A Golden Spike in Time
In the Three Gorges region of Hubei Province, a specific point in a rock outcrop defines the official beginning of the Cambrian Period. Geologists call this a Global Boundary Stratotype Section and Point (GSSP). It is the internationally agreed-upon reference section for the boundary between the Ediacaran and Cambrian periods, which occurred approximately 538.8 million years ago. This location, known as the Wangcun section, is marked by a "golden spike" to signify its global importance. The layers of carbonate rock here provide a continuous record of a major shift in Earth's chemistry and biology.
The rock layers belong to the Dengying Formation, a thick sequence of carbonates deposited in a shallow sea. This formation contains the important chemical and fossil evidence that geologists use to correlate rock layers across the globe. By studying these rocks, scientists can pinpoint the precise moment that corresponds to the dawn of the animal kingdom as we know it. The selection of this site by the International Commission on Stratigraphy means that any other rock exposure in the world showing the Ediacaran-Cambrian transition is compared against this standard reference in Hubei.