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At least 1,243 records · Page 69Linked to original sources

USGS1975

Building stones of our Nation's Capital

The buildings of our Nation's Capital serve as an unusual geologic display, for the city has been constructed with rocks from quarries throughout the United States and many distant lands. Each building is a unique museum that not only displays the important features of various stones and the geologic environment in which they were formed, but also serves as an historic witness to the city's growth and to the development of its architecture. This booklet describes the source and appearance of the stones used in Washington, D.C.; it includes a map and a walking guide to assist the visitor in examining them.

General Information Product↗

USGS2018

Quartz-pebble-conglomerate gold deposits

Quartz-pebble-conglomerate gold deposits represent the largest repository of gold on Earth, largely due to the deposits of the Witwatersrand Basin, which account for nearly 40 percent of the total gold produced throughout Earth’s history. This deposit type has had a controversial history in regards to genetic models. However, most researchers conclude that they are paleoplacer deposits that have been modified by metamorphism and hydrothermal fluid flow subsequent to initial sedimentation. The deposits are found exclusively within fault-bounded depositional basins. The periphery of these basins commonly consists of granite-greenstone terranes, classic hosts for lode gold that source the detrital material infilling the basin. The gold reefs are typically located along unconformities or, less commonly, at the top of sedimentary beds. Large quartz pebbles and heavy-mineral concentrates are found associated with the gold. Deposits that formed prior to the Great Oxidation Event (circa 2.4 giga-annum [Ga]) contain pyrite, whereas younger deposits contain iron oxides. Uranium minerals and hydrocarbons are also notable features of some deposits. Much of the gold in these types of deposits forms crystalline features that are the product of local remobilization. However, some gold grains preserve textures that are undoubtedly of detrital origin. Other heavy minerals, such as pyrite, contain growth banding that is truncated along broken margins, which indicates that they were transported into place as opposed to forming by in situ growth in a hydrothermal setting. The ore tailings associated with these deposits commonly contain uranium-rich minerals and sulfides. Oxidation of the sulfides releases sulfuric acid and mobilizes various metals into the environment. The neutralizing potential of the tailings is minimal, since carbonate minerals are rare. The continuity of the tabular ore bodies, such as those of the Witwatersrand Basin, has allowed these mines to be the deepest in the world. The extreme depths create engineering complications and safety issues for the miners, such as rock bursts as a result of pressure release. The richness of these deposits makes them a desirable exploration target. However, the likelihood of future discoveries is minimal. Small deposits found in the United States include those found at Nemo in the Black Hills of South Dakota and Deep Lake in the Sierra Madre of Wyoming.

Scientific Investigations Report↗

USGS2015

Lithology, hydrologic characteristics, and water quality of the Arkansas River Valley alluvial aquifer in the vicinity of Van Buren, Arkansas

A study to assess the potential of the Arkansas River Valley alluvial aquifer in the vicinity of Van Buren, Arkansas, as a viable source of public-supply water was conducted by the U.S. Geological Survey in cooperation with the Little Rock, District, U.S. Army Corps of Engineers. An important study component was to identify possible changes in hydrologic conditions following installation of James W. Trimble Lock and Dam 13 (December 1969) on the Arkansas River near the study area. Data were gathered for the study in regard to the lithology, hydrologic characteristics, and water quality of the aquifer. Lithologic information was obtained from drillers’ logs of wells drilled from 1957 through 1959. Water-quality samples were collected from 10 irrigation wells and analyzed for inorganic constituents and pesticides. To evaluate the potential viability of the alluvial aquifer in the Van Buren area, these data were compared to similar stratigraphic, lithologic, and groundwater-quality data from the Arkansas River Valley alluvial aquifer at Dardanelle, Ark., where the aquifer provides a proven, productive, sole-source of public-supply water. Drillers’ logs for 59 wells in the Van Buren study area revealed well depths ranging from 25 to 52 feet (ft), with a mean depth of 42 ft. The thickness of the lower sand/gravel interval serving as the water-producing zone ranged from 5 to 47 ft, with a mean thickness of 29 ft. The presence of gravel was noted in only 4 of 59 well logs available for review from the study area. Percent sand was calculated from well logs in the study area, and these sand percentages were overlain onto an orthophotograph map to examine the areal distribution of sand percentage in relation to geomorphologic features of the flood plain in the study area. The logs denoting the greatest percent sand tend to occur in areas near to the river and on the concave (point bar) side of abandoned channels, while the lower percent sand tends to occur on the convex (channel fill and backswamp deposits) side of the abandoned channels. Comparison of hydrographs from water levels collected between 1957 and 1972 to cumulative departure from mean monthly and mean annual precipitation showed overall good fit and explained the long-term decreasing water levels from the earliest period of record through October 1967, followed by a sharp rise in water levels concurrent with rises in cumulative departure from mean monthly and mean annual precipitation. Hydrographs for four wells ranging from 0.8 to 4.5 miles upstream from the dam and potentially affected by rising river stage were compared to graphs of river stage and cumulative departure from mean monthly precipitation. Water levels for these wells showed minimal discernible effect by rising river stage following dam completion. Periods of increased precipitation compared closely to increases in water level for all hydrographs, regardless of river stage, and periods of no precipitation resulted in declining water levels, although river stage continued to slowly rise during these same periods. The Arkansas River has greater salinity than local groundwater, providing a quantitative tracer for any groundwater recharge originating from the river. Comparison of predam and postdam groundwater-chloride concentrations showed no increase in chloride concentrations after dam installation, which is consistent with hydrologic data. These data suggest that the dominant source of groundwater recharge in the Arkansas River Valley alluvial aquifer is infiltration of precipitation through proximal, coarse channel deposits, with minimal influx of river water. Groundwater-quality data collected from 10 wells in the study area indicated a calcium-bicarbonate water type. No primary drinking-water standards were exceeded for any constituents, and iron and manganese were the only constituents exceeding secondary drinking-water regulations. Six of the 10 well-water samples were analyzed for the presence of pesticides, as row-crop agriculture is the dominant land use in the study area. Six herbicide compounds and one herbicide metabolite were detected at concentrations substantially below those of the Federal primary drinking-water standards and health advisories. The hydrologic and geochemical data gathered for this study provide a qualitative assessment of the potential of the Arkansas River Valley alluvial aquifer as a source of public water supply in the Van Buren area. Results indicate minimal influx of water from the Arkansas River, and recharge to the aquifer appears to be dominantly by infiltration of precipitation through overlying alluvium. If vertical wells are used as a source of public water supply, then several wells will have to be used in combination at relatively low pumping rates and placed in areas with a greater percent sand. Use of a horizontal well configuration near the river to increase production may depend on infiltration of river water to supplement water removed from storage, especially where areas of lower permeability sediments might be encountered within the surrounding alluvium. If a poor hydraulic connection exists between the river and the alluvium, as indicated by this study, then production will depend on ample precipitation and recharge throughout the year and groundwater storage sufficient to prevent declining water levels where pumping rates exceed recharge.

