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Source-linked reports with geographic coverage including Colorado.

At least 1,639 records · Page 91Linked to original sources
USGS1977

Water-level records for Adams, Larimer, Logan, Morgan, Sedgwick, Washington, and Weld Counties, Colorado, 1973-77

Water levels measured during March 1977 in 350 wells tapping alluvial aquifers in Adams, Larimer, Logan, Morgan, Sedgwick, Washington, and Weld Counties, Colo., are included in this report. Water-level records for the 4 preceding years also are included to serve as references illustrating declining or rising water levels. Water-level measurements made in March 1977 do not reflect the precipitation deficiencies of the winter of 1976-77.

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USGS1977

Reconnaissance survey of the helium content of soil gas in Black Hawk, Eldorado Springs, Evergreen, Golden, Morrison, Ralston Buttes, and Squaw Pass quadrangles, Colorado

A reconnaissance survey of the helium content of soil gas was performed in parts of Black Hawk, Eldorado Springs, Evergreen, Golden, Morrison, Ralston Buttes, and Squaw Pass quadrangles, Colorado. The intent of this survey was to obtain initial background information on the gross effects of structure, underlying rock type, and soil moisture content on the helium content of the soil gas. Sample localities were adjacent to roads and trails. The results, tentatively categorized as qualitative, suggest that structure and soil moisture content have pronounced observable effects, whereas effects of rock type could not be recognized in this study.

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USGS1977

Water-resources investigations of the U.S. Geological Survey in Colorado, fiscal year 1977

Water-resources investigations of the U.S. Geological Survey in Colorado consist of collecting water-resources data and conducting interpretive hydro-logic investigations. The water-resources data and the results of the investigations are published or released by either the U.S. Geological Survey or by cooperating agencies. This report describes the water-resources investigations in Colorado for the 1977 fiscal year (October 1, 1976, to September 30, 1977). The U.S. Geological Survey's investigations of the water-resources of Colorado are under the direction of James E. Biesecker, District Chief. The Colorado District office is located in Building 53, Denver Federal Center, Lakewood, Colo. (fig. 1). The Colorado District has four subdistrict offices located in Grand Junction, Lakewood, Meeker, and Pueblo (fig. 1).

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USGS1977

Preliminary data on some Precambrian deposits of zinc-copper-lead sulfides and zinc spinel (granite) in Colorado

Precambrian sulfide deposits in the Southern Rocky Mountains in Colorado are being studied and re-evaluated according to geologic concepts which were developed in recent years in other parts of the world during successful research regarding economic massive sulfide deposits. These studies, initiated in 1974 in Colorado by the U.S. Geological Survey, have indicated that a new look at areas containing long dormant mines and prospects may well lead to the discovery of minable Precambrian sulfide deposits. The zinc, copper, and lead contents of ores investigated to date, supplemented by silver and gold contents, indicate that many long-forgotten deposits are minable in terms of grade. The deposits occur in Precambrian rocks metamorphosed to the lower amphibolite facies in one major region and to the upper amphibolite facies in other regions. Field studies have provided ample evidence indicating that the search for commercial tonnages can he facilitated by using newer concepts of economic geology regarding ore-host rock associations as prospecting guides and by using structural considerations aimed toward learning how metamorphism and folding have modified the shapes and distribution of the ore bodies. A newly recognized concept, originating from the current studies by the U.S. Geological Survey in Colorado, concerns the potential economic significance of gahnite, a zinc spinel. The field and laboratory data indicate that gahnite can be used by geologists as a prospector's guide to ore and can be considerd by mining engineers as a potential major ore mineral, contributing significant amounts of zinc to the sulfide ores in many of the deposits. Studies to date indicate that the Gunnison area, the Salida area, and the Guffey area are particularly favorable to the search for minable deposits, and the potential is equally present in many other areas.

