Paleontology and geology
Silurian rocks are almost entirely absent in Colorado. The only examples are known from fragments preserved in diamond-bearing igneous intrusions near Fort Collins in the north-central part of the state. These fragments contain distinctive Silurian marine fossils, including brachiopods and corals, indicating that part of the state was covered by shallow water during a portion of the Silurian. Uplift of the land must have occurred some time after these marine sediments were deposited, draining the sea from the state. Erosion then removed most of the Silurian rocks.