Geologists have made a timeline of events, which we call the Geologic Time Scale, that help us understand the order of important geological events relative to one another in the billions of years of Earth’s history.
The Devonian is the time (416 – 359 million years ago) when fish with jaws began to diversify and control the waters.
The Marcellus is found throughout the Allegheny Plateau region of the northern Appalachian Basin of North America.
In the United States, the Marcellus shale runs across the Southern Tier and Finger Lakes regions of New York, in northern and western Pennsylvania, eastern Ohio, through western Maryland, and throughout most of West Virginia extending across the state line into extreme western Virginia.
Stratigraphically, the Marcellus is the lowest unit of the Devonian age Hamilton Group, and is divided into several sub-units.