Stratigráfiai

Stratigráfiai, or stratigraphy, is the branch of geology that studies the arrangement, composition, and age of rock layers (strata) in order to reconstruct the Earth’s depositional and environmental history. The term combines Latin strata, meaning layers, with the Greek suffix -graphia, meaning description. Stratigraphy focuses on describing and interpreting the order and relative timing of sedimentary and other layered rocks.

Core concepts include the principles of superposition (younger layers lie above older ones), original horizontality (deposited layers are initially horizontal), lateral continuity (layers extend laterally until thinning or boundary; boundaries may cut across what would otherwise be continuous layers), and the principle of cross-cutting relationships (features that disturb rocks are younger than the rocks they cut). The law of faunal succession, based on predictable changes in fossil assemblages through time, is used to correlate strata across regions. Stratigraphy subdivides rocks into units such as beds, members, formations, and groups, and distinguishes among lithostratigraphy (rock-type units), chronostratigraphy (time-based units), biostratigraphy (fossil-based correlations), and sequence stratigraphy (depositional sequences linked to sea-level change).

Methods involve field mapping, the measurement of stratigraphic sections, and core logging, along with dating techniques. Absolute ages come from radiometric dating and isotopic methods, while relative dating uses fossils, magnetostratigraphy, chemostratigraphy, and lithologic correlations to build timelines and interpret environments and tectonics.

Historically, stratigraphy developed from early ideas of Steno and was advanced by William Smith’s principle of faunal succession and the first geological maps in the 19th century. Today it remains fundamental to geology, paleontology, petroleum exploration, groundwater studies, and environmental reconstructions.