title: Chronostratigraphy of KNM-ER 3733 and other Area 104 hominins from Koobi Fora.
abstract: A magnetostratigraphy for ∼ 60 m of Koobi Fora Formation sediment in Area 104 was derived from 46 oriented samples that produced well-resolved characteristic magnetizations from progressive thermal demagnetization. Approximately 59 m below the Morte Tuff, previously dated to ∼ 1.51 Ma (millions of years ago), the Olduvai-Matuyama boundary (∼ 1.78 Ma) was found to be at the level of marker bed A2--inconsistent with the Area 102 type section and thus contrary to fossil dating schemes that utilize temporal equivalence between A2 [104] and A2 [102]. The magnetostratigraphic data, coupled with the Morte Tuff, provide a means to interpolate new ages for marker beds A2 [104] and the White Tuff, as well as multiple Area 104 hominin fossils. Noteworthy is the new date of ∼ 1.63 Ma for KNM-ER 3733, which now implicates KNM-ER 2598 as the sole early African Homo erectus fossil demonstrably older than Dmanisi and Java Homo specimens. Re-dating KNM-ER 3733 creates a ∼ 300-kyr gap at 1.9 to 1.6 Ma in the African fossil record of H. erectus, which might be partially spanned by hand axes recently dated at ∼ 1.76 Ma, if the Acheulian is indeed proprietary to this species.
authors.affiliation: Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA; Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA. Electronic address: lepre@ldeo.columbia.edu.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Lepre
authors.affiliation: Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA; Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA.
authors.forename: Dennis V
authors.initials: DV
authors.lastname: Kent
mesh_terms: D000818:Animals; D000885:Anthropology, Physical; D005580:Fossils; D019015:Geologic Sediments / Q000032:analysis*; D015186:Hominidae; D007630:Kenya; D055110:Radiometric Dating
keywords: Early Pleistocene; Homo erectus; Kenya; Magnetostratigraphy; Olduvai Subchron; Turkana Basin