BASIN ARCHITECTURE AND LITHOSPHERIC STRUCTURE OF THE BARENTS SEA REGION FROM GEOPHYSICAL MODELLING

L. Marello (1,2); J. Ebbing (1,2); L. Gernigon (1)1 Geological Survey of Norway (NGU), Trondheim. 2 Department for Petroleum Engineering and Applied Geophysics,

Norwegian University of Science and Technology (NTNU), Trondheim.

Part of:PETROBAR Project

“Petroleum-related regional studies of the Barents Sea region" project funded by NFR and Statoil and includes participants from the University of Oslo, PGP, University of Bergen, International Re-search Institute of Stavanger, Geological Survey of Norway and Volcanic Basin Petroleum Re-search.

Contact: laura.marello@ngu.no

NGUNorges geologiske undersøkelseGeological Survay of Norway

Magnetic model made by 6 layers with homogeneous properties

Magnetic Basement blocks and geological implica-

Svalbard : Magnetic lineaments are correlating with Caledonian structures

West Barents Sea: anomaly trends represent Caledonian Thrust Front

West Barents Sea: high magnetic block; high pseudogravity; shallowing of deep dense lowercrust could be a methamorphic core complex formed during the exumation of the lower crustalrocks by low-angle detachments

Central Barents Sea High Anomalies:seems to be part of two different basement blocks

E-Svalbar : Sill intrusions are related to the CretaceusMagmatic event

NE-Barents Sea : pseudogravity coincident with Bouguer gravity

Central-N Novaya Zemlya : susceptibility inversion and forward modelling not coinciding

N and S East Barents Sea Basin:have different basement

SW Barents Sea: Magnetic block: Early Proterozoic and Archeancomplexes are near the surfaceNon Magnetic block: thick turbidite succession

SW Barents Sea: Anomaly trends coincide with Timanian trends

S Novaya Zemlya : Anomaly trends coincide with Timaniantrends

E-Svalbard : Small scale anomalies have shallower Euler solutions and are considered the effect of sill intrusion

NE-Barents Sea 1:Lineaments are following Uralian setting

4) INTEGRATION OF RESULTS

Fendinsky High: lineaments seems to be the prolongations of Timanian linea-ments (e.g. BF: Baidaratsky Fault)

The magnetic field analysis and the in-version results combined with the for-ward models give a regional overview of the Barents Sea basement and allow to organize the area in sub-domains with similar magnetic properties.The magnetic patterns in comparison with geological trends and the suscepti-bility distribution help to illustrate the tectonic setting.

Bibliography- Blakely, R., 1995. Potential Theory in Gravity and Magnetic Applications. Cambridge University Press. , 461 pp.-Dimakis, P., Braathen, B.I., Faleide, J.I., Elverhoi, A. and Gudlaugsson, S.T., 1998. Cenozoic erosion and the preglacial uplift of the Svalbard-Barents Sea region. Tectonophysics, 300(1-4): 311-327.- Grad, M., Tiira, T. and Group, E.W., 2009. The Moho depth map of the European Plate. Geophys. J. Int., 176,(279-292).- Gramberg, I.S., Glebovsky, V.Y., Grikurov, G.E., Ivanov, V.L., Korago, E.A., Kos'ko, M.K., Maschenkov, S.P., Piskarev, A.L., Pogrebitsky, Y.E., Shipelkevitch, Y.V. and Suprunenko, O.I., 2001. Eurasian Arctic Margin: Earth Science Problems and Research Challenges. Polarforschung, 69: 3-25.-Jakobsson, M., Macnab, R., Mayer, L., Anderson, R., Edwards, M., Hatzky, J., Schenke, H.W. and Johnson, P., 2008. An improved bathymetric portrayal of the Arctic Ocean: Implications for ocean modeling and geological, geophysical and oceanographic analyses. Geophysical Research Letters, DOI: doi: 10.1029/2008gl033520.- Johansen, S.E., Ostisty, B.K., Birkeland, Ø., Fedorovsky, Y.F., Martirosjan, V.N., Christensen, O.B., Cheredeev, S.I., Ignatenko, E.A. and Margulis, L.S., 1992. Hydrocarbon potential in the Barents Sea region: play distribution and potential. In: T.O. Vorren et al. (Editors), Arctic Geology and Petroleum Potential. Norwegian Petroleum Society (NPF), Special Publication, pp. 273-320.- Ritzmann, O., Maercklin, N., Faleide, J.I., Bungum, H., Mooney, W.D. and Detweiler, S.T., 2007. A three-dimensional geophysical model of the crust in the Barents Sea region: Model construction and basement characteriza-tion. Geophysical Journal International, 170(1): 417-435.- Skilbrei, J.R., 1991. Interpretation of Depth to the Magnetic Basement in the Northern Barents Sea (South of Svalbard). Tectonophysics, 200 (1-3): 127-141

