Chickies Formation

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The Cambrian Chickies Formation is a mapped bedrock unit in Pennsylvania 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]

Depositional age[edit]

Relative age dating places the Chickies in the Lower Cambrian Period, deposited between 542 and 520 million years ago (±2 million years).[2]

Economic uses[edit]

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]

See also[edit]


  1. ^ Berg, T.M., Edmunds, W.E., Geyer, A.R. and others, compilers, (1980). Geologic Map of Pennsylvania: Pennsylvania Geologic Survey, Map 1, scale 1:250,000.
  2. ^ Blackmer, G.C., (2005). Preliminary Bedrock Geologic Map of a Portion of the Wilmington 30- by 60-Minute Quadrangle, Southeastern Pennsylvania. Pennsylvania Geologic Survey, Open-File Report OFBM-05-01.0.
  3. ^