| Chickies Formation | |
| Type: | Metamorphic |
| Age: | Cambrian |
| Period: | Cambrian |
| Prilithology: | Quartzite |
| Otherlithology: | Slate, schist |
| Namedfor: | Chickies Rock |
| Namedby: | J. Peter Lesley |
| Year Ts: | 1876 |
| Region: | Pennsylvania, New Jersey, Maryland |
| Subunits: | Hellam Conglomerate Member |
| Extent: | Mid-Atlantic United States |
The Cambrian Chickies Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and Maryland. It is named for Chickies Rock, north of Columbia, Pennsylvania along the Susquehanna River.
The Chickies Formation is described as a light-gray to white, hard, massive quartzite and quartz schist with thin interbedded dark slate at the top. Included at the base is the Hellam Conglomerate Member. It is a rare metamorphic rock that has fossils; Skolithos is found throughout the formation.[1]
Relative age dating places the Chickies in the Lower Cambrian Period, deposited between 542 and 520 million years ago (±2 million years).[2]
The Chickies is quarried as a building stone and for aggregate. The stone used to build the restrooms at Valley Forge National Historical Park is Chickies quartzite.[3]