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• Garcia, Aurora Machado; Bellwald, Benjamin; Planke, Sverre; Anell, Ingrid; Myklebust, Reidun & Sternai, Pietro [Vis alle 7 forfattere av denne artikkelen] (2024). Sedimentation record of a complete glacial-interglacial cycle: Down-slope deposits, contourites and plumites of the North Sea trough mouth fan. Quaternary Science Reviews. ISSN 0277-3791. 339. doi: 10.1016/j.quascirev.2024.108839. Fulltekst i vitenarkiv Vis sammendrag

  Trough mouth fans (TMFs) are major submarine depocentres that form in front of ice streams advancing onto the continental shelf, and they provide extensive records of past glaciations and ice-sheet dynamics. However, early research about TMFs was conducted using primarily 2D seismic data, which limits the insights on the deposit's geometries and internal structures and more recent studies using 3D data have focused on the general depositional history of TMFs. Here, we assess the spatial and temporal changes of the glacio-marine landforms and deposits throughout the last glacial-interglacial cycle (Marine Isotope Stage (MIS) 6 to 1, ∼130 ka to present) recorded in a >550 m thick progradational sequence. We use 3D reflection seismic data with significant vertical resolution (up to 2 m) imaging over 14000 km2 from the uppermost North Sea Fan (NSF) to document the seismic stratigraphy and sedimentary processes, by combining horizon picking and geomorphological analyses. The studied interval comprises five mappable units, four on the slope and one on the shelf, spanning from the modern seabed down to the top of the Tampen Slide (∼130 ka). Five different channel types (here included slide scars), as well as contourite and plumite packages are described based on their seismic facies, morphology, geometry, and stratigraphical position. We propose that contour currents are responsible for sediment delivery after the Tampen Slide deposition during the interglacial period before the onset of the Last Glacial Maximum, when high meltwater influx from the shelf produced turbidites. Sedimentation became debris-flow-dominated towards the end of the period of shelf-edge glaciation. The deglacial interval is characterized by the deposition of plumites on the slope. On the shelf, subglacial tills are deposited during both glacial and deglacial periods. We calculate an average sedimentation rate of <1 m/kyr during the interglacial (MIS 5-3), and around 50–65 m/kyr during the glacial and deglacial periods (MIS2-early MIS1). Thus, we document a change of two orders of magnitude in sedimentation rate during a glacial cycle on the slope of a glaciated margin.

• Rosa, Eduardo Menozzo da; Isbell, John L.; Vesely, Fernando; Sedorko, Daniel; Garcia, Aurora Machado & McNall, Natalie (2024). Reassessing the late Paleozoic glacial sedimentation in western Paraná Basin, Brazil: A record of a slope and glaciated outer shelf setting in the Aquidauana Formation. Sedimentary Geology. ISSN 0037-0738. 466. doi: 10.1016/j.sedgeo.2024.106640. Fulltekst i vitenarkiv
• Bellwald, Benjamin; Planke, Sverre; Vadakkepuliyambatta, Sunil; Buenz, Stefan; Batchelor, Christine L. & Manton, Ben [Vis alle 11 forfattere av denne artikkelen] (2022). Quaternary and Neogene Reservoirs of the Norwegian Continental Shelf and the Faroe-Shetland Basin. First Break. ISSN 0263-5046. 40(6), s. 43–54. doi: 10.3997/1365-2397.fb2022045. Fulltekst i vitenarkiv Vis sammendrag

  Glaciogenic reservoirs host important hydrocarbon resources across the globe. Examples such as the Peon and Aviat discoveries in the North Sea show that Quaternary and Neogene reservoirs can be prospective in the region. In this study, we interpret 2D and 3D reflection seismic data combined with borehole information to document unconventional play models from the shallow subsurface of the Norwegian Continental Shelf and the Faroe-Shetland Basin. These plays include (i) glacial sands in ice-marginal outwash fans, sealed by stiff subglacial tills (the Peon discovery), (ii) meltwater turbidites, (iii) contouritic fine-grained glacimarine sands sealed by gas hydrates, (iv) remobilized oozes above large evacuation craters which are sealed by megaslides and glacial muds, and (v) Neogene sand injectites. The hydrocarbon reservoirs are characterized by negative-polarity reflections with anomalously high amplitudes in the reflection seismic data as well as density and velocity decreases in the borehole data. Extensive new 3D reflection seismic data are crucial to correctly interpret glacial processes and distinguish shallow reservoirs from shallow seals. These data document a variety of play models with the potential for gas in large quantities and enable the identification of optimal drilling targets at stratigraphic levels which have so far been overlooked.

