Initial ﹩[\alpha /\mathrm{Fe}]﹩ vs. initial ﹩[\mathrm{Fe}/{\rm{H}}]﹩ for our sample of main-sequence turn-off stars in bins of orbital eccentricity (left) and age (right). The online version of this figure toggles chemistry-based selection boxes on click. Chemically distinct components have different orbital properties: metal-poor stars are eccentric, low-α metal-rich stars are circular, while the high-α metal-rich component spans the entire range of eccentricities. These components also formed at different times: metal-poor stars are ancient (median age of 11.5 Gyr, and few younger than 9 Gyr), while the star formation histories of the high- and low-α metal-rich are more extended.