We have assembled ~120 spectroscopically-confirmed halo AGB carbon stars in the Milky Way halo, drawn from the literature, and exhibiting measurable variability in the Catalina Surveys. These surveys cover most of the visible sky, except for the crowded Galactic disc region, providing excellent multi-epoch photometry. Periods and amplitudes of these stars derived from the Catalina light curves, are employed to obtain robust distance estimates - using known period-luminosity relationships. These intermediate-age tracers can probe substructure in the Milky Way halo in a manner difficult with older tracers, such as RR Lyrae, and we use then to address a number of issues in the build-up of the Milky Way.

Our results show that the majority of the carbon star sample can be attributed to the ongoing Sagittarius dSph accretion. However, we also find evidence that the canonical simulation model (Law and Majewski, 2010) of this event does not match the observations in many aspects, but support more recent models. Our results also show that the Triangulum-Andromeda feature is unlikely to be the debris from a dwarf galaxy accretion - as previously suggested - but possibly evidence of a disturbed Galactic disc at large galactocentric radii. Ongoing spectroscopic follow-up observations are being undertaken to refine the kinematics of these features, and throw new light on the assembly of our Galaxy.