|Name||Ordovician - Cambrian Hurd Mountain Formation, basalt member|
|Geologic age||Ordovician - Cambrian|
Igneous > Volcanic > Mafic-volcanic > BasaltW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith V - Basaltic volcanic rocks
|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.|
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.