Arkansas↗

USGS1983

Mineral resource potential map of the Raywood Flat Roadless Areas, Riverside and San Bernardino counties, California

Geologic, geochemical, and geophysical studies within the Raywood "Flat Roadless Areas, together with an investigation of mines and prospects within the further planning area, resulted in (1) identification of nonmetallic mineral resources at a marble mine in the further planning area and (2) recognition of a small area in the recommended wilderness that has moderate potential for base-metal resources. Except for these two areas of identified and suspected resources, we did not observe indications of resource potential elsewhere in the Raywood Flat Roadless Areas. The area having nonmetallic mineral resources is in the vicinity of the Mill Creek mine near the northeastern boundary of the further planning area (B5-187); there, we identified marginal reserves of marble suitable for the production of lime and construction stone. The reserves are marginal because of their remote location and poor accessibility. Geologic mapping did not reveal any additional marble occurrences within the study area. The area having moderate potential for base-metal resources forms a small zone in the eastern part of the recommended wilderness (A5-187). Within this zone, evidence provided by stream-sediment geochemistry suggests that crystalline bedrocks in several drainages contain concentrations of metallic elements. Because the terrain is inaccessible and covered with dense brush, most of the bedrock in the specific drainages containing the geochemical anomalies could not be examined. Thus, although we infer that mineral occurrences exist in the drainage basins, we have little data on which to base an estimate of their extent and quality. Locally, the crystalline rocks probably contain hydrothermal veins or disseminated occurrences where lead, copper, molybdenum, tin, cobalt, bismuth, and arsenic have been concentrated. However, the geochemical anomalies for these metals are small, and the stream drainages also are relatively small. Therefore, the inferred occurrences of metallic minerals probably are small scale, scattered, and low grade. There is only low probability that the inferred mineral occurrences are large scale.

California↗

USGS1975

Geochemical Exploration Techniques Applicable in the Search for Copper Deposits

Geochemical exploration is an important part of copper-resource evaluation. A large number of geochemical exploration techniques, both proved and untried, are available to the geochemist to use in the search for new copper deposits. Analyses of whole-rock samples have been used in both regional and local geochemical exploration surveys in the search for copper. Analyses of mineral separates, such as biotite, magnetite, and sulfides, have also been used. Analyses of soil samples are widely used in geochemical exploration, especially for localized surveys. It is important to distinguish between residual and transported soil types. Orientation studies should always be conducted prior to a geochemical investigation in a given area in order to determine the best soil horizon and the best size of soil material for sampling in that area. Silty frost boils, caliche, and desert varnish are specialized types of soil samples that might be useful sampling media. Soil gas is a new and potentially valuable geochemical sampling medium, especially in exploring for buried mineral deposits in arid regions. Gaseous products in samples of soil may be related to base-metal deposits and include mercury vapor, sulfur dioxide, hydrogen sulfide, carbon oxysulfide, carbon dioxide, hydrogen, oxygen, nitrogen, the noble gases, the halogens, and many hydrocarbon compounds. Transported materials that have been used in geochemical sampling programs include glacial float boulders, glacial till, esker gravels, stream sediments, stream-sediment concentrates, and lake sediments. Stream-sediment sampling is probably the most widely used and most successful geochemical exploration technique. Hydrogeochemical exploration programs have utilized hot- and cold-spring waters and their precipitates as well as waters from lakes, streams, and wells. Organic gel found in lakes and at stream mouths is an unproved sampling medium. Suspended material and dissolved gases in any type of water may also be useful media. Samples of ice and snow have been used for limited geochemical surveys. Both geobotanical and biogeochemical surveys have been successful in locating copper deposits in many parts of the world. Micro-organisms, including bacteria and algae, are other unproved media that should be studied. Animals can be used in geochemical-prospecting programs. Dogs have been used quite successfully to sniff out hidden and exposed sulfide minerals. Tennite mounds are commonly composed of subsurface material, but have not as yet proved to be useful in locating buried mineral deposits. Animal tissue and waste products are essentially unproved but potentially valuable sampling media. Knowledge of the location of areas where trace-element-associated diseases in animals and man are endemic as well as a better understanding of these diseases, may aid in identifying regions that are enriched in or depleted of various elements, including copper. Results of analyses of gases in the atmosphere are proving valuable in mineral-exploration surveys. Studies involving metallic compounds exhaled by plants into the atmosphere, and of particulate matter suspended in the atmosphere are reviewed these methods may become important in the future. Remote-sensing techniques are useful for making indirect measurements of geochemical responses. Two techniques applicable to geochemical exploration are neutron-activation analysis and gamma-ray spectrometry. Aerial photography is especially useful in vegetation surveys. Radar imagery is an unproved but potentially valuable method for use in studies of vegetation in perpetually clouded regions. With the advent of modern computers, many new techniques, such as correlation analysis, regression analysis, discriminant analysis, factor analysis, cluster analysis, trend-surface analysis, and moving-average analysis can be applied to geochemical data sets. Selective use of these techniques can provide new insights into the interpretatio

