Although hybrid event beds (HEBs) occur in many of deep-water systems, the mechanisms responsible for their formation remain ambiguous. Most workers agree that acquisition of mud or muddy material is a key factor, with many hybrid flow models favoring an origin for the mud in up-dip channels, channel-lobe transition zones or slope sectors. In this study, Fonnesu and others describe outer-fan-lobe and confined-basin-plain sheet deposits of the Cretaceous–Paleocene Gottero Sandstone cropping out on Mount Ramaceto and Mount Zatta (NW Apennines, Italy). The succession includes cm- to m-deep erosional scours below sheet-like HEBs, features which appear to provide the mud necessary for local flow transformation. Extensive substrate delamination in distal deep-water environments has not been described in detail before nor linked to the local formation of HEBs.This hybrid flow model may apply generally, with implications for the distribution and heterogeneity of HEB muddy divisions and hence hydrocarbon reservoir properties.
Marco Fonnesu, Marco Patacci, Peter D.W. Haughton, Fabrizio Felletti, and William D. McCaffrey