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Research about Colorado

Source-linked reports with geographic coverage including Colorado.

At least 1,495 records · Page 83Linked to original sources
USGS1981

Aeromagnetic and complete Bouguer gravity anomaly maps of the Hunter-Fryingpan Wilderness area, Pitkin County, Colorado

Behrendt and others (1968) pointed out the close correlation between a belt of extreme gravity lows (Behrendt and Bajwa, 1974) and a zone of precious and base mineral deposits (Tweto and Simms, 1963, fig. 1). Tweto and Case (1972) showed that this belt of gravity lows probably reflects a series of Laramide and post-Laramide intrusions of relatively low density which may have influenced the hydrothermal systems responsible for much of the mineralization in the Colorado Mineral Belt.

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USGS1981

Hydrology and chemical quality of ground water in Kiowa County, Colorado

Ground water is available in Kiowa County, Colo., in quantities suitable for municipal or irrigation uses from at least two aquifers, the Big Sandy-Rush Creek alluvial aquifer and the Ogallala aquifer. The Dakota Sandstone and the Cheyenne Sandstone Member of the Purgatoire Formation may provide marginally sufficient water for municipal or irrigation purposes. Whil e wells in parts of the Ogallala aquifer have shown significant water-level declines in recent years, the Dakota Sandstone and Cheyenne Sandstone Member of the Purgatoire Formation are virtually undeveloped in the county , primarily because of the depth to the top of these formations (500-1,00 feet). Where water is not available from the Big Sandy-Rush Creek and Ogallala aquifers in the county, supplies sufficient for domestic or stock use may be obtained from shallow wells in several minor aquifers. The quality of ground water in the county varies widely, but dissolved-solids concentrations are usually greater than 500 milligrams per liter, except in parts of the Ogallala aquifer. The water is generally very hard and sulfate concentrations are usually greater than 250 milligrams per liter, except in parts of the Ogallala aquifer. High concentrations of selenium (greater than 10 micrograms per liter) in three-fourths of the wells sampled and locally high concentrations of fluoride, nitrate, iron, and manganese limit the suitability of the ground water for municipal and domestic use. (USGS)

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USGS1981

Measured sections of the Browns Park Formation (Miocene) in Moffat County, Colorado, 1980

Eight partial sections of the Browns Park Formation of Miocene age were measured in Moffat County, northwestern Colorado, during the 1980 field season, as part of a study of the stratigraphy and depositional environments of the formation. These newly measured sections are intended to complement other surface sections of the Browns Park Formation measured (Hansen, 1965) to the west in Uintah County, Utah, and measured (Buffler, 1967) or diagrammed (Kucera, 1968) to the east in, respectively, Routt and Rio Blanco Counties, Colorado. Rock samples collected, indicated parenthetically by 80-SL prefixes, are shown in the section descriptions purely for reference purposes; petrographic and analytical results will be reported in later publications. Color names with numbers are based on comparison with the rock-color chart by Goddard and others (1948). Field investigations were supported by the National Uranium Resource Evaluation (NUKE) program of the Grand Junction Office, U. S. Department of Energy, under contract No. DE-A113-78GJ01686.

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USGS1981

Rainfall-runoff modeling and preliminary regional flood characteristics of small rural watersheds in the Arkansas River basin in Colorado

Both recorded and synthetic rainfall-runoff and annual peak-discharge data for 17 rural watersheds were analyzed to evaluate the magnitude, frequency, and volume of floods in the plains region of the Arkansas River basin in Colorado. Flood-frequency relations from analysis of recorded data were weighted or combined with flood-frequency relations from analysis of synthetic data to provide improved estimates of selected flood characteristics for 15 of these watersheds. The 10-, 25-, 50-, and 100-year peak discharges were regionalized using multiple-regression and station-year methods. Regression relations were developed to determine peak discharge from effective drainage area (standard error of estimate 30 to 50 percent) and flood volume from peak discharge (standard error of estimate 62 percent) for ungaged basins between 0.5 and 15 square miles in size. Using these two flood characteristics, a dimensionless hydrograph method provides synthetic hydrographs very similar in shape to recorded flood hydrographs. (USGS)

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USGS1981

Simulated interactions between the proposed Narrows Reservoir and the water-table aquifer along the South Platte River, Morgan County, Colorado

