Ivar Midtkandal

• Gilmullina, Albina; Mordasova, Alina; Grundvåg, Sten-Andreas; Pedersen, Leif-Erik Rydland; Jelby, Mads Engholm & Midtkandal, Ivar [Vis alle 10 forfattere av denne artikkelen] (2026). Cretaceous provenance, sediment supply and source-to-sink evolution in the Greater Barents Sea Basin. Journal of the Geological Society. ISSN 0016-7649. doi: 10.1144/jgs2025-224. Fulltekst i vitenarkiv Vis sammendrag

  The Greater Barents Sea Basin (GBSB) is a unique area in the Arctic, as it hosts relatively well-preserved large-scale Cretaceous progradational wedges. Multiple regional studies document temporal and spatial variations in clinoform progradation directions and sedimentation styles across different parts of the GBSB and reveal a fundamental tectonically driven reorganization of drainage systems during the Early Cretaceous. This study uses an integrated source-to-sink approach combining regional seismic datasets with new detrital zircon U-Pb ages from the analysis of 11 samples spanning Valanginian to Campanian that are combined with seismic interpretation and mass balance calculations. This work presents a unified chronostratigraphic frame for the whole GBSB and correlates internal changes to large-scale plate tectonic events, and major volcanism, in the source area and the Arctic in general. It reveals that sediment input varied throughout the Cretaceous with low sediment input from local sources in the Late Jurassic-Hauterivian, which dramatically increased in the Barremian due to High Arctic large Igneous Province (HALIP) activity. Relatively high sediment input took place in the Albian-Cenomanian due to catchment reorganization, followed by relatively low sediment input in the Turonian-Coniacian with a last increase in the Campanian. A new provenance dataset, including new zircon data, confirms a catchment reorganization to a dominant northeasterly source, and constrains this change to the Aptian-Albian.

• Holden, Nora; Skurtveit, Elin; Alaei, Behzad; Midtkandal, Ivar & Braathen, Alvar (2025). Influence of growth fault complexities on fault seal assessments in the Smeaheia CO2 storage site, northern North Sea. Journal of Structural Geology. ISSN 0191-8141. 200. doi: 10.1016/j.jsg.2025.105501. Fulltekst i vitenarkiv Vis sammendrag

  Growth faults exhibit great variability in their structural and sedimentological architecture. While these faults create structural traps that are critical for effective CO2 storage, their complexities are often overlooked in the integrity assessment of storage sites. This study focuses on the Vette Fault Zone in the Smeaheia CO2 storage site, northern North Sea. Here, the intended Upper Jurassic storage complex in the footwall juxtaposes predominately Lower Cretaceous syn-rift strata in the hanging wall. The primary seal in the footwall shows signs of degradation, with increased erosion occurring in the fault zone's eastward concave sections. The hanging wall features transverse folding of pre-rift units, overlain by thick syn-rift strata sourced from the immediate fault scarp and catchments beyond the fault block crest. These structures and deposits are not captured in nearby wells and therefore insufficiently considered when assessing fault rock composition and sealing potential. Incorporating these features, we find that the level of detail used to define the syn-rift layering has the most significant influence, whereas restoring the footwall to its pre-erosional state has only a minor effect. Not considering these structural complexities likely leads to underestimating the Vette Fault Zone's sealing potential. For fault seal assessments in settings with complex growth faults, we stress the importance of a detailed understanding of the structural development, defining confidence in host rock composition, utilizing a scenario-based approach for fault seal assessment, and presenting related uncertainties.

• Kjøll, Hans Jørgen; Midtkandal, Ivar; Manton, Ben & Planke, Sverre (2025). Seismic Geomorphology of an Early Eocene Canyon‐Channel‐Lobe System North of Shetland. Basin Research. ISSN 0950-091X. 37(3), s. 78–105. doi: 10.1111/bre.70031. Fulltekst i vitenarkiv Vis sammendrag

  Submarine canyon and channel systems are the primary paths for sediment transport from platforms to deep‐sea terminal depositional fans and are present on all continental margins. The temporal morphological expression of such systems should be documented in order to fully understand the development of these important sediment pathways. We utilise a 3D seismic dataset from the northern Shetland Platform to the southern Møre Basin region and map two regionally continuous seismic horizons. The dataset includes an early Eocene northward‐oriented canyon‐channel system that allows high‐resolution mapping of erosion and sedimentation. The morphology of the system allows a subdivision of platform, upper, middle, and lower slope, and basin floor. It is further subdivided from east to west according to the degree of erosive maturity. The platform contains channel shapes and their fill stretching from the south towards the platform edge and upper slope, where dendritic canyon heads developed. Scars in the canyon sidewalls indicate slope failure as an important widening mechanism. The slope canyons progressively shallow and widen basinward. At the canyon exits, deepwater submarine channels developed and continued onto the basin floor. We document progressive filling and overspilling of channels towards the terminal fan. The filling of the channels that resulted in overbank deposition is likely due to a decrease in slope gradient leading to an increased deposition rate that exceeds the channel capacity. Post‐depositional differential compaction of the clastic channel fill and the surrounding muddy sediments causes the channel fills to form elongated ridges that lead towards the terminal fan. It is further shown that the morphological elements observed in the canyon‐channel system adjust towards an equilibrium profile with a shallower gradient. These detailed observations provide an enhanced understanding of how canyon‐channel systems develop on active margins and how sediment transport pathways are influenced by the submarine equilibrium profile and post‐depositional processes.

• Galland, Olivier; Sartell, Anna Marie Rose; Horota, Rafael Kenji; Kjøll, Hans Jørgen; Runge, Jonathan J. S. & Midtkandal, Ivar [Vis alle 7 forfattere av denne artikkelen] (2025). Stratigraphic Influence on Emplacement and 3‐Dimensional Structure of a Large Mafic Sill in Sedimentary Strata. Basin Research. ISSN 0950-091X. 37(4). doi: 10.1111/bre.70047. Fulltekst i vitenarkiv Vis sammendrag

  Sills are fundamental elements of volcanic plumbing systems emplaced in sedimentary basins. Even though sills are commonly considered simple, planar concordant igneous sheets, they are actually complex 3‐dimensional objects. Detailed knowledge of the 3D structure of sills and their host rocks is of primary relevance to better constrain the emplacement mechanisms and the impacts of sills on sedimentary basins. This study describes the results of 3‐dimensional geological mapping of a large (~14 × 9 km), well‐exposed Early Cretaceous dolerite sill in Central Spitsbergen, Svalbard, Arctic Norway, using a combination of digital outcrop modelling and field mapping. The sill was emplaced within Upper Palaeozoic sedimentary formations of Svalbard. It is made of distinct segments emplaced at different stratigraphic levels of the host rock stratigraphy. The mapping shows a clear stratigraphic control on the intrusion morphology. Sill segments emplaced at the boundary between two formations, which mark a strong lithological and rheological boundary, are straight and concordant. Conversely, segments emplaced within a more homogeneous formation exhibit more irregular, locally discordant shapes. The sill segments emplaced at distinct stratigraphic levels are connected by steeply dipping steps, which formed through dilatant shearing between the tips of the sill segments. The preferred NW‐SE orientation of the steps and the thinning of the sill towards the SE suggests a propagation direction of the magma towards the SE. Our study shows how 3‐dimensional knowledge of igneous intrusions is key for revealing their emplacement mechanisms.

• Nygaard, Madeleine Skov; Planke, Sverre; Zastrozhnov, Dmitry; Midtkandal, Ivar; Huismans, Ritske Sipke & Faleide, Jan Inge [Vis alle 13 forfattere av denne artikkelen] (2025). A tectonostratigraphic interpretation of the Mimir High through seismic-borehole tie: New insights into the Paleogene evolution of the Vøring Transform Margin. SEG technical program expanded abstracts. doi: 10.1190/image2025-4307795.1. Fulltekst i vitenarkiv Vis sammendrag

  The Mimir High is a structural high along the Vøring Transform Margin (VTM), offshore Mid-Norway, having excellent coverage of high-resolution seismic 2D and 3D data and borehole data from five wells drilled during the International Ocean Discovery Program (IODP) Expedition 396. The Mimir High developed through rift tectonics and thermal uplift that resulted in a transition through different paleoenvironments from shallow marine to coastal or subaerial and finally marine again.

• 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.

• Whattam, Jack William; Midtkandal, Ivar; Jerram, Dougal Alexander; Callegaro, Sara & Svensen, Henrik Hovland (2024). The episodic onset of explosive and silicic-dominated volcanism in a continental rift; insights from the Permian Oslo Rift, Norway. Volcanica. 7(2), s. 925–951. doi: 10.30909/vol.07.02.925951. Fulltekst i vitenarkiv Vis sammendrag

  The nature of rifting episodes and their associated volcanism mark key stratigraphic events in the evolution of volcano-sedimentary basins. Following the final assemblage of Pangea, the European region was subject to rifting and magmatism during crustal re-equilibration throughout the Permian. The aborted, partially eroded Oslo Rift is an excellent archive of this Permian magmatism, but the late-stage volcanological evolution is poorly understood. We present the first detailed documentation of a succession covering this period, with mafic lavas and volcaniclastic (tuff breccia) deposits, trachy-andesitic tuffs, and rheomorphic to moderately welded ignimbrites. Contrary to previous ideas, we show evidence suggesting the development of Strombolian-type scoria-cones, silicic fissure-fed eruptions, and major periods of rift-wide volcanic quiescence. Our observations highlight episodic silicic volcanism characterised by rapid evolution from high-grade ignimbrites to moderately and poorly welded ignimbrites. We infer rapid emptying of large, shallow silicic reservoirs and frequent source switching is responsible for the observed characteristics.

