Quaternary Glaciations and Palaeoclimate of Mount Kenya, East Africa

Abstract

Quaternary glacial and periglacial deposits, in several drainages on Mount Kenya, have been dated using relative (RD) and absolute dating (AD) methods to assist in refining the glacial chronology and in reconstructing palaeoclimate. Topographic position of deposits, weathering features, degree of soil development, and radiocarbon assist in assigning ages to Quaternary deposits in the Afroalpine and bamboo forest-Hagenia woodland zones. AD and RD methods provide reasonably precise ages for late Pleistocene and Holocene deposits; however, early and middle Pleistocene deposits proved difficult to date with precision. Palaeosols provide information on palaeoclimate and allow palaeoenvironmental reconstruction to and beyond the last interglacial > 100,000 yrs BP.In the higher valleys sequences of younger glacial deposits mapped between 4500 and 4800 m a.s.1., belong to the late Holocene (<1000 yrs BP). Moraines, formerly mapped by other workers as mid-Holocene glacial deposits, are considered to date from recession of valley ice during the late glacial (−12,000 yrs BP). Ice advance during the last glacial (Liki Glaciation) presumably began < 100,000 yrs BP, ending −15,000 yrs BP, and reaching to 3200 m a.s.1. Only minimum ages of −15,000 yrs BP are available from bog-bottom sediments recovered from cores taken in the lower valleys around the margin of glaciation. In Teleki Valley, a sequence of pre-Liki tills, loesses, and tephras provides information on the nature and character of environmental fluctuations over the period > 100,000 yrs BP to > 730,000 yrs BP. These glaciations produced a succession of four tills older than the last glaciation, from youngest to oldest: Teleki, Naro Moru, Lake Ellis, and Gorges drifts. The Teleki glaciation occurred prior to deposition of post-Teleki loess; Teleki till, high in ferromagnetic minerals, and almost free of quartz, contains more highly weathered feldspars and altered glass than is commonly found in younger Liki palaeosols. The compound palaeosol formed in these sediments is the product of weathering during and after the Teleki/Liki interglaciation.The older Naro Moru, Lake Ellis and Gorges tills have variable ages that can be established by topographic position, K/Ar ages on outwash, and palaeomagnetism. The oldest tills, dating from the Gorges and Lake Ellis glaciations, have strong reversed remanent magnetism placing them in the Matuyama Chron. Younger drift of Naro Moru age has stong normal remanent magnetism placing it in the lower to middle Brunhes Chron.KeywordsLate PleistoceneNatural Remanent MagnetizationEastern FlankGlacial DepositSoil Survey StaffThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.