Silurian - Precambrian Z Berwick Formation (MESZb;0)

State	Maine
Name	Silurian - Precambrian Z Berwick Formation
Geologic age	Silurian - Precambrian Z
Original map label	SZb
Comments	Named Berwick gneiss for development at Berwick, York Co., ME. Consists chiefly of graywacke gneiss, but contains clean quartzites, mica schist, and argillite schist and slate. Beds range in thickness from an inch to a few feet. Almost all rocks are moderately fine-grained and delicately banded with colors of dark gray, bluish gray, and brown. Total thickness is undeterminable. The age of the Berwick is unknown, but is probably pre-Carboniferous. (ME062) Unit description from USGS GEOLEX website (ME078). GS - Greenschist facies E - Epidote-amphibolite facies Protolith K - Calcareous feldspathic sandstone
Primary rock type	gneiss
Secondary rock type	quartzite
Other rock types	schist; slate
Lithologic constituents	Major Metamorphic > GneissGS - Greenschist facies E - Epidote-amphibolite facies Protolith K - Calcareous feldspathic sandstone Minor Metamorphic > SchistGS - Greenschist facies E - Epidote-amphibolite facies Protolith K - Calcareous feldspathic sandstone Metamorphic > Metasedimentary > Metaclastic > SlateGS - Greenschist facies E - Epidote-amphibolite facies Protolith K - Calcareous feldspathic sandstone Metamorphic > Metasedimentary > Metaclastic > QuartziteGS - Greenschist facies E - Epidote-amphibolite facies Protolith K - Calcareous feldspathic sandstone
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. Katz, F.J., 1917, Stratigraphy in southwestern Maine and southeastern New Hampshire, IN Shorter contributions to general geology, 1917: U.S. Geological Survey Professional Paper, 108-I, p. 165-177. [http://pubs.er.usgs.gov/publication/pp108I] USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	York