Sea surface temperatures from oxygen isotopes in marine molluscs in middle and later stone age sites, South Africa

Thesis

The southernmost coast of South Africa has been proposed to have been a uniquely important region in later human evolution, in part due to the abundance of nutritious and dense coastal resources. Yet, strong contrasts in the Middle Stone Age (MSA) and subsequent Later Stone Age (LSA) archaeological records cast uncertainty on the significance of shellfish utilisation for processes of human evolution. Further, climatic shifts are frequently advanced as drivers of widespread technological change but few climate proxy records correspond adequately to the archaeological evidence at a temporal or spatial level to be unambiguously linked to human cultural activity. This thesis presents a temporally and spatially distributed record of near-shore seasonal sea surface temperatures (SSTs) from serial δ¹⁸O shell measurements of archaeological Turbo sarmaticus opercula. In addition, the annual timing of shellfish harvesting captured in the temperature signal of the shells' final few growth increments is indicative of the scheduling of foraging behaviours and social organisation.

A non-destructive method for evaluating the preservation of the original aragonitic shell carbonate using Fourier transform infrared spectrometry with an attenuated reflectance attachment is presented, allowing for robust SST reconstructions. Near-shore SST reconstructions are presented from the LSA levels of Nelson Bay Cave and Byneskranskop 1, with new radiocarbon chronologies spanning the terminal Pleistocene and the Holocene, and the MSA deposits at Pinnacle Point 5-6 and Klasies River Main site, dated to periods in Marine Isotope Stage (MIS) 5 and across the MIS5/4 transition. These reconstructions confirm the utility of near-shore SST records for terrestrial climate reconstructions, indicating summer rainfall shifts during the Holocene and across MIS5/4. The annual timing of shellfish foraging is shown to be markedly different between the MSA and LSA, and more nuanced assessments of foraging behaviours within the MSA and LSA emerge.

Authors: Loftus, E

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford