Jebel Marra,a dormant volcano in Darfur Province,Western Sudan

The geology of the Tertiary-Recent Marra mountains is shown on photogeological maps and described using data from short field visits and from previous literature. The 200 km long mass is aligned N-S parallel to basement trends; it comprises a stratified complex 2000 m thick of olivine basalts, pyroclastics and trachytes. Coarse detrital deposits testify to concomitant erosion. The spectacular Deriba caldera contains a deep crater lake and associated hot springs and fumeroles. The Marra mountains lie at the intersection of two transcontinental tectono-volcanic zones, ENE from Cameroon to Red Sea and SSE from Libya to Kenya.