scholarly journals Evidence for rapid paraglacial formation of rock glaciers in southern Norway from 10Be surface-exposure dating

2020 ◽  
Vol 97 ◽  
pp. 55-70 ◽  
Author(s):  
Henriette Linge ◽  
Atle Nesje ◽  
John A. Matthews ◽  
Derek Fabel ◽  
Sheng Xu
Keyword(s):  
Climatic Conditions ◽  
Rock Glacier ◽  
Surface Exposure Dating ◽  
Exposure Dating ◽  
Environmental Controls ◽  
Short Period ◽  
Rock Glaciers ◽  
Valley Site ◽  
Southern Norway ◽  
Exposure Ages

AbstractWe evaluate the timing and environmental controls on past rock-glacier activity at Øyberget, upper Ottadalen, southern Norway, using in situ 10Be surface-exposure dating on (1) boulders belonging to relict rock-glacier lobes at c. 530 m asl, (2) bedrock and boulder surfaces at the Øyberget summit (c. 1200 m asl), and (3) bedrock at an up-valley site (c. 615 m asl). We find that the rock-glacier lobes became inactive around 11.1 ± 1.2 ka, coeval with the timing of summit deglaciation (11.2 ± 0.7 ka). This is slightly older than previously published Schmidt-hammer surface-exposure ages. The timing does not match known climatic conditions promoting rock-glacier formation in the early Holocene; hence we infer that lobe formation resulted from enhanced debris supply and burial of residual ice during and soon after deglaciation. The results demonstrate that rock glaciers may form over a relatively short period of time (hundreds rather than thousands of years) under non-permafrost conditions and possibly indicate a paraglacial type of process.

scholarly journals Rock glaciers in Daxue Shan, south-eastern Tibetan Plateau: an inventory, their distribution, and their environmental controls

2018 ◽  
Vol 12 (7) ◽  
pp. 2327-2340 ◽  
Author(s):  
Zeze Ran ◽  
Gengnian Liu
Keyword(s):  
Tibetan Plateau ◽  
Climatic Conditions ◽  
Google Earth ◽  
Raw Material ◽  
Eastern Tibetan Plateau ◽  
Rock Glacier ◽  
South Eastern ◽  
Environmental Controls ◽  
Monzonitic Granite ◽  
Rock Glaciers

Abstract. Rock glaciers are typical periglacial landforms. They can indicate the existence of permafrost, and can also shed light on the regional geomorphological and climatic conditions under which they may have developed. This article provides the first rock glacier inventory of Daxue Shan, south-eastern Tibetan Plateau. The inventory is based on analyses of Google Earth imagery. In total, 295 rock glaciers were identified in Daxue Shan, covering a total area of 55.70 km2 between the altitudes of 4300 and 4600 m above sea level. Supported by ArcGIS and SPSS software programmes, we extracted and calculated morphometric parameters of these rock glaciers, and analysed the characteristics of their spatial distribution within Daxue Shan. Our inventory suggests that the lower altitudinal boundary for permafrost across the eight aspects of observed slopes differs significantly and that the lower altitudinal permafrost boundary is ∼ 104 m higher on western than eastern-facing slopes. Moraine-type and talus-derived rock glaciers exhibit mean gradients that are all concentrated within the 22–35∘ range. However, lobate rock glaciers (27–45∘) have a higher mean gradient than tongue-shaped rock glaciers (22–35∘). Shady (i.e. N, NE, and E) slopes appear related to the presence of moraine-type rock glaciers, whereas sunny (i.e. W, SW, and S) slopes appear related to the presence of talus-derived rock glaciers. Rock glaciers in Daxue Shan are more concentrated within tertiary monzonitic granite, which is more sensitive than other lithological components to the freeze–thaw process. Continuous weathering of this substrate provides the ideal raw material for the rock glacier development. These results show that environmental controls (i.e. topographical, climatic, lithological factors) greatly affect the formation and development of rock glaciers. This study provides important data for exploring the relation between maritime periglacial environments and the development of rock glaciers on the south-eastern Tibetan Plateau (TP). It may also highlight the characteristics typical of rock glaciers found in a maritime setting.

