Geomorphic evidence for active and inactive phases of Late Devensian ice in north-central Ireland

Knight, Jasper

doi:10.1016/j.geomorph.2004.08.019

Cited by 13 publications

(8 citation statements)

References 46 publications

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“…The presence of upward-going sediment injection structures, however, suggests steep proglacial hydraulic gradients, possible controlled by permafrost aquicludes that can act to focus groundwater movement ahead of the ice margin and allow porewater to burst through overlying sediments causing large-scale fluidisation (Boulton and Caban, 1995). This process has been reported from proglacial forefields (Knight, 2006).…”

Section: Resultssupporting

confidence: 62%

“…Upward-going dewatering structures and associated deformation at Double Bluff (Fig. 12) is typical of upward water injection caused by high-porewater pressure ahead of the ice margin (Knight, 2006; Rijsdijk and other, 2010). Such structures have been termed extrusion moraines and have been noted as proglacial features directed ahead of a low-permeability zone with proglacial permafrost (Knight, 2006).…”

Section: Discussionmentioning

confidence: 99%

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Coeval brittle and ductile deformation beneath the late Wisconsinan Puget Lobe, Washington State, USA

Knight

2019

Ann. Glaciol.

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Late Wisconsinan glacial sediments, exposed on Whidbey Island and Camano Island, Puget Sound (Washington State, USA), were deposited in a proglacial shallow marine/outwash environment during northward retreat of the Puget Lobe of the Cordilleran ice sheet. Sediments mainly comprise massive and cross-bedded sand and gravels, and rhythmically-bedded clay and silt/fine sand couplets, interbedded with diamictons that were deposited by a range of mass flows of different viscosities. Although sediment stratigraphy and ice advance–retreat patterns are well established for the Puget Lobe, brittle and ductile deformation structures within, and separating, these sediment units are less well understood. These structures record the nature of ice–bed interactions taking place in subglacial and proglacial environments. This study examines evidence for these processes and environments. Key deformation structures identified include open to overturned folds, normal and reverse faults, clastic dikes and hydrofractures and passive-loading structures. Evidence for coeval development of ductile and brittle deformation structures shows the close relationship between porewater changes, sediment rheology and sediment system responses to changes in strain caused by ice–bed interactions.

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Section: Resultssupporting

confidence: 62%

Section: Discussionmentioning

confidence: 99%

Coeval brittle and ductile deformation beneath the late Wisconsinan Puget Lobe, Washington State, USA

Knight

2019

Ann. Glaciol.

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“…(, ), Jansson & Glasser (), Johnson (, b) Johnson et al . (), Jordan (, ), Jowett (), Jowett & Charlesworth (), Kendall (, ), Kilfeather (), Kinahan (), King & Gage (), Knight (, , , , b, ), Knight et al . (, ), Knowles (), Lamb & Ballantyne (), Lawson (), Letzer (, ), Lewis (), Lewis & Richards (), Lintern (), Livingstone et al .…”

Section: References For Britice Glacial Map V2unclassified

BRITICE Glacial Map, version 2: a map and GIS database of glacial landforms of the last British–Irish Ice Sheet

Clark

Ely

Greenwood

et al. 2017

Boreas

123

118

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During the last glaciation, most of the British Isles and the surrounding continental shelf were covered by the BritishIrish Ice Sheet (BIIS). An earlier compilation from the existing literature (BRITICE version 1) assembled the relevant glacial geomorphological evidence into a freely available GIS geodatabase and map (Clark et al. 2004: Boreas 33, 359). New high-resolution digital elevation models, of the land and seabed, have become available casting the glacial landform record of the British Isles in a new light and highlighting the shortcomings of the V.1 BRITICE compilation. Here we present awholesale revision of the evidence, onshore and offshore, to produce BRITICE version 2, which now also includes Ireland. All published geomorphological evidence pertinent to the behaviour of the ice sheet is included, up to the census date of December 2015. The revised GIS database contains over 170 000 geospatially referenced and attributed elements -an eightfold increase in information from the previous version. The compiled data include: drumlins, ribbed moraine, crag-and-tails, mega-scale glacial lineations, glacially streamlined bedrock (grooves, roches moutonn ees, whalebacks), glacial erratics, eskers, meltwater channels (subglacial, lateral, proglacial and tunnel valleys), moraines, trimlines, cirques, trough-mouth fans and evidence defining ice-dammed lakes. The increased volume of features necessitates different map/database products with varying levels of data generalization, namely: (i) an unfiltered GIS database containing all mapping; (ii) a filtered GIS database, resolving data conflicts and with edits to improve geo-locational accuracy (available as GIS data and PDF maps); and (iii) a cartographically generalized map to provide an overviewof the distribution and types of features at the ice-sheet scale that can be printed at A0 paper size at a 1:1 250 000 scale. All GIS data, the maps (as PDFs) and a bibliography of all published sources are available for download from: https://www.sheffield.ac.uk/geography/staff/clark_chris/britice. Palaeo-ice sheets provide the opportunity to study icesheet behaviour over a longer time period (10 000s of years) than can be achieved by studying current ice sheets (10s of years) thereby permitting exploration of the long-term role of ice sheets in the climate system. The extent, geometry and dynamics of palaeo-ice sheets can be reconstructed from the geomorphological and geological evidence they leave behind, with the mapping, logging and description of such evidence being the vital ingredients. For many palaeo-ice sheets, such as the British-Irish Ice Sheet (BIIS), the accumulation of evidence at individual field-sites has been ongoing for well over 100 years (e.g. Geikie 1894) yielding thousands of publications. Using such work to build local to regional reconstructions of ice dynamics is feasible, but at the ice-sheet scale the volume of information becomes unmanageable. Often the information is spread across so many publications and across many decades of work, where...

