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Mouth bars are the fundamental architectural elements of proximal deltaic successions. Understanding their internal architecture and complex interaction with coastal processes (fluvial, tide and wave‐dominated) is paramount to the interpretation of ancient deltaic successions. This is particularly challenging in low‐accommodation systems, because they are commonly characterized by thin, condensed and top‐truncated sections. This study analyses the exhumed Cenomanian Mesa Rica Sandstone (Dakota Group, Western Interior Seaway, USA), a fluvio‐deltaic system covering a ca 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 ca 25 km2 study area at the rim of the Tucumcari Basin. Analysis of facies distributions, depositional architecture and spatial extent of stratigraphic surfaces reveals a 6–10 m thick, sharp‐based and sand‐prone deltaic package, comprising several laterally extensive (>1.4 km width) mouth bars. Composite erosional surfaces infilled with multi‐storey fluvial and marine‐influenced channel deposits (12–20 m thick, 100–250 m wide) scour locally into the deltaic package. Based on differences in sedimentary structures, bed thicknesses, occurrence of interflood beds and bioturbation indexes, four different sub‐environments within single mouth bars were distinguished. These range from mouth‐bar axis, off‐axis, fringe to distal‐fringe deposits, which reflect waning depositional energy with increasing distance 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 fringe and distal fringe components. 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. These features reflect successive coalescence of mouth bars in a low accommodation/supply (A/S) setting. These conditions promoted recurrent channel avulsion/bifurcation and thus the potential reworking of previously deposited mouth‐bar fringe and distal‐fringe sediments, where time and background processes are better recorded. Results of this study evidence internal process‐regime variability within mouth‐bar components. They also caution against the possible loss of preservation of subordinate coastal processes (e.g. tidal indicators), and consequent underestimation of the true mixed influence in low‐accommodation deltaic settings.

Most of the Arctic region is contained within the territory of Norway, Russia, USA, Canada and Denmark/Greenland, yet the natural boundaries and processes do not conform to these political borders. This remote region requires special logistics, equipment and substantial financial support. The last decade has seen an increase in knowledge about the northern polar region for economic and political reasons, such as the extended continental shelf claims under UNCLOS and Arctic Council activities.It is crucial that scientific research, activities and their outcome are visible to the broader scientific community and communicated to the wider public. In recent years considerable effort has been invested by several groups and institutions to make various data and results available online and to use it for education and outreach. Examples include: the Arctic Observing Viewer which is a web mapping application in support of U.S. SEARCH, AON, SIOS, and other Arctic Observing networks (https://arcticobservingviewer.org/); Arctic Research Mapping Application (https://armap.org/) and the NSF Arctic Data Center (https://arctic data.io) for locating projects and data supported by US funding agencies; Svalbox (www.svalbox.no), a database for digital outcrop models from Svalbard, the comprehensive PANGAEA database (https://www.pangaea.de), a data publisher for Earth and Environmental sciences; and GeoMapApp (http://www.geomapapp.org/), a map-based application for browsing, visualizing and analyzing a diverse suite of curated global and regional geoscience data sets.While a wealth of data can be located and viewed in these databases and data repositories, the scientific community and geoscience educators may benefit from a collection of geological and geophysical data that can be easily visualized, analyzed and used for a quick assessment of present-day geodynamic setting and further for paleogeographic reconstructions in the circum-Arctic region.Consequently, a group of scientists from four Arctic countries and their collaborators are aiming to consolidate and further develop the Arctic-related common scientific basis and educational programmes under the auspices of the Norwegian Research Council programme INTPART (International Partnerships for Excellent Education, Research and Innovation).The project NOR-R-AM (https://norramarctic.wordpress.com/), established in 2017, focused on assessing the openly available information accumulated at participating institutes. During the first phase of this project, we have gathered and interpreted data in various sub-regions, especially in Svalbard and in Russia. The second phase of the NOR-R-AM project aims to complete and launch the digital Circum-Arctic geodynamics platform. This web-based platform will incorporate geological and geophysical data and models, tomographic and kinematic models and paleogeography and paleoclimate indicators. The digital Circum-Arctic geological repository, to be hosted by our project webpage https://norramarctic.wordpress.com/, assembles the data in openly accessible formats that are compatible with GPlates, GeomapApp and Google Earth. These data are consistently formatted to simplify exchange and completely open to the scientific community.

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 km2) 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.The contourites were fed by fluvial systems on the East Shetland Platform and the Norwegian mainland, and are, in turn, often trapped by megaslide escarpments or deeper structural elements. The rapid glacial deposition of debris flows and turbidites delivered large sediment volumes to gently-dipping slopes, which then failed as megaslides. Trough mouth fans are excellent depocenters to study the interaction between along-slope and down-slope processes in high-resolution, both in space and time. We suggest that contourites are most active during interglacial periods, while turbidites and debris flows are more common during glacial periods. The timing of the megaslides, however, still includes large uncertainties. Meltwater contribution seems to be a more dominant factor for sedimentary processes in mid-latitude glacial fans than in their high-latitude counterparts.

Trough mouth fans are important depocenters for glacial sedimentation in high latitude margins, recording sedimentological processes and their relationship with paleoclimatic fluctuations on short timescales - from decades to millennia. The volume of sediments accumulated in these fans varies significantly depending on the phase of the glacial cycle, with higher values typically reached during early retreats. The input of large volumes during short time intervals can potentially trigger submarine landslides and overpressure build-up, making the understanding of processes and proportions related to sedimentation in glaciated margins crucial, especially during periods of global warming. In this study we use high-quality 3D seismic cubes (vertical resolution of 2 m and bin size of 6.25 x 18.75 m) to delimitate different types of deposits on an area over 14000 km2 on the 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 deposit their volumes were calculated using the mean thickness of the beds multiplied by their extent. The base 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 happening during approximately 4 ka (~23 to 19 ka). The package is then completed with plume settling related to the full retreat of the ice stream. Although not completely interpreted due to limitations of the dataset extent and remobilization of a part of the fan by the Storegga Slide in the northern part, 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 comprise volumes of 1105 km3 and 1205 km3. This accounts to a significant variability of the magnitude of sediment volume coming into the sink per year, with the downslope deposits having over 100 times more sediment input and the plumites 5 times more when compared to the contourites. These results highlight the range of sediment volume that can be delivered in a glaciated margin depending on changes in processes and climatic fluctuations, which may also entail changes in the potential geohazards.

