Oxygen abundance distribution in the Galactic disc resulting from Model A after 11 Gyr of evolution and projected onto the Galactic plane after the start of disc formation (see Table 1 and text for model details). Upper panel: [O/H] values. Lower panel: distribution of residual azimuthal variations Δ [O/H] in oxygen. In each panel, we also highlight the annular regions where the three co-rotational radii are situated using black edges.