Silurian - Ordovician Frontenac Formation Canada Falls volcanic member (MESOfc;0)

State	Maine
Name	Silurian - Ordovician Frontenac Formation Canada Falls volcanic member
Geologic age	Silurian - Ordovician
Original map label	SOfc
Comments	Volcanic rocks of the Canada Falls Member of the Frontenac Formation crop out in three northeast-trending lens-shaped bodies in southwestern ME. Estimated thickness of the largest is 1000 to 2000 m. Predominantly green basalt, which weathers light green. Exposures are of two types: well-pillowed and poorly cleaved and poorly pillowed and well-cleaved. Pillows range in diameter from 10 cm to 2 m. A thin pyroclastic layer of volcanic bombs and tuff is located near base of unit. Also contains minor beds of intercalated siltstone and mudstone slate that generally drape over the pillow basalt and are only a few meters thick. Author considers Frontenac to be no older than Silurian or latest Ordovician. (ME011) Unit description from USGS GEOLEX website (ME078). W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite GS - Greenschist facies Protolith V - Basaltic volcanic rocks
Primary rock type	basalt
Secondary rock type
Other rock types
Lithologic constituents	Major Igneous > Volcanic > Mafic-volcanic > BasaltW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite GS - Greenschist facies Protolith V - Basaltic volcanic rocks
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. Marvinney, R.G., 1989, Bedrock geology of the southeastern margin of the Connecticut Valley-Gaspe synclinorium in Somerset County, Maine, IN Berry, A.W., Jr., Guidebook for field trips in southern and west-central Maine: New England Intercollegiate Geological Conference Guidebook, 81st Annual Meeting, Farmington, ME, October 13-15, 1989, p. 212-237. USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Somerset