// Workers AI · dad joke modeWhat did the Chickies Formation say? "I'm a rock-solid 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
[edit]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 geology
[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]
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
[edit]References
[edit]- ↑ 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.
- ↑ 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.
- ↑ "Pennsylvania Trail of Geology" (PDF). Archived from the original (PDF) on 2009-03-27.