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TitleSeismic and gravity constraints on the crustal architecture of the Intermontane terranes, central Yukon
AuthorCalvert, A J; Hayward, N; Vayavur, R; Colpron, M
SourceCanadian Journal of Earth Sciences vol. 54, issue 7, 2017 p. 789-811, https://doi.org/10.1139/cjes-2016-0189
Year2017
Alt SeriesEarth Sciences Sector, Contribution Series 20160199
PublisherNRC Research Press
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceYukon
NTS115I; 115H; 105E; 105F; 105K; 105L
AreaWhitehorse trough
Lat/Long WENS-136.6667 -134.6667 62.5000 61.2500
Subjectsstructural geology; general geology; geophysics; seismic reflection surveys; seismic data; seismic velocities; Yukon - Tanana terrane; Snowcap assemblage; Quesnellia assemblage; Laberge Group; Lewes River Group; Tantalus Formation; Carmacks Group; Big Salmon fault
Illustrationsgeological sketch maps; location maps; stratigraphic charts; seismic reflection profiles; schematic diagrams
ProgramWestern Cordillera, Redefinition of crustal blocks, GEM2: Geo-mapping for Energy and Minerals
AbstractIn 2004, two seismic reflection lines were shot across the Mesozoic Whitehorse trough and adjacent terranes. Three-dimensional first-arrival tomographic inversion is used to constrain lithology to 800 - 1200mdepth, and surface structures are extrapolated into the middle crust using the coincident reflection data. In the Yukon - Tanana terrane, the metasedimentary Snowcap assemblage is characterized by velocities of 4.5 - 5.5 km/s, while in Quesnellia, velocities of 5.0 - 6.0 km/s occur at 500m depth, and probably represent igneous rocks of the Tatchun batholith. Across the Whitehorse trough, velocities >4.0 km/s correspond to clastic rocks of the Jurassic Laberge and Triassic Lewes River groups; velocities <4.0 km/s probably present the clastic Jurassic to Cretaceous Tantalus Formation. Several near-surface units with velocities of 2.0 - 3.0 km/s are identified; some correlate well with volcanic rocks of the Upper Cretaceous Carmacks Group, but others could be attributable to alluvial deposits or faulting. The Big Salmon fault is interpreted to dip southwest, implying that rocks of the Yukon - Tanana terrane extend beneath Quesnellia. Stikinia and Quesnellia underlie up to 5 - 8 km of Triassic to Early Cretaceous sedimentary strata, and appear to be a single allochthon within an 18 - 20 km deep synform above the Yukon - Tanana terrane, which we name the Northern Intermontane synform. In general, reflection geometries in the upper crust are complex, but are consistent with large-scale imbricate structures that have been dissected into numerous blocks by displacement along moderately to steeply dipping strike-slip faults, which may be part of a crustal-scale flower structure extending to the base of the crust.
Summary(Plain Language Summary, not published)
The Whitehorse Trough is a northwest-trending Mesozoic sedimentary basin, southeast of Carmacks, Yukon. It may contain up to 5-8 km of sedimentary rocks with hydrocarbon potential. The reprocessing of geophysical data has led to a new interpretation of the basin's geological context, structure and geometry. A model of the speed of sound in near-surface rocks provides new information on their type and thickness to depths of up to approximately 1 km. Interpretations of other geophysical data reveal new information on the make-up of the earth's crust in this region, including the location of faults separating large-scale blocks of rock, with different origins, within the crust.
GEOSCAN ID299287