Browsing by Author "Morrissey, Peter"

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    Environmental Reconstruction at Nahoon Point during MIS 5e: Contextualising Human Occupation using a Geoarchaeological Approach
    (2019) Morrissey, Peter
    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.
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    Reassessing the stratigraphy and formation of the basal deposits at Klasies River Main Site with a multiscale and multiproxy approach
    (University of the Witwatersrand, Johannesburg, 2024) Morrissey, Peter; Wurz, Sarah; Mentzer, Susan
    The basal deposits at Klasies River Main site, associated with the MSA I and II lithic cultural phases and dating from >120 ka to ~80 ka, have yielded highly significant archaeological assemblages and human fossils across multiple phases of excavation since the late 1960s. These finds have contributed to a growing understanding of the appearance and intensification of modern human behaviours and provide rare insight into Homo sapiens anatomy during the early parts of the Late Pleistocene. The three recesses occupied during this period represent distinct depositional environments with differing degrees of attractiveness for human activities. Significant climatic, environmental, and geomorphic changes, including large fluctuations in sea level, occurred, impacting formation processes within the site complex. Stratigraphic relationships across a space like this would always be complicated but understanding them here is even more difficult because there are not continuous deposits between the recesses for all or part of their respective sequences. Geoarchaeological research has taken place alongside all three phases of excavation at Klasies. Until Sarah Wurz began her field programme in 2013, this work entailed macroscopic descriptions of standing sections (at differing resolutions) and the sedimentological analysis of bulk samples. Given the finely laminated nature of many of the deposits, even higher resolution bulk sampling resulted in the incorporation of multiple visible deposits into individual samples in many cases. More recently, archaeological micromorphology and other microscale analyses have been applied to deposits in the site complex by Susan Mentzer and colleagues. This work has provided important new insights into human behaviour and the spatially and temporally variable impacts of different diagenetic processes. Here, field observations of standing sections and microcontextual analysis are used to provide greater insight into the formation of deposits in two areas of the site complex. This information is used, along with unpublished field notes and profile drawings and critical engagement with the extensive, but seldom detailed, literature to assess and refine stratigraphic correlations of the basal deposits both between different recesses and different stratigraphic systems (the layers used in the initial excavations and the excavation units grouped into members and sub-members in subsequent work). The results demonstrate that the formation of any particular deposit could involve any number of combinations and relative intensities of different depositional and post- depositional processes. Furthermore, the interplay between geogenic, biogenic, and anthropogenic processes is often significant. Anthropogenic deposition has long been recognised as being highly significant at Klasies, but it is now also clear that humans played a major role in reworking sediment through daily activities during occupations, very likely including trampling and site maintenance activities. Chemical diagenesis had a major impact on the preservation of anthropogenic features, but variations in the intensity and frequency of anthropogenic deposition also influenced how susceptible deposits were to diagenesis. It has proven possible to correlate between the two stratigraphic systems in Cave 1B, a particularly understudied area of the site complex, providing clarity on the cultural association of a highly significant human fossil. The overall stratigraphic system used at the site complex is now also better understood, both in terms of correlations and the nature of the system. Finally, this study highlights the utility of a multiscale geoarchaeological approach to site complexes like Klasies for understanding site formation and stratigraphy. It also highlights the vital, but often ignored or underplayed, connection between site formation processes and stratigraphy, especially in such a complicated context.