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USGS1977

Chemical analysis, physical property tests, and lithologic description of cores and cuttings of lignite and overburden rocks from an area near Watkins, Colorado

The data presented in this report represents analytical and testing information from cores drilled by the Geophysics Department, Colorado School of Mines, assisted by the U.S. Geological Survey. The drilling was done in conjunction with the establishment of a geophysical testing facility by the Colorado School of Mines. Location of the study area and drill holes is shown in Figure 1. A total of 15 holes were drilled and geophysically logged; holes 9-1 and 7-11 were cored, and attempts to core hole 3-1 were made, but the lignite was very incompetent due to weathering and oxidation and recovery was very poor. Lithologic descriptions of the cores and cuttings for holes 9-1, 7-11, and 3-1 are listed on pages 13-21. Calculationdbased on hole 9-1 indicate that of the total lignite zone, 56 percent consists of partings and 44 percent is lignite. These percentages were obtained by statistical analysis of the core description and natural gamma logs of the hole. The total thickness of the lignite zone in hole 9-1 is approximately 18 m.

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USGS1977

Quantity and quality of drainage from the Argo Tunnel and other sources related to metal mining in Gilpin, Clear Creek and Park Counties, Colorado

Eighteen metal-mine drainage sources have been located in that part of Gilpin, Clear Creek, and Park Counties, Colo., lying within the Missouri River basin. At least 13 of these sources are known to contain high acidity and (or) trace-element concentrations or to contribute water to adversely affected streams. From January 1976 to March 1977, drainage from the Argo Tunnel in Idaho Springs--one of the major metal-mine drainage sources in the study area--exhibited variations in discharge from 0.35 to 0.55 cubic feet per second (0.010 to 0.016 cubic meters per second), a relatively constant temperature of 16 degrees Celsius, and variations in specific conductance from 2,680 to 3,410 micromhos per centimeter at 25 degrees Celsius (though a value of about 3,100 micromhos persisted throughout most of the period of record). High, but relatively constant, total concentrations (in micrograms per liter) of arsenic (100 to 180), cadmium (140 to 170), copper (5,000 to 6,000), iron (160,000 to 200,000), lead (less than 100 to 200), manganese (80,000 to 110,000), and zinc (40,000 to 49,000) were measured in the Argo Tunnel drainage from March 1976 to March 1977. Except for lead, the trace elements were mostly dissolved (82 percent or greater) and appear to represent baseline concentrations. Long-term degradation of water flowing from the Argo Tunnel is shown by increases of at least 2.5 to 8.0 times for dissolved solids, dissolved iron, calcium, magnesium, and sulfate since 1906. The acidity has changed from neutral in 1906 to a median pH value of 2.9 in 1976-77. Comparison of current Argo Tunnel data with those collected previously by other investigators indicates that spring chemical flushes containing higher than baseline trace-element concentrations occurred in 1973 and 1974, but not in 1975 or 1976, and probably not in 1972. The spring chemical flushes appear to be associated with increased infiltration from snowmelt in the catchment of the Argo Tunnel. Because of the wide ranges in mine-drainage quality and quantity expected for discharges from abandoned mines in the study area, each situation must be examined individually, and the management alternative chosen for mine-drainage abatement must be tailored to solve the particular mining and hydrologic problems at a given site.

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USGS1977

Density and porosity estimates from borehole gravity data in the Castle Pines #3, #2, and #1 water wells, Douglas County, Colorado

Borehole gravity surveys were carried out in the Castle Pines #3, #2, and #1 water wells using the U.S. Geological Survey-LaCoste and Romberg borehole gravity meter (McCulloh and others, 1967a; McCulloh and others, 1967b). The objectives were to estimate the density and porosity of the formations penetrated, and to determine the precision and repeatability of borehole gravity data in shallow wells. A detailed account of field techniques and analysis of data quality has been given by Byerley (1977). This report tabulates the borehole gravity data collected, and presents densities and porosities computed from the subsurface gravity data.

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USGS1977

Ground-water quality near a sewage-sludge recycling site and a landfill near Denver, Colorado

