The tectonic evolution of the Whitehorse trough in central Yukon is largely preserved by the Early to Middle Jurassic Laberge Group, an ~3000-m thick succession of synorogenic clastic strata that unconformably overlies arc and arc marginal rocks of the Lewes River Group. A two-year project was initiated to test a Sinemurian to Toarcian transgression of basal Laberge Group strata westward across the Whitehorse trough and examine the regional relationships between the timing of Jurassic exhumation, sedimentation, and terrane accretion in the northern Canadian Cordillera. Field studies in 2017 targeted basal Laberge Group strata at seven locations in central Yukon. At each field locality, basal Laberge Group strata are known or inferred to unconformably overlie the Povoas formation and multiple units of the Aksala formation. Pre-Early Jurassic unconformities may indicate variable basin topography due to the complex internal stratigraphy of the Lewes River Group, or that regional exhumation and erosion affected the Whitehorse trough prior to Laberge Group sedimentation.

Whitehorse trough is a northwestward-tapering belt of Upper Triassic to Lower Cretaceous volcanic and sedimentary rocks extending ~650 km from the British Columbia–Yukon border, north to the vicinity of Carmacks in south-central Yukon. It consists of three main stratigraphic units (i.e., the Lewes River Group, Laberge Group and Tantalus Formation) representing three sedimentary basins, partially overlapping in space and time. The Laberge Group (Lower-Middle Jurassic), informally subdivided into the Richthofen, Tanglefoot and Nordenskiold formations, was deposited in the Laberge basin, a collapsing fore-arc basin in which the arc was undergoing uplift and erosion. The Richthofen formation consists of conglomerate, massive sandstone, sandstone-mudstone couplets, volcaniclastic rocks and minor limestone interpreted as submarine fan systems. The Tanglefoot formation consists of coal-bearing sandstone, mudstone, conglomerate, volcaniclastic rocks and minor limestone interpreted as delta systems and shallow marine deposits. The Richthofen and Tanglefoot formations are the same age (i.e., Sinemurian to Bajocian), but the Richthofen formation is restricted to the southern half of the basin, whereas the Tanglefoot formation occurs in the northern half. The Nordenskiold formation consists of subaerially erupted, resedimented volcaniclastics deposited mainly during Pliensbachian time. The Richthofen formation is interpreted as a spent source rock and the Nordenskiold formation is not a source rock. The Tanglefoot formation is interpreted as a potential source rock and possibly an effective source rock. It contains petroleum fluid inclusions (mainly 23°- 32° and 40°- 44° API gravity) indicating a minimum trapping temperature of 110-115°C. The Tanglefoot formation is also a potential reservoir rock.

Whitehorse Trough is a frontier basin in south-central Yukon that is thought to contain gas and possibly oil. It formed in the early Triassic as an arc-marginal basin between the ancient North American margin to the east and the volcano-plutonic Stikine Terrane to the west. Three stratigraphic units, termed the Lewes River Group (Upper Triassic), the Laberge Group (Lower-Middle Jurassic) and the Tantalus Formation (Upper Jurassic-Lower Cretaceous), are recognized in the Whitehorse Trough. The Laberge Group is informally subdivided into four units, which, from the base upwards includes the Richthofen, Conglomerate, Nordenskiold and Tanglefoot formations. The Richthofen formation in the Laberge map area (NTS 105E) is characterized by thin- to mediumbedded turbidites, massive sandstone, matrix- and clast-supported conglomerate, scarce ammonites and belemnites, and abundant trace fossils, particularly Chondrites. No comprehensive stratigraphic section exists for the Richthofen formation, but it is estimated to be at least 500 m thick and appears to consist of a lower clast-supported conglomerate unit, a middle unit dominated by thin- to-medium bedded turbidites with minor amounts of massive sandstone and clast- and matrix-supported conglomerate, and an upper clast-supported conglomerate unit. The Richthofen formation unconformably overlies the Lewes River Group and was deposited by a southeast-prograding submarine fan (or fans) during the Early Jurassic. It is correlative with the Inklin Formation in northwestern British Columbia. Programmed pyrolysis using Rock-Eval 6 analysis of 63 samples from the Richthofen formation indicates that it is a poor to fair source rock and is gas-prone.

