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At least 1,423 records · Page 79Linked to original sources
USGS1882

Tertiary history of the Grand Canon District, with atlas

This work is chiefly devoted to a description of the methods and results of EROSION upon a grand scale. Since erosion depends for its efficiency principally upon the progressive elevation of a region, and upon its climatal conditions, these collateral subjects are also discussed in their relations to the principal theme. And in general such an erosion influences and is in turn influenced by the whole train of phenomena of which physical geology takes account. I have endeavored to show in what manner and to what extent the most important of these events and groups of events are correlated. In the analysis and synthesis of these processes may be found the materials for reconstructing the history of the evolution of the physical features of the region. This history is indeed but an outline, but in it appear many things which would not readily be discerned without such a comparison.

Arizona, Utah↗
USGS1978

Coastal mapping handbook

Passage of the Coastal Zone Management Act of 1972 focused attention on the Nation's coastal land and water areas. As plans for more effective management of the coastal zone evolved, it soon became apparent that improved maps and charts of these areas were needed. This handbook was prepared with the requirements of the entire coastal community in mind, giving greatest attention to the needs of coastal zone managers and planners at the State and local levels. Its principal objective is to provide general information and guidance; it is neither a textbook nor a technical manual, but rather a primer on coastal mapping. This handbook should help planners and managers of coastal programs to determine their mapping requirements, select the best maps and charts for their particular needs, and to deal effectively with personnel who gather data and prepare maps. The sections on "Sources of Assistance and Advice" and "Product and Data Sources" should be especially useful to all involved in mapping the coastal zone. Brief summaries of the mapping efforts of several State coastal zone management programs are included. "Future outlook" discusses anticipated progress and changes in mapping procedures and techniques. Illustrations are inserted, where appropriate, to illustrate the products and equipment discussed. Because of printing restrictions, the colors in map illustrations may vary from those in the original publication. The appendixes include substantial material which also should be of interest. In addition a glossary and an index are included to provide easy and quick access to the terms and concepts used in the text. For those interested in more technical detail than is provided in this handbook, the "Selected references" will be useful. Also, the publications of the professional societies listed in appendix 4 will provide technical information in detail.

Report↗
USGS1994

Subsidence and carbon fluxes in the Sacramento/San Joaquin Delta, California

The Sacramento/San Joaquin Delta was once tidal marshland and was formed by the confluence of the Sacramento and the San Joaquin Rivers. The delta covers more than 1,000 square miles and is bordered by the major population centers of the San Francisco Bay area, Sacramento, and Stockton (fig. 1). The delta took its current form by the 1930's when drainage of 100 islands and tracts and construction of 2,250 miles of levees were completed. The land surface on the delta islands has progressively subsided below sea level since the early 20th century. The integrity of the levee network is threatened because subsidence increases the differences in water levels maintained by the levees, which can cause levee failure and consequent flooding of the delta islands. Levee failure affects the quality and beneficial use of water in the delta, which is the major source of California's water supply to millions of residents and acres of agricultural land. This Fact Sheet briefly summarizes the research done by the U.S. Geological Survey, in cooperation with the California Department of Water Resources to assess the causes of subsidence, processes that affect subsidence, and carbon fluxes in the delta.

California↗
USGS2015

Photomosaics and event evidence from the Frazier Mountain paleoseismic site, trench 1, cuts 5–24, San Andreas Fault Zone, southern California (2010–2012)

The Frazier Mountain paleoseismic site is located within the northern Big Bend of the southern San Andreas Fault (lat 34.8122° N., lon 118.9034° W.), in a small structural basin formed by the fault (fig. 1). The site has been the focus of over a decade of paleoseismic study due to high stratigraphic resolution and abundant dateable material. Trench 1 (T1) was initially excavated as a 50-m long, fault-perpendicular trench crossing the northern half of the basin (Lindvall and others, 2002; Scharer and others, 2014a). Owing to the importance of a high-resolution trench site at this location on a 200-km length of the fault with no other long paleoseismic records, later work progressively lengthened and deepened T1 in a series of excavations, or cuts, that enlarged the original excavation. Scharer and others (2014a) provide the photomosaics and event evidence for the first four cuts, which largely show the upper section of the site, represented by alluvial deposits that date from about A.D. 1500 to present. Scharer and others (2014b) discuss the earthquake evidence and dating at the site within the context of prehistoric rupture lengths and magnitudes on the southern San Andreas Fault. Here we present the photomosaics and event evidence for a series of cuts from the lower section, covering sediments that were deposited from about A.D. 500 to 1500 (fig. 2).

