Piney Branch Complex (VACAZpb;0)

State	Virginia
Name	Piney Branch Complex
Geologic age	Proterozoic Z-Cambrian
Original map label	[Zpb
Comments	Western Piedmont, Northern. From expanded explanation (ref. VA002): Piney Branch Complex (Drake and Morgan, 1981). Heterogeneous assemblage of metamorphosed peridotite, pyroxenite, and gabbro; dominant rock-types include serpentinite, soapstone, and actinolite schist. The unit contains dikes and sheets of plagiogranite. Secondary unit decription from USGS Geologic Names lexicon (ref. VA004): It is a tectonic melange resulting from the deformation of a layered complex that contained repetitive cycles of ultramafic and mafic rocks that are now metamorphosed to serpentinite, soapstone, actinolite schist, and metagabbro, and intruded by dikes and sheet of plagiogranite. It has a discontinuous underlying border of precursory ophiolitic melange, the Yorkshire Formation. The allochthon consisting of the Piney Branch and Yorkshire was thrust upon the Peters Creek Schist, and with it form a composite allochthon that was emplaced on the Sykesville Formation perhaps by gravity sliding. It unconformably underlies the Popes Head Formation. Movement of the Piney Branch began in the Late Proterozoic after the metamorphism of the Peters Creek, and ended during the Taconic Orogeny. Age is Late Proterozoic and (or) Early Cambrian.
Primary rock type	serpentinite
Secondary rock type	schist
Other rock types	plagiogranite
Lithologic constituents	Major Metamorphic > Metaigneous > Serpentinite Metamorphic > Schist Minor Igneous > Plutonic > Graniticplagiogranite
Map references	Digital Representation of the 1993 Geologic Map of Virginia", 2003, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, viewing software not included. This is a digital version of "Geologic Map of Virginia" published in 1993. Available from: https://www.dmme.virginia.gov/commerce/ [https://www.dmme.virginia.gov/commerce/]
Unit references	Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000 Digital Representation of the 1993 Geologic Map of Virginia - expanded explanation: 2003, Commonwealth of Virginia, Department of Mines, Minerals, and Energy, Divsion of Mineral Resources, Publication 147, 85 pp Digital Representation of the 1993 Geologic Map of Virginia", 2003, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, viewing software not included. This is a digital version of "Geologic Map of Virginia" published in 1993. Available from: https://www.dmme.virginia.gov/commerce/ [https://www.dmme.virginia.gov/commerce/]
Geographic coverage	Fairfax - Prince William - Fairfax