1 Introduction The mid Norwegian passive margins has been studied well as a volcanic margin which mainly belongs to the North Atlantic Igneous Province. The North Atlantic Igneous Province has been studied and associated with the intrusive and massive extrusive magmatism which happened to be as a result of the see floor spreading and the continental break up (Berndt, 2001). Figure 1 (Regional Setting of the Norwegian Margins) These magmatism are covered by the magnesium contents and the iron contents mostly calling the “Mafic rock”. The margin has a history of spanning between the Early Eocene break -up & the Carboniferous and episodic rifting. During the period of the extensional stress field, it resulted into
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1 Introduction
The mid Norwegian passive margins has been studied well as a volcanic margin which mainly
belongs to the North Atlantic Igneous Province. The North Atlantic Igneous Province has been
studied and associated with the intrusive and massive extrusive magmatism which happened to be
as a result of the see floor spreading and the continental break up (Berndt, 2001).
Figure 1 (Regional Setting of the Norwegian Margins)
These magmatism are covered by the magnesium contents and the iron contents mostly calling the
“Mafic rock”. The margin has a history of spanning between the Early Eocene break-up & the
Carboniferous and episodic rifting. During the period of the extensional stress field, it resulted into
the oblique formation of younger rifts over the older rifts. Various studies have been conducted on
the mid Norwegian margin collecting the seismic refraction data, experimental drilling & the
commercial drilling on the Voring plateau & the continental shelf (Callot, 2011).
2 Volcanic Passive Margins
The large igneous provinces have been found of having volcanic passive margins (VPM). These
igneous provinces are said to be comprised of the transitional narrow crust which is formed due to
the rifting over the hot mantle and the continental breakup. A volcanic passive margin can be
characterized by the following attributes; firstly massive intrusion of the dyke and sill happens into
the sediments. Secondly, the lava flows reflect dipping seaward and thirdly, the ultra-mafic and
the mafic intrusion happen into the middle and the upper continental crust. Presence of seismic
velocity bodies is also found to be present at the lower crust which cause the magma under-plating
(Eldholm & Grue, 1994). The continental breakup during the Late Paleocene and the Early Eocene
resulted in the spreading of the magmatism which developed into the intrusive and extrusive
structures alongside the mid-Norwegian margin.
Figure 2 (Structural Map Related to the Rifting Phases)
3 Mid-Norwegian Volcanic Passive Margin
The mid Norwegian margin is constituted by three segments mainly i.e. Voring, More and Lofoten-
Vesteralen. These three segments are separated by the Bivrost Lineament zone and East Jan Mayen
Fracture and each has the length of 400 – 500 km. On the margins of More Basin and Voring
segments, a lower crustal body has been developed which is characterized by P-wave velocities
forming the thickened crust beneath them and continue to the thick western oceanic crust (Faleide,
2008). The md Norwegian margin is said to be formed due to the tectono-magmatic evolution in
the following three ways. Firstly, the change of the accretionary magma volumes from normality
to the maturation and continental margin subsidence. Secondly, lithospheric extension has
occurred due to the rift episode in Cretaceous-Paleocene which led to the plate separation and
breakup. Thirdly, the central rift tend to enhance the igneous activity and uplift it during the late
rifting and culmination of voluminous outbursts of the Early Eocene’s basaltic lavas. These three
tectono-magmatic evolution described the formation of mid Norwegian margins and the increased
igneous activity (Gernigon, 2004).
3.1 The More Margin
The more margin is largely comprised of the deep and wide More Basin, Gentle/ wide slope
consisting of the thick Cretaceous fill. The inner flank is dipped basin ward in a steep way and the
curst which is crystalline in nature gets thin rapidly reaching to smaller than ten kilometer. The
More Basin is mainly comprised of the sub basins which are segregated by the Jurassic-Early
Cretaceous rift that formed the intra-basinal highs between the sub basins. The sedimentary
succession further gets thinner and deeper decreasing to twelve kilometer landwards. The
structural relief in the More Basin was filled mainly during the Mid-Cretaceous time while
intrusions are still wide spreading within this crust getting deepened in the western and central
parts of the More Basin (Lundin, 2013).
The western part of the More Basin is covered by the lava flows as well as a thick LCB with lower
than seven kilometer P-wave velocity is evident to be present under the Basin covering most of its
part. The magmatic under-plating is being evident during the interpretations of the body related to
the breakup of the crust. It has also been researched and found that the More marginal heights,
shallowing of the Cretaceous sediment, crystalline crust thickening and the making of crystalline
basement all occur near the ocean-continent transition. These mid Norwegian margins are evolved
through a process of rifting episodes and breakups related to the Cretaceous sediments which
ultimately resulted in the formation of Greenland margins and the mid Norwegian margins. The
complex structure of these volcanic margins have been studies by various researchers in order to
investigate their formation and expansion with the passage of time (Scheck-Wenderoth, 2007).
The East Greenland Margins and the NW European margins have a distinct history associated to
their development starting from the post-Caledonian orogenic backsliding to the post-Eocene
passive margin formation. The evolutionary process has been given in the later section of this
report.