scholarly journals New evidence for active talus-foot rock glaciers at Øyberget, southern Norway, and their development during the Holocene

The Holocene ◽  
2021 ◽  
pp. 095968362110332
Author(s):  
Atle Nesje ◽  
John A Matthews ◽  
Henriette Linge ◽  
Marie Bredal ◽  
Peter Wilson ◽  
...  
Keyword(s):  
Surface Layer ◽  
Regional Climate ◽  
Age Dating ◽  
Rock Glacier ◽  
The Holocene ◽  
Synthetic Aperture Radar Interferometry ◽  
Compressive Flow ◽  
Rock Glaciers ◽  
Southern Norway ◽  
Exposure Ages

Synthetic aperture radar interferometry (InSAR) measurements demonstrate that lobate, blocky depositional landforms, located in southern Norway at an altitude of ~530 m above sea level, with an estimated mean annual air temperature of ~1.6°C, currently exhibit deformation attributed to viscous creep. Five years of InSAR measurements for six lobes demonstrate average surface velocities of 1.2–22.0 mm/year with maximum rates of 17.5–55.6 mm/year. New Schmidt-hammer exposure-age dating (SHD) of two proximal lobes reveals mid-Holocene ages (7.6 ± 1.3 ka and 6.0 ± 1.2 ka), which contrast with the early-Holocene SHD and 10Be ages obtained previously from distal lobes, and late-Holocene SHD ages presented here from two adjacent talus slopes (2.3 ± 1.0 ka and 2.4 ± 1.0 ka). Although passive transport of boulders on the surfaces of these small, slow-moving rock glaciers affected by compressive flow means that the exposure ages are close to minimum estimates of the time elapsed since lobe inception, disturbance of boulders on rock glaciers is a source of potentially serious underestimates of rock-glacier age. Rock-glacier development at Øyberget began shortly after local deglaciation around 10 ka before present and continued throughout the Holocene in response to microclimatic undercooling within the coarse blocky surface layer of the talus and rock-glacier lobes. We suggest this enhanced cooling lowers mean annual surface-layer temperature by at least ~3.6°C, which is needed at such a low altitude to sustain sporadic permafrost and avoid fast thawing as atmospheric temperatures rise. Our results point to circumstances where inferences about rock glaciers as indicators of regional climate should be interpreted with caution, and where they may be less useful in palaeoclimatic reconstruction than previously thought.

scholarly journals Short-term velocity variations at three rock glaciers and their relationship with meteorological conditions

2016 ◽  
Vol 4 (1) ◽  
pp. 103-123 ◽  
Author(s):  
V. Wirz ◽  
S. Gruber ◽  
R. S. Purves ◽  
J. Beutel ◽  
I. Gärtner-Roer ◽  
...  
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Surface ◽  
Climatic Conditions ◽  
Water Infiltration ◽  
High Temporal Resolution ◽  
Rock Glacier ◽  
Short Term ◽  
Rock Glaciers ◽  
Velocity Variations

Abstract. In recent years, strong variations in the speed of rock glaciers have been detected, raising questions about their stability under changing climatic conditions. In this study, we present continuous time series of surface velocities over 3 years of six GPS stations located on three rock glaciers in Switzerland. Intra-annual velocity variations are analysed in relation to local meteorological factors, such as precipitation, snow(melt), and air and ground surface temperatures. The main focus of this study lies on the abrupt velocity peaks, which have been detected at two steep and fast-moving rock glacier tongues ( ≥  5 m a−1), and relationships to external meteorological forcing are statistically tested.The continuous measurements with high temporal resolution allowed us to detect short-term velocity peaks, which occur outside cold winter conditions, at these two rock glacier tongues. Our measurements further revealed that all rock glaciers experience clear intra-annual variations in movement in which the timing and the amplitude is reasonably similar in individual years. The seasonal decrease in velocity was typically smooth, starting 1–3 months after the seasonal decrease in temperatures, and was stronger in years with colder temperatures in mid winter. Seasonal acceleration was mostly abrupt and rapid compared to the winter deceleration, always starting during the zero curtain period. We found a statistically significant relationship between the occurrence of short-term velocity peaks and water input from heavy precipitation or snowmelt, while no velocity peak could be attributed solely to high temperatures. The findings of this study further suggest that, in addition to the short-term velocity peaks, the seasonal acceleration is also influenced by water infiltration, causing thermal advection and an increase in pore water pressure. In contrast, the amount of deceleration in winter seems to be mainly controlled by winter temperatures.

