Norwegian Barents Sea Research Articles

Formation of the Population Structure of the Atlantic Cod Gadus morhua Linnaeus, 1758 in the Quaternary Period

This paper presents a comparative analysis of the variability of genetic characteristics in samples from the largest stocks of the Atlantic cod Gadus morhua Linnaeus, 1758 in the Northeast Atlantic (NEA) and the Northwest Atlantic (NWA) waters. The results of a pairwise estimation of the genetic differentiation, performed using allozyme and microsatellite markers, detected a significant difference between the cod sample from the New England Shelf (NWA) and the cod of the Icelandic–Greenlandic and Norwegian–Barents Sea stocks. At the same time, cod samples from areas of East and West Greenland and samples from the Barents Sea, despite considerable geographic differences, demonstrated a high level of identity according to molecular genetic markers. The peculiarities of the formation of the cod population structure in the Quaternary period are considered in connection with the dynamics of global climatic and oceanological processes.

Statistical Analysis of Displacement and Length Relation for Normal Faults in the Barents Sea

This paper is devoted to the statistical analysis of dependence between fault length (L) and displacement (D). The main purpose of this work is to study the scaling relations between fault length and displacement using a database that includes datasets of 21 faults with geometric data extracted from 3D seismic coherence cubes of the Norwegian Barents Sea. Multiple linear regression and Bayesian and Akaike information criterions are applied to obtain optimal regression parameters. Our dataset is unique since it includes segment lengths of individual faults, unlike the previously published datasets. Hence, we studied both the dependence of fault segment length and accumulated fault length on displacement. The latter relation (accumulated fault length versus displacement) shows a general agreement (positive correlation and power-law relation) with the previously published results that are mainly obtained from outcrop studies, although the slopes vary for different lithologies. The differences could be attributed to the unique characteristics of our dataset that includes data of all segment lengths of individual faults.

Normal fault 3D geometry and displacement revisited: Insights from faults in the Norwegian Barents Sea

Abstract Utilizing seismic attributes, we image fault 3D geometry for 21 normal faults of different sizes in the Norwegian Barents Sea. We revisit the published models of fault shape and growth using the new dataset. Based on the maximum accumulated length ( L m a x ) of faults, we have classified them into two classes: medium size (1 ≤ L m a x ≤ 1000 m ) and long faults ( L m a x > 1000 m ). The common characteristics of these faults are: i) the medium size faults show mainly irregular shapes while long faults show a variety of shapes including irregular, rectangular, and elliptical. ii) in medium size faults maximum displacement is located close to the fault upper tip-line. iii) no lateral segmentation was observed for most of the medium size faults while long faults contain several internal segments at each depth. iv) linkage with other faults is less common in medium size faults in comparison to the long ones. v) long faults with an elliptical shape have several displacement maxima located near the fault centre or close to the upper tip-line. vi) long faults with irregular to rectangular shapes show the displacement maxima close to either upper or lower fault tip-line. Our results show that for many of the analyzed faults, the maximum displacement is located on the faults longest segment; however, this is not the case for some of the faults. We found that power-law fits well with the displacement-length and displacement-height relations of the faults. Furthermore, the aspect ratio, the ratio between fault maximum accumulated length and height is high for the studied faults and ranges between ∼1.5 and ∼16. The results can shed light on the understanding of fault geometry and growth for a variety of applications including geological and mechanical models incorporating faults.

Late Paleozoic seismic sequence stratigraphy and paleogeography of the paleo-Loppa High in the Norwegian Barents Sea