California↗
USGS1992

Summary of ground-water hydrology of the Cambrian-Ordovician aquifer system in the northern Midwest, United States

The Cambrian-Ordovician aquifer system contains very productive aquifers throughout an area of about 161,000 square miles in the northern Midwest. The aquifer system is used extensively for industrial and rural water supplies and is the primary source of water for many municipalities in most of its area of occurrence, except in Indiana, central and southern Illinois, and western Iowa, where the aquifer system contains saline water. About 680 million gallons per day was withdrawn from drilled wells in the aquifer system in 1980. Rocks of Cambrian and Ordovician age, mainly marine sandstones and carbonate rocks, constitute most of the bedrock and subcrop beneath glacial drift in southeastern Minnesota, northeastern Iowa, Wisconsin, northern Illinois, and extreme northwestern Indiana. These strata dip generally to the south and east off the Transcontinental arch in Minnesota and the Wisconsin arch, which are structurally high areas of the Precambrian basement, into the structural lows of the Forest City basin of southwestern Iowa, the Illinois basin, and the Michigan basin. The Cambrian and Ordovician rocks are buried by younger rocks in the remainder of Iowa, Illinois, and Indiana and in most of northern Missouri. Silurian and Devonian carbonate rocks immediately overlie the Cambrian and Ordovician rocks in those areas and are termed the "Silurian-Devonian aquifer" in this study. The balance of the Devonian rocks and the overlying Mississippian and Pennsylvanian rocks generally are fine-grained sediment or dense carbonate rocks and collectively are considered to be a regional confining unit. Most of the area is covered by a veneer of glacial drift, which, along with Cretaceous sandstone in northwestern Iowa, is treated as a regional water-table aquifer. The Cambrian-Ordovician aquifer system is composed of six hydrogeologic units, which are, in descending order, the Maquoketa confining unit, St. Peter-Prairie du Chien-Jordan aquifer, St. Lawrence- Franconia confining unit, Ironton-Galesville aquifer, Eau Claire confining unit, and Mount Simon aquifer. The uppermost confining unit is the least permeable; it consists primarily of the Maquoketa Shale but includes the dense carbonate rocks of the Galena Dolomite and the Decorah, Platteville, and Glenwood Formations where they are overlain by the Maquoketa Shale. The presence of the Maquoketa in Iowa, eastern Wisconsin, northeastern Illinois, and Indiana effectively confines the entire aquifer system below. The aquifer system is a leaky-artesian system in which movement of ground water is controlled partly by the internal confining units. In the northern outcrop area, unconfined conditions prevail in shallow parts of the aquifer system and where the system is thin. Much of the recharge in upland areas discharges to streams through local flow systems, which are no more than a few miles in length. The remainder of the recharge moves slowly downward to deeper formations and downgradient to form or join the regional flow system. Computer simulations of regional ground-water flow improve understanding of the regional character of the Cambrian-Ordovician aquifer system. Ground-water flow in the confined part of the aquifer system is mainly horizontal, away from the structural highs in the north, toward the structural basins in the south and east. The rate of ground-water movement is very slow, and the flux along flow paths into the basins decreases because of a progressive loss of head and small but widespread upward leakage. Saline water in the basins restricts movement of freshwater into the deeper parts of the basins, thereby forcing flow upward through confining units. Principal regional discharge areas are the Mississippi and Missouri Rivers, the Illinois and Michigan structural basins, and Lake Michigan. However, the lake is not in direct hydraulic connection with the Cambrian-Ordovician aquifer system and receives flow primarily from the Silurian-Devonian aquifer, which it directly overlies. The longest regional flow paths originate in recharge areas in northwestern Iowa and extend southeastward as much as 400 miles toward the Illinois basin. Simulated predevelopment recharge and discharge for the Cambrian- Ordovician aquifer system balance at 351 million gallons per day. Development of the aquifer system began in various parts of the northern Midwest in the 1860's and 1870's with the drilling of deep, generally flowing artesian wells near Lake Michigan in eastern Wisconsin and northeastern Illinois and along the valleys of the Mississippi River and its tributaries. Initial heads of 186 and 130 feet above Lake Michigan at Milwaukee and Chicago, respectively, have been reported. Large-scale pumping has produced cones of depression in these two areas, with respective head declines of as much as 375 and 900 feet. Other major pumping centers generally have had much smaller declines. The largest withdrawals from the aquifer system were about 180 million gallons per day in each of the major metropolitan areas of Chicago and Minneapolis-St. Paul (Twin Cities). However, the total decline in head in the St. Peter-Prairie du Chien-Jordan aquifer in the Twin Cities by 1980 was only 90 feet because the aquifer is unconfined. Most of the eastern two-thirds of Iowa, where the aquifer system is tightly confined, is characterized by more than 50 feet of head decline, with 200 feet or more at Mason City and the Quad Cities. Pumpage from the Cambrian-Ordovician aquifer system throughout the study area averaged 683 million gallons per day for the period 1976-80. Results of a transient-model simulation show that recharge increased over predevelopment recharge by 447 million gallons per day. Natural discharge decreased by 99 million gallons per day, and 137 million gallons per day was released from aquifer storage. Mineralization of ground water in the aquifer system increases from slightly mineralized calcium magnesium bicarbonate water in the northern recharge areas, through more mineralized, mixed water types with increased sodium and sulfate, to highly mineralized sodium chloride brines in the deeper parts of the structural basins.

