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At least 235 records · Page 13Linked to original sources
USGS1916

Guidebook of the western United States: Part C - The Santa Fe route, with a side trip to Grand Canyon of the Colorado

The United States of America comprise an area so vast in extent and so diverse in natural features as well as in characters due to human agency that the American citizen who knows thoroughly his own country must have traveled widely and observed wisely. To 'know America first' is a patriotic obligation, but to meet this obligation the railroad traveler needs to have his eyes directed toward the more important or essential things within his field of vision and then to have much that he sees explained by what is unseen in the swift passage of the train. Indeed, many things that attract his attention are inexplicable except as the story of the past is available to enable him to interpret the present. Herein lie the value and the charm of history, whether human or geologic. The present stimulus given to travel in the home country will encourage many thousands of Americans to study geography at first hand. To make this study most profitable the traveler needs a handbook that will answer the questions that come to his mind so readily along the way. Furthermore, the aim of such a guide should be to stimulate the eye in the selection of the essentials in the scene that so rapidly unfolds itself in the crossing of the continent. In recognition of the opportunity afforded in 1915 to render service of this kind to an unusually large number of American citizens, as well as to visitors from other countries, the United States Geological Survey has prepared a series of guidebooks covering four of the older railroad routes west of the Mississippi. These books are educational in purpose, but the method adopted is to entertain the traveler by making more interesting what he sees from the car window. The plan of the series is to present authoritative information that may enable the reader to realize adequately the scenic and material resources of the region he is traversing, to comprehend correctly the basis of its development, and above all to appreciate keenly the real value of the country he looks out upon, not as so many square miles of territory represented on the map in a railroad folder by meaningless spaces, but rather as land - real estate, if you please - varying widely in present appearance because differing largely in its history and characterized by even greater variation in values because possessing diversified natural resources. One region may be such as to afford a livelihood for only a pastoral people; another may present opportunity for intensive agriculture; still another may contain hidden stores of mineral wealth that may attract large industrial development; and taken together these varied resources afford the promise of long-continued prosperity for this or that State. Items of interest in civic development or references to significant epochs in the record of discovery and settlement may be interspersed with explanations of mountain and valley or statements of geologic history. In a broad way, the story of the West is a unit, and every chapter should be told in order to meet fully the needs of the tourist who aims to understand all that he sees. To such a traveler-reader this series of guidebooks is addressed. To this interpretation of our own country the United States Geological Survey brings the accumulated data of decades of pioneering investigation, and the present contribution is only one type of return to the public which has supported this scientific work under the Federal Government. In preparing the description of the country traversed by the Santa Fe Route the geographic and geologic information already published as well as unpublished material in the possession of the Geological Survey has been utilized, but to supplement this material Mr. Darton made a field examination of the entire route in 1914. Information has been furnished by Erasmus Haworth, J. E. Todd, and R. T. Hill, as well as by others whose writings are listed in the bibliography at the end of the text. Cooperation has been rendered by the United States Reclamation Service and by bureaus of the Department of Agriculture. Railroad officials and other citizens have also generously given their aid, and other members of the Survey have freely cooperated in the work. For the purpose of furnishing the traveler with a graphic presentation of each part of his route, the accompanying maps, 25 sheets in all, have been prepared, with a degree of accuracy probably never bsfore attained in a guidebook, aiid their arrangement has been planned to meet the convenience of the reader. The special topographic surveys necessary to complete these maps of the route were made by W. O. Tufts.

Bulletin↗
USGS2009

Archive of digitized analog boomer seismic reflection data collected from the Mississippi-Alabama-Florida Shelf During cruises onboard the R/V Kit Jones, June 1990 and July 1991

In June of 1990 and July of 1991, the U.S. Geological Survey (USGS) conducted geophysical surveys to investigate the shallow geologic framework of the Mississippi-Alabama-Florida shelf in the northern Gulf of Mexico, from Mississippi Sound to the Florida Panhandle. Work was done onboard the Mississippi Mineral Resources Institute R/V Kit Jones as part of a project to study coastal erosion and offshore sand resources. This report is part of a series to digitally archive the legacy analog data collected from the Mississippi-Alabama SHelf (MASH). The MASH data rescue project is a cooperative effort by the USGS and the Minerals Management Service (MMS). This report serves as an archive of high-resolution scanned Tagged Image File Format (TIFF) and Graphics Interchange Format (GIF) images of the original boomer paper records, navigation files, trackline maps, Geographic Information System (GIS) files, cruise logs, and formal Federal Geographic Data Committee (FGDC) metadata.

Alabama, Florida, Mississippi↗
USGS1981

Mineral deposits and geology of northern Oman as of 1974

An investigation of the mineral resources of northern Oman was carried out under an agreement between the U. S. Geological Survey and the Ministry of Development, Sultanate of Oman, during late 1973 and early 1974. The purpose of the investigation was to provide an evaluation of the mineral potential of northern Oman and produce recommendations leading toward the utilization of any viable mineral deposits that were found. The widespread copper deposits located within the Semail volcanics appear to be mineable, the iron-nickel laterites developed upon the weathered surface of the Semail ophiolite have economic potential. Manganese and chromite deposits investigated have only a marginal value and are not likely to be of economic importance in the near future. Discovery of economic copper and iron deposits warrants further geologic mapping and mineral exploration in northern Oman. In addition to this, recommendations regarding the organization of a geological and mining group within the Directorate of Petroleum and Minerals are presented.

