Kelly Lake is 13 kilometres southwest of Clinton in a valley in the Pavillion Ranges, west of the Interior Plateau.
The lake is a semi-evaporitic playa lake located in the dry valley along the Lillooet-Clinton road. Bedrock is chert, argillite and siltstone with minor tuff and limestone (GSC Map 1278A) of the Permian to Triassic Cache Creek Group.
Bedded deposits of calcite admixed with some gypsum and hydrous magnesium carbonate, are present in the shallow parts of Kelly Lake where they lie in a few centimetres of water (GSC Memoir 118, page 28). Samples taken from the northeast shore of the lake and from the mudflat west of the lake contained respectively: 83.5 per cent and 66.1 per cent calcite, 0.5 per cent and 0.5 per cent gypsum and anhydrite and 0.9 per cent and 1.9 per cent magnesium carbonate and hydroxide (GSC Memoir 118, page 32).