Distribution of [Mg/Fe] (upper panel) and [Ca/Fe] (lower panel) as a function of [Fe/H] for the GIBS high-resolution fields studied in this work and for the measurements from Johnson et al. (2014) for giant stars (black squares) and microlensed dwarfs from Bensby et al. (2013; blue triangles). In the upper panel, the solid lines show the best-fit relation between [Mg/Fe] and [Fe/H] for the metal-poor and metal-rich regime. The intersection point is shown and represents the position of the knee. The uncertainties for [Ca/Fe] and [Mg/Fe] abundances of this work are shown as a light blue contour in both panels.