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Research about Colorado, New Mexico

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

At least 55 records · Page 3Linked to original sources
USGS2007

Pliocene and Quaternary deposits in the northern part of the San Juan Basin in southwestern Colorado and northwestern New Mexico

Unconsolidated late Cenozoic deposits in the northern part of the San Juan Basin range in age from late Pliocene to Holocene. Most of the deposits are alluvial gravel composed of resistant quartzite, sandstone, and igneous, metamorphic, and volcanic rocks derived from the uplifted central core of the San Juan Mountains 20-50 miles (32-80 kilometers) north of the basin. Alluvial deposits are most voluminous in the Animas Valley, but deposits of gravel of the same general age are present in the La Plata, Florida, Los Pinos, and Piedra River valleys as well. Alluvial gravel forms tabular deposits, generally about 20 feet (6 meters) thick, that are exposed beneath a sequence of terraces at many levels above the rivers. Gravel layers 360 feet (110 meters) or less above the Animas River are glacial outwash. The gravel layers begin at the south toes of end moraines and extend discontinuously downvalley at least 10-20 miles (16-32 kilometers). Farther south, distinction between outwash and nonglacial alluvium is problematical. Alluvial gravel beneath higher terraces does not grade to end moraines. Glacial till forms a series of end moraines at the north edge of the town of Durango. The oldest moraines are farthest downvalley, are higher above the river, and have more mature surficial soils than do moraines farther north. The two youngest moraines, the Animas City moraines, are interpreted to be Pinedale in age. They have narrow, ridgelike crests and form nearly unbroken arcs across the valley floor. Small segments of still more weathered moraines, the Spring Creek moraines, are 170-230 feet (52-70 meters) above the river and are 660-990 feet (200-300 meters) farther downvalley. The oldest moraines, the Durango moraines, are on the north end of the unnamed mesa on which Fort Lewis College is located. The base is about 180 feet (55 meters) above the river. These oldest moraines may be of Bull Lake age. Alluvial fans, pediment gravel, and landslides are scattered at several levels in various valleys within the northern San Juan Basin. Except where the Lava Creek B volcanic ash (0.639 mega-annum) is interbedded in them, these crudely bedded accumulations of sandy or clayey material washed from side drainages and added little to our reconnaissance stratigraphic study. Scattered landslide deposits consist of unsorted, mixed soil and fragments of rock. Loess and local silty and clayey sheetwash alluvium 6-12 feet (2-4 meters) thick form a veneer on low terraces. On higher terraces, such as Red Mesa east of the La Plata River and Florida Mesa east of the Animas River, loess and sheetwash alluvium generally are about 20 feet (6 meters) thick but can be as thick as 40-50 feet (12-15 meters) in places on Florida Mesa. When using the Lava Creek B volcanic ash as a time datum, apparently the timing of late Cenozoic continental deposition in the region was broadly similar to that in the Denver Basin-Front Range region and some other glaciated mountain ranges in the Rocky Mountains. A more accurate dating of Quaternary alluviation must await a thorough dating of the deposits. Thick, extensive outwash gravel indicates enhanced deposition during glacial epochs.

Colorado, New Mexico↗
USGS2006

Establishment of non-native plant species after wildfires: Effects of fuel treatments, abiotic and biotic factors, and post-fire grass seeding treatments

Establishment and spread of non-native species following wildfires can pose threats to long-term native plant recovery. Factors such as disturbance severity, resource availability, and propagule pressure may influence where non-native species establish in burned areas. In addition, pre- and post-fire management activities may influence the likelihood of non-native species establishment. In the present study we examine the establishment of non-native species after wildfires in relation to native species richness, fire severity, dominant native plant cover, resource availability, and pre- and post-fire management actions (fuel treatments and post-fire rehabilitation treatments). We used an information-theoretic approach to compare alternative hypotheses. We analysed post-fire effects at multiple scales at three wildfires in Colorado and New Mexico. For large and small spatial scales at all fires, fire severity was the most consistent predictor of non-native species cover. Non-native species cover was also correlated with high native species richness, low native dominant species cover, and high seeded grass cover. There was a positive, but non-significant, association of non-native species with fuel-treated areas at one wildfire. While there may be some potential for fuels treatments to promote non-native species establishment, wildfire and post-fire seeding treatments seem to have a larger impact on non-native species. ?? IAWF 2006.

