Geology and Mineral Deposits of Nootka Sound map area Vancouver Island, British Columbia
Authors: Muller J E , Cameron B E B , Northcote K E 
Published: November 2013

The map area encompasses glacially sculptured mountains bordering Nootka Sound and adjacent inlets on the west coast of Vancouver Island, the principal part of the Insular Belt of the Canadian Cordillera. It is underlain by mainly volcanic and crystalline rocks
and by minor sedimentary rocks. The Sicker Croup includes volcanics and clastic and carbonate sediments of low metamorphic grade; the few fossils found indicate a late Paleozoic age. The Vancouver Croup (redefined) is composed of three formations: a thick sequence of pillowed to layered basalts
(Karmutsen), overlain by Upper Triassic, Karnian to Norian carbonates (Quatsino) and carbonate-clastic sediments (Parson Bay). North of the map area pelites with Ladinian fossils, intruded by diabase sills, form the base of the group. The relationship suggests that a Paleozoic volcanic arc was
rifted, engulfed and covered by oceanic basalt, whereon in Late Triassic time carbonate-clastic shelf deposits were laid down. The Bonanza Croup (redefined) consists of Lower Jurassic intermediate volcanic rocks and Pliensbachian clastic sediments. The Westcoast Complex is composed of basic gneiss,
agmatite and amphibolite, probably derived from the pre-Jurassic rocks. Island Intrusions are Early Jurassic batholiths which range in composition from quartz diorite to granite (new IUCS definition). The three groups of Jurassic plutonic and volcanic rocks are considered to be successive stages and
products of the same plutonic-volcanic process. The Upper Jurassic lowermost Cretaceous Kyuquot Croup (new) includes three formations: Kapoose (new), Callovian to Portlandian; One Tree, Berriasian to lower Valanginian; and Longarm, Valanginian to Barremian (only in Alert Bay map area). The group
represents an eastward transgressive clastic wedge, deposited in shelf seas that invaded the eroded Early Jurassic plutonic­volcanic complex. The Pacific Rim Complex is approximately coeval and represents off-shelf clastic, cherty and volcanic rocks, commonly deformed into melange, probably as a
result of underthrusting of the Pacific Plate beneath the North American Plate. Catface Intrusions (new name) are small, early Tertiary stocks and sills of fine-grained, K-feldspar poor, granitoid rocks and porphyries. The Carmanah Croup (redefined) of Tertiary clastic sediments is composed of a
basal conglomerate, the Escalante Formation, Narizian; the main component Hesquiat Formation (redefined), Refugian to early Zemorrian, or late Eocene to early Oligocene; and the Sooke Formation, late Zemorrian? or late Oligocene? (mainly in Victoria map area). The beds were laid down mainly in deep
water on the continental slope (?), partly in quiet water and partly in turbulent submarine channels. The structure of the region is generally a southwest dipping homocline of early Mesozoic rocks, disrupted by Jurassic batholiths. Steep to vertical major faults domina to the structural pattern.
They are broadly categorized in sets of northerly and westerly faults of probable early Mesozoic origin, and late Mesozoic to Tertiary northwesterly and north-easterly faults.