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A gravity survey was made of an area in the Wallace 2° quadrangle, Montana and Idaho (fig. 1), to provide information on structural relationships and subsurface geology as part of regional geophysical studies in northwestern Montana.
Two bituminous coal zones, the San Pedro and the Santo Tomas, in the middle Eocene Claiborne Group of Webb County, south Texas (Figure 1), are among the coal resources that are not evaluated quantitatively as part of the current Gulf Coastal Plain coal resource assessment. Coal beds within these zones were mined by underground methods northwest of Laredo until 1939 and have been intermittently mined at the surface since 1979. These coals have long been regarded as unique within the Gulf Coast Tertiary coal-bearing section because they are high-volatile C bituminous in rank and because their physical characteristics resemble upper Carboniferous cannel coals of the Appalachians and Europe. Discontinuous exposures of the Santo Tomas and the underlying San Pedro coal zone extend northwestward from Dolores for approximately 15 to 21 mi along the breaks of the Rio Grande and its tributaries in Webb County (Figure 1). This part of south Texas lies along the southwestern flank of the Rio Grande Embayment, which extends south and southeastwardly through the Mexican States of Coahuila, Nuevo León, and Tamaulipas (Figure 1). Within the embayment, the lower to middle part of the Claiborne Group consists of marine mudstones (Reklaw Formation) in the east and northeast and sandstones and mudstones (Bigford Formation) in the south and southwest (Figure 2). The marine mudstones coarsen upward into fluvial-deltaic sandstones (Queen City Sand) that prograded gulfward across eastern and central Texas (Guevara and Garcia, 1972). To the west and southwest, the interval overlying the Bigford Formation becomes less sandy, and claystones (El Pico Clay) predominate. Although the San Pedro coal zone has been placed traditionally near the top of the Bigford Formation and the Santo Tomas coal zone near the base of the El Pico Clay, recent work has failed to validate a mappable contact between these formations (Warwick and Hook, 1995). The coal beds dip northeast at less than 2 degrees towards the synclinal axis of the basin. The following summary is based upon published and unpublished reports; drillhole records (geophysical logs, descriptions of cores and cuttings); coal-quality data obtained from the permit files of the Railroad Commission of Texas and recent sampling by the U.S. Geological Survey (USGS); a preliminary review of proprietary data acquired recently by the USGS; and field work conducted by the USGS since 1994. A total of approximately 200 drillhole records was examined.
Lithium is classified as a U.S. critical mineral commodity, and its demand is projected to drastically increase through 2040, driven by electric vehicle production and energy storage applications (IEA 2021).Most global lithium production is not in the United States increasing vulnerability to a supply disruption. The U.S. Geological Survey is actively assessing domestic lithium deposits including lithium-bearing pegmatites in the Appalachian orogen. Permissive tracts for lithium pegmatite deposits were delineated by integrating lithological, tectonic, geochemical, geophysical, and mineral occurrence data. The geospatial data and permissive tracts were used to estimate the number of undiscovered lithium pegmatite deposits. Estimates were then integrated into probabilistic simulations along with a new global lithium pegmatite grade and tonnage dataset to quantify potential contained undiscovered lithium resources. An economic filter was used to estimate the amount of potentially recoverable undiscovered resources. Preliminary computations for the northern Appalachians, including application of the economic filter to the median recoverable contained resource, yields 900,000 metric tons of Li 2 O that correspond to enough Li 2 O to replace 127 years of import reliance at the current rate (7,100 t Li 2 O/yr; USGS, 2025). For the southern Appalachians, preliminary computations yielded 1,430,000 metric tons of Li 2 O, which corresponds to 201 years of import reliance.
