Chronology of Quaternary glaciations in East Africa

A new glacial chronology for equatorial East Africa is developed using in situ cosmogenic 36Cl measured in 122 boulders from moraines on Mount Kenya and Kilimanjaro. The oldest deposits sampled on Kilimanjaro yield a limiting 36Cl age of >360 calendar kyr (all 36Cl ages are in calendar years, cal. kyr or cal. yr). On Mount Kenya, the oldest moraines give ages of 355–420 kyr (Liki I) and 255–285 kyr (Teleki). Given the uncertainty in our 36Cl ages, the Liki I moraine may correspond to either marine isotope stage 10 or 12, whereas the Teleki moraine correlates with stage 8. There is no evidence for stage 6 on either mountain. The Liki II moraines on Mt. Kenya and moraines of the Fourth Glaciation on Kilimanjaro give ages of 28±3 kyr and 20±1 kyr, respectively. They represent the last glacial maximum (LGM) and correlate with stage 2 of the marine isotope record. A series of smaller moraines above the LGM deposits record several readvances that occurred during the late glacial. On Mt. Kenya, these deposits date to 14.6±1.2 kyr (Liki IIA), 10.2±0.5 kyr (Liki III), 8.6±0.2 kyr (Liki IIIA) and ∼200 yr (Lewis); the corresponding deposits on Kilimanjaro have mean ages of 17.3±2.9 kyr (Fourth Glaciation–Saddle), 15.8±2.5 kyr (Little Glaciation–Saddle), and 13.8±2.3 kyr (Fourth Glaciation–Kibo). These data indicate that the climate of the tropics was extremely variable at the end of the last glacial cycle.