Lateglacial ice-cap dynamics in NW Scotland: evidence from the fjords of the Summer Isles region

Stoker, Martyn S.; Bradwell, Tom; Howe, John; Wilkinson, Ian P.; McIntyre, Kate

doi:10.1016/j.quascirev.2009.09.012

Cited by 49 publications

(92 citation statements)

References 61 publications

(53 reference statements)

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“…Warm-based westward ice flow is corroborated by glacial striae across the study area (Fig. 2), the occurrence of a field of E-W oriented bedrock megagrooves just east of the study area, and streamlined landforms offshore to the west (Bradwell et al, 2008c;Stoker et al, 2009). Ice thickness was at least 700 m but possibly greater (Bradwell and Krabbendam, 2003;Mathers et al, 2010).…”

Section: Palaeoglacial Settingmentioning

confidence: 81%

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Glacial erosion and bedrock properties in NW Scotland: Abrasion and plucking, hardness and joint spacing

Krabbendam

Glasser

2011

Geomorphology

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Subglacial erosion beneath glaciers occurs predominantly by abrasion and plucking, producing distinct erosional forms. The controls on the relative importance of abrasion vs. plucking are poorly understood. On the one hand, glacial conditions that favour or suppress cavity formation (ice velocity, ice thickness, and water pressure) are thought to favour plucking or abrasion, respectively.Conversely, bedrock properties are also known to control landforms, but this has rarely been analysed quantitatively. In this study we compare landforms and bedrock properties of sandstone and quartzite at the bed of a palaeo-ice stream near Ullapool in NW Scotland. The boundary between the rock types is at right angles to the westward palaeo-ice flow, and palaeoglacial conditions on both rock types were similar. We report quantitative parameters for bedrock properties (Schmidt hammer hardness and joint spacing) and use morphometric parameters to analyse the landforms. Torridon sandstone is soft but thick-bedded and with a wide joint spacing. Erosional bedforms include roche moutonnées with smoothed tops and concave stoss sides, whalebacks, and elongate p-forms, indicating a high proportion of abrasion over plucking. Cambrian quartzite is hard but thin-bedded with narrow joint spacing. Erosional landforms are angular to subangular with abundant plucked lee faces, suggesting a high proportion of plucking over abrasion. Hardness and joint spacing thus exert a strong control on subglacial erosional landforms and the mechanisms that formed them. Thus glacial conditions (ice velocity, ice thickness) can only be inferred from glacial erosional landforms if the effects of bedrock properties of the substrate are considered.

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Section: Palaeoglacial Settingmentioning

confidence: 81%

“…The study area was deglaciated at c. 14-13 ka (Bradwell et al, 2008b;Stoker et al, 2009). The study area occurs in the centre of a palaeo-ice stream (Fig.…”

Section: Palaeoglacial Settingmentioning

confidence: 99%

Glacial erosion and bedrock properties in NW Scotland: Abrasion and plucking, hardness and joint spacing

Krabbendam

Glasser

2011

Geomorphology

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“…Cosmogenic isotope exposure ages show that high elevation areas (> 800 m) had deglaciated by ~ 16 ka BP (Fabel et al, 2012). However, the timing of Late-Devensian deglaciation of the low ground is still debated and is the subject of continuing research (Bradwell et al, 2008b;Stoker et al, 2009;Ballantyne and Stone, 2011). Glaciation during the Younger Dryas (13-11 ka BP) resulted in the development of ice caps and local cirque glaciers on high ground, but ice cover at this time did not reach the low ground within the study area (Lawson, 1986;Benn and Lukas, 2006;Bradwell, 2006).…”

Section: Glaciological Settingmentioning

confidence: 99%

Quaternary evolution of glaciated gneiss terrains: pre-glacial weathering vs. glacial erosion

