Hyaloclastite pillow breccia (Kline and others, 1990). Poorly-sorted assemblages of ellipsoidal to angular clasts of metabasalt in a finer-grained matrix; clasts range in size from 1 cm to greater than 1 m across, but generally are on the order of 2 to 15 cm. Mineralogy and textural features in clasts are identical to those in Catoctin metabasalt (CZb). Matrix consists of coarse- to fine-grained material of similar mineralogy to clasts, in a mesostasis that may constitute up to 30 percent of the matrix. Breccias are gen er al ly matrix supported. Pillows and pillow breccias are locally delineated by concentrations of epidote + quartz on rims and in interstices; pillows are flattened and ellipsoidal, and range up to about 3 m in maximum dimension (Kline and others, 1990). Thickness is on the order of 300 m.
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.