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Research about Colorado

Source-linked reports with geographic coverage including Colorado.

At least 1,621 records · Page 90Linked to original sources
USGS1978

Hydrologic analysis of the U.S. Bureau of Mines' underground oil-shale research-facility site, Piceance Creek Basin, Rio Blanco County, Colorado

The U.S. Bureau of Mines plans to develop an underground oil-shale research facility near the center of Piceance Creek basin in Colorado. The oil-shale zone, which is to be penetrated by a shaft, is overlain by 1,400 feet of sedimentary rocks, primarily sandstone and marlstone, consisting of two aquifers separated by a confining layer. Three test holes were drilled by the U.S. Bureau of Mines to obtain samples of the oil shale, and to test the hydraulic properties of the two aquifers. The data collected during construction of the test holes were used to update an existing ground-water-flow computer model. The model was used to estimate the maximum amount of water that would have to be pumped to dewater the shaft during its construction. It is estimated that it would be necessary to pump as much as 3,080 gallons per minute to keep the shaft dry. Disposal of waste water and rock are the principal hydrologic problems associated with constructing the shaft. (Woodard-

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USGS1978

Transit losses and traveltimes of reservoir releases along the Arkansas River from Pueblo Reservoir to John Martin Reservoir, southeastern Colorado

The need for accurate information regarding the transit losses and traveltimes associated with releases from Pueblo Reservoir has been stimulated by construction of the U.S. Bureau of Reclamation's Fryingpan-Arkansas Project and a proposed winter-water storage program in Pueblo Reservoir. To meet this need, the U.S. Geological Survey, in cooperation with the Southeastern Colorado Water Conservancy District, studied the Arkansas River from Pueblo Reservoir to John Martin Reservoir, a distance of 142 river miles. The volumes of reservoir releases are decreased or delayed during tran-sit by bank storage, channel storage, and evaporation. Results from a com-puter model, calibrated by a controlled-test release from Pueblo Reservoir, indicate transit losses are greatest for small releases of short duration that are made during periods of low antecedent streamflow. For equivalent releases, transit losses during the winter are about 7 percent less than losses during the summer. Based on available streamflow records, the traveltime of reservoir releases in the study reach ranges from about 1.67 hours per mile at the downstream end of the study reach when antecedent streamflow is 10 cubic feet per second, to about 0.146 hour per mile at the upstream end of the study reach when antecedent streamflow is 3,000 cubic feet per second. Consequently, the traveltime of a release increases as antecedent streamflow diminishes. Management practices that may be used to benefit water users in the study area include selection of the optimum time, rate, and duration of a reservoir release to minimize the transit losses, determination of an accurate traveltime, and diversion at several incremental rates.

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USGS1978

Granite of Rosalie Peak, a phase of the 1700-million-year-old Mount Evans Pluton, Front Range, Colorado

The Rosalie Granite was a name applied by S. H. Ball in 1906 to a granite which forms a ridge between Mount Evans and Mount Rosalie (renamed Rosalie Peak). The type locality originally designated for the Rosalie Granite was in a pluton (later called the Rosalie lobe) 10 kilometers southeast of Rosalie Peak on Deer and Elk Creeks. The name "Rosalie Granite" was abandoned by T. S. Levering in 1929 because the granite of the Rosalie lobe is actually the distinctly younger Pikes Peak Granite, only 1,030 m.y. (million years) old, whereas the "Rosalie Granite" between Mount Evans and Rosalie Peak is a felsic phase of the l,700-m.y.-old Mount Evans pluton. In addition, the Rosalie Granite has more MgO and Sr and less Na 2 O, F, and Rb than the Pikes Peak Granite, and the two granites differ petrographically. In order to avoid confusion in correlation, the name Rosalie should not be applied to rocks in this area. Therefore, we propose that the Rosalie lobe be renamed Lone Rock pluton and that the "Rosalie Granite" be informally referred to as the granite of Rosalie Peak until it can be attached to a formal geologic rock unit.

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USGS1978

Petrology of the Precambrian intrusive center at Lake George, southern Front Range, Colorado

The intrusive center at Lake George, at the western margin of the Pikes Peak batholith (1030 m.y.) of central Colorado, contains rocks of both the potassic and sodic differentiation trends recognized in the batholith. Finer grained variants of the Pikes Peak Granite initially formed a texturally zoned stock 8 kilometers in diameter that cut the dominant coarse-grained granite of the batholith. This granite stock (potassic trend) was later intruded by partial ring dikes of quartz syenite to fayalite granite and by a central stock of quartz syenite to syenomonzonite (sodic trend). Xenoliths of alkali gabbro, diorite porphyry, and granodiorite are included within rocks of both differentiation trends. All major rock types of the intrusive center are thought to be derivatives of alkali basaltic magma from the mantle, modified by fractional crystallization and reaction melting of crustal rocks. The geometry of the intrusive center was controlled by ring-dike/cauldron-subsidence mechanisms.

