plate reconstruction methodology; ways to check reconstruction quality by bruce eglington,...
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Plate Reconstruction Methodology:
Ways to check reconstruction quality
Bruce Eglington
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
Li et al (2013)
Sedimentary depositional environment at the timeof the global Marinoan glaciation
Palaeoproterozoic large C isotope excursion at ~2200 Ma, shortly after Great Oxidation Event
Martin et al (2013)
Ath
ab
asca
Elu
H B
ay
Th
elo
n
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
Conventional approach to model development using APWP
Li et al. (2008)
Model palaeolatitude for a point in the centre of the Abitibi plate
Palaeolatitude for various palaeomagnetic poles in the Abitibi plate
Palaeolatitude for poles from other plates fixed relative to Abitibi
Other ways to assess a plate model
Palaeolatitude of the VGPPalaeo-azimuth of the VGP
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
VGP palaeo-azimuth ~+3 degrees
VGP palaeo-azimuth should be close to 0 degrees
VGP palaeo-azimuth ~-90 degrees
VGP palaeo-azimuth should be close to 0 degrees
Abitibi example – palaeolatitude
Model is not yet developed prior to ~2100 Ma
Abitibi example – palaeo-azimuth
Model is not yet developed prior to ~2100 Ma
Abitibi example – palaeolatitude and palaeo-azimuth
Model is not yet developed prior to ~2100 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
Abitibi example – changes in plate azimuth with time
N
W
E
S
S
Rodinia and Pangaea palaeolongitude
Mitchell et al. (2011)
Palaeolongitude constraints
Pangaea Rodinia
Modelled palaeolongitude
Model plate velocity
Siberia as an example
Li et al. (2013)
Similar orientation to present
Siberia as an example
Plate azimuth
Palaeolatitude
Siberia as an example
Siberia needs to be upside down
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
Geodynamically realistic plate motions through time
Li et al. (2013)
Urals
Kazakhstan
Sengor and Natal’in (1996)
Complex fold structures represented by semi-rectangular blocks
Sengor and Natal’in (1996)
Unfolding the oroclines
Sengor and Natal’in (1996)
Long, semi-linear arcs strongly influence the geometry of permissible plate motions for other plates
Sengor and Natal’in (1996)
Long, semi-linear arcs strongly influence the geometry of permissible plate motions for other plates
Several major oroclines in theEarly Palaeozoic are importantwhen trying to reconstructthe breakup of Rodinia