Devonian - Precambrian Z Gonic Formation (MEDZg;0)

State	Maine
Name	Devonian - Precambrian Z Gonic Formation
Geologic age	Devonian - Precambrian Z
Original map label	DZg
Comments	Named for exposures near Gonic, Strafford Co., southeastern NH. Consists of whitish or light-gray to dark-gray, thin-bedded, fine-grained arenaceous (graywacke) and argillaceous materials metamorphosed to schist and phyllite. Includes mica schist and phyllite and interbedded fine- to medium-grained micaceous graywacke schists in beds up to 2 ft thick; light- and dark-gray, fine-grained phyllites abundantly studded with dark staurolite crystals; and minor coarse muscovite schist composed almost wholly of mica and very thin quartz laminae. Argillaceous materials predominate, but graywacke is also prominent. Thickness is unknown. Probably underlies Rindgemere formation. (ME036) Unit description from USGS GEOLEX website (ME078). GS - Greenschist facies; E - Epidote-amphibolite facies; Protolith A - Pelite
Primary rock type	schist
Secondary rock type	phyllite
Other rock types
Lithologic constituents	Major Metamorphic > SchistGS - Greenschist facies; E - Epidote-amphibolite facies; Protolith A - Pelite Metamorphic > Metasedimentary > Metaclastic > PhylliteGS - Greenschist facies; E - Epidote-amphibolite facies; Protolith A - Pelite
Map references	Digital bedrock data downloaded from Maine Office of GIS in September 2005 from http://apollo.ogis.state.me.us/catalog/catalog.asp?state=2&extent=cover#bedrock Bedrock units table (publication date 11/15/2002) downloaded from same site. Permission to redistribute these data granted by Dr. Robert Marvinney, State Geologist of Maine, in September 2006. [http://apollo.ogis.state.me.us/catalog/catalog.asp?state=2&extent=cover#bedrock]
Unit references	Osberg, P. H., Hussey, A.M., and Boone, G. M., 1985, Bedrock geologic map of Maine: Maine Geological Survey, Dept. of Conserv., scale 1:500,000. Boudette, E.L., Hatch, N.L., Jr., and Harwood, D.S., 1976, Reconnaissance geology of the Upper St. John and Allagash river basins, Maine: U.S. Geol. Surv., Bull. 1406, 37 p. USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	York