scholarly journals Thrust-fault architecture of glaciotectonic complexes in Denmark

1969 ◽  
pp. 17-20
Author(s):  
Stig A. Schack Pedersen ◽  
Lars Ole Boldreel
Keyword(s):  
Sea Level ◽  
Cross Sections ◽  
Thrust Fault ◽  
Basal Part ◽  
The North ◽  
The North Sea ◽  
Fault Deformation ◽  
Seismic Sections ◽  
Structural Levels ◽  
Fault Architecture

Cross sections of glaciotectonic complexes are exposed in coastal cliff s in Denmark, which allow structural studies of the architecture of thin-skinned thrust-fault deformation (Pedersen 2014). However, the basal part of the thrust-fault complex is never exposed, because it is located 50 to 100 m below sea level. It is in the basal part the most important structure – the décollement zone – of the complex is found. Th e décollement zone constitutes the more or less horizontal surface that separates undeformed bedrock from the displaced thrust-sheet units along the décollement level. One of the most famous exposures of glaciotectonic deformations in Denmark is the Møns Klint Glaciotectonic Complex. Th e structures above sea level are well documented, whereas the structures below sea level down to the décollement level are poorly known. Modelling of deep structures was carried out by Pedersen (2000) but still needs documentation. A glaciotectonic c omplex aff ecting comparable rock units, such as the chalk at Møns Klint, was recently recognised in seismic sections from Jammerbugten in the North Sea (Fig. 1). Th ese sections provide an excellent opportunity for comparable studies of the upper and lower structural levels in thin-skinned thrust-fault deformation, which is discussed in this paper with examples from three major glaciotectonic complexes.

scholarly journals Structural analysis of the Rubjerg Knude Glaciotectonic Complex, Vendsyssel, northern Denmark

2005 ◽  
Vol 8 ◽  
pp. 1-192 ◽  
Author(s):  
Stig A. Schack Pedersen
Keyword(s):  
Structural Analysis ◽  
North Sea ◽  
Hanging Wall ◽  
Ice Sheet ◽  
Proximal Part ◽  
Thrust Fault ◽  
The North ◽  
Thrust Sheets ◽  
The North Sea ◽  
Fault Deformation

Pedersen, S.A.S. 2005: Structural analysis of the Rubjerg Knude Glaciotectonic Complex, Vendsyssel, northern Denmark. Geological Survey of Denmark and Greenland Bulletin 8, 192 pp. The Rubjerg Knude Glaciotectonic Complex is a thin-skinned thrust-fault complex that was formed during the advance of the Scandinavian Ice Sheet (30 000 – 26 000 B.P.); it is well exposed in a 6 km long coastal profile bordering the North Sea in northern Denmark. The glaciotectonic thrust-fault deformation revealed by this cliff section has been subjected to detailed structural analysis based on photogrammetric measurement and construction of a balanced cross-section. Thirteen sections are differentiated, characterising the distal to proximal structural development of the complex. The deformation affected three stratigraphic units: the Middle Weichselian arctic marine Stortorn Formation, the mainly glaciolacustrine Lønstrup Klint Formation and the dominantly fluvial Rubjerg Knude Formation; these three formations are formally defined herein, together with the Skærumhede Group which includes the Stortorn and Lønstrup Klint Formations. The Rubjerg Knude Formation was deposited on a regional unconformity that caps the Lønstrup Klint Formation and separates pre-tectonic deposits below from syntectonic deposits above. In the distal part of the complex, the thrust-fault architecture is characterised by thin flatlying thrust sheets displaced over the footwall flat of the foreland for a distance of more than 500 m. Towards the proximal part of the complex, the dip of the thrust faults increases, and over long stretches they are over-steepened to an upright position. The lowest décollement zone is about 40 m below sea level in the proximal part of the system, and shows a systematic step-wise change to higher levels in a distal (southwards) direction. The structural elements are ramps and flats related to hanging-wall and footwall positions. Above upper ramp-hinges, hanging-wall anticlines developed; footwall synclines are typically related to growth-fault sedimentation in syntectonic piggyback basins, represented by the Rubjerg Knude Formation. Blocks and slump-sheets constituting parts of the Lønstrup Klint Formation were derived from the tips of up-thrusted thrust sheets and slumped into the basins. Mud diapirs are a prominent element in the thrust-fault complex, resulting from mud mobilisation mainly at hanging-wall flats and ramps. Shortening during thrust-fault deformation has been calculated as 50%. Only about 11% of the initial stratigraphic units subjected to thrust faulting has been lost due to erosion. The thrust-fault deformation was caused by gravity spreading of an advancing ice sheet. Overpressured mud-fluid played an important role in stress transmission. The average velocity of thrust-fault displacement is estimated at 2 m per year, which led to compression of a 12 km stretch of flat-lying sediments, c. 40 m in thickness, into a thrust-fault complex 6 km in length. The thrust-fault complex is truncated by a glaciotectonic unconformity, formed when the advancing ice sheet finally overrode the complex. When this ice sheet melted away, a hilland- hole pair was formed, and meltwater deposits derived from a new ice-advance (NE-Ice) filled the depression. The NE-Ice overran the complex during its advance to the main stationary line situated in the North Sea. When this ice in turn melted away (c. 19 000 – 15 000 B.P.), the glacial landscape was draped by arctic marine deposits of the Vendsyssel Formation (new formation defined herein).

