Chemical information extracted from the star formation history shown in Fig. 11. Upper panel: [Si/Fe] versus [Fe/H] diagram. The evolution track is colour-coded with the stellar ages while the star markers indicate the maxima in the SFR (t_max). The evolutionary track is blurred with a 2D Gaussian kernel of width 0.05 dex (greyscale contour plot). Lower panel: age-metallicity (solid black line) and [Si/Fe] versus age (solid grey line) relations predicted by the same model as the upper panel. Dashed vertical lines denote the ages associated with t_max (star markers in the upper panel and dashed vertical lines in Fig. 11) and follow the same colour code convention as the upper panel.