Stratigrafien

Stratigrafien, or stratigraphy, is the science that studies the order, relative position, and age of rock layers. It aims to reconstruct the history of sedimentation and rock formation by describing and correlating strata across regions, from outcrops to subsurface sequences. Stratigraphy provides a framework for dating geological and archaeological records and for interpreting past environments.

Key concepts in stratigraphy include the principles of superposition (younger layers over older ones), original horizontality, lateral continuity, cross-cutting relationships, and faunal succession. These principles enable the correlation of rock units and the construction of a stratigraphic framework that links distant outcrops. Stratigraphy integrates lithology, paleontology, and geochronology to establish relative ages and to identify time-equivalent units.

Subdisciplines include lithostratigraphy, which classifies units by rock type; biostratigraphy, which uses fossils to define temporal intervals; chronostratigraphy, which defines time-rock units such as formations and stages; and magnetostratigraphy and chemostratigraphy, which employ magnetic polarity and chemical signatures, respectively. Sequence stratigraphy analyzes sedimentary sequences formed during changes in relative sea level, aiding interpretations of depositional environments and basin history.

Methods combine field observations, stratigraphic logging, and the examination of fossils, rock microfossils, sedimentary structures, and lithology. Dating often relies on radiometric techniques for absolute ages, while correlation uses index fossils, facies associations, and subsurface data such as well logs and seismic surveys.

Applications of stratigraphy span oil and gas exploration, groundwater research, paleoclimatology, tectonics, and the stratigraphic context of archaeological sites. Historical foundations trace to early geologists such as Nicolas Steno and William Smith, whose principles established the basis for modern stratigraphic thought.