The Metropolitan Denver Sewage Disposal District and the City and County of Denver operate a sewage-sludge recycling site and a landfill in an area about 15 miles (24 kilometers) east of Denver. The assessment of the effects of these facilities on the ground-water system included determining the direction of ground-water movement in the area, evaluating the impact of the wastedisposal activities on the chemical quality of local ground water, and evaluating the need for continued water-quality monitoring. Surficial geology of the area consists of two principal units: (1) Alluvium with a maximum thickness of about 25 feet (7.6 meters) deposited along stream channels, and (2) bedrock consisting of undifferentiated Denver and Dawson Formations. Ground water in formations less than 350 feet (110 meters) deep moves to the north, as does surface flow, while ground water in formations between 570 and 1,500 feet (170 and 460 meters) deep moves to the west. Estimates of ground-water velocity were made using assumed values for hydraulic conductivity and porosity, and the observed hydraulic gradient from the study area. Lateral velocities are estimated to be 380 feet (120 meters) per year in alluvium and 27 feet (8.2 meters) per year in the upper part of the bedrock formations. Vertical velocity is estimated to be 0.58 foot (0.18 meter) per year in the upper part of the bedrock formations. Potentiometric head decreases with depth in the bedrock formations indicating a potential for downward movement of ground water. However, waterquality analysis and the rate and direction of ground-water movement suggest that ground-water movement in the area is primarily in the lateral rather than the vertical direction. Five wells perforated in alluvium were found to have markedly degraded water quality. One well was located in the landfill and water that was analyzed was obtained from near the base of the buried refuse, two others were located downgradient and near sewage-sludge burial areas, and the remaining two are located near stagnant surface ponds. Concentrations of nitrate in wells downgradient from fields where sludge is plowed into the soil were higher than background concentrations due to the effects of the sludge disposal. No evidence of water-quality degradation was detected in deeper wells perforated in the bedrock formations. Continued water-quality monitoring is needed because of the continuing disposal of wastes. A suggested monitoring program would consist of monitoring wells near the landfill twice a year and monitoring wells near the sludge-disposal areas on an annual basis.

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USGS1977

Reconnaissance of ground-water resources in a part of the Yampa River basin between Craig and Steamboat Springs, Moffat and Routt counties, Colorado

This report presents the results of an investigation of ground-water resources in that part of the Yampa River basin between the towns of Craig and Steamboat Springs. The location of the study area is shown on the index map. The investigation was begun in 1975 by the U.S. Geological Survey in cooperation with the Colorado Department of Natural Resources, Division of Water Resources, Office of the State Engineer.

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USGS1977

Water-level changes in the northern high plains of Colorado, 1964 to 1976 and 1972 to 1976

The northern High Plains of Colorado is an area of about 9,500 mi 2 (24,600 km 2 ) in the eastern part of the State (index map). The boundaries of the High Plains of Colorado are the State line and the limit of the Ogallala Formation of late Tertiary age. The Ogallala Formation is an unconsolidated or partly consolidated deposit of sand, gravel, clay, and silt and is the major aquifer in the northern High Plains.

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USGS1977

Modeling chloride movement in the alluvial aquifer at the Rocky Mountain Arsenal, Colorado

A solute-transport model that can be used to predict the movement of dissolved chemicals in flowing ground water was applied to a problem of ground-water contamination at the Rocky Mountain Arsenal, near Denver, Colo. The model couples a finite-difference solution to the ground-water flow equation with the method-of-characteristics solution to the solute-transport equation. From 1943 to 1956 liquid industrial wastes containing high chloride concentrations were disposed into unlined ponds at the Arsenal. Wastes seeped out of the unlined disposal ponds and spread for many square miles in the underlying shallow alluvial aquifer. Since 1956 disposal has been into an asphalt-lined reservoir, which contributed to a decline in ground-water contamination by 1972. The simulation model quantitatively integrated the effects of the major factors that controlled changes in chloride concentrations and accurately reproduced the 30-year history of chloride ground-water contamination. Analysis of the simulation results indicates that the geologic framework of the area markedly restricted the transport and dispersion of dissolved chemicals in the alluvium. Dilution, from irrigation recharge and seepage from unlined canals, was an important factor in reducing the level of chloride concentrations downgradient from the Arsenal. Similarly, recharge of uncontaminated water from the unlined ponds since 1956 has helped to dilute and flush the contaminated ground water.

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USGS1977

Relation of surflcial erosion on hillslopes to profile geometry

Differences in erosion rates in relation to the geometry of hillslope profiles were hypothesized by R. E. Horton in 1945. Experimental testing of this hypothesis is described for natural hillslopes in western Colorado using a rainfall simulator to apply five "storms" each having an intensity of 1.85 inches per hour (47 millimeters per hour). Erosion from straight hillslope segments was about twice the amount from convex and concave segments along nine hillslope transects. Standard deviations of erosion measurements for each segment show that the greatest variation occurs in concave slope segments. This is probably because the concave segment is the only place on the profile where deposition occurs. Analysis of variance indicates that the amount of erosion is significant at the 1-percent level of confidence between convex and straight slope segments and at the 5-percent level of confidence between straight and convex slope segments.