Abstract The paleo-Loppa High in the SW Barents Sea is a ridge structure, which developed during the late Paleozoic when the earliest phase of the Atlantic rifting between Greenland and Norway occurred. The southwest of the Barents Sea, located at the northern margin of Pangaea during the Carboniferous and Permian, was characterized by a structural style of half-graben geometries. The northward drift of the northern Pangaea triggered changes in regional climatic conditions that are reflected in the preserved sedimentary deposits. 2D/3D seismic combined with well and core data were used to define depositional seismic sequences and to understand the stratigraphic evolution of the paleo-Loppa High during the late Paleozoic. Based on the geometry of the defined seismic sequences and the character of observed sedimentary facies, a paleogeographic reconstruction of the key stages in the paleo-Loppa High evolution is also proposed and discussed in relation to local tectonic, global sea-level oscillations, and climatic changes. A total of seven seismic sequences, ranging from clastic-dominated to transitional clastic-carbonate sedimentation followed by an evaporitic drawdown phase, then shifting to carbonate-dominated sequences and finally capped by silica- and chert-dominated deposits, have been defined and represent the infill evolution of the paleo-Loppa High. Tectonics processes associated with the rifting are the principal controls in the 3-D morphology of the defined sequences. Sea-level fluctuations and climate changes have modified the biotic evolution and were responsible of the small-scale features inside each sequence. A renewed interest, in the study of the late Paleozoic sedimentary deposits of the paleo-Loppa High, has been manifested due to the recent discoveries of hydrocarbons in the Gohta and Alta prospects.

Basement inheritance and salt structures in the SE Barents Sea: Insights from new potential field data

The tectonic evolution of the former ‘grey zone’ between Russia and Norway has so far remained poorly constrained due to a lack of geophysical data. In 2014, the Geological Survey of Norway (NGU) carried out a new state-of-the-art aeromagnetic survey (BASAR-14) in the southern part of the new Norwegian offshore territory. The new BASAR-14 survey completes and extends the pre-existing aeromagnetic compilation and mapping of the Norwegian Barents Sea. We present this new magnetic dataset and its interpretation combined with gravity and seismic data. Caledonian and Timanian structures, highlighted by the new potential field data, dominate the basement patterns and have exerted a strong influence on the structure and development of the overlying basins and basement highs. Clearly associated with NW-SE-oriented Timanian trends, the Tiddlybanken Basin represents an atypical sag basin that developed at the southern edge of the Fedynsky High. Quantitative modelling along 2D seismic transects was also carried out to constrain the structural and basement composition of the study area. The predominant NE-SW Mesozoic trend of the Nordkapp Basin represents a major crustal hinge zone between the Finnmark Platform, poorly affected by major crustal deformation, and the Bjarmeland Platform where Late Palaeozoic rifting controlled the widespread accumulation of salt deposits in Late Carboniferous-Early Permian time. The entire structure and segmentation of the Nordkapp Basin have been influenced by the inherited basement configuration highlighted by the new aeromagnetic data. At present, quite a few large diapiric salt domes along the Nordkapp and Tiddlybanken basins are relatively shallow, locally reaching the seabed and thus show a clear bathymetric and magnetic signature. Both the Nordkapp and the Tiddlybanken basins appear to lie at the edge of a peculiar thick and rigid crustal feature that coincides with a highly magnetic region. The abrupt termination of the eastern Nordkapp Basin at the edge of this magnetic domain suggests the presence of an old and thick Precambrian continental block. This magnetic and rigid tectonic buffer controlled the Late Palaeozoic pre-salt and Mesozoic post-salt tectonic development of the southeastern Barents Sea.

Late Triassic (early Carnian–Norian) palynology of the Sentralbanken High, Norwegian Barents Sea

