Fauquier Formation - Metasiltstone and phyllite

Medium- to dark-gray (fresh), very-pale-orange (weathered), very-fine grained, laminated metasiltstone, composed of alternating silty and micaceous layers on the order of a millimeter to several millimeters thick, and phyllite without discernable layers; major minerals are silt-size quartz and sericite; chlorite, biotite, and magnetite occur locally. Thiesmeyer (1939) described these rocks as "varved slates" interpreted as lacustrine deposits. Espenshade (1986) called this unit metarhythmite. The unit is on strike with, and in part equivalent to the Monumental Mills Formation of Wehr (1985), interpreted as de pos it ed in a delta front-slope environment.
State Virginia
Name Fauquier Formation - Metasiltstone and phyllite
Geologic age Proterozoic Z
Lithologic constituents
Major
Metamorphic > Metasedimentary > Metaclastic > Phyllite
Metamorphic > Metasedimentary > Metaclastic > Metasiltstonemeta-argillite
Comments Blue Ridge Anticlinorium (Northern)
References

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.

NGMDB product
Counties Albemarle - Culpeper - Fauquier - Greene - Loudoun - Madison - Rappahannock