In my report on Olduvai, which was published in 1951, a brief chapter was included which had been written by the late Professor Hans Reck. In it he summarised the geological evidence which was then available as the result of his own 1913 expedition and of his work with us during 1931. This preliminary chapter had, in fact, been written at a time when he had not yet worked through all his field notes. He had planned to prepare a much more detailed report, accompanied by drawings of selected sections of the geological deposits, after his return from his expedition to Portuguese East Africa. Owing to his sudden death on that expedition, this full report was never written, and after the end of the war in 1945 it proved impossible for his widow to trace his many books of field notes. Thus, all that was available for me to use in the 1951 volume was the original preliminary note prepared before the war.

Dr P. E. Kent was a member of my 1935 expedition to Olduvai and he subsequently published a brief general note on the geology of a small part of the exposures which he had examined.

In 1961 Dr R. Pickering, a member of the Tanganyika Geological Survey, spent some four and a half months with us at Olduvai, by kind permission of the Director. He concentrated, mainly, upon making a detailed map of the FLK region where Zinjanthropus had been found in 1959.