Is part of Mona Schist and named for exposures near Nealy Creek in southwest corner sec 18, T48N, R26W, Marquette Co, northwestern MI in Lake Superior region. Is generally a fine-grained dark-gray to greenish-gray and thinly foliated quartz-feldspar-sericite-chlorite schist. Scattered fine-grained pyrite and brown iron stain on weathered surfaces. Also includes sericitic slate. Is of volcanic origin, possibly from air-fall tuff of intermediate composition. Intrusion of north-bounding Dead River pluton has locally recrystallized schist, enlarging mica minerals and quartz; granoblastic intergrowths of quartz-feldspar in laminae separated by chlorite-biotite. Cataclastic deformation observed locally. Bounded on south by massive greenstone and on north by plutonic rocks or by unconformity at base of Michigamme Slate. Maximum mapped width in area is about 3,000 ft. Is westward extension of chloritic and felsic slate in Lighthouse Point Member as mapped by Gair and Thaden (1968). Is older than Dead River pluton and appears to intertongue with sheared rhyolite tuff member of Mona Schist. Geologic map, correlation chart, detailed lithology. Assigned to the early Precambrian.

Source: GNU records (USGS DDS-6; Reston GNULEX).

Nealy Creek Member of Mona Schist not used. Mona Schist is here revised to Mona Formation "because many rocks within the unit are not schists and because they have recognizable parent lithologies and are heterogeneous." It is also proposed that all members of the Mona be informal. Basal unit is here called the basalt flow unit of the Mona Formation; the sheared rhyolite tuff is called the lapilli tuff of the Mona Formation, and the Nealy Creek Member is here called the upper tuff of the Mona Formation.

Source: GNU records (USGS DDS-6; Reston GNULEX).