Precise 40Ar/39Ar geochronology for the upper Koobi Fora Formation, Turkana Basin, northern Kenya

McDougall, Ian and Brown, Francis H. (2006) Precise 40Ar/39Ar geochronology for the upper Koobi Fora Formation, Turkana Basin, northern Kenya. Journal of the Geological Society, 163 1: 205-220. doi:10.1144/0016-764904-166


Author McDougall, Ian
Brown, Francis H.
Title Precise 40Ar/39Ar geochronology for the upper Koobi Fora Formation, Turkana Basin, northern Kenya
Formatted title
Precise 40Ar/39Ar geochronology for the upper Koobi Fora Formation, Turkana Basin, northern Kenya
Journal name Journal of the Geological Society   Check publisher's open access policy
ISSN 0016-7649
2041-479X
Publication date 2006-01-01
Sub-type Article (original research)
DOI 10.1144/0016-764904-166
Volume 163
Issue 1
Start page 205
End page 220
Total pages 16
Editor Angharad Hills
Place of publication Bath, U.K.
Publisher Geological Society
Language eng
Subject 0403 Geology
Formatted abstract
The Plio-Pleistocene Koobi Fora Formation, about 560 m thick, crops out east of Lake Turkana and is part of the much larger depositional system of the Omo-Turkana Basin. The upper half of the Koobi Fora Formation from just below the KBS Tuff to above the Chari Tuff is particularly notable for its wealth of hominid fossils and archaeological sites. Silicic tuffaceous horizons have provided the basis for stratigraphic subdivision and correlation. Pumice clasts within the tuffs contain anorthoclase phenocrysts, ideal for 40Ar/39Ar single-crystal dating. Feldspars from pumice clasts in about 15 tephra within the stratigraphic interval from the KBS Tuff to the Silbo Tuff have yielded precise ages that allow much finer definition of the numerical time framework for the sedimentary sequence between the KBS Tuff (1.869 ± 0.021 Ma) and the Chari Tuff (1.383 ± 0.028 Ma) and to yet higher in the sequence to the Silbo Tuff (0.751 ± 0.022 Ma). These results provide a precise and accurate time scale for the upper part of the sequence in the whole of the Omo-Turkana Basin. A number of these tuffs are recognized elsewhere in East Africa; thus ages determined at Koobi Fora also apply to the wider region.
Copyright Geological Society Publishing House.
Keyword Archaeological evidence
Basin fill
Fossil
Geochronology
Pleistocene
Pliocene
Regional index
East Africa
Sub-Saharan Africa
Turkana Basin
Hominidae
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Earth Sciences Publications
 
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