About 252 million years ago, near the end of the Permian, the Earth experienced its most dramatic mass extinction, caused by magmatic intrusions and volcanic eruptions associated with the Siberian Traps Large Igneous Province. This led to catastrophic global climatic changes, impacts of which lasted well into the Early Triassic.Here, we summarise the results gathered from the study of sedimentary successions spread across the Barents Shelf that recorded the End Permian Mass Extinction (EPME) and its aftermaths across the Permian-Triassic boundary. Data and samples were collected from the Festningen section in western Spitsbergen; the DD-1 core and the associated river section in Deltadalen, central Spitsbergen; a core (7933/4-U-3) drilled by the Norwegian Petroleum Directorate offshore Kvitøya in northern Svalbard; and a core (7130/4-1; production licence 586) recovered from the Finnmark Platform in the Barents Sea. A series of state-of-the-art analyses were conducted on the collected material, including detailed facies analysis, organic and C-isotope geochemistry, mercury content, geochronology, high resolution XRF core scanning, petrography, ichnology, and palaeontology. Analyses were, where relevant, tied to the outcrops using digital outcrop models.Traditionally, the Permian-Triassic boundary in Svalbard (and across the High Arctic regions) was placed at the marked and rapid facies change at the top of the siliceous mudstones and spiculites of the Kapp Starostin Formation, which are overlain by soft, non-siliceous mudstones and siltstones of the Vardebukta and Vikinghøgda formations. This abrupt facies change, which also marks the collapse of sponges, occurs across a few centimetres. Given that the non-siliceous mudstones were definitely of Early Triassic age, based on ammonoid biostratigraphy, this lithostratigraphic boundary was believed to represent a lacuna or a hiatus of several million years, with the uppermost Permian strata absent from the sedimentary record.The base of the Triassic, however, is not defined by ammonoid biostratigraphy but by the conodont Hindeodus parvus, which was recently reported to occur a few meters above the lithostratigraphic boundary in the Deltadalen section. This means that the lithostratigraphic boundary is of Permian age. Additionally, our new data show that sedimentation was continuous across this lithostratigraphic boundary, corresponding to major environmental changes, potentially associated with a reorganisation of the basin(s) physiography.Furthermore, the 6-8 ‰ δ13Corg negative excursion associated with the EPME falls between the lithostratigraphic and the Permian-Triassic boundary at all measured sections. These negative carbon isotope excursions occur in intervals with numerous tephra layers, the lowest of which has been dated at 252.13 ± 0.62 Ma, potentially connecting the recorded changes to the Siberian Traps. The EPME is also corroborated by the very abrupt decline of trace fossil abundance and diversity, as anoxia extended from proximal and shallow water to deeper settings. Geochemical and ichnological data support the existence of multiple anoxic pulses, separated by very brief periods of enhanced oxygen levels. It took ca. 150 Kyr for life to recover after the EPME, based on sedimentation rate calculations. Data also suggest that the hinterland of the basin experienced a shift towards more arid climatic conditions and increased eutrophication.

Failed continental rifts are diverse intra-continental sedimentary basins that hold records of major Earth-history events. They are representative of huge tectonic forces involved in the break-up and reorganisation of continental masses and are typically accompanied by the deposition of large volumes of volcanic and sedimentary material. A significant hurdle in determining the geological history of these ancient rift zones is the recognition of, and distinction between primary volcanic material and partial reworking of unconsolidated volcanics as dominantly volcaniclastic sediments of alluvial origin. This is a fundamental distinction when interpreting geological histories and depositional settings, the difference between continued volcanism and relative quiescence. The Permian Oslo Rift is a well-studied example of a failed continental rift, nevertheless, there is much still to be investigated, especially regarding the explosive volcanism and re-sedimentation of volcaniclastic material in the later stages of the rift. The Oslo rift hosted up to 18 large calderas, formed in the middle to late stages of rift activity, yet despite the significance of this phase in the Oslo Rift these deposits have not yet been the focus of any detailed study. Significant post-rift erosion (estimated at 1-3km) has removed the youngest deposits and much of what remains is hidden by soil and undergrowth cover. The calderas are now dominated by larvikite, syenite, and granite batholiths, with lava and pyroclastic deposits in varied amounts. There is one known locality at the north-eastern edge of Oslo city, the Alnsjø field, that contains a volcaniclastic and sedimentary succession that has a partial record of the caldera volcanism phase, thought to have been preserved by subsidence within a caldera centre (the Nittedal caldera). The succession comprises aphyric to porphyritic lavas, ignimbrites, tuffs, breccias, conglomerates, sandstones, and mudstones, with faulting and a moderate degree of contact metamorphism overprinting obscuring geological reconstruction and interpretation. Although the majority of deposits are dominated by volcanic clasts and grains, many have neither a clear volcanic nor sedimentary origin. Initial results show that the succession comprises, among other things, what is likely the youngest basalt flow preserved in the rift, early explosive felsic volcanism , a thick lacustrine mudstone reflecting an extended period of quiescence, and renewed explosive activity with the transition phase clearly preserved in the upper section of the mudstone. To clarify the uncertain origins of these deposits we combine standard geological field methods with thin section analyses (microscope, scanning electron microscope (SEM), and electron microprobe), micro-computed-tomography (µCT) scanning, and geochemical analyses. Initial results suggest that the examination of matrix components may be a way to differentiate between primary and secondary origins for deposits in the Alnsjø field. Visualisation of 3D textures from µCT scans provides a more accurate understanding of paleo-flow directions, quantitative measurements of clast properties (rounding, orientation, dimensions, clast-clast relationships etc), and can be used to place the high resolution SEM analyses of thin sections (2D slice) in a 3D context. Volcanic activity was more significant at this time than previously thought as indicated by the predominantly volcanic deposits that have previously been considered alluvial.