• Braathen, Alvar; Midtkandal, Ivar & Osmundsen, Per Terje (2024). Geomorphological traits of landscapes in continental rifts—From fault-elastic rebound to sedimentary sinks. Basin Research. ISSN 0950-091X. 36(4). doi: 10.1111/bre.12881. Fulltekst i vitenarkiv
• Galland, Olivier; Villar, Héctor J.; Mescua, José; Jerram, Dougal Alexander; Messager, Gregoire Eugene Philippe & Medialdea, Adrian [Vis alle 11 forfattere av denne artikkelen] (2024). Structural control of igneous intrusions on fluid migration in sedimentary basins: the case study of large bitumen seeps at Cerro Alquitrán and Cerro La Paloma, northern Neuquén Basin, Argentina. Geological Society Special Publication. ISSN 0305-8719. 547(1), s. 231–259. doi: 10.1144/SP547-2023-115. Fulltekst i vitenarkiv
• Wong, Po Wan; Midtkandal, Ivar & Faleide, Jan Inge (2023). Origin of paired extension-compression during rotational rifting: An early Paleogene example from the northeast Atlantic region and its implications. Geology. ISSN 0091-7613. 52(1), s. 27–32. doi: 10.1130/G51730.1. Fulltekst i vitenarkiv Vis sammendrag

  Abstract The formation of paired extension-compression (PEC) postulated by rotational kinematics of rift propagation is demonstrated by analogue models but rarely observed in nature. In our study of the early Paleogene continental rift in the northeast Atlantic, a PEC is proposed based on the northeastward propagation and the coeval compression at the rift tip. The propagation is deduced from tectono-magmatic trends, including along-axis development of magmatism, and migration of tectonic faulting inward and toward the rift tip. Where this propagation terminated, we documented coeval extension and compression in the form of a horst-and-graben system (H&amp;G) and V-shaped anticline (VA), respectively. Given their structural characteristics and spatiotemporal relationships with the rift, their origin is best illustrated by a three-stage model: (1) Rifting initiated at the site of mantle upwelling and propagated northeastward in the Paleocene. (2) The rift tip was stalled by an elevated mafic-ultramafic body at the Barents Shelf, which led to forward projection of the rift’s driving force to create the H&amp;G and the VA (PEC), dissipating the along-axis force component. (3) Domination of axis-perpendicular components then promoted orthogonal extension and sheared margin development. Our study suggests that PEC has a crucial role in both termination of propagation and rift-mode conversion.

• Kjøll, Hans Jørgen; Midtkandal, Ivar; Planke, Sverre; Millett, John; Manton, Ben & Anderskouv, Kresten (2023). The interplay between siliciclastic and carbonate depositional systems: Maastrichtian to Danian basin-floor sediments of the mid-Norwegian Møre Basin. Basin Research. ISSN 0950-091X. 36(1). doi: 10.1111/bre.12827. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Source‐to‐sink sedimentary systems associated with volcanic rifted margins serve as important archives for basin development by recording lithospheric changes affecting the depositional systems. Distinguishing between sediment transport processes and their sediment source(s) can guide the interpretation of a basin's history, and thereby inform regional paleogeographic reconstructions. In this contribution, we integrate and utilize wireline geophysical logs, detailed petrographic observations from side‐wall cores, and seismic analysis to describe and decipher a Maastrichtian to Danian‐aged basin‐floor depositional system in the deep outer Møre Basin, mid‐Norwegian margin. Well 6302/6‐1 (Tulipan) is a spatially isolated borehole drilled in 2001 that penetrates Maastrichtian and younger strata. A succession of hitherto undescribed carbonates and sandstones in the outer Møre Basin was discovered. It is investigated for sediment transport, provenance, and depositional processes on the basin floor surrounded by structural highs and ridges. The strata from the lower parts form a basin‐floor apron consisting of redeposited carbonate sourced from a westerly sub‐aerial high. The apron transitions vertically from mixed siliciclastic and carbonate into a purely siliciclastic fan with intercalated sandstone and mudstone, providing a rare high‐resolution record of how depositional environments experience a complete shift in dominant processes. The development coincides with similar latest Cretaceous‐earliest Palaeocene sequences recorded south of this region (e.g., well 219/20‐1) and may have been influenced by regional uplift associated with the onset of magmatism in the Northeast Atlantic. This study improves our understanding of a late, pre‐breakup source‐to‐sink sedimentary system developed near the breakup axis of an infant ocean, and documents what is possibly the northernmost chalk deposit in the Chalk Group.

• Anell, Ingrid; Olsen, Stine Grimsrud; Haugen, M.; Jahren, Jens; Midtkandal, Ivar & Poyatos-Moré, M. (2023). A discourse on factors influencing the formation of sigmoidal and linear slope-geometries in the deltaic clinoforms of the calciclastic Sobrarbe Delta, Ainsa Basin, Spain. Marine and Petroleum Geology. ISSN 0264-8172. 153. doi: 10.1016/j.marpetgeo.2023.106287. Fulltekst i vitenarkiv
• Würtzen, Camilla Louise; Hassaan, Muhammad; Anell, Ingrid; Nystuen, Johan Petter; Faleide, Jan Inge & Midtkandal, Ivar (2023). Alluvial development during climate fluctuations depicted with spectral decomposition of the Middle Triassic to Lower Jurassic post-rift succession in the Horda Platform (Norway) and the impact on reservoir properties. Basin Research. ISSN 0950-091X. 35(6), s. 2301–2327. doi: 10.1111/bre.12799. Fulltekst i vitenarkiv Vis sammendrag

  Abstract For the first time, this study presents interpretations of alluvial fans in spectral decomposition RGB Blends, analysed in seismic time slices from the Middle Triassic to Lower Jurassic stratigraphical interval of the Horda Platform (northern North Sea). The time slices record a shifting alluvial fan front, fluvial variability, uplift and erosion and reveals depositional elements that may set the common conception of the geological development of this area during the Early–Middle Mesozoic up for discussion. Results show that the Upper Triassic Lunde Formation in the eastern margin of the Horda Platform was characterized by the deposition of coalesced alluvial fans. A variable extent of the fan front through the Upper Triassic is linked to interplaying allogenic factors: uplifted source areas in the aftermath of Early–Middle Triassic rifting determined sediment availability; climate transitioning from arid to semi‐humid, with increasingly fluctuating precipitation, controlled sedimentation, and run‐off; provenance dictated bulk sedimentology and affected prevailing alluvial processes. An overall retreat of the fan system through the Late Triassic coincided with a significant change in landscape characteristics at the transition into the overlying Statfjord Group. Uplift and initial tilting of the Horda Platform caused landscape degradation and the formation of plateaus and incised valleys, contemporaneous with increased humidity and marine transgression, forming estuaries. The shift in depositional style has implications for reservoir properties, creating complexity and heterogeneity in terms of facies distribution and connectivity, which may benefit potential CO 2 storage. Upper Triassic alluvial fan development in the Horda Platform (northern North Sea) depicted through spectral decomposition of seismic time slices Enhanced level of seismic stratigraphic interpretation with RGB blending Impact of allogenic factors on alluvial depositional development Implications of alluvial variability on reservoir properties

• Vickers, Madeleine Larissa; Jelby, Mads E.; Sliwinska, Kasia; Percival, L.M.E.; Wang, Feiyue & Sanei, Hamed [Vis alle 17 forfattere av denne artikkelen] (2023). Volcanism and carbon cycle perturbations in the High Arctic during the Late Jurassic – Early Cretaceous. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 613. doi: 10.1016/j.palaeo.2023.111412. Fulltekst i vitenarkiv Vis sammendrag

  Large perturbations in the global carbon cycle recorded as carbon-isotope (δ13C) excursions (CIEs) in both organic carbon and carbonate records have been linked to volcanism during the emplacement of Large Igneous Provinces (LIPs). This link is based primarily on the purported temporal coincidence between CIEs and LIP emplacement. Mercury (Hg) concentration in sedimentary rocks has been used as a regional to global tracer of large-scale volcanic activity, yet few studies have been undertaken on Upper Jurassic – Lower Cretaceous sediments from Boreal localities compared to those for Tethyan (northern mid-latitude) successions. This has limited our understanding of the regional-to-global spatial impact of volcanic activity during this period. This study examines the Hg record as a proxy for volcanism, and the δ13C records from organic matter (δ13Corg) of CIEs from the uppermost Jurassic to Lower Cretaceous (Callovian – Aptian) successions from Axel Heiberg and Spitsbergen in the Canadian Arctic and Svalbard archipelagos, respectively. This interval includes three regional- to global CIEs. These sections show no significant variation in the ratio of Hg to total organic carbon (TOC) across the Boreal-wide Volgian negative CIE (Volgian Isotopic Carbon Excursion, “VOICE”), which has not been associated with LIP volcanism. The examined successions spanning this interval all show some influence from changing environmental or post-burial parameters, however, which could have (partially) overprinted a volcanic signal. Despite some problems in stratigraphically constraining the Weissert Event, increased Hg/TOC ratios are observed across this interval, which may be partially driven by volcanism associated with the emplacement of the Paraná-Etendeka Traps. A spike in Hg/TOC is observed immediately prior to the negative peak of the Aptian Oceanic Anoxic Event (OAE1a) CIE, supporting recent evidence of a pulse of High Arctic Large Igneous Province (HALIP) volcanic activity preceding this oceanic anoxic event.

• Galland, Olivier; Villar, Héctor J.; Mescua, José; Jerram, Dougal Alexander; Midtkandal, Ivar & Palma, J. Octavio [Vis alle 8 forfattere av denne artikkelen] (2023). The long-term legacy of subvolcanic intrusions on fluid migration in sedimentary basins: The Cerro Alquitrán case study, northern Neuquén Basin, Argentina. Basin Research. ISSN 0950-091X. 35(5), s. 1840–1855. doi: 10.1111/bre.12782. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Cooling subvolcanic igneous intrusions are known to have a substantial impact on fluid flow in the shallow Earth's crust, for example activation of geothermal systems, circulation of mineralized fluids in ore deposits, fast maturation of organic matter in sedimentary rocks and the potential release of large volumes of greenhouse gases, which have triggered mass extinctions during the Earth's history. However, the long‐term post‐cooling legacy of subvolcanic intrusions on fluid flow received much less attention. Here we describe a demonstrative geological example in the Andean foothills, Argentina, showing that igneous intrusions have long‐term effects on fluid flow after their emplacement and cooling. The case study is a ca. 11‐million‐year‐old, eroded subvolcanic conduit, at the rims of which large volumes of bitumen are naturally seeping out on the Earth's surface. This contribution highlights that intense syn‐emplacement fracturing of the magma has created high‐permeability pathways that affect the regional fluid circulations, even millions of years after cooling. Our observations reveal how extinct subvolcanic intrusions have long‐term consequences on subsurface fluid circulations, which need to be accounted for in the exploration of geothermal energy, drinkable groundwater, hydrocarbons and CO 2 sequestration in volcanic basins and regions hosting ancient shallow magma intrusions.

