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Drumlin sedimentology in a hard-bed, lowland setting, Connemara, western Ireland : implications for subglacial bedform generation in areas of sparse till cover.

Evans, D.J.A. and Roberts, D.H. and O'Cofaigh, C. (2015) 'Drumlin sedimentology in a hard-bed, lowland setting, Connemara, western Ireland : implications for subglacial bedform generation in areas of sparse till cover.', Journal of quaternary science., 30 (6). pp. 537-557.

Abstract

Cores of coastal drumlins in Connemara contain stratified diamictons that interdigitate with gravelly clinoforms and finer grained rhythmites. The diamictons are interpreted as subaqueous mud apron deposits delivered by subglacial till advection to continuously failing subaqueous ice-contact fans, whose strata were being syn-depositionally over-steepened by glacitectonic deformation. The localized nature of the stratified sediments reflects the emergence of subglacial deforming tills and meltwater deposits in a glacilacustrine environment to produce interdigitated mass flow diamictons and grounding line fans/wedges. These depo-centres became glacitectonized and subglacially streamlined during glacier overriding and hence regional drumlin sedimentology reflects the varying degrees of inheritance of pre-existing glacigenic deposits and suggests that drumlin production relates more to the position of localized sediment accumulations at the glacier bed than full-depth till deformation processes (e.g. instability mechanisms) within the same drumlin field. Till cored drumlins give way down ice to stratified cored drumlins with till caps and then to stratified drumlins. This zonation is compatible with the increased lateral variability in drumlin composition that would arise from the occurrence of linear assemblages of glacifluvial (esker) and subaqueous (grounding line) sediments in an otherwise marginal-thickening till sheet.

Item Type:Article
Keywords:Drumlins, Glacitectonics, Sedimentology, Subaqueous fans, Subglacial.
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1002/jqs.2801
Publisher statement:This is the accepted version of the following article: Evans, D.J.A., Roberts, D.H. and O'Cofaigh, C. (2015), Drumlin sedimentology in a hard-bed, lowland setting, Connemara, western Ireland: implications for subglacial bedform generation in areas of sparse till cover. Journal of Quaternary Science, 30(6): 537–557, which has been published in final form at http://dx.doi.org/10.1002/jqs.2801. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.
Date accepted:13 July 2015
Date deposited:01 September 2015
Date of first online publication:13 August 2015
Date first made open access:13 August 2016

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