Electron-Microbeam investigation of late quaternary sand sediments from the lagoon of venice (Italy)

Abstract

Electron probe microanalysis (EPMA) has been used to investigate the mineral assemblage of sand samples from the Venice Lagoon Quaternary sediments. These sediments consist mainly of sand, silt and clay layers with some peat lenses. The boundary between the Holocene and Late-Pleistocene is marked by an overconsolidated layer of clay, related to the origin of the Venetian Lagoon. Because in some area of the basin this clay layer has been eroded away it is not always possible to accurately define the limit between the Holocene and Pleistocene sedimentations.Seventeen continuous cores collected for geotechnical purposes along the offshore sandy bar that separates the Lagoon of Venice from the open Adriatic Sea, were available for this investigation. The cores 25 to 30 m long included the Holocene and Late-Pleistocene sediments. For this preliminary study about 130 sand samples were selected at different depth in order to characterize the various levels of the sediments, recognize and define possible correlations between the layers in the 17 cores and, most important, define the boundary between the Holocene and Pleistocene sediments.