GRAIN-SIZE OF FLUVIAL DEPOSITS AND LATE QUATERNARY CLIMATE - A CASE-STUDY IN THE PO RIVER VALLEY (ITALY)

By stacking the grain-size data interpreted from many logs of borings (down to 200 m deep) in a sector of the Po River valley, we have obtained a curve of the clay + silt fraction vs. depth that matches the oxygen isotope curve of paleotemperatures for the late Quaternary. Contour maps and plots for selected subzones show that the northern half of the study area is characterized by this correlation, whereas the southern part adds only a random low-amplitude noise to the curve. The suggested dependence of grain size of fluvial deposits on climate in a part of the study area would provide an indirect way to date these not otherwise datable sediments, allowing an evaluation of the sedimentation rates and of the total subsidence since the last interglacial.