Professional Paper↗

USGS2003

Influence of elk grazing on soil properties in Rocky Mountain National Park

We used three 35-year exclosures to examine the effects of high elk populations on a variety of soil properties in three vegetation types: upland sagebrush, aspen, and meadow. Grazing and hoof action by elk significantly increased bulk density (from 0.87 kg/l ungrazed to 0.94 kg/l grazed), with greater effects on soils with fewer rocks. Grazing substantially reduced extractable calcium, magnesium, potassium and phosphorus in the sagebrush type, but not in the aspen or meadow types. The only grazing effect on pH came in aspen types, where grazing prevented aspen establishment, and kept soil pH about 0.7 units higher than under aspen inside the exclosures. Grazing had no overall effect on total soil C and N across all exclosures and vegetation types. The availability of soil nitrogen, indexed by in-field resin bags and net mineralization in soil cores, showed little overall effect of grazing. Limited data on soil leaching indicated a possibility of strong increases in nitrate leaching with grazing for an aspen vegetation type at one exclosure. Although we found little effect of grazing on soil N supply, we note that N fertilization doubled the production of grasses and shrubs; if grazing eventually led to changes in soil N supply, species composition and growth would likely change. ?? 2003 Elsevier B.V. All rights reserved.

Forest Ecology and Management↗

USGS2011

Sulfur geochemistry and microbial sulfate reduction during low-temperature alteration of uplifted lower oceanic crust: Insights from ODP Hole 735B

Sulfide petrography plus whole rock contents and isotope ratios of sulfur were measured in a 1.5 km section of oceanic gabbros in order to understand the geochemistry of sulfur cycling during low-temperature seawater alteration of the lower oceanic crust, and to test whether microbial effects may be present. Most samples have low SO 4 /ΣS values (≤ 0.15), have retained igneous globules of pyrrhotite ± chalcopyrite ± pentlandite, and host secondary aggregates of pyrrhotite and pyrite laths in smectite ± iron-oxyhydroxide ± magnetite ± calcite pseudomorphs of olivine and clinopyroxene. Compared to fresh gabbro containing 100–1800 ppm sulfur our data indicate an overall addition of sulfide to the lower crust. Selection of samples altered only at temperatures ≤ 110 °C constrains microbial sulfate reduction as the only viable mechanism for the observed sulfide addition, which may have been enabled by the production of H 2 from oxidation of associated olivine and pyroxene. The wide range in δ 34 S sulfide values (− 1.5 to + 16.3‰) and variable additions of sulfide are explained by variable ε sulfate-sulfide under open system pathways, with a possible progression into closed system pathways. Some samples underwent oxidation related to seawater penetration along permeable fault horizons and have lost sulfur, have high SO 4 /ΣS (≥ 0.46) and variable δ 34 S sulfide (0.7 to 16.9‰). Negative δ 34 S sulfate –δ 34 S sulfide values for the majority of samples indicate kinetic isotope fractionation during oxidation of sulfide minerals. Depth trends in sulfide–sulfur contents and sulfide mineral assemblages indicate a late-stage downward penetration of seawater into the lower 1 km of Hole 735B. Our results show that under appropriate temperature conditions, a subsurface biosphere can persist in the lower oceanic crust and alter its geochemistry.

Chemical Geology↗

USGS2002

A serotype-specific polymerase chain reaction for identification of Pasteurella multocida serotype 1

A serotype-specific polymerase chain reaction (PCR) assay was developed for detection and identification of Pasteurella multocida serotype 1, the causative agent of avian cholera in wild waterfowl. Arbitrarily primed PCR was used to detect DNA fragments that distinguish serotype 1 from the other 15 serotypes of P. multocida (with the exception of serotype 14). Oligonucleotide primers were constructed from these sequences, and a PCR assay was optimized and evaluated. PCR reactions consistently resulted in amplification products with reference strains 1 and 14 and all other serotype 1 strains tested, with cell numbers as low as 2.3 cells/ml. No amplification products were produced with other P. multocida serotypes or any other bacterial species tested. To compare the sensitivity and further test the specificity of this PCR assay with traditional culturing and serotyping techniques, tissue samples from 84 Pekin ducks inoculated with field strains of P. multocida and 54 wild lesser snow geese collected during an avian cholera outbreak were provided by other investigators working on avian cholera. PCR was as sensitive (58/64) as routine isolation (52/64) in detecting and identifying P. multocida serotype 1 from the livers of inoculated Pekins that became sick or died from avian cholera. No product was amplified from tissues of 20 other Pekin ducks that received serotypes other than type 1 (serotype 3, 12 × 3, or 10) or 12 control birds. Of the 54 snow geese necropsied and tested for P. multocida , our PCR detected and identified the bacteria from 44 compared with 45 by direct isolation. The serotype-specific PCR we developed was much faster and less labor intensive than traditional culturing and serotyping procedures and could result in diagnosis of serotype 1 pasteurellosis within 24 hr of specimen submission.

