Conglomerate in the Triassic of Virginia, USA.

The Newark Supergroup is a thick, geographically-widespread stratigraphic unit in eastern America. It is Late Triassic to Early Jurassic in age and represents sediments and some lava flows that filled up old rift valleys roughly paralleling the modern-day Eastern Seaboard of America. The rift basins formed in the Triassic when the ancient Pangaea supercontinent attempted to break apart, but failed. A successful breakup of Pangaea occurred during the Jurassic. Most of the basin-filling rocks are terrestrial redbeds - hematite-rich siliciclastic sedimentary rocks, such as conglomerate, sandstone, siltstone, and shale, deposited in nonmarine environments.

Seen here is a coarse-grained siliciclastic sedimentary rock from the easternmost Dan River Basin (Danville Basin), a half graben rift valley. Gravel and sand (now conglomerate and sandstone) were deposited adjacent to the half graben's eastern boundary fault, which is a major normal fault.

Stratigraphy: Pinehall Formation, Newark Supergroup, Upper Triassic

Locality: loose piece from roadcut along the northbound exit ramp from Route 58 to Oak Ridge Farms Road, just west of Vandola & west of Danville, southern Pittsylvania County, southern Virginia, USA (36° 34’ 30.09” North latitude, 79° 31’ 20.13” West longitude)

For more info., see: