The Cambrian is a geologic period of the Paleozoic Era, spanning approximately 539–485 million years ago, characterized by a major diversification of multicellular life known as the Cambrian explosion. It follows the Ediacaran Period and precedes the Ordovician. Stratigraphically, its base is defined by the first appearance datum of complex trace fossils such as Treptichnus pedum, and it is subdivided into series and stages based on biostratigraphic markers, particularly trilobites and small shelly fossils. The Cambrian is critical for calibrating early Phanerozoic evolutionary, paleoenvironmental, and tectonic reconstructions.
In a first-of-its-kind study, Stanford researchers have measured how the abundance of ocean life has changed over the past half-billion years of Earth's history.
Earth Sciences
Jun 25, 2025
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