This dataset is presented and discussed in the research article "Rare Earth Element geochemistry in saline alkaline lakes from the East African Rift, Kenya: The Case of the “Missing” Ce Anomaly" by Klose et al. This manuscript will be submitted to Geochimica et Cosmochimica Acta and was prepared by the following authors: Lukas Klose1*, Timmu Kreitsmann1,2, Lydia A. Olaka3, Moses O. Misongo4, and Michael Bau1 1 CritMET - Critical Metals for Enabling Technologies, School of Sciences, Constructor University, Campus Ring 1, 28759 Bremen, Germany 2 Department of Geology, University of Tartu, Tartu, Estonia 3 Department of Physics Earth and Environmnetal Science, Technical University of Kenya, Nairobi, Kenya 4 Department of Earth & Climate Sciences, University of Nairobi, Nairobi, Kenya *corresponding author: luklose@constructor.university The supplementary material contains Detailed description of sampling locations, model parameters for organic speciation modelling and analyzed reference materials.