Waterford Group - Rope Ferry Gneiss (RIZwr;0)

Waterford Group - Rope Ferry Gneiss

Light- 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; local layers of amphibolite.

State	Rhode Island
Name	Waterford Group - Rope Ferry Gneiss
Geologic age	Late Proterozoic? or older?
Lithologic constituents	Major 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. Incidental Metamorphic > Amphibolite
Comments	Part of Hope Valley Subterrane. Per printed map: age of rock based on radiometric data from RI012.
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. 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.
NGMDB product	NGMDB product page for 19719
Counties	Washington

Waterford Group - Rope Ferry Gneiss

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.