Sensitivity experiments on True Polar Wander

Abstract

Using sensitivity experiments based on the position of subductions and of superplumes, we derive models for the temporal evolution of 3-D mass anomalies in the mantle and compute the associated inertia perturbations and polar wander. We show that although the large length-scale mantle dynamics during the Earth's history may have been dominated by coupled supercontinent-superplume cycles, subductions alone are sufficient to trigger major True Polar Wander (TPW) episodes, or rotation of the whole lithosphere and mantle with respect to the Earth's rotation axis. We present two examples. We speculate that the distribution of continents with respect to the equator on the Earth's surface is driven by episodic subductions during the Wilson cycle: alternating fast subduction girdles around continents and upwellings during the divergence phases, with both reduced or stopped subductions activity around continents and moderate inter-continental subductions during the convergence phases, lead to successive equatorial or polar distributions of continents, both configurations being separated by strong episodes of TPW. Finally, using plate reconstructions and geologic maps, over the period 1100-720 Ma, the period of amalgamation and destruction of the Rodinia supercontinent, we explain with our model the observed large eastward/ westward and poleward/equatorward motions of the rotation axis.

Jurassic Monster Polar Shift Confirmed by Sequential Paleopoles From Adria, Promontory of Africa

“…We stress that better age constraints are needed to pin down angular velocities more precisely within the Jurassic monster shift, for example, if the motion first accelerated and then decreased. A suggested geodynamic trigger for such an episode of TPW (Kent et al, ) is the break‐off and sinking of a cold, dense subducting slab through the mantle at an optimal distance from the Euler pole (Greff‐Lefftz & Besse, ), such as apparently occurred at about the right time in the America Cordillera (Sigloch & Mihalynuk, ).…”

True Polar Wander: A Key Indicator for Plate Configuration and Mantle Convection During the Late Neoproterozoic

“…Geochemistry, Geophysics, Geosystems compute I ij , we used the kernel of geoid presented in Figure 1.b. of Greff-Lefftz and Besse (2014). This degree 2 kernel of geoid integrates both the direct effect of mass anomalies on geoid and the dynamic topographies produced by the rearrangement of mass in response to density perturbations.…”

Tracking the Late Jurassic apparent (or true) polar shift in U‐Pb‐dated kimberlites from cratonic North America (Superior Province of Canada)

“…A beguiling option is that slab break off and flip in subduction polarity in the Americas Cordillera starting about 165 Ma [ Sigloch , ; Sigloch and Mihalynuk , ] were able to induce and sustain the fast polar shift between 160 and 145 Ma. The detached slab sinking through the upper to the lower mantle may produce a change in sign in the effect of the mass anomaly on the geoid, as suggested by models of Greff‐Lefftz and Besse [], and this could explain the sharp polar wander cusp at ∼145 Ma. The Euler pivot for the polar shift from 160 to 145 Ma is in the vicinity of what is now the Bight of Benin of western Africa (Figure , top), about the same place where the pivot also seems to be located for the rotation in the opposite sense between 145 and 120 Ma (Figure , bottom).…”

“…This geometry is ostensibly consistent with the quasistationary African assumption . However, the apparent centrality of Africa may simply reflect that the sources of major plate driving torques or mass anomalies are located in the subduction complexes around the periphery of the dispersing Pangea continent [e.g., Greff-Lefftz and Besse, 2014], which is also where latitudinal changes were most pronounced during these polar shifts. Finally, if the monster shift does represent a major episode of TPW, it may have influenced geomagnetic field behavior such as reversal frequency [Courtillot and Besse, 1987;Biggin et al, 2012].…”