ABSTRACTFour stratigraphic cores (7533/2-U-1, 2-U-2, 3-U-7 and 7534/4-U-1) drilled in the Sentralbanken High provide important reference sections for the Upper Triassic succession in the northern Barents Sea. The cores span the De Geerdalen, Flatsalen and Svenskøya formations (Kapp Toscana Group), which are equivalent to the Snadd to middle Fruholmen formations of the southern Barents Sea. Only cursory palynological study of the cores has been conducted previously, and no published palynofacies data is available. We present a detailed palynostratigraphy from the cores, and describe six informal palynological assemblages. Comparison with independently dated sections from elsewhere in the region enables a revised age interpretation of early Carnian to Norian for the cored interval, thereby improving correlation between Sentralbanken, Svalbard and the southern Barents Sea. A dominance of amorphous organic matter (AOM) and marine palynomorphs indicates a distal suboxic–anoxic marine depositional environment for the lower De Geerdalen Formation, with an abrupt change to a nearshore marine environment above an erosion surface in core 7534/4-U-1. Palynofacies from the remainder of the formation are characterised by a dominance of phytoclasts and are interpreted as indicative of a delta front to coastal plain environment. The reappearance of AOM, microforaminiferal test linings and marine microphytoplankton in the Flatsalen Formation in cores 7533/2-U-1 and 2-U-2 reflects a regional transgression of early Norian age. Reworked palynomorphs, shale rip-up clasts and a transition to phytoclast-dominated palynofacies above an erosion surface at the base of the overlying Svenskøya Formation is consistent with a disconformity, which was previously identified as a possible sequence boundary on the neighbouring island of Hopen.

Reservoir characterization of the Triassic Kobbe and Snadd formations — Bjarmeland Platform, Norwegian Barents Sea

A reservoir characterization study of the Triassic Kobbe and Snadd formations is carried out in the Bjarmeland Platform area, Norwegian Barents Sea, through detailed petrophysical analysis and rock physics diagnostics. Results are tied to depositional environments and discussed in the context of burial depth and cementation as present burial depth is less than maximum burial depth due to upliftment. Marginal marine sandstones in the Snadd Formation display marginally better reservoir quality on average than those of fluvial origin, yet higher quality individual reservoirs are observed within both facies. As expected, the Kobbe Formation reservoirs are consistently poorer. The sensitivity of existing rock physics models to the data is shown to be reasonably valid (via porosity, water saturation, shale volume). Snadd Formation reservoir sandstones not affected by cementation are only observed at shallow depth in the west of the study area. This is supported by comparison to an experimental compaction trend as well as rock physics models. All Kobbe Formation reservoir units show consistent signs of chemical compaction due to deeper burial. The main findings of this study are estimates of important reservoir properties and examples of how results from petrophysical analysis are validated and complemented in various rock physics domains.

Structural style and evolution of the Nordkapp Basin, Norwegian Barents Sea

After three decades of research and hydrocarbon exploration in the Nordkapp Basin (Norwegian Barents Sea), the dynamics of Mesozoic salt mobilization is still poorly understood. Both, progradationa ...

Clinoform development and topset evolution in a mud‐rich delta – the Middle Triassic Kobbe Formation, Norwegian Barents Sea

AbstractClinoform surfaces are routinely used to mark transitions from shallow waters to deep basins. This concept represents a valuable tool for screening potential reservoir intervals in frontier basins where limited data are available. Variations in the character of clinoform geometries and shoreline and shelf‐edge trajectories are indicators of a range of different factors, such as palaeobathymetry, changes in relative sea‐level and sediment supply. Applications of conceptual and generalized models might, however, lead to erroneous assumptions about the supply of coarse‐grained material to the delta front and basin when superficial similarities between clinoform geometries are not treated holistically. The present study examines the mudstone‐dominated Middle Triassic Kobbe Formation – a potential hydrocarbon reservoir interval in the Barents Sea, where prodeltaic to deltaic deposits can be examined in cores, well logs and two‐dimensional and three‐dimensional seismic data. Despite pronounced acoustic impedance contrast to the surrounding shale, channel belt networks are not observed close to the platform edge in seismic datasets, even at maximum regressive stages. However, sub‐seismic prodeltaic deposits observed on the shallow platform indicate that prodeltaic deposits were sourced directly from the delta plain. Clinoform surfaces with different geometries and scale are observed basinward of the palaeoplatform edge of underlying progradational sequences, correlative to mudstone‐dominated prodeltaic core sections. Results indicate that platform‐edge deltas developed at discrete sites in the basin due to normal regression, but the positions of these deltas are not directly relatable to variations in clinoform geometries. Transitions from third‐order to fourth‐order clinoform geometries record discrete transgressive–regressive cycles but are not necessarily good indicators of sandstone deposition. Because of prolonged periods with high accommodation, channel avulsions were frequent and only very fine‐grained sandstone was deposited in heterolithic units at the delta front. Sandstones with good reservoir properties are predominantly found along basin margins.

