozoic deformation along the eastern margin of the Northern Cordillera. We further investigated the potential mechanisms of this widespread deformation and suggest exhumation may relate to kinematic changes of the North American plate relative to structural trends along the margin of the Northern Cordillera.
Summary(Plain Language Summary, not published)
Rock samples from the Richardson Mountains were analysed for U-Th-He isotopes in order to develop a cooling model. The cooling model reconstructs when the Richardson Mountains were uplifted from below sea level to form the present mountains, which occurred mainly in the Tertiary approximately 40-30 million years before present.

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