Late Quaternary palaeoenvironmental reconstruction of northern Namibia using palaeolake sediments from Etosha Pan

Thesis

Palaeoenvironmental reconstructions are an important tool in understanding major environmental and climatic changes from the past and into the future. They are critical in parts of southwestern Africa where existing records are sparse and future rates of climate change are predicted to be high. Etosha Pan is situated in the drylands of northern Namibia and has long attracted the interest of researchers who hypothesised changes in its geomorphological and palaeoenvironmental context over the late Quaternary. One of the reasons for uncertainty about the basin’s palaeohydrological history is the lack of precision in age control to uncover the history of the pan over past millennia. In this thesis, a dual approach of optically stimulated luminescence (OSL) and radiocarbon dating of lakebed sediments and marginal sand ridges was adopted to better constrain the timing of major palaeoenvironmental changes. The work was undertaken by extracting samples from the north-western part of the pan and subjecting them to a range of sedimentological and geochemical analyses.

The new data from this study were used to reconstruct palaeoenvironmental and palaeohydrological dynamics in the Etosha basin from the last 40 ka. Key findings are that the pan underwent fluctuating lake levels in response to changing climate. This study proposes that, during the last glacial maximum (LGM, 23 - 19 ka), Etosha Pan sustained a deep lake under a wetter climate. The pan later experienced shallow lake levels at the start of the Holocene, which increased again due to a more humid climate during the mid-Holocene (7 - 5 ka). The key source of moisture during both periods is likely summer rainfall due to a temporary southward migration of the African tropical rain belt. These findings have implications for palaeoclimate modelling exercises for the LGM and mid-Holocene periods and assist in clarifying conflicting hypotheses of pan geomorphological evolution.

Authors: Maboya, M

• DOI: 10.5287/ora-ae2jx0b1a
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: last glacial maximim; palaeoenvironmental reconstruction; Etosha; Northern Namibia; late quarternary; salt pan
• Subjects: Geomorphology; Late Quarternary Environments; Palaeoenvironmental Reconstruction