• Würtzen, Camilla Louise; Braathen, Alvar; Poyatos-Moré, Miquel; Mulrooney, Mark Joseph; Line, Lina Hedvig & Midtkandal, Ivar (2022). Impact of faulting in depocentres development, facies assemblages, drainage patterns, and provenance in continental half-graben basins: An example from the Fanja Basin of Oman. Basin Research. ISSN 0950-091X. 00, s. 1–39. doi: 10.1111/bre.12731. Fulltekst i vitenarkiv Vis sammendrag

  Fault throw gradients create transverse folding, and this can influence accommodation creation and sedimentary routing and infill patterns in extensional half-graben basin. The Fanja half-graben basin (Oman) offers an excellent outcrop of an alluvial fan succession displaying cyclical stacking and basin-scale growth-fold patterns. These unique conditions allow for an investigation of fault-timing and accommodation development related to fault-transverse folding. Our study combines geological mapping, structural analysis, sedimentary logging and correlation, and bulk mineralogical compositions. Mapping reveals that the basin is bounded by a regional-scale fault, with local depocentres changing position in response to transverse syncline and anticline development ascribed to fault-displacement gradients. The alluvial Qahlah Formation (Late Cretaceous) is unconformably overlying the Semail Ophiolite, and is in turn overlain by the marine Jafnayn Formation (Late Palaeocene). Facies and stratigraphic analysis allows for subdivision of the Qahlah Formation into four informal units, from base to top: (i) laterite in topographic depressions of the ophiolite, (ii) greenish pebbly sandstones, deriving from axially draining braided streams deposited in the low-relief half-graben basin. This green Qahlah grades vertically into the red Qahlah, formed by alluvial fanglomerates and floodplain mudstones, with drainage patterns changing from fault-transverse to fault-parallel with increasing distance to the main fault. The red Qahlah can be divided into (iii) the Wadi al Theepa member, found in a western basin depocentre, with higher immaturity and sand: mud ratio, suggesting a more proximal source, and (iv) the Al Batah member, located in the eastern part of the basin. The latter shows better sorting, a lower sand: mud ratio, and more prominent graded sub-units. It also shows eastward expansion from an orthogonal monocline, ascribed to accommodation developed in a relay ramp. Changes in sedimentary facies and depositional patterns are consistent with differential mineralogical composition. The Green Qahlah is composed of quartz and lithic mafic rock fragments, sourced from the ophiolite and schists of the metamorphic basement. The Red Qahlah is composed of chert and kaolinite sourced from the Hawasina Nappe succession in the footwall of the master fault. These changes in source area are linked to unroofing of fault-footwalls and domal structures during the extensional collapse of the Semail Ophiolite. The novelty of this study resides in linking sedimentology and fault-displacement events controlling fault-perpendicular folding, and its influence on depocentre generation and stratigraphic architecture. This is an approach seldom considered in seismic analysis, and rarely analysed in outcrop studies, thus placing the results from this study among the key outcrop-based contributions to the field.

• Serck, Christopher Sæbø; Braathen, Alvar; Hassaan, Muhammad; Faleide, Jan Inge; Riber, Lars & Messager, Grégoire [Vis alle 7 forfattere av denne artikkelen] (2022). From metamorphic core complex to crustal scale rollover: Post-Caledonian tectonic development of the Utsira High, North Sea. Tectonophysics. ISSN 0040-1951. 836. doi: 10.1016/j.tecto.2022.229416. Fulltekst i vitenarkiv
• Liberty, Lee M.; Yelton, Jonathan; Skurtveit, Elin; Braathen, Alvar; Midtkandal, Ivar & Evans, James P. (2022). Regolith and host rock influences on CO<inf>2</inf> leakage: Active source seismic profiling across the Little Grand Wash fault, Utah. International Journal of Greenhouse Gas Control. ISSN 1750-5836. 119. doi: 10.1016/j.ijggc.2022.103742. Fulltekst i vitenarkiv Vis sammendrag

  Understanding carbon dioxide (CO2) reservoir to surface migration is crucial to successful carbon capture and sequestration approaches; especially fault/reservoir interactions under injection pressure. Through seismic imaging, we explore regolith and shallow stratigraphy across the Little Grand Wash fault. The presence of natural CO2 seeps, travertine and tufa deposits confirm modern and ancient fault-controlled CO2 leakage. We consider this an analogue for a long-failed sequestration site. We estimate bulk porosity and fracture density for host rock, regolith, and fault zone from petrophysical relationships. When combined with existing geochemical and geological data, we characterize a 60 m wide damage zone that represents the primary surface delivery channel for CO2 originating from reservoir depths. Within this damage zone, low seismic velocities suggest sediments have formed through host rock chemical dissolution or mechanical weathering. In contrast, velocities within the adjacent host rock are consistent with low fracture density clastic rocks. We measure anomalously high seismic velocities within the fault zone along one profile that best represents a sealed (cemented/plugged) low permeability, relic flow channel. This suggests that shallow fault zone permeability varies along strike. While regional stress changes may account for decadal- to millennial-scale changes in CO2 pathways, we speculate that the total fluid pressure has locally reduced the fault's minimum horizontal effective stress; thereby producing both low- and high-permeability fault segments that either block or promote fluid migration. Studying CO2 migration in this system can inform potential risks to future sequestration projects and guide monitoring efforts.

• More, Miquel Poyatos; García-García, F.; Rodríguez-Tovar, F.J.; Soria, J.; Viseras, C. & Pérez-Valera, F. [Vis alle 7 forfattere av denne artikkelen] (2022). Sharp-based, mixed carbonate–siliciclastic shallow-marine deposits (upper Miocene, Betic Cordillera, Spain): The record of ancient transgressive shelf ridges? Sedimentary Geology. ISSN 0037-0738. 429. doi: 10.1016/j.sedgeo.2021.106077. Fulltekst i vitenarkiv Vis sammendrag

  Isolated sharp-based sedimentary bodies in shelf settings can develop via the reworking of regressive deposits during transgressions. An example of these are shelf ridges, formed under a wide range of processes, and widely studied due to their high reservoir potential. However, there is still a lack of examples in mixed (carbonate–siliciclastic) successions. This study presents an outcrop example from the Upper Miocene of the Betic Cordillera (Spain), with the aim to propose a model for the development of transgressive sharp-based mixed carbonate–siliciclastic deposits, and to provide criteria to differentiate these from their regressive counterparts. The studied succession is ca. 300 m-thick, and shows a cyclic alternation of coarse and fine-grained mixed deposits. Depositional cycles start with siliciclastic-dominated offshore to offshore transition deposits, progressively replaced by lower shoreface deposits. These are abruptly truncated by sharp erosive contacts bioturbated by passively-infilled large burrows; their ichnological features allow assignation to the Glossifungites ichnofacies. These contacts are interpreted as ravinement surfaces. They are overlain by mixed carbonate–siliciclastic barforms, rich in skeletal fragments and extraclasts, and displaying large-scale cross bedding. These form several m-thick and hundreds of m-long depositional elements interpreted as mixed shelf ridges. These ridges formed in a fine-grained, shallow-water shelf, which occasionally received coarse siliciclastic sediment supply via gravity flows, but had a coeval offshore carbonate factory, which provided the skeletal fragments. The sharp-based, coarser-grained nature and lithological break at the base of these mixed carbonate–clastic deposits could lead to their misinterpretation as forced-regressive wedges. However, the nature of their lower contact, combined with the reworked offshore skeletal fragments, and their stacking pattern are consistent with these mixed units forming during transgression. Other studies in relatively time-equivalent deposits have demonstrated the existence of coeval regressive, coarser siliciclastic-dominated shoreline systems in relatively close localities. These evidence a complex basin configuration in the area during the upper Miocene, with the development of local depocentres and relatively narrow corridors or seaways in the Mediterranean–Atlantic connection, which could have favoured shelf reworking processes, but also promoted the development of diverse stacking patterns, reflecting the differential interaction between active tectonics and sedimentation across the region.

• 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.

• Würtzen, Camilla Louise; Osmond, Johnathon; Faleide, Jan Inge; Nystuen, Johan Petter; Anell, Ingrid & Midtkandal, Ivar (2021). Syn- to post-rift alluvial basin fill: seismic stratigraphic analysis of Permian-Triassic deposition in the Horda Platform, Norway. Basin Research. ISSN 0950-091X. doi: 10.1111/bre.12644. Fulltekst i vitenarkiv
• Faleide, Thea Sveva; Braathen, Alvar; Lecomte, Isabelle Christine; Mulrooney, Mark Joseph; Midtkandal, Ivar & Bugge, Aina J. [Vis alle 7 forfattere av denne artikkelen] (2021). Impacts of seismic resolution on fault interpretation: Insights from seismic modelling. Tectonophysics. ISSN 0040-1951. 816. doi: 10.1016/j.tecto.2021.229008. Fulltekst i vitenarkiv Vis sammendrag

  Seismic mapping of subsurface faults is hampered by factors such as seismic resolution, velocity control for depth conversion and human bias. Here, we explore the challenges and pitfalls related to interpreting normal faults by comparing objective and subjective uncertainties. A panel of 20 interpreters, with different geoscientific backgrounds, interpreted faults in modern conventional (dominant frequency 40 Hz) and high-resolution P-Cable (dominant frequency 150 Hz) 3D seismic data from the Hoop area, SW Barents Sea. The interpretations created by the test-panel were sorted into 10 scenarios characterized by different fault geometries. These scenarios were explored with 2(3)D point-spread function based convolution seismic modelling to investigate the potential of seismic data to image detailed fault architectures. The results reveal that: (1) Statistical analysis shows considerable variations between manually picked faults. (2) Identifying the location of fault tips is challenging and smaller antithetic faults are rarely recognizable. (3) Uncertainties arise from masking of closely spaced fault segments even where displacement values are large, showing distorted reflection signatures of apparent extensional fault tip monoclines. The distortion is larger for conventional versus high-resolution data. (4) In the conventional and high-resolution seismic data the vertical resolution of closely spaced reflections and small offset faults is 20 m and 5 m, respectively. (5) The utilisation of high-resolution seismic data, combined with seismic modelling, add confidence to interpretation of conventional seismic data in the same area. We conclude that subsurface fault mapping with seismic data requires insight in objective uncertainties associated with the data. Automatic machine-learning fault interpretation is void of subjective bias but still hampered by objective limitations. Further, a risking workflow requires acknowledgement of uncertainties that are transferred to seismic based fault analysis techniques such as juxtaposition analysis, quantitative fault seal analysis, and fault stability analysis.

