SOILS DEVELOPED FROM COLLUVIUM IN THE RIDGE AND VALLEY AREA OF PENNSYLVANIA

Soils developed from colluvium are found on the side slopes of all the major and many of the secondary ridges in the unglaciated Ridge and Valley area of Pennsylvania. The texture of these soils varies from sandy loam to clay and, for the most part, has been inherited from the parent material. Vertically within these soils there are many textural changes. These changes are the result of argillic horizon development and textural heterogeneity of the parent material. These soils are well leached in the well-drained sites and less thoroughly leached in the more poorly drained sites. Fragipans occur in all the medium textured soils, but not in the finer textured ones or in the soils that have significant limestone influence in their parent material. The clay mineral content of these soils indicates significant illite weathering with a trend of less intensive weathering with depth and with increasingly poorer drainage. The presence of argdlic horizons, fragipans, significant illite weathering, and appreciable leaching indicates that these soils are moderately well developed. This implies that the landscapes on which these soils are found are relatively stable today, probably dating back to the Wisconsinan glacial time. © 1979 The Williams & Wilkins Co.