Subglacial water‐escape structures and till structures, sléttjökull, Iceland

Meer, J.J.M. van der; Kjær, Kurt H.; Krüger, Johannes

doi:10.1002/(sici)1099-1417(199905)14:3<191::aid-jqs436>3.0.co;2-#

Cited by 92 publications

(34 citation statements)

References 22 publications

(15 reference statements)

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“…Stone lags and the concentration of clasts in the looser, upper part of unit F may reflect material that escaped subglacial frictional deposition, and was melted out beneath a retreating ice-sheet or through mass wasting (cf. Krü ger and Humlum, 1981; Van der Meer et al, 1999). The unit F glacial diamicton was unrecognised by Manley et al (2001).…”

Section: Age Control For Units A-esupporting

confidence: 63%

Glaciotectonised Quaternary sediments at Cape Shpindler, Yugorski Peninsula, Arctic Russia: implications for glacial history, ice movements and Kara Sea Ice Sheet configuration

Lokrantz

Inǵólfsson

Forman

2003

J Quaternary Science

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The coastal cliffs of Cape Shpindler, Yugorski Peninsula, Arctic Russia, occupy a key position for recording overriding ice sheets during past glaciations in the Kara Sea area, either from the Kara Sea shelf or the uplands of Yugorski Peninsula/Polar Urals. This study on Late Quaternary glacial stratigraphy and glaciotectonic structures of the Cape Shpindler coastal cliffs records two glacier advances and two ice-free periods older than the Holocene. During interglacial conditions, a sequence of marine to fluvial sediments was deposited. This was followed by a glacial event when ice moved southwards from an ice-divide over Novaya Zemlya and overrode and disturbed the interglacial sediments. After a second period of fluvial deposition, under interstadial or interglacial conditions, the area was again subject to glacial overriding, with the ice moving northwards from an inland ice divide. The age-control suggests that the older glacial event could possibly belong to marine oxygen isotope stage (MOIS) 8, Drenthe (300-250 ka), and that the underlying interglacial sediments might be Holsteinian (>300 ka). One implication of this is that relict glacier ice, buried in sediments and incorporated into the permafrost, may survive several interglacial and interstadial events. The younger glacial event recognised in the Cape Shpindler sequence is interpreted to be of Early-to-Middle Weichselian age. It is suggested to correlate to a regional glaciation around 90 or 60 ka. The Cape Shpindler record suggests more complex glacial dynamics during that glaciation than can be explained by a concentric ice sheet located in the Kara Sea, as suggested by recent geological and model studies.

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Section: Age Control For Units A-esupporting

confidence: 63%

Glaciotectonised Quaternary sediments at Cape Shpindler, Yugorski Peninsula, Arctic Russia: implications for glacial history, ice movements and Kara Sea Ice Sheet configuration

Lokrantz

Inǵólfsson

Forman

2003

J Quaternary Science

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“…At the first site, site A (4m, Figure 4), the stratified silts and sands of Lithofacies B are cut by a 1.8m long steeply-inclined (35-52° south), upwards tapering fracture (AF1) filled by weakly laminated to massive reddish brown (2.5Y 4/2) sand and dark greyish brown (2.5Y 4/2) sandy silt (Figure 7a). The stratification within this fill occurs parallel to sub-parallel to the margins of the fracture, consistent with either the pulsed injection of sediment-laden fluid upwards through the fracture, or repeated reactivation of this hydrofracture system (van der Meer et al, 1999Meer et al, , 2009Phillips & Merritt, 2008;Phillips et al, 2012). The margins of the hydrofracture vary from sharp to diffuse; the latter potentially resulting from the infiltration of water and sediment into the adjacent walls of the fracture.…”

Section: Hydrofractures and Small-scale Sediment-lined Normal Faultsmentioning

confidence: 93%

“…[ACCEPTED MANUSCRIPT] flow associated with fluctuating porewater availability (Phillips and Merritt 2008;Phillips et al, 2013b). Hydrofractures provide clear evidence for the passage of over-pressurised meltwater through glacial environments and are thought to be mainly developed in ice-marginal, sub-marginal to subglacial settings where the overburden pressure exerted by the ice leads to the required periodic over-pressurisation of the hydrogeological system (van der Meer et al, 1999Meer et al, 2009Roberts et al, 2009;Phillips et al, 2013b;Phillips & Hughes, 2014). This suggests that Lithofacies C was probably developed in an ice-marginal to proglacial setting with the periodic build-up of the hydrostatic pressures possibly reflecting a seasonal (spring-summer) increase in meltwater production.…”

