Culpeper Basin

The Culpeper Basin is one of the Newark Supergroup's Triassic rift basins.[1] Its formation is tied to the initial rifting of the supercontinent Pangea. Volcanism associated with the Culpeper basin was part of a much larger event known as the Central Atlantic magmatic province (CAMP); one of the largest flood basalt eruptions in Earth's history.[2] It lies east of the Appalachian Mountains and extends from the Madison County—Orange County line in Virginia to Frederick, Maryland.[3] A diverse group of sedimentary rocks including siltstone, sandstone, and conglomerate within the basin were intruded by igneous rocks (primarily diabase), which caused thermal metamorphism at the contact with sedimentary rock.[4]

The Culpeper Basin is nearly continuous with the Gettysburg Basin to the north and with the Barboursville Basin to the south.

The Groveton Member of the Bull Run Formation is exposed there.[1] The formation has produced disarticulated fish remains including isolated bones and scales.[1]

Each Sedimentary formation has large basaltic lava flows associated with the initial rifting of Pangea. These are broken up into three pulses:

Mount Zion Church Basalt: This was the first eruption during CAMP volcanism.[5]

Hickory Grove Basalt: This was the second outpouring of basaltic lava during the CAMP eruptions.[6]

Sanders Basalt: This was the final pulse of volcanic activity in the Culpeper Basin.

The large body of diabase in central Montgomery County, Maryland, is known as the Boyds Sill,[7] named after the town of Boyds.

  • Jurassic diabase boulders in the Culpeper Basin northeast of Dulles Airport
  • Balls Bluff Siltstone with diabase intrusion, northern face of Luck Stone Quarry, Manassas
  • Limestone conglomerate of Leesburg Member
  • Another sample of limestone conglomerate
  • Sandstone from southwest the Boyds Sill in Montgomery County, Maryland
  • Unnamed stream exposing diabase of Boyds Sill, Hoyles Mill Trail, Montgomery County, Maryland

Footnotes

  1. ^ a b c "Manassas National Battlefield Park," Hunt, Santucci, and Kenworthy (2006); page 64.
  2. ^ Marzoli, Andrea; Jourdan, Fred; Puffer, John H.; Cuppone, Tiberio; Tanner, Lawrence H.; Weems, Robert E.; Bertrand, Hervé; Cirilli, Simonetta; Bellieni, Giuliano; De Min, Angelo (1 March 2011). "Timing and duration of the Central Atlantic magmatic province in the Newark and Culpeper basins, eastern U.S.A." Lithos. 122 (3): 175–188. doi:10.1016/j.lithos.2010.12.013. ISSN 0024-4937. Retrieved 14 December 2025.
  3. ^ 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.
  4. ^ 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
  5. ^ Weems, Robert; Olsen, Paul (February 1997). "Synthesis and revision of groups within the Newark Supergroup, eastern North America" (PDF). ldeo.columbia.edu. Geological Society of America Bulletin. Retrieved 27 November 2025.
  6. ^ Woodruff, L.G.; Froelich, A.J.; Belkin, H.E.; Gottfried, David (March 1995). "Evolution of tholeiitic diabase sheet systems in the eastern United States: examples from the Culpeper Basin, Virginia-Maryland, and the Gettysburg Basin, Pennsylvania". Journal of Volcanology and Geothermal Research. 64 (3–4): 143–169. doi:10.1016/0377-0273(94)00085-U. Retrieved 29 November 2025.
  7. ^ Fisher, G. W., 1964, The Triassic rocks of Montgomery County. In Geology of Howard and Montgomery Counties, Maryland Geological Survey, Baltimore, Maryland, 1964.)

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.
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