Morphology and geological setting of Iseo Lake (Lombardy) through multibeam bathymetry and high-resolution seismic profiles

The Regione Lombardia geological mapping program (CARG), in collaboration with the Istituto Nazionale di Oceanografia e Geofisica Sperimentale of Trieste (OGS), realized a geophysical study of Iseo Lake (Sebino). A multibeam survey and high-resolution single-channel seismic lines allowed the recognition of five physiographic units with different morphologies and evolution: the Oglio prodelta in the northern part of the lake; a central basin with a regular flat floor between –240 and –256 m in depth; the Monte Isola submerged escarpment, bounding the western shores of Monte Isola and emerging at the small islands of San Paolo and Loreto; the Sale Marasino plateau, with a maximum depth of –100 m, between Monte Isola and the eastern shores of the lake; and the southern Sarnico Basin. In the single-channel seismic profiles crossing the central basin, the uppermost part of the sedimentary infill of Iseo Lake can be subdivided into three sequences, interpreted from top to base as recent lacustrine deposits, glacial deposits recording the last glacial maximum expansion, and lacustrine deposits. The morphology of the lake was to a large degree shaped prior to the last glacial maximum (LGM) expansion, as erosional action exerted by the LGM glacier was much reduced. The Oglio prodelta, the fan deltas skirting the lake shores and the landslides along the submerged slopes of the lake occurred subsequent to the retreat of the LGM glacier.