On the Development of Transverse Ridges on Rock Glaciers

1989 ◽  
Vol 35 (121) ◽  
pp. 383-391 ◽  
Author(s):  
Deborah S. Loewenherz ◽  
Christopher J. Lawrence ◽  
Richard L. Weaver
Keyword(s):  
Stability Analysis ◽  
Newtonian Fluid ◽  
Lower Layer ◽  
Elastic Solid ◽  
Surface Region ◽  
Finite Amplitude ◽  
Climatic Conditions ◽  
Rock Glacier ◽  
Rock Glaciers ◽  
The Stability

AbstractThe stability of a low Reynolds number flow on an inclined plane is investigated with respect to modelling the initiation of transverse wave-like ridges which commonly occur on the surfaces of rock-glacier forms. In accordance with field observations indicating the presence of stratification in rock glaciers, two models of rock-glacier structure are considered, each stratified and possessing a lower layer which is treated as a Newtonian fluid. An upper, less compliant layer is treated, alternatively, as a Newtonian fluid of viscosity greater than that of the lower layer, or as an elastic solid under longitudinal compression induced by a decrease in the slope of the underlying incline. A linear stability analysis is used to examine the behaviour of each of the proposed models, and both are found to generate instabilities at wavelengths comparable to those associated with transverse surficial ridges on rock glaciers. The growth rates of a flow disturbance predicted by the viscous-stratified model appear to be too slow to account fully for the development of wave forms of finite amplitude, suggesting that other mechanisms are involved in the amplification of an initial disturbance. The results of the stability analysis of the elastic lamina model indicate that finite surficial ridges may develop on rock glaciers as a product of a buckling instability in the surface region if there is a decrease in the slope of the underlying incline. Both of the analyses illustrate that transverse ridges can occur on the surface of a rock glacier in the absence of any variations in debris supply to the system. The results further imply that the use of these features in the paleoreconstruction of Holocene climatic conditions must entail an assessment of the relative roles of external climatically driven forcingversusinternal Theologically derived instability.

Cosmogenic Be-10 surface exposure data from the Sub-Antarctic Kerguelen Archipelago

2020 ◽  
Author(s):  
Henriette Linge ◽  
Jostein Bakke ◽  
Talin Tuestad ◽  
Philip Deline ◽  
Ludovic Ravanel ◽  
...  
Keyword(s):  
Hydrothermal Fluids ◽  
Large Igneous Province ◽  
Geochemical Composition ◽  
Surface Exposure Dating ◽  
Exposure Dating ◽  
Ice Cap ◽  
Wide Range ◽  
Exposure Ages ◽  
Kerguelen Archipelago

