GEOLOGY OF SVALBARD. A Window into the Barents Sea Hydrocarbon Province. SVALEX 2009 Arild Andresen

Transcription

1 GEOLOGY OF SVALBARD A Window into the Barents Sea Hydrocarbon Province SVALEX 2009 Arild Andresen

2 Svalbard- An uplifted part of the Barents Sea The Barents Sea/Svalbard is bordered to the N by a rifted margin Spreading ridge bordered to the SW by a sheared or transtensional margin

3 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

4 Simplified W-E profile across central Spitsbergen and the Olga Basin, Western Barents Sea

5 Seismic data in the fjords of Svalbard SVALEX cruises in 2006

6 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

7 Opening of the Fram Strait illustrating movement of Spitsbergen past NE Greenland

8 Pre-Devonian Basement

9 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

10 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 )

11 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

12 A B Billefjorden A B SvalSim Synthetic seismic

13 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

14 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

15 Permian Stable marine carbonate platform. Kapp Starostin Formation: Spiculitic limestone and chert.

16 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

17 Mesozoic Festningen

18 Early? Cretaceous intrusives Dolerite/diabas dyke Dolerite intrusives into the Permian Kapp Starostin Fm

19 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

20 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.

21 Arctic Plate Tectonics and Opening of the North Atlantic Ocean A24B 55 Ma A13 33 Ma Present M Ma 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

22 Opening of the Fram Strait illustrating movement of Spitsbergen past NE Greenland

23 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.

24 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.

25 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

26 Folds in Mesozoic shales and sandstones Miterhuken Nordfjorden/Mediumfjellet

27 Tertiary thin-skinned structures due horisontal shortening Duplex associated with the Lower Decollement Zone, Kongsfjorden

28 Tertiary strata

29 Foreland basin infill Infill of the Tertiary foreland basin This section will be studied in the Van Kaulen Fjord.

30 Tertiary deposits Tertiary clinoforms at Storvola (right) in Van Keulenfjord, Spitsbergen. The sediments were transported from left (NW) towards right (SE)

31 Eocene Continued shortening of the basin Basin inversion and deformation along the Billefjorden and Lomfjorden Fault Zones

32 Thin-skinned shortening structures Local thickening in Triassic shale/siltstone associated with the Middle Decollement Zone (gliding horison). Loc.: Vendomdalen

33 Middle Decollement Zone?

34 The entire fold in late summer!

35 Thin-skinned shortening structures Close-up view of the decollement folds at Midterhuken

36 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)

37 Summary Heckla Devonian Carboniferous Mesozoic Late Tertiary Paleozoic Hoek foreland Old silicilastic : Pre- rift Red carbonates basins Devonian, Sandstone deposits affected deposits, by fault the Caledonian controlled orogeny