Paleoenvironmental reconstruction from LGM to historical time in the lower coastal plain of the Piave river. Preliminary pollen analysis on a 20 m core of lagoon and fluvial sediments

This work presents the first results of a multidisciplinary study in the flood plain of the Piave River located NE of the Venice Lagoon.The aim of the work is to reconstruct the late Quaternary geomorphological evolution of the area. This study is part of a wider researchon the Veneto-Friuli plain based on geomorphological surveys, remote-sensing, sediment analyses, archaeological and historical mapanalyses. In the frame of this study, three cores of 20 m depth were collected along a N-S transect 20 km long between San Donà diPiave and the coast of the Adriatic Sea. The transect crosses the present course of the Piave River and its fluvial ridge, while the corings were performed on the surface of old flat marshes, now reclaimed. Pollen-stratigraphical data and 14C dates are presented forthe intermediate core of Palazzetto. The results of radiocarbon dating indicate that the sequence spans the Last Glacial Maximum(LGM) and the Holocene. At the base of the sequence, a peat layer (21,250±150 yr BP) is characterised by dominance of Cyperaceae (pollen, epidermal and roots fragments, fruits) as many other peat layers formerly described by other Authors in the Veneto and Friuliplain. Fine fluvial sediments attributed to the Piave River bury the basal peat. The changes in the local plant communities from freshwater to brackish/salt water communities have been recognised at the depth of ca. 6 m. This level testifies the Flandrian transgression not yet investigated in the San Donà di Piave area. The geochronological dating and the pollen analysis of the three cores will let usknow the dynamic of the ingression of the sea at NE of the Venice Lagoon. At the top of the core the pollen assemblage of a peat layer(500±70 yr BP) suggests the presence of a marsh environment.