Sedimentary facies characterization through <scp>CPTU</scp> profiles: An effective tool for subsurface investigation of modern alluvial and coastal plains

Cone penetration tests, a method that is typically used to determine the engineering properties of soils, can be as an effective tool for refined subsurface stratigraphic investigations alluvial and coastal plains, aside from geographic location. High-resolution calibration piezocone tests (CPTU) with 20 sediment cores enabled detailed characterization alluvial, deltaic depositional systems Po Plain. Twelve cored facies associations, typical plain environments, were characterized based on four distinct CPTU profiles: basic cone resistance (Qc), sleeve friction (Fs), water pore pressure (U) ratio (FR). Sandy associations (fluvial/distributary channel, bay-head delta, transgressive barrier, delta-front/beach-ridge) have high (>4 MPa) Qc, low-to-negative U low (<2%) FR. Muddy deposits (well-drained/poorly-drained floodplain, swamp, lagoon prodelta) exhibit opposite trends. Heterolithic (crevasse-levée, offshore/delta-front transition) display characteristic seesaw profiles. Plotting late Quaternary onto latest version test soil behaviour chart (Robertson, 2010) enables identification distinctive reflecting grain size. interpretation leads sedimentary recognition well beyond simple lithological differentiation and, in particular, allows clay-rich silt-rich units (swamp clays peats, central-inner outer lagoon, proximal/distal prodelta deposits) only subtle differences lithology. data also serve accurate detection key surfaces potential applications, such Pleistocene–Holocene boundary. This latter, common feature several successions, commonly marked by abrupt upward decrease Late Pleistocene, pedogenized, stiff strata overlying Holocene, organic-rich, soft deposits. study offers updated CPTU-facies could suitable modern plains worldwide.