Heritage Cases

The HR despoit at Swartkrans Cave has yielded some of the most iconic specimens of Paranthropus robustus fossils, including the complete SK48 skull, as well as SK15, which is the first recorded instance of early Homo coexisting alongside P. robustus (Brain, 1993). In fact, the Hanging Remnant has yielded the largest collection of P. robustus in southern Africa (Grine, 1993). Despite the significance of its fossil collections, the Hanging Remnant has never been directly dated, which is thought to be younger than the Lower Bank, the latter now dated to ~2.2 Ma (Kuman et al. 2021). Currently, age estimates based on faunal biochronology place the Hanging Remnant around ~1.9 to ~1.8 Ma (Brain, 1993; Pickering et al. 2011). Morphological comparisons with Drimolen have suggested difference in craniodental features with the Hanging Remnant sample of P. robustus (Martin et al. 2021). This has been suggested to reflect microevolutionary changes through time, albeit this argument is reliant on difference in chronology (i.e. Drimolen Main Quarry is older than Swartkrans Hanging Remnant). As such, developing a chronology specifically for the Hanging Remnant has important implications for understanding the evolutionary history of P. robustus in southern Africa. Furthermore, in 2018 we identified a hard breccia mass from the HR in the northwestern portion of Swartkrans, which was subsequently excavated (Fig. 1). We used a total station to map the Hanging Remnant mass, as well as produced a photogrammetry model before and after its excavation. We first sectioned this mass into smaller blocks that were removed through exploiting natural cracks. We then mapped outlines with the total station of the blocks before after their removal from the Hanging Remnant mass. Well-preserved fossils were recovered, which currently under study by T. Pickering and R. Clarke. The faunal remains are encased in hard breccia (i.e. consolidated) and being prepared in the Sterkfontein shed by Andrew Phashwana, who has 20 years of experience in fossil preparation and excavation. We have collected six chert and one quartz clasts from ‘block 5’ of the HR mass and we therefore propose to use cosmogenic nuclide dating techniques to produce a complete chronology for the Member 1 sedimentary unit at Swartkrans. We also have collected sediment samples of the breccia itself to calibrate the results of cosmogenic nuclide dates. A total of 60 total station points captured the outline of block 5, which define the spatial provenance of the chert and brecciated sediment samples.