4 transects FORWARD MODELLING

To validate the inversion results, to test the susceptibility distribu-tion and to refine the top basement geometry we apply forward modelling.The seismic models reflect the main structures and constrain the geometry.Density modelling provides extra constraints for the deep struc-tures (e.g. Moho). The results of the susceptibility inversion have been used to set the average susceptibility on the initial magnetic domains.After large number of tests the initial magnetics, densities and crustal geometries were jointly refined.The results along the WE lines are integrated and combined using the SNBS.

Error= 2.2927

= Calculated= Observed,

Grav

ity (m

Gal)

-10

0

10

20

Mag

netic

s (nT

)

-100

0

100

200

300

Dept

h (k

m)

40

30

20

10

0

0 400 800 1200Distance (km)

0.0032700

0.0032500

Cenozoic/Mesozoic sediments

Paleozoic sedimentsPaleozoic/Riphean complex

Finmark Platform

Central Barents

Monocine Tiddlybanken

BasinFedynskiy

High

North East Barents

Sea BasinKola-KaninMonocline

MaliginskiyGraben

Paleozoic/Riphean complex

0.0082760

0.0182760

0.0132730 0.04

2910

0.0352810 0.079

27900.0522880

0.0212850

0.0272800

0.0292720

0.0232710

0.00013290

Error=35.34

= Calculated= Observed,

Mantle

0.0053020

0.0053020

0.0053000

SBS

line

CBS

line

NBS

line

D1 D2 D3

BasmABasmB

Susceptibility SIDensity kg/m3

SNBS line

0.0022810

0.012840 0.035

2950

0.0272830

0.01628500.027

2750

0.003 ?2810|

0.0032700

0.0013060

0.0013110

0.0013000

0.019 ?2770

0.0012500

Cenozoic/Mesozoic sediments

Paleozoic sediments

Grav

ity (m

Gal)

0

50

100

Mag

netic

s (nT

)

-100

0

100

200

Dept

h (k

m)

40

30

20

10

0

500 1000 1500Distance (km)

Error= 50.149

= Calculated= Observed,

Error= 15.142

= Calculated= Observed,

0.0032760

0.0092890

02700

02800

0.0042830

02500

0.00063290 Mantle

NO DATANO DATA

BasmABasmB

Bille�ordenFault Zone

Norwegian Greenland Sea

Svalbard Margin

Franz Victoria Basin

Kong KarlsPlatform

North East Barents Sea Basin

Skalistoe Uplift

C1 C2 C3 C4 C5

NSBS

line

Susceptibility SIDensity kg/m3

NBS line

D=2700, S=0.006

0.0053040

0.0053010

0.0182820

0.0312850 0.014

28400.0112930

0.0192820

0.0272820

0.0013290

Mantle

027500.022

2880

0.0152780

0.0272730

0.0012500

Central Barents Sea Monocline

Kong KarlsPlatform

OlgaBasin

SørdkappBasin

EdgeøyaPlatrdorm

Norwegian Greenland Sea

Cenozoic/Mesozoic sediments

Paleozoic sediments 0.003, 2700

Error= 10.606

= Calculated= Observed,

NavayaZamlya

0 500 1000 1500

SNBS

line

Distance (km)

0

-30

30

60

0

10

20

30

40

Error= 35.631

= Calculated= Observed,

Dep

th (K

m)

