Who was the first person to use fossils for dating rock layers?
No context provided
Who was the first person to use fossils for dating rock layers theoretically?
Nicolaus Stenonius Niels Steensen Nicolaus Steno Nicholas Steno
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Who was the first person to use fossils for dating rock layers in large-scale practical application?
William Smith William 'Strata' Smith
William Smith (geologist)
https://en.wikipedia.org/wiki/William%20Smith%20%28geologist%29
Geochronology
https://en.wikipedia.org/wiki/Geochronology
Nicolas Steno
https://en.wikipedia.org/wiki/Nicolas%20Steno
Catholic priest Nicholas Steno established the theoretical basis for stratigraphy when he introduced the law of superposition, the principle of original horizontality and the principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment.

The first practical large-scale application of stratigraphy was by William Smith in the 1790s and early 19th century. Known as the "Father of English geology",[1] Smith recognized the significance of strata or rock layering and the importance of fossil markers for correlating strata; he created the first geologic map of England. O
Stratigraphy
Catholic priest Nicholas Steno established the theoretical basis for stratigraphy when he introduced the law of superposition, the principle of original horizontality and the principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment. The first practical large-scale application of stratigraphy was by William Smith in the 1790s and early 19th century, he is known as the "Father of English geology", Smith recognized the significance of strata or rock layering and the importance of fossil markers for correlating strata; he created the first geologic map of England. 