A fresh look at marine magnetic anomalies, one of e key datasets in the development of plate tectonic Ian Norton, Larry Lawver, Lisa Gahagan Institute for Geophysics University of Texas at Austin From Vine and Matthews, 1963: culated with reversals Observed Calculated with constant magnetization Carlsberg Rid ge Sandwell gravity
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A Fresh Look at Marine Magnetic Anomalies, One of the Key Datasets in the Development of Plate Tectonics by Ian Norton - 2014 PaleoGIS & PaleoClimate Users Conference
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A fresh look at marine magnetic anomalies, one ofthe key datasets in the development of plate tectonics.
Ian Norton, Larry Lawver, Lisa GahaganInstitute for Geophysics
University of Texas at Austin
From Vine and Matthews, 1963:
Calculated with reversals Observed
Calculated with constant magnetization Carlsberg Ridge
Sandwell gravity
The EDSAC-2 computer used by Vine & Matthews http://en.wikipedia.org/wiki/EDSAC_2
• Plate model• Database: oceanic magnetic and tectonic (plate boundaries, paleomagnetic, hot spots, geological and geophysical data to extend the span and accuracy of global plate reconstructions)• This talk: a look at magnetic anomalies.
Crust Code
Green – Cande & Stock, 2004Black – Granot et al., 2013
Data from Global Magnetics Database http://www.soest.hawaii.edu/PT/GSFML/ML/index.html
Database run by Paul Wessel (Hawaii) & Dietmar Müller (Sydney)
Australia
Antarctica
-60
-50
-40
100 140
115˚E 120˚E
60˚S
Mismatches 5-6 km to as much as 35 km• Great dataset, needs work to use
Green – Cande & Stock, 2004Black – Granot et al., 2013
Data from Global Magnetics Database http://www.soest.hawaii.edu/PT/GSFML/ML/index.html
Example magnetic profile from Mascarene Basin
Base: Sandwell free air gravity 23.1
Base: Sandwell vertical gravity gradient 23.1
Example magnetic profile from Mascarene Basin• VGG emphasizes fracture zones and extinct ridges
ModMag model of Mascarene Basin profile• Really good match between synthetic and observed• Easy to map details of age interpretation
ModMag: Matlab program by Mendel, Munschy & Sauter, 2005. This profile is from example data files that are included with download.
Line SO183-11 from Mozambique Basin• Good match over parts of profile• Need multiple lines for regional identifications• Mapping of young-old edges of anomalies not quite so accurate
Data from König and Jokat, 2010
Young end close to max –ve, old end close to max +ve
Greenland motion: Plates project database
Overlap between Greenland and Barents – Svalbard margin
Overlap
Overlap between Greenland and Barents – Svalbard margin
Next slide
Overlap between Greenland and Barents – Svalbard margin
120-130 km
Point path visualization, Greenland relative to Europe
Gaina et al. (2009) poles 100 km
The Svalbard Margin – Paleocene-Eocene foldbelt followed by some rifting (age?)
Leever et al. 2011 after Bergh et al., 1997 and Braathen et al. 1999FG = Forlandsundet Graben
Leever et al. 2011 after Faleide et al. 2008
G
E
Stylized present-day
G
E
Stylized 33 Ma(e.g. Engen et al. 2008)
GE
Stylized Oligocene(overlap to account for transtension)
G
E
Stylized Paleocene(gap to account for transpression)
Reconstructions should show (in sequence) transpression to transtension to oblique divergence with spreading
Present-day
47 Ma
Should show a gap at 47 Ma, not overlap
120-130 km overlap
47 Ma reconstruction
Europe fixed, Gaina et al. 2009 poles
47 Ma reconstruction – can Greenland be shifted to avoid overlap with Svalbard?• Check magnetic lineation identifications in Labrador Sea
Greenland
Canada
Labrador Sea magnetic data
Data from http://gdr.agg.nrcan.gc.ca/gdrdap/dap/index-eng.php?dapid=8127
Canada
Labrador Sea magnetic data – modeled profile
Data from http://gdr.agg.nrcan.gc.ca/gdrdap/dap/index-eng.php?dapid=8127
ModMag model• This version provides a reasonable match
This is the currently accepted interpretation• These essentially sinusoidal anomalies are hard to identify with certainty, need
regional context to settle on interpretation
This area not modeled
Magnetic anomalies around N Atlantic triple junction
Maus et al. 2008 magnetics
120-130 km overlap
47 Ma reconstruction
Europe fixed, Gaina et al. 2009 poles
47 Ma reconstruction – can Greenland be shifted to avoid overlap with Svalbard?• Labrador Sea identifications not definitive• Triple junction provides strong constraint – can’t move Greenland• How to fix the overlap? Hopefully PhD student Bereke Karainov at UiS can figure it out!