Reconstructing the late pleistocene palaeoenvironment of the Richtersveld using fossil charcoal

Bachelor Thesis


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University of Cape Town

The Succulent Karoo is recognised as an important biodiversity hotspot and many of the key plant lineages that characterise the biome are thought to have originated during the Pleistocene epoch. However, due to the paucity of palaeobiological proxy data available for the Succulent Karoo, relatively little is known about its environmental history and how an important core of this region, Namaqualand and its subregion the Richtersveld, may have responded to Pleistocene changes. Recent excavations at Spitzkloof Rockshelter A in the Richtersveld have provided a rare source of palaeoenvironmental data in the form of fossil wood charcoal assemblages that span a sequence from the last glacial maximum (LGM) to ~14 500 yrs BP. The present study analysed the fossil charcoal deposits from the rockshelter in order to reconstruct woody species assemblage patterns as a proxy for late Pleistocene palaeoclimate. Identification of the fossil charcoal specimens was achieved by anatomical comparison with transverse section photomicrographs of identified reference specimens of woody taxa currently growing at the site. Patterns in the charcoal data set were sought by assessing the changes in woody species assemblages over time. An assessment of the environmental correlates of the contemporary distributions of taxa found in the archaeological sequence provided the basis for palaeoenvironmental reconstruction. Based on the current generalisation for glacial climates in the winter rainfall zone (WRZ), it was hypothesised that the study region experienced an increase in rainfall at the LGM, and a steady aridification towards the terminal Pleistocene. However, Spitzkloof's charcoal records provide little evidence to suggest that the LGM supported a more mesic vegetation community than more recent time-periods. Instead, results suggest that the region experienced fairly limited climatic change as there is compelling evidence for the persistence of Succulent Karoo elements – namely Stoeberia arborea, Hermannia disermifolia and Lycium spp. - throughout the late Pleistocene. The localised appearance at the terminal Pleistocene (~14 ka) of all of the most abundant taxa at the site today is interpreted as a consequence of terminal Pleistocene changes in sea-level and CO2 concentration within a persistent context of minimal climatic change. These results have important implications for the applicability of a generalised WRZ model of climate change to the Succulent Karoo and for hypothetical predictions of future climate change impacts in the biome.