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Ministry of Energy Mines and Responsible for Core Review

Preliminary Map No. 48: Geology of the Tertiary Rocks of the
Afton-Tranquille Area
(Map Area 92I/09, 10)

by Tom Ewing, 1982

View Map (PDF, 1.7 MB) (1:50 000)


View marginal notes (PDF, 0.9 MB)


Preliminary Map 48 presents the geology of Tertiary rocks of the Afton-Tranquille area (92I/9, 10) west of Kamloops, British Columbia. The 1:50 000 scale geology map includes a legend.


The Late Triassic country rocks include argillites and meta-andesite and tuff of the Nicola Group. Unconformably over these is Jurassic polymictic conglomerate. Unconformably above the older rocks are Eocene Kamloops Group strata. The basal Kamloops Group unit is the Tranquille Formation. It consists of 8 units: basal lithic and arkosic wacke, shale and local coal; lacustrine mudstones, tuffaceous siltstones and tuff; coarse-grained andesite to basalt; siltstone, mudstone and tuff; lacustrine sedimentary rocks and tuffs; pillowed andesite, breccia and deformed sedimentary rocks; tuffs and lacustrine sediments; and hyaloclastite and aquagene tuff. The overlying Dewdrop Flats Formation contains 15 units: the Nipple basalt breccia; the Kissick andesite breccia; the Mara Hill member of basaltic andesite flows; the Wheeler Mountain breccia with 4 units: andesite flow breccia and mud flows, andesitic phreatic breccia and flow breccia, coarse andesite flow breccia, and phreatic basalt breccia; the Castle Butte plagioclase phyric andesite breccia, with local hyaloclastites and aquagene tuff; the Doherty Creek member of basaltic andesite, flows and intermediate to felsic tuffs; the Rosseau Mountain basalt breccia with local hyaloclastite facies; the Red Plateau member with basaltic andesite flows and sedimentary rocks; and the Opax aphanitic andesite flow breccia. Quaternary cover materials include gravels, terrace gravels, drift, proglacial lakebeds, delta fan deposits, landslide debris, alluvial fan deposits and alluvium.


Intrusive country rocks consist of Upper Triassic to Lower Jurassic diorite and syenite of both the Iron Mask batholith and the Cherry Bluff pluton. Tertiary intrusive rocks include the basal, middle and upper sills; the Battle Bluff diabasic intrusive complex; andesite dome-plugs and related sills; hypabyssal andesite; and andesite to dacite dikes and subvolcanic masses.


The Triassic rocks host the Afton alkalic porphyry copper deposits and have potential for other porphyry deposits and gold-copper veins deposits. The Tertiary strata have potential to host epithermal precious metal deposits.


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