Explosive Volcanism in the Kenyan Rift: A Tephrostratigraphic Perspective

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This PhD seeks to build on ongoing work to establish a widespread and detailed tephrostratigraphic framework for the East African Rift. When complete this framework will provide essential chronological control for palaeoenvironmental and archaeological records, thus helping to further our understanding of tropical hydroclimatic variability and human evolution during the Pleistocene and early Holocene. Here the tephrostratigraphy of the Kenyan Rift Valley will be investigated through the identification and characterisation of cryptotephra (microscopic tephra) layers within three lake records. The first of these will be Lake Challa, a crater lake at the base of Mt Kilimanjaro providing 250kyrs of environmental data. A subsection of this core focusing on MIS1-3 will be analysed for cryptotephra, where correlations will be made with source eruptions using their unique glass composition. For known eruptions this will provide accurate dates for precise depths of the core, thus helping to refine Blaauw et al.'s (2011) radiocarbon-based age-depth model. This research is also anticipated to document new, unknown eruptions which will prompt further investigation into their age and origin. Once cryptotephra layers are fully characterised within Lake Challa, parallel investigations will take place on the 30kyr sediment cores of Lake Naivasha and Lake Rutundu, with possible extension to nearby archaeological sequences. Where cryptotephra layers can be correlated across these records, and with the already established tephrostratigraphy of the Lake Victoria Basin, a master chronology for palaeoenvironmental and archaeological research will be proposed.