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Research about Gallup, New Mexico

Source-linked reports with geographic coverage including Gallup, New Mexico.

6 recordsLinked to original sources
USGS1977

Pleistocene apparent ages by U-Pb isotope and U-series methods for uranium ore in Dakota Sandstone near Gallup, New Mexico

Radiometric dates of a high-grade uranium ore from the Hogback No. 4 mine in Dakota Sandstone near Gallup, N. Mex., indicate a late Pleistocene age of mineralization. The 206 Pb/ 238 U and 207 Pb/ 235 U apparent ages of about 70 000 yr and 100000 yr, respectively, are discordant, but are in broad agreement with the discordant 230 Th/ 238 U and 231 Pa/ 235 U apparent ages of 130000 yr and 78000 yr, respectively. Although it is not clear how the analyzed sample relates to the main period of mineralization at this mine, these dates are consistent with previous age limits suggested for Dakota Sandstone uranium-ores.

New Mexico↗
USGS1961

Availability of ground water in the Gallup area, New Mexico

A thick succession of sedimentary rocks (about 6,000 feet) underlies the town of Gallup and crops out nearby. Although all the sedimentary rocks are capable of yielding some water, only a few units of sandstone and limestone yield water in sufficient quantity and of acceptable quality to be considered as sources of large supplies. The five stratigraphic units that are most productive of ground water form three aquifers, as follows: (a) the Glorieta sandstone and San Andres limestone, (b) the Westwater Canyon member of the Morrison formation and the Dakota sandstone, and (e) the Gallup sandstone. The Glorieta sandstone yields only small amounts of water to wells, except where it is intensely fractured. It probably contributes large amounts of water to the overlying, more permeable San Andres limestone by slow vertical leakage over large areas, as water is withdrawn from the San Andres. The San Andres limestone is discontinuous in the eastern part of the area, wedging out entirely a few miles east of Gallup. Its permeability varies widely because locally the permeability has been greatly increased by fractures and solution channels. On the north flank of the Zuni Mountains, near its outcrop, the San Andres yields as much as 1,100 gpm (gallons per minute) of water to wells. The specific capacity of wells that tap the aquifer formed by this Glorieta sandstone and San Andres limestone ranges from 0.1 to 29 gpm per foot of drawdown. In general, the water in the Glorieta sandstone and San Andres limestone is hard, because it contains much calcium. Both bicarbonate and sulfate anions are abundant. The chemical quality of the water deteriorates with increasing distance from the outcrop. The Westwater Canyon member of the Morrison formation and the Dakota sandstone form a single hydrologic unit extending from about 5 miles east of Gallup westward into Arizona. To the east they are separated by shale of the Brushy Basin member of the Morrison formation. The water-bearing properties of the Westwater Canyon member and the Dakota sandstone are ill defined, because few wells in the area tap either of them exclusively. The specific capacity of wells that tap the Westwater Canyon member, the Dakota sandstone, or both ranges from 0.02 to 2.3 gpm per foot of drawdown. Water in this aquifer generally contains less that 1,000 ppm (parts per million) of dissolved solids. The concentration of sodium and bicarbonate typically is high, and the concentration of sulfate is high locally. The Gallup sandstone is the principal aquifer in the immediate vicinity of, and to the north and south of, Gallup. It yields as much as 260 gpm of water to wells; the specific capacity of wells that tap the Gallup sandstone ranges from 0.08 to 4.7 gpm per foot of drawdown. In general, the water in the Gal]up sandstone is potable, although in places it yields water high in iron, sulfate, and dissolved solids; the concentration of dissolved solids generally is less than 1,000 ppm. Because the yields of all the formations tested at Gallup are small, the town needs a better source of water. The San Juan River discharges annually a larger volume of water than is available from any other source in northwestern New Mexico. Gallup has applied for 15,000 acre-feet of San Juan River water a year, an average of 13,400,000 gpd (gallons per day). This water would be expensive, because about 50 miles of pipeline would be required to transport the water, and it would have to be liked about 1,000 feet over a high ridge north of town. Despite the expense involved, at this time the San Juan River seems to offer the most secure long-term supply of water for the Gallup area.

New Mexico↗
USGS1951

Alluvial fills near Gallup, New Mexico

Valleys near Gallup, N. Mex., similar to many in the Southwest, were filled in Recent time with alluvium. This material is now being eroded by systems of gullies, and the walls of these gullies provide exposures by which the history of the deposition of the alluvium can be traced. Alluvial fills near Gallup have been eroded at least twice previously within Recent time. The middle fill of the three that are recognizable contains potsherds of Pueblo II age, indicating that deposition was occurring as late as A. D. 1200. The chronology of alluviation and degradation for valleys in the Gallup area appears to agree with that for other valleys in the Southwest which have been studied.

New Mexico↗