Travaux et Recherches Archéologiques
sur les Cultures, les Espaces et les Sociétés
UMR 5608 T.R.A.C.E.S

le 2 avril 2015



Nature (2015)

New cosmogenic burial ages for Sterkfontein Member 2 Australopithecus and Member 5 Oldowan

par  Darryl E. Granger, Ryan J. Gibbon, Kathleen Kuman, Ronald J. Clarke, Laurent Bruxelles & Marc W. Caffee

Des chercheurs d’institutions américaines, canadiennes, sud-africaines, et françaises publient cette semaine dans la revue Nature la datation de Little Foot. Découvert au nord-ouest de Johannesburg, au cœur du berceau de l’Humanité, dans la grotte de Silberberg (Sterkfontein), ce squelette presque complet d’un australopithèque est exceptionnel. Treize années ont été nécessaires à l’équipe de Ron Clarke (université de Witwatersrand, Afrique du Sud) pour dégager Little Foot (ou StW 573) de sa gangue rocheuse, des millions d’années après sa mort.
Visage-de-StW-573-australopithecus. Cliché Ronald Clarke

The cave infills at Sterkfontein contain one of the richest assemblages of Australopithecus fossils in the world, including the nearly complete skeleton StW 573 (‘Little Foot’) in its lower section, as well as early stone tools in higher sections. However, the chronology of the site remains controversial owing to the complex history of cave infilling. Much of the existing chronology based on uranium–lead dating and palaeomagnetic stratigraphy has recently been called into question by the recognition that dated flowstones fill cavities formed within previously cemented breccias and therefore do not form a stratigraphic sequence. Earlier dating with cosmogenic nuclides suffered a high degree of uncertainty and has been questioned on grounds of sediment reworking. Here we use isochron burial dating with cosmogenic aluminium-26 and beryllium-10 to show that the breccia containing StW 573 did not undergo significant reworking, and that it was deposited 3.67 ± 0.16 million years ago, far earlier than the 2.2 million year flowstones found within it. The skeleton is thus coeval with early Australopithecus afarensis in eastern Africa15, 16. We also date the earliest stone tools at Sterkfontein to 2.18 ± 0.21 million years ago, placing them in the Oldowan at a time similar to that found elsewhere in South Africa at Swartkans17 and Wonderwerk.






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