Preliminary geologic map of the west half of the Pocatello 1° x 2° quadrangle, Idaho
No abstract available.
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Geology topics
Research about Idaho
Source-linked reports with geographic coverage including Idaho.
Geology of the Arco-Big Southern Butte area, eastern Snake River Plain, and potential volcanic hazards to the radioactive waste management complex, and other waste storage and reactor facilities at the Idaho National Engineering Laboratory, Idaho
The Arco-Big Southern Butte area of the eastern Snake River Plain, Idaho, includes a volcanic rift zone and more than 70 Holocene and late Quaternary basalt volcanoes. The Arco volcanic rift zone extends southeast for 50 km from Arco to about 10 km southeast of Big Southern Butte. The rift zone is the locus of extensional faults, graben, fissure basaltic volcanic vents, several rhyolite domes at Big Southern Butte, and a ferrolatite volcano at Cedar Butte. Limited radiometric age data and geological field criteria suggest that all volcanism in the area is younger than 700,000 years; at least 67 separate basaltic eruptions are estimated to have occurred within the last 200,000 years. The average volcanic recurrence interval for the Arco-Big Southern Butte area is approximately one eruption per 3,000 years. Radioactive waste storage and reactor facilities at the Idaho National Engineering Laboratory may be subject to potential volcanic hazards. The geologic history and inferred past volcanic events in the Arco-Big Southern Butte area provide a basis for assessing the volcanic hazard. It is recommended that a radiometric age-dating study be performed on rocks in cored drill holes to provide a more precise estimate of the eruption recurrence interval for the region surrounding and including the Radioactive Waste Management Complex. It is also recommended that several geophysical monitoring systems (dry tilt and seismic) be installed to provide adequate warning of future volcanic eruptions.
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Progress toward a ground-water-quality monitoring network for Idaho
A ground-water-quality monitoring network is being designed for Idaho. The primary objectives of the network are to (1) determine the present quality of the State's ground water, (2) provide continual monitoring of groundwater quality for water-management purposes, and (3) serve as a warning system of undesirable changes in ground-water quality. Data are compiled for geohydrologic conditions, groundwater quality, cultural elements, and pollution sources. A "Hydrologic Unit Priority Index" is calculated from these data to select priority areas for monitoring purposes. New ground-water-quality data were collected where existing data were lacking and at some sites that were previously sampled. Old and new data at common sites correlated well, indicating that the water quality has not changed significantly. Most ground water in Idaho is of good quality for common uses; however, water quality may pose problems in local areas. The problems result from both natural and human causes. The potential for pollution of the aquifers is expected to be greatest in areas of greatest development. In Idaho, population centers and industries tend to be in areas of privately owned irrigated and arable · land. Therefore, these areas are of primary concern for monitoring ground-water quality. Other areas requiring monitoring include those with second-home development, mining and its related processes, and radioactive-waste disposal.