Gra

vity

(mG

al)

Mag

netic

s (n

T)

50

-80

80

0

0.0052000

AdmiralityHigh Kara Sea

BasmABasmB

Noth-East Barents Sea Basin

B1 B2 B3 B4

Susceptibility SIDensity kg/m3

CBS line

Dep

th (K

m)

Gra

vity

(mG

al)

Mag

neti

cs (n

T)

0.0452710 0.046

2720

0.062940

0.042780

0.0012450

0.0262750

0.0482980

0.0142770

0.0013290

Mantle

0.0052930

0.0342810 0.027

2850

02740

0.0242730

0.0012500

Central Barents Sea High

S-East Barents Sea Basin

NavayaZemlya

NordkappBasin

OttarBasin

NorselHigh

SvalisDome

BjørnyaBasin

StappenHigh

VastbakkenVolcanicProvince

SNBS

line0 400 800 1200

0

10

20

30

40

0

-30

30

60

-100

0

100

200

Distance (km)

Error= 6.662

Error= 39.625

= Calculated= Observed,

= Calculated= Observed,

Cenozoic/Mesozoic sediments

Paleozoic sediments 0.002, 2700

A1 A2 A3 A4

BasmABasmB

Susceptibility SIDensity kg/m3

SBS line

2) MAGNETIC BASEMENT STUDY FROM INVERSION

Layers Susceptibility (SI*10-3) Boundaries layer0 km constant grid

1-Water 0Bathymetry1

2-Upper sediments 0.314 8 km constant grid

3-Lower sediments 2.51 Top basement2

4-Upper crust 12.57-37.7 25 km constant grid

5-Lower crust 5.03Moho 3

6-Mantle 0.6283

3) BASEMENT STUDY FROM COMBINED FORWARD MODELLING

NGU-VESEGEI compilation 2009

H ig h p a s s m a g n e tic fie ld L o w p a s s m a g n e tic fie ld

T ilt d e riva tive m a g n e tic fie ld P s e u d ogra vity

High pass 70 km trendsHigh pass 120 km trendsTilt derivative trends

On the map the picks of the filtering and tilt derivatives are displayed. The pseu-dogravity in the background helps to define the magnetic anomaly regions.

MAGNETIC FIELD ANALYSIS

Anomalies enhancement

3D INVERSION TECHNIQUE

3D Euler solutions

Shallower solutions :1-Kola kanin Monocline extending northward up to the Nordkapp Basin2- Eastern part of Svalbard

Medium solutions1- Central North Barents Sea

Deep solutions:1- Noethwest of Admirallity Highand Myszheniya Highs2- southern part of the South East Barents Sea3- two central Barents Sea anomalies

SI= 0.5 Thick step

4 . 18 8 .38 12.6 17 .8 23 28 .3 33 .5 3 8 . 7 SI x 10-3

HM

HM

LM

HM

MM

MM

LM

HMMM

HM LM

LM

MM HM

LM HM

HM HM

MM

LM

HM

LM HM MMHM

LM MM HMHM

NBS line

CBS line

SBS lineSNBS line

a)

b)

c)

d)

e)

NBS

CBS

SBS

SNBS

Sensitivity test Influence onsusceptibility results

Top basement uncertainty depths max8kmshallower

-3,8 SI*10-3

Top basement uncertainty depths max6 km deeper

6 SI*10-3

Low pass filtered magnetic field -2,5 – 2,5 SI*10-3

Upper continued magnetic field -5,6 – 5 SI*10-3

All basement magnetic -7,5 – 5 SI*10-3

Uncertainty ≈ 30%

3D INVERSION TECHNIQUE

inversion tests

SUSCEPTIBILITY INVERSIONMAGNETIC RESIDUAL

1=IBCAO model (Jakobsson et al., 2008); 2=W-Barents Sea (Skjlbrei et al. 1991); E-Barents Sea (Johansen at al., 1992: Gramberg et al., 2001); 3=combination of Barents 50 (Ritzmann et al., 2007) and Moho depth of the European Plate (Grad et al., 2009)

SENSITIVITY TEST

First regional indication of the mag-netization distribution in the Barents

Sea basement.

