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At least 235 records · Page 13Linked to original sources
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.

Montana↗
USGS2014

Hydrology and numerical simulation of groundwater movement and heat transport in Snake Valley and surrounding areas, Juab, Miller, and Beaver Counties, Utah, and White Pine and Lincoln Counties, Nevada

Snake Valley and surrounding areas, along the Utah-Nevada state border, are part of the Great Basin carbonate and alluvial aquifer system. The groundwater system in the study area consists of water in unconsolidated deposits in basins and water in consolidated rock underlying the basins and in the adjacent mountain blocks. Most recharge occurs from precipitation on the mountain blocks and most discharge occurs from the lower altitude basin-fill deposits mainly as evapotranspiration, springflow, and well withdrawals. The Snake Valley area regional groundwater system was simulated using a three-dimensional model incorporating both groundwater flow and heat transport. The model was constructed with MODFLOW-2000, a version of the U.S. Geological Survey’s groundwater flow model, and MT3DMS, a transport model that simulates advection, dispersion, and chemical reactions of solutes or heat in groundwater systems. Observations of groundwater discharge by evapotranspiration, springflow, mountain stream base flow, and well withdrawals; groundwater-level altitudes; and groundwater temperatures were used to calibrate the model. Parameter values estimated by regression analyses were reasonable and within the range of expected values. This study represents one of the first regional modeling efforts to include calibration to groundwater temperature data. The inclusion of temperature observations reduced parameter uncertainty, in some cases quite significantly, over using just water-level altitude and discharge observations. Of the 39 parameters used to simulate horizontal hydraulic conductivity, uncertainty on 11 of these parameters was reduced to one order of magnitude or less. Other significant reductions in parameter uncertainty occurred in parameters representing the vertical anisotropy ratio, drain and river conductance, recharge rates, and well withdrawal rates. The model provides a good representation of the groundwater system. Simulated water-level altitudes range over almost 2,000 meters (m); 98 percent of the simulated values of water-level altitudes in wells are within 30 m of observed water-level altitudes, and 58 percent of them are within 12 m. Nineteen of 20 simulated discharges are within 30 percent of observed discharge. Eighty-one percent of the simulated values of groundwater temperatures in wells are within 2 degrees Celsius (°C) of the observed values, and 55 percent of them are within 0.75 °C. The numerical model represents a more robust quantification of groundwater budget components than previous studies because the model integrates all components of the groundwater budget. The model also incorporates new data including (1) a detailed hydrogeologic framework, and (2) more observations, including several new water-level altitudes throughout the study area, several new measurements of spring discharge within Snake Valley which had not previously been monitored, and groundwater temperature data. Uncertainty in the estimates of subsurface flow are less than those of previous studies because the model balanced recharge and discharge across the entire simulated area, not just in each hydrographic area, and because of the large dataset of observations (water-level altitudes, discharge, and temperatures) used to calibrate the model and the resulting transmissivity distribution. Groundwater recharge from precipitation and unconsumed irrigation in Snake Valley is 160,000 acre-feet per year (acre-ft/yr), which is within the range of previous estimates. Subsurface inflow from southern Spring Valley to southern Snake Valley is 13,000 acre-ft/yr and is within the range of previous estimates; subsurface inflow from Spring Valley to Snake Valley north of the Snake Range, however, is only 2,200 acre-ft/yr, which is much less than has been previously estimated. Groundwater discharge from groundwater evapotranspiration and springs is 100,000 acre-ft/yr, and discharge to mountain streams is 3,300 acre-ft/yr; these are within the range of previous estimates. Current well withdrawals are 28,000 acre-ft/yr. Subsurface outflow from Snake Valley moves into Pine Valley (2,000 acre-ft/yr), Wah Wah Valley (23 acre-ft/yr), Tule Valley (33,000 acre-ft/yr), Fish Springs Flat (790 acre-ft/yr), and outside of the study area towards Great Salt Lake Desert (8,400 acre-ft/yr); these outflows, totaling about 44,000 acre-ft/yr, are within the range of previous estimates. The subsurface flow amounts indicate the degree of connectivity between hydrographic areas within the study area. The simulated transmissivity and locations of natural discharge, however, provide a better estimate of the effect of groundwater withdrawals on groundwater resources than does the amount and direction of subsurface flow between hydrographic areas. The distribution of simulated transmissivity throughout the study area includes many areas of high transmissivity within and between hydrographic areas. Increased well withdrawals within these high transmissivity areas will likely affect a large part of the study area, resulting in declining groundwater levels, as well as leading to a decrease in natural discharge to springs and evapotranspiration.

