Tunnel valley deposits from the southern North Sea – material provenance and depositional processes

Benvenuti, Antonio; Šegvić, Branimir; Moscariello, Andrea

doi:10.1111/bor.12292

Cited by 10 publications

(3 citation statements)

References 71 publications

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“…This can include remnants of coarse subglacial sediment, deposited during the formation of the valley (Praeg 2003; Benvenuti et al . 2018), postglacial fluvial sediments (Moreau & Huuse 2014; Fleischer et al . 2023), stiff glacilacustrine and homogeneous outwash sediments (Kirkham et al .…”

Section: Geological History Of the Southern North Seamentioning

confidence: 99%

“…2; Huuse et al 2001). This can include remnants of coarse subglacial sediment, deposited during the formation of the valley (Praeg 2003;Benvenuti et al 2018), postglacial fluvial sediments (Moreau & Huuse 2014;Fleischer et al 2023), stiff glacilacustrine and homogeneous outwash sediments (Kirkham et al 2021) and sandy interglacial marine sediments (Huuse & Lykke-Andersen 2000). Because the infill of the tunnel valley usually has different acoustic properties to the surrounding substrate, and the seismic facies within the valleys can be highly variable, seismic imaging beneath tunnel valleys is often poor or disturbed.…”

Section: Tunnel Valleysmentioning

confidence: 99%

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An integrated geological characterization of the Mid‐Pleistocene to Holocene geology of the Sørlige Nordsjø II offshore wind site, southern North Sea

Petrie,

Eide,

Haflidason

et al. 2024

Boreas

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Subsurface deposits in recently glaciated marine areas are highly heterogeneous, representing a range of glacial and postglacial environments and processes including glacitectonism, overconsolidation, fluvial and lacustrine deposition, and transgression. These heterogeneities are often linked to variations in engineering properties, with important implications for the design and installation of offshore wind infrastructure. In this study we present an integrated geological characterization of the Sørlige Nordsjø II offshore wind site, located in waters of 50–70 m depth along the southern border of the Norwegian North Sea, focusing on the evolution of the area's depositional setting during the late Quaternary period and its implications for offshore wind development. We integrate interpretations from a marine geological data set acquired in 2022 with legacy 3D seismic data and a review of the current understanding of the southern North Sea's complex glacial history. A preliminary ground model and accompanying risk map for the site is presented with five main geological units: (i) homogeneous and layered marine sands covering most of the site, with patchy distribution and coarser‐grained deposits in the east; (ii) buried, layered channel deposits containing organic material and possible associated shallow gas; (iii) buried, stiff glacilacustrine clay deposits; (iv) a buried, layered, glacitectonized unit incised by tunnel valleys, with a sandy marine infill; and (v) mounded tills and glacitectonized deposits containing boulders, exposed to shallowly buried in the east. Salt diapirism and gas migration were also found to be important potential geohazards at the site. Three‐dimensional seismic attribute maps were found to be a powerful aid to understanding the distribution and genesis of seismic facies identified on 2D high‐resolution sub‐bottom profiles. This type of data integration is an under‐utilized methodology for generating detailed preliminary ground models, which can inform more cost‐effective site survey and early foundation concept planning at geologically complex offshore wind sites.

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Section: Geological History Of the Southern North Seamentioning

confidence: 99%

Section: Tunnel Valleysmentioning

confidence: 99%

An integrated geological characterization of the Mid‐Pleistocene to Holocene geology of the Sørlige Nordsjø II offshore wind site, southern North Sea

Petrie,

Eide,

Haflidason

et al. 2024

Boreas

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“…Rather than filled by subglacial deposits, Moreau and Huuse (2014) expect the infill sediments were supplied from the southeast by the Rhine-Meuse systems which consistently flowed towards the North Sea basin during glacial periods. This view has been challenged by Benvenuti et al (2018) who inferred from provenance analysis that the infill of a large Elsterian tunnel valley consists mainly of reworked glacially derived sediment. This is in line with observations by Kirkham et al (2021) demonstrating that over 40 % of the examined tunnel valleys in the North Sea between Scotland and Norway contain buried glacial landforms such as eskers, crevasse-squeeze ridges, glaciotectonic structures, and kettle holes.…”

Section: Examples From Northern Central Europementioning

confidence: 99%

Comparison of overdeepened structures in formerly glaciated areas of the northern Alpine foreland and northern central Europe

Gegg

Preusser²

2023

E&G Quaternary Sci. J.

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Abstract. Overdeepened structures occur in formerly and presently glaciated regions around the earth and are usually referred to as overdeepenings or tunnel valleys. The existence of such troughs has been known for more than a century, and they have been attributed to similar formation processes where subglacial meltwater plays a decisive role. This comparison highlights that (foreland) overdeepenings and tunnel valleys further occur in similar dimensions and share many characteristics such as gently sinuous shapes in plan view, undulating long profiles with terminal adverse slopes, and varying cross-sectional morphologies. The best explored examples of overdeepened structures are situated in and around the European Alps and in the central European lowlands. Especially in the vicinity of the Alps, some individual troughs are well explored, allowing for a reconstruction of their infill history, whereas only a few detailed studies, notably such involving long drill core records, have been presented from northern central Europe. We suggest that more such studies could significantly further our understanding of subglacial erosion processes and the regional glaciation histories and aim to promote more intense exchange and discussion between the respective scientific communities.

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Tunnel valleys of the central and northern North Sea (56°N to 62°N): Distribution and characteristics

et al. 2020

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The analysis of buried tunnel valleys in the North Sea can provide information about the past configuration and dynamics of the Scandinavian and British ice sheets and the processes by which sediment and meltwater were transported at the ice-sheet base. However, little is presently known about the distribution and characteristics of tunnel valleys in the Norwegian sector of the North Sea. Here we use an extensive database of 3D seismic and high-resolution magnetic data to map more than 2200 tunnel valleys in the Norwegian and British sectors of the North Sea between 56°N and 62°N. With the exception of the deep Norwegian Channel, in which evidence for tunnel valleys is absent, the geological setting of the North Sea is interpreted to have been conducive to tunnel-valley formation and preservation because of its poorly consolidated substrate and shallow water depths. The highest density of tunnel valleys is located in the central part of the North Sea where Quaternary sediments are thickest. The extreme length of some of the tunnel valleys, which are up to 155 km long, supports theories that tunnel valleys form in stages rather than catastrophically. Detailed analysis of the orientation of tunnel valleys and their relative age relationships within four representative subareas shows that tunnel-valley orientation varies significantly across the central and northern North Sea and between different generations of valleys. This suggests that the pattern of subglacial meltwater drainage in the central and northern North Sea was different between each deglacial event in which tunnel valleys were formed, which is in contrast to the southerly meltwater drainage route that is indicated by the generally north-south orientation of tunnel valleys in the southern North Sea.

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Tunnel valley deposits from the southern North Sea – material provenance and depositional processes

Cited by 10 publications

References 71 publications

An integrated geological characterization of the Mid‐Pleistocene to Holocene geology of the Sørlige Nordsjø II offshore wind site, southern North Sea

An integrated geological characterization of the Mid‐Pleistocene to Holocene geology of the Sørlige Nordsjø II offshore wind site, southern North Sea

Comparison of overdeepened structures in formerly glaciated areas of the northern Alpine foreland and northern central Europe

Tunnel valleys of the central and northern North Sea (56°N to 62°N): Distribution and characteristics

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