Gjallar Ridge Research Articles

Magnetotelluric evidence for massive sulphide mineralization in intruded sediments of the outer Vøring Basin, mid-Norway

A highly conductive body (0.1–0.8Ω·m) is identified at mid-crustal depth (8–13km) in the north Gjallar Ridge from magnetotelluric (MT) data and further investigated in light of other remote-sensing geophysical data (seismic reflection, gravity, aeromagnetic). A commercial 3D controlled-source electromagnetic survey was conducted in the Vøring Basin in 2014 and, although primarily designed for hydrocarbon exploration, good quality MT data were extracted at periods ranging from 100 to 103s. Dimensionality analysis indicates clear 1D to 2D characteristics in the MT data. 2D inversion was carried out on four profiles (totalling ~94km) oriented perpendicular to the electromagnetic strike and one profile along strike (~45km), using a 1D subset of the data. All inversions converged quickly to RMS values close to unity and display a very good agreement with borehole resistivity data from well 6705/10-1 located in the survey area. A striking feature on all profiles is a highly conductive (0.1–0.8Ω·m) body at 8–13km depth. To explain the prominent conductive anomaly, integration of geophysical data favours the hypothesis of electrical conduction across well-connected mineral network in pre-Cretaceous sediments. Seismic interpretation suggests a link between the conductor and intruded sedimentary successions below a detachment level and associated low-angle faults. In the Vøring Basin, low magnetic signal and temperature at the conductor's depth indicate that such thick mineral deposits could display non-magnetic behaviour while occurring well below the magnetite Curie isotherm (~585°C). Natural occurrences and magnetic properties of common iron-sulphide minerals favour a geological interpretation of mid-crustal conductivity as thick pyrrhotite deposits formed in intrusion's contact metamorphic aureoles.

Repeated inversion and collapse in the Late Cretaceous–Cenozoic northern Vøring Basin, offshore Norway

The Norwegian Atlantic margin, although frequently described as passive, has seen several significant and highly variable deformation events prior to and after early Cenozoic break-up. This chronology is strongly exemplified in the northern Vøring Basin, where deformation resulted in significant vertical motions, including deep erosion and sediment reworking. Post-break-up compressional deformation is well documented in the NE Atlantic margins, and is represented in the north Vøring Basin by the Vema and Naglfar domes. A prominent Maastrichtian–Paleocene pre-break-up phase of compression inverted the northern prolongation of the latest Turonian Vigrid Syncline. This syncline was the fairway for the approximately 1 km-thick Santonian–Campanian Nise Formation sandstone, shed from NE Greenland and/or the western Barents Sea margin. The inversion focused on the Vigrid Syncline axis, forming an anticline here referred to as the Vema–Nyk Anticline. The anticline may have been a major trap but was breached by erosion prior to collapse due to Late Paleocene extension. The remnant eastern half of the anticline is the Nyk High. The associated flanking syncline, the Någrind Syncline, also remains preserved. The collapsed side of the anticline is the Hel Graben, which itself was inverted in the Middle Miocene time forming the Naglfar and Vema domes. More speculatively, the development of the Vigrid Syncline and its bounding structural highs, the Gjallar Ridge and Utgard High, may also represent folds, marking the onset of compressional buckling in the mid-Norwegian–NE Greenland rift system. The repeated compressional deformation, as well as the extensional collapse, was focused on the area subjected to Early Cretaceous hyperextension. Compressional buckling under relatively low stress levels is proposed to have been due to significant lithosphere weakening caused by the hyperextension, whereby both high attenuation of the crystalline crust and serpentinization of the upper mantle contribute to the weakening. The Late Cenozoic compression post-dated the hyperextension by approximately 110 Ma, which suggests that the weakening is long-lived and that lithosphere has not been strengthened significantly through time.

