postdepositional

Postdepositional describes processes that modify materials after deposition. It encompasses chemical, physical, and biological changes that alter sedimentary deposits, rocks, or artifacts after their initial formation or deposition. The term is used across geology, archaeology, paleontology, and related sciences to distinguish later alterations from the conditions present at deposition.

In geology and sedimentology, postdepositional changes include diagenesis: compaction, cementation, mineral dissolution and precipitation, and recrystallization, as well as burial metamorphism under increasing pressure and temperature. Water-rock interactions can change mineralogy and porosity. Bioturbation by organisms and physical reworking by wind or water can mix or sort grains and disrupt original layers.

In archaeology and taphonomy, postdepositional processes affect artifacts and ecofacts after burial: trampling, rooting, burrowing, weathering, chemical alteration, leaching, and movement by water or gravity. These processes can distort stratigraphy, redistribute materials, or alter their condition, complicating interpretations of context, dating, and behavior.

Study and implications: Understanding postdepositional alteration is essential for accurate reconstructions of past environments, depositional histories, and preservation states. Researchers use petrographic microscopy, X-ray diffraction, electron microscopy, isotopic analyses, and stratigraphic and taphonomic assessments to identify and account for postdepositional changes.