scholarly journals Weichselian sedimentary record and ice-flow patterns in the Sodankylä area, central Finnish Lapland

2020 ◽  
Vol 92 (2) ◽  
pp. 77-98
Author(s):  
Annika Katarina Åberg ◽  
◽  
Seija Kultti ◽  
Anu Kaakinen ◽  
Kari O. Eskola ◽  
...  
Keyword(s):  
Flow Direction ◽  
Flow Patterns ◽  
Ice Flow ◽  
Fluvial Deposits ◽  
Finnish Lapland ◽  
Aeolian Deposits ◽  
Scandinavian Ice Sheet ◽  
Lidar Dem ◽  
Flow Directions ◽  
Late Weichselian

Three different till units separated by interstadial fluvial deposits were observed in the Sodankylä area in the River Kitinen valley, northern Finland. The interbedded glaciofluvial sediments and palaeosol were dated by OSL to the Early (79±12 to 67±13 ka) and Middle (41±9 ka) Weichselian. A LiDAR DEM, glacial lineations, the flow direction of till fabrics, esker chains and striations were applied to investigate the glacial flow patterns of the Sodankylä, Kittilä and Salla areas. The analysis revealed that the youngest movement of the Scandinavian Ice Sheet is not visible as DEM lineations within the studied areas. The modern morphology in Kittilä and Salla shows streamlined landforms of various dimensions mainly oriented from the NW and NNW, respectively, corresponding to the Early/Middle Weichselian ice-flow directions inferred from till fabrics. The Late Weichselian ice flow has produced an insignificant imprint on the landforms. This study suggests a northern location for the ice-divide zone during the Early/Middle Weichselian, and a more western–southwestern position during the Late Weichselian. The OSL ages of 14±3.3 ka from the aeolian deposits may indicate ice-free areas during the Bølling–Allerod warm period in the vicinity of the River Kitinen.

scholarly journals Morphology, Stratigraphy, and Genesis of Small Drumlins in Front of the Glacier Mýrdalsjökull, South Iceland

1984 ◽  
Vol 30 (104) ◽  
pp. 94-105 ◽  
Author(s):  
Johannes Krüger ◽  
Henrik Højmark Thomsen
Keyword(s):  
Internal Structure ◽  
Flow Direction ◽  
Characteristic Pattern ◽  
Essential Factor ◽  
Ice Flow ◽  
Axis Orientation ◽  
Fluvial Deposits ◽  
The Core ◽  
Melt Water ◽  
Till Fabric

AbstractInvestigations have been made of the geomorphology, internal structure, and till fabric of small drumlins in a drumlin field exposed in front of the retreating northern part of Mýrdalsjökull, Iceland. The drumlins either comprise irregular drumlin complexes or they show clearly the shape of typical drumlins with their highest points at the up-glacier ends of streamlined hills.The core of each drumlin consists either of undisturbed glacio-fluvial deposits or glacio-dynamically deformed drift. The distribution of the first type often has a characteristic en échelon arrangement, similar to the interstream areas in the upper reaches of outwash fans. The second type forms a pattern with a predominant trend conforming to the glacier margin; this type is superimposed on overridden ice-margin push-moraine ridges. It is shown that the material in the drumlin cores is only slightly eroded by the glacier that formed the drumlins. The core is mantled by subglacial lodgement till about 0.1–1.5 m in thickness.Seventeen fabric analyses of 25 clasts each were performed on material from within the till mantle. These analyses show a preferred long-axis orientation but indicate a considerable between-site variability ranging up to 45° even between samples taken a few metres apart. The preferred clast orientation for samples taken along the drumlin crests only deviates 0–10° from the regional ice-flow direction indicated by fluted moraines, whereas the deviation for samples from the flanks and the stoss-sides is up to 35°. However, the fabrics show a characteristic pattern relative to the shape of the drumlin; on their tops, the clast fabric parallels the ice-flow direction, whereas it tends to follow the contour direction on the flanks and stoss-sides.It is concluded that the cores of the drumlins consist of pre-existing deposits, whereas the mantles are composed of subglacial till. Regarding the processes involved, the material contained in the core is mainly eroded by pro-glacial melt-water streams and not by ice. During the subsequent flow of ice across the area, the most prominent terrain elements have acted as subglacial obstacles, leading to localized till deposition and drumlin formation. Thus, the drumlins were formed mainly by subglacial deposition of till but the obstacles acted as an essential factor favouring their initiation.

