Chris Chris ParryParry

With With acknowledgementsacknowledgements to to KhalidKhalid SoofiSoofi and and GuyGuy FlanaganFlanagan

FRACTURES ZONES AND THEIR FRACTURES ZONES AND THEIR ROLE IN THE OPENING OF THE ROLE IN THE OPENING OF THE ATLANTIC ATLANTIC –– LESSONS FROM THE LESSONS FROM THE SOUTH ATLANTICSOUTH ATLANTIC

Talk Outline

• South Atlantic Fracture Zones,• North Atlantic Remote Sensing Observations:

Gravity,Magnetics,Sparse 2D seismic (where available)and Bathymetric data

• Integrated to derive a model for the opening of the North Atlantic, based on the South Atlantic.

West Africa Conjugate Margin

Romanche FZCharcot FZ

Boda Verde FZ

Rio de Janeiro FZ

Benguela FZ

Ascension FZ

Martin Vaz FZ

Lower Plate

Upper Plate

Upper Plate

5 KM

West African Offshore Fracture Zone

OCEANIC CRUST

Basement structural highs related to volcanic activity along “leaky” fracture zones in the oceanic crust set up the initial basin structural

framework.

5 KM

West African Offshore Fracture Zone

OCEANIC CRUST

Basement structural highs related to volcanic activity along “leaky” fracture zones in the oceanic crust set up the initial basin structural

framework.

Deepwater sedimentation on- lapped these basement highs which continued to propagate

into younger strata by differential compaction.

5 KM

Fracture Zones divide the deep water into discrete depo-centres

with different fill histories.

West African Offshore Fracture Zone

OCEANIC CRUST

Basement structural highs related to volcanic activity along “leaky” fracture zones in the oceanic crust set up the initial basin structural

framework.

Deepwater sedimentation on- lapped these basement highs which continued to propagate

into younger strata by differential compaction.