Nevada, Utah↗
USGS2016

Mapping marginal croplands suitable for cellulosic feedstock crops in the Great Plains, United States

Growing cellulosic feedstock crops (e.g., switchgrass) for biofuel is more environmentally sustainable than corn-based ethanol. Specifically, this practice can reduce soil erosion and water quality impairment from pesticides and fertilizer, improve ecosystem services and sustainability (e.g., serve as carbon sinks), and minimize impacts on global food supplies. The main goal of this study was to identify high-risk marginal croplands that are potentially suitable for growing cellulosic feedstock crops (e.g., switchgrass) in the US Great Plains (GP). Satellite-derived growing season Normalized Difference Vegetation Index, a switchgrass biomass productivity map obtained from a previous study, US Geological Survey (USGS) irrigation and crop masks, and US Department of Agriculture (USDA) crop indemnity maps for the GP were used in this study. Our hypothesis was that croplands with relatively low crop yield but high productivity potential for switchgrass may be suitable for converting to switchgrass. Areas with relatively low crop indemnity (crop indemnity <$2 157 068) were excluded from the suitable areas based on low probability of crop failures. Results show that approximately 650 000 ha of marginal croplands in the GP are potentially suitable for switchgrass development. The total estimated switchgrass biomass productivity gain from these suitable areas is about 5.9 million metric tons. Switchgrass can be cultivated in either lowland or upland regions in the GP depending on the local soil and environmental conditions. This study improves our understanding of ecosystem services and the sustainability of cropland systems in the GP. Results from this study provide useful information to land managers for making informed decisions regarding switchgrass development in the GP.

GCB Bioenergy↗
USGS2018

Estimation of unregulated monthly, annual, and peak streamflows in Forest City Stream and lake levels in East Grand Lake, United States-Canada border between Maine and New Brunswick

The U.S. Geological Survey, in cooperation with the International Joint Commission, compiled historical data on regulated streamflows and lake levels and estimated unregulated streamflows and lake levels on Forest City Stream at Forest City, Maine, and East Grand Lake on the United States-Canada border between Maine and New Brunswick to study the effects on streamflows and lake levels if two or all three dam gates are left open. Historical regulated monthly mean streamflows in Forest City Stream at the outlet of East Grand Lake (referred to as Grand Lake by Environment Canada) fluctuated between 114 cubic feet per second (ft3 /s) (3.23 cubic meters per second [m3 /s]) in November and 318 ft3 /s (9.01 m3 /s) in September from 1975 to 2015 according to Environment Canada streamgaging data. Unregulated monthly mean streamflows at this location estimated from regression equations for unregulated sites range from 59.2 ft3 /s (1.68 m3 /s) in September to 653 ft3 /s (18.5 m3 /s) in April. Historical lake levels in East Grand Lake fluctuated between 431.3 feet (ft) (131.5 meters [m]) in October and 434.0 ft (132.3 m) in May from 1969 to 2016 according to Environment Canada lake level data for East Grand Lake. Average monthly lake levels modeled by using the estimated hydrology for unregulated flows, and an outflow rating built from a hydraulic model with all gates at the dam open, range from 427.7 ft (130.4 m) in September to 431.1 ft (131.4 m) in April. Average monthly lake levels would likely be from 1.8 to 5.4 ft (0.55 to 1.6 m) lower with the gates at the dam opened than they have been historically. The greatest lake level changes would be from June through September.

Maine, New Brunswick↗
USGS2026

Assessing natural recharge in Indian Wells Valley, California: A Basin Characterization Model case study

The communities in Indian Wells Valley (IWV), in the northern Mojave Desert in California, rely on groundwater for domestic and agricultural use. Mountain front recharge from the surrounding Sierra Nevada is the main source of natural recharge to the valley. Increased urbanization, agricultural development, and groundwater pumping during recent decades put IWV in a state of critical overdraft. The U.S. Geological Survey Basin Characterization Model, version 8 (BCMv8) was used to evaluate historical and future climate and hydrologic conditions in IWV. The BCMv8 estimated natural recharge in IWV at 10.7 million cubic meters (Mm 3 ) per year for the period from 1981 to 2010. Future patterns of water balance variables using three future climate scenarios, hot-wet, hot-dry, and warm-moderately wet, were calculated for mid-century (2040–69) and end-of-century (2070–99) periods. Results for both wet models projected an increase in recharge in both periods, whereas the hot-dry model projected a decrease in recharge in both periods. All models reported a large increase in seasonal variability in recharge, indicating more future availability and frequent occurrences of drought years. All climate scenarios projected an increase in climatic water deficit in both periods. These increases in irrigation demand and variability of water supply highlight the importance of strategic management planning for the sustainability of water resources in IWV.

