Soil and Saprolite Characteristics of Vertic and Aquic Hapludults Derived from Triassic Basin Sandstones

Abstract

AbstractThe chemical, morphological, and mineralogical properties of two soil‐saprolite profiles from the Durham Triassic Basin were determined. The relationship between clay mineralogy and shrink‐swell activity of the soils was also determined. The parent rock from the Vertic Hapludult profile was a fine‐grained red sandstone with muscovite mica, quartz, and feldspars as the dominant primary minerals. The parent rock from the Aquic Hapludult profile was a coarse‐grained gray sandstone with feldspars, muscovite mica, and quartz as the dominant primary minerals. The argillic horizons in both profiles had cracks, slickensides, high clay contents, moderate to high coefficient of linear extensibility (COLE) values, and smectite as the dominant clay mineral. The COLE values are greatest in horizons that display evidence of shrink‐swell activity (cracks and slickensides). The COLE values do not correlate well with either fine or total clay content, which implies that factors other than fine or total clay content influence COLE values. Base saturation percentage increases abruptly below the paralithic contact requiring close examination for correct Ultisol or Alfisol placement.