Temporal variations in the controls of lacustrine sedimentation during continental rift evolution: evidence from the northern Kenya Rift Valley

This study will examine rock and sediment outcrops ranging in age from the Miocene to the present (~15–0 million years) in two areas of the northern Kenya Rift Valley. These include the arid Suguta Valley and, to the southwest, the eroded Tugen Hills. Both areas contain well-exposed deposits laid down in a variety of terrestrial and aquatic environments. This investigation will focus on those deposits formed in spring systems and fresh to saline lakes.

The research will pursue four major lines of investigation: 1) a study of modern hot and cold springs and their deposits in the Suguta Valley; 2) characterising modern sedimentation in permanent and ephemeral lakes in the Suguta Valley, as well as changes in water chemistry between spring and river sources and modern saline lakes of the Suguta; 3) An investigation of past environments and sediments formed in ancient fresh to saline lakes that date back several million years in both the Suguta Valley and the Tugen Hills; and 4) integrating information on ancient and modern lakes in the northern Kenya Rift in order to determine if their are any systematic changes that can be related to rifting and volcanism in an evolving rift valley.

The project will explore these major aims through field studies and systematic analyses of water (modern lake waters, rivers, springs and groundwater inflows) and sediment (outcrops, short cores) samples. We will provide field descriptions of sediment sequences and return samples for geochemical, sedimentological and diatom analyses. The results of this work will allow us to characterise the modern environments and to decipher the past depositional settings in which ancient sediments accumulated.

In previous studies of the southern Kenya Rift, two members of the research team have detected many changes in the types of sediment that have accumulated at different times. These changes in deposition partly reflect varying past climates, but also mirror changes in the stage of development of the rift valley. This study will allow the research team to explore if their are similar, or different, long-term variations in deposition that may reflect changes in the evolving northern Kenya Rift and its tectonic setting and volcanic environments.

We will then combine models from our earlier studies in the southern Kenya Rift with new models from this investigation in order to develop a broader-based understanding of how sedimentation changes with time in an evolving rift system.