• Bellwald, Benjamin; Batchelor, Christine L.; Garcia, Aurora Machado; Barrett, Rachel; Rosenqvist, Marija Plahter & Planke, Sverre [Vis alle 9 forfattere av denne artikkelen] (2022). Contourites of the Northern North Sea, North Sea Fan, and Mid-Norwegian Margin, 83rd EAGE Annual Conference & Exhibition 2022. European Association of Geoscientists and Engineers (EAGE). ISSN 9789073834125. doi: 10.3997/2214-4609.202210247. Fulltekst i vitenarkiv Vis sammendrag

  Contourites contribute to the shaping and building of continental margins, and have an economic importance for the offshore-energy sector by acting both as reservoir and seal rock. Here we study the different contourites of the northern North Sea, North Sea Fan and mid-Norwegian margin formed in the Neogene and Quaternary, which are unconventional targets in the region. Based on extensive 3D reflection seismic data combined with borehole data, we suggest that fine-grained drifts form regionally large and thick accumulations, while relatively coarse-grained sediment deposits develop locally. Sourced from the East Shetland Platform and the northern North Sea, the contour currents transported the available sediments northwards, where the regional physiography enhanced the ocean currents and hosted contouritic deposition. The Pliocene to early-Quaternary contourites are characterized by continuously laminated sediments, and most likely contain gas-charged sands in selected locations. Trapped by megaslide escarpments, the late-Quaternary contourites have a transparent facies, most likely representing fine-grained muds. The contourites to the north of the North Sea Fan are further sealed by a bottom-simulating reflection, indicating the presence of a gas-hydrate barrier. Contourites are thus a promising unconventional play model in the region, but caution is required when interpreting the sedimentologic characteristics of these deposits.

• Mottin, Thammy; Iannuzzi, Roberto; Vesely, Fernando; Montañez, Isabel; Griffis, Neil & Canata, Rafael [Vis alle 9 forfattere av denne artikkelen] (2022). A glimpse of a Gondwanan postglacial fossil forest. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 588. doi: 10.1016/j.palaeo.2021.110814. Fulltekst i vitenarkiv Vis sammendrag

  The rooted nature of vegetation allows for individual plants or entire communities to be buried in life position under exceptional geological conditions, thereby preserving their ecology and spatial distribution in the stratigraphic record. Upright lycopsids are not uncommon within paleoequatorial Carboniferous coal-bearing deposits, but they are rare in mid- to high-paleolatitude Gondwana, where they have only been found in lower Permian strata. An exceptionally well preserved in situ Brasilodendron-like lycopsid forest is described from an early Permian postglacial paleolandscape of western Gondwana (Paraná Basin, Brazil). The forest depicted here is unique given its extratropical location, as well as the exceptional preservation of abundant specimens and their morphological and paleoecological aspects. Over 150 lycopsid stumps, with a clustered spatial organization, were mapped. The host succession, overlying glaciomarine diamictites by a few tens of meters, captures the terminal deglaciation in the Paraná Basin, and shows that these forests could establish dense communities on poorly developed soils in postglacial times. Sedimentological data suggest that the death and burial of these lycopsids in life position were caused by crevasse splay progradation over the colonized interdistributary bay areas as a consequence of a major river flooding event.

• Garcia, Aurora Machado; Trzaskos, Barbara; Vesly, Fernando; Rosa, Eduardo Da & Isbell, John (2021). Rochas glaciais sob o microscópio: Microtexturas e microestruturas em fácies do Grupo Itararé. Boletim Paranaense de Geosciencias. ISSN 0067-964X. 78, s. 44–64. doi: 10.5380/geo.v78i0.80090. Fulltekst i vitenarkiv

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• Garcia, Aurora Machado; Bellwald, Benjamin; Midtkandal, Ivar; Planke, Sverre; Anell, Ingrid & Sternai, Pietro [Vis alle 7 forfattere av denne artikkelen] (2022). Mixed sedimentation of the North Sea Fan - insights on volumes of contourites, plumites and downslope deposits during a full glacial- interglacial cycle. EGU General Assembly Conference Abstracts. doi: 10.5194/egusphere-egu22-10658. Fulltekst i vitenarkiv Vis sammendrag