Facies arrangement and cyclostratigraphic architecture of the Templet Member and the Kapp Starostin Formation (Permian) on Spitsbergen, Svalbard

Because of outstanding outcrops, Spitsbergen (Svalbard archipelago) provides unique opportunities to investigate the whole Upper Palaeozoic succession in great detail. This study can help to interpret the stratigraphic history and depositional evolution at other locations exposing coeval shelf strata along the northern margin of Pangea, e.g., the southern Barents Sea and Arctic Canada. Bed-scale outcrop observations are combined with microfacies studies to interpret the sedimentary settings and depositional environment of the Upper Palaeozoic strata. A sequencestratigraphic analysis has been carried out to evaluate the relative timing of sediment facies deposition in response to sea-level changes. The Early Artinskian to Kazanian successions of the Templet Member and the Kapp Starostin Formation were divided into five parasequences that are superimposed on a long-term, second-order, sea-level fall. These parasequences record a fundamental change of the sedimentary setting, from a restricted-marine, warm-water carbonate platform to an open-marine, cold-water, biosiliceous-carbonate ramp system. A cross-section across Svalbard comprising nine onshore sections shows that during deposition of the Kapp Starostin Formation a major depocentre marked by thick parasequences and a higher proportion of deep-water facies (bedded cherts) is located in the southwest of Spitsbergen (at Akseloya), whereas northeastern Svalbard records shallow-water microfacies. Svalbard was tectonically passive during the Permian; the local differences in accommodation space and facies were most likely linked to the rejuvenation of pre-existing structural elements, inherited from the Carboniferous. A deepening of the depositional environment combined with cold-water climatic conditions as recorded in our study area has also been documented in other Upper Palaeozoic successions around the Arctic, such as the Finnmark Platform (Norwegian Barents Sea) and the Sverdrup Basin (Arctic Canada). This transition in the depositional environment along the northern margin of Pangea is the result of large-scale changes in oceanic circulation patterns and local palaeogeographic changes during the northward movement of Pangea.

A statistical sensitivity method for CSEM — implications for petroleum exploration in the Barents Sea

This paper describes a statistical method for determining the probability for hydrocarbon detection by Controlled Source Electromagnetic (CSEM) data. The method can be used to quantitatively estimate the reliability and predictability of CSEM results and the validity of a CSEM interpretation over a specific target with given geological parameters (e.g. porosity and clay content). Wells and case studies from the Norwegian Barents Sea are used to highlight how the uncertainty of the geological model affects CSEM interpretation. All types of geoscientific applications face challenges on how to handle uncertainties; CSEM sensitivity studies are no different. The proposed method constrains the uncertainties by first establishing a statistical resistivity model containing expected resistivity and other geological parameters, then running Monte Carlo simulations to generate target specific sensitivity plots. Finally, the reservoir properties, e.g. porosity and clay content, can be varied to quantitatively establish if CSEM can detect a potential hydrocarbon column. The most important aspect of this method is that the CSEM integration and interpretation is now strongly controlled by the geoscientist, who must provide the expected reservoir parameters and their uncertainties for each target or case study under evaluation.

Clay coating preserving high porosities in deeply buried intervals of the Stø Formation

