Subglacial channels of Northern Germany a brief review

Stackebrandt, Werner

doi:10.1127/1860-1804/2009/0160-0203

Cited by 35 publications

(23 citation statements)

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“…The spacing metrics are within the range of previously reported values for tunnel valleys (Praeg, 2003;Jørgensen and Sandersen, 2006;Stackebrandt, 2009;Moreau et al, 2012;Kehew et al, 2013) but smaller than the average spacing of eskers (Storrar et al, 2014a, and references therein). Theory suggests that the spacing of subglacial conduits is controlled by substrate properties, basal melt rate and the hydraulic potential gradient (e.g.…”

Section: Southern Sector Of the Former Laurentide Ice Sheetsupporting

confidence: 70%

Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation

Livingstone

Clark

2016

Earth Surf. Dynam.

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Abstract. Tunnel valleys have been widely reported on the bed of former ice sheets and are considered an important expression of subglacial meltwater drainage. Although known to have been cut by erosive meltwater flow, the water source and development of channels has been widely debated; ranging between outburst flood events through to gradually occurring channel propagation. We have mapped and analysed the spatial pattern and morphometry of tunnel valleys and associated glacial landforms along the southern sector of the former Laurentide Ice Sheet from high-resolution digital elevation models. Around 2000 tunnel valleys have been mapped, revealing an organised pattern of sub-parallel, semi-regularly spaced valleys that form in distinctive clusters. The tunnel valleys are typically < 20 km long, and 0.5-3 km wide, although their width varies considerably down-valley. They preferentially terminate at moraines, which suggests that formation is time dependent; while we also observe some tunnel valleys that have grown headwards out of hill-hole pairs. Analysis of cross-cutting relationships between tunnel valleys, moraines and outwash fans permits reconstruction of channel development in relation to the retreating ice margin. This palaeo-drainage reconstruction demonstrates incremental growth of most valleys, with some used repeatedly or for long periods, during deglaciation, while others were abandoned shortly after their formation. Our data and interpretation support gradual (rather than a single-event) formation of most tunnel valleys with secondary contributions from flood drainage of subglacial and or supraglacially stored water down individual tunnel valleys. The distribution and morphology of tunnel valleys is shown to be sensitive to regional factors such as basal thermal regime, ice and bed topography, timing and climate.

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Section: Southern Sector Of the Former Laurentide Ice Sheetsupporting

confidence: 70%

Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation

Livingstone

Clark

2016

Earth Surf. Dynam.

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“…On the basis of his work in the British sector of the southern North Sea, Praeg () demonstrated that the depth of tunnel valleys in this area is influenced by the thickness of the Pleistocene substratum. Similar behaviour is apparent in northern Germany, where the tunnel valleys reach their greatest depth within the limits of the Central European Subsidence Zone, which has been a depocentre for thick unconsolidated and unlithified sediments (Stackebrandt ).…”

Section: Tunnel Valleys and The Substratum – Previous Observationssupporting

confidence: 52%

Effects of the substratum on the formation of glacial tunnel valleys: an example from the Middle Pleistocene of the southern North Sea Basin

Janszen

Spaak

Moscariello

2012

Boreas

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2012 (October): Effects of the substratum on the formation of glacial tunnel valleys: an example from the Middle Tunnel valleys are elongated incisions formed by meltwater underneath ice sheets that rest on unlithified bed materials. The formation of tunnel valleys is commonly believed to be influenced by the properties of the preglacial bed; however, a detailed analysis of this relationship has not been performed to date. To determine whether tunnel-valley location and morphology are controlled by the substratum, a 3D seismic survey was combined with lithological data from the Wadden Sea area in the Dutch sector of the southern North Sea Basin. This study shows that tunnel-valley floors often coincide with seismic reflectors that mark lithological boundaries in the substratum, and that the location and depth of tunnel-valley incision vary as a function of the properties of the substratum as expressed by lithological and geophysical-log variations. Tunnel valleys are incised preferentially into fine-grained layers, while the top of coarser-grained units commonly coincide with the tunnel-valley floor. These observations indicate that the geometry and orientation of tunnel valleys in the study area are controlled by contrasts in lithological properties of the bed. An explanation for the observed lithological control might lie in large water-pressure differences over fine-grained and impermeable layers along the flow-path of subglacial meltwater flowing through the substratum, from areas with high pore-water pressure towards areas with relatively low pressures in the vicinity of meltwater channels. These pressure differences might have been sufficient for the fracturing and fluidization of these layers. The concepts presented here have implications for existing genetic models and for the prediction of tunnel-valley morphology in understudied areas.

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“…Older Pleistocene deposits, especially of pre‐Saalian age, are mainly preserved in subglacial valleys in the northern Central European lowland areas (Gabriel et al . ; Stackebrandt ; von Bülow ) or in halokinetical graben structures above salt anticlines (Müller & Obst ; Obst & Müller ). Subglacial channels or tunnel valleys were also detected in offshore seismic profiles, e.g.…”

Section: Regional Settingmentioning

confidence: 99%

Late Saalian and Weichselian glaciations in the German Baltic Sea documented by Pleistocene successions at the southeastern margin of the Arkona Basin

Obst

Nachtweide²,

Müller

2016

Boreas

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Seismic profiles and numerous sediment cores of a planned offshore wind farm area northeast of Rügen Island provide a unique insight into the distribution and thickness of glacial deposits in the southern Baltic Sea. Fine gravel analysis enabled recognition of five tills that correspond to different ice advances. On the basis of a 3D structural model, the main Pleistocene events could be reconstructed and correlated with stratigraphical records in the circum‐Baltic area comprising Marine Isotope Stages (MIS) 6 to 2. The oldest till was deposited during the Late Saalian Warthe advance (qs2; c. 150–130 ka). It is only preserved in ENE–WSW trending subglacial channels incised into Upper Cretaceous soft chalk. Isolated rafts and remnants of two Middle Weichselian tills occur locally, whereas Eemian interglacial sediments are missing. The older till (qw*) has an unusual fine gravel composition and might have formed during ice advances known only from northern Denmark and northern Poland (c. 65–60 ka). The younger till represents the Warnow advance (qw0) in NE Germany that can be correlated with the Danish Ristinge advance (c. 55–50 ka). Furthermore, two tills deposited during the Late Weichselian Last Glacial Maximum (c. 24–16 ka) occur. One can be correlated with the Pomeranian advance (qw2), while the other has characteristics typical for the Mecklenburg advance (qw3). These advances eroded older Pleistocene deposits, thus probably also removing the till of the Brandenburg/Frankfurt advance (qw1) – in contrast to the onshore areas. The Pomeranian till is limited to the southeast, close to the shallow Adlergrund, but the Mecklenburg till covers the whole study area. This first detailed lithostratigraphical classification of till units from the Arkona Basin allows for the identification and correlation of Pleistocene successions in other parts of the southern Baltic Sea.

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Subglacial channels of Northern Germany a brief review

Cited by 35 publications

References 0 publications

Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation

Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation

Effects of the substratum on the formation of glacial tunnel valleys: an example from the Middle Pleistocene of the southern North Sea Basin

Late Saalian and Weichselian glaciations in the German Baltic Sea documented by Pleistocene successions at the southeastern margin of the Arkona Basin

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