The Umm ar Rummf copper prospect, located about 30 km east of Al Qunfudhah, Kingdom of Saudi Arabia, consists of zones of malachite disseminations and fracture fillings in outcrops of north-trending impure quartzite of the Bahah group. Systematic Crone electromagnetic and self-potential surveys indicate that weakly conductive tabular bodies having a weak to moderate self-potential effect extend downdip from two discontinuously exposed, parallel ridges of mineralized quartzite. Crone electromagnetic data were quantitatively interpreted using characteristic parameter lines adapted for use at 1830 and 5010 Hz, the frequencies employed at Umm ar Rummf. Depths to the top of the conductors were computed to be from 20 to 40 m or about the thickness of the oxidized zone, which behaves as a variably conductive overburden. Both tabular conductors can also be traced geophysically to the north and south of the copper-bearing outcrops. The association of the geophysical anomalies with copper-mineralized rocks has been proved by drilling. Reconnaissance MAXMIN electromagnetic profiles across the target using a wide coil separation show broad, low-amplitude anomalies that may indicate mineralized rocks at depth, and reconnaissance ground-magnetic profiles show strong total-field intensity anomalies associated with basaltic dikes of probable Tertiary age. In the central part of the area of investigation, these dikes produce large disturbances of the electrical fields.
A geochemical survey was conducted in the Mount Henry Roadless Area, Kootenai National Forest, Lincoln County, Mont. by the U.S. Geological Survey during the summer of 1981. The sampling and analytical programs were designed to locate mineralized zones in outcrops or in rocks buried at shallow depth. The geochemical results should be evaluated in context with geological and geophysical results. Possible types of mineralization, as judged from occurrences in nearby areas where the rocks are similar to those in the study area, include strata-bound copper-silver occurrences in rocks of the Ravalli Group, specifically the Burke and Revett Formations; the less probable lead-zinc massive sulfide deposits of the Sullivan-type in the pre-Ravalli (middle Prichard Formation); potential metal-enriched, sulfide vein systems; and gold-bearing veins or placer occurrences. All samples collected for this study are plotted on the map. Element symbols shown at sample sites indicate an anomalous concentration for that element at the site. Tables 1–3 list the values of selected elements determined to be critical for a mineral evaluation of this particular geologic setting. All analytical results, including those selected for this report, are given in a U.S. Geological Survey Open-File report (Siems and others, 1983).
This U.S. Geological Survey Open-File Report contains a listing of publications authored or co-authored by members of the Branch of Atlantic Marine Geology and published in calendar year 1992. The Branch conducts a broad geologic and geophysical research and mapping program, primarily along the U.S. Atlantic Margin, in the Great Lakes, the Gulf of Mexico, the Caribbean and polar regions. A long range objective of this program is to develop a comprehensive understanding of the geology of the continental margin and a predictive capability to guide and assess the consequences of its use. Headquarters of the Branch of Atlantic Marine Geology are located in Woods Hole, MA., and personnel are located in Woods Hole, MA., St Petersburg, FL., Reston, VA., Denver, CO., and San Juan, Puerto Rico. A brochure describing the Branch of Atlantic Marine Geology may be obtained by writing to Chief, Branch of Atlantic Marine Geology, Quissett Campus, Woods Hole, MA 02543. Results of Branch investigations are distributed in a variety of ways, including maps, journal articles, abstracts and U.S.G.S. publications. Copies of U.S.G.S. Open File Reports may be obtained from the author. Book publications can be obtained from U.S. Geological Survey, Books and Reports Sales, Federal Center, Box 25425, Denver, CO 80225. Copies of U.S.G.S. Maps may be obtained from the U.S. Geological Survey, Map Sales, Federal Center, Box 25286, Denver, CO 80225.
