Ordovician Chase lake formation (MEOcl;0)

State	Maine
Name	Ordovician Chase lake formation
Geologic age	Ordovician
Original map label	Ocl
Comments	Named for Chase Lake, Piscataquis Co., north-central ME. Consists of a lower member composed of slate and graywacke and an upper member composed of conglomerate and graywacke. Thickness is at least 610 m. Unconformably overlies Chase Brook Formation; conformably underlies Bluffer Pond Formation. (ME017) Unit description from USGS GEOLEX website (ME078). W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith H - Lithic sandstone and conglomerate
Primary rock type	graywacke
Secondary rock type	conglomerate
Other rock types	slate
Lithologic constituents	Major Sedimentary > Clastic > Sandstone > GraywackeW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith H - Lithic sandstone and conglomerate Minor Sedimentary > Clastic > ConglomerateW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith H - Lithic sandstone and conglomerate Metamorphic > Metasedimentary > Metaclastic > SlateW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith H - Lithic sandstone and conglomerate
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