In search of a paleomagnetic “smoking gun” for Precambrian

plate tectonics

Conclusions:

Dipole hypothesis likely OK but not certain

Total terrane motion = TPW + individual motion

Smoking gun: Match APW paths and geology

Outer core( )geodynamo

TPW

Obliquity = 23°

Mantle

Ecliptic

plane

Solarradiation

Innercore

TPW on Earth from Evans, 2003

Richards & Engebretson, 1992 Nature

ω

Imin

TPW

Imax

I intEquator

TPW on a prolate spheroid

from Evans, 1998, EPSL v.157, p.1-8

Supercontinent – TPW predictions

TPW legacy

A common TPW axis

Buchan et al., 2000

Superior2.22-1.88

Ga

Kaapvaal2.22-1.87

Ga

Buchan et al., 1998Halls and Heaman, 2000

De Kock et al., in press

2101±2 Ma

MOLSON1880 Ma

Paleomagnetic success story

afterMcElhinny, 1973

Nuna: United Plates of America

Hoffman, 1988

Smoking gun at 1.8 Ga

2.1-2.0 Ga

1.88 Ga

1.75 Ga

1.96 Ga

New synthesis of Slave+Superior

Smoking gun at 1.8 Ga

2.1-2.0 Ga

1.75 Ga

1.96 Ga

New synthesis of Slave+Superior

Conclusions:

Dipole hypothesis likely OK but not certain

Total terrane motion = TPW + individual motion

Smoking gun: Match APW paths and geology