Approximately 1097 metres of the Cretaceous Naniamo Group sequence are present in the Huknish Lagoon, northeast of Winter Harbour on Forward Inlet and the surrounding areas. Coal is present interbedded with shale and sandstone. At Huknish Lagoon one band of coal 0.3 metre thick is interbedded with shale and shale/coal bands. In an adjacent area 0.9 metre of shale and coal were encountered. The coal bearing horizon extends laterally to the Koprino Harbour area.

The beds at Winter Harbour dip 5 degrees to 60 degrees north but locally folds and faults produce varying dip directions and angles. Dips are generally 10 degrees to 20 degrees north in the Koprino area.

The West Vancouver Island Commercial Company operated in the area in the late 1800's.