Iowa, Illinois, Indiana, Michigan, Minnesota, Miss↗
USGS1949

Suggested correlation in Simpson seeps region

During the 1949 drilling season eight core tests were completed in the Simpson Seeps area up to October 25th„ This program, which is still in progress, was undertaken to provide an explanation for the surface seeps near Caps Simpson. The shallowest of the eight holes reached 800 feet; the deepest was drilled to a depth of 1460 feet. Geophysical data on the shallow horizons indicate that the Simpson Seeps Core Tests shown on the section have been drilled in an area of nearly north-south strike. The five core tests that most nearly approximate a section normal to the strike were chosen for the accompanying cross Section. An east-west strike, accompanied by strong anomalous dips of fifteen to twenty degrees to the north is indicated by geophysical data about five miles north of the cross section.

Alaska↗
USGS2017

Application of paleoflood surveys for the southern Black Hills of South Dakota

Flood-frequency analyses for the Black Hills area have especially large uncertainties and are especially important for planning purposes because of a history of extremely large and damaging floods, such as the extreme floods of June 9–10, 1972. Geology, topography, and climatology are additional complicating factors for flood-frequency characterization for the area. Two previous paleoflood studies for the Black Hills area indicated good potential for improving flood-frequency analyses through implementation of paleoflood investigations. The objectives of this study (SD2010-04) for the southern Black Hills were to (1) develop long-term flood chronologies and associated peak-flow frequency analyses for selected stream reaches by applying paleoflood hydrology approaches; and (2) develop flood-frequency information regarding “high-elevation” stream reaches to help address questions regarding differential potential for generation of exceptionally strong rain-producing thunderstorms across elevation gradients in the area. Neither objective was accomplished because the study was terminated before planned completion. Substantial efforts could be applied for only 2 of the 12 research tasks prior to study termination. These were task 3 (preliminary reconnaissance) and task 4 (activities associated with Section 106 of the National Historic Preservation Act). Field reconnaissance conducted along 10 candidate streams indicated that conditions in the southern Black Hills appear quite favorable for conducting paleoflood investigations. All 10 candidate streams had moderate to good potential for favorable paleoflood evidence, and in general are well constrained in relatively narrow canyon reaches, which provides good sensitivity for changes in stage, relative to discharge. Task 4 (Section 106 activities) was needed because alcoves and rock shelters that are well suited for deposition and preservation of paleoflood evidence may have been used as shelters or cache locations by indigenous inhabitants and thus may be eligible for consideration as historic properties because of possible archaeological or cultural materials. The complexity of the Section 106 concerns and issues became progressively more apparent as the study evolved. The study eventually was terminated when it became apparent that the resources needed to address the Section 106 issues would overwhelm the resources available for study implementation. In the event of consideration of future re-implementation, approaches that might help expedite Section 106 issues could include (1) a partnership with another Federal agency that has substantial experience with the Section 106 process; (2) securing assistance from a consultant that could help with both the Section 106 process and the required archaeological component; and (3) partnering with a tribal college with archaeological or earth science/hydrology programs, which could help make this study become part of a learning exercise.

South Dakota↗
USGS1968

Variation of Nb-Ta, Zr-Hf, Th-U and K-Cs in two diabase-granophyre suites

Concentrations of Nb, Ta, Zr, Hf, Th, U and Cs have been determined in samples of igneous rocks representing the diabase-granophyre suites from Dillsburg, Pennsylvania, and Great Lake, Tasmania. Niobium and tantalum have a three to fourfold increase with differentiation in each of the suites. The chilled margin of the Great Lake intrusion contains half the niobium and tantalum content (5.3 ppm and 0.4 ppm, respectively) of the chilled basalt from Dillsburg (10 ppm and 0.9 ppm, respectively). The twofold difference between the suites is correlated with differences in their titanium content. The average Nb Ta "> NbTa ratios for each suite are similar: 13.5 for the Great Lake suite, and 14.4 for the Dillsburg suite. The zirconium content of the two suites is essentially the same and increases from 50 to 60 ppm in the chilled margins to 240–300 ppm in the granophyres. Hafnium is low in the early formed rocks (0.5 –1.5 ppm and achieves a maximum in the granophyres (5–8 ppm). The Zr Hf "> ZrHf ratio decreases from 68 to 33 with progressive differentiation. In the Dillsburg suite thorium and uranium increase from 2.6 ppm and 0.6 ppm, respectively, in the chilled samples to 11.8 ppm and 3.1 ppm in the granophyres. The chilled margin of the Great Lake suite contains 3.2 ppm thorium and 9.8 ppm uranium; the granophyre contains 11.2 ppm thorium and 2.8 ppm uranium. The average Th U "> ThU ratios of the Dillsburg and Great Lake suites are nearly the same—4.1 and 4.4, respectively. Within each suite the Th U "> ThU ratio remains quite constant. Cesium and the K Cs "> KCs ratio do not vary systematically in the Dillsburg suite possibly because of redistribution or loss of cesium by complex geologic processes. Except for the chilled margin of the Great Lake suite, the variation of Cs and the K Cs "> KCs ratio are in accord with theoretical considerations. Cesium increases from about 0.6 ppm in the lower zone to 3.5 ppm in the granophyre; the K Cs "> KCs ratio varies from 10 × 10 3 in the lower zone to 6 × 10 3 in the granophyre. A comparison of the abundance of some of these elements is made with those reported on oceanic tholeiites from the Atlantic and Pacific oceans. Trace elements with large ionic radii (Th, U, Cs) are present in significantly greater concentrations in the two continental tholeiitic series than in the oceanic tholeiites. However, this does not seem to be true for lithophilic elements of smaller ionic radii (Zr and Nb). These trace element distribution patterns, when considered with other minor element and isotopic studies, indicate that 1. crustal contamination does not entirely account for differences between continental and oceanic tholeiites, and 2. the oceanic tholeiites do not necessarily delimit the geochemical characteristics of the mantle.

