![]() Isotopic ages on the Kibish Formation correspond to ages of Mediterranean sapropels, which reflect increased flow of the Nile River, and necessarily increased flow of the Omo River. Geological evidence indicates rapid deposition of each member of the Kibish Formation. A younger age limit of 104 +/- 7 kyr is provided by feldspars from pumice clasts in a Member III tuff. 40Ar/39Ar ages on feldspar crystals from pumice clasts within a tuff in Member I below the hominid levels place an older limit of 198 +/- 14 kyr (weighted mean age 196 +/- 2 kyr) on the hominids. Here we confirm that the Omo I and Omo II hominid fossils are from similar stratigraphic levels in Member I of the Kibish Formation, despite the view that Omo I is more modern in appearance than Omo II. However, the provenance and age of the fossils have been much debated. ![]() In 1967 the Kibish Formation in southern Ethiopia yielded hominid cranial remains identified as early anatomically modern humans, assigned to Homo sapiens. ![]()
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