Stratigrafia

Stratigrafia, commonly known in English as stratigraphy, is the branch of geology that studies the arrangement, distribution, and age of rock layers (strata). It interprets the history of sedimentation and tectonics by examining lithology, fossils, and sedimentary structures to reconstruct past environments and chronologies.

Historical development: Stratigraphy emerged from the work of early pioneers such as Nicolaus Steno, who formulated the basic principles of relative dating (superposition, original horizontality, lateral continuity, and faunal succession). In the 19th century, William Smith and others advanced biostratigraphy and regional correlations, while later developments introduced chronostratigraphy and sequence stratigraphy.

Key concepts and units: Stratigraphy relies on principles including superposition, original horizontality, lateral continuity, and cross-cutting relationships, along with faunal succession to correlate beds. Stratigraphic units include lithostratigraphic units (formations, members, beds), biostratigraphic units, and chronostratigraphic units (ages and stages). Correlation uses fossils, rock type, and age dating.

Methods and dating: Field work involves mapping, outcrop description, and core logging. Dating combines relative dating based on stratigraphic position with absolute dating using radiometric methods, magnetostratigraphy, isotopic dating, and luminescence dating. Sequence stratigraphy focuses on bounding surfaces and systems tracts to interpret depositional sequences and sea-level changes.

Applications and subfields: Stratigraphy informs petroleum geology, groundwater studies, and environmental reconstructions. Subfields include lithostratigraphy, biostratigraphy, chronostratigraphy, magnetostratigraphy, chemostratigraphy, and sequence stratigraphy, and it plays a key role in archaeology when stratified deposits are used to interpret material culture and dating.