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Research about Montana

Source-linked reports with geographic coverage including Montana.

At least 433 records · Page 24Linked to original sources
USGS2003

Effects of channel modification on fish habitat in the upper Yellowstone River: Final report to the USACE, Omaha

A two-dimensional hydrodynamic simulation model was coupled with a geographic information system (GIS) to produce a variety of habitat classification maps for three study reaches in the upper Yellowstone River basin in Montana. Data from these maps were used to examine potential effects of channel modification on shallow, slow current velocity (SSCV) habitats that are important refugia and nursery areas for young salmonids. At low flows, channel modifications were found to contribute additional SSCV habitat, but this contribution was negligible at higher discharges. During runoff, when young salmonids are most vulnerable to downstream displacement, the largest areas of SSCV habitat occurred in side channels, point bars, and overbank areas. Because of the diversity of elevations in the existing Yellowstone River, SSCV habitat tends to be available over a wide range of discharges. Based on simulations in modified and unmodified sub-reaches, channel simplification results in decreased availability of SSCV habitat, particularly during runoff. The combined results of the fish population and fish habitat studies present strong evidence that during runoff, SSCV habitat is most abundant in side channel and overbank areas and that juvenile salmonids use these habitats as refugia. Channel modifications that result in reduced availability of side channel and overbank habitats, particularly during runoff, will probably cause local reductions in juvenile abundances during the runoff period. Effects of reduced juvenile abundances during runoff on adult numbers later in the year will depend on (1) the extent of channel modification, (2) patterns of fish displacement and movement, (3) longitudinal connectivity between reaches that contain refugia and those that do not, and (4) the relative importance of other limiting factors.

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USGS2002

Interannual variations in snowpack in the Crown of the Continent Ecosystem

Ecosystem changes such as glacier recession and alpine treeline advance have been documented over the previous 150 years in the Rocky Mountains of northern Montana and southern British Columbia and Alberta, a region known as the Crown of the Continent Ecosystem (CCE). Such changes are controlled, at least partially, by variations in snowpack. The CCE consists primarily of public lands, the majority of which is undeveloped or wilderness. Consequently, this region is well suited for an examination of long-term snowpack variation and associated ecosystem change. Data from nine SNOTEL sites provide an indication of the daily accumulation and ablation of snowpack over the period 1977-2001, as well as the relationship between precipitation, temperature and snowpack. 1 April data from 21 snow courses indicated the extent of regional snowpack variation and trends over the period 1950-2001, and 1 May data from three snow courses in Glacier National Park allow this record to be extended back to 1922. SNOTEL data suggest CCE snowpacks are larger and more persistent than in most regions of the western USA, and that water year precipitation is the primary control on 1 April snow water equivalent (SWE). Snow course data indicate that variations in both 1 April and 1 May mean SWE are closely tied to the Pacific decadal oscillation, an El Nino-southern oscillation-like interdecadal pattern of Pacific Ocean climate variability. Despite relatively stable snowpacks and summer temperatures since 1922, the glaciers in Glacier National Park have receded steadily during this period, implying a significant climatic shift between their Little Ice Age glacial maxima (ca 1860) and 1922. Published in 2002 by John Wiley and Sons, Ltd.

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USGS2002

Hydrologic processes and nutrient dynamics in a pristine mountain catchment

Nutrient dynamics in watersheds have been used as an ecosystem-level indicator of overall ecosystem function or response to disturbance (e.g. Borman.N et al. 1974, WEBSTER et al. 1992). The examination of nutrients has been evaluated to determine responses to logging practices or other changes in watershed land use. Nutrient dynamics have been related to changing physical and biological characteristics (Mulholl AND 1992, CHESTNUT & McDowell 2000). Herein, the concentrations and dynamics of nitrogen, phosphorus and particulate organic carbon were examined in a large pristine watershed because they are affected by changes in discharge directly from the catchment and after passage through a large oligotrophic lake.

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USGS2002

Fuzzy logic merger of spectral and ecological information for improved montane forest mapping.

Environmental data are often utilized to guide interpretation of spectral information based on context, however, these are also important in deriving vegetation maps themselves, especially where ecological information can be mapped spatially. A vegetation classification procedure is presented which combines a classification of spectral data from Landsat‐5 Thematic Mapper (TM) and environmental data based on topography and fire history. These data were combined utilizing fuzzy logic where assignment of each pixel to a single vegetation category was derived comparing the partial membership of each vegetation category within spectral and environmental classes. Partial membership was assigned from canopy cover for forest types measured from field sampling. Initial classification of spectral and ecological data produced map accuracies of less than 50% due to overlap between spectrally similar vegetation and limited spatial precision for predicting local vegetation types solely from the ecological information. Combination of environmental data through fuzzy logic increased overall mapping accuracy (70%) in coniferous forest communities of northwestern Montana, USA.

