Sandymush Felsic Gneiss is here defined and formally named in the central Blue Ridge of NC. It is one of five map units composing the Middle Proterozoic basement sequence that underlies 60% of the study area. The unit extends diagonally across the Sandymush quad. and the northwest corner of the Canton quad., underlying approximately 50 sq mi. Described as a monotonous, repetitive sequence of layered rocks perhaps more than 15,000 ft thick. Consists predominantly of biotite granitic gneiss to quartz dioritic gneiss, interlayered and intergraded with biotite gneiss, biotite schist, amphibolite, and very minor calc-silicate granofels. Fresh color ranges from very light gray to very pale orange to medium light gray. Grain size varies from coarse to fine; texture is generally equigranular. Contact with the Earlies Gap Biotite Gneiss (new name) is gradational. Probably intruded by the protoliths of both the Spring Creek Granitoid Gneiss and Doggett Gap Protomylonitic Granitoid Gneiss (new names). Although not dated locally, it correlates, at least in part, with rocks to the northeast (Mars Hill quad), which have been radiometrically dated at 1214+/_83 and 1270+/_44 Ma.

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