Felsenmeer persistence under non-erosive ice in the Torngat and Kaumajet mountains, Quebec and Labrador, as determined by soil weathering and cosmogenic nuclide exposure dating

2004 ◽  
Vol 41 (1) ◽  
pp. 19-38 ◽  
Author(s):  
Geneviève C Marquette ◽  
James T Gray ◽  
John C Gosse ◽  
François Courchesne ◽  
Lisa Stockli ◽  
...  
Keyword(s):  
Cosmic Ray ◽  
High Elevation ◽  
Secondary Minerals ◽  
Soil Weathering ◽  
Exposure Dating ◽  
Cosmogenic Nuclide ◽  
Late Wisconsinan ◽  
Exposure Ages ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Soil analyses and terrestrial cosmogenic nuclide exposure dating are combined and a conceptual model proposed to explain altitudinal weathering contrasts in high-latitude highlands. We show that summits in the Torngat and Kaumajet mountains were covered by ice during the Last Glacial Maximum, and that their felsenmeer cover probably survived multiple glaciation events. For similar lithologies, soils on felsenmeer covered summits are signigicantly more weathered than those below the felsenmeer limit, displaying higher concentrations of crystalline iron, amorphous aluminium, and silicium extracted with oxalate. Secondary minerals such as gibbsite and kaolinite occur in felsenmeer soils, whereas those formed in till lacked these secondary minerals. 10Be and 26Al exposure ages for nine of ten samples, from high-elevation tors and autochthonous felsenmeer blocks, range from 73 ± 6 to 157 ± 15 ka. By contrast, ages of 11.4 ± 1.0 and 11.7 ± 1.0 ka are measured for bedrock in the much lower Saglek zone, indicating extensive (>3 m) glacial erosion of this zone during Late Wisconsinan glaciation. 26Al/10Be ratios demonstrate that exposure of the high-elevation surfaces was interrupted during at least one cosmic ray shielding event by either ice or till cover. In either case, Late Wisconsinan glaciers could not have extensively eroded these surfaces. Five erratics dated above the Saglek zone, including one in the felsenmeer zone, have exposure ages ranging from 11.6 ± 1.0 to 13.6 ± 0.7 ka. This indicates that valley and high-elevation ice persisted through the Younger Dryas Chron and provides further evidence that the highlands were not nunataks during the Late Wisconsinan period.

scholarly journals Glacial geomorphology and cosmogenic 10Be and 26Al exposure ages in the northern Dufek Massif, Weddell Sea embayment, Antarctica

2012 ◽  
Vol 24 (4) ◽  
pp. 377-394 ◽  
Author(s):  
Dominic A. Hodgson ◽  
Michael J. Bentley ◽  
Christoph Schnabel ◽  
Andreas Cziferszky ◽  
Peter Fretwell ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Weddell Sea ◽  
Glacial Geomorphology ◽  
Last Glacial ◽  
Exposure Dating ◽  
Exposure Ages ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractWe studied the glacial geomorphology and geochronology of two ice-free valleys in the Dufek Massif (Antarctic Specially Protected Area 119) providing new constraints on past ice sheet thickness in the Weddell Sea embayment. 10Be and 26Al cosmogenic surface exposure dating provided chronological control. Seven glacial stages are proposed. These include an alpine glaciation, with subsequent (mid-Miocene?) over-riding by a warm-based ice sheet. Subsequent advances are marked by a series of minor drift deposits at 760 m altitude at > 1 Ma, followed by at least two later ice sheet advances that are characterized by extensive drift sheet deposition. An advance of plateau ice field outlet glaciers from the south postdated these drift sheets. The most recent advance involved the cold-based expansion of the ice sheet from the north at the Last Glacial Maximum, or earlier, which deposited a series of bouldery moraines during its retreat. This suggests at most a relatively modest expansion of the ice sheet and outlet glaciers dominated by a lateral ice expansion of just 2–3 km and maintaining a thickness similar to that of the northern ice sheet front. These observations are consistent with other reports of modest ice sheet thickening around the Weddell Sea embayment during the Last Glacial Maximum.

scholarly journals Constant wind regimes during the Last Glacial Maximum and early Holocene: evidence from Little Llangothlin Lagoon, New England Tablelands, eastern Australia

