This means the rocks formed during the Devonian Period, which lasted from about 419 to 359 million years ago.
Here's a breakdown of the common rock types and their specific ages:
* Catskill Formation: The most prominent formation in the Allegheny Plateau, this red sandstone and shale unit dates back to the Late Devonian (about 385-360 million years ago).
* Chemung Formation: Another important unit, this formation is also made up of red sandstone and shale, but it's slightly older, dating back to the Middle Devonian (about 385-375 million years ago).
* Hamilton Group: Found in lower elevations, this group consists mainly of black shale and some limestone. It dates back to the Early Devonian (about 419-385 million years ago).
The Allegheny Plateau's geology is a testament to its long and fascinating history. The Devonian rocks were formed in a shallow sea environment, with sediment accumulating over millions of years. Later, uplift and erosion shaped the landscape, creating the rugged hills and valleys we see today.