<p>The Kerguelen archipelago (around 49°S 69°E) is the emerged part of the Kerguelen Plateau, a large igneous province in the southwestern Indian Ocean. Information on past climatic and environmental conditions in the region is vital for understanding the past behaviour of the southern westerly winds. The cross-disciplinary project SOUTHSPERE seeks to investigate past variations in this weather system through reconstruction of temporal and spatial glacier variability from lake records and glacial landforms N and NE of the Cook Ice Cap. Reliable and accurate chronological control is crucial in this context.</p><p>Surface exposure dating of glacial geomorphological features S and SE of the Cook Ice Cap has previously been done using in situcosmogenic Cl-36 [1, 2]. Solifluction and gelifraction processes appear very active in our field area, as do aeolian erosion. Also, highly variable geochemical composition of the basalts and associated intrusions, as well as the degree and type of metamorphosis, lead to strong lithology-dependant weathering and erosion rates, as evident from differential weathering reliefs on cm and m scales. The very active surface environment constitutes a challenge for obtaining accurate surface exposure ages.</p><p>In the NW part of the archipelago, basaltic lava units altered by meteoric-hydrothermal fluids contain a wide variety of secondary silicate and carbonate minerals [3]. In settings where quartz-filled geodes and fractures in the basalt are located in favourable positions on bedrock and boulder surfaces, analysis of Be-10 in euhedral and microcrystalline quartz offers a means of validating in situ Cl-36 surface exposure ages. Moreover, multi-nuclide analysis would open up for a wide range of process and landscape development studies on this young archipelago. Percolation of hydrothermal fluids in fractures and geodes is probably related to the intrusion of younger (15-5 Ma) subvolcanic rocks [see 3 and references therein]. A meteoric source of the fluids would imply that the secondary silicates contain meteoric Be-10. As meteoric production is greater than in situ production, this may represent a problem for utilising in situ Be-10 for surface exposure dating. If secondary silicate formation occurred early, rather than late in the intrusive phase, complete radioactive decay of the meteoric Be-10 component is expected prior to surface exposure.</p><p>110 rock samples were collected for surface exposure dating with in situ cosmogenic nuclides during a field campaign in November and December 2019. Here we present the first Be-10 data from rock surfaces of glacially transported boulders and exposed bedrock.</p><p>[1] Jomelli et al. 2017. Quaternary Science Reviews 162, 128-144.</p><p>[2] Jomelli et al. 2018. Quaternary Science Reviews 183, 110-123.</p><p>[3] Renac et al. 2010. European Journal of Mineralogy 22, 215-234.</p>

scholarly journals Towards a palaeoclimatic model of rock-glacier formation in the Swiss Alps

2000 ◽  
Vol 31 ◽  
pp. 281-286 ◽  
Author(s):  
Regula Frauenfelder ◽  
Andreas Kääb
Keyword(s):  
Regional Scale ◽  
Thermal Conditions ◽  
Late Glacial ◽  
Climatic Conditions ◽  
Swiss Alps ◽  
Inventory Analysis ◽  
Rock Glacier ◽  
Altitudinal Distribution ◽  
Polymorphic Type ◽  
Rock Glaciers

AbstractClimate and its long-term variability govern ground thermal conditions, and for this reason represent one of the most important impacts on creeping mountain permafrost. The decoding and better understanding of the present-day morphology and distribution of rock glaciers opens up a variety of insights into past and present environmental, especially climatic, conditions on a local to regional scale. The present study was carried out in the Swiss Alps using two different approaches: (1) kinematic analysis of specific active rock glaciers, and (2) description of the altitudinal distribution of relict rock glaciers. Two theoretical shape concepts of active rock-glacier morphology were derived’ a"monomorphic" type, representing presumably undisturbed, continuous development over several millennia and a ˚polymorphic" type, reflecting a system of (possibly climatically affected) individual creep streams several centuries old. The topoclimatic-based inventory analysis indicated an average temperature increase at relict rock-glacier fronts of approximately +2°C since the time of their decay, which is a sign of rock-glacier ages reaching back to the Alpine Late Glacial. The temperature difference of some tenths of a degree Celsius found for active/inactive rock glaciers is typical for the bandwidth of Holocene climate variations. These results confirm the importance of Alpine rock glaciers as highly sensitive indicators of past temperature evolution.

scholarly journals OSL rock surface exposure dating as a novel approach for reconstructing transport histories of coastal boulders over decadal to centennial timescales

2020 ◽  
Author(s):  
Dominik Brill ◽  
Simon Matthias May ◽  
Nadia Mhammdi ◽  
Georgina King ◽  
Christoph Burow ◽  
...  
Keyword(s):  
Local Source ◽  
Rock Surface ◽  
Surface Exposure Dating ◽  
Erosion Rates ◽  
Exposure Dating ◽  
Relative Chronology ◽  
Novel Approach ◽  
Calibration Samples ◽  
Exposure Ages ◽  
Boulder Deposits

