Geoscience Map 1991-1: Geology of the Port Alberni-Nanaimo Lakes Area
View Map (8.1 MB)
Scale 1:50 000
See Paper 1992-2
Geoscience Map 1991-1 presents the geology of the Port Alberni-Nanaimo Lakes area (NTS 092F/1W, 2E and part of 092F/7E) and is at 1:50 000 scale. The map covers the northwestern portion of the Cowichan uplift. This geanticlinal uplift is cored by island-arc volcanics of the Devonian Sicker Group overlain by marginal basin and platformal sediments of the Mississippian to Lower Permian Buttle Lake Group. The uplift is flanked by basalts of the Upper Triassic Karmutsen Formation and granodiorite intrusions of the Island plutonic suite. Clastic sediments of the Upper Cretaceous Nanaimo Group overlie older rocks and are intruded by Eocene porphyries. The uplift is dissected by numerous faults, including major contractional faults of the Eocene Cowichan fold and thrust system. The map sheet contains 113 known mineral deposits and occurrences. Past production has been confined to placer and lode gold deposits, although volcanogenic massive sulphides and oxide exhalites, porphyry copper-molybdenum veins and stockworks, iron-copper skarns, base-metal veins and various industrial minerals are also found within the area.
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