Bella Coola and Laredo Sound map - Areas, British Columbia, 93d and 103a

Bella Coola and Laredo Sound map-areas cross the Coast Mountains of British Columbia between latitudes 52° and 53° N. They are underlain mainly by plutonic and metamorphic rocks. In the east half of Bella Coola map-area, volcanic rocks of andesitic composition form three units : Lower Jurassic and older; Middle Jurassic; and Upper Cretaceous ( ?). Only the Middle Jurassic strata have yielded fossils. Plutonic rocks include gabbro, diorite, quartz diorite, granodiorite, quartz monzonite, and granite. Some of them are pre-Middle Jurassic, and others are Upper Cretaceous or younger, but the age of most of them is unknown. A northwesterly structural trend is dominant in the area mapped, but it has been superposed on an older, northeasterly or easterly trend in parts of the area. The northwesterly trend is more pronounced in the central part of the area, whereas a northeasterly trend is common in the western and eastern parts of the area. No mineral deposits have been proved economic.