The Whitehorse Trough, a Mesozoic sedimentary basin in south-central Yukon that has potential for gas and oil, consists of the Lewes River Group (Triassic), the Laberge Group (Jurassic), and the Tantalus Formation (Jura-Cretaceous). The Laberge Group in the Carmacks (115I) and Laberge (105E) map areas is subdivided into four informal lithostratigraphic units: the Richthofen, Tanglefoot, Conglomerate and Nordenskiold formations. The Richthofen formation, distinguished by siltstone to very fine sandstone and mudstone couplets, is exposed in the southern part of the Laberge map area where it rests unconformably to conformably on the Lewes River Group and is unconformably and/or conformably overlain by the Tanglefoot formation. The Tanglefoot formation, distinguished by coalbearing, interbedded sandstone and mudstone, is exposed in the northern part of the Laberge map area and the southern part of the Carmacks map area where it rests unconformably on the Lewes River Group, and is overlain by the Tantalus Formation. The Conglomerate (conglomerate) and Nordenskiold (dacite tuff) formations occur as minor units within the Tanglefoot formation. The Richthofen-Tanglefoot formation unconformity and/or conformity is a potential petroleum play in the central Whitehorse Trough, whereas the Lewes River Group-Tanglefoot formation unconformity is a potential petroleum play in the northern Whitehorse Trough.

Mafic volcanic and clastic strata of the Middle Triassic Joe Mountain Formation, east of Lake Laberge, Yukon, represent a juvenile volcanic arc sequence. Mafic volcanic rocks of the Upper Triassic Lewes River Group were formed in the spatial and temporal continuity of Joe Mountain volcanism. Carbonate sedimentation took place in shallow oceanic subbasins adjacent to the arc from the Carnian to Rhaetian; these subbasins were separated by physiographic boundaries inherent to the arc, resulting in lateral stratigraphic variations. Polymictic conglomerate and turbiditic sequences of the Lower-Middle Jurassic Laberge Group unconformably overlie Triassic rocks. Two north-northwest strike-slip faults, the Laurier Creek and the Goddard, control the distribution of units. Joe Mountain Formation rocks are characterized by an east-west structural trend, whereas the Upper Triassic and Jurassic sequences are characterized by north-northwest trending tight folds and thrust faults. At least five post-accretion igneous suites intrude or overlie older stratigraphy, including the Late Cretaceous Open Creek volcanic complex.

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Stratigraphic and structural relationships within Stikinia, and overlap assemblages of the Whitehorse trough, are investigated in the Teslin Mountain area, southern Yukon. The Middle Triassic Joe Mountain Formation is dominated by a thick sequence of aphyric basalt produced by subaqueous volcanism. The Upper Triassic Lewes River Group displays complex lateral and vertical lithological and facies changes. It illustrates synvolcanic terrane exhumation, with erosion of the volcanic upland leading to deposition of thick volcaniclastic sequences, in parallel with ongoing clastic and carbonate sedimentation in marginal basins. Unravelling the Lewes River Group stratigraphy is critical in understanding the latest stages of Stikinia arc volcanism and the onset of Whitehorse trough marine sedimentation in the Early-Middle Jurassic. Further mapping and analytical work will focus at characterizing the Joe Mountain Formation and Lewes River Group, to determine how Stikinia evolved prior to final amalgamation of the Intermontane terranes with North America.

Paleozoic rocks of the Pelly Mountains, central Yukon, preserve greater than 150 m.y. of sedimentation, magmatism and base-metal mineralization. To identify secular trends in regional tectonics and metallogeny, a multi-year project on the stratigraphy of the Pelly Mountains in the Quiet Lake (105F) and Finlayson Lake (105G) map areas was initiated. Field studies during summer 2015 focused on two stratigraphic intervals: (1) mafic volcanic, volcaniclastic and clastic rock successions assigned to the Cambrian-Ordovician Cloutier and Groundhog formations (Kechika group); and (2) felsic volcanic, volcaniclastic and clastic rock successions assigned to the Devonian-Mississippian Black Slate and Felsic Volcanic formations (Seagull group). Cambrian-Ordovician strata were deposited in a marine environment characterized by episodic mafic volcanism and extensional tectonism. Devonian-Mississippian strata record the transition from an extensional turbidite basin to a metalliferous volcanic rift basin, and resemble key rock assemblages of the Selwyn basin (Earn Group) and Yukon-Tanana terrane (Grass Lakes and Wolverine Lake groups).

