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Mineral Resources > Online Spatial Data > Geology > by state > Virginia Geology

Geologic units in Loudoun county, Virginia

[Additional scientific data in this geographic area]

Frederick Limestone (Cambrian) at surface, covers < 0.1 % of this area

Frederick Limestone - Limestone.

Lithology: limestone

Metatrondhjemite (Proterozoic Y) at surface, covers < 0.1 % of this area

Metatrondhjemite

Lithology: biotite gneiss

Swift Run Formation (Proterozoic Z) at surface, covers 2 % of this area

Swift Run Formation - Phyllite, metasandstone, and metaconglomerate.

Lithology: phyllite; sandstone; meta-conglomerate; schist; quartzite; slate

Fauquier Formation - Metasiltstone and phyllite (Proterozoic Z) at surface, covers 0.2 % of this area

Fauquier Formation - Meta-argillite is laminated metasiltstone; and phyllite.

Lithology: meta-argillite; phyllite

Layered Leucocratic Granite Gneiss (Proterozoic Y) at surface, covers 4 % of this area

Layered leucocratic granite gneiss

Lithology: granitic gneiss

Diabase (Jurassic) at surface, covers 9 % of this area

Diabase

Lithology: diabase

Newark Supergroup; Conglomerate, mixed clasts (Upper Triassic) at surface, covers 3 % of this area

Conglomerate, mixed clasts

Lithology: conglomerate

Newark Supergroup; Conglomerate, greenstone clasts (Upper Triassic) at surface, covers 4 % of this area

Conglomerate, greenstone clasts

Lithology: conglomerate

Biotite Granite Gneiss (Proterozoic Y) at surface, covers 1 % of this area

Biotite granite gneiss

Lithology: granitic gneiss

Quartzite and Quartz-Sericite Tectonite (Proterozoic Y) at surface, covers 0.5 % of this area

Quartzite and quartz-sericite tectonite

Lithology: quartzite; tectonite

Charnockite (Proterozoic Y) at surface, covers 0.4 % of this area

Charnockite.

Lithology: granitic gneiss

Newark Supergroup; Triassic shale and siltstone (Triassic) at surface, covers 6 % of this area

Interbedded shale and siltstone

Lithology: shale; siltstone

Fauquier Formation - Arkosic metasandstone (Proterozoic Z) at surface, covers 0.3 % of this area

Fauquier Formation - Arkosic metasandstone

Lithology: metasedimentary rock

Fauquier Formation -Meta-arkose and metasiltstone (Proterozoic Z) at surface, covers 0.2 % of this area

Fauquier Formation - Crossbedded metasandstone

Lithology: metasedimentary rock

Newark Supergroup; Jurassic Basalt (Lower Jurassic) at surface, covers 1 % of this area

basalt

Lithology: basalt

Metanorite and Metadiorite (Proterozoic Y) at surface, covers 0.5 % of this area

Metanorite and Metadiorite - Metanorite and metadiorite

Lithology: norite

Marshall Metagranite (Proterozoic Y) at surface, covers 12 % of this area

Marshall Metagranite - Medium-granied biotite metagranite

Lithology: granite

Marshall Metagranite (Proterozoic Y) at surface, covers 1 % of this area

Marshall Metagranite - Coarse-grained metagranite

Lithology: granite

Mather Gorge Formation -- Schist (Proterozoic Z-Cambrian) at surface, covers < 0.1 % of this area

Mather Gorge Formation - Schist.

Lithology: schist; gneiss; metasedimentary rock; calc-silicate rock

Tomstown Dolomite (Cambrian) at surface, covers < 0.1 % of this area

Tomstown Dolomite - Dolomite, in part cherty.

Lithology: dolostone (dolomite); chert

Porphyoblastic Biotite-Plagioclase Augen Gneiss (Proterozoic Y) at surface, covers < 0.1 % of this area

Porphyoblastic biotite-plagioclase augen gneiss

Lithology: augen gneiss

New Oxford Formation (Triassic) at surface, covers < 0.1 % of this area

New Oxford Formation - Red, maroon, and gray sandstone, siltstone, and shale; basal conglomerate member: From vicinity of Maryland Rte. 73 and southward, limestone conglomerate with red and gray calcareous matrix; northward, quartz conglomerate with red sandy matrix; estimated total thickness 4,500 feet.

Lithology: shale; sandstone; siltstone; conglomerate

Newark Supergroup; Jurassic Interbedded Sandstone and Siltstone (Lower Jurassic) at surface, covers 1 % of this area

Interbedded sandstone and siltstone

Lithology: sandstone; siltstone

Chilhowee Group (Cambrian) at surface, covers 4 % of this area

Chilhowee Group - Appalachian Plateaus and Valley and Ridge: Quartzite, conglomerate, feldspathic sandstone, phyllite, and minor ferruginous sandstone and volcanic rocks. Blue Ridge Anticlinorium: Conglomerate, quartzite, metasiltstone, and phyllite.

