Rhode Island Formation (MAPAr;0)

Rhode Island Formation - Sandstone, graywacke, shale and conglomerate; minor beds of meta-anthracite. Fossil plants. Rhode Island Formation is thickest and most extensive formation in Narragansett basin. Does not extend to Norfolk basin. Consists of gray sandstone and siltstone and lesser amounts of gray to black shale, gray conglomerate, and coal beds 10 m thick. Interfingers with Wamsutta Formation in Narragansett basin. In places overlies Dedham Granite. Age is Middle and Late Pennsylvanian (Goldsmith, 1991).

State	Massachusetts
Name	Rhode Island Formation
Geologic age	Upper and Middle Pennsylvanian
Original map label	Pr
Comments	Part of Milford-Dedham Zone (Tertiary and Older Rocks) Secondary unit description per MA023.
Primary rock type	sandstone
Secondary rock type	graywacke
Other rock types	shale; conglomerate
Lithologic constituents	Major Sedimentary > Clastic > Sandstone > Graywacke Sedimentary > Clastic > Sandstone Minor Sedimentary > Coal > Anthracite (Bed)meta-anthracite Sedimentary > Clastic > Conglomerate Sedimentary > Clastic > Mudstone > Shalesome black shale
Map references	Unpublished Digital Geologic Map of Massachusetts received from Rudi Hon at Boston College in 1998.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. [http://pubs.er.usgs.gov/publication/pp1366EJ]
Geographic coverage	Bristol - Norfolk - Plymouth