The Nelson Formation was originally called the Nelson Amphibolite by T. B. Nolan and was later designated a formation for exposures near Nelson Ranch in the southwestern portion of the Mountain City Quadrangle in Sec. 2, T. 45 N., R. 53 E. (Coats, 1969).

The Nelson Formation overlies and locally grades into the Banner Formation and is gradationally overlain by the Mountain City Formation. It is considered Late Mississippian in age based upon its stratigraphic position (Coats, 1969, 1985).

In the Mountain City and Owyhee Quadrangles, the Nelson Formation consists predominantly of andesitic and basaltic flows and tuff breccias, and minor diabase sills and rhyolitic tuff (Coats, 1969, 1971). The flows are metamorphosed to greenstone and meta-andesite, meta-diabase, and amphibolite along intrusives in the Mountain City Quadrangle (Coats, 1969). The metamorphism is contact in origin, and is related to surrounding quartz monzonite. The Nelson is non-fossiliferous and grades laterally into the Mississippian Banner Formation (Coats, 1985).

The Nelson is about 600 feet thick at its type locality at Nelson Ranch, and may be about 2,500 feet thick at Fawn Creek based upon discontinous and probable fault repeated outcrops in the eastern portion of the Owyhee Quadrangle (Coats, 1969, 1971).

The Nelson Formation is exposed on Banner Hill and along Fawn Creek in the Mountain City and Owyhee Quadrangles.

The details of depositional or eruptive setting for the Nelson Formation are unknown.