Mill Priviledge Brook Formation (new name) is the oldest unit in the Prentiss Group (also new) and underlies in ascending order, the Sam Rowe Ridge Formation (new), the Ellen Wood Ridge Formation (new), and the Daggett Ridge Formation (revised), all here assigned to the Prentiss. Consists mostly of lithic sandstones and granule conglomerates interbedded with carbonaceous slate. Bedding ranges from massive to graded. Slates are strongly cleaved. Cobble conglomerates, which crop out in Baskahegan Stream in the Danforth quad, are tentatively referred to the Mill Priviledge Brook and probably represent a more proximal facies. Late Ordovician to Early Silurian age assignment based on interfingering relationship with the Carys Mills Formation.

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

Post-Caradocian Miramichi rocks may be divided into four formations. All four (Daggett Ridge, Mill Priveledge Brook, Sam Rowe Ridge, and Ellen Wood Ridge Formations) appear to interfinger. The Mill Priveledge Brook consists primarily of dark gray, thinly bedded, pyritiferous, and locally carbonaceous pelite, siltstone, and wacke. Minor amounts of conglomerate, calcareous pelite and wacke, and felsic tuff are also found. Clast in the conglomerates are identical in composition to those in the Daggett Ridge. Pyrite is nearly ubiquitous and causes a distinctive brown- to orange-weathering rind. Most outcrops show rhythmically bedded sections of wacke and pelite. Unconformably overlies the Stetson Mountain Formation. Shown to interfinger with Carys Mills Formation to the west. Age thought to range from Late Ordovician to Silurian.

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