Climatic signature of two mid-late Holocene fluvial incisions formed under sea-level highstand conditions (Pisa coastal plain, NW Tuscany, Italy)

摘要

A multi-proxy (stratigraphic, geomorphological, palynological, geophysical) study of mid-late Holocene deltaic-alluvial deposits beneath the Pisa Plain (Tuscany, Italy) reveals short-term enhances of fluvial activity under relative sea-level highstand (HST) conditions (last -7000 cal yr BP). Early HST delta progradation led to the progressive infill of a broad lagoon area (similar to 5000 cal yr BP), followed by the development of a stable alluvial depositional environment (similar to 4000 cal yr BP). The intense phase of alluvial aggradation was punctuated by two events of enhanced fluvial incision that cut down to 10 m the underlying lagoonal substrate. The two erosive events, which reflect centennial-scale changes in the aggradation/degradation ratio, are chronologically constrained to the Eneolithic-Bronze age transition (similar to 3800 cal yr BP) and to the Bronze-Iron age transition (2900-2800 cal yr BP), respectively.