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Water resources of Camas Prairie, south-central Idaho
Ground-water pumpage in Camas Prairie, Idaho, for irrigation and municipal supplies totaled nearly 9,500 acre-feet in 1977. Declines of pressure head in the artesian aquifer have ranged from 3 to 12 feet since 1974 when increased ground-water pumping began. A comparison of water-level measurements made in September 1957 and September 1977 shows declines of more than 30 feet in places in the artesian aquifer. Camas Prairie aquifers are recharged by percolation from streams and by precipitation on the valley floor. Estimated mean annual recharge to the artesian aquifer is 37,000 acre-feet. Vertical recharge from the artesian aquifer to the overlying water-table aquifer is estimated to be 20,000 acre-feet annually. Declines in artesian pressure caused by increased irrigation pumping will result in a reduction of recharge from the artesian aquifer to the water-table aquifer. Yields from irrigation wells in the prairie ranged from 400 to slightly more than 2,000 gallons per minute. Flows in Camas Creek in the 1977 drought year averaged 9,400 acre-feet, compared with 138,000 acre-feet in a normal year. Surface and ground waters sampled in the basin were either a sodium or calcium bicarbonate type water. Dissolved-solids concentrations ranged from 61 to 284 milligrams per liter. (Woodard-USGS)
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Regional gravity and magnetic anomalies in the eastern Snake River Plain, Idaho
Over the eastern Snake River Plain, the Bouguer gravity anomaly and the magnetic intensity are, in general, high. In detail, both the gravity and the magnetic anomalies are a complex of highs and lows, in contrast to the simpler anomalies over the western Snake River Plain. The broad gravity high associated with the eastern Snake River Plain cannot be produced by a dense mass at shallow depth under the plain, but must be produced either by a deep feature under the plain or by a broader, shallower feature extending well beyond the plain. The high could be produced by a thinning of the crust under the plain by 4.5 to 7 kilometers. The data suggest that the Cenozoic rocks of the plain are underlain by rocks that have density and magnetization similar to the density and magnetization of the pre-Cenozoic rocks north and south of the plain. The data do not suggest rifting of the upper crust such as is inferred for the western Snake River Plain. The plain is in approximate isostatic equilibrium with adjoining regions to the north and south and thus contrasts with the adjoining areas where the basin-and-range topography is not in isostatic equilibrium. The local gravity anomalies on the plain are probably produced by variations in the thickness of Cenozoic rocks, but the wavelength of the anomalies is about twice that of the basin-and-range structural features in areas adjoining the plain. The gravity expression of basin-and-range structural features does not extend far onto the plain. Magnetic anomalies on the plain are produced by Cenozoic volcanic rocks.
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Wood River mining district, Idaho - intrusion-related lead-silver deposits derived from country rock source
Lead-silver deposits in the Wood River mining district occur in shear zones in hornfelsed argillite of the Devonian Milligen Formation near granitic plutons and under the Wood River thrust fault. The principal ore minerals are argentiferous galena and sphalerite; siderite is the principal gangue. The δ 34 S values of the sulfide minerals range from +2.2 to +15.0 permil, indicating that the sulfur had a shallow crustal source. Δ 34 S values between sphalerite and galena range from +2.3 to +3.4 permil, corresponding to sulfur isotope temperatures between 280° and 182 °C. Hydrothermal barite has a δ 34 S of +13.2 permil. Lead isotope ratios are radiogenic, also pointing to a shallow crustal source. Quartz gangue has δ 18 O of +16.4 permil and a calculated δ 18 O H20 at 270°C of +8.4 permil. This value is reasonable for a hydrothermal fluid that had reached equilibrium with the argillite country rock. The siderite gangue has δ 18 O and δ 13 C values of +14.0 and -5.5 permil, respectively. Fluid inclusions have homogenization temperatures of 244°-307°C and average 270°C. Freezing-stage measurements ranged from -1.85 to -2.8°C, suggesting salinities of 3.2 to 4.8 weight percent. The δD values of inclusion fluid in ore and gangue minerals are -110 to -120 permil. The geology, isotope, and fluid-inclusion data are consistent with a model of hydrothermal systems of meteoric water in faulted and shattered Paleozoic rocks near plutonic masses. This environment permitted deep circulation of the hydrothermal fluids, which dissolved the metals and sulfur from the Paleozoic host rocks and deposited ore in favorable beds or structures under the regional Wood River thrust fault.
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Map showing areas of potential rockfalls in the Snake River Canyon near Twin Falls, Idaho
Explore the source record for details and available documents.