Open-File Report↗
USGS2013

Knowledge and understanding of dissolved solids in the Rio Grande–San Acacia, New Mexico, to Fort Quitman, Texas, and plan for future studies and monitoring

Availability of water in the Rio Grande Basin has long been a primary concern for water-resource managers. The transport and delivery of water in the basin have been engineered by using reservoirs, irrigation canals and drains, and transmountain-water diversions to meet the agricultural, residential, and industrial demand. In contrast, despite the widespread recognition of critical water-quality problems, there have been minimal management efforts to improve water quality in the Rio Grande. Of greatest concern is salinization (concentration of dissolved solids approaching 1,000 mg/L), a water-quality problem that has been recognized and researched for more than 100 years because of the potential to limit both agricultural and municipal use. To address the issue of salinization, water-resource managers need to have a clear conceptual understanding of the sources of salinity and the factors that control storage and transport, identify critical knowledge gaps in this conceptual understanding, and develop a research plan to address these gaps and develop a salinity management program. In 2009, the U.S. Geological Survey (USGS) in cooperation with the U.S. Army Corps of Engineers (USACE), New Mexico Interstate Stream Commission (NMISC), and New Mexico Environment Department (NMED) initiated a project to summarize the current state of knowledge regarding the transport of dissolved solids in the Rio Grande between San Acacia, New Mexico, and Fort Quitman, Texas. The primary objective is to provide hydrologic information pertaining to the spatial and temporal variability present in the concentrations and loads of dissolved solids in the Rio Grande, the source-specific budget for the mass of dissolved solids transported along the Rio Grande, and the locations at which dissolved solids enter the Rio Grande. Dissolved-solids concentration data provide a good indicator of the general quality of surface water and provide information on the factors governing salinization within the Rio Grande study area. The pattern in dissolved-solids concentrations along the Rio Grande is one of increasing concentration with increasing distance downstream from Elephant Butte and Caballo Reservoirs. The concentration of dissolved solids in the Rio Grande doubles (approximately 500 to 1,000 mg/L) from below Elephant Butte Reservoir to El Paso and increases by more than a factor of 5 (approximately 500 to 3,200 mg/L) from below Elephant Butte Reservoir to Fort Quitman. Marked increases in the concentration of dissolved solids commonly coincide with contributions from agricultural drains, wastewater-treatment plants, regional groundwater, and upward-flowing saline groundwater. The greatest factor, from the surface-water system, in controlling dissolved solids in the Rio Grande is the amount of water that is being transported or stored. Annual variation in streamflow is influenced primarily by climate (precipitation and evaporation) and management of Elephant Butte and Caballo Reservoirs (water storage and release cycles). Seasonal variation in streamflow within the Rio Grande study area is generally categorized generally as irrigation (March–September) and nonirrigation (October–February) seasons; with streamflow in the Rio Grande is highest during the irrigation season and lowest during the nonirrigation season. Dissolved-solids loads during the irrigation season decrease between Leasburg and Fort Quitman primarily because of irrigation diversions and losses to the underlying alluvial aquifer. Conversely, dissolved-solids loads during the nonirrigation season increase between Caballo Dam and Fort Quitman primarily because of the inflow of dissolved solids from agricultural drains, wastewater-treatment plants, and groundwater with elevated concentrations of dissolved solids. Many studies have mass-balance budgets that account for the mass of dissolved solids transported along the Rio Grande. Results from mass-balance budgets developed for dissolved solids indicated that (1) the inflow of saline groundwater, inflow of regional groundwater, and chemical reactions between mineral phases are the primary sources controlling dissolved solids in the Rio Grande, and (2) groundwater pumping and mineral precipitation are causing a net storage of dissolved solids in the Leasburg to El Paso and El Paso to Fort Quitman reaches of the Rio Grande. Looking forward, multiple water-resource managers from State and local agencies in New Mexico and Texas and Federal agencies formed the Rio Grande Salinity Management Coalition with the goal to reduce the amount of dissolved solids that are transported and stored in the Rio Grande study area. The recommendations for additional monitoring to assist the coalition are as follows: -Monitoring: Couple water-quality and streamflow monitoring in the Rio Grande and agricultural drains; perform groundwater-seepage investigations in the Rio Grande and major agricultural drains; nonitor groundwater water-quality conditions in the Mesilla and Hueco Basins. -Focused Hydrogeology Studies at Inflow Sources: Map dissolved-solids concentrations in the Rio Grande and underlying alluvial aquifer; perform hydrogeologic characterization of subsurface areas containing unusually high concentrations of dissolved solids. -Modeling of Dissolved Solids: Develop models to simulate the transport and storage of dissolved solids in both surface-water and groundwater systems.

New Mexico;Texas↗
USGS2016

Hydrogeologic investigations of the Miocene Nogales Formation in the Nogales Area, Upper Santa Cruz Basin, Arizona

