Chronostratigraphy of KNM-ER 3733 and other Area 104 hominins from Koobi Fora

A magnetostratigraphy for similar to 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 similar to 1.51 Ma (millions of years ago), the Olduvai-Matuyama boundary (similar to 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 horninin fossils. Noteworthy is the new date of similar to 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 similar to 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 similar to 1.76 Ma, if the Acheulian is indeed proprietary to this species. (C) 2015 Elsevier Ltd. All rights reserved.