The genetic and morphological characteristics of Hagerstown silt loam, Pisgah silt loam and Clarksville cherty silt loam, three southwest Virginia soils which were formed from material weathered from limestone, were studied by means of mechanical and chemical analyses, and field studies or the soil profiles. The soils used in this investigation are all related in a general way, that is, they all occur within the Gray-Brown Podzolic region and are all derivatives of relatively highly carbonated rocks. Samples of all three soils were taken in Russell County, Virginia within the same vicinity. Therefore, the variation in the physical and chemical composition are due to variation in parent rock and relief and not to variations in climate. Chemical analyses of the parent rock showed that the Hagerstown silt loam and Clarksville cherty silt loan were formed from material weathered from a dolomitic limestone, and that the Pisgah silt loan was formed from material weathered from a high grade limestone. Total chemical analyses of the various horizons of the soil profiles showed that the soil forming processes of the three soils studied were podzolic is nature. The parent materials or C horizons of all the soil profiles studied were clays. Hagerstown, which contained approximately 38 percent clay in the A₁ horizon and 75 percent clay in the C horizon, was the heaviest of the three soils studied. Laboratory and field classifications of soil class conflicted in the case of the Hagerstown profile. The ratios of silica to alumina, and silica to iron showed clearly the accumulation of alumina or iron in the lower horizons. The base to alumina ratio showed the thoroughness of the weathering of the three soil profiles. Calculations of the percentages of bases lost during the soil forming processes showed that calcium was lost from the soil to a greater extent than the magnesium. / Master of Science

The Cullen soil series concept in the Virginia Piedmont has been the subject of much debate. This series was originally named Lloyd and was mapped throughout the southeastern Piedmont. In 1969 the Lloyd series was deactivated because of conflicting concepts. The Cullen series was established in 1970 to cover the Lloyd concept in Virginia. This soil is developed from a mixed felsic and mafic parent material and has been mapped over various rock types. A dark red (10R or 2.5YR 3/6) B subhorizon is the major morphologic feature of this soil series. Field and laboratory evaluations were undertaken to: (1) examine the relationship of Cullen and associated soil series and provide a method for their separation, (2) determine if geomorphic or weathering differences exist in Cullen and associated soil series, and (3) determine the classification of the Cullen series in Soil Taxonomy. The majority of Cullen pedons sampled classified as Typic Hapludults, clayey, mixed, thermic, but bordered on the kaolinitic and oxidic mineralogy classes. Chemical and physical properties were consistent in the pedons sampled and did not relate well to parent rock type or B horizon color. Weathering for an extensive time period has brought soils derived from various parent materials to a similar mineralogical state. We recommend that the Cullen series concept be broadened to include red (10R or 2.5YR) soils that have a mixed mineralogy. This concept covers a range between the Davidson and Tatum series and includes what has been mapped as Georgeville in Virginia. / Master of Science

Soils overlying residuum on upland divides and interfluves that formed from transported material are common in the Virginia Piedmont. They are thought to occur on the oldest landscapes in the region. A study was initiated in Appomattox County and a small portion of Buckingham County encompassing an area of 238 square miles. The origin, age and characterization of these soils is studied. Mapping units comprised of red subsoil components and mapping units with non-red subsoil components are compared. Trend-surface analysis of the elevations at which they occur and chemical and physical data from twenty-four pedons in Appomattox County are used. The mapping units contain a complex mixture of taxonomic classifications that encompass pedons with and without palic clay distributions. Wetness due to perched water tables at variable depths also affects classifications. The red subsoil mapping units tend to occupy the older landscapes. Age estimates are derived from a comparison of trend-surface elevations between the transported soils and the present-day surface. These comparisons result in age estimates of 0.8 million years to 6.25 million years BP. Therefore, the oldest geomorphic surfaces in the south central Piedmont of Virginia may be estimated as late Pliocene to Miocene age landscapes. These soil materials were deposited through a process of landscape inversion dominated by subsidence and colluviation. / Master of Science