File:Weathered claystones (Pekin Formation, Upper Triassic; Boren Clay Pit, Gulf, North Carolina, USA) 12 (51383713109).jpg

Weathered claystones in the Triassic of North Carolina, 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 an outcrop of soft, weathered claystones in a disused quarry that mined clay to make tile, terra cotta pipes, flower pots, and other objects. The quarry has been inactive for 15 to 20 years before this visit in fall 2012. The site is in the Sanford Sub-Basin of the Deep River Basin, one of many named Triassic rift basins. The rocks are all fine-grained siliciclastics: blocky, yellowish-brown siltstones, silty mudrocks, and soft silty claystones.

Good plant fossils are present in the claystones, usually as whitish-colored impressions / imprints - ferns, horsetails, cycads, cycadeoids, and conifers. Identified plants here include Pekinopteris auriculata, Eoginkgoites, Neocalamites, Otozamites hespera, Cladophebis microphylla, Cynepteris lashiophora, Dictyophyllum, Phlebopteris smithii, and Hopetedion praetermissa. The oldest known plant fossils in all of North Carolina are at this locality.

Stratigraphy: middle Pekin Formation, Chatham Group, Newark Supergroup, Upper Triassic

Locality: western wall of the Boren Clay Pit - inactive clay quarry along the northern side of Gulf Road (= State Road 2139) in the town of Gulf, far-southern Chatham County, central North Carolina, USA (35° 34’ 03.10” North latitude, 79° 17’ 49.30” West longitude)

Geologic map of this area:

Reid, Taylor, & Cumberbatch (2010) - Digital compilation map, Sanford Sub-Basin, Deep River Basin, parts of Lee, Chatham and Moore Counties, North Carolina. North Carolina Geological Survey Open-File Report 2010-07.

For more info., see: