Light-gray to pink, fine- to medium-grained granite and granodiorite; zoned plagioclase crystals with epidotized and saussuritized cores are characteristic. The granite contains xenoliths of mafic volcanic rocks near its margins. The granite intrudes volcanic rocks east of the Hollister fault zone southeast of Petersburg. Samples from the quarry at Skippers were dated by Rb-Sr whole-rock methods (Bottino and Fullagar, 1968); these data show considerable scatter, implying age of crystallization ranging from 460 Ma to as old as 690 Ma. This unit was shown as Petersburg Granite on the 1963 Geologic Map of Virginia, but field relations, petrology, and the apparent age indicate that it is a separate pluton.
Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000.
Virginia Division of Mineral Resources, 2003, Digital Representation of the 1993 Geologic Map of Virginia, Publication 174, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, scale 1:500,000.