scholarly journals Glacial Erosion Rates Determined at Vorab Glacier: Implications for the Evolution of Limestone Plateaus

Geosciences ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 356
Author(s):  
Olivia Steinemann ◽  
Alicia Martinez ◽  
Vincenzo Picotti ◽  
Christof Vockenhuber ◽  
Susan Ivy-Ochs
Keyword(s):  
Eastern Alps ◽  
Crystalline Rock ◽  
High Elevation ◽  
Glacial Erosion ◽  
Mountain Ranges ◽  
Glacier Forefield ◽  
Erosion Rates ◽  
Cosmogenic Nuclide ◽  
Crystalline Bedrock ◽  
The Relationship

Understanding how fast glaciers erode their bedrock substrate is one of the key elements in reconstructing how the action of glaciers gives mountain ranges their shape. By combining cosmogenic nuclide concentrations determined in glacially abraded bedrock with a numerical model, we quantify glacial erosion rates over the last 15 ka. We measured cosmogenic 36Cl in fourteen samples from the limestone forefield of the Vorab glacier (Eastern Alps, Switzerland). Determined glacial erosion rates range from 0.01 mm a−1 to 0.16 mm a−1. These glacial abrasion rates differ quite markedly from rates measured on crystalline bedrock (>1 mm a−1), but are similarly low to the rates determined on the only examined limestone plateau so far, the Tsanfleuron glacier forefield. Our data, congruent with field observations, suggest that the Vorab glacier planed off crystalline rock (Permian Verrucano) overlying the Glarus thrust. Upon reaching the underlying strongly karstified limestone the glacier virtually stopped eroding its bed. We attribute this to immediate drainage of meltwater into the karst passages below the glacier, which inhibits sliding. The determined glacial erosion rates underscore the relationship between geology and the resulting landscape that evolves, whether high elevation plateaus in limestone terrains or steep-walled valleys in granitic/gneissic areas.

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

2016 ◽  
Vol 4 (4) ◽  
pp. 895-909 ◽  
Author(s):  
Jean L. Dixon ◽  
Friedhelm von Blanckenburg ◽  
Kurt Stüwe ◽  
Marcus Christl
Keyword(s):  
Eastern Alps ◽  
European Alps ◽  
Glacial Erosion ◽  
Erosion Rates ◽  
The Alps ◽  
Glacial Processes ◽  
Cosmogenic 10Be ◽  
Topographic Forcing ◽  
Eastern Edge

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.

Propagating uplift controls on formation of low-relief, high-elevation surfaces in the SE Tibetan Plateau

2020 ◽  
Author(s):  
Xiaoping Yuan ◽  
Kimberly Huppert ◽  
Jean Braun ◽  
Laure Guerit
Keyword(s):  
Tibetan Plateau ◽  
High Elevation ◽  
Step Change ◽  
Loss Mechanism ◽  
Mountain Ranges ◽  
Horizontal Advection ◽  
Erosion Rates ◽  
Relief Surface ◽  
Deposition Processes ◽  
Three Rivers

<p>The SE Tibetan Plateau has extensive broad, low-relief, high-elevation surfaces perched above deep valleys, as well as in the headwaters of the three rivers (the Salween, the Mekong, and the Yangtze). However, understanding the presence of these low-relief surfaces is a long-standing challenge because their formation process remains highly debated. While alternate mechanisms have been proposed to explain the low-relief surface formation in this setting (e.g., drainage-area loss mechanism due to horizontal advection; Yang et al., 2015, Nature), a long-standing hypothesis for the formation of low-relief surfaces is by a step change in uplift and incision into a pre-existing, low-relief surface (Clark et al., 2006, JGR; Whipple et al., 2017, Geology).</p><p>The morphology of low-relief surfaces in the SE Tibetan Plateau is largely consistent with formation by a step change in uplift, but one problem with this model is that low-relief surfaces formed by a step change in uplift are relatively short-lived, since they are incised and steepened by erosion, which sweeps upstream at the response time of mountain ranges (in the order of several million years). Using a landscape evolution model that combines erosion, sediment transport and deposition processes (Yuan et al., 2019, JGR), we demonstrate that propagating uplift form large parallel rivers, with broad low-relief, high-elevation interfluves that persist for tens to hundreds of million years, consistent with various dated ages. These low-relief surfaces can be long-lived because the drainage areas in these interfluves are insufficient to keep up with rapid incision of the large parallel mainstem rivers. Our simulated features match various observations in the SE Tibetan Plateau: (i) low-relief surfaces are approximately co-planar in headwaters, and decrease in elevation smoothly from northwest to southeast across the plateau margin; (ii) χ-elevation plots of the mainstem rivers are convex; (iii) low-relief surfaces have low erosion rates; and (iv) erosion rates are high in the mainstem rivers at the propagating margin.</p>

