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Hoppin Formation

Hoppin Formation - Quartzite, argillite, and minor limestone; contains Middle Cambrian fauna.
StateMassachusetts
NameHoppin Formation
Geologic ageMiddle and Lower Cambrian
Original map labelEh
CommentsPart 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 typeargillite
Secondary rock typequartzite
Other rock typeslimestone
Lithologic constituents
Major
Metamorphic > Metasedimentary > Metaclastic > Argillite
Minor
Sedimentary > Carbonate > Limestone
Metamorphic > Metasedimentary > Metaclastic > Quartzite
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Unpublished Digital Geologic Map of Massachusetts received from Rudi Hon at Boston College in 1998.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)
Geographic coverageBristol - Norfolk

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