Anatomy of a fluid pipe in the Norway Basin: Initiation, propagation and 3D shape

An exploration 3D seismic data set from the Gjallar Ridge off mid-Norway images a giant fluid seep structure, 3×5km wide, which connects to late Palaeocene magmatic sills at depth. Two of the pipes that have developed as hydrothermal vents reach all the way to the modern seafloor implying that they either were active much longer than the original hydrothermal activity or have been reactivated. We combine detailed seismic analysis of the northern pipe and sandbox modeling to constrain pipe initiation and propagation. Although both the seismic data and the sandbox models suggest that fluids at depth are focused through a vertical conduit, sandbox models show that fluids ascend and reach a critical depth migration where focused migration abruptly transforms into distributed fluid flow through unconsolidated sediments. This indicates that at this level the sediments are intensely deformed during pipe propagation, creating a V-shaped structure, i.e. an inverted cone at depth and a positive relief anomaly, 5 to 10m high, at the seafloor, which is clearly identified on 3D seismic data. Comparison of the geometries observed in sandbox modeling with the seismically observed geometries of the Giant Gjallar Vent suggests that the Giant Gjallar Vent may be a proto-fluid seep at an early stage of its development, preceding the future collapse of the structure forming a seafloor depression. Our results imply that the Gjallar Giant Vent can be used as a window into the geological processes active in the deep parts of the Vøring Basin.

High-resolution architecture of a polygonal fault interval inferred from geomodel applied to 3D seismic data from the Gjallar Ridge, Vøring Basin, Offshore Norway

3D seismic data located in the Gjallar Ridge (Vøring Basin, offshore Norway) reveals a closely-spaced polygonal fault system affecting more than 800m of homogeneous mud-dominated Quaternary and Tertiary sequences. As some faults reach the modern seafloor, they represent an active polygonal fault system at present day. Even if the processes remain unclear and are still under debate, it is generally agreed that the initiation of polygonal faults is the result of shallow burial dewatering of fine-grained unconsolidated sediments by volumetric compaction. 3D seismic data are commonly interpreted by propagating horizons automatically and by picking faults manually. However, in the case of polygonal fault intervals, this approach is time consuming due to the huge number of faults and because automatic propagation can be misleading. In this study, we applied a new technique of 3D seismic interpretation based on a sequential stratigraphy analysis, using the new PaleoScan© software (Eliis Company). It allowed us to build a 3D geological model computing more than 300 horizons within the faulted intervals. We then used the coherency attribute, depicting anomalies in the shape of seismic waveform like faults, in order to constrain a possible link between fault distribution and stratigraphic levels. Our approach allows fault throws to be calculated in milliseconds on any polygonal fault plane. The result shows that fault segments have been reactivated by dip-linkage. Distribution of faults depends on mechanical units, intervals characterized by different petrophysical properties, which are independent from lithological and diagenetic changes. According to these results, we propose a model showing the evolution of polygonal fault intervals in which faulting stages are separated by a quiescence phase during burial. A first tier of polygonal faults is initiated at a specific depth, according to the Cam–clay model. Then, following a period of quiescence during which mud-rich sediments continued to accumulate, new fault segments are initiated above the first mechanical unit and within this undeformed interval. New nucleated faults then connect downward to pre-existing underlying polygonal fault system, thus progressively increasing the thickness of the faulted interval.

Structure of a silica diagenetic transformation zone: the Gjallar Ridge, offshore Norway

AbstractThree‐dimensional seismic data from the Gjallar Ridge were used together with X‐ray diffraction data, scientific boreholes and wireline logs to analyse the seismic structure of a silica diagenetic transformation zone. The following features were identified: (i) an interval some 150 to 300 m thick that contains anomalously high‐amplitude reflections; (ii) a strong reflection event at the top of this interval which cross‐cuts stratigraphy, interpreted as the transformation boundary between opal‐A‐rich and opal‐CT‐rich sediment; (iii) amplitude variations on stratigraphic reflections within the interval, attributed to variations in the proportions of opal‐A and opal‐CT; and (iv) a second, deeper, cross‐cutting reflection event within the interval, interpreted as the transformation boundary between opal‐CT‐rich and quartz‐rich sediment. The base of the interval containing the anomalously high‐amplitude reflections is interpreted as a stratigraphic reflection demarcating the base of the silica‐rich strata. On a stratigraphic reflection within the interval of high amplitudes, roughly circular regions of anomalously high amplitude with diameters of 0·8 to 2·5 km are separated by lower amplitude regions. This pattern is similar to the cells previously identified at the opal‐A to opal‐CT transformation boundary and probably results from more complete transformation of opal‐A to opal‐CT. All of these observations provide the first recognition from seismic data that silica diagenetic transformations are not always narrow boundaries represented by single cross‐cutting seismic reflection events, as implied previously, but can be heterogeneous and hundreds of metres in thickness, as observed at outcrop.

