Diachronous Crustal Localization and Onset of Seafloor Spreading in the Central Atlantic:

Application of Inverse Continuum-based Plate Reconstruction Methods

Erik A. Kneller and Christopher A. Johnson

With Contributions from Garry Karner and Kim Klitgord

ExxonMobil, Upstream Research Company

ENAM GeoPRISMS-EarthScope Workshop2011

Summary

After decades of work, Central Atlantic plate reconstructions are still debated in the literature (Schettino and Turco, 2009; Labails et al., 2010).

The Central Atlantic imposes important boundary conditions on the Mesozoic evolution of the Gulf of Mexico

New Basement Type Maps

• Published reflection and refraction data, potential field data and field observations

Refined Tight-fit Pangaea Reconstruction

• Palinspastic restoration of crustal thickness grid constrained by refraction and receiver functions (e.g. Dunbar and Sawyer, 1989)

Rift to drift kinematics based on 3D non-rigid continuum plate models and linking ECMIP and CAMP events (Kneller et al., submitted to C&G)

Explore multiple scenarios for Jurassic seafloor spreading

Characterizing the Lithosphere with Basement Type

Stable Continental

Stretched Continental

Normal Oceanic

Thick Oceanic

Volcanic Margin (Mafic Intrusives and Extrusives, Highly Extended Continental)

SDR’s

Exhumed Mantle, Volcanic Margin or Highly Extended ContinentalCrustal Hinge Line

Receiver Functions (Li et al, 2002; Ramesh et al., 2002; Fnais, 2004)

?

?

?

?

Conjugate Refraction Lines (Talwani et al., 1995; Funk et al., 2004; Wu et al., 2006; Contrucci et al., 2004; Klingehoeferet al., 2009)

DSDP 534: Mid-Callovian Basalt

Toarcian NMORB (Steiner et al., 1998)

Yucatan

North America

South America

West Africa

?

?ECMIP

BSMA

M25?

Receiver Function or Refraction Moho

Best Fit Isostatic Moho10 39

Crustal Thickness (km)

Crustal Thickness and Palinspastic RestorationsRestored Boundary Using Crustal Thickness Model (Dunbar and Sawyer, 1989)

Restored Boundary Using Crustal Thickness Model (This study)

Restored Refraction Lines

~500 km

Yucatan

North America

West Africa

Comparison of Models at Maximum Closure

Schettino and Turco, 2009

Labails et al., 2010

This Study

~500

0 km

Maus et al., 2009

Holbrook et al., 1994; Talwani et al., 1995; Kelemen and Holbrook, 1995

Nomade et al., 2007

Hypothesis for Breakup Timing: Linking ECMIP and CAMP Events

ECMA

CAMPECMIP

GO

M S

yn-r

ift (

Eag

le M

ills)

Diachronous initiation of seafloor spreading is inf erred from Newark Supergroup stratigraphy (e.g. Withjack et al., 1998).

Diachronous localization of extensional strain may also contribute to a diachronous end to syn-rift extension in the proximal part of the s ystem

Yucatan

North America

?

?

?

Olsen (1997)

Newark Supergroup and Rift to Drift Kinematics

Continental Crust of Plate A Continental Crust of Plate B

Overlap

Localization Boundary2) Rigid Reconstruction

Original node locationsRestored node locations

Linking Plate Kinematics to 3D Crustal Deformation• 3D Pure Shear Deformation with Mass Conservation

• Particle displacement is along Euler Pole Flow lines and is a function of overlap and integrated extension from both plates.

• Localization controlled with prescribed boundaries.

• Airy Isostasy (No Flexure), No Erosion, No Sedimentation

• The goal is capture plate-scale lateral strain and crustal thinning not detailed subsidence

Kneller et al., submitted to C&G

3D Deformable Lagrangian Continuum

3) Non-Rigid Reconstruction

1) Present Day

9

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a

Flow lines parallel to the Grand Banks Transform Margin and Coeval ECMIP and CAMP:

• diachronous breakup

• a pattern of syn-rift extension consistent with the Newark Supergroup

240 Ma

West Africa

North America

H

F

N

T

Boundary Effects

SG

Kneller et al., submitted to C&G

10

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a235 Ma

H

F

N

T

SG

Kneller et al., submitted to C&G

11

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a230 Ma

H

F

N

T

SG

Kneller et al., submitted to C&G

12

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a225 Ma

H

F

N

T

SG

Kneller et al., submitted to C&G

13

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

220 Ma

H

F

N

T

Early Localization

Testing Syn-extension Models with Deforming Continu a

SG

Kneller et al., submitted to C&G

14

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

215 Ma

H

F

N

T

SGEarly Localization

Testing Syn-extension Models with Deforming Continu aKneller et al., submitted to C&G

15

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a210 Ma

H

F

N

T

SGEarly Localization

Kneller et al., submitted to C&G

16

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a205 Ma

H

F

N

T

SGEarly Localization

Kneller et al., submitted to C&G

17

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a200 Ma

H

F

N

T

SG

Initiation of ECMP and Early Breakup

Kneller et al., submitted to C&G

18

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a199 Ma

H

F

N

T

SG

Kneller et al., submitted to C&G

19

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a198 Ma

H

F

N

T

SG

Kneller et al., submitted to C&G

20

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a197 Ma

H

F

N

T

SG

Breakup and SDR Formation

Kneller et al., submitted to C&G

21

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a196 Ma

H

F

N

T

SG

Kneller et al., submitted to C&G

22

240

230

220

210200

197

210

220230

240

10 39Crustal Thickness (km)

