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Breivik, Asbjørn Johan; Tan, Pingchuan & Mjelde, Rolf
(2019).
Dynamic topography development north of Iceland from subaerial exposure and erosion of the igneous Logi Ridge.
Vis sammendrag
The Logi Ridge, located north of the West Jan Mayen Fracture Zone, is E-W oriented and 140-150 km long,
terminating in an isolated seamount in the east. The seafloor surrounding the Logi Ridge is ~0.65 km shallower than
conjugate seafloor east of the Mohn's Ridge, which has been attributed to dynamic uplift due to asthenospheric flow.
Eight reflection seismic lines across the Logi Ridge constrain its development. Both the western and eastern parts
have flat tops, indicating erosion at sea-level. Three different basement types surrounding the Logi Ridge are
observed: rough basement represents abyssal hills; smooth basement caused by basalt flows overprinting early
sediments; and irregular basement formed by basalt flows and intrusions. The surrounding sediments have two
distinct units, where the age of the unit boundary is Middle Miocene (~12 Ma). Lava flows and erosion products from
the Logi Ridge appears episodically in the lower unit throughout Late Oligocene to Middle Miocene. Ridge
development may have started just after the Traill Ø intrusions were emplaced onshore Greenland. No erosion
products are seen in the upper unit, proving Middle Miocene submergence. The end of erosion age can also be
estimated from seamount height, or present top seamount depth, using the age-dependent oceanic floor subsidence.
The two methods have different sensitivity to parameters, which constrains uncertainty when compared. In the west
there is good agreement with the age constrained by the sedimentation, proving little dynamic topography change. In
the east, discrepancies between the methods are best explained by 0.15-0.3 km increase of dynamic uplift after
submergence. Hence, most of the regional dynamic uplift occurred before the end of the Logi Ridge development in
the Middle Miocene, suggesting a causative relationship. Minor recent magmatic growth and seafloor uplift over a
~100 km zone southeast of the Logi Ridge may be tied to the younger dynamic uplift in the east.
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Breivik, Asbjørn Johan; Faleide, Jan Inge; Mjelde, Rolf; Flueh, Ernst R. & Murai, Yoshio
(2019).
Wide angle seismic data constraints on crustal structure and erosion of the northernmost Norwegian shelf.
Vis sammendrag
The Norwegian continental shelf has been through several rift phases since the Caledonian orogeny. Early Cretaceous rifting created the largest sedimentary basins, and Early Cenozoic continental breakup between East Greenland and Europe affected the continental shelf to various degrees. The Lofoten/Vesterålen shelf is located off Northern Norway, bordering the epicontinental Barents Sea to the northeast, and the oceanic Lofoten Basin to the west. An ocean bottom seismometer (OBS) survey was conducted over the area in 2003. This study documents Profile 8-03, located between the outer islands and the shelf edge. The wide-angle seismic data were modeled using raytracing to build a crustal velocity-depth transect. Gravity modeling could resolve an ambiguity in seismic Moho identification in the south. Results show a crustal thickness of 30-31 km, thicker and thus less affected by breakup tectonism than previously believed. The results of the new survey shows that older nearby refraction profiles may be too short to constrain Moho depth in the area. Profile 8-03 and other OBS profiles to the southwest show high sedimentary velocities at or near the seafloor, suggesting greater burial in the past. Velocities from the current profile and from a previously published crossing profile of the same survey were compared to the velocity-depth function derived from an OBS profile at the Barents Sea margin, tied to a coincident well log, where there is little erosion. Results indicate three major erosion episodes; Late Triassic-Early Jurassic, tentatively mid-Cretaceous, Late Cretaceous-early Cenozoic breakup-related, and a minor late glacial erosion episode off Vesterålen.
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Tan, Pingchuan; Breivik, Asbjørn Johan & Mjelde, Rolf
(2018).
Development of the igneous Logi Ridge and surrounding sedimentation, NE Atlantic, from seismic reflection data.
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Gibbons, Steven John; Maupin, Valerie; Kolstad, Christian; Kværna, Tormod & Breivik, Asbjørn Johan
(2018).
Improved location estimates for seismicity along the northern North Atlantic Ridge.
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Breivik, Asbjørn Johan
(2018).
Along-Margin Variability in Breakup Magmatism, NE Atlantic.
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Breivik, Asbjørn Johan; Tan, Pingchuan & Mjelde, Rolf
(2018).
Development of the Igneous Logi Ridge, NE Atlantic, From Seismic Reflection Data.
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Breivik, Asbjørn Johan; Faleide, Jan Inge; Mjelde, Rolf; Flueh, Ernst R. & Murai, Yoshio
(2017).
Origin of the Vøring Plateau, offshore Norway – interplay between timing of rifting and emplacement of plume material.
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Aarseth, Iselin; Mjelde, Rolf; Breivik, Asbjørn Johan; Minakov, Alexander; Huismans, Ritske & Faleide, Jan Inge
(2016).
Barents Sea Crustal and Upper Mantle Structure from Deep Seismic and Potential Field Data.
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Tan, Pingchuan; Sippel, Judith; Breivik, Asbjørn Johan; Scheck-Wenderoth, Magdalena & Meeßen, Christian
(2016).
Crustal and mantle structure of the greater Jan MayenEast
Greenland region (NE Atlantic)
from combined 3D structural, Swave
velocity, and gravity modeling.
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Mjelde, Rolf; Breivik, Asbjørn Johan; Minakov, Alexander; Huismans, Ritske & Faleide, Jan Inge
(2016).
Barents Sea Crustal and Upper Mantle Structure from Deep Seismic and Potential Field Data.
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Aarseth, Iselin; Mjelde, Rolf; Breivik, Asbjørn Johan; Huismans, Ritske & Faleide, Jan Inge
(2016).
Barents Sea Paleozoic basement and basin configurations: Crustal structure from deep seismic and potential field data.
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Aarseth, Iselin; Mjelde, Rolf; Breivik, Asbjørn Johan; Huismans, Ritske & Faleide, Jan Inge
(2016).
Barents Sea Paleozoic basement and basin configurations:
Crustal structure from deep seismic and potential field data
.
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Faleide, Jan Inge; Mahajan, Aatisha; Gabrielsen, Roy Helge; Breivik, Asbjørn Johan; Planke, Sverre & Myklebust, Reidun
(2015).
Basement and Late Paleozoic basin configurations in the western and central Barents Sea.
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Tan, Pingchuan; Breivik, Asbjørn Johan; Mjelde, Rolf & Azuma, Ryosuke
(2015).
Constraining formation of the Eggvin Bank (West of Jan Mayen, N. Atlantic) from OBS data.
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Abdelmalak, Mohamed Mansour; Faleide, Jan Inge; Planke, Sverre; Theissen-Krah, Sonja; Zastrozhnov, Dmitrii & Breivik, Asbjørn Johan
[Vis alle 8 forfattere av denne artikkelen]
(2014).
Breakup magmatism style on the North Atlantic Igneous Province: insight from Mid-Norwegian volcanic margin.
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Faleide, Jan Inge; Breivik, Asbjørn Johan; Blaich, Olav A.; Tsikalas, Filippos; Planke, Sverre & Abdelmalak, Mohamed Mansour
[Vis alle 8 forfattere av denne artikkelen]
(2014).
Structure and degree of magmatism of North and South Atlantic rifted margins.
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Breivik, Asbjørn Johan; Faleide, Jan Inge; Mjelde, Rolf; Murai, Yoshio & Flueh, Ernst R.
(2014).
Breakup Style and Magmatic Underplating West of the Lofoten Islands, Norway, Based on OBS Data.
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Rai, Abhishek Kumar; Breivik, Asbjørn Johan & Mjelde, Rolf
(2013).
Lower Crustal Reflectivity bands and Magma Emplacement in Norwegian Sea, NE Atlantic.
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Rai, Abhishek Kumar; Breivik, Asbjørn Johan; Mjelde, Rolf & Pedersen, Rolf-Birger
(2013).
Nature of the seismic crust at the Aegir Ridge: A downward continuation approach.
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Breivik, Asbjørn Johan; Faleide, Jan Inge; Mjelde, Rolf; Flueh, Ernst R. & Murai, Yoshio
(2013).
Magmatic development of the outer Vøring Margin.
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Faleide, Jan Inge; Planke, Sverre; Abdelmalak, Mohamed Mansour; Theissen-Krah, Sonja; Zastrozhnov, Dmitry & Tsikalas, Filipos
[Vis alle 12 forfattere av denne artikkelen]
(2013).
Structure and evolution of the NE Atlantic conjugate margins off Norway and Greenland.
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Abdelmalak, Mohamed Mansour; Faleide, Jan Inge; Planke, Sverre; Breivik, Asbjørn Johan; Gernigon, Laurent & Myklebust, Reidun
(2013).
Magmatism and break-up on the NE Atlantic: the nature and influence of the lower crustal body on margin structure.
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Planke, Sverre; Sassier, Caroline; Polteau, Stephane; Faleide, Jan Inge; Galland, Olivier & Breivik, Asbjørn Johan
[Vis alle 7 forfattere av denne artikkelen]
(2013).
Salt distribution and sub-salt basins on the conjugate Barents Sea - Northeast Greenland continental shelves.
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Rai, Abhishek Kumar; Breivik, Asbjørn Johan; Mjelde, Rolf; Hanan, Barry; Ito, Garrett & Howell, Samuel M.
