Cottonwood and Widow Creeks flow south off of El Capitan Mountain to the north shore of Cowichan Lake.
The area is underlain by Upper Devonian McLaughlin Ridge Formation (Sicker Group) mafic volcanics, Mississippian to Pennsylvanian Fourth Lake Formation (Buttle Lake Group) ribbon cherts and crinoidal limestone and basaltic volcanic rocks of the Upper Triassic Karmutsen Formation (Vancouver Group) to the north. These have been intruded by gabbroic to dioritic intrusives of the Late Triassic Mount Hall Gabbro and granodioritic rocks of the Jurassic Island Plutonic Suite. A major anticline occurs to the east and the area is highly faulted.
Placer gold is reported to occur in the head waters of Cottonwood and Widow Creeks. This could be related to known gold-copper quartz vein occurrences such as the El Capitan (MINFILE 092C 019) prospect.
It appears that most of the gold was derived from bars or in crevices in the bedrock of the river bed, or from benches along the side of the creek.
In 2008, a 1 by 2 by 0.5 metre pit was excavated, in the head waters of Widow Creek. Sluicing of the material yielded fine gold and a number of small flakes (Assessment Report 30172).