California↗
USGS2021

Geologic and geophysical maps of the Newfoundland Mountains and part of the adjacent Wells 30' x 60' quadrangles, Box Elder County, Utah

The Newfoundland Mountains map area (Newfoundland Mountains and adjacent part of Wells 30' x 60' quadrangles) is located in Box Elder County, northwestern Utah. The map encompasses broad expanses of the Great Salt Lake Desert as well as several picturesque mountain ranges (figures 1, 2, and 3). The geology of the area was last mapped and summarized by Doelling (1980). Since that landmark study, much of the area has been mapped in greater detail and new paleontologic, geochronologic, and structural data provide for an updated view of the geology. In addition, new geophysical studies (Langenheim and others, 2013; Langenheim, 2016) provide key data for improved interpretation of subsurface geology. The geologic map (plate 1) was compiled from fifteen 7.5' quadrangles mapped at a scale of 1:24,000 (mostly in the western part of the area), one map covering the Newfoundland Mountains at a scale of 1:31,680 (Allmendinger and Jordan, 1989), unpublished geologic mapping at scales from 1:24,000 to 1:50,000 (most by Miller; Bovine Mountain by T.E. Jordan), and reconnaissance mapping and aerial photo interpretation in intervening areas by Miller. Some published maps were remapped or reinterpreted by the authors in light of more recent studies north of the map area. Geologic mapping conducted as part of several theses/dissertations and a few published papers also were used (plate 2, index to geologic mapping). Concealed faults under valley bottoms were interpreted from gravity and aeromagnetic data. Our approach for this map was to integrate across the main themes of the mapped geology by generalizing units, structures, and polygons. This has the aim of illustrating the principal tectonic and stratigraphic packages, as well as illustrating the patterns of surficial units and geomorphology. Cross sections (plate 2) were constructed to coincide with representative cross sections for several detailed geologic maps. This approach required large bends across valleys. Basin geometry shown in the cross sections was constrained by gravity data and a seismic line since few deep drill holes are available.

Utah↗
USGS1989

Sedimentary framework of the southern Maine inner continental shelf: Influence of glaciation and sea-level change

Although the tidally influenced shoreline of Maine is longer than that of virtually any other state, almost no research on its geology has been published. In order to go some way towards remedying this, 1500 km of high-resolution seismic reflection data and 800 km of sidescan sonar imagery have been collected. On the basis of these data and observations made during ten submersible dives, more than 800 bottom samples were collected and evaluated for texture and composition. The understanding of the sedimentary framework of the southern Maine shelf and the processes that maintain it are summarized, and future research directions to evaluate the strategic mineral potential are indicated. In the past 14,000 years, the Maine shelf has experienced a deglaciation and two marine transgressions separated by a regression. The deglaciation was accompanied by the first transgression and deposited till interbedded with up to 40 m of glaciomarine sediment (the Presumpscot Formation) across the shelf. The first transgression culminated about 12,500 yrs B.P., and its landward limit is marked by large glaciomarine deltas 50-100 km landward of the present-day coast. Sea level fell until about 9500 yrs B.P., when shorelines were cut at about the 65 m depth and some large "lowstand deltas" were deposited. Sea level has risen since then and in the general absence of modern river sediment input marine processes have reworked the older sediment. Five shelf environments have been defined in terms of their surficial sediment and stratigraphy. Nearshore ramps are sandy regions extending to about 30 m deep offshore of sandy beaches. These may be reworked lowstand deltas, and possess the thickest bodies of sand in the region. Nearshore basins are mud-filled troughs seaward of coastal areas lacking significant river input. Slumping glaciomarine deposits provide most of the Holocene mud that floors these basins. Rocky zones are extensive areas of exposed rock most common in the 30-50 m depth range. These are areas of high carbonate productivity and provide shell fragments to adjacent areas. The outer basins are muddy regions that begin at the 65 m shoreline and extend beyond the 100 m isobath to the deep Gulf of Maine. Finally, shelf valleys are former stream courses that connect nearshore ramps and basins to the outer basins. These bedrock-framed valleys are filled with sand and mud and are apparently still active conduits for the offshore movement of sediment. The mineralogy of the shelf sediment is complex, and it is not yet clear whether glacial homogenization has obliterated distinctions between river drainage basins and the adjacent shelf. Studies are continuing into northern Maine and analysis of the heavy mineralogy of the shelf sediment utilizing a 2 m Humphrey Spiral to process large grab samples and cores has begun. ?? 1989.

