Lunga Reservoir Formation (VACAl;0)

State	Virginia
Name	Lunga Reservoir Formation
Geologic age	Cambrian
Original map label	[l
Comments	Western Piedmont, Northern. From expanded explanation (ref. VA002): Lunga Reservoir Formation (Pavlides, 1989; 1990). Metadiamictite, characterized by a nonstratified, micaceous quartzofeldspathic matrix resembling a granitoid, containing rounded to subrounded silt- to sand-sized quartz and plagioclase grains, fine-grained and porphyroblastic muscovite, green porphyroblastic biotite, garnet and magnetite. Granule-, pebble-, and cobble-sized lumps of milky quartz are ubiquitous; mica schist and gneiss clasts are common; calc-silicate clasts are rare. Pebble-, cobble-, and boulder-sized fragments of mafic and ultramafic rock are sparsely distributed in the southern part of the outcrop belt, but are locally abundant in the north. Locally along the contact with the Chopawamsic Formation, the Lunga Resevoir contains exotic fragments similar to lithologies found in the Chopawamsic. The Lunga Resevoir is intruded by Occoquan Granite.
Primary rock type	metasedimentary rock
Secondary rock type	meta-conglomerate
Other rock types
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > Metasandstonemetadiamictite Minor Metamorphic > Metasedimentary > Metaclastic > Metaconglomerate
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	Prince William - Stafford