scholarly journals Structural analysis of the Rubjerg Knude Glaciotectonic Complex, Vendsyssel, northern Denmark

2005 ◽  
Vol 8 ◽  
pp. 1-32 ◽  
Author(s):  
Stig A. Schack Pedersen
Keyword(s):  
Structural Analysis ◽  
North Sea ◽  
Hanging Wall ◽  
Ice Sheet ◽  
Proximal Part ◽  
Thrust Fault ◽  
The North ◽  
Thrust Sheets ◽  
The North Sea ◽  
Fault Deformation

The Rubjerg Knude Glaciotectonic Complex is a thin-skinned thrust-fault complex that was formed during the advance of the Scandinavian Ice Sheet (30 000 – 26 000 B.P.); it is well exposed in a 6 km long coastal profile bordering the North Sea in northern Denmark. The glaciotectonic thrust-fault deformation revealed by this cliff section has been subjected to detailed structural analysis based on photogrammetric measurement and construction of a balanced cross-section. Thirteen sections are differentiated, characterising the distal to proximal structural development of the complex. The deformation affected three stratigraphic units: the Middle Weichselian arctic marine Stortorn Formation, the mainly glaciolacustrine Lønstrup Klint Formation and the dominantly fluvial Rubjerg Knude Formation; these three formations are formally defined herein, together with the Skærumhede Group which includes the Stortorn and Lønstrup Klint Formations. The Rubjerg Knude Formation was deposited on a regional unconformity that caps the Lønstrup Klint Formation and separates pre-tectonic deposits below from syntectonic deposits above. In the distal part of the complex, the thrust-fault architecture is characterised by thin flatlying thrust sheets displaced over the footwall flat of the foreland for a distance of more than 500 m. Towards the proximal part of the complex, the dip of the thrust faults increases, and over long stretches they are over-steepened to an upright position. The lowest décollement zone is about 40 m below sea level in the proximal part of the system, and shows a systematic step-wise change to higher levels in a distal (southwards) direction. The structural elements are ramps and flats related to hanging-wall and footwall positions. Above upper ramp-hinges, hanging-wall anticlines developed; footwall synclines are typically related to growth-fault sedimentation in syntectonic piggyback basins, represented by the Rubjerg Knude Formation. Blocks and slump-sheets constituting parts of the Lønstrup Klint Formation were derived from the tips of up-thrusted thrust sheets and slumped into the basins. Mud diapirs are a prominent element in the thrust-fault complex, resulting from mud mobilisation mainly at hanging-wall flats and ramps. Shortening during thrust-fault deformation has been calculated as 50%. Only about 11% of the initial stratigraphic units subjected to thrust faulting has been lost due to erosion. The thrust-fault deformation was caused by gravity spreading of an advancing ice sheet. Overpressured mud-fluid played an important role in stress transmission. The average velocity of thrust-fault displacement is estimated at 2 m per year, which led to compression of a 12 km stretch of flat-lying sediments, c. 40 m in thickness, into a thrust-fault complex 6 km in length. The thrust-fault complex is truncated by a glaciotectonic unconformity, formed when the advancing ice sheet finally overrode the complex. When this ice sheet melted away, a hilland-hole pair was formed, and meltwater deposits derived from a new ice-advance (NE-Ice) filled the depression. The NE-Ice overran the complex during its advance to the main stationary line situated in the North Sea. When this ice in turn melted away (c. 19 000 – 15 000 B.P.), the glacial landscape was draped by arctic marine deposits of the Vendsyssel Formation (new formation defined herein).

