scholarly journals Genesis of the glaciotectonic thrust-fault complex at Halk Hoved, southern Denmark.

2012 ◽  
Vol 60 ◽  
pp. 61-80
Author(s):  
Tillie M. Madsen
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Ice Sheet ◽  
Thrust Fault ◽  
Complex Deformation ◽  
North East ◽  
Macro Scale ◽  
Scandinavian Ice Sheet ◽  
Late Weichselian ◽  
Southern Fringe

The coastal cliff of Halk Hoved, southern Jutland, Denmark, is a major glaciotectonic complex formed by proglacial deformation of the North-East (NE) advance from the Scandinavian Ice Sheet in Late Weichselian. We describe and interpret the pre-, syn- and post-tectonic sedimentary successions and macro-scale architecture of this complex. Initially, the Lillebælt Till Formation (unit 1) and the overlying glaciofluvial sediments (unit 2) were deposited during the Warthe glaciation in Late Saalian. During the NE advance towards the Main Stationary Line (MSL) in Late Weichselian, these sediments were pushed along a décollement surface whereby a thrust-fault complex was formed. In a cross section the complex extends for more than 900 m and consists of eighteen c. 15–20 m thick thrust sheets stacked by piggyback thrusting. Accumulated displacement amounts to at least 235 m along thrust faults dipping at 30–40° towards N-NE, resulting in at least 24% glaciotectonic shortening of the complex. Deformation was presumably facilitated by elevated pore-water pressure in the Lillebælt Till Formation. As the compressive stress exceeded the shear strength of the weakened till, failure occurred, and a décollement horizon formed along the lithological boundary between the Lillebælt Till Formation and the underlying aquifer. During deformation, piggyback basins formed wherein sediments of hyperconcentrated flow (unit 3) and glaciolacustrine diamicton (unit 4) were deposited. The whole thrust-fault complex and the intervening sediments were truncated subglacially as the NE advance finally overrode the complex. Following the retreat of the NE advance, a succession of glaciofluvial sediments (unit 5) and finally the East Jylland Till Formation (unit 6) were deposited during the advance of the Young Baltic Ice Sheet. The Halk Hoved thrust-fault complex is a prominent example of glaciotectonism at the southern fringe of the Scandinavian Ice Sheet.

scholarly journals Late Weichselian thermal state at the base of the Scandinavian Ice Sheet

2019 ◽  
Author(s):  
Dmitry Y. Demezhko ◽  
Anastasia A. Gornostaeva ◽  
Alexander N. Antipin
Keyword(s):  
Thermal State ◽  
Ice Sheet ◽  
Ground Surface ◽  
Substantial Part ◽  
Temperature Pattern ◽  
Glacial Cycle ◽  
Surface Temperatures ◽  
Scandinavian Ice Sheet ◽  
Late Weichselian ◽  
The Last Glacial

Abstract. Geothermal estimates of the ground surface temperatures for the last glacial cycle in Northern Europe has been analyzed. During the Middle and Late Weichselian (55–12 kyr BP) a substantial part of this area was covered by the Scandinavian Ice Sheet. The analysis of geothermal data has allowed reconstructing limits of the ice sheet extension and its basal thermal state in the Late Weichselian. Ground surface temperatures outside the ice sheet were extremely low (from −8 to −18 °C). Within the ice sheet, there were both thawed and frozen zones. The revealed temperature pattern is generally consistent with the modern one for the ground surface temperatures in Greenland that makes it possible to consider these ice sheets as analogues. The anomalous climatically induced surface heat flux and orbital insolation of the Earth varied consistently outside the glaciation and independently within the limits of the ice sheet.

scholarly journals Response of sediment to ice-sheet loading in northwestern Germany: effective stresses and glacier-bed stability

1997 ◽  
Vol 43 (145) ◽  
pp. 495-502 ◽  
Author(s):  
Jan A. Piotrowski ◽  
Anna M. Kraus
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Ice Sheet ◽  
Bed Deformation ◽  
Pore Water Pressures ◽  
Sediment Consolidation ◽  
Western Germany ◽  
Bed Stability ◽  
North Western

