The area is underlain by Lower-Middle Jurassic Dewdney Creek Formation (Ladner Group) tuffaceous sediments comprised of volcanic sandstone, siltstone, wacke, tuff and argillite with interlayered fossiliferous limestone. These rocks are separated from the Lower- Upper Cretaceous Pasayten Group sediments to the east, by the major northwest trending Chuwanten fault.

The U.S. Rambler showing occurs in bedded quartzite which strikes 015 degrees. There is minor shearing along the bedding planes. The rock is altered and oxidized with extensive limonitic staining. Vein-filling along these shears is comprised mainly of altered hostrock and contains disseminated pyrite, galena and sphalerite.

In 1913, a 15-metre adit was driven along one of these shears and a 0.76-metre sample taken near the face of the tunnel assayed trace gold and 17.14 grams per tonne silver. In 1985, a 10-centimetre sample taken 100 metres east of the main fork of Dewdney Creek from the oxidized shears along the bedding planes, yielded 15.43 grams per tonne silver (Assessment Report 14714).