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USGS2002

Spawning characteristics of redband trout in a headwater stream in Montana

I investigated the spawning characteristics of redband trout Oncorhynchus mykiss gairdneri (a rainbow trout subspecies) during the spring of 1998 in Basin Creek, a third-order headwater stream located in the Kootenai River drainage in northwestern Montana. I examined the timing of spawning as related to discharge and water temperature and analyzed microhabitat selection of 30 completed redds in a low-gradient (0.5–1.5%) reach. Redband trout spawned as flow declined after peak runoff and as mean daily water temperature exceeded 6.0C and maximum daily temperature exceeded 7.0C. Redband trout began spawning on 6 June (mean daily discharge = 2.1 m3/s), 10 d after the peak discharge (8.7 m3/s) occurred. The last redd was completed on 24 June, when discharge was 1.5 m3/s. The mean total redd length was 53 cm (SD = 14; range = 31–91 cm), and the mean total area was 51 cm2 (SD = 8; range= 46– 76 cm2). Eighty percent of the redds were located in pool tailouts, 13% in runs, and 7% in riffles. Spawning redband trout selected redd sites based on substrate size and water depth but not water velocity. Fish selected substrate sizes of 2–6 mm, water depths of 20–30 cm, and water velocities of 40–70 cm/s. My results suggest that redband trout in a low-gradient, third-order mountain stream found suitable spawning habitat in pool tail-outs that contained abundant gravels.

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USGS2002

Grassland birds orient nests relative to nearby vegetation

We studied orientation of nest sites relative to nearby vegetation for dabbling ducks (Cinnamon Teal, Anas cyanoptera ; Blue-winged Teal, A. discors ; Gadwall, A. strepera ; Mallard, A. platyrhynchos ; and Northern Shoveler, A. clypeata ) and Short-eared Owls ( Asio flammeus ) in ungrazed grassland habitat during 1995–1997 in westcentral Montana. We estimated an index of vegetation height and density in intercardinal directions (NE, SE, SW, NW) immediately around nests. All species oriented nests with the least vegetation to the southeast and the most vegetation to either the southwest or northwest. Furthermore, maximum vegetation around nests shifted from the southwest to the northwest with increasing nest initiation date, apparently as a response of individuals tracking seasonal change in the afternoon solar path. Thus, nests were relatively exposed to solar insolation during cool morning hours but were shaded from intense insolation in the afternoon throughout the breeding season. We suggest that nest microhabitat was selected in part to moderate the thermal environment.

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USGS2002

SHRIMP U-Pb and 40Ar/39Ar age constraints for relating plutonism and mineralization in the Boulder batholith region, Montana

The composite Boulder batholith, Montana, hosts a variety of mineral deposit types, including important silver-rich polymetallic quartz vein districts in the northern part of the batholith and the giant Butte porphyry copper-molybdenum pre-Main Stage system and crosscutting copper-rich Main Stage vein system in the southern part of the batholith. Previous dating studies have identified ambiguous relationships among igneous and mineralizing events. Mineralizing hydrothermal fluids for these types of deposits and magma for quartz porphyry dikes at Butte have all been considered to be late-stage differentiates of the Boulder batholith. However, previous dating studies indicated that the Boulder batholith plutons cooled from about 78 to 72 Ma, whereas copper-rich Main Stage veins at Butte were dated at about 61 Ma. Recent efforts to date the porphyry copper-molybdenum pre-Main Stage deposits at Butte resulted in conflicting estimates of both 64 and 76 Ma for the mineralizing events. Silver-rich polymetallic quartz vein deposits elsewhere in the batholith have not been dated previously. To resolve this controversy, we used the U.S. Geological Survey, Stanford, SHRIMP RG ion microprobe to date single-age domains within zircons from plutonic rock samples and 40 Ar/ 39 Ar geochronology to date white mica, biotite, and K-feldspar from mineral deposits. U-Pb zircon ages are Rader Creek Granodiorite, 80.4 ± 1.2 Ma; Unionville Granodiorite, 78.2 ± 0.8 Ma; Pulpit Rock granite, 76.5 ± 0.8 Ma; Butte Granite, 74.5 ± 0.9 Ma; altered Steward-type quartz porphyry dike (I-15 roadcut), 66.5 ± 1.0 Ma; altered Steward-type quartz porphyry dike (Continental pit), 65.7 ± 0.9 Ma; and quartz monzodiorite of Boulder Baldy (Big Belt Mountains), 66.2 ± 0.9 Ma. Zircons from Rader Creek Granodiorite and quartz porphyry dike samples contain Archean inheritance. The 40 Ar/ 39 Ar ages are muscovite, silver-rich polymetallic quartz vein (Basin district), 74.4 ± 0.3 Ma; muscovite, silver-rich polymetallic quartz vein (Boulder district), 74.4 ± 1.2 Ma; muscovite, early dark micaceous vein (Continental pit), 63.6 ± 0.2 Ma; biotite, early dark micaceous vein (Continental pit), 63.6 ± 0.2 Ma; potassium feldspar, early dark micaceous vein (Continental pit), 63 to 59 Ma; and biotite, biotite breccia dike (Continental pit), 63.6 ± 0.2 Ma. Outlying silver-rich polymetallic quartz veins of the Basin and Boulder mining districts probably are directly related to the 74.5 Ma Butte Granite, whereas Steward-type east-west quartz porphyry dikes and Butte pre-Main Stage deposits are parts of a 66 to 64 Ma magmatic-mineralization system unrelated to emplacement of the Boulder batholith. The age of the crosscutting Main Stage veins may be about 61 Ma as originally reported but can only be bracketed as younger than the 64 Ma pre-Main Stage mineralization and older than the about 50 Ma Eocene Lowland Creek intrusions. The 66 Ma age for the quartz monzodiorite of Boulder Baldy and consideration of previous dating studies in the region indicate that small ca. 66 Ma plutonic systems may be common in the Boulder batholith region and especially to the east. The approximately 64 Ma porphyry copper systems at Butte and gold mineralization at Miller Mountain are indicative of regionally important mineralizing systems of this age in the Boulder batholith region. Resolution of the age and probable magmatic source of the Butte pre-Main Stage porphyry copper-molybdenum system and of the silver-rich polymetallic quartz vein systems in the northern part of the Boulder batholith documents that these deposits formed from two discrete periods of hydrothermal mineralization related to two discrete magmatic events.

