The Late Devensian glaciation of the eastern Lleyn Peninsula, North Wales: evidence for terrestrial depositional environments

Thomas, G. S. P.; Chester, David K.; Crimes, Peter

doi:10.1002/(sici)1099-1417(199805/06)13:3<255::aid-jqs353>3.0.co;2-u

Cited by 21 publications

(29 citation statements)

References 30 publications

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“…Further depositional features that have initiated debate are the Cors Geirch sand and gravel terraces, interpreted as the deposits of glacial lake Bodfean by Matley (1936). They were later studied by Saunders (1968c) Recent mapping of Quaternary geology and geomorphology on the eastern Lleyn by Thomas et al (1990Thomas et al ( , 1998 has highlighted complex glacifluvial sequences and moraines with glacitectonic structures, suggestive of glacier halts or minor readvances. Specifically, they report a large outwash tract (the Rhoslan sandur) that was deposited between the Irish and Welsh ice as they decoupled over eastern Lleyn and morainic ridges that document ice marginal recession.…”

Section: North Walesmentioning

confidence: 99%

The last British Ice Sheet: A review of the evidence utilised in the compilation of the Glacial Map of Britain

Evans

Clark

Mitchell

2005

Earth-Science Reviews

126

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This paper reviews the evidence presently available (as at December 2003) in an effort to stimulate further research on the last British Ice Sheet and promote a reconstruction of ice sheet behaviour based on glacial geology and geomorphology. The wide range of evidence that has been scrutinized for inclusion on the glacial map is assessed with respect to the variability of its quality and quantity and the existing controversies in ice sheet reconstructions. Landforms interpreted as being of unequivocal ice-marginal origin (moraines, ice-contact glacifluvial landforms and lateral meltwater channels) and till sheet margins are used in conjunction with available chronological control to locate former glacier and ice-sheet margins throughout the last glacial cycle. Subglacial landforms (drumlins, flutings and eskers) have been used to demarcate former flow patterns within the ice sheet. The compilation of evidence in a regional map is crucial to any future reconstructions of palaeo-ice sheet dynamics and will provide a clearer understanding of ice sheet configuration, ice divide migration and ice thickness and coverage for the British Ice Sheet as it evolved through the last glacial cycle.2

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Section: North Walesmentioning

confidence: 99%

The last British Ice Sheet: A review of the evidence utilised in the compilation of the Glacial Map of Britain

Evans

Clark

Mitchell

2005

Earth-Science Reviews

126

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“…More recent and extensive stratigraphic description, mapping and interpretation (Thomas et al, 1998;Thomas and Chiverrell, 2007) across the Llŷn Peninsula have since established a lithostratigraphical framework, recording a set of sediment-landform assemblages that reflect rapidly changing erosional and depositional environments during ice interaction and deglaciation within a single glaciation.…”

Section: Geological Contextmentioning

confidence: 83%

“…However, given that present water depths in Tremadog Bay range from 8 to 22 m, and many coastal sections around the central and southern Irish Sea Basin have been shown to be deposited terrestrially (e.g. Thomas et al, 1998;Glasser et al, 2001;Lambeck and Purcell, 2001), we suggest that subaerial processes are more probable. A possible source for proglacial meltwater discharge on this flank of the sarn is the frontal margin of the adjacent Mawddach Glacier.…”

Section: Parallel Ridges and Linear Depressionsmentioning

confidence: 90%

“…As the Tremadog glacier reached maximum mass turnover, sediments at its base were being reworked, producing the streamlined bedforms observed within the bay and along the northern sarn edge. Abundant Irish Sea erratics exposed at Tonfanau indicate the Irish Sea Ice Welsh ice coalesced, the boundary defined by offshore borehole records (Garrard and Dobson, 1974) and geomorphological mapping on the Llŷn Peninsula (Thomas et al, 1998). Irish Sea erratics at Tonfanau (T) suggest possible impingement here after advance of Welsh ice (Patton and Hambrey, 2009).…”

Section: Sequence Of Eventsmentioning

confidence: 99%

“…Irish Sea erratics at Tonfanau (T) suggest possible impingement here after advance of Welsh ice (Patton and Hambrey, 2009). (C) During deglaciation, Welsh Ice still dominated Cardigan Bay, helping create the lacustrine delta terraces at Cors Geirch (Thomas et al, 1998 Stream impinged along the coastline here after a period of Welsh advance (Patton and Hambrey, 2009), possibly as a result of migration of the confluence zone between the two ice masses. Convergence of Welsh and Irish Sea ice flow units along the Irish Sea "drift" limit would probably have extended and deflected sarn-deposition southeastwards.…”

Section: Sequence Of Eventsmentioning

confidence: 99%

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Rapid marine deglaciation: asynchronous retreat dynamics between the Irish Sea Ice Stream and terrestrial outlet glaciers

et al. 2013

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Abstract. Understanding the retreat behaviour of past marine-based ice sheets provides vital context for accurate assessments of the present stability and long-term response of contemporary polar ice sheets to climate and oceanic warming. Here new multibeam swath bathymetry data and sedimentological analysis are combined with high resolution ice-sheet modelling to reveal complex landform assemblages and process dynamics associated with deglaciation of the Celtic ice sheet within the Irish Sea Basin. Our reconstruction indicates a nonlinear relationship between the rapidly receding Irish Sea Ice Stream and the retreat of outlet glaciers draining the adjacent, terrestrially based ice cap centred over Wales. Retreat of Welsh ice was episodic; superimposed over low-order oscillations of its margin are asynchronous outlet readvances driven by catchment-wide mass balance variations that are amplified through migration of the ice cap's main ice divide. Formation of large, linear ridges which extend at least 12.5 km offshore (locally known as sarns) and which dominate the regional bathymetry are attributed to repeated frontal and medial morainic deposition associated with the readvancing phases of these outlet glaciers. Our study provides new insight into ice-sheet extent, dynamics and non-linear retreat across a major palaeo-ice stream confluence zone, and has ramifications for the interpretation of recent fluctuations observed by satellites over short timescales across marine sectors of the Greenland and Antarctic ice sheets.

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Glacial meltwater erosion of the Mid-Cheshire Ridge: implications for ice dynamics during the Late Devensian glaciation of northwest England

Glasser

Smith

1999

J. Quaternary Sci.

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The Late Devensian glaciation of the eastern Lleyn Peninsula, North Wales: evidence for terrestrial depositional environments

Cited by 21 publications

References 30 publications

The last British Ice Sheet: A review of the evidence utilised in the compilation of the Glacial Map of Britain

The last British Ice Sheet: A review of the evidence utilised in the compilation of the Glacial Map of Britain

Rapid marine deglaciation: asynchronous retreat dynamics between the Irish Sea Ice Stream and terrestrial outlet glaciers

Glacial meltwater erosion of the Mid-Cheshire Ridge: implications for ice dynamics during the Late Devensian glaciation of northwest England

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