Abstract Stress distribution in mountainous areas is influenced by local morphology. Valley morphology and the relationship between main and tributary valleys strongly depend on geological characteristics and evolution. They may control the evolution of slope instabilities, especially when interacting with pervasive structural features. We performed parametric three-dimensional (3D) numerical modelling of simplified slope geometries with variable slope angle (from 21° to 35°), length, combining different orientations for different slope sectors and changing attitude of pervasive planes of anisotropy (foliation, schistosity, bedding). Data used in the 3D models are the initial slope geometry, rock mass properties and internal anisotropy. We assumed Mohr–Coulomb behaviour, with the presence of ubiquitous joints and different piezometric levels. The model results show that plastic deformation initiates near the highest ridge just after deglaciation commences. A shear zone develops and propagates toward the toe of the slope, and its shape is strongly controlled by slope geometry, anisotropy and in situ stresses. The thickness of the failing mass, for model slope reliefs up to 3200 m, increases from 50 m to some hundreds of metres during glacier retreat, and it depends on geometry of slopes, anisotropy and in situ stresses. Results are compared to examples of deep-seated slope deformations from the Alps, which helps in the interpretation of such phenomena and in the understanding of their influence on valley evolution.

Abstract The provenance history of sediments deposited in the piggy-back basins of the Northern Apennines has been drawn by means of a petrographic study of nearly 200 sandstone samples collected over 250 km of the belt; it allows the evolution of the eroded part of the belt in Oligocene-Early Miocene times to be determined in detail, with special emphasis on the age of the exhumation and the onset of erosion of the high-pressure/low-temperature Pennine metamorphic units of the Ligurian Alps and Corsica that form the innermost part of the chain. Five petrofacies were distinguished, representing three sources that were active separately (three ‘pure’ petrofacies) or together (two ‘mixed’ petrofacies). The resulting sandstone composition reflects the erosion of different source units, changing through time and space along the belt. The stratigraphic distribution of petrofacies records a change in the main clastic source from Ligurian calcareous units to Penninic units. This change occurred over most of the study area, reflecting the complete exhumation of the Penninic metamorphic units within the innermost part of the belt. It occurred at different times along the chain, migrating from northwest to southeast from Late Rupelian to Aquitanian. This time shift is interpreted to be related to the obliquity of the Northern Apennines convergent system.

Abstract The Tertiary Piedmont Basin was reshaped as the Apennines progressively overrode the Alpine retroforeland. Nine basin-wide unconformities were followed by abrupt accommodation turnarounds or high-accommodation/high sediment supply intervals. Unusual stratigraphic discontinuities require a different perspective to reconcile allostratigraphy and sequence stratigraphy, highlighting a wider range of tectonically driven discontinuities (subaerial/subaqueous/regressive/transgressive), diachronism of accommodation and sediment–fairway turnarounds, unusual routing to deepwater, and relationships between fourth- and fifth-order sequences. This approach allows innovative play concepts and prediction of reservoir heterogeneity. Steep gradients and high sediment fluxes favour the development of coarse-grained deltas dominated by hyperpycnal processes and large-scale instability/sediment failures, often expressed by retrogressive slump scars, owing to over-steepening generated by drowning unconformities related to orogenic collapse or basin inversion. During increasing-accommodation intervals, subaqueous erosion leaves remnants of drowned deltas forming stratigraphic traps sealed by prodelta-slope muds. The sediments removed feed turbidites, generated during transgressive intervals and deposited at the toe of oversteepened slopes. These may eventually back-fill the slump scar system and show a fining-upward stacking-pattern owing to the re-establishment of the equilibrium profile. Another play concept relies on the combination of onlapping non-marine to marginal marine deposits against fault-bounded basement highs, sealed by marine muds deposited during the subsequent drowning.