Fission-track dating of bed I, Olduvai Gorge

The discoveries of a series of hominid remains in the Olduvai Gorge, Tanganyika, has focused attention upon the age of the deposits of Bed I, in which both Zinjanthropus and Homo habilis were found. Because the age of 1.75 million years, as determined by the radioactive decay of potassium and argon, has been questioned several times, a fission-track age was measured for the pumice from Bed 1. The result is 2.03 ± 0.28 million years, in good agreement with the result obtained by the potassium-argon decay method.