• Stokke, Ella W.; Jones, Morgan Thomas; Riber, Lars; Haflidason, Haflidi; Midtkandal, Ivar & Schultz, Bo [Vis alle 7 forfattere av denne artikkelen] (2021). Rapid and sustained environmental responses to global warming: The Paleocene-Eocene Thermal Maximum in the eastern North Sea. Climate of the Past. ISSN 1814-9324. 17(5), s. 1989–2013. doi: 10.5194/cp-17-1989-2021. Fulltekst i vitenarkiv Vis sammendrag

  The Paleocene–Eocene Thermal Maximum (PETM; ∼ 55.9 Ma) was a period of rapid and sustained global warming associated with significant carbon emissions. It coincided with the North Atlantic opening and emplacement of the North Atlantic Igneous Province (NAIP), suggesting a possible causal relationship. Only a very limited number of PETM studies exist from the North Sea, despite its ideal position for tracking the impact of both changing climate and NAIP activity. Here we present sedimentological, mineralogical, and geochemical proxy data from Denmark in the eastern North Sea, exploring the environmental response to the PETM. An increase in the chemical index of alteration and a kaolinite content up to 50 % of the clay fraction indicate an influx of terrestrial input shortly after the PETM onset and during the recovery, likely due to an intensified hydrological cycle. The volcanically derived zeolite and smectite minerals comprise up to 36 % and 90 % of the bulk and clay mineralogy respectively, highlighting the NAIP's importance as a sediment source for the North Sea and in increasing the rate of silicate weathering during the PETM. X-Ray fluorescence element core scans also reveal possible hitherto unknown NAIP ash deposition both prior to and during the PETM. Geochemical proxies show that an anoxic to sulfidic environment persisted during the PETM, particularly in the upper half of the PETM body with high concentrations of molybdenum (MoEF > 30), uranium (UEF up to 5), sulfur (∼ 4 wt %), and pyrite (∼ 7 % of bulk). At the same time, export productivity and organic-matter burial reached its maximum intensity. These new records reveal that negative feedback mechanisms including silicate weathering and organic carbon sequestration rapidly began to counteract the carbon cycle perturbations and temperature increase and remained active throughout the PETM. This study highlights the importance of shelf sections in tracking the environmental response to the PETM climatic changes and as carbon sinks driving the PETM recovery.

• Braathen, Alvar; Petrie, Elisabeth; Nystuen, Tonje; Sundal, Anja; Skurtveit, Elin & Zuchuat, Valentin [Vis alle 8 forfattere av denne artikkelen] (2020). Interaction of deformation bands and fractures during progressive strain in monocline - San Rafael Swell, Central Utah, USA. Journal of Structural Geology. ISSN 0191-8141. 141. doi: 10.1016/j.jsg.2020.104219. Fulltekst i vitenarkiv Vis sammendrag

  Folds in porous sandstone in cases allow identification of progressive deformation in an evolving strain field. In the Navajo Sandstone of the km-scale Laramide-style monocline of the San Rafael Swell (Utah, USA), four populations of small-scale structures record different kinematics and deformation mechanisms, depending on orientation to bedding within the first-order fold. Small-scale structures span from cataclastic (shear-) compaction and shear-isochoric deformation bands to dominant disaggregation (shear-) dilation bands. Extension and shear fractures record transformations from band to fracture formation, adding to the structural diversity. Early structures record semi-penetrative shear deformation guided by bedding and lamination in eolian deposits, consistent with layer-parallel shortening. Subsequent deformation is localized and at a higher angle relative to bedding, recording forward-directed and subsequently backward-directed shear structures within the east-verging monocline. Final deformation is highly localized and appears as a conjugate set of sub-vertical shear zones with shortening-extension axes oblique to the monocline. For the given conditions in a progressive shear system in highly porous sandstones, interactions of deformation bands and fractures suggest a revival of deformation bands by mutual shear band-fracture systems as developing band swarms rotate into an extensional strain sector during folding. In cases of deformation by shear-dilation strain, deformation bands may evolve directly into fractures, as grain contacts are lost.

• Braathen, Alvar; Petrie, Elizabeth; Nystuen, Tonje; Sundal, Anja; Midtkandal, Ivar & Skurtveit, Elin [Vis alle 7 forfattere av denne artikkelen] (2020). Interaction of deformation bands and fractures during progressive strain in monocline - San Rafael Swell, Central Utah, USA. Journal of Structural Geology. ISSN 0191-8141. Fulltekst i vitenarkiv
• Sleveland, Arve; Midtkandal, Ivar; Galland, Olivier & Leanza, Hector Armando (2020). Sedimentary Architecture of Storm-Influenced Tidal Flat Deposits of the Upper Mulichinco Formation, Neuquén Basin, Argentina. Frontiers in Earth Sciences. ISSN 1863-4621. 8. doi: 10.3389/feart.2020.00219. Fulltekst i vitenarkiv Vis sammendrag

  This study reports on the Lower Cretaceous upper Mulichinco Formation in the Neuquén Basin, west-central Argentina. The studied succession comprises shallow marine strata, deposited in a mixed wave and tidal flat environment where ebb-tidal currents dominated. We describe mixed storm- and tide-influenced deposits within progradationally stacked high-frequency sequences and discuss process interaction, sediment dispersal, and preservation potential. These storm and tidal deposits mix spatially on bed, bedset, and sequence scales, suggesting multi-scale process interactions. The study investigates a 12-km-long continuous outcrop, oriented sub-parallel to the paleocoastline. The succession comprises subtidal flat and meandering tidal channel complexes, with interbedding and interfingering of storm and tidal deposits. The tidal deposits are widespread and comprise moderately sorted sandstones with bimodal paleocurrent directions, single and double mud drapes, reactivation surfaces, and inclined heterolithic stratification. Varying bimodal paleocurrent directions suggest that the paleocoastline was irregular, consisting of both protrusions and bays. Storm deposits are mainly found erosively interbedded with subtidal flat sandstones, and exhibit decimeter-thick, well-sorted hummocky and swaley cross-stratified sandstones. These storm deposits show systematic lateral variations in abundance, from dominant to absent, which are linked to subtle variations in water depth along the irregular paleocoastline. As the tidal deposits are widespread across the study area, and with no significant facies change, the varying dispersal of storm-influenced deposits is considered a product of wave refraction, with converging and diverging wave energy at interpreted positions of coastal protrusions and embayments, respectively. Consequently, the irregular paleocoastline morphology caused spatial variability in wave impact and controlled preservation of interbedded storm and tidal deposits at the coastal protrusions while facilitating complete tidal remobilization of sediments in the embayments. With no evidence for fluvial influence, ebb-tidal currents are considered as the main drivers for sediment dispersal onto the subtidal flat, through the meandering tidal channels.

