Paleoecological archives unraveling the early land-use history at the emergence of the Bronze Age settlement of Bergamo (Italian Alps)

The hilltop town of Bergamo, at the southern fringe of the Italian Alps, represents a typical example of the stepped emergence of a prehistoric settlement developing into a proto-historic urban center in the Iron Age. We present here unprecedented multidisciplinary evidence based on several near-site stratigraphies, supported by a robust radiocarbon chronology and by a continuous fine-resolution sedimentary and paleoecological record from a pond used for livestock watering, which was intercepted by drilling underneath the modern Catholic Cathedral. The obtained chronostratigraphy documents the development of arable and fallow land including cereals, legumes and livestock husbandry starting as early as 3355 yrs. cal BP (median of modeled calibrated ages, i.e., 15th century BC). This evidence indicates that already in the Middle Bronze Age the very center of the hilltop of the Bergamo Hill supported an early farming center. Land use reached an acme between 2980 and 2753 yrs. cal BP, triggering intense soil erosion by runoff processes. Paleobotanical evidence suggests uphill grapevine cultivation at the southern Alpine fringe at 2900 yrs. cal BP. Data support settlement continuity until around 2700 yrs. cal BP (8th century BC), before the growth of the Celtic town in the 6th–5th century BC. The location and development of the farming center yet in the Bronze Age might have been promoted by topographical diversification, high geomorphic weathering rate, soil suitability for agriculture and pastoralism, and water availability on the northern side of the hill, secured by orographic precipitation in warmer seasons.