Texture contrast profile with stonelayer in the Cape Peninsula, South Africa: Autochthony and polygenesis

- The studied soil-geomorphic unit has a duplex morphology.
- Palaeosols are reliable indicators of palaeoclimate and palaeoenvironments.
- We used palaeosol-based proxies to evaluate weathering intensity and palaeoclimate.
- The studied profile confirms palaeoclimate oscillations in the Cape Peninsula.
- Dating of the palaeosols is needed to put the changes into a temporal framework.

We studied a soil-geomorphic unit with a stonelayer at the Cape Peninsula, South Africa, for which there is no previous documented research, to characterize the soils and draw inferences regarding their pedogenesis and palaeoenvironment aspects. Mineralogy and element geochemistry were determined using XRD and XRF respectively; micromorphology by thin section description. Physicochemical properties were determined by routine procedures. The operational pedogenic process in the buried horizons include plinthization; and in the younger overlying soil, podzolization. Element abundance followed SiO2 > Al2O3 > Fe2O3 > TiO2. Variations in climate and parent material are the principal causes of differences in the soil properties. The stonelayer appears to have been deposited as a lag by a palaeoriver as the energy decreased and the material was later mixed with the soil matrix by turbation. Two regional climate cycles are in evidence: a relatively warm and humid subtropical climate which gave rise to the formation of the buried palaeosol and a drier, more seasonal semi-arid Mediterranean climate under which the soils overlying the stone line are currently forming. Like many other places, the Cape Peninsula has also been subjected to global climate oscillations. Palaeosol-based proxies are capable of providing insights into palaeoenvironments.