The Yorkshire Formation, here named, is a thin discontinuous precursory melange underlying the Piney Branch Complex in Fairfax Co., VA. It consists of quartz-plagioclase-chlorite granofels with a pronounced scaly foliation, and contains fragments of quartz, serpentinite, metagabbro, plagiogranite and mafic volcanic rocks. It and the Piney Branch form an allochthon which was emplaced on the Peters Creek Schist after the metamorphism of the Peters Creek. The discontinuous nature of the Yorkshire is attributed to partial shearing-out during transport. Age is Late Proterozoic and (or) Early Cambrian as movement of the allochthon began in Late Proterozoic and ended during the Taconic Orogeny.

Source: GNU records (USGS DDS-6; Reston GNULEX).