Extract

The northern part of the Lake Turkana (formerly Lake Rudolf) Basin offers unique opportunities for testing and cross-checking methods of correlation in continental sediments. Such methods include ⁴⁰K-³⁹Ar and ⁴⁰Ar-³⁹Ar dating, fission track dating, paleomagnetic reversal stratigraphy, faunal similarities and major and minor element analysis. Intensive research on deposits of the Omo Basin and the East Lake Turkana region have shown that the different methods of correlation indicate time equivalence between the upper parts of the Shungura Formation and the Koobi Fora Formation. However, correlations between the lower parts of the sequences differ, depending on which method is used. Faunal similarities can be used to show a correlation between Shungura F–G and Koobi Fora faunal zone ‘a’. Radiometric dating and paleomagnetic reversal stratigraphy have indicated a correlation between Shungura units G–D in the Omo basin and the KBS Tuff in the East Lake Turkana area, which lies above faunal zone ‘a’. Discrepancies in the correlation suggest either: (a) that the KBS Tuff is 0.5 to 0.7 m.y. younger than its radiometric age of about 2.6 m.y., (b) that Shungura F–G is 0.5 to 0.7 m.y. older than indicated by radio-metric and paleomagnetic data, (c) that strong faunal similarities can be time-transgressive, (d) that dates and faunal correlations are all in error to some degree. Interest generated by the conflicting results has resulted in re-examination and further intensive research in all methods of correlation. Although the correlation in the northern part of the Lake Turkana Basin remains unresolved, issues relevant to