Alkaline Rocks and Carbonatites of the World

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Suswa Area


Occurrence number: 
Longitude: 36.25, Latitude: -1.25

The Suswa ‘quarter degree area’ (Randel and Johnson, 1991) is dominated by the Suswa volcano which occurs in the northeastern part and is described separately (No. 085-00-061). The low western wall of the rift lies in the western part of the area, and the southern part is heavily faulted to give horst and trough structures. The whole area is covered by volcanic rocks which, excluding those of the Suswa centre, include trachyte lavas and Pleistocene ashes that mantle much of the northwest and which probably derive from either the Suswa or Longonot volcanoes. In the southwest are a group of Tertiary basalts and pyroclastic sediments. The trachytes are feldsparphyric rocks with a groundmass of alkali feldspar, augite, aegirine, aenigmatite, arfvedsonite, katophorite and rare quartz.

Ages vary from 2.5-3.1 Ma for the Tertiary Kirikiti basalts to Recent for the latest products of Suswa volcano. For detailed discussion of stratigraphy and ages see Baker et al. (1988) and Randel and Johnson (1991, Table 1).
BAKER, B.H., MITCHELL, J.G. and WILLIAMS, L.A.J. 1988. Stratigraphy, geochronology and volcano-tectonic evolution of the Kedong-Naivasha-Kinangop region, Gregory Rift valley, Kenya. Journal of the Geological Society of London, 145: 107-16.RANDEL, R.P. and JOHNSON, R.W. 1991. Geology of the Suswa area. Report, Geological Survey of Kenya, 97: 1-41.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith