Palaeoenvironmental changes and human-environment interactions in the surroundings of La Silla del Papa, SW Spain

The surroundings of the Strait of Gibraltar in southern Iberia are well known as a crossroads for population movements, cultural exchange and trade from Late Prehistory to Modern Times. However, questions remain about how this historical development has impacted the environment. The settlement of La Silla del Papa, an important hillfort located in the Sierra de la Plata in southern Andalusia (Cádiz), and its territory represent an ideal location for long-term studies of human-environment interactions. It was occupied throughout the entire Iron Age, replaced by the coastal town of Baelo Claudia during Roman times, and reoccupied in the early Middle Ages. Therefore, the geoarchaeological investigations in the surroundings of La Silla del Papa within the framework of the interdisciplinary project “Archeostraits” aimed at constraining the ecological conditions and human-environment interactions during the Mid- and Late Holocene and during the most important human occupation phases. Our investigations included sedimentological, geochemical, chronological (OSL, 14C-AMS, diagnostic pottery), microfaunal and palynological analyses of nine sediment profiles as well as nine vibracores from the catchment of the Río del Cachón, a small river originating in the Sierra de la Plata, just below La Silla del Papa. Our results document an early Mid-Holocene open marine embayment in what is now the lower floodplain, which rapidly transformed into a coastal lagoon and later into freshwater-dominated wetlands. After ~2100 BP, fluvial and alluvial deposition considerably increased, suggesting high anthropogenic impact on the local landscape during the Roman or post-Roman times. Palynological results reveal fluctuating agricultural and pastoral activities and suggest two distinct periods of landscape opening between 7000-6000 BP and during the Phoenician and Iron Age period.