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Geochemical exploration studies in the Coeur d'Alene district, Idaho
The principal ore deposits in the Coeur d'Alene district are lead-zinc-silver replacement veins in Precambrian rocks of the Belt Supergroup. The main ore minerals are galena, tetrahedrite, andsphalerite. The host rocks are mainly quartzite, siltite, andargillite. Cretaceous quartz monzonite locally intrudes the Belt rocks. The geochemical investigations reported here were carried out to determine if geochemical methods would be useful in the search for concealed ore deposits. About 8,700 soil samples and 4,000 rock samples were collected from a 300-square-mile (778 km 2 ) area for this study. The samples were analyzed for 35 elements. Antimony, silver, lead, manganese, and copper form dispersion patterns and halos that are related to many of the ore deposits within the district, and these same elements were found to be most usefulin delineating the known mineral belts that contain most of the orebodies. The dispersion patterns are probably primary, havingonly minor modifications due to secondary redistribution of theoreforming elements. The mineral belts and geochemical-dispersion patterns have been laterally offset, perhaps as much as 16 miles (25.6 km), by postore faulting. Prefault dispersion patterns can be restored by adjusting the geochemical maps along the postore faults to match the dispersion patterns across the fault trace. The reconstructed dispersion patterns of antimony, arsenic, lead, sulfur, and the ratio of cadmium to zinc form concentric halos around the restored position of the Gemstocks. Most of the Coeur d'Alene ore has been mined from this halo. It appears that the geochemical-exploration methods reported here successfully delineate the major mineral belts and indicate unexplored areas in which to search for new deposits.
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Ground water-surface water relations in the Silver Creek area, Blaine County, Idaho
The relations between ground water and surface water were studied by the U.S. Geological Survey in the Silver Creek area, Blaine County, Idaho, as part of a comprehensive investigation of the area's water resources. Ground-water withdrawals calculated for 1975 totaled about 16,000 acre-feet (2.0 x10 7 cubic meters) of pumped ground water and 12,000 acre-feet (1.5x10 7 cubic meters) of ground water extracted through flowing wells. The ground water is contained in alluvial and basalt aquifers comprised of gravel, sand, and basalt interbedded with fine-grained silt and clay. Nineteen shallow test holes were drilled and cased to define the extent and effectiveness of confining layers in the southern part of the valley. Water-level fluctuations monitored in about 75 wells showed seasonal variations of 40 feet (12 meters) in the northern part of the area and less than 5 feet (1.5 meters) in some wells in the southern part of the area. Numerous stream-discharge measurements were made to define areal and temporal distribution of groundwater discharge. Most of the flow in Silver Creek rises from springs discharging from the shallow aquifer near the edge of the confining beds. Only a small amount of discharge to the creek is attributable to upward movement of water through the confining beds. Discharge from the artesian aquifer near Stanton Crossing may contribute a significant portion of the spring flow which feeds the Big Wood River. Seasonal fluctuations in spring discharges are directly related to fluctuations in ground-water levels. Although losses from Silver Creek downstream from the confining beds were documented during various times of the year, losses were relatively small. A deposit of fine-grained sediments near Picabo effectively perches Silver Creek above the deep basalt aquifer.
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Reconnaissance of ground-water resources in the Mountain Home plateau area, southwest Idaho
The Mountain Home plateau area occupies approximately 1,220 square miles of the western Snake River Plain in southwestern Idaho. About 40,000 acres are presently (1977) irrigated with ground water, about 30,000 acres with surface water. An estimated 450,000 acres are potentially irrigable, if water is available. Development of ground-water re- sources has caused water-level declines in several places. Largest declines are south of Mountain Home, where water levels dropped more than 20 feet in the last 9 years. Ground water in the area occurs primarily under water-table conditions. Perched-water zones are present in several locations. The most productive aquifer in the eastern part of the plateau is basalt of the Bureau Formation of the Idaho Group. In the western part, the most productive aquifers are sand and gravel of the older terrace gravel lithologic unit and the Idaho Group. Recharge to the ground-water system is water from the Boise River drainage basin, precipitation on the plateau and adjacent mountains, and leakage from irrigation structures. Ground-water movement is generally south or southwest. Natural ground-water discharge from the plateau is about 18,000 acre-feet annually. The chemical composition of the ground water generally reflects water characteristics in the area of the source of recharge and, for the most part, is good. Deuterium and oxygen-18 isotope analyses suggest that the water at the lower end of the ground-water flow system underlying the plateau was recharged a long time ago, although climatic conditions then were similar to current conditions in the Boise River basin. Additional large-scale ground-water development will probably result in economically prohibitive pumping lifts, which also would consume excessive amounts of energy. Therefore, large-scale new agricultural development would depend heavily on the availability of surface water. However, one or several deep test holes, in selected places, could help answer some questions about the occurrence of ground water and perhaps encourage further exploration for untapped deep artesian aquifers. The occurrence of perched-water zones beneath lands irrigated by surface water suggests that more zones of this type could develop if water is imported into the area to irrigate additional lands, and if the efficiency of the present distribution systems remains unchanged.
