Reconstructing the Triassic northern Barents Shelf; basin infill patterns controlled by gentle sags and faults Alvar Braathen, Snorre Olaussen, Ingrid Anell, Kei Ogata, UNIS; Jan Inge Faleide, Roy Gabrielsen, Johan Petter Nystuen, UiO; William Helland-Hansen, Wojtek Nemec, UiB; Atle Mørk, NTNU; Per Terje Osmundsen, NGU/UNIS; Harmon Maher, UoN/USA; Fabrizio Storti, Fabrizio Balsamo, UoP/Italy
Combining onshore and offshore observations From Svalbard towards the south and east
1) Setting: Caledonian to Devonian infra-structure 2) Setting: Carboniferous rifting before the Permian platform 3) Triassic foreland sag basins and their infill characteristics 4) Triassic extensional faulting modifying sediment routing 5) Summary
Force workshop, Stavanger, 4th April 2013 Project proposal submitted to Petromaks2 the 150213:
Reconstructing the Triassic northern Barents Shelf ProjectProposal group from: builds on a UNIS, UiO, UiB, NGU, NTNU, UoP/Italy, UoN/USA, Middle UU/Netherlands,series ofCanadian observations, Survey Triassic Backed by Spring Energy (Tullow Oil Norway) presented here Aims: Integrate onshore and offshore datasets to improve the understanding of basin development and tectonic activity of the northern Triassic Barents Shelf Clinoform migration across regional sag-type basins,
Fluvial and shallow marine depositional systems of the Image from Google Earth, .kmz-file based migrating shelf, on Ron Blakeys palaeogeography Growth faulting in the distribution of reservoir sandstones, Interaction between shelf progradation, sag-basin development and faulting, Deep-seated zones of weakness and far-field stress configurations
How did this foreland basin fill in? What controlled infill patterns? Can we establish sediment routing?
Braathen et al. 2012 1) SETTING Grogan et al. 1999 Todays exposures … Late Cretaceous+Tertiary N-side up from Late Cretaceous to Oligocene events … controlling the map pattern domains Onshore study sites Eocene-Oligocene N side up => rifting W-side up W side up => rifting
Tertiary fold-thrust belt • Stacked crust in f-t belt • Foredeep Open seismic grid • Forebulge • Backbulge Where are they? 1) SETTING: Paleogene and Cretaceous
Paleogene transpression => transtension Extensive Cretaceous (125 Ma) intrusive tectonics during North Atlantic break-up and extrusive basaltic rocks (HALIP) N-S domain Stéphane Polteau et al. 2011
Fold-thrust E-W belt domain
NE-SW domain
Fault- basin inversion NGU grav.-mag. 1) SETTING: basement data linking Norway with Linking mainland with Svalbard Svalbard tectonics across the shelf Devonian basins and Current deep infrastructure: tectonics Restoration: Caledonian Caledonian nappes modified by nappes in initial position Devonian extension
N-S
Braathen et al. 1999
Gernigon & Brønner 2012 Devonian basement grain … infra-structural controlling later faulting
Top-N, corrugation- and orogen-parallel Orogen-parallel shear zone extenion, Extension-normal basement ridges
Thrust front? SCANDINAVIAN CALEDONIDES Orogen-normal/ oblique extension, Extension-parallel basement ridges SVALBARD Poorly consolidated coarse-clastic alluvial fan and fluvial S deposits, with seismic-scale sedimentary architecture N Osmundsen, Braathen & Maher, in progress Braathen et al. 2010: e Extensional shear e e e Te zone with top-N Mz kinematics, truncating syn-tectonic hanging- e e e e wall basin fill, also with younger fault activity 2) SETTING: Carboniferous rift basin, reactivating N-S Devonian fault zone
Billefjorden Fault Zone reactivated as Carboniferous extensional fault Billefjorden Trough in the hanging-wall
Bælum & Braathen 2012 Bergh et al. 2011 Carboniferous extensional basin Regional W-E seismic line, Isfjorden Devonian reverse faulting Carboniferous Billefjorden Trough Karst development
Palaeoaplysina bioherms Av. Φ/Perm; Asselian 17.9 %/55.3 mD reefs
Basin shoulder Fault-tip monoclines reefs/buildups Localized fan in evaporite complexes dominated areas Karst systems around/above intra-basin fault
Braathen et al. 2011
Johannessen and Steel 1992
Detailed 3D geometries unravel basin configuration Billefjorden Trough Boundary fault domain (west)
• N-S fault zone with relay structure between master faults