Geochimica et Cosmochimica Acta↗
USGS1957

River channel patterns: Braided, meandering, and straight

Channel pattern is used to describe the plan view of a reach of river as seen from an airplane, and includes meandering, braiding, or relatively straight channels. Natural channels characteristically exhibit alternating pools or deep reaches and riffles or shallow reaches, regardless of the type of pattern. The length of the pool or distance between riffles in a straight channel equals the straight line distance between successive points of inflection in the wave pattern of a meandering river of the same width. The points of inflection are also shallow points and correspond to riffles in the straight channel. This distance, which is half the wavelength of the meander, varies approximately as a linear function of channel width. In the data we analysed the meander wavelength, or twice the distance between successive riffles, is from 7 to 12 times the channel width. It is concluded that the mechanics which may lead to meandering operate in straight channels. River braiding is characterized by channel division around alluvial islands. The growth of an island begins as the deposition of a central bar which results from sorting and deposition of the coarser fractions of the load which locally cannot be transported. The bar grows downstream and in height by continued deposition on its surface, forcing the water into the flanking channels, which, to carry the flow, deepen and cut laterally into the original banks. Such deepening locally lowers the water surface and the central bar emerges as an island which becomes stabilized by vegetation. Braiding was observed in a small river in a laboratory. Measurements of the adjustments of velocity, depth, width, and slope associated with island development lead to the conclusion that braiding is one of the many patterns which can maintain quasi-equilibrium among discharge, load, and transporting ability. Braiding does not necessarily indicate an excess of total load. Channel cross section and pattern are ultimately controlled by the discharge and load provided by the drainage basin. It is important, therefore, to develop a picture of how the several variables involved in channel shape interact to result in observed channel characteristics. Such a rationale is summarized as follows: Channel width appears to be primarily a function of near-bankfull discharge, in conjunction with the inherent resistance of bed and bank to scour. Excessive width increases the shear on the bed at the expense of that on the bank and the reverse is true for very narrow widths. Because at high stages width adjustment can take place rapidly and with the evacuation or deposition of relatively small volumes of debris, achievement of a ,relatively stable width at high flow is a primary adjustment to which the further interadjustments between depth, velocity, slope, and roughness tend to accommodate. Channel roughness, to the extent that it is determined by particle size, is an independent factor related to the drainage basin rather than to the channel. Roughness in streams carrying fine material, however, is also a function of the dunes or other characteristics of bed configuration. Where roughness is independently determined as well as discharge and load, these studies indicate that a particular slope is associated with the roughness. At the width determined by the discharge, velocity and depth must be adjusted to satisfy quasi-equilibrium in accord with the particular slope. But if roughness also is variable, depending on the transitory configuration of the bed, then a number of combinations of velocity, depth, and slope will satisfy equilibrium. An increase in load at constant discharge, width, and caliber of load tends to be associated with an increasing slope if the roughness (dune or bed configuration) changes with the load. In the laboratory river an increase of load at constant discharge, width, and caliber resulted in progressive aggradation of long reaches of channel at constant slope. The adjustments of several variables tending toward the establishment of quasi-equilibrium in river channels lead to the different channel patterns observed in nature. For example, the data indicate that at a given discharge, meanders occur at smaller values of slope than do’ braids. Further, at the same slope braided channels are associated with higher bankfull discharges than are meanders. An additional example is provided by the division of discharge around islands in braided rivers which produces numerous small channels. The changes in slope, roughness, and channel shape which accompany this division are in accord with quasi-equilibrium adjustments observed in the comparison of large and small rivers.

