Underhill Formation, Mount Abraham Schist Member (VTCAua;0)

Underhill Formation, Mount Abraham Schist Member - Light gray sericite (muscovite-paragonite)-quartz-chloritoid rock with silvery sheen; porphyroblasts of magnetite are common and porphyroblasts of chlorite, chloritoid, garnet, and kyanite occur locally. (Northern and Central Vermont). Four distinctive units of Mount Abraham Schist occur within the Fayston-Buels Gore area, which are recognized on the basis of mineralogy, contact relationships, and geographic distribution. All are composed predominantly of white mica (muscovite and paragonite)-quartz-chlorite-chloritoid schist. One unit contains intraformational greenstone and metawacke; a second is a similar white mica schist but without the greenstone and metawacke; the third contains allanite; and the fourth, kyanite (Walsh, 1992).

State	Vermont
Name	Underhill Formation, Mount Abraham Schist Member
Geologic age	Cambrian
Original map label	Cua
Comments	Part of Green Mountains, Camels Hump Group Secondary unit description per VT014. The Underhill lies stratigraphically above basement rocks of Mount Holly Complex of Grenville (1 b.y.) age. Age changed to Late Proterozoic and(or) Early Cambrian (Slack and others, 1988) per VT020.
Primary rock type	mica schist
Secondary rock type
Other rock types
Lithologic constituents	Major Metamorphic > Schist > Mica-schist > Muscovite-schistLight gray sericite (muscovite-paragonite)-quartz-chloritoid rock with silvery sheen; porphyroblasts of magnetite are common and porphyroblasts of chlorite, chloritoid, garnet, and kyanite occur locally.
Map references	Nicholson, S.W., Dicken, C.L., Horton, J.D., Foose, M.P., Mueller, J.A.L., and Hon, Rudi, 2006, Preliminary integrated geologic map databases for the United States: Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, Rhode Island, and Vermont: U.S. Geological Survey Open-File Report 2006-1272. [http://pubs.er.usgs.gov/publication/ofr20061272]
Unit references	Doll, C.G., Cady, W.M., Thompson, J.B., Jr., and Billings, M.P., 1961, Centennial Geologic Map of Vermont: Vermont Geological Survey, Miscellaneous Map MISCMAP-01, scale 1:250,000. Walsh, G.J., 1992, Bedrock geology of the Fayston-Buels Gore area, central Vermont: Vermont Geological Survey Special Bulletin, no. 13, 74 p., scale 1:24,000. Slack, J.F., Atelsek, P.H. and Grosz, A.E., 1988, Geology and geochemical survey of the Bristol Cliffs Wilderness, Addison County, Vermont: U.S. Geological Survey Miscellaneous Field Studies Map, MF-1593-A, 1 sheet, scale 1:24,000. [http://pubs.er.usgs.gov/publication/mf1593A]
Geographic coverage	Addison - Washington