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Part III. Regional Studies in the Gregory Rift Valley |
In this paper I have concentrated on the lower Omo valley in Ethiopia, to the north of the Lake Turkana Basin. I have extended the study to include not only mammals, but all aspects of palaeontology related to the reconstruction of palaeoenvironments.
Geologically, the Omo Group is composed of four formations: The Mursi Formation, 4.5 to 4 millions years old:N’Kalabong Formation and Shungura Formation, including the Usno Formation, 3.5 to 1 million years old, and the much younger, Kibish Formation, possibly 100 000 years old. The most important is the Shungura Formation, which is divided into members by tuffs widely distributed throughout the area.
The group of formations is over 1000 metres thick, well exposed, fossiliferous and so well dated by radiometry, magnetostratigraphy and biostratigraphy, that it has developed into a type of standard scale. Unfortunately, the preservation of fossil vertebrates is not good as most of them were transported by streams. This makes palaeoecological studies more difficult.
Nevertheless, for its length and continuity of sequence, the amount of fossils collected and the range of dates obtained, the Omo succession is unique. As several Hominids are present in these strata as well as artifacts, it is particularly interesting to see how the environment changed during the period when the Hominids were evolving.
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This 250-word extract was created in the absence of an abstract.
1 Various sections of this paper owe a great deal to the work of my colleagues whose contributions are noted in the Acknowledgement