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• Wagner, Jan David; Serié, Christophe; Mosociova, Tereza; Polonio, Israel & Midtkandal, Ivar (2026). Rewriting the Source: Seismic Evidence for Norwegian Mainland Provenance in the Åre Formation, Mid-Norwegian Margin. Fulltekst i vitenarkiv
• Mosociova, Tereza; Serié, Christophe; Wagner, Jan David; Polonio, Israel & Midtkandal, Ivar (2026). Source-to-sink dynamics during a multi-stage rifting, mid-Norwegian continental margin. Fulltekst i vitenarkiv
• Wagner, Jan David; Serié, Christophe; Mosociova, Tereza; Polonio, Israel & Midtkandal, Ivar (2025). Rewriting the Source: Seismic Evidence for Norwegian Mainland Provenance in the Åre Formation, Mid-Norwegian Margin. Fulltekst i vitenarkiv
• Mosociova, Tereza; Serié, Christophe; Wagner, Jan David; Polonio, Israel & Midtkandal, Ivar (2025). Tectonostratigraphic Evolution of the Permo-Triassic Rift Basin Fill, Offshore Mid-Norway. Fulltekst i vitenarkiv
• Serié, Christophe; Polonio, I.; Mosociova, Tereza & Midtkandal, Ivar (2025). Regional 3D Seismic Tectono-Stratigraphy and Geomorphology Study Documenting Rift Initiation Along the Mid-Norwegian Continental Margin. First EAGE Workshop on the Triassic and Jurassic Plays in Northwest Europe. 2025, s. 1–5. doi: 10.3997/2214-4609.202534012. Fulltekst i vitenarkiv
• Ghinassi, M.; Baccarin, M.; Yperen, Anna van; Finotello, A.; Maitan, R. & Midtkandal, Ivar [Vis alle 7 forfattere av denne artikkelen] (2025). Assessing the reliability of tidal sedimentary structures to detect efficiency of tidal processes: examples from the Venice Lagoon and the Po River Delta, Northern Italy. Fulltekst i vitenarkiv
• Mosociova, Tereza; Serie, Christophe & Midtkandal, Ivar (2025). Tectonostratigraphic Evolution of the Permo-Triassic Rift Basin Fill, Offshore Mid-Norway. First EAGE Workshop on the Triassic and Jurassic Plays in Northwest Europe. 2025, s. 1–5. doi: https:/www.earthdoc.org/content/proceedings/jurassic-triassic-plays-2025. Fulltekst i vitenarkiv
• Gilmullina, Albina; Mordasova, Alina V.; Grundvåg, Sten-Andreas; Pedersen, Leif-Erik Rydland; Jelby, Mads Engholm & Jelby, Mads E. [Vis alle 10 forfattere av denne artikkelen] (2025). Provenance and sediment supply during the Cretaceous in the Great-er Barents Sea Basin. Fulltekst i vitenarkiv
• Mosociova, Tereza; Serie, Christophe & Midtkandal, Ivar (2025). Tectonostratigraphic Evolution of the Permo-Triassic Rift Basin Fill, Offshore Mid-Norway. Fulltekst i vitenarkiv
• Nygaard, Madeleine Skov; Planke, Sverre; Berndt, Christian; Zastrozhnov, Dmitry; Faleide, Jan Inge & Jones, Morgan Thomas [Vis alle 18 forfattere av denne artikkelen] (2025). Mimir High Core-log-seismic Integration. Fulltekst i vitenarkiv
• Svensen, Henrik Hovland; Callegaro, Sara; Kjøll, Hans Jørgen; Midtkandal, Ivar; Whattam, Jack William & Dalslåen, Bjørgunn Heggem [Vis alle 10 forfattere av denne artikkelen] (2024). Rhomb porphyry lavas from the Oslo Rift revisited: New insights from construction-related boreholes and cores. Fulltekst i vitenarkiv
• Whattam, Jack; Svensen, Henrik Hovland; Midtkandal, Ivar; Jerram, Dougal Alexander & Callegaro, Sara (2024). Mafic volcaniclastic deposits in the Oslo Rift. Fulltekst i vitenarkiv
• Holden, Nora; Alaei, Behzad; Skurtveit, Elin; Braathen, Alvar; Midtkandal, Ivar & Osmond, Johnathon L. [Vis alle 8 forfattere av denne artikkelen] (2024). CO2 storage on the Horda Platform - Assessing structural complexities and fault-seal integrity. Fulltekst i vitenarkiv
• Holden, Nora; Skurtveit, Elin; Braathen, Alvar; Alaei, Behzad; Midtkandal, Ivar & Osmond, Johnathon L. [Vis alle 8 forfattere av denne artikkelen] (2024). CO2 storage on the Horda Platform. Fulltekst i vitenarkiv
• Holden, Nora; Alaei, Behzad; Skurtveit, Elin; Braathen, Alvar; Midtkandal, Ivar & Osmond, Johnathon L. [Vis alle 8 forfattere av denne artikkelen] (2024). Structural de-risking of CO2 storage sites on the Horda Platform. Fulltekst i vitenarkiv
• Yperen, Anna van; Holbrook, John; Miquel, Poyatos-More & Midtkandal, Ivar (2024). Backwater length estimates in modern and ancient fluvio-deltaic settings: review and proposal of standardized workflows. Fulltekst i vitenarkiv Vis sammendrag

  The backwater effect (i.e. adjustments in open-channel flow as a response to proximity of standing water) is used to predict down-dip changes in fluvial morphodynamics and consequent sediment distribution on delta plains. However, there is currently no standardized method to obtain input parameters to estimate backwater length, nor consensus on where to measure these variables, for both modern and ancient settings. This study reviews existing methods for estimating backwater lengths in ancient and modern settings and proposes workflows to minimize ambiguity in resultant estimates. The proposed workflows are tailored to both modern and ancient settings and are prioritized based on practicality, accuracy, smallest uncertainty ranges and allow different data types as input parameters. For the first time, application of multiple methods, i.e. the proposed workflows, is tested on a single modern and ancient river system. In the modern case study, riverbed intersection with sea level matches previously documented major changes in sedimentary trends. However, backwater lengths based on h/S (h = maximum bankfull channel dept, S = slope) plot downstream of this zone characterized by major changes, when input parameters are derived from discharge and grain size. In the ancient case study, backwater lengths based on maximum bankfull channel depth and slope based on Shields’ empirical relation with grain size, match changes in fluvial architectural style interpreted as a result of backwater effects. The proposed workflows facilitate comparability and applicability of future backwater length estimates and their corresponding influence on the hydrodynamic environment and ultimately quantification of source-2-sink segments.

• Yperen, Anna van; Holbrook, John; Poyatos-Moré, Miquel & Midtkandal, Ivar (2024). Backwater length estimates in modern and ancient fluvio-deltaic settings: review and proposal of standardized workflows. Fulltekst i vitenarkiv Vis sammendrag

  The backwater effect (i.e. adjustments in open-channel flow as a response to proximity of standing water) is used to predict down-dip changes in fluvial morphodynamics and consequent sediment distribution on delta plains. However, there is currently no standardized method to obtain input parameters to estimate backwater length, nor consensus on where to measure these variables, for both modern and ancient settings. This study reviews existing methods for estimating backwater lengths in ancient and modern settings and proposes workflows to minimize ambiguity in resultant estimates. The proposed workflows are tailored to both modern and ancient settings and are prioritized based on practicality, accuracy, smallest uncertainty ranges and allow different data types as input parameters. For the first time, application of multiple methods, i.e. the proposed workflows, is tested on a single modern and ancient river system. In the modern case study, riverbed intersection with sea level matches previously documented major changes in sedimentary trends. However, backwater lengths based on h/S (h = bankfull thalweg channel dept, S = slope) plot downstream of this zone characterized by major changes, when input parameters are derived from discharge and grain size. In the ancient case study, backwater lengths based on bankfull thalweg channel depth and slope based on Shields’ empirical relation with grain size, match changes in fluvial architectural style interpreted as a result of backwater effects. The proposed workflows facilitate comparability and applicability of future backwater length estimates and their corresponding influence on the hydrodynamic environment and ultimately quantification of source-2-sink segments.

• Wong, Po Wan; Midtkandal, Ivar & Faleide, Jan Inge (2024). Early Paleogene rift-to-drift transition at the NE Atlantic – new insights from rift propagation and paired extension-compression. Fulltekst i vitenarkiv
• Bello, G.; More, M. Poyatos; Cabello, P.; Yperen, Anna van; Holbrook, J. & Midtkandal, Ivar [Vis alle 7 forfattere av denne artikkelen] (2024). . 3D characterization of sedimentary heterogeneity and its impact on reservoir properties in amalgamated fluvial sheet sandstones: Montllobar Formation (Ypresian, Tremp-Graus Basin, Spain). Fulltekst i vitenarkiv
• Rodriguez-Blanco, Leticia; Poyatos-Moré, Miquel; Anell, Ingrid & Midtkandal, Ivar (2024). Controls and geometries of small-scale nested clinoforms within a larger clinothem in the Sobrarbe Deltaic Complex, Ainsa Basin, Spain. Fulltekst i vitenarkiv
• More, Miquel Poyatos; Anell, Ingrid & Midtkandal, Ivar (2024). Controls and geometries of small-scale nested clinoforms within a larger clinothem in the Sobrarbe Deltaic Complex, Ainsa Basin, Spain. Fulltekst i vitenarkiv
• Yperen, Anna van; Tognin, Davide; Maitan, Riccardo; Bellizia, E.; Finotello, Alvise & Midtkandal, Ivar [Vis alle 7 forfattere av denne artikkelen] (2024). Finding tidal signatures in river-flood bar deposits in a micro-tidal mixed-energy deltaic setting (Po River, Italy). Fulltekst i vitenarkiv Vis sammendrag

  Recent advances in understanding the morpho-sedimentary dynamics of mixed-energy coastal systems highlight that the interplay of processes (i.e., tides, waves, river) can be cryptic to decipher in ancient sedimentary successions, where common evidence for tidal sedimentary processes can lead to ‘overinterpretation’ of tidal energy. Modern river-and-delta systems offer direct measurements of whether tidal signatures may be present in deltas without clear evidence of tidal control on their overall morphology. To this end, we evaluated the relative importance of tidal and river processes in deposition occurring in the backwater and fluvial marine transition zone (180 km long), of the Po River (Italy). The Po River debouches in the micro-tidal Northern Adriatic Sea and is considered a river-wave, mixed-energy, fluvio-deltaic system based on the absence of macro-morphometric features considered diagnostic of tidal control on morpho-sedimentary processes (e.g., channel funneling). Sediment cores from side-attached bars in the distalmost ~30 river kilometers show heterolithic facies, sparse double mud drapes, sand-mud couplets and sporadic bidirectional current ripples. Trenches reveal meter-scale cycles of alternating intervals with well-defined and poorly-defined laminae in the distal reaches of the delta. In combination with historical water-level data, these cycles are interpreted to result from semi-diurnal tidal modulation during river floods. This contrasts the lack of cyclic patterns in trenches in proximal reaches of the study area, and the rare occurrence of similar cycles in the medial reaches. This study highlights that preservation of tidal rhythmites within intertidal bar deposits is possible, despite the microtidal setting and dominance of river energy at times of deposition. Further, despite no discernible control of tidal forcing on the Po River delta morphodynamics, tide-related structures are widespread. Hence, we support the idea that care should be taken in interpreting dominance of processes based on the occurrence of sedimentary structure, and vice versa.

