The Holocene history of the White Sands dune field and influences on eolian deflation and playa lakes

White Sands National Monument is the world's largest gypsum dune field. The dunes are downwind of a 20-m-deep, 19-km-wide deflation basin containing large playa lakes. Today, the gypsum sand is derived from the edge of the deflation basin, next to the dune field, rather than the alkali flat and playa lakes, where gypsum crystals are forming. Three erosional shorelines mark wetter episodes, when playa lakes formed in the deflation basin. Successively, younger shorelines formed within older ones as the basin deepened, but was not widened by deflation. The modern shoreline is forming around Lake Lucero Playa. The oldest shoreline, termed L1, is degraded and formed near the Pleistocene-Holocene transition. Deflation from the L1 to the L2 shoreline cut through Pleistocene bedded evaporites and probably marks initiation of the dune field. This event was before 5840 yr BP, based on radiocarbon dates. This reinforces an evolving consensus that episodes of deflation have characterized desert basins in the southwestern United States. Regional deflation events have been dated at 7000 and 4000 yr BP. The shorelines imply the White Sands dune field was created in short episodes and the modern dune field may not represent conditions during expansion of the dune sea. (C) 2002 Elsevier Science Ltd and INQUA. All rights reserved.