|Name||Perry Mountain Formation, Volcanic facies in Piermont allochthon|
|Geologic age||Lower? - Middle? Silurian|
Igneous > Volcanic > Felsic-volcanic
Igneous > Volcanic > Mafic-volcanic
|Comments||Note that the digital map unit symbol (Spvx) does not match what is on the printed map (Spv) (possible typo?). 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. Perry Mountain Formation = 414+/-4 U/Pb (tuff bed), 412+/-2 U/Pb (tuffisite sill), <430 and >410 U/Pb (rhyolite intrusive unit) per J.N. Aleinikoff, oral commun., June8, 1990. Felsic metatuff = 418+/-4 U/Pb per NH046.|
Lyons, J.B., Bothner, W.A., Moench, R.H., and Thompson, J.B., Jr., 1997, Bedrock Geologic Map of New Hampshire: Reston, VA, U.S. Geological Survey Special Map, 2 sheets, scale 1:250,000.
Lyons, J.B., Zartman, R.E., and Aleinikoff, J.N., 1983, U-Pb ages of zircons from the Ordovician Highlandcroft Plutonic Suite and from Silurian intrusives [abs.]: Geological Society of America Abstracts with Programs, v. 15, p. 187.
|Counties||Coos - Grafton|