Dr R. B. Whitmarsh said that a hole recently drilled by Glomar Challenger during Leg 23 of the Deep-Sea Drilling Project is relevant to the authors’ discussion of the possible southward extent of the axial valley of the Red Sea. This hole was drilled about 15 miles south of Zubayir Island in a water depth of 852 metres. A total section of 212 metres of Holocene to Late Pleistocene greenish calcareous ooze was penetrated before the hole had to be abandoned. The oldest recovered sediments were about 500,000 years old and indicate therefore very rapid sedimentation of primarily biogenous material. A minimum of about 550 metres of sediment was present at this site so it seems unlikely that the deepest sediments are older than the Pliocene. These facts, together with an above average heat flow measurement at this site, suggest that the axial valley does in fact extend south of Zubayir Island but that it is filled with a thick sequence of biogenous Quaternary sediments.

Professor Gass thanked Dr Whitmarsh for providing this information.

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