Mean metallicity as a function of distance from the disk plane, |z|, in the range 6 < r < 10 kpc. Red filled circles and error bars show SEGUE data from Schlesinger et al. (2012), while the blue-dashed line represents the Bovy et al. model. The solid black curve is our model. A very good agreement between the two models in found for the metallicity variation with |z|, including the flattening at |z| ≳ 1.5 kpc. In Sect. 5.7 this was associated with the predominance of old/high-[O/Fe] stars at large distances from the plane (see Fig. 9).