• Major alluval fan complex building out from relay zone Alluvial fan complex in • Large basin-parallel monocline fault relay zone along fault zone; Petuniabukta syncline
Geographic reconstruction of basin fill
Braathen et al. 2012 Lidar scan of Billefjorden Trough sub-basin near Central-East dip-slope side basin center of half-graben Wedge-shaped sub-basin • N-S intra-basin faults and sub-basins
• Filled with interfingering siliciclastic, carbonate and evaporite rocks
• Fault-tip monocline and sharp- breaking extensional faults, controlled by evaporite fill
Extensional fault-tip monocline, with lenticular-shaped, HW sub-basin
Braathen et al. In press Seismic interpretation of Carboniferous extensional basin
Applying onshore basin geometries and facies distribution models to cultivate a viable basin description
well Reindalen Hydro line
Tertiary detachment thrust Post-rift Late-rift thinning
lenticular lenticular
monocline wedging Pre-rift
basement monocline Smelror et al. 2009 3) TRIASSIC N-S domain
SYSTEM… E-W± domain Peak of Uralides collision orogen … N-S domain
• Low relief NNE-SSW Foredeep? sed. systems domain Forebulge? • Sag basins
• Local high relief sed. Faults? systems • Grabens
West East Te foredeep Te forebulge? Compiled by Thickness 3-5 km Statoil Where is the Forebulge? Foredeep Heavy root? Distance > 700 km Triassic Palaeogeography .. clinoforms filling a foreland shallow sea
Braathen et al. 2012 Anell et al. in prep.
Riis et al., 2008 Onshore: Triassic succession showing regional basin configuration
Regional shallow sag (foreland) basin with clinoforms infilling mainly from the ESE to SE Widespread upper Triassic fault-bound basins of mainly the Snadd Fm age Offshore: Riis et al. 2008 Regional sedimentary Hopen-2 system bypassing eastern foredeep basin
Tying seismics to well Hopen-2, and Glørstad-Clark et al. 2011 previous studies
Limited distribution seismics Triassic sags and up-warps Gardarbanken High (GH) Regional up-warping in Early Triassic (Forebulge - Deep salt - Other?) Limited distribution seismics Blocking Early-Mid Triassic clinoform migration Bypassed in Mid. Triassic Sørkapp basin (SB) Regional sag basin (back-bulge?) Thick, continuous(?) Triassic succession
Limited distribution seismics Comparison of Snadd Fm channels (seismics) to
Details: Sediment routing systems De Geerdalen1000 Fm channels (onshore Hopen)
Correlation between Barents Sea 3D 2a (m) 100 seismics and databases … 2b … ongoing work (Helland-Hansen et al., UiB) w/t 10 w/t 100 thickness thickness 10
w/t 1000 Max Where are the sand sinks? Upper Triassic w/t 1 drainage patterns identified with seismic 1 Hopen 10 100 1000 10000 1000001000000 attributes in the Hoop Graben area Maximum width (m)
Limited distribution seismics Fluvial/Distributary channels
Outline of Hopen Hopen: Fluvial channel sandstone … point bar progradation Paleocurrent … partly on subseismic scale
Nørdstefjellet
1000
Fining-up 2a (m) successions 100 2b w/t 10 Comparison of
Snadd Fm 10 w/t 100 thickness thickness channels w/t 1000
(seismics) to 1 Max De Geerdalen 10 1000 100000 w/t 1 Fluvial channels of Hopen Fm channels Maximum width (m) Hopen (Hopen) 4) TRIASSIC FAULTING – steep, planar faults of Hopen
View from the SE of the Fault-tip defined as a major monocline in shale northernmost fault on Hopen
T2
T1 Fault throw T1>T2 c. 60 m U.Tr. De Geerdalen Fm Snadd Fm
Dip slip normal fault o striking c. 115
Fluvial channel belt? U D
c. 100 m Fault reading= 133 64 64 NOTE OBLIQUE VIEW Faulting of Klinkhammaren, Poles to bedding, Edgeøya indicating an N=22 approximately ESE-WNW rotation • Faults inferred from truncated sandstone sections axis • Domino-style block faulting above bedding-parallel detachment near top Kobbe Fm • Growth deposits seen in the upper shale section to the south. • Erosional base below the upper succession that buries the faults. • Snadd/DeGeerdalen Fm develops from a marine, thick- bedded and sandstone dominated lower succession, into variable paralic deposits in the upper half.
Atle-170809 Rita-170809 SSE Alvar-170809 Heli-Lidar scanned slope Alvar 190809
Snadd/De Geerdalen Fm Tschermakfjellet Fm Kobbe/Botneheia Fm
c. 200 m Onlap? Growth wedges?
