TY - JOUR A1 - Kober, Florian A1 - Ivy-Ochs, Susan A1 - Zeilinger, Gerald A1 - Schlunegger, Fritz A1 - Kubik, Peter W. A1 - Baur, Heinrich A1 - Wieler, Rainer T1 - Complex multiple cosmogenic nuclide concentration and histories in the arid Rio Lluta catchment, northern Chile N2 - Terrestrial cosmogenic nuclide (TCN) concentrations measured in river sediments can be used to estimate catchment-wide denudation rates. By investigating multiple TCN the steadiness of sediment generation, transport and depositional processes can be tested. Measurements of Be-10, Ne-21 and Al-26 from the hyper- to semi-arid Rio Lluta catchment, northern Chile, yield average single denudation rates ranging from 12 to 75 m Myr(-1) throughout the catchment. Paired nuclide analysis reveals complex exposure histories for most of the samples and thus the single nuclide estimates do not exclusively represent catchment-wide denudation rates. The lower range of single nuclide denudation rates (12-17 m Myr(-1)), established with the noble gas Ne-21, is in accordance with palaeodenudation rates derived from Ne-21/Be-10 and Al-26/Be-10 ratio analysis. Since this denudation rate range is measured throughout the system, it is suggested that a headwater signal is transported downstream but modulated by a complex admixture of sediment that has been stored and buried at proximal hillslope or terrace deposits, which are released during high discharge events. That is best evidenced by the stable nuclide Ne-21, which preserves the nuclide concentration even during storage intervals. The catchment-wide single Ne-21 denudation rates and the palaeodenuation rates contrast with previous TCN-derived erosion rates from bedrock exposures at hillslope interfluves by being at least one order of magnitude higher, especially in the lower river course. These results support earlier studies that identified a coupling of erosional processes in the Western Cordillera contrasting with decoupled processes in the Western Escarpment and in the Coastal Cordillera. Y1 - 2009 UR - http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291096-9837 U6 - https://doi.org/10.1002/Esp.1748 SN - 0197-9337 ER - TY - JOUR A1 - Schlunegger, Fritz A1 - Norton, Kevin P. A1 - Zeilinger, Gerold T1 - Climatic forcing on channel profiles in the eastern cordillera of the Coroico Region, Bolivia JF - The journal of geology N2 - Orographic precipitation has a large impact on channel morphology and rock uplift via a positive feedback to erosion. We show that in the Eastern Cordillera of Bolivia, channel concavities reach their highest values where annual precipitation increases in the downstream direction, exceeding 3000 mm. The steepest channels are upstream of this zone of high concavity, where precipitation rates are <1000 mm yr(-1). Channels exhibit graded forms both upstream and downstream of this transient reach. We conclude that the prolonged effect of orographic erosion and related tectonic uplift is the preservation of channels with extreme concavities in the Eastern Cordillera. Y1 - 2011 U6 - https://doi.org/10.1086/657407 SN - 0022-1376 VL - 119 IS - 1 SP - 97 EP - 107 PB - Univ. of Chicago Press CY - Chicago ER - TY - JOUR A1 - Savi, Sara A1 - Norton, Kevin P. A1 - Picotti, Vincenzo A1 - Akcar, Naki A1 - Delunel, Romain A1 - Brardinoni, Francesco A1 - Kubik, Peter A1 - Schlunegger, Fritz T1 - Quantifying sediment supply at the end of the last glaciation: Dynamic reconstruction of an alpine debris-flow fan JF - Geological Society of America bulletin N2 - In this paper we quantify the sediment dynamics in the formerly glaciated Zielbach catchment in the Italian Alps from the end of the Last Glacial Maximum (LGM) until today. As a basis for our quantification, we use the stratigraphic record offered by a 3.5 km(2) large fan that we explore with a seismic survey, stratigraphic analyses of drillhole material, and C-14 ages measured on organic matter encountered in these drillings. In addition, we calculate past denudation rate variability in the fan deposits using concentrations of cosmogenic Be-10. We merge this information into a scenario of how the sediment flux has changed through time and how this variability can be related to climatic variations, framed within well-known paraglacial models. The results document a highly complex natural system. From the LGM to the very early Holocene, ice-melted discharge and climate variability promoted a high sediment flux (sedimentation rate up to 40 mm/yr). This flux then dramatically decreased toward interglacial values (0.8 mm/yr at 5-4 calibrated kyr B.P.). However, in contrast to the trend of classic paraglacial models, the flux recorded at Zielbach shows secondary peaks at 6.5 ka and 2.5 ka, with values of 13 mm/yr and 1.5 mm/yr, respectively. Paleo-denudation rates also decrease from similar to 33 mm/yr at the beginning of the Holocene to 0.42 mm/yr at 5 ka, with peaks of similar to 6 mm/yr and 1.1 mm/yr at 6.5 ka and 2.5 ka. High-amplitude climate change is the most likely cause of the secondary peaks, but anthropogenic activities may have contributed as well. The good correlation between paleo-sedimentation and paleo-denudation rates suggests that the majority of the deglaciated material destocked from the Zielbach catchment is stored in the alluvial fan. Y1 - 2014 U6 - https://doi.org/10.1130/B30849.1 SN - 0016-7606 SN - 1943-2674 VL - 126 IS - 5-6 SP - 773 EP - 790 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Savi, Sara A1 - Delunel, Romain A1 - Schlunegger, Fritz T1 - Efficiency of frost-cracking processes through space and time: An example from the eastern Italian Alps JF - Geomorphology : an international journal on pure and applied geomorphology N2 - It is widely accepted that climate has a strong impact and exerts important feedbacks on erosional processes and sediment transport mechanisms. However, the extent at which climate influences erosion is still a matter of debate. In this paper we test whether frost-cracking processes and related temperature variations can influence the sediment production and surface erosion in a small catchment situated in the eastern Italian Alps. To this extent, we first present a geomorphic map of the region that we complement with published Be-10-based denudation rates. We then apply a preexisting heat-flow model in order to analyze the variations of the frost-cracking intensity (FCI) in the study area, which could have controlled the sediment production in the basin. Finally, we compare the model results with the pattern of denudation rates and Quaternary deposits in the geomorphic map. The model results, combined with field observations, mapping, and quantitative geomorphic analyses, reveal that frost-cracking processes have had a primary role in the production of sediment where the intensity of sediment supply has been dictated and limited by the combined effect of temperature variations and conditions of bedrock preservation. These results highlight the importance of a yet poorly understood process for the production of sediment in mountain areas. (C) 2015 Elsevier B.V. All rights reserved. KW - Frost-cracking KW - Sediment production KW - Sediment supply KW - Spatial and temporal denudation rate KW - Climatic variations KW - Holocene Y1 - 2015 U6 - https://doi.org/10.1016/j.geomorph.2015.01.009 SN - 0169-555X SN - 1872-695X VL - 232 SP - 248 EP - 260 PB - Elsevier CY - Amsterdam ER -