scholarly journals Spatio-temporal variability and controlling factors for postglacial erosion dynamics in the Dora Baltea catchment (western Italian Alps)

2021 ◽  
Author(s):  
Elena Serra ◽  
Pierre Gaston Valla ◽  
Romain Delunel ◽  
Natacha Gribenski ◽  
Marcus Christl ◽  
...  
Keyword(s):  
Drainage System ◽  
Western Alps ◽  
Climatic Conditions ◽  
Sediment Flux ◽  
European Alps ◽  
Italian Alps ◽  
River Sand ◽  
Denudation Rate ◽  
Denudation Rates ◽  
Mont Blanc Massif

Abstract. Disentangling the influence of bedrock erodibility from the respective roles of climate, topography and tectonic forcing on catchment denudation is often challenging in mountainous landscapes due to the diversity of geomorphic processes in action and of spatial/temporal scales involved. The Dora Baltea catchment (western Italian Alps) appears the ideal setting for such investigation, since its large drainage system, extending from the Mont Blanc Massif to the Po Plain, cuts across different major litho-tectonic units of the western Alps, whereas this region has experienced homogeneous climatic conditions and glacial history throughout the Quaternary. We acquired new 10Be-derived catchment-wide denudation rates from 18 river-sand samples collected both along the main Dora Baltea river and at the outlet of its main tributaries. The inferred denudation rate results vary between 0.2 and 0.9 mm/yr, consistent with values obtained across the European Alps by previous studies. Spatial variability in denudation rates was statistically compared with topographic, environmental and geologic metrics. 10Be-derived denudation records do not correlate with the distribution of modern precipitation and rock geodetic uplift. We find, rather, that catchment topography, in turn conditioned by bedrock erodibility (litho-tectonic origin) and glacial overprint, has the main influence on denudation rates. We calculated the highest denudation rate for the Mont Blanc Massif, whose granitoid rocks and long-term tectonic uplift support steep slopes and high relief and thus favour intense glacial/periglacial processes and recurring rock fall events. Finally, our results, in agreement with modern sediment budgets, demonstrate that the high sediment input from the Mont Blanc catchment dominates the Dora Baltea sediment flux, explaining the constant low 10Be concentrations measured along the Dora Baltea course even downstream the multiple junctions with tributary catchments.

scholarly journals <sup>10</sup>Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

2017 ◽  
Author(s):  
Maarten Lupker ◽  
Jérôme Lavé ◽  
Christian France-Lanord ◽  
Marcus Christl ◽  
Didier Bourlès ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Sediment Flux ◽  
Coarse Grained ◽  
The Tibetan Plateau ◽  
Data Set ◽  
Denudation Rate ◽  
Cosmogenic Nuclide ◽  
Denudation Rates ◽  
The Impact ◽  
Eastern Himalayan Syntaxis

Abstract. The Tsangpo-Brahmaputra River drains the eastern part of the Himalayan range, flowing from the Tibetan Plateau through the eastern Himalayan syntaxis and downstream to the Indo-Gangetic floodplain. As such it is a unique natural laboratory to study how denudation and sediment production processes are transferred to river detrital signals. In this study, we present a new 10Be data set to constrain denudation rates across the catchment and to quantify the impact of rapid erosion within the syntaxis region on cosmogenic nuclide budgets and signals. 10Be denudation rates span around two orders of magnitude across the catchments (ranging from 0.03 mm/yr to > 4 mm/yr) and sharply increase as the Tsangpo-Brahmaputra flows across the eastern Himalaya. The increase in denudation rates however occurs ~ 150 km downstream of the Namche Barwa-Gyala Peri massif (NBGPm), an area which has been previously characterized by extremely high erosion and exhumation rates. We suggest that this downstream lag is mainly due to the physical abrasion of coarse grained, low 10Be concentration, landslide material produced within the syntaxis that dilutes the upstream high concentration 10Be flux from the Tibetan Plateau only after abrasion has transferred sediment to the studied sand fraction. A simple abrasion model produces typical lag distances of 50 to 150 km compatible with our observations. Abrasion effects reduce the spatial resolution over which denudation can be constrained in the eastern Himalayan syntaxis. In addition, we also highlight that denudation rate estimates are dependent on the sediment connectivity, storage and quartz content of the upstream Tibetan Plateau part of the catchment which tends to lead to an overestimation of downstream denudations rates. Taking these effects into account we estimate a denudation rates of ca. 2 to 5 mm/yr for the entire syntaxis and ca. 4 to 28 mm/yr for the NBGPm, which is significantly higher than other to other large catchments. Overall, 10Be concentrations measured at the outlet of the Tsangpo-Brahmaputra in Bangladesh suggest a sediment flux between 780 and 1430 Mt/yr equivalent to a denudation rate between 0.7 and 1.2 mm/yr for the entire catchment.