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

2016 ◽  
Author(s):  
Jean L. Dixon ◽  
Friedhelm von Blanckenburg ◽  
Kurt Stüwe ◽  
Marcus Cristl
Keyword(s):  
Eastern Alps ◽  
European Alps ◽  
Glacial Erosion ◽  
Erosion Rates ◽  
The Alps ◽  
Glacial Processes ◽  
Cosmogenic 10Be ◽  
Topographic Forcing ◽  
Eastern Edge

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 through glaciation sustains isostatic uplift and topography in a decaying orogen. But, some insist that the Alps are an orogen still actively uplifting (e.g., Hergarten et al., 2010). 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 eastern-most, non-glaciated basins range from 40 to 150 mm/ky and likely reflect underlying tectonic forcings in this region, which have previously been attributed to recent (post 5 Ma) uplift (Legrain et al., 2015). By contrast, erosion rates in previously glaciated catchments range from 170 to 240 mm/ky 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 two orders of magnitude with poor topographic indicators of controls. 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.

scholarly journals Synchronous acceleration of ice loss and glacial erosion, Glaciar Marinelli, Chilean Tierra del Fuego

2009 ◽  
Vol 55 (190) ◽  
pp. 207-220 ◽  
Author(s):  
Michèle Koppes ◽  
Bernard Hallet ◽  
John Anderson
Keyword(s):  
Sediment Flux ◽  
Tierra Del Fuego ◽  
Climate Data ◽  
Seismic Profiles ◽  
Glacial Erosion ◽  
Ice Dynamics ◽  
Erosion Rates ◽  
Basal Sliding ◽  
History Of ◽  
The Relationship

AbstractTo contribute to the understanding of the influence of climate on glacial erosion and on orogenic processes, we report contemporary glacial erosion rates from a calving glacier in the Southern Andes and elucidate the influence of ice dynamics on erosion. Using seismic profiles of sediments collected in a proglacial fjord and a documented history of retreat, we determine the time-varying sediment flux of Glaciar Marinelli as a measure of basin-wide erosion rates, and compare these rates with the annual ice budget reconstructed using NCEP–NCAR reanalysis climate data from 1950 to 2005. The rate of erosion of the largest tidewater glacier in Tierra del Fuego averaged 39 ± 16 mm a−1 during the latter half of the 20th century, with an annual maximum approaching 130 mm a−1 following a decade of rapid retreat. A strong correlation emerges between the variable rate of ice delivery to the terminus and the erosion rate, providing quantitative insight into the relationship between ice fluxes and glacial erosion rates. For Glaciar Marinelli, as for other calving glaciers for which suitable data exist, the marked retreat and thinning over the past 50 years have resulted in a period of accelerated basal sliding and unusually rapid erosion.

scholarly journals The periglacial engine of mountain erosion – Part 2: Modelling large-scale landscape evolution

2015 ◽  
Vol 3 (2) ◽  
pp. 327-369 ◽  
Author(s):  
D. L. Egholm ◽  
J. L. Andersen ◽  
M. F. Knudsen ◽  
J. D. Jansen ◽  
S. B. Nielsen
Keyword(s):  
Large Scale ◽  
Landscape Evolution ◽  
High Elevation ◽  
Climatic Conditions ◽  
Mean Annual Temperature ◽  
Late Cenozoic ◽  
Mountain Ranges ◽  
Model Experiments ◽  
Erosion Rates ◽  
Bedrock Erosion

