What killed the Tertiary Southalpine carbonate platform?

The carbonate platforms of the Tertiary Alpine basins (Northalpine Molassa and Southalpine Foredeep basin) are shaped by the different geodynamic settings. According to the classification of Bosence (2005-Sed.Geo.), the Northalpine basin hosted a foreland margin platform (Nummulitic Limestones), whereas the Southalpine basin probably hosted a thurst-top platform that supplied the shallow-water carbonate turbidites of the Ternate Formation. Actually, this latter carbonate platform is no more present, rapidly eroded during the Oligo-Miocene evolution of the Southern Alps, but a paleoecological reconstruction have been provided by Coletti et al. (in prep.) through the analysis of pebbles encountered in the Oligo-Miocene siliciclastic turbidite fan of the Gonfolite Lombarda Group. Here, we first reconstructed the suitable conditions of rise and growth of this narrow platform on top of the active thrusts of the Southern Alps during the Eocene and Early Oligocene, and then investigated the geodynamic processes that have contributed to killing it in the Early Oligocene. We envisaged a top-thrust platform grown up in front of gentle relieves of Jurassic to Cretaceous sedimentary covers, as suggested by the abundant and angular Mesozoic pebbles encountered in the turbidite fan of the Ternate Formation. The large presence of mass flow deposits and marly, often plurimetric soft clasts also suggests that a small, instable delta was frequently discharging terrigenous detritus through flash flood events moving across the platform deep into the basin.  The abrupt disappearance of re-sedimented shallow-water carbonates probably corresponded to the death of the platform soon after the Early Oligocene, but doubts are still present on the causes that triggered it. The temporal gap (at least 5 Ma) that divides the top of the Ternate Formation and the first clastic inputs of the Gonfolite Lombarda Group (~27 Ma) may indicate that the onset of the major phase of growth of the Alpine belt was not the primary cause of the disappearance of the narrow Tertiary Southalpine platform, but maybe the changed climate conditions exposed it to karsification processes and prevented its survival.