<div>A poster presented at the 15th Symposium of the Study of the Earth's Deep Interior (SEDI 2016); 24-29th July, Nantes, France</div><div><b><br></b></div><div><b>Abstract</b></div><div><br></div><div>The profound changes in physical properties across the Earth’s core-mantle boundary
makes this region key for the understanding of global-scale dynamics. As well as moderating
any interaction between the metallic core and rocky mantle, the lowermost mantle also hosts
the basal limb of mantle convection acting as a kind of inaccessible inverse lithosphere. In
principle, knowledge of seismic anisotropy permits us to probe mantle flow in this region.
However, in order to understand anisotropy in terms of flow, we need to know how the
minerals present in the lowermost mantle deform and generate the textures that lead to
bulk anisotropy. Previously, by combining predictions of mantle flow with the simulation
of texture development in deforming post-perovskite aggregates, we have explored how different
slip system activities give different predictions for the long-wavelength anisotropy in
the lowermost mantle. By converting these results into models compatible with global scale
radially anisotropic seismic tomography we have shown how different predictions correlate
with tomographic inversions. We found that the most recent experimental indication of the
active slip systems in post-perovksite, where dislocations gliding on (001) are most mobile,
give predictions that were anti-correlated with results from tomography at long wavelengths.
This means that it is difficult to explain the observed patterns of seismic anisotropy in the
lowermost mantle as being due to the generation of lattice-preferred orientation in post-perovskite.
A possible resolution to this difficulty is offered by experiments on analogues,
which show that texture can be inherited during the perovskite to post-perovskite phase
transition. Here we modify our previous approach to include this effect. This results in distributions
of predicted seismic anisotropy that are in better agreement with tomography. In
particular, we find that models where texture is generated by deformation of post-perovskite
dominated by dislocations gliding on (001) followed by texture inheritance during the phase
transition to perovskite driven by increasing temperature results in models that correlate
with tomography at spherical harmonic degrees 1-5. In particular, texture inheritance in
our models results in a better match to tomography in regions where the vertically polarised
shear waves propagate more quickly than horizontally polarised shear waves.</div