Stratigraphic

Stratigraphic refers to stratigraphy, the branch of geology that studies layered rocks and their temporal and spatial relationships. It seeks to interpret the history of deposition by examining the sequence, thickness, composition, and bounding surfaces of strata, and by correlating layers across regions to reconstruct past environments and tectonic settings.

Stratigraphic units are defined to enable correlation and description. The principal frameworks include lithostratigraphy (rock-type based units such as formations and members), biostratigraphy (fossil-based zones), and chronostratigraphy (time-rock units such as eras, periods, and the stratigraphic column). Chemostratigraphy (geochemical signatures) and sequence stratigraphy (genesis by changes in accommodation space and sea level) supplement these approaches.

Stratigraphic correlation aligns strata using key criteria: lithology, fossil content, chemostratigraphic markers, and radiometric ages where available. A stratigraphic column summarizes the vertical order of units, while unconformities mark gaps in the record. Core concepts include the law of superposition, original horizontality, and faunal succession, forming the basis for interpreting relative ages.

Applications include petroleum geology, hydrogeology, and archaeology, where stratigraphic frameworks guide resource assessment, groundwater flow, and stratigraphic dating of sites. The field underpins the modern geologic time scale and sequence stratigraphy, widely used in basin analysis and paleogeographic reconstructions.