[Vis alle 8 forfattere av denne artikkelen]
(2012).
Analysis of converted S-waves and gravity anomaly along Aegir Ridge: implications for crustal lithology.
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Breivik, Asbjørn Johan
(2012).
Mantle melting in the NE Atlantic Igneous Province.
Vis sammendrag
The northeast Atlantic margins form part of a large mafic igneous province, which has been attributed to the arrival of the Iceland mantle plume. Sill complexes and magmatic underplating formed at the outer margins at breakup, followed by the formation of oceanic crust 2-4 times normal thickness. High magma productivity typically lasted 3-6 Ma after breakup. After that, excess magmatism continued along the Faeroe-Iceland-Greenland Ridge. Other models, ranging from small-scale convection to increased mantle fertility, have also been proposed to explain the excess magmatism. By comparing the oceanic crustal thickness of the volcanic margins with average P-wave velocities, the melting process of the mantle can be estimated. The results indicate elevated mantle temperatures confined to a finite reservoir underneath the margins at breakup time, consistent with a plume model. But additional processes appear to augment the melt production at some margin segments. Later magmatic rejuvenation may also mask original processes in some areas.
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Breivik, Asbjørn Johan; Mjelde, Rolf; Rai, Abhishek Kumar & Frassetto, Andy
(2012).
Geophysical survey of the Eggvin Bank and Logi Ridge - Greenland Sea.
Vis sammendrag
The northern Greenland Sea has a number of features associated with excess volcanism. These include the Jan Mayen island, the Jan Mayen Plateau north of, and the Eggvin Bank west of Jan Mayen, and the Vesteris Seamount far to the north. In the summer of 2011, we collected an Ocean Bottom Seismometer (OBS) profile across the Eggvin Bank, returning four good data sets. We also collected single-channel reflection seismic (SCS) data along the OBS line. The profile crosses the transform part of the West Jan Mayen Fracture Zone (WJMFZ), which connects seafloor spreading between the Kolbeinsey and Mohn ridges. Between the WJMFZ and the Vesteris Seamount there is a narrow ridge 170-180 km long, ending in a few seamounts in the east. It disturbs the magnetic seafloor anomalies, and has no conjugate on the Norwegian margin. It thus appears to be younger than the Eocene seafloor it lies on. Trend and position points to Traill Ø in East Greenland, which had magmatism at ~36 Ma. We name it the Logi Ridge after Norse mythology, where Logi is the master of fire, brother of Aegir, master of the sea. We have collected five SCS profiles across this ridge in order to study the surrounding sedimentation pattern. We also collected gravity and magnetic data along all profiles. Initial results show two flat-topped seamounts on the Eggvin Bank, and a flat-topped Logi Ridge, indicating that these have been at sealevel. The sedimentary strata show recent vertical movement north of the WJMFZ near the Jan Mayen Plateau, and compression around the Logi Ridge.
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Howell, Samuel M.; Breivik, Asbjørn Johan & Mjelde, Rolf
(2012).
Mantle Convection beneath the Aegir Ridge, a Shadow in the Iceland Hotspot.
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Sayit, Kaan; Breivik, Asbjørn Johan; Mjelde, Rolf & Pedersen, Rolf-Birger
(2012).
The trace and Pb isotope chemistry of the Jan Mayen Fracture Zone and the extict Aegir Ridge.
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Sayit, Kaan; Breivik, Asbjørn Johan; Mjelde, Rolf & Pedersen, Rolf-Birger
(2012).
The trace and Pb isotope chemistry of the Jan Mayen Fracture Zone and the extinct Aegir Ridge.
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Savit, K; Hanan, Barry; Ito, Garrett; Howel, SM; Vogt, Peter & Breivik, Asbjørn Johan
[Vis alle 8 forfattere av denne artikkelen]
(2012).
The trace and Pb isotope chemistry of the Jan Mayen Fracture Zone and the extinct Aegir Ridge.
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Breivik, Asbjørn Johan; Mjelde, Rolf; Faleide, Jan Inge & Murai, Yoshio
(2011).
The Eastern Jan Mayen Micro-Continent Volcanic Margin.
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Sayit, Kaan; Hanan, Barry; Ito, Garrett; Howell, S.; Vogt, Peter R. & Breivik, Asbjørn Johan
[Vis alle 8 forfattere av denne artikkelen]
(2011).
Geochemistry and Pb Isotopes from the Jan Mayen Fracture Zone and the Extinct Aegir Ridge.
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Rai, Abhishek Kumar; Breivik, Asbjørn Johan & Mjelde, Rolf
(2011).
Seismic Structure of the Extinct Aegir Ridge in Norwegian Basin, N.E. Atlantic.
