Bedrock and Surficial Geology of the Fawnie Creek Map Area
BCMEMPR Open File 1994-02
View Bedrock Geology (PDF, 4.3MB)
View Surficial Geology (PDF, 3.6 MB); for further information regarding legend or otherwise, see Open Files 1994-09, 1994-10 and 1995-10.
Open File 1994-02 presents the bedrock and surficial geology of the Fawnie Creek map area (93F/3) in central British Columbia. The map portrays the geology at 1:50 000 scale, a legend, references, and a table of assay results.
The oldest rocks exposed in the area are the Naglico Formation of the Hazelton Group; they are of Middle Jurassic age. Units are augite phyric basalt and lesser andesite flows; volcanic sandstone, siltstone and conglomerate; and sandstone and siltstone with detrital quartz. Subordinate rocks interlayered with the flows include dacitic tuffs, andesitic lapilli tuff, quartz-bearing lapilli and finer tuffs, rhyolite lithic tuffs, and volcanic sandstone and siltstone. Eocene rocks of the Ootsa Lake Group occur as outliers. Near Cow Lake, basal conglomerate is overlain by dacite flows and rhyolitic flows and intrusives. Along the west-facing slope of the Fawnie Range, rhyolite flows, andesite flows and lapilli tuff containing quartz fragments. Miocene and Pliocene Chilcotin Group comprise basalt flows. Bedrock exposure in the area is sparse, except in higher areas.
Intrusive rocks are varied. Middle Jurassic augite porphyry plugs, dikes and sills are the oldest. Late Cretaceous intrusions include quartz diorite, quartz porphyry dikes, and quartz monzonite and granodiorite of the Capoose batholith. Tertiary felsite dikes and sills occur.
Late Pleistocene units are morainal diamictons, glaciofluvial pebble to boulder gravel and sand, and glaciolacustrine sand, silt or clay. Holocene units are fluvial sand, pebble gravel, and silt and organic deposits.
The area is part of a regional east-trending horst that produced the mountain ranges. Faults typically trend north and northwest.
Epithermal veins and disseminated precious metal mineralization occur at the Wolf property. Most other known occurrences are near the margin of the Capoose batholith. Both epithermal precious metal and skarn mineralization occur.
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