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Colin K. Ballantyne - One of the best experts on this subject based on the ideXlab platform.
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trimlines blockfields and the vertical extent of the Last Ice Sheet in southern ireland
Boreas, 2015Co-Authors: Colin K. Ballantyne, John O StoneAbstract:Trimlines separating glacially abraded lower slopes from blockfield-covered summits on Irish mountains have traditionally been interpreted as representing the upper limit of the Last Ice Sheet during the Last Glacial Maximum (LGM). Cosmogenic 10Be exposure ages obtained for samples from glacially deposited perched boulders resting on blockfield debris on the summit area of Slievenamon (721 m a.s.l.) in southern Ireland demonstrate emplacement by the Last Irish Ice Sheet (IIS), implying preservation of the blockfield under cold-based Ice during the LGM, and supporting the view that trimlines throughout the British Isles represent former englacial thermal regime boundaries between a lower zone of warm-based sliding Ice and an upper zone of cold-based Ice. The youngest exposure age (22.6±1.1 or 21.0±0.9 ka, depending on the 10Be production rate employed) is statistically indistinguishable from the mean age (23.4±1.2 or 21.8±0.9 ka) obtained for two samples from Ice-abraded bedrock at high ground on Blackstairs Mountain, 51 km to the east, and with published cosmogenic 36Cl ages. Collectively, these ages imply (i) early (24–21 ka) thinning of the Last IIS and emergence of high ground in SE Ireland; (ii) relatively brief (1–3 ka) glacial occupation of southernmost Ireland during the LGM; (iii) decoupling of the Irish Sea Ice Stream and Ice from the Irish midlands within a similar time frame; and (iv) that the southern fringe of Ireland was deglaciated before western and northern Ireland.
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rock slope failure following late pleistocene deglaciation on tectonically stable mountainous terrain
Quaternary Science Reviews, 2014Co-Authors: Colin K. Ballantyne, John O Stone, Graeme F Sandeman, P WilsonAbstract:The ages of 31 postglacial rock-slope failures (RSFs) in Scotland and NW Ireland, derived from 89 cosmogenic isotope exposure ages, are employed to analyse the temporal pattern of failure and its relationship to the timing of deglaciation, rates of glacio-isostatic crustal uplift and periods of rapid climate change. RSF ages span almost the whole period since Ice-Sheet retreat, from 18.2 � 1.2 ka to 1.7 � 0.2 ka, or from 17.1 � 1.0 ka to 1.5 � 0.1 ka, depending on the production rate used in 10 Be age calculation, but catastrophic failure of rock slopes was w4.6 times more frequent prior to w11.7 ka than during the Holocene. 95% of dated RSFs at sites deglaciated during retreat of the Last Ice Sheet occurred within w5400 years after deglaciation, with peak RSF activity 1600e1700 years after deglaciation. This time lag is inferred to represent (1) stress release initiated by deglacial unloading, leading to (2) time-dependent rock mass strength degradation through progressive failure plane development, and ultimately (3) to either spontaneous kinematic release or failure triggered by some extrinsic mechanism. By contrast,11 dated RSFs at sites reoccupied by glacier Ice during the Younger Dryas Stade (YDS) of w12.9e11.7 ka exhibit no clear temporal pattern, suggesting that glacial reoccupance during the YDS was ineffective in preconditioning a renewed cycle of enhanced RSF activity. Comparison of timing of individual RSFs with that of deglaciation and rapid warming events at w14.7 ka and w11.7 ka suggests that glacial debuttressing, enhanced joint waterpressuresduringdeglaciationandthawofpermafrostIceinrockjointscouldhavetriggeredfailurein only a small number of cases. Conversely, the timing of maximum RSF activity following Ice-Sheet deglaciation corresponds broadly with maximum rates of glacio-isostatic crustal uplift, suggesting that the two are linked by enhanced seismic activity. A seismic failure trigger is consistent with full-slope failure at all sites where failure planes are clearly defined. Our results indicate that numerous RSFs must have occurred in areas that were reoccupied by glacier Ice during the YDS, but have not been identified because runout debris was removed by YDS glaciers. More generally, they provide the first reliably-dated body of evidence to support the view that retreat of the Last Ice Sheets in tectonically-stable mountainous terrain initiated a period of enhanced rock slope failure due to deglacial unloading and probably Lateglacial seismic activity, implying that most undated RSFs in such areas are probably of Lateglacial or veryearly Holocene age. They also demonstrate, however, that a low frequency of RSF activity extended throughout the Holocene.