What can idealized storm surge simulations tell us about worst case scenarios?

2021 ◽  
Author(s):  
Elin Andrée ◽  
Jian Su ◽  
Martin Drews ◽  
Morten Andreas Dahl Larsen ◽  
Asger Bendix Hansen ◽  
...  
Keyword(s):  
Wind Speed ◽  
Sea Level ◽  
North Sea ◽  
Wind Direction ◽  
Water Levels ◽  
Sea Levels ◽  
The North ◽  
The North Sea ◽  
Sea Coast ◽  
North Sea Coast

<p>The potential impacts of extreme sea level events are becoming more apparent to the public and policy makers alike. As the magnitude of these events are expected to increase due to climate change, and increased coastal urbanization results in ever increasing stakes in the coastal zones, the need for risk assessments is growing too.</p><p>The physical conditions that generate extreme sea levels are highly dependent on site specific conditions, such as bathymetry, tidal regime, wind fetch and the shape of the coastline. For a low-lying country like Denmark, which consists of a peninsula and islands that partition off the semi-enclosed Baltic Sea from the North Sea, a better understanding of how the local sea level responds to wind forcing is urgently called for.</p><p>We here present a map for Denmark that shows the most efficient wind directions for generating extreme sea levels, for a total of 70 locations distributed all over the country’s coastlines. The maps are produced by conducting simulations with a high resolution, 3D-ocean model, which is used for operational storm surge modelling at the Danish Meteorological Institute. We force the model with idealized wind fields that maintain a fixed wind speed and wind direction over the entire model domain. Simulations are conducted for one wind speed and one wind direction at a time, generating ensembles of a set of wind directions for a fixed wind speed, as well as a set of wind speeds for a fixed wind direction, respectively.</p><p>For each wind direction, we find that the maximum water level at a given location increases linearly with the wind speed, and the slope values show clear spatial patterns, for example distinguishing the Danish southern North Sea coast from the central or northern North Sea Coast. The slope values are highest along the southwestern North Sea coast, where the passage of North Atlantic low pressure systems over the shallow North Sea, as well as the large tidal range, result in a much larger range of variability than in the more sheltered Inner Danish Waters. However, in our simulations the large fetch of the Baltic Sea, in combination with the funneling effect of the Danish Straits, result in almost as high water levels as along the North Sea coast.</p><p>Although the wind forcing is completely synthetic with no spatial and temporal structure of a real storm, this idealized approach allows us to systematically investigate the sea level response at the boundaries of what is physically plausible. We evaluate the results from these simulations by comparison to peak water levels from a 58 year long, high resolution ocean hindcast, with promising agreement.</p>

Subsidence and sea-level rise in the Thames Estuary

1972 ◽  
Vol 272 (1221) ◽  
pp. 121-130 ◽  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Average Rate ◽  
Thames Estuary ◽  
The North ◽  
Storm Waves ◽  
Late Cretaceous Period ◽  
The North Sea ◽  
Sea Area ◽  
Cretaceous Period

The development of the area, of the Thames Estuary is briefly traced since the late Cretaceous period, with its present outline being due to a combination of factors. The overall subsidence of the North Sea area, the ‘Alpine5 fold movements, and the transgression of the sea since the retreat of the Weichselian icesheets have all contributed. The positions of the shore-line during the critical phase, 9600 b.p. to 8000 b.p., of this last transgression of the sea are shown. Subsequent to this main transgressive phase, erosion of the shoreline has been rapid due to storm-waves and tidal current action. An estimation of the average rate of subsidence and/or sea-level rise is given based on the concept of sedimentary equilibrium in which a figure of 12.7 cm (5 in) per century is arrived at.

scholarly journals Mean sea level variability in the North Sea: Processes and implications

2014 ◽  
Vol 119 (10) ◽  
pp. n/a-n/a ◽  
Author(s):  
Sönke Dangendorf ◽  
Francisco M. Calafat ◽  
Arne Arns ◽  
Thomas Wahl ◽  
Ivan D. Haigh ◽  
...  
Keyword(s):  
Sea Level ◽  
North Sea ◽  
Sea Level Variability ◽  
Mean Sea Level ◽  
The North ◽  
The North Sea ◽  
Mean Sea Level Variability

