Britannica Sources used in this answer

How did William Smith contribute to the development of the geologic time scale?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Plumb the depths of geologic time. — geologic history of Earth Discover how old Earth is and discover the timing of important events in Earth's history in our interactive.

William Smith, often called the "Founder of Stratigraphy," was instrumental in developing the geologic time scale through his discovery of faunal succession.12

While working as a surveyor and engineer, Smith observed that specific rock strata consistently contained unique assemblages of fossils. He realized that these organic remains could be used to identify and correlate rock layers across widely separated geographic areas. This insight allowed him to establish a clear order in both the spatial arrangement of rock units and the progression of ancient life forms.321

His monumental contribution culminated in the 1815 publication of his "Geologic Map of England, Wales and Part of Scotland," which applied these principles to map 20 distinct rock units. By demonstrating that strata could be identified by their fossil content, Smith provided the essential framework for stratigraphic correlation, which remains a fundamental basis for organizing Earth's history into a coherent system.32