Abstract
Large-scale submarine gravitational land movements involving even more than 1,000 m thick sedimentary successions are known as megalandslides. We prove the existence of large-scale gravitational phenomena off the Crotone Basin, a forearc basin located on the Ionian side of Calabria (southern Italy), by seismic, morpho-bathymetric and well data. Our study reveals that the Crotone Megalandslide started moving between Late Zanclean and Early Piacenzian and was triggered by a contractional tectonic event leading to the basin inversion. Seaward gliding of the megalandslide continued until roughly Late Gelasian, and then resumed since Middle Pleistocene with a modest rate. Interestingly, the onshore part of the basin does not show a gravity-driven deformation comparable to that observed in the marine area, and this peculiar evidence allows some speculations on the origin of the megalandslide.
Highlights
Kilometer- to tens of km-scale submarine gravitational collapses, here referred to as megalandslides, consist of land movements involving up to 1 km thick sedimentary successions sliding on a basal surface that may classify as ‘basal overpressured shale detachment’ or ‘salt detachment’[1]
The Crotone Basin is interpreted as a forearc basin located on the Ionian side of the Calabrian Arc (Southern Italy) (Fig. 1A); it is partly exposed in the Crotone area (Fig. 1B,C) and it is widely documented offshore
Migration was facilitated by the formation of major NW-trending shear zones, which are frequent in the NE sector of the Calabrian arc and represent the NE and the SW boundaries of the Crotone Basin[23,24,25] (Fig. 1A,B)
Summary
Kilometer- to tens of km-scale submarine gravitational collapses, here referred to as megalandslides, consist of land movements involving up to 1 km (or even more) thick sedimentary successions sliding on a basal surface that may classify as ‘basal overpressured shale detachment’ or ‘salt detachment’[1]. Gravity gliding may be instantaneous, associated with mass wasting and shallow detachment, or slow, in connection with a deep detachment and long-term geological processes such as high sedimentation rates or uplift in adjacent areas[1] These large-scale phenomena typically produce an updip extensional domain and a downdip contractional domain, which are linked via a basal detachment surface[2,3]. Many uncertainties remain about the origin, timing, extent and existence itself of the large-scale gravitational phenomenon involving the Crotone Basin This generalized uncertainty is highlighted by the different interpretation provided by other authors about the nature of the Crotone Swell[34], and by the modest deformation and overall good preservation of the Messinian to Plio-Pleistocene succession in the onshore part of the basin, which even contains stratotypes[27,28]. The existence of a still active large-scale gravitational collapse involving the onshore part of the basin would have social impacts, as it would raise security concerns about the population of this area, where the city of Crotone (64.000 inhabitants) is located
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