• Rodriguez-Blanco, Leticia; Anell, Ingrid; Midtkandal, Ivar & Poyatos-Moré, Miquel (2024). Assessing controls on clinoform geometries from outcrop studies. Fulltekst i vitenarkiv
• Bello, G.; Tejedor, F.; Poyatos-More, M.; Cabello, P.; Yperen, Anna van & Holbrook, J. [Vis alle 8 forfattere av denne artikkelen] (2024). 3D characterization of sedimentary heterogeneity and its impact on reservoir properties in amalgamated fluvial sandstones: Montllobar Formation (Ypresian, Tremp-Graus Basin). Fulltekst i vitenarkiv Vis sammendrag

  In this work we present the study of an amalgamated fluvial sandstone body in the Montllobar Formation (Lower Eocene, Tremp-Graus Basin, Pyrenees), based on facies and paleocurrent analysis, fluvial architecture and stratigraphic correlation, complemented by UAV imagery, together with 3D modelling of facies and reservoir properties. The studied unit shows a multi-storey pattern, with up to three vertically stacked channel fills, mainly composed by coarse- to fine-grained sandstones. These sandstones stack and amalgamate forming mid-channel and lateral bars, interbedded with lenticular mudstone levels, and occasionally conglomerate layers. These features are consistent with the interpretation of a braided fluvial system with a sinuous component, developed under low accommodation conditions and/or high sedimentary input, with a nearby alluvial fan. 3D modelling of the unit characterises the internal facies variability, with porosity, vertical and horizontal permeability values based on subsurface analogs from the North Sea. The presence of thin mudstone lenses results in local baffles and low vertical connectivity; however, the lateral migration of channels and horizontal accumulation of bar deposits would enhance lateral connectivity and fluid expansion in a hypothetical reservoir.

• Toribio, A.; Yperen, Anna van; Poyatos-More, M.; Fuste, J.; Gomez-Gras, D. & Lopez, E. [Vis alle 10 forfattere av denne artikkelen] (2024). The influence of marine processes in fluvial architecture from the Montllobar and Castigaleu formations (Ypresian, Pyrenees). Fulltekst i vitenarkiv Vis sammendrag

  In this study we analise the effect of marine processes in the variability of channel deposits from the Montllobar and Castigaleu formations (Tremp-Graus Basin). Through a stratigraphic, sedimentological, and petrological analysis of different examples of channel deposits (isolated/amalgamated), we have defined their geometry, facies and depositional processes, and established their sedimentary provenance. Our results reveal that channels in the more proximal sections are dominated by sandstones and conglomerates, forming laterally accreting bar complexes (isolated channels) or multistorey complexes (amalgamated channels) with evidence of subaerial exposure and root bioturbation. Basinward, the aspect ratio of channels increases in width (isolated channels) or becomes more variable (amalgamated channels), and a decrease in the root bioturbation is observed, together with a progressive increase in mudstones, bioclasts and invertebrate bioturbation in the channel-fill deposits, all attributed to a higher marine influence. However, the petrological analysis reveals the median grain size of sandstones stays relatively coarse and constant throughout all channels, together with a moderate to poor sorting. This is interpreted to reflect the continuous influence of two transverse alluvial systems: one closer to the proximal part of the system, with a source area dominated by Mesozoic cover rocks, and another closer to the distal part of the system, dominated by igneous rocks. Results of this work suggest that in this case the influence of the marine basin had a stronger effect in the resulting geometry of the channels, than the presence of local coarse-grained supply from transverse alluvial systems.

• Augland, Lars Eivind; Midtkandal, Ivar; Svensen, Henrik Hovland & Planke, Sverre (2024). Detrital zircons in reworked tephra deposits – a proxy for contourites? Fulltekst i vitenarkiv
• Nygaard, Madeleine Skov; Planke, Sverre; Berndt, Christian; Zastrozhnov, Dmitry; Faleide, Jan Inge & Jones, Morgan Thomas [Vis alle 24 forfattere av denne artikkelen] (2024). PALMAR – Paleogene Basin Development on the Vøring and Møre Margins. Fulltekst i vitenarkiv
• Nygaard, Madeleine Skov; Planke, Sverre; Berndt, Christian; Zastrozhnov, Dmitry; Faleide, Jan Inge & Jones, Morgan Thomas [Vis alle 24 forfattere av denne artikkelen] (2024). IODP Exp. 396 Drilling and High-Resolution 3D Seismic on the Mimir High. Fulltekst i vitenarkiv
• Skurtveit, Elin; Midtkandal, Ivar & Braathen, Alvar (2023). A naturally occurring CO2 laboratory in Utah. Fulltekst i vitenarkiv
• Skurtveit, Elin; Petrie, Elizabeth S.; Smith, Scott Adam; Faleide, Thea Sveva; Sundal, Anja & Choi, Jung Chan [Vis alle 10 forfattere av denne artikkelen] (2023). Core analysis from Little Grand Wash fault, Utah, and application for fault risk assessment for co2 storage in the Norwegian North Sea. Fulltekst i vitenarkiv Vis sammendrag

  Fault zones contain a mixture of lithologies, various fault structures, and evidence for fluid-rock interaction events, representing a record of multiple deformation events during the faulting history. The resulting complex and highly variable mixture of properties makes faults challenging structures to model, and specifically assessing the fault zone permeability and probability of reactivation is difficult. The ability of fault zones to transport fluids has received renewed attention during the last 10 years of developing subsurface, geological storage reservoirs for CO2. The North Sea sedimentary basin offshore Norway has an enormous potential for storing CO2. However, to qualify fault traps in saline aquifers for storage, improved workflows for fault risk assessment focusing on fault zone flow properties and mechanical stability is needed. An improved approach for fault modelling is under development: we quantify the uncertainties in fault rock properties to address the probability of failure and subsequent changes in permeability. To support our understanding of subsurface faults in the North Sea, we utilize knowledge from the Little Grand Wash (LGW) fault, located in Emery County, Utah. The LGW fault zone provides a natural laboratory to study fault zone development in geological analogues, failure mechanisms, and fluid migration. As a supplement to already published well data and core descriptions from this area, three new cores were retrieved from the fault in 2019. In total 16.5 meters of core, covering both the hanging wall (Jurassic Brushy Basin Member of the Morrison Formation) and footwall (Jurassic Summerville Formation) damage zone, have been logged and sampled for petrophysical analysis and mechanical testing. The current work presents new data on variation of permeability, porosity, strength, and sonic velocity inside the fault damage zone, including measurements on different lithologies, various types of cementation and selected deformation bands, fractures, and veins. Petrophysical and chemical analysis combined with visual identification of oil stains and bleaching provide the possibility for a holistic understanding of the system and we derive valuable knowledge for improving fault risk workflows applicable for CO2 storage projects in the Norwegian North Sea.

• Whattam, Jack; Svensen, Henrik Hovland; Midtkandal, Ivar; Callegaro, Sara & Jerram, Dougal Alexander (2023). Intermittent cessation and renewal of volcanism in the Oslo Rift revealed through detailed mapping and stratigraphy. Fulltekst i vitenarkiv
• Midtkandal, Ivar (2023). Changes in basin fill instigated by tectonic scenarios. Fulltekst i vitenarkiv
• Midtkandal, Ivar (2023). COTEC-prosjektet - økt kunnskap om CO2-inneslutninger og overvåkningsteknikker. Fulltekst i vitenarkiv
• Braathen, Alvar & Midtkandal, Ivar (2023). Plans for a Suprabasins-II proposal. Fulltekst i vitenarkiv
• Rodriguez-Blanco, Leticia; Poyatos-Moré, Miquel; Anell, Ingrid & Midtkandal, Ivar (2023). Controls and geometries of nested clinoforms in the Sobrarbe deltaic system, Ainsa Basin, Spain. Fulltekst i vitenarkiv
• Vicedo, v; Robles-Salcedo, R; Poyatos-Moré, Miquel; Braathen, Alvar & Midtkandal, Ivar (2022). Evolution of a Paleogene shallow-marine platform in the northern sector of the Ibra Basin (NE Oman). Fulltekst i vitenarkiv
• Anell, Ingrid; Braathen, Alvar; Midtkandal, Ivar; Olsen, Stine Grimsrud; Haugen, Maria & Wallace, Malcolm W (2022). Geometric controls on clinoforms, the building blocks of sedimentary basins – from ripple to shelf-edge. Fulltekst i vitenarkiv
• Yperen, Anna van; Holbrook, John M.; More, Miquel Poyatos & Midtkandal, Ivar (2022). Assessing predictability in tide-influenced river channel morphology – can we take previous concepts one step further? Fulltekst i vitenarkiv Vis sammendrag

  An increasing number of studies link down-dip changes in channel morphodynamics on rivers and their delta plains to backwater effects, i.e. non-uniform flows causing flow deceleration and subsequent net deposition during low water discharge, or flow acceleration leading to net erosion during high water discharge (e.g. Chatanantavet et al., 2012; Lamb et al., 2012; Nittrouer et al., 2012; Fernandes et al., 2016; Martin et al., 2018; Trower et al., 2018; Ganti et al., 2019; Smith et al., 2020). A potential predictability exists on backwater-mediated trends in changing channel width, depth, sinuosity, and grain size, which in turn controls resulting sedimentary architecture and distribution of heterogeneities. However, backwater concepts originated and are predominantly tested on fluvial-dominated modern river systems. A recent study on large tide-dominated modern river deltas (n=5) shows a consistent area of change in upstream to downstream trends in channel morphology, of which some changes in channel morphodynamics are different from expected backwater-mediated changes (Gugliotta and Saito, 2019). In this study we use satellite data analysis to examine down-dip changes in channel width and sinuosity from 15 modern tide-influenced deltas along their fluvial to marine transition zone. Distances are normalized for comparison across different delta plain sizes. Previously published backwater lengths are sensitive to different acquisition methods which weakens their comparability. We aim to minimize ambiguity by combining digital elevation profiles with channel depth from bathymetric surveys or empirically derived from width-thickness relationships, to detect where the riverbed equals sea level and subsequent backwater length. The results show no significant distance relationship between the backwater length and area of morphological change (i.e. zone recording a change in channel width and sinuosity). Eight out of fifteen deltas show a clear area of morphological change. The other delta plains lack clear areas of morphological change, or changes in channel morphology (i.e. sinuosity or width) occur at different areas along the river system. By comparing the area of morphological change with the apex-to-shoreline distance, the regression line shows a near-one-to-one relationship although the five largest delta plains plot outside the 95% confidence interval. This suggests that factors controlling the area of morphological change and apex location may be different on the largest delta plains than on smaller tide-influenced systems. This presentation will discuss the potential and shortcomings of combining previously established concepts to improve predictability of changes in tide-influenced channel morphology. Preliminary results show that the expected upstream-to-downstream changes (i.e. an increase in channel width and a decrease in channel depth and sinuosity) in large tide-dominated deltas cannot be directly applied to smaller and/or tide-influenced deltas. This cautions against inferring knowledge from large and/or river-dominated delta plains to directly apply to systems with any size and/or process regime system, as the response scale to changes in controlling factors will be different depending on delta plain size and dominant controlling factors. Additionally, it suggests uncertainty in applying these concepts to ancient fluvio-deltaic systems, as the influence of additional variables such as differences in global sea-level conditions is currently not investigated.