Abstract. An increasing number of studies point to a strong periglacial control on bedrock erosion in mountain landscapes. Periglacial processes have also been suggested to control the formation of block-fields on high-elevation, low-relief surfaces (summit flats) found in many alpine landscapes. However, to which degree periglacial processes took part in accelerating global erosion rates in response to Late Cenozoic cooling still remains as an unanswered question. In this study, we present a landscape evolution model that incorporates two periglacial processes; frost cracking and frost creep, which both depend on the mean annual temperature (MAT) and sediment thickness. The model experiments allow us to time-integrate the contribution of periglacial processes to mountain topography over million-year time scales. It is a robust result of our experiments that periglacial frost activity leads to the formation of smooth summit flats at elevations dominated by cold climatic conditions through time periods of millions of years. Furthermore, a simplistic scaling of temperatures to δ18O values through the late-Cenozoic indicates that many of the highest summit flats in mid- to high-latitude mountain ranges can have formed prior to the Quaternary. The model experiments also suggest that cooling in the Quaternary accelerated periglacial erosion by expanding the areas affected by periglacial erosion significantly. A computational experiment combining glacial and periglacial erosion furthermore suggests that landscape modifications associated with glacial activity may increase the long-term average efficiency of the frost-related processes.

The origin of elevated low-relief surfaces in the Eastern Alps from geomorphic criteria and cosmogenic nuclide dating

2021 ◽  
Author(s):  
Gerit Gradwohl ◽  
Kurt Stüwe ◽  
Moritz Liebl ◽  
Jörg Robl
Keyword(s):  
Eastern Alps ◽  
Northern Calcareous Alps ◽  
Glacial Erosion ◽  
Field Mapping ◽  
Northern Calcareous ◽  
Cosmogenic Nuclide ◽  
Cave Sediments ◽  
Cosmogenic Nuclide Dating ◽  
Longitudinal Channel

<p>Elevated low-relief surfaces are peculiar landforms found in many areas across the Eastern Alps, most notably on the plateaus of the Northern Calcareous Alps and the southern metamorphic ranges from Nock Mountains to Koralpe. Found in domains both glaciated and unglaciated during the Pleistocene, (peri-)glacial erosion as well as fluvial prematurity have been cited as two opposing models for their formation. In order to contribute to this debate, we present a map of the existing low-relief surfaces in the Eastern Alps, bridging both glaciated and unglaciated regions, using a combined effort of field mapping and GIS-based mapping. Hypsometric statistics and analysis of longitudinal channel profiles show clear differences between formerly glaciated, partly-glaciated and unglaciated regions and their relations to the mapped surfaces. Furthermore, the pace of late- to post-Miocene incision is quantified via cosmogenic nuclide dating (<sup>26</sup>Al, <sup>10</sup>Be, <sup>21</sup>Ne) of allogenic siliceous sediments from discrete elevations correlating with the low-relief surfaces, in particular from cave sediments in the Northern Calcareous Alps. This information can be used to demonstrate that low-relief surfaces in many unglaciated regions, but also in some glaciated regions can be interpreted in terms of pre-Pleistocene relict landscapes.</p>

Boulders as a lithologic control on river and landscape response to tectonic forcing at the Mendocino triple junction

2020 ◽  
Author(s):  
Charles M. Shobe ◽  
Georgina L. Bennett ◽  
Gregory E. Tucker ◽  
Kevin Roback ◽  
Scott R. Miller ◽  
...  
Keyword(s):  
Triple Junction ◽  
High Elevation ◽  
River Channels ◽  
Erosion Rates ◽  
Coastal Belt ◽  
Sediment Mass ◽  
Mendocino Triple Junction ◽  
Landscape Response ◽  
Channel Steepness ◽  
Tectonic Forcing