The Stø Formation is the most important reservoir interval in the Norwegian Barents Sea, however the reservoir quality can be highly affected by the detrimental effects of quartz cement where there have been extensive post depositional burial. Core plug data from well 7219/8-2 in the Southwestern Barents Sea shows abnormally high porosity and permeability values in certain units of the deeply buried and otherwise highly quartz cemented Stø Formation. The amount of quartz cement in the samples is inversely proportional to the porosity. Samples with high and low porosities are similar texturally and mineralogically, but the high porosity samples have a layer of illitic clay coating the majority of the detrital quartz grains. Illitic clay coating present at grain contacts can result in a lowered IGV given they aid in the dissolution of quartz at interfaces, also creating a source of dissolved silica. Clay induced dissolution means that silica saturation is not a limiting factor in quartz cementation in these samples. The results show that the illitic clay coating is capable of limiting the amount of authigenic quartz overgrowth from 20 to 23% in samples with negligible grain coating to 5–11% in the intervals with high coating coverage. The illitic clay coating inhibits quartz overgrowth by limiting the surface area available for nucleation on detrital grains. The Stø Formation comprises mainly shallow marine deposits of highly reworked clean sandstone. Abnormally high porosities appear to be linked to settings where sediments of a more proximal location are preserved without extensive reworking. The grain coating clay is illitic and most likely originates from clay infiltration processes prior to final deposition. The difference in extent of clay coating in similar facies can mostly be correlated with varying amount of post depositional reworking. This study suggests that there is a potential for considerable porosity and permeability to be preserved in deeply buried sandstones in the Barents Sea. This study could be important in the future exploration activity of deeply buried structures in the area.

Structural evolution of sheared margin basins: the role of strain partitioning. Sørvestsnaget Basin, Norwegian Barents Sea

AbstractSpatio‐temporal analysis of basins formed along sheared margins has received much less attention than those formed along orthogonally extended margins. Knowledge about the structural evolution of such basins is important for petroleum exploration but there has been a lack of studies that document these based on 3D seismic reflection data. In this study, we demonstrate how partitioning of strain during deformation of the central and southern part of the Sørvestsnaget Basin along the Senja Shear Margin, Norwegian Barents Sea, facilitated coeval shortening and extension. This is achieved through quantitative analysis of syn‐kinematic growth strata using 3D seismic data. Our results show that during Cenozoic extensional faulting, folds and thrusts developed coevally and orthogonal to sub‐orthogonal to normal faults. We attribute this strain partitioning to be a result of the right‐lateral oblique plate motions along the margin. Rotation of fold hinge‐lines and indications of hinge‐parallel extension indicate that the dominating deformation mechanism in the central and southern Sørvestsnaget Basin during opening along the Senja Shear Margin was transtensional. We also argue that interpretation of shortening structures attributed to inversion along the margin should consider that partitioning of strain may result in shortening structures that are coeval with extensional faults and not a result of a separate compressional phase.

Palynology and depositional environments of the Middle – Late Triassic (Anisian – Rhaetian) Kobbe, Snadd and Fruholmen formations, southern Barents Sea, Arctic Norway

The Middle to Upper Triassic series in the Norwegian Barents Sea represents an important target for hydrocarbon exploration. However, the dating and correlation of these rocks are problematic due to the scarcity of age-diagnostic macrofossils, lateral facies variation and the overall thickness of the succession. Palynology has proven to be a useful dating tool but further work is necessary to improve the zonal resolution, particularly for the Upper Triassic Series. The current paper presents a detailed palynostratigraphy of the Middle – Upper Triassic succession in four exploration wells (7120/12-2, 7228/2-1s, 7-1a and 9-1s) drilled in the Hammerfest and Nordkapp basins. Eleven informal palynological zones are described from the stratigraphic interval spanning the Kobbe, Snadd and Fruholmen formations, which constitute regionally significant hydrocarbon source and reservoir rock facies. The results of this study contribute to a higher resolution palynostratigraphy for the Middle to Upper Triassic strata of the southern Barents Sea (SBS), and an improved correlation with the stratigraphy of the Svalbard Archipelago. Palynofacies data for the succession, presented here for the first time, indicates depositional environments ranging from fluvio-deltaic to offshore marine.

