Earth Geology Geologic Time Scale Pennsylvanian Period

Pennsylvanian Period

The Pennsylvanian time period lasted from 325 to 286 million years ago, a time span of 39 million years. The term Pennsylvanian was first used in the late 1800s to describe a sequence of rocks in, of all places, Pennsylvania. In Europe the time period just above the Devonian was named the Carboniferous because of the abundant coal beds found in them. However, in the United States geologists divided the Carboniferous into two periods, the Mississippian and the Pennsylvanian. These Pennsylvanian rocks were defined based on a particular type of fossil assemblage contained within them. They are located above the rocks of the Mississippian System and below the rocks of the Permian System.