Tectonic control on the distribution of Palaeocene marine syn-rift deposits in the Fenris Graben, northwestern Vøring Basin, offshore Norway

ABSTRACT The location, shape and stacking pattern of deep‐marine clastic sediments on drifting stage passive continental margins are strongly influenced by the slope and basin floor topography. The tectonic control on sediment routes and dispersal patterns, however, is less understood on rift margins, particularly the impact of subaqueous transfer zones or relay ramps. In this study, an area of the Palaeocene marine syn‐rift succession in the Voring Basin is mapped in detail to unravel the relationship between fault geometries and sedimentary infill patterns. Using root‐mean‐square (RMS) amplitudes and deposit thicknesses interpreted from seismic data, sedimentary elements in the Fenris Graben and the Gjallar Ridge are related to the fault patterns and the overall basin geometry. Older deposits are found to be aligned parallel to the basin axis, with the greatest sediment thicknesses on the hanging walls and adjacent to rotated faults. The main sediment supply is interpreted to be sourced from the Voring Marginal High and Greenland, presumably containing a significant proportion of coarser grained material and comprising numerous local depocentres. With continued rifting and decreased fault activity, finer grained deposition draped the previous basin infill and smoothed the basin floor topography. Deposits close to the foot of relay ramps along the Gjallar Ridge, however, suggest that the high may have acted as a local sediment source leading to local depocentres. Transfer zones played a significant role in sediment transport during the early rifting phase, and were able to maintain some influence into the late rifting and early drifting stage. Identification of early‐ and late‐stage transfer zones may therefore help in locating coarser grained depocentres and potential hydrocarbon reservoirs.

Thermal modelling of magmatic intrusions in the Gjallar Ridge, Norwegian Sea: implications for vitrinite reflectance and hydrocarbon maturation

ABSTRACTExtensive magmatic activity took place in the Vøring Basin, offshore Norway, related to the Early Cenozoic rifting. The break‐up of the North‐Atlantic at the Palaeocene–Eocene transition induced strong volcanism. There are numerous magmatic sills below 3 km depth in the area. They are predominantly layer parallel and thin compared with their lateral extent. Igneous intrusions, sills and dykes affected the temperature history, and thus need to be taken into account in petroleum prospect analysis. We have calculated the temperature and maturity effects in the sedimentary layers in the Gjallar area associated with the emplacement of single sill and sill complexes. A 120‐m‐thick sill produces a theoretical vitrinite reflectance (%R0) 0.8% higher than normal at a distance of 100 m from the sill. Vitrinite reflectance changes caused by a swarm of seven sills varying from 8 to 80 m in thickness were calculated. It is shown that the calculated thermal profile can account for the observed shift in vitrinite reflectance in the well. A two‐dimensional section crossing the Gjallar Ridge, consisting of numerous magmatic intrusions, is also modelled. The modelled geological development and temperature history over the profile show that there are significant maturation effects in the interval under investigation. Based on this work, the sill swarm observed in the area could more than double the fraction of the kerogen that has been transformed to petroleum at the (present) depth of 4 km.

A moderate melting model for the Vøring margin (Norway) based on structural observations and a thermo-kinematical modelling: Implication for the meaning of the lower crustal bodies

High P-wave velocities (7.1–7.8 km/s) lower crustal bodies (LCBs) imaged along volcanic margins are commonly interpreted as plume and breakup-related thick mafic underplating. This interpretation is partly challenged in this paper based on new seismic observations and modelling of the outer Vøring Basin (Norway). An exceptional strong amplitude reflection, the T Reflection, is particularly well defined below the North Gjallar Ridge (NGR) between 7and 8 s TWT. The T Reflection is located near the volcanic lava flows emplaced during the NE Atlantic breakup (∼ 55–54 Ma ago) and coincides with the top of the LCB, forming a mid-crustal dome. Based on structural and temporal relationships, we show that the dome clearly influences the structural development of the NGR and predates the continental breakup at least by 10–15 Ma. Using a thermo-kinematical model, we tried also to investigate and quantify the relationships between the extension, LCB and the magmatic production. Modelling suggests that significant Paleocene–Early Eocene magmatism can be produced without any temperature anomaly in the mantle if differential stretching occurs during the breakup initiation. The conclusion of 2D thermo-kinematical parametric analysis is that the magmatic model predicts, either little extension ( β < 2) with no melting or high extension ( β > 5) with significant melting along the outer Vøring Basin. We suggest that the continental part of the LCB could not necessarily be breakup-related and so magmatic, as has often been stated previously. It is concluded here that the continental part of the LCB observed beneath the outer Vøring Basin may be partly (or fully) attributed to inherited, high-pressure granulite/eclogite lower crustal rocks. The real amount of mafic material emplaced along the outer Vøring Basin could be 20–40% less than thought.