scholarly journals Towards a GIS assessment of numerical ice-sheet model performance using geomorphological data

2007 ◽  
Vol 53 (180) ◽  
pp. 71-83 ◽  
Author(s):  
Jacob Napieralski ◽  
Alun Hubbard ◽  
Yingkui Li ◽  
Jon Harbor ◽  
Arjen P. Stroeven ◽  
...  
Keyword(s):  
Flow Direction ◽  
Ice Sheet ◽  
Model Performance ◽  
Initial Step ◽  
Ice Flow ◽  
Flow Models ◽  
Flow Directions ◽  
The Last Glacial Maximum ◽  
Basal Flow ◽  
The Last Glacial

AbstractA major difficulty in assimilating geomorphological information with ice-sheet models is the lack of a consistent methodology to systematically compare model output and field data. As an initial step in establishing a quantitative comparison methodology, automated proximity and conformity analysis (APCA) and automated flow direction analysis (AFDA) have been developed to assess the level of correspondence between modelled ice extent and ice-marginal features such as end moraines, as well as between modelled basal flow directions and palaeo-flow direction indicators, such as glacial lineations. To illustrate the potential of such an approach, an ensemble suite of 40 numerical simulations of the Fennoscandian ice sheet were compared to end moraines of the Last Glacial Maximum and the Younger Dryas and to glacial lineations in northern Sweden using APCA and AFDA. Model experiments evaluated in this manner were ranked according to level of correspondence. Such an approach holds considerable promise for optimizing the parameter space and coherence of ice-flow models by automated, quantitative assessment of multiple ensemble experiments against a database of geological or glaciological evidence.

Lift-off moraines: markers of last ice-flow directions on the Scotian Shelf

2000 ◽  
Vol 37 (12) ◽  
pp. 1723-1734 ◽  
Author(s):  
Michael R Gipp
Keyword(s):  
High Resolution ◽  
Continental Margin ◽  
Flow Direction ◽  
Seismic Profiles ◽  
Scotian Shelf ◽  
Ice Flow ◽  
Reflection Seismic ◽  
Flow Directions ◽  
Lift Off ◽  
Seismic Lines

Lift-off moraines are acoustically incoherent, subparallel ridges observed on sidescan sonograms and high-resolution reflection seismic profiles on the southeastern continental margin of Canada. They are up to 3 m high, 20–80 m wide, and are commonly overlain by stratified proglacial sediments. Although little is known about them, detailed study of high-resolution seismic profiles from the Emerald Basin and the LaHave Basin, on the Scotian Shelf, show that their height:width ratio varies with the sounder–seabed separation, suggesting that the ridges may be narrower than they appear. Their morphology is similar to DeGeer moraines or cross-valley moraines, which form perpendicular to ice-flow direction. As their orientations can be estimated at the intersection of seismic lines, they can be used to estimate ice-flow directions. Since proglacial sediments are draped directly over top of them, they are assumed to record the direction of last ice flow. This directional data suggests that ice retreated not only northward (to Nova Scotia), but also toward local topographic highs on the continental shelf, which acted as anchoring points for ice rises around both the Emerald and LaHave Basins. This pattern of ice-flow directions suggests that ice flowed from the high ground of banks, converging into basin deeps, suggesting that small moraines within the basins are probably of interlobate origin.

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

A note on the glacial geology and postglacial emergence of the Lake Harbour region, Baffin Island, N.W.T.

1985 ◽  
Vol 22 (12) ◽  
pp. 1864-1871 ◽  
Author(s):  
Peter Clark
Keyword(s):  
Large Scale ◽  
Flow Direction ◽  
Baffin Island ◽  
Ice Streams ◽  
Ice Flow ◽  
The North ◽  
West Antarctic ◽  
Ice Stream ◽  
Flow Directions ◽  
Late Wisconsinan