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Breivik, Asbjørn Johan
(2010).
Volcanic margins – hotspot origin or not? A closer look at the NE Atlantic.
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Breivik, Asbjørn Johan; Mjelde, Rolf; Raum, Thomas; Faleide, Jan Inge; Murai, Yoshio & Flueh, ER
(2010).
Crustal structure of the inner mid-Norwegian continental margin – Trøndelag Platform, from wide-angle seismic and potential field data.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2010).
The Norwegian volcanic margin revisited.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2009).
Conjugate volcanic margin breakup of the mid-Norwegian and East Greenland Margins –using crustal scale velocity and thickness data to determine breakup style.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2009).
Oceanic Intraplate Magmatism Off The Vøring Volcanic Passive Margin, Norway – Constraints On Origin From Seismic Velocity Structure.
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Mjelde, Rolf; Breivik, Asbjørn Johan & Faleide, Jan Inge
(2009).
Northeast Atlantic Igneous Province volcanic margin development.
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Tsikalas, Filippos; Faleide, Jan Inge; Blaich, Olav Antonio; Breivik, Asbjørn Johan; Mjelde, Rolf & Eldholm, O
(2009).
Late Mesozoic-Cenozoic Evolution of the Conjugate Lofoten-Vesterålen (Nordland VI-VII) and NE Greenland Continental Margins: Implications for the Potentially Developed Petroleum System.
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Clark, SA; Ritzmann, Oliver; Faleide, Jan Inge; Mjelde, Rolf; Glørstad, Evy & Leever, K
[Vis alle 8 forfattere av denne artikkelen]
(2009).
Rift basin architecture and crustal thinning in the southwestern Barents Sea.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2009).
Northeast Atlantic Igneous Province volcanic margin development.
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Faleide, Jan Inge; Tsikalas, Filippos; Breivik, Asbjørn Johan & Mjelde, Rolf
(2009).
Structure and evolution of the continental margin off Norway and the Barents Sea and its conjugate off Greenland.
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Faleide, Jan Inge; Tsikalas, Filippos; Breivik, Asbjørn Johan; Mjelde, Rolf; Blaich, Olav Antonio & eldholm, olav
(2009).
Structure and Evolution of the NE Atlantic Region and Links to the Arctic.
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Clark, Stephen Anthony; Ritzmann, Oliver; Faleide, Jan Inge; Mjelde, Rolf; Leever, Karen Agneta & Glørstad-Clark, Evy
[Vis alle 8 forfattere av denne artikkelen]
(2008).
Linking deep structures and basin formation in the Barents Sea.
33rd International Geological Congress, Abstracts.
CD-ROM.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2008).
Determining volcanic continental margin breakup style on the Norwegian Margin - Which criteria are important and can they be generalized?
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Faleide, Jan Inge; Tsikalas, Filippos; Breivik, Asbjørn Johan; Mjelde, Rolf; Ritzmann, Oliver & Engen, Øyvind
[Vis alle 8 forfattere av denne artikkelen]
(2008).
Basin evolution at the Norwegian-Greenland conjugate margins in the NE Atlantic.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2008).
Enigmatic Neogene magmatism NE of Iceland - Major magmatic underplating off the Norwegian margin.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2008).
Enigmatic Neogene magmatism NE of Iceland - major magmatic underplating off the Norwegian margin.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2008).
East Greenland – mid-Norway asymmetric conjugate volcanic margin development.
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Tsikalas, Filippos; Faleide, Jan Inge; Breivik, Asbjørn Johan; Mjelde, Rolf; Wilson, Jonas & Eldholm, Olav
[Vis alle 7 forfattere av denne artikkelen]
(2007).
Structure and evolution of the northern Vøring and Lofoten-Vesterålen margins, and their conjugate NE Greenland margin.
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Tsikalas, Filippos; Breivik, Asbjørn Johan; Faleide, Jan Inge; Mjelde, Rolf & Eldholm, Olav
(2007).
Crustal structure, continental breakup and magmatism at the Lofoten-Vesterålen margin, off Norway, constrained by the Euromargins 2003 OBS Experiment.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2007).
The dynamics of continental breakup-related magmatism on the Norwegian volcanic margin.
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Breivik, Asbjørn Johan; Faleide, Jan Inge; Mjelde, Rolf & Tsikalas, Filippos
(2007).
Continental breakup and magmatic development of the mid-Norwegian margin, Euromargins 2003 OBS Experiment.
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Breivik, Asbjørn Johan; Faleide, Jan Inge; Mjelde, Rolf & Tsikalas, Filippos
(2007).
Timing of Continental breakup at the mid-Norwegian margin, Euromargins 2003 OBS Experiment.