2016 ◽  
Vol 12 (7) ◽  
pp. 1435-1444 ◽  
Author(s):  
James Shulmeister ◽  
Justine Kemp ◽  
Kathryn E. Fitzsimmons ◽  
Allen Gontz
Keyword(s):  
Last Glacial Maximum ◽  
High Elevation ◽  
Glacial Maximum ◽  
Early Holocene ◽  
Luminescence Dating ◽  
Ice Age ◽  
Last Glacial ◽  
Eastern Australia ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Here we present the results of a multi-proxy investigation – integrating geomorphology, ground-penetrating radar, and luminescence dating – of a high-elevation lunette and beach berm in northern New South Wales, eastern Australia. The lunette occurs on the eastern shore of Little Llangothlin Lagoon and provides evidence for a lake high stand combined with persistent westerly winds at the Last Glacial Maximum (LGM – centring on 21.5 ka) and during the early Holocene (ca. 9 and 6 ka). The reconstructed atmospheric circulation is similar to the present-day conditions, and we infer no significant changes in circulation at those times, as compared to the present day. Our results suggest that the Southern Hemisphere westerlies were minimally displaced in this sector of Australasia during the latter part of the last ice age. Our observations also support evidence for a more positive water balance at the LGM and early Holocene in this part of the Australian sub-tropics.

The Magnitude and Proximate Cause of Ice-Sheet Growth Since 35,000 yr B.P.

2001 ◽  
Vol 56 (3) ◽  
pp. 299-307 ◽  
Author(s):  
Isaac J. Winograd
Keyword(s):  
North Atlantic ◽  
Ice Sheet ◽  
Proximate Cause ◽  
Ice Volume ◽  
The North ◽  
Data Compilation ◽  
Sst Warming ◽  
Late Wisconsinan ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractThe magnitude of late Wisconsinan (post-35,000 yr B.P.) ice-sheet growth in the Northern Hemisphere is not well known. Ice volume at ∼35,000 yr B.P. may have been as little as 20% or as much as 70% of the volume present at the last glacial maximum (LGM). A conservative evaluation of glacial–geologic, sea level, and benthic δ18O data indicates that ice volume at ∼35,000 yr B.P. was approximately 50% of that extant at the LGM (∼20,000 yr B.P.); that is, it doubled in about 15,000 yr. On the basis of literature for the North Atlantic and a sea-surface temperature (SST) data compilation, it appears that this rapid growth may have been forced by low-to-mid-latitude SST warming in both the Atlantic and Pacific Oceans, with attendant increased moisture transport to high latitudes. The SST ice-sheet growth notion also explains the apparent synchroneity of late Wisconsinan mountain glaciation in both hemispheres.

Constraining past bedrock surface temperatures at the Gorner glacier, Switzerland, using feldspar thermoluminescence for surface paleothermometry. 

2021 ◽  
Author(s):  
Joanne Elkadi ◽  
Rabiul Biswas ◽  
Georgina King ◽  
Frédéric Herman
Keyword(s):  
Last Glacial Maximum ◽  
Room Temperature ◽  
Continuous Distribution ◽  
Planetary Science ◽  
Glacial Maximum ◽  
Past Climate ◽  
Last Glacial ◽  
Exposure Ages ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Our ability to quantify past climate conditions is crucial for predicting future scenarios and landscape evolution. To date, reconstructions of the Earth’s past climate have mostly relied on the use of climate proxies to infer previous surface conditions (e.g. Jones and Mann, 2004 for a review). However, few methods exist that are capable of directly measuring past temperature histories, particularly in terrestrial settings.</p><p>The aim of this study is to contribute towards a more detailed understanding of glacial and interglacial temperature fluctuations across the Central and Western Alps, from the Last Glacial Maximum to present day, by constraining past temperatures of exposed bedrock surfaces adjacent to the Gorner glacier in Zermatt, Switzerland. This is done through the recently developed application of feldspar thermoluminescence to surface paleothermometry (Biswas et al., 2018; 2020). The thermoluminescence signal of feldspar, from room temperature to 450°C, is sourced from a continuous distribution of electron traps within the crystal lattice (Biswas et al., 2018). The release of this trapped charge is temperature dependent and thus, at room temperature, results in traps with a range of thermal stabilities with electron residence times ranging from less than a year to several billion years (Aitken 1985). Traps sensitive to typical surface temperature variations (e.g. ∼10°C) have been shown to lie between 200°C and 250°C of the TL glow curve (Biswas et al., 2020). From this temperature range, five thermometers (200°C to 250°C in 10°C intervals) can be used together as a multi-thermometer, and subsequently combined with a Bayesian inversion approach to constrain thermal histories over the last ∼50 kyr (Biswas et al., 2020).</p><p>In this study, the preliminary temperature histories of five bedrock samples with independently constrained exposure ages, exposed progressively since the Last Glacial Maximum, will be presented.</p><p><strong>References:</strong></p><p>Aitken, M.J., 1985. Thermoluminescence Dating. Academic Press, London.</p><p>Jones, P.D., Mann, M.E., 2004. Climate over past millennia. Reviews of Geophysics, 42, 2004.</p><p>Biswas, R.H., Herman, F., King, G.E., Braun, J., 2018. Thermoluminescence of feldspar as a multi-thermochronometer to constrain the temporal variation of rock exhumation in the recent past. Earth and Planetary Science Letters, 495, 56-68.</p><p>Biswas, R.H., Herman, F., King, G.E., Lehmann, B., Singhvi, A.K., 2020. Surface paleothermometry using low temperature thermoluminescence of feldspar. Climate of the Past, 16, 2075-2093.</p>

