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At least 469 records · Page 26Linked to original sources
USGS1984

Origins and exploration significance of replacement and vein-type alunite deposits in the Marysvale volcanic field, west central Utah

Alunite deposits formed 23 m.y. ago in near-surface, highly oxidizing conditions at the tops of hydrothermal plumes that were spaced at 3- to 4-km intervals around a monzonite stock. The delta 34 S values of 11.5 to 15.4 per mil for replacement alunite along with geologic constraints indicate that sulfate sulfur was derived from underlying Mesozoic evaporites. The delta 34 S values of -15.3 to +5.1 per mil of underlying pyrite, however, indicate that reduced sulfur, necessary to produce low pH during oxidation, either was produced by partial reduction of the evaporite sulfate or came from another source. Vein-type alunite deposits formed 14 m.y. ago as open-space fillings in extension fractures above a concealed stock. Crystals of alunite grew inward from the walls, forming veins of nearly pure alunite as much as 20 m thick. The delta 34 S values near zero per mil indicate that the vein-type alunite sulfur probably had a magmatic source, and it appears that the sulfur may have been present as SO 2 shortly after degassing from the magma. The probable magmatic origin for sulfur in the 14-m.y.-old vein-type alunite and its deposition from vapor-rich fluids, as well as the probable magmatic origin for sulfur in the surrounding base and precious metal deposits, suggest that the underlying stock may host porphyry-type deposits.

Economic Geology↗
USGS1994

A special issue on volcanic centers as targets for mineral exploration; preface

NEPTUNE or Pluto? Since the days of Hutton and Werner, every generation of economic geologists has addressed this question in a new light. Most papers in this special issue deal with the thin and leaky roof of Pluto's underworld. It allows hot emanations from Hades to leak out, only to be quenched and diluted by waters percolating down from Neptune's realm.

Economic Geology↗
USGS2007

Interaction and influence of two creeks on Escherichia coli concentrations of nearby beaches: Exploration of predictability and mechanisms

The impact of river outfalls on beach water quality depends on numerous interacting factors. The delivery of contaminants by multiple creeks greatly complicates understanding of the source contributions, especially when pollution might originate up- or down-coast of beaches. We studied two beaches along Lake Michigan that are located between two creek outfalls to determine the hydrometeorologic factors influencing near-shore microbiologic water quality and the relative impact of the creeks. The creeks continuously delivered water with high concentrations of Escherichia coli to Lake Michigan, and the direction of transport of these bacteria was affected by current direction. Current direction reversals were associated with elevated E. coli concentrations at Central Avenue beach. Rainfall, barometric pressure, wave height, wave period, and creek specific conductance were significantly related to E. coli concentration at the beaches and were the parameters used in predictive models that best described E. coli variation at the two beaches. Multiple inputs to numerous beaches complicates the analysis and understanding of the relative relationship of sources but affords opportunities for showing how these complex creek inputs might interact to yield collective or individual effects on beach water quality.

Journal of Environmental Quality↗
USGS2008

Exploring visitor acceptability for hardening trails to sustain visitation and minimize impacts

Protected natural area managers are challenged to provide high quality recreation opportunities and ensure the protection of resources from impacts associated with visitation. Development of visitor use facilities and application of site hardening practices are commonly applied tools for achieving these competing management objectives. This study applies stated choice analysis to examine visitor opinions on acceptability when they are asked to make tradeoffs among competing social, resource and management attributes in backcountry and frontcountry settings of Acadia National Park. This study demonstrates that asking visitors about recreation setting attributes uni-dimensionally, a common approach, can yield less informative responses. Analyses that considered direct tradeoffs revealed more divergent opinions on acceptability for setting attributes than a unidimensional approach. Findings revealed that visitors to an accessible and popular attraction feature supported trail development options to protect resource conditions with unrestricted visitor access. In contrast, visitors to a remote undeveloped island expressed stronger support for no or limited trail development and access restrictions to protect resource conditions.

Journal of Sustainable Tourism↗
USGS1874

[Seventh] Annual Report of the United States Geological and Geographical Survey of the Territories, embracing Colorado: being a report of progress of the exploration for the year 1873

In accordance with the recommendation of the Secretary of the Interior, an appropriation of $75,000 was made for the systematic survey of Colorado, and, at as early a date as the season would permit, the party reached Denver. This place formed our starting point for the various portions of the territory which had previously been marked out for the season's work. Early in the winter, the area to be surveyed in Colorado was divided into three districts, and a preliminary map was constructed, based on the land-surveys of the portions concerning which there was any definite knowledge. We found that none of the existing maps were of any great service in the more elevated portions of Colorado. The area to be surveyed comprised the eastern portion of the mountainous part of Colorado, and it was separated into three districts: North, Middle, and South districts.

Colorado↗
USGS1883

Twelfth Annual Report of the United States Geological and Geographical Survey of the Territories: A report of progress of the exploration in Wyoming and Idaho for the year 1878, Part I: Geology, paleontology, and zoology

This report includes the labors of the corps for the field season of 1878, and the office work until the close of the existence of the Survey by law June 30, 1879. Several of the members have, however, performed very important work since that time in elaborating their individual reports, which has added greatly to their interest and value. A general summary of the work for the season of 1878 will be appropriate in this connection. Owing to the length of the session, Congress did not pass the usual appropriation for the work of the Survey until July, and consequently the period for work in the field was comparatively short. The headquarters of the Survey was at Cheyenne, Wyo., the same as the preceding season. Four parties were organized, but in such a manner that in case of necessity they could be divided for special duty. All our outfit and animals were transported from Cheyenne to Point of Rocks and Green River Stations on the Union Pacific Railroad, and from thence the parties pursued their way northward to their respective fields of labor.

Colorado, Idaho, Utah, Wyoming↗
USGS1871

Report of the Geological Exploration of the Fortieth Parallel, Volume V: Botany

The territory within which botanical collections have been nmade in connection with the United States Geological Survey of the 40th Parallel lies wholly within the limits of Northern Nevada and Utah. It forms a narrow tract at no point exceeding seventy miles in width, between the meridians of 111° and 120°, and extending frorn the parallel of 39° at the southwestern limit to that of 42° at the northeastern. This region constitutes the northern portion of what was at first designated as the "Great Basin" the high plateau, without outlet for its waters, separated on the north by low divides from the valley of the Snake River and continuing southward until it merges into the desert of the Lower Colorado. Geologically considered, however, as well as botanically, the term is now properly made to include the whole similar arid stretch of country northward to the plains of the Columbia in latitude 48°.

Nevada;Utah↗