Seismically-induced slumps in Lower-Maastrichtian peritidal carbonates of the Apulian Platform (southern Italy)

Abstract

In the southeastern Murge (Apulian Foreland, southern Italy), a Lower-Maastrichtian carbonate section showing soft-sediment deformation structures is composed of peritidal lithofacies associations developed in a wide low-energy inner-platform system. Shear-induced soft-sediment deformation structures correspond to multilayer deformed horizons, 1.5 to 2 m in thickness, sandwiched between undeformed layers. Overturned and recumbent folds lying on décollement surfaces and asymmetrical fault-inception folds allow us to interpret the observed deformed horizons as slump sheets. The detailed description of the main morphological features of the deformed beds and the recognition of unconformable surfaces and undeformed beds between slumped beds allow us to distinguish three different events of deformation. Preferential orientation of slump folds has been measured and every slumped bed shows a different direction of shortening. Randomly oriented direction of shortening suggests that each deformation event was driven by the presence of local very gentle gradients developed in peritidal settings. By excluding other potential trigger mechanisms of deformation, the observed slumps are interpreted as seismically-induced slides. Even if no data about the distance of the seismic source may be obtained, near-field earthquake tectonics affected the Apulian Platform during Late Cretaceous times.