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Faleide, Jan Inge; Engen, Øyvind; Tsikalas, Filippos; Breivik, Asbjørn Johan & Ritzmann, Oliver
(2007).
Crustal structure of the mainly sheared western Barents Sea-Svalbard margin.
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Faleide, Jan Inge; Tsikalas, Filippos; Breivik, Asbjørn Johan; Mjelde, Rolf; Wilson, Jonas & Eldholm, Olav
(2007).
NE Atlantic breakup and evolution of the Norwegian-Greenland conjugate volcanic margins.
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Faleide, Jan Inge; Engen, Øyvind; Tsikalas, Filippos; Breivik, Asbjørn Johan & Ritzmann, Oliver
(2007).
Opening of the northern North Atlantic and formation of the sheared western Barents Sea-Svalbard and NE Greenland margins.
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Faleide, Jan Inge; Wilson, Jonas; Mjelde, Rolf; Ritzmann, Oliver & Breivik, Asbjørn Johan
(2006).
Crustal structure and deep basin configuration - key observations and modelling constraints.
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Ritzmann, Oliver; Faleide, Jan Inge; Breivik, Asbjørn Johan & Mjelde, Rolf
(2006).
Tectonic development and temperature history of the Vøring area, mid Norway - Task Seismic wave field modelling along deep-seismic transects.
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Mjelde, Rolf; Breivik, Asbjørn Johan & Faleide, Jan Inge
(2006).
Crustal profile across the North Atlantic.
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Mjelde, Rolf; Breivik, Asbjørn Johan & Faleide, Jan Inge
(2006).
Crustal transect across the North Atlantic.
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Mjelde, Rolf; Breivik, Asbjørn Johan & Raum, Thomas
(2006).
Sub-basalt imaging on the mid-Norwegian margin, using OBS data.
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Ljones, Frode; Breivik, Asbjørn Johan; Mjelde, Rolf & Faleide, Jan Inge
(2006).
Stacking of wide-angle OBS data as multichannel data – outer Vøring Margin.
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Breivik, Asbjørn Johan; Mjelde, Rolf & Faleide, Jan Inge
(2006).
Magma-starved seafloor accretion in the Norway Basin caused by the Iceland hotspot.
Vis sammendrag
The Norway Basin was initiated by continental breakup between northern Europe and Greenland/Jan Mayen in the earliest Eocene (~54Ma). Being part of the North Atlantic Igneous Province, continental breakup and early seafloor spreading produced voluminous magmatism, which subsided as seafloor spreading progressed. An ocean bottom seismometer (OBS) profile acquired in the year 2000 from the Norwegian Møre margin to the extinct spreading axis of the Aegir Ridge was used to estimate variations in magma productivity as the oceanic basin evolved. Due to low magnetic data coverage, a satellite derived gravity map proved suitable to reinterpret the East Jan Mayen Fracture Zone (EJMFZ) system, but no other fracture zones could be identified within the Norway Basin. The revised EJMFZ trace was used to re-evaluate spreading in the Norway Basin, which appears more asymmetric than previously believed, being condensed mostly on the southwestern side. The magnetic track recorded along the OBS profile was used to identify magnetic seafloor spreading anomalies by forward modeling, and projected onto synthetic flow lines half spreading rates were derived along-profile. Maximum rate was above 3 cm/a between A24A and A24b, falling off to ~0.7 cm/a (ultra-slow) by C20 (42.7 Ma) which lasted to the Late Oligocene (25-28 Ma) termination of seafloor spreading. Breakup magmatism created oceanic crust up to 10-11 km thick, tapering down to thin crust by C23 time (51.4 Ma); the increased melt potential was thus spent ~2.5 Ma after continental breakup. While oceanic crust created during ultra-slow spreading is thin (3.9 km), crust created during slow spreading is also thinner than the world average (5.3 vs. 7.1 km), indicating a somewhat depleted mantle source. A V-shaped pattern seen in the gravity field only around the northern part of the Aegir Ridge corresponds to increased crustal thickness in the OBS model, demonstrating Middle Eocene-Early Oligocene northeast migration of asthenosphere zones with slightly increased melt production at a speed of 0.3-0.6 cm/a. The thin crust and lack of fracture zones in the Norway Basin is typical for ultra-slow seafloor spreading, even if much of it was created during slow spreading (~1.5 cm/a half rate). This character may have developed not despite the closeness to the Iceland Hotspot, but because of it, as mantle partially depleted by high magma production during the construction of the aseismic Iceland-Faeroe Ridge to the south was transported to the northeast to feed oceanic accretion. The southern part of the Norway Basin lacks V-shaped ridges and the Aegir Ridge has a deeper axial valley, indicating a lower magma budget than in the north, consistent with this model.