Abstract. Wave-transported boulders represent important records of storm and tsunami impact over geological timescales. Their use for hazard assessment requires chronological information that in many cases cannot be achieved by established dating approaches. To fill this gap, this study investigated, for the first time, the potential of optically stimulated luminescence rock surface exposure dating (OSL-RSED) for estimating transport ages of wave-emplaced coastal boulders. The approach was applied to calcarenite clasts at the Rabat coast, Morocco. Calibration of the OSL-RSED model was based on samples with rock surfaces exposed to sunlight for ~ 2 years, and OSL exposure ages were evaluated against age control deduced from satellite images. Our results show that the dating precision is limited for all boulders due to the local source rock lithology which has low amounts of quartz and feldspar. The dating accuracy may be affected by erosion rates on boulder surfaces of 0.06–0.2 mm/year. Nevertheless, we propose a robust relative chronology for boulders that are not affected by significant post-depositional erosion and that share surface angles of inclination with the calibration samples. The relative chronology indicates that (i) most boulders were moved by storm waves; (ii) these storms lifted boulders with masses of up to ~ 40 t; and (iii) the role of storms for the formation of boulder deposits along the Rabat coast is much more significant than previously assumed. Although OSL-RSED cannot provide reliable absolute exposure ages for the coastal boulders in this study, the approach has large potential for boulder deposits composed of rocks with larger amounts of quartz or feldspar, older formation histories and less susceptibility to erosion.

10BE SURFACE EXPOSURE AGES FROM RELICT TALUS-DERIVED ROCK GLACIER LOBES AT ØYBERGET, SOUTHERN NORWAY

2018 ◽  
Author(s):  
Henriette Linge ◽  
◽  
John A. Matthews ◽  
Atle Nesje ◽  
Derek Fabel ◽  
...  
Keyword(s):  
Rock Glacier ◽  
Southern Norway ◽  
Exposure Ages

scholarly journals LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from <sup>10</sup>Be surface exposure dating

2007 ◽  
Vol 3 (4) ◽  
pp. 623-635 ◽  
Author(s):  
R. Zech ◽  
Ch. Kull ◽  
P. W. Kubik ◽  
H. Veit
Keyword(s):  
North Atlantic ◽  
Late Quaternary ◽  
Late Glacial ◽  
Tropical Andes ◽  
Surface Exposure Dating ◽  
Exposure Dating ◽  
The North ◽  
Innovative Tool ◽  
Cordillera Real ◽  
Exposure Ages

Abstract. Surface exposure dating (SED) is an innovative tool already being widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22–25 ka and was thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11–13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions farther west and south.

On the Development of Transverse Ridges on Rock Glaciers

1989 ◽  
Vol 35 (121) ◽  
pp. 383-391
Author(s):  
Deborah S. Loewenherz ◽  
Christopher J. Lawrence ◽  
Richard L. Weaver
Keyword(s):  
Stability Analysis ◽  
Newtonian Fluid ◽  
Lower Layer ◽  
Elastic Solid ◽  
Surface Region ◽  
Finite Amplitude ◽  
Climatic Conditions ◽  
Rock Glacier ◽  
Rock Glaciers ◽  
The Stability

AbstractThe stability of a low Reynolds number flow on an inclined plane is investigated with respect to modelling the initiation of transverse wave-like ridges which commonly occur on the surfaces of rock-glacier forms. In accordance with field observations indicating the presence of stratification in rock glaciers, two models of rock-glacier structure are considered, each stratified and possessing a lower layer which is treated as a Newtonian fluid. An upper, less compliant layer is treated, alternatively, as a Newtonian fluid of viscosity greater than that of the lower layer, or as an elastic solid under longitudinal compression induced by a decrease in the slope of the underlying incline. A linear stability analysis is used to examine the behaviour of each of the proposed models, and both are found to generate instabilities at wavelengths comparable to those associated with transverse surficial ridges on rock glaciers. The growth rates of a flow disturbance predicted by the viscous-stratified model appear to be too slow to account fully for the development of wave forms of finite amplitude, suggesting that other mechanisms are involved in the amplification of an initial disturbance. The results of the stability analysis of the elastic lamina model indicate that finite surficial ridges may develop on rock glaciers as a product of a buckling instability in the surface region if there is a decrease in the slope of the underlying incline. Both of the analyses illustrate that transverse ridges can occur on the surface of a rock glacier in the absence of any variations in debris supply to the system. The results further imply that the use of these features in the paleoreconstruction of Holocene climatic conditions must entail an assessment of the relative roles of external climatically driven forcing versus internal Theologically derived instability.

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