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USGS1977

Further paleomagnetic results for the San Juan volcanic field of southern Colorado

Combining paleomagnetic data for 17 new sites from the northwest portion of the (Oligocene) San Juan volcanic field of southern Colorado with data for 29 sites previously published yields a paleomagnetic pole at 85°N, 114°E (with a 95% confidence circle of 7.5° radius). A further combination of the San Juan data with the results of other studies on rocks of Oligocene age from tectonically stable parts of North America gives a mid-Tertiary reference pole located at 81°N, 132.5°E, with a confidence circle of approximately 4°. Mid-Tertiary paleomagnetic poles for the western edge of the continent diverge markedly from this reference pole.

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USGS1977

Solution of three-dimensional groundwater flow equations using the strongly implicit procedure

A three-dimensional numerical model has been coded to use the strongly implicit procedure for solving the finite-difference approximations to the ground-water flow equation. The model allows for: (1) the representation of each aquifer and each confining bed by several layers; and (2) the use of an anisotropic hydraulic conductivity at each finite-difference block. The model is compared with a previously developed quasi-three-dimensional model by simulating the steady-state flow in an aquifer system in the Piceance Creek Basin, Colorado. The aquifer system consists of two aquifers separated by a leaky confining bed. The upper aquifer receives recharge from precipitation and is hydraulically connected to streams. For this problem, in order to make a valid comparison of results, a single layer was used to represent each aquifer. Furthermore, the need for a layer to represent the confining bed was eliminated by incorporating the effects of vertical leakage into the vertical component of the anisotropic hydraulic conductivity of the adjacent aquifers. Thus, the problem was represented by only two layers in each model with a total of about 2,100 equations. This restricted the effects of flow in the confining layer to the vertical component, but simulations with a third layer in the three-dimensional model permitting horizontal flow in the confining bed show that the two-layer approach is reasonable. Convergence to a solution of this problem takes about one minute of computer time on the IBM/155. This is about 30 times faster than the time required using the quasi-three-dimensional model.

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USGS1977

Reconnaissance drilling in the Yampa coal field, Hayden-Williams Fork Mountains area (Yampa No. 3), Moffat and Routt counties, Colorado, during 1976

Under Contract No. 14-08-0001-15727, awarded by the U.S. Geological Survey, Jim Feighny, of Loveland, Colo., drilled 42 test holes in the Williams Fork Mountains near Hayden, Colo., in September 1976. The area is referred to in the Contract as Yampa No. 3, which includes the Bureau of Land Management's (ELM) tracts WF-10, WF-12, WF-16, and WF-17. The purpose of the drilling was to obtain information on the quality and extent of the coal in the area. All holes were logged using either Gamma-Gamma (density), Natural Gamma, Caliper, Resistivity, or spontaneous-potential (SP) geophysical logs. The logging was done by the U.S. Geological Survey, the Birdwell Division of Seismograph Service Corp., Century Geophysical, and Geodynamics, Inc. The water level is indicated in table 1 for each drill hole at the time the hole was logged. All holes were drilled on private surface, and surface ownership is shown in table 1.

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USGS1977

Water-level records for the San Luis Valley of Colorado, 1973-77

Water-level measurements were made in 122 wells in January 1977. Changes in water levels from January 1976 to January 1977 ranged from a rise of 10.0 feet (3.0 meters) to a decline of 8.6 feet (2.6 meters) both of which occurred in Costilla County. Measurements for the three preceding winters are included to illustrate longer term water-levels changes .

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USGS1977

Laboratory measurements of complex resistivity characteristics of oil shales from Saterdal No.1 corehole, Piceance Creek Basin, Colorado

Laboratory measurements of the complex electrical resistivity characteristics of more than 120 oil shale samples from Saterdal #1 corehole, Piceance Creek Basin, Colorado, indicate the following: (1) The presence of kerogen in wet Green River Formation marls increases their d.c. resistivities from about 300 ohm-m to more than 10 5 ohm-m, makes them isotropic, and causes a substantial frequency dependence. (2) Microanisotropy coefficient increases with water content from about 2 to as much as 200. The effect seems to be due to an extreme porosity and/or permeability anisotropy, involving a drop in longitudinal resistivity from about 10 8 ohm-m for dry samples to as low as 10 5 ohm-m for wet ones, while transverse resistivities stay relatively constant at about 10 8 ohm-m. (3) Intermediate grade oil shales show the most extreme anisotropy effect; both very rich and very lean oil shales are more nearly isotropic. (4) Both wet and dry oil shales show a pronounced frequency effect for frequencies >10Hz, and may make good IP targets.

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