The Tantalus Formation developed within confined intermontane river valleys during the late stages of collision and amalgamation of Stikinia and associated arc systems with the North American plate in Upper Jurassic and early Lower Cretaceous times. While most of the extensive chert pebble conglomerate in the Tantalus Formation can be interpreted as shallow braided gravel-bed river deposits, some may represent the products of deposition from deeper, braided and meandering gravel-bed rivers. Floodplain and lake deposits are restricted to poorly exposed slope forming intervals. Coal deposits developed locally on abandoned segments of floodplains in confined river valleys, in places associated with high constructive river deposits. The age profiles of detrital zircons indicate major contributions from reworking of older strata, combined with continued un-roofing of the Stikine terrane. In addition more distal sources were tapped in the Yukon-Tanana and adjacent terranes to the north and west of the Whitehorse trough. Much of the chert in the Tantalus Formation appears petrographically similar to chert in the Cache Creek terrane, now preserved only to the south of the Whitehorse trough. As both decrease in maximum grain size, and paleocurrents, are generally south to southwesterly trending, this source is considered unlikely. Chert may have been derived from now eroded supracrustal rocks that once formed the top of the Yukon-Tanana terrane, or more likely from an obducted block of Cache Creek terrane once present to the north and west of the Whitehorse trough. The latter may have been thrust over metamorphosed rocks of the Yukon-Tanana terrane beginning in the early Bajocian, and has subsequently been removed by erosion. A proximal North American cratonic source is excluded, as there are no Archean zircon grains in the Tantalus Formation. The possibility that strata of the Tantalus Formation may host significant conventional reserves of oil or gas is very low, due to lack of trapping mechanisms. There may be some undiscovered coal reserves, and limited potential for coal-bed methane production.

Upper Paleozoic strata in the eastern Richardson Mountains, northern Mackenzie Mountains and Peel Plateau of the Yukon consist of basinal sediments overlain by a siliciclastic sedimentary wedge derived from the Late Devonian Ellesmerian orogeny. Unconformably overlying Paleozoic strata in the Peel Plateau are Cretaceous sedimentary rocks that were deposited in the foreland basin of the Cretaceous Cordilleran orogeny. This study, as part of the interdisciplinary “Regional Geoscience Studies and Petroleum Potential, Peel Plateau and Plain” project, examines the sedimentology, stratigraphy and hydrocarbon potential of Upper Paleozoic strata in the Peel region and adjacent Richardson and Mackenzie mountains. Units investigated as part of this study include the Canol (Upper Devonian), Imperial (Upper Devonian) and Tuttle (Upper Devonian-Lower Carboniferous) formations, ‘Cf’ map unit (?Upper Devonian-Lower Carboniferous), and ‘Mo’ map unit (?Upper Devonian-Lower Carboniferous). Preliminary analyses suggest the Canol, Imperial, Tuttle, ‘Cf’ and ‘Mo’ are potential hydrocarbon source rocks for the region. The Tuttle Formation is the best prospective reservoir rock of the Upper Paleozoic strata.

Most chert-pebble conglomerate units within the Late Jurassic to mid-Cretaceous Tantalus Formation were deposited in shallow, deep and meandering gravel-bed rivers. However, the presence of largescale angle of repose foresets of large- to small-pebble conglomerate, with distinct down-slope termination in laminated mudrocks, indicates that at least some >5 m foresets were formed by episodic flood-controlled progradation of a small river-dominated lobate delta. Architectural analysis of exposures at the Whitehorse Coal deposit, 26 km south-southwest of Whitehorse, indicates periodic rapid progradation into a small lake that was at least 6 m deep. Thinning and downlap of some foreset units indicate shifting location of topset distributary channels. Down-slope transition of gravel foresets into thin sub-horizontal beds of massive and graded sandstone and pebbly sandstone suggests that the foresets were inertia-dominated. Deformation of bottomset beds is directly related to foreset progradation over under-compacted lacustrine clays.

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.

Marble, calc-silicate rock and pelitic layers of the Ram Creek assemblage surrounding the Dan Zn (± Cu-Pb-Ag) occurrence display ample evidence of a monocyclic structural evolution with three main events of progressive deformation (D1-D3). These events developed a tightly folded package of west-northwest-trending tectonites. Primary planar structures (S0) generally lie sub-parallel to two tectonic foliations (S1 and S2), which dip shallowly to steeply southwest. Inter-foliation slip (D3) resulted in a transverse, sub-vertical foliation (S3) that dips generally shallowly to moderately north. Cross-sections based on new mapping and fold analysis indicate that similar folds containing stratabound zinc-sulphide mineralization should be present south of the Dan occurrence, as part of regional north-northeast-verging folds or a thrust-fault-repeated succession.

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).

The Eagle Plain basin, having proven hydrocarbon potential, is a relatively underexplored intermontane basin located in northern Yukon . Previous studies of the middle Albian-Cenomanian Parkin Formation and the Turonian Fishing Branch Formation are based on broad lithostratigraphic correlations. The primary goal of the study is to refine the sequence stratigraphic framework of the middle to Upper Cretaceous succession based on sedimentological observations. New findings from this study require subdivision of the stratigraphic nomenclature by defining new informal lithological members. Facies transitions, paleoflow indicators and isopach maps indicate overall westward deepening of the basin. Large-scale, sand-prone mass transport deposits observed in the upper part of the lower Parkin shale member in western Eagle Plain indicate the presence of shelf-to-basin floor relief of at least 100 m. Recognition of significant shelf-to-basin floor topography greatly increases the potential for hydrocarbon reservoirs (gas-dominated) in stratigraphic traps associated with the shelf edge.

A copy of this thesis is available at the EMR library – TN806.C3.Y8.H9 1989.

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.

Between the Cretaceous granitic rocks (Hake Batholith on the west; Cassiar Batholith to the east) are three belts of metamorphic rocks, collectively part of Yukon-Tanana terrane. These are remnants of oceanic and continental volcanic arcs, and marginal basin sediments of Early to mid-Paleozoic age. At the head of Borden Creek are thick carbonate and andesitic volcanic rocks correlated with Klinkit Group. The Ram Creek fault and Hidden Lake fault are not exposed but deduced to be steeply dipping brittle structures with northeastward thrust or transpressional offset, based upon more complete exposure to the southeast in 105B/3 map area. The former is likely of Cretaceous age; the latter was active between mid-Permian and Early Jurassic time.