Feeding of Greenland halibut Reinhardtius hippoglossoides (Pleuronectidae) in the Kara Sea

Feeding of Greenland halibut Reinhardtius hippoglossoides in the northern Kara Sea was studied based on data collected in summer–autumn 2007–2013. The main food of all size groups of halibut were fish—up to 98% of weight of the food bolus. Larger individuals had lower intensity of feeding as compared to juveniles, which was probably owing to the lack of suitable food for large fish and, along with gonad maturation process, could be one of the reasons of their migration to the Barents Sea. The northern part of the Kara Sea, as well as the adjacent areas of Barents Sea, can be considered as an important area of habitation of juvenile Greenland halibut of the Norwegian–Barents Sea population.

Multi-attribute Bayesian risk modification – a case study from the Norwegian Barents Sea

The assessment of the probability of geological success (i.e. the chance that a well encounters mobile hydrocarbons) is an important task in the prospect evaluation workflow. After the initial assessment of a geological probability of success, POSg, we use the geophysical direct hydrocarbon indicators (DHI) as extra information in a second Bayesian risk modification step. The Bayesian risk modification (BRM) is a very flexible approach, allowing many data types to be considered. The BRM is extended in this paper to include multiple DHI attributes. If we want to use two seismic attributes (e.g. top reservoir reflection and flat spot amplitudes), then possible interdependences between the attributes must be carefully investigated before application. We suggest a simple approach to determine the degree of attribute dependence and we demonstrate how to compute the scenario conditional probabilities (likelihoods) of these attributes for all possible exploration outcomes. A case study from the Barents Sea shows the feasibility of the multi-attribute BRM to solve a complex risking situation for a prospect with a flat spot. The later drilling and well results confirmed the plausibility of the risking modification outcome.

Evidence for Late Triassic provenance areas and Early Jurassic sediment supply turnover in the Barents Sea Basin of northern Pangea

We used detrital zircon fractions from the Late Triassic to Early Jurassic sedimentary succession in the Norwegian Barents Sea to constrain the role of eastern provenance areas in the basin infill history of the Northern Pangea Boreal basin. Geochronological data from sedimentary rocks in this succession reveal detrital zircon ages that are very close to the biostratigraphically defined maximum depositional age of the two lowermost intervals: The Norian to Rhaetian Fruholmen Formation show U-Pb minimum ages of 208.3 ± 4.2 Ma (discordant by -0.58) and 213.8 ± 5 Ma (discordant by 0.8), and the Rhaetian to Sinemurian Tubaen Formation is 200.6 ± 4.9 Ma (discordant by -3.99) at its minimum. These are the youngest ages thus far documented in the Norwegian Barents Sea, and they demonstrate that a provenance area was magmatically active while, or shortly before, these formations were being deposited. Such protolith ages have not been documented close to the study area, but based on the regional tectonic setting and paleogeography, we argue that the Novaya Zemlya protrusion of the northern Uralian orogen was the most likely provenance area in the region. The Sinemurian to Pliensbachian Nordmela Formation samples yielded, with an exception of a single detrital zircon age of 211 ± 4.3 Ma, a consistent 240–237 Ma minimum detrital zircon age, which suggests that either the magmatic activity or the sediment supply had come to an end by Sinemurian times. This turnover can be explained by a change in the hinterland drainage pattern. This study documents that eastern provenance areas were actively supplying sediments into the Norwegian Barents Sea Basin later than previously assumed, and our data offer age constraints for tectonic activity in the basin and its hinterland inferred from the changes in sediment supply to the basin.

Facies and seismic analysis of the Late Carboniferous–Early Permian Finnmark carbonate platform (southern Norwegian Barents Sea): An assessment of the carbonate factories and depositional geometries