Constraining Earth’s sediment mass balance over geologic time requires a quantitative understanding of how landscapes respond to transient tectonic perturbations. However, the mechanisms by which bedrock lithology governs landscape response remain poorly understood. Rock type influences the size of sediment delivered to river channels, which controls how efficiently rivers respond to tectonic forcing. The Mendocino triple junction region of northern California, USA, is one landscape in which large boulders, delivered by hillslope failures to channels, may alter the pace of landscape response to a pulse of rock uplift. Boulders frequently delivered by earthflows in one lithology, the Franciscan mélange, have been hypothesized to steepen channels and slow river response to rock uplift, helping to preserve high-elevation, low-relief topography. Channels in other units (the Coastal Belt and the Franciscan schist) may experience little or no erosion inhibition due to boulder delivery. Here we investigate spatial patterns in channel steepness, an indicator of erosion resistance, and how it varies between mélange and non-mélange channels. We then ask whether lithologically controlled boulder delivery to rivers is a possible cause of steepness variations. We find that mélange channels are steeper than Coastal Belt channels but not steeper than schist channels. Though channels in all units steepen with increasing proximity to mapped hillslope failures, absolute steepness values near failures are much higher (∼2×) in the mélange and schist than in Coastal Belt units. This could reflect reduced rock erodibility or increased erosion rates in the mélange and schist, or disproportionate steepening due to enhanced boulder delivery by hillslope failures in those units. To investigate the possible influence of lithology-dependent boulder delivery, we map boulders at failure toes in the three units. We find that boulder size, frequency, and concentration are greatest in mélange channels and that Coastal Belt channels have the lowest concentrations. Using our field data to parameterize a mathematical model for channel slope response to boulder delivery, we find that the modeled influence of boulders in the mélange could be strong enough to account for some observed differences in channel steepness between lithologies. At the landscape scale, we lack the data to fully disentangle boulder-induced steepening from that due to spatially varying erosion rates and in situ rock erodibility. However, our boulder mapping and modeling results suggest that lithology-dependent boulder delivery to channels could retard landscape adjustment to tectonic forcing in the mélange and potentially also in the schist. Boulder delivery may modulate landscape response to tectonics and help preserve high-elevation, low-relief topography at the Mendocino triple junction and elsewhere.

scholarly journals Cosmogenic nuclide dating of cave sediments in the Eastern Alps and implications for erosion rates

2020 ◽  
Vol 49 (2) ◽  
pp. 107-118
Author(s):  
Philipp Häuselmann ◽  
◽  
Lukas Plan ◽  
Peter Pointner ◽  
Markus Fiebig ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Eastern Alps ◽  
Western Alps ◽  
Valley Bottom ◽  
Cosmogenic Nuclide ◽  
Base Level ◽  
Multi Level ◽  
Slow Evolution ◽  
Karst Systems ◽  
Cosmogenic Nuclide Dating

Karstic caves are created by water eroding and corroding rocks that can be dissolved. Since both the spring areas of caves (normally at the valley bottom) as well as the recharge is controlled by superficial processes, the morphology of the cave bears strong links to these influences. Lowering of local base levels promotes the development of horizontal phreatic cave passages at progressively lower elevations, resulting in the formation of multi-level karst systems. Upon the next lowering of base level, these upper systems become fossilized, and sediment trapped within them may remain preserved for millions of years. Dating these sediments gives clues regarding the time when the passages were last active, and thus may yield age information for old valley floors. The present paper presents cosmogenic nuclide datings of twelve samples from eight caves in the central part of the Northern Calcareous Alps of Austria. Besides three samples that gave no results, most of the obtained ages are at the Mio-Pliocene boundary or within the Pliocene, as was expected before sampling. No multi-level caves could be sampled at different elevations, thus, the obtained valley deepening rates are averages between the age of sediment deposition and the present-day valley floor. However, the valley deepening rates of 0.12 to 0.21 km/Ma are in accordance to previous findings and corroborate a comparatively slow evolution of base level lowering in the Eastern Alps compared to the fast (Late Quaternary) evolution in the Central and Western Alps.

