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Colorado Geological Survey
<br />6.7 RATON BASIN
<br />The Raton Basin is a structural basin located in
<br />Las Animas and Huerfano counties, and is within
<br />the jurisdiction of Water Division 2. The basin
<br />extends from the vicinity of Walsenburg on its
<br />northeast side southward into New Mexico
<br />(Figure 6.7 -1). In Colorado, the axis of the basin
<br />trends north - northwest. The Colorado portion of
<br />the basin is bounded on the west by the Culebra
<br />Range, on the east by the east edge of the Park
<br />Plateau, on the north by the extent of the Poison
<br />Canyon Formation, and on the south by the state
<br />line. The location and extent of the Raton Basin,
<br />as defined herein, is shown on Figure 6.7 -1.
<br />Based on the 2000 Census, the population density
<br />in Las Animas County is 3.2 persons per square
<br />mile, while Huerfano County contains 4.9 persons
<br />per square mile (U.S. Census Bureau, 2000). The
<br />major towns within the basin are Walsenburg
<br />(population 4,182) and La Veta (population 924).
<br />Other significant towns include Aguilar, Cuchara,
<br />Cokedale, Segundo, and Weston. Trinidad, the
<br />Las Animas county seat and a major population
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<br />center lies just outside the eastern edge of the
<br />basin.
<br />Average annual precipitation ranges from 15 to 16
<br />inches along the eastern edge of the basin to over
<br />40 inches in the Culebra Range along the western
<br />boundary. Average annual evaporation is much
<br />greater than precipitation, ranging from about 55
<br />inches per year at the western edge of the basin to
<br />over 70 inches along the eastern boundary (see
<br />Chapter 1). Annual runoff is low, ranging from
<br />about 5 inches along the western boundary to
<br />abut 0.5 inches along the eastern boundary (see
<br />Chapter 1). July and August are the wettest
<br />months, with localized, intense, and fast - moving
<br />storms. Winter storms generally leave only short -
<br />lived snow on the ground at the lower elevations.
<br />Snowpack in the mountains west of the basin,
<br />however, generally does not melt until June and
<br />provides runoff to the streams.
<br />Topography ranges from fairly flat along the
<br />Cucharas River west of Walsenburg to very steep
<br />and rugged in the vicinity of
<br />the igneous stocks of the
<br />Spanish Peaks and Mount
<br />Mestas. The lowest elevation
<br />is just over 6,000 feet along
<br />the Purgatoire River west of
<br />Trinidad, while the highest
<br />elevation of 13,626 feet occurs
<br />at West Spanish Peak. The
<br />Park Plateau, which covers
<br />most of the area south of the
<br />Spanish Peaks, is highly dis-
<br />sected with elevations over
<br />8,400 feet. The area described
<br />in this publication is part of
<br />r the much larger Raton Basin
<br />sub -area of the Great Plains
<br />physiographic province (see
<br />Chapter 1).
<br />The intrusive igneous stocks of the Spanish Peaks are surrounded by the
<br />Cuchara Formation in the northern Raton Basin.
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<br />SCALE 1:850,000
<br />100 meter Digital Elevation Model
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<br />courtesy U.S. Geological Survey
<br />50 Miles
<br />Figure 6.7 -I. Location and extent of the Raton Basin showing the distribution of permitted water wells.
<br />Land use is primarily forest with some agricultur-
<br />al use. The major industry in the basin is coal
<br />mining. Historically, extensive coal mining
<br />occurred west of Trinidad and some mining con-
<br />tinues today. Currently, coalbed methane produc-
<br />tion is very active in the basin.
<br />Surficial geologic formations range from the
<br />Cretaceous Dakota Sandstone to the Eocene age
<br />Cuchara Formation, which crops out in the vicinity
<br />and north of the Spanish Peaks. A generalized
<br />cross - section showing the geology in the southern
<br />part of the basin is presented as Figure 6.7 -2.
<br />The transitional marine to fluvial Dakota
<br />Sandstone is overlain by gray shales, with
<br />interbedded thin layers of limestone and sand-
<br />stone, consisting of the Graneros Shale,
<br />Greenhorn Limestone, Carlile Shale, Niobrara
<br />Formation, and Pierre Shale. The Trinidad
<br />Sandstone, a regressive marine beach sand 45 to
<br />over 300 feet thick, overlies the Pierre Shale. The
<br />Trinidad is, in turn, overlain by the Vermejo
<br />Formation, a gray carbonaceous and sandy shale
<br />with lenses of sandstone and coal. The Trinidad
<br />Sandstone and the Vermejo Formation of the
<br />Raton Basin are stratigraphic equivalents of the
<br />Fox Hills Sandstone and Laramie Formation of
<br />the Denver Basin. Unconformably overlying the
<br />Vermejo Formation is the Raton Formation, con-
<br />sisting of a basal sandstone and conglomerate
<br />
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