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USGS2015

Data categories for marine planning

The U.S. National Ocean Policy calls for a science- and ecosystem-based approach to comprehensive planning and management of human activities and their impacts on America’s oceans. The Ocean Community in Data.gov is an outcome of 2010–2011 work by an interagency working group charged with designing a national information management system to support ocean planning. Within the working group, a smaller team developed a list of the data categories specifically relevant to marine planning. This set of categories is an important consensus statement of the breadth of information types required for ocean planning from a national, multidisciplinary perspective. Although the categories were described in a working document in 2011, they have not yet been fully implemented explicitly in online services or geospatial metadata, in part because authoritative definitions were not created formally. This document describes the purpose of the data categories, provides definitions, and identifies relations among the categories and between the categories and external standards. It is intended to be used by ocean data providers, managers, and users in order to provide a transparent and consistent framework for organizing and describing complex information about marine ecosystems and their connections to humans.

Open-File Report↗

USGS1999

U.S. Geological Survey middle Rio Grande basin study; proceedings of the third annual workshop, Albuquerque, New Mexico, February 24-25, 1999

Approximately 40 percent (about 600,000 people) of the total population of New Mexico lives within the Middle Rio Grande Basin, which includes the City of Albuquerque. Ongoing analyses of the central portion of the Middle Rio Grande Basin by the U.S. Geological Survey (USGS) in cooperation with the City of Albuquerque and other agencies have shown that ground water in the basin is not as readily accessible as earlier studies indicated. A more complete characterization of the ground-water resources of the entire Middle Rio Grande Basin is hampered by a scarcity of data in the northern and southern areas of the basin. The USGS Middle Rio Grande Basin study is a 5-year effort by the USGS and other agencies to improve the understanding of the hydrology, geology, and land-surface characteristics of the Middle Rio Grande Basin. The primary objective of this study is to improve the understanding of the water resources of the basin. Of particular interest is to determine the extent of hydrologic connection between the Rio Grande and the Santa Fe Group aquifer. Additionally, ground-water quality affects the availability of water supplies in the basin. Improving the existing USGS-constructed ground-water flow model of the Middle Rio Grande Basin will integrate all the various tasks that improve our knowledge of the various components of the Middle Rio Grande water budget. Part of this improvement will be accompanied by extended knowledge of the aquifer system beyond the Albuquerque area into the northern and southern reaches of the basin. Other improvements will be based on understanding gained through process-oriented research and improved geologic characterization of the deposits. The USGS and cooperating agencies will study the hydrology, geology, and land-surface characteristics of the basin to provide the scientific information needed for water-resources management and for managers to plan for water supplies needed for a growing population. To facilitate exchange of information among the scientists working on the Middle Rio Grande Basin study, yearly technical meetings have been held for each of the first 3 years of the anticipated 5-year study. These meetings provide an opportunity to present research results and plan new field efforts. This report documents the results of research presented at the third annual technical workshop held in Albuquerque, New Mexico, February 24-25, 1999. The report is organized into this introduction and five chapters that focus on Middle Rio Grande Basin study investigations in progress in the Middle Rio Grande Basin. The first chapter describes geographic data and analysis efforts in the basin. The second chapter details work being done on the hydrogeologic and geologic framework of the basin. The third chapter describes studies on ground-water recharge in the basin. The fourth chapter provides details on the research on the ground-water flow system in the basin, including modeling efforts. The fifth chapter is devoted to an overview of New Mexico District Cooperative Program studies in the basin. The information in this report presents preliminary results of an evolving study. As the study progresses and individual projects publish their results in more detail, the USGS hopes to expand the scientific basis needed for management decisions regarding the Middle Rio Grande Basin.