  Trough mouth fans are important depocenters for glacial sedimentation in high latitude margins,recording sedimentological processes and their relationship with paleoclimatic fluctuations onshort timescales - from decades to millennia. The volume of sediments accumulated in these fansvaries significantly depending on the phase of the glacial cycle, with higher values typically reachedduring early retreats. The input of large volumes during short time intervals can potentially triggersubmarine landslides and overpressure build-up, making the understanding of processes andproportions related to sedimentation in glaciated margins crucial, especially during periods ofglobal warming. In this study we use high-quality 3D seismic cubes (vertical resolution of 2 m andbin size of 6.25 x 18.75 m) to delimitate different types of deposits on an area over 14000 km2 onthe North Sea Trough Mouth Fan during a full glacial-interglacial cycle of the last glaciation(Weichselian). After mapping the corresponding top and base surfaces of each type of deposittheir volumes were calculated using the mean thickness of the beds multiplied by their extent. Thebase of the studied package comprises a contourite body deposited on top of the Tampen Slide,whose failure is estimated to have happened around 130 ka ago. Next we have a thick (> 400 m)mixed package of debris flows and meltwater turbidites, with its rapid deposition happeningduring approximately 4 ka (~23 to 19 ka). The package is then completed with plume settlingrelated to the full retreat of the ice stream. Although not completely interpreted due to limitationsof the dataset extent and remobilization of a part of the fan by the Storegga Slide in the northernpart, the last glacial cycle comprises a total of 7160 km3 of sediments, with more than half of it(4850 km3) originated from the downslope processes. The plumites and contourites comprisevolumes of 1105 km3 and 1205 km3. This accounts to a significant variability of the magnitude ofsediment volume coming into the sink per year, with the downslope deposits having over 100times more sediment input and the plumites 5 times more when compared to thecontourites. These results highlight the range of sediment volume that can be delivered in aglaciated margin depending on changes in processes and climatic fluctuations, which may also entail changes in the potential geohazards.

• Bellwald, Benjamin; Garcia, Aurora Machado; Batchelor, Christine L; Barrett, Rachel; Maharjan, Dwarika & Planke, Sverre [Vis alle 8 forfattere av denne artikkelen] (2022). Trough mouth fans as high-resolution source-to-sink archives. EGU General Assembly Conference Abstracts. doi: 10.5194/egusphere-egu22-9630. Fulltekst i vitenarkiv Vis sammendrag

  Trough mouth fans comprise the largest sediment deposits along glaciated margins, and record Pleistocene climate changes on a multi-decadal time scale. Sedimentation related to climate warming in polar regions and new challenges associated with the energy transition highlight the urge for better knowledge of these depocenters. Here, we present sedimentation models for the two largest of these depocenters-the Bear Island Fan on the western Barents Sea margin and the North Sea Fan on the northern North Sea margin-which are analogues for large glacial fans along the Antarctic and Greenland margins. We use extensive high-quality 3D reflection seismic cubes (37,200 km 2) as well as conventional 2D reflection seismic lines, and combine these datasets with lithological and geophysical borehole logs. The stratigraphy of trough mouth fans is dominated by contourites, glacigenic debris flows, meltwater turbidites, and megaslides, which together result in a thickness exceeding 2 km. Neogene to early Quaternary-age contourites are characterized by continuous and high-amplitude reflections in the seismic data. The contourites of the late Quaternary, in contrast, have a more transparent seismic facies, and onlap the escarpments shaped by the megaslides. The lithology of the contourites varies from fine clays to coarse sands. Meltwater turbidites are identified as high-amplitude reflections characterized by 4-100 m deep channels and sourced from multiple regions along the paleo-shelf break. The well-connected turbidite channels are 90-2100 m wide, and can be traced for distances of >100 km. These channels are both deeper and wider in the North Sea Fan compared to the Bear Island Fan. The lithology of these deposits has yet to be cored. Glacigenic debris flows are transparent packages of sediments, with a lens-shaped expression in the seismic profiles and lobe-shaped geomorphology in planar view. The grain size of glacigenic debris flows is typically more mud-dominated than for contourites, but glacigenic debris flows do include sandy beds at selected intervals. Glacigenic debris flows are more dominant in the high-latitude Bear Island Fan compared to the mid-latitude North Sea Fan. Megaslides consist of high-amplitude, deformed sediment that is constrained by steep headwalls and sidewalls. The megaslides within these two trough mouth fans have mainly occurred since the Late Pleistocene and fail along contouritic basal layers.