Hydrogeologic investigations were conducted to evaluate the groundwater resource potential for the Miocene Nogales Formation in the Nogales area, southern Arizona. Results indicate that parts of the formation may provide new, deeper sources of groundwater for the area. Geologic mapping determined the hydrogeologic framework of the formation by defining lithologic, mineralogic, and stratigraphic characteristics; identifying potential aquifers and confining units; and mapping faults and fractures which likely influence groundwater flow. Geophysical modeling was used to determine the basin geometry and thickness of the Nogales Formation and younger alluvial aquifers and to identify target areas (deep subbasins) which may prove to be productive aquifers. Volcaniclastic sandstone samples from the formation were analyzed for porosity, bulk density, saturated hydraulic conductivity, and fabric. Effective porosity ranges from 16 to 42 percent, bulk density from 1.6 to 2.47 grams per cubic centimeter, and saturated hydraulic conductivity (SHC) from 4 to 57 centimeters per day (4.9×10 -5 to 6.7×10 -4 centimeters per second). Thin sections show that sandstone framework grains consist of quartz, feldspar, biotite, hornblende, pumice, volcanic glass, and opaque minerals. The matrix in most samples consists of pumice fragments, and some contain predominantly silt and clay. Samples with a mostly silt and clay matrix have lower porosity and SHC compared to samples with mostly pumice, which have higher and wider ranges of porosity and SHC. Pore space in the Nogales Formation sediments includes moldic, intercrystalline, and fracture porosity. Some intercrystalline pore space is partially filled with calcite cement. About one third of the samples contain fractures, which correspond to fractures noted in outcrops in all members of the formation. Scanning electron microscope (SEM) and x-ray diffraction (XRD) analyses indicate that most of the samples contained the zeolite clinoptilolite and mixed-layer clay. X-ray diffraction analyses verified clinoptilolite as the only zeolite in Nogales Formation samples; they also verified the presence of smectite and illite clay and some kaolinite. Samples which contain greater amounts of clinoptilolite and lesser amounts of smectite have high porosity and SHC in narrow ranges. However, samples with abundant smectite and lesser amounts of clinoptilolite span the entire ranges of porosity and SHC for the formation. All members of the Nogales Formation are fractured and faulted as a result of Tertiary Basin and Range extensional deformation, which was broadly contemporaneous with deposition of the formation. These structures may have significant influence on groundwater flow in the upper Santa Cruz basin because, although many of the sediments in the formation have characteristics indicating they may be productive aquifers based only on porous-media flow, fracturing in these sediments may further enhance permeability and groundwater flow in these basin-fill aquifers by orders of magnitude.

Arizona↗
USGS2013

Reconnaissance investigation of the rough diamond resource potential and production capacity of Côte d’Ivoire

Ethnic and political conflict developed into open civil war in Côte d’Ivoire in 2002, leading to a de facto partitioning of the country into the government-controlled south and the rebel-controlled north. Côte d’Ivoire’s two main diamond mining areas, Séguéla and Tortiya, are located in the north, under what was, until recently, rebel-controlled territory. In an effort to prevent proceeds from diamond mining from funding the conflict, the United Nations (UN) placed an embargo on the export of rough diamonds from Côte d’Ivoire in 2005. That same year, the Kimberley Process (KP), the international initiative charged with stemming the flow of conflict diamonds, acted to enforce this ban by adopting the Moscow Resolution on Côte d’Ivoire, which contained measures to prevent the infiltration of Ivorian diamonds into the legitimate global rough diamond trade. Though under scrutiny by the international community, diamond mining activities continued in Côte d’Ivoire, with artisanal miners exploiting both alluvial deposits in fluvial systems and primary kimberlitic dike deposits. However, because of the embargo, there has been no official record of diamond production since the conflict began in 2002. This lack of production statistics represents a significant data gap and hinders efforts by the KP to understand how illicitly produced diamonds may be entering the legitimate trade. This study presents the results of a multiyear effort to monitor the diamond mining activities of Côte d’Ivoire’s two main diamond mining areas, Séguéla and Tortiya. An innovative approach was developed that integrates data acquired from archival reports and maps, high-resolution satellite imagery, and digital terrain modeling to assess the total diamond endowment of the Séguéla and Tortiya deposits and to calculate annual diamond production from 2006 to 2013. On the basis of currently available data, this study estimates that a total of 10,100,000 carats remain in Séguéla and a total of 1,100,000 carats remain in Tortiya. Production capacity was calculated for the two study areas for the years 2006–2010 and 2012–2013. Production capacity was found to range from between 38,000 carats and 375,000 carats in Séguéla and from 13,000 carats and 20,000 carats in Tortiya. Further, this study demonstrates that artisanal mining activities can be successfully monitored by using remote sensing and geologic modeling techniques. The production capacity estimates presented here fill a significant data gap and provide policy makers, the UN, and the KP with important information not otherwise available.

Scientific Investigations Report↗
USGS1952

Pegmatites of the Crystal Mountain district, Larimer County, Colorado

The Front Range of Colorado is composed chiefly of schists of the pre-Cambrian Idaho Springs formation which have been intruded by a variety of granitic batholiths. In the Crystal Mountain district the Mount Olympus granite, a satellite of the Longs Peak batholith, forms sills and essentially concordant multiple intrusions in quartz-mica schist that dips southward at moderate to steep angles. A great number of pegmatites accompanied and followed the intrusion of the sills, and formed concordant and discordant bodies in schist and granite. Over 1,300 pegmatites in the Hyatt area north of the Big Thompson River are mapped and individually described. There are 27 pegmatites in the area that are made up of a wall zone and a core, and one, the pegmatite at the Hyatt mine, is composed of five zones. The largest pegmatites in the area are discordant in schist and occupy zones that are interpreted to be tear faults and tension fractures produced by the successive intrusions of granite that formed multiple sills. The majority of pegmatites in the large multiple sills were emplaced along the foliation and fractures. The composition of 96 percent of the pegmatites is granitic, 3.5 percent are quartz-rich pegmatites, and a few are tourmaline-rich. The pegmatites were intruded over a period of time and probably were derived from a granitic magma at different stages during differentiation. Solutions escaping from many of the pegmatites tournalinized and silicified the wall rocks for a few inches to two feet, but chemical and spectrographic analyses fail to show the transport of any other constituents. Perthite, plagioclase, and quartz are the essential minerals of the pegmatites, and muscovite is a minor but widespread constituent. Tourmaline, garnet, beryl, and apatite are common accessory minerals, and lithiophillitite-triphylite, bismuthinite, uraninite, columbite-tantalite, and chrysoberyl are rare constituents. Beryl is found in 250 or 27 percent of the pegmatites and makes up 0.01 percent or more of 77 bodies. The beryl-bearing pegmatites are richest in two of the three large granite masses, and are somewhat less rich at a distance of more than a thousand feet from the margins of the intrusives, but contain the least beryl in the thousand-foot belt immediately surrounding the intrusives. The Hyatt pegmatite is by far the richest deposit of beryl in the area mapped. Most of the pegmatites mapped are "unzoned" or homogeneous pegmatites. All gradations are visible between bodies consisting of uniform texture and mineral distribution to zoned pegmatites. The interpretation is made that, for most pegmatites, the initial composition determines whether or not zones will form. Pegmatites containing many zones can form from a magma composed of the elements in perthite, plagioclase, quartz, and muscovite, depending on the proportions of the components crystallizing at any given time. The complexly zoned deposits depend for their formation on the presence of a number of the rarer elements, principally lithium. Replacement textures in zones result from the interaction of the rest-liquid with the earlier-formed solid crystals. No mappable pegmatite in the Crystal Mountain district formed from the replacement of pre-existing pegmatite by solutions escaping from the rest-liquid, or by solutions originating outside the pegmatite. Three beryl-bearing zoned pegmatites, the Hyatt, Big Boulder, and Buckhorn Mica deposits, were explored by core drilling. Each deposit is mapped and described in detail, and the mineral reserves evaluated. The exploration indicates a total of 2,000 tons of beryl, of which 480 tons is estimated to be recoverable by hand sorting. The mapping of the 3 3/4-square mile Hyatt area indicates beryl in sufficient abundance to infer beryl resources of an additional 1,150 tons. Small tonnages of scrap mica and perthite may be obtained from the Hyatt and Big Boulder prospects, and columbite-tantalite may occur in sufficient amounts at the Buckhorn Mica mine and Tantalum claim to produce several hundred pounds as a byproduct of beryl mining. Dumps at the various deposits contain 25 to 50 tons of beryl.