Open-File Report↗

USGS2023

Hydrogeologic framework of the Red River alluvial aquifer and Carrizo-Wilcox aquifer in northwestern Louisiana

Groundwater in northwestern Louisiana is a valuable resource needed for expanding public-supply needs as well as possible energy development needs arising from Haynesville Formation natural-gas production. The Red River alluvial and the Carrizo-Wilcox aquifers are two of the most important and heavily pumped aquifers in northwestern Louisiana; however, little documentation of the regional hydrogeologic framework is available. The U.S. Geological Survey and the Louisiana Department of Transportation and Development have consolidated information from, and built upon, previous studies of the Red River alluvial and the Carrizo-Wilcox aquifers to characterize and document the regional hydrogeologic framework of northwestern Louisiana. The study area has been tectonically modified and includes abundant structural features such as salt domes and areally extensive faulting in addition to minor folding related to these features, all of which impact the sedimentological and hydraulic characteristics of the freshwater-bearing strata. The hydrogeologic framework of northwestern Louisiana comprises a sequence of structurally modifi ed, complexly interbedded, varyingly interconnected, clayey, sandy, and gravelly alluvial sediments. The important freshwater hydrogeologic units include the Quaternary Red River alluvial and upland terrace aquifers, and the underlying Tertiary Sparta, Cane River, and Carrizo-Wilcox aquifers. The Midway confining unit underlies the Carrizo-Wilcox aquifer throughout the study area. No freshwater is present in or below the Midway Group. Tertiary-age formations exposed at land surface in the study area have been incised by the Red River and are hydraulically connected to the Quaternary Red River alluvium in the Red River valley. In 2010, 7.73 million gallons per day (Mgal/d) of water were withdrawn from the Red River alluvial aquifer in the study area, representing an increase of 2.00 Mgal/d, or about 35 percent, over 2005 withdrawal rates. The Tertiary Carrizo Sand and Wilcox Group crop out across much of the study area. The two units are hydraulically connected and function as a single hydrologic unit referred to as the Carrizo-Wilcox aquifer. In 2010, 19.33 Mgal/d of water were withdrawn from the Carrizo-Wilcox aquifer in the study area, representing an increase of nearly 1.8 Mgal/d, or about 10 percent, over 2005 withdrawal rates. Any expansion in energy development, as well as water needs of an increasing population, could result in an increased demand on groundwater in northwestern Louisiana.

Louisiana↗

USGS2017

Geologic map of the Beacon Rock quadrangle, Skamania County, Washington

The Beacon Rock 7.5′ quadrangle is located approximately 50 km east of Portland, Oregon, on the north side of the Columbia River Gorge, a scenic canyon carved through the axis of the Cascade Range by the Columbia River. Although approximately 75,000 people live within the gorge, much of the region remains little developed and is encompassed by the 292,500-acre Columbia River Gorge National Scenic Area, managed by a consortium of government agencies “to protect and provide for the enhancement of the scenic, cultural, recreational and natural resources of the Gorge and to protect and support the economy of the Columbia River Gorge area.” As the only low-elevation corridor through the Cascade Range, the gorge is a critical regional transportation and utilities corridor (Wang and Chaker, 2004). Major state and national highways and rail lines run along both shores of the Columbia River, which also provides important water access to ports in the agricultural interior of the Pacific Northwest. Transmission lines carry power from hydroelectric facilities in the gorge and farther east to the growing urban areas of western Oregon and Washington, and natural-gas pipelines transect the corridor (Wang and Chaker, 2004). These lifelines are highly vulnerable to disruption by earthquakes, landslides, and floods. A major purpose of the work described here is to identify and map geologic hazards, such as faults and landslide-prone areas, to provide more accurate assessments of the risks associated with these features. The steep canyon walls of the map area reveal extensive outcrops of Miocene flood-basalt flows of the Columbia River Basalt Group capped by fluvial deposits of the ancestral Columbia River, Pliocene lavas erupted from the axis of the Cascade arc to the east, and volcanic rocks erupted from numerous local vents. The Columbia River Basalt Group unconformably rests on a sequence of late Oligocene and early Miocene rocks of the ancestral Cascade volcanic arc, which underlies most of the map area. The resistant flood-basalt flows form some of the famous landforms in the map area, such as Hamilton Mountain. Extensive landslide complexes have developed where the basalt flows were emplaced on weak volcaniclastic rocks.

