Stratigrafisi

Stratigrafisi, or stratigraphy, is the branch of geology concerned with the description, correlation, and interpretation of layered rocks (strata) and their placement in geologic time. It aims to reconstruct the history of deposition and the environments in which strata formed, from ancient bedrock to recent sediments. Stratigraphic work underpins the geologic time scale and supports resource exploration, paleoenvironmental reconstruction, and archaeological dating.

Historically, stratigraphy rests on several guiding principles established by Nicolaus Steno and refined over time. The law of superposition states that younger layers lie above older ones. Original horizontality holds that sedimentary layers are deposited roughly horizontally. Lateral continuity asserts that beds extend laterally until they thin out or terminate. Cross-cutting relationships indicate that features cutting across rocks are younger than the rocks they dissect. Inclusions are older than the enclosing rock. These principles enable relative dating and correlation of distant outcrops.

Stratigraphy is divided into subfields such as lithostratigraphy (rock-type based units), biostratigraphy (fossil content for correlation), chronostratigraphy (time-based rock units), sequence stratigraphy (depositional sequences in response to sea-level changes), and chemistratigraphy or magnetostratigraphy (chemical or magnetic signatures). Correlation relies on stratigraphic sections, outcrops, cores, and seismic data to align strata across regions and to construct stratigraphic columns and a consistent time framework. The International Commission on Stratigraphy maintains the official Geological Time Scale and oversees standardization of stratigraphic nomenclature and units. Applications include oil and gas exploration, groundwater and environmental geology, palaeoenvironmental reconstructions, and archaeological dating.