High Gypsum Content Soils: Relating Micromorphology to Landscapes

Gypseous soils are found in a variety of landscape positions ranging from uplands to fluvial terraces and floodplains. A number of soils located in Culberson and Hudspeth counties in West Texas were sampled in order to ascertain the relationship between the micromorphological properties of gypseous soils and their landscape position. Soils selected for study were formed primarily in a variety of parent materials ranging from gypsic bedrock (Permian, Castile Formation) along with gypsum rich aeolian sediments and fluvially deposited silicate material. Sampling of soils from a variety of parent materials allowed for a more representative look at the possible mineralogies and micromorphologic features which could form given a range of soil gypsum contents. Thin section analyses were utilized in order to compare micromorphic gypsum features to the larger scale features observed in hand-specimen and then relate the formation of these features to the landscape positions from which they were sampled. Gypsum content, apparent field texture, depth of profile development, extent of distribution of gypsum throughout the profile, and the presence or absence of a gypsic or petrogypsic horizon were among the features that were observed in order to elucidate a relationship between geomorphology and gypsum features forming in the soil.