The Cambrian

Cambrian

The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...

 Chickies Formation is a mapped bedrock unit in Pennsylvania

Pennsylvania

The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...

 and Maryland

Maryland

Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...

. It is named for Chickies Rock, north of Columbia, Pennsylvania

Columbia, Pennsylvania

Columbia, once colonial Wright's Ferry, is a borough in Lancaster County, Pennsylvania, 28 miles southeast of Harrisburg on the left bank Susquehanna River across from Wrightsville and York County. Originally, the area may have been called Conejohela Flats, for the many islands and islets in the...

 along the Susquehanna River

Susquehanna River

The Susquehanna River is a river located in the northeastern United States. At long, it is the longest river on the American east coast that drains into the Atlantic Ocean, and with its watershed it is the 16th largest river in the United States, and the longest river in the continental United...

.

Description

The Chickies Formation is described as a light-gray to white, hard, massive quartzite and quartz schist with thin interbedded dark slate at top. Included at the base is the Hellam Conglomerate Member. It is a rare metamorphic rock

Metamorphic rock

Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...

 that has fossils; Skolithos

Skolithos

Skolithos is a common trace fossil ichnogenus whose original form consisted of approximately vertical cylinders. One well-known occurrence of Cambrian trace fossils is the famous 'Pipe Rock' of northwest Scotland...

is found throughout the formation.

Depositional Age

Relative age dating places the Chickies in the lower Cambrian

Cambrian

The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...

 period, deposited between 542 mya to 520 mya (±2 my).

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

Valley Forge National Historical Park

Valley Forge National Historical Park is the site where the Continental Army spent the winter of 1777–1778 near Valley Forge, Pennsylvania, during the American Revolutionary War. The National Historical Park preserves the site and interprets the history of the Valley Forge encampment. ...

is Chickies quartzite.