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Three allochthonous terranes, igneous rocks of the Cretaceous and Tertiary Coast Plutonic Complex and associated volcanic complexes comprise the geology between Whitehorse and the Yukon-BC border. The Paleozoic and older(?) Nisling Terrane is composed of the quartz-rich Nisling assemblage, the carbonaceous Nasina assemblage and orthogneiss assumed to be Devono-Mississippian in age. The Nakina sub-terrane of the northern Cache Creek Terrane is composed of Mississippian to Permian spilitized basalt, ultramafite, chert and limestone characterized by Tethyan faunal assemblages and dramatic facies variations. The northern Stikine Terrane is composed of the Upper Triassic Lewes River arc and its plutonic roots. Upper Triassic to Middle Jurassic sedimentary rocks of the Lewes River and Laberge groups collectively comprise the Whitehorse Trough overlap assemblage. Basal augite-phyric volcanic rocks of the Lewes River Group (Povoas Fm) are unconformably overlain by sedimentary debris derived from the eroding arc (Aksala Fm). These rocks are disconformably overlain by Laberge Group coarse clastics (Takwahoni Fm) deposited in laterally discontinuous submarine fans and conformably overlain by distal fine-grained equivalents (Inklin Fm). Siliciclastic rocks of the Tantalus Formation were deposited in a variety of marine environments in a successor basin to the Whitehorse Trough during Upper Jurassic and Late Cretaceous(?) times. Plutonic rocks cover approximately 40% of the project area and comprise over 30 individual bodies with a wide range of compositions. Plutonic rocks have been divided into six chrono-lithologically distinct suites: Late Triassic batholiths of the Klotassin plutonic suite; Early Jurassic syn-tectonic(?) foliated diorite; mid-Cretaceous granodiorite of the Whitehorse plutonic suite; mid-Cretaceous granophyric quartz monzonite of the Mount McIntyre plutonic suite; a poorly defined suite of Late Cretaceous intrusions with associated volcanism; and quartz-rich high-level Late Paleocene/Early Eocene intrusions of the Nisling Range Plutonic Suite which form the plutonic roots to Skukum Group volcanism. The Klotassin suite is assumed to form the plutonic roots to the Lewes River arc, but are isotopically dissimilar. The Bennett Granite provides a Late Triassic link between Nisling Terrane and Lewes River arc. Cretaceous and Tertiary intrusions are peraluminous and comprise the Coast Plutonic Complex. Isolated but widespread accumulations of intermediate mid- and Late Cretaceous volcanic rocks form the Mt. Nansen and Carmacks groups. Four Late Paleocene/Early Eocene volcanic complexes of the Skukum Group are aligned in a northerly trend and represent deeper levels of erosion to the north. Skukum Group activity is also represented by numerous northeast-trending rhyolite dyke swarms representative of a transtensional regime. Strata of the Whitehorse Trough were deformed into a set of open to tight, northwest-trending folds during Middle and(?) Latest Jurassic/Early Cretaceous compressional event(s). In northern Cache Creek Terrane, much of the deformation took place during Middle Jurassic terrane accretion, but Late Cretaceous southerly verging thrust faults are documented. Nisling Terrane metasedimentary rocks were metamorphosed prior to the intrusion of the Late Triassic Bennett Granite. The Tally Ho shear zone is a narrow domain of penetrative, ductile deformation with evidence of Late Triassic, sinistral strike-slip displacement. It strikes northwest and dips steeply and marks the easternmost limit of Nisling Terrane exposures. It may represent a terrane boundary between the Lewes River arc and the Nisling Terrane; alternatively it may be a transpressional structure within the arc itself.