A computer model, including a ground-water-flow component and a mass balance reservoir-operations component, was developed to simulate the proposed Narrows Reservoir and the adjacent alluvial aquifer of the South Platte River, Morgan County, Colo. This model, using a weekly time step, simulated the transient interactions of these two systems for an initial-fill condition and general-operational condition. A sensitivity analysis was made to test the effects of possible errors in the description of aquifer characteristics on the model results. The initial-fill simulation indicated that to fill the reservoir when hydraulic connection between the surface-water system and the aquifer is simulated would take 2 additional years than if no connection was assumed. Simulated ground-water return flow to the river downstream of the proposed dam was about 85 percent of the estimated maximum values, computed under steady-state conditions in an earlier study. The general operation simulation indicated that during the period of lowest reservoir contents the aquifer provided about 80,000 acre-feet of recoverable storage to the reservoir 's capacity. Average return flow was only about 70 percent of the estimated maximum values computed in the earlier, steady-state analysis. Monthly ground-water outflow from the reservoir to the aquifer ranged from 55,200 to -10,400 acre-feet. Parameters tested for sensitivity, in order of decreasing sensitivity, were: Hydraulic conductivity, specific yield, hydraulic connection between reservoir and aquifer, local recharge, boundary conditions, and dam permeability. The probable error in the parameters tested would not seem to warrant significant new data collection. (USGS)

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USGS1981

Effects of a cattle feedlot on ground-water quality in the South Platte River Valley near Greeley, Colorado

Changes in water quality in an alluvial aquifer resulting from the operation of a feedlot stocked with 90,000 cattle have been minimal. Monitoring water quality in 19 observation wells from April 1974, prior to the operation of the feedlot, to June 1978, after about 4 years of operation, indicates that chloride concentrations have increased slightly in one well downgradient from a runoff-retention pond. Chemical analyses of water from two lysimeters installed in the unsaturated zone indicate that leachate from the feedlot has percolated to a depth of at least 5 feet but has not percolated to a depth of 20 feet. The small changes in ground-water quality caused by the feedlot are likely the result of the limited available recharge, a relatively impermeable manure pack, soil clogging under the cattle pens resulting in slow vertical movement of leachate through the unsaturated zone, soil clogging under the unlined runoff-retention ponds, and denitrification in the unsaturated zone.

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USGS1981

Whooping crane preyed upon by golden eagle

The Golden Eagle ( Aquila chrysaetos ) is the largest predatory bird in North America and is well known for its predatory abilities. Attacks have been reported on mammals such as whitetail jackrabbits ( Lepus townsendi ) (McGahan 1967, J. Wildl. Mgmt. 31: 496), pronghorn antelope ( Antilocapra americana ) (Bruhns 1970, Can. Field-Natur. 84: 301), Mallards ( Anas platyrhynchos ) (Kelleher and O'Malia 1971, Auk 88: 186), and Great Blue Herons ( Ardea herodias ) (Carnie 1954, Condor 56: 3). This communication describes an attack on an immature Whooping Crane ( Grus americana ) by a Golden Eagle and the subsequent necropsy findings.

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USGS1981

Sedimentology of Great Sand Dunes, Colorado

Eolian and adjacent deposits of Great Sand Dunes Colorado form a small but sedimentologically complex deposit Eolian sediments can be subdivided into three provinces trending downwind northeast I low as much as 10 m high alkali cemented dunes forming discontinuous rings around broad flat bottomed ephemeral lakes II undulating vegetated dunes as high as 10 m of barchan parabolic shrub coppice and transverse type with varying interdune types III high as much as 200 m transverse dunes with little or no vegetation and no true interdune deposits Eolian deposits are in contact with or intercalated with fluvial lacustrine and alluvial fan deposits and lap onto crystalline basement rocks of the Sangre de Cristo Range. Analysis of a 40 year-span of aerial photographs and field observation of sand transport and cross bedding dip directions indicate that the main dune mass province III is accreting vertically and that dune types are growing in complexity in particular the star dunes This change from lateral migration to vertical growth most probably reflects Holocene changes in wind regime. The Great Sand Dunes are an example of a localized cool climate intermontane eolian deposit characterized by extensive fluvial reworking With its rapid variation in thicknesses sedimentary structures and associated sedimentary deposits such a deposit would be difficult to interpret accurately in the ancient rock record However such a deposit could be of economic importance in petroleum and uranium exploration and in aquifer evaluation

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USGS1980

Pliocene intrusive rocks and mineralization near Rico, Colorado

Fission-track and potassium-argon studies of intrusive rocks in the vicinity of Rico, Colorado, have shown that there are at least two periods of igneous activity and that significant ore mineralization is associated with alaskites and latites that are 3 to 5 m.y. old. Discordant fission track ages of apatite and zircon in the older rocks reveal a major heat source that cooled in late Miocene or early Pliocene and is centered under the mineralized rocks near the townsite of Rico. This heating may indicate the presence of a buried stock that is related to the mineralization.

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USGS1980

Results and assessment of uranium series dating of vertebrate fossils from Quaternary alluvium in Colorado

An average uranium-series age of 102,000 ± 14,000 yr for bones from Louviers Alluvium, near Denver, Colorado, is compatible with the inferred geologic age of from 120,000 to 150,000 yr. A uranium-series date of about 190,000 yr for a bone from Slocum Alluvium, near Canon City, Colorado, is consistent with the inferred geologic age of from 150,000 to 260,000 yr. Age determinations for the Broadway Alluvium are inconsistent but its geologic age is considered to be 15,000 to 30,000 yr BP.

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