title: 40Ar/(39)Ar dating of Chemeron Formation strata encompassing the site of hominid KNM-BC 1, Tugen Hills, Kenya.
abstract: A fossil hominid temporal bone (KNM-BC 1) from surface exposures at Baringo Paleontological Research Project site BPRP#2 in the Chemeron Formation outcropping in a tributary drainage of the Kapthurin River west of Lake Baringo, Kenya has been attributed to Homo sp. indet. K-feldspar phenocrysts from lapilli tuffs bracketing the inferred fossiliferous horizon yield single-crystal(40)Ar/(39)Ar ages of 2.456+/-0.006 and 2.393+/-0.013 Ma. These age determinations are supported by stratigraphically consistent ages on higher tuff horizons and from nearby sections. In addition, new(40)Ar/(39)Ar ages on tuffaceous units near the base and top of the formation along the Kapthurin River yield 3.19+/-0.03 and 1.60+/-0.05 Ma respectively. The base of the formation along the Kapthurin River is thus approximately 0.5 Ma younger than the uppermost Chemeron Formation strata exposed at Tabarin, 23 km to the north-northwest. The upper half of the formation along the Kapthurin River was deposited at an average rate of approximately 11 cm/ka, compared to 21-23 cm/ka at Tabarin.
authors.affiliation: Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, California, 94709, USA. al@bgc.org
authors.forename: Alan L
authors.initials: AL
authors.lastname: Deino
authors.forename: Andrew
authors.initials: A
authors.lastname: Hill
mesh_terms: D000818:Animals; D001128:Argon; D005580:Fossils; D019015:Geologic Sediments / Q000032:analysis*; D015186:Hominidae / Q000033:anatomy & histology* / Q000145:classification; D006801:Humans; D007630:Kenya; D011868:Radioisotopes; D011874:Radiometry / Q000379:methods; D013701:Temporal Bone; D013997:Time Factors
chemical_list: D011868:Radioisotopes; D001128:Argon