Discrepancies in models of continental rift-basin dynamics and stratigraphic response calls on further investigation on the subject. Geometric- and lithological trends between stages of faulting is studied in the Permian- Triassic continental rift succession in the Horda Platform. The Horda Platform occupies the northeastern margin of the North Sea aulacogen where Late Permian-Early Triassic faulting shaped the Caledonian pre-rift landscape into a series of N-S trending half-graben basins, filled by Permian-Triassic strata. A tectonostratigraphic model developed from seismic- and well-data details the Permian-Triassic basin fill and structural basin development. Regional unconformities mark the top and base of the succession, while internally, six depositional sequences are delineated by erosional- and transgressive surfaces. Thickness maps reveal three syn-rift stages, where strain migrated and concentrated in different parts of the developing rift basin, from disconnected faults and scattered depocentres with varying accommodation space hosting deposits of different thicknesses, to fully linked faults bounding half-graben basins with expanded and connected depocentres. The lithology through the syn-rift stages reflect how sedimentation gradually outpace accommodation space creation. The overlying thick post-rift succession shows no evidence of rifting besides a minor fault-displacement along the Øygarden Fault Zone in the Late Triassic, reflected by slight wedging. Meanwhile distinct interchanging sand- and mud-dominated intervals reflect strong climatic fluctuations during the post-rift. The spatio-temporal heterogeneity in fluvial facies makes stratigraphic correlation challenging and is further complicated by discontinuous surfaces caused by basin floor tilting. With this study, classical sequence stratigraphic models are evaluated and revised against the observations from the Horda Platform. The stratigraphic model presented takes into account the dynamics of strain along faults through time and space and the resulting diachronic boundaries between the rift stages.

A comprehensive dataset is collated in a study on sediment transport, timing and basin physiography during the Early Cretaceous Period in the Boreal Basin (Barents Sea), one of the world’s largest and longest active epicontinental basins. Long-wavelength tectonic tilt related to the Early Cretaceous High Arctic Large Igneous Province (HALIP) set up a fluvial system that developed from a sediment source area in the NW, which flowed SE across the Svalbard archipelago, terminating in a low-accommodation shallow sea within the Bjarmeland Platform area of the present-day Barents Sea. The basin deepened to the SE with a ramp-like basin floor with gentle dip. Seismic data show sedimentary lobes with internal clinoform geometry that advanced from the NW. These lobes interfingered with, and were overlain by, another younger depositional system with similar lobes sourced from the NE. The integrated data allow mapping of architectural patterns that provide information on basin physiography and control factors on source-to-sink transport and depositional patterns within the giant epicontinental basin. The results highlight how low-gradient, low-accommodation sediment transport and deposition has taken place along proximal to distal profiles for several hundred kilometres, in response to subtle changes in base level and by intra-basinal highs and troughs. Long-distance correlation along depositional dip is therefore possible, but should be treated with caution to avoid misidentification of timelines for diachronous surfaces.

Low-accommodation deltaic systems are often challenging to interpret due to their condensed, low-gradient nature, which often results in extensive, sheet-like sandstone bodies. As a result, detailed studies of such systems are scarce, and their internal depositional architecture is still poorly understood. We analyze one such system, the Cenomanian deltaic Mesa Rica Sandstone (Dakota Group), which was deposited in the Western Interior Seaway, in east-central New Mexico, USA. A > 20-km-long escarpment, subparallel to the main delta progradation direction, allows a detailed analysis of facies distribution, depositional architecture, and the spatial extent of stratigraphic surfaces. Results reveal an arrangement of laterally variable shallowing-upward facies successions with three depositional cycles preserved. The first cycle is characterized by deltaic sheet-like sandstone bodies that are consistently overlain by sand-filled amalgamated distributary-channel deposits. The two successive cycles record a progressive reduction of sediment supply into the basin. Vertical and lateral relationships between facies associations and architectural geometries allow the recognition of regional key stratal surfaces, incised-valley fills, and the presence of lagoonal deposits at a sub-regional scale.The Mesa Rica deltaic system represents a river-dominated delta with multiple distributary channels. The sheet-like delta-front sandstone bodies are interpreted as the result of the combined effect of high sandy-sediment supply and low accommodation. The latter acted as an accelerator for autogenic depositional mechanisms such as mouth-bar deposition and abandonment, and for the highly avulsive character of distributary channels. After deposition, minor wave reworking facilitated lateral sand redistribution and favored bioturbation. This study demonstrates that sheet-like delta-front sandstone geometries from low-accommodation systems can be formed without the dominance of wave redistribution processes. This cautions against interpretations of amalgamated shoreline systems based solely on apparent sandstone geometries, without taking into account the preservation potential and postdepositional modification of primary deltaic characteristics.

