The Dasht-i-Kavir or Great Salt Desert of north central Iran occupies a northeast-trending elongate area of about 9,000 square miles. Its geographic center is about 225 miles southeast of Teheran. The average surface elevation of the essentially flat desert plain is close to 2,000 feet above sea-level; maximum relief within the plain is probably about 50 feet.

Structurally, the desert basin area is a graben separated from the adjoining highlands by major active faults. Metamorphic rocks of pre-Mesozoic age and Jurassic and Cretaceous sediments crop out in the bordering mountains and are presumed to underlie the graben at depth. The post-Mesozoic sequence includes a thick Eocene sedimentary and volcanic section with possibly some evaporites. Oligo-Miocene evaporites and marine limestone and Miocene red beds and evaporites overlie the Eocene. The post-Cretaceous section probably totals as much as several thousand meters in thickness. Approximately 35 salt plugs occur within a restricted area on the north side of the graben. The major part of these salt masses is tentatively considered to originate in the Oligo-Miocene evaporitic section.

Available maps show the Kavir as a salt waste apparently without topographic pattern. This is essentially true for most of the area occupied by salt pans; however, when viewed from the air the remaining area shows a striking pattern of light and dark brown bands which closely resemble form lines on a structural contour map.

On-the-ground examinations confirm this relation. In areas not covered by recent salt pans the surface is mantled by puffy, saline, "self-rising" soil which ranges from a few inches to a few feet in thickness. The underlying bedded rocks which are known to have dips as great as 50° or more do not crop out. The visible color banding is entirely a surface soil pattern which reflects the structure at the base of the soil mantle. Surface color differences do not appear to conform to color difference in underlying unweathered rocks. It is suggested that the color contrast is at least in part a function of the moisture content or "wettability" of the surface soils. This is in turn dependent on the physical-chemical properties of the particular rock layer from which the soil is derived nd on the water-table level and rate of evaporation.

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