The northeast Anvil area, 15 km north of Mount Mye (NTS 105K/6, 105K/7), is underlain by a conformable Cambrian-Devonian volcanic and sedimentary package with an aggregate thickness of greater than 1600 m. The lowest unit, with an exposed thickness of 120 m, consists of calcareous phyllites of the Cambrian-Ordovician Vangorda formation. Conformably overlying the phyllites is a >900-m-thick Ordovician-Silurian sequence of submarine basalt flows and volcaniclastic sedimentary rocks of the Menzie Creek formation. Volcaniclastic sediments are dominantly coarse, proximal, fragmental breccias with lesser conglomerates, sandstones, and siltstones. Carbonaceous shales with lesser siltstones, limestones, dolostones, and quartzites of the Ordovician-Devonian Road River Group (>450 m) are intercalated with and overlying the basalt flows.
The east margin of the map area is a depositional edge of basalt volcanism with only scattered thin flows occurring further to the east. This depositional edge is considered to be a north-trending, west-side-down, Ordovician-Silurian syndepositional, normal fault forming the east margin of a sedimentary sub-basin infilled with volcanic rocks. Hornfelsing on the east margin of the map area indicates a large, shallowly buried, northwest extension of the mid-Cretaceous Orchay Batholith.