Can 14C-10Be detect transient patterns of denudation ? Application to the French Massif Central.

2021 ◽  
Author(s):  
Sebastien J.P. Lenard ◽  
Maarten Lupker ◽  
Irene Schimmelpfennig ◽  
Vincent Godard ◽  
Clement Desormeaux ◽  
...  
Keyword(s):  
Agricultural Practices ◽  
Climatic Conditions ◽  
Integration Time ◽  
Mountain Range ◽  
River Sand ◽  
Massif Central ◽  
Erosion Processes ◽  
Denudation Rates ◽  
Extreme Precipitation Events

&lt;p&gt;Denudation rates are routinely derived from concentrations of terrestrial in situ produced cosmogenic nuclides (TCN), particularly from &lt;sup&gt;10&lt;/sup&gt;Be concentrations in river sand. Denudation rates are calculated assuming that they remain steady throughout the integration time scale of the TCN. However, such an assumption is possibly unverified in settings with negligible tectonics, where rates typically range from 10 to 100 mm/ky. In those settings, the TCN conveys a signal that integrates denudation over a time span longer than a few thousand years. The signal may include periods when anthropogenic and climatic forcing on denudation was distinct from modern times. For instance, agricultural practices were limited before 6,000 years B.P. and climatic conditions were colder and drier before 10,000 years B.P. A variable forcing may produce variable and transient denudation rates. In that case, the assumption of steady denudation rates is invalid, and their derivation may introduce a bias.&lt;/p&gt;&lt;p&gt;To detect transient landscapes and resolve such a bias, we can take advantage of the different sensitivity of the &lt;sup&gt;14&lt;/sup&gt;C and &lt;sup&gt;10&lt;/sup&gt;Be TCNs to recent and short-term changes in surface denudation. In situ &lt;sup&gt;14&lt;/sup&gt;C is more sensitive than &lt;sup&gt;10&lt;/sup&gt;Be to such changes, because of a shorter half-life (5,700 y compared to 1.4 My). This potential application of coupled &lt;sup&gt;14&lt;/sup&gt;C - &lt;sup&gt;10&lt;/sup&gt;Be measurements has recently been discussed in several theoretical studies (Hippe, 2017; Mudd, 2017; Skov et al., 2019). Despite the improvement of &lt;sup&gt;14&lt;/sup&gt;C extraction lines and measurement facilities (Hippe et al., 2009; Lupker et al., 2019), sensitivity tests remain limited on natural cases (Hippe et al., 2012).&lt;/p&gt;&lt;p&gt;Here, we propose assessing this new application by in situ &lt;sup&gt;14&lt;/sup&gt;C - &lt;sup&gt;10&lt;/sup&gt;Be measurements on river sand from the Cevennes and the Monts Margeride within the Variscan Massif Central in France. With an average elevation of ~700 m, this mountain range presents an asymmetrical topography, composed of a low-relief surface reaching 1,700 m, and bordered by a gently sloping flank to the west and a steep escarpment to the southeast, along the Cevennes fault. This escarpment receives frequent and seasonal extreme precipitation events (300-700 mm in 48h) on its southeast flank.&lt;/p&gt;&lt;p&gt;The range is subject to very limited seismic activity and appears relevant for an application of the &lt;sup&gt;14&lt;/sup&gt;C-&lt;sup&gt;10&lt;/sup&gt;Be couple. Basins are rich in quartz and have homogeneous lithology. The recent paleoclimatic context is well constrained, with substantial climatic variations but with limited Pleistocene glaciations (e.g. Fauquette et al., 1999; Magny et al., 2003; Mayewski et al., 2004). The Massif Central is subject to active erosion processes, without major contribution from stochastic events such as landslides. Denudation rates are in the range of the theoretical study of Skov et al. 2019 (Schaller et al. 2001; Molliex et al. 2016; Olivetti et al. 2016; Desormeaux et al., 2021) and several studies have suggested transient denudation patterns (Schaller et al. 2001; Olivetti et al. 2016). With our new measurements, we will verify whether the &lt;sup&gt;14&lt;/sup&gt;C-&lt;sup&gt;10&lt;/sup&gt;Be couple has sufficient resolution to detect such transience in natural cases.&lt;/p&gt;

scholarly journals Postglacial erosion of bedrock surfaces and deglaciation timing: New insights from the Mont Blanc massif (western Alps)

