Death Valley 01: Bush on Caliche

Image Commentary

As you enter the Tucki dune-field in Death Valley, walking in from the west side off Highway 190, you first traverse a stretch of stoney desert sprayed with creosote bush and occasional cactus (see Image DV07). After 100 yards or so you begin to enter a series of low sand dunes that are anchored in place by creosote bushes, beyond which, the main dunes begin. As you start across the dunes, you first notice that in the lows between them, the desert floor is more than sand, here there are patches, some quite extensive, of hard, white "rock", that seem to poke out from beneath the dunes, as if the dunes were migrating over a "platform" surface. These rocks are caliche beds, or "hard-pan", that evidences wetter times that preceeeded the advance of the dunes. During times of extensive standing water, fine grained calcareous muds would line the floors of large ponds and as the ponds evaporated, the muds would eventually dry out and harden through a combination of sun-baking and chemical reaction. The muds became calcium carbonate (limestone) or magnesium carbonate (dolomite) or occasionally an evaporite deposit called gypsum. As one traverses these platforms one is immediately struck by the extensive mosaics of preserved mud cracks (or dessication cracks) typical of the modern dry lake beds elsewhere in the Death Valley area (e.g. The Racetrack Valley Image DV37).

As the valley became increasingly drier with time, the dunes began to form and eventually migrated across the hard-pan surface until only small segments are visible along the edges of the dune field.