Description of the Walsenburg Quadrangle

DESCRIPTION OF THE WALSENBURG QUADRANGLE. GEOGRAPHY. The bottom land along the streams consists of bedded, but sometimes shaly on the weathered consists, as a rule, of yellowish-gray sandstone of a rich, dark-colored loam several feet in depth, surface. It apparently corresponds to part of the a coarse, porous texture, and some of the layers The Walsenburg quadrangle is bounded by below which there are deposits of clay Fountain formation, but to what por- are really fine conglomerate. Cross bedding is meridians 104° 30' and 105° and parallels 37° 30; and gravel to the " bed rock," which tion of it is uncertain. The lower half rather common. This lower portion is separated and 38°. It is 34.5 miles long north and south may be from 10 to 50 feet below the surface. consists of about the same thickness of very coarse from the upper by a bed of gray shale from 8 to and 27.3 miles wide east and west, and contains Nearly all the low-lying areas afford a loess-like conglomerate of a brownish-red color. The forma 10 feet in thickness, called the fire-clay bed, owing 944 square miles. Of the total area, nearly three- eolian deposit, several feet in depth, of light- tion outcrops in contact with the Archean around to the highly refractory nature of the material. fourths lies in Huerfano County and about one- colored sandy loam, admirably adapted for culti the southern end of the mountains, but the expo The upper sandstones, aggregating from 100 to fourth in Pueblo County; a small fraction in the vation when irrigated. sures occupy a very limited area. The upper part 150 feet in thickness, are light gray when fresh, southeast corner lies in Las Animas County. The agricultural products are such as meet of the Fountain formation is exposed for a short of fine grain, close texture, and regular bedding. The topography is greatly diversified. The the requirements of the mixed American and distance in the canyon of the Cuchara. No organic They resist erosion to such an extent that the central portion is mainly an open, rolling country, Mexican population and of the coal remains by which the age of these beds A e of the removal of the softer beds of the marine Creta Agriculture. traversed by the cultivated valleys of camps. At present tillage is mostly could be satisfactorily determined have beds* ceous exposes extensive horizontal floors of the Topography. the Huerfano and Cuchara and having confined to the bottom land. Oats, wheat, corn, been found within the limits of the quadrangle. sandstone, the surface barely masked by a thin an elevation of from 5500 to 6100 feet. The potatoes, beans, and garden vegetables are staple In the Sangre de Cristo Range, to the westward, layer of soil. The effect of stream erosion is the north-central and eastern portions are somewhat crops, and alfalfa is one of the largest and most the stratigraphic section corresponds very nearly formation of deep, narrow canyons bounded by higher and the profile of the surface is more profitable. Irrigation is usually resorted to with that at the southern extremity of the Green vertical, inaccessible walls that rise to the general often undulating than otherwise. In the north wherever water for the purpose is available. It horn Mountains except in respect to the thickness level of the surface. The canyons of the Huer eastern portion the country is traversed by the is practicable, however, to cultivate corn without of the conglomerate. Below the Cretaceous beds fano, Cuchara, and their tributaries in the north deep, narrow canyons of the Huerfano and irrigation when the season is favorable, though and the Morrison formation there is in each case eastern portion of the district are of this character. Cuchara, which are bounded by cliffs of varying the yield never equals that obtained by the judi about the same thickness of capping red sand Graneros shale. Resting on the Dakota is a height, up to 100 feet or more, that terminate cious use of water. On the high mesa at Rye a stone, but the coarse conglomerate and sandstone bed of soft shale from 200 to 210 feet thick, the abruptly in the general level of the surface. The fair yield of corn, oats, or rye can be obtained on which it rests attain in the Sangre de Cristo a basal formation of the Benton group and the low southwestern portion of the district includes the without irrigation even in an ordinary season. thickness of several thousand feet. In that local est of the marine Cretaceous beds of the country. northern extension of the Park Plateau, a rugged, Sheep raising is a very important industry, for ity the beds have afforded remains of an upper The top and bottom portions are dark gray; the deeply scored area which has a mean elevation which the grazing facilities of the low country Carboniferous fauna