plate reconstruction methodology; ways to check reconstruction quality by bruce eglington,...
Post on 18-Jul-2015
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Geodynamic settingRock ClassAge limitsGIS codeDomain
DateView
Geochronology TectonicLithostratigraphy EconomicLIP
Unit DomainUnit DepositLIP
MaterialIsotope systemInterpretationAgeLocationReferenceDomainLIP
MetamorphismDeformationAge limitsMetph. Grade
ClanCommoditiesAge limitsInfo. sourceDomainLocality
SizeMorphol.RatingAge limitsUnitLocalityReferences
StratDB
ESRI GeodatabasePolygons Lines
Plates
PlateIDNameAge limitsLocality
Dykes
SwarmIDNameAge limitsLocality
UnitsMapIDGIS ID
Palaeoproterozoic large C isotope excursion at ~2200 Ma, shortly after Great Oxidation Event
Martin et al (2013)
Reconstructions <~ 170 Ma
• Hotspots• Oceanic plates
and ‘magnetic stripes’
• Palaeomagnetics• Plate extent and
geometry• Vergence
directions• Igneous activity• Metamorphic
activity• Sediment
characteristics
Variable Latitude control, longitude require assumptions
Sparse data
Reconstructions in Precambrian
• Palaeomagnetics• Plate extent and
geometry• Vergence
directions• Igneous activity• Metamorphic
activity• Sediment
characteristics
Latitude and Longitude control
Lots of data
VGP palaeolatitude ~85 degrees N
VGP palaeolatitude ~0 degrees
VGP palaeolatitude should be close to +/- 90 degrees
Example using two poles for Dominica at about 44 Ma
Abitibi example – reconstructpalaeolatitude and palaeo-azimuth
Model is not yet developed prior to ~2100 Ma
Plate orientation expressed as azimuth
Centroid
Point north of centroid
Azimuth of line fromcentroid to point
Present day
Plate orientation expressed as azimuth
Centroid
Point north of centroid
Azimuth of line fromcentroid to point
Azimuth changes withchanging orientationof the plate
Present day
Reconstructed plate
Li et al. (2008)
530 Marotated
550 Marotated
600 MaNot rotated
Geodynamically realistic plate motions through time
Li et al. (2008)
1000 MaN India faces east
1050 MaN India faces east
1100 MaN India faces west
Geodynamically realistic plate motions through time
Urals
Kazakhstan
Sengor and Natal’in (1996)
Complex fold structures represented by semi-rectangular blocks
Sengor and Natal’in (1996)
Long, semi-linear arcs strongly influence the geometry of permissible plate motions for other plates
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