Evolution of an overdeepened trough in the northern Alpine Foreland at Niederweningen, Switzerland

Dehnert, Andreas; Lowick, Sally E.; Preusser, Frank; Anselmetti, Flavio S.; Drescher-Schneider, Ruth; Graf, H.; Heller, Friedrich; Horstmeyer, Heinrich; Kemna, Hans Axel; Nowaczyk, Norbert R; Züger, Andreas; Furrer, Heinz

doi:10.1016/j.quascirev.2011.12.015

Cited by 62 publications

(70 citation statements)

References 55 publications

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“…Preusser and Fiebig, 2009; Thiel et al., 2011) and lake sediment samples (e.g. Dehnert et al., 2012), values of up to ∼7 Gy/ka were determined for some inner-alpine sites (e.g. Klasen et al., 2007; Lukas et al., 2012).…”

Section: Results and Interpretationmentioning

confidence: 99%

“…from Greenland (Dansgaard et al., 1993). These rapid climate changes are only rarely recorded by sediments in the Alps and the northern alpine foreland (e.g., by speleothems, lake and loess deposits; Haesaerts et al., 1996; Spötl et al., 2006; Anselmetti et al., 2010; Thiel et al., 2011; Dehnert et al., 2012) and suggest a long-term climatic deterioration towards the end of MIS 3 leading eventually to maximum ice extent during the LGM (MIS 2).…”

Section: Introductionmentioning

confidence: 99%

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Late Pleistocene climate change and landscape dynamics in the Eastern Alps: the inner-alpine Unterangerberg record (Austria)

Starnberger

Drescher-Schneider

Reitner

et al. 2013

Quaternary Science Reviews

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Drill cores from the inner-alpine valley terrace of Unterangerberg, located in the Eastern Alps of Austria, offer first insights into a Pleistocene sedimentary record that was not accessible so far. The succession comprises diamict, gravel, sand, lignite and thick, fine grained sediments. Additionally, cataclastic deposits originating from two paleo-landslide events are present. Multi-proxy analyses including sedimentological and palynological investigations as well as radiocarbon and luminescence data record the onset of the last glacial period (Würmian) at Unterangerberg at ∼120–110 ka. This first time period, correlated to the MIS 5d, was characterised by strong fluvial aggradation under cold climatic conditions, with only sparse vegetation cover. Furthermore, two large and quasi-synchronous landslide events occurred during this time interval. No record of the first Early Würmian interstadial (MIS 5c) is preserved. During the second Early Würmian interstadial (MIS 5a), the local vegetation was characterised by a boreal forest dominated by Picea, with few thermophilous elements. The subsequent collapse of the vegetation is recorded by sediments dated to ∼70–60 ka (i.e. MIS 4), with very low pollen concentrations and the potential presence of permafrost. Climatic conditions improved again between ∼55 and 45 ka (MIS 3) and cold-adapted trees re-appeared during interstadials, forming an open forest vegetation. MIS 3 stadials were shorter and less severe than the MIS 4 at Unterangerberg, and vegetation during these cold phases was mainly composed of shrubs, herbs and grasses, similar to what is known from today's alpine timberline. The Unterangerberg record ended at ∼45 ka and/or was truncated by ice during the Last Glacial Maximum.

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Section: Results and Interpretationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Late Pleistocene climate change and landscape dynamics in the Eastern Alps: the inner-alpine Unterangerberg record (Austria)

Starnberger

Drescher-Schneider

Reitner

et al. 2013

Quaternary Science Reviews

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“…All OSL ages were in stratigraphic agreement and (excluding MAS1) gave ages between 17 and 34 ka. The SAR protocol (Wintle and Murray, 2000) has proved very successful when dating quartz (Murray and Olley, 2002;Wintle and Murray, 2006), and often provides ages beyond the last interglacial (Pawley et al, 2008(Pawley et al, , 2010Dehnert et al, 2012). Beyond 70 ka, and D e values above 150e200 Gy however, problems have been reported at some sites, where independent dating has shown the quartz OSL to underestimate, despite the methods meeting all the standard criteria set for testing the performance of the SAR protocol (Wintle and Murray, 2006), (Lai, 2010;Lowick et al, 2010;Timar et al, 2010).…”

