Dan River Group
Geologic group in the United States
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The Dan River Group is a geologic group in Virginia and North Carolina associated with the initial rifting of the supercontinent Pangea. It is located on the southern end of a much larger rift valley sequence (the Newark Supergroup) which together formed the Central Atlantic Magmatic Province (CAMP); an extremely large flood basalt eruption that occurred around 201 Ma. It preserves fossils dating back to the Triassic period.[3]
| 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) |
Formations
It contains six geological formations:[2]
- Stoneville Formation (cyclical red mudstone). Sedimentary layer around 600 ft.[4]
- Leaksville Formation (Predominantly red mudstone.)
- Cow Branch Formation (cyclical fossiliferous black/dark grey mudstone with rare coarser lithologies). Sedimentary thickness is around 545 ft. [4]
- 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). It's 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 metamophisis. The extent and volume of magma is unknown due to no exposed dikes or sills at the surface.[5]
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