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Friday, 12 July 2019

More on the Scoresby Sund piedmont glacier


In this interpretation it is argued that the whole of Jameson Land was deeply submerged beneath ice from the Greenland ice Sheet during the Salian Glaciation.  Glacial deposits referred to the "older drift" glaciation are dated to this phase, as are some of the glacial deposits found in the "driftless" area.  Other deposits in that area are assumed to be even older -- and are largely destroyed.  The "newer drift" deposits are dated to the LGM or Late Weichselian: these are closer to the coast, and suggest that the ice from the piedmont Glacier pressed inland up to altitudes around 250m, buttressed by cold and non-erosive ice formed on the Jameson Land uplands.  This ice cap covered and protected older deposits.  Other active glaciers flowed westwards, down from the accumulation areas on the mountains of Liverpool Land, maybe feeding a south-flowing glacier in Hurry Fjord..

This is an important paper from which I have quoted before -- check things out by doing a search for "Jameson Land."

https://www.academia.edu/17754297/Late_Pleistocene_glacial_history_of_Jameson_Land_central_East_Greenland_derived_from_cosmogenic_10_Be_and_26_Al_exposure_dating

Hakansson, L., Alexanderson, H., Hjort, C., Moller, P., Briner, J. P., Aldahan, A. & Possnert, G.: 2008.  Late Pleistocene ¨ glacial history of Jameson Land, central East Greenland, derived from cosmogenic 10Be and 26Al exposure dating. Boreas, Vol. 38, pp. 244–260.
10.1111/j.1502-3885.2008.00064.x. ISSN 0300–9483.

Previous work has presented contrasting views of the last glaciation on Jameson Land, central East Greenland, and still there is debate about whether the area was: (i) ice-free, (ii) covered with a local non-erosive ice cap(s), or (iii) overridden by the Greenland Ice Sheet during the Last Glacial Maximum (LGM). Here, we use cosmogenic exposure ages from erratics to reconcile these contrasting views. A total of 43 erratics resting on weathered sandstone and on sediment-covered surfaces were sampled from four areas on interior Jameson Land; they give 10Be ages between 10.9 and 269.1 kyr. Eight erratics on weathered sandstone and till-covered surfaces cluster around 70 kyr, whereas 10Be ages from erratics on glaciofluvial landforms are substantially younger and range between 10.9 and 47.2 kyr. Deflation is thought to be an important process on the sediment-covered surfaces and the youngest exposure ages are suggested to result from exhumation. The older (470 kyr) samples have discordant 26Al and 10Be data and are interpreted to have been deposited by the Greenland Ice Sheet several glacial cycles ago. The younger exposure ages ( 70 kyr) are interpreted to represent deposition by the ice sheet during the Late Saalian and by an advance from the local Liverpool Land ice cap in the Early Weichselian. The exposure ages younger than Saalian are explained by periods of shielding by non-erosive ice during the Weichselian glaciation. Our work supports previous studies in that the Saalian Ice Sheet advance was the last to deposit thick sediment sequences and western erratics on interior Jameson Land. However, instead of Jameson Land being ice-free throughout the Weichselian, we document that local ice with limited erosion potential covered and shielded large areas for substantial periods of the last glacial cycle.

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Then there is this -- the article itself is behind a paywall, but we get the gist of it from the abstract:



LARS RONNERT and MATS R. NYBORG, 1994.  The distribution of different glacial landscapes on southern Jameson Land, East Greenland, according to Landsat Thematic Mapper Data.
Boreas, Volume 23, Issue 4
Pages: 281-536
December 1994

https://doi.org/10.1111/j.1502-3885.1994.tb00603.x

Abstract


Four geologic units previously mapped in southern Jameson Land. East Greenland (Funder 1978, 1990) are identifiable on a false colour composite of Landsat Thematic Mapper (TM) spectral hands TM5. TM4 and TM1. The area covered by the Weichselian glaciations has a fresh glacial morphology and a less developed drainage system than the older landscape. The Weichselian glaciers reached more than 200 m a.s.l. in the west. but only about 100 m a.s.l. in the east. A contextual analysis (local frequency and local orientation) was included in a Maximum Likelihood classification (M‐L) to map the extent of the Weichselian glaciations. Deposits correlated with the Saalian Scoreshy Sund glaciation are found on the central plateaux of Jameson Land. Landsat TM geological mapping of the surficial distribution of deposits from the Scoreshy Sund glaciation and of weathered Jurassic sandstone or deposits with a high percentage of such sandstone was done using a supervised Maximum Likelihood procedure. Except for the mapping of thc extent of the Late Weichselian Flakkerhuk glaciation, the Maximum Likelihood boundaries between units are in general agrecnient with earlier mapping or with the visual interpretation of the false colour composite. A strong vegetational influence. and similar spectral reflectance lrom deposits of different age due to similarities in lithological composition reduced the possibility of an independent remote sensing approach. Taking already existing general geological knowledge and chronology into account allowed successful Landsat TM geological mapping.

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