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trimlines blockfields mountain top erratics and the vertical dimensions of the Last british irish Ice Sheet in nw scotland
Quaternary Science Reviews, 2012Co-Authors: Derek Fabel, Colin K. BallantyneAbstract:Periglacial trimlines separating glacially eroded lower slopes from blockfield-covered plateaus on British and Irish mountains have been interpreted either (1) in terms of representing the maximum altitude of the Last Ice Sheet during the Last Glacial Maximum (LGM), or (2) as a thermal boundary separating wet-based Ice at pressure melting point from cold-based Ice on summit plateaus. We test these competing hypotheses through 10Be exposure dating of high-level erratic boulders above trimlines on five mountains in NW Scotland. Nine out of 14 erratics yielded post-LGM exposure ages ranging from 14.0 ± 0.7 ka to 16.5 ± 0.9 ka or from 14.9 ± 0.9 ka to 17.6 ± 1.1 ka, depending on the 10Be production rate employed in exposure age calculation. These ages refute hypothesis (1) as they imply that the Last Ice Sheet overtopped the mountains. Preservation of apparently intact blockfields on the summits implies cold-based Ice cover, supporting hypothesis (2). As altitudinally consistent high-level trimlines extend from our sampled sites across much of NW Scotland and the Hebrides, our conclusions apply to all trimlines in this broader area, and probably to all high-level trimlines elsewhere in the British Isles. Preservation of blockfields under cold-based Ice is consistent with blockfield evolution on plateaus throughout much or all of the Quaternary. Averaged exposure ages of ∼15–16 ka for plateau-top erratics implies nunatak emergence from the downwasting Ice Sheet prior to a regional readvance of the Ice margin (the Wester Ross Readvance) and before rapid warming at ∼14.7 ka at the onset of the Lateglacial Interstade, but after the timing of Ice-Sheet thinning as retrodicted by recent proxy climate-driven thermo-mechanical coupled models. Our findings provide an additional constraint on the future development of such models by implying that high-level trimlines represent the altitude of a former transition zone between Ice at pressure-melting point and Ice below pressure melting point.
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dimensions and chronology of the Last Ice Sheet in western ireland
Quaternary Science Reviews, 2008Co-Authors: Colin K. Ballantyne, John O Stone, Danny MccarrollAbstract:Abstract On the mountains of Western Ireland, the upper limit of glacial evidence descends from 730 m in the Connemara Mountains to 400 m on Achill Island. This limit is interpreted as a trimline marking the upper limit of erosive, warm-based Ice, implying that higher summits remained above a former Ice Sheet as nunataks or supported a cover of cold-based Ice. Significantly greater representation of gibbsite in soils above the trimline indicates that it relates to the Last glacial stage. 10 Be exposure ages for bedrock samples above the trimline fall within the range (>) 36.0±2.3 ka to (>) 61.6±4.0 ka, whereas Ice-scoured bedrock below the trimline yielded 10 Be exposure ages ⩽24.0±1.6 ka (and in all but two cases ⩽17.2±1.1 ka), consistent with deglaciation after the LGM. Reconstruction of the minimum altitude of the LGM Ice surface implies that inland Ice was diverted northwestwards by an Ice dome on the Connemara Mountains and extended at least 25 km offshore. This evidence conflicts with previous accounts that place the LGM Ice limit onshore and implies that recent models underestimate LGM Ice thickness in Western Ireland.
