in search of a paleomagnetic “smoking gun” for precambrian plate tectonics
DESCRIPTION
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. from Evans, 2003. TPW on Earth. Richards & Engebretson, 1992 Nature. - PowerPoint PPT PresentationTRANSCRIPT
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