Stratigraphy

Stratigraphy is one of the branches of geology, which deals with the study of rock layers and stratification (layering). Stratigraphy is used for studying about the layered volcanic rocks and sedimentary rocks. Stratigraphy consists of two subfields such as lithostratigraphy or lithologic stratigraphy and biostratigraphy or biologic stratigraphy.  The theoretical concept for the stratigraphy was developed Nicholas Steno. He re-introduced the principle of original horizontality, law of superposition and the principle of lateral continuity in the year 1669, in a work on the fossilization of the organic remains in the layers of sediment. William Smith was the first person to apply the stratigraphy on a large scale during early 19^th century and in 1790s.

William Smith is now called as the Father of English Geology, since he was the first person to create the geologic map of the England.  He was the first person to recognize the importance of the rock layering or strata and the significance of the fossil markers for correlating strata.  Another important application of the stratigraphy in the early nineteenth century was a study done by Alexandre Brongniart and Georges Cuvier about the geology of the region across Paris.  Paleontologic stratigraphy or biostratigraphy is usually based on the fossil records in the rock layers.  The strata from extensive places comprising the same fossil fauna are correlatable in time. Paleontologic stratigraphy was based on the principle of faunal succession of William Smith that predated, and which was one of the most powerful and first lines of proof for the biological evolution. Paleontologic stratigraphy gives strong proof for the speciation (formation) of and the extinction of the species. The geologic time scale which was created during the nineteenth century was actually based on the evidence of faunal succession and biologic stratigraphy.

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