The Culpeper Basin is one of the

Newark Supergroup The Newark Supergroup, also known as the Newark Group, is an assemblage of Upper Triassic and Lower Jurassic sedimentary rocks which outcrop intermittently along the United States East Coast. They were deposited in a series of Triassic basins ...

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

rift basins In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben wi ...

. It lies east of the

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. The ...

and extends from the Madison County—

Orange County Orange County most commonly refers to: *Orange County, California, part of the Los Angeles metropolitan area Orange County may also refer to: U.S. counties *Orange County, Florida, containing Orlando *Orange County, Indiana *Orange County, New ...

line in

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the East Coast of the United States, Atlantic Coast and the Appalachian Mountains. The geography an ...

Frederick Frederick may refer to: People * Frederick (given name), the name Nobility Anhalt-Harzgerode * Frederick, Prince of Anhalt-Harzgerode (1613–1670) Austria * Frederick I, Duke of Austria (Babenberg), Duke of Austria from 1195 to 1198 * Frederi ...

Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; ...

.Bedrock map and geotechnical properties of rocks of the Culpeper basin, Virginia and Maryland
Leavy, B.D., Froelich, A.J., and Abram, E.C. Miscellaneous Investigations Series Map I-1313-C. 1983. Map Scale: 1:125,000. A diverse group of sedimentary rocks including

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

, and congolmerate within the basin were intruded by igneous rocks (primarily

diabase Diabase (), also called dolerite () or microgabbro, is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine-gra ...

), which caused thermal

metamorphism Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of ...

at the contact with sedimentary rock.''Geologic history and stratigraphy of the Triassic-Jurassic Culpeper Basin, Virginia'', R. C. Lindholm. GSA Bulletin (1979) 90 (11_Part_II): 1702–1736. https://doi.org/10.1130/GSAB-P2-90-1702 The Culpeper Basin is nearly continuous with the

Gettysburg Basin Gettysburg may refer to: Events * Gettysburg Campaign, a series of American Civil War military engagements in the Main Eastern Theater. ** Battle of Gettysburg, July 1–3 military engagements during the 1863 Gettysburg Campaign ** Retreat from ...

to the north and with the

Barboursville Basin Barboursville is the name of several places in the United States of America: * Barboursville, Virginia * Barboursville, West Virginia * Barboursville (James Barbour) Barboursville is the ruin of the mansion of James Barbour, located in Barbours ...

to the south. The Groveton Member of the Bull Run Formation is exposed there. The formation has produced disarticulated fish remains including isolated bones and scales. The large body of diabase in central

Montgomery County Montgomery County may refer to: Australia * The former name of Montgomery Land District, Tasmania United Kingdom * The historic county of Montgomeryshire, Wales, also called County of Montgomery United States * Montgomery County, Alabama * Mon ...

, Maryland, is known as the Boyds

Sill Sill may refer to: * Sill (dock), a weir at the low water mark retaining water within a dock * Sill (geology), a subhorizontal sheet intrusion of molten or solidified magma * Sill (geostatistics) * Sill (river), a river in Austria * Sill plate, a ...

,Fisher, G. W., 1964, The Triassic rocks of Montgomery County. ''In'' Geology of Howard and Montgomery Counties, Maryland Geological Survey, Baltimore, Maryland, 1964.) named after the town of Boyds. File:Diabase boulders 20210302.jpg, Jurassic

boulders in the Culpeper Basin northeast of

Dulles Airport Washington Dulles International Airport , typically referred to as Dulles International Airport, Dulles Airport, Washington Dulles, or simply Dulles ( ), is an international airport in the Eastern United States, located in Loudoun County and F ...

File:Balls Bluff Siltstone with Diabase Intrusion (4802113326).jpg, Balls Bluff Siltstone with diabase intrusion, northern face of Luck Stone Quarry, Manassas File:Leesburg Member, Balls Bluff Siltstone (4802116200).jpg, Limestone conglomerate of Leesburg Member File:Limestone conglomerate Leesburg VA Lb1.jpg, Another sample of limestone conglomerate File:Sandstone Culpepper Basin Maryland.jpg, Sandstone from southwest the Boyds Sill in

, Maryland File:Diabase of Boyds Sill Hoyles Mill Trail 2021.jpg, Unnamed stream exposing diabase of Boyds Sill, Hoyles Mill Trail, Montgomery County, Maryland

Footnotes

References

* Hunt, ReBecca K., Vincent L. Santucci and Jason Kenworthy. 2006. "A preliminary inventory of fossil fish from National Park Service units." in S.G. Lucas, J.A. Spielmann, P.M. Hester, J.P. Kenworthy, and V.L. Santucci (ed.s), Fossils from Federal Lands. New Mexico Museum of Natural History and Science Bulletin 34, pp. 63–69. {{Authority control Geology of Maryland