Multi-proxy analysis for reconstructing the late Quaternary sedimentary evolution and stratigraphy of a south-Alpine alluvial basin (Venetian Plain, Italy)

The research investigates the sedimentary evolution of the Venetian Plain (NE Italy) with a focus on the Middle and lower Upper Pleistocene climatic and environmental changes. This period is still poorly known in the area, due to the few available cores reaching the relative sediments, generally found at a depth higher than 30 meters. The Venetian Plain constitutes part of the foreland basin of the southern Eastern Alps, the Northern Apennines and the External Dinarides. Its particular position, characterized by the proximity of both the orogenic belts and the Adriatic Sea, has influenced its sedimentary evolution during the glacial-interglacial cycles occurred since the Middle Pleistocene. General aim of the research is to enhance the comprehension of the stratigraphy and prograding mechanisms of the alluvial systems (megafans) of the plain in relation to climatic fluctuations, sea - level change and active tectonics. This will allow to extrapolate the depositional history and the drainage pattern of the plain, to define the paleoenvironmental evolution and to improve the climatic proxy dataset on the southern side of the Alps needed for bio - chronostratigraphic subdivision and correlation with neighboring Mediterranean, north-Alpine and eastern European regions. We are focusing on a 130 m deep core ("GER1") drilled in Padua, in the distal part of the megafan of the Brenta River, analyzing different environmental and sedimentological proxies and testing stratigraphic and bio - chronological correlation with others deep cores in the area. Basing on lithofacies assemblages, the presence of paleosoils, and the micropaleontological content, we divided "GER1" into 8 depositional units, mainly constituted by fluvial sediments but with evidence of marine intercalations. In one of these units we find foraminifera such as Ammonia beccarii tepida and Elphidium granosum suggesting a shallow-marginal marine environment during an interglacial phase. Sediment provenance analysis (gross composition of both sand and gravel levels and transparent heavy mineral associations) allows us to distinguish the different supply of fluvial sediments in the area (Brenta, Adige, Bacchiglione and Piave rivers) and to infer the variation in the drainage pattern during the Middle - Upper Pleistocene. Fundamental environmental and biostratigraphic information derive from pollen and NPP analysis, in particular for sediments older than the radiocarbon dating limit. Along the core we identified two principal components of tree pollen types: a group of broadleaf taxa including Quercus robur - pubescens type and a group of conifers (Pinus undiff., Larix, Juniperus) with Betula. In the deeper part of the core we find ancient taxa such as Zelkova, Buxus, Carya and Keteleeria/Abies in association with temperate forest types. Thanks to the finding of the last two, we can hypothesize the MIS correspondence of the proximal marine unit and suppose that we are in an ecological refuge area.