Efficiency of frost-cracking processes through space and time: An example from the eastern Italian Alps

Savi, Sara; Delunel, Romain; Schlunegger, Fritz

doi:10.1016/j.geomorph.2015.01.009

Cited by 37 publications

(27 citation statements)

References 38 publications

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“…In the Western and Italian Alps, several lines of evidence were used to suggest that post-glacial climates drive the bulk of exhumation and erosion in the region. Multiple studies have suggested that temperature-driven frost-cracking processes likely control Holocene erosion rates, based on correlations between elevation and erosion rates (Delunel et al, 2010;Savi et al, 2015). It might be hypothesized that the intensity of frost-cracking processes is (or was) greatest in our previously glaciated catchments, thus potentially explaining the distribution of erosion rates.…”

Section: Competing Controls On Holocene Erosion Ratesmentioning

confidence: 98%

Glaciation's topographic control on Holocene erosion at the eastern edge of the Alps

et al. 2016

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Abstract. What is the influence of glacial processes in driving erosion and uplift across the European Alps? It has largely been argued that repeated erosion and glaciation sustain isostatic uplift and topography in a decaying orogen. But some parts of the Alps may still be actively uplifting via deep lithospheric processes. We add insight to this debate by isolating the role of post-glacial topographic forcing on erosion rates. To do this, we quantify the topographic signature of past glaciation on millennial-scale erosion rates in previously glaciated and unglaciated catchments at the easternmost edge of the Austrian Alps. Newly measured catchment-wide erosion rates, determined from cosmogenic 10Be in river-borne quartz, correlate with basin relief and mean slope. GIS-derived slope–elevation and slope–area distributions across catchments provide clear topographic indicators of the degree of glacial preconditioning, which further correlates with erosion rates. Erosion rates in the easternmost, non-glaciated basins range from 40 to 150 mm ky−1 and likely reflect underlying tectonic forcings in this region, which have previously been attributed to recent (post 5 Ma) uplift. By contrast, erosion rates in previously glaciated catchments range from 170 to 240 mm ky−1 and reflect the erosional response to local topographic preconditioning by repeated glaciations. Together, these data suggest that Holocene erosion across the Eastern Alps is strongly shaped by the local topography relict from previous glaciations. Broader, landscape-wide forcings, such as the widely debated deep mantle-driven or isostatically driven uplift, result in lesser controls on both topography and erosion rates in this region. Comparing our data to previously published erosion rates across the Alps, we show that post-glacial erosion rates vary across more than 2 orders of magnitude. This high variation in post-glacial erosion may reflect combined effects of direct tectonic and modern climatic forcings but is strongly overprinted by past glacial climate and its topographic legacy.

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Section: Competing Controls On Holocene Erosion Ratesmentioning

confidence: 98%

Glaciation's topographic control on Holocene erosion at the eastern edge of the Alps

et al. 2016

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“…Because climate and tectonics can affect sediment production rates, any changes in those conditions may lead to the formation of fluvial terraces in the transfer zone or changes in sedimentation rates in the deposition zone (Alloway et al, 2007;Bull, 1990;Scherler et al, 2015;Zhang et al, 2001). Many past studies have used such records to reconstruct paleoenvironmental conditions (fluvial terraces: Litty et al, 2016;Poisson and Avouac, 2004;Schaller et al, 2004;sedimentation rates: Hardy et al, 1996;Zhang et al, 2001). Quantitative interpretations of either record, however, require a clear understanding of how terraces are formed or how sedimentary signals are altered in the transfer zone (Romans et al, 2016, and references therein).…”

