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<br /> <br />'. <br /> <br />SOILS <br /> <br />The soil survey of the Grand Junction Area lissued 1955} covers 121,600 <br /> <br />acres of land in the Grand Valley within the boundaries of the irrigation <br /> <br /> <br />canal system. The' soils as described in this survey are typical of <br /> <br />desert soils -- they are low in organic matter, high in weatherable <br /> <br />minerals and associated salts and are chemically similar to the geologic <br /> <br />materials from which they were derived. <br /> <br />Extens ive field and laboratory checking of sal inity during the progress <br /> <br />of the survey found that about one-third of the area was affected by <br /> <br />accumulations of salts, alkali, or both, and that sodium sulfate is by <br /> <br />far the most prevalent salt. <br /> <br />Strongly saline Cretaceous formations (primarily Mancos shale} dominate <br /> <br />the parent material of the area, with approximately 78 percent of the <br /> <br />area having soils directly related to the Mancos shale. The deep Fruita, <br /> <br />Genola, Green River, Hinmon, Mesa. Naples, and Thoroughfare soils which <br /> <br />are formed in mixed material of other than Mancos shale amount to about <br /> <br />22% of the area. <br /> <br />Of those soils directly related to the Mancos shale the shallow Chipeta <br /> <br />and Persayo soils and the moderately deep phases of the Fruita and Mesa <br /> <br />soils resting on Mancos shale amount to 31 percent of the total area. <br /> <br />The deep Bi 11 ings (29%), Mack (3%) and Ravola C15%} soils developed in <br /> <br />.alluviam from the Mancos shale comprlze about 47 percent of the total <br /> <br />area. <br /> <br />16 <br /> <br />