Washington↗

USGS1997

Natural and mining-related sources of dissolved minerals during low flow in the Upper Animas River Basin, southwestern Colorado

As part of the Clean Water Act of 1972 (Public Law 92-500), all States are required to establish water-quality standards for every river basin in the State. During 1994, the Colorado Department of Public Health and Environment proposed to the Colorado Water Quality Control Commission (CWQCC) an aquatic-life standard of 225 µg/L (micrograms per liter) for the dissolved-zinc concentration in the Animas River downstream from Silverton (fig.1). The CWQCC delayed implementation of this water-quality standard until further information was collected and a plan for the cleanup of abandoned mines was developed. Dissolved-zinc concentrations in this section of the river ranged from about 270 µg/L during high flow, when rainfall and snowmelt runoff dilute the dissolved minerals in the river (U.S. Geological Survey, 1996, p. 431), to 960 µg/L (Colorado Department of Public Health and Environment, written commun., 1996) during low flow (such as late summer and middle winter when natural springs and drainage from mines are the main sources for the streams). Mining sites in the basin were developed between about 1872 and the 1940's, with only a few mines operated until the early 1990's. For local governments, mining sites represent part of the Nation's heritage, tourists are attracted to the historic mining sites, and governments are obligated to protect the historic mining sites according to the National Historic Preservation Act (Public Law 89-665). In the context of this fact sheet, the term "natural sources of dissolved minerals" refers to springs and streams where no effect from mining were determined. "Mining-related sources of dissolved minerals" are assumed to be: (1 ) Water draining from mines , and (2) water seeping from mine-waste dump pile where the waste piles were saturated by water draining from mines. Although rainfall and snowmelt runoff from mine-waste piles might affect water quality in streams, work described in this fact sheet was done during low-flow conditions when springs and drainage from mine were the main sources of dissolved minerals affecting the streams. Data are being collected by the U.S. Geological Survey (USGS) to determine the magnitude and sources of dissolved minerals during rainfall- and snowmelt-runoff periods. This fact sheet presents results of studies done by the USGS in collaboration with the Animas River Stakeholders Group and was prepared in cooperation with the Southwestern Colorado Water Conservation District. The studies were done at selected sites in the Upper Animas River Basin to determine natural and mining-related sources of dissolved minerals and are continuing in the basin with the Animas River Stakeholders Group and as part of the Department of the Interior Abandoned Mine Lands Initiative. The results of these studies will provide useful information for determining water-quality standards in the basin.

Colorado↗

USGS2012

Summary of the diamond resource potential and production capacity assessment of Guinea

In May of 2000, a meeting was convened in Kimberley, South Africa, by representatives of the diamond industry and leaders of African governments to develop a certification process intended to assure that export shipments of rough diamonds were free of conflict concerns. Outcomes of the meeting were formally supported later in December of 2000 by the United Nations in a resolution adopted by the General Assembly. By 2002, the Kimberley Process Certification Scheme (KPCS) was ratified and signed by diamond-producing and diamond-importing countries. As of August 2012, the Kimberley Process (KP) had 51 participants representing 77 countries. With the passing of the AD, the Plenary agreed that further efforts should be made to assess Guinea's diamond production capacity. In support of this objective, the U.S. Geological Survey (USGS) partnered with the Kimberley Process Working Group of Diamond Experts (WGDE) and Guinea's Ministry of Mines and Geology (MMG) to conduct a field campaign in Guinea from April 24 through May 2, 2010. The field team was composed of Mark Van Bockstael of the WGDE, Peter Chirico of the USGS, and several geologists from the MMG. The team visited diamond mining sites in western Guinea's Kindia, Forècariah, Coyah, and Tèlimèlè Prefectures, in which the Guinean government identified newly discovered deposits mined by artisans. Several mining sites within the Kissidougou Prefecture in southeastern Guinea were also visited as part of this study. Geologic and geomorphic information on the diamond deposits was collected at each site. The fieldwork conducted during this trip served as a means of acquiring critical data needed to conduct a full assessment of diamond resources and production capacity.