AbstractLaboratory tests on sediment over-ridden by the last ice sheet in north-western Germany reveal very low ice-induced pre-consolidation and high palaeo-pore-water pressures. Sediment consolidation at the base of the glacier was largely controlled by hydraulic properties of the substratum. Generally low permeabilities of the bed caused sustained high pore-water pressure in over-ridden sediments close to the flotation point. This implies a serious possibility of hydraulic lifting of the ice sheet. It is believed that the reduced basal coupling limited the transformation of glacier shear stress on to the bed sediments, which is indicated by a lack of sedimentological evidence for widespread pervasive bed deformation. Ice motion was probably focused at the glacier sole by some combination of sliding and ploughing. However, isolated spots with deformation occur, so that the subglacial system in the study area can be characterized as a stable/deforming mosaic.

scholarly journals Groundwater flow beneath Late Weichselian glacier ice in Nordfjord, Norway

2007 ◽  
Vol 53 (180) ◽  
pp. 84-90 ◽  
Author(s):  
Carolyn A. Moeller ◽  
D.M. Mickelson ◽  
M.P. Anderson ◽  
C. Winguth
Keyword(s):  
Groundwater Flow ◽  
Flow Model ◽  
Water Pressure ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Overburden Pressure ◽  
Glacier Ice ◽  
Late Weichselian ◽  
Southern Norway ◽  
Basal Melting

AbstractBasal water pressure and water flow patterns are significant factors in controlling the behavior of an ice sheet, because they influence ice-sheet thickness, stability and extent. Water produced by basal melting may infiltrate the subsurface, or occur as sheet or channelized flow at the ice/bed interface. We examine subglacial groundwater conditions along a flowline of the Scandinavian ice sheet through Nordfjord, in the western fjords region of southern Norway, using a steady-state, twodimensional groundwater-flow model. Meltwater input to the groundwater model is calculated by a two-dimensional, time-dependent, thermomechanically coupled ice-flow model oriented along the same flowline. Model results show that the subglacial sediments could not have transmitted all the meltwater out of the fjord during times of ice advance and when the ice sheet was at its maximum position at the edge of the continental shelf. In order for pore-water pressures to remain below the overburden pressure of the overlying ice, other paths of subglacial drainage are necessary to remove excess water. During times of retreat, the subglacial aquifer is incapable of transmitting all the meltwater that was probably generated. Pulses of meltwater reaching the bed could explain nonclimatically driven margin readvances during the overall retreat phase.

scholarly journals Thickness evolution of the Scandinavian Ice Sheet during the Late Weichselian in Nordfjord, western Norway: evidence from ice-flow modeling

Boreas ◽  
2005 ◽  
Vol 34 (2) ◽  
pp. 176-185 ◽  
Author(s):  
Cornelia Winguth ◽  
David Mickelson ◽  
Eiliv Larsen ◽  
Jessica Darter ◽  
Carolyn Moeller ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Flow Modeling ◽  
Ice Flow ◽  
Western Norway ◽  
Scandinavian Ice Sheet ◽  
Late Weichselian

scholarly journals Response of sediment to ice-sheet loading in northwestern Germany: effective stresses and glacier-bed stability

1997 ◽  
Vol 43 (145) ◽  
pp. 495-502 ◽  
Author(s):  
Jan A. Piotrowski ◽  
Anna M. Kraus
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Ice Sheet ◽  
Bed Deformation ◽  
Pore Water Pressures ◽  
Sediment Consolidation ◽  
Western Germany ◽  
Bed Stability ◽  
North Western

