Pennsylvanian

The Pennsylvanian is, on the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly 323.4 million years ago to 298.9 million years ago. As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain by a few hundred thousand years. The Pennsylvanian is named after the U.S. state of Pennsylvania, where the coal beds of this age are widespread.