Roof of the World: Tibet, Pamirs

2013 ◽  
Author(s):  
Mike Searle
Keyword(s):  
Tibetan Plateau ◽  
High Elevation ◽  
Tien Shan ◽  
Palm Tree ◽  
The Tibetan Plateau ◽  
Wet Season ◽  
North West ◽  
Mountain Ranges ◽  
The North ◽  
The World

The Tibetan Plateau is by far the largest region of high elevation, averaging just above 5,000 metres above sea level, and the thickest crust, between 70 and 90 kilometres thick, anywhere in the world. This huge plateau region is very flat—lying in the internally drained parts of the Chang Tang in north and central Tibet, but in parts of the externally drained eastern Tibet, three or four mountain ranges larger and higher than the Alps rise above the frozen plateau. Some of the world’s largest and longest mountain ranges border the plateau, the ‘flaming mountains’ of the Tien Shan along the north-west, the Kun Lun along the north, the Longmen Shan in the east, and of course the mighty Himalaya forming the southern border of the plateau. The great trans-Himalayan mountain ranges of the Pamir and Karakoram are geologically part of the Asian plate and western Tibet but, as we have noted before, unlike Tibet, these ranges have incredibly high relief with 7- and 8-kilometre-high mountains and deeply eroded rivers and glacial valleys. The western part of the Tibetan Plateau is the highest, driest, and wildest area of Tibet. Here there is almost no rainfall and rivers that carry run-off from the bordering mountain ranges simply evaporate into saltpans or disappear underground. Rivers draining the Kun Lun flow north into the Takla Makan Desert, forming seasonal marshlands in the wet season and a dusty desert when the rivers run dry. The discovery of fossil tropical leaves, palm tree trunks, and even bones from miniature Miocene horses suggest that the climate may have been wetter in the past, but this is also dependent on the rise of the plateau. Exactly when Tibet rose to its present elevation is a matter of great debate. Nowadays the Indian Ocean monsoon winds sweep moisture-laden air over the Indian sub-continent during the summer months (late June–September). All the moisture is dumped as the summer monsoon, the torrential rains that sweep across India from south-east to north-west.

scholarly journals Environmental factors as drivers for macroinvertebrate and diatom diversity in Alpine lakes: New insights from the Stelvio National Park (Italy)

2019 ◽  
Vol 78 (2) ◽  
Author(s):  
Angela Boggero ◽  
Silvia Zaupa ◽  
Simona Musazzi ◽  
Michela Rogora ◽  
Elzbieta Dumnicka ◽  
...  
Keyword(s):  
High Altitude ◽  
National Park ◽  
Geographical Area ◽  
National Research Council ◽  
Nutrient Content ◽  
Eastern Alps ◽  
High Elevation ◽  
Alpine Lakes ◽  
High Altitude Lakes ◽  
The Alps

Information on the biodiversity of high altitude lakes in the Stelvio National Park was scarce and fragmentary, in most cases limited to a few studies on a single biological issue. To fill this gap, a multidisciplinary research program was established in 2011 to investigate macroinvertebrates, diatoms, and water chemistry in 8 high altitude lakes within the boundaries of the Park (Rhaetian Alps, Eastern Alps). The results of this study were compared with data on biological assemblages and chemical parameters of Alpine lakes in the Pennine-Lepontine Alps (Western Alps), to evaluate the role of local drivers with respect to regional ones. This comparison was possible thanks to the adoption of standardized sampling methodologies developed since the ’90s by the National Research Council-Water Research Institute (Verbania), in collaboration with several European Research centers. Despite located in a restricted geographical area, the lakes of the Stelvio National Park showed a high variability of chemical composition, and of sensitivity to acidification, lower than that of the Pennine-Lepontine Alpine lakes. Macroinvertebrate and diatom taxa were ubiquitous and frequent along the Alps, and mainly represented by cold-stenothermal species. Richness, Shannon, Simpson, and Pielou indices applied to phyto- and zoobenthos highlighted significantly lower values in Stelvio National Park lakes than in those of Pennine-Lepontine for macroinvertebrates, while no significant differences were found for diatoms. Two groups of lakes were identified by Cluster Analysis, mainly on the basis of major ion concentrations. Canonical Correspondence Analysis showed that the macroinvertebrate assemblage of the lakes studied is driven mainly by altitude and lake surface, and, to a lesser extent, by nutrient content. On the contrary, pH and acid-related variables played a secondary role for diatoms, while nutrients and, more in general, ionic content had significant effects on their species composition. Overall, the results of this first investigation showed that the high elevation of these lakes affects their macroinvertebrate assemblages, while their diatom communities are comparable throughout the Alps.

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