3D seismic expression of fluid migration and mud remobilization on the Gjallar Ridge, offshore mid‐Norway

AbstractThis paper presents a three‐dimensional (3D) seismic analysis of sediment remobilization and fluid migration in a 2000‐km2 area above the Gjallar Ridge located in the Vøring Basin, offshore Norway. Three distinct types of mounded structures have been identified as resulting from focused fluid/gas migration and associated mud remobilization and intrusion. Type A structures are gently mounded, and we infer that these structures formed because of in situ remobilization of Middle Eocene to Lower–Middle Oligocene fine‐grained sediments in response to fluid and minor sediment injection via deep‐seated normal faults. Type B structures comprise relatively steep‐sided mounds and are restricted to the pre‐Miocene interval. They are often located above narrow zones of discontinuous low‐amplitude reflections resembling gas chimneys. Some of the Type B structures are associated with stacked amplitude anomalies and possible mud volcanoes at the base Pleistocene indicating their long‐term significance as vertical fluid conduits. Type C structures comprise discrete mound features that seem to jack up the Top Palaeocene (Top Brygge) horizon. These are similar to hydrothermal mounds found elsewhere on the Norwegian Margin and associated with igneous sill intrusion during North Atlantic breakup. This study highlights the utility of 3D seismic data for mapping of fluid and sediment mobilization through time over large basinal areas.

Cretaceous to Palaeogene 3D palaeobathymetry and sedimentation in the Vøring Basin, Norwegian Sea

A new approach to constrain the Cretaceous and early Palaeogene depositional systems in the Vøring Basin has been achieved by combining 3D palaeobathymetry reconstructed from seismic sequence geometries, indicators of zero or shallow water depth, compaction and isostasy. The restorations were calibrated to known exposed intrabasinal highs. The Vøring Basin started out as a segmented and locally deep syn-rift basin during the Late Ryazanian. Water depths in the range 1000–2000m have been restored in the deeper areas. In Late Cenomanian broader deep-water areas formed in the eastern part of the basin. The broadening of the basin was accompanied by shallower water depths during the Coniacian. A switch in basin configuration was fully established during the Early Campanian. The previously deep areas in the Rås and Træna basins became very shallow and the Vigrid and Någrind synclines started to subside, as a response to the reactivation of the Fles Fault Complex. The shallowing trend continued during Late Cretaceous time until regional uplift of the basin floor, and total emergence of the intrabasinal highs known as Gjallar Ridge, Vema Dome, Nyk High and Utgard High occurred around Maastrichtian–Paleocene time. This was followed bydeepening in the Early Paleocene expressed in the depocentres, where the Vigrid and Rås basins now attained water depths of 300–400 m. Further increased subsidence occurred during the Late Paleocene, resulting inwater depths up to 1000min the eastern Vøring Basin.

Deep structures and breakup along volcanic rifted margins: insights from integrated studies along the outer Vøring Basin (Norway)

Three-dimensional multichannel seismic survey and well data allows a deeper insight into rifting mechanisms and crustal structure of the Norwegian volcanic rifted margin. A surprising high-velocity lower crustal dome marked by a strong amplitude reflection (T Reflection) is described below the north Gjallar Ridge (NGR) near the volcanic plateau formed during the late Paleocene–Early Eocene breakup. Faulting along the NGR occurs during Early Campanian–Paleocene and is controlled by the crustal dome. The T Reflection was previously related to either the top of mafic underplated crust or soft lower crust updomed during the continental breakup. The influence and timing of the crustal dome on the basin structure shows clearly that the dome predates the continental breakup. Based on the structural relationship and the results of the modelling, it is therefore concluded that the T Reflection does not necessarily originate from an anomalous Tertiary magmatic event related to the breakup (underplated material), but could be also partly attributed to pre-breakup mafic material or/and inherited, high pressure granulite/eclogite rocks in the continental domain.

