3D Seismic Investigations of Pleistocene Mass Transport Deposits and Glacigenic Debris Flows on the North Sea Fan, NE Atlantic Margin

The North Sea has arguably the most extensive geophysical data coverage of any glacier-influenced sedimentary regime on Earth, enabling detailed investigation of the thick (up to 1 km) sequence of Quaternary sediments that is preserved within the North Sea Basin. At the start of the Quaternary, the bathymetry of the northern North Sea was dominated by a deep depression that provided accommodation for sediment input from the Norwegian mainland and the East Shetland Platform. Here we use an extensive database of 2D and 3D seismic data to investigate the geological development of the northern North Sea through the Quaternary.Three main sedimentary processes were dominant within the northern North Sea during the early Quaternary: 1) the delivery and associated basinward transfer of glacier-derived sediments from an ice mass centred over mainland Norway; 2) the delivery of fluvio-deltaic sediments from the East Shetland Platform; and 3) contourite deposition and the reworking of sediments by contour currents. The infilling of the North Sea Basin during the early Quaternary increased the width and reduced the water depth of the continental shelf, facilitating the initiation of the Norwegian Channel Ice Stream.

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Extensive, Gas-charged Quaternary Sand Accumulations of the Northern North Sea and North Sea Fan

10.5194/egusphere-egu2020-18701 ◽

2020 ◽

Author(s):

Benjamin Bellwald ◽

Sverre Planke ◽

Sunil Vadakkepuliyambatta ◽

Stefan Buenz ◽

Christine Batchelor ◽

...

Keyword(s):

North Sea ◽

Seismic Data ◽

Data Sets ◽

3D Seismic ◽

Fine Grained ◽

The North ◽

Northern North Sea ◽

Well Data ◽

Sea Fan ◽

3D Seismic Data

Sediments deposited by marine-based ice sheets are dominantly fine-grained glacial muds, which are commonly known for their sealing properties for migrating fluids. However, the Peon and Aviat hydrocarbon discoveries in the North Sea show that coarse-grained glacial sands can occur over large areas in formerly glaciated continental shelves. In this study, we use conventional and high-resolution 2D and 3D seismic data combined with well information to present new models for large-scale fluid accumulations within the shallow subsurface of the Norwegian Continental Shelf. The data include 48,000 km2 of high-quality 3D seismic data and 150 km2 of high-resolution P-Cable 3D seismic data, with a vertical resolution of 2 m and a horizontal resolution of 6 to 10 m in these data sets. We conducted horizon picking, gridding and attribute extractions as well as seismic geomorphological interpretation, and integrated the results obtained from the seismic interpretation with existing well data.The thicknesses of the Quaternary deposits vary from hundreds of meters of subglacial till in the Northern North Sea to several kilometers of glacigenic sediments in the North Sea Fan. Gas-charged, sandy accumulations are characterized by phase-reserved reflections with anomalously high amplitudes in the seismic data as well as density and velocity decreases in the well data. Extensive (>10 km2) Quaternary sand accumulations within this package include (i) glacial sands in an ice-marginal outwash fan, sealed by stiff glacial tills deposited by repeated glaciations (the Peon discovery in the Northern North Sea), (ii) sandy channel-levee systems sealed by fine-grained mud within sequences of glacigenic debris flows, formed during shelf-edge glaciations, (iii) fine-grained glacimarine sands of contouritic origin sealed by gas hydrates, and (iv) remobilized oozes above large evacuation craters and sealed by megaslides and glacial muds. The development of the Fennoscandian Ice Sheet resulted in a rich variety of depositional environments with frequently changing types and patterns of glacial sedimentation. Extensive new 3D seismic data sets are crucial to correctly interpret glacial processes and to analyze the grain sizes of the related deposits. Furthermore, these data sets allow the identification of localized extensive fluid accumulations within the Quaternary succession and distinguish stratigraphic levels favorable for fluid accumulations from layers acting as fluid barriers.

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Glacigenic debris flows on the North Sea Trough Mouth Fan during ice stream maxima

Marine Geology ◽

10.1016/s0025-3227(98)00072-3 ◽

1998 ◽

Vol 152 (1-3) ◽

pp. 217-246 ◽

Cited By ~ 133

Author(s):

E.L King ◽

H Haflidason ◽

H.P Sejrup ◽

R Løvlie

Keyword(s):

North Sea ◽

Debris Flows ◽

The North ◽

Ice Stream ◽

The North Sea

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Stratigraphy of Maastrichtian Foraminiferida from the United Kingdom; the Maastrichtian of Norfolk