Modern, tide‐dominated and tide‐influenced coastlines are characterised by a range of environments, including deltas, estuaries, and lagoons. However, some tide‐dominated basins and related sedimentary units in the rock record, such as the semi‐enclosed, shallow, Utah‐Idaho Trough foreland basin of the Jurassic Curtis sea, do not correspond to any of these modern systems. Persistent aridity caused the characteristic severe starvation of perennial fluvial input throughout this basin, in which the informal lower, middle, and upper Curtis, as well as the underlying Entrada Sandstone, and the overlying Summerville Formation were deposited. Wave energy was efficiently dissipated by the shallow basin's elongated morphology (approximately 800x150 km), as its semi‐enclosed morphology further protected the system from significant wave impact. Consequently, the semi‐enclosed, shallow‐marine system was dominated by amplified tidal forces, resulting in a complex distribution of heterolithic deposits.\ud \ud Allocyclic forcing strongly impacted upon the system's intrinsic autocyclic processes as the lower Curtis was deposited. Short‐lived relative sea‐level variations, along with uplift and deformation episodes, resulted in the accumulation of three parasequences, each separated by traceable flooding and ravinement surfaces. The subsequent transgression, which defines the base of the middle Curtis, allowed for the shallow‐marine part of the system to enter into tidal resonance as a consequence of the flooded basin reaching the optimal configuration of approximately 800 km in length, corresponding to an odd multiple of the quarter of the tidal wavelength given an average minimum water depth of 20 to 25 m. This resonant system overprinted the effects of allocyclic forcing and related traceable stratigraphic surfaces. However, the contemporaneous and neighbouring coastal dune field sedimentary rocks of the Moab Member of the Curtis Formation, characterised by five stacked aeolian sequences, as well as the supratidal deposits of the Summerville Formation, lingered to record allocyclic signals, as the Curtis sea regressed.\ud \ud This study shows that a tide‐dominated basin can enter into tidal resonance as it reaches its optimal morphological configuration, leading to the overprinting of otherwise dominant allocyclic processes by autocyclic behaviour. It is only by considering the sedimentological relationships of neighbouring and contemporaneous depositional systems that a full understanding of the dynamic stratigraphic history of a basin alternatively dominated by autocyclic and allocyclic processes can be achieved.

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.

Thick shallow-marine successions associated with long-term transgressions are less well known than their thin, well-sorted counterparts, widely studied due to their potential to form good reservoirs. In these successions, particularly in storm-dominated examples, bioturbation can obliterate primary sedimentary characteristics, making stacking patterns and sequences difficult to define, and challenging our understanding of the main controls in their resulting depositional architecture. This study presents an example from the Jurassic of the Neuquén Basin (Argentina), with the aim to: a) refine the depositional model of a thick, shallow-marine succession associated with a long-term, early post-rift transgression, b) constrain multi-scale controls on stratigraphic architecture and lateral facies variability, and c) discuss their preservation and response to post-depositional processes. To do this, a 10 km continuous exposure, with mapping, sedimentary logging and correlation of stratigraphic units, integrated with subsurface, biostratigraphic and ichnological data. The succession shows an overall retrogradational-aggradational-retrogradational stacking pattern, with several higher frequency regressive units (parasequences and parasequence sets, PSS). The lower part (PSS I) comprises laterally-discontinuous (10's of m) mouth-bars and distributary channel fills, dominated by several m-thick coarsening- and fining-up sandstone packages and m-scale erosive conglomeratic lenses. Above these, the succession (PSS II-IV) is composed by laterally-continuous (>100's of m) storm-dominated lower-shoreface to upper-offshore deposits, dominated by

Arctic carbon cycling and its regional climate have been observed to deviate from global trends in the Late Jurassic and across the Jurassic–Cretaceous boundary interval, but appear to recouple with global trends in the Early Cretaceous (Galloway et al., 2019; Jelby et al., 2020). We investigate the possible link between these observed trends and volcanism by examining the mercury (Hg) and other element records from Arctic sites in Svalbard (Norway) and the Queen Elizabeth Islands, Canada. We assess whether pulsed phases of the High Arctic Large Igneous Province, or the globally significant emplacement of Paraná-Etendeka or Greater Ontong-Java Plateau, are expressed by stratigraphic Hg trends recorded in the studied sites of Arctic Canada and Svalbard, and how any signals correlate with the regional stable carbon-isotope (δ13C) record. We compare these new data to Hg and δ13C records from other globally distributed sites, focusing on the carbon isotope excursion (CIE) intervals: the Arctic-wide Volgian CIE (“VOICE”), the global Valanginian positive CIE (“Weissert Event”), and the global early Aptian CIE associated with Ocean Anoxic Event 1a (OAE1a).

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.

Thick (>100 m-thick), highly bioturbated storm-influenced shallow-marine deposits are not frequent in the stratigraphic record, but they tend to be common in aggradational to retrogradational successions. Individual storm-event beds have typically low preservation potential in these successions, yet depositional settings are characterized on the basis of storms processes. Here we present a sedimentological study of a thick, bioturbated exhumed succession deposited during the early post-rift stage of the Neuquen Basin (Argentina) and compare its stratigraphic record with examples worldwide, in order to discuss the potential factors controlling the total overprint of storm-event beds during several million years. The Bardas Blancas Formation being 170–220 m thick in the study area is dominated by muddy sandstones and sandy mudstones, and it also includes subordinate proportions of clean sandstones and pure mudstones, collectively representing different environments of a storm-influenced shoreface-offshore system. The offshore transition and proximal offshore strata invariably comprise intensely bioturbated deposits, with only a few preserved HCS-sandstone beds. The unit shows for most of its thickness a long-term aggradational pattern spanning 7–10 Myr and is associated with low riverine influence. By combining the observations and interpretations of the Bardas Blancas Formation with other subsurface and exhumed intensely bioturbated, shallow-marine successions, we dispute the general assumption that these are associated with low frequency or low magnitude of storms. Alternatively, we argue that the long-lived efficiency of benthic fauna on overprinting most if not all the storm-event beds that reached the offshore-transition sector, results from the combination of several factors: deposition in relatively confined marine depocentres, persistent low riverine influence, and long-term aggradational stacking pattern. As these conditions can develop in a variety of basin styles, such as rift, early post-rift, and foreland settings, the recognition of thick, bioturbated successions as the ones discussed here can be used to infer more realistic constrains for depositional models and better predict facies distribution in such storm-influenced systems., Centro de Investigaciones Geológicas

The uncertainty in the safety of CO2 storage is directly linked to the understanding of potential seepage or leakage along faults or fracture zones within a storage complex. To study this phenomenon, we investigate natural CO2 leakage along the Little Grand Wash Fault (Utah, USA). Current surface flow and former seep patterns have been identified and analyzed in light of guiding deformation structures, stacked reservoir-seal systems, diagenetic status and rock strength. Preliminary active source seismic lines have been conducted at the site, including time-lapse seismics of CO2-migration events, which will be complemented with passive seismic observations in 2021. This study describes the preparation phase and first results of a multidisciplinary study including geological, geomechanical and active & passive seismic investigations.