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Faleide, Jan Inge; Tsikalas, Filippos; Breivik, Asbjørn Johan; Wilson, Jonas; Engen, Øyvind & Eldholm, Olav
(2006).
Late Mesozoic-Cenozoic evolution of the NE Atlantic region and links to the Arctic.
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Tsikalas, Filippos; Breivik, Asbjørn Johan; Faleide, Jan Inge; Raum, Thomas; Mjelde, Rolf & Eldholm, Olav
(2006).
Crustal structure of the Lofoten-Vesterålen margin, off Norway, constrained by new OBS data.
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Faleide, Jan Inge; Mjelde, Rolf; Tsikalas, Filippos; Breivik, Asbjørn Johan; Raum, Thomas & Wilson, Jonas
[Vis alle 7 forfattere av denne artikkelen]
(2006).
A regional 3D model of the crustal architecture and evolution of the mid-Norwegian continental margin.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2006).
Continental breakup and magmatism at the mid-Norwegian margin, Euromargins 2003 OBS Experiment.
Vis sammendrag
The continental margin off mid-Norway is a volcanic passive margin created during the earliest Eocene, and large volumes of magmatic rocks were emplaced during and a few M.y. after continental breakup. In 2003, an ocean bottom seismometer/hydrophone survey was acquired on the Vøring and Lofoten-Vesterålen Margins. The main targets are continental breakup processes, early seafloor spreading, and along-margin variation of magma productivity. The P-wave data were modeled by a combined forward ray-tracing and inversion into 2D velocity-depth models. The continent-ocean transition zone is usually well defined as a rapid increase of P-wave velocities at mid- to lower-crustal levels. This transition may occur over a distance of only 15-20 km. Maximum igneous crustal thickness was found to be about 18 km on both of the Euromargins profiles across the outer Vøring Plateau, which is 5-7 km less than reported from older surveys in the area. Lower crustal P-wave velocities of up to 7.3 km s-1 were found at the bottom of the igneous crust here, similar to earlier studies. Magmatic underplating of continental crust was for the first time identified at the Lofoten-Vesterålen margin. At 2 km thickness this is a third of what is typical for the Vøring Plateau, and oceanic crustal thickness adjacent to the continent is close to normal, both showing the distal location of this part of the margin to the Iceland hotspot influence. In the absence of an early spreading axis jump, continental breakup must have occurred 1-2 M.y. later here than on the Møre Margin to the south. A previously unknown episode of magmatic underplating of oceanic crust off the Vøring Plateau was also identified, creating an igneous crust up to 15 km thick. This episode is completely unrelated to the breakup magmatism, but belongs to a family of Neogene intra-plate magmatism observed in the North Atlantic. The underplating was dated from the inversion of overlying sedimentary strata in the oceanic basin to be Late Miocene.
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Tsikalas, Filippos; Breivik, Asbjørn Johan; Faleide, Jan Inge; Raum, Thomas; Mjelde, Rolf & Eldholm, Olav
(2006).
OBS data constrain the crustal structure of the Lofoten-Vesterålen margin, off Norway.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2006).
MORB-hijacking by the Iceland Plume.
Vis sammendrag
The Iceland plume is one of the prime examples supporting the mantle plume theory, i.e., cooling of the Earth’s interior by localized large vertical mass transport. The plume caused pre-breakup and voluminous breakup magmatism on the North Atlantic continental margins, and formed an aseismic ridge from the continental margins to Iceland. According to theory, the plume initially had a broad head affecting a region ~2000 km wide, while a narrow, long-lived trailing stem interacted with the seafloor spreading to create the exceptionally thick igneous crust of Iceland, and to drive asthenosphere zonation away from Iceland to create V-shaped ridges in the oceanic crust around the spreading axes. However, there are centres of magmatism at distance from the plume, spanning from Miocene to recent, which do not fit with the plume theory. Here we present new data to document an unexpected province of diffuse Late Miocene magmatic underplating of older oceanic crust north of the Aegir Ridge, an extinct seafloor spreading axis in the Norway Basin. Based on correlation between the province and the extinct axis, and similarity to the region northeast of the present spreading on the Kolbeinsey Ridge north of Iceland, we present a new model of plume - spreading ridge interaction to explain these two magmatic provinces: The asthenosphere flow out from Iceland ’hijacks’ deeper, low-degree partially molten asthenosphere regions created underneath the spreading ridges and carry these across the terminating fracture zones, to subsequently add to the base of the oceanic crust or to build seamounts.
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Breivik, Asbjørn Johan; Faleide, Jan Inge; Mjelde, Rolf & Tsikalas, Filippos
(2006).
Continental breakup and magmatic development of the mid-Norwegian margin, Euromargins 2003 OBS Experiment.