Geology ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 139-144 ◽  
Author(s):  
Benjamin Lehmann ◽  
Frédéric Herman ◽  
Pierre G. Valla ◽  
Georgina E. King ◽  
Rabiul H. Biswas ◽  
...  
Keyword(s):  
Erosion Rate ◽  
Western Alps ◽  
Optically Stimulated Luminescence ◽  
European Alps ◽  
Erosion Rates ◽  
Exposure Dating ◽  
The Last Glacial Maximum ◽  
Mont Blanc Massif ◽  
The Last Glacial

Abstract Since the Last Glacial Maximum, ∼20 k.y. ago, Alpine glaciers have retreated and thinned. This transition exposed bare bedrock surfaces that could then be eroded by a combination of debuttressing or local frost cracking and weathering. Quantification of the respective contributions of these processes is necessary to understand the links between long-term climate and erosion in mountains. Here, we quantified the erosion histories of postglacial exposed bedrock in glacial valleys. Combining optically stimulated luminescence and terrestrial cosmogenic nuclide (TCN) surface exposure dating, we estimated the erosion rate of bedrock surfaces at time scales from 101 to 104 yr. Bedrock surfaces sampled from the flanks of the Mer de Glace (Mont Blanc massif, European Alps) revealed erosion rates that vary from 3.5 ± 1.2 ⋅ 10−3 mm/yr to 4.3 ± 0.6 mm/yr over ∼500 m of elevation, with a negative correlation between erosion rate and elevation. The observed spatial variation in erosion rates, and their high values, reflect morphometric (elevation and surface slope) and climatic (temperature and snow cover) controls. Furthermore, the derived erosion rates can be used to correct the timing of deglaciation based on TCN data, potentially suggesting very rapid ice thinning during the Gschnitz stadial.

scholarly journals <sup>10</sup>Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

2017 ◽  
Vol 5 (3) ◽  
pp. 429-449 ◽  
Author(s):  
Maarten Lupker ◽  
Jérôme Lavé ◽  
Christian France-Lanord ◽  
Marcus Christl ◽  
Didier Bourlès ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Sediment Flux ◽  
Coarse Grained ◽  
The Tibetan Plateau ◽  
Data Set ◽  
Denudation Rate ◽  
Cosmogenic Nuclide ◽  
Denudation Rates ◽  
The Impact ◽  
Eastern Himalayan Syntaxis

Abstract. The Tsangpo-Brahmaputra River drains the eastern part of the Himalayan range and flows from the Tibetan Plateau through the eastern Himalayan syntaxis downstream to the Indo-Gangetic floodplain and the Bay of Bengal. As such, it is a unique natural laboratory to study how denudation and sediment production processes are transferred to river detrital signals. In this study, we present a new 10Be data set to constrain denudation rates across the catchment and to quantify the impact of rapid erosion within the syntaxis region on cosmogenic nuclide budgets and signals. The measured 10Be denudation rates span around 2 orders of magnitude across individual catchments (ranging from 0.03 to > 4 mm yr−1) and sharply increase as the Tsangpo-Brahmaputra flows across the eastern Himalaya. The increase in denudation rates, however, occurs  ∼  150 km downstream of the Namche Barwa–Gyala Peri massif (NBGPm), an area which has been previously characterized by extremely high erosion and exhumation rates. We suggest that this downstream lag is mainly due to the physical abrasion of coarse-grained, low 10Be concentration, landslide material produced within the syntaxis that dilutes the upstream high-concentration 10Be flux from the Tibetan Plateau only after abrasion has transferred sediment to the studied sand fraction. A simple abrasion model produces typical lag distances of 50 to 150 km compatible with our observations. Abrasion effects reduce the spatial resolution over which denudation can be constrained in the eastern Himalayan syntaxis. In addition, we also highlight that denudation rate estimates are dependent on the sediment connectivity, storage, and quartz content of the upstream Tibetan Plateau part of the catchment, which tends to lead to an overestimation of downstream denudation rates. While no direct 10Be denudation measurements were made in the syntaxis, the dilution of the upstream 10Be signal, measured in Tsangpo-Brahmaputra sediments, provides constraints on the denudation rates in that region. These denudation estimates range from ca. 2 to 5 mm yr−1 for the entire syntaxis and ca. 4 to 28 mm yr−1 for the NBGPm, which is significantly higher than other large catchments. Overall, 10Be concentrations measured at the outlet of the Tsangpo-Brahmaputra in Bangladesh suggest a sediment flux between 780 and 1430 Mt yr−1 equivalent to a denudation rate between 0.7 and 1.2 mm yr−1 for the entire catchment.