Avian Diseases↗

USGS1983

Lineaments and fracture traces, Decatur County, Indiana

Lineanents and fracture traces have been mapped throughout Decatur County, Indiana. These lineaments and fracture traces may indicate that solution enlarged vertical fractures in the limestone and dolonite aquifers underlie most of the county. The use of lineament and fracture-trace maps in selecting bedrock-drilling sites results in a significant increase in the number of usable sites. Bedrock wells drilled on or near mapped lineaments and fracture traces have a higher average yield than veils drilled into interfracture areas. Parts of Decatur County and several adjacent counties are economically restricted by inadequate water supplies. The Greensburg Municipal Water Works, supplying 35 percent of the county's population, obtains 25 percent of its water from six wells in Greensburg. The remaining 75 percent is pumped from the Flat Rock River. This water is piped 8.25 miles and lifted 183 feet to the treatment station. Although the Flatrock River has adequate flow to supply Greensburg's water needs, a ground-water supply can probably be developed nearer the treatment plant. Pleistocene till covers most of the nearly horizontal bedrock. Although averaging about 50 feet thick, this unconsolidated unit does not seem to inhibit the mapping of lineaments and fracture traces. Bedrock is middle Paleozoic limestone, dolomite, and shale. Two sequences of limestone and dolomite, separated by a thin shale unit, constitute the principal aquifer. The extremely variable well yields from this aquifer indicate that the bedrock permeability is also variable. Well placement is important in a fractured bedrock terrane, as fractures are a principal source of water to the well. Here, the most productive bedrock wells are at the mapped intersection of two or more fracture traces or lineaments and at the lowest local altitude. Use of a fracture-trace map will not guarantee a sufficient supply of ground water but will reduce the chance of drilling an inadequate well.

Indiana↗

USGS2014

California State Waters Map Series — Offshore of Half Moon Bay, California

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. The Offshore of Half Moon Bay map area is located in northern California, on the Pacific coast of the San Francisco Peninsula about 40 kilometers south of the Golden Gate. The city of Half Moon Bay, which is situated on the east side of the Half Moon Bay embayment, is the nearest significant onshore cultural center in the map area, with a population of about 11,000. The Pillar Point Harbor at the north edge of Half Moon Bay offers a protected landing for boats and provides other marine infrastructure. The map area lies offshore of the Santa Cruz Mountains, part of the northwest-trending Coast Ranges that run roughly parallel to the San Andreas Fault Zone. The Santa Cruz Mountains lie between the San Andreas Fault Zone and the San Gregorio Fault system. The flat coastal area, which is the most recent of numerous marine terraces, was formed by wave erosion about 105 thousand years ago. The higher elevation of this same terrace west of the Half Moon Bay Airport is caused by uplift on the Seal Cove Fault, a splay of the San Gregorio Fault Zone. Although originally incised into the rising terrain horizontally, the ancient terrace surface has been gently folded into a northwest-plunging syncline by compression related to right-lateral strike-slip movement along the San Gregorio Fault Zone. The lowest elevation coincides with the deepest part of Half Moon Bay; the terrace surface rises both to the north and to the south. Uplift in this map area has resulted in relatively shallow water depths within California’s State Waters and, thus, little accommodation space for sediment accumulation. Sediment is observed in the shelter of Half Moon Bay and on the outer half of the California’s State Waters shelf. Sediment in the area is mobile, often forming dunes and sand waves. A westward bend in the San Andreas Fault Zone, southeast of the map area, coupled with right-lateral movement along the Seal Cove Fault, which comes ashore in Pillar Point Harbor, has resulted in the folding and uplifting of sedimentary rocks of the Purisima Formation in the offshore. Differential erosion of these folded and faulted layers of the Purisima Formation has exposed the parallel curved-rock ridges that are visible on the seafloor from the headland at Pillar Point. During the winter, strong North Pacific storms generate large, long-period waves that shoal and break over this bedrock reef at the world-famous surfing location known as Mavericks. The Offshore of Half Moon Bay map area lies within the cold-temperate biogeographic zone that is called either the “Oregonian province” or the “northern California ecoregion.” This biogeographic province is maintained by the long-term stability of the southward-flowing California Current, an eastern limb of the North Pacific subtropical gyre that flows from Oregon to Baja California. At its midpoint off central California, the California Current transports subarctic surface (0–500 m deep) waters southward, about 150 to 1,300 km from shore. Seasonal northwesterly winds that are, in part, responsible for the California Current, generate coastal upwelling. The south end of the Oregonian province is at Point Conception (about 365 km south of the map area), although its associated phylogeographic group of marine fauna may extend beyond to the area offshore of Los Angeles in southern California. The ocean off central California has experienced a warming over the last 50 years that is driving an ecosystem shift away from the productive subarctic regime towards a depopulated subtropical environment. Seafloor habitats in the Offshore of Half Moon Bay map area, which lies within the Shelf (continental shelf) megahabitat, range from significant rocky outcrops that support kelp-forest communities nearshore to rocky-reef communities in deep water. Biological productivity resulting from coastal upwelling supports populations of sea birds such as Sooty Shearwater, Western Gull, Common Murre, Cassin’s Auklet, and many other less populous bird species. In addition, an observable recovery of Humpback and Blue Whales has occurred in the area; both species are dependent on coastal upwelling to provide nutrients. The large extent of exposed inner shelf bedrock supports large forests of “bull kelp,” which is well adapted for high wave-energy environments. Common fish species found in the kelp beds and rocky reefs include lingcod and various species of rockfish and greenling.