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USGS2002

A half century of change in alpine treeline patterns at Glacier National Park, Montana, U.S.A.

Using sequential aerial photography, we identified changes in the spatial distribution of subalpine fir (Abies lasiocarpa) habitat at the alpine treeline ecotone. Six 40-ha study sites in the McDonald Creek drainage of Glacier National Park contained subalpine fir forests that graded into alpine tundra. Over a 46-yr period, altitudinal changes in the location of alpine treeline ecotone were not observed. However, over this 46-yr period the area of krummholz, patch-forest, and continuous canopy forest increased by 3.4%, and tree density increased within existing patches of krummholz and patch-forest. Change in subalpine fir vegetation patterns within 100 m of trails was also compared to areas without trails. Within 100 m of trails, the number of small, discrete krummholz stands increased compared to areas without trails, but there was no significant change in total krummholz area. We used historical terrestrial photography to expand the period (to 70 yr) considered. This photography supported the conclusions that a more abrupt ecotone transition developed from forest to tundra at alpine treeline, that tree density within forested areas increased, and that krummholz became fragmented along trails. This local assessment of fine-grained change in the alpine treeline ecotone provides a comparative base for looking at ecotone change in other mountain regions throughout the world.

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USGS2002

Reconnaissance study of the geology of U.S. vermiculite deposits: Are asbestos minerals common constituents?

Unusually high incidences of asbestos-related mortality and respiratory disease in the small town of Libby, Montana, have been linked to amphibole mineral fibers intergrown with the vermiculite deposits mined and milled near the town from 1923 to 1990. A study conducted by the U.S. Agency for Toxic Substances and Disease Registry concluded that mortality due to asbestosis in Libby mine and mill workers and residents during 1979 to 1998 was much higher than expected for a similar Montana or United States population group. Recent medical testing of past and present mineworkers and residents of Libby showed lung abnormalities in nearly one-fifth of the adult study participants. The U.S. Environmental Protection Agency, under Superfund authority, is completing sampling and cleanup of asbestos-bearing materials in the mine, mill, and town sites. The U.S. Geological Survey is conducting a study, reviewed herein, to investigate the mineral content of other U.S. vermiculite deposits and to determine if the amphibole asbestos minerals like those found in the Libby deposits are common in other vermiculite deposits.

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USGS2002

Geologic map of the Stillwater Complex, Montana: A digital database

This report provides a digital version of the Geologic map of the Stillwater Complex, Montana by Page and Nokleberg (1974). Paper copies of the four geologic map sheets from the original report were scanned and initially attributed by Optronics Specialty Co., Inc. (Northridge, CA) and remitted to the U.S. Geological Survey for further attribution and publication of the geospatial digital files. The resulting digital geologic dataset can be queried in a geographic information system (GIS) in many ways to produce a variety of geological maps.

