Amino acids in buried paleosols on Mount Kenya

Abstract

A sequence of buried paleosols ranging from ∼900 to > 42,000 radiocarbon yr BP, formed in a succession of different parent materials on Mount Kenya, East Africa, was utilized to determine the fate of amino acids over time. Amino acids were studied in whole-soil samples, hydrolyzed for 24 hours following standard laboratory procedures. Aspartic acid proved most useful as a relative age indicator yielding progressively higher D/L ratios with increasing age. The sequential change in composition with time confirms that the amino acids are mostly fossil types. This technique appears useful for determining whether paleosol samples used for radiocarbon dating might be contaminated with younger material. The sequential decline in amino acids in paleosols appears useful also as a relative dating method, and may eventually prove useful in dating paleosols beyond the range of radiocarbon.