PRELIMINARY RESULTS OF DUST EMISSION DATA FROM YELLOW LAKE PLAYA, WEST TEXAS, USA

We investigated the relationship between groundwater and dust emission rates at Yellow Lake, a saline “wet” playa in West Texas with a long history of wind erosion. Deflation of the playa surface has generated lunettes composed of silt-clay aggregates and gypsum. Saltation sensors indicate that most wind erosion occurs in the winter and spring in response to strong westerly winds (Stout, 2003). We used the PI-SWERL (Portable in situ Wind Erosion Lab) to measure dust emission and saltation potential along three transects of the playa during June 2011, when West Texas was in the midst of a severe drought. The playa surface was dominated by thin salt crusts composed of halite, thenardite, gypsum, and possibly other, minor evaporite phases, and bare mud-cracked surfaces. Small gypsum crystals, common on the playa floor, were likely exhumed by deflation. Direct eolian entrainment of small amounts of dust, therefore, occurred on a supply-limited surface. In contrast, loose dune sands associated with the lunettes were highly emissive because aggregates would break apart during saltation transport. Out measured saltation thresholds of 7.4 to 10 m/s for dune sand are consistent with those measured by saltation sensors. Local groundwater is rich in solutes, including sulfates that contribute to the growth of selenite crystals as much as 17 cm in length. Shallow groundwater (<30 cm) along the margins of the playa provides a moist substrate and encourages the near-surface crystallization of salts. Small dunes have blocked gullies incised into the lunettes that drain towards the playa, generating infiltration points that contribute to shallow groundwater and small springs. Continued drought may result in a declining water table that would minimize salt crust formation and transform Yellow Lake into a “dry” playa.