The region in which the Mount Greer showing occurs is within the Intermontane Belt, underlain dominantly by Lower to Middle Jurassic volcanic and sedimentary rocks of the Hazelton Group. These as- semblages are overlain by the Upper Cretaceous to Lower Tertiary Ootsa Lake Group and Miocene plateau basalt. Intruding Lower Jurassic rocks of the Hazelton Group in the northeastern part of the map sheet is a belt of granodiorite, diorite and quartz diorite plutons of the Lower Jurassic Topley intrusive suite. Felsic plutons of probable Cretaceous age intrude both Lower and Middle Jurassic Hazelton strata.

Underlying Late Tertiary andesite and plateau basalt in the northeastern part of mapsheet 93F are sedimentary beds, possibly of Oligocene age which have been correlated with the Endako Group. These sedimentary beds comprise shale, siltstone, bentonite and sandstone with interbedded lignite horizons. These sediments rest unconformably on rocks of the Ootsa Lake Group. The lignite outcrops as stringers and lenses usually less than 45 centimetres thick, although a thickness of 80 centimetres has been intersected in a drill hole. The lignite comprises 36.99 per cent volatile matter, 34.72 per cent ash, 28.29 per cent fixed carbon and 0.74 per cent sulphur, estimated from the analysis of one sample only (on a dry basis).