undifferentiated rock units

Paleontology and geology

Tectonically, the Nevada region was quiet, with no mountain-building activity during the Silurian. Warm shallow seas covered the continental shelf in the eastern and southern parts of the state, and limy sediment accumulated on the sea floor. A deeper ocean basin opened to the northwest, where silt and sand were deposited and eventually formed the siltstones and fine-grained sandstones seen today. The sandstones are light-colored and contain little organic material, which indicates that circulation was good, and plenty of oxygen was available on the ocean bottom. Brachiopods are common in the shelf deposits, and graptolites can occasionally be found preserved in the deeper water siltstone deposits.