Abstract
THE geology of East Equatorial Africa has been recorded in a very general way in the maps of the region published by Mr. Jos. Thomson in his “Through Masai Land,” and in the more recent one of Prof. Toula; from these it was known that the area consists of a basal plateau of gneiss and schists, covered by a series of lavas in the interior and marked along the coast by patches of Jurassic rocks. My work therefore lay in the main in the examination of the gneisses and schists with a view to the determination of the method of their formation; also to the study of the volcanic rocks —which range from basalts to quartz trachytes—and of the relations of the old lava plateaus and sheets to the craters of various ages which play such a striking part in the scenery of the district. The most interesting part of the work consisted in the examination of the great “Graben”or valley of subsidence which runs north and south across the district; on the floor and on the sides of this are many old lake deposits now buried by lava flows, while the walls are also marked by terraces formed by the existing lakes when at a higher level than at present, or by old ones that have long since disappeared. In some of these terraces are shells with Nilotic affinities, though the localities are now far from the Nile basin. The collections made from the coast Jurassics will allow the age of these beds to be definitely settled, and the fossils—Ainmonites,Lytoceras, Belemnites, &c.— suggest that they are probably Callovian. An interesting addition to the geology of tropical Africa has been the discovery of some Palaeozoic shales, more than 130 miles from Mombasa, which have yielded a fairly good fauna, though richer in individuals than species.
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GREGORY, J. The Natural History of East Equatorial Africa. Nature 49, 12 (1893). https://doi.org/10.1038/049012a0
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DOI: https://doi.org/10.1038/049012a0