Moisture control on high-altitude cooling during the Last Glacial Maximum

2021 ◽  
Author(s):  
Guillaume Leduc ◽  
Etienne Longrain ◽  
Pierre-Henri Blard ◽  
Julien Charreau
Keyword(s):  
High Altitude ◽  
Last Glacial Maximum ◽  
High Elevation ◽  
Glacial Maximum ◽  
Sea Surface ◽  
Lapse Rate ◽  
Central Pacific ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Reconstructing the spatial and temporal variabilities of the vertical atmospheric temperature gradient (lapse rate, LR) is key to predict the evolution of glaciers in a changing climate. Variations in this parameter may amplify or mitigate the future warming at high elevation, implying contrasted impacts on the stability of glaciers. Several regional studies suggested that the tropical LR was steeper than today during the last glacial maximum (LGM) (Loomis et al., 2017; Blard et al.,  2007), while another study concluded that the LGM lapse rate was similar than today (Tripati et al., 2014).</p><p>Here we combine published LGM sea surface temperatures (SSTs) data and LGM moraines dated by cosmogenic nuclides to reconstruct the lapse rate along the American Cordillera. To do so, we combined paleo-Equilibrium Line Altitudes (ELAs) of glaciers with independent precipitation proxies to derive high latitude atmospheric temperatures. The whole dataset includes 34 paleo-glaciated sites along a North-South transect in the American Cordillera, ranging in latitude from 40°N to 36°S. Our reconstruction indicates that the lapse rate (LR) was steeper than today in the tropical American Cordillera (20°N – 11°S). The average ΔLR (LGM – Modern) for this Tropical Andes region (20°N – 11°S) is ~-1.5 °C.km<sup>-1</sup> (20 sites). At higher latitude, in both hemispheres (Central Andes, 15°S – 35°S (8 sites); Sierra Nevada and San Bernardino mountains (40°N – 34°N) (6 sites), the LR was constant during the LGM. </p><p> Our results show that a drier climate during the LGM is systematically associated with a steeper LR. Modification of LR during LGM was already observed from other tropical regions, in Hawaii-Central Pacific (Blard et al 2007), and in Eastern Africa (Loomis et al., 2017). Similarly, in these regions, precipitation did not increase during the LGM. With this multi-site exhaustive synthesis, we make a case that drier Tropical LGM conditions induce a steeper LR. This corresponds to an amplification of cooling at high altitude during the LGM. These results highlight the necessity to consider LR variations in modelling future climate. In a warmer and wetter Earth, temperature increase may be amplified at high elevation, due to smoother LR. If valid, this mechanism implies that tropical glaciers are more vulnerable than predicted by current climate modelling.</p><p> </p><p>References</p><p>Blard, P.-H., Lavé, J., Pik, R., Wagnon, P., & Bourlès, D. (2007). Persistence of full glacial conditions in the central Pacific until 15,000 years ago. Nature, 449(7162), 591.</p><p>Loomis, S. E., Russell, J. M., Verschuren, D., Morrill, C., De Cort, G., Damsté, J. S. S., … & Kelly, M. A. (2017). The tropical lapse rate steepened during the Last Glacial Maximum. Science advances, 3(1), e1600815.</p><p>Tripati, A. K., Sahany, S., Pittman, D., Eagle, R. A., Neelin, J. D., Mitchell, J. L., & Beaufort, L. (2014). Modern and glacial tropical snowlines controlled by sea surface temperature and atmospheric mixing. Nature Geoscience, 7(3), 205.</p>

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