• Garcia, Aurora Machado; Bellwald, Benjamin; Midtkandal, Ivar; Planke, Sverre; Sternai, Pietro & Anell, Ingrid [Vis alle 7 forfattere av denne artikkelen] (2022). Stratigraphy of a complete glacial-interglacial cycle: The sedimentary record of the last glaciation at the North Sea Fan. Fulltekst i vitenarkiv Vis sammendrag

  Trough mouth fans are major submarine depocentres that form in front of ice streams that advance onto the continental shelf. They provide extensive records of past glaciations and ice sheet dynamics, and understanding their deposits and sedimentary processes is key when interpreting glaciated margins. In this study, we use high-quality 3D reflection seismic data with a vertical resolution of 2 m and a bin size of 6.25 x 18.75 m extending over 14000 km2 at the uppermost North Sea Fan. The aim is to document the seismic stratigraphy, sedimentary processes and glacio-marine landforms shaped during different paleo-geographical configurations prevailing since Marine Isotope Stage 6 (last 130 ka). Using facies analyses and seismic geomorphology the sequence is subdivided into eight seismic units (U1-8), separated by high-amplitude continuous reflections. The uppermost stratigraphy of the fan is characterized by >400 m of prograding strata, spanning from the top of the Tampen Slide at its deepest to the seabed on the more shallow shelf, accounting to 7160 km3 of sediments. The lowermost two units, U1 and U2, are characterized by continuous reflections with increasing amplitude contrasts near the Tampen Slide headwall. U1 is a tabular body and covers the entire study area, while U2 is lenticular and limited to the northern part, confined by a secondary headwall. Units U3-6 are characterized by a combination of chaotic, transparent, structurally deformed or parallel to sub-parallel seismic facies. They are limited by high-amplitude reflections with erosional features with varying dimensions from

• Garcia, Aurora Machado; Bellwald, Benjamin; Midtkandal, Ivar; Anell, Ingrid; Planke, Sverre & Sternai, Pietro [Vis alle 7 forfattere av denne artikkelen] (2021). Sedimentary Processes and Deposits of the Last Glaciation at the North Sea Fan, Offshore Norway. Fulltekst i vitenarkiv Vis sammendrag

  Understanding the sedimentary processes and resulting deposits along glaciated margins, that can be recorded in trough mouth fans (TMF), is crucial to increase knowledge about ice sheet dynamics. Their behavior influences Earth’s climate system and sea level variations, from regional to global scale, during relatively rapid timescales (up to millennia). This study uses high-quality 3D seismic reflection data of the uppermost North Sea Trough Mouth Fan to document the seismic stratigraphy, sedimentary processes and glacio-marine landforms shaped during the last glacial highstand (23-19 ka). The stratigraphy of the fan is characterized by thick (~400m) prograding sequences. Facies analyses and seismic geomorphology show three main depositional processes (contour-currents, gravity-driven flows and setting of plumes), mappable as seven seismic sub-units in the studied interval. Contour currents are responsible for the deposition of the lowermost two sub-units (U1 and U2), characterized by continuous reflections with increasing amplitude contrasts near the Tampen Slide escarpment. U1 is dominated by positive amplitudes with mostly tabular geometry. U2, identified in the northern part, is dominated by negative amplitudes with lenticular geometry and is synchronous with the glaciation onset. These sub-units are followed by a succession of relatively homogeneous facies interrupted by continuous high-frequency horizons that subdivide the succession into four sub-units (U3-6). These sub-units are characterized by channels, presumably generated by meltwater-fed turbidity flows, varying in width, varying in depth from 10 to 60m and with suggesting high-energy episodes that creates channels deeper than 100m. They are pervasive throughout the sequences and across the fan and are commonly isolated with low sinuosity. The uppermost sequence (U7) is dominated by deposition of the suspended load and ice-raft debris, characterized by parallel and slightly undulated continuous inner reflections, thinning out downslope. Along the shelf, multiple cross-cutting of iceberg scours and pits are observed. The succession with channels evidence that meltwater can play a major role in TMF sedimentation. These new insights about the smaller-scale processes within seismic resolution demonstrate the variability of active processes during a fast sedimentation period of the Weichselian Glaciation at the North Sea Trough Mouth Fan.

• Garcia, Aurora Machado; Midtkandal, Ivar; Bellwald, Benjamin & Anell, Ingrid Margareta (2021). A Source to Sink Approach to the North Sea Fan Pleistocene Glacial Sediments. Fulltekst i vitenarkiv Vis sammendrag

  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 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 “S2S – Future: Signal propagation in source to sink for the future of the Earth resources and energy” 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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