The British Columbia Geological Survey has completed extensive geological mapping and mineral deposits studies on northern Vancouver Island over the last several years. This is an ongoing program of mapping and mineral deposits studies.  Northern Vancouver Island, and particularly the Quatsino Sound area, is richly endowed in mineral occurrences, has had a successful mining history, such as the former Island Copper mine (092L 158). The region also has numerous mineral occurrences, some of which are under-explored but with excellent potential. The release of these three 1:50 000-scale Geoscience Maps covers an area extending from Winter Harbour - San Josef Bay on the west coast to Port Hardy - Port McNeill on the east coast, an area encompassing NTS sheets 102I/8, 9 and 92L/6, 11, and 12. Geoscience Map 2006-3 covers the Holberg - Winter Harbour area, 092L/12W, 102I/8, 9.

The area is underlain by a folded and faulted sequence of Upper Triassic to Middle Jurassic volcanic and sedimentary rocks of the Vancouver and Bonanza Groups intruded by granitoids of the Island Plutonic suite. The latter rocks are associated with important calcalkaline Cu-Mo-Au porphyry, and base and precious-metal skarn and epithermal mineral occurrences. Cretaceous marine clastic and Tertiary volcanic-sedimentary strata with lower mineral potential overlie the Triassic-Jurassic rocks.

These geoscience maps provide a new stratigraphic framework for the Early Mesozoic sequences, calibrated by 40Ar/39Ar and U-Pb isotopic dating and macrofossil and microfossil (conodont and radiolarian) faunas. The Bonanza group now includes the Upper Triassic Parson Bay Formation, which contains mapable volcanic/volcaniclastic horizons, overlain by unnamed volcaniclastic-sedimentary strata of uppermost Triassic to lowermost Jurassic age, in turn succeeded by Lower to Middle Jurassic, predominantly volcanic and volcaniclastic sequences of the informally named LeMare Lake volcanics, formerly "Bonanza volcanics". The latter term is usefully retained for all volcanic lithologies within the Bonanza Group, which spans some 40 million years of magmatic arc evolution from the Late Triassic (Carnian) to the Middle Jurassic (Bajocian).