Professional Paper↗
USGS2004

Third U.S. Geological Survey Wildland Fire-Science Workshop : Denver, Colorado, November 12-15, 2002

Executive Summary -- The historically significant wildland fire events that occurred in the United States during 2000 and 2002, together with the associated recognition of the need for a different national policy of forest management, has led to an increased awareness of the need for cooperative effort among all Federal agencies in planning for and managing the risks and consequences of wildland fire. The expertise and capabilities of the U.S. Geological Survey (USGS) are significant resources in this regard, and the agency is becoming increasingly involved in fire-science activities in support of the various land-management agencies that are dealing directly with this issue. The First USGS Wildland Fire Workshop was held in Sioux Falls, South Dakota, in 1997 and helped to establish the direction of USGS in sharing its expertise with the fire-management agencies. The Second USGS Wildland Fire Workshop was held in Los Alamos, New Mexico, in 2000 and brought together all the agencies involved in the management of wildland fires in order to determine their needs, to demonstrate USGS capabilities to meet those needs, and to establish methods for the USGS to distribute data and tools useful in fire management. It enhanced the relationships developed during the 1997 workshop and helped to define USGS' role in the fire-management community. The Third USGS Wildland Fire-Science Workshop, held in Denver, Colorado, November 12?15, 2002, was an opportunity for exchange of information on recent progress in the area of fire science and to determine the gaps in fire-science research that could be addressed by the USGS. In addition to more than 90 USGS scientists engaged in fire-related research and managers of organizational units involved in some aspect of wildland fire activities, the workshop was attended by about 30 representatives of 11 other Federal agencies. There also were a number of attendees affiliated with several universities, private companies, and State and local agencies. The 4-day meeting consisted of a pre-workshop field trip to the Hayman Fire area, several keynote presentations, five panel discussions, presentation and 'breakout' discussion of four 'white paper' topics, and a poster session with more than 30 presentations.

Scientific Investigations Report↗
USGS2011

Mapping the Natchez Trace Parkway

Based on a National Park Service (NPS) landcover classification, a landcover map of the 715-km (444-mile) NPS Natchez Trace Parkway (hereafter referred to as the "Parkway") was created. The NPS landcover classification followed National Vegetation Classification (NVC) protocols. The landcover map, which extended the initial landcover classification to the entire Parkway, was based on color-infrared photography converted to 1-m raster-based digital orthophoto quarter quadrangles, according to U.S. Geological Survey mapping standards. Our goal was to include as many alliance classes as possible in the Parkway landcover map. To reach this goal while maintaining a consistent and quantifiable map product throughout the Parkway extent, a mapping strategy was implemented based on the migration of class-based spectral textural signatures and the congruent progressive refinement of those class signatures along the Parkway. Progressive refinement provided consistent mapping by evaluating the spectral textural distinctiveness of the alliance-association classes, and where necessary, introducing new map classes along the Parkway. By following this mapping strategy, the use of raster-based image processing and geographic information system analyses for the map production provided a quantitative and reproducible product. Although field-site classification data were severely limited, the combination of spectral migration of class membership along the Parkway and the progressive classification strategy produced an organization of alliances that was internally highly consistent. The organization resulted from the natural patterns or alignments of spectral variance and the determination of those spectral patterns that were compositionally similar in the dominant species as NVC alliances. Overall, the mapped landcovers represented the existent spectral textural patterns that defined and encompassed the complex variety of compositional alliances and associations of the Parkway. Based on that mapped representation, forests dominate the Parkway landscape. Grass is the second largest Parkway land cover, followed by scrub-shrub and shrubland classes and pine plantations. The map provides a good representation of the landcover patterns and their changes over the extent of the Parkway, south to north.

Alabama;Mississippi;Tennessee↗
USGS1999

Digital mapping techniques '99 -- workshop proceedings

The Digital Mapping Techniques '99 (DMT'99) workshop was attended by 91 technical experts from 42 agencies, universities, and private companies, including representatives from 30 state geological surveys (see Appendix A ). This workshop was similar in nature to the first two meetings, held in June, 1997, in Lawrence, Kansas (Soller, 1997), and in May, 1998, in Champaign, Illinois (Soller, 1998a). This year's meeting was hosted by the Wisconsin Geological and Natural History Survey, from May 19 to 22, 1999, on the University of Wisconsin campus in Madison. As in the previous meetings, the objective was to foster informal discussion and exchange of technical information. When, based on discussions at the workshop, an attendee adopts or modifies a newly learned technique, the workshop clearly has met that objective. Evidence of learning and cooperation among participating agencies continued to be a highlight of the DMT workshops (see example in Soller, 1998b, and various papers in this volume). The meeting's general goal was to help move the state geological surveys and the USGS toward development of more cost-effective, flexible, and useful systems for digital mapping and geographic information systems (GIS) analysis. Through oral and poster presentations and special discussion sessions, emphasis was given to: 1) methods for creating and publishing map products (here, ìpublishingî includes Web-based release); 2) continued development of the National Geologic Map Database; and 3) progress toward building a standard geologic map data model. Especially to support the interest in map preparation and publication, five representatives of the GIS hardware and software vendor community were invited to participate. The three annual DMT workshops were coordinated by the AASG/USGS Data Capture Working Group, which was formed in August, 1996, to support the Association of American State Geologists and the USGS in their effort to build a National Geologic Map Database (see Soller and Berg, this volume, and http://ncgmp.usgs.gov/ngmdbproject/standards/datacapt/datacaptureWG.html ). The Working Group was formed because increased production efficiencies, standardization, and quality of digital map products were needed to help the Database, and the State and Federal geological surveys, provide more high-quality digital maps to the public.

