Rétegtanban

Rétegtanban (stratigraphy) is the branch of geology that studies layered rocks and sediments, their distribution, texture and composition, and the temporal relationships between them. It aims to reconstruct the geological history of a region by developing and correlating rock sequences, their fossil content, and, where possible, assigning ages to layers.

The discipline relies on core principles such as the law of superposition (in undisturbed sequences, older layers lie beneath younger ones), original horizontality (sediments are deposited horizontally), and cross-cutting relationships (features that cut through rocks are younger than the rocks they cut). Faunal and floral succession allows correlation of layers across distances by using characteristic fossil assemblages. Stratigraphic units are organized into beds, members, and formations in lithostratigraphy; biostratigraphy uses fossils to correlate units; chronostratigraphy links units to ages; sequence stratigraphy analyzes deposition in response to changes in sea level.

Methods used in rétegtanban include detailed lithologic description, fossil identification, and correlation across regions. Dating techniques such as radiometric methods, magnetostratigraphy, and chemostratigraphy provide absolute or calendar-like ages that complement relative ordering. Stratigraphy informs several fields, including petroleum geology, hydrogeology, paleoclimatology, archaeology, and environmental reconstruction.

History and development trace to early pioneers like Nicolaus Steno and William Smith, who established fundamental principles of layering and fossil succession. Since then, stratigraphy has evolved into several subfields and analytical frameworks that enable regional correlation, construction of the geological time scale, and interpretation of Earth’s history through layered records.