Catchment and Depositional Studies for the Reconstruction of Past Environmental Change in Southern Africa

Abstract

Terrestrial signals in marine sedimentary archives are often used for reconstructing past environments, vegetation and climate, as well as for determining sediment fluxes, pathways, and depositional sites and changes in erosional runoff. It is therefore important to understand the origin, transport, and depositional processes of the various terrestrial sedimentary components in a depositional system. In this chapter, we use examples from southern Africa to show how source-to-sink studies have led to a clearer interpretation of downcore proxy records. Twelve rivers in four river catchment areas of various scales and in distinct climatic settings and geological formations are included in this compilation. We also discuss studies from the current-swept South African east coast, the broad western and southern margins, and investigations from protected marine embayment settings. We consider a large suite of commonly used proxies (plant wax isotopes, elemental composition, and fossil pollen) as well as hydroacoustic surveying techniques (PARASOUND and multibeam bathymetric profiling). Sampling strategies and sample types that may be used in catchment analyses are discussed. Challenges and limitations of the above-mentioned approaches are outlined. In conclusion, we underline the importance of a thorough source-to-sink approach to paleo-environmental reconstructions using terrigenous proxies.