Gypsum occurrence in soild on the margin of semipermanent prairie pothole wetlands.
Steinwand A.L. | Richardson J.L.
A series of three wetlands in a local recharge-throughflow-discharge groundwater flow system were investigated to determine factors controlling concentration of gypsum at the wetland edge. The three wetlands differ in pond size, permanence, salinity, and in their relationships to the groundwater hydrology. We believe gypsum accumulation resulted from long term hydrologic, geomorphic, and climatic factors. Wetland salinity appeared to control the distribution and amount of gypsum in soils around individual wetlands and between wetlands. In all wetlands gypsum was concentrated at the edge; presumably as a result of dissolved salt transport to an area of low water potential created by evapotranspiration and freezing (edge effect). The water flow from the edge effect converged on the peninsulas and diverged in the bays. Consequently in less saline wetlands, the bay soils contained minimal amounts of gypsum; peninsula soils were very gypsiferous. Wetlands of high salinity were surrounded by a continuous band of evaporites including gypsum. Within individual wetlands, differences in the degree and number of ponding events and groundwater recharge-discharge resulted in variations in gypsum distribution across soils of the low prairie, wet meadow, and shallow marsh vegetation zones.
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