The Topographic History of the Alps and its Tectonic and Climatic Drivers (TOPOALPS)
Final Report Abstract
This project was embedded in the European Research Unit TOPOAlps. The general scope was to characterize the modern rates and processes of erosion in the Alps, relate these to tectonic and climatic processes and to extrapolate these back in time. Our project contributed to the overall aims by quantifying modern and post-glacial denudation rates using river loads, reservoir siltation and cosmogenic nuclides as well as by analysing regional trends over the Alps and coupling of denudation with mountain uplift. Part one of the project dealt with a comprehensive compilation of riverine sediment yield and dissolved yield as well as reservoir siltation rates across the Alps from published data. In total, 202 drainage basins are captured which cover about 50% of the total area of the Alps. Modern glaciated basins have the highest sediment yields which are on average 5 to 10 times higher than in non-glaciated basins. The strong glacial impact in the correlations is due to glacier recession and glacial conditioning during repeated Quaternary glaciations. We suggest that this is the major cause for ca. 3 fold enhanced denudation of the western compared to the eastern Alps. Chemical denudation rates are highest in the external Alps dominated by carbonate sedimentary rocks, where they make up about one third of total denudation. We estimated that only 45% of the sediments mobilised in headwaters are exported out off the Alps, most sediments being trapped in artificial reservoirs. When corrected for sediment storage, we obtain an area-weighted mean total denudation rate for the Alps of about 0.32 mm a-1. This rate is not enough to out pace modern rock uplift. Pattern of sediment yield across the Alps coincides roughly with the intensity of glacial conditioning and modern rock uplift, supporting the hypothesis of an erosion-driven uplift of the Alps. Part two determined erosion rates in the Eastern Alps by cosmogenic nuclides in river sediment. Rates are highest in the Central Topographic ridge of the Eastern Alps and in valles that have been oversteepened during the Quaternary glaciations. Plateau samples of non- glaciated valleys yield low erosion rates. The increase at the eastern edge of the Eastern Alps where the inversion of the Pannonic basin lead the tectonic landscape rejuvenation. Part three established the first stable isotope paleoaltimetry reconstruction for the central Alps. Combined low elevation (foreland molasse) and high elevation (Simplon shear zone) stable isotope data a) document the presence of meteoric fluids in ductile shear zones of the central Alps and b) indicate middle Miocene paleoelevation of the central Alps in excess of 2300 m. The long-term foreland basin δ18O record from pedogenic carbonates further indicates protracted climate stability along the orogenic system, yet regional differences across the individual North Alpine foreland megafans.
Publications
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(2010) Cosmogenic nuclide-derived rates of diffusive and episodic erosion in the glacially sculpted upper Rhone Valley, Swiss Alps. Earth Surface Processes and Landforms, 35
Norton, K.P., von Blanckenburg, F., Kubik, P.W.
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(2010) Silicate weathering of soil-mantled slopes in an active Alpine landscape. Geochimica et Cosmochimica Acta 74, 5243-5258
Norton, K.P., von Blanckenburg, F.
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(2011) Cosmogenic 10Be-derived denudation rates of the Eastern and Southern European Alps. Int J Earth Sci 100, 1163-1179
Norton, K.P., von Blanckenburg, F., DiBiase, R., Schlunegger, F., Kubik, P.W.
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(2012) From gullies to mountain belts: a review of sediment budgets at various scales. Sedimentary Geology 280: 21-59
Hinderer, M.
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(2012) Miocene paleotopography of the Central Alps. Earth and Planetary Science Letters, 337-338, 174-185
Campani, M., Mulch, A., Kempf, O., Schlunegger, F., Mancktelow, N.
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(2013) River loads and modern denudation of the Alps – a review, Earth Science Reviews. 118: 11-44
Hinderer, M., Kastowski, M., Kamelger, A., Bartolini, C., Schlunegger, F.
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(2014) Analytical methods for the measurement of hydrogen isotope composition and water content in clay minerals by TC/EA. Chemical Geology, 363, 229-240
Bauer, K.K., Vennemann, T.W.
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(2015) Post-Miocene landscape rejuvenation at the eastern end of the Alps. Lithosphere 7, 3-13
Legrain, N., Dixon, J., Stüwe, K., von Blanckenburg, F., Kubik, P.
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(2015) Timing and conditions of brittle faulting on the Silltal-Brenner Fault Zone, Eastern Alps (Austria). Swiss Journal of Geosciences, 108, 305-326
Mancktelow, N., Zwingmann, H., Campani, M., Fügenschuh, B., Mulch, A.
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(2016) Glaciation's topographic control on Holocene erosion at the eastern edge of the Alps. Earth Surface Dynamics 4, 895-909
Dixon, J.L., von Blanckenburg, F., Stüwe, K., Christl, M.
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(2016) Stable isotope composition of bentonites from the Swiss and Bavarian Freshwater Molasse as a proxy for paleoprecipitation. Paleogeography, Paleoclimatology, Paleoecology, 455, 53-64
Bauer, K.K., Vennemann, T.W., Gilg, H.A.
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(2016) Stable isotope paleoaltimetry and the evolution of landscapes and life. Earth and Planetary Science Letters, 433, 180-191
Mulch, A.
