Chickies Formation

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.

Chickies Formation Stratigraphic range: Cambrian
Type	metamorphic
Sub-units	Hellam Conglomerate Member
Lithology
Primary	quartzite
Other	slate, schist
Location
Region	Mid-Atlantic United States
Country	United States
Extent	Pennsylvania, New Jersey, Maryland
Type section
Named for	Chickies Rock
Named by	J. Peter Lesley, 1876

Specimen of Chickies Banded Slate. Shows older folded schistosity parallel to bedding cut by younger cleavage inclined to bedding.

Specimen of mica schist from upper beds of Chickies Quartzite. Shows stretched epigenetic tourmaline.

Description

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

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

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

• Geology of Pennsylvania

References

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. http://www.dcnr.state.pa.us/topogeo/ParkGuides/pg08.pdf