Open AccessThe rotational stability of a convecting earth: assessing inferences of rapid TPW in the late cretaceous
Author(s) -
Chan N.H.,
Mitrovica J.X.,
Matsuyama I.,
Creveling J.R.,
Stanley S.
Publication year - 2011
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2011.05245.x
Subject(s) - mantle convection , lithosphere , mantle (geology) , geology , geophysics , amplitude , convection , forcing (mathematics) , physics , mechanics , atmospheric sciences , paleontology , tectonics , quantum mechanics
SUMMARY We outline a linearized rotational stability theory for predicting the time dependence of true polar wander (TPW) on a Maxwell viscoelastic body in response to mantle convective loading. The new theory is based on recent advances in ice age rotation theory. A comparison between predictions based on the new theory and analytic expressions for equilibrium (infinite‐time) TPW on planetary models with elastic lithospheres demonstrates that the linearized theory can, in the case of loading at mid‐latitudes, predict TPW of over 20° to better than 5 per cent accuracy. We present predictions of TPW for loading with periodic and net ramp‐up time histories. Moreover, we compare the time dependence of TPW under assumptions consistent with the canonical equilibrium stability theory adopted in most previous analyses of convection‐induced TPW, and a stability theory that includes two effects that have not been considered in previous geophysical analyses: (1) the so‐called ‘remnant rotational bulge’ associated with the imperfect reorientation of the rotational bulge due to the presence of an elastic lithosphere; and (2) a stable (over the timescale of the forcing) excess ellipticity. As a first application of the new theory, we consider recent inferences of rapid (order 1 Myr) TPW motion of amplitude 10°–20° during the Late Cretaceous. We conclude that excursions of this amplitude and timescale are physically implausible.