• Yperen, Anna van; Holbrook, John M.; More, Miquel Poyatos & Midtkandal, Ivar (2022). Improving predictability of changes in tide-influenced channel morphology – can we take previously established concepts one step further? Fulltekst i vitenarkiv Vis sammendrag

  An increasing number of studies links down-dip changes in riverine morphodynamics on delta plains to backwater effects, i.e. flow deceleration as a river approaches a standing water body and subsequent deposition. A potential predictability exists on backwater-mediated trends in changing river channel width, depth, sinuosity, and grain size, which in turn controls resulting sedimentary architecture and distribution of heterogeneities. However, backwater concepts originated and are predominantly tested on fluvial-dominated modern rivers. A recent study on large tide-dominated modern river deltas (n=5) shows a consistent area of change in upstream to downstream trends in channel morphology, of which some are different than expected backwater-mediated changes. Preliminary results of our study on a larger data set with tide-influenced deltas, show that the expected upstream-to-downstream changes in large tide-dominated deltas cannot be directly applied to smaller and/or tide-influenced deltas. This presentation will discuss the potential and shortcomings of combining previously established concepts to improve predictability of changes in tide-influenced channel morphology. Caution is needed when inferring knowledge from large and/or river-dominated delta plains, as the response scale to changes in controlling factors will be different depending on delta plain size and dominant controlling factors.

• 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.

• Würtzen, Camilla Louise; More, M.P; Midtkandal, Ivar & Braathen, Alvar (2022). The impact of faulting in depocentre development, facies assemblages, drainage patterns, and provenance in continental half‐graben basins: an example from the Fanja Basin of Oman. Basin Research. Fulltekst i vitenarkiv
• Braathen, Alvar; Midtkandal, Ivar & Osmundsen, Per Terje (2022). Geomorphology of continental rift landscapes - analyses inspired by North Sea observations. Fulltekst i vitenarkiv
• Braathen, Alvar & Midtkandal, Ivar (2022). Suprabasins – where do we go? Fulltekst i vitenarkiv
• Würtzen, Camilla Louise; Midtkandal, Ivar; Mulrooney, Mark Joseph & Braathen, Alvar (2022). Fault-influence in alluvial deposits of the Qahlah Formation - provenance, depocenter development, drainage patterns, and facies assemblage of Upper Cretaceous Fanja Basin, northeastern Oman. Fulltekst i vitenarkiv
• Midtkandal, Ivar (2022). Depositional signatures of tectonic keel basin – Ibra Basin. Fulltekst i vitenarkiv
• Braathen, Alvar & Midtkandal, Ivar (2022). Suprabasins – where do we go? Fulltekst i vitenarkiv
• 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

• Midtkandal, Ivar (2022). Clinothemes next to a fault-tip monocline in the Ibra Basin, Oman. Fulltekst i vitenarkiv
• Zuchuat, Valentin; Augland, Lars Eivind; Jones, Morgan Thomas; Sleveland, Arve R.N.; Twitchett, Richard & Tovar, Francisco J Rodríguez [Vis alle 13 forfattere av denne artikkelen] (2022). The Permian-Triassic boundary across the Barents Shelf: an intricate record of climate change, mass extinction, recovery, and basin reorganisation. EGU General Assembly. doi: 10.5194/egusphere-egu22-2379. Fulltekst i vitenarkiv
• Serck, C.S; Braathen, Alvar; Faleide, J.I.; Midtkandal, Ivar & Kjølhamar, Bent (2021). Multi-stage rifting, fault reactivation styles and growth basin architecture; evolution of the Terningen Fault Complex, southwestern Barents Sea. Fulltekst i vitenarkiv
• 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.

• Midtkandal, Ivar; Zuchuat, Valentin; Petrie, Elizabeth & Liberty, Lee (2021). COTEC. Fulltekst i vitenarkiv Vis sammendrag

  The multi-disciplinary, multi-institution approach to monitoring CO2-flow in the subsurface is presented, and represented by examples from sedimentology, structural geology, and seismic monitoring.

• Osmundsen, Per Terje; Braathen, Alvar; Gresseth, Julie Linnea; Midtkandal, Ivar; More, M.P & Peron-Pinvidic, Gwenn [Vis alle 7 forfattere av denne artikkelen] (2021). Detachment faulting, successive incision and supradetachment basin evolution in large-magnitude extensional systems. Fulltekst i vitenarkiv
• Faleide, Thea Sveva; Braathen, Alvar; Lecomte, Isabelle; Mulrooney, Mark Joseph; Midtkandal, Ivar & Bugge, A.J [Vis alle 7 forfattere av denne artikkelen] (2021). Exploring extensional fault interpretations from seismic reflection data of various resolution substantiated by seismic modelling. Fulltekst i vitenarkiv
• Zuchuat, Valentin; Liberty, Lee; Petrie, Elizabeth; Hafner, Alison; Arvesen, Brock & Alterskjær, Camilla [Vis alle 10 forfattere av denne artikkelen] (2021). On CO2 monitoring techniques and the importance of collaborating during times of crisis. Fulltekst i vitenarkiv
• Serck, Christopher Sæbø; Riber, Lars; Braathen, Alvar; Faleide, Jan Inge & Midtkandal, Ivar (2021). Structural development of the Utsira High - ideas and challenges. Fulltekst i vitenarkiv
• Yperen, Anna van; Holbrook, John M.; Poyatos-Moré, Miquel; Ahokas, Juha & Midtkandal, Ivar (2021). Improving predictability of changes in tide-influenced channel morphology – implications for exploration and reservoir analogue studies. Fulltekst i vitenarkiv
• Holbrook, John M.; More, Miquel Poyatos; Ahokas, Juha & Midtkandal, Ivar (2021). Improving predictability of changes in tide-influenced channel morphology – implications for exploration and reservoir analogue studies. Fulltekst i vitenarkiv Vis sammendrag

  An increasing number of studies links down-dip changes in riverine morphodynamics on delta plains to backwater effects, i.e. flow deceleration as a river approaches a standing water body and subsequent deposition. Because of the enhanced deposition, this particular transitional zone of changing river and coastal controls is of interest for exploration studies targeting coastal plain depositional systems. A potential predictability should exist on backwater-mediated trends in changing river channel width, depth, sinuosity, and grain size, which in turn controls resulting sedimentary architecture and distribution of heterogeneities in tide-influenced channel-fill bodies. However, backwater concepts originated and are predominantly tested on fluvially-dominated modern rivers and supported by numerical models assuming simplified input parameters. Consequently, the downdip changes of morphological configuration of channels on tide-influenced delta plains, and the role that backwater effect plays on this are yet to be tested. These backwater effects hold potential to better understand and predict changes in fluvio-depositional style in the subsurface as well. Ancient delta plains of the Triassic Boreal Ocean are among the largest in Earth’s history and characterized by a low-gradient depositional setting, which is considered one of the key factors for the development of such large delta plains. Here, differences in channel types are documented but controlling factors on their distribution and sediment partitioning are not fully understood. Large modern rivers building vast delta plains show similar characteristic, typically having high sediment loads, deep channels and low-gradient slopes. The latter two characteristics imply that there backwater lengths will be longer compared to smaller river systems. Are there differences is channel behavior because of these scaling differences, or is the response scale invariant? In order to investigate potential scaling relationships between the backwater length and morphological trends on tide-influenced coastal plains, the minimum information required is river channel depth, width, sinuosity and backwater length, the latter depending on river slope and river depth. Other potential forcing factors on river patterns are the catchment area, total river length, prevailing climate, discharge, and coastal plain gradient. Shelf width, tidal range, tidal prism and wave height constitute factors linked to the ocean basin. For most of these components, publicly available global datasets exists. However, access to one of the key parameters to perform this study, i.e. river depth, is rather problematic as bathymetric surveys are unavailable for most of the planet. The use of remote sensing techniques is limited due to the high suspended sediment concentrations typical of coastal plain rivers which hampers penetration of radar or laser beams. Indirect estimates of river depth by using statistical river width-depth relations are considered inapplicable as tidal dynamics can modify these relationships, and is among the targets for this study. This presentation discusses the ideal dataset for performing such a study and highlights the main challenges obtaining some of the key parameters. We will show preliminary results and discuss their potential to establish predictable scaling relationships between backwater length and changes in tide-influenced channel morphology. Additionally, results will provide insights into controls on channel patterns on tide-influenced delta plains, which can be used to select modern analogues for subsurface case studies and improve reservoir characterization.

