Cretaceous sandstones. One of these gas discoveries is
now under development (Aasta Hansteen). It has been
possible to map the distribution of sands from amplitude analysis of the seismic data.
The large Ormen Lange gas field was proven in
1997. It is located at water depths of 800–1,100 m in
the eastern Møre Basin within the Storegga Slide area.
The gas is found in Palaeocene and uppermost Cretaceous reservoir rocks (sandstones).
25.4 Barents Sea
25.4.1 Structure
The Barents Sea covers the northwestern corner of the
Eurasian continental shelf. It is bounded by young
passive margins to the west and north that developed
in response to the Cenozoic opening of the
Norwegian-Greenland Sea and the Eurasia Basin,
respectively (Figs. 25.1 and 25.2).
The western Barents Sea is underlain by large
thicknesses of Upper Palaeozoic to Cenozoic rocks
constituting three distinct regions (Figs. 25.14, 25.15
and 25.16). (1) The Svalbard Platform is covered by a
relatively flat-lying succession of Upper Palaeozoic
and Mesozoic, mainly Triassic, sediments. (2) A
basin province between the Svalbard Platform and
the Norwegian coast is characterised by a number of
sub-basins and highs with an increasingly accentuated
structural relief westwards. Jurassic-Cretaceous, and
in the west Palaeocene-Eocene, sediments are preserved in the basins. (3) The continental margin
consists of three main segments: (a) a southern sheared
margin along the Senja Fracture Zone; (b) a central
rifted complex southwest of Bjørnøya associated with
volcanism and (c) a northern, initially sheared and
later rifted margin along the Hornsund Fault Zone.
The continent-ocean transition occurs over a narrow
zone along the line of Early Tertiary break-up and the
margin is covered by a thick Upper Cenozoic sedimentary wedge.
The post-Caledonian geological history of the
western Barents Sea is dominated by three major rift
phases, Late Devonian?-Carboniferous, Middle
Jurassic-Early Cretaceous, and Early Tertiary, each
comprising several tectonic pulses. During Late
Palaeozoic times most of the Barents Sea was affected
by crustal extension. The later extension is
characterised by a general westward migration of the
rifting, the formation of well-defined rifts and pullapart basins in the southwest, and the development of a
belt of strike-slip faults in the north. Apart from epeirogenic movements which produced the present day
elevation differences, the Svalbard Platform and the
eastern part of the regional basin have been largely
stable since Late Palaeozoic times.
25.4.2 Stratigraphy/Evolution
The Barents Sea is underlain by a thick succession of
Palaeozoic to Cenozoic strata showing both lateral and
vertical variations in thickness and facies –
characterised by Upper Palaeozoic mixed carbonates,
evaporites and clastics, overlain by MesozoicCenozoic clastic sedimentary rocks (Fig. 25.4). Direct
information on the nature of the crystalline crust
beneath the Barents Sea sedimentary basins is scarce,
but the available, mostly indirect, evidence indicates
that the basement underlying much of its western part
was metamorphosed during the Caledonian Orogeny
and that the structural grain within the Caledonian
basement may have influenced later structural development. The Caledonian crystalline basement has a
NE-SW grain and was folded during Silurian time.
25.4.2.1 Upper Palaeozoic
Within the Caledonian domain Devonian molasse
sediments were deposited in intermontane basins
undergoing extensional collapse. A Devonian tectonic
regime comprising both extensional and compressional events is so far only known on Svalbard, located
on the northwestern corner of the Barents Shelf. Here,
thick Devonian strata are found in a north-south
trending graben structure and the graben fill is discordantly overlain by Carboniferous strata (Fig. 25.17).
Lower to lower Upper Carboniferous strata, mainly
clastics, were deposited in extensional basins ranging
from wide downwarps to narrow grabens. A 300 km
wide rift zone, extending at least 600 km in a northeasterly direction (Fig. 25.14), was formed mainly
during mid-Carboniferous times. The rift zone was a
direct continuation of the northeast Atlantic rift
between Greenland and Norway, but a subordinate
tectonic link to the Arctic rift was also established.