Rio Muni & Gabon Basins: Cretaceous Pre Rift Configuration

Lower Plate

Romanche FZCharcot FZ

Boda Verde FZ

Rio de Janeiro FZ

Benguela FZ

Upper Plate

Ascension FZ

Martin Vaz FZ

Upper Plate

Rio Muni & Gabon Basins: Cretaceous Pre Rift Configuration

Lower Plate

Romanche FZCharcot FZ

Boda Verde FZ

Rio de Janeiro FZ

Benguela FZ

Upper Plate

Ascension FZ

Martin Vaz FZ

200 Km

Bata FZ

Kribi FZ

Cameroon FZ

Fang FZ

N’Komi FZ

Mayumba FZPa

nA

fric

anM

obile

Bel

t

CongoCratonAscension FZ

Simplified after Meyers et al 1996

Pre-Cambrian basement

Cretaceous rift basins

Transfer fault zone

Modern coastline

Mid Atlantic Ridge

Upper Plate

Rio Muni & Gabon Basins: Cretaceous Pre Rift Configuration

Lower Plate

Romanche FZCharcot FZ

Boda Verde FZ

Rio de Janeiro FZ

Benguela FZ

Upper Plate

Ascension FZ

Martin Vaz FZ

200 Km

Bata FZ

Kribi FZ

Cameroon FZ

Fang FZ

N’Komi FZ

Mayumba FZPa

nA

fric

anM

obile

Bel

t

CongoCratonAscension FZ

Simplified after Meyers et al 1996

Some major fracture zones originate along pre-Cambrian

structural grain

Pre-Cambrian basement

Cretaceous rift basins

Transfer fault zone

Modern coastline

Mid Atlantic Ridge

Upper Plate

Jan Mayen Island

Gravity Expression of the Jan Mayen Fracture Zones

Jan Mayen Island

West Jan Mayen FZ

Gravity Expression of the Jan Mayen Fracture Zones

Ægi

rRi

dge

Ægi

rRi

dge

Ægi

r Rid

ge

East Jan Mayen FZ

Central Jan Mayen FZ

Magnetic Expression of the Jan Mayen Fracture Zones

Jan Mayen Island

Magnetic Expression of the Jan Mayen Fracture Zones

Jan Mayen Island

Ægi

rRi

dge

Ægi

rRi

dge

West Jan Mayen FZ

Ægi

rRi

dge

Ægi

rRi

dge

East Jan Mayen FZ

Central Jan Mayen FZ

Norway Basin FZ

Magnetic expression of the Mohn Ridge Spreading Centre

Jan Mayen Island

West Jan Mayen FZ

Kolb

eins

eyRi

dge

Magnetic expression of the Mohn Ridge Spreading Centre

Jan Mayen Island

West Jan Mayen FZ

Kolb

eins

eyRi

dge Mohn Ridge

Gleipna FZ

Surt FZ

Bivost FZ

Magnetic Anomalies (NE Greenland)

Magnetic Anomalies (NE Greenland)

Bivost FZ

Lofoten FZ

Jennega FZ

Bathymetry off East Iceland

Conv

entio

nal T

race

ofÆ

gir R

idge

Deep Water Fan?

Bathymetry off East Iceland

Scoresby Sund Fan

Bathymetry

Scoresby Sund Fan

Bathymetry Free Air Gravity

Scoresby Sund Fan

Bathymetry Free Air Gravity Magnetics

East Iceland Sea Floor Feature

East Iceland Sea Floor Feature

Free Air Gravity

East Iceland Sea Floor Feature

Free Air Gravity Magnetics

Color variations due to rock and soil composition differences; temperature differences are expressed as brightness variations.

Red hues on the left and right sides are probably underlain by rocks with high silicon-dioxide content,

White and lavender in the central part are dominantly basaltic lava flows and cinder cone deposits.

Dark areas within the complex of basaltic rocks are mainly domes, which are highly fractured.

http://www.nasa.gov/multimedia/imagegallery/image_feature_491.html

Afar Triangle Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)

Ægir Ridge Spreading History

Symmetrical opening of North Atlantic in Early Eocene

Ægir

Ridge

Mohns

Ridge

Reykja

nes

Ridge

Anton

Dohrn

Wyville Thompson

Judd

ClairVictory

MagnusErland

Faroe

West Jan Mayen

East Jan MayenCentral Jan Mayen

Norway Basin

Spar

Marflo

Additional fracture zones present e.g. Westray

GleipnaSurt

Bivost

LofotenLEGEND

Spreading RidgeHot spotFracture Zones

Relative Plate Motion:

Age of Oceanic Crust:Chron 24 – 21 E Eocene

0 Kilometers 250

C13

C24Present

C21C24

C24

C21

Symmetrical spreading of North Atlantic throughout Middle - Late Eocene

LEGENDSpreading RidgeHot spotFracture Zones

Relative Plate Motion:

Age of Oceanic Crust:Chron 24 – 21 E EoceneChron 21 – 13 M/L Eocene

0 Kilometers 250

C13

C24Present

Jennega

SenjaVesterålen

Slower spreading

rate

C13C21

C21

C13

Oligocene plate re-organisation, change of spreading direction

Fram Strait opening - relative plate motion changes from right-lateral shear to oblique divergence (left-lateral shear on Victory FZ)

LEGENDSpreading RidgeHot spotFracture Zones

Relative Plate Motion:

Age of Oceanic Crust:Chron 24 – 21 E EoceneChron 21 – 13 M/L EoceneChron 13 – 6 Oligo/E Mio

0 Kilometers 250

C13

C24Present

C13C6

C6C13

Slower spreading

rate

Oligocene: change of spreading from Ægir-Kolbeinsey Ridge

LEGENDSpreading RidgeHot spotFracture Zones

Relative Plate Motion:

Age of Oceanic Crust:Chron 24 – 21 E EoceneChron 21 – 13 M/L EoceneChron 13 – 6 Oligo/E MioOligocene volcanics

0 Kilometers 250

C13

C24Present

C13C6

C6C13

Westerly migration of volcanic centre, flows locally obscure Eocene oceanic

crust magnetic anomalies

Location of future Kolbeinsey Ridge

Early Miocene: Kolbeinsey Ridge becoming active

LEGENDSpreading RidgeHot spotFracture Zones

Relative Plate Motion:

