Spectral reflectance curves of selected soil characterization samples and standard clay minerals were studied over the wavelength interval 0.5 to 2.6µm. Results reported include reflectance data from three Hagerstown profiles and the Ap horizons of a Berks, Penn, and Ellery profile. Hagerstown soils are developed from limestone while the Berks, Penn, and Ellery are developed from shale, sandstone, and glacial deposits, respectively. Spectral curves for standard clay mineral samples of nontronite, kaolinite, and illite are also included.Spectral reflectance data indicate that clay type and the amount of organic matter, free iron oxides and silt influence the intensity of energy reflected by soils in the 0.5 to 2.6µm range. High contents of organic matter and free iron oxides reduced reflectance intensity in the 0.5‐to‐1.2µm range while clay type influenced curve shape and intensity over the entire range studied. For the Hagerstown profiles silt is highly correlated with percent reflectance in the 0.8‐to‐2.5µm range.
Computer analyses of multispectral imagery collected from aircraft shows promise for reducing preparation time and increasing the accuracy of soil survey maps. The study area in southeastern Pennsylvania included soils formed from limestone, shale, sandstone, alluvium, and local colluvium. Four study sites ranging in size from 8.5 to 30 ha were selected from a 72 km flightline. Surface reflectance properties of nonvegetated fields were classified using pattern recognition techniques. Computer printout maps showing areal distribution of soil spectral classes were compared with field conditions. Limestone, shale, sandstone, and local colluvial soils were separated with a high degree of accuracy. Erosion classes separated by spectral maps were comparable in location and extent to field observations. The feasibility of preparing computer display maps for potential use as soil mapping aids was demonstrated.
A study was made to determine the origin of the calcareous material found in certain floodplain soils of the limestone valleys of Virginia. The CaCO 3 in these soils was derived from the highly fractured and faulted limestone underlying the area. Groundwater, high in dissolved CO 2 , percolated through the crushed limestone, dissolving an appreciable amount of Ca and Mg carbonate. This water issued at the surface in the form of large springs and lost some of the dissolved CO 2 which resulted in a saturated solution with respect to calcium. The CaCOa depositing alga Oocardium stratum Nag was found below the point of saturation in the streams and was thought to be of major importance in the deposition of CaCO 3 . In a 200-foot section of stream channel beginning 450 feet below a spring having a rate of flow of 104 gallons/min, approximately 2.85 tons of CaCOa were deposited annually as tufa. Algal-deposited tufa is torn from stream channels during heavy rains and redeposited downstream by flood waters. Calcareous material occurs several miles from the source area and is a constituent of the flood plain soils along the creeks and rivers of the area.
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