Colorado↗
USGS2000

Hydrology of the Helena area bedrock, west-central Montana, 1993-98

The Generalized Bedrock Geologic Map of the Helena Area, West-Central Montana (plate 1 in the report) provides an intermediate-scale overview of bedrock in the Helena area. The geologic map has been compiled at a scale of 1:100,000 from the most widely available sources of geologic map information (see index to geologic mapping on pl. 1). That information has been updated by M.W. Reynolds for this report with more recent geologic mapping and field revision of published maps. All well locations and all bedrock units penetrated during drilling have been confirmed on geologic maps at the largest scale available. Source geologic maps are all at scales larger than 1:100,000 scale. Care has been taken to ensure accurate representation of the original geology at the compilation scale. However, positional accuracy of some features might be somewhat diminished at the smaller scale of the base map when compared with the original data source. Also, line thicknesses for contacts and faults necessarily assume a greater width, relative to the real geologic feature, at the scale of the generalized map than on any original map. The map is not intended for large-scale, site-specific detailed planning. Bedrock units throughout the Helena area are generally covered by young surficial deposits such as alluvium, colluvium, glacial debris, or windblown sediment. Thickness of such deposits varies from veneers through which the underlying bedrock is clearly discernible to major thicknesses that conceal all underlying bedrock and structure. Boundaries of major accumulations of surficial deposits are attributed separately from bedrock contacts. These boundaries should not be considered precise at the map scale or at larger scales. Boundaries shown may be less accurate positionally than bedrock contacts and faults because (1) surficial deposits commonly thin to a knife edge; (2) different mappers will interpret the edge differently when drawing a boundary; or (3) the original geologic map maker was concerned principally with bedrock units and structure and thus overlooked, or did not originally map as consistently, some surficial deposits. Veneers of surficial sediment, when saturated, can be local sources of recharge to underlying bedrock. Use of the generalized map to define their distribution does not substitute for site specific mapping of such deposits. Specific knowledge is needed to determine the water-bearing properties of the geologic units at and surrounding a site because the units, including the igneous and metamorphic rocks, have internal differences in stratigraphy, composition, mineralogy and grain size or crystallinity. These differences, together with structural imprints such as faults, folds, and the spacing, orientation, degree of openness of fractures, and extent and type of mineral filling in fractures and faults, all affect the ability of rocks to store and transmit water.

Montana↗
USGS1986

Map showing slope movements in the Oak Forest Quadrangle, Greene County, southwestern Pennsylvania

This map is the first example in the eastern United States of a 1:24,000-scale 7.5– minute quadrangle map that identifies areas with slope—stability problems in detail. Such a map enables the user to make a rapid evaluation of the potential for mass movement. Furthermore, detailed slope movement inventory of this type can serve as a framework for statistical analyses of several factors that cause slope failures, such as the effects of bedrock lithology, soil and slope characteristics, and precipitation. Planners, engineers, soil scientists, geologists, and elected officials should find the map useful in the assessment of slope hazards and planning for future land use. Final evaluation of any site within the quadrangle should be based on an examination by a soils engineer or an engineering geologist. Field investigations in the springs of 1981 and 1982 and the fall of 1981 involved nearly 60 days of traverses. The foot traverses were supplemented by the interpretation of the land surface on vertical black-and-white aerial photography flown in January and February of 1973 at a scale of nearly 1:24,000. Earlier aerial photography flown in June and July 1939 at a scale of 1:20,000 and more recent but significantly smaller scale photography (1:80,000) flown in June 1977 supplied additional documentation. More than 1,200 active or recently active and 900 older slope movements were identified. The geologic map of the Oak Forest quadrangle (Roen, 1972) is one of several geologic maps at a scale of 1:24,000 in eastern and central Greene County. Stone (1932) wrote an earlier report of the geology and mineral resources of Greene County. A series of reconnaissance landslide maps at 1:24,000 scale based mainly on aerial photographic interpretation included Greene and adjacent counties (Hackman and Thomas, 1978). Selection of the Oak Forest quadrangle for a more comprehensive study of the slope movements was based on the existence of a recent geologic map (Roen, 1972), sizeable tracts of both forested and non-forested land, nearby precipitation record stations, a large number of pipelines which could offer pertinent data, and good accessibility of terrain from secondary roads. Finally, Hackman and Thomas (1978) showed that the area was representative of any quadrangle in the northern part of the Dunkard basin in its distribution and density of slope movements. The quadrangle is located about 65 km southwest of Pittsburgh, Penn. (fig. 1). Three distinct drainage systems (north, east, and south trending) are represented within the quadrangle (fig. 2).

Pennsylvania↗
USGS1906

The geography and geology of Alaska; a summary of existing knowledge, with a section on climate, and a topographic map and description thereof

Alaska, the largest outlying possession of the United States, is that great land mass forming the northwestern extremity of the North American continent, whose western point is within 60 miles of the Asiatic coast (PI. II). About one-quarter of this area lies within the Arctic Circle, and from the standpoint of geographic position must be regarded as an arctic province; but the southern seaboard, exposed to the warm winds and waters of the Pacific, gives to the entire southern portion of the territory" a comparatively warm climate. It is not generally realized that the range of climate in Alaska is greater than that between Florida and Maine. At the southernmost point of the Pacific coast the mean annual temperature is not far from that of the city of Washington, the winters being warmer and characterized by less snowfall; the Yukon Valley on the other hand has a winter climate similar to that of northern Montana and Dakota; while in the extreme northern part of the territory the meteorologic conditions are invariably arctic. Though as yet only sparsely settled, Alaska's vast area and great resources make it one of the most important possessions of the United States and promise its rapid development. During the years 1890 to 1900 the population increased from 32,052* to 63,592. The mineral output, which in 1890 was valued at less than $800,000, exceeded $9,000,000 in 1904, and the fisheries show a corresponding growth. This rapid development has attracted public attention and led to urgent demand for explorations, surveys, and other investigations. So actively has this work been pushed, both by public and private enterprise, that exact knowledge of the geography, geology, and mineral resources of the interior has made greater strides within the last eight years than during the preceding thirty-one years since the acquisition of Alaska. The facts regarding the geography and geology, scattered as they are through the many books and reports of this period, are not always readily accessible, and the time seems ripe to present them in a summarized form. The topography of Alaska is varied and complex (see PI. I), and it is not easy to present briefly even the salient features. The limited number of pages here devoted to the subject precludes the possibility of detailed treatment, even if the facts were available. Much of the description has been taken from the results attained by other investigators, the writer being personally familiar with only a part of this large province. A list of the publications consulted is appended. The larger geographic features of Alaska are now fairly well known, though the detailed surveys which are demanded by the development of many localities have hardly been begun. Preliminary surveys have been completed of all but three 8 of the larger rivers. The most important mountain ranges have been at least outlined (fig. 3). Only three large areas remain almost entirely unmapped: One in southwestern Alaska, between Cook Inlet and the lower Kuskokwim, and the others in northern Alaska, embracing the Arctic watershed east and west of the Colville River. Nearly all the surveys of the interior, however, have been of a preliminary and exploratory character, and to meet the requirements of exact geography must be followed by more detailed mensuration. Though the coast line has been fairly well known for more than half a century, knowledge of the interior has been gained chiefly within the last two decades. This has not yet found its way into text-books and has too often been entirely ignored by cartographers. If facts are presented which may seem elementary, it is because even well-informed people have been known to harbor misconceptions in regard to the orographic features, climate, and general character of Alaska. Those who read of the perils and privations of winter travel and explorations are apt to picture a region of ice and snow; others, again, who have personal knowledge of the tourist route of southeastern Alaska, regard the whole district as one of rugged mountains and glaciers. In point of fact, glaciers are now nearly limited to the ranges bordering the Pacific and to the two slopes of the Alaska range; and even during the greatest development of glaciers but a small portion of Alaska was under ice (see map, PI. XXII). As a treatise on geography would hardly be complete without some discussion of the climate, meteorologic data have been compiled by Mr. Cleveland Abbe, jr., but the discussion of this does not pretend to be more than a cursory treatment of the subject. The scope of the paper seems to require also a brief summary of the development of geographic knowledge of Alaska. This subject, with its many ramifications, is of fascinating interest and offers a magnificent field for the trained historian. If the accompanying sketch of discovery and exploration awakens any measure of popular interest the writer will feel amply rewarded for having attacked a theme which hardly falls within the scope of his investigations. When this compilation was begun it was intended to be chiefly a description of the topography of Alaska, as illustrated by the accompanying map (PI. XXXIV, in pocket), which was compiled under the direction of the late R. U. Goode. In the course of the work there accumulated much geologic as well as geographic material which seemed worthy of inclusion in the report. As no comprehensive statement of the geology of Alaska has been made since the modern epoch of investigation was begun, an attempt will be made to give a summary of all results achieved. Since the writer has obtained much of his knowledge of the facts from the work of others, he disclaims any pretense of making an entirely original contribution to geologic science. He feels, however, that a personal familiarity with a considerable part of the province, gained during seven consecutive seasons of field work, will justify Mm in presenting conclusions which may in some cases be at variance with those in the reports on which he must draw for his facts. Throughout this report attempt will be made to credit borrowed material to the source from which it is drawn. Where such matter has been obtained entirely from published reports there is no difficulty in so doing; but as regards investigators of the Geological Survey, with whom the writer has collaborated both in field and in office, the case is somewhat different, for it is not always possible to know whether this or that theory originated with the writer or with one of his colleagues. It will, then, perhaps suffice to state that this report could not have been prepared without the explorations and researches of the geologists, F. C. Schrader, Walter C. Mendenhall, Arthur J. Collier, J. E. Spurr, and Arthur C. Spencer; and the surveys of the topographers, T. G. Gerdine, D. C. Witherspoon, D. L. Reaburn, W. J. Peters, and E. C. Barnard. Each of these men, in the course of from two to six years of field work, has made important contributions to the knowledge of the geography and geology of Alaska, and not all of these results have yet been put in print. In the last season (1903) L. M. Prindle, C. W. Wright, Arthur Hollick, G. C. Martin, F. L. Hess, and Fred H. Moffit have carried on geologic work in Alaska, and the writer has made use of their work now in course of publication. He has also been fortunate in having access to the manuscript reports of Walter C. Mendenhall and F. C. Schrader on the Copper River basin, to which references will be made. The matter here presented should be credited in a measure to all of these investigators, but for many of the theories advanced the writer alone is responsible. As this manuscript goes to press there has been opportunity to incorporate some of the results of the field work of 1904. As far as possible these have been embodied in the text, but in some instances it has been found advisable to add them only as footnotes. During the past summer F. E. and C. W. Wright extended the geologic reconnaissance in southeastern Alaska. In southwestern Alaska G. C. Martin and T. W. Stanton have determined the general Mesozoic section, while F. H. Moffit has made a reconnaissance of the northern part of the Kenai Peninsula. A. J. Collier has mapped the geology of the Cape Lisburne region, and L. M. Prindle and F. L. Hess have made contributions to the knowledge of the metamorphic terranes of the Yukon-Tanana district. It is the writer's purpose to describe in nontechnical language the larger geographic features and discuss their relation as far as the data available will permit. In the treatment of the geology, however, less effort will be made to make the matter acceptable to the lay reader. It is hoped, however, that a brief summary of the salient features of the geologic history' may be not without interest to the general public. If this paper serves in some measure to dispel the popular fallacies regarding Alaska and to disseminate more accurate knowledge of its geographic and geologic features, the purpose of its publication will be accomplished.

Alaska↗
USGS2013

Automated mapping of mineral groups and green vegetation from Landsat Thematic Mapper imagery with an example from the San Juan Mountains, Colorado

Multispectral satellite data acquired by the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) and Landsat 7 Enhanced Thematic Mapper Plus (TM) sensors are being used to populate an online Geographic Information System (GIS) of the spatial occurrence of mineral groups and green vegetation across the western conterminous United States and Alaska. These geospatial data are supporting U.S. Geological Survey national-scale mineral deposit database development and other mineral resource and geoenvironmental research as a means of characterizing mineral exposures related to mined and unmined hydrothermally altered rocks and mine waste. This report introduces a new methodology for the automated analysis of Landsat TM data that has been applied to more than 180 scenes covering the western United States. A map of mineral groups and green vegetation produced using this new methodology that covers the western San Juan Mountains, Colorado, and the Four Corners Region is presented. The map is provided as a layered GeoPDF and in GIS-ready digital format. TM data analysis results from other well-studied and mineralogically characterized areas with strong hydrothermal alteration and (or) supergene weathering of near-surface sulfide minerals are also shown and compared with results derived from ASTER data analysis.

Colorado↗
USGS2013

Metallogenic belt and mineral deposit maps of northeast Asia

This report contains explanatory material and summary tables for lode mineral deposits and placer districts (Map A, sheet 1) and metallogenic belts of Northeast Asia (Maps B, C, and D on sheets 2, 3, and 4, respectively). The map region includes eastern Siberia, southeastern Russia, Mongolia, northeast China, and Japan. A large group of geologists—members of the joint international project, Major Mineral Deposits, Metallogenesis, and Tectonics of Northeast Asia—prepared the maps, tables, and introductory text. This is a cooperative project with the Russian Academy of Sciences, Mongolian Academy of Sciences, Mongolian National University, Ulaanbaatar, Mongolian Technical University, Mineral Resources Authority of Mongolia, Geological Research Institute, Jilin University, China Geological Survey, Korea Institute of Geoscience and Mineral Resources, Geological Survey of Japan, and U.S. Geological Survey. This report is one of a series of reports on the mineral resources, geodynamics, and metallogenesis of Northeast Asia. Companion studies include (1) a detailed geodynamics map of Northeast Asia (Parfenov and others, 2003); (2) a compilation of major mineral deposit models (Rodionov and Nokleberg, 2000; Rodionov and others, 2000); (3) a series of metallogenic belt maps (Obolenskiy and others, 2004); (4) location map of lode mineral deposits and placer districts of Northeast Asia (Ariunbileg and others, 2003b); (5) descriptions of metallogenic belts (Rodionov and others, 2004); (6) a database on significant metalliferous and selected nonmetalliferous lode deposits and selected placer districts (Ariunbileg and others, 2003a); and (7) a series of summary project publications (Ariunbileg and 74 others, 2003b).

Asia↗
USGS2007

Volcanogenic Massive Sulfide Deposit Density

A mineral-deposit density model for volcanogenic massive sulfide deposits was constructed from 38 well-explored control areas from around the world. Control areas contain at least one exposed volcanogenic massive sulfide deposit. The control areas used in this study contain 150 kuroko, 14 Urals, and 25 Cyprus massive sulfide subtypes of volcanogenic massive sulfide deposits. For each control area, extent of permissive rock, number of exposed volcanogenic massive sulfide deposits, map scale, deposit age, and deposit density were determined. The frequency distribution of deposit densities in these 38 control areas provides probabilistic estimates of the number of deposits for tracts that are permissive for volcanogenic massive sulfide deposits-90 percent of the control areas have densities of 100 or more deposits per 100,000 square kilometers, 50 percent of the control areas have densities of 700 or more deposits per 100,000 square kilometers, and 10 percent of the control areas have densities of 3,700 or more deposits per 100,000 square kilometers. Both map scale and the size of the control area are shown to be predictors of deposit density. Probabilistic estimates of the number of volcanogenic massive sulfide deposits can be made by conditioning the estimates on sizes of permissive area. The model constructed for this study provides a powerful tool for estimating the number of undiscovered volcanogenic massive sulfide deposits when conducting resource assessments. The value of these deposit densities is due to the consistency of these models with the grade and tonnage and the descriptive models. Mineral-deposit density models combined with grade and tonnage models allow reasonable estimates of the number, size, and grades of volcanogenic massive sulfide deposits to be made.

Scientific Investigations Report↗
USGS2015

Bedrock geologic map of the Spring Valley, West Plains, and parts of the Piedmont and Poplar Bluff 30'x60' quadrangles, Missouri, including the upper Current River and Eleven Point River drainage basins

This map covers the drainage basins of the upper Current River and the Eleven Point River in the Ozark Plateaus physiographic province of southeastern Missouri. The two surface drainage basins are contiguous in their headwaters regions, but are separated in their lower reaches by the lower Black River basin in the southeast corner of the map area. Numerous dye-trace studies demonstrate that in the contiguous headwaters areas, groundwater flows from the Eleven Point River basin into the Current River basin. Much of the groundwater discharge of the Eleven Point River basin emanates from Big Spring, located on the Current River. This geologic map and cross sections were produced to help fulfill a need to understand the geologic framework of the region in which this subsurface flow occurs. The map includes all of the Ozark National Scenic Riverways, a national park created by an Act of Congress in 1964 to protect 134 miles of the Current and Jacks Fork Rivers in south-central Missouri. Located within the park are numerous large springs, including Big Spring, the largest spring in Missouri and one of the ten largest springs in the world. Also within the map area is Greer Spring, which is the main source of the Eleven Point River. Greer Spring is the largest spring on National Forest land in the United States. During flood, flow from Greer Spring is almost as large, volumetrically, as that from Big Spring. The Wild and Scenic Rivers Act in 1968 established a 44-mile section of the Eleven Point River as the Eleven Point National Scenic River, which is entirely within the boundaries of this map. Potentially economic mineral resources are present in the subsurface in the map area. Exploration drill-hole data indicate that anomalously high concentrations of base-metal sulfides locally occur within the Cambrian Bonneterre Formation. The geologic setting of these anomalous concentrations is similar to that found in the Viburnum Trend, part of the largest lead-mining district in the world. The southernmost part of the Viburnum Trend extends into the northern part of the map area and is exploited by the Sweetwater Mine. Undeveloped and potentially economic occurrences of base metals are known also beneath Blair Creek, a tributary to the Current River in the north-central part of the map area.

Missouri↗
USGS2011

Recovery and reprocessing of legacy geophysical data from the archives of the State Company of Geology and Mining (GEOSURV) of Iraq and Iraq Petroleum Company (IPC)

Aeromagnetic data belonging to the State Company of Geology and Mining of Iraq (GEOSURV) have been recovered from magnetic tapes and early paper maps. In 1974 a national airborne survey was flown by the French firm Compagnie General de Geophysique (CGG). Following the survey the magnetic data were stored on magnetic tapes within an air conditioned archive run by GEOSURV. In 1990, the power supply to the archive was cut resulting in the present‐day poor condition of the tapes. Frontier Processing Company and the U.S. Geological Survey (USGS) have been able to recover over 99 percent of the original digital data from the CGG tapes. Preliminary reprocessing of the data yielded a total magnetic field anomaly map that reveals fine structures not evident in available published maps. Successful restoration of these comprehensive, high quality digital datasets obviates the need to resurvey the entire country, thereby saving considerable time and money. These data were delivered to GEOSURV in a standard format for further analysis and interpretation. A parallel effort by GETECH concentrated on recovering the legacy gravity data from the original field data sheets archived by IPC (Iraq Petroleum Company). These data have been compiled with more recent GEOSURV sponsored surveys thus allowing for the first time a comprehensive digital and unified national gravity database to be constructed with full principal facts. Figure 1 shows the final aeromagnetic and gravity data coverage of Iraq. The only part of Iraq lacking gravity and aeromagnetic data coverage is the mountainous areas of the Kurdish region of northeastern Iraq. Joint interpretation of the magnetic and gravity data will help guide future geophysical investigations by GEOSURV, whose ultimate aim is to discover economical mineral and energy resources.

SEG Technical Program Expanded Abstracts↗
USGS1992

The Alaska Mineral Resource Assessment Program: Background information to accompany geologic and mineral-resource maps of the Cordova and Middleton Island quadrangles, southern Alaska

This report summarizes recent results of integrated geological, geochemical, and geophysical field and laboratory studies conducted by the U.S. Geological Survey in the Cordova and Middleton Island 1°x3° quadrangles of coastal southern Alaska. Published open-file reports and maps accompanied by descriptive and interpretative texts, tables, diagrams, and pertinent references provide background information for a mineral-resource assessment of the two quadrangles. Mines in the Cordova and Middleton Island quadrangles produced copper and byproduct gold and silver in the first three decades of the 20th century. The quadrangles may contain potentially significant undiscovered resources of precious and base metals (gold, silver, copper, zinc, and lead) in veins and massive sulfide deposits hosted by Cretaceous and Paleogene sedimentary and volcanic rocks. Resources of manganese also may be present in the Paleogene rocks; uranium resources may be present in Eocene granitic rocks; and placer gold may be present in beach sands near the mouth of the Copper River, in alluvial sands within the canyons of the Copper River, and in smaller alluvial deposits underlain by rocks of the Valdez Group. Significant coal resources are present in the Bering River area, but difficult access and structural complexities have discouraged development. Investigation of numerous oil and gas seeps near Katalla in the eastern part of the area led to the discovery of a small, shallow field from which oil was produced between 1902 and 1933. The field has been inactive since, and subsequent exploration and drilling onshore near Katalla in the 1960's and offshore near Middleton Island on the outer continental shelf in the 1970's and 1980's was not successful.