Age of Oceanic Crust:Chron 24 – 21 E EoceneChron 21 – 13 M/L EoceneChron 13 – 6 Oligo/E MioOligocene volcanicsMiocene volcanics

0 Kilometers 250

C13

C24Present

C13C6

C6C13

Flood basalts cover future Jan Mayen Micro-Continent

Location of future Kolbeinsey Ridge

Middle Miocene – Present: Kolbeinsey Ridge active

LEGENDSpreading RidgeHot spotFracture Zones

Relative Plate Motion:

Age of Oceanic Crust:Chron 24 – 21 E EoceneChron 21 – 13 M/L EoceneChron 13 – 6 Oligo/E MioChron 6 – 0 M Mio/RecentOligocene volcanicsMiocene volcanics

0 Kilometers 250

C13

C24Present

C6Present

PresentC6

Segmentation of Jan Mayen Micro Continent described by Scott et al., 2005

Kolb

eins

eyRi

dge

C13

C24

Present

C24

C13Present

C13

C24

Present

C24

C13Present

Plate vectors fromEngen et al., 2008

Plate Motion relative to hot spot

NW European plate

N American plate

Conclusions

Oligocene and Miocene lava flows locally obscure Eocene magnetic anomalies in the Iceland/Jan Mayen Micro-Continent area

Conclusions

Oligocene and Miocene lava flows locally obscure Eocene magnetic anomalies in the Iceland/Jan Mayen Micro-Continent area

A simple symmetric spreading model can be used to explain the opening of the North Atlantic

Assuming the position of Iceland’s hot spot/mantle plume has remained stationary, the NW European plate has migrated eastwards ~300 Km since ocean spreading ceased on the Ægir Ridge near the end of the Eocene.

Conclusions

Oligocene and Miocene lava flows locally obscure Eocene magnetic anomalies in the Iceland/Jan Mayen Micro-Continent area

A simple symmetric spreading model can be used to explain the opening of the North Atlantic

Assuming the position of Iceland’s hot spot/mantle plume has remained stationary, the NW European plate has migrated eastwards ~300 Km since ocean spreading ceased on the Ægir Ridge near the end of the Eocene.

A similar magnitude of coeval eastwards movement of Svalbard, relative to Greenland, is associated with the opening of Fram Strait.

Conclusions

Oligocene and Miocene lava flows locally obscure Eocene magnetic anomalies in the Iceland/Jan Mayen Micro-Continent area

A simple symmetric spreading model can be used to explain the opening of the North Atlantic

Assuming the position of Iceland’s hot spot/mantle plume has remained stationary, the NW European plate has migrated eastwards ~300 Km since ocean spreading ceased on the Ægir Ridge near the end of the Eocene.

NW-SE trending, coast perpendicular transfer zones, are recognized regionally in the deepwater and adjacent shelf, probably linked to onshore pre-Cambrian basement fabric.

A similar magnitude of co-eval eastwards movement of Svalbard, relative to Greenland, is associated with the opening of Fram Strait.

Conclusions

Oligocene and Miocene lava flows locally obscure Eocene magnetic anomalies in the Iceland/Jan Mayen Micro-Continent area

A simple symmetric spreading model can be used to explain the opening of the North Atlantic

Assuming the position of Iceland’s hot spot/mantle plume has remained stationary, the NW European plate has migrated eastwards ~300 Km since ocean spreading ceased on the Ægir Ridge near the end of the Eocene.

NW-SE trending, coast perpendicular transfer zones, are recognized regionally in the deepwater and adjacent shelf, probably linked to onshore pre-Cambrian basement fabric.

Transtensional, transpressional and inversion structuring associated with mid ocean fracture zones has already been recognized in the seismic data on the Jan Mayen Micro Continent.

A similar magnitude of co-eval eastwards movement of Svalbard, relative to Greenland, is associated with the opening of Fram Strait.

Conclusions

Oligocene and Miocene lava flows locally obscure Eocene magnetic anomalies in the Iceland/Jan Mayen Micro-Continent area

A simple symmetric spreading model can be used to explain the opening of the North Atlantic

Thank You!