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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.
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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.
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. The deposition of calcitic sediments is indicative of a climate with high evaporation rates.
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.