Colorado, New Mexico↗
USGS2005

Mark-resight superpopulation estimation of a wintering elk Cervus elaphus canadensis herd

We executed four mark-resight helicopter surveys during the winter months January–February for each of the three years 1999–2001 at 7–10 day intervals to estimate population size of a wintering elk Cervus elaphus canadensis herd in northern New Mexico. We counted numbers of radio-collared and uncollared elk on a simple random sample of quadrats from the study area. Because we were unable to survey the entire study area, we adopted a superpopulation approach to estimating population size, in which the total number of collared animals within and proximate to the entire study area was determined from an independent fixed-wing aircraft. The total number of collared animals available on the quadrats surveyed was also determined and facilitated detectability estimation. We executed superpopulation estimation via the joint hypergeometric estimator using the ratio of marked elk counted to the known number extant as an estimate of effective detectability. Superpopulation size estimates were approximately four times larger than previously suspected in the vicinity of the study area. Despite consistent survey methodology, actual detection rates varied within winter periods, indicating that multiple resight flights are important for improved estimator performance. Variable detectability also suggests that reliance on mere counts of observed individuals in our area may not accurately reflect abundance.

Colorado, New Mexico↗
USGS2003

Reconnaissance-level application of physical habitat simulation in the evaluation of physical habitat limits in the Animas Basin, Colorado

The Animas River is in southwestern Colorado and flows mostly to the south to join the San Juan River at Farmington, New Mexico (Figure 1). The Upper Animas River watershed is in San Juan County, Colorado and is located in the San Juan Mountains. The lower river is in the Colorado Plateau country. The winters are cold with considerable snowfall and little snowmelt in the mountains in the upper part of the basin. The lower basin has less snow but the winters are still cold. The streamflows during the winter are low and reasonably stable. The native trout in the Animas Basin is the cutthroat trout. Few native trout remain and the trout found in the upper watershed are brook trout with rainbow and brown trout in the lower river. There is considerable metal contamination in the upper basin near Silverton but a brook trout fishery does exist in the Animas River from just above Howardsville to where the Animas joins Cement Creek in Silverton. There are two principle objectives of the habitat studies in the Animas Basin: (1) to improve understanding of the fate of sediment from mining operations from the view point of physical habitat impacts, and (2) to determine if reconnaissance level physical habitat studies can be useful in understanding the impacts of mining on the aquatic ecosystem. Part of the project was to apply the Physical Habitat Simulation System (PHABSIM) to selected locations in the Upper Animas River Basin, Colorado in order to demonstrate the importance of physical habitat in evaluating the efficacy of mined land remediation activities. Physical habitat analysis included the use of sedimentation variables in physical habitat simulations. A map of the Upper Animas Basin is presented in Figure 2. The project involves collecting data for the following locations: Animas River above Magee Creek; Animas River above Howardsville; Animas River below Howardsville; Animas River above Silverton at Hillsdale Cemetery; Animas River at Silverton; Cement Creek above Silverton; Cement Creek at Silverton; Mineral Creek at Powerline above Silverton; Mineral Creek at Campground; South Mineral Creek at Overflow Campground; Mineral Creek above Bear Creek; Mineral Creek at Silverton; Animas River below Silverton; and Animas River at Elk Park. Bed material samples were collected at each site. These included samples of the armour, the substrate, and sand and fines deposited on the surface. At selected sites the stream morphology was measured. These measurements included one to three cross sections, stream discharge, and water surface elevations. The data are located in the files of the Fort Collins Science Center.

Colorado, New Mexico↗
USGS2002

Cripple Creek and other alkaline-related gold deposits in the Southern Rocky Mountains, USA: Influence of regional tectonics