California↗

USGS2000

Geologic map database of the El Mirage Lake area, San Bernardino and Los Angeles Counties, California

This geologic map database for the El Mirage Lake area describes geologic materials for the dry lake, parts of the adjacent Shadow Mountains and Adobe Mountain, and much of the piedmont extending south from the lake upward toward the San Gabriel Mountains. This area lies within the western Mojave Desert of San Bernardino and Los Angeles Counties, southeastern California. The area is traversed by a few paved highways that service the community of El Mirage, and by numerous dirt roads that lead to outlying properties. An off-highway vehicle area established by the Bureau of Land Management encompasses the dry lake and much of the land north and east of the lake. The physiography of the area consists of the dry lake, flanking mud and sand flats and alluvial piedmonts, and a few sharp craggy mountains. This digital geologic map database, intended for use at 1:24,000-scale, describes and portrays the rock units and surficial deposits of the El Mirage Lake area. The map database was prepared to aid in a water-resource assessment of the area by providing surface geologic information with which deepergroundwater-bearing units may be understood. The area mapped covers the Shadow Mountains SE and parts of the Shadow Mountains, Adobe Mountain, and El Mirage 7.5-minute quadrangles. The map includes detailed geology of surface and bedrock deposits, which represent a significant update from previous bedrock geologic maps by Dibblee (1960) and Troxel and Gunderson (1970), and the surficial geologic map of Ponti and Burke (1980); it incorporates a fringe of the detailed bedrock mapping in the Shadow Mountains by Martin (1992). The map data were assembled as a digital database using ARC/INFO to enable wider applications than traditional paper-product geologic maps and to provide for efficient meshing with other digital data bases prepared by the U.S. Geological Survey's Southern California Areal Mapping Project.

California↗

USGS2006

Reserve Growth in Oil Fields of West Siberian Basin, Russia

Although reserve (or field) growth has proven to be an important factor contributing to new reserves in mature petroleum basins, it is still a poorly understood phenomenon. Limited studies show that the magnitude of reserve growth is controlled by several major factors, including (1) the reserve booking and reporting requirements in each country, (2) improvements in reservoir characterization and simulation, (3) application of enhanced oil recovery techniques, and (4) the discovery of new and extensions of known pools in discovered fields. Various combinations of these factors can affect the estimates of proven reserves in particular fields and may dictate repeated estimations of reserves during a field's life. This study explores the reserve growth in the 42 largest oil fields in the West Siberian Basin, which contain about 55 percent of the basin's total oil reserves. The West Siberian Basin occupies a vast swampy plain between the Ural Mountains and the Yenisey River, and extends offshore into the Kara Sea; it is the richest petroleum province in Russia. About 600 oil and gas fields with original reserves of 144 billion barrels of oil (BBO) and more than 1,200 trillion cubic feet of gas (TCFG) have been discovered. The principal oil reserves and most of the oil fields are in the southern half of the basin, whereas the northern half contains mainly gas reserves. Sedimentary strata in the basin consist of Upper Triassic through Tertiary clastic rocks. Most oil is produced from Neocomian (Lower Cretaceous) marine to deltaic sandstone reservoirs, although substantial oil reserves are also in the marine Upper Jurassic and continental to paralic Lower to Middle Jurassic sequences. The majority of oil fields are in structural traps, which are gentle, platform-type anticlines with closures ranging from several tens of meters to as much as 150 meters (490 feet). Fields producing from stratigraphic traps are generally smaller except for the giant Talin field which contains oil in Jurassic river-valley sandstones. Principal source rocks are organic-rich marine shales of the Volgian (uppermost Jurassic) Bazhenov Formation, which is 30-50 m (98- 164 feet) thick. Bazhenov-derived oils are mostly of medium gravity, and contain 0.8-1.3 percent sulfur and 2-5 percent paraffin. Oils in the Lower to Middle Jurassic clastics were sourced from lacustrine and estuarine shales of the Toarcian Togur Bed. These oils are medium to low gravity, with low sulfur (less than 0.25 percent) and high paraffin (commonly to 10 percent) contents. Among the 42 fields analyzed for reserve growth, 30 fields are located in the Middle Ob region, which includes the Samotlor field with reserves of more than 25 BBO and the Fedorov field with reserves of about 5 BBO. Data used in the study include year of discovery, year of first production, annual and cumulative production, and remaining reserves reported by Russian reserve categories (A+B+C1 and C2) in January of each year. Correlation of these Russian resource categories to U.S. categories of the Society of Petroleum Engineers classification is complex and somewhat uncertain. Reserve growth in oil fields of West Siberia was calculated using a newly developed Group Growth method, which requires that the total reserve (proven reserve plus cumulative production) of individual fields with an equal length of reserve record be added together starting with discovery year or the first production year. Then the annual growth factor (AGF), which is the ratio of total reserves of two consecutive years, is calculated for all years. Once AGFs have been calculated, the cumulative growth factor (CGF) is calculated by multiplying the AGFs of all the previous years. The CGF data are used to develop reserve growth models. The West Siberian oil fields show a 13-fold reserve growth 20 years after the discovery year and only about a 2-fold growth after the first production year. This difference is attributed to extensive exploration and field delineation activities between the discovery and the first production years. Because of uncertainty in the length of evaluation time and in reported reserves during this initial period, reserve growth based on the first production year is more reliable for model development. However, reserve growth models based both on discovery year and first production year show rapid growth in the first few years and slower growth in the following years. In contrast, the reserve growth patterns for the conterminous United States and offshore Gulf of Mexico show a steady reserve increase throughout the productive lives of the fields. The different reserve booking requirements and the lack of capital investment for improved reservoir management and production technologies in West Siberian fields relative to U.S. fields are the probable causes for the difference in growth patterns. Reserve growth models based on the first production year predict that the reserve growth potential in the 42 largest oil fields of West Siberia over a five-year period (1998-2003) ranges from 270-330 million barrels or 0.34-0.42 percent per year. For a similar five-year period (1996-2001), models for the conterminous United States predict a growth of 0.54-0.75 percent per year. This abstract presents the contents of a poster prepared for the AAPG Hedberg Research Conference on Understanding World Oil Resources, November 12-17, 2006 - Colorado Springs, Colorado. A paper 'Reserve Growth in Oil Fields of West Siberian Basin, Russia' was published in Natural Resources Research, v. 12, no. 2, June, 2003.

