Models for true polar wander from palaeomagnetism, geoid and hotspot studies

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Abstract

Various analyses of palaeomagnetic data have indicated that the configuration of the time averaged geomagnetic field approximates an offset rather than a geocentric dipole. The displacement of the dipole from the geocentre' relative to present-day Eurasia is inferred to be directed, irrespective of age, toward the western equatorial Pacific-an area which is also characterized by the largest positive geoid height. It is argued that the close association between this geoid high and offset of the magnetic centre has a common cause, a long-standing quadrupolar heterogeneity which is connected ultimately to the Earth's core. With this assumption a conceptual model of true polar wander is outlined which predicts that the above referred mass anomaly was aligned with the Earth's rotation axis in the early Palaeozoic and was moved smoothly to the equator by the Goldreich-Toomre mechanism before the late Cretaceous. If seen from the mantle related hotspot frame, which has now been extrapolated back to include the Permian, a more complex model emerges. As a premise to the model, it is shown that the Pacific geoid high is composed of two positive height anomalies of which only the eastern one is correlatable with the Pacific hotspot province. Thus, only this and the Atlantic-African positive geoidal feature are hotspot related and the western Pacific positive residual is assumed, essentially as above, to be originating from the core. Given that the geoid anomalies in question are stable against time, the hotspot related model requires a 30° true polar wander with respect to the mantle as well as the core in roughly opposite directions from early Permian to late Cretaceous. During this time the mantle moved counterclockwise about an equatorial pole at approximate longitude 37° and the core clockwise about a nearby pole both with respect to the rotation axis. For times preceding the Permian the extrapolation can be done at least in principle on similar grounds as with the simpler model.

Original languageEnglish
Pages (from-to)331-344
Number of pages14
JournalTectonophysics
Volume121
Issue number2-4
DOIs
Publication statusPublished - Jan 15 1986

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paleomagnetism
geoid
Permian
Earth mantle
anomalies
mantle
anomaly
poles
dipoles
Cretaceous
Earth core
Earth rotation
equators
geomagnetism
longitude
geomagnetic field
extrapolation
Paleozoic
causes
configurations

ASJC Scopus subject areas

  • Earth-Surface Processes
  • Geophysics

Cite this

Models for true polar wander from palaeomagnetism, geoid and hotspot studies. / Márton, P.

In: Tectonophysics, Vol. 121, No. 2-4, 15.01.1986, p. 331-344.

Research output: Contribution to journalArticle

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