Base surge deposits in pleistocene volcanic ash near Rome

Abstract

Volcanic base surge deposits, recorded from the Pacific volcanic belts, Iceland, and the Azores, are here reported for the first time from Italy. Dune forms produced by deposition from base surges occur in the products of phreatic eruptions of Vulsini, Vico, and Sabatini volcanoes north of Rome. The occurrence of cross bedding, drag and slump features, normal dunes, symmetric and asymmetric antidunes, and radial troughs can in some cases be related to individual volcanic craters. Antidune features are more common on crater rims than farther from the craters, and the antidunes appear to be favored by high particle velocities and high water contents in the eruption, and perhaps by density and cohesiveness of the underlying material.