Earth Geology Geologic Time Scale Ordovician Period

Ordovician Period

The Ordovician time period lasted from 505 to 440 million years ago, a time span of 65 million years. The term Ordovician was first used in the 1870s to describe a sequence of rocks in Wales. The name Ordovician was derived from the name of an ancient British tribe. These Ordovician rocks were defined based on a particular type of fossil assemblage contained within them. They are located above the rocks of the Cambrian System and below the rocks of the Silurian System.