Rangeley Formation, undivided

Rangeley Formation, undivided.
State New Hampshire
Name Rangeley Formation, undivided
Geologic age Lower Silurian (Llandoverian)
Lithologic constituents
Major
Metamorphic > Metasedimentary > Metaclastic > Metasandstonemetapelite, metasandstone, and local coarse-grained metasandstone lentils
Minor
Metamorphic > Metaigneous > Metavolcanicfelsic metavolcanic rocks
Metamorphic > Metasedimentary > Metaclastic > Quartzitefeldspathic quartzite
Sedimentary > Clastic > Conglomeratequartz-pebble conglomerate
Metamorphic > Granoblastic > Granofelsbiotite granofels
Metamorphic > Metasedimentary > Calc-silicate-rockribbon-banded calc-silicate, calc-silicate pods
Metamorphic > Schist > Pelitic-schist
Comments Part of the Central Maine Composite Terrane (Central Maine Trough) - Variably metamorphosed sedimentary and volcanic rocks of greenschist to granulite facies, locally migmatized. Area includes structural belts between the Monroe fault on the west and the Campbell Hill fault on the east; that is, the Bronson Hill anticlinorium, Piedmont allochthon, Kearsarge-central Maine synclinorium, central New Hampshire anticlinorium, and Rochester-Lebanon (Maine) antiformal synclinorium. Secondary unit description from USGS Geologic Names lexicon (ref. NH047): Mapped undivided and as eight subdivisions. Subdivisions include ribbon-banded calc-silicate of eastern NH (probable equivalent of Patch Mountain Member of Sangerville Formation of central ME); unnamed lower part of Rangeley, which consists of gray, thinly laminated metapelite with local lentils of turbidites and thin quartz conglomerates in western NH and sparse calc-silicate pods and coticule (probable equivalent of member B of Rangeley in ME); basaltic metavolcanics in Dixville region in Piermont allochthon; felsic metavolcanics in Dixville region in Piermont allochthon; schist matrix conglomerate within gray uppermost part of Rangeley in southwestern NH; pink to green, thinly bedded calc-silicate and purple biotite granofels close to transition from lower to upper parts of Rangeley; member C of Rangeley in northeastern NH and ME, consisting of quartz-pebble conglomerate overlain by rusty metapelite and feldspathic quartzite; and an unnamed upper part consisting of rusty-weathering pelitic schist, metasandstone, and local grits with common calc-silicate pods and minor coticule (probable equivalent of member C of Rangeley in ME). Unnamed calcsilicate and granofels unit is traced into Paxton Formation in north-central MA, where it was mapped as a "western belt" of Paxton and Littleton Formations on MA State Geologic Map by Zen and others (1983); rocks previously assigned to Paxton and Littleton Formations are now reassigned to Rangeley Formation in MA on the basis of more recent mapping (Robinson and Goldsmith, 1991). Aleinikoff and Moench (1987) determined an isotopic age of 432 +/-8 Ma using U/Pb methods on felsic metatuff from Rangeley.
References
NGMDB product
Counties Carroll - Coos - Grafton - Hillsborough