The Cambrian in Washington, US

Paleontology and geology

In Cambrian times, a very small part of Washington was on the eastern edge of a growing ocean, Panthalassa. Although not identified on this map, pure quartz sandstones representing ancient Cambrian beaches are overlain by shale and finally by limestone, marking the rise of sea levels during the Cambrian. Fossils in these rocks include some of the world’s oldest sponges and a diversity of archaeocyaths, trilobites, hyolithids, and brachiopods.