The eastern part of the Kachila volcano is partly concealed by younger volcanic rocks from the Oliyamur and Kanatim volcanoes and in the north interdigitates with products of the Nasaken volcano (No. 085-00-017). In the south it is partly concealed by alluvium. The exposed area is some 25x7 km and the succession includes mugearites and basalts which form, untypically for this area, a high proportion of the volcanic products, pumice tuffs, welded pumice lapilli tuffs and trachyte. Abundant vertebrate fossils have been found in sediments intercalated with the volcanic rocks. The trachytes contain plagioclase and alkali feldspar phenocrysts in a groundmass of sanidine, aegirine, arfvedsonite, olivine and magnetite. Five rock analyses are quoted in Key (1987b).
KEY, R.M. 1987b. Geology of the Maralal area. Report, Geological Survey of Kenya, 105: 1-93.