Varve dating method
Using these key or index fossils as markers, Smith could identify a particular layer of rock wherever it was exposed.
Because fossils actually record the slow but progressive development of life, scientists use them to identify rocks of the same age throughout the world.
The most compelling argument for an age of the earth of 4.5 billion years are the large number of independent tests that have been used to confirm this date.
These tests have been performed on what are thought to be the earth's oldest surviving rocks, meteorites, and moon rocks.
He concluded, after studying rocks at many outcrops, that each layer represented a specific interval of geologic time.
See more information about "Strata" Smith and his original geologic map of England.
Information about Simon Winchester's delightful biography of Smith, The Map That Changed the World is available at Tree-Ring dating is based on the principle that the growth rings on certain species of trees reflect variations in seasonal and annual rainfall.
[ While this may be true, a shrub in Tasmania could be 40,000 years old.
See Oldest Living Organism.] The Sheffield Laboratory now has a continuous master sequence for England going back to about 5000BC. This article should be a "must read" for any person interested in factualy accurate information on dating methods.