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18 • <br />Soil Forming Intervals <br />Past episodic intervals of time during which elevated temperatures coincided <br />with available soil moisture to favor accelerated rates of soil formation <br />are termed soil-forming intervals. The idea that soils do not form continu- <br />ously so long as the land surface remains stationary with respect to erosion <br />and deposition has been one that has only recently received considerable <br />attention among geologists and soil scientists. Dbrrison has developed many <br />of the geologic arguments favoring the non-steady-state soil development <br />hypothesis through his work in the arid western interior basins of Utah and <br />Nevada. His review volume (T~brrison 1967) concludes that soil formation <br />was episodic during the Pleistocene and Holocene and that: <br />. all Quaternary soil-stratigraphic units .., were formed <br />during distinct, intermittently recurring episodes of weathering <br />that were separated by long intervening periods when little or <br />no pedogenic weathering took place, at least in temperate zones." <br />If this concept is valid or partly valid, it becomes quite important from <br />the standpoint of potential reclamation success to know how present climates <br />compare with those during which soils form and how soil-forming climates <br />have varied to produce those soils found at the surface of the ground today. <br />If soil-forming intervals are short and if it is possible to form soils <br />under today's climate or one slightly modified by irrigation or other micro- <br />climatic alteration for short periods of time, then proponents of short-term <br />high-energy-input reclamation may have support for claims that soils can be <br />