Surface features of the Salt Basin of Lancaster County, Nebraska

The Salt Basin of Lancaster County, Nebraska is distinguished by the presence of ephemeral to semi-permanent saline wetlands, salt flats, surface accumulations of salt, zones of bacterial sulfate reduction in wetland soils and stream sediments, and soil cryptogam layers. Salt flat soils are unique in the region and have laminated surface horizons, which probably result from a combination of soil crusting, salt crusting, and microbial binding of grains, with vesicular horizons characteristic of desert soils directly underneath. Soil-surface salt accumulations are dominated by halite (NaCl) and contain minor amounts of thenardite (Na2SO4); they range in morphology from thin, powdery, and very transient efflorescences to thicker, more persistent, soil-cementing crusts. The salt crusts form by the upward wicking of Na+- and Cl−-dominated groundwaters and their subsequent surface evaporation. Although it has been largely ignored by geologists for over a century, the Salt Basin can now be viewed as an unusual occurrence of inland sebkhas.