This work was funded in part by the National Science Foundation through grants 1015669 and 1135382. This work utilized the Janus supercomputer, supported by the National Science Foundation (award CNS-0821794) and the University of Colorado Boulder as well as XSEDE allocation TG-EAR080022N through the Computational Infrastructure for Geodynamics (geodynamics.org).
Geochemistry, Geophysics, Geosystems
Earth (Planet) -- Mantle, Lithosphere, Earth (Planet) -- Rotation, Earth (Planet) -- Crust
The net rotation of Earth’s lithosphere with respect to the underlying mantle is the longestwavelength component of toroidal flow in the mantle and is sensitive to both mantle buoyancy structure and lateral viscosity variations. The lithospheric net rotation in the geologic past implied by plate reconstructions using a hotspot reference frame for the past 100 Myr is up to five times greater than the presentday rate of lithospheric net rotation. We explore the role of lateral viscosity variations associated with subcontinental keels in producing the lithospheric net rotation for the geologic past and find that the introduction of subcontinental keels improves the agreement between modeled net rotation and the net rotation present in the plate reconstructions for the past 25 Myr. However, our models with continental keels produce at most 0.16o/Myr of differential rotation between the lithosphere and lower mantle for present-day, and explaining the most rapid rates of lithospheric net rotation during the Cretaceous and Paleogene remains challenging. This suggests the need for either an additional mechanism for generating lithospheric net rotation, or an adjustment to the absolute mantle reference frame relative to which plate motions are specified.
Rudolph, M. L., and S. J. Zhong (2014), History and dynamics of net rotation of the mantle and lithosphere, Geochem. Geophys. Geosyst., 15, doi:10.1002/2014GC005457.