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vertical dimensions and age of the wicklow mountains Ice dome eastern ireland and implications for the extent of the Last irish Ice Sheet
Quaternary Science Reviews, 2006Co-Authors: Colin K. Ballantyne, Danny Mccarroll, John O StoneAbstract:Abstract Patterns of erratic distribution show that the Wicklow Mountains formerly supported an independent Ice cap or Ice dome. Geomorphological mapping of the upper limits of evidence for glaciation (Ice-scoured and moulded bedrock, perched boulders) and the distribution of features indicative of prolonged periglacial conditions (tors, frost-shattered rock, blockfields) indicates that along the main axis of high ground erosive warm-based Ice buried all but the highest (>725 m) summits and over-ran adjacent lower peaks and cols. The presence of gibbsite in soil samples from above the inferred upper limit of glacial erosion and its absence in all samples from below this limit is consistent with the geomorphological evidence and implies removal of gibbsitic soils below ∼725 m by glacial erosion during the Last glacial stage. Cosmogenic 10 Be exposure ages for rock outcrops above the inferred upper limit of glacial erosion yield pre-Last glacial maximum (LGM) ages of (>) 46.9±3.0 ka to (>) 95.9±6.1 ka, whereas rock outcrops on summits over-ridden by warm-based Ice give post-LGM ages of 18.2±1.2 to 19.1±1.2 ka. All geomorphological and dating evidence thus indicates an LGM age for the Ice dome. The thickness of the Ice dome and limited lateral dispersal of erratics indicate that at the LGM the Wicklow Ice was encircled by and confluent with thick, powerful Ice streams moving SE from the Irish Midlands and southwards down the Irish Sea basin. This conclusion is irreconcilable with the traditional view that the Last Irish Ice Sheet terminated at the ‘South Ireland end moraine’, but consistent with recent proposals that the Last Ice Sheet was much more extensive than previously believed, and over-ran the south coast of Ireland.
John O Stone - One of the best experts on this subject based on the ideXlab platform.
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trimlines blockfields and the vertical extent of the Last Ice Sheet in southern ireland
Boreas, 2015Co-Authors: Colin K. Ballantyne, John O StoneAbstract:Trimlines separating glacially abraded lower slopes from blockfield-covered summits on Irish mountains have traditionally been interpreted as representing the upper limit of the Last Ice Sheet during the Last Glacial Maximum (LGM). Cosmogenic 10Be exposure ages obtained for samples from glacially deposited perched boulders resting on blockfield debris on the summit area of Slievenamon (721 m a.s.l.) in southern Ireland demonstrate emplacement by the Last Irish Ice Sheet (IIS), implying preservation of the blockfield under cold-based Ice during the LGM, and supporting the view that trimlines throughout the British Isles represent former englacial thermal regime boundaries between a lower zone of warm-based sliding Ice and an upper zone of cold-based Ice. The youngest exposure age (22.6±1.1 or 21.0±0.9 ka, depending on the 10Be production rate employed) is statistically indistinguishable from the mean age (23.4±1.2 or 21.8±0.9 ka) obtained for two samples from Ice-abraded bedrock at high ground on Blackstairs Mountain, 51 km to the east, and with published cosmogenic 36Cl ages. Collectively, these ages imply (i) early (24–21 ka) thinning of the Last IIS and emergence of high ground in SE Ireland; (ii) relatively brief (1–3 ka) glacial occupation of southernmost Ireland during the LGM; (iii) decoupling of the Irish Sea Ice Stream and Ice from the Irish midlands within a similar time frame; and (iv) that the southern fringe of Ireland was deglaciated before western and northern Ireland.
