Micromorphic record and interpretations of carbonate forms in the Rolling Plains of Texas

• Published in: Geoderma 1987-09, Vol.40 (1), p.157-175
• Main Authors: Drees, L.R., Wilding, L.P.
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; Soils; Surficial geology
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/0016-7061(87)90020-6

The Rolling Plains of Texas comprises about 10 million hectares of soils developed in Permianage deposits. Most soils occur on erosional landscape positions. Soils have ustic moisture regimes and thermic temperature regimes. These soils have developed in a wide variety of sediments ranging from red bed shales to sandstones. Most of the soils have carbonate-enriched Bk horizons while parent materials are slightly- to non-calcareous. Pedogenic calcite usually occurs as nodules, calcans, neocalcans and crystallaria. Calcite nodules are the dominant form in upper Bk horizons, while the other forms occur primarily in lower Bk/Cr horizons. Additional forms of calcite include pseudomorphs after gypsum and equant anhedral calcite which fill fracture or joint seams, and sand-calcite crystals (poikilotopic). These are considered pedogenic although formed under an earlier climatic regime. Dolomite, a post-depositional lithogenic mineral, occurs as nodules, intercalary crystals and clustered to dispersed microsparite crystals. Micromorphic forms of calcite indicate that the soils have been through several major and minor fluctuations in the soil chemical environment. On stable landscape positions, carbonate minerals preserve the long-term pedogenic record of soil development.