Distal deposits of the Avellino eruption as a marker for the detailed reconstruction of the Early Bronze Age depositional environment in the Agro Pontino and Fondi Basin (Lazio, Italy)

The presence of the Early Bronze Age Avellino (AV) tephra in the Holocene lacustrine deposits of the AgroPontino and Fondi basin provides a unique opportunity to reconstruct the Holocene depositional envi-ronment at the time of AV-tephra deposition. Marine terraces of the last Pleistocene transgression havebeen consolidated by soil formation and incised during the last glacial. This created a gully landscape inthe Fondi basin and in the southeastern Agro Pontino. The inland central part of the Agro Pontino wasdrained by one major gully. At thefinal part of subsequent Holocene sea level rise, beach ridges closedthe southeastern marine lagoons, creating a lacustrine and marshy environment. Shortly after, theAvellino eruption deposited its sandy tephra in these freshwater environments. By comparing altitudesof the AV-tephra in different environments two major implications emerge. First, at those locationswhere the AV-tephra is underlain by thick Holocene peaty and clayey deposits, significant subsidenceoccurred, while this has been limited at locations where the Pleistocene marine terrace occurs close tothe surface. This subsidence is independently checked by comparing a modern LiDAR DEM and a detailedDEM from 1928. Second, the altitude of the AV-tephra reflects sea level in the coastal positionsaround1.5 to2 m a.s.l., while the only gully draining the lacustrine and marshy inland Agro Pontinowas blocked around 0.5 m a.s.l. by the expanding sediment wedge of the Amaseno River, the majordraining axis of the Agro Pontino. The AV-tephra layer will continue to play an important role in regionalgeological, palaeoenvironmental and geo-archaeological research