The paper entitled “An investigation of the flow‐duration characteristics of North Carolina streams,” by Thorndlke Saville and John Dargan Watson, which was published by the American Geophysical Union in its report of the Fourteenth Annual Meeting in 1933 (pp. 406–425), stimulated the writer, who is familiar with the streams discussed, having been assigned for several years to the United States Geological Survey offices that collected the base data. Knowing that there is a marked similarity in runoff‐characteristics of the western North Carolina streams and also that fairly good similarity is shown by New England streams within reasonable zones, he felt it would be desirable to carry the investigation to a part of the country where stream‐flow characteristics are diverse. The present investigation was therefore made to cover all the long‐time records in Illinois on streams of definite drainage‐area, particular attention being paid to comparisons of records from the same stream. The record on the Rock River at Afton, Wisconsin, was also included. The streams studied are listed in Table 1.
Recent investigations of the Talkeetna Mountains in south-central Alaska were undertaken to study the region's framework geophysics and to reinterpret structures and crustal composition. Potential field (gravity and magnetic) and magnetotelluric (MT) data were collected along northwest-trending profiles as part of the U.S. Geological Survey's Talkeetna Mountains transect project. The Talkeetna Mountains transect area comprises eight 1:63,360 quadrangles (∼9500 km 2 ) in the Healy and Talkeetna Mountains 1° × 3° sheets that span four major lithostratigraphic terranes ( Glen et al., this volume ) including the Wrangellia and Peninsular terranes and two Mesozoic overlap assemblages inboard (northwest) of Wrangellia. These data were used here to develop 2½-dimensional models for the three profiles.
The Great Valley fault system defines the tectonic boundary between the Coast Ranges and the Central Valley in California, is active throughout the Quaternary, and has been the source of several significant ( M > 6) historic earthquakes, including the 1983 M 6.5 Coalinga earthquake and the 1892 Vacaville–Winters earthquake sequence. However, the locations and geometries of individual faults in the Great Valley fault system are poorly constrained, and fault slip rates and paleoearthquake chronology are largely unknown. Here, we report geomorphic and subsurface geophysical evidence of surface‐deforming displacement on a strand of the Great Valley fault system west of Winters, California. Detailed geomorphic mapping and a high‐resolution seismic reflection and tomography survey along an ∼800 m profile across the Bigelow Hills document a fault, which we call the West Winters strand of the Great Valley fault system, with apparent east side‐up displacement of surficial geologic units. These data together suggest that the West Winters strand is active in the latest Quaternary. Together with local reports from the time, this raises the possibility that the West Winters strand may have ruptured and deformed the surface during the 1892 M 6 Vacaville–Winters earthquake sequence. Future earthquakes with vertical displacement on this and Great Valley fault system structures could have significant hazard implications, given the region’s low relief and the presence of major water conveyance infrastructure.
No abstract available.
This report summarizes geophysical investigations in the Amargosa Desert and surrounding areas conducted between 1997 and 2000 in support of the Death Valley Regional Water-Flow Modeling Project of the U.S. Geological Survey. These investigations used both gravity and aeromagnetic data to develop a regional-scale tectonic and lithologic model for the near-surface. Gravity data were inverted in order to estimate the depth to pre-Cenozoic basement throughout the study area. This basement surface is interpreted to be the contact between pre-Cenozoic carbonate rocks and overlying alluvium, an important component of water-flow models. Gravity data also were used to identify locations where basement rocks are anomalously dense, possibly indicating areas resistant to water flow. A new aeromagnetic survey of the central part of the study area was used to map concealed faults and areas underlain by volcanic rocks.
The U.S. Geological Survey (USGS) National Crustal Model (NCM) is being developed to assist in the modeling of seismic hazards across the conterminous United States. The NCM is composed of a grid of geophysical profiles, extending from the Earth’s surface into the upper mantle. It is constructed from a 3D geologic framework and geophysical rules defined by: (1) a petrologic and mineral physics database; (2) a 3D temperature model; and (3) a calibrated rock type- and age-dependent porosity model. Parameters needed to estimate site response for existing ground motion models (GMMs), including the time-averaged velocity in the upper 30 meters ( V S 30 ) and the depths to 1.0 and 2.5 km/s shear-wave velocity ( Z 1.0 and Z 2.5 ), can be extracted from the NCM. As GMMs develop, other metrics could also be extracted or derived from the NCM such as sediment thickness and travel times, fundamental frequency, a fully frequency-dependent site response function, or 3D geophysical volumes for wavefield simulations. Application of the NCM may also benefit other aspects of seismic hazard analysis including better accounting for path-dependent attenuation and geometric spreading, more accurate estimation of earthquake source properties such as hypocentral location and stress drop, and calculation of crustal strength profiles that inform estimates of the base of seismicity.
