Rhode Island Formation

Conglomerate, sandstone, and graywacke. 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
Lithologic constituents
Major
Sedimentary > Clastic > Siltstone
Sedimentary > Clastic > Sandstone
Minor
Sedimentary > Coal > Anthracite
Sedimentary > Clastic > Conglomerate
Sedimentary > Clastic > Mudstone > Shale > Black-shale
Comments Part of Milford-Dedham Zone (Tertiary and Older Rocks). Secondary unit description per MA023.
References
NGMDB product
Counties Bristol