Fact Sheet↗

USGS2020

Expert bioblitzes facilitate non-native fish tracking and interagency partnerships

Documenting the distribution and composition of non-native species populations can be challenging, especially when species cross jurisdictional boundaries that require interagency coordination. Herein I report the development of three tools that have been used in Florida over the past seven years to assist with tracking of non-native fishes: 1) an overarching organization to increase coordination and communication amongst stakeholders (Florida Non-Native Fish Action Alliance); 2) regularly-scheduled expert bioblitzes (Fish Slams); and 3) symposia (Fish Chats). Ten Fish Slams were held since 2012, which have included nearly 100 individuals from 20 organizations. Participants have sampled nearly 200 unique sites, capturing 36 non-native fish taxa. These activities have generated over 600 records for the U.S. Geological Survey’s Nonindigenous Aquatic Species database. Many specimens collected during Fish Slams are deposited into natural history museums or used by researchers. Informal interactions amongst colleagues working together in the field, at check-in meetings at the end of the day, and during more structured Fish Chat symposia allow members of various organizations to become acquainted, build trust, and share information and technology, which may then lead to professional collaborations. While this program is focused on non-native fish species in south Florida, I also discuss how the expert bioblitz may be adapted to suit other taxonomic groups and a variety of conservation needs.

Florida↗

USGS2019

Three new species of small-eared shrews, genus Cryptotis, from El Salvador and Guatemala (Mammalia: Eulipotyphla: Soricidae)

The Cryptotis goldmani group of small-eared shrews (Eulipotyphla: Soricidae: Cryptotis Pomel, 1848) is a clade of semifossorially adapted species discontinuously distributed in moist highlands from central Mexico to western Panama. Inspection of a recent collection of small mammals resulting from field work in Guatemala provided the impetus for a re-evaluation of one member of that group, Goodwin’s small-eared shrew, Cryptotis goodwini Jackson, 1933. On the basis of the results of that study, three new species of small-eared shrews are described from (1) disturbed cloud forest on Cerro Cucurucho, Sacatepéquez Department, Guatemala; (2) highlands east of Mataquescuintla, Jalapa Department, Guatemala; and (3) Cerro Montecristo, a massif at the mutual borders of northern El Salvador, eastern Guatemala, and western Honduras. The new species are most similar morphologically to the Guatemalan endemic species C. goodwini and C. mam Woodman, 2010, from which they are distinguished by a variety of external and cranial characters. Recognition of the three new species more narrowly defines the distribution of C. goodwini (sensu stricto) , which is now known only from portions of the western Sierra Madre of Guatemala.

Report↗

USGS2018

Biodiversity of amphibians and reptiles at the Camp Cady Wildlife Area, Mojave Desert, California and comparisons with other desert locations

We examined the biodiversity of amphibian and reptile species living in and near constructed ponds in the riparian area at the Camp Cady Wildlife Area (CCWA) in the Mojave Desert of San Bernardino County, California, based on field work from 1998-1999, 2016-2017, review of the literature, and searches for museum specimens using VertNet.org. A total of 11 species (201 captures), including two frogs and toads (one non-native frog), one turtle, three snakes, and five lizards were captured at terrestrial drift fences with pitfall traps encircling two ponds (0.5 hectares total) on the property in 1999. Four additional species (one frog, one lizard, and two snakes) were previously reported in 1978 from a ranch 1.6 km southwest from CCWA for a total of 15 species in the local area. The southwestern pond turtle (Actinemys pallida), was commonly observed at CCWA from 1998 to 1999 and documented as a breeding population. However, the species was extirpated at CCWA sometime after 2014 when the last individuals were photographed, and none have been detected since then despite significant efforts to do so. Biodiversity of amphibians and reptiles at CCWA is relatively low compared with sites elsewhere in the Mojave Desert with more elevational diversity. The 14 native species documented at CCWA accounts for approximately 21% of the native reptile and amphibian species reported by Stewart (1994) for the entire Mojave Desert, including peripheral species. Our smaller sample likely represents a group of easily detected species and is biased toward those found in or near water, especially amphibians. However, the relative proportion of amphibians vs. reptiles that inhabited CCWA in the last 40 years is not significantly different from the recently compiled proportions at five military installations in the California deserts. The herpetofauna inhabiting CCWA is notable for including riparian obligates like the western toad (Anaxyrus boreas), Northern Baja California treefrog (Pseudacris h. hypochondriaca), and A. pallida that are otherwise absent from large portions of the Mojave Desert. Other species are typical of those that are expected in the low-elevation creosote scrubdominated ecosystem in the area.