Marine Geology↗
USGS2023

Assessment of salinity retention or mobilization by sediment-retention ponds near Delta, Colorado, 2019

Salinity control efforts in the Colorado River Basin have focused on mobilization of salts from irrigated land, but nonirrigated rangelands are also a source of salinity. In particular, lands where soils have formed from the Late Cretaceous Mancos Shale under arid and semiarid climates contain considerable quantities of salt, mainly in the subsurface. Hundreds of thousands of contour furrows and check dams (gully plugs) were constructed by the Bureau of Land Management (BLM) and Bureau of Reclamation in the late 1950s and 1960s to reduce runoff, sedimentation, and salt mobilization from ephemeral stream channels on rangelands. Sediment-retention ponds associated with check dams are dry most of the year, except immediately following substantial rain events. Generally, no maintenance has been performed on these structures, some have degraded over time, and their current and past influence on salinity is poorly understood. To assess the influence of check dams and their associated ponds on salt retention and mobilization, the U.S. Geological Survey, in cooperation with the BLM, conducted a study of such ponds within the Gunnison Gorge National Conservation Area (GGNCA) near Delta, Colorado. This report includes conceptual models of how sediment-retention ponds function relative to salinity, and a collection of environmental data to evaluate the conceptual models. An inventory of 69 ponds indicated that 38 percent no longer had water holding capacity, and another 20 percent could hold 1 foot or less of water. Check-dam degradation was the main cause, but sediment infill of ponds contributed as well. Water content of soil profiles collected beneath ponds and immediately downstream from check dams indicated little penetration of water below 60 centimeters for most ponds and little evidence for lateral movement of water beneath check dams. Patterns of salt content in the soil profiles indicated no accumulation of salts at the pond surface from evaporating waters and little evidence for salt redistribution in the form of salt bulges or salt depletion curves at intermediate depths. Based on the conceptual models presented and interpretations of data collected by this study, it appears that the sediment-retention ponds in the GGNCA have neither mobilized nor retained substantial quantities of salt during their lifetimes.

Colorado↗
USGS2014

Geologic and hydrogeologic frameworks of the Biscayne aquifer in central Miami-Dade County, Florida

Evaluations of the lithostratigraphy, lithofacies, paleontology, ichnology, depositional environments, and cyclostratigraphy from 11 test coreholes were linked to geophysical interpretations, and to results of hydraulic slug tests of six test coreholes at the Snapper Creek Well Field (SCWF), to construct geologic and hydrogeologic frameworks for the study area in central Miami-Dade County, Florida. The resulting geologic and hydrogeologic frameworks are consistent with those recently described for the Biscayne aquifer in the nearby Lake Belt area in Miami-Dade County and link the Lake Belt area frameworks with those developed for the SCWF study area. The hydrogeologic framework is characterized by a triple-porosity pore system of (1) matrix porosity (mainly mesoporous interparticle porosity, moldic porosity, and mesoporous to megaporous separate vugs), which under dynamic conditions, produces limited flow; (2) megaporous, touching-vug porosity that commonly forms stratiform groundwater passageways; and (3) conduit porosity, including bedding-plane vugs, decimeter-scale diameter vertical solution pipes, and meter-scale cavernous vugs. The various pore types and associated permeabilities generally have a predictable vertical spatial distribution related to the cyclostratigraphy. The Biscayne aquifer within the study area can be described as two major flow units separated by a single middle semiconfining unit. The upper Biscayne aquifer flow unit is present mainly within the Miami Limestone at the top of the aquifer and has the greatest hydraulic conductivity values, with a mean of 8,200 feet per day. The middle semiconfining unit, mainly within the upper Fort Thompson Formation, comprises continuous to discontinuous zones with (1) matrix porosity; (2) leaky, low permeability layers that may have up to centimeter-scale vuggy porosity with higher vertical permeability than horizontal permeability; and (3) stratiform flow zones composed of fossil moldic porosity, burrow related vugs, or irregular vugs. Flow zones with a mean hydraulic conductivity of 2,600 feet per day are present within the middle semiconfining unit, but none of the flow zones are continuous across the study area. The lower Biscayne aquifer flow unit comprises a group of flow zones in the lower part of the aquifer. These flow zones are present in the lower part of the Fort Thompson Formation and in some cases within the limestone or sandstone or both in the uppermost part of the Pinecrest Sand Member of the Tamiami Formation. The mean hydraulic conductivity of major flow zones within the lower Biscayne aquifer flow unit is 5,900 feet per day, and the mean value for minor flow zones is 2,900 feet per day. A semiconfining unit is present beneath the Biscayne aquifer. The boundary between the two hydrologic units is at the top or near the top of the Pinecrest Sand Member of the Tamiami Formation. The lower semiconfining unit has a hydraulic conductivity of less than 350 feet per day. The most productive zones of groundwater flow within the two Biscayne aquifer flow units have a characteristic pore system dominated by stratiform megaporosity related to selective dissolution of an Ophiomorpha-dominated ichnofabric. In the upper flow unit, decimeter-scale vertical solution pipes that are common in some areas of the SCWF study area contribute to high vertical permeability compared to that in areas without the pipes. Cross-hole flowmeter data collected from the SCWF test coreholes show that the distribution of vuggy porosity, matrix porosity, and permeability within the Biscayne aquifer of the SCWF is highly heterogeneous and anisotropic. Groundwater withdrawals from production well fields in southeastern Florida may be inducing recharge of the Biscayne aquifer from canals near the well fields that are used for water-management functions, such as flood control and well-field pumping. The SCWF was chosen as a location within Miami-Dade County to study the potential for such recharge to the Biscayne aquifer from the C–2 (Snapper Creek) canal that roughly divides the well field in half. Geologic, hydrogeologic, and hydraulic information on the aquifer collected during construction of monitoring wells within the SCWF could be used to evaluate the groundwater flow budget at the well-field scale.