and flora. The evidence of middle portion is almost black. Large calcareous of about 6500 feet and terminates in a line of are better adapted than for cattle raising, though a similar character from the Fountain formation concretions, arranged parallel with the bedding, bluffs facing northeastward. In the west-central in the plateau and mountainous portions the con on the eastern slope of the Rocky Mountains is are somewhat numerous near the base. These portion, near the boundary, there are two small ditions are reversed. meager and contradictory, and it is still a ques shales outcrop very persistently in the northeast but extremely precipitous mountains about 3 tion whether it should be classed as Permian or ern portion of the quadrangle and along the eastern miles apart, the south one known as Black Moun GENERAL GEOLOGY. Triassic. As the Fountain and Sangre de Cristo base of the Greenhorn Mountains, but are not tain. The northwestern portion of the district formations have not sufficient geologic importance exposed over any considerable area. They are includes the eastern half of the southern exten In the geology of the Walsenburg quadrangle to warrant their separation on the Areal Geology usually very soft and easily eroded, and present sion of the Greenhorn Mountains, which, within all the grand divisions of geologic time are repre sheet, advantage is taken of this doubt to group steep slopes only where the outcrop is protected the limits of the quadrangle, rise to an elevation sented by rocks, though in some cases not to an them together under the name Badito formation by the resistant limestone of the beds overlying of nearly 12,000 feet, though the culminating important extent. Thus, there are no beds assign and to refer them to the upper Carboniferous. them. point, known as Greenhorn Peak, lies west of the able to the earlier periods of the Paleozoic or the Greenhorn formation. This consists of layers, boundary. A high mesa several miles wide, but earlier epochs of the Cretaceous period, and less JURATRIAS PERIOD. from 3 to 4 inches thick, of cross-fractured, dove- narrowing rapidly to the southward, extends east than 300 feet of strata have been assigned to the Morrison formation. This formation aggre colored limestone, separated from one another by ward from the base of the mountains. Juratrias period, while the Neocene is represented gates about 270 feet in thickness at the southern thin layers or partings of gray shale. The aggre The principal drainage channels are the Huer only by the remnants of a formation doubtfully extremity of the Greenhorn Mountains, %Thickness gate thickness is about 30 feet. While this for fano and Cuchara, which now in a generally assigned to its latest epoch. On the other hand, where there is a narrow outcrop extend- and extent- mation is of limited thickness, it is one of the northeasterly course to their junction the Archean, later Cretaceous, and Eocene forma ing along the foothills a distance of about 5 miles prominent horizons of the Cretaceous section and, Drainage. near the northeast corner of the quad tions are well represented, as are also certain and passing on beyond the west boundary of the owing to its relatively greater capacity for resist rangle. At times these streams are raging tor varieties of intrusive eruptive rocks. quadrangle. It is also exposed along the canyons ing erosion, affords a very persistent, though nar rents, but except during the flood season the UNCLASSIFIED CRYSTALLINE BOCKS. of the Cuchara and Huerfano for a distance of row and meandering, outcrop, generally bounded irrigating ditches take most of the water. The over 20 miles. About midway between the by a low escarpment. The area, however, is less ARCHEAN PERIOD. drainage from the Greenhorn Mountains is of extremities of the Greenhorn Mountains out than that of any sedimentary formation in the less importance, though it includes several small The principal mass of the Greenhorn Moun crop the inclination varies from 45° to nearly district except the Nussbaum. The most charac streams flowing eastward into the Huerfano, tains consists of coarse- and fine-grained granites vertical. The lower portion consists of about 60 teristic and commonly occurring fossil is Inocera- Greenhorn, and Saint Charles. In the southern and ogneisses, ' hornblende-,' mica-,' and Character_. of, feet of soft,' white sandstone havingo a Character_. of, muslabiatus a flat, concentrically ringed shell and southwestern portions of the district there chlorite-schist, and subordinate masses therocks- conglomerate layer at the base. This the rocks- from 3 to 4 inches long and from 2 to 3 inches are other small streams, rising in the Spanish of garnet- and epidote-schist and occasional vein- is followed by hard, shaly beds of pinkish and broad.

Load more