California↗

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↗

USGS2016

Spatial modeling of wild bird risk factors to investigate highly pathogenic A(H5N1) avian influenza virus transmission

One of the longest-persisting avian influenza viruses in history, highly pathogenic avian influenza virus (HPAIV) A(H5N1), continues to evolve after 18 years, advancing the threat of a global pandemic. Wild waterfowl (family Anatidae), are reported as secondary transmitters of HPAIV, and primary reservoirs for low-pathogenic avian influenza viruses, yet spatial inputs for disease risk modeling for this group have been lacking. Using GIS and Monte Carlo simulations, we developed geospatial indices of waterfowl abundance at 1 and 30 km resolutions and for the breeding and wintering seasons for China, the epicenter of H5N1. Two spatial layers were developed: cumulative waterfowl abundance (WAB), a measure of predicted abundance across species, and cumulative abundance weighted by H5N1 prevalence (WPR), whereby abundance for each species was adjusted based on prevalence values then totaled across species. Spatial patterns of the model output differed between seasons, with higher WAB and WPR in the northern and western regions of China for the breeding season and in the southeast for the wintering season. Uncertainty measures indicated highest error in southeastern China for both WAB and WPR. We also explored the effect of resampling waterfowl layers from 1 km to 30 km resolution for multi-scale risk modeling. Results indicated low average difference (less than 0.16 and 0.01 standard deviations for WAB and WPR, respectively), with greatest differences in the north for the breeding season and southeast for the wintering season. This work provides the first geospatial models of waterfowl abundance available for China. The indices provide important inputs for modeling disease transmission risk at the interface of poultry and wild birds. These models are easily adaptable, have broad utility to both disease and conservation needs, and will be available to the scientific community for advanced modeling applications.

Avian Diseases↗

USGS2011

U.S. Geological Survey Karst Interest Group Proceedings, Fayetteville, Arkansas, April 26-29, 2011

Karst aquifer systems are present throughout parts of the United States and some of its territories and are developed in carbonate rocks (primarily limestone and dolomite) that span the entire geologic time frame. The depositional environments, diagenetic processes, and post-depositional tectonic events that form carbonate rock aquifers are varied and complex, involving both biological and physical processes that can influence the development of permeability. These factors, combined with the diverse climatic regimes under which karst development in these rocks has taken place result in the unique dual or triple porosity nature of karst aquifers. These complex hydrologic systems often present challenges to scientists attempting to study groundwater flow and contaminant transport. The concept for developing a Karst Interest Group evolved from the November 1999 National Groundwater Meeting of the U.S. Geological Survey (USGS), Water Resources Division. As a result, the Karst Interest Group was formed in 2000. The Karst Interest Group is a loose-knit grass-roots organization of USGS employees devoted to fostering better communication among scientists working on, or interested in, karst hydrology studies. The mission of the Karst Interest Group is to encourage and support interdisciplinary collaboration and technology transfer among USGS scientists working in karst areas. Additionally, the Karst Interest Group encourages cooperative studies between the different disciplines of the USGS and other Federal agencies, and university researchers or research institutes. This fifth workshop is a joint workshop of the USGS Karst Interest Group and University of Arkansas HydroDays workshop, sponsored by the USGS, the Department of Geosciences at the University of Arkansas in Fayetteville. Additional sponsors are: the National Cave and Karst Research Institute, the Edwards Aquifer Authority, San Antonio, Texas, and Beaver Water District, northwest Arkansas. The majority of funding for the proceedings preparation and workshop was provided by the USGS Groundwater Resources Program, National Cooperative Mapping Program, and the Regional Executives of the Northeast, Southeast, Midwest, South Central and Rocky Mountain Areas. The University of Arkansas provided the rooms and facilities for the technical and poster presentations of the workshop, vans for the field trips, and sponsored the HydroDays banquet at the Savoy Experimental Watershed on Wednesday after the technical sessions.

Scientific Investigations Report↗

USGS1962

Magnesite and brucite in the United States, exclusive of Alaska and Hawaii

The important deposits of magnesite (MgCO 3 ) and brucite (MgO.H 2 O) in the United States (exclusive of Alaska and Hawaii) are shown on the accompanying map. Single deposits and groups of deposits are shown by geometric symbols according to four size categories based on estimated production plus reserves. These categories are: less than 10,000 tons, 10,000 to 100,000 tons, 100,000 to 1,000,000 tons, and more than 1,000,000 tons. Occurrences of mineralogic interest only are not shown. All map locations are numbered consecutively in each State and keyed to the locality index. The geographical coordinates in the locality index represent the centers of the geometric symbols. Thus, the same coordinates are assigned to all deposits covered by a group symbol. The map was compiled from published reports and data in the files of the United States Geological Survey. The names, geographic coordinates, and geologic types of deposits are given in the locality index. The principal published reports used in compiling the map are listed in the selected references. The main types of commercial deposits of magnesite in the United States are: (1) replacement bodies in limestone and dolomite; (2) replacements and veins in serpentine; and (3) sedimentary beds. Other magnesite deposits of varied origin and less common occurrence include beds associated with talc, chlorite, and mica schists; and veins and lenses in altered tuffs. Brucite is a relatively rare mineral of secondary origin which usually accompanies other magnesian minerals, particularly magnesite and hydromagnesite, and is associated with carbonate rocks and serpentine. Magnesite was first mined in California in 1886, and the State was the only domestic producer until the development of the Washington deposits began in 1916. In recent years, the main production of magnesite has been from Stevens County, Washington, and Nye County, Nevada. Production in California has been intermittent since 1945. Magnesite deposits in Texas were mined during and immediately after World War II. At present (1961) the only brucite deposits being worked are those at Gabbs, Nye County, Nevada. They have been mined almost continuously since 1935.

Mineral Investigations Resource Map↗

USGS1972

Reconnaissance geology of the Jabal Bitran quadrangle, Kingdom of Saudi Arabia

The Jabal Bitten quadrangle covers an area of 2833 sq km in the eastern part of the Precambrian Shield in Saudi Arabia. The rocks in the quadrangle are divided geographically alone arcuate north-trending lines into an eastern area of granite intruded by a swarm of dikes of rhyolite and andesite, and a western area of dominantly pelitic chlorite-sericite schist, separated by the narrow central complex of the Idsas Range. This complex is composed of pyroclastic rocks, lava, conglomerate, marble, and plutonic mafic rocks that have been intricately modified by episodes of metamorphism, igneous intrusion, and faulting. The Idsas Range contains ancient gold and copper mines, and deposits of magnetite, copper, asbestos, and chromite. The rocks in the Jabal Bitten quadrangle are here interpreted to consist of three major sedimentary and volcanic groups, the lowermost of which was deposited unconformably on hornblende-biotite granite gneiss, and all of which are intruded by granite dikes and plutons. From oldest to youngest the layered rocks are called Halaban Group, Bi'r Khountina Group, and Murdama Group, A biotite-hornblende granite is older than uppermost Bi'r Khountina, and peralkalic granite is younger than Murdama. The layered rocks of these groups are generally metamorphosed to the greenschist facies. The metamorphic grade rises abruptly at the Idsas Range to the albite-epidote-amphibolite facies and lower subfacies of the amphibolite facies in parts of the Halaban Group; some skarn east of the range may be in the upper part of the amphibolite facies. Characteristically, the Halaban Group has the highest grade and the greatest range in metamorphic grade, and the Murdama Group has the lowest but most uniformly developed metamorphic grade. The metamorphism of the rocks was caused by three successive pulses of regional dynamothermal metamorphism plus contact metamorphism around the younger bodies of plutonic igneous rocks. Four major structural elements of the quadrangle are reflected in the geography and geologic units. These are a mantled gneiss dome on the east separated from a north-plunging synclinorium in rocks of the Murdama and Bi?r Khountina Groups on the west by a narrow dejective zone of the Halaban and lower Bi?r Khountina. The dejective zone is much modified by impricate overthrusts and accompanying tear faults. These major faults have pushed elements of the Halaban and Bi?r Khountina westward over Bi?r Khountina and Murdama, with the result that very complex fault patterns have evolved. Open geochemical reconnaissance of the area disclosed one positive anomaly for nickel and 40 threshold indications of several elements, principally nickel, chromium, copper, and tungsten. Heavy-mineral and radiometric reconnaissance showed 18 areas containing scheelite and/or powellite and four areas of anomalous radioactivity. Most of these features are in the dejective zone, as are five of the nine ancient workings, the massive and disseminated magnetite, most of the secondary copper minerals, and the traces of asbestos, magnesite, and chromite known in the quadrangle. The mantled gneiss dome and a complex of gabbro and amphibolite on its southwestern flank are the next most mineralized areas. Scant evidence of mineralization is present in the Murdama Group west of the dejective zone. Magnetite deposits at Jabal Idsas have the greatest potential of the mineral deposits in the Jabal Bitran quadrangle. Further study of gold at Fawara and Selib mines is recommended, as is investigation of a positive nickel anomaly that shows threshold cobalt and above background radioactivity. The garnetiferous skarn in the east-central part of the quadrangle should be examined for composition and abrasive character of the garnet and for the remote possibility of tungsten in scheelite and beryllium in helvite.

