Stratigraphy
![The Permian through Jurassic strata of the Colorado Plateau area of southeastern Utah demonstrate the principles of stratigraphy.](/Images/godic/202501/19/SEUtahStrat3048.JPG")
![Engraving from William Smith's monograph on identifying strata based on fossils](/Images/godic/202501/19/Smith_fossils13048.jpg")
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![Chalk layers in Cyprus, showing sedimentary layering](/Images/godic/202501/19/Geology_of_Cyprus-Chalk3048.jpg")
Stratigraphy is a branch of geology which studies rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy includes two related subfields: lithologic stratigraphy or lithostratigraphy, and biologic stratigraphy or biostratigraphy.