1002 - Under the Sea

425 million years ago, during the Silurian Period, most of Door County was covered by a warm sea. The area was rich with marine life and coral reefs. Most of the fossils found at Whitefish Dunes are from this time period.

What is a brachiopod?

The brachiopod was a clam-like creature that lived in the Silurian Sea. They had two shells and fed by filtering microscopic food from the water. There were so many of them that their fossilized shells helped make the limestone bluffs found in Door County.

What is a fossil?

Fossils are the preserved remains of ancient plants and animals. Some fossils date back almost four billion years!

Not everything becomes a fossil–the conditions have to be just right. An organism must be covered by sediment immediately after it dies. Since oxygen and bacteria can no longer reach the organism through the sediment, it does not decompose. Instead, minerals in the sediment replace all hard body parts over time, and a fossil is created.