Chickies Formation Explained

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.

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

Notes and 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. Web site: https://wayback.archive-it.org/all/20090327030718/http://www.dcnr.state.pa.us/topogeo/ParkGuides/pg08.pdf . Pennsylvania Trail of Geology. 2009-03-27 .