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• <br />• <br />I• <br />Geology and Soils The general landform in the Nucla area is a result of the Nucla Syncline, a <br />northwest trending geologic structure containing the coal reserves in the study area. This shallow, <br />broad syncline is a simple fold with gently dipping flanks. The Cretaceous-age Dakota sandstone <br />is the youngest formation found in the study area, excepting Quaternary deposits. The Dakota <br />formation consists primarily of resistant yellowish to gray fissile sandstone, and conglomeratic <br />sandstones interbedded with dark gray carbonaceous shales, impure coal, and a basal <br />conglomerate. It forms resistant but thin sandstone ledges that are scattered throughout the study <br />area. These ledges are often exposed at the surface or are encountered within a few feet of the <br />surface. Quaternary age deposits, which are also present in the study area, consist of wind <br />deposited material, stream lain alluvium, and local slopewash. See Section 2.04.6, Geology <br />Description for a more detailed discussion of the geology for the study and surrounding areas. <br />Soil - 1987 The dominant soils within the study area are the Barx, Progresso, Bond, Bowdish, <br />Lazear, Travessilla, and Pinon (sic) series. Also included are large areas of Haplaquolls (no series <br />names assigned). The Barx, Progresso, and Bond series are the predominant cropland soils and <br />were originally dominated bysagebrush-grassland native vegetation prior to cultivation. The Barx <br />series consists of deep well drained sandy loam soils on flat to gently sloping uplands formed in <br />alluvium derived from sandstone. The Bond and Progresso series consist of shallow to moderately <br />deep well drained sandy loam soils on uplands formed in alluvium derived from sandstone. Mixed <br />with the above soils are smaller inclusions of Lazear and Bowdish sandy clay foams. These upland <br />soils are shallow to moderately deep, well drained, and were formed in residuum derived from <br />sandstone and interbedded shales. The Travessilla and Pinon channery sandy loam soils occur <br />on uplands that cannot be cropped or irrigated because of rock outcrops, shallow soils, and <br />topography. These areas have a sagebrush-grass/forb vegetation cover, but the original native <br />vegetation was dominated bypinyon-juniper with associated understory shrubs and herbaceous <br />species. The Travessilla and Pinon channery sandy foams are shallow to very shallow well drained <br />soils formed from sandstone. In terms of agriculture, the latter two soils are the poorest in the <br />study area. Other soils found on the study area include the Haplaquolls (no series name <br />assigned). These are poorly drained shallow to deep soils and range from silty clay foams to sandy <br />foams. They have formed in alluvium from recently deposited sediments in minor intermittent <br />streams, sloughs, flood plains, and seepy areas below areas of ground water discharge. The <br />Haplaquoll soils would most probably not be represented in the area if not for the large amounts <br />(Revised August 2006) 2.04.10-10 <br />