Archaeological Stratigraphy
The study of the vertical sequence of layers and features at an archaeological site, and the basis of excavation and relative dating.
Archaeological stratigraphy is the study of the vertical sequence of soil layers (strata) and features — pits, walls, floors, burials — at a site. Its fundamental principle is the law of superposition: in an undisturbed sequence, lower layers were deposited before upper layers and are therefore older. Archaeologists excavate by removing deposits in reverse chronological order, recording every context as a distinct unit with its own boundaries and contents.
Modern practice treats the record as a network of contexts linked by stratigraphic relationships: a layer lies above or below another, a pit cuts through earlier deposits, a fill sits inside a cut. The Harris matrix, developed by Edward Harris in the 1970s, is the standard diagram that summarizes these relationships, allowing excavators to phase a site — to group contexts into periods and detect reoccupation, abandonment, and disturbance.
Stratigraphy is a relative dating method: it establishes sequence, not calendar age. Absolute dates come from radiocarbon dating, dendrochronology, and other techniques applied to material recovered from individual contexts, and the reliability of such dates depends on stratigraphic integrity. If a sample has been redeposited or mixed across layers, the date misleads.
Disturbance is a constant concern. Pits, burrowing animals, roots, and the reuse of sites by later occupants can invert or mix layers, and old material can be brought up and re-deposited in younger contexts. Careful recording and stratigraphic analysis are what separate reliable site histories from mere inventories of finds.
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archaeology dating excavation methodology stratigraphy