The Tuff of Hall Creek is applied to exposures along Hall Creek in the central Toiyabe Range, in the southwest corner of the Hall Creek Quadrangle (Stewart and McKee, 1968c).

The Tuff of Hall Creek is considered Oligocene in age. It often lies on pre-Tertiary rocks, but can be seen overlying Oligocene andesitic-dacitic lava flows about 35 Ma, and is overlain by 32.5 Ma Caetano Tuff in most places (Stewart and McKee, 1977).

The Tuff of Hall Creek is a thick, massive, and very lenticular pile of non-welded to weakly welded tuff and tuff breccia, which is only exposed at its source in the central Toiyabe Range. Most of the unit is a non-welded massive, white to gray, lithic-pumice tuff. Phenocrysts of quartz and feldspar are present in a shard-bearing matrix. The most diagnostic feature of the tuff is abundant sand to cobble-size lithic xenoliths of chert and various lavas (Stewart and McKee, 1968c, 1977).

The Tuff of Hall Creek is at least several thousand feet in thickness (Stewart and McKee, 1968c, 1977).

The Tuff of Hall Creek is exposed over an area of about 40 square miles, where it makes up most of the central part of the Toiyabe Range (Stewart and McKee, 1977).