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. (C) 2000 Elsevier Science B.V. All rights reserved.