Original paper
Late Pleistocene deglaciation of Mount Kenya
Mahaney, William C.
Zeitschrift für Geomorphologie Volume 32 Issue 2 (1988), p. 227 - 230
12 references
published: Jul 5, 1988
ArtNo. ESP022003202007, Price: 29.00 €
Abstract
Mount Kenya and other East African mountains were extensively glaciated during the Quaternary (Nilsson 1931, Downie 1964, and Hastenrath 1984). Mount Kenya has ten glaciers remaining in the Cental Peaks Area above ~ 4500 m. During the Liki (= Würm) and pre-Liki glaciations glaciers descended to ~ 3000 m constructing a sequence of end and lateral moraines (Mahaney 1979, 1987 a). Recent 14C age determinations of Liki I and II moraines in lower Teleki Valley establish the time of deglaciation at ~ 15,000 yr BP (Mahaney 1987). Mount Kenya (fig. 1), a Plio-Pleistocene composite volcano rising to 5199 m, contains a well developed moraine record in all major drainages. The lowermost moraines on the western flank have extensive bogs from which organic sediments were collected for 14C dating. Three samples of organic-rich sediment (fig. 2) collected from silty and clayey core sections at depths of 105 cm, 128 cm, and 123 cm, respectively, gave the following ages: 10,380 ± 250 yr BP (GaK-11261), 12,230 ± 280 yr BP (GaK-11,263) and 10,550 ± 260 yr BP (GaK-11,257). While it appears impossible to obtain bog-bottom sediments sufficiently high in organic matter for radiocarbon dating, it is possible to reach tills or pebbly sand at ~ 170 cm depths. The approximate age of these substrates, as determined from sedimentation rates in overlying core sections, suggests that bogs started to form between — 14,500 and ~ 15,500 yr BP. These inferred substrate dates should be considered minimum ages because the amount of time required to form bog depressions following deglaciation is unknown. That these cores tend to coarsen downward suggests higher-energy sediment transport during the initial stage of development, presumably when meltwater from receding Liki glaciers was abundant.
Keywords
Liki • Würm • glacier • sediment • deglaciation • organic-rich • moraine • sediment • tills • pebbly sand • Mount Kenya • East Africa