At Anderson Lake, up to 10 coal seams are present in the Upper Cretaceous Comox Formation (Nanaimo Group). The coal occurs in seams approximately 0.4 to 5.0 metre thick which are interbedded with shale and sandstone. Seam thicknesses are laterally variable and splitting occurs in places as a result of faulting. Average seam thicknesses in areas A and B (seams greater than 0.3 metres) are 0.92 and 0.87 metre respectively. Average overburden thicknesses are 11.9 and 9.0 metres respectively.
The dominant structures in the area are faults which range from north-northeast trending through approximately north to west-northwest trending, and are predominantly normal faults. In many areas Comox Formation sediments are uplifted in association with lateral and radial faults close to Tertiary intrusions. A number of the upper coal beds have been subsequently eroded from these areas. Strata appears to generally strike northwest and dip towards the northeast.
Two zones of economic interest, Areas A and B (or North and South), were designated and contain unclassified resources of 1,675,000 tonnes of low to medium volatile bituminous coal (Coal Assessment Report 39).