Netherlands Journal of Geosciences – Geologie en Mijnbouw ◽

10.1017/s0016774600020825 ◽

2003 ◽

Vol 82 (3) ◽

pp. 233-245 ◽

Cited By ~ 1

Author(s):

M. Hart ◽

T. Swiecicki

Keyword(s):

United Kingdom ◽

North Sea ◽

Upper Cretaceous ◽

North Coast ◽

Flood Basalts ◽

Glacial Sediments ◽

The North ◽

The United Kingdom ◽

The North Sea ◽

Atlantic Margin

AbstractOnshore Maastrichtian strata in the United Kingdom are limited to a few small, isolated blocks of chalk floating within glacial sediments on the Norfolk coast. Isolated outcrops of Campanian and Maastrichtian chalks used to be available around Norwich but the majority of these exposures are now badly degraded. Offshore, in the North Sea Basin, there are complete chalk successions that range throughout the Upper Cretaceous and Lower Cenozoic. There is a limited succession of Maastrichtian chalks exposed on the north coast of Northern Ireland below the Cenozoic flood basalts. In the Western Approaches Basin, Maastrichtian and Danian chalks are known from exploration wells and core samples. West of the United Kingdom a number of DSDP/ODP boreholes have penetrated the Upper Cretaceous succession.Beginning in the Cenomanian, in southeast England, the whole of the Upper Cretaceous is within the chalk facies, possibly one of the longest intervals of relatively stable environment in the geological record. The Foraminiferida of the chalk have been studied for more than a hundred years and therefore the fauna is exceptionally well known and fully documented. Fifty years ago, the benthonic Foraminiferida were identified as having the potential to provide a viable zonation of the chalk facies and we now have precise, cross-basinal correlation using these taxa.The planktonic fauna is restricted by both palaeolatitude and water depth. The latter appears to be the most influential as the faunas from onshore are more limited than those recorded from the deeper waters of the North Sea Basin and the Atlantic Margin. Even with this restricted fauna, however, it is still possible to develop a general correlation with the standard Tethyan zonation based on planktonic taxa.

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A Source to Sink Approach to the North Sea Fan Pleistocene Glacial Sediments

10.5194/egusphere-egu21-12600 ◽

2021 ◽

Author(s):

Aurora Machado Garcia ◽

Ivar Midtkandal ◽

Benjamin Bellwald ◽

Ingrid Margareta Anell

Keyword(s):

Sediment Transport ◽

North Sea ◽

Signal Propagation ◽

Sedimentation Rates ◽

The North ◽

Sediment Routing ◽

Source To Sink ◽

Essential Components ◽

The North Sea ◽

Sea Fan

Trough mouth fans are large depocentres forming the ultimate sinks in glacial source-to-sink systems. Their architecture, sedimentological aspects (origin and processes) and their role as paleoclimatic archives are essential components in improving our understanding of Pleistocene and ongoing climate changes. For many years, these depocentres were thought to be dominated by debris flows accumulated in front of ice streams located at the shelf break. However, recent studies have shown that meltwater plays a major role in bringing sediment to the most distal parts of these fans, especially in lower latitudes. The North Sea Trough Mouth Fan encompasses ~110,000&#8201;km2 with water depths of up to 3500 m. It has received sediments throughout the Quaternary, with increased sedimentation rates in the last 1.1 Ma when the Norwegian Channel Ice Stream was active. Recent insight of the fan shows that meltwater turbidites play a major role in sediment delivery to the continental slope and deep-sea basin. The results could entail distinct morphologies for mid-latitude and high-latitude fans. As a result of glacial erosion and the absence of clear imprints of ice sheets on the paleo-shelves, studying trough mouth fan deposits becomes paramount in understanding glacial-interglacial cycles. This project will assess the source-to-sink parameters of the last glaciation (Weichselian) at the North Sea Fan, elucidating the dominant marine and terrestrial processes that led to the studied sedimentary sequences. High-resolution 2D and 3D seismic data, core, volumetric and numerical modeling data will be assimilated to establish a source-to-sink model for the target interval. These results will contribute to the knowledge of how glaciations affect surface mass redistribution, directly affecting the landscape dynamics and sediment routing from Fennoscandia via the North Sea to the slopes and deep basin. Sediment production will be evaluated, assessing whether it increases during the glaciation or if observed higher sedimentation rates are a result of enhanced sediment transport. This project is a part of the Marie Sklodowska-Curie Innovative Training Networks &#8220;S2S &#8211; Future: Signal propagation in source to sink for the future of the Earth resources and energy&#8221; and will further advance how trough mouth flans are highly dynamic areas where sediment transport, dispersal, remobilization and deposition take place, and serve as excellent proxies to the dynamics of glacial pulses in the hinterland.

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