Alkaline-related epithermal vein, breccia, disseminated, skarn, and porphyry gold deposits form a belt in the southern Rocky Mountains along the eastern edge of the North American Cordillera. Alkaline igneous rocks and associated hydrothermal deposits formed at two times. The first was during the Laramide orogeny (about 70–40 Ma), with deposits restricted spatially to the Colorado mineral belt (CMB). Other alkaline igneous rocks and associated gold deposits formed later, during the transition from a compressional to an extensional regime (about 35–27 Ma). These younger rocks and associated deposits are more widespread, following the Rocky Mountain front southward, from Cripple Creek in Colorado through New Mexico. All of these deposits are on the eastern margin of the Cordillera, with voluminous calc-alkaline rocks to the west. The largest deposits in the belt include Cripple Creek and those in the CMB. The most important factor in the formation of all of the gold deposits was the near-surface emplacement of relatively oxidized volatile-rich alkaline magmas. Strontium and lead isotope compositions suggest that the source of the magmas was subduction-modified subcontinental lithosphere. However, Cripple Creek alkaline rocks and older Laramide alkaline rocks in the CMB that were emplaced through hydrously altered LREE-enriched rocks of the Colorado (Yavapai) province have 208 Pb/ 204 Pb ratios that suggest these magmas assimilated and mixed with significant amounts of lower crust. The anomalously hot, thick, and light crust beneath Colorado may have been a catalyst for large-scale transfer of volatiles and crustal melting. Increased dissolved H 2 O (and CO 2 , F, Cl) of these magmas may have resulted in more productive gold deposits due to more efficient magmatic-hydrothermal systems. High volatile contents may also have promoted Te and V enrichment, explaining the presence of fluorite, roscoelite (vanadium-rich mica) and tellurides in the CMB deposits and Cripple Creek as opposed to deposits to the south. Deep-seated structures of regional extent that formed during the Proterozoic allowed the magmas to rise to shallow crustal levels. Proterozoic sites of intrusions at 1.65, 1.4, and 1.1 Ga were also important precursors to alkaline-related gold deposits. Many of the larger gold deposits are located at sites of Proterozoic intrusions, and are localized at the intersection of northeast-trending ductile shear zones formed during Mesoproterozoic deformation, and an important north-trending fault formed during 1.1 Ga rifting.

Colorado, New Mexico↗
USGS2002

Dinosaurs that did not die: Evidence for Paleocene dinosaurs in the Ojo Alamo Sandstone, San Juan Basin, New Mexico

Palynologic and paleomagnetic data confirm a Paleocene age for the Ojo Alamo Sandstone (and its contained dinosaurs) throughout the San Juan Basin of New Mexico. The recently reported discovery of 34 skeletal elements from a single hadrosaur in the Ojo Alamo provides unequivocal evidence that these bones were not reworked from underlying Cretaceous strata. Geochemical studies of samples from several single-dinosaur-bone specimens from the Paleocene Ojo Alamo Sandstone and the underlying Late Cretaceous (Campanian) Kirtland Formation show that mineralized bones from these two rock units contain distinctly different abundances of uranium and rare-earth elements and demonstrate that Cretaceous and Paleocene bones were mineralized at different times when mineralizing fluids had distinctly different chemical compositions. These findings indicate that the dinosaur bone from the Paleocene Ojo Alamo is indigenous and not reworked. These data show that a relatively diverse assemblage of dinosaurs survived the end-Cretaceous asteroid-impact extinction event of 65.5 Ma. The San Juan Basin’s Paleocene dinosaur fauna is herein named the Alamoan fauna. Magnetic-polarity chronology shows that these survivors lived for about one million years into the Paleocene and then became extinct around 64.5 Ma. We suggest that a plausible survival mechanism for this Lazarus fauna may have been the large numbers of buried dinosaur eggs, laid just before the asteroid impact occurred. These buried eggs would have provided a safe haven for developing dinosaur embryos for the first one to two years after the impact, thereby making it possible for them to survive the worst of the impact’s early devastation.

Colorado, New Mexico↗
USGS2001

Potential for a basin-centered gas accumulation in the Raton Basin, Colorado and New Mexico

The Raton Basin appears to contain a significant continuous or basin-centered gas accumulation in sandstones of the Upper Cretaceous Trinidad Sandstone and Vermejo Formation and Upper Cretaceous and Paleocene Raton Formation. The accumulation is underpressured and occurs at comparatively shallow (<3,500 ft) depths. The sandstones are interbedded with coal beds that are currently being developed for coal-bed methane, and the coals are the likely source for gas found in the sandstones. Based on analogs with other Rocky Mountain basins, relatively water-free production should occur where levels of thermal maturity in the coals exceed a vitrinite reflectance value of 1.1 percent. This level of thermal maturity occurs over much of the central part of the Raton Basin. Because of the shallow depths, some of the accumulation has probably been degraded by surface water invasion.

