Hoppin Formation (RICAh;0)

State	Rhode Island
Name	Hoppin Formation
Geologic age	Cambrian
Original map label	Ch
Comments	Part of Esmond-Dedham Subterrane (West Bay Area) Secondary unit description from USGS Geologic Names lexicon (ref. RI013): 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. Report includes geologic maps, measured sections, and correlation charts. [Chapters A-J in U.S. Geological Survey Professional Paper 1366 are intended as explanations and (or) revisions to 1:250,000-scale MA State bedrock geologic map of Zen and others (1983).] Source: GNU records (USGS DDS-6; Reston GNULEX).
Primary rock type	argillite
Secondary rock type	arenite
Other rock types	limestone
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > Argillite Sedimentary > Clastic > Sandstone > Arenitequartz arenite Minor Sedimentary > Carbonate > Limestone
Map references	Hermes, O.D., Gromet, L.P., Murray, D.P., Hamidzada, N.A., 1994, Geologic Map of Rhode Island, file name = bedrock_shp.zip (870kb) obtained from Rhode Island Geographic Information System, http://www.edc.uri.edu/rigis-spf/Statewide/state.html#geology , shapefile or interchange file, scale 1/100,000. [http://www.edc.uri.edu/rigis-spf/Statewide/state.html#geology]
Unit references	Hermes, O.D. (comp.), Gromet, L.P. (comp.), Murray, D.P. (comp.), Hamidzada, N.A., Skehan, J.W., and Mosher, S., 1994, Bedrock geologic map of Rhode Island: Rhode Island Map Series No. 1, Kingston, Rhode Island, scale 1: 100,000. USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Providence