Quaternary hydrostratigraphy in the Po Plain: multiscale geology and forward modelling

Hydrogeological modelling at different scales is best performed if the hydrostratigraphic architecture is well described, accounting for the hierarchic arrangement of heterogeneities and the multiple scales of the geological features. To this purpose, an efficient combination of surface geology data (high detail and accuracy, 1D - 3D data, small to large-scale, low-rank) with subsurface borehole/geophysical data (1D - 2D, very small to very large scale, low detail and accuracy, undistinguished rank) is mandatory. The management of such a multi-scale and heterogeneous dataset is the starting point of this work. The aim is to define a 3-D stratigraphic framework at different scale, constrained by all the available data, as a mean to validate the different evolutionary and geometrical hypotheses formulated in the 1 - and 2-D data analysis carried out in a GIS environment. The study area is a 25x50 km, N-S transect of the Central Po Plain, the widest alluvial basin of Italy hosting multi-layered aquifers of Quaternary age. A reliable geological reconstruction in this area contributes to better define the 3-D geometries of the stratigraphic units, verifying the existent 2-D geological maps and sections. It also contributes to validate the evolutionary history of the Basin, as the result of the interaction of Quaternary Alpine glacial cycles (North), tectonic evolution driven by the Apennine thrusts (South), and changes in the accommodation and sedimentation rates. The method relies on the integration of geological, field-based “hard” data, interpretative cross-sections and maps, geo-history and evolutionary hypotheses, with GIS and GeoModeller software. GIS is dedicated to data management and pre-processing for the 3-D analysis; GeoModeller permits to simulate and visualize the stratigraphic/tectonic relations rapidly, honouring the geological constraints, in order to elaborate several forward models comparing contrasting architectural end evolutionary hypotheses. The dynamic approach I want to discuss is multi-scale and hierarchical. It refers to i) the hierarchic order of the different “geological entities” and ii) the nature/number of constraints that have to be taken into account at each scale of reconstruction, by the integration of both surface and subsurface geological data.