Plate Reconstruction Methodology; Ways to Check Reconstruction Quality by Bruce Eglington, University of Saskatchewan - 2014 PaleoGIS & PaleoClimate Users Conference

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