Colorado, New Mexico↗
USGS2000

Snowpack chemistry at selected sites in Colorado and New Mexico during winter 1999-2000

Snowpacks at two high-elevation (> 3,000 m) sampling sites near McPhee and Sanchez Reservoirs in southern Colorado were selected to collect representative samples of atmospheric deposition to the surrounding watersheds during winter 1999-2000. In February 2000, annual snowpacks at two sites were sampled to determine concentrations of nitrate and sulfate; concentrations of the trace elements arsenic, mercury, and selenium; and the sulfur isotope ratios that result from atmospheric deposition to the area. Snowpack chemistry data at the two sites sampled in 1999-2000 are compared to 1993-99 averages at 10 other snow-sampling sites in Colorado and New Mexico that generally are downwind of the Four Corners area of the southwestern United States. Although concentrations of ammonium and nitrate in the 1999-2000 snowpacks were fairly typical compared to averages established at nearby sites in southern Colorado and northern New Mexico, chloride and sulfate concentrations were below the 1993-99 average, while arsenic, mercury, and selenium in snow were much below the 1993-99 average. However, very similar sulfur-isotope ratios (that are not a function of precipitation amounts) deposited in snowpacks at the nearby sites indicate the snowpack chemistries at the new sampling locations near McPhee and Sanchez reservoirs were affected by similar sources of sulfate. Representative samples of coal burned during the 1999-2000 snowfall season at three power plants near Four Corners also were analyzed for sulfur content and trace elements. Results from separate, independent laboratories show similar concentrations and provide an initial baseline that will be used for general comparisons of coal chemistry to snowpack chemistry.

Colorado, New Mexico↗
USGS1994

Sources and migration pathways of natural gas in near-surface ground water beneath the Animas River valley, Colorado and New Mexico

In July 1990, the U.S. Geological Survey began a study of the occurrence of natural gas in near-surface ground water in the Animas River valley in the San Juan Basin between Durango, Colorado, and Aztec, New Mexico. The general purpose of the study was to identify the sources and migration pathways of natural gas in nearsurface ground water in the study area. The purpose of this report is to present interpretive conclusions for the study, primarily based on data collected by the U.S. Geological Survey from August 1990 to May 1991. Seventy of the 205 (34 percent) groundwater samples collected during August-November 1990 had methane concentrations that exceeded the reporting limit of 0.005 milligram per liter. The maximum concentration was 39 milligrams per liter, and the mean concentration was 1.3 milligrams per liter. Samples from wells completed in bedrock have greater mean concentrations of methane than samples from wells completed in alluvium. Correlations indicate weak or nonexistent associations between dissolved-methane concentrations and concentrations of dissolved solids, major ions, bromide, silica, iron, manganese, and carbon dioxide. Dissolved methane was associated with hydrogen sulfide. Soil-gas-methane concentrations were measurable at few of 192 ground-water sites, even at sites at which ground water contained large concentrations of dissolved methane, which indicates that soil-gas surveys are not useful to delineate areas of gas-affected ground water. The reporting limit of 0.005 milligram per liter of gas was equaled or exceeded by 40 percent of soil-gas measurements adjacent to 352 gas-well casings. Concentrations of at least 100 milligrams per liter of gas were measured at 25 (7 percent) of the sites. Potential sources of gases in water, soil, gas-well surface casings, and cathodic-protection wells were determined on the basis of their isotopic and molecular compositions and available information about gas-well construction or leaks. Biogenic and thermogenic sources of gas exist in the near-surface environment of the study area. Biogenic gas is present locally in the near-surface Animas and Nacimiento formations, and biogenic gas has been detected in water wells completed in those rocks. Most gas probably is thermogenic gas from deep reservoirs, including the Dakota Sandstone, Mesaverde Group, Lewis Shale, Pictured Cliffs Sandstone, and coals in the Fruitland Formation. Less important sources include sandstones in the upper Fruitland Formation and the Kirtland Shale. Although migration of gas by diffusion or through natural fractures is possible, manmade conduits probably account for most of the upward migration of gas to the near-surface environment of the study area. Primary migration pathways largely consist of 1) leaking, conventional gas wells and 2) uncemented annuli of conventional gas wells along coals in the Fruitland Formation. Secondary migration pathways are gas-well annuli, cathodic-protection wells, seismic-test holes, and bedrock water wells.