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“…The large body of literature (see review in Benn and Evans, 2010) focusing on the formation of drumlins, their morphology, spatial characteristics, and relations with other subglacial landforms reflects the relevance of drumlins for the study of the ice/bed interface, in particular the mechanisms of ice movement over soft beds, and sediment transport, deposition and deformation (e.g., Smalley and Unwin, 1968;Kleman and Borgström, 1996;Fowler, 2000Fowler, , 2010Rattas and Piotrowski, 2003;Phillips et al, 2010;Stokes et al, 2013a;Margold et al, 2015;Eyles and Doughty, 2016). Morphological characteristics of drumlins are used to constrain spatially and temporally variable ice flow dynamics (Colgan and Mickelson, 1997;Knight, 2006;Greenwood and Clark, 2009;Spagnolo et al, 2012) whereas their internal composition informs about erosion, deposition and deformation during the drumlinizing events (e.g. Menzies, 1979;Stokes et al, 2011;McCracken et al 2016;Iverson et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

An erosional origin for drumlins of NW Poland

Hermanowski

Piotrowski

Szuman

2019

Earth Surf Processes Landf

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Drumlins are landforms essential to understanding of ice sheet movement over soft beds, sediment transport along the ice/bed interface, and the formation of a wide range of glacial deposits. Although investigated more than any other glacial landform, the origin of drumlins remains contentious. Using high‐resolution LiDAR imagery and field data, we investigate the geomorphology and internal composition of one of the biggest drumlin fields in the North European Lowland. The Stargard drumlin field consists of over 1300 drumlins and related streamlined subglacial bedforms in a terminal part of a major Weichselian palaeo‐ice stream of the southern Scandinavian Ice Sheet. The drumlins are typically 600‐800 m long, 200‐250 m wide, 3‐6 m high and have axial elongation ratios ~2 but in some cases exceeding 15. Several subzones inferred from drumlin morphometry exist reflecting different ice flow dynamics. The most elongated drumlins occur in areas where ice moved down‐slope and where thick fine‐grained deposits of low hydraulic conductivity occur in the substratum. The largest portion of land occupied by drumlins and the greatest frequency density of drumlins occur where the ice moved up‐slope. Stargard drumlins are composed of a wide variety of glacial deposits including various types of tills and meltwater sediments, which range from undisturbed to heavily deformed. There is no correlation between the deposits in the drumlins and the drumlin forms indicating that the deposits pre‐date the drumlinizing process. It is suggested that the drumlin field was generated by a combination of direct glacial erosion and subglacial meltwater erosion by removing antecedent material from the inter‐drumlin areas and streamlining the resultant bumps. Our data support the search for a unifying theory of drumlin formation and suggest erosion as the most plausible single mechanism generating drumlin landscapes. © 2019 John Wiley & Sons, Ltd.

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Geomorphic evidence for active and inactive phases of Late Devensian ice in north-central Ireland

Cited by 13 publications

References 46 publications

Coeval brittle and ductile deformation beneath the late Wisconsinan Puget Lobe, Washington State, USA

Coeval brittle and ductile deformation beneath the late Wisconsinan Puget Lobe, Washington State, USA

BRITICE Glacial Map, version 2: a map and GIS database of glacial landforms of the last British–Irish Ice Sheet

An erosional origin for drumlins of NW Poland

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