undifferentiated rock units

Paleontology and geology

The Silurian record in Idaho is rather sparse; apparently most of the state was above sea level, and any terrestrial deposits have since been removed by erosion. There are some early Silurian marine sediments in central and southeastern Idaho (included as undifferentiated on this map) that contain a modest fauna of brachiopods, gastropods, corals, graptolites, and crinoids.