Sylur

The rocks of the area are late middle Silurian period.

During the Silurian period the state was home to significant reef systems.

Sea levels rose even further during the ensuing Silurian period.

Thus, the first insects probably appeared earlier, in the Silurian period.

By the end of the Silurian period, approximately 420 million years ago, the ocean had disappeared.

Hughes has several different kinds of rock from the Silurian period.

Local sea levels had dropped by the ensuing Silurian period.

The first was during the Silurian period, just over three hundred million years ago.

It is the only marrellomorph known from the Silurian period.

These rocks are from the Silurian period around 414 million years old.