Allegheny Formation facts for kids
Quick facts for kids Allegheny FormationStratigraphic range: Pennsylvanian |
|
|---|---|
| Type | Sedimentary |
| Underlies | Conemaugh Group |
| Overlies | Kanawha Formation and Pottsville Formation |
| Lithology | |
| Primary | Sandstone, coal |
| Location | |
| Region | Appalachian Mountains |
| Country | United States |
| Extent | Pennsylvania, Maryland, West Virginia, Ohio |
| Type section | |
| Named by | H. D. Rogers, 1840 |
The Pennsylvanian Allegheny Formation is a special group of rocks. You can find these rocks in western and central Pennsylvania, western Maryland and West Virginia, and southeastern Ohio. It is a very important rock unit because it contains a lot of coal. This coal is found in the Appalachian Plateau region of the eastern United States.
What is the Allegheny Formation?
In Pennsylvania, the Allegheny Formation includes many different types of rocks. These rocks stretch from the bottom of the Brookville Coal layer to the top of the Upper Freeport Coal layer. Scientists defined this formation to include all the important coal layers from the upper Pennsylvanian period.
This formation is made up of repeating layers of different rocks. These layers are called cyclothemic sequences. They include:
- coal
- shale (a type of soft rock)
- limestone (another type of rock)
- sandstone (rock made from sand)
- clay
The Allegheny Formation has six main coal layers. These layers are listed here from the newest (top) to the oldest (bottom):
- Upper Freeport Coal
- Lower Freeport Coal
- Upper Kittanning Coal
- Middle Kittanning Coal
- Lower Kittanning Coal
- Brookville Coal
How Old is the Allegheny Formation?
Scientists use special methods to figure out the age of rocks. These methods show that the Allegheny Formation was formed during the middle Pennsylvanian period. This period was a very long time ago, millions of years in Earth's history.