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rock slope failure following late pleistocene deglaciation on tectonically stable mountainous terrain
Quaternary Science Reviews, 2014Co-Authors: Colin K. Ballantyne, John O Stone, Graeme F Sandeman, P WilsonAbstract:The ages of 31 postglacial rock-slope failures (RSFs) in Scotland and NW Ireland, derived from 89 cosmogenic isotope exposure ages, are employed to analyse the temporal pattern of failure and its relationship to the timing of deglaciation, rates of glacio-isostatic crustal uplift and periods of rapid climate change. RSF ages span almost the whole period since Ice-Sheet retreat, from 18.2 � 1.2 ka to 1.7 � 0.2 ka, or from 17.1 � 1.0 ka to 1.5 � 0.1 ka, depending on the production rate used in 10 Be age calculation, but catastrophic failure of rock slopes was w4.6 times more frequent prior to w11.7 ka than during the Holocene. 95% of dated RSFs at sites deglaciated during retreat of the Last Ice Sheet occurred within w5400 years after deglaciation, with peak RSF activity 1600e1700 years after deglaciation. This time lag is inferred to represent (1) stress release initiated by deglacial unloading, leading to (2) time-dependent rock mass strength degradation through progressive failure plane development, and ultimately (3) to either spontaneous kinematic release or failure triggered by some extrinsic mechanism. By contrast,11 dated RSFs at sites reoccupied by glacier Ice during the Younger Dryas Stade (YDS) of w12.9e11.7 ka exhibit no clear temporal pattern, suggesting that glacial reoccupance during the YDS was ineffective in preconditioning a renewed cycle of enhanced RSF activity. Comparison of timing of individual RSFs with that of deglaciation and rapid warming events at w14.7 ka and w11.7 ka suggests that glacial debuttressing, enhanced joint waterpressuresduringdeglaciationandthawofpermafrostIceinrockjointscouldhavetriggeredfailurein only a small number of cases. Conversely, the timing of maximum RSF activity following Ice-Sheet deglaciation corresponds broadly with maximum rates of glacio-isostatic crustal uplift, suggesting that the two are linked by enhanced seismic activity. A seismic failure trigger is consistent with full-slope failure at all sites where failure planes are clearly defined. Our results indicate that numerous RSFs must have occurred in areas that were reoccupied by glacier Ice during the YDS, but have not been identified because runout debris was removed by YDS glaciers. More generally, they provide the first reliably-dated body of evidence to support the view that retreat of the Last Ice Sheets in tectonically-stable mountainous terrain initiated a period of enhanced rock slope failure due to deglacial unloading and probably Lateglacial seismic activity, implying that most undated RSFs in such areas are probably of Lateglacial or veryearly Holocene age. They also demonstrate, however, that a low frequency of RSF activity extended throughout the Holocene.
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dimensions and chronology of the Last Ice Sheet in western ireland
Quaternary Science Reviews, 2008Co-Authors: Colin K. Ballantyne, John O Stone, Danny MccarrollAbstract:Abstract On the mountains of Western Ireland, the upper limit of glacial evidence descends from 730 m in the Connemara Mountains to 400 m on Achill Island. This limit is interpreted as a trimline marking the upper limit of erosive, warm-based Ice, implying that higher summits remained above a former Ice Sheet as nunataks or supported a cover of cold-based Ice. Significantly greater representation of gibbsite in soils above the trimline indicates that it relates to the Last glacial stage. 10 Be exposure ages for bedrock samples above the trimline fall within the range (>) 36.0±2.3 ka to (>) 61.6±4.0 ka, whereas Ice-scoured bedrock below the trimline yielded 10 Be exposure ages ⩽24.0±1.6 ka (and in all but two cases ⩽17.2±1.1 ka), consistent with deglaciation after the LGM. Reconstruction of the minimum altitude of the LGM Ice surface implies that inland Ice was diverted northwestwards by an Ice dome on the Connemara Mountains and extended at least 25 km offshore. This evidence conflicts with previous accounts that place the LGM Ice limit onshore and implies that recent models underestimate LGM Ice thickness in Western Ireland.