• Zuchuat, Valentin; Midtkandal, Ivar; More, Miquel Poyatos; Costa, Sigrid Da; Brooks, Hannah Louise & Halvorsen, Kristine [Vis alle 9 forfattere av denne artikkelen] (2021). Mind The Gap: Composite and diachronous stratigraphic surfaces in low-gradient, transitional settings: The J-3 “unconformity” and the Curtis Formation, east-central Utah, U.S.A. Fulltekst i vitenarkiv
• Yperen, Anna Elisabeth van; Midtkandal, Ivar; More, Miquel Poyatos & Holbrook, John M. (2021). Diachronous key stratigraphic surfaces in low-accommodation settings fluvio-deltaic settings. Fulltekst i vitenarkiv Vis sammendrag

  The adequate documentation and interpretation of regional-scale stratigraphic surfaces is paramount to establish correlations between continental and shallow marine strata. In active depositional systems however, these surfaces are often composite and hence diachronous, which contradicts their original appreciation. This is particularly true in low-accommodation settings due to their amalgamated nature. This study utilizes the ~400 km transect of the Cenomanian Mesa Rica Sandstone (Dakota Group, USA); an example of an exhumed depositional profile across a river-to-delta system. The near-continuous outcrop exposure allows mapping of down-dip changes in facies, thickness distribution, fluvial architecture and spatial extent of stratigraphic surfaces. The two sandstone units of the Mesa Rica Sandstone represent contemporaneous fluvio-deltaic deposition in the Tucumcari sub-basin (Western Interior Basin) during two regressive phases. Multivalley deposits pass down-dip into single-story channel sandstones and eventually into distributary channel deposits and delta-front strata. Additionally, multi-storey channel deposits bound by erosional composite scours incise into underlying deltaic deposits. These represent incised-valley fill deposits. The erosional composite surface below fluvial strata in the continental realm represents a sequence boundary/regional composite scour (RCS) and can be mapped for >300 km. Basal distributary composite scours, composite surfaces bounding incised valleys, and basal surfaces below dispersed trunk channels incising into deltaic deposits occur at sub-regional scale. The RCS’ diachronous nature demonstrates that its down-dip equivalent disperses into several surfaces in the marine part of the depositional system, which challenges the idea of a single, correlatable surface. Formation of a regional composite scour in the fluvial realm throughout a relative sea-level cycle highlights that erosion and deposition occur virtually contemporaneously at any point along the depositional profile. This contradicts stratigraphic models that interpret low-accommodation settings to dominantly promote bypass, especially during forced regressions. Source-to-sink analyses should account for this in order to adequately resolve timing and volume of sediment storage in the system throughout a complete relative sea-level cycle.

• Würtzen, Camilla Louise; Osmond, Johnathon L.; Faleide, Jan Inge; Nystuen, Johan Petter; Anell, Ingrid Margareta & Midtkandal, Ivar (2021). Syn- to post rift alluvial basin fill: seismic stratigraphic analysis of Permian-Triassic deposition in the Horda Platform. Fulltekst i vitenarkiv
• Yperen, Anna Elisabeth van; Holbrook, John M.; More, Miquel Poyatos & Midtkandal, Ivar (2021). Diachronous key stratigraphic surfaces in low-accommodation fluvio-deltaic settings: from the Dakota Group (USA) to the Cretaceous on Svalbard/Barents Sea. Fulltekst i vitenarkiv Vis sammendrag

  The adequate documentation and interpretation of regional-scale stratigraphic surfaces is paramount to establish correlations between continental and shallow marine strata. In active depositional systems however, these surfaces are often composite and hence diachronous, which contradicts their original appreciation. This is particularly true in low-accommodation settings due to their amalgamated nature. This study utilizes the ~400 km transect of the Cenomanian Mesa Rica Sandstone (Dakota Group, USA), which offers an outstanding example of an exhumed full-transect depositional profile across a river-to-delta system. The near-continuous outcrop exposure allows mapping of down-dip changes in facies, thickness distribution, fluvial architecture and spatial extent of stratigraphic surfaces. The two sandstone units of the Mesa Rica Sandstone represent contemporaneous fluvio-deltaic deposition in the Tucumcari sub-basin (Western Interior Basin) during two regressive phases. Multivalley deposits pass down-dip into single-story channel sandstones and eventually into contemporaneous distributary channel deposits and delta-front strata. Additionally, multi-storey channel deposits bound by erosional composite scours incise into underlying deltaic deposits. These represent incised-valley fill deposits, based on their regional occurrence, estimated channel tops below the surrounding topographic surface and coeval downstepping delta-front geometries. The erosional composite surface below fluvial strata in the continental realm represents a sequence boundary/regional composite scour (RCS) and can be mapped for >300 km. Basal distributary composite scours, composite surfaces bounding incised valleys, and basal surfaces below dispersed trunk channels incising into deltaic deposits occur at sub-regional scale. The RCS’ diachronous nature demonstrates that its down-dip equivalent disperses into several surfaces in the marine part of the depositional system, which challenges the idea of a single, correlatable surface. This work is important to understand other low-accommodation systems elsewhere, such as Lower Cretaceous strata on Svalbard and in the Barents Sea. Here, correlation between onshore and offshore depositional systems has been hampered due to – amongst others – the lack of preserved Lower Cretaceous strata in parts of the northern Barents Sea. Acknowledgment of the diachronous nature of key stratigraphic surfaces holds potential to improve the understanding of fluvio-marine correlations and sandstone distribution. In general, formation of a regional composite scour in the fluvial realm throughout a relative sea-level cycle highlights that erosion and deposition occur virtually contemporaneously at any point along the depositional profile. This contradicts stratigraphic models that interpret low-accommodation settings to dominantly promote bypass, especially during forced regressions. Source-to-sink analyses should account for this in order to adequately resolve timing and volume of sediment storage in the system throughout a complete relative sea-level cycle.

• Yperen, Anna Elisabeth van; More, Miquel Poyatos; Holbrook, John M. & Midtkandal, Ivar (2021). Internal mouth-bar variability and differential preservation of coastal-process indicators in low-accommodation deltaic settings. Fulltekst i vitenarkiv Vis sammendrag

  Mouth bars are fundamental architectural elements of deltaic successions. Understanding their internal architecture and complex interaction with coastal processes (fluvial-, tide- and wave-dominated) is therefore paramount to the interpretation of ancient deltaic successions. This is particularly challenging in low-accommodation systems because they are commonly characterized by a thin, condensed and top-truncated expression. In this study we analyze the exhumed Cenomanian Mesa Rica Sandstone (Dakota Group, Western Interior Seaway, USA), which encompasses a fluvio-deltaic system along a ~450 km depositional dip-parallel profile. The study targets the proximal deltaic expression of the system, using 22 sedimentary logs (total of 390 m) spatially correlated within a ~25 km2 study area at the Tucumcari Basin margin. Analysis of facies distribution, depositional architecture and stratigraphic surfaces mapping reveals a 6–10-m-thick, sharp-based and sand-prone deltaic package, comprising several laterally-extensive (>1.4 km width) mouth bars. Within those, we distinguish four different along-strike sub-environments based on differences in grain size, sedimentary structures, bed thicknesses, and bioturbation indices; these are mouth bar axis, off-axis, lateral fringe to distal lateral fringe deposits, and overall reflect waning depositional energy with increasing distality from the distributary channel mouth. The interpreted mouth-bar components also show internal variability in dominant process regime, with overall river dominance but local preservation of tide influence in the lateral fringe and distal fringe environments. However, mouth-bar deposits amalgamate to form an extensive sand-rich sheet body throughout the study area, in which interflood mudstone to very-fine grained sandstone beds are nearly absent. This indicates a low accommodation/supply (A/S) setting, which promoted recurrent channel avulsion/bifurcation and thus reworking of mouth-bar fringe and distal-fringe sediments, where background coastal processes tend to be better recorded. Trends in along-strike changes in sedimentary characteristics from axial to lateral environments are also recognized in other wave- and river-dominated deltaic settings as well, where axial components consist of higher energy facies associations resulting from high-density currents, whereas heterolithics become dominant towards the fringes, where there is an alternation of low- and high-density deposits combined with an increased recording of finer-grained facies associations. Complemented with our study, this suggests that internal hierarchy of mouth bars is evident and observed regardless of dominant coastal processes. Consequently, subdivision of mouth bars into different components can reduce complexity of models deriving from a myriad of facies subdivisions, and guide prediction of facies changes and sand distribution in future studies of proximal deltaic settings. Finally, results of this study evidence internal process-regime variability within mouth-bar components. This cautions against relying solely on the preserved deposits at one given location in a system to infer dominant and subordinate coastal processes (e.g. tidal indicators), with a consequent risk of underestimating the true mixed-influence nature of low-accommodation deltaic settings.

• Serck, Christopher Sæbø; Poyatos-Moré, Miquel; Midtkandal, Ivar; Braathen, Alvar; Olaussen, Snorre & Osmundsen, Per Terje [Vis alle 7 forfattere av denne artikkelen] (2021). Tectonic basins around basement domes, Oman II. Fulltekst i vitenarkiv
• Holbrook, John M.; More, Miquel Poyatos & Midtkandal, Ivar (2021). Sheet-like delta-front sandstone deposits in a river-dominated low-accommodation setting (Dakota Group, USA). Fulltekst i vitenarkiv
• Midtkandal, Ivar (2021). Isostatic rollback of faults and perched basins – some observations. Fulltekst i vitenarkiv
• Midtkandal, Ivar (2021). Fan complexes in rifts – can we forecast their tectonic setting? Fulltekst i vitenarkiv
• Serck, Christopher Sæbø; Braathen, Alvar; Faleide, Jan Inge; Hassaan, Muhammad; Riber, Lars & Midtkandal, Ivar (2021). Pre-Jurassic structural configuration of the Utsira High - Restoring the Viking Graben Boundary Fault. Fulltekst i vitenarkiv
• 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.

• More, Miquel Poyatos; Schwarz, Ernesto; Boya, Salvador; Gomis-Cartesio, Luz Elena & Midtkandal, Ivar (2021). Multi-scale influence of topography on shallow-marine successions associated with long-term transgressions. Fulltekst i vitenarkiv
• Serck, Christopher Sæbø; Braathen, Alvar; Faleide, Jan Inge; Hassaan, Muhammad; Riber, Lars & Midtkandal, Ivar (2021). The Utsira High: Fault kinematics, structural restoration and the importance of unconformities. Fulltekst i vitenarkiv
• Faleide, Thea Sveva; Braathen, Alvar; Lecomte, Isabelle; Mulrooney, Mark Joseph; Anell, Ingrid Margareta & Midtkandal, Ivar [Vis alle 7 forfattere av denne artikkelen] (2020). Testing seismic interpretation of faults by modelling; viable geometries versus seismic resolution in the subsurface. EAGE extended abstracts. 2020. doi: 10.3997/2214-4609.202011930. Fulltekst i vitenarkiv
• Braathen, Alvar; Osmundsen, Per Terje; Midtkandal, Ivar & Serck, Christopher Sæbø (2020). Devonian extensional tectonics in Svalbard; Raudfjorden’s synclinal basin above the Keiserhjelmen detachment. Fulltekst i vitenarkiv

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