Stratigraafias

Stratigraafias is the scientific study of the arrangement and interpretation of rock layers (strata) and their ages. It aims to reconstruct the sequence of geological and environmental events in Earth’s history, correlate strata across distances, and provide a framework for dating rocks.

Key principles include the law of superposition, original horizontality, lateral continuity, and faunal succession. In practice, stratigraphers identify and describe stratigraphic units such as formations, measure their thicknesses, and assemble them into a stratigraphic column or time-scale. Correlation is built from lithology, fossils, and geochemical signatures, while disturbances such as faults and unconformities are interpreted to understand tectonic history.

Stratigraafias comprises several subdisciplines: lithostratigraphy (rock-type correlations), biostratigraphy (fossil-based dating), chronostratigraphy (construction of the actual time scale), chemostratigraphy (chemical indicators, such as isotope ratios), magnetostratigraphy (magnetic polarity data), and sequence stratigraphy (deposition in systems of order). Dating methods range from relative dating to absolute radiometric dating (e.g., U-Pb, Ar-Ar, K-Ar) and radiocarbon for younger materials. Index fossils and astronomical tuning are also used.

Applications include petroleum and mineral exploration, hydrogeology, palaeoenvironmental and climate reconstruction, and archaeological site context. Limitations arise from tectonic deformation, erosion, diagenetic alteration, and diachronous boundaries, which require integration with other geological evidence and robust uncertainty assessment.