Changes in the metallicity distribution function (MDF) for samples at different distances from the disk plane. First column: distribution of birth radii for stars ending up in the bin 7 < r < 9 kpc (green rectangle) at the final time. The bar CR and OLR (estimated at the final time) are indicated by the dotted red and solid blue vertical lines. From top to bottom, we have applied the selection criteria |z| < 0.5, |z| > 0.5, and |z| > 1.5 kpc. Second column: MDF for the same particle subsets as on the left. The black line shows the total population for each selection, while the red and blue colors indicate [O/Fe] > 0.3 and [O/Fe] < 0.3, respectively. A shift in the peak from [Fe/H] = 0 to negative values is seen with increasing distance from the disk plane.