Open-File Report↗

USGS2008

Geophysical Logs, Aquifer Tests, and Water Levels in Wells in and Near the North Penn Area 7 Superfund Site, Upper Gwynedd Township, Montgomery County, Pennsylvania, 2002-2006

Ground water in the vicinity of several industrial facilities in Upper Gwynedd Township and Lansdale Borough, Montgomery County, Pa., is contaminated with several volatile organic compounds (VOCs). The 2-square-mile area was placed on the National Priorities List as the North Penn Area 7 Superfund Site by the U.S. Environmental Protection Agency (USEPA) in 1989. The U.S. Geological Survey (USGS) conducted geophysical logging, aquifer testing, water-level monitoring, and streamflow measurements in the vicinity of North Penn Area 7 from October 2002 through December 2006. This followed work that began in 2000 to assist the USEPA in developing an understanding of the hydrogeologic framework in the area as part of the USEPA Remedial Investigation. The study area is underlain by Triassic- and Jurassic-age sandstones, siltstones, and shales of the Lockatong Formation and the Brunswick Group. Regionally, these rocks strike northeast and dip to the northwest. The sequence of rocks form fractured-rock aquifers that act as a set of confined to semi-confined layered aquifers of differing permeabilities. The aquifers are recharged by precipitation and discharge to streams and wells. The Wissahickon Creek headwaters are less than 1 mile northeast of the study area. This stream flows southwest approximately parallel to strike and bisects North Penn Area 7. Ground water is pumped in the vicinity of North Penn Area 7 for industrial use and public supply. The USGS collected geophysical logs for 42 wells that ranged in depth from 40 to 477 ft. Aquifer-interval-isolation testing was done in 17 of the 42 wells, for a total of 122 zones tested. A multiple-well aquifer test was conducted by monitoring the response of 14 wells to pumping and shutdown of a 600-ft deep production well in November-December 2004. In addition, water levels were monitored continuously in four wells in the area from October 2002 through September 2006, and streamflow was measured quarterly at two sites on Wissahickon Creek from December 2002 through September 2005. Geophysical logging identified water-bearing zones associated with high-angle fractures and bedding-plane openings throughout the depth of the boreholes. Heatpulse-flowmeter measurements under non-pumping, ambient conditions in 16 wells greater than 200 ft in depth indicated that borehole flow, where detected, was only upward in 2 wells and only downward in 5 wells. In nine wells, both upward and downward flow were measured. Geologic structure and pumping in the area affect the spatial distribution of vertical gradients. Heatpulse-flowmeter measurements under pumping conditions were used to identify the most productive intervals in wells. Correlation of natural-gamma-ray logs indicated bedding in the area probably strikes about 45 to 65 degrees northeast and dips about 9 degrees northwest. Aquifer intervals isolated by inflatable packers in 17 wells were pumped to test productivity of water-bearing zones and to collect samples to determine chemical quality of water produced from the interval. Interval-isolation testing confirmed the vertical hydraulic gradients indicated by heatpulse-flowmeter measurements. The specific capacities of the 122 isolated intervals ranged over about three orders of magnitude, from 0.01 to 10.6 gallons per minute per foot, corresponding to calculated transmissivities of 1.2 to 2,290 feet squared per day. Intervals adjacent to isolated pumped intervals commonly showed little response to pumping of the isolated zone. The presence of vertical hydraulic gradients and lack of adjacent-interval response to pumping in isolated intervals indicate a limited degree of vertical hydraulic connection between the aquifer sections tested. Differences were apparent in inorganic water quality of water from isolated intervals, including pH, specific conductance, and dissolved oxygen. Concentrations of most VOC contaminants in most wells with predominantly upward vertical gradients were g

Scientific Investigations Report↗

USGS2006

A new reference section for palynostratigraphic zonation of Paleocene rocks in the Rocky Mountain region

