Ordovician unnamed sulfidic pelite

Ordovician unnamed sulfidic pelite
State Maine
Name Ordovician unnamed sulfidic pelite
Geologic age Ordovician
Lithologic constituents
Major
Sedimentary > Clastic > Mudstone (Carbonaceous)GS - Greenschist facies; Protolith C - Sulfidic/carbonaceous pelite
Comments Divided into lower graywacke member 300 m thick and upper shale member 600 m thick in type area. Overlies Middle Ordovician volcanic rocks; underlies Silurian Greenvale Cove Formation. (ME041) Also: Geographically extended into NH from western ME. Mapped in various areas in Bronson Hill-Boundary Mountains anticlinorium. In area of Rangeley Lake, ME, divided into euxinic shale and graywacke member, an underlying graywacke member, and a felsic volcanic member that grades laterally with graywacke member; also includes garnet granofels unit at Loon Lake. In Old Speck Mountain, ME, and Milan, NH, 15-min quads, only euxinic shale and graywacke member is exposed. In Littleton and Moosilauke, NH, 15-min quads, divided into upper euxinic shale and graywacke member and a conformably underlying felsic volcanic member (which, north of Ammonoosuc fault, is divided into two layers separated by a sedimentary and mafic volcanic facies). Felsic volcanic member and sedimentary and mafic volcanic facies were previously mapped as upper member of Ammonoosuc Volcanics by Moench (1990, 1992). Quimby is here assigned Ordovician (Cincinnatian) age on basis of U-Pb zircon age of 444 +/-4 Ma obtained from basal felsic metatuff of felsic volcanic member (Aleinikoff and Moench, 1992); because age is within error margin of Ordovician-Silurian boundary of Tucker and others (1991; about 441 Ma) possibility exists that uppermost Quimby may be Silurian. Unit description from USGS GEOLEX website (ME078). GS - Greenschist facies; E - Epidote-amphibolite facies; AA - Low rank amphibolite facies; AB - Medium rank amphibolite facies; Protolith Q - Interbedded pelite and sandstone.
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.

NGMDB product
Counties Aroostook - Penobscot - Washington