Vis sammendrag
The continental margin off mid-Norway is a volcanic passive margin created during the earliest Eocene, and large volumes of magmatic rocks were emplaced during and a few M.y. after continental breakup. In 2003, an ocean bottom seismometer/hydrophone survey was acquired on the Vøring and Lofoten-Vesterålen Margins. The main targets are continental breakup processes, early seafloor spreading, and along-margin variation of magma productivity. The P-wave data were modeled by a combined forward ray-tracing and inversion into 2D velocity-depth models. The continent-ocean transition zone is usually well defined as a rapid increase of P-wave velocities at mid- to lower-crustal levels. This transition may occur over a distance of only 15-20 km. Maximum igneous crustal thickness was found to be about 18 km on both of the Euromargins profiles across the outer Vøring Plateau, which is 5-7 km less than reported from older surveys in the area. Lower crustal P-wave velocities of up to 7.3 km s-1 were found at the bottom of the igneous crust here, similar to earlier studies. Magmatic underplating of continental crust was for the first time identified at the Lofoten-Vesterålen margin. At 2 km thickness this is a third of what is typical for the Vøring Plateau, and oceanic crustal thickness adjacent to the continent is close to normal, both showing the distal location of this part of the margin to the Iceland hotspot influence. Continental breakup appears to occur at least 1 M.y. later here than on the Møre Margin to the south. A previously unknown episode of magmatic underplating of oceanic crust off the Vøring Plateau was also identified, creating an igneous crust up to 15 km thick. This episode is completely unrelated to the breakup magmatism, but belongs to a family of Neogene intra-plate magmatism observed in the North Atlantic. The underplating was dated from the inversion of overlying sedimentary strata in the oceanic basin to be Late Miocene.
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Breivik, Asbjørn Johan & Mjelde, Rolf
(2006).
Seismic evidence for the Barents Sea - Svalbard Caledonides.
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The western Barents Sea and the Svalbard archipelago share a common history of Caledonian basement formation and subsequent sedimentary deposition. Rocks from the period are accessible on Svalbard, but studies of the near offshore areas rely on seismic data and shallow drilling. Offshore mapping is reliable down to the Permian sequence, but multichannel reflection seismic (MCS) data does not give a coherent picture of older stratigraphy. A survey of ten Ocean Bottom Seismometer (OBS) profiles was collected around Svalbard in 1998. Modeling the data by ray-tracing gives whole-crust depth and velocity transects. Results show a highly variable thickness of pre-Permian sedimentary strata. Depth-to-basement and -Moho maps for two areas south of and southwest of Svalbard were produced from this survey. The observed gravity can in some parts of the platform be directly related to velocity variations in the crystalline crust, but often not to basement or Moho depth. The area around the Olga Basin - Sentralbanken High southeast of Svalbard was one of the targets for the survey, and combined velocity and gravity modeling of the OBS data and results, show crustal roots associated with heterogeneous crystalline crust. The area is very similar to the Ural suture zone, and is the first direct indication for an eastern continuation of the Svalbard Caledonides through the Barents Sea. The other target area is located between Bjørnøya and Svalbard, where older deep MCS profiles indicate a westwards dipping suture zone. The OBS data shows that the suture zone is associated with a strong P-wave velocity contrast from east to west. Supported by modeling of the S-wave and gravity data, we conclude that this corresponds to a change from mafic to more felsic composition. Two of the profiles were shot coincident with earlier MCS lines, confirming the crustal root imaged earlier. Combined, these different seismic datasets indicate both a continuous basement high and crustal root trending towards the Billefjorden Fault Zone (BFZ) onshore Svalbard. The eastern side of the BFZ correlates closely with coincident positive gravity and magnetic anomalies on western Ny Friesland, originating from an antiform with high-grade metamorphic Caledonian rocks. A double linear magnetic anomaly appears on the BFZ trend south of Spitsbergen, sub-parallel and located 10-50 km west of the crustal root. Based on this correlation, we propose that the suture or major thrust zone seen south of Svalbard correlates to the BFZ. The preservation of the relationship between the crustal suture, the crustal root, and upper mantle reflectivity south of Svalbard, challenges the large-offset, post-collision sinistral transcurrent movement on the BFZ and other trends proposed in the literature. Also, the seismic data south of Svalbard does not show clear signs of major lateral offsets, as seen in deep seismic data around the British Isles. We conclude that the main Caledonide sutures branched to continue both through Svalbard and through the eastern Barents Sea by collision with one or more microplates caught between Laurentia and Baltica.
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Wilson, Jonas; Raum, Thomas; Mjelde, Rolf; Faleide, Jan Inge; Breivik, Asbjørn Johan & Murai, Yoshio
[Vis alle 7 forfattere av denne artikkelen]
(2006).
