Lockatong Formation

Lockatong Formation Stratigraphic range: Carnian PreЄ Є O S D C P T J K Pg N
Type	Geological formation

The Triassic Lockatong Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and New York. It is named after the Lockatong Creek in Hunterdon County, New Jersey.

Description

The Lockatong is defined as a light to dark gray, greenish-gray, and black very fine grained sandstone, silty argillite, and laminated mudstone. In New Jersey, the cyclic nature of the formation is noted with hornfels near diabase and basalt flows.^[1]

Depositional environment

The Lockatong is often described as lake or litoral sediments. The interfingering nature of the sediments with the surrounding Stockton Formation and Passaic Formation suggests that these litoral environments shifted as climate or as the dynamic terrane of the area developed.^[2] The deposition of calcitic sediments is indicative of a climate with high evaporation rates.^[2]

Fossils

Tetrapods

Genus	Species	Locality	Member	Material
Gwyneddosaurus[3]	G. erici[3]	Gwynedd[3]	Gwynedd or North Wales[3]	Gastric ejection[3]
Hypuronector[4]	H. limnaios[4]	Granton Quarry[4]	Ewing Creek (?)[4]	Several partial skeletons[4]
Rhabdopelix[3]	R. longispinis[3]	Gwynedd[3]	Gwynedd or North Wales[3]	Isolated vertebrae and other remains, now lost[3]

Ichnofossils of the Lockatong Formation

Ichnogenus	Ichnospecies	Member
Anchisauripus[3]	A. gwyneddensis[3]
Gwyneddichnium[3]	G. majore[3]
	G. minore[3]
	G. elongatum[3]
Kintneria[3]	sp.[3]
Platypterna[3]	P. lockatong[3]

Age

Relative age dating of the Lockatong places it in the Upper Triassic, being deposited between 237 and 207 (±5) million years ago. It rests unconformably below many different formations of the Atlantic Coastal Plain. It interfingers with both the Stockton Formation and Passaic Formation. There are numerous diabase intrusions and basalt into the Stockton with local contact metamorphic rocks.^[5]

See also

• Geology of Pennsylvania
• Geology of New Jersey

References

1. Orndorff, R.C., et al., (1998). Bedrock Geologic Map of Central and Southern New Jersey. United States Geological Survey, Scale 1:100,000.
2. Faill, R.T., (2004). The Birdsboro Basin. Pennsylvania Geology V. 34 n. 4.
3. Olsen, Paul E.; Flynn, John J. (1989). "Field guide to the vertebrate paleontology of Late Triassic age rocks in the southwestern Newark Basin (Newark Supergroup, New Jersey and Pennsylvania)". The Mosasaur. 4: 1–43.
4. Colbert, Edwin H.; Olsen, Paul E. (2001). "A new and unusual aquatic reptile from the Lockatong Formation of New Jersey (Late Triassic, Newark Supergroup)". American Museum Novitates (3334): 1–24.
5. Berg, T.M., et al., (1983). Stratigraphic Correlation Chart of Pennsylvania: G75, Pennsylvania Geological Survey, Harrisburg, Pennsylvania.