The Clark Lakes area is located along the northern boundary of the Selwyn fold belt, and is underlain by the Ediacaran to Cambrian Hyland Group. In the surrounding region, the Hyland Group and Paleozoic platformal carbonate rocks host several Au and polymetallic mineral deposits. The Clark Lakes area is bordered by regional-scale, southeast-striking thrust faults, which include the Dawson thrust to the northeast, and the Tombstone and Robert Service thrusts to the southwest. Based on stratigraphic relationships identified during 1:50000-scale bedrock mapping, Hyland Group rocks in the Clark Lakes area are considered to belong to the Cryogenian–Ediacaran Yusezyu Formation, the Ediacaran Algae Formation and the Ediacaran–Terreneuvian Narchilla Formation. The Yusezyu Formation has been subdivided into five units based on dominant siliciclastic lithofacies, which form a broadly coarsening-upward sequence. The Yusezyu and Narchilla formations host gabbro sills, and quartz monzonite occurs locally in the upper Yusezyu Formation. Rocks in the Clark Lakes area exhibit a steeply northeast-to-southwest-dipping foliation that is axial planar to southeast-trending folds.