Volcanic Associations in the Gregory Rift Valley, East Africa

THE Tertiary to Recent volcanic rocks associated with the Gregory Rift Valley cover large areas in Kenya and northern Tanzania, and the Miocene volcanic and intrusive centres of eastern Uganda belong to the same sodic alkaline province. In addition to numerous reports dealing with specific areas, there are several regional accounts 1–6 which summarize some aspects of the petrology. A recent review 7 of the distribution of nephelinite–phonolite and basalt–trachyte–phonolite associations at major volcanoes in East Africa not only emphasized the need to extend the investigation to the entire volcanic field, but also indicated the necessity for further distinctions among the products of the main centres.