Chickies Formation

Chickies Formation
Stratigraphic range: Cambrian
Chickies Rock (1892)
Type	Metamorphic
Sub-units	Hellam Conglomerate Member
Lithology
Primary	Quartzite
Other	Slate, schist
Location
Region	Pennsylvania, New Jersey, Maryland
Country	United States
Extent	Mid-Atlantic United States
Type section
Named for	Chickies Rock
Named by	J. Peter Lesley
Year defined	1876

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.

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 geology

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]

• 
  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.
• 
  Cobble bed in Hellam Conglomerate Member

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. "Pennsylvania Trail of Geology" (PDF). Archived from the original (PDF) on 2009-03-27.