Several aeromagnetic dipolar anomalies occur over flat, alluvial areas near Yucca Mountain that resemble anomalies typically associated with subaerial basaltic volcanic centers. Detailed gravity and ground magnetic data were collected along a surveyed traverse across an aeromagnetic anomaly in Amargosa Valley, south of Yucca Mountain, Nevada. Modeling of the ground magnetic data collected over the largest of these anomalies, the Lathrop Wells aeromagnetic anomaly, indicates that the top of the causative body, most likely basalt, is less than 250 m below the surface. Gravity data indicate an apparent lack of an associated gravity anomaly and suggest that either the causative body may be tuff rather than basalt, or the volume of the body is small. Both drilling and collection of more magnetic and gravity data are necessary because ages and volumes of buried volcanic centers are important constraints for estimating the probability of potential volcanism near the proposed nuclear waste repository at Yucca Mountain.
Geophysical investigations of Mountain Pass and vicinity were begun as part of an effort to study regional crustal structures as an aid to understanding the geologic framework and mineral resources of the eastern Mojave Desert. The study area encompasses Mountain Pass, host to one of the world’s largest rare earth element carbonatite deposits. The deposit is found along a north-northwest-trending, fault-bounded block that extends along the eastern parts of the Clark Mountain Range, Mescal Range, and Ivanpah Mountains. This Paleoproterozoic block is composed of a 1.7-Ga metamorphic complex of gneiss and schist that underwent widespread metamorphism and associated plutonism during the Ivanpah orogeny. The Paleoproterozoic rocks were intruded by a Mesoproterozoic (1.4 Ga) ultrapotassic alkaline intrusive suite and carbonatite body. The intrusive rocks include, from oldest to youngest, shonkinite, mesosyenite, syenite, quartz syenite, potassic granite, carbonatite, carbonatite dikes, and late shonkinite dikes. The diverse physical properties of rocks that underlie the study area are well suited to geophysical investigations. Contrasts in radiogenic signatures between Paleoproterozoic crystalline basement, rocks of the Mesoproterozoic carbonatite body and the associated alkaline intrusive suite, Paleozoic carbonate rocks, Mesozoic granitoids, Tertiary volcanic rocks, and unconsolidated alluvium, for example, produce a distinctive pattern of radiometric anomalies that can aid in understanding the geologic framework and mineral resource potential of the eastern Mojave Desert. A high-resolution radiometric survey of Mountain Pass was flown by helicopter over parts of the Clark Mountain Range, Mescal Range, and Ivanpah Mountains. Aeroradiometric surveys measure the intensity and energy spectrum of gamma-ray radiation from the three most common naturally occurring radioelements: potassium ( 40 K), thorium ( 232 Th), and uranium ( 238 U). For 232 Th and 238 U, the source of the gamma-rays comes from their thallium ( 208 Tl) and bismuth ( 214 Bi) decay products, respectively, and, thus, concentrations for Th and U are referred to as “equivalent concentration,” assuming radioactive equilibrium. The concentrations of these radioelements can be used together to estimate changes in geochemistry and lithology. Carbonatite deposits typically have distinctive geophysical signatures because they are relatively dense, magnetic, and radiogenic. Specifically, the carbonatite and alkaline intrusive suite at Mountain Pass is ultrapotassic and contains relatively significant amounts of K, Th, and U, which can be delineated using airborne radiometric surveys.
