Madrid Formation

Massive to weakly foliated, purple biotite-feldspar granofels, layered calc-silicate, and dark pelitic-sulfidic schist containing calc-silicate pods in upper member; an eastern facies equivalent to the upper part of the Fitch Formation. Locally mapped as the Warner Formation of Nielson (1981) in southern New Hampshire.
State New Hampshire
Name Madrid Formation
Geologic age Upper Silurian?
Lithologic constituents
Major
Metamorphic > Granoblastic > Granofelsmassive to weakly foliated, purple biotite-feldspar granofels
Metamorphic > Metasedimentary > Calc-silicate-rocklayered calc-silicate, dark pelitic-sulfidic schist containing calc-silicate pods in upper member
Metamorphic > Schist > Pelitic-schistdark pelitic-sulfidic 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.
References

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.

https://ngmdb.usgs.gov/Prodesc/proddesc_37338.htm

Nielson, D.L., 1981, The bedrock geology of the Hillsboro quadrangle, New Hampshire: New Hampshire Department of Resources and Economic Developement Bulletin 8, 76 p.

NGMDB product
Counties Carroll - Coos - Grafton - Hillsborough - Merrimack - Strafford