Low Magneticbasement

Medium Magneticbasement

High Magneticbasement

Magnetic Map Anomaly

Magnetic anomaly regions defined from field analysis.

Parameters used for the susceptibility inversion:

- Total magnetic field-inverted layer (upper crust) simpliffied as the sum of vertical prisms of

infinite depth extension.-Inversion routine for basement: combination of filters and inverse Earth

filter (Blakley, 1995)-Starting susceptibility: 0.031 SI

-Maximum standard deviation= 10 nT-Maximum number of iterations= 9

-No changes in geometries

Forward modelling results:

- give reasonable explanation of magnetic and gravity anomalies- are consistent with the inversion results- refine the magnetic basement

++++ Observed magnetic anomaly++++ Calculated magnetic anomaly

W E

W E

W ES N

T33A-1867

Dimakis at al. 1998

Density-depth relation

1) Linear function 2) Exponential function

Petrophysical database(density and susceptibility)

Velocity / density relation

Structural maps

1) EXISTING DATA Seismic informations

Moho depths from BARENTS50 modelhttp://www.norsar.no/c-90-Barents-Sea-3D-Model.aspx

Top Basement models

The uplift and the con-sequent emersion and erosion of the West Bar-ents Sea have implica-tion in the physical property distribution.

BasmA: form Skilbrei et al., 1991 (West Barents Sea) and Johansen et al., 1992 (East Barents Sea).BasmB: from Skilbrei et al., 1991 (West Barents Sea) and Gramberg et al., 2001 (East Barents Sea).

Contour lines every 2.5 km.

The Barents Sea tectonic setting is the result of multiple tectonic processes including three orogenic phases (Timanian, Caledonian and Uralian) and several episodes of rifting leading to a complex tectonic setting. Most prominently this can be observed in the differences between the rift basins configuration of the West Barents Sea and the mega-sag basins of the Eastern Barents Sea. The mechanisms leading to the present day basin and crustal architecture are still not completely understood.

In the present study we investigate the top basement geometry and the basement properties of the Barents Sea by testing the validity of previ-ous studies and trying to overcome the discrepancies between them. To reach our interest beside the conventional magnetic field analysis, we run inversion magnetic modelling and sensitivity tests. The inversion re-sults are then integrated along four profiles with seismic and gravity data and using 2D combined forward modelling we refine the magnetic properties along the profiles. The four lines are linked together and illus-trate the main crustal units of the all Barents Sea associated as different magnetic basement domains. Finally we discuss the meaning of the magnetic anomalies and of our results in terms of tectonic and geologi-cal implications.

Neog

ene

Pale

ogen

eCr

etac

eous

Jura

ssic

Tria

ssic

Perm

ian

Carb

onife

rous

Devo

nian

Silu

rian

Ord

ovici

anCa

mb-

rian

MES

OZO

ICPA

LEO

ZOIC

rifting (N. Atlantic, Arctic, W. Siberia)

episodic rifting episodes

Verkhoyansk orogenyEast Siberia

uplift-erosion in Arctic areas

Initiation of EurekanOrogeny

N. Atlantic riftingleading to breakup

BREAKUP EURAMERICAN BASIN

BREAKUP N. ATLANTIC

carbonate platformorganic buildups

evaporites

progressive closure ofthe Iapetus

CollisionBaltica-Greenland(Scandian Orogen)

Post-orogenic collapse

GEODYNAMIC EVENTS

TERT

IARY

Q u a te rn a ry

widespreadintracratonic

rifting

Uralideorogeny

Ellesmerian/Caledonian

orogeny

Iapetus formation

major plate reorganisation

Siberiantrapps

renewed uplift and erosionof Ural orogen

transtensionnal and transpressive regimes along the Western Barents shelf

humid climate affects sedimentation

Boreal and Thetys oceans disconnected

Pale

o-pr

oter

ozoi

c

PRO

TERO

ZOIC

Mes

o-pr

oter

ozoi

cNe

o-pr

oter

ozoi

c

Timanianorogeny

INTRODUCTION