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Water resources of the Weiser River basin, west-central Idaho
The study area comprises about 1,600 square miles (4,100 square kilometers) in west-central Idaho and includes the entire Weiser River basin and small areas both west and south of Weiser outside the basin. The basin is sparsely populated and the economy is chiefly agricultural.
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Remote sensing techniques for monitoring impacts of phosphate mining in southeastern Idaho
No abstract available.
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Teton Dam flood of June 1976, Newdale quadrangle, Idaho
The failure of the Teton Dam caused extreme flooding along the Teton River, Henrys Fork, and Snake River in southeastern Idaho on June 5-8, 1976. No flooding occurred downstream from American Falls Reservoir. The inundated areas and maximum water-surface elevations are shown in a series of 17 hydrologic atlases. The area covered by the atlases extends from Teton Dam downstream to American Falls Reservoir, a distance of 100 miles. The extent of flooding shown on the maps was obtained by field inspections and aerial photographs made during and immediately after the flood. There may be small isolated areas within the boundaries shown that were not flooded, but the identification of these sites was beyond the scope of the study. The elevation data shown are mean-sea-level elevations of high-water marks identified in the field. This particular map (in the 17-map series) shows conditions in the Newdale quadrangle. (Woodard-USGS)
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Teton Dam flood of June 1976, St. Anthony quadrangle, Idaho
The failure of the Teton Dam caused extreme flooding along the Teton River, Henrys Fork, and Snake River in southeastern Idaho on June 5-8, 1976. No flooding occurred downstream from American Falls Reservoir. The inundated areas and maximum water-surface elevations are shown in a series of 17 hydrologic atlases. The area covered by the atlases extends from Teton Dam downstream to American Falls Reservoir, a distance of 100 miles. The extent of flooding shown on the maps was obtained by field inspections and aerial photographs made during and immediately after the flood. There may be small isolated areas within the boundaries shown that were not flooded, but the identification of these sites was beyond the scope of the study. The elevation data shown are mean-sea-level elevations of high-water marks identified in the field. This particular map (in the 17-map series) shows conditions in the St. Anthony quadrangle. (Woodard-USGS)
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Teton Dam flood of June 1976, Parker quadrangle, Idaho
The failure of Teton Dam caused extreme flooding along the Teton River, Henrys Fork, and Snake River in southeastern Idaho on June 5-8, 1976. No flooding occurred downstream from American Falls, Reservoir. The inundated areas and maximum water-surface elevations are shown in a series of 17 hydrologic atlases. The area covered by the atlases extends from Teton Dam downstream to American Falls Reservoir, a distance of 100 miles. The extent of flooding shown on the maps was obtained by field inspections and aerial photographs made during and immediately after the flood. There may be small isolated areas within the boundaries shown that were not flooded, but the identification of these sites was beyond the scope of the study. The elevation data shown are mean-sea-level elevations of high-water marks identified in the field. This particular map (in the 17-map series) shows conditions in the Parker quadrangle. (Woodard-USGS)
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