Snadd Fm Kobbe Fm Fault style summary: Edgeøya (Hopen)
Steep, planer 50-100m faults cutting Kobbe/Botnheia Fm shale Listric faults rooting in Kobbe/Botnheia Fm shale
Hopen Both fault systems with similar strike (~ E-W) Both fault systems with sedimentary growth wedges, hence active in Late Triassic time
Detachment in Kobbe/ Botnheia Fm pro-delta shale
Klinkhammaren Decoupled but linked deep-rooted (planar) and shallow-rooted (listric) faulting
Rotated blocks No-rotation blocks
Skrukkefjellet Shallow rooted
Deep-rooted Orientation of Triassic fault system, as seen in onshore and offshore data
Anell et al., in press. World class example of interacting Growth fault = contemporaneous faulting shallow and deep rooted fault and sedimentation, evidenced by abrupt system increase of thickness across fault …… Kvalpynten growth fault system, South Edgeøya e.g., Edwards (1976)
c. 8 km
DeGeerdalen Fm
8 9 11 2 3 4b 5 6 7 10 Fault blocks 1 4a
Fault interactions
No-rotation block => Planar ft Rotation block Rotation block => Listric fault => Listric fault
next Fault block 6 7 8 Kvalpynten fault 2 characteristics c. 20 m
Note rotated low-angle to bedding ”normal” fault
Slip surface with 2-5 cm sheared sand membrane on HW side, and 5-10 cm sheared shale mebrane on FW side
Disaggregation (grain rolling) deformation Sheared sand membrane (c. 10 band with sand smear cm) hosting mixed-in clay and diagenetic pyrite. No slip surface! Snadd Fm Top of growth section, succession regional(?) flooding surface
DeGerdalen Fm, Kvalpynten, Progradational Edgeøya paralic systems
Growth-basin infill wedges Growth basin successions
Draping marine and tidal (paralic) units
c. 100 m
Shallow-rooted listric fault Steep planar fault Cyclic sandbody architecture reflects variations in N accommodation creation rate in subsiding hanging-wall basins S
Draping unit: clinoforms, sandstone sheets and shales
c. 100 m
offshore shoreface
Tidal flat Channelized unit (sandst/shales)
3. Sandy massflow wedge filling fault-driven basin
2. Aggradational (top)sets
1. HW and SW-directed progradation of tidal depostis Growth successions – typical facies associations (FA)
Growth cycles Deep-rooted faults terminating in the Snadd Fm, as seen in seismic lines of SE Svalbard Complex reflection patterns in the upper Triassic succession could be caused by listric, shallow rooted faults, setting up 100m deep (< 100 ms) growth basins. This will be pursued through comparison with synthetic seismics
Limited distribution seismics
Deep Deep Deep root root root
Distorted level Distorted level
Growth Growth
Deep root Anell et al., in press Triassic faulting is regional
Hoop Graben with Triassic fault activity; Loppa High ongoing PhD work on growth successions as seen in 3D seismics
K faulting event
TGS data in Geo Mai 2012 Høy & Lundschien 2011 .. the larger picture Top Triassic Stacked shelf-edge position? Fault zones interacting with Triassic clinoforms? sedimentary system
Research approach: localized fill • Interaction of deep (basement?) and shallow-rooted faults? • Are stacked shelf-edges localized suggesting fault- fill clinoform interaction? • Impact on sediment routing - sags/highs vs. grabens? • Sedimentary system characteristics
localized basin fill Top Permian Late Carboniferous 5) SUMMARY: Triassic growth basins vs clinoform shelf infilling
Clinoform progradation interacts with sags and highs; forebulge– backbulge, deep salt or other drivers? Clinoforms locally arrested by Triassic fault-bound basins of the Snadd Fm age
Regional faulting event rather than delta collapse (proposed earlier) Reactivated Carboniferous, basement-rooted faults? N-S Partly detached fault system, rooted domain in Kobbe Fm shales (Edgeøya and E-W distorted seismic levels) domain Snadd Fm growth wedges: Pro-delta shales to delta/shoreline and partly fluvial deposits. Strong signals of tidal influence. Basins locally filled with massive sandstone, considered as fault- triggered instability massflow deposits. Significant variation in reservoir sandstone location and geometries => exploration strategy? Growth fault observations; onland + marine DATASETS FROM: NPD EXPEDITION, 2009 UNIS EXPEDITION 2012
Atle Bjørn
Thank you ... Tore