title: Deep mantle structure as a reference frame for movements in and on the Earth.
abstract: Earth's residual geoid is dominated by a degree-2 mode, with elevated regions above large low shear-wave velocity provinces on the core-mantle boundary beneath Africa and the Pacific. The edges of these deep mantle bodies, when projected radially to the Earth's surface, correlate with the reconstructed positions of large igneous provinces and kimberlites since Pangea formed about 320 million years ago. Using this surface-to-core-mantle boundary correlation to locate continents in longitude and a novel iterative approach for defining a paleomagnetic reference frame corrected for true polar wander, we have developed a model for absolute plate motion back to earliest Paleozoic time (540 Ma). For the Paleozoic, we have identified six phases of slow, oscillatory true polar wander during which the Earth's axis of minimum moment of inertia was similar to that of Mesozoic times. The rates of Paleozoic true polar wander (<1°/My) are compatible with those in the Mesozoic, but absolute plate velocities are, on average, twice as high. Our reconstructions generate geologically plausible scenarios, with large igneous provinces and kimberlites sourced from the margins of the large low shear-wave velocity provinces, as in Mesozoic and Cenozoic times. This absolute kinematic model suggests that a degree-2 convection mode within the Earth's mantle may have operated throughout the entire Phanerozoic.
authors.affiliation: Centre for Earth Evolution and Dynamics, University of Oslo, 0316 Oslo, Norway;Centre for Advanced Study, 0271 Oslo, Norway;Geodynamics, Geological Survey of Norway, 7491 Trondheim, Norway;School of Geosciences, University of the Witwatersrand, WITS 2050 Johannesburg WITS 2050, South Africa; t.h.torsvik@geo.uio.no.
authors.forename: Trond H
authors.initials: TH
authors.lastname: Torsvik
authors.affiliation: Centre for Advanced Study, 0271 Oslo, Norway;Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109;
authors.forename: Rob
authors.initials: R
authors.lastname: van der Voo
authors.affiliation: Centre for Earth Evolution and Dynamics, University of Oslo, 0316 Oslo, Norway;Centre for Advanced Study, 0271 Oslo, Norway;
authors.forename: Pavel V
authors.initials: PV
authors.lastname: Doubrovine
authors.affiliation: Centre for Advanced Study, 0271 Oslo, Norway;School of Geosciences, University of the Witwatersrand, WITS 2050 Johannesburg WITS 2050, South Africa;Department of Geosciences, University of Houston, Houston, Texas 77204;
authors.forename: Kevin
authors.initials: K
authors.lastname: Burke
authors.affiliation: Centre for Earth Evolution and Dynamics, University of Oslo, 0316 Oslo, Norway;Centre for Advanced Study, 0271 Oslo, Norway;Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, 14473 Potsdam, Germany; and.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Steinberger
authors.affiliation: School of Geosciences, University of the Witwatersrand, WITS 2050 Johannesburg WITS 2050, South Africa;
authors.forename: Lewis D
authors.initials: LD
authors.lastname: Ashwal
authors.affiliation: Centre for Earth Evolution and Dynamics, University of Oslo, 0316 Oslo, Norway;Centre for Advanced Study, 0271 Oslo, Norway;Natural History Museum, University of Oslo, 0318 Oslo, Norway.
authors.forename: Reidar G
authors.initials: RG
authors.lastname: Trønnes
authors.affiliation: School of Geosciences, University of the Witwatersrand, WITS 2050 Johannesburg WITS 2050, South Africa;
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Webb
authors.affiliation: Centre for Earth Evolution and Dynamics, University of Oslo, 0316 Oslo, Norway;
authors.forename: Abigail L
authors.initials: AL
authors.lastname: Bull
keywords: plate reconstructions; thermochemical piles