Paleontology and geology
During the Cambrian, the central and eastern parts of Arizona were above water, and the edge of the continent went from southern California through central Nevada. In between, most of Arizona was covered by a shallow carbonate platform. Although not shown on this map, Cambrian rocks from northern and southern Arizona record shoreline, lagoonal, and shallow marine environments. The sandstones, siltstones, and limestones that originated in these environments contain abundant invertebrate fossils, such as trilobites and brachiopods.