The region is underlain by the Coast Plutonic Complex, consisting of pre- to post-kinematic quartz diorite to granodiorite batholiths intruded into Paleozoic to Mesozoic metasedimentary and metavolcanic rocks. Younger supracrustal assemblages overlying deformed rocks include the (?)Cretaceous Gambier Group and Tertiary Bella Bella Formation volcanic rocks.

The Bentinck Arm graphite showing, located approximately 24.1 kilometres south of Bella Coola, occurs as small thin graphite flakes widely dispersed in a quartz rich gneiss. Geological Survey of Canada mapping, however, has shown that this area is underlain by metavolcanic rocks which have been intruded by a now foliated granodiorite. No further geological information is available.