Ordovician - Cambrian Chase Brook Formation (MEOCAcb;0)

State	Maine
Name	Ordovician - Cambrian Chase Brook Formation
Geologic age	Ordovician - Cambrian
Original map label	OCAcb
Comments	Named for Chase Brook, Piscataquis Co., north-central ME. Consists of gray, black, and green-gray slate with interbedded limestone and siltstone. Thickness is 760 m. Unconformably underlies Chase Lake Formation. Age is Cambrian(?). (ME017) Unit description from USGS GEOLEX website (ME078). W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith Z - Melange
Primary rock type	slate
Secondary rock type	limestone
Other rock types	siltstone
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > SlateW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith Z - Melange Minor Sedimentary > Clastic > SiltstoneW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith Z - Melange Sedimentary > Carbonate > LimestoneW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith Z - Melange
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. Hall, B.A., 1970, Stratigraphy of the southern end of the Munsungun anticlinorium, Maine: Maine Geol. Surv., Bull. 22, 63 p. USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Aroostook - Piscataquis