Open-File Report↗
USGS2003

A rehabilitation plan for walleye populations and habitats in Lake Superior

The walleye ( Stizostedion vitreum vitreum ) has been historically important in regional fisheries and fish communities in large bays, estuaries, and rivers of Lake Superior. Significant negative impacts on the species caused by overharvesting, habitat degradation, and pollution during the late 1800s and early 1900s have led to the preparation of a strategic rehabilitation plan. The lakewide goal is to maintain, enhance, and rehabilitate habitat for walleye and to establish self-sustaining populations in areas where walleyes historically lived. Population objectives that support the goal are to increase the abundance of juvenile and adult walleyes in selected areas. Habitat objectives that support the goal include increasing spawning and nursery habitat in four areas: enhancing fish passage, reducing sedimentation, increasing water quality, and reducing contaminants in walleyes. Progress toward achieving the habitat objectives should be measured by documenting increases in spawning and nursery habitats, resolving fish-passage issues, reducing sediments in rivers, and reducing contaminant levels in walleyes. Stocking various life stages of walleye should be considered to rehabilitate certain degraded populations. Total annual mortality of walleye populations should be less than 45% to allow populations to either increase or be maintained at target levels of abundance. Routine assessments should focus on gathering the data necessary to evaluate abundance and mortality and on taking inventories of spawning and nursery habitats. Research should be conducted to understand the specific habitat requirements for Lake Superior walleye populations and the habitat-abundance relationships for populations and for the lake as a whole.

Miscellaneous Publication↗
USGS1974

Metallogenic provinces of southeastern Pacific region

Metalliferous mineral deposits of the southeastern Pacific region include: (1) hydrothermal, magmatic, and sedimentary deposits of the Andean region, one of the great mineral belts of the world; (2) scattered hydrothermal deposits in the Antarctic Peninsula; and (3) metal-enriched pelagic sediments and ferromanganese nodules on the seafloor. Andean metalliferous deposits, the chief topic of this report, are for the most part spatially and genetically related to calc-alkaline plutons, subvolcanic intrusions, and volcanic rocks emplaced during the Andean orogeny of Late Triassic to Quaternary age. They are components of a single metallogenic province superimposed on two or more pre-Andean metallogenic provinces of Paleozoic and Precambrian(?) age. Deposits in the Antarctic Peninsula are similar in age and origin to the deposits in the Andes and are considered to belong to the Andean province. The Andean metallogenic province may be divided into several subprovinces, each parallel with the Andes and the continental margin and each having a dominant metal or suite of metals. The central Andes of Peru, northern Chile, and Bolivia, which contain the greatest concentration of exploitable deposits and the greatest variety of ore types, have as many as five linear, partly overlapping subprovinces. These subprovinces, from west to east (Pacific coast to the eastern Andean front), are characterized, respectively, by deposits of iron, copper, polymetallic base metals, tin, and gold. Calc-alkaline plutonic and volcanic rocks of the Andes, which probably originated by partial melting in the Benioff zone, show a general, though nonuniform progression of decreasing age from west to east. Igneous rocks of Jurassic and Cretaceous age are most abundant near the coast, whereas those of Tertiary and Quaternary age dominate in the Andes. Locally, intrusive rocks and associated ore deposits of widely different ages are juxtaposed. Several sources of the metals are probable; they include oceanic crust and pelagic sediments in the Benioff zone, some of which may have been enriched previously in certain metals at the ancestral East Pacific Rise, and metal-rich zones in the overlying mantle and continental crust.

AAPG Memoir↗
USGS2008

Environmental factors affecting mercury in Camp Far West Reservoir, California, 2001-03

