Pekin Formation

On the surface, the Pekin Formation is exposed only as a long, narrow strip along the western edge of the Sanford Sub-basin. It is both the oldest and stratigraphically lowest formation in the sub-basin. As such, it unconformably overlies the much older eroded and metamorphosed Proterozoic to Cambrian aged metasediments and metavolcanic rocks of the Piedmont. The upper boundary grades into the overlying Cumnock Formation, distinguished by its fine-grained grey lacustrine sediments. The Pekin Formation was deposited in a half-graben that formed as part of a series of rift basins that make up the Newark Supergroup during the breakup of the supercontinent Pangaea and subsequent opening of the Atlantic Ocean. As such, the Pekin, Cumnock and Sanford formations have been restricted to just the Sanford Sub-basin where they can be recognised. ==Geology==

The base of the formation is composed of a roughly thick layer of grey conglomerate, historically referred to as "millstone grit". This unit has been interpreted as alluvial fan deposits made up of material derived from the Piedmont to the west flowing down in a southeasterly direction. The remainder of the Pekin Formation is made up of red to brown and purple sandstones, siltstones and mudstones, along with deposits of conglomerate and shale that altogether support a fluvial and floodplain deposition environment. Unlike the lowest layers, sedimentation for the rest of the Pekin Formation had switched to a source in the highlands to the southeast, with rivers and streams in the upper Pekin flowing towards the north and northwest. The overall climate is interpreted as being warm and humid with highly seasonal rainfall. Clays from the Pekin Formation have been used extensively for the production of pottery, bricks and tiles, namely the Boren and Pomona pits. These two quarries have historically been the site of fossil discoveries, preserving both plants and animals, as well as trace fossils, although these quarries are now disused and some have filled with water. However, excavations by palaeontologists have been continued in a new brick quarry (Merry Oaks Quarry) by the North Carolina Museum of Natural Sciences (NCMNS) at a site labelled NCPALEO 1902. These excavations have uncovered various new vertebrate fossil discoveries, including the relatively complete remains of new Triassic archosaurs. The age of the Pekin Formation has been estimated based on biostratigraphy and magnetostratigraphy to the Late Carnian (or Tuvalian), supported by correlations with faunas in western North America. ==Paleobiota==

, Eoginkgoites, Neocalamites, Otozamites hespera, Cladophebis microphylla, Cynepteris lashiophora, Dictyophyllum, Phlebopteris smithii, and Hopetedion praetermissa''. A variety of plant and vertebrate fossils have been recovered from the Pekin Formation, the including partial skeletons of large vertebrates. The Boren pits preserves abundant plant megafossils, most commonly cycads and bennettitales, as well as horsetails, various ferns and conifers. Some of the most notable finds include an intact specimen of the early palm-like cycad Leptocycas gracilis, as well as a new species of the bennettitale Williamsonia, W. carolinensis, that preserves rare reproductive organs and suggests that it and the leaf Eoginkgoites belong to the same plant. Invertebrate fossils from the Boren pits include conchostracans (clam shrimps) and clams, as well as numerous Scoyenia burrow trace fossils likely made by a crayfish-like decapod. Vertebrate remains are more common in the Pomona pit, which has preserved the fragmentary remains of archosaurs, phytosaurs, and synapsids, as well as fish bones and scales. Fossil footprints and trackways of tetrapods have also been recorded from the Pomona pit (with a single print from the Boren pit), including bipedal three-toed footprints that may have been made by early dinosaurs. Archosaurus and Rhynchosaurus are likely only provisional labels. Phytosaurs Pseudosuchians Synapsids Fishes Crustaceans Plants A diverse flora is known from the formation: ==See also==