The South Snohoosh diatomite occurrence is located on the east side of the Deadman Valley/Vidette Lake access road, on the east side on Snohoosh Lake. The area is accessible on a good-quality gravel road north from the Trans-Canada Highway, 7.4 kilometres west of Savona, 41 (air) kilometres to the south.
Basalts of the Miocene Chasm Formation (Chilcotin Group) mantle most of the area, however, beneath the basalts, massive rhyolite ash of the Miocene Deadman River Formation (Chilcotin Group) is exposed in cliffs on the east side of the Deadman Valley for a length of 6.5 kilometres east of Snohoosh and Skookum Lakes. The rhyolite ash is the predominant lithology in a Miocene channel filling of fluviatile and lacustrine sediments occupying the northwest trending Mio-Snohoosh Channel (Open File 1989-21). The flat-lying channel is more than 200 metres in thickness. A section measured by Campbell and Tipper contained a minimum aggregate thickness of 3.8 metres of diatomaceous earth in two beds lying within 50.9 metres of the base of the section (Geological Survey of Canada Memoir 363, pages 58 and 59). The unit lies within the Deadman River Formation of the Chilcotin Group. Economic interest in the area has been directed mainly towards the volcanic ash/pozzolan potential of the Miocene section immediately overlying the lacustrine diatomite (see Sherwood Creek Volcanic Ash, 092P 093).
The South Snohoosh showing (Read, 1990) is based on a slumped roadcut from which samples yield numerous diatoms in oil immersion mounts. The showing is in the Deadman River Formation near the western edge of the northwestward-draining Mio-Snohoosh channel. Nearby at 5659540mN, 649780mE, Read (1990) has described the Knight Lake Road 1 diatomite occurrence, which is exposed in a roadcut on the old Knight Lake logging road, as "bedded rhyolite tuff and diatomaceous earth which was verified by oil immersion grain mounts." Read (1990) also described a third occurrence at 5659200mN, 649430mE, in the area that he termed the Knight Lake Road 2 diatomite occurrence which is also exposed in a roadcut on the old Knight Lake logging road. It is described as "bedded rhyolite tuff and A fourth diatomite occurrence called the Deadman River showing is exposed in a cut 0.8 kilometre south of Snohoosh Lake (5658500mN, 648700mE), where a 2 metre thick bed of diatomaceous earth is exposed for a length of 15 metres. Read (1990) was not able to locate the showing - it is shown as diatomite occurrence D9 in Open File 1989-21.