Open Access
Origin of coarsely crystalline gypsum domes in a saline playa environment at the White Sands National Monument, New Mexico
Author(s) -
Szynkiewicz Anna,
Moore Craig H.,
Glamoclija Mihaela,
Bustos David,
Pratt Lisa M.
Publication year - 2010
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009jf001592
Subject(s) - evaporite , geology , groundwater , gypsum , geochemistry , permian , sabkha , aeolian processes , meteoric water , aquifer , geomorphology , structural basin , sedimentary rock , paleontology , geotechnical engineering
Dome‐like structures up to 3 m in height, composed predominantly of coarse crystals of selenite gypsum, occur on the surface of Alkali Flat, a saline playa lake in White Sands National Monument, New Mexico. The structures were investigated using field observations, aerial images, and geochemical methods. The domes are inferred to be remnants of lake sediments that have been preserved from Holocene eolian erosion due to higher cementation resulting from crystallization of large gypsum (selenite) crystals in the playa's clay‐rich sediments. Low δ 2 H values of the selenite, from −90 to −69 ‰, suggest precipitation from saturated solutions associated with groundwater seepage in the playa related to the upward flows of groundwater, primarily fed by meteoric water rather than the evaporation of the playa water. Values of δ 34 S for selenite range from 12.1 to 13.8 ‰ (median 13.0 ‰) and are notably higher than the dissolved sulfate in the modern groundwater system that has δ 34 S values from 10.2 to 11.8 ‰ (median 11.4 ‰). The two main regional sources of sulfate are Middle Permian evaporites with median δ 34 S values of 12.0 ‰ and Lower Permian evaporites with median δ 34 S values of 13.0 ‰. The δ 34 S values measured in domes suggest their formation during a period of time when groundwater seepage might have been dominated by deeply circulating water that interacted with Lower Permian evaporites buried in the basin center. The apparent alignments of domes suggest that past groundwater seepage was controlled by fractures beneath Alkali Flat which are associated with a regional fault system in the area.