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Hoppin Formation

Hoppin Formation - Quartzite, argillite, and minor limestone; contains Middle Cambrian fauna.
State Massachusetts
Name Hoppin Formation
Geologic age Middle and Lower Cambrian
Comments Part of Milford-Dedham Zone (Tertiary and Older Rocks) Secondary unit description per MA023 as found in USGS Geologic Names lexicon (ref. MA024): Hoppin Formation consists of green and red slaty shale, locally containing calcareous nodules, and lenses of red argillaceous limestone; arkosic quartzite (locally conglomeratic) and sandstone occur at base of formation. Nonconformity at base of formation over Dedham Granite is clearly exposed at Hoppin Hill; Early Pennsylvanian Pondville Conglomerate lies with angular unconformity above. Maximum thickness is approx 244 m. Age is Early and Middle Cambrian (Goldsmith, 1991).
Primary rock type argillite
Secondary rock type quartzite
Other rock types limestone
Lithologic constituents
Major
Metamorphic > Metasedimentary > Metaclastic > Argillite
Minor
Metamorphic > Metasedimentary > Metaclastic > Quartzite
Sedimentary > Carbonate > Limestone
Map references
Unpublished Digital Geologic Map of Massachusetts received from Rudi Hon at Boston College in 1998.
Unit references
Zen, E-An (ed.), Goldsmith, R. (comp.), Ratcliffe, N.M. (comp.), Robinson, P. (comp.), Stanley, R.S. (comp.), Hatch, N.L., Jr., Shride, A.F., Weed, E.G.A., Wones, D.R., 1983, Bedrock Geologic Map of Massachusetts: U.S. Geological Survey, Reston, VA, scale 1: 250,000.
Goldsmith, Richard, 1991, Stratigraphy of the Milford-Dedham zone, eastern Massachusetts; an Avalonian terrane, Chapter E, IN Hatch, N.L., Jr., ed., The bedrock geology of Massachusetts: U.S. Geological Survey Professional Paper, 1366-E-J, p. E1-E62.
USGS Geologic Names Lexicon (GEOLEX)
Counties Bristol - Norfolk