Environmental Reconstruction at Nahoon Point during MIS 5e: Contextualising Human Occupation using a Geoarchaeological Approach

Morrissey, Peter
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Several published sites – the Nahoon Point footprint site, Blind River and Bats Cave – and a number of previously unreported artefactual deposits indicate human occupation around East London, Eastern Cape, South Africa, during Early Marine Isotope Stage (MIS) 5 (130–105 ka). These finds are within aeolianite deposits of the Nahoon Formation and shallow marine deposits of the Salnova Formation. Past research has mainly focussed on dating the deposits and on analysing the anatomical details preserved in the human footprints and the Blind River femur. Published work on the stratigraphy and sedimentology of these deposits has been limited in both geographic scale and detail. Depositional and erosional features in the area have been considered to represent both of the two MIS 5e sea-level highstands that are known from global and South African records. However, this argument is undermined by significant uncertainties about stratigraphic relationships between different deposits. The goal of this study was to reconstruct the palaeoenvironmental conditions associated with human occupation during this time period, with a particular focus on resolving stratigraphic uncertainties and determining how many highstands are represented in the local sequence. To this end, logging and sampling of 20 profiles was conducted along several kilometres of coastline around the published sites. The stratigraphic sequence in the study area records the interplay between, and changes in the relative dominance of, aeolian and marine depositional processes and their respective environments of deposition. Two distinct phases of aeolian deposition are preserved in the aeolianites. High-angle cross-bedding and low-angle convex-upwards lamination are the dominant depositional structures. Winds from between the south and the northwest were primarily responsible for dune formation in both phases. This pattern is most similar to the present winter wind regime in the area. Depositional and erosional features in the study area indicate the occurrence of a sea level transgression phase between the two phases of aeolian deposition. This stepped highstand reached a peak of up to 7.82 ± 0.82 m above present mean sea level at around 117.3 ± 6.2 ka. The updated stratigraphy, combined with the dates previously obtained for various deposits, indicate that the Phase 1 aeolianites correlate broadly with the mid-MIS 5e relative lowstand and that the Phase 2 marine deposits formed during the second MIS 5e highstand, while the Phase 3 aeolianites were deposited during late MIS 5e and MIS 5d. No evidence for the first MIS 5e highstand was found in the study area, although this may have been overprinted by later events. The presence of lithic artefacts in coastal marine deposits at several locations indicates human activity within the intertidal and supratidal zones. Palaeoenvironmental data and trace fossil evidence, from both this work and previous studies, suggest that a variety of marine and terrestrial species were (or may have been) present in the area. The available archaeological information on early MIS 5 human subsistence strategies indicates that human populations would have been able to exploit available food and water resources. Therefore, it is not surprising that the distribution of archaeological deposits within the stratigraphic sequence suggests fairly continuous human occupation of this changing landscape despite environmental variations during early MIS 5.
A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science FACULTY OF SCIENCE 2019