Alaska↗
USGS2025

Combining scanning electron microscopy, X-ray diffraction, and X-ray fluorescence to characterize shear zones at the Pogo gold deposit, Alaska

This study employs a multi-method analytical approach to characterize the mineralogical, geochemical, and textural properties of fault rocks from the Pogo gold mine in the Yukon-Tanana Upland, central Alaska. Specifically, we examine cataclasites, to document the structural and geochemical evolution of shear zones and their associations with gold mineralization. To investigate the shear zone, we integrate portable X-ray fluorescence (pXRF), scanning electron microscopy-based automated mineralogy (SEM-AM), X-ray diffraction (XRD), and high-resolution micro-X-ray fluorescence (micro-XRF) mapping. These methods collectively provide insights into bulk and trace element chemistry, mineralogical composition, and deformation-related textures across multiple scales. Handheld pXRF enables rapid geochemical screening, guiding SEM-AM and XRD analyses to ensure consistent mineralogical interpretation. X-ray diffraction identifies and quantifies crystalline phases, while SEM-AM produces high-resolution mineral maps, revealing mineral abundances, grain-scale textures, and gold associations. Micro-XRF mapping further refines our understanding by showing visual trace element distributions at sub-millimetre resolution. By integrating these techniques, we improve our understanding of the nature and geochemistry of Pogo shear zones, their role in gold mineralization, and support metallurgical processing strategies. This approach enhances exploration models and resource characterization for structurally complex gold deposits.

Alaska↗
USGS2021

Groundwater hydrology and chemistry of Jamestown Island, Virginia—Potential effects of tides, storm surges, and sea-level rise on archaeological, cultural, and ecological resources

As the site of the first permanent English settlement in North America in 1607, Jamestown Island, Colonial National Historical Park (COLO), Virginia, contains a rich archaeological record that extends from the Paleoindian period (15,000 to 8,000 years ago) through the 20th century. The island is located on the lower James River near the mouth of Chesapeake Bay. Jamestown Island vegetation is dominated by upland forests surrounded by tidal, freshwater-to-oligohaline marshes. Along the Virginia coast, relative sea-level rise was more than 2.5 times the global average during the 20th century. Consequently, the National Park Service (NPS) has identified COLO as one of the 25 national parks most threatened by climate change. Surface waters across the island are hydraulically connected to the laterally continuous Surficial aquifer. The land-surface altitude of the island is low, with two-thirds of the island less than 5 feet (ft) above the North American Vertical Datum of 1988 (NAVD 88). Consequently, sea-level rise, combined with tides and storm surges, threatens the island and its resources as surface-water and groundwater levels rise, saltwater enters the Surficial aquifer, and groundwater chemistry changes. The impact of sea-level rise on the island’s surface-water resources has been well studied, but groundwater effects have been largely ignored. Quantifying the effects of tides, storm surges, and sea-level rise on groundwater levels and chemistry is essential to developing an effective strategy for managing climate-induced changes. The first step in developing a response strategy includes a parkwide general risk assessment for archaeological sites on the island, so that sites can be prioritized for management actions. The U.S. Geological Survey and the NPS began a study in 2015 to develop a long-term groundwater-monitoring program to evaluate this risk and to develop an updated management strategy. The groundwater-monitoring program consists of 45 wells and piezometers in two individual clusters and three transects across the island in different hydrologic and chemical settings. Samples for water quality were collected from the wells and piezometers from October 2015 through September 2018 at variable time intervals. Results of the monitoring identified disparate hydrologic and chemical responses to saltwater intrusion across the island. Specific conductance (an indicator of salinity) of groundwater beneath several marshes responded differently to changes in James River salinity. Groundwater response to changes in James River specific conductance appeared to be controlled by land-surface altitude and slope, differences in lateral and vertical sediment characteristics, distance from surface waters, and the degree of surface water/groundwater connectivity between channels and the aquifer. Groundwater chemistry data from monitoring wells at Black Point, a low-altitude, upland setting, are in contrast with conditions observed in Island House observation wells, a high-altitude, upland setting. Specific conductance (less than 200 microsiemens per centimeter [μS/cm]) and pH (greater than 5.0) of groundwater beneath much of the uplands that characterize the Island House observation wells are typical of groundwater in noncarbonate sedimentary aquifers recharged by precipitation. At Black Point, specific conductance ranged from 2,490 to 15,200 μS/cm, and pH ranged from 3.1 to 6.6 standard units. At the Black Point observation wells, the most saline and dense water was at the water table rather than deeper in the aquifer, causing a density inversion that persisted throughout the study. The density inversion likely resulted from differences in permeability between the shallow clay and fine-grained sands and the deeper coarse-grained sand and gravel. Groundwater with the lowest pH was at the water table. As saline groundwater flows through organic sediment beneath the marshes, bacterial biodegradation of organic matter creates anoxic conditions. Continued biodegradation concomitantly reduces iron-oxide minerals in the sediment and sulfate in saline water. When oxygen is reintroduced into groundwater, iron and sulfur can reoxidize to form sulfuric acid, locally lowering the pH of the water. This report describes the groundwater monitoring network design, rationale for site selection, monitoring approach, and results of monitoring from October 2015 through September 2018. Maps of inundation at selected water-level altitudes are included to identify the risk to archaeological, cultural, and ecological resources. The monitoring results of the hydrology and chemistry data are interpreted, and the different hydrologic and chemical settings are described. The implications of the study results for management decisions are presented, and suggestions for improving the monitoring network are included.

Virginia↗