Ordovician - Cambrian Dead River formation lower member (MEOCAdp;0)

State	Maine
Name	Ordovician - Cambrian Dead River formation lower member
Geologic age	Ordovician - Cambrian
Original map label	OCAdp
Comments	Secondary unit description from USGS Geologic Names lexicon (ref. ME078): Dead River Formation of Bronson Hill-Boundary Mountains anticlinorium was previously mapped as Albee Formation in Cupsuptic 15-min quad by Harwood (1973) and in Oquossoc 15-min quad by Guidotti (1977) in ME and in wide areas of northern NH by Billings (1956) and Green (1968). In Cupsuptic quad, consists of a main body of thinly interbedded greenish-gray slate and typically subordinate quartzite or feldspathic quartzite. Unit is also divided into three parts not shown on this map--a main body, a green slate and phyllite member, and a red, maroon, and purplish-gray slate member. A quartzite-rich member is mapped separately in Kennebago Lake 15-min quad, ME, and further east. An unnamed quartzite and phyllite member at Percy, in Percy, NH, 15-min quad, is mapped separately and consists of quartzite and grit interbedded with phyllite; possibly a volcaniclastic facies of Perry Mountain Formation. Dead River Formation is undated, but is assigned a Late Cambrian(?) and Ordovician (Whiterockian) age based on position below Ordovician (Whiterockian and Mohawkian) Ammonoosuc Volcanics and above Cambrian(?) Hurricane Mountain Formation. AA - Low rank amphibolite facies AB - Medium rank amphibolite facies E - Epidote-amphibolite facies GS - Greenschist facies W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith Q - Interbedded pelite and sandstone
Primary rock type	quartzite
Secondary rock type	phyllite
Other rock types
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > Quartzite (Bed)Protolith Q - Interbedded pelite and sandstone AA - Low rank amphibolite facies AB - Medium rank amphibolite facies E - Epidote-amphibolite facies GS - Greenschist facies W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Minor Metamorphic > Metasedimentary > Metaclastic > Phyllite (Bed)Protolith Q - Interbedded pelite and sandstone AA - Low rank amphibolite facies AB - Medium rank amphibolite facies E - Epidote-amphibolite facies GS - Greenschist facies W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite
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. USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Franklin - Oxford - Piscataquis - Somerset