This U.S. Geological Survey Open-File Report [extract] contains a listing of publications authored or co-authored by members of the Branch of Atlantic Marine Geology and published in calendar year 1990. The Branch conducts a broad geologic and geophysical research and mapping program, primarily along the U.S. Atlantic Margin, in the Great Lakes, the Gulf of Mexico, the Caribbean and polar regions. A long range objective of this program is to develop a comprehensive understanding of the geology of the continental margin and a predictive capability to guide and assess the consequences of its use. Headquarters of the Branch of Atlantic Marine Geology are located in Woods Hole, MA., and personnel are located in Woods Hole, MA., St Petersburg, FL., Reston, VA., Denver, CO., and San Juan, Puerto Rico. A brochure describing the Branch of Atlantic Marine Geology may be obtained by writing to Chief, Branch of Atlantic Marine Geology, Quissett Campus, Woods Hole, MA 02543. Results of Branch investigations are distributed in a variety of ways, including maps, journal articles, abstracts and U.S.G.S. publications. Copies of U.S.G.S. Open File Reports may be obtained from the author. Book publications can be obtained from U.S. Geological Survey, Books and Reports Sales, Federal Center, Box 25425, Denver, CO 80225. Copies of U.S.G.S. Maps may be obtained from the U.S. Geological Survey, Map Sales, Federal Center, Box 25286, Denver, CO 80225.
This U.S. Geological Survey Open-File Report [extract] contains a listing of publications authored or co-authored by members of the Branch of Atlantic Marine Geology and published in calendar year 1993. The Branch conducts a broad geologic and geophysical research and mapping program, primarily along the U.S. Atlantic Margin, in the Great Lakes, the Gulf of Mexico, the Caribbean and polar regions. A long range objective of this program is to develop a comprehensive understanding of the geology of the continental margin and a predictive capability to guide and assess the consequences of its use. Headquarters of the Branch of Atlantic Marine Geology are located in Woods Hole, MA., and personnel are located in Woods Hole, MA., St Petersburg, FL., Reston, VA., Denver, CO., and San Juan, Puerto Rico. A brochure describing the Branch of Atlantic Marine Geology may be obtained by writing to Chief, Branch of Atlantic Marine Geology, Quissett Campus, Woods Hole, MA 02543. Results of Branch investigations are distributed in a variety of ways, including maps, journal articles, abstracts and U.S.G.S. publications. Copies of U.S.G.S. Open File Reports may be obtained from the author. Book publications can be obtained from U.S. Geological Survey, Books and Reports Sales, Federal Center, Box 25425, Denver, CO 80225. Copies of U.S.G.S. Maps may be obtained from the U.S. Geological Survey, Map Sales, Federal Center, Box 25286, Denver, CO 80225.
By virtue of the Geothermal Steam Act of 1970, the U.S. Geological Survey is required to appraise geothermal resources of the United States prior to competitive lease sales. This appraisal involves coordinated input from a variety of disciplines, starting with reconnaissance geology and geophysics. This paper describes how the results of several geophysical methods used in KGRA evaluation were interpreted by the authors, two geophysicists, involved with both the Evaluation Committee and the research program responsible for obtaining and interpreting the geophysical data to be used by the committee. ?? 1979.
As part of a continuing program by the U.S. Geological Survey to collect and chemically analyze representative samples of U.S. coals, 45 coal samples were collected from the Upper Cretaceous Mesaverde Formation, Grand Mesa coal field, Delta and Mesa Counties, Colorado. These samples were collected from cores (30 samples, 11 locations), mines (11 face channel samples, 9 locations), and from drill cuttings (4 samples, 1 location). U.S. Geological Survey sample numbers, index map locations, coal thickness or depth interval sampled, and brief descriptions for the 45 samples are listed in table 1. Sampling locations are shown in figure 1. Geophysical logs for all samples summarized in this report can be found in Eager (1978,1979).