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.

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. publishedVersion

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.

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.

Fracture stiffness and flow properties have been measured in the laboratory using naturally fractured fault rock samples from the Little Grand Wash fault, Utah, USA. We compare fracture closure and related flow change during isotropic loading of two fractures which have been subject to various amounts of paleo‐reactive flow. The two tested fractures are described as (i) a small‐aperture fracture (0.1 mm) with negligible geochemical alterations of the fracture surface and (ii) a large‐aperture fracture (0.53 mm) where precipitates are observed on the fracture surface. X‐ray imaging is used for quantification of fracture aperture and fracture surface contact distribution. The petrographical characterisation using scanning electron microscopy and x‐ray powder diffraction is performed pre‐test and describes burial and uplift diagenesis as well as pulses of reactive fluid flow within the fault. The stress dependent flow and deformation experiment provides new data on fracture stiffness and flow for naturally developed fractures in siliciclastic rock. Fracture stiffness is found to be highest for the small‐aperture fracture due to its high fracture contact ratio and well‐developed surface mating during closure. For the naturally altered and rougher, large‐aperture fracture, fracture stiffness is lower and a highly stress dependent decay in flow is observed during initial closure. The results illustrate that a natural fracture with high contact ratio and well mated surfaces will close during loading, whereas a fracture associated with high flow rates and affected by previous geochemical alteration maintains a high flow rate compared to the host rock during similar loading. Experimental investigation of natural fracture stiffness and flow properties in a faulted CO2 bypass system (Utah, USA)

The end-Permian Siberian Traps large igneous province (LIP) is temporally associated with the major extinction event at the Paleozoic-Mesozoic boundary. The extinction was likely triggered by massive eruption of carbon and halocarbon gases released from metamorphic aureoles around sill complexes in the Tunguska Basin. Additional environmental pollution was likely associated with magma degassing, forest fires, and extensive tuff formation during magma-water interaction. We have conducted detailed field work in the Norilsk area since 2006 to study the environment during the initial lava eruptions in the Siberian Traps. The field work included mapping, photogrammetric drone surveying, sampling, and subsequent inorganic geochemical and petrographic analyzes. The sediment-lava transition is particularly well exposed in the Norilsk area. In the Kajerkan quarry, shallow basaltic igneous intrusions were emplacement into the coal-rich upper part of the Tunguska Group of Late Carboniferous and Permian age. In the Ore Brook and Red Rocks localities, more than ten sub-vertical tree trunks have been mapped and sampled in the lowermost lava flow. The tree trunks are petrified wood of end-Permian age. Pillow basalts are found at the same levels, showing that the lava flow was emplaced in a wet environment. Ropy pahoehoe structures are found at the top of this flow, which suggests that the uppermost part of the lava flow was emplaced in a subaerial environment. Further south, in the Bratsk area, extensive sill intrusions and magnetite-rich hydrothermal vent complexes are abundant, documenting extensive eruptions of metamorphic gases and tuffs to the atmosphere. We have been drilling two 100-m long stratigraphic boreholes across the Permian-Triassic boundary in Svalbard, arctic Norway, to study the effect of the Siberian Traps magmatism on the sedimentary basin development some 2000-km away from the main eruption sites. The near complete core recovery, complemented by material collected in a river section ca. 1 km north-east of the drill site, allowed high-resolution analyses of the Permian-Triassic boundary interval. The cores have been logged and analyzed in detail, including organic and inorganic geochemistry, isotope geochemistry, petrography, and biostratigraphy. The Permian-Triassic boundary (PTB) is identified in the cores and lies within the Reduviasporonites chalastus Assemblage Zone, 2.50 m above the lithological change from bioturbated to dark grey, laminated mudstones. This corresponds to the local position of the Late-Permian Mass Extinction event (LPME) and its associated sharp negative δ13Corg excursion. High-resolution environmental proxies indicate a dramatic change in provenance across the PTB, and a transition towards a more arid climate in the earliest Triassic. This transition was contemporaneous with prolonged bottom-water dysoxic or anoxic conditions, following a Late Permian increase in volcanic activity, probably linked to the emplacement of the Siberian Traps LIP. Zircons have been separated from numerous basaltic ash layers in this sequence, and a few have been successfully dated with the U-Pb TIMS method and overlap in age with the Siberian Traps magmatism. This study shows that the Siberian Traps LIP had a major impact of both the basin development and life in the arctic Barents Sea region.

The Triassic continental succession located in the eastern side of the Horda Platform (northern North Sea) represents a potential supplementary CO2 storage formation to the principal Jurassic sandstones above. Several 1-2.5 kilometer-thick packages of Triassic sediment lie within a series of large eastward-dipping half-grabens east of the Viking Graben. The deeply buried Triassic deposits (1.8-3 km) within the prospective area are confined between the Øygarden Fault Zone to the east and the Vette Fault Zone to the west, the latter separating the prospective area from the Troll hydrocarbon fields. Despite extensive petroleum exploration within the Horda Platform, the entire Triassic interval remains largely untested and its storage potential poorly understood. The lack of wellbore penetrations and 3D seismic coverage means that reservoir quality can only be assessed using conceptual predictions and analogue studies.A seismic stratigraphic model is built using available 2D and 3D seismic and integrated well log data to discern the Triassic basin fill history and structural development of the area. The stratigraphic succession is subdivided into seismic facies, where reflection patterns infer depositional characteristics. A shift in log facies trend between mud- and sand-rich intervals indicates a variance in subsidence rate and sedimentation supply related to tectonic displacement rate and climate. Visual analyses of the seismic data along key horizons also reveal depositional features such as channels, hanging wall fans, and footwall fans. The location and distribution of the channels are mapped in order to assess the connectivity of possible storage bodies.Analogous Triassic sandstone reservoirs of the Snorre field (Tampen Spur) roughly 125 km away are similar in terms of stratigraphic facies and mineralogy. The Snorre field reservoirs are dominantly subarkosic and arkosic sandstones with illite-smectite and chlorite-smectite and lesser amounts of kaolinite and chlorite clay minerals within the matrix and pore spaces. Furthermore, the Triassic succession is composed of sandstones and mudstones deposited in fluvial systems with subordinate alluvial plain environments. The sandstones possess highly variable poro-perm values closely related to the depositional facies. As the Horda Platform sediments were deposited more proximal to the source than those of the Tampen Spur, it is expected that coarser grain sizes persist within the prospective interval, but perhaps at a lower degree of maturity and higher grain size variability. Overall, this preliminary assessment suggests that thick Triassic channel sandstones present in the eastern Horda Platform have promising CCS potential. Keywords. Triassic, Horda Platform, CCS, basin fill history, seismic facies, tectonic displacement, climate, reservoir quality