Exploration 3D Seismic over the Gjallar Ridge, Mid-Norway: Visualization of Structures on the Norwegian Volcanic Margin from Moho to Seafloor

Abstract We present an analysis of a unique 3D survey that allows us to relate the deep structure of the crystalline crust to the shallow structure of the overlying, potentially hydrocarbon-rich sedimentary basins. The survey is located over the Gjallar Ridge, Mid-Norway, and extends from a Moho-level reflector at around 15 km depth to polygonal faulting and diapiric structures at or near the seabed. 3D visualization techniques using seismic workstations and the Cave immersive environment have been used to illustrate the geometries of these features. The deep reflector is correlated with the top of a deep, high-density, high-velocity body that is interpreted to indicate the presence of magmatic underplating and is intimately related to localized uplift of the Gjallar Ridge. Abundant high-amplitude reflectors in the deep Cretaceous sections of the survey are interpreted as sills emplaced during the Palaeocene magmatic event and are therefore interpreted to be coeval with the magmatic underplate. In contrast, the shallow parts of the survey have numerous gas-charged mud diapirs and an extensive network of polygonal faults extending to the seabed. Study of such very deep or very shallow features is not standard industry practice. However, the intention here is to demonstrate that, by utilizing the full volume of 3D seismic data, it is not only of scientific interest but also results in a greater understanding of the tectonic history of a hydrocarbon prospect.

Extension, crustal structure and magmatism at the outer Vøring Basin, Norwegian margin

Regional analysis of new 2D and 3D multichannel seismic data has improved interpretation of the crustal configuration and structural style along the Norwegian margin. Five domains with different structural styles and evolutions are defined along the outer Vøring Basin: (1) the Nyk High–Naglfar Dome; (2) the north Gjallar Ridge; (3) the Gleipne saddle; (4) the south Gjallar Ridge; (5) the Rån ridge. Early Campanian–Early Paleocene and Early to mid-Cretaceous extensional events are evidenced. Timing of deformation and structural styles observed along each segment reflect a lateral variation of the rifted system, probably affected by magma-tectonic processes. Correlation with the deep structures of the outer Vøring Basin shows that the shallow structure in that basin is directly controlled by a deep-seated, strong, high-amplitude reflection (the T reflection), marking the top of a high-velocity body ( V p &gt;7 km s −1 ). The relation between the lower-crustal architecture and the subsurface basin structures has implications for the margin evolution and for the nature of the high-velocity body.

Late Cretaceous and Tertiary structural evolution of the northeastern part of the Vøring Basin, Norwegian Sea

Abstract The Late Cretaceous-Tertiary structural evolution of the northeastern part of the Vøring Basin, mid-Norway, is highly complicated. Although tectonic activity occurred throughout Cretaceous time in much of the Vøring Basin, including the Gjallar Ridge and along the Fles Fault Zone, in the Vema Dome-Nyk High area evidence of such activity is not observed until the latest Maastrichtian time. In the Vema Dome-Nyk High area, several faults with both a NW-SE orientation and a NE-SW orientation have experienced lateral movements. The NE-SW orientation is the old Caledonian trend. The complex structural evolution of the Vema Dome-Nyk High area is probably related to the existence of continental weakness zones, which are the onshore extension of known oceanic fracture zones. The two lineaments that delineate these weakness zones, and that delineate the Vema Dome-Nyk High area, namely the Bivrost and Surt Lineaments, diverge slightly from one another toward the SE. This complex structural framework of NW-SE oriented lineaments and NE-SW oriented deep-seated basement structures of Caledonian compressional and/or Mesozoic rift origin, facilitated minor clockwise rotation of the area between the two lineaments during the extensional regime before the break-up of the North Atlantic, as well as during the compressional regime that has been proposed after the break-up.

A tectonostratigraphic framework for the Mid-Norway region

The tectonostratigraphic analysis presented here aims to establish a broad stratigraphic framework within which the likely distribution of both reservoir and source rock intervals within the deep-water Vøering and More basins can be evaluated. In terms of hydrocarbon potential, the Devonian to Triassic interval can be effectively discounted by its extreme depth of burial across most of the study area. The Middle Jurassic is interpreted to provide a potential reservoir target in the Gjallar Ridge area. The Cretaceous is seismically mappable across the region and has been divided into five tectonostratigraphic sequences. Late Cretaceous reservoirs are considered to offer targets in the Nyk High area. Six tectonostratigraphic sequences are described within the Cenozoic succession. Paleocene reservoirs are interpreted to offer targets over both the Ytterskallen and Ormen Lange areas of the Møre Basin. Source rock maturity is critical for exploration success. Mapping shows the Late Jurassic/earliest Cretaceous Spekk Formation to be overmature over most of the area, though the presence of possible DHIs indicates the probable presence of major gas accumulations in the region. Only on the western flank of the Vigrid Syncline does the Spekk shallow sufficiently to lie within the potential oil window. It is concluded that the region has the potential to become a significant new hydrocarbon province for the 21st century.

