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Morphodynamics and Morphogenesis of Pediments in the Deserts of Iran
Otfried R. Weise
The Geographical Journal
Vol. 144, No. 3 (Nov., 1978), pp. 450-462
Published by: geographicalj
Stable URL: http://www.jstor.org/stable/634821
Page Count: 14
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The present semiarid to arid climatic conditions in Iran lead to morphodynamics that form pediments. Study of fossil weathering profiles and correlative sediments provides evidence that processes similar to those of today were also active in Neogene and Pleistocene times. The pediments in Iran have no savannah type planation surfaces as precursors. However, small scale climatic variations and/or tectonic movements led to the development of several pediment levels and different kinds of pediment dissection. Pediments are formed not only by the retreat of mountain fronts, as some authors have claimed, but also by the planation of the mountains from drainage lines within them. Autochthonous slope development in Iran is capable of steepening slopes without lateral undercutting. Fluvial flattening of slopes of small residual hills can also be observed. Pediments are not only plains of transportation, but are lowered and flattened by autochthonous denudational processes. This degradation results largely from the so-called 'exchange of components', which is effective because of intensive weathering during the long intervals between floods. The morphogenesis of pediments is considered to embrace four stages, here styled: the mountain-bahada stage, the pediment stage, the pediplain stage and the desert dome stage.
The Geographical Journal © 1978 The Royal Geographical Society (with the Institute of British Geographers)