Preliminary Map 34 describes the geology of the Mount Fisher-Sand Creek area, east of Fort Steele in southeastern British Columbia. The 1:50 000 scale geology map has a legend, cross sections, and a table of mineral workings. Accompanying notes describe the geologic setting.
The oldest exposed rocks are of Middle Proterozoic Purcell Supergroup rocks. The Aldridge Formation consists of a quartzite, grey siltite, and argillite unit is overlain by a grey siltite, argillite unit with two dolomitic siltite layers near the top. The Creston Formation has two units. The lower has three subdivisions: a siltite with or without quartzite unit, a green siltite unit, and a purple siltite, white quartzite unit; the upper has two subdivisions: a coarse siltite to fine quartzite and white quartzite unit, and a mainly green siltite unit with dolomitic siltite near the top and white quartzite. Kitchener Formation has a lower dolomitic siltite and green siltite unit, and a silty dolomite, dolomitic siltite, siltite and stromatolytic dolomite unit. Above the Kitchener is a generally green non-dolomitic siltite unit. Middle Proterozoic rocks include parts of the Purcell Supergroup and a metadiorite to metagabbro Moyie sill. The lowest lava and sediment unit consists of andesitic lava, sandstone and siltite. The Sheppard Formation has stromatolytic dolomite, siltite, quartzite, and silty dolomite. The Gateway Formation contains siltite with dolomitic siltite near the top. The Phillips Formation consists of red micaceous quartzite and siltite. Cambrian rocks are represented by the Eager Formation with shale, limestone, siltstone and quartzite, and the ‘Tanglefoot Unit’ with shaly limestone, limestone, sandy shale and dolomite. Middle Devonian and perhaps earlier rocks comprise shaly limestone, shaly dolomite, limestone breccia, and gypsum. Upper Devonian to Permian rocks are undifferentiated limestone, shaly limestone, shale, quartzite, and dolomitic quartzite.
The area is divided into three segments by the right lateral, reverse Dibble Creek and Bull Canyon faults. The stratigraphy of the Purcell Supergroup differs in each segment. The Dibble Creek fault trends easterly and dips northerly. North of the fault are a series of asymmetric overturned anticlines; cleavage is axial to these structures. The entire region is cut by a series of northeast trending transverse faults with complex offsets. South of the fault, the area forms part of the upright limb of the Hosmer Nappe.
One important copper-silver-gold deposit and numerous smaller copper-gold and/or lead-silver with or without zinc showings. Known showings are veins, generally in the Aldridge and Creston Formations. The Bull River deposit consists of chalcopyrite-siderite-quartz veins that cut argillite, siltite and quartzite of the Aldridge Formation.