Section: Introductionmentioning

confidence: 99%

Alluvial channel response to environmental perturbations: fill-terrace formation and sediment-signal disruption

et al. 2019

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The sensitivity of fluvial systems to tectonic and climatic boundary conditions allows us to use the geomorphic and stratigraphic records as quantitative archives of past climatic and tectonic conditions. Thus, fluvial terraces that form on alluvial fans and floodplains as well as the rate of sediment export to oceanic and continental basins are commonly used to reconstruct paleoenvironments. However, we currently lack a systematic and quantitative understanding of the transient evolution of fluvial systems and their associated sediment storage and release in response to changes in base level, water input, and sediment input. Such knowledge is necessary to quantify past environmental change from terrace records or sedimentary deposits and to disentangle the multiple possible causes for terrace formation and sediment deposition. Here, we use a set of seven physical experiments to explore terrace formation and sediment export from a single, braided channel that is perturbed by changes in upstream water discharge or sediment supply, or through downstream base-level fall. Each perturbation differently affects (1) the geometry of terraces and channels, (2) the timing of terrace cutting, and (3) the transient response of sediment export from the basin. In general, an increase in water discharge leads to near-instantaneous channel incision across the entire fluvial system and consequent local terrace cutting, thus preserving the initial channel slope on terrace surfaces, and it also produces a transient increase in sediment export from the system. In contrast, a decreased upstream sediment-supply rate may result in longer lag times before terrace cutting, leading to terrace slopes that differ from the initial channel slope, and also lagged responses in sediment export. Finally, downstream base-level fall triggers the upstream propagation of a diffuse knickzone, forming terraces with upstream-decreasing ages. The slope of terraces triggered by base-level fall mimics that of the newly adjusted active channel, whereas slopes of terraces triggered by a decrease in upstream sediment discharge or an increase in upstream water discharge are steeper compared to the new equilibrium channel. By combining fillterrace records with constraints on sediment export, we can distinguish among environmental perturbations that would otherwise remain unresolved when using just one of these records.Published by Copernicus Publications on behalf of the European Geosciences Union.

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“…The altitude of the present-day 0°-isotherm in the Fedoz 1071 ALPINE 10 BE DENUDATION RATES OVER 6 KYR catchment is~2200 m while during the warmer Middle Holocene it was likely a few hundred meters higher (cf. Savi et al, 2015). This means that given the catchment hypsometry, a larger area was subject to frost-cracking processes during the warmer Holocene.…”

Section: Discussionmentioning

confidence: 99%

Constant denudation rates in a high alpine catchment for the last 6 kyrs

Grischott

Kober

Lupker

et al. 2016

Earth Surf Processes Landf

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Terrestrial cosmogenic nuclides (TCN) have widely been used as proxies in determining denudation rates in catchments. Most studies were limited to samples from modern active streams, thus little is known about the magnitude and causes of TCN variability on millennial time scales. In this work we present a 6 kyrs long, high resolution record of 10Be concentrations (n = 18), which were measured in sediment cores from an alluvial fan delta at the outlet of the Fedoz Valley in the Swiss Alps. This record is paired with a 3‐year time series (n = 4) of 10Be measured in sediment from the active stream currently feeding this fan delta. The temporal trend in the 10Be concentrations after correction for postdepositional production of 10Be was found to be overall constant and in good agreement with the modern river 10Be concentration. The calculated mean catchment‐wide denudation rate amounts to 0.73 ± 0.18 mm yr−1. This fairly constant level of 10Be concentrations can be caused by a constant denudation rate over time within the catchment or alternatively by a buffered signal. In this contribution we suggest that the large alluvial floodplain in the Fedoz Valley may act as an efficient buffer on Holocene time scales in which sediments with different 10Be signatures are mixed. Therefore, presumable variations in the 10Be signals derived from changes in denudation under a fluctuating Holocene climate are only poorly transferred to the catchment outlet and not recorded in the 10Be record. However, despite the absence of high frequency signals, we propose that the buffered and averaged 10Be signal could be meaningfully and faithfully interpreted in terms of long‐term catchment‐averaged denudation rate. Our study suggests that alluvial buffers play an important role in regulating the 10Be signal exported by some alpine settings that needs to be taken into account and further investigated. Copyright © 2016 John Wiley & Sons, Ltd.

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Efficiency of frost-cracking processes through space and time: An example from the eastern Italian Alps

Cited by 37 publications

References 38 publications

Glaciation's topographic control on Holocene erosion at the eastern edge of the Alps

Glaciation's topographic control on Holocene erosion at the eastern edge of the Alps

Alluvial channel response to environmental perturbations: fill-terrace formation and sediment-signal disruption

Constant denudation rates in a high alpine catchment for the last 6 kyrs

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