The Cumnock Formation is a

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch a ...

-age

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

. It is found in the Sanford sub-basin of the

Deep River Basin Deep or The Deep may refer to: Places United States * Deep Creek (Appomattox River tributary), Virginia * Deep Creek (Great Salt Lake), Idaho and Utah * Deep Creek (Mahantango Creek tributary), Pennsylvania * Deep Creek (Mojave River tributary) ...

, the southernmost of the large

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

basins forming the

Newark Supergroup The Newark Supergroup, also known as the Newark Group, is an assemblage of Upper Triassic and Lower Jurassic sedimentary and volcanic rocks which outcrop intermittently along the east coast of North America. They were deposited in a series of Tr ...

. It is the middle unit of the Chatham Group, overlying the

Pekin Formation The Pekin Formation is a Late Triassic (Carnian) geological Formation (geology), formation in North Carolina. The Pekin Formation is specific to the Sanford Sub-Basin of the Deep River Basin of North Carolina, although it may be equivalent to the ...

and underlying the Sanford Formation. Both of these encompassing formations are primarily red

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

. The Cumnock Formation, on the other hand, represents a sequence of darker

lacustrine A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

(lake) or paludal (swampy/marshy) sediments deposited in a tropical climate. These primarily include

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

s and

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...

, with some thin layers of coarser sediment such as

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

and sandstone. The formation preserves some fossils, including a diverse assemblage of microvertebrates (tiny fragments of

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

fossils) from a quarry near Moncure, NC.

Palynology Palynology is the study of microorganisms and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and occur in sediments, sedimentary rocks, and even some metasedimentary rocks. Palynomorphs are the mic ...

and general geological characteristics suggest that the Cumnock Formation is equivalent in age to the

Cow Branch Formation The Cow Branch Formation is a Late Triassic geologic Formation (geology), formation in Virginia and North Carolina in the eastern United States. The formation consists of Cyclostratigraphy, cyclical beds of black and grey Lacustrine deposits, lacus ...

of the

Dan River Dan River may refer to: * Dan River (Virginia) * Dan River (China) * Dan River (Middle East) Other * Little Dan River * Browns Dan River * Dan Hole River See also * Dan (disambiguation) Dan or DAN may refer to: People * Dan (name), inc ...

/ Danville basin on the

Virginia Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...

-North Carolina border. It has also been compared to the Stockton and Lockatong formations of the

Newark Basin The Newark Basin is a sediment-filled rift basin located mainly in northern New Jersey but also stretching into south-eastern Pennsylvania and southern New York. It is part of the system of Eastern North America Rift Basins. Geology Approxim ...

in the northeastern United States. Some authors even reduce the Cumnock Formation to a member of the Lockatong Formation, in a broad interpretation of the latter. The Cumnock Formation is probably early

Norian The Norian is a division of the Triassic geological period, Period. It has the rank of an age (geology), age (geochronology) or stage (stratigraphy), stage (chronostratigraphy). It lasted from ~227.3 to Mya (unit), million years ago. It was prec ...

in age based on comparisons to similar strata in the eastern United States, as well as early sections of the

Chinle Formation The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In ...

further west.

References

* Triassic geology of North Carolina Shale formations of the United States Sandstone formations of the United States Siltstone formations of the United States Coal formations {{Triassic-stub