AbstractLaboratory tests on sediment over-ridden by the last ice sheet in north-western Germany reveal very low ice-induced pre-consolidation and high palaeo-pore-water pressures. Sediment consolidation at the base of the glacier was largely controlled by hydraulic properties of the substratum. Generally low permeabilities of the bed caused sustained high pore-water pressure in over-ridden sediments close to the flotation point. This implies a serious possibility of hydraulic lifting of the ice sheet. It is believed that the reduced basal coupling limited the transformation of glacier shear stress on to the bed sediments, which is indicated by a lack of sedimentological evidence for widespread pervasive bed deformation. Ice motion was probably focused at the glacier sole by some combination of sliding and ploughing. However, isolated spots with deformation occur, so that the subglacial system in the study area can be characterized as a stable/deforming mosaic.

scholarly journals Numerical Analysis of the Geotechnical Problems of Seepage Effects underneath Chafta Weir, North East of Amara City

2020 ◽  
Vol 55 (2) ◽  
Author(s):  
Riaed S. Jassim Alsiede
Keyword(s):  
Safety Factor ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Harvesting ◽  
Foundation Soil ◽  
North East ◽  
Common Problems ◽  
Piping Erosion ◽  
Southern Iraq ◽  
Geotechnical Problems

Seepage is a very important issue in the design and construction stages of hydraulic structures and represents one of the most common problems in dams. This study aims to estimate seepage and piping erosion in the foundation soil, especially downstream (toe), of Chafta weir, north east of Amara city, Southern Iraq. Chafta weir is part of the water harvesting project in the area. This project will play an important economic and environmental role in the future development of the eastern Maysan area and is also significant as it is the first water harvesting project in the province. A simulation model was created by SEEP/W software to calculate the amount of seepage, the distribution of pore-water pressure under the weir foundation, seepage velocity and hydraulic gradient. Then, the actual safety factor of the weir was calculated. Seepage depends mainly on the head differences between upstream and downstream weir sides. Seepage causes piping erosion and increasing the uplift pressure below weir body, so factor of safety must include all these factors. The safety factor showed that the suggested weir body is relatively stable.

scholarly journals Intercomparison of subglacial sediment-deformation models: application to the Late Weichselian western Barents margin

2000 ◽  
Vol 30 ◽  
pp. 187-196 ◽  
Author(s):  
Daniel Howell ◽  
Martin J. Siegert
Keyword(s):  
Sediment Transport ◽  
Normal Load ◽  
Water Pressure ◽  
Ice Sheet ◽  
Model Parameters ◽  
Sediment Layer ◽  
Ice Stream ◽  
Sediment Deformation ◽  
Late Weichselian ◽  
Deformation Models

AbstractNumerical experiments, where a simple ice-sheet model was coupled with sediment-deformation models, were performed to investigate the transport of glacigenic material to the western Barents Shelf during the Late Weichselian. The ice-sheet model, and its environmental inputs, has been matched previously with a series of geological datasets relating to the maximum extent of the ice sheet (Howell and others, http://www.ggg.qub.ac.uk [rp05/1999]). Additional geological data on the volumes of sediment delivered to the Bear Island fan (Barents continental margin) are available for comparison. The experiments indicate the sensitivity of sediment transport and deposition to variations in (a) the ice-stream model and (b) a variety of model parameters. Two ice-stream models were used: (1) a height-above-buoyancy model, in which basal velocity is controlled by basal driving stress and a buoyancy-induced reduction in the normal load beneath a marine-based ice sheet; and (2) a modified version of the method presented by Alley (1990) in which basal velocity is related to pore-water pressure, sediment thickness, and driving basal stress. The results of the two different models were then compared. An extensive set of sensitivity tests was carried out to determine sediment-transport response to changes in the model’s parameters. Results indicate that, using physically realistic parameters for deforming subglacial sediment, both models reproduce the volume of Late Weichselian sediment measured on the Bear Island fan. Results from both models are sensitive to (1) cohesion of the sediment and (2) the thickness of deforming sediment beneath the ice sheet. The two models exhibited different degrees of sensitivity to the sediment parameters, with the height-above-buoyancy model proving to be less sensitive to variations in the thickness of the deforming sediment layer than the model proposed by Alley (1990). The differences between the two models examined here highlight the need for a comprehensive comparison of all the methodologies for calculating basal-ice motion currently in use.

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