Conversaziones, 1971

1971 ◽  
Vol 26 (2) ◽  
pp. 125-133
Keyword(s):  
North Sea ◽  
Oil Fields ◽  
Scale Model ◽  
British Petroleum ◽  
The North ◽  
Company Limited ◽  
The North Sea ◽  
Seismic Sections ◽  
Petroleum Company ◽  
Gas Fields

CONVERSAZIONES were held this year on 6 May and 24 June. At the first conversazione twenty-four exhibits and a film were shown. Dr P. E. Kent, F.R.S., and Mr P. J. Walmsley of The British Petroleum Company Limited arranged an exhibit demonstrating the latest progress in the exploration for hydrocarbons in the North Sea. The established gas fields and the recently discovered oil fields were shown on maps together with sections which illustrated their structure. Seismic sections and geological interpretations were exhibited to show the type of information being obtained in the North Sea and the structural complexities which arise. A scale model of one of the semi-submersible drilling outfits used in North Sea exploration was on display together with a sample of British North Sea oil.

Storm surges in the North Sea during the winter 1953-4

1956 ◽  
Vol 235 (1201) ◽  
pp. 260-274 ◽  
Keyword(s):  
Sea Level ◽  
North Sea ◽  
Storm Surges ◽  
Rate Of Change ◽  
The North ◽  
Order Of Magnitude ◽  
The North Sea ◽  
Sea Ports ◽  
Phase Angles

Records of sea level for several North Sea ports for the winter of 1953-4 have been in vestigated. They were split into 14-day intervals, and each 14-day record was Fourieranalyzed to determine if any non-astronomical periods were present. There was evidence of some activity between 40 and 50 h period, and a determination of the phase angles at different ports showed that the activity could be due to a disturbance travelling southwards from the north of the North Sea. The disturbance was partly reflected somewhere near the line from Lowestoft to Flushing, so that one part returned past Flushing and Esbjerg towards Bergen while the other part travelled towards Dover, and there was evidence of its existence on the sea-current records taken near St Margaret's Bay. These results were confirmed by subtracting the predicted astronomical tidal levels from the observed values of sea level and cross-correlating the residuals so obtained for each port with those found at Lowestoft. The residuals at Lowestoft and Aberdeen were compared with the meteorological conditions, and it was found that, although they could be attributed to a large extent to conditions within the North Sea, there was an additional effect due to a travelling surge which was of the same order of magnitude at both Lowestoft and Aberdeen and which was closely related to the rate of change with time of the atmospheric pressure difference between Wick and Bergen.

Rendezvous on the High Plateau

2013 ◽  
Author(s):  
Lars Öhrström
Keyword(s):  
World War Ii ◽  
Sea Level ◽  
World War ◽  
Life And Death ◽  
High Plateau ◽  
The North ◽  
Starting Point ◽  
The North Sea ◽  
National Flag ◽  
The Hill

The two men in white anoraks were slowly approaching, skiing in the bitter cold over the Hardangervidda mountain plateau in the winter of 1943. Were they friends or foes? This was a matter of life and death for the six young men watching the only other living beings in sight for miles of snow-clad wilderness. Their pace was slow, the men were thin and didn’t look too well, just as if they might well have spent 130 days of the winter of 1942–43 hidden in a rudimentary hut on the mountain, surviving on moss and poached reindeer. It had to be them. The group’s leader, Joachim Rønneberg, decided to make contact. This story is first a tragedy and then a success, and it does not begin on the Hardangervidda but in Scotland where Britain’s ski capital, the small town of Aviemore in the Cairngorms National Park, is going to be our starting point for several dangerous journeys across the North Sea. A few years ago we drove up the main mountain road, eventually leading to the Cairn Gorm peak itself, 4,084 feet (1,245 metres) above sea level, and passed the park’s visitors’ centre located in pretty surroundings by a small lake. We glimpsed something flapping in the wind that did look a bit like the Union Jack, an unlikely occurrence in the highlands. We turned around and took the path up the hill, and soon discovered that what we first mistook for the British ensign, because of its colours, was in fact the Norwegian national flag. In 1468, when the Norwegians gave away their last Scottish possessions to King James III in Edinburgh, the Norwegian flag had not even been invented, so we were a wee bit curious as to why it was flying here, in the heart of the Cairngorms. But of course, mountains, snow, and skiing—what could be more Norwegian? And this simplistic reasoning is actually closer to the answer than we might have thought, as a commemorative sign told us that on this spot were the lodgings of the famous Kompani Linge during World War II.

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