Upper Cretaceous and Paleocene sandstone strata represent promising reservoirs along the NE Atlantic margins, including new discoveries in recent years that has spurred increased activity in the area. Exploration and seismic imaging is complicated by massive Paleocene magmatism related to late rifting and early breakup, forming voluminous sill and dyke complexes hosted in the sedimentary succession and extrusive complexes, such as volcanic edifices and lava flows along the margin. Such igneous activity may have played an important role in the thermal and chemical history of reservoir zones. Their diagenetic properties as well as their physical appearance is expected to have been altered by the intrusions, breaking predictive trends otherwise common for deep-marine sedimentary strata. A new understanding of the nature and implication of igneous processes and deposition of sediments, combined with new understanding of sand source-to-sink systems in the region, is thus important to better evaluate the prospectivity of the southern Møre Basin. The focus of this project will therefore be to asses sand provenance and depositional systems in basins in this area by incorporating on shore field work with integrated borehole and seismic studies. The main goal is to develop a new understanding of deposition of sand fairways during the Late Cretaceous and Paleogene to better understand this part of the break-up history of the NE Atlantic.

The study describes the depositional development and sediment partitioning in a prograding paralic Triassic succession. The deposits are associated with the advance of large prism‐scale clinoforms across a shallower platform area. Approaching the platform, the limited accommodation and associated relative higher rates of deposition generated straighter clinoforms with lower foreset angles. The vertical restriction across the platform is interpreted to have amplified the tidal signature. Sediment was redistributed from the coast into increasingly sandy delta‐front deposits, compared to offshore equivalents. The deposits comprise extensive compound dune fields of amalgamated and increasingly clean sandbodies up‐section. Rapid deposition of significant amounts of sand led to differential subsidence and growth‐faulting in the delta front, with downthrown fault blocks further amplifying the tidal energy through funnelling. A mixed‐energy environment created along‐strike variability along the delta front with sedimentation governing process‐regime. Areas of lower sedimentation were reworked by wave and storm‐action, whereas high sedimentation rates preserved fluvially dominated mouth bars. A major transgression, however, favoured tidally dominated deposits also in these areas, attributed to increasing rugosity of the coastline. Formation of an extensive subaqueous platform between the coast and delta front dampened incoming wave energy, and tidally dominated deposits dominate the near‐shore successions. Meanwhile formation of wave‐built sand‐bars atop the platform attest to continued wave influence. The strong tidal regime led to the development of a heterolithic near‐shore tidally dominated channel system, and sandier fluvial channels up‐river. The highly meandering tidal channels incising the subaqueous platform form kilometre wide successions of inclined heterolithic stratification. The fluvially dominated channels which govern deposition on the delta plain are narrower and slightly less deep, straighter, generally symmetric and filled with cleaner sands. This study provides important insight into tidal amplification and sand redistribution during shallowing on a wide shelf, along with along‐strike process‐regime variability resulting from variations in sediment influx. © 2020 The Authors. Basin Research published by International Association of Sedimentologists and European Association of Geoscientists and Engineers and John Wiley & Sons Ltd This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

A transition from supradetachment to rift basin signature is recorded in the ~1,500 m thick succession of continental to shallow marine conglomerates, mixed carbonate‐siliciclastic shallow marine sediments and carbonate ramp deposits preserved in the Bandar Jissah Basin, located southeast of Muscat in the Sultanate of Oman. During deposition, isostatically‐driven uplift rotated the underlying Banurama Detachment and basin fill ~45° before both were cut by the steep Wadi Kabir Fault as the basin progressed to a rift‐style bathymetry that controlled sedimentary facies belts and growth packages. The upper Paleocene to lower Eocene Jafnayn Formation was deposited in a supradetachment basin controlled by the Banurama Detachment. Alluvial fan conglomerates sourced from the Semail Ophiolite and the Saih Hatat window overlie the ophiolitic substrate and display sedimentary transport directions parallel to tectonic transport in the Banurama Detachment. The continental strata grade into braidplain, mouth bar, shoreface and carbonate ramp deposits. Subsequent detachment‐related folding of the basin during deposition of the Eocene Rusayl and lower Seeb formations marks the early transition towards a rift‐style basin setting. The folding, which caused drainage diversion and is affiliated with sedimentary growth packages, coincided with uplift‐isostasy as the Banurama Detachment was abandoned and the steeper Marina, Yiti Beach and Wadi Kabir faults were activated. The upper Seeb Formation records the late transition to rift‐style basin phase, with fault‐controlled sedimentary growth packages and facies distributions. A predominance of carbonates over siliciclastic sediments resulted from increasing near‐fault accommodation, complemented by reduced sedimentary input from upland catchments. Hence, facies distributions in the Bandar Jissah Basin reflect the progression from detachment to rift‐style tectonics, adding to the understanding of post‐orogenic extensional basin systems. © 2020 The Authors. Basin Research published by International Association of Sedimentologists and European Association of Geoscientists and Engineers and John Wiley & Sons Ltd This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Summary Resolution and illumination issues in seismic data curtail identification of fault geometries and fault-initiated rock damages when mapping subsurface faults. Our goal is therefore to increase confidence in seismic interpretation of steep, normal faults by combining high-resolution seismic data and seismic modelling. The baseline case is from the Hoop area in the SW Barents Sea, covered by conventional and high-resolution P-Cable 3D seismic data. Seismic modelling is used to further test fault imaging. The seismic data were interpreted by several structural geologists and converging results from these interpretations were utilized to build a geo-model (geometry), which also include elastic parameters from well data (properties). Parameters required for the geological model include the overall fault geometry, host-rock lithofacies and the distribution of architectural elements (fault facies) within the fault zones. Misinterpretation of faults is reduced in the high-resolution dataset due to better imaging. The seismic modelling utilises a 2(3)D Point-Spread-Function based convolution approach applied to the input elastic model. A synthetic seismic modelling approach allows scenario-testing and comparison with observed faults in outcrop analogues. By combining datasets and approaches, typical pitfalls in seismic fault interpretation are highlighted, and viable fault geometries are better identified.

