Is named as a unit within Mille Lacs Group (new) in east-central MN in Lake Superior region. Name designated for well developed occurrences in Glen Township (T46N, R25W) in southwestern Aitkin Co. Except for several outcrops of altered mafic rock in secs 8, 9, and 10 of Glen Township, formation is confined entirely to subsurface. Type material obtained from drilling logs and core samples from 55 holes intersecting approximately 3,000 m of rock in sec 28, T46N, R25W. Author states logs and samples available for study at offices of Minnesota Department of Natural Resources, Division of Minerals, Hibbing, MN. Composed mostly of interbedded pyrite- and pyrrhotite-rich, carbonaceous slate, recrystallized cherty iron-formation, metabasalt, highly altered diabase and lesser quartzite and quartz-rich metasedimentary rocks. Drilling and geophysical data suggests unit extends northeastward from near Mille Lacs Lake in T45N, R26W through T46N, Rs25 and 26W and into T47N, Rs23 and 24W. Overlies and is laterally equivalent to Denham Formation (new). Passes upward into undivided Mille Lacs Group. Detailed lithology, geologic map. Is assigned a middle Precambrian age.

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