Modern and Ancient Animal Traces in the Extreme Environments of Lake Magadi and Nasikie Engida, Kenya Rift Valley

Modern Lake Magadi and Nasikie Engida in the inner southern Kenya Rift exemplify the extreme conditions in some continental rift settings, with abundant inflow from hot springs and magmatic CO2, producing high-carbonate-bicarbonate, high-sodium waters with little calcium in a semi-arid closed lake basin. Hypersalinity, hyperalkalinity, and hydrothermal conditions characterize the modern lake and lake margins, and also contributed to the environmental conditions represented by the Pleistocene to Holocene sedimentary record of the basin. Micro- and macro-organisms are restricted in diversity and distribution in the modern lake basin. This study documents modern animal traces present in lake-margin sites around Lake Magadi and Nasikie Engida, and those preserved in Pleistocene and Holocene sediment outcrops in the Magadi Basin. These findings are then applied to the interpretation of examples preserved in drill-cores (HSPDP-MAG14) that span the Pleistocene to recent sedimentary record of Lake Magadi. Observed associations among animal traces, substrates, and environmental conditions in the modern sedimentary lake-margin environments help to interpret ancient lacustrine sediments in the geologic record.