Florida↗
USGS2007

Insight into the geology of the East Antarctic hinterland: a study of sediment inclusions from ice cores of the Lake Vostok borehole

The borehole at the southern part of subglacial Lake Vostok has been drilled into an ice layer that has been refrozen from the lake water. This ice layer contains random sediment inclusions, eight of which have been studied using state-of the-art analytical techniques. Six inclusions comprise soft aggregates consisting mainly of clay-mica minerals and micron-sized quartz grains while two others are solid clasts of fine-grained cemented rocks. The largest rock clast consists of poorly-rounded quartz and minor amounts of accessory minerals and is classified as quartzose siltstone. More than twenty grains of zircon and monazite have been identified in this siltstone and dated by SIMS SHRIMP-II. Two age clusters have been recognized for these detrital grains, in the ranges 0.8−1.2 Ga and 1.6−1.8 Ga. The compositions of the rock clasts suggest that the bedrock situated to the west of Lake Vostok is sedimentary. The age data on the detrital accessory minerals suggest that the provenance of these sedimentary rocks − the Gamburtsev Mountains and Vostok Subglacial Highlands, is mainly represented by Paleoproterozoic and MesoproterozoicNeoproterozoic crustal provinces

Open-File Report↗
USGS1990

Digital recordings of aftershocks of the 17 October 1989 Loma Prieta, California, earthquake

After the 17 October 1989 Loma Prieta, central California, earthquake (291 00:04:15.25 UTC, M s =7.1), the U. S. Geological Survey recorded aftershocks at sites of seismologic and engineering interest. This report describes a seismic-waveform dataset collected from 17 October 1989 (291 UTC) to 14 March 1990 (073 UTC) with GEOS digital seismographs deployed from USGS offices in Menlo Park, California. It is a summary of field and data-playback information that is intended to facilitate use of the waveform data in seismologic and engineering studies. It includes station locations, instrumentation histories (trigger parameters, sensor parameters, clock corrections, etc.), listings of waveform records, preliminary seismicity listings, and information about data availability. Our principal research goal is to understand the influence of seismic-source and wave-propagation phenomena on damaging ground motions, and to use this knowledge to predict hazards from future earthquakes. Source processes encompass the spatial and temporal variations in the excitation of seismic waves at the fault. Wave-propagation processes include amplification and deamplification as seismic energy radiates away from the fault through rocks and soils of variable seismic properties. Since shallow geology at a site (upper tens to hundreds of meters) can exert a relatively great influence on damaging ground motions, it is useful to separate wave-propagation phenomena into whole-path and site parts. In studying these phenomena, aftershock waveform recordings can play an important role. Compared to main shocks, aftershocks are simple earthquakes and aftershock records tend to be relatively dominated by wave-propagation effects. Geometrically, since aftershocks are distributed over the fault zone, aftershock records should resemble part of the main-shock ground motion contributed by localized rupture. This observation forms the basis of the empirical-Green's-function method wherein main-shock ground motion is modeled by summing aftershock records. The Loma Prieta earthquake provided a rare opportunity that motivated the intensive aftershock-recording effort described in this report. In a seismically noisy urban environment like the San Francisco Bay area, such a large set of high quality seismic data would otherwise be unobtainable.

