Apatite (U-Th-Sm)/He ages from the Karawanken Mountains range between 12 and 5 Ma and indicate an episode of fault-related exhumation leading to the formation of a positive flower structure and an associated peripheral foreland basin. In the Southern Alps, apatite (U-Th-Sm)/He and fission-track data combined with previous data also indicate a pulse of mainly Late Miocene exhumation, which was maximized along thrust systems, with highly differential amounts of displacement along individual structures. Our data contribute to mounting evidence for widespread Late Miocene tectonic activity, which followed a phase of major exhumation during strain localization in the Tauern Window. We attribute this exhumational phase and more distributed deformation during Adriatic indentation to a major change in boundary conditions operating on the orogen, likely due to a shift from a decoupled to a coupled system, possibly enhanced by a shift in convergence direction.

The Aufsess River catchment (97 km2) in northern Bavaria, Germany, is studied to establish a Holocene sediment budget and to investigate the sediment dynamics since the early times of farming in the third millennium BCE. The temporal characterization of the sediment dynamics is based on an intensive dating program with 73 OSL and 14 14C ages. To estimate soil erosion and deposition, colluvial and alluvial archives are investigated in the field by piling and trenching, supported by laboratory analyses. The sediment budget shows that 58% of these sediments are stored as colluvium in on- and foot-slope positions, 9% are stored as alluvium in the floodplains and 33% are exported from the Aufsess River catchment. Colluviation starts in the end-Neolithic ( c. 3100 BCE), while first indicators of soil erosion-derived alluviation is recorded c. 2–3 ka later. The pattern of sedimentation rates also displays differences between the colluvial and alluvial system, with a distinct increase in the Middle Ages ( c. 1000 CE) for the alluvial system, while the colluvial system records low sedimentation rates for this period. A contrast is also observed since Modern times ( c. 1500 CE), with increasing sedimentation rates for the colluvial system, whereas the alluvial system records decreasing rates. The different behavior of the colluvial and alluvial systems clearly shows the non-linear behavior of the catchment’s fluvial system. The results further suggest that human impact is most probably the dominant factor influencing the sediment dynamics of the catchment since the introduction of farming.

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The Bergell intrusion (European Alps) was one of the first locations where thermochronometry was used to resolve changes in erosion rate, yet, relating these changes to variations in climate or in local tectonics remains challenging. One approach that enables changes in erosion rate to be related to changes in climate or rock uplift rate is to utilize landscape evolution models, as topographic response to these forcing parameters is unique. Furthermore, low temperature thermochronometric systems have the potential to resolve topography through time and thus topographic response. We present new (U-Th)/He data for samples collected across 2 km of relief from the Bergell. The ages range from $2 to $16 Ma and define an age elevation with an apparent exhumation rate of 0.1 km/Myr. In order to infer erosion rates, we use a thermokinematic model to solve the heat equation in the crust, track material points through time and predict thermochronometric data. Paleo-topography and erosion rate are parameterized using the stream power model. We find that rock uplift rates were 0.4 km/Myr from $25 to $20 Ma and subsequently decreased to 0.05 km/Myr. This results in a gradual decrease in erosion rate from rates of 0.4 to 0.1 km/Myr. A recent increase in rock uplift rate at $4 Ma to $0.6 km/Myr is required to explain the youngest ages and high topographic relief.

Large alluvial fans characterize the piedmonts of the White Mountains, California–Nevada, USA, with large boulders strewn across their surfaces. The boulders are interpreted as flash floods deposits with an unclear trigger for the transport process. Several triggers are possible, including glacial lake outburst floods (GLOFs), thunderstorms or rainfall on snow cover. From a paleoenvironmental perspective, the origin of the flash floods is of fundamental importance. The alluvial fans that flank the White Mountains at Leidy Creek display particularly impressive examples of these deposits. The boulder deposits and the source catchment at Leidy Creek were examined using 10Be terrestrial cosmogenic nuclide (TCN) surface exposure dating to help elucidate their age and origin. All boulders dated on the alluvial fans date to the Holocene. This is in accordance with the geomorphic analyses of the Leidy Creek catchment and its terraces and sediment ridges, which were also dated to the Holocene using optically stimulated luminescence (OSL) and 10Be surface exposure. The results suggest that the boulders on the alluvial fan were deposited by flash floods during thunderstorm events affecting the catchment of the Leidy Creek valley. Paleomonsoonal-induced mid-Holocene flash floods are the most plausible explanation for the discharges needed for these boulder aggradations, but a regional dataset is needed to confirm this explanation.

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