Luminescence dating and associated analyses in transition landscapes of the Alto Ribatejo, central Portugal

Abstract

Artefacts and regolith (soils, sediments, colluvia, etc.) from passage tombs, pit fills, stone scatter and clay structures, related to the transition to agro-pastoralism in the Alto Ribatejo, were analysed by optically stimulated luminescence, neutron activation analysis, field and high-resolution gamma spectrometry, and X-ray diffraction. Indications of anthropogenic, autogenic, and allogenic site formation and diagenetic processes, including radionuclide exchange, were applied to interpret 28 date estimates from the 9th to 1st millennia BC. Results from regolith samples relate to different phases of landscape activation and stability from the late 6th millennium BC to the Roman conquest. However, simple archaeological questions were best answered using heated materials, where present. Different chronological phases were often represented by different sample types in sites with multi-phase stratigraphies, indicating the importance of parallel analyses. Results from a fire pit coincide with the first indications of clearance in the regional pollen record (late 9th millennium BC): these features appear promising to map early Holocene human presence in the Alto Ribatejo landscape.