Geological Map of Anvil District, Yukon (1:100 000 Scale)

The Anvil District contains the most westerly off-shelf basinal facies of the Cordilleran miogeocline, a prism of sedimentary rocks of Precambrian to Jurassic age deposited along the relatively stable continental margin of western North America. Cordilleran miogeocline stratigraphy is presented in Abbott et al. (1986). More detailed discussion of the stratigraphy and structure of the Anvil District is given in Jennings and Jilson (1986) and Pigage (1990). The District is part of Selwyn Basin, a large area of central Yukon in which deep water clastic rocks, chert, and minor carbonate accumulated along the ancient North American continental margin during Neoproterozoic and early Paleozoic time (Gabrielse, 1967). Northeast of the basin, a shallow carbonate platform (Mackenzie Platform) formed the near-shore facies of ancient North America (Abbott et al., 1986). Anvil District lies immediately northeast of the Slide Mountain and Yukon-Tanana Terranes, the most easterly of the allochthonous terranes (Coney et al., 1980). Yukon-Tanana Terrane has been interpreted as a middle to late Paleozoic continental margin volcanic arc assemblage related to east-dipping subduction beneath distal North America (Mortensen and Jilson, 1985; Creaser et al., 1999; 4 Bedrock geology compilation of the Anvil District, central Yukon Territory (Piercey et al., 2002). Slide Mountain Terrane consists of oceanic basalt and bedded cherts interpreted as a late Paleozoic back-arc or marginal ocean basin (Anvil or Slide Mountain Ocean) formed by rifting and westward migration of Yukon-Tanana Terrane relative to North America (Tempelman-Kluit, 1979a,b; Creaser et al., 1999). Tempelman-Kluit (1979a,b) and Gordey (1990a,b,c) interpreted the allochthonous terranes as being thrust northeastward over the North American rocks. Mortensen and Jilson (1985) interpreted the contact as a transpressive suture. More recently, crustal-scale seismic studies as part of Lithoprobe have confirmed the Yukon-Tanana and Slide Mountains terranes are a thin crustal veneer of arc-related and oceanic metasedimentary and metavolcanic rocks thrust over a westward-dipping wedge of North American sedimentary rocks resting on continental basement (Snyder et al., 2002). Deformation and metamorphism associated with accretion of the allochthonous terranes was inititated in Jurassic and culminated in the Cretaceous (Tempelman-Kluit, 1979b). More recently, strike-slip faulting along the Tintina fault zone resulted in approximately 425 km of right lateral displacement during Early Tertiary time (Roddick, 1967; Murphy and Mortensen, 2003).