A biostratigraphic (palynostratigraphic) zonation of Paleocene rocks was established in the northeastern Wind River Basin near Waltman, Natrona County, Wyoming, in 1978 and subsequently applied extensively by various workers throughout the Rocky Mountain region. Because the original study on which the zonation was based was proprietary, precise details about the locations of the two reference sections and the samples on which the zonation was based were not published and are no longer retrievable. Therefore, it is useful (although not required) to designate formally a new reference section for the Paleocene biozones. Accordingly, exposures of Paleocene and associated strata within and west of the Castle Gardens Petroglyph Site in Fremont County, Wyoming, in the east-central part of the Wind River Basin, were selected for this purpose. At this location, composite stratigraphic sections encompassing 740 m of strata were measured, described, and sampled. Productive samples yielded characteristic Maastrichtian palynomorphs from the lower part of the sampled interval and diagnostic species of the six palynological biozones zones widely known as P1 (lower Paleocene) through P6 (upper Paleocene), through an interval of about 580 m. The Paleocene biozones are present in the same consistent stratigraphic order in the Castle Gardens area as observed in the 1978 study and subsequent studies throughout the Rocky Mountain region. In accordance with the North American Stratigraphic Code, the historical background is presented; intent to establish the Castle Gardens reference section is declared; the category, rank, and formal names of biostratigraphic units within it are specified; and the features of the biozonation are described, including biozone boundaries, ages, and regional relations. Occurrences of biostratigraphically significant palynological species within each biozone in the reference section are tabulated, and presence of these and other species in correlative biozones are discussed. The new reference section in the Castle Gardens area replaces the original reference sections near Waltman and provides a better-documented foundation for Paleocene palynostratigraphy in the Rocky Mountain region.

Mountain Geologist↗

USGS1964

Deep geothermal brine near Salton Sea, California

A well drilled for geothermal power near Salton Sea in Imperial Valley, Calif., is 5,232 feet deep; it is the deepest well in the world (1962) in a high-temperature hot spring area. In the lower half of the hole temperatures are too high to measure with available equipment, but are at loast 270°C, and may be as much as 370°C. For comparison, maximum temperature heretofore reported at depth (1962) for hot spring areas is 295°C. The well taps a very saline brine of Na-Ca-K-Cl type (about 185,000 ppm Cl) with exceptionally high potassium, and with the highest content of minor alkali elements known for natural waters; Fe, Mn, Zn, Pb, Cu, Ag, and some other metals are also exceptionally high. This brine may be connate, but present evidence favors a source in the magma chamber at depth that supplied late Quaternary rhyolite domes of the area. If the latter is correct, the brine is an undiluted magmatic water that is residual from the separation of a more volatile phase high in CO 2 , H 2 S, and with some alkali halides. Elsewhere, the hypothesized volatile phase may account for near-surface hot spring activity of most thermal areas of volcanic association. The residual brine of high salinity may ordinarily remain relatively deep in the volcanic systems because of high specific gravity and low content of volatiles, seldom appearing at the surface except in a greatly diluted form. The hot springs of Arima, Japan, may be a rare example of this type of magmatic water discharging at the surface in moderate concentration (Cl as much as 42,000 ppm). Independent evidence from fluid inclusions in minerals of high-temperature base-metal deposits also favors the existence of magmatic water high in Na, Ca, and Cl, and low in CO 2 and other volatile components. During a three-month production test several tons of material precipitated in the horizontal discharge pipe from the well. Amorphous silica with iron and manganese, and bornite are the dominant recognized components. This material contains the astonishingly high contents of about 20 percent copper, 2 percent silver, and notable sulfur, arsenic, bismuth, lead, antimony, and some other minor elements. Total quantities of all elements in the original whole brine are not yet known, but calculated amounts corresponding to 1 to 3 ppm of copper and 0.1 to 0.3 ppm of silver were precipitated from the brine to form the pipe deposits. The brine, therefore, may be man’s first sample of an « active » ore solution. Equally fascinating to many geologists is the possibility that in the lower part of the hole temperatures are so high and pressures are sufficient for young sedimentary rocks to be undergoing transformation into rocks with mineral assemblages of the greenschist facies of metamorphism. Drill cores from 4,400 to 5,000 feet in depth contain chlorite, albite, K-feldspar, epidote, mica, and quartz, with some indication of increase in metamorphic grade downward. Regional geological and geophysical studies favor a depth of about 20,000 feet to pre-Tertiary basement rocks in the general area. A shallow basement or local upfaulting of old metamorphic rocks are not likely possibilities for the thermal area.

California↗

USGS2003

Seismic evidence for a mantle source for mid-Proterozoic anorthosites and implications for models of crustal growth

Voluminous anorthosite intrusions are common in mid-Proterozoic crust. Historically, two end-member models have been proposed for the origin of these anorthosites. In the first model anorthosites derive from fractionation of a mantle source leaving a residue of metagabbro in the lower crust; in the second model anorthosites are the product of partial melting of the lower crust with residual pyroxene and high-grade minerals (i.e. a pyroxenitic and/or metapelitic lower crust). Although a general consensus has developed that the first model provides the best fit to petrological and geochemical constraints, the sparse evidence for mafic and ultramafic counterparts to the anorthosites leaves the issue still unresolved. We use the absolute P-wave velocity and the ratio between P- and S-wave velocities ( V P / V S ) to infer the composition of the lower crust beneath the Marcy Anorthosite (New York State, USA). Seismic refraction data reveal a lower crust 20 km thick, where V P and V P /V S range from top to bottom between 7.0 km s −1 and 7.2 ± 0.1 and 1.84 km s −1 and 1.81 ± 0.02, respectively. Laboratory measurements on rock samples indicate that these seismic properties are typical of plagioclase-rich rocks. Magmatic underplating of basaltic melts is a mechanism to form plagioclase-rich bulk composition for the Grenville crust. At the bottom of the lower crust, increase of P-wave velocity, slight decrease of V P / V S ratios and the presence of a low-reflective seismic Moho are additional observations supporting crustmantle interactions related to magmatic underplating. High P-wave velocity (8.6 km s −1 ) in the upper mantle may indicate that the ultramafic portion (e.g. pyroxenites) of the underplated magma has become eclogite. High average P-wave velocity (6.7 km s −1 ) and V P / V S (1.81), and the exceptional abundance of anorthosites-norites-troctolites among the rocks exposed at the surface, indicate that the Grenville Proterozoic crust may have a unique plagioclase-rich bulk composition. We suggest magmatic underplating, occurring either over a wide time span or with separate syn- and post-collisional magmatic pulses, as being a major crust-forming mechanism operating in mid-Proterozoic time.