Section: 1mentioning

confidence: 99%

“…Subsequent fault reactivation as hydrofracture systems provide clear evidence for variable and fluctuating groundwater conditions and periodic over-pressurisation of the local hydrological system leading to the rapid expulsion of water from the substrate (Phillips & Merritt 2008;Phillips et al, 2013b). Hydrofracture systems have been widely recognised within subglacial to ice-marginal and proglacial settings (van der Meer et al, 1999(van der Meer et al, , 2009Roberts et al, 2009) and are important regulators of the hydrogeological system in glacial areas (Boulton et al, 1993). The behaviour of glacial hydrogeological systems is known to vary 17 Lee, J.R., Wakefield, O.J.W., .…”

Section: 4mentioning

confidence: 99%

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Sedimentary and structural evolution of a relict subglacial to subaerial drainage system and its hydrogeological implications: an example from Anglesey, north Wales, UK

Lee

Wakefield

Phillips

et al. 2015

Quaternary Science Reviews

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Subglacial drainage systems exert a major control on basal-sliding rates and glacier dynamics. However, comparatively few studies have examined the sedimentary record of subglacial drainage. This is due to the paucity of modern analogues, the limited recognition and preservation of upper flow regime deposits within the geological record, and the difficulty of distinguishing subglacial meltwater deposits from other meltwater sediments (e.g. glacier outburst flood deposits). Within this study, the sedimentological and structural evolution of a subglacial to subaerial (ice-marginal / proglacial) drainage system is examined. Particular emphasis is placed upon the genetic development and preservation of upper flow regime bedforms and specifically recognising them within a subglacial meltwater context. Facies attributed to subglacial meltwater activity record sedimentation within a confined, but progressively enlargening, subglacial channel system produced under dune to upper flow regime conditions. Bedforms include rare large-scale sinusoidal bedding with syn-depositional deformation produced by current-induced traction and shearing within the channel margins. Subglacial sedimentation culminated with the abrupt change to a more ephemeral drainage regime indicating channel-abandonment or a seasonal drainage regime. Retreat of the ice margin, led to the establishment of subaerial drainage with phases of sheet-flow punctuated by channel incision and anastomosing channel development under diurnal, ablation-related, seasonal discharge. The presence of extensive hydrofracture networks demonstrate that proglacial groundwater-levels fluctuated markedly and this may have influenced later overriding of the site by an ice stream.

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“…The role played by water during deformation is also increasingly being recognised (Boulton et al, 1974;Boulton, G.S. and Caban, P. 1995;Hiemstra and van der Meer, 1997;Rijsdijk et al, 1999;van der Meer et al, 1999;Phillips and Auton, 2000;Boulton et al, 2001;Khatwa and Tulaczyk, 2001;Phillips, 2006;Baroni and Fasano, 2006). This paper synthesises the results of field observations, sedimentological analyses and micromorphological studies from five sites from across Scotland.…”

Section: Introductionmentioning

confidence: 99%

Microstructures in subglacial and proglacial sediments: understanding faults, folds and fabrics, and the influence of water on the style of deformation

Phillips

Merritt

Auton

et al. 2007

Quaternary Science Reviews

104

120

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Macroscopic field and micromorphological studies have been carried out on subglacially and proglacially deformed glacigenic sequences at a number of sites throughout Scotland, UK. Examination of microstructures (folds, faults, hydrofractures, plasmic fabrics) aided understanding of the deformation histories preserved in the sediments, but a similar range of structures were developed in both subglacial and proglacial settings. Discrimination between subglacial and proglacial deformation was only possible when micromorphological data was used in conjunction with larger-scale field observations. Variations in lithology and water content were controlling factors influencing the style and apparent intensity of deformation recorded. Changes in pore-water content and pressure during deformation can lead to liquefaction and hydrofracturing, with early formed structures locally controlling the pattern of water-escape. Liquefaction can also lead to homogenisation of the sediments and the destruction of earlier deformation structures, even at relatively low strains. Beds or zones of liquefied sand and silt may form highly 'lubricated' detachments within the sediment pile, resulting in a marked reduction in the amount of shear transmitted to underlying units. A multidisciplinary approach, involving sedimentological, geomorphological, stratigraphical and structural field observations, combined with micromorphological analysis, is recommended to confidently unravel the glacitectonic history and depositional environment of most deformed glacigenic sedimentary sequences.

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Subglacial water‐escape structures and till structures, sléttjökull, Iceland

Cited by 92 publications

References 22 publications

Glaciotectonised Quaternary sediments at Cape Shpindler, Yugorski Peninsula, Arctic Russia: implications for glacial history, ice movements and Kara Sea Ice Sheet configuration

Glaciotectonised Quaternary sediments at Cape Shpindler, Yugorski Peninsula, Arctic Russia: implications for glacial history, ice movements and Kara Sea Ice Sheet configuration

Sedimentary and structural evolution of a relict subglacial to subaerial drainage system and its hydrogeological implications: an example from Anglesey, north Wales, UK

Microstructures in subglacial and proglacial sediments: understanding faults, folds and fabrics, and the influence of water on the style of deformation

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