Krabbendam

Bradwell

2014

Quaternary Science Reviews

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Vast areas previously covered by Pleistocene ice sheets consist of rugged bedrock-dominated terrain of innumerable knolls and lake-filled rock basins -the 'cnoc-and-lochan' landscape or 'landscape of areal scour'. These landscapes typically form on gneissose or granitic lithologies and are interpreted (1) either to be the result of strong and widespread glacial erosion over numerous glacial cycles; or (2) formed by stripping of a saprolitic weathering mantle from an older, deeply weathered landscape.We analyse bedrock structure, erosional landforms and weathering remnants and within the 'cnoc-andlochan' gneiss terrain of a rough peneplain in NW Scotland and compare this with a geomorphologically similar gneiss terrain in a non-glacial, arid setting (Namaqualand, South Africa). We find that the topography of the gneiss landscapes in NW Scotland and Namaqualand closely follows the old bedrock-saprolite contact (weathering front). The roughness of the weathering front is caused by deep fracture zones providing a highly irregular surface area for weathering to proceed. The weathering front represents a significant change in bedrock physical properties. Glacial erosion (and aeolian erosion in Namaqualand) is an efficient way of stripping saprolite, but is far less effective in eroding hard, unweathered bedrock. Significant glacial erosion of hard gneiss probably only occurs beneath palaeo-ice streams.We conclude that the rough topography of glaciated 'cnoc-and-lochan' gneiss terrains is formed by a multistage process: 1) Long-term, pre-glacial chemical weathering, forming deep saprolite with an irregular weathering front;2) Stripping of weak saprolite by glacial erosion during the first glaciation(s), resulting in a rough land surface, broadly conforming to the pre-existing weathering front ('etch surface');3) Further modification of exposed hard bedrock by glacial erosion. In most areas, glacial erosion is limited, but can be significant beneath palaeo-ice stream. The roughness of glaciated gneiss terrains is crucial for modelling of the glacial dynamics of present-day ice sheets. This roughness is shown here to depend on the intensity of pre-glacial weathering as well as glacial erosion during successive glaciations.

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“…Hybridised versions of these stratigraphic approaches are now widely applied to many onshore and offshore Quaternary successions in northern Europe (Larsen and Andersen, 2005;McMillan, 2005;Rijsdijk et al, 2005;Sejrup et al, 2005;Weerts et al, 2005;Rose, 2009;Stoker et al, 2009;Hughes, 2010;Lüthgens et al, 2010).…”

Section: Lithostratigraphy -Important Conceptsmentioning

confidence: 99%

Quaternary glaciations of northern Europe

Böse

Lüthgens

Lee

et al. 2012

Quaternary Science Reviews

120

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This paper presents the outcome of a workshop, held in Berlin in February 2009, concerned with current research on the glacial history of northern Europe, including the British Isles. The methodologies presently used to resolve this topic are outlined. Particular attention is given to new analytical methods deriving from high resolution remote imaging of glacial terrain both on land and on the sea-bed, key new stratigraphic sections, higher resolution results from conventional geochronological methods like radiocarbon and more recently developed technologies such as luminescence and cosmogenic radionuclide dating. The relationships between the results derived from these two methods are discussed in further detail along with possible explanations for these differences. An outline of a 'most likely' glacial history of the Scandinavian and British and Irish Ice Sheets is presented along with possible links to global climate change as represented by the marine isotope (MIS) record. Tentative evidence for glaciation is identified in MIS 22, 16, 12, 10, 8, 6, 4 and 2 and correlations of 'phases' within the Last Glaciation are also explored for both the Scandinavian and British and Irish Ice Sheets. The results show that the character and extent of glaciation in different parts of the region are not synchronous and much more geochronological work is required before regional correlations can be established with confidence. Keywords: glaciation, marine isotope stages (MIS), Scandinavian Ice Sheet (SIS), British and Irish Ice Sheet (BIIS), Last Glacial Maximum Introduction and objectivesThe glaciation of northern Europe has been a subject of interest and debate for over 200 years and today, at a time of greater awareness to the consequences of climate change, the subject retains its relevance to science and society. With the development of new methodologies for dating glacial deposits and important new findings for modelling glacier response to climate change this subject requires re-evaluation and re-interpretation. Likewise it has been possible to identify critical issues that should be the focus for future research. Consequently, in February 2009 an exploratory workshop was held at the Freie Universität Berlin to examine the frequency and timing of glaciations in northern Europe (including Britain) during the Middle and Late Pleistocene. The workshop was funded by the DFG (Deutsche Forschungsgmeinschaft/ German Research Foundation) and involved 24 participants. This issue of Quaternary Science Reviews includes a number of the contributions presented and discussed at the meeting along with certain invited papers that present new findings on the topic of the special issue. This paper will begin by briefly reviewing the contents of the issue giving particular attention to new and important findings. This will be followed by a section that will evaluate the methodologies currently being applied to understand the glaciations of northern Europe. Some of these methodologies, such as lithostratigraphy and morphostratig...

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Lateglacial ice-cap dynamics in NW Scotland: evidence from the fjords of the Summer Isles region

Cited by 49 publications

References 61 publications

Glacial erosion and bedrock properties in NW Scotland: Abrasion and plucking, hardness and joint spacing

Glacial erosion and bedrock properties in NW Scotland: Abrasion and plucking, hardness and joint spacing

Quaternary evolution of glaciated gneiss terrains: pre-glacial weathering vs. glacial erosion

Quaternary glaciations of northern Europe

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