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USGS2002

Composition, age, and petrogenesis of Late Cretaceous intrusive rocks in the central Big Belt Mountains, Broadwater and Meagher counties, Montana

Cretaceous intrusions hosted by the Proterozoic Newland Formation. The northern intrusion, centered on Boulder Baldy, consists of outer, intermediate, and core zones composed of aegirine-augite quartz monzonite, hornblende quartz monzodiorite, and biotite granodiorite, respectively. The southern intrusion, north of Mount Edith, is compositionally indistinguishable from the intermediate zone of the northern intrusion.

Montana↗
USGS2002

Water resources data, Montana, water year 2001

The U.S. Geological Survey (USGS), in cooperation with other Federal, State, and local agencies, and Tribal governments, collects a large amount of data pertaining to the water resources of Montana each water year. These data, accumulated over many years, constitute a valuable data base for developing an improved understanding of the water resources of the State. To make these data readily available to interested parties outside the USGS, the data are published annually, by water year, in this report series entitled, "Water Resources Data, Montana."

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USGS2002

Metal concentrations and sources in the Miller Creek watershed, Park County, Montana, August 2000

Miller Creek is a tributary of Soda Butte Creek in south-central Montana near the northeast corner of Yellowstone National Park. Surface-water and streambed-sediment samples were collected from streams and seeps throughout the Miller Creek watershed during low-flow conditions on August 28-31, 2000, to characterize metal concentrations and identify possible sources contributing metal to Miller Creek. Most water in Miller Creek appears to be unaffected by mining disturbances or natural weathering of mineralized rocks, although such effects are common elsewhere in the New World Mining District. Values for pH were near neutral to basic. Total-recoverable copper, lead, and zinc concentrations were low, relative to State of Montana water-quality standards, with many concentrations less than the analytical minimum reporting levels. Metal concentrations in Miller Creek during this study ranged from 1 to 6 micrograms per liter (µg/L) for total-recoverable copper, <1 to 5 µg/L for total-recoverable lead, and <1 to 26 µg/L for total-recoverable zinc. Concentrations of cadmium, copper, lead, and zinc in all samples from Miller Creek were less than the chronic aquatic-life criteria, except for one total-recoverable lead value (5 µg/L) just downstream from the Black Warrior Mine inflow. Leachable lead and zinc concentrations in streambed-sediment samples collected during this study were highest at the Black Warrior Mine inflow. Leachable concentrations at this site were about 20 times greater for lead and 11 times greater for zinc than concentrations in the streambed-sediment sample collected from Miller Creek upstream from this inflow. However, these elevated concentrations had little effect on the leachable metal concentrations in the streambed-sediment sample collected downstream from the Black Warrior Mine inflow. Metal loading to Miller Creek during this low-flow study was relatively small. Three small left-bank inflows having elevated copper concentrations entered Miller Creek near the middle of the study reach and their combined total-recoverable copper load accounted for about 96 percent of the copper load in Miller Creek. Small loads of lead (about 2 micrograms per second) entered Miller Creek from the Black Warrior Mine inflow and a right bank inflow. None of the loads entering Miller Creek had an appreciable effect on mainstem metal concentrations. In addition, substantial differences between mining related areas and areas influenced by local geology could not be determined.

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USGS2002

Modeling and measuring snow for assessing climate change impacts in Glacier National Park, Montana

A 12-year program of global change research at Glacier National Park by the U.S. Geological Survey and numerous collaborators has made progress in quantifying the role of snow as a driver of mountain ecosystem processes. Spatially extensive snow surveys during the annual accumulation/ablation cycle covered two mountain watersheds and approximately 1,000 km2 . Over 7,000 snow depth and snow water equivalent (SWE) measurements have been made through spring 2002. These augment two SNOTEL sites, 9 NRCS snow courses, and approximately 150 snow pit analyses. Snow data were used to establish spatially-explicit interannual variability in snowpack SWE. East of the Continental Divide, snowpack SWE was lower but also less variable than west of the Divide. Analysis of snowpacks suggest downward trends in SWE, a reduction in snow cover duration, and earlier melt-out dates during the past 52 years. Concurrently, high elevation forests and treelines have responded with increased growth. However, the 80 year record of snow from 3 NRCS snow courses reflects a strong influence from the Pacific Decadal Oscillation, resulting in 20-30 year phases of greater or lesser mean SWE. Coupled with the fine-resolution spatial snow data from the two watersheds, the ecological consequences of changes in snowpack can be empirically assessed at a habitat patch scale. This will be required because snow distribution models have had varied success in simulating snowpack accumulation/ablation dynamics in these mountain watersheds, ranging from R2=0.38 for individual south-facing forested snow survey routes to R2=0.95 when aggregated to the watershed scale. Key ecological responses to snowpack changes occur below the watershed scale, such as snow-mediated expansion of forest into subalpine meadows, making continued spatially-explicit snow surveys a necessity.

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