Morphotectonics and late Quaternary seismic stratigraphy of Lake Garda (Northern Italy)

Lake Garda, the largest lake in Italy at the southern front of the central Alps, provides a unique opportunity to reconstruct Quaternary geological processes related to the interplay between deglaciation driven sedimentation and tectonic activity. In fact, the topographic depression presently occupied by the lakewas site of amajor glacial tongue during the LGM, and is located close to the epicentral areas of two of the largest magnitude historical earthquakes recorded in the Po Plain, the Verona (Jan. 13, 1117) and Brescia, (Dec. 25, 1222) seismic events, characterized by Io IX-X MCS, respectively. Despite this peculiarity, geophysical surveys of the lake are scant. We present results of a waterborne geophysical survey of Lake Garda, leading to the acquisition of a denselyspaced grid of high-resolution seismic reflection profileswhich image the lake floor and uppermost sedimentary sequence. These data enabled us to compile thematicmapswhich provide insights on active geologic processes in different sectors of the basin.We focused ourwork on a prominent seismic reflector (H1), correlated over the entire lake surface, to estimate the sediment deposition rate at the scale of the last 10 ka, and to evaluate the variability of seismic facies and geological processes in different sectors of the basin. Based on available stratigraphic data,we discusswhether H1 could mark the diachronic glacial/fluvio-glacial transition after the Last GlacialMaximum, when the ice tongues south of the Alps started to melt and collapse. We observed that sediments of the southern Lake Garda are affected by incipient tectonic deformation, and two major seismoturbiditehomogenite beds might represent over 50% of the Holocene sedimentary record in the lake depocenter,making the study of the LakeGarda stratigraphy an interesting tool for assessing earthquake hazards at the southern front of the Alpine chain.