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vertical dimensions and age of the wicklow mountains Ice dome eastern ireland and implications for the extent of the Last irish Ice Sheet
Quaternary Science Reviews, 2006Co-Authors: Colin K. Ballantyne, Danny Mccarroll, John O StoneAbstract:Abstract Patterns of erratic distribution show that the Wicklow Mountains formerly supported an independent Ice cap or Ice dome. Geomorphological mapping of the upper limits of evidence for glaciation (Ice-scoured and moulded bedrock, perched boulders) and the distribution of features indicative of prolonged periglacial conditions (tors, frost-shattered rock, blockfields) indicates that along the main axis of high ground erosive warm-based Ice buried all but the highest (>725 m) summits and over-ran adjacent lower peaks and cols. The presence of gibbsite in soil samples from above the inferred upper limit of glacial erosion and its absence in all samples from below this limit is consistent with the geomorphological evidence and implies removal of gibbsitic soils below ∼725 m by glacial erosion during the Last glacial stage. Cosmogenic 10 Be exposure ages for rock outcrops above the inferred upper limit of glacial erosion yield pre-Last glacial maximum (LGM) ages of (>) 46.9±3.0 ka to (>) 95.9±6.1 ka, whereas rock outcrops on summits over-ridden by warm-based Ice give post-LGM ages of 18.2±1.2 to 19.1±1.2 ka. All geomorphological and dating evidence thus indicates an LGM age for the Ice dome. The thickness of the Ice dome and limited lateral dispersal of erratics indicate that at the LGM the Wicklow Ice was encircled by and confluent with thick, powerful Ice streams moving SE from the Irish Midlands and southwards down the Irish Sea basin. This conclusion is irreconcilable with the traditional view that the Last Irish Ice Sheet terminated at the ‘South Ireland end moraine’, but consistent with recent proposals that the Last Ice Sheet was much more extensive than previously believed, and over-ran the south coast of Ireland.
Colm O Cofaigh - One of the best experts on this subject based on the ideXlab platform.
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Ice marginal dynamics of the Last british irish Ice Sheet in the southern north sea Ice limits timing and the influence of the dogger bank
Quaternary Science Reviews, 2018Co-Authors: David H Roberts, David J A Evans, Louise S Callard, Chris D Clark, Mark D Bateman, Alicia Medialdea, Dayton Dove, Carol Cotterill, Margot Saher, Colm O CofaighAbstract:The southern North Sea is a particularly important area for understanding the behaviour of the British-Irish Ice Sheet (BIIS) during the Last glacial cycle. It preserves a record of the maximum extent of the eastern sector of the BIIS as well as evidence for multiple different Ice flow phases and the dynamic re-organisation of the BIIS. However, to date, the known Ice Sheet history and geochronology of this region is predominantly derived from onshore geological evidence, and the offshore imprint and dynamic history of the Last Ice Sheet remain largely unknown. Using new data collected by the BRITIce-CHRONO project this paper explores the origin and age of the Dogger Bank; re-assesses the extent and age of the glaciogenic deposits across the shallow areas of the North Sea between the Dogger Bank and the north Norfolk coast and; re-examines the dynamic behaviour of the BIIS in the southern North Sea between 31.6 and 21.5 ka. This paper shows the core of the Dogger Bank to be composed glaciolacustrine sediment deposited between 31.6 and 25.8 ka. Following its formation the western end of the Dogger lake was overridden with Ice reaching ∼54°N where the Ice margin is co-incident with the southerly extent of subglacial tills previously mapped as Bolders Bank Fm. This initial Ice override and retreat northwards back across the Dogger lake was complete by 23.1 ka, but resulted in widespread compressive glaciotectonism of the lake sediments and the formation of thrust moraine complexes. Along the northern edge of the bank moraines are on-lapped by later phase glaciolacustrine and marine sediments but do not show evidence of subsequent Ice override. The shallow seafloor to the west and southwest of the Dogger Bank records several later phases of Ice advance and retreat as the North Sea Lobe flowed between the Dogger Bank and the Yorkshire/Lincolnshire coasts and reached North Norfolk. New optically stimulated luminescence (OSL) ages from Garrett Hill on outwash limit the arrival of the BIIS on the Norfolk coast to 22.8–21.5 ka. Multiple till Sheets and chains of