California↗
USGS2012

Flood-inundation maps for the Leaf River at Hattiesburg, Mississippi

Digital flood-inundation maps for a 1.7-mile reach of the Leaf River were developed by the U.S. Geological Survey (USGS) in cooperation with the City of Hattiesburg, City of Petal, Forrest County, Mississippi Emergency Management Agency, Mississippi Department of Homeland Security, and the Emergency Management District. The Leaf River study reach extends from just upstream of the U.S. Highway 11 crossing to just downstream of East Hardy/South Main Street and separates the cities of Hattiesburg and Petal, Mississippi. The inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/ , depict estimates of the areal extent of flooding corresponding to selected water-surface elevations (stages) at the USGS streamgage at Leaf River at Hattiesburg, Mississippi (02473000). Current conditions at the USGS streamgage may be obtained through the National Water Information System Web site at http://waterdata.usgs.gov/ms/nwis/uv/?site_no=02473000&PARAmeter_cd=00065,00060 . In addition, the information has been provided to the National Weather Service (NWS) for incorporation into their Advanced Hydrologic Prediction Service (AHPS) flood-warning system ( http://water.weather.gov/ahps/ ). The NWS forecasts flood hydrographs at many places that are often collocated at USGS streamgages. The forecasted peak-stage information, available on the AHPS Web site, may be used in conjunction with the maps developed in this study to show predicted areas of flood inundation. In this study, flood profiles were computed for the stream reach by means of a one-dimensional step-backwater model. The model was calibrated using the most current stage-discharge relations at the Leaf River at Hattiesburg, Mississippi, streamgage and documented high-water marks from recent and historical floods. The hydraulic model was then used to determine 13 water-surface profiles for flood stages at 1.0-foot intervals referenced to the streamgage datum and ranging from bankfull to approximately the highest recorded water-surface elevation at the streamgage. The simulated water-surface profiles were then combined with a geographic information system digital elevation model [derived from Light Detection and Ranging (LiDAR) data having a 0.6-foot vertical accuracy and 9.84-foot horizontal resolution] in order to delineate the area flooded at each 1-foot increment of stream stage. The availability of these maps, when combined with real-time stage information from USGS streamgages and forecasted stream stage from the NWS, provides emergency management personnel and residents with critical information during flood-response activities, such as evacuations and road closures, as well as for post-flood recovery efforts.

Mississippi↗
USGS2025

Grammar to graph—An approach for semantic transformation of annotations to triples

Data annotation is the process of labeling data to show the outcome that a related data model should predict. In this study, annotation data were transformed into semantic graph triples, mainly for use with the Resource Description Framework (RDF), a type of entity-relationship-attribute data model for graph databases. The transformation of annotation data to semantic graph triples provides complex linguistic meaning with data handling advantages such as reduced data storage needs, improved logical specification of relations between objects, and reusable classes and properties that support logic and inference. A grammar-based framework in graph form supports user questions and queries. The words defining approximately 334 topographic feature types compiled by the U.S. Geological Survey were tokenized as units of analysis and grouped by part of speech. Their dependency relations were identified for this study using natural language processing libraries. Dependency concepts are used as structured semantic relations among part-of-speech classes. Tokens, units equivalent to words, form instances of classes and were quantified within a tabular output format using PostgreSQL data storage software. Table data were logically aligned as triples following a mapping file and stored with an ontology file using Ontop virtual triplestore software. A grammar ontology schema for the data was synchronized to match queries whose results validated the graph’s structure. The text analysis produced 8 part-of-speech classes of content words for object representations and 4 classes of function words for operational applications. Dependency relations formed 27 ontology properties for topographic subgraph structures. Token occurrences shaped overall ontology salience and formed a lexicon of syntactic terms for subgraph objects and properties. The schema ontology of class and property population shapes formed the lexicon of English terms. SPARQL Protocol and RDF Query Language (SPARQL) was used with the lexicon to conform data to RDF guidelines. This study confirms the hypothesis that although linguistic logic varies from description logic, its approximation applies to ontology design. Property and query use case patterns extracted from the analysis support queries concerning complex topographic relations and patterns normally embedded within text definitions. The method used in this study could be applied to text forms in other domains, such as survey notes.

Scientific Investigations Report↗
USGS2020

Quantification of trace element loading in the upper Tenmile Creek drainage basin near Rimini, Montana, September 2011

