Stratigrafii

Stratigrafii is the branch of geology that studies rock layers, their order, composition, and physical relationships. It aims to reconstruct the sequence of geological events from the present backward through time by analyzing the distribution and characteristics of strata. The term derives from Greek stratós 'layer' and graphía 'writing'.

Stratigrafii combines several subdisciplines, including lithostratigraphy (rock-type units), biostratigraphy (fossil content for correlation), chronostratigraphy (defining time intervals), chemostratigraphy (chemical signatures), and sequence stratigraphy (depositional sequences in many basins). These approaches enable relative dating and correlation across regions.

Key principles include original horizontality, superposition, lateral continuity, and the principle of faunal succession. Inclusions and cross-cutting relationships refine age estimates. These principles, articulated by early scientists such as Nicolas Steno, underpin most stratigraphic reasoning.

Stratigraphic units include formations, members, beds, and groups. Correlation uses lithology, fossil assemblages, and isotopic or chemical markers. Chronostratigraphy links rock units to absolute ages, while sequence stratigraphy interprets fills and unconformities in depositional systems.

Dating methods such as radiometric ages, magnetostratigraphy, and chemostratigraphy provide numerical ages and constrain the rock record. GSSP—Global Boundary Stratotype Section and Point—defines internationally accepted boundaries in the geological time scale.

Stratigraphy informs natural resource exploration, basin analysis, and palaeoenvironmental reconstructions. In archaeology and paleoclimatology, stratigraphic framing helps interpret human activity layers and past climate changes. The field remains essential for understanding Earth's history and the development of the geologic time scale.