Dan River Group
| Dan River Group | |
|---|---|
| Stratigraphic range: Late Triassic | |
| Type | Half graben rift basin; principle normal fault zone on the northwest basin margin.[1] |
| Unit of | Newark Supergroup |
| Sub-units | Stoneville Formation, Cow Branch Formation, Leaksville Formation, Dry Fork Formation, Walnut Cove Formation, Pine Hall Formation |
| Area | 126,300 acres |
| Thickness | 5,000-8,000 ft[1][2] |
| Location | |
| Region | Virginia, North Carolina |
| Country | United States |
| Type section | |
| Named for | Dan River |
| Named by | Thayer (1970) |
The Dan River Group is a geologic group in Virginia and North Carolina associated with the initial rifting of the supercontinent Pangea. Consisting of nearly 15,000 feet of conglomerate, sandstone, and mudrock overlain in an unconformity on top of older metamorphic rocks that is in fault contact with[3], it is located on the southern end of a much larger rift valley sequence (the Newark Supergroup.) This together formed the Central Atlantic Magmatic Province (CAMP); an extremely large flood basalt eruption that occurred around 201 Ma, causing the Triassic-Jurassic extinction event.[4] It preserves fossils dating back to the Triassic period.[5]
Formations
It contains six geological formations:[2]
- Stoneville Formation (cyclical red mudstone). Sedimentary layer around 600 ft.[3]
- Leaksville Formation (Predominantly red mudstone.)
- Cow Branch Formation (cyclical fossiliferous black/dark grey mudstone with rare coarser lithologies). Sedimentary thickness is around 545 ft. [3]
- Dry Fork Formation (cyclical tan/red sandstone and grey/purple/red mudstone)
- Walnut Cove Formation (cyclical black/grey mudstone, sandstone, and coal)
- Pine Hall Formation (coarse tan sandstone and red mudstone). Its thickness ranges between 524-2,000 feet in depth.[2]
Volcanism
While the exact extent of lava erupted in the Dan River formation is not known, there is evidence of diabase dikes/sills found here. These magma bodies heated the ground around them, causing sedimentary rocks and coal to alter; a process known as contact metamorphosis. The extent and volume of magma is unknown due to no exposed dikes or sills at the surface.[6]
See also
References
- 1 2 Reid, Jeffrey; Taylor, Kenneth (January 2013). "Mesozoic rift basins – Onshore North Carolina and southcentral Virginia, U.S.A.: Deep River and Dan River - Danville total petroleum systems (TPS) and assessment units (AU) for continuous gas accumulation". www.deq.nc.gov. North Carolina Geological Survey. Retrieved 22 October 2025.
- 1 2 3 Olsen, P. E.; Schlische, R. W; Gore, P. J. W. (1989). "GEOLOGY OF THE DAN RIVER-DANVILLE BASIN" (PDF). ldeo.columbia.edu. Field Guide to the Tectonics, stratigraphy, sedimentology, and paleontology of the Newark Supergroup, eastern North America. International Geological Congress. Archived (PDF) from the original on 2017-03-09. Retrieved 22 October 2025.
- 1 2 3 "Geolex — CowBranch publications". ngmdb.usgs.gov. GNU records (USGS DDS-6; Reston GNULEX). Retrieved 22 October 2025.
- ↑ Blackburn, Terrence J.; Olsen, Paul E.; Bowring, Samuel A.; McLean, Noah M.; Kent, Dennis V.; Puffer, John; McHone, Greg; Rasbury, E. Troy; Et-Touhami, Mohammed (2013-05-24). "Zircon U-Pb Geochronology Links the End-Triassic Extinction with the Central Atlantic Magmatic Province". Science. 340 (6135): 941–945. doi:10.1126/science.1234204. ISSN 0036-8075.
- ↑ Ghatak, A.; Basu, A. R. (December 2012). "Central Atlantic Magmatic Province (CAMP): The Palisade Sill Connection". AGU Fall Meeting Abstracts. pp. DI53A–2371. Retrieved 22 October 2025.
- ↑ Reid, Jeffery; Milici, Robert (8 November 2008). "Hydrocarbon Source Rocks in the Deep River and Dan River Triassic Basins, North Carolina" (PDF). pubs.usgs.gov. The USGS. Retrieved 22 October 2025.
- Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Archived from the original on 25 March 2022. Retrieved 17 December 2021.