Crustal structure and composition beneath the Trøndelag Platform, mid-Norwegian margin, derived from wide-angle seismic and gravity data.
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Tsikalas, Filippos; Breivik, Asbjørn Johan; Faleide, Jan Inge; Mjelde, Rolf & Eldholm, Olav
(2006).
Crustal structure, continental breakup and magmatism at the Lofoten-Vesterålen margin, off Norway, constrained by the Euromargins 2003 OBS Experiment.
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Breivik, Asbjørn Johan; Faleide, Jan Inge & Mjelde, Rolf
(2006).
Continent-ocean transition at the northern Vøring Margin, Norway, Euromargins 2003 OBS Experiment.
Vis sammendrag
The continental margin off mid-Norway is a volcanic passive margin created during the earliest Eocene, and large volumes of magmatic rocks were emplaced during and a few M.y. after continental breakup. In 2003, an ocean bottom seismometer/hydrophone survey was acquired on the Vøring and Lofoten-Vesterålen Margins. The main targets are continental breakup processes, early seafloor spreading, and along-margin variation of magma productivity. The profile presented here is one of five profiles from the survey crossing the continent-ocean boundary. It crosses the northern part of the Vøring Plateau and continues into the oceanic basin out to magnetic anomaly 21 (~47 Ma). The P-wave data were modeled by a combined forward ray-tracing and inversion into a 2D velocity model. Strong lower crustal reflectivity in the thick igneous section imparted ambiguity on Moho interpretation from the OBS/H data. Gravity modeling was used interactively with the ray-tracing to obtain a consistent model. The forward gravity model was corrected by a lithospheric mantle density model based on estimated thermal expansion. The thermal model was calculated by a 2D finite-element program, using the opening history of the oceanic basin. This procedure removed a ~70 mGal regional misfit, and the final fit between observed and calculated gravity is good. Also upper mantle reflectivity is abundant under the thick igneous crust, limited mostly to a zone 2-4 km below the Moho. This indicates a Moho transition zone where mafic and ultramafic rocks interfinger. The profile shows a rapid transition over a distance of 15-20 km from continent to oceanic crust (COT), similar to earlier results. Maximum igneous crustal thickness was found to be 18 km, and from the COT the thickness decreases to ~6.5 km over a distance of 120 km, indicating magmatism abating over a period of at least ~6 M.y. after continental breakup. Lower crustal P-wave velocities of up to 7.3 km s-1 were found at the bottom of the crust. Combined with modeling of the S-wave data, we conclude that the crust is primarily of igneous origin here, though some continental contamination may exist at middle-lower crustal levels in a ~30 km wide zone underneath the continental slope.
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Brandsdottir, Bryndis; Hooft, Emilie; Mjelde, Rolf; Shimamura, Hideki; Murai, Yoshio & Barclay, Andrew
[Vis alle 8 forfattere av denne artikkelen]
(2006).
Evolution of a divergent plate boundary; from the active Kolbeinsey Ridge, N-Iceland to the exinct Ægir Ridge, Norwegian Sea.
Vis sammendrag
The continental margin off mid-Norway is a volcanic passive margin created during the earliest Eocene, and large volumes of magmatic rocks were emplaced during and a few M.y. after continental breakup. In 2003, an ocean bottom seismometer/hydrophone survey was acquired on the Vøring and Lofoten-Vesterålen Margins. The main targets are continental breakup processes, early seafloor spreading, and along-margin variation of magma productivity. The P-wave data were modeled by a combined forward ray-tracing and inversion into 2D velocity-depth models. The continent-ocean transition zone is usually well defined as a rapid increase of P-wave velocities at mid- to lower-crustal levels. This transition may occur over a distance of only 15-20 km. Maximum igneous crustal thickness was found to be about 18 km on both of the Euromargins profiles across the outer Vøring Plateau, which is 5-7 km less than reported from older surveys in the area. Lower crustal P-wave velocities of up to 7.3 km s-1 were found at the bottom of the igneous crust here, similar to earlier studies. Magmatic underplating of continental crust was for the first time identified at the Lofoten-Vesterålen margin. At 2 km thickness this is a third of what is typical for the Vøring Plateau, and oceanic crustal thickness adjacent to the continent is close to normal, both showing the distal location of this part of the margin to the Iceland hotspot influence. Continental breakup appears to occur at least 1 M.y. later here than on the Møre Margin to the south. A previously unknown episode of magmatic underplating of oceanic crust off the Vøring Plateau was also identified, creating an igneous crust up to 15 km thick. This episode is completely unrelated to the breakup magmatism, but belongs to a family of Neogene intra-plate magmatism observed in the North Atlantic. The underplating was dated from the inversion of overlying sedimentary strata in the oceanic basin to be Late Miocene.