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Geologic units in Jefferson county, West Virginia

Additional scientific data in this geographic area

Elbrook Formation (Cambrian) at surface, covers 30 % of this area

Elbrook Formation - thin-bedded blue-gray argillaceous limestone and platy shale, with some siliceous limestone and minor dolomite.

Stonehenge Limestone (Ordovician) at surface, covers 15 % of this area

Stonehenge Limestone - gray, thin-bedded to massive, fossiliferous limestone, largely mechanically deposited, with small black chert nodules and beds of "edgewise" conglomerate. The highly resistant Stoufferstown Limestone member is found at the base.

Rockdale Run Formation (Ordovician) at surface, covers 12 % of this area

Rockdale Run Formation - bluish to light gray and brown, thick-bedded dolomite and limestone, containing gray chert and zones of Cryptozoa and Lecanospira.

Harpers Formation (Cambrian) at surface, covers 10 % of this area

Harpers Formation (Chilhowee Group) - greenish-gray phyllite, with interbeds of fine-grained quartzite.

Lithology: phyllite; quartzite

Waynesboro Formation (Cambrian) at surface, covers 9 % of this area

Waynesboro Formation - variegated shale and sandstone, commonly red or brown. Middle zone contains much dolomite and limestone. Contains the Olenellus fauna of Early Cambrian age, although its upper portion may be of Middle Cambrian age.

Tomstown Dolomite (Cambrian) at surface, covers 9 % of this area

Tomstown Dolomite - thick-bedded, blue-gray, aphanitic, saccharoidal, and splintery dolomite, weathering coffee-brown; some siliceous limestone and black chert. Contains commercial beds of white, pure, low-silica dolomite.

Ordovician, middle calcareous units (Ordovician) at surface, covers 5 % of this area

Ordovician - middle calcareous units.

Lithology: limestone

Antietam Formation (Cambrian) at surface, covers 5 % of this area

Antietam Formation (Chilhowee Group) - gray to white quartzite, sandstone and quartz-schist; thick-bedded, and resistant; contains Scolithus.

Lithology: quartzite; sandstone; schist

Weverton-Loudoun Formation (Cambrian) at surface, covers 3 % of this area

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

Pinesburg Station Dolomite (Ordovician) at surface, covers 2 % of this area

Pinesburg Station Dolomite - fine- to medium-crystalline, brown to light gray dolomite, containing nodular chert.

Conococheague Formation (Cambrian) at surface, covers 0.5 % of this area

Conococheague Formation - predominantly algal and mechanically deposited limestone, with interbeds of aphanitic limestone and dolomite. Contains siliceous and dolomitic laminations. Resistant sandy Big Spring Station Member near the base.

Trenton Group and Black River Group, undivided (Ordovician) at surface, covers 0.2 % of this area

Trenton Group and Black River Group, undivided - Trenton Group: dark, crystalline, nodular, and argillaceous limestones, with some metabentonite streaks. Includes the Nealmont, Oranda, Edinburg, and the upper part of the Chambersburg Limestones of northeastern West Virginia; also the Moccasin and Eggleston Formation of Mercer and Monroe Counties. Black River Group: predominantly gray aphanitic limestones, with many bioclastic streaks; siliceous in the lower part.

Lithology: limestone; bentonite

Martinsburg Formation (Ordovician) at surface, covers 0.1 % of this area

Martinsburg Formation - predominantly gray to dark shale, yellowish in the upper portion. Contains scattered thin limestone and sandstone interbeds, particularly in the lower portion. The upper portion constitutes the Reedsville Shale.

Lithology: shale; limestone; sandstone

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.

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.

Chilhowee Group; Harpers Formation (Cambrian) at surface, covers < 0.1 % of this area

Harpers Formation - Brown to dark bluish-gray banded shale, to light bluish-gray, finely laminated phyllite; distinctively pale purple in basal part; bedding obscured by cleavage; increasingly metamorphosed toward east from shale to slate and phyllite; estimated thickness 2,000 feet.

Lithology: shale; phyllite; slate

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

Tomstown Dolomite - Interbedded light gray to yellowish-gray, thin- to thick-bedded dolomite and limestone; some shale layers; gradational contact with Antietam; thickness 200 to 1,000 feet.

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

Elbrook Limestone - Light blue, laminated, argillaceous limestone and calcareous shale; some dolomite; thickness 1,400 to possibly 3,000 feet.