|Name||Waterford Group - Rope Ferry Gneiss|
|Geologic age||Late Proterozoic? or older?|
Metamorphic > GneissLight- to dark gray, fine- to medium-grained tonalite gneiss composed of plagioclase, quartz biotite, and hornblende, commonly interlayered with granite gneiss composed of microcline, plagioclase, quartz, biotite, and hornblende.
Metamorphic > Amphibolite
|Comments||Part of Hope Valley Subterrane. Per printed map: age of rock based on radiometric data from RI012.|
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.
Zartman, R.E., Hermes, O.D., and Pease, M.H., Jr., 1988, Zircon crystallization ages, and subsequent disturbance events, in Gneissic rocks of eastern Connecticut and western Rhode Island: American Journal of Science, v. 288, p. 376-402.