Various parallel bands of Permian limestone of the Teslin Formation (Cache Creek Complex) extend west-northwest from Little Dease Creek and Killarney Creek along French Range, just west of Dease Lake.

The bands of limestone are the result of repeated folding of the Teslin Formation and underlying tuff and agglomerate of the Permian French Range Formation (Cache Creek Complex). The most significant band outcrops for 30 kilometres northwestward to the Tuya River along the west limb of a syncline. The limestone unit is estimated to be at least 300 metres thick.

The bands are generally composed of fine to medium grained, massive to bedded, dark grey limestone that has undergone variable amounts of dolomitization and minor silicification. Some silica nodules and thin chert layers (less than 1 centimetre) are present. Rare argillite interbeds also occur. The limestone becomes tuffaceous at the contact with the underlying French Range Formation.