Late Cretaceous-Paleocene extension on the Vøring Volcanic Margin

High-quality seismic data document a Maastrichtian-Paleocene rift episode on the Voring margin lasting for ∼20 m.y. prior to continental breakup. The rift structures are well imaged in the Fenris Graben and Gjallar Ridge region in the western Voring Basin, and are characterized by low-angle detachment faults with variable fault geometries from south to north. The structural restoration has facilitated the division of pre- and syn-rift sediments across the extensional terrain, which is subsequently used to evaluate mode and mechanism for the lithospheric deformation. Extension estimates based on the structural restoration, subsidence analysis and crustal thickness evaluations yield stretching factors ranging between 1.5 to 2.3 across the main fault zone just landward of the early Tertiary flood basalts. The structural restoration also shows that a middle crustal dome structure, observed beneath the low-angle faults, can be explained by extensional unroofing. Thus, the dome structure may represent a possible metamorphic core complex. Calculations of the effects on vertical motion, assuming uniform and two-layer differential stretching models combined with the arrival of the Iceland mantle plume during rifting, indicate that the uniform extension model may account for both observed early rift subsidence and subsequent late rift uplift and erosion. Although the differential model can not be excluded, it implies early rift uplift which is not compatible with our seismic interpretation. The direct and indirect effects of the Iceland mantle plume may have caused as much as 1.2 km of late rift uplift. Comparison of the volcanic Voring margin and the non-volcanic West Iberian margin shows similarities in terms of structural style as well as in mode and distribution of extension.

Structural evolution of the Vøring Basin, Norway, during the Late Cretaceous and Palaeogene

The Vøring Basin forms an integral part of the passive margin off central Norway. Three phases of extension and three phases of compression record the transition from rifting to sea-floor spreading between Norway and Greenland. The first regional extensional event is of Early Cenomanian age, causing relative uplift of the Gjallar Ridge and development of a regional depocentre in the Rås Basin. A second extensional event is represented by Late Campanian faulting on the Nyk High and along the Fles Fault Complex. A compressional event in the Late Maastrichtian led to inversion of the Râs Basin. This was followed by a regional extensional event in Late Palaeocene, leading to the continental break-up between Norway and Greenland in Earliest Eocene. After the onset of sea-floor spreading, the Vøring Basin has remained in overall compression, with two major compressional events identified in Early Eocene and Mid-Oligocene.

A tectonic model for the Norwegian passive margin with implications for the NE Atlantic: Early Cretaceous to break-up

A sub-regional tectonic study of the mid-Norwegian margin has been assimilated into a broader, regional study of the NE Atlantic margin. The NE Atlantic margin experienced several extensional events between Devonian post-orogenic collapse and break-up in Early Tertiary. This paper focuses on the extensional events between Early Cretaceous and Early Tertiary. It is suggested that NE-trending Early Cretaceous rifting followed the entire margin from the southern Rockall Trough to the Bjørnøya Basin of the SW Barents Sea. This rift had a markedly different trend than the preceding N-trending Late Jurassic rift of, e.g., the North Sea. Seamounts may have been emplaced in the highly thinned basin axes during Early Cretaceous rifting. Subsequent rift events followed the Early Cretaceous rift trend. An enigmatic 'mid'-Cretaceous event, probably extensional, is observed in the northern part of the mid-Norwegian margin. The event is expressed by faulting in the inner Vøring Basin, and by uplift of the outer Vøring and Lofoten margins. Uplift is associated with a widespread unconformity. Uplift of the Gjallar Ridge in the Vøring Basin culminated during the latest Cretaceous to Early Tertiary rifting, with structural geometries broadly similar to those seen in core complexes. A new tectonic model for NE Atlantic margin is proposed based on these observations, and builds on analogues from the modern rift system in the Red Sea and Woodlark Basin of Papua New Guinea.

Temperature Effect of Magmatic Underplating in the Gjallar Ridge, Mid-Norway: ABSTRACT

Temperature Effect of Magmatic Underplating in the Gjallar Ridge, Mid-Norway: ABSTRACT