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Research about Colorado

Source-linked reports with geographic coverage including Colorado.

At least 1,405 records · Page 78Linked to original sources
USGS1986

Sediment-data sources and estimated annual suspended-sediment loads of rivers and streams in Colorado

Sources of sediment data collected by several government agencies through water year 1984 are summarized for Colorado. The U.S. Geological Survey has collected suspended-sediment data at 243 sites; these data are stored in the U.S. Geological Survey 's water data storage and retrieval system. The U.S. Forest Service has collected suspended-sediment and bedload data at an additional 225 sites, and most of these data are stored in the U.S. Environmental Protection Agency 's water-quality-control information system. Additional unpublished sediment data are in the possession of the collecting entities. Annual suspended-sediment loads were computed for 133 U.S. Geological Survey sediment-data-collection sites using the daily mean water-discharge/sediment-transport-curve method. Sediment-transport curves were derived for each site by one of three techniques: (1) Least-squares linear regression of all pairs of suspended-sediment and corresponding water-discharge data, (2) least-squares linear regression of data sets subdivided on the basis of hydrograph season; and (3) graphical fit to a logarithm-logarithm plot of data. The curve-fitting technique used for each site depended on site-specific characteristics. Sediment-data sources and estimates of annual loads of suspended, bed, and total sediment from several other reports also are summarized. (USGS)

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USGS1986

Avian tuberculosis and salmonellosis in a whooping crane (Grus americana)

The whooping crane has been the subject of intensive scientific study and management because it is an endangered species and has high public interest. Programs have been developed to identify critical habitat, to increase production through captive breeding, and in recent years, to use sandhill cranes (Grus canadensis) as surrogate parents in establishing new populations of wild whooping cranes. Only a few reports describing diseases and parasites in wild whooping cranes appear in the literature because opportunities to secure specimens are limited for this rare, protected bird (for review, see Carpenter and Derrickson, In Proc. International Crane Workshop of 1983, Bharatur, India, in press). Avian tuberculosis and concurrent salmonellosis in a wild whooping crane are described in this case report.

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USGS1986

Changing landscapes and the cosmopolitism of the eastern Colorado avifauna

The avifauna of continental North America has changed dramatically since colonial times. Excessive hunting contributed, at least in part, to the extinction of birds such as the great auk ( Pinguinus impennis ) and passenger pigeon ( Ectopistes migratorius ), while more recently organochlorine insecticide residues have resulted in drastic reductions in numbers of brown pelicans ( Pelecanus occidentalis ) (Anderson et al. 1975) and other species. Generally, however, vertebrate populations change in direct response to changes in their habitats. For example, herring gulls ( Larus argentatus ) have increased in numners (Kadlec and Drury 1968) with urbanization of the New England coastline, in the same locations formerly occupied by the extinct heath hen ( Tympanuchus cupido cupido ). Also, passerine birds of forest interiors have declined in numbers with fragmentation of the eastern deciduous forest into small stands; this fragmentation has led to increases in numbers of edge species (Robbins 1979, Ambuel and Temple 1983). Even subtle community shifts can introduce new competitive processes that can augment population changes among species (Brittingham and Temple 1983). Such studies of broad-scale changes in vegetative communities and their influence on native wildlife species have fostered the recent topical emphasis on "conservation biology" (Soule and Wilcox 1980, Soule 1985) and "landscape ecology" (Burgess and Sharpe 1981, Harris 1984:25-43). As changes in landscapes are causing subtle (but potentially dramatic) changes in the distribution of native species, conservation biologists are finding that mere presence-absence data on populations, or even accurate information on reproductive success, is inadequate to evaluate management activities or environmental perturbations. The principles of "conservation genetics" are attracting interest in the management of natural preserves especially (Schonewald-Cox et al. 1983). Changing patterns in landscape complexion or genetic makeup of a population are difficult to detect locally. Contemporary issues in the conservation of native species demand regional and continental perspectives (Samson and Knopf 1982). Thus, management activities at specific sites are often viewed as short-sighted by planners and conservation critics. This paper illustrates how these contemporary theories can influence a local conservation perspective. That perspective is developed around historical processes that have led to cosmopolitism of the local avifauna on the Colorado Division of Wildlife's South Platte Wildlife Management Area (SPWMA) near Crook, Colorado.

