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Desert Diary


Desert badlands show shades of brown, red, sometimes even green. And in much of the region, whitish layers form prominent bands. These are deposits of calcium carbonate, known in this context as caliche. Close inspection reveals that they are formed by deposition of the caliche as cement between particles of sediments.

How did these caliche beds form? Certainly not in oceans like the older limestones so common here. No, these are dryland deposits. Waters falling on the alkaline areas of the region dissolve small amounts of calcium. In wet times, such mineral-charged waters are flushed away in ground or surface waters. In drier regimes, though, ground penetration is limited, and water only makes it a few feet down—the minerals build up and impede water that might sink lower. The caliche layer is in place and continues to grow until new sediments bury the ground surface deep enough that water no longer gets to the layer. Revealing the past, most caliches record stable ground surfaces, lasting perhaps hundreds or thousands of years.
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Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.

sediments showing caliche deposits

Caliche forms the uppermost layer—the "caprock"—of the sediments except for wind-blown sand and lag deposits left behind where wind has stripped away the finer particles. Edge of La Mesa Surface, west of the Rio Grande Valley. Photograph by A.H. Harris.