Geoarchaeological insights from a Roman age incineration feature (ustrinum) at Enconsta de Sant'Ana (Lisbon,Portugal)

Ustrina are incineration funerary structures that are relatively common in Roman age cemeteries. Salvage excavations at Encosta de Sant'Ana (Lisbon, Portugal) in 2002 brought to light a part of the necropolis of the Roman town of Olisipo, including some ustrina. One of them, designated Burial 1 during fieldwork, is analyzed here from a geoarchaeological viewpoint to understand the formation processes of such an archaeological feature, namely its construction technique, use and function. The study of site context and subsurface pedofeatures, and the application of archaeological soil micromorphology, revealed that the ustrinum was constructed digging a hollow in bedrock and building a mud-brick ridge around it, with raw material taken from the local bedrock. The structure was used at various times and remodelled at least once, and its base was not always thoroughly cleaned – according to the custom called “pars pro toto” by Roman authors – and probably left open when not in use.