The Mesozoic group near Mombasa, Kenya

The Mesozoics near Mombasa are composed chiefly of Triassic non-marine arkosic sandstone and Jurassic marine shale dipping gently southeastwards. In the latter shale facies, rhythmically interbedded sandstone (feldspathic quartz arenite) and shale are locally developed. A swarm of sole markings, mostly flute casts, are well preserved on the base of feldspathic quartz arenite, suggesting that the sandstone was deposited by turbidity currents. Detrital fragments of ortho-quartzite sandstone are commonly embraced in feldspathic quartz arenite. The paleocurrent direction indicates that the clastic material came from the northwest provenance and that the dispersal system was controlled exclusively by a lateral supply. The lateral transportation of elastics as well as the progressive change of sedimentary facies from the Triassic to the Jurassic may be interpreted as a result of the rifting of the Gondwanaland.