Provenance of Southern Cape rivers: Links to hydroclimate and early humans

Pryor, Ellie 2023. Provenance of Southern Cape rivers: Links to hydroclimate and early humans. PhD Thesis, Cardiff University. Item availability restricted.

Preview	PDF - Accepted Post-Print Version Download (56MB) | Preview
	PDF (Cardiff University Electronic Thesis and Dissertation Form) - Supplemental Material Restricted to Repository staff only Download (109kB)

Abstract

Blombos Cave coastal archaeological site in the southern Cape of South Africa exhibits artifacts from the Late Middle Stone Age (LMSA); 100–50 ka BP - a time interval when human cognition and technological advances underwent rapid development. Two such time intervals which represent important phases in the cognitive and cultural development of Anatomically Modern Humans (AMHs) are the Still Bay (72-71 ka) (SB) and Howiesons Poort (64–59 ka) (HP) industries. Research suggests environmental and climatic conditions in the region facilitated the cultural evolution of AMHs. This hypothesis is particularly relevant for coastal sites located at the dynamic land-ocean interface, which are influenced by the Greater Agulhas Current system in the Southwest Indian Ocean. However, our understanding of climatic conditions in the region is limited by the fact only a few continuous high-resolution archives exist. Terrestrial sediments from river channels of drainage basins between Durban and Cape Town using geochemical (87Sr/86Sr and ÁNd), clay mineralogy and lithogenic grain size data define two key sediment source regions: the Karoo and Cape Supergroup from South Africa. These new radiogenic isotope endmembers within the <2 μm grain size fraction were generated by unmixing of river sediment radiogenic isotope signatures. The ÁNd represents source rock age whereas variability in the 87Sr/86Sr is due to the degree of chemical weathering. These endmembers are used as a provenance tracer for reconstructions related to palaeoclimate variability utilising marine sediment cores offshore of the Southeast African coastline from modern and Last Glacial Maximum (LGM) dated samples. Major rivers drain into this region, these are the local South African sediments, as well as the Limpopo and Zambezi rivers. Through targeting the <2 μm, 2-10 μm and 10-63 μm size fractions of lithogenic sediments, this study reveals that during the LGM, there was an increase in Zambezi river input in the <2 μm fraction, transported downstream in the Agulhas Current mixed with local South African river sediment and a deep water signal in the 10-63 μm fraction, coming from the South Atlantic Ocean. The temporal variability is further explored in sediment core, MD20-3591 (36°43.707 S; 22°9.151 E, water depth 2464 m) as this site records marine hydrographic (Agulhas Current) and terrestrial hydrological variability. This study finds that during MIS 5, low latitude summer insolation changes, paced by orbital precession, explain the long-term climate variability in ÁNd whereas abrupt climate oscillations in the northern high latitudes are the main driver for the observed millennialscale wet phases, inferred from 87Sr/86Sr isotope ratios. During MIS 4, the effect of sea level on the local sediment signal is apparent, with a coarser sediment input during this glacial interval. This study further explores the variability of regional hydroclimate in relation to the early human archaeological record during the MSA interval.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Earth and Environmental Sciences
Subjects:	Q Science > QE Geology
Funders:	NERC
Date of First Compliant Deposit:	17 May 2024
Last Modified:	17 May 2024 13:54
URI:	https://orca.cardiff.ac.uk/id/eprint/169000

Actions (repository staff only)

Edit Item