Geological Society Special Publication↗

USGS2014

California State Waters Map Series — Offshore of San Gregorio, California

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California's State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. The Offshore of San Gregorio map area is located in northern California, on the Pacific coast of the San Francisco Peninsula about 50 kilometers south of the Golden Gate. The map area lies offshore of the Santa Cruz Mountains, part of the northwest-trending Coast Ranges that run roughly parallel to the San Andreas Fault Zone. The Santa Cruz Mountains lie between the San Andreas Fault Zone and the San Gregorio Fault system. The nearest significant onshore cultural centers in the map area are San Gregorio and Pescadero, both unincorporated communities with populations well under 1,000. Both communities are situated inland of state beaches that share their names. No harbor facilities are within the Offshore of San Gregorio map area. The hilly coastal area is virtually undeveloped grazing land for sheep and cattle. The coastal geomorphology is controlled by late Pleistocene and Holocene slip in the San Gregorio Fault system. A westward bend in the San Andreas Fault Zone, southeast of the map area, coupled with right-lateral movement along the San Gregorio Fault system have caused regional folding and uplift. The coastal area consists of high coastal bluffs and vertical sea cliffs. Coastal promontories in the northern and southern parts of the map area are the result of right-lateral motion on strands of the San Gregorio Fault system. In the south, headlands near Pescadero Point have been uplifted by motion along the west strand of the San Gregorio Fault (also called the Frijoles Fault), which separates rocks of the Pigeon Point Formation south of the fault from rocks of the Purisima Formation north of the fault. The regional uplift in this map area has caused relatively shallow water depths within California's State Waters and, thus, little accommodation space for sediment accumulation. Sediment is observed offshore in the central part of the map area, in the shelter of the headlands north of the east strand of the San Gregorio Fault (also called the Coastways Fault) around Miramontes Point (about 5 km north of the map area) and also on the outer half of the California's State Waters shelf in the south where depths exceed 40 m. Sediment in the outer shelf of California's State Waters is rippled, indicating some mobility. The Offshore of San Gregorio map area lies within the cold-temperate biogeographic zone that is called either the "Oregonian province" or the "northern California ecoregion." This biogeographic province is maintained by the long-term stability of the southward-flowing California Current, an eastern limb of the North Pacific subtropical gyre that flows from Oregon to Baja California. At its midpoint off central California, the California Current transports subarctic surface (0–500 m deep) waters southward, about 150 to 1,300 km from shore. Seasonal northwesterly winds that are, in part, responsible for the California Current, generate coastal upwelling. The south end of the Oregonian province is at Point Conception (about 350 km south of the map area), although its associated phylogeographic group of marine fauna may extend beyond to the area offshore of Los Angeles in southern California. The ocean off of central California has experienced a warming over the last 50 years that is driving an ecosystem shift away from the productive subarctic regime towards a depopulated subtropical environment. Seafloor habitats in the Offshore of San Gregorio map area, which lies within the Shelf (continental shelf) megahabitat, range from significant rocky outcrops that support kelp-forest communities nearshore to rocky-reef communities in deep water. Biological productivity resulting from coastal upwelling supports diverse populations of sea birds such as Sooty Shearwater, Western Gull, Common Murre, Cassin's Auklet, and many other less populous bird species. In addition, an observable recovery of Humpback and Blue Whales has occurred in the area; both species are dependent on coastal upwelling to provide nutrients. The large extent of exposed inner shelf bedrock supports large forests of "bull kelp," which is well adapted for high wave-energy environments. Common fish species found in the kelp beds and rocky reefs include lingcod and various species of rockfish and greenling.

California↗

USGS2021

A rock record of complex aeolian bedforms in a Hesperian desert landscape: The Stimson formation as exposed in the Murray Buttes, Gale Crater, Mars

Lithified aeolian strata encode information about ancient planetary surface processes and the climate during deposition. Decoding these strata provides insight regarding past sediment transport processes, bedform kinematics, depositional landscape, and the prevailing climate. Deciphering these signatures requires a detailed analysis of sedimentary architecture to reconstruct dune morphology, motion, and the conditions that enabled their formation. Here, we show that a distinct sandstone unit exposed in the foothills of Mount Sharp, Gale crater, Mars, records the preserved expression of compound aeolian bedforms that accumulated in a large dune field. Analysis of Mastcam images of the Stimson formation shows that it consists of cross‐stratified sandstone beds separated by a hierarchy of erosive bounding surfaces formed during dune migration. The presence of two orders of surfaces with distinct geometrical relations reveals that the Stimson‐era landscape consisted of large dunes (draas) with smaller, superimposed dunes migrating across their lee slopes. Analysis of cross‐lamination and subset bounding surface geometries indicate a complex wind regime that transported sediment toward the north, constructing oblique dunes. This dune field was a direct product of the regional climate and the surface processes active in Gale crater during the fraction of the Hesperian Period recorded by the Stimson formation. The environment was arid, supporting a large aeolian dune field; this setting contrasts with earlier humid depositional episodes, recorded by the lacustrine sediments of the Murray formation (also Hesperian). Such fine‐scale reconstruction of landscapes on the ancient surface of Mars is important to understanding the planet’s past climate and habitability.

Journal of Geophysical Research - Planets↗