The principle sources of trace elements entering upper Tenmile Creek, Montana, during September 2011, four trace metals and the metalloid arsenic, were identified and quantified by combining and analyzing streamflow data determined from tracer injection with trace-element concentrations and related water-quality data determined from synoptic sampling. The study reach was along upper Tenmile Creek, beginning downstream from the city of Helena’s diversion and extending 5,020 feet downstream. Results from the 2011 study, completed by the U.S. Geological Survey in cooperation with the Montana Department of Environmental Quality, were compared to results from a similar study conducted in 1998 to assess the effectiveness of mine reclamation and remediation work to reduce trace-element loading to upper Tenmile Creek, which has been ongoing throughout the drainage basin. Main-stem concentrations of most trace elements analyzed were generally greater in 1998 than in 2011. However, the State of Montana human-health criteria for total-recoverable cadmium and arsenic were exceeded in parts of upper Tenmile Creek, and concentrations of cadmium and zinc exceeded the acute aquatic-life criteria at all main-stem sites during both studies. Total-recoverable copper concentrations observed in 2011 exceeded the chronic aquatic-life criterion upstream from the Lee Mountain adit, whereas, in 1998, all sites exceeded the acute aquatic-life criteria. Direct comparison of loads from the 1998 and 2011 tracer studies were complicated by the differences in hydrologic conditions. Streamflow in 1998 was about 10 percent of the 2011 streamflow. The Lee Mountain Mine and Susie Lode adit were identified as major contributors of trace elements to upper Tenmile Creek in both studies. However, trace-element loading from the Lee Mountain Mine area was substantially reduced between 1998 and 2011. Total-recoverable loads of all trace elements showed substantial loss in 1998 but increased in 2011 downstream from the Susie Lode adit to the end of the study reach. This reach was one of the primary sources of trace-element loading to upper Tenmile Creek in 2011. This difference indicated that the streambed may act as a sink or a source for trace elements, depending on hydrologic conditions.

Montana↗
USGS2026

Characterizing precariously balanced rocks (PBRs) in the eastern United States for estimating maximum past earthquake ground motions

Fragile geologic features (FGFs) can be used to estimate an upper bound to the strength of earthquake ground shaking in the past thousands to tens of thousands of years. FGFs could be especially useful in the eastern United States, where few active faults are available for paleoseismic studies and where low seismic attenuation means that an earthquake could damage FGFs at large distances. This article describes a pilot study of one form of FGF, precariously balanced rocks (PBRs), in the Blue Ridge of Virginia, ∼160 km from the central Virginia seismic zone (CVSZ) and ∼100 km from Virginia’s Giles County seismic zone (GCSZ). The main goal is to develop and refine methods for studying PBRs in the eastern United States. Photogrammetric 3D models of the rocks were used to locate their centers of mass and delineate their basal contacts, with the latter corroborated by wrapping a wire around the bases to verify the circumferences. Relations between hill geometry and amplification were used to estimate topographic amplification. Seismometers on the PBRs provided the frequencies, amplitudes, and directions of rocking after giving the rocks gentle pushes. The levels of ground shaking likely to topple the rocks were compared with the median hazard curves from the U.S. Geological Survey’s National Seismic Hazard Model and were used to map magnitudes of earthquakes in the nearby region likely to topple the rocks. Results indicate that an M w ≥ 7.5 earthquake is needed in the CVSZ or near the 2020 Sparta, North Carolina, earthquake to topple the two most fragile PBRs and that an earthquake of ~ M w 7–7.5 in the GCSZ is needed. The fragilities and estimated ages of the PBRs (20–40 ka) are thus consistent with the absence of such events in the historical record in the nearby region.

eastern United States↗
USGS2002

A three-dimensional numerical model of predevelopment conditions in the Death Valley regional ground-water flow system, Nevada and California

In the early 1990's, two numerical models of the Death Valley regional ground-water flow system were developed by the U.S. Department of Energy. In general, the two models were based on the same basic hydrogeologic data set. In 1998, the U.S. Department of Energy requested that the U.S. Geological Survey develop and maintain a ground-water flow model of the Death Valley region in support of U.S. Department of Energy programs at the Nevada Test Site. The purpose of developing this 'second-generation' regional model was to enhance the knowledge an understanding of the ground-water flow system as new information and tools are developed. The U.S. Geological Survey also was encouraged by the U.S. Department of Energy to cooperate to the fullest extent with other Federal, State, and local entities in the region to take advantage of the benefits of their knowledge and expertise. The short-term objective of the Death Valley regional ground-water flow system project was to develop a steady-state representation of the predevelopment conditions of the ground-water flow system utilizing the two geologic interpretations used to develop the previous numerical models. The long-term objective of this project was to construct and calibrate a transient model that simulates the ground-water conditions of the study area over the historical record that utilizes a newly interpreted hydrogeologic conceptual model. This report describes the result of the predevelopment steady-state model construction and calibration. The Death Valley regional ground-water flow system is situated within the southern Great Basin, a subprovince of the Basin and Range physiographic province, bounded by latitudes 35 degrees north and 38 degrees 15 minutes north and by longitudes 115 and 118 degrees west. Hydrology in the region is a result of both the arid climatic conditions and the complex geology. Ground-water flow generally can be described as dominated by interbasinal flow and may be conceptualized as having two main components: a series of relatively shallow and localized flow paths that are superimposed on deeper regional flow paths. A significant component of the regional ground-water flow is through a thick Paleozoic carbonate rock sequence. Throughout the flow system, ground water flows through zones of high transmissivity that have resulted from regional faulting and fracturing. The conceptual model of the Death Valley regional ground-water flow system used for this study is adapted from the two previous ground-water modeling studies. The three-dimensional digital hydrogeologic framework model developed for the region also contains elements of both of the hydrogeologic framework models used in the previous investigations. As dictated by project scope, very little reinterpretation and refinement were made where these two framework models disagree; therefore, limitations in the hydrogeologic representation of the flow system exist. Despite limitations, the framework model provides the best representation to date of the hydrogeologic units and structures that control regional ground-water flow and serves as an important information source used to construct and calibrate the predevelopment, steady-state flow model. In addition to the hydrogeologic framework, a complex array of mechanisms accounts for flow into, through, and out of the regional ground-water flow system. Natural discharges from the regional ground-water flow system occur by evapotranspiration, springs, and subsurface outflow. In this study, evapotranspiration rates were adapted from a related investigation that developed maps of evapotranspiration areas and computed rates from micrometeorological data collected within the local area over a multiyear period. In some cases, historical spring flow records were used to derive ground-water discharge rates for isolated regional springs. For this investigation, a process-based, numerical model was developed to estimat

