Till formation under a soft-bedded palaeo-ice stream of the Scandinavian Ice Sheet, constrained using qualitative and quantitative microstructural analyses

Narloch, Włodzimierz; Piotrowski, Jan A.; Wysota, Wojciech; Tylmann, Karol

doi:10.1016/j.sedgeo.2015.06.011

Cited by 11 publications

(7 citation statements)

References 92 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A similarly complex distribution of processes can be envisaged at any time slice in different places at the ice/bed interface. This diversity of subglacial processes suggested by the pattern of groundwater flow yielded by our simulations is consistent with the time‐transgressive and space‐transgressive models of basal conditions envisaged by Narloch et al (), Piotrowski et al (), and Tylman et al () and is supported by the genetic and structural complexity of subglacial deposits such as traction tills (Evans, ; Evans et al, ).…”

Section: Discussionsupporting

confidence: 91%

Groundwater Flow Under a Paleo‐Ice Stream of the Scandinavian Ice Sheet and Its Implications for the Formation of Stargard Drumlin Field, NW Poland

Hermanowski

Piotrowski

2019

JGR Earth Surface

Self Cite

View full text Add to dashboard Cite

Subglacial groundwater flow was an integral part of glaciological systems of past ice sheets, but its impact on the origin of active-ice landforms remains unexplored. Using numerical experiments, we attempt to constrain groundwater flow dynamics under a major paleo-ice stream of the southern Scandinavian Ice Sheet and its impact on the formation of the Stargard drumlin field. Flow models show a total reorganization of groundwater dynamics under the advancing ice stream to a depth of up to~200 m. A mosaic of intervening groundwater recharge and discharge areas originates, whereby the same areas may experience multiple shifts in flow directions. A prominent time-and space-transgressive pressure pump recharges groundwater in a subglacial zone up to about 20 km within the ice margin and discharges it in front of the ice sheet. The simulated groundwater flow pattern suggests that drumlins occupying a portion of the ice stream area occur preferentially where groundwater upwells and discharges at the ice/bed interface. Consistent with the geological composition, a possible drumlin-forming mechanism involves an excess of pressurized water under the ice reducing the strength of the subglacial deposits and facilitating glacial erosion, erosion by turbulent meltwater flows or both, streamlining antecedent deposits into drumlin shapes. This study emphasizes the importance of causal feedback between subglacial groundwater flow and the ice sheet dynamics and suggests an impact of the former on the formation of streamlined subglacial landforms in general.

show abstract

Section: Discussionsupporting

confidence: 91%

Groundwater Flow Under a Paleo‐Ice Stream of the Scandinavian Ice Sheet and Its Implications for the Formation of Stargard Drumlin Field, NW Poland

Hermanowski

Piotrowski

2019

JGR Earth Surface

Self Cite

View full text Add to dashboard Cite

show abstract

“…Shear zones are defined as continuous thin layers of reduced or very low clay content and limited contacts between sand grains; in thin sections these zones appear as thin domains with sharp bottom and top boundaries. All these microstructures provide information of syn‐ and post‐depositional processes and help to decipher the subglacial conditions during till deposition and deformation, in particular the palaeo‐strain level (Menzies et al, 2010, 2016; Narloch et al, 2012, 2015).…”

Section: Methodsmentioning

confidence: 99%

Till kinematics in the Stargard drumlin field, NW Poland constrained by microstructural proxies

Hermanowski

Piotrowski

Duda

2020

J Quaternary Science

Self Cite

View full text Add to dashboard Cite

Deciphering the relationships between streamlined subglacial landforms and deposits therein helps to constrain the dynamics of past ice sheets. Here we present microstructural analyses of till from the largest drumlin field in the North European Lowland generated by a major palaeo-ice stream of the Scandinavian Ice Sheet. Data derived from thin sections and X-ray microtomography (μCT) reveal multiple microstructures including microshears, circular structures, grain stacks and crushed grains. Long axes of micro-clasts measured in thin sections are directionally clustered and have low, down-ice-oriented dip angles. Some samples reveal subordinate clustering oriented at high angles to the main direction. The μCT data show low clustering strengths of clasts and no systematic fabric pattern in the entire set of samples. There is no correspondence between the clast orientations and the directions of drumlin long axes, suggesting that the till is antecedent in relation to the drumlin-shaping process. The observations indicate spatially and temporally variable, shallow-seated brittle and ductile deformation controlled by porewater pressure fluctuations and generated time-transgressively parallel to till accretion. Consistently with previous studies, the data suggest that the Stargard drumlins are erosional remnants of a pre-existing terrain shaped by material removal from the inter-drumlin areas.

show abstract

“…Experimental laboratory work has demonstrated that uneven strain distribution results in the formation of discrete shear planes that focus sediment advection whereas grains between the shear planes either remain largely stable or undergo rotational movement (cf. Damsgaard et al, 2013) leading to sediment 'skeleton' evolution (e.g., Larsen et al, 2006Larsen et al, , 2007Narloch et al, 2012Narloch et al, , 2015Menzies et al, 2013). The latter may generate grain bridges that support stresses up to several times (Iverson et al, 1996) or even an order of magnitude (Mandl et al, 1977) greater than the general stress in the surrounding material.…”

Section: Discussionmentioning

confidence: 99%

Can glacial shearing of sediment reset the signal used for luminescence dating?

et al. 2018

Self Cite

View full text Add to dashboard Cite

Understanding the geomorphology left by waxing and waning of former glaciers and ice sheets during the late Quaternary has been the focus of much research. This has been hampered by the difficulty in dating such features. Luminescence has the potential to be applied to glacial sediments but requires signal resetting prior to burial in order to provide accurate ages. This paper explores the possibility that, rather than relying on light to reset the luminescence signal, glacial processes underneath ice might cause resetting. Experiments were conducted on a ring-shear machine set up to replicate subglacial conditions and simulate the shearing that can occur within subglacial sediments. Luminescence measurement at the single grain level indicates that a number (albeit small) of zero-dosed grains were produced and that these increased in abundance with distance travelled within the shearing zone. Observed changes in grain shape characteristics with increasing shear distance indicates the presence of localised high pressure grain-to-grain stresses caused by *Revised manuscript with no changes marked Click here to view linked References grain bridges. This appears to explain why some grains became zeroed whilst others retained their palaeodose. Based on the observed experimental trend, it is thought that localised grain stress is a viable luminescence resetting mechanism. As such relatively short shearing distances might be sufficient to reset a small proportion of the luminescence signal within subglacial sediments. Dating of previously avoided subglacial sediments may therefore be possible.

show abstract

Till formation under a soft-bedded palaeo-ice stream of the Scandinavian Ice Sheet, constrained using qualitative and quantitative microstructural analyses

Cited by 11 publications

References 92 publications

Groundwater Flow Under a Paleo‐Ice Stream of the Scandinavian Ice Sheet and Its Implications for the Formation of Stargard Drumlin Field, NW Poland

Groundwater Flow Under a Paleo‐Ice Stream of the Scandinavian Ice Sheet and Its Implications for the Formation of Stargard Drumlin Field, NW Poland

Till kinematics in the Stargard drumlin field, NW Poland constrained by microstructural proxies

Can glacial shearing of sediment reset the signal used for luminescence dating?

Contact Info

Product

Resources

About