Growth and decay of a marine terminating sector of the last British–Irish Ice Sheet: a geomorphological reconstruction

Finlayson, Andrew; Fabel, Derek; Bradwell, Tom; Sugden, David E.

doi:10.1016/j.quascirev.2013.10.009

Cited by 48 publications

(89 citation statements)

References 80 publications

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“…The geomorphic observations presented here are broadly consistent with the spatial reconstructions and event timescale proposed by Finlayson et al (2014). Under this model the Hebrides Ice Stream was active approximately 32-17 ka, though with significant fluctuations in mass-flux and spatial extent over time.…”

Section: Discussion: Landform Assemblage Around the Inner Hebrides Ssupporting

confidence: 88%

“…Evidence of this more westerly flow regime is observed on bedrock at higher elevations on the nearby islands of Islay and Arran where glacial evidence is found to summit level (e.g. Finlayson et al 2014). The more confined flow described here is indicative of a thinner ice-mass governed significantly by local topography.…”

Section: Discussionmentioning

confidence: 48%

“…The preservation of these landforms at the seabed suggests they represent the last regional-scale ice-streaming event from the Inner Hebrides towards the outer shelf. As the ice stream diminished, becoming inactive around 17-16.5 ka (Finlayson et al 2014), ice-sheet margins retreated to the topographically confined fjords and basins where further flow was recorded (Fig 2). Further decay, and final ice-sheet retreat from the marine environment was likely achieved within these fjords along partially grounded tidewater margins between approximately 16.5 ka and 16 ka (Fig.…”

Section: Discussion: Landform Assemblage Around the Inner Hebrides Smentioning

confidence: 99%

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Deglacial landform assemblage records fast ice-flow and retreat, Inner Hebrides, Scotland

Dove

Finlayson

Bradwell

et al. 2016

Memoirs

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High-resolution bathymetry data have been central to many recent advances in the understanding of past dynamics of the former British-Irish Ice Sheet (BIIS). As approximately two thirds of the former BIIS was probably marine-based during the Last Glacial Maximum (LGM) (~29-23 ka), geomorphic observations of the seabed are increasingly required to understand the extent, pattern, and timing of past glaciation. Until recently, glacial reconstructions for the Inner Hebrides, offshore western Scotland, have been based primarily on terrestrial observations and data. Previous workers have proposed generalised reconstructions in which the Inner Hebrides are located within a significant former ice-sheet flow pathway that drained the western Scottish sector of the BIIS, feeding the Barra Fan during the LGM and earlier glaciations (Fig. 1). Results from numerical ice-sheet modelling suggest that former ice-flow velocities within the region were on the order of hundreds to thousands of metres per year, but also yield further insight by demonstrating how dynamic binge/purge cycles affected ice-sheet mass balance over time (Hubbard et al. 2009). Following the LGM, ice-sheet retreat through the area is estimated to have been in the order of 20 m per year (Clark et al. 2012). Here we present swath bathymetry data from the Inner Hebrides that provide in situ constraints on the ice-sheet flow, and subsequent retreat dynamics from within this important sector of the BIIS. DescriptionWithin the Inner Hebrides (Fig 1a.), Howe et al. (2012) used high-resolution swath bathymetry to identify the first direct evidence relating to subglacial processes and fast ice-flow on the inner shelf. These data have been compiled together with newer bathymetry, as well as terrestrial airborne radar data, to form a near-continuous offshore-onshore digital elevation model (DEM) (horizontal resolution -5 m) that covers the majority of the Inner Hebrides region (Dove et al. 2015). These data cover an extensive an area (~7,000 km²), and our interpretation of the style, location, and pattern of glacial landform assemblages reveals new evidence on the configuration and relative timing of past phases of ice-sheet flow and retreat in the region.On multiple submarine rock platforms and within overdeepened troughs, a diverse assemblage of streamlined ridges and elongate landforms oriented broadly parallel, or sub-parallel to major basin axes is observed (Figs. 1, 2). These streamlined landforms occur in areas of both bedrock and unlithified sediment and are up to several kilometres in length. Sedimentary features range in height up to 20 m, with elongation ratios between 2:1 and 10:1. Streamlined landforms comprising some

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Section: Discussion: Landform Assemblage Around the Inner Hebrides Ssupporting

confidence: 88%

Section: Discussionmentioning

confidence: 48%

Section: Discussion: Landform Assemblage Around the Inner Hebrides Smentioning

confidence: 99%

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Deglacial landform assemblage records fast ice-flow and retreat, Inner Hebrides, Scotland

