Interpretation of clay mineral associations of Quaternary sediments at Alto Ribatejo (Central Portugal)

Abstract

Research has been carried out in Alto Ribatejo (central Portugal, western Iberia) with the purpose of contextualizing Late Pleistocene and Early Holocene archaeological remains within the coeval landscape. Several regional Quaternary deposits were analysed in terms of their sand fraction mineralogy (microscopic observation) and clay mineralogy (X-ray diffraction of orientated aggregates).

The sedimentary record ascribed to the ~30-12 ka interval (Last Glacial and Tardi-glacial periods) is represented by colluviums and aeolian sands with predominance of illite. Illite is progressively replaced by vermiculite and some kaolinite or smectite in the upper stratigraphic levels of the Holocene deposits. The obtained data indicates cold and dry conditions during the Last Glacial/Tardi-glacial and a temperate climate in the Holocene.