Whitehorse Trough records Late Triassic–Cretaceous accretionary orogenesis in the Northern Canadian Cordillera via detrital mineral thermochronometry

Author:

Kellett Dawn A.1ORCID,Coutand I.2,Zagorevski A.3,Grujic D.2ORCID,Dewing K.4ORCID,Beranek L.5

Affiliation:

1. Geological Survey of Canada—Atlantic, Natural Resources Canada, 1 Challenger Dr., Dartmouth, NS B2Y 4A2, Canada

2. Department of Earth and Environmental Sciences, Dalhousie University, Halifax, NS B3H 4R2, Canada

3. Geological Survey of Canada—Central, Natural Resources Canada, 601 Booth St., Ottawa, ON K1A 0E9, Canada

4. Geological Survey of Canada—Calgary, Natural Resources Canada, 33033 33 St NW, Calgary, AB T2L 2A7, Canada

5. Department of Earth Sciences, Memorial University of Newfoundland, 9 Arctic Ave, St. John's, NL A1B 3X5, Canada

Abstract

The Whitehorse Trough formed during early Mesozoic accretion of the Intermontane terranes to northwestern North America. Here we investigate its thermal history using detrital mineral thermochronology, including 171 single-crystal (U–Th)/He zircon (ZHe) ages from 35 samples, 158 single-crystal (U–Th)/He apatite (AHe) ages from 33 samples, and apatite fission track (AFT) ages from 12 samples. ZHe single crystal ages range from 222 to 42 Ma and define Triassic–Early Jurassic, Late Jurassic, and Cretaceous–Paleogene age groups. AFT central ages range from 95 to 30 Ma with a dominant age peak at ∼50 Ma, and AHe single crystal ages range from 228 to 13 Ma with a dominant age peak between 50 and 40 Ma. Forward and inverse models of thermochronological data are compatible with two regional burial/heating stages that variably reset He in zircon. Maximum temperatures of the Whitehorse Trough strata locally exceeded 150 °C during Early Jurassic burial and shortening into a fold and thrust belt. Following Middle to Late Jurassic exhumation-related cooling and development of a prominent unconformity, Whitehorse Trough strata were buried again. Temperatures locally exceeded 150 °C during the Cretaceous, suggesting maximum burial of between ∼4 and 7.5 km. Heating and cooling rates during the Early–Middle Jurassic were ∼10 °C/myr, coinciding with deposition, fold and thrust belt development, and regional crustal thickening during the final stages of Intermontane terrane accretion. Maximum heating rates during the Cretaceous were ∼4–7 °C/myr and likely correspond to regional crustal thickening of the northern Cordillera hinterland and establishment of an outboard, Andean-type continental arc system.

Funder

Natural Resources Canada

Publisher

Canadian Science Publishing

Subject

General Earth and Planetary Sciences

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