ADVANCES IN MEASURING AUTOGENIC DYNAMICS IN FLUVIO-DELTAIC STRATIGRAPHY

Fluvio-deltaic stratigraphy contains important archives of internal, self-formed (autogenic) processes, including channel bifurcation and avulsion. Paul Heller’s work established approaches to reconstructing avulsion dynamics from ancient deposits. Here, we present recent advances in characterizing the spatial and temporal distribution of channel avulsion activity from fluvial and deltaic stratigraphy. In an effort to constrain how channel-deposit organization can be quantified from outcrop and subsurface datasets with limited exposure or sampling, we applied the compensation statistic and a spatial-point-process statistic to stratigraphic datasets produced with physical experiments and numerical models. Using uncertainties established with this analysis, we then evaluated avulsion channel stacking in two Upper Cretaceous fluvial and two Cretaceous deltaic outcrop exposures. We show evidence that the ancient fluvial systems had different characteristic avulsion patterns (ranging from random in one case to clustered in another) and that the distribution of sediment across delta deposits was influenced strongly by basin depth in one case and potentially by tidal processes in another. These results highlight the potential for interpreting paleochannel avulsion dynamics from the stratigraphic record and provide a useful framework for comparing autogenic sedimentation patterns across different depositional systems.