Lithology: quartzite; conglomerate; sandstone; phyllite; meta-argillite; volcanic rock (aphanitic)

Hornblende Gneiss (Proterozoic Y) at surface, covers 3 % of this area

Hornblende gneiss

Lithology: mafic gneiss

Catoctin Formation - Metabasalt (Proterozoic Z-Cambrian) at surface, covers 15 % of this area

Catoctin Formation - Metabasalt.

Lithology: meta-basalt

Chilhowee Group; Weverton Formation (Late Precambrian - Cambrian) at surface, covers < 0.1 % of this area

Weverton Formation - Interbedded white to dark gray, thin-bedded, micaceous, ferruginous, and sericitic quartzites, phyllites, and white, thick-bedded, ledge-making quartzites; some gray to brown ferruginous quartz conglomerate and purple-banded phyllite; thickness approximately 100 feet in south, increases to 425 feet in north.

Lithology: quartzite; phyllite; conglomerate

Leucocratic Metagranite (Proterozoic Y) at surface, covers 5 % of this area

Leucocratic metagranite

Lithology: granite

Catoctin Formation - Metasedimentary rocks (Proterozoic Z-Cambrian) at surface, covers < 0.1 % of this area

Catoctin Formation - Metasedimentary rocks

Lithology: quartzite; sandstone; meta-argillite; phyllite

Fauquier Formation - Metaconglomerate (Proterozoic Z) at surface, covers < 0.1 % of this area

Fauquier Formation - Pebble or cobble conglomerate.

Lithology: conglomerate

Robertson River Igneous Suite - Cobbler Mountain alkali feldspar quartz syenite (Proterozoic Z) at surface, covers 0.2 % of this area

Robertson River Igneous Suite - Cobbler Mountain alkali feldspar quartz syenite

Lithology: alkali syenite

Metaperidotite, Metapyroxenite, and Hornblende Metagabbro (Proterozoic Y) at surface, covers < 0.1 % of this area

Metaperidotite, Metapyroxenite, and Hornblende Metagabbro - Serpentinite is metaperidotite, Hornblende metagabbro

Lithology: serpentinite; greenstone

Mather Gorge Formation - Metagraywacke (Proterozoic Z-Cambrian) at surface, covers < 0.1 % of this area

Mather Gorge Formation - Metargillite is metagraywacke

Lithology: meta-argillite

Catoctin Formation - Metarhyolite (Proterozoic Z-Cambrian) at surface, covers 0.4 % of this area

Catoctin Formation- Metarhyolite

Lithology: rhyolite

Catoctin Metabasalt (Late Precambrian) at surface, covers < 0.1 % of this area

Catoctin Metabasalt - Thick-bedded metabasalt with amygdaloidal layers and secondary veins of quartz, calcite, and epidote; interbedded green tuffaceous phyllite and blue amygdaloidal metaandesite.

Lithology: meta-basalt; phyllite

Catoctin Formation - Metabasalt breccia (high titanium) (Proterozoic Z-Cambrian) at surface, covers < 0.1 % of this area

Catoctin Formation - Metabasalt breccia (high titanium)

Lithology: meta-basalt

Garnetiferous Leucocratic Metagranite (Proterozoic Y) at surface, covers 8 % of this area

Garnetiferous leucocratic metagranite

Lithology: granite

Newark Supergroup; Sandstone, undifferentiated (Upper Triassic) at surface, covers 4 % of this area

Sandstone, undifferentiated

Lithology: sandstone

Weverton-Loudoun Formation (Cambrian) at surface, covers 0.1 % of this area

Weverton-Loudoun Formation (Chilhowee Group) - tough quartzitic sandstones, conglomerates, and shale.

Lithology: sandstone; shale; conglomerate

Newark Supergroup; Triassic Sandstone, Siltstone, and Shale (Upper Triassic) at surface, covers 11 % of this area

Interbedded sandstone, siltstone, and shale

Lithology: sandstone; siltstone; shale

Marble (Proterozoic Z) at surface, covers 0.2 % of this area

Marble.

Lithology: marble

Porphyroblastic Granite Gneiss (Proterozoic Y) at surface, covers 2 % of this area

Porphyroblastic granite gneiss

Lithology: granitic gneiss

Garnet-Graphite Paragneiss (Proterozoic Y) at surface, covers 0.9 % of this area

Garnet-graphite paragneiss

Lithology: paragneiss

Catoctin Formation (Cambrian/Precambrian) at surface, covers < 0.1 % of this area

Catoctin Formation - predominantly a greenstone. Basic lava flows, schist and gneiss, containing chlorite, plagioclase, amphibolite, and epidote. Includes minor quantities of arkose and thin clastics. Western subsurface extension presently unknown.

Lithology: greenstone; schist; gneiss; amphibolite; arkose