GEOLOGY OF SVALBARD
A Window into the Barents Sea
Hydrocarbon Province
SVALEX 2009
Arild Andresen
Svalbard- An uplifted part of
the Barents Sea
– bordered to the
SW by a
sheared or
transtensional
margin
Sp
re
ad
ing
– bordered to the
N by a rifted
margin
rid
ge
• The Barents
Sea/Svalbard is
Svalbard
Barents
Sea
Bjørnøya
Norway
• Svalbard
represents the
uplifted and
exhumed part
of the Barents
Sea
• Post-Devonian
rocks on
Svalbard can
be considered
as field
analogues for
many of the
source and
reservoir rocks
in the deeper
part of the
Barents Sea
Simplified W-E profile across central
Spitsbergen and the Olga Basin,
Western Barents Sea
SVALEX cruises in 2006
Seismic data in the fjords of Svalbard
Geology of Svalbard
•
•
•
•
•
•
Pre-Devonian Hecla Hoek
Basement, variably
reworked during the
Caledonian orogeny
Devonian continental
deposits (Old Red
Sandstone)
Early/mid-Carboniferous rift
deposits
Mid CarboniferousPermian shelf carbonates
Mesozoic silisiclastic
deposits
Tertiary deposits, including
foreland basin deposits
Opening of the Fram Strait illustrating movement of Spitsbergen past
NE Greenland
Pre-Devonian Basement
Devonian deposits
•
•
•
•
Strike-slip
movement on
major fault zones
Fault -bounded
basins (Pull apart
basins?)
”Old Red
Continent”
deposits
The deposits are
dominated by
conglomerates
and sandstones
Devonian sedimentation and deformation
West
East
•
Deposition of continental sediments in fault-bounded basins
•
Combined strike-slip and reverse movement (transpression)
along the Billefjorden Fault Zone results in folding of the
Devonian deposits (“Svalbardian Phase”)
Early- to Mid-Carboniferous
West
East
•
Deposition of Early Carboniferous coal-bearing (pre-rift)
fluvial deposits
•
Mid-Carboniferous syn-rift marginal marine deposits,
including conglomerate, sandstone, anhydrite/gypsum and
dolomite, in the Billefjorden and St. Jonsfjorden Troughs
A
B
Billefjorden
B
A
SvalSim
www.svalex.net
5.2
5.0
5.2
4.8
5.0
5.2
6.0
Synthetic seismic
Carboniferous deposits
• Pre-rift: Coal-bearing continental
deposits
• Syn-rift: Alluvial fan and sabkha
conditions
• Early post-rift: Marine carbonate
platform
• This part of the stratigraphy will be
studied in the Billefjorden area
Late Carboniferous and
Permian
• Slow thermal subsidence and post-rift deposition
• Stable carbonate platform with little influx of clastic
sediments
• Deposition of a thick succession of carbonates and
evaporites
Permian
• Stable marine carbonate
platform.
• Kapp Starostin Formation:
Spiculitic limestone and chert.
Mesozoic
• Change from carbonate to
silisiclastic deposition
• Continental shelf conditions
• The deposits are dominated by
shales and sandstones
• Little or no tectonic activity
• This part of the stratigraphy will
be studied in the Festningen
section
Mesozoic
Festningen
Early? Cretaceous
intrusives
D
•
dy
s
a
iab
d
/
e
it
oler
ke
Dolerite intrusives into the Permian Kapp Starostin
Fm
Early Tertiary
• Prior to formation of a transpressional orogen in
West Spitsbergen, coal-bearing sediments (black)
were deposited in much of the area occupied by
Spitsbergen today. This Early Tertiary coal is today
mined in Barentsburg, Longyearbyen and Svea
Tertiary
•
•
•
Horisontal shortening of
beds is caused by “space
problems” as Spitsbergen
moves past NE Greenland
Compression
(transpression) of the
region resulted in creation
of a foreland basin.
This basin can now be
observed in the Central
Basin of Spitsbergen.
Arctic Plate Tectonics and Opening of
the North Atlantic Ocean
A24B
55 Ma
A13
33 Ma
Present
Schettino & Scotese (2000)
M10
132 Ma
Transpressional regime when Svalbard was forced around the NE
“corner” of Greenland along the DeGeer zone. Svalbard is marked by
red triangle
Opening of the Fram Strait illustrating movement of Spitsbergen past
NE Greenland
Foreland basin profile
•
Right-lateral displacement along the DeGeer Zone in the
Paleocene created a transpressional orogen (orogenic belt) in
the west and a foreland basin to the East. A perpheral bulge
existed most probably further to the east.
Foreland basin analogue
”Orogenic belt”
”Foreland basin”
•
Formation of a foreland basin (pond) can be compared with
the bending of an ice sheet next to a pressure ridge due to
increased weight. The lithosphere is likewise elastically bent
in front of an orogen.
Paleocene
Evolutionary model:
• The foreland basin starts to develop
• Development of a thrust wedge in the west and 3 regionally
extensive dècollement zones in the underlying strata
Folds in Mesozoic
shales and sandstones
•
•
•
•
Miterhuken
Nordfjorden/Mediumfjellet
Tertiary ”thin-skinned” structures
due horisontal shortening
•
Duplex associated with the Lower Decollement Zone,
Kongsfjorden
Tertiary strata
Foreland basin infill
• Infill of the
Tertiary
foreland
basin
• This
section will
be studied
in the Van
Kaulen
Fjord.
Tertiary deposits
Tertiary clinoforms at Storvola (right) in Van Keulenfjord,
Spitsbergen. The sediments were transported from left (NW)
towards right (SE)
Eocene
• Continued shortening of the basin
• Basin inversion and deformation along the
Billefjorden and Lomfjorden Fault Zones
Thin-skinned shortening
structures
•
Local thickening in Triassic shale/siltstone associated
with the Middle Decollement Zone (gliding horison).
Loc.: Vendomdalen
Middle Decollement Zone
?
The entire fold in late summer!
Thin-skinned shortening
structures
Close-up view of the decollement folds at Midterhuken
Inversion structures along
Billefjorden Fault Zone
(Remember that the Billefjorden Fault Zone acted as a left-lateral strike-slip
fault in the Devonian, and as a down-to-the-east extensional fault in the
Mid-Carboniferous)
Summary
• Late
Tertiary
Heckla
Devonian
Carboniferous
Mesozoic
Paleozoic
Hoek
foreland
”Old
silicilastic
: Prerift
Red
carbonates
basin
basins
Devonian,
Sandstone”
deposits affected
deposits,
by fault
the
Caledonian orogeny
controlled