Evolution of the Selwyn Basin region, Sheldon Lake and Tay River map areas, central Yukon

Abstract

Late Precambrian to Cretaceous, weakly metamorphosed strata of the ancestral North American margin comprise four sequences: Upper Precambrian to Middle Devonian (more than 3000 m) turbiditic sandstone, deep-water limestone, shale, and chert (Selwyn Basin), flanked southwesterly in the Siluro-Devonian by shallow-water carbonate and clastic sediments (McEvoy Platform). Early Cambrian pelite hosts deposits of stratiform lead-zinc. Upper Devonian and Mississippian turbiditic quartz-chert sandstone and chert-pebble conglomerate (2000 m) shed from elevated fault blocks of Selwyn Basin strata. Stratiform barite occurs within siliceous shale of mid- to Upper Devonian age. Mississippian to Triassic shale, chert, limestone, minor sandstone, and siltstone (1700 m) deposited on a shallow-marine shelf; and Lower Cretaceous clastic sediments (120+ m) derived from Jura-Cretaceous deformation and uplift. Regional Jura-Cretaceous deformation formed décollement style, northwest-trending folds and large, shallow-dipping thrust faults. Incompetent Cambro-Ordovician to Lower Devonian strata are complexly deformed above a regional flat-lying detachment. Deformation was accompanied by obduction of oceanic ultramafite, basalt, chert, and carbonate (Slide Mountain Terrane) as well as siliceous mylonite and schist (Yukon-Tanana Terrane). Granitic intrusions of the mid-Cretaceous (100 Ma) Selwyn Plutonic Suite crosscut regional structure and are responsible for small skarn and base-metal vein deposits. Coeval pyroclastic rocks of the South Fork volcanics are preserved within huge calderas. Cretaceous-Tertiary dextral slip along Tintina Fault has offset geological elements at least 430 km and formed pull-apart basins along and near the fault. Eocene fill of fluvial clastic and bimodal volcanic rocks host epithermal precious-metal veins.

Late Devonian magmatism and clastic deposition in the upper Earn Group (central Yukon, Canada) mark the transition from passive to active margin along western Laurentia

“…1). In this region, volcanic rocks are widespread in the upper Earn Group and a series of Late Devonian diorite plutons intrude underlying lower Paleozoic rocks, but were poorly documented in previous studies (Campbell 1967;Gordey 2013a). We present new geochemical, biostratigraphic, and U-Pb zircon data for igneous and detrital samples that refine the stratigraphy of the Earn Group in central Yukon.…”

Mapping Curie Depth Across Western Canada From a Wavelet Analysis of Magnetic Anomaly Data

“…The Cordillera west of the Tintina‐RMT boundary is characterized by short‐wavelength anomalies, and east of this boundary until the Cordilleran Deformation Front there are little to no magnetic anomalies (Figure a). West of the Tintina‐RMT boundary are a collection of accreted oceanic and arc terranes, and sandwiched between the Tintina‐RMT and the Deformation Front are passive margin rocks of ancestral North America (e.g., Colpron et al, ; Gordey, ). The lack of magnetic anomalies in these areas may be explained by the thick sedimentary material.…”

“…The depth to the top of the magnetic layer is chosen to be the thickness of the sedimentary layer overlying the bedrock, since this layer is most likely weakly magnetic and is assumed to not contribute to the magnetic anomalies. However, this map has limitations; for instance, the seismic model used does not resolve older, denser, and deformed sedimentary rocks such as the late Proterozoic to Devonian Selwyn Basin and Mackenzie Platform in Yukon (Gordey, , and references therein).…”

“…The crustal‐scale, right‐lateral Tintina Fault accommodated >400 km of displacement between the Cenozoic to the present day (Gabrielse et al, ; Hayward, ; Leonard et al, ; Roddick, ; Saltus, ). This marks an important boundary in terms of geology, separating the oceanic and accretionary terranes west of the fault from the deformed and weakly metamorphosed sedimentary rocks from ancestral North America's passive margin on the eastern side, up to the Cordilleran Deformation Front (e.g., Colpron et al, ; Gordey, ). East of the Deformation Front, an aggregation of multiple Archean cratons constitutes the North American craton, overlain by Proterozoic juvenile arcs and orogens to the west near the craton edge, overlapping to the other side of the Cordilleran Deformation Front (Figure a).…”

Landscape antiquity and Cenozoic drainage development of southern Yukon, through restoration modeling of the Tintina Fault

“…The Yukon plateaus represent a low-relief erosional surface that truncates polydeformed metamorphic rocks and intrusions of the Yukon-Tanana Terrane. The surface is locally overlain by mid-and Lower Cretaceous rhyolitic volcanic rocks (Gordey 1988(Gordey , 2013Bacon et al 1990Bacon et al , 2014, and early Cenozoic magmatism at 50-60 Ma produced felsic and mafic intrusive and extrusive rocks, sporadically distributed in central and east-central Alaska and adjacent western Yukon (Jackson et al 1986;Dusel-Bacon et al 2016, and references therein). In southern Yukon, the surface of the Yukon plateaus is best preserved beyond the limits of regional glaciation; principally in the Klondike Plateau where only limited alpine glaciation occurred during the late Pliocene or earliest Pleistocene (Lowey 2000;Nelson and Jackson 2003;Jackson et al 2009).…”