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
TypeMetamorphic
Sub-unitsHellam Conglomerate Member
Lithology
PrimaryQuartzite
OtherSlate, schist
Location
RegionPennsylvania, New Jersey, Maryland
Country United States
ExtentMid-Atlantic United States
Type section
Named forChickies Rock
Named byJ. Peter Lesley
Year defined1876
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 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]

See also

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
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