Section: Datingmentioning

confidence: 99%

Loess and soils in the eastern Ebro Basin

Boixadera

Poch

Lowick

et al. 2015

Quaternary International

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“…Yet, erosional features such as overdeepenings are found close to earlier positions of the ice margin of the Rhine glacier ( Fig. 2; Preusser et al, 2011;Dehnert et al, 2012), necessitating basal conditions favorable for erosion. These could have occurred as a result of more humid conditions with higher ice flow velocity and increased sliding during ice advances across the Swiss Plateau, or during the rapid down-wasting of the ice mass that is likely to have taken place during the retreat phases, generating large quantities of water necessary for subglacial erosion.…”

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confidence: 92%

“…Average ice flow velocity through the main outlets of the Rhine glacier was estimated to be less than 200 m a −1 (Keller and Krayss, 2005b), a value relatively small compared to present-day ice bodies of comparable size. Extreme cold conditions also favored the development of permafrost up to about 150 m thick north of the marginal zone of the Rhine glacier Delisle et al, 2003;Lindgren et al, 2016). Subsurface temperatures and groundwater flow conditions must have been strongly influenced by the presence of extended surface and subsurface ice (Speck, 1994).…”

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confidence: 99%

Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum

et al. 2018

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Abstract. At the Last Glacial Maximum (LGM), the Rhine glacier in the Swiss Alps covered an area of about 16 000 km 2 . As part of an integrative study about the safety of repositories for radioactive waste under ice age conditions in Switzerland, we modeled the Rhine glacier using a thermodynamically coupled three-dimensional, transient Stokes flow and heat transport model down to a horizontal resolution of about 500 m. The accumulation and ablation gradients that roughly reproduced the geomorphic reconstructions of glacial extent and ice thickness suggested extremely cold (T July ∼ 0 • C at the glacier terminus) and dry (∼ 10 % to 20 % of today's precipitation) climatic conditions. Forcing the numerical simulations with warmer and wetter conditions that better matched LGM climate proxy records yielded a glacier on average 500 to 700 m thicker than geomorphic reconstructions. Mass balance gradients also controlled ice velocities, fluxes, and sliding speeds. These gradients, however, had only a small effect on basal conditions. All simulations indicated that basal ice reached the pressure melting point over much of the Rhine and Linth piedmont lobes, and also in the glacial valleys that fed these lobes. Only the outer margin of the lobes, bedrock highs beneath the lobes, and Alpine valleys at high elevations in the accumulation zone remained cold based. The Rhine glacier was thus polythermal. Sliding speed estimated with a linear sliding rule ranged from 20 to 100 m a −1 in the lobes and 50 to 250 m a −1 in Alpine valleys. Velocity ratios (sliding to surface speeds) were > 80 % in lobes and ∼ 60 % in valleys. Basal shear stress was very low in the lobes (0.03-0.1 MPa) and much higher in Alpine valleys (> 0.2 MPa). In these valleys, viscous strain heating was a dominant source of heat, particularly when shear rates in the ice increased due to flow constrictions, confluences, or flow past large bedrock obstacles, contributing locally up to several watts per square meter but on average 0.03 to 0.2 W m −2 . Basal friction acted as a heat source at the bed of about 0.02 W m −2 , 4 to 6 times less than the geothermal heat flow which is locally high (up to 0.12 W m −2 ). In the lobes, despite low surface slopes and low basal shear stresses, sliding dictated main fluxes of ice, which closely followed bedrock topography: ice was channeled in between bedrock highs along troughs, some of which coincided with glacially eroded overdeepenings. These sliding conditions may have favored glacial erosion by abrasion and quarrying. Our results confirmed general earlier findings but provided more insights into the detailed flow and basal conditions of the Rhine glacier at the LGM. Our model results suggested that the trimline could have been buried by a significant thickness of cold ice. These findings have significant implications for interpreting trimlines in the Alps and for our understanding of ice-climate interactions.

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Evolution of an overdeepened trough in the northern Alpine Foreland at Niederweningen, Switzerland

Cited by 62 publications

References 55 publications

Late Pleistocene climate change and landscape dynamics in the Eastern Alps: the inner-alpine Unterangerberg record (Austria)

Late Pleistocene climate change and landscape dynamics in the Eastern Alps: the inner-alpine Unterangerberg record (Austria)

Loess and soils in the eastern Ebro Basin

Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum

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