stratigraphiques

Stratigraphiques is the French adjective referring to anything related to stratigraphy, the branch of geology that studies layered rocks and their arrangement through time. In English, the corresponding term is stratigraphic or stratigraphy. The field aims to reconstruct the history of the Earth by describing, mapping, and interpreting the sequence of rock layers, or strata, and their temporal relationships.

Stratigraphic analysis uses a framework of units and relationships. Stratigraphic units include formations, members, and beds, which are correlated across distances to build a continuous record. Core principles developed in the field include original horizontality (deposits accumulate in near-horizontal layers), superposition (younger layers overlie older ones), lateral continuity (layers extend laterally until thinning or termination), cross-cutting relationships (features that cut through others are younger), and inclusions (fragments contained within a unit are older than the unit that contains them). Biostratigraphy, using fossils to align and date layers, and chronostratigraphy, which assigns rocks to specific intervals of geologic time, are foundational approaches.

Subfields include lithostratigraphy (rock-type classification), biostratigraphy, chronostratigraphy, sequence stratigraphy (depositional systems and their changes), chemostratigraphy, and magnetostratigraphy. Dating methods—from radiometric ages to marker beds and index fossils—are used to supplement relative stratigraphy with absolute time.

Applications span petroleum geology, groundwater and civil engineering, archaeology, and paleoenvironmental reconstruction. Classic contributions by early workers such as Nicolas Steno and William Smith established the principles and utility of stratigraphy in understanding Earth's history.