[Abstract The adequate documentation and interpretation of regional‐scale stratigraphic surfaces is paramount to establish correlations between continental and shallow marine strata. However, this is often challenged by the amalgamated nature of low‐accommodation settings and control of backwater hydraulics on fluvio‐deltaic stratigraphy. Exhumed examples of full‐transect depositional profiles across river‐to‐delta systems are key to improve our understanding about interacting controlling factors and resultant stratigraphy. This study utilizes the ~400 km transect of the Cenomanian Mesa Rica Sandstone (Dakota Group, USA), which 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 channels and delta‐front strata. Down‐dip changes reflect accommodation decrease towards the paleoshoreline at the Tucumcari basin rim, and subsequent expansion into the basin. 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. This opposes criteria offered to differentiate incised valleys from flood‐induced backwater scours. As the incised valleys evidence relative sea‐level fall and flood‐induced backwater scours do not, the interpretation of incised valleys impacts sequence stratigraphic interpretations. The erosional composite surface below fluvial strata in the continental realm represents a sequence boundary/regional composite scour (RCS). 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., Simplified depositional profile of the study area and Wheeler diagram showing the dispersive nature of the sequence boundaray/Regional Composite Scour (RCS) in the marine realm. Discrete parts of the composite, highly diachronous and amalgamated erosional composite surface below the fluvial deposits in the proximal zone, are time‐equivalent to individual regressive marine surfaces. Each segment of the RCS is contemporaneous to the clinoform surface underlying the genetically‐related clinothem. Similarly, segments of the composite scour bounding an incised valley are formed contemporaneously with deposition in the valley, trunk channel deposition in the proximal zone, and clinothem deposition in the distal zone. 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. ]

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.

Mud-rich prograding sediment lobes make for most of the Barremian – Albian stratigraphic record in the SW Barents Sea. Submarine canyons and channels potentially represent key components of sediment transport from shelf to basin floor but geological evidences are lacking. We present high-resolution seismic data and scrutinize an elongated, ∼150-km long bright seismic amplitude and resistive anomaly located alongslope of a NW-sourced Barremian delta in the SW Barents Sea. Seismic interpretation is performed on a comprehensive database comprising 3D/2D high-resolution P-Cable and conventional seismic data, tied to three exploration wells to provide age-control on key horizons. Our results highlight that the elongated geophysical anomaly originates from a soft layer deposited over a harder, erosional surface. The erosive morphology displays three narrow, V-shaped incisions to the NE of the Hoop area which develop into a single, ∼6 km-wide, U-shaped channel towards the transition to the Fingerdjupet Subbasin. The geological feature is named Ceres and interpreted as a submarine channel carved in Aptian, a period of marked sea level rise and sediment starvation in the Hoop area. An evolutionary model of a diverted submarine channel is proposed where a flooded delta lobe acted as a topographic barrier, funneling bottom currents and thereby carving an alongslope, possibly contouritic channel. This is the first documented case of a submarine channel pathway – delta lobe interaction on the Norwegian continental shelf. To account for the geophysical expression of Ceres, two competing explanations are discussed: (1) hydrocarbon-bearing sands, and (2) organic-rich source rock. Both scenarios have important implications for petroleum prospectivity: a faulted stratigraphic trap holding large volumes of hydrocarbons or alternatively the channel-controlled distribution of mature Aptian source rock in the SW Barents Sea. © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

Topographic depressions in mountain regions function as sediment traps and their morpho-sedimentary archives provide important insight into erosion and sediment dynamics in mountain ranges. In order to establish the (direct) drivers and timing of erosion phases in the southern central Pyrenees, small non-glaciated headwater catchments in the highly erodible Valle de la Fueva drainage basin were investigated as to their morphogenetic development. Geomorphic mapping revealed three morphogenetic complexes associated with the Valle de la Fueva drainage basin development: (i) high-lying talus plateaus and lateral slopes, (ii) extensive glacis and pedimentation surfaces, and (iii) deeply incised ravines with late-stage fluvial-cut terraces. The talus slopes are the oldest preserved geomorphic units of the Valle de la Fueva and potentially denote the initial drainage basin topography. Talus bedrock and boulder exposure ages cluster yet between 21 and 40 10Be-ka, indicating that the carbonate-dominated talus surfaces were rejuvenated during the last glacial cycle (MIS 4–MIS 2). The younger morphogenetic complexes (ii, iii) point to successive basin erosion stages from diffusive surface pedimentation under cold climate conditions (ii) to rapid linear fluvial dissection and late-stage terrace formation (iii). Denoting the abandonment of pediments as actively eroding surfaces, 10Be depth profiles of glacis cover sediments yielded consistent late MIS 2 exposure ages. The abandoning of pediments marks the onset of rapid fluvial downcutting of deep ravines (iii) around the Holocene climate transition, which involved substantial sediment routing and basin scale erosion. Lower fluvial-cut terraces denote the termination of intense catchment erosion at around 14–8–10Be-ka and minor fluvial incision during Middle-Late Holocene. This research shows that small non-glaciated mountain catchments feature valuable high-resolution morpho-sedimentary archives that are useful for assessing the direct impact of major climate transitions on surface processes and landscape transformation in mountain regions. Improvements in quantifying the timing and rates of (paleo-) surface processes are vital for enhancing regional glaciofluvial chronologies and large-scale basin erosion models that are possibly afflicted with time-averaging biases.

