Pedology of soils within the spray zone of the Victoria Falls (Zimbabwe)

Six profiles were sampled in the Victoria Falls National Park (Zimbabwe) in order to investigate the influence of the abundant spray of the falls on t he pedogenesis in the otherwise semi-a-rid environment. Depending upon the thickness of the alluvium, soils developed in the sediment with variable ad mixture of basalt gravel, or practically directly on the underlying Karroo plateau basalt layer. Those near the gorge are subject to a continuous spra y during most of the year; the more remote ones get only the natural precip itation. Chemical, mineralogical and micromorphological analyses indicate t hat the parent material is a more dominant factor determining chemical, min eralogical and micromorphological characteristics than precipitation. The m ain active process is bioturbation. Phytolites and sponge spicules are abun dant. In most profiles basalt-derived laumontite is observed in thin sectio ns and in the silt fraction. Weathering of the basalt gravel is limited, al though pedogenesis has been active for at least 50-100 ka. A subdivision of enaulic c/f related distribution patterns is proposed. (C) 2001 Elsevier S cience B.V. All rights reserved.