Ice-flow indicators in the Lake Harbour region of northern Hudson Strait define two flow directions affecting this area during the late Wisconsinan glaciation. A pronounced southward flow direction indicated by medium- and large-scale erosional and depositional features represents ice flow from an ice dome centered to the north, perhaps Foxe Basin and (or) Amadjuak Lake. Carbonate-rich till and striations represent eastward–southeastward ice flow down the axis of Hudson Strait. Convergence of ice-sheet flow with a rapidly moving ice stream has been observed and modelled for West Antarctic ice streams and involves sharp bending of flow lines at the point of convergence. A similar scenario is proposed for the Lake Harbour region to explain the two contrasting ice-flow patterns. Impingement of an ice stream in Hudson Strait onto the southern coast of Baffin Island suggests the influence of northerly flowing ice, perhaps from the Ungava plateau.Radiocarbon dates on marine shells and archeological samples are used to reconstruct the postglacial emergence of the Lake Harbour region. The marine limit (90 m aht) and deglaciation are dated by extrapolation at ca. 8300 years BP. Postglacial emergence is characterized by an initial uplift rate of 4.4 m/100 years, which decreased to 0.2 m/100 years over the last 3900 years. The initial rate (4.4 m/100 years) is nearly 50% lower than rates calculated elsewhere in the Hudson Strait region and is interpreted to reflect the influence of an ice load centered over Amadjuak Lake directly north of the Lake Harbour region.

scholarly journals The last Scandinavian Ice Sheet in northwestern Russia: ice flow patterns and decay dynamics

Boreas ◽  
2006 ◽  
Vol 35 (3) ◽  
pp. 425-443 ◽  
Author(s):  
Igor Demidov ◽  
Michael Houmark-Nielsen ◽  
Kurt Kjær ◽  
Eiliv Larsen
Keyword(s):  
Ice Sheet ◽  
Flow Patterns ◽  
Ice Flow ◽  
Scandinavian Ice Sheet ◽  
Northwestern Russia

Unexpected ice flow directions during the Late Weichselian deglaciation of the south Baltic area indicated by a new lithostratigraphy in NW Poland and NE Germany

1995 ◽  
Vol 28 ◽  
pp. 127-144 ◽  
Author(s):  
Erik Lagerlund ◽  
Kärstin Malmberg Persson ◽  
Dariusz Krzyszkowski ◽  
Per Johansson ◽  
Elzbieta Dobracka ◽  
...  
Keyword(s):  
The South ◽  
Ice Flow ◽  
Ne Germany ◽  
Flow Directions ◽  
Late Weichselian ◽  
Baltic Area ◽  
Nw Poland

scholarly journals Ice-sheet scale distribution and morphometry of triangular-shaped hummocks (murtoos): a subglacial landform produced during rapid retreat of the Scandinavian Ice Sheet

2019 ◽  
Vol 60 (80) ◽  
pp. 115-126 ◽  
Author(s):  
Antti E. K. Ojala ◽  
Gustaf Peterson ◽  
Joni Mäkinen ◽  
Mark D. Johnson ◽  
Kari Kajuutti ◽  
...  
Keyword(s):  
Hydraulic System ◽  
Flow Direction ◽  
Ice Sheet ◽  
Younger Dryas ◽  
Light Detection And Ranging ◽  
Ice Flow ◽  
Digital Elevation ◽  
Scandinavian Ice Sheet ◽  
Glacial Landform ◽  
Oriented Parallel

AbstractHigh-resolution digital elevation models of Finland and Sweden based on LiDAR (Light Detection and Ranging) reveal subglacial landforms in great detail. We describe the ice-sheet scale distribution and morphometric characteristics of a glacial landform that is distinctive in morphology and occurs commonly in the central parts of the former Scandinavian Ice Sheet, especially up-ice of the Younger Dryas end moraine zone. We refer to these triangular or V-shaped landforms as murtoos (singular, ‘murtoo’). Murtoos are typically 30–200 m in length and 30–200 m in width with a relief of commonly <5 m. Murtoos have straight and steep edges, a triangular tip oriented parallel to ice-flow direction, and an asymmetric longitudinal profile with a shorter, but steeper down-ice slope. The spatial distribution of murtoos and their geomorphic relation to other landforms indicate that they formed subglacially during times of climate warming and rapid retreat of the Scandinavian Ice Sheet when large amounts of meltwater were delivered to the bed. Murtoos are formed under warm-based ice and may be associated with a non-channelized subglacial hydraulic system that evacuated large discharges of subglacial water.

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