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Efflorescent salt crusts composed primarily of halite dominate the saline mudflats of Saline Valley and Death Valley, California. These crusts form by the complete evaporation of saline groundwater at the sediment-air interface. Efflorescent crusts also form where halite dust is introduced by wind, then dissolved by rain and reprecipitated as the rainwater is evaporated. Wind-blown silt and clay adhere to thin hydroscopic water films coating crystals in the efflorescent crusts, and coarser sediment is trapped in surface depressions. The sediment is left as a lag deposit when the halite dissolves at the base of the crust in the undersaturated waters below the surface. Efflorescent crust deposits slowly aggrade producing irregular sand and silt lenses in poorly sorted porous mud. The sand and silt lenses have distinctive cuspate contacts, ragged edges, and irregular layering and grain-size distributions. Efflorescent crusts growing on sandy sediment distort the upper surface into polygonal bowl shapes, or deform ripples into hump-shaped lenses. Deposition during flooding over an efflorescent crust commonly produces local areas of solution collapse, which are filled with the sediment as it accumulates. The latter resemble load casts but do not have associated flame structures. Efflorescent crust fabrics similar to those in Saline Valley and Death Valley are documented in the lacustrine Blomidon Formation (Fundy basin, Nova Scotia, Canada) and Bigoudine Formation (Argana basin, Morocco). Efflorescent crusts composed of less soluble minerals, such as gypsum or borates, may leave humpy layers of broken crystals and plates. Powdery efflorescence of minerals, such as thenardite or thermonatrite, generally only disturbs the internal layering of sandy deposits. Puffy ground in dry mudflats, formed by powdery efflorescence growth in mudcracks, produces a distinctive granular fabric.

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