The late Palaeozoic buried Finnmark platform, in the Norwegian Barents Sea, is a depositional system which developed under major modifications of palaeoclimatic and palaeoceanographic conditions, given by the northward drifting of the Arctic depositional domain beyond the tropical belt, the activity of the Gondwanan icecaps, and the gradual closure of the Eastern European seaway. In this study, detailed core/microfacies analysis from the explorations wells 7128/4-1 and 7128/6-1, combined with new 2D seismic sections and available dataset from previous studies in the eastern Finnmark area, have allowed a re-evaluation of the depositional scenarios associated with the Ørn and Isbjørn/Polarrev Formations. The late Asselian–early Sakmarian depositional record of the Ørn Formation, followed by the middle Sakmarian transition to the Isbjørn/Polarrev Formations, shows depth-related variations in sedimentation modes and a change of the platform morphology.In particular, a shift from Chloroforam to Bryonoderm sedimentation mode took place through a stratified water column during the deposition of the Ørn Formation, over what we suggest was a distally steepened ramp. In the late Sakmarian, the deposition of the Isbjørn/Polarrev Formations, characterised by a full Bryonoderm sedimentation mode, took place through a cooler non stratified water column, leading to the gradual instauration of a homoclinal ramp profile.Among the other results, our integrated study suggests the development of subtidal heterozoan mounds associated with the Ørn Formation, predating the formation of the larger, stacked and well-known heterozoan distal complexes of the Polarrev Formation. Given the good potential of the Ørn Formation within the Finnmark depositional domain, our results may help to improve the assessment of future evaluations of reservoir properties in the area, which are closely associated with the depositional style and their post-depositional modifications.

Large-scale seismically guided anisotropic inversion of towed-streamer EM data in the Barents Sea

This paper presents a fast and efficient large-scale anisotropic inversion technique for towed streamer electromagnetic (EM) data, which incorporates seismic constraints. The inversion algorithm is based on the 3D contraction integral equation method and utilizes a reweighted regularized conjugate gradient technique to minimize the objective functional (Zhdanov et al. 2014a, b). We have also introduced the concept of a moving sensitivity domain for seismically guided EM inversion, originally developed for airborne EM surveys (Zhdanov and Cox, 2013), which makes it possible to invert the entire large-scale towed streamer EM survey data while keeping the accuracy of the computation of the EM fields. The developed algorithm and software can take into account the constraints based on seismic and well-log data, and provide the inversion guided by these constraints. To demonstrate the practical effectiveness of this approach for large-scale inversion of marine EM data, as well as integration with seismic data, we apply the method to the inversion of about 2000 line-km of towed streamer EM data. The data form part of a larger survey in the Norwegian Barents Sea (McKay et al., 2016). We show that the technique produces a single resistivity model that is consistent with both the measured EM data and the main seismically defined structures. Thus, the resistivity model is ready to be interpreted and used in further quantitative interpretation studies.

Progradational and backstepping shoreface deposits in the Ladinian to Early Norian Snadd Formation of the Barents Sea

AbstractShoreface sandstone deposits within the Early Carnian part of the Snadd Formation of the Norwegian Barents Sea can be traced for hundreds of kilometres in the depositional strike direction and for tens of kilometres in the depositional‐dip direction. This study uses three‐dimensional seismic attribute mapping and two‐dimensional regional seismic profiles to visualize the seismic facies of these shoreface deposits and to map their internal stratigraphic architecture at a regional scale. The shoreface deposits are generally elongate but show variable width from north‐east to south‐west, which corresponds to a sediment source in the northern part of the basin and a southward decrease in longshore sediment transport. The Snadd Formation presents an example of how large‐scale progradational shoreface deposits develop. The linear nature of its shoreface deposits contrasts with more irregular, cuspate wave‐dominated deltaic shorelines that contain river outlets, and instead implies longshore drift as the main sediment source. In map view, discrete sets of linear features bounded by truncation surfaces scale directly to beach ridge sets in modern counterparts. The shoreface deposits studied here are characteristic in terms of scale and basin‐wide continuity, and offer insight into the contrast between shallow marine deposition under stable Triassic Greenhouse and fluctuating Holocene Icehouse climates. Findings presented herein are also important for hydrocarbon exploration in the Barents Sea, because they describe a hitherto poorly understood reservoir play in the Triassic interval, wherein the most prominent reservoir plays have so far been considered to be found in channelized deposits in net‐progradational delta‐plain strata that form the topsets to shelf‐edge clinoforms. The documented presence of widespread wave‐dominated shoreface deposits also has implications for how the relative importance of different sedimentary processes is considered within the basin during this period.