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USGS1986

Morphology and age of fault scarps in the Rio Grande Rift, south-central Colorado

Fault scarps in the Rio Grande rift of Colorado provide most of the evidence of paleoseismicity in the state, and are thus a major focus of assessments of earthquake hazards. Critical components of such assessments are the ages of past faulting events; age control is scarce and generally coarse for the Rio Grande rift in Colorado. Ages estimated from fault-scarp morphology are thus valuable, partly because they are directly related to the fault eVents, and partly for want of alternative methods. The processes responsible for scarp degradation are poorly understood and the many variables that affect the rates and relative importance of those processes limits the precision and accuracy of age estimates derived from scarp morphology. Both analytical and empirical methods are available for relating scarp degradation processes to scarp morphology and age. Diffusion-equation models that have been derived for scarp degradation are useful for their predictive value and for the insight they provide about the degradation processes. However, because of the limitations mentioned above and because of the multiple-event nature of the scarps in the Rio Grande rift, the simpler empirical approach involving the relation between scarp angle and the logarithm of scarp height is used here. The scarp-morphology data from the Rio Grande rift suggest that the youngest movements on all of the scarps examined occurred less than 15,000 years ago, with the exception of two scarps that are formed on lithologically dissimilar deposits. This age estimate is consistent with the observation that all of the scarps occur at least in part on deposits of Pinedale age. The scarp-morphology data suggest that some of the scarps are closer to 5,000 years than to 15,000 years in age; several of these scarps occur on deposits of early Holocene age and are associated with early Holocene radiocarbon dates. One scarp occurs on deposits with radiocarbon dates of only a few thousand years, although the morphology of this scarp is unusual for its age. Three scarps have morphologies that suggest that they may represent fault events younger than 5,000 years old. Although no corroboration is available, these scarps may represent some of the youngest fault movements in Colorado.

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USGS1985

Estimates of average major ion concentrations in bulk precipitation at two high-altitude sites near the continental divide in southwestern Colorado

The composition of bulk precipitation from two high-altitude sites, established in 1971 near the Continental Divide in southwestern Colorado, has been monitored by season during the past decade. Calcium ions are the predominant cationic species; sulfate is the major anionic constituent. Bulk precipitation major ion concentrations exhibit log-normal distributions. Representative mean and standard deviation values for the major inorganic ionic species present in bulk precipitation have been calculated for three years of consecutive seasons. Standard deviations for all species, except nitrate, are similar. For two years of data grouped into quarters, deviations from mean values fall well within the plus or minus two standard deviation limit. There does not seem to be a systematic deviation from the mean concentration values, with respect to either ionic component or season.

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USGS1985

Hydraulic gradient control for groundwater contaminant removal

The Rocky Mountain Arsenal near Denver, Colorado, U.S.A., is used as a realistic setting for a hypothetical test of a procedure that plans the hydraulic stabilization and removal of a groundwater contaminant plume. A two-stage planning procedure successfully selects the best wells and their optimal pumping/recharge schedules to contain the plume while a well or system of wells within the plume removes the contaminated water. In stage I, a combined groundwater flow and solute transport model is used to simulate contaminant removal under an assumed velocity field. The result is the approximated plume boundary location as a function of time. In stage II, a linear program, which includes a groundwater flow model as part of the set of constraints, determines the optimal well selection and their optimal pumping/recharge schedules by minimizing total pumping and recharge. The simulation—management model eliminates wells far from the plume perimeter and activates wells near the perimeter as the plume decreases in size. This successfully stablizes the hydraulic gradient during aquifer cleanup.

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USGS1985

Adsorption and desorption of hexavalent chromium in an alluvial aquifer near Telluride, Colorado

A laboratory investigation of reactions between hexavalent chromium [Cr(VI)] and alluvium was conducted to evaluate reactions of Cr(VI) contaminating an alluvial aquifer near Telluride, CO and to determine the mechanisms responsible for these reactions. Uncontaminated alluvium and groundwater (spiked with CrO 4 2− ) from the study site were used in batch and column experiments. Results of these experiments show that Cr(VI) was adsorbed by the alluvium. Distribution coefficients from batch experiments ranged from 52 L/kg at an equilibrium CrO 4 2− concentration of 0.4 µ mol/L to 1.7 L/kg at an equilibrium concentration of 1400 µ mol/L. The zero point of charge for the alluvium was approximately 8.3, and the alluvium had a positive net charge at the groundwater pH of 6.8. Visual and chemical evidence indicated that Fe oxide and hydroxide coatings on the alluvial particles principally were responsible for the adsorption of Cr(VI). During column experiments, Cr(VI) initially was desorbed easily from the alluvium by Cr‐free groundwater; however, the rate of desorption decreased rapidly, and > 60 pore volumes of groundwater were required to decrease the effluent concentration of Cr(VI) to 3 µ mol/L [drinking water standard for Cr(VI) = 1 µ mol/L]. The quantity of Cr(VI) adsorbed varied with the type and concentration of other anions in solution.