The overall structure of the rift zone is a fan-shaped
array of rift basins and intrabasinal highs with
626
J.I. Faleide et al.
now under development (Aasta Hansteen). It has been
possible to map the distribution of sands from amplitude analysis of the seismic data.
The large Ormen Lange gas field was proven in
1997. It is located at water depths of 800–1,100 m in
the eastern Møre Basin within the Storegga Slide area.
The gas is found in Palaeocene and uppermost Cretaceous reservoir rocks (sandstones).
25.4 Barents Sea
25.4.1 Structure
The Barents Sea covers the northwestern corner of the
Eurasian continental shelf. It is bounded by young
passive margins to the west and north that developed
in response to the Cenozoic opening of the
Norwegian-Greenland Sea and the Eurasia Basin,
respectively (Figs. 25.1 and 25.2).
The western Barents Sea is underlain by large
thicknesses of Upper Palaeozoic to Cenozoic rocks
constituting three distinct regions (Figs. 25.14, 25.15
and 25.16). (1) The Svalbard Platform is covered by a
relatively flat-lying succession of Upper Palaeozoic
and Mesozoic, mainly Triassic, sediments. (2) A
basin province between the Svalbard Platform and
the Norwegian coast is characterised by a number of
sub-basins and highs with an increasingly accentuated
structural relief westwards. Jurassic-Cretaceous, and
in the west Palaeocene-Eocene, sediments are preserved in the basins. (3) The continental margin
consists of three main segments: (a) a southern sheared
margin along the Senja Fracture Zone; (b) a central
rifted complex southwest of Bjørnøya associated with
volcanism and (c) a northern, initially sheared and
later rifted margin along the Hornsund Fault Zone.
The continent-ocean transition occurs over a narrow
zone along the line of Early Tertiary break-up and the
margin is covered by a thick Upper Cenozoic sedimentary wedge.
The post-Caledonian geological history of the
western Barents Sea is dominated by three major rift
phases, Late Devonian?-Carboniferous, Middle
Jurassic-Early Cretaceous, and Early Tertiary, each
comprising several tectonic pulses. During Late
Palaeozoic times most of the Barents Sea was affected
by crustal extension. The later extension is
characterised by a general westward migration of the
rifting, the formation of well-defined rifts and pullapart basins in the southwest, and the development of a
belt of strike-slip faults in the north. Apart from epeirogenic movements which produced the present day
elevation differences, the Svalbard Platform and the
eastern part of the regional basin have been largely
stable since Late Palaeozoic times.
25.4.2 Stratigraphy/Evolution
The Barents Sea is underlain by a thick succession of
Palaeozoic to Cenozoic strata showing both lateral and
vertical variations in thickness and facies –
characterised by Upper Palaeozoic mixed carbonates,
evaporites and clastics, overlain by MesozoicCenozoic clastic sedimentary rocks (Fig. 25.4). Direct
information on the nature of the crystalline crust
beneath the Barents Sea sedimentary basins is scarce,
but the available, mostly indirect, evidence indicates
that the basement underlying much of its western part
was metamorphosed during the Caledonian Orogeny
and that the structural grain within the Caledonian
basement may have influenced later structural development. The Caledonian crystalline basement has a
NE-SW grain and was folded during Silurian time.
25.4.2.1 Upper Palaeozoic
Within the Caledonian domain Devonian molasse
sediments were deposited in intermontane basins
undergoing extensional collapse. A Devonian tectonic
regime comprising both extensional and compressional events is so far only known on Svalbard, located
on the northwestern corner of the Barents Shelf. Here,
thick Devonian strata are found in a north-south
trending graben structure and the graben fill is discordantly overlain by Carboniferous strata (Fig. 25.17).
Lower to lower Upper Carboniferous strata, mainly
clastics, were deposited in extensional basins ranging
from wide downwarps to narrow grabens. A 300 km
wide rift zone, extending at least 600 km in a northeasterly direction (Fig. 25.14), was formed mainly
during mid-Carboniferous times. The rift zone was a
direct continuation of the northeast Atlantic rift
between Greenland and Norway, but a subordinate
tectonic link to the Arctic rift was also established.
The overall structure of the rift zone is a fan-shaped
array of rift basins and intrabasinal highs with
626
J.I. Faleide et al.