moraines on the seafloor north of Norfolk mark dynamic oscillation of the North Sea Lobe margin as it retreated northwards. This pattern of behaviour is broadly synchronous with the terrestrial record of deposition of subglacial, glaciofluvial and glaciolacustrine sediments along the Yorkshire coast which relate to post Dimlington Stadial Ice marginal oscillations after 21.5 ka. With respect to forcing mechanisms it is likely that during the early phases of the Last glacial maximum (∼30-23ka) the interaction between the southern margin of the BIIS and the Dogger Lake was critical in influencing flow instability and rapid Ice advance and retreat. However, during the latter part of the Last glacial maximum (22–21 ka) late-phase Ice advance in the southern North Sea became restricted to the western side of the Dogger Bank which was a substantial topographic feature by this time. This topographic confinement, in addition to decoupling of the BIIS and the Fennoscandian Ice Sheet (FIS) further north, enabled Ice to reach the north Norfolk coast, overprinting the seabed with late-phase tills of the Bolders Bank Fm.
Danny Mccarroll - One of the best experts on this subject based on the ideXlab platform.
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dimensions and chronology of the Last Ice Sheet in western ireland
Quaternary Science Reviews, 2008Co-Authors: Colin K. Ballantyne, John O Stone, Danny MccarrollAbstract:Abstract On the mountains of Western Ireland, the upper limit of glacial evidence descends from 730 m in the Connemara Mountains to 400 m on Achill Island. This limit is interpreted as a trimline marking the upper limit of erosive, warm-based Ice, implying that higher summits remained above a former Ice Sheet as nunataks or supported a cover of cold-based Ice. Significantly greater representation of gibbsite in soils above the trimline indicates that it relates to the Last glacial stage. 10 Be exposure ages for bedrock samples above the trimline fall within the range (>) 36.0±2.3 ka to (>) 61.6±4.0 ka, whereas Ice-scoured bedrock below the trimline yielded 10 Be exposure ages ⩽24.0±1.6 ka (and in all but two cases ⩽17.2±1.1 ka), consistent with deglaciation after the LGM. Reconstruction of the minimum altitude of the LGM Ice surface implies that inland Ice was diverted northwestwards by an Ice dome on the Connemara Mountains and extended at least 25 km offshore. This evidence conflicts with previous accounts that place the LGM Ice limit onshore and implies that recent models underestimate LGM Ice thickness in Western Ireland.
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vertical dimensions and age of the wicklow mountains Ice dome eastern ireland and implications for the extent of the Last irish Ice Sheet
Quaternary Science Reviews, 2006Co-Authors: Colin K. Ballantyne, Danny Mccarroll, John O StoneAbstract:Abstract Patterns of erratic distribution show that the Wicklow Mountains formerly supported an independent Ice cap or Ice dome. Geomorphological mapping of the upper limits of evidence for glaciation (Ice-scoured and moulded bedrock, perched boulders) and the distribution of features indicative of prolonged periglacial conditions (tors, frost-shattered rock, blockfields) indicates that along the main axis of high ground erosive warm-based Ice buried all but the highest (>725 m) summits and over-ran adjacent lower peaks and cols. The presence of gibbsite in soil samples from above the inferred upper limit of glacial erosion and its absence in all samples from below this limit is consistent with the geomorphological evidence and implies removal of gibbsitic soils below ∼725 m by glacial erosion during the Last glacial stage. Cosmogenic 10 Be exposure ages for rock outcrops above the inferred upper limit of glacial erosion yield pre-Last glacial maximum (LGM) ages of (>) 46.9±3.0 ka to (>) 95.9±6.1 ka, whereas rock outcrops on summits over-ridden by warm-based Ice give post-LGM ages of 18.2±1.2 to 19.1±1.2 ka. All geomorphological and dating evidence thus indicates an LGM age for the Ice dome. The thickness of the Ice dome and limited lateral dispersal of erratics indicate that at the LGM the Wicklow Ice was encircled by and confluent with thick, powerful Ice streams moving SE from the Irish Midlands and southwards down the Irish Sea basin. This conclusion is irreconcilable with the traditional view that the Last Irish Ice Sheet terminated at the ‘South Ireland end moraine’, but consistent with recent proposals that the Last Ice Sheet was much more extensive than previously believed, and over-ran the south coast of Ireland.
