Ordovician - Cambrian Dead River formation (MEOCAd;0)

State	Maine
Name	Ordovician - Cambrian Dead River formation
Geologic age	Ordovician - Cambrian
Original map label	OCAd
Comments	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. (ME004) Unit description from USGS GEOLEX website (ME078). AB - Medium rank amphibolite facies E - Epidote-amphibolite facies Protolith Q - Interbedded pelite and sandstone
Primary rock type	slate
Secondary rock type	quartzite
Other rock types	phyllite
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > SlateAB - Medium rank amphibolite facies E - Epidote-amphibolite facies Protolith Q - Interbedded pelite and sandstone Minor Metamorphic > Metasedimentary > Metaclastic > PhylliteAB - Medium rank amphibolite facies E - Epidote-amphibolite facies Protolith Q - Interbedded pelite and sandstone Metamorphic > Metasedimentary > Metaclastic > QuartziteAB - Medium rank amphibolite facies E - Epidote-amphibolite facies Protolith Q - Interbedded pelite and 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. Moench, R.H., Boone, G.M., Bothner, W.A., Boudette, E.L., Hatch, N.L., Jr., Hussey, A.M., III, Marvinney, R.G. and Aleinikoff, J.N., 1995, Geologic map of the Sherbrooke-Lewiston area, Maine, New Hampshire, and Vermont, United States, and Quebec, Canada: U.S. Geological Survey Miscellaneous Investigations Series Map, I-1898-D, 56 p., 2 sheets, scale 1:250,000, Prepared in cooperation with the Maine Geological Survey and the New Hampshire Geological Survey. [http://pubs.er.usgs.gov/publication/i1898D] USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Franklin - Oxford