Dictionary:Stratigraphy

The study of rock strata, their original succession and age relations, their lithologic composition, physical, chemical, and biological properties, distribution, and other characteristics, and their interpretation in terms of environment or mode of origin and geologic history. Rocks may be classified in various ways; see stratigraphic classification. Principles of stratigraphy include (1) principle of superposition (lower layers are older than upper layers), (2) principle of original horizontality (stratified rocks are originally deposited nearly horizontally), and (3) principle of lateral continuity (a stratified rock body originally extended laterally until it terminated at the edge of a basin, thinned to zero thickness, or changed character into another deposit).