3.2 The Voring Margin
It is comprised of the northwest to the southeast area, the Voring Basin, the Halten terraces, the
Voring Marginal High, the Trondelag platform and the Donna terraces. The platform is highly
stable since the deep basins got filled by the upper Paleozoic sediment and the Triassic sediment
including the deep basins which were filled during the Jurassic time. The deep MCS profiles and
the seismic refraction profiles which are wide-angle are mostly constrained by the deep Moho
reaching about thirty two kilometer close to the mainland in Norway. Like the More Basin, the
Voring Basin can also be divided into the highs and the sub Basins reflecting the vertical
movements during the Early Cretaceous and the Late Jurassic basin evolutions (Raum, 2011).
The deep Moho undulates at twenty five kilometer under the deep basin while the velocity reaches
to the 7.6 km in most of the area under the lower crust and the magmatic under-plating. A study
conducted by Gernigon et al (2004) to investigate the formation of the mid Norwegian margins
and the Basins reveals the alternative interpretation of the LCB. It included the melted continental
crust, inherited high pressure eclogite & granulite rocks, the mantle rocks and the description of
the thickness of the body. It has been said in that study that the thickness of the body varies within
the area and these variations could be the result of the spatial variations which was caused during
the magma distribution process or the variations during the pre-breakup structures. The Voring
Margin is comprised of the Voring Escarpment and the Voring Marginal Highs consisting of the
landward part of continental stretched crust and the outer part of an oceanic crust which is thick
anomalously covered by the Early Eocene basalts (kogseid, 2000).
4 The Process of Margin Evolution
4.1 Pre-breakup Basin Evolution
The structural pre-opening and the margin framework has caused the development of the Voring
and the More Basins of the mid Norwegian region which is characterized by the Late Jurassic &
Early Cretaceous rifting activity in the NE Atlantic-Arctic region. A considerable thinning and
crustal extension during the Earliest Cretaceous rifting activity led to the formation of the
Cretaceous basin of mid Norwegian VPM as well as the development of the East Greenland in the
Southwestern Barents Sea. However, in a study conducted by Skogseid (2000), it has been said
that no distinct structures have been identified associated to the Voring Basin. But in the mid
cretaceous time, the structural relief in the Voring and the More Basins was filled with the thick
upper Cretaceous strata (Blystad, 1995).
4.2 Break up Related Magmatism and Tectonism
At the onset of the pre-breakup related rifting of the NE Atlantic, the area between the Greenland
Margins and the NW Europe got extensively weakened caused by the previous rifting. This rifting
resulted afterwards in the detachment structures of the thick Cretaceous sequence and the intra-
crustal levels of the Voring Basin. Lately, the rifting episodes were taken up by the deformation
of the De Geer Zone resulting in the pull-apart formation of the SE Barents. Tectonic
reorganization happened during this era and the Greenland moved in a direction to the west of the
Eurasia. Marin shallowing occurred and the rifting related to the relative plate motion caused the
reactivation of the Volcanic Province (Eldholm & Grue, 1994).
4.3 Post-breakup Margin Evolution
The modest sedimentation and the regional subsidence in the Norwegian- Greenland Sea resulted
into the development of the mid Norwegian margin. The deep water sedimentation in the Miocene
succession expanded the sediment drifts of the contrite. Plate tectonic reconstruction occurred and
it impact mainly the ocean circulation which resulted into the deep water exchanges through a
southern gateway of the Scotland- Greenland Ridge (Lundin, 2013). At the western side of the
Barents Sea, a pre-glacial tectonic uplift occurred and led to the formation of the Vestbakken
Volcanic Province. These glacial tectonic components composed over a half of the total area of
the mid Norwegian margins afterward. The continental margins as well as the mid Norwegian
margins have been opened in the response of the Greenland- Norwegian Sea as main rifting,
exhibiting the distinct segmentation of structural inheritance which extend back to the pre-breakup
history (Faleide, 2008).
5 Works Cited
Berndt, C. (2001). Seismic volcanostratigraphy of the Norwegian Margin: constraints on
tectonomagmatic break-up processes. Journal of the Geological Society.
Blystad, P. (1995). Structural elements of the Norwegian continental shelf Part II: the Norwegian
Sea Region: NPD-Bulletin, . The Norwegian Petroleum Directorate.
Callot, J. (2011). Development of volcanic passive margins: Two‐dimensional laboratory models.
Tectonics.
Eldholm, O., & Grue, K. (1994). North Atlantic volcanic margins: dimensions and production
rates. Journal of Geophysical Research: Solid Earth.
Faleide, J. (2008). Structure and evolution of the continental margin off Norway and the Barents
Sea: Episodes. The Journal of Geography.
Gernigon, L. (2004). Deep structures and breakup along volcanic rifted margins: insights from
integrated studies along the outer Vøring Basin (Norway). Marine and Petroleum Geology.
kogseid, J. (2000). NE Atlantic continental rifting and volcanic margin formation, in NOTTVEDT,
A. e. a., ed., Dynamics of the Norwegian Margin, Volume 167. London, Geological
Society.
Lundin, E. (2013). Repeated inversion and collapse in the Late Cretaceous–Cenozoic northern