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  • 1
    Publication Date: 2015-04-02
    Description: 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 Africa. 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 Swartkans and Wonderwerk.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Granger, Darryl E -- Gibbon, Ryan J -- Kuman, Kathleen -- Clarke, Ronald J -- Bruxelles, Laurent -- Caffee, Marc W -- England -- Nature. 2015 Jun 4;522(7554):85-8. doi: 10.1038/nature14268. Epub 2015 Apr 1.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, USA. ; Department of Anthropology, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada. ; 1] Evolutionary Studies Institute, University of the Witwatersrand, WITS 2050, Johannesburg, South Africa [2] School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, WITS 2050, Johannesburg, South Africa. ; Evolutionary Studies Institute, University of the Witwatersrand, WITS 2050, Johannesburg, South Africa. ; 1] School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, WITS 2050, Johannesburg, South Africa [2] French National Institute for Preventive Archaeological Research (Inrap), 561 rue Etienne Lenoir, km delta, 30900 Nimes, France [3] University of Toulouse Jean Jaures, UMR 5608 du CNRS (TRACES), Maison de la Recherche, 5 Allees Antonio Matchado, F-31058 Toulouse, France. ; 1] Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, USA [2] Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25830884" target="_blank"〉PubMed〈/a〉
    Keywords: Africa, Eastern ; Aluminum ; Animals ; Beryllium ; Burial ; *Fossils ; Geologic Sediments/analysis/chemistry ; *Hominidae/anatomy & histology/classification ; Paleontology/*methods ; Radioisotopes ; Radiometric Dating/*methods ; *Skeleton ; Skull/anatomy & histology ; South Africa ; Time Factors ; Tool Use Behavior
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2015-10-20
    Description: Deformed lunar zircons yielding U-Pb ages from 4333 Ma to 1407 Ma have been interpreted as dating discrete impacts on the Moon. However, the cause of age resetting in lunar zircons is equivocal; as ex situ grains in breccias, they lack lithologic context and most do not contain microstructures diagnostic of shock that are found in terrestrial zircons. Detrital shocked zircons provide a terrestrial analog to ex situ lunar grains, for both identifying diagnostic shock evidence and also evaluating the feasibility of dating impacts with ex situ zircons. Electron backscatter diffraction and sensitive high-resolution ion microprobe U-Pb analysis of zircons eroded from the ca. 2020 Ma Vredefort impact structure (South Africa) show that complete impact-age resetting did not occur in microstructural domains characterized by microtwins, planar fractures, and low-angle boundaries, which record ages from 2890 Ma to 2645 Ma. An impact age of 1975 ± 39 Ma was detected in neoblasts within a granular zircon that also contains shock microtwins, which link neoblast formation to the impact. However, we show that granular texture can form during regional metamorphism, and thus is not unique to impact environments. These results demonstrate that dating an impact with ex situ shocked zircon requires identifying diagnostic shock evidence to establish impact provenance, and then targeting specific age-reset microstructures. With the recognition that zircon can deform plastically in both impact and magmatic environments, age-resetting in lunar zircons that lack diagnostic shock deformation may record magmatic processes rather than discrete impacts. Identifying shock microstructures that record complete age resetting for geochronological analysis is thus crucial for constructing accurate zircon-based impact chronologies for the Moon, Earth, or other planetary bodies.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 3
    Publication Date: 2017-06-29
    Description: Prepared core technology illustrates in-depth planning and the presence of a mental template during the core reduction process. This technology is, therefore, a significant indicator in studying the evolution of abstract thought and the cognitive abilities of hominids. Here, we report on Victoria West cores excavated from the Canteen Kopje site in central South Africa, with a preliminary age estimate of approximately 1 Ma (million years ago) for these cores. Technological analysis shows that the Victoria West cores bear similarities to the ‘Volumetric Concept’ as defined for the Levallois, a popular and widely distributed prepared core technology from at least 200 ka (thousand years ago). Although these similarities are present, several notable differences also occur that make the Victoria West a unique and distinctive prepared core technology; these are: elongated and convergent core shapes, consistent blow directions for flake removal, a predominance of large side-struck flakes, and the use of these flakes to make Acheulean large cutting tools. This innovative core reduction strategy at Canteen Kopje extends the roots of prepared core technology to the latter part of the Early Acheulean and clearly demonstrates an increase in the cognitive abilities and complexities of hominids in this time period.
    Keywords: cognition, evolution
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 4
    Publication Date: 2012-11-01
    Description: The high plateau of southern Africa is considered to be either uplifting due to mantle-driven dynamic topography, or to have been stable since Mesozoic rifting. To address this debate, we determined rock uplift in South Africa from the long-term incision rate of the Sundays River, near Port Elizabeth, and from an uplifted marine terrace near Durban. We dated the terraces with cosmogenic 26 Al and 10 Be, using both isochron and simple burial dating methods. We find that the Sundays River has incised at 16.1 ± 1.3 m/m.y. for the past ~4 m.y., and the marine terrace yields a rock uplift rate of 9.4 ± 2.2 m/m.y. These results are inconsistent with rapid Neogene uplift.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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