Marine geophysics reveals the character of the now submerged Paleo-Agulhas Plain

Summary

This work was undertaken to understand the evolution of the terrestrial landscape now submerged by high sea levels offshore of Mossel Bay. Two marine geophysical surveys and scuba diving were used to examine evidence of past sea-level fluctuations and interpret seafloor geological deposits. Eight seismic sequences characterise the shelf, extending from the Mid-Cretaceous to the Holocene time. Geological mapping dating by Optically Stimulated Luminescence (OSL) revealed that the most prominent Quaternary units are associated with the MIS 6 glacial to MIS 5 interglacial periods and include incised lowstand river channels and regressive aeolianites. MIS 5 transgressive beachrock and regressive beach and dune deposits on the shelf are associated with the subsequent fall in sea level. MIS 4 lowstand incised river channels were infilled with sediment truncated during rapid landward shoreface migration at the MIS 4 termination. Back-barrier MIS 4/3 sediments are preserved as a result of overstepping associated with meltwater pulses of the MIS 2 termination. Accommodation space for coastal deposits on the South Coast continental shelf is controlled by antecedent drainage pathways and shelf gradient. The geological deposits on the emergent shelf indicate an expanded glacial coastal plain dominated by low-gradient meandering rivers and wetland lakes.

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This Resource is Part of the Following Collections

• Building the hunter-gatherer’s paleoscape on the South African coast: Environment, landscape, and foraging resources   •
• Society for American Archaeology 80th Annual Meeting, San Francisco, CA (2015)

Keywords

Spatial Coverage