Palaeomagnetic and synchrotron analysis  of >1.95 Ma fossil-bearing palaeokarst at  Haasgat, South Africa

Andy I.R. Herries; Peter Kappen; Anthony D.T. Kegley; David Patterson; Daryl L. Howard; Martin D. de Jonge; Stephany Potze; Justin W. Adams

doi:10.1590/sajs.2014/20130102

Authors

Andy I.R. Herries Australian Archaeomagnetism Laboratory, Archaeology, Environment and Community Planning, La Trobe University, Melbourne, Australia
Peter Kappen 1. Physics, La Trobe University, Melbourne, Australia 2. Australian Synchrotron, X-ray Fluorescence Microprobe Beamline, Melbourne, Australia
Anthony D.T. Kegley Biomedical Sciences, Grand Valley State University, Allendale, MI, USA
David Patterson Australian Synchrotron, X-ray Fluorescence Microprobe Beamline, Melbourne, Australia
Daryl L. Howard Australian Synchrotron, X-ray Fluorescence Microprobe Beamline, Melbourne, Australia
Martin D. de Jonge Australian Synchrotron, X-ray Fluorescence Microprobe Beamline, Melbourne, Australia
Stephany Potze Plio-Pleistocene Palaeontology Section, Ditsong National Museum of Natural History, Pretoria, South Africa
Justin W. Adams Anatomy and Developmental Biology, Monash University, Melbourne, Australia

DOI:

https://doi.org/10.1590/sajs.2014/20130102

Keywords:

biochronology, X-ray flourescence, synchrotron radiation;, iron, primate fossils, magnetostratigraphy

Abstract

Palaeomagnetic analysis indicates that Haasgat, a fossil-bearing palaeocave in the Gauteng Province of South Africa, is dominated by reversed magnetic polarity in its oldest, deepest layers and normal polarity in the younger layers. The presence of in-situ Equus specimens suggests an age of less than ~2.3 Ma, while morphological analysis of faunal specimens from the ex-situ assemblage suggests an age greater than 1.8 Ma. Given this faunal age constraint, the older reversed polarity sections most likely date to the beginning of the Matuyama Chron (2.58–1.95 Ma), while the younger normal polarity deposits likely date to the very beginning of the Olduvai Sub-Chron (1.95–1.78 Ma). The occurrence of a magnetic reversal from reversed to normal polarity recorded in the sequence indicates the deposits of the Bridge Section date to ~1.95 Ma. All the in-situ fossil deposits that have been noted are older than the 1.95 Ma reversal, but younger than 2.3 Ma. Haasgat therefore dates to an interesting time period in South African human evolution that saw the last occurrence of two australopith species at ~2.05–2.02 Ma (Sts5 Australopithecus africanus from Sterkfontein Member 4) to ~1.98 Ma ( Australopithecus sediba from Malapa) and the first occurrence of early Homo (Sk847), Paranthropus and the Oldowan within Swartkrans Member 1 between ~2.0 Ma and ~1.8 Ma.