This report documents water quality in Camp Far West Reservoir from October 2001 through August 2003. The reservoir, located at approximately 300 feet above sea level in the foothills of the northwestern Sierra Nevada, California, is a monomictic lake characterized by extreme drawdown in the late summer and fall. Thermal stratification in summer and fall is coupled with anoxic conditions in the hypolimnion. Water-quality sampling was done at approximately 3-month intervals on eight occasions at several stations in the reservoir, including a group of three stations along a flow path in the reservoir: an upstream station in the Bear River arm (principal tributary), a mid-reservoir station in the thalweg (prereservoir river channel), and a station in the deepest part of the reservoir, in the thalweg near Camp Far West Dam. Stations in other tributary arms of the reservoir included those in the Rock Creek arm of the reservoir, a relatively low-flow tributary, and the Dairy Farm arm, a small tributary that receives acidic, metal-rich drainage seasonally from the inactive Dairy Farm Mine, which produced copper, zinc, and gold from underground workings and a surface pit. Several water-quality constituents varied significantly by season at all sampling stations, including major cations and anions, total mercury (filtered and unfiltered samples), nitrogen (ammonia plus organic), and total phosphorus. A strong seasonal signal also was observed for the sulfurisotope composition of aqueous sulfate from filtered water. Although there were some spatial differences in water quality, the seasonal variations were more profound. Concentrations of total mercury (filtered and unfiltered water) were highest during fall and winter; these concentrations decreased at most stations during spring and summer. Anoxic conditions developed in deep parts of the reservoir during summer and fall in association with thermal stratification. The highest concentrations of methylmercury in unfiltered water were observed in samples collected during summer from deepwater stations in the anoxic hypolimnion. In the shallow (less than 14 meters depth) oxic epilimnion, concentrations of methylmercury in unfiltered water were highest during the spring and lowest during the fall. The ratio of methylmercury to total mercury (MeHg/HgT) increased systematically from winter to spring to summer, largely in response to the progressive seasonal decrease in total mercury concentrations, but also to some extent because of increases in MeHg concentrations during summer. Water-quality data for Camp Far West Reservoir are used in conjunction with data from linked studies of sediment and biota to develop and refine a conceptual model for mercury methylation and bioaccumulation in the reservoir and the lower Bear River watershed. It is hypothesized that MeHg is produced by sulfate-reducing bacteria in the anoxic parts of the water column and in shallow bed sediment. Conditions were optimal for this process during late summer and fall. Previous work has indicated that Camp Far West Reservoir is a phosphate-limited system - molar ratios of inorganic nitrogen to inorganic phosphorus in filtered water were consistently greater than 16 (the Redfield ratio), sometimes by orders of magnitude. Therefore, concentrations of orthophosphate were expectedly very low or below detection at all stations during all seasons. It is further hypothesized that iron-reducing bacteria facilitate release of phosphorus from iron-rich sediments during summer and early fall, stimulating phytoplankton growth in the fall and winter, and that the MeHg produced in the hypolimnion and metalimnion is released to the entire water column in the late fall during reservoir destratification (vertical mixing). Mercury bioaccumulation factors (BAF) were computed using data from linked studies of biota spanning a range of trophic position: zooplankton, midge larvae, mayfly nymphs, crayfish, threadfin shad, bluegill,

California↗
USGS2011

Geodatabase of Wyoming statewide oil and gas drilling activity to 2010

The U.S. Geological Survey (USGS) compiled a geographic information system (GIS) of Wyoming statewide historical oil and gas drilling activity for the Wyoming Landscape Conservation Initiative (WLCI). The WLCI is representative of the partnerships being formed by the USGS with other Department of the Interior bureaus, State and local agencies, industry, academia, and private landowners that are committed to maintaining healthy landscapes, sustaining wildlife, and preserving recreational and grazing uses as energy resources development progresses in southwestern Wyoming. This product complements the 2009 USGS publication on oil and gas development in southwestern Wyoming http://pubs.usgs.gov/ds/437/) by approximating, based on database attributes, the time frame of drilling activity for each well (start and stop dates). This GIS product also adds current oil and gas drilling activity not only in the area encompassing the WLCI, but also statewide. Oil and gas data, documentation, and spatial data processing capabilities are available and can be downloaded from the USGS website. These data originated from the Wyoming Oil and Gas Conservation Commission (WOGCC), represent decades of oil and gas drilling (1900 to 2010), and will facilitate a landscape-level approach to integrated science-based assessments, resource management and land-use decision making.

Wyoming↗
USGS1995

Sedimentology, Behavior, and Hazards of Debris Flows at Mount Rainier, Washington

Mount Rainier is potentially the most dangerous volcano in the Cascade Range because of its great height, frequent earthquakes, active hydrothermal system, and extensive glacier mantle. Many debris flows and their distal phases have inundated areas far from the volcano during postglacial time. Two types of debris flows, cohesive and noncohesive, have radically different origins and behavior that relate empirically to clay content. The two types are the major subpopulations of debris flows at Mount Rainier. The behavior of cohesive flows is affected by the cohesion and adhesion of particles; noncohesive flows are dominated by particle collisions to the extent that particle cataclasis becomes common during near-boundary shear. Cohesive debris flows contain more than 3 to 5 percent of clay-size sediment. The composition of these flows changed little as they traveled more than 100 kilometers from Mount Rainier to inundate parts of the now-populated Puget Sound lowland. They originate as deep-seated failures of sectors of the volcanic edifice, and such failures are sufficiently frequent that they are the major destructional process of Mount Rainier's morphologic evolution. In several deposits of large cohesive flows, a lateral, megaclast-bearing facies (with a mounded or hummocky surface) contrasts with a more clay-rich facies in the center of valleys and downstream. Cohesive flows at Mount Rainier do not correlate strongly with volcanic activity and thus can recur without warning, possibly triggered by non-magmatic earthquakes or by changes in the hydrothermal system. Noncohesive debris flows contain less than 3 to 5 percent clay-size sediment. They form most commonly by bulking of sediment in water surges, but some originate directly or indirectly from shallow slope failures that do not penetrate the hydrothermally altered core of the volcano. In contrast with cohesive flows, most noncohesive flows transform both from and to other flow types and are, therefore, the middle segments of flow waves that begin and end as flood surges. Proximally, through the bulking of poorly sorted volcaniclastic debris on the flanks of the volcano, flow waves expand rapidly in volume by transforming from water surges through hyperconcentrated stream flow (20 to 60 percent sediment by volume) to debris flow. Distally, the transformations occur more slowly in reverse order - from debris flow, to hyperconcentrated flow, and finally to normal streamflow with less than 20 percent sediment by volume. During runout of the largest noncohesive flows, hyperconcentrated flow has continued for as much as 40 to 70 kilometers. Lahars (volcanic debris flows and their deposits) have occurred frequently at Mount Rainier over the past several thousand years, and generally they have not clustered within discrete eruptive periods as at Mount St. Helens. An exception is a period of large noncohesive flows during and after construction of the modern summit cone. Deposits from lahar-runout flows, the hyperconcentrated distal phases of lahars, document the frequency and extent of noncohesive lahars. These deposits also record the following transformations of debris flows: (1) the direct, progressive dilution of debris flow to hyperconcentrated flow, (2) deposition of successively finer grained lobes of debris until only the hyperconcentrated tail of the flow remains to continue downstream, and (3) dewatering of coarse debris flow deposits to yield fine-grained debris flow or hyperconcentrated flow. Three planning or design case histories represent different lengths of postglacial time. Case I is representative of large, infrequent (500 to 1,000 years on average) cohesive debris flows. These flows need to be considered in long-term planning in valleys around the volcano. Case II generalizes the noncohesive debris flows of intermediate size and recurrence (100 to 500 years). This case is appropriate for consideration in some structural design. Case III flows are