Based on a methodic sedimentological analysis, the Late Jurassic (Oxfordian) Curtis Formation unravels the intricate facies variability which occurs in a tide-dominated, fluvially starved, low-gradient, semi-enclosed epicontinental basin. This unit crops out in east-central Utah, between the eolian deposits of the underlying Middle Jurassic (Callovian) Entrada Sandstone, from which it is separated by the J-3 unconformity, and the conformable overlying supratidal Summerville Formation of Oxfordian age. A high-resolution sedimentary analysis of the succession led to the recognition of eight facies associations (FA) with six sub-facies associa¬tions. Based on the specific three-dimensional arrangement of these eight facies associations, it is proposed to separate the Curtis Formation into three sub-units: the lower, middle and upper Curtis. The J-3 unconformity defines the base of the lower Curtis, which consists of upper shoreface to beach deposits (FA 2), mud-domi¬nated (FA 3a) and sand-dominated heterolithic subtidal flat (FA 3b), sand-rich sub- to supratidal flat (FA 4a) and correlative tidal channel infill (FA 4c). It is capped by the middle Curtis, which coincides with the sub- to intertidal channel-dune-flat complex of FA 5, and its lower boundary corresponds to a transgressive surface of regional extent, identified as the Major Transgressive Surface (MTS). This surface suggests a potential correla¬tion between the middle and the upper Curtis and the neighboring Todilto Member of the Wanakah Forma¬tion or Todilto Formation. The upper Curtis consists of the heterolithic upper sub- to intertidal flat (FA 6) and coastal dry eolian dunes belonging to the Moab Member of the Curtis Formation (FA 7), and it conformably overlies the middle Curtis. The spatial distribution of these sub-units supports the distinction of three different sectors across the study area: sector 1 in the north, sector 2 in the south-southwest, and sector 3 in the east. In sector 1, the Curtis For¬mation is represented by its three sub-units, whereas sector 2 is dominated by the middle and upper Curtis, and sector 3 encompasses the extent of the Moab Member of the Curtis Formation. This study also highlights the composite nature of the J-3 unconformity, which was impacted by various processes occurring before the Curtis Formation was deposited, as well as during the development of the lower and middle Curtis. Local collapse features within the lower and middle Curtis are linked to sand fluid over¬pressure within a remobilized sandy substratum, potentially triggered by seismic activity. Furthermore, the occurrence of a sub-regional angular relationship between the middle Curtis and substratum implies that the area of study was impacted by a regional deformational event during the Late Jurassic, before the deposition of the middle Curtis.

Investigations of syn‐sedimentary growth faults in the Last Chance delta (Ferron Sandstone, Utah, USA) show that fault‐bounded half‐grabens arrested high amounts of sand in the mouth bar and/or distributary channel areas. Fault‐controlled morphology causes changes in routing of the delta top to delta front drainage towards the long axis of half‐grabens. Faulting was spatially and temporally non‐systematic, and polyphase, with 3D cusp/listric fault geometries instigated by linkage of variously oriented segments. Hanging wall rollover folds consisting of wedge‐shaped syn‐kinematic sand attest to rapid

Understanding geodynamic reservoir and seal performance is important in order to ensure safe storage of CO 2 . In Utah leakage from natural gas reservoirs through sandstones and along faults may be observed as diagenetic alteration traces. Aeolian deposits, stained red by iron oxides, have commonly been bleached by reducing fluids of varying density. At the study site, bleaching is observed within and along the base of a low-permeability, regionally sealing unit; the lowermost Carmel Formation. Compactional stress during progressive deformation in the San Rafael monocline induced pressure gradients driving flow through the seal and towards venting fractures. Chemical transport processes are interpreted to be a combination of diffusion and advection. Capillary barriers may be overcome as transient in situ pressures and temperatures affecting fluid properties. The same geological unit may behave as a conduit during some parts of burial/uplift-history and as a sealing unit at other times.

Regional Early Cretaceous uplift of the northern Barents Sea associated with the High Arctic Large Igneous Province (HALIP) caused the development of the fluvial to open-marine depositional system, terminating in the southwestern Barents Sea. This study has established a new temporal and spatial evolution of the Lower Cretaceous deposits in the Hoop area, in particular the location and age of the intrashelf platform lobe front and subsequent block-faulting. A composite high-resolution 3D and 2.5D P-Cable and conventional 3D seismic dataset image the strata and cross-cutting faults in the Hoop area. The P-Cable data typically have a resolution of 3–7 m in the shallow subsurface, up to four times better than the conventional seismic data, contributing to a new and better mapping hence understanding of the Lower Cretaceous strata and faults. Seismic horizon and facies mapping reveal large-scale clinoforms, with present-day heights of 150–200 m and dips of 0.65–1.13°. The highresolution data furthermore display complex stratigraphic and structural features, such as small-scale clinoforms and numerous faults. The shelf platform succession is block-faulted, and the main Early Cretaceous fault activity thus postdates the arrival of the delta and platform sediments from the northwest. Detailed seismo-stratigraphic ties to the 7324/2–1 (Apollo) and 7325/1–1 (Atlantis) wells, and ties to the adjacent Fingerdjupet Subbasin, document a Barremian age for the shelf platform deposits and an Aptian?–early Albian age for the main faulting event. The faulting was likely initiated in the Aptian, but a hiatus or condensed section above the Barremian strata makes it difficult to constrain the onset of deformation in the Hoop area.