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USGS1985

Map showing upper Cenozoic rocks and deposits and Quaternary faults, Rio Grande rift, south-central Colorado

This map shows the faults and faulted rocks and deposits in the tectonically active part of the Rio Grande rift in Colorado, with particular emphasis on faults and deposits of Quaternary age. The Rio Grande rift in Colorado has been the subject of considerable recent geologic investigation. General compilations of the late Cenozoic tectonic features of the state of Colorado have been made by others. More detailed work used in compiling the map is shown in figure 1.

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USGS1985

Maps showing anomaly patterns for silver, molybdenum, lead, and zinc in altered rocks and soils, Williams Fork and St. Louis Peak Roadless Areas, Clear Creek, Grand, and Summit counties, Colorado

The U.S. Geological Survey and the U.S Bureau of Mines conducted field studies from 1979 through 1982 to assess the mineral resource potential of the Williams Fork and St. Louis Peak Roadless Areas and the Vasquez Peak Wilderness Study Area. Included were geological, geochemical, and geophysical studies by the U.S. Geological Survey and investigation of known prospects and mines by the U.S. Bureau of Mines. The area of study is located in the Arapaho National Forest, nort of Interstate Highway 70, west of U.S. Highway 40, and east of the Blue River, on the west side of the Front Range (fig. 1).

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USGS1985

Map showing the distribution of selected mineral assemblages in nonmagnetic heavy-mineral concentrates from stream sediments from the Vasquez Peak Wilderness Study Area, and the Williams Fork and St. Louis Peak Roadless Areas, Clear Creek, Grand, and Summit counties, Colorado

The U.S. Geological Survey and the U.S. Bureau of Mines conducted field studies from 1979 through 1983 to assess the mineral resource potential of the Vasquez Peak Wilderness Study Area (acreage: 16,000), the Williams Fork Roadless Area (acreage: 74,820), and the St. Louis Peak Roadless Area (acreage: 12,800). Included were geological, geochemical, and geophysical studies by the U.S. Geological Survey and investigation of known prospects and mines by the U.S. Bureau of Mines.

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USGS1985

Reference section for the Minturn Formation (Middle Pennsylvanian), northern Sangre de Cristo Range, Custer County, Colorado

This reference section of the Middle Pennsylvanian Minturn Formation was measured in the northern Sangre de Cristo Range; the section provides a basis for comparison with the type Minturn and with possibly equivalent strata elsewhere in southern Colorado. The name "Minturn" was first applied to strata of Middle Pennsylvanian age near the town of Minturn in central Colorado (Tweto, 1949, p. 194-228; Tweto and Lovering, 1977, p. 33–53), about 180 km north of the section described, and has been extended to strata of approximately the same age that contain marine limestones in the northern Sangre de Cristo Range (Brill, 1952; Bolyard, 1959; Scott and Taylor, 1974). The Minturn reference section continues upward into the principal reference section of the overlying Pennsylvanian and Permian Sangre de Cristo Formation (Lindsey and Schaefer, 1984), and these two sections together provide a continuous record of upper Paleozoic strata in the northern Sangre de Cristo Range. The reference section was measured by tape and compass in the summer of 1980; observations were recorded on a microcassette tape recorder in the field and transcribed in the office. This method permitted rapid acquisition of data on thickness, mature of contacts, color, grain size, and sedimentary features. These data are shown on the graphic section for each distinct rock unit. Rock units having common attributes or genetic relationships have been grouped together for descriptive and interpretative purposes.

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USGS1985

Stratigraphic sections, depositional environments, and metal content of the upper part of the Middle Pennsylvanian Minturn Formation, Northern Sangre De Cristo Range, Custer and Saguache counties, Colorado

The calcareous upper part of the 2,000-meter-thick Middle Pennsylvanian Minturn Formation (Lindsey and others, 1985) in the northern Sangre de Cristo Range is a key stratigraphic interval for correlating rocks and mapping the structure of the range. The stratigraphy of this complex and heretofore poorly known interval is reported here in order to provide a basis for correlation among the structural blocks in the range. Inferred depositional environments of the upper part of the Minturn Formation are described briefly. The upper part of the Minturn contains numerous occurrences of stratiform uranium and copper that were examined and sampled in order to document the concentration and distribution of metals within the established stratigraphic framework. The occurrences studied are classified according to the inferred depositional setting of the host rock in order to assess the extent of paleogeographic and paleohydrologic control of mineralized horizons.

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