In the 1790s he noticed that layers of fossil-bearing stone seen in road cuts and quarries were stacked in the same way in different parts of England.
Smith mapped the layers of rocks in a cut from a quarry for the Somersetshire coal canal and observed that his map could be applied over a wide band of territory.
For most of his career he was cold-shouldered by most of the geologists in Britain because he was not of the gentleman class, but by 1831 Smith widely accepted and awarded the Geological Society's first Wollaston medal.
An individual layer is called a stratum; multiple layers are called strata.
Modern principles of stratigraphic analysis were worked out by several geologists including Georges Cuvier and Lyell in the 18th and 19th centuries.
The amateur geologist William "Strata" Smith (1769-1839) was one of the earliest practitioners of stratigraphy in geology.
Mark Schmitz at Boise State University (BSU) is designed to provide new radiometric dates and further refine the chronstratigraphy of the region's strata.
The BSU lab uses the highest precision dating methods available, with U/Pb analyses of zircons yielding dates with an error around 0.1%.