Dove

Finlayson

Bradwell

et al. 2016

Memoirs

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“…The Härminge small‐scale drumlins and the De Geer moraines associated with them are thus at an angle of ∼38° to the north–south esker trend. It should be noted that for both the De Geer moraines and especially for the small‐scale drumlins in this sub‐area there is the potential for a shrouding effect (Finlayson et al , ; Spagnolo et al ., ) when surrounded by on‐lapping glacial/postglacial aquatic sediments (silt and clay; Fig. ).…”

Section: Resultsmentioning

confidence: 99%

Rapid subglacial streamlined bedform formation at a calving bay margin

Dowling

Möller

Spagnolo

2016

J Quaternary Science

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Using the LiDAR‐derived Swedish national height model we have identified previously undescribed shallow streamlined glacial bedforms, small‐scale drumlins, on the Närke plain in south‐central Sweden. These drumlins could only be detected with high‐resolution LiDAR, due to both their subtle size and forest cover. In this area the ice margin receded in a subaqueous environment with a proglacial water depth in the order of 100 m during the last deglaciation. As indicated by the configuration of marginally formed De Geer moraine ridges draping the drumlinoids, the receding ice margin formed deeply indented calving bays. These were located around subaqueous outlets of the subglacial melt‐water drainage, with their apex position marked geomorphologically by beaded esker ridges. The mapped small‐scale drumlins are aligned perpendicular to the reconstructed ice sheet margin and suggest formation along flow lines adjusted to the configuration of these calving embayments as they propagated up‐flow with ice margin retreat. Based on these geometric relationships we argue that the emplacement of the drumlins was near‐marginal, ∼7.7–1 km from the margin, on a short timescale (∼5–35 years).

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“…The British-Irish Ice Sheet, on the other hand, had iceinception centres located centrally with respect to the maximum margins of the ice sheet. It started to grow at approximately 35 ka BP through merging of small mountain ice caps in the Scottish Highlands (Finlayson et al, 2014).…”

Section: Waxing and Waning Glaciers Towards The Maxima Positionsmentioning

confidence: 99%

Causes of time-transgressive glacial maxima positions of the last Scandinavian Ice Sheet

Larsen¹,

Fredin²,

Lyså³

et al. 2016

NJG

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Reconstructions of ice cover during the time spanning the Late Weichselian maximum show a confluent Eurasian ice sheet with the Scandinavian Ice Sheet positioned between the Svalbard-Barents-Kara and the British-Irish ice sheets. It has long been suspected among glacial geologists that the maximum ice-marginal position was asynchronous, but only recently has it been possible to explore this in some detail. Dates pertaining to the ice margin of the Scandinavian Ice Sheet reveal an old (29-25 ka) maximum position along its western flank, whereas a younger (18-16 ka) maximum position has been delineated along its eastern flank. A time -distance diagram across the Scandinavian Ice sheet shows an oscillatory western ice front, as opposed to a steadily growing and decaying eastern ice margin. The largest age difference between maximum positions is as much as 10 ka between different sectors of the Scandinavian Ice Sheet. Older maximum positions of the western margin can be explained by its proximity to icegrowth centres, initial windward ice growth, efficient ice drainage in ice streams on the Norwegian continental shelf, and the continental shelf break being a barrier to further westward expansion. Younger maximum positions of the eastern margin can be explained by a very long distance between ice-growth centres and marginal positions, slow flow in a wide zone of cold-based to partly cold-based ice, and punctuated advances of low-gradient ice lobes into proglacial lakes along the extreme eastern perimeter of the ice sheet. The influence of these lakes on the glacier dynamics of adjoining ice lobes prolonged the ice sheet advance by some 1 to 3 ka compared with adjacent interlobate areas.

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Growth and decay of a marine terminating sector of the last British–Irish Ice Sheet: a geomorphological reconstruction

Cited by 48 publications

References 80 publications

Deglacial landform assemblage records fast ice-flow and retreat, Inner Hebrides, Scotland

Deglacial landform assemblage records fast ice-flow and retreat, Inner Hebrides, Scotland

Rapid subglacial streamlined bedform formation at a calving bay margin

Causes of time-transgressive glacial maxima positions of the last Scandinavian Ice Sheet

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