Figure 3. The main units of the Layered Series and the Upper Border Series [McBirney, 1996]. The LS zones are defined by the appearance or disappearance of primary phases, or, in the case of LZb, by the transition from the poikilitic form of the Ca-pyroxene to the granular one. The Upper Border Series is divided into three subzones ( a, b, and g ) equivalent to the LZ, MZ and UZ. The compositions given for Ol, Pl, and Aug at zone boundaries are approximate and may vary laterally.