Colorado, New Mexico↗
USGS1993

Geochemical evaluation of upper cretaceous fruitland formation coals, San Juan Basin, New Mexico and Colorado

Geochemical analyses of coal samples from the Upper Cretaceous Fruitland Formation in the San Juan Basin of New Mexico and Colorado were used to determine thermal maturity, type of kerogen, and hydrocarbon generation potential. Mean random vitrinite reflectance (% R m ) of the Fruitland coal ranges from 0.42 to 1.54%. Rock-Eval pyrolysis data and saturated to aromatic hydrocarbon ratio indicate that the onset of thermal hydrocarbon generation begins at about 0.60% R m and peak generation occurs at about 0.85% R m . Several samples have hydrogen index values between 200 and 400, indicating some potential for liquid hydrocarbon generation and a mixed Type III and II kerogen. Pentacyclic and tricyclic terpanes, steranes, aromatic steroids and methylphenanthrene maturity parameters were observed through the complete range of thermal maturity in the Fruitland coals. Aromatic pentacyclic terpanes, similar to those found in brown coals of Australia, were observed in low maturity samples, but not found above 0.80% R m . N -alkane depleted coal samples, which occur at a thermal maturity of approx. 0.90% R m , paralleling peak hydrocarbon generation, are fairly widespread throughout the basin. Depletion of n -alkanes in these samples may be due to gas solution stripping and migration fromthe coal seams coincident with the development of pressure induced fracturing due to hydrocarbon generation; however, biodegradation may also effect these samples.

Colorado, New Mexico↗
USGS1992

Thermal maturity patterns of Cretaceous and Tertiary rocks, San Juan Basin, Colorado and New Mexico

Horizontal and vertical thermal maturity patterns and time-temperature modeling of Cretaceous and Tertiary rocks in the San Juan Basin of southwestern Colorado and northwestern New Mexico indicate that the high levels of thermal maturity in the northern part of the basin are due to either (1) convective heat transfer associated with a deeply buried heat source located directly below the northern part of the basin or (2) the circulation of relatively hot fluids into the basin from a heat source north of the basin located near the San Juan Mountains. Vitrinite-reflectance (R m ) well profiles through Cretaceous and Tertiary rocks in the basin are commonly nonlinear, with two to four segments having different gradients. The different gradients most likely represent the combined effects of contrasting thermal conductivities associated with lithologic variations and differences in heat transfer processes (conductive versus convective). Time-temperature and kinetic modeling of nonlinear R m profiles indicates that present-day heat flow is insufficient to account for the measured levels of thermal maturity. Furthermore, in order to match the nonlinear R m profiles, it is necessary to assign artificially high thermal-conductivity values to some of the stratigraphic units. These unrealistically high thermal conductivities are interpreted as evidence of convective heat transfer.

Colorado, New Mexico↗
USGS1991

Oil-generating coals of the San Juan Basin, New Mexico and Colorado, U.S.A.

Coal beds of the Upper Cretaceous Fruitland Formation in the San Juan Basin of northwestern New Mexico and southwestern Colorado have significant liquid hydrocarbon generation potential as indicated by typical Rock-Eval Hydrogen Indexes in the range of 200–400 mg hydrocarbon/g organic carbon (type II and III organic matter). Small, non-commercial quantities of oil have been produced from the coal beds at several locations. The oils are characterized by high pristane/phytane ( ca 4) and pristane/ n -C 17 ratios ( ca 1.2), abundant C 21+ alkanes in the C 10+ fraction with a slight predominance of odd carbon-numbered n -alkanes, abundant branched-chain alkanes in the C 15+ region, and a predominance of methylcyclohexane in the C 4 -C 10 fraction. The oils are indigenous to the Fruitland Formation coals and probably migrated at thermal maturities corresponding to vitrinite reflectance values in the range 0.7–0.8%. Although the oils found to date are not present in commercial amounts, these findings illustrate the potential of some coals to generate and expel oil under conditions of moderate thermal heating.

Colorado, New Mexico↗