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<br /> <br />East of the river some smaller terraces are found; however, most of <br />this area is typified by undulating to rolling landforms formed by the <br />irregular erosion surface of the underlying formation of soft, marine <br />Mancos Shale. The Manco~ Formation, from 4,000 to 5,000 feet thick, <br />rests on the Dakota Sandstone and consists of dark, calcareous shales that <br />weather rapidly into gray to dark gray clay loam to silty clay soils. <br />Soils derived from this source are relatively high in gypsum and other <br />salts because the shale of the Mancos Formation is of marine origin. <br /> <br />Soils <br /> <br />Soils within the area are generally of two types. With a few minor <br />exceptions, the soils on the east side of the Uncompahgre Valley are <br />derived principally from the Mancos Shale formation and are heavy clays <br />referred to locally as "adobe" soils. The soils in large portions of <br />this area are shallow over the shale bedrock. Soils on the west side <br />of the valley are known locally as "mesa" soils and are generally deeper <br />and lighter in texture than the soils of the east side. The west side <br />soils are mostly of alluvial origin, although there are small areas of <br />shallow residual soils derived from sandstone. <br /> <br />Because of the semiarid climate' of the area, the soils have been <br />formed under a sparse vegetative cover with only moderate to low organic <br />matter content. These soils have not been leached to any great depths <br />and, therefore, retain constituents of the parent material. They are <br />moderately calcareous and have slight to moderate soil profile development. <br /> <br />climate <br /> <br />Most of the Uncompahgre Valley is semiarid, but precipitation and <br />temperature vary widely with elevation. The prevailing wind is from the <br />west, but a wide range of surface wind conditions exists as influenced <br />by specific topographic features. Average annual precipitaion ranges <br />from 8 inches at Delta and 13 inches in the Ridgway area to as much as <br />40 inches in mountainous areas outside the study area. The frost-free <br />period averages about 150 days annually. Temperatures occasionally <br />reach 100' F in summer and fall to below O. F in winter. <br /> <br />Wildlife and Vegetation <br /> <br />Wildlife habitat in the project area includes agricultural lands as <br />well as interspersed areas of native vegetation. Irrigation in the <br />valley has created many wetland areas and helps support pheasant, quail, <br />waterfowl, mule deer, and other species. The endangered bald eagle, <br />peregrine falcon, and the whooping crane have been observed in the valley <br />during migration or during the winter months. <br /> <br />Historically, wetlands in the project area occurred as bands of <br />cottonwood trees, willows, grasses, and other water-tolerant plants along <br />the Gunnison and Uncompahgre Rivers and their major tributaries. Away <br />from the influence of these waterways, the limited precipitation supports <br /> <br />6 <br /> <br />Ol"{f\ (' <br />