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USGS1977

Electrical soundings near Yellow Creek, Rio Blanco County, Colorado

Ten vertical electrical soundings were made in the Piceance Creek Basin in October 1974-5 along Yellow Creek, 2 in Big Duck Creek, and 1 each along Corral Gulch, on the hill in sec. 20, 1 kilometre northwest of 84 Ranch, and along the White River between the mouths of Yellow and Piceance Creeks. Interpretations of these soundings indicate that the anisotropy of the upper oil shales decreases from 2 in the basin center to 1 at a location on its flank. This decrease could result from a greater number of vertical water-filled fractures in the upper shales near the edge of the basin. On the other hand, the anisotropy coefficient for the lower shales increases from 2 to around 9 along the same section, indicating the presence of an increasing number of isolated horizontal aquifers in the lower shales on the basin flank. It is speculated that this trend for the lower shales reverses nearer the basin edge in the area of recharge of these splintered horizontal aquifers.

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USGS1977

Age and tectonic setting of lower Paleozoic alkalic and mafic rocks, carbonatites, and thorium veins in South-central Colorado

Alkalic igneous rocks were emplaced into heterogeneous terrane of Precambrian X and Precambrian Y rocks about 570 m.y. ago (Cambrian or upper Precambrian) in the Powderhorn area in Gunnison County and about 520 m.y. ago (Cambrian) in the McClure Mountain, Gem Park, and Democrat Creek areas in the northern Wet Mountains, Fremont and Custer Counties. The radiometric ages are based upon studies by K-Ar, Rb-Sr, and fission-track methods. Associated with these alkalic rock complexes are numerous thorium-bearing veins and red syenite dikes; some, if not all, in the northern Wet Mountains were formed about 495 m.y. ago. Diabase, gabbro, and other mafic dikes appear to be slightly younger than the thorium veins in the Powderhorn area and both older and younger in the Wet Mountains region. In the Powderhorn district, an older group of syenites also intruded Precambrian rocks as plugs or small stocks about 1350-1400 m.y. ago. The various dike rocks and the thorium veins were formed in extensive, deep fractures, indicating a condition of tension or shear in this part of the crust during Cambrian or very late Precambrian to Ordovician time. The localized alkalic magmatisin may reflect melting spots in the mantle. In the two principal areas, 135 km apart, the episodes of alkalic magmatism differ in age by about 50 m.y., the younger toward the east. The age relations might be explained by migration of the sites of localized melting or volatile enrichment in the mantle or westward movement of the continent above a single site.

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USGS1977

Gravitational spreading of steep-sided ridges ("sackung") in Colorado

Large-scale gravitational spreading and fracturing of steep-sided ridges in the mountainous area of Colorado are characterized by horizontal linear fissures, trenches, and uphill-facing scarps on tops and sides of ridges. A pronounced north-trending cleft and several minor scarps have split a ridge extending northward from Dolores Peak in the San Miguel Mountains of southwestern Colorado. This ridge is capped by granogabbro of a Tertiary laccolith that intruded the Cretaceous Mancos Shale. Numerous active landslides in shale mantle the once glaciated lower slopes. Trenches in the granogabbro probably originated after glacial ice melted, leaving steep sides of the ridge unsupported. The soft Mancos shale moved outward toward the direction of least stress, placing the overlying granogabbro under tension. A ridge that extends southwest from Bald Eagle Mountain, north of Mount Massive in central Colorado, is marked by a graben on the top and several trenches on the northwest side, parallel to the long axis of the ridge. Rock exposed in graben and trenches is the Precambrian St. Kevin Granite, which includes some schist and migmatite. Gravitational movement probably took place after steepening of the valley sides by glacial erosion and melting of the glaciers. Movement followed preexisting discontinuities in the rock. A survey course approximately 2.4 km (1.5 mi) long has been placed across .the fractured ridge. It will be monitored periodically to determine whether movement is continuing, and if so, at what rate.

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