{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T02:28:38Z","timestamp":1771468118595,"version":"3.50.1"},"reference-count":55,"publisher":"Geological Society of London","issue":"2","license":[{"start":{"date-parts":[[2008,2,13]],"date-time":"2008-02-13T00:00:00Z","timestamp":1202860800000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-002"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JGS"],"published-print":{"date-parts":[[2008,3]]},"abstract":"<jats:p>\n            The Omo\u2013Turkana Basin of northern Kenya and southern Ethiopia developed in the northern Kenya Rift about 4.3 Ma ago in the Early Pliocene. Nearly 800 m of sediments, included within the Omo Group, crop out in the basin. Numerous rhyolitic tuffs in the sequence not only have facilitated secure correlations between the formations of the Omo Group but also have provided material for precise\n            <jats:sup>40<\/jats:sup>\n            Ar\/\n            <jats:sup>39<\/jats:sup>\n            Ar age measurements. Here we report ages on alkali feldspar crystals from pumice clasts within tuffs in the lower part of the Omo Group up to the level of the KBS Tuff, which has previously been dated at 1.87 \u00b1 0.02 Ma. The results from 17 stratigraphic levels encompassing the 2.4 Ma time interval from the base of the group to the KBS Tuff provide a numerical time framework for the geological history of the lower part of the Pliocene sequence. The new ages, which have a precision of the order of 1%, are all consistent with the stratigraphic order, providing confidence that they accurately record the ages of the volcanic eruptions, with deposition of the tuffs and pumices occurring shortly thereafter.\n          <\/jats:p>","DOI":"10.1144\/0016-76492006-170","type":"journal-article","created":{"date-parts":[[2008,2,13]],"date-time":"2008-02-13T16:18:41Z","timestamp":1202919521000},"page":"549-562","source":"Crossref","is-referenced-by-count":117,"title":["Geochronology of the pre-KBS Tuff sequence, Omo Group, Turkana Basin"],"prefix":"10.1144","volume":"165","author":[{"given":"IAN","family":"McDOUGALL","sequence":"first","affiliation":[{"name":"Research School of Earth Sciences, Australian National University, Canberra, A.C.T. 0200, Australia (e-mail: )"}]},{"given":"FRANCIS H.","family":"BROWN","sequence":"additional","affiliation":[{"name":"Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112-0112, USA"}]}],"member":"1881","published-online":{"date-parts":[[2008,2,13]]},"reference":[{"key":"e_1_3_2_1_1","doi-asserted-by":"publisher","DOI":"10.1006\/jhev.2001.0476"},{"key":"e_1_3_2_2_1","doi-asserted-by":"publisher","DOI":"10.1038\/300631a0"},{"key":"e_1_3_2_3_1","doi-asserted-by":"publisher","DOI":"10.1038\/299212a0"},{"key":"e_1_3_2_4_1","doi-asserted-by":"publisher","DOI":"10.1144\/gsjgs.143.2.0297"},{"key":"e_1_3_2_5_1","doi-asserted-by":"crossref","unstructured":"Brown F.H. & Fuller C.R. 2008. Stratigraphy and tephra of the Kibish Formation . Journal of the Geological Society London southwestern Ethiopia. Journal of Human Evolution in press.","DOI":"10.1016\/j.jhevol.2008.05.009"},{"key":"e_1_3_2_6_1","doi-asserted-by":"publisher","DOI":"10.1038\/229483a0"},{"key":"e_1_3_2_7_1","unstructured":"Brown F.H. & Nash W.P. 1976. Radiometric dating and tuff mineralogy of Omo Group deposits. In: Coppens Y. Howell F.C. Isaac G.Ll. & Leakey R.E.F. (eds) Earliest Man and Environments in the Lake Rudolf Basin . University of Chicago Press Chicago IL 50\u201363."},{"key":"e_1_3_2_8_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1365-246X.1978.tb05492.x"},{"key":"e_1_3_2_9_1","unstructured":"Brown F.H. McDougall I. Davies T. & Maier R. 1985. An integrated Plio-Pleistocene chronology for the Turkana Basin. In: Delson E. (ed.) Ancestors: The Hard Evidence . Liss New York 82\u201390."},{"key":"e_1_3_2_10_1","first-page":"55","volume":"13","year":"1992","unstructured":"Brown, F.H., Sarna-Wojcicki, A.M., Meyer, C.E. & Haileab, B. 1992. Correlation of Pliocene and Quaternary tephra layers between the Turkana Basin and the Gulf of Aden. Quaternary International, 13-14, 55\u201367.","journal-title":"Quaternary International"},{"key":"e_1_3_2_11_1","doi-asserted-by":"publisher","DOI":"10.1144\/0016-764904-165"},{"key":"e_1_3_2_12_1","doi-asserted-by":"publisher","DOI":"10.1007\/BF00620796"},{"key":"e_1_3_2_13_1","unstructured":"Butzer K.W. 1976. The Mursi Nkalabong and Kibish Formations Lower Omo Basin Ethiopia. In: Coppens Y. Howell F.C. Isaac G.Ll. & Leakey R.E.F. (eds) Earliest Man and Environments in the Lake Rudolf Basin . University of Chicago Press Chicago IL 12\u201323."},{"key":"e_1_3_2_14_1","doi-asserted-by":"publisher","DOI":"10.1029\/94JB03098"},{"key":"e_1_3_2_15_1","doi-asserted-by":"publisher","DOI":"10.1038\/299216a0"},{"key":"e_1_3_2_16_1","doi-asserted-by":"publisher","DOI":"10.1038\/279118a0"},{"key":"e_1_3_2_17_1","unstructured":"de Heinzelin J. (ed.) 1983. The Omo Group. Koninklijk Museum voor Midden-Afrika Tervuren Geologische Wetenschappen 85.."},{"key":"e_1_3_2_18_1","doi-asserted-by":"crossref","unstructured":"deMenocal P.B. & Brown F.H. 1999. Pliocene tephra correlations between East African hominid localities the Gulf of Aden and the Arabian Sea. In: Agusti J. Rook L. & Andrews P. (eds) The Evolution of Neogene Terrestrial Ecosystems in Europe . 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