Landscape evolution and aquifer building processes in a carbonate fold-and-thrust belt, Italian Southern Alps: Insights from 3D geo-modelling

Carbonate aquifers of fold-and-thrust mountain belts supply a large amount of human water demand all over the world. Aiming to improve carbonate aquifer modelling, we investigated the relationships between landscape evolution and aquifer building processes in the Southalpine thrust belt of Lombardy Region. The rationale was to learn about the coevolution of tectono-stratigraphic, karstic and landscape genetic processes that led to the present-day carbonate aquifer configuration. Morpho-structural analyses and 3D geo-modelling permitted to relate the assemblage of aquifer heterogeneities to the geomorphological evolution of the Gaverina springs setting. Mesozoic pre- and syn-rift stratigraphy predisposed the future different limestone aquifer types (extensive cave vs. phreatic systems). The inherited Mesozoic extensional structures controlled alpine thrusting, shaping, sizing and deploying the different carbonate aquifers and shale aquitards. Coevolution of different karst systems and landscape started since the Neogene emersion above sea level. Three Miocene increments of slip and uplift rates, erosional unroofing of tectonic units, epi- and endokarst genesis and exhumation are recorded by landforms and sediments that witness the stabilization and raising steps of the relative base levels before the Pliocene marine transgression. The present-day elevation (350 m above sea level) of the late Pliocene coastal sediments onlapping the local relief, constrains the minimum estimates of Neogene and Quaternary uplift amounts, during which the karst systems developed downwards chasing the lowering of the reference base levels. Pleistocene glacial advances mainly acted on the valley floor, eroding and lowering the local base level. On the slopes, ablation tills and ice-contact deposits dammed some low-elevation springs, plausibly contributing to expand the phreatic zone upwards. The geo-morphological controls on hydrostratigraphy and the landscape-aquifer coevolution described at the Gaverina site are comparable to those of many settings of the Mediterranean peri-Tethyan fold-and-thrust belts, suggesting that this approach might find a broad application.