Yonkers Gneiss and Pound Ridge Granite Gneiss ages are post-Grenvillian [post-Middle Proterozoic]. Probably related to Late Proterozoic extensional tectonics in Laurentia. Yonkers has Rb-Sr whole-rock isochron age of 563 +/-35 Ma (Long, 1969; recalculated by D.W. Rankin and others).
Source: GNU records (USGS DDS-6; Reston GNULEX).
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