Professional Paper↗
USGS2019

Petrology of volcanic rocks associated with silver-gold (Ag-Au) epithermal deposits in the Tonopah, Divide, and Goldfield Mining Districts, Nevada

Miocene calc-alkaline volcanic rocks, part of the southern segment of the ancestral Cascades magmatic arc, are spatially, temporally, and likely genetically associated with precious metal epithermal deposits in the Tonopah, Divide, and Goldfield Districts of west-central Nevada. In the Tonopah mining district, volcanic rocks include the Mizpah Trachyte, Fraction Tuff, and Oddie Rhyolite; in the Divide mining district, they include the Heller Tuff, Brougher Rhyolite, trachyandesite of Red Mountain, Divide Andesite, and volcanics of Donovan Peak (which includes rhyolite, dacite, and rhyodacite units); in the Goldfield mining district they include the Milltown Andesite, an unnamed porphyritic andesite, and latite. All these rocks are porphyritic and contain phenocryst assemblages that include plagioclase, pyroxene, hornblende, biotite, quartz, alkali feldspar, and olivine. These mostly subalkaline, metaluminous, calc-alkalic, and magnesian rocks range from basaltic trachyandesite to rhyolite and contain 54 to 78 weight percent silicon dioxide. In the Divide mining district, the Divide Andesite and the volcanics of Donovan Peak are compositionally distinct from volcanic rocks in the other two mining districts. These rocks define a somewhat more restricted range of silicon dioxide content; are more alkalic; have greater titanium dioxide, sodium oxide, barium, hafnium, lanthanum, niobium, tantalum, yttrium, ytterbium, and zirconium abundances; and lower magnesium oxide, strontium, and vanadium abundances. Elevated zirconium contents are particularly characteristic of these rocks, which are also distinctly younger than most of the rocks in the other two mining districts. The alkalic character (principally higher sodium oxide abundances) and elevated zirconium contents characteristic of the Divide Andesite and the volcanics of Donovan Peak suggest that distinctive sources and (or) processes contributed to the petrogenesis of these rocks. In the Tonopah, Divide, and Goldfield mining districts the geochemistry of Oligocene and Miocene volcanic rocks constrain the processes that contributed to the petrogenesis of these rocks. Specifically, major oxide compositional variation among these rocks is consistent with crystallization and fractionation of the observed phenocryst minerals. In addition, these rocks have negatively sloping rare-earth element patterns consistent with partial melting in a high-pressure, garnet stable regime. Elevated strontium concentrations and small negative europium anomalies are consistent with partial melting in a plagioclase-unstable setting. However, larger negative europium anomalies among the more silica-rich volcanic rocks indicates a progressively greater role for plagioclase fractionation among these rocks. The importance of hornblende in the petrogenesis of these rocks is reflected in subtly U-shaped middle rare-earth element pattern segments. Increasing lead/cerium and decreasing phosphorus pentoxide/potassium oxide with increasing silicon dioxide are characteristic of these volcanic rocks. These characteristics and their distinctive pre-Cenozoic xenolith content suggest a significant role for crustal contamination in their petrogenesis. Diagnostic textural features preserved by phenocrysts, especially plagioclase, constitute additional evidence that open-system behavior, including reservoir-scale mixing, recharge, and assimilation, was critical to the petrogenesis of volcanic rocks in the Tonopah, Divide, and Goldfield mining districts.

Nevada↗