scholarly journals Area and volume loss of the glaciers in the Ortles-Cevedale group (Eastern Italian Alps): controls and imbalance of the remaining glaciers

2013 ◽  
Vol 7 (5) ◽  
pp. 1339-1359 ◽  
Author(s):  
L. Carturan ◽  
R. Filippi ◽  
R. Seppi ◽  
P. Gabrielli ◽  
C. Notarnicola ◽  
...  
Keyword(s):  
Near Infrared ◽  
Climatic Conditions ◽  
Ratio Method ◽  
European Alps ◽  
Volume Loss ◽  
Italian Alps ◽  
Landsat Images ◽  
Band Ratio ◽  
1960S And 1970S ◽  
Area And Volume

Abstract. A widespread loss of glacier area and volume has been observed in the European Alps since the 1980s. In addition to differences among various regions of the Alps, different responses to climate change characterize neighboring glaciers within the same region. In this study we describe the glacier changes in the Ortles-Cevedale group, the largest glacierized area in the Italian Alps. We analyze the spatial variability, the drivers, and the main factors controlling the current loss of ice in this region, by comparing mean elevation changes derived from two digital terrain models (DTMs), along with glacier extents and snow-covered areas derived from Landsat images acquired in 1987 and 2009, to various topographic factors. Glacier outlines were obtained using the band ratio method with manual corrections. Snow was classified from a near-infrared image after topographic correction. The total glacierized area shrank by 23.4 ± 3% in this period, with no significant changes in the mean altitude of the glaciers. In 2009 the snowline was 240 m higher than in the 1960s and 1970s. From the snow-covered area at the end of summer 2009, which fairly represents the extent and local variability of the accumulation areas in the 2000s, we estimate that approximately 50% of the remaining glacier surfaces have to melt away to re-establish balanced mass budgets with present climatic conditions. The average geodetic mass budget rate, calculated for 112 ice bodies by differencing two DTMs, ranged from −0.18 ± 0.04 to −1.43 ± 0.09 m w.e. a−1, averaging −0.69 ± 0.12 m w.e. a−1. The correlation analysis of mass budgets vs. topographic variables emphasized the important role of hypsometry in controlling the area and volume loss of larger glaciers, whereas a higher variability characterizes smaller glaciers, which is likely due to the higher importance of local topo-climatic conditions.

scholarly journals Area and volume loss of the glaciers in the Ortles-Cevedale group (Eastern Italian Alps): controls and imbalance of the remaining glaciers

2013 ◽  
Vol 7 (1) ◽  
pp. 267-319 ◽  
Author(s):  
L. Carturan ◽  
R. Filippi ◽  
R. Seppi ◽  
P. Gabrielli ◽  
C. Notarnicola ◽  
...  
Keyword(s):  
Near Infrared ◽  
Infrared Image ◽  
Climatic Conditions ◽  
European Alps ◽  
Volume Loss ◽  
Italian Alps ◽  
Landsat Images ◽  
Band Ratio ◽  
1960S And 1970S ◽  
Area And Volume

Abstract. A widespread loss of glacier area and volume was observed in the European Alps since the 1980s. Besides differences among various regions of the Alps, different responses characterize neighboring glaciers within the same region. In this study we describe the glacier changes in the Ortles-Cevedale group, the largest glacierized area in the Italian Alps. We characterize the drivers, the spatial variability and the main factors controlling the current loss of ice in this region by comparing glacier extents and snow covered areas derived from Landsat images acquired in 1987 and 2009. Glacier outlines were obtained from a band ratio with manual corrections and snow was classified from a near infrared image after topographic correction. The total glacierized area shrank by 23% in this period, with no significant changes in the mean altitude of the glaciers. The snowline is now 240 m higher than in the 1960s and 1970s. From the snow covered area of 2009, which fairly represents the extent of the accumulation areas over the last decade, we estimate that about 50% of the remaining glacier surfaces have to melt away to re-establish equilibrium with present climatic conditions. The average geodetic mass budget rate, calculated for 112 ice bodies by differencing two Digital Terrain Models (DTMs), ranged from −0.15 to −1.50 m w.e. a−1, averaging −0.68 m w.e. a−1. A correlation analysis of mass budgets vs. topographic variables confirmed the important role of the hypsometry in controlling area and volume loss of larger glaciers, while a higher variability characterizes smaller glaciers and glacierets, likely due to the increasing importance of local topo-climatic conditions.