Water-Resources Investigations Report↗
USGS1983

Petroleum and mineral resources of Antarctica

No known petroleum or mineral resources occur in Antarctica. The data on these subjects have been collected, mainly since the IGY (International Geophysical Year), 1957-58, as a part of other research carried out by geologists and geophysicists from a number of countries. Specific resource-related studies have not been made. Wright and Williams (1974) summarized what was known of Antarctic mineral resources a decade ago. The U.S. Geological Survey has been actively pursuing various investigations in Antarctica since 194 7. In the course of this work and that of our colleagues elsewhere in the United States and in other countries, much information relevant to petroleum and mineral resources has been obtained. Since 1976, modern state-of-the-art multichannel seismic reflection and aeromagnetic surveys by several countries over the continental margin of Antarctica have indicated thick sedimentary basins. However, no offshore drilling beneath the continental shelf has taken place since the DSDP (Deep Sea Drilling Project) holes in the Ross Sea in 1973. Geologic field investigations begun at the turn of the twentieth century have been intensified in the past two decades; most rock outcrops have been visited and samples collected. Technology to exploit resources, particularly in the Arctic, has been developing at a rapid rate, and much of it could be applied to Antarctica. As a result of the petroleum price increases of the past decade, the attention of a number of countries has turned to Antarctica, but under the policy of "voluntary restraint" adopted by the Antarctic Treaty nations, no active petroleum or mineral exploration is taking place. The Antarctic treaty countries are in the process of negotiating an Antarctic mineral resources regime that is anticipated to be completed within the next several years. Therefore it seemed timely to us to readdress the question of petroleum and mineral resources. These reports review and summarize the available information. The first report summarizes the information relevant to petroleum resources. Although uneconomic at present, petroleum is generally considered more likely to be exploited (if supergiant fields were ever found) in the next few decades than hard minerals. The second report reviews the reported occurrences of minerals in Antarctica and discusses their significance. The final report discusses the Dufek layered mafic intrusion, second only to the Bushveld Complex in size in the world; the Dufek intrusion might be considered as a potential target for mineral exploration.

Circular↗
USGS2003

Changes in nutrient and pesticide concentrations in urban and agricultural areas of the South Platte River Basin, Colorado, Wyoming, and Nebraska, 1994–2000

As part of the National Water-Quality Assessment (NAWQA) Program, the U.S. Geological Survey (USGS) monitored two sites on the main-stem South Platte River? an urban site in Denver and a mixed urban/agricultural site near Kersey?to determine changes in nutrient and pesticide concentrations from 1994 through 2000. Concentrations of nitrate, nitrite, ammonia, and orthophosphorus decreased at the Denver site during the study period, likely due to an increase in instream dilution of wastewater-treatment plant (WWTP) discharge and upgrades at the WWTPs. In contrast, only concentrations of orthophosphorus decreased at the Kersey site; agricultural inputs between Denver and Kersey may have offset the observed decreases in other nutrients upstream. During the extreme low-flow conditions in 1994, when there was relatively little snowmelt to dilute instream pesticide concentrations, total median pesticide concentrations at both sites were the highest of the study period. During the less extreme conditions in 1997 through 2000, greater amounts of snowmelt likely led to lower total median pesticide concentrations at both sites. Because pesticide-use data are not available, the contribution of changes in the amount and type of pesticides applied on the land to changes in the concentration of pesticides in the river is not known but likely was substantial. In general, insecticides predominated at the Denver site, whereas herbicides predominated at the Kersey site.

Colorado, Nebraska, Wyoming↗