Grand Banks Transform Margin

Northern Profile

Southern Profile

Crustal Thinning Subsidence

Testing Syn-extension Models with Deforming Continu a195 Ma

H

F

N

T

SG

Kneller et al., submitted to C&G

2310 39Crustal Thickness (km)

Grand Banks Transform Margin

Testing Syn-extension Models with Deforming Continu a194 Ma

Northward Propagation of Breakup

Kneller et al., submitted to C&G

2410 39Crustal Thickness (km)

Grand Banks Transform Margin

Testing Syn-extension Models with Deforming Continu a193 Ma

Kneller et al., submitted to C&G

2510 39Crustal Thickness (km)

Grand Banks Transform Margin

Testing Syn-extension Models with Deforming Continu a192 Ma

Kneller et al., submitted to C&G

2610 39Crustal Thickness (km)

Grand Banks Transform Margin

Testing Syn-extension Models with Deforming Continu a191 Ma

Northward Propagation of Breakup

Kneller et al., submitted to C&G

2710 39Crustal Thickness (km)

Grand Banks Transform Margin

Testing Syn-extension Models with Deforming Continu a190 Ma

Kneller et al., submitted to C&G

2810 39Crustal Thickness (km)

Grand Banks Transform Margin

Testing Syn-extension Models with Deforming Continu a189 Ma

ECMIP

Kneller et al., submitted to C&G

2910 39Crustal Thickness (km)

Grand Banks Transform Margin

Testing Syn-extension Models with Deforming Continu a188 Ma

Kneller et al., submitted to C&G

3010 39Crustal Thickness (km)

Grand Banks Transform Margin

Testing Syn-extension Models with Deforming Continu a187 Ma

Kneller et al., submitted to C&G

3110 39Crustal Thickness (km)

Grand Banks Transform Margin

Testing Syn-extension Models with Deforming Continu a186 Ma

Kneller et al., submitted to C&G

3210 39Crustal Thickness (km)

Grand Banks Transform Margin

Testing Syn-extension Models with Deforming Continu a185 Ma

Kneller et al., submitted to C&G

Syn-rift Basin (Costain and Coruh, 1989; Salvador, 1991; Olsen, 1997)

CAMP Flows (Nomade et al., 2007)

CAMP Dikes (Nomade et al., 2007)

Volcanic/Magmatic Margin

SDR’s (Grow et al., 1993; Talwani et al., 1995; Oh et al., 1995)

Newark

Gettysburg

Taylorsville

FundyHartford

South Georgia

GOM Eagle Mills

Central Atlantic Plate Model: Ridge Jump at 180 Ma

Newark

Gettysburg

Taylorsville

FundyHartford

South Georgia

GOM Eagle Mills

Central Atlantic Plate Model: Ridge Jump at 180 Ma

Syn-rift Basin (Costain and Coruh, 1989; Salvador, 1991; Olsen, 1997)

CAMP Flows (Nomade et al., 2007)

CAMP Dikes (Nomade et al., 2007)

Volcanic/Magmatic Margin

SDR’s (Grow et al., 1993; Talwani et al., 1995; Oh et al., 1995)

240

Newark Supergroup Syn-rift

NGOM GOM Transitional Crust Formation

Scenario C

NAM (Fixed)

WAFR

176 Ma 164.7 Ma

154 Ma

240 Ma

200 Ma164.7 Ma

154 Ma

Scenario A

Scenario B

NAM (Fixed)

WAFR

NAM (Fixed)

WAFR

240 Ma

154 Ma

240 Ma 200 Ma190 Ma

170 Ma (ridge jump)

Scenario D

154 Ma

NAM (Fixed)

WAFR

240 Ma 200 Ma190 Ma

180 Ma (ridge jump)

140 150 160 170 180 190 200 210 220 230

1

2

3

4

5

6

M25 (154.3 Ma)DSDP site 534 Basalt (~164.7 Ma)

Canary Island NMORB (~ 176-183 Ma)

Age (Ma)

Ful

l spr

eadi

ng r

ate

(cm

/yr)

WA

FR

w.r

.t. N

AM

CAMP Magma Production and Formation of ECMA crust

AB

C

GOM Oceanic Crust Formation

Ultraslow Spreading

Klitgord and Schouten (1986)

130

D

176 Ma

Multiple Scenarios and Implications for GOM Transitional Crust

Schettino and Turco (2009)

Labails et al. (2010)

Bird et al. (2007)

ConclusionsAccurately mapping the distribution of magmatic crust is essential for constraining Central Atlantic plate kinematics.

Recently published plate models are inconsistent with geologic and geophysical observations, include unrealistic gaps and cannot restore extended crust to a reasonable initial thickness.

Palinspastic restorations constrained by receiver functions and refraction data closely match restored refraction lines and improve tight fit reconstructions.

Inverse continuum models linked to plate kinematics can restore extended crust to a reasonable initial thickness if extension initially occurs over a wide zone and then subsequently localizes in the distal part of the system

The occurrence and timing of diachronous breakup inferred from the Newark Supergroup can be produced with continuum models if

• the ECMIP formation begins at peak CAMP time

• transform motion occurs between southern Grand Banks and West Africa

The diachronous end to syn-rift extension in the so uth may be associated with early localization of extens ional strain

A range of kinematic scenarios with different ridge jump timing are permissible during the Jurassic. Our preferred scenario involves a ridge jump at 180 Ma.