Use of oxygen isotope ratios in correlation of tuffs,East Rudolf Basin,northern Kenya

Oxygen isotope determinations were made using CoF₃ to extract oxygen from 27 volcanic glass samples from the East Rudolf Basin, northern Kenya. Results show that the older tuffs are progressively enriched in¹⁸O and that this index can be used in the correlation of volcanic ash units. This method could not distinguish individual samples from the youngest units studied because their ranges of δ¹⁸O overlap. The δ¹⁸O values for the shards in the Tulu Bor Tuff, the KBS Tuff, the Koobi Fora Tuff and the Chari Tuff range from 14.5 to 16.4, from 8.9 to 9.5, from 6.6 to 7.0 and from 7.0 to 7.2, respectively, in decreasing age. Determinations from pumice cobbles are consistently higher than the above values.