Late Quaternary glacial-interglacial cycle of climatic and environmental change on Mount Kenya, Kenya

Abstract

Sediments from Sacred Lake and Lake Nkunga on the northeastern flank of Mount Kenya have a sequential palaeoclimatic and palæoenvironmental record covering most of the Late Quaternary period: from ca 115 to 0 ka. Most of the Late Quaternary period (110 to 14 ka - glacial period) was characterised by terrestrial C4 vegetation types (grassland) at higher altitudes and mixed C3–C4 (grassland with scattered trees and shrubs) vegetation types at lower altitudes, while low, productivity-related 13C discrimination occurred in the aquatic environment. The last interglacial and Holocene vegetation consisted of C3 forest-type elements, and high 13C discrimination occurred in the aquatic environment. The period 14 to 9 ka is transitional to Holocene climatic conditions, with progressive expansion of terrestrial C3 vegetation, and increased 13C discrimination in the aquatic environment. These changes occurred in step with, and were primarily driven by, palaeo-atmospheric CO2 changes. Thus, the estimates of temperature depression in the tropics during the last glaciation need to be revised as they are probably overestimated. Regionally, the changes on Mount Kenya are coherent with those observed at other high altitude sites across the tropics. Globally, they show a high coherency with Milankovitch periodicities, and are coupled to ocean circulation changes and ice sheet growth and disintegration cycles in the North Atlantic.