scholarly journals The mass balance of a cirque glacier in the Italian Alps (Ghiacciaio Della Sforzellina, Ortles–Cevedale Group)

1993 ◽  
Vol 39 (131) ◽  
pp. 87-90
Author(s):  
G. Catasta ◽  
C. Smiraglia
Keyword(s):  
Mass Balance ◽  
Mean Value ◽  
Climatic Conditions ◽  
Mass Balances ◽  
Italian Alps ◽  
Variation Data ◽  
Using Data

AbstractThe net mass balance (1986/87–1989/90) was calculated for a small cirque glacier in the Italian Alps (Ghiacciaio della Sforzellina, 0.42 k m2, Ortles–Cevedale Group). Four annual mass balances are presented here. All four balances were negative (mean value: –0.90 m year−1), with a maximum deficit of –1.16 m year−1 in 1989–90. The climatic conditions (which are analyzed using data from the S. Caterina Valfurva Station) consisted of a succession of cold, dry winters with little snowfall. Frontal-variation data available since 1925 show a constant retreat until 1966, followed by a brief advance period which has already terminated.

New Workflow of Sediment Mass Balancing, from Local Datasets, for Predicting Basin Scale Trends

2021 ◽  
Author(s):  
Nikolaos A. Michael ◽  
Rainer Zuhlke
Keyword(s):  
Grain Size ◽  
Integrated Approach ◽  
Sediment Flux ◽  
New Approach ◽  
Sediment Volume ◽  
Denudation Rates ◽  
Sediment Routing ◽  
Local Areas ◽  
Catchment Size ◽  
Areas Of Interest

Abstract Objectives/Scope Sediment volumetric budget estimates are very important input parameters for process-based depositional modelling (forward stratigraphic modelling). This paper presents a new integrated approach for analyze sediment volumetric budgets in sedimentary basins that is based on the reconstruction of regional grain size trends. In subsurface studies of sediment routing systems, noticeable uncertainties in estimated total sediment volumes occur when available datasets are limited to local areas that do not cover the entire sediment routing system. These uncertainties also affect models of catchment areas, structural uplift, and denudation rates as well as net:gross predictions. Methods, Procedures, Process The new integrated approach focuses on reconstructing sediment budgets for entire sediment fairways from limited local datasets. It uses a combination of sediment mass balancing and local grain size distributions to predict basin-wide grain size distributions. The comparison of local grain size to fairway-scale grain size trends is key in correcting sediment volumetrics for significantly reduced uncertainties in catchment reconstruction and net:gross ratios predictions at the scale of sediment fairways, sub-basins, prospects and exploration/production fields. Results, Observations, Conclusions The new approach has been applied successfully to two subsurface continental to marine delta systems. They cover periods of approximately 7 My in total and include four limited local areas of interest (AOI). These local AOIs measure 200×200 km, while the entire sub-basin measures 500×800 km. The new approach indicates that only up to 40% of the total sediment volume of each fairway could be captured by previous methodologies with limited local areas of interest. A maximum of 70% of the entire sink sediment volume could be incorporated in local areas of interest. The new approach presented in this paper significantly lowers the uncertainties in sediment volume estimates, depositional rates and lithology distribution input parameters in forward stratigraphic modelling. For the two case studies, previous sediment flux models indicated rates of 10,000 km/Myr. The new integrated approach indicates that sediment flux actually reached 30,000 km/Myr with major implications for sediment distribution, net:gross prediction and catchment size and denudation rates estimates. Novel/Additive Information The new integrated approach reduces uncertainties in catchment size and tectonic exhumation rate estimates for clastic depositional systems. It provides lower uncertainty parameters (sediment volume, source locations, sediment fractions, diffusion coefficients) for forward stratigraphic modelling, e.g., for reservoir quality prediction in hydrocarbon exploration. In fundamental research, provenance analyses can be better constrained by improved catchment size prediction and sediment grain size distribution models for sink areas

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