A 10,000-year record of environmental change and human forcing in the Po Delta (northern Italy)

Deltaic successions are complex archives of both natural and human-driven landscape changes, which govern the preservation and temporal resolution of palaeoenvironmental signals in the stratigraphic record. Integrated sedimentological, meiofaunal, and palynological analyses of a 40 m-long borehole, constrained by a robust chronological framework based on radiocarbon (14C) and short-lived radionuclide (137Cs, 210Pb) dating, delineate Holocene vegetation changes and environmental evolution in the Po Delta area. High-resolution stratigraphic analysis, supported by the identification of six pollen zones and ten subzones, highlights the strong potential of stratigraphically expanded, prograding deltaic successions to preserve records of environmental change particularly over the last ∼2500 yr B.P. These records reflect the combined influence of climatic variability, anthropogenic activity, and catchment dynamics, providing an integrated view of landscape evolution across the land-sea continuum. Transgressive, open-bay to inner-shelf deposits document the rapid landward shift of the shoreline during the Early-Middle Holocene. This interval, associated with depositional hiatuses and stratigraphic condensation (0.11 cm/yr), records early afforestation, punctuated by short-lived phases of climatic deterioration, followed by the establishment of persistently warm and humid conditions during the Holocene Climatic Optimum. The 31-m-thick Late Holocene succession of prodelta, delta-front and delta-plain deposits, accumulated under increasing Po River influence and high sedimentation rates (up to 8 cm/yr), provides centennial- to sub-centennial-scale resolution of vegetation-based environmental and climate variability. Pollen assemblages record the onset and progressive intensification of human impact since the Iron Age. Despite strong anthropogenic forcing over the last two millennia, climatic signals remain clearly detectable in the pollen record, which captures short-lived episodes of regional cooling, including the onsets of the Late Antique Little Ice Age (LALIA) and Little Ice Age (LIA), as well as associated intervals of reduced solar activity.