undifferentiated rock units

Paleontology and geology

Little is known of the Early Precambrian history of Nevada, as few rocks of this age are preserved. In the Late Precambrian, shallow seas began to flood onto the edge of a quiet continental margin, one where no tectonic activity was occurring. The land was a flat plain with no mountains, and rivers deposited quartz-rich sandstones at the river mouths and nearshore areas. In slightly deeper water, silts and clays were deposited on muddy bottoms. The rocks formed from these sediments can be seen today in the southern and eastern parts of the state. Some very unusual fossils---shelly tubes a few millimeters in length---have been described from Precambrian rocks in Esmeralda County in western Nevada.