Editing Stratigraphy (section)

==Biostratigraphy==
{{main|Biostratigraphy}}

Biostratigraphy or [[paleontology|paleontologic]] stratigraphy is based on [[fossil]] evidence in the rock layers. Strata from widespread locations containing the same fossil fauna and flora are said to be correlatable in time. Biologic stratigraphy was based on William Smith's [[principle of faunal succession]], which predated, and was one of the first and most powerful lines of evidence for, [[biological evolution]]. It provides strong evidence for the formation ([[speciation]]) and [[extinction]] of [[species]]. The [[geologic time scale]] was developed during the 19th century, based on the evidence of biologic stratigraphy and faunal succession. This timescale remained a relative scale until the development of [[radiometric dating]], which was based on an absolute time framework, leading to the development of chronostratigraphy.

One important development is the [[Vail curve]], which attempts to define a global historical sea-level curve according to inferences from worldwide stratigraphic patterns. Stratigraphy is also commonly used to delineate the nature and extent of [[hydrocarbon]]-bearing reservoir rocks, seals, and traps of [[petroleum geology]].