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GEOLOGY OF SVALBARD
SVALEX 2009 Arild Andresen
A Window into the Barents Sea Hydrocarbon Province
Svalbard- An uplifted part of the Barents Sea• The Barents
Sea/Svalbard is
– bordered to the N by a rifted margin
– bordered to the SW by a sheared or transtensional margin
Spre
ading
ridge
• 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
Svalbard
Barents Sea
Bjørnøya
Norway
Simplified W-E profile across central Spitsbergen and the Olga Basin, Western Barents Sea
Seismic data in the fjords of Svalbard
SVALEX cruises in 2006
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 Carboniferous- Permian 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
• Deposition of continental sediments in fault-bounded basins
EastWest
• Combined strike-slip and reverse movement (transpression) along the Billefjorden Fault Zone results in folding of the Devonian deposits (“Svalbardian Phase”)
Early- to Mid-CarboniferousWest 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
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Billefjorden
Synthetic seismic
SvalSim
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
• Dolerite intrusives into the Permian Kapp Starostin Fm
Dolerite/diabas dyke
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
M10132 Ma
A24B55 Ma
A1333 Ma
Present
Schettino & Scotese (2000)
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
• 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.
”Foreland basin”
”Orogenic belt”
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
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Folds in Mesozoicshales 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 clinoforms at Storvola (right) in Van Keulenfjord, Spitsbergen. The sediments were transported from left (NW) towards right (SE)
Tertiary deposits
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-slipfault in the Devonian, and as a down-to-the-east extensional fault in theMid-Carboniferous)
Summary
• Heckla Hoek : Pre- Devonian, affected by the Caledonian orogeny
• Devonian ”Old Red Sandstone” deposits, fault controlled
• Carboniferous rift basins• Mesozoic silicilastic deposits• Late Paleozoic carbonates• Tertiary foreland basin