Contrasting the postglacial morphodynamic evolution of Alpine and Apennine river systems in the central Po Valley, Italy

Understanding how fluvial systems respond to geological controls is challenging due to their sensitivity to a wide range of environmental conditions. These factors determine the characteristics of preserved stratigraphic successions, which may not be accounted for by traditional continental sequence-stratigraphic models. Such models tend to be overly simplistic in the way they consider morphodynamic behaviours, especially for setting where distinct river systems, fed by distinct sediment sources and exhibiting different geomorphic dynamics, interact with each other. Moreover, the extent to which different geomorphological river types are preserved in the stratigraphic record has not been fully documented.

This study aims to elucidate the dynamic interactions and contrasting evolution of adjoining axial and transverse river systems through the study of Quaternary successions and geomorphic elements across a transect of the central Po Valley (Northern Italy). The Po Basin is an asymmetric alluvial foredeep basin and represents an excellent laboratory for this purpose, because it records the geological history of rivers draining the Alps and the Apennines, and converging in the axial Po River channel belt.

A comprehensive geological dataset is constructed by integrating field-based mapping of geomorphological, sedimentological and pedological features with shallow-subsurface borehole observations and remote-sensing data. Petrographic and micromorphological data are being collected with which to undertake analyses of sediment provenance and pedogenetic processes. A chronostratigraphic framework is being erected based on radiometric and luminescence dating, palaeomagnetic data and archaeological evidence.

The results shed light on the contrasting geomorphological and stratigraphic features in the postglacial fluvial evolution of the central Po Plain. The northern alpine tributaries are characterized by incision-dominated dynamics, driven by a marked decrease in sediment supply following the transition from proglacial outwash systems to the postglacial configuration, in which the development of pre-Alpine lakes has been of considerable importance, effectively trapping detritus from upstream catchments.

By contrast, southern rivers draining Apennine catchments have built a postglacial unit dominated by widespread aggradation, characterized by the coalescence of small fluvial fans traversed by alluvial ridges linked with a topographic control on sediment distribution via repeated avulsions.

This asynchronous evolution of aggradational and degradational phases reflects contrasting sedimentary and geomorphic trends driven by differences in sediment supply rates and delivery mechanisms. Indeed, these findings provide a valuable framework for interpreting the stratigraphic architecture of Quaternary successions of the Po Basin, and for comparing the observed post-15 ka evolution with traditional sequence stratigraphic models (LST–TST–HST transition).

This research enables a critical evaluation of the applicability of sequence stratigraphic models in continental settings, emphasizing the necessity for more sophisticated models that account for spatial and temporal variability in fluvial responses to external forcings. Current work seeks to expand this study to successions and landforms recording the earlier Pleistocene evolution of these river systems. By highlighting these processes, this study focuses on the key role of source-to-sink approaches for understanding fluvial system dynamics in continental settings.