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Abstract: This paper explores the mechanisms by which inner gorges in the Alps were formed. It focuses on the ca. 1.5-km-long, 80-m-deep, and a few hundred meter wide Lammschlucht located in the northern foothills of the central Alps. We reconstructed the glacial cover using lateral moraines and hanging talus cones that record the elevation of the ice surface at the deglaciation stage of the LGM (Last Glacial Maximum). We used the reconstructed ice thickness patterns to calculate the erosional potential of the subglacial meltwater. The applied model is based on the principle of energy conservation and yields the pattern of downstream changes of the dynamic pressure, which is considered a measure for erosion potential. The model results suggest a maximum of the dynamic pressure at the end of the inner gorge. We interpret, therefore, that the subglacial meltwater scoured the reach toward the end of the Lammschlucht because of the enhanced dynamic pressure, which was ultimately controlled by the ice overburden. Post-glacial fluvial erosion then resulted in a readjustment through a regressive shift of the erosional front along the inner gorge farther upstream. The current location of this front lies almost in the middle of the Lammschlucht inner gorge where a step-pool channel changes into a straight plane-bed channel flowing on a deeply scoured bedrock. [Copyright &y& Elsevier]

Abstract: Previous studies have interpreted landforms east of Mount Shiroumadake (2932m asl), in the Northern Japanese Alps, as lateral and terminal moraines and outwash terraces of glacial origin. However, recent studies in other areas of the Northern Japanese Alps have interpreted similar landforms as characteristic landslide bodies. We re-examined the origin and age of moraine-like landforms on the eastern side of Mount Shiroumadake through field geological surveys and landform analysis. We show that terminal moraine-like landforms in our study area consist of beds of brecciated or crushed gravel with locally derived crackle clasts and are unrepresentative of the variety of bedrock expose in the plausible source areas of Pleistocene glaciers. We interpret these deposits as induced by mass rock creep and landsliding at the terminus of a steep ridge or a steep valley side slope. Similarly, terrace surfaces formerly-interpreted as of outwash or fluvial origin consist of gravel beds with many fractured rock clasts of landslide origin. Although the timing of the landslides is not well constrained, they may have occurred in the early to middle Holocene. The highly deformed rocks of the study area, combined with the humid climate with much snowfall and rainfall, have left the landscape with an inherent predisposition for landsliding. Paleoearthquakes on nearby active faults in the piedmont area of Mount Shiroumadake may have provided a direct trigger for landsliding. [Copyright &y& Elsevier]

Fluvial incision is the consequence of landscape readjustment to combined tectonic and climatic processes. In the southwestern Alps (Haute Provence Geopark), deep gorges incised by the Bès River attest of efficient erosional processes at the front of the Alpine mountain range. This catchment stands in a peripheral Alpine position, out of the glaciated domain during the last glacial periods, which makes it suitable to quantify fluvial incision and related erosional processes in a glacier-free environment. In this paper, we combine high resolution 3D topographic mapping and in situ produced cosmogenic 36Cl dating of a mountain gorge (the "Clue de Barles" Gorge). First, the very high-resolution 3D topographic modeling from aerial and drone surveys permits to map the erosion markers on the gorge walls and to accurately determine the topographic shielding factor for Cosmic Ray Exposure (CRE) dating. Secondly, 36Cl CRE age distribution highlights two distinct geomorphic domains along the vertical profile: i) the higher section is characterized by clusters of similar CRE ages, interpreted as related to paraglacial rockfall events; ii) the lower section shows increasing ages with height, which are ascribed to fluvial incision occurring at a rate of 0.15 mm/yr since 25 ka, and of 2 mm/yr since 2 ka. Our results for the Clue de Barles, compared to other sites in the South French Alps highlight that: i) the gorge morphology is the result of the combination of both vertical fluvial incision and lateral gravitational processes, ii) the mean Quaternary fluvial incision rate in the Bès River catchment is at least twice lower than further east in the formerly glaciated Alps. • Bès river fluvial incision rate is 0.15 mm/yr since 25 ka. • Clusters of similar exposure ages are interpreted as postglacial rock fall events. • The gorge is shaped by vertical fluvial incision and lateral gravitational processes. • Bès River Quaternary incision rate is at least twice lower than in the SE Alps. [ABSTRACT FROM AUTHOR]