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periglacial trimlines former nunataks and the altitude of the Last Ice Sheet in wester ross northwest scotland
Journal of Quaternary Science, 1997Co-Authors: Colin K. Ballantyne, Atle Nesje, Danny Mccarroll, Svein Olaf DahlAbstract:High-level weathering limits separating Ice-scoured topography from frost-weathered detritus were identified on 28 mountains in Wester Ross at altitudes of 700–960 m, and a further 22 peaks support evidence of Ice scouring to summit level. Weathering limits are defined most clearly on sandstone and gneiss, which have resisted frost shattering during the Late Devensian Lateglacial, but can also be distinguished on schists and quartzite. Schmidt hammer measurements and analyses of clay mineral assemblages indicate significantly more advanced rock and soil weathering above the weathering limits. The persistence of gibbsite above weathering limits indicates that they represent the upper limit of Late Devensian glacial erosion. The regular decline of weathering-limit altitudes along former flowlines eliminates the possibility that the weathering limits represent former thermal boundaries between protective cold-based and erosive warm-based Ice. The weathering limits are therefore interpreted as periglacial trimlines that define the maximum surface altitude of the Last Ice Sheet. Calculated basal shear stresses of 50–95 kPa are consistent with this interpretation. Reconstruction of Ice-Sheet configuration indicates that the former Ice-shed lay above 900 m along the present watershed, and that the Ice surface descended northwestwards, with broad depressions along major troughs and localised domes around independent centres of Ice dispersal. Extrapolation of the Ice surface gradient and altitude suggests that the Ice Sheet did not overrun the Outer Hebrides, but was confluent with the independent Outer Hebrides Ice-cap in the North Minch basin. Erratics located up to 140 m above the reconstructed Ice surface are inferred to have been emplaced by a pre-Late Devensian Ice Sheet (or Ice Sheets) of unknown age. © 1997 John Wiley & Sons, Ltd.
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nunataks of the Last Ice Sheet in northwest scotland
Boreas, 1995Co-Authors: Danny Mccarroll, Atle Nesje, Colin K. Ballantyne, Svein Olaf DahlAbstract:High-level weathering limits separating Ice-scoured topography from an upper zone of frost-weathered detritus were identified on 17 mountains in NW Scotland at altitudes of 500 m over the extreme NW tip of Scotland and to 700–730 m at the head of Little Loch Broom.
Robin Wingfield - One of the best experts on this subject based on the ideXlab platform.
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the extension of the late weichselian late devensian Ice Sheets in the north sea basin
Journal of Quaternary Science, 1991Co-Authors: Jürgen Ehlers, Robin WingfieldAbstract:The distribution of large channel-like features, comprising Weichselian/Devensian incisions, in the western North Sea provides evidence for a much larger extension of the Last Ice Sheet than currently assumed. Morphological comparison of the incisions with those in North Germany and Poland reveals a striking similarity in shape and distribution. The features on the North Sea floor are interpreted as being formed by meltwater erosion within the margin of the Ice Sheet. The widespread absence of Weichselian/Devensian till in the area under consideration may be attributed to later erosion. Large-scale reworking and redistribution of sediments is indicated by the complete sediment infill of the majority of the incisions.
