"The distribution of Tertiary to Recent lavas in part of south-west Kenya is outlined, and attention drawn to the predominance of nepheline-rich Miocene lavas over other types west of the rift valley, which contrasts with the Pliocene olivine basalt-trachyte-comendite association predominating within the rift valley. It is inferred that widespread Miocene phonolites west of the rift valley derived from a parent of approximate melanephelinitic composition, while within the rift valley extensive Pleistocene trachytes differentiated from an olivine basaltic parent. . . . The frequent association of nephelinitic lavas and carbonatite complexes in Kenya is discussed and the possibility mooted that the presence of nephelinite lavas may be indicative of nearby carbonatite complexes."