Pound Ridge Granite Gneiss of Bell (1936) and Yonkers Gneiss are post-Grenvillian in age. Probably related to Late Proterozoic extensional tectonics in Laurentia. Pound Ridge has Rb-Sr whole rock isochron age of 583 +/-25 Ma (Mose and Hayes, 1975; D.W. Rankin, unpub. data; recalculated by D.W. Rankin and others).
Source: GNU records (USGS DDS-6; Reston GNULEX).
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