New single crystal 40Ar/ 39Ar ages improve time scale for deposition of the Omo Group, Omo-Turkana Basin, East Africa

McDougall, Ian, Brown, Francis H., Vasconcelos, Paulo M., Cohen, Benjamin, Thiede, David and Buchanan, Michael (2012) New single crystal 40Ar/ 39Ar ages improve time scale for deposition of the Omo Group, Omo-Turkana Basin, East Africa. Journal of the Geological Society, 169 2: 213-226. doi:10.1144/0016-76492010-188


Author McDougall, Ian
Brown, Francis H.
Vasconcelos, Paulo M.
Cohen, Benjamin
Thiede, David
Buchanan, Michael
Title New single crystal 40Ar/ 39Ar ages improve time scale for deposition of the Omo Group, Omo-Turkana Basin, East Africa
Journal name Journal of the Geological Society   Check publisher's open access policy
ISSN 0016-7649
2041-479X
Publication date 2012-03-01
Year available 2012
Sub-type Article (original research)
DOI 10.1144/0016-76492010-188
Open Access Status Not yet assessed
Volume 169
Issue 2
Start page 213
End page 226
Total pages 14
Place of publication Bath, United Kingdom
Publisher Geological Society Publishing House
Language eng
Abstract Six tuffaceous beds within the Omo Group of the Omo–Turkana Basin have been dated using the 40Ar/39Ar single crystal total fusion method on anorthoclase, yielding eruption ages. The Omo Group constitutes up to 800 m of subaerially exposed sediments surrounding Lake Turkana within the East African Rift system in northern Kenya and southern Ethiopia. Rhyolitic explosive eruptions produced tuffs and pumice clasts that are considered to have been deposited shortly after eruption. The new age data on feldspars from the pumice clasts range from 4.02 ± 0.04 Ma for the Naibar Tuff of the Koobi Fora Formation to 1.53 ± 0.02 Ma for Tuff K of the Shungura Formation. The Orange Tuff in the KBS Member of the Koobi Fora Formation was dated at 1.76 ± 0.03 Ma, providing good control in this part of the sequence where formerly there was a >200 ka gap. Data are consistent with earlier measurements and significantly improve age resolution within the Omo Group, which has yielded many vertebrate fossils, including hominin fossils comprising a number of species. We suggest new age estimates for a limited number of hominin specimens.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Earth Sciences Publications
Official 2013 Collection
 
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Created: Tue, 28 Feb 2012, 02:18:03 EST by Ashleigh Paroz on behalf of School of Earth Sciences