Cave of Hearths: Cosmogenic Nuclide Dating

Aim/rationale:
The Cave of Hearths (CoH), located in the Makapan Valley in the Limpopo Province close to the modern town of Mokopane, has long been an influential site to trace the evolution of hominins in southern Africa (Mason 1969; 1988, McNabb and Sinclair 2009). Apart from some earlier investigations, excavations were initiated in the 1940s and continued into the 1950s (Mason 1969). The CoH yielded in situ Acheulian (Early Stone Age; ESA) occupation in Beds 1 to 3. The ESA beds have been dated to between 780 000 and 500 000 years ago using palaeo-magnetism dating (Herries and Latham 2009). The CoH also has an extensive Middle Stone Age (MSA) occupation, found in Beds 4 to 9. The presence of lithics from the Pietersburg Industry places the MSA at the CoH in the MSA I and II, dating to between 128 000 and 75 000 (Wurz 2013). The site also has Later Stone Age (LSA), Iron Age and historical occupations in Beds 10 and 11. The presence of Oakhurst-style lithics in the LSA bed suggest an age between 12 000 and 7000 years ago (Lombard et al. 2012), and the ceramic style may suggest an occupation during the Early Iron Age (AD 400 – 900, Huffman 2007). The material from the surface likely relates to the siege of 1854 (Mason 1969, 1988).

Few archaeological sites in South Africa have such an extensive and successive occupations by hominins over millennia. The earlier radiocarbon dates (Mason 1969) vastly underestimated the time depth of the occupations, and these dates are no longer accepted (cf. Wadley 2015). The imprecise dating of the CoH beds remains a serious constraint. Despite the site’s importance in earlier discussions on the evolution of hominins in South Africa, it has largely been excluded from archaeological debates on the ESA and MSA in particular due to the imprecise dating (Wadley 2015). At many other sites, each time period show variation in terms of material culture, and without more precise dates, the artefacts (fauna, lithics, human remains, ceramics, bone tools, etc) from the CoH remain limited in their study-potential. Moreover, due to the lack of precise dating, little remains known about the palaeoenvironment of the Makapan Valley.

I recently initiated a dating programme at the CoH, including using amino-acid racemization, OSL, ESR and radiocarbon dating. These studies are in progress. However, with a lack of breccia from the MSA beds, and no in situ material, these beds cannot be dated using the above-mentioned methods. However, the soils kept by Mason from the MSA beds can be dated using cosmogenic nuclide dating.