U-Pb Isotopic Age of the StW 573 Hominid from Sterkfontein, South Africa

Abstract

Sterkfontein cave, South Africa, has yielded an australopith skeleton, StW 573, whose completeness has excited great interest in paleoanthropology. StW 573, or "Little Foot," was found 25 meters below the surface in the Silberberg Grotto. 238U-206Pb measurements on speleothems immediately above and below the fossil remains, corrected for initial 234U disequilibrium, yield ages of 2.17 +/- 0.17 million years ago (Ma) and 2.24(-0.07)(+0.09) Ma, respectively, indicating an age for StW 573 of close to 2.2 Ma. This age is in contrast to an age of approximately 3.3 Ma suggested by magnetochronology and ages of approximately 4 Ma based on 10Be and 26Al, but it is compatible with a faunal age range of 4 to 2 Ma.

An earlyAustralopithecus afarensispostcranium from Woranso-Mille, Ethiopia

“…urements on speleotherms suggest a recent age (2.2 Ma) (49), which is consistent with the deposit's faunal similarities with sites in eastern Africa (50,51) and with age estimates from magnetochronology (49) and electron spin resonance (52).…”

Investigation of chemical changes in bone material from South African fossil hominid deposits

“…The bones of Australopithecus Africanus originating from the dolomite caves (''Cradle of Humankind'') located in the Transvaal Supergroup, near Krugersdorf in Gauteng, close to Johannesburg (Rep. S. Africa) were selected for the study. Earlier estimations of the age brought surprisingly old data of w4 Ma (Partridge et al, 2003), however, the newest studies (Walker et al, 2006) on the chronology of remains lowered the age to 2.2 Ma, still giving a respectable oldness to them. It allowed expecting the greater diagenetic and environmental changes in the material.…”

The age of Homo naledi and associated sediments in the Rising Star Cave, South Africa

“…In the absence of volcanic deposits, it is generally difficult to obtain accurate ages for the fossils, not just because reliable techniques are few, but mostly because the stratigraphic sequences in the caves are complex, discontinuous and frequently reworked (e.g., Brain, 1993; Pickering et al, 2011a; Bruxelles et al, 2014; Stratford et al, 2014). Workers have relied on a combination of biochronology of faunal remains, palaeomagnetic work and a range of radiometric methods, including U-Pb, U-Th and ESR dating targeting flowstones and fossil teeth (e.g., Vrba, 1975; Partridge et al, 1999; Berger et al, 2002; Walker et al, 2006; Herries et al, 2006, 2013, 2014; Herries and Shaw, 2011; Dirks et al, 2010; Pickering and Kramers, 2010; Pickering et al, 2011a; Herries and Adams, 2013), as well as limited cosmogenic ( 10 Be, 16 Al) dating (e.g., Partridge et al, 2003; Granger et al, 2015; Dirks et al, 2016b). Whilst some of these techniques are well established, others such as the application of cosmogenic isochrons (e.g., Granger et al, 2015) are relatively new and not without significant analytical (and interpretative) challenges (Kramers and Dirks, 2017), and all efforts are strongly dependent on the stratigraphic interpretation of the fossils or units that are being dated.…”