Open-File Report↗

USGS1978

Ore controls at the Mahd adh Dhahab gold mine, Kingdom of Saudi Arabia

Mahd adh Dhahab is the largest of numerous ancient gold mines scattered through the Precambrian shield of Saudi Arabia and the only one with recent production. Free gold and silver, tellurides, pyrite, galena, sphalerite, and chalcopyrite are in and associated with quartz veins and quartz veinlet stockworks. Country rocks consist of a sequence of pyroclastic and transported pyroclastic rocks of the Halaban Group that are locally highly silicified and potassium-feldspathized. Two known ore zones occur in a north-trending zone of quartz veins and breccias, faults, alteration, and metallization approximately 400 m wide and 1,000 m long. The ancient and recent workings are located in the northern part of this zone, and a significant new discovery, the southern mineralized zone, is in the southern part. A potential resource of 1.1 million tons of 27 g/t Au and 73 g/t Ag ore is contained in the southern mineralized zone. Geologic setting of ore bodies is similar in both zones. Significant mineralization occurs only within altered and fractured agglomerate directly beneath a cap of fine-grained tuff and sedimentary rock where the layered rocks are cut by metalliferous quartz veins. Ore was localized by four interacting controls; depth, an impervious cap, metalliferous quartz veins and a receptive host rock.

Open-File Report↗

USGS2024

Reply to “comment on ‘an evaluation of the timing accuracy of global and regional seismic stations and networks’ by Yang et al. (2021)” by Xin Zhang and Lianxing Wen

The finding of Yang et al. (2021 ; hereafter, YSR21) casts fundamental doubts on all the previous studies on the temporal changes of the inner core (IC) surface that are based on absolute arrival times, including Wen (2006 ; hereafter, WEN06) and its follow‐up studies. The reports of small time shifts of the IC‐reflected phase ( PKiKP ) likely misinterpreted station‐related issues (clock errors and instrument changes) as evidence for rapid localized deformation at the IC surface. The comment by Zhang and Wen (2024 ; hereafter, ZW24) aims at defending the results and conclusions of WEN06 by questioning a tiny portion of the results (2 out of over 400 doublets and 3 out of over 400 problematic stations) in YSR21. In response, we acknowledge an accidental error in table S1 of YSR21, which is corrected in an erratum ( Yang et al. , 2023 ), although this does not affect the results or interpretations of YSR21. However, we strongly disagree with the criticisms in ZW24 due to many problems therein, especially the issue of irreproducibility due to its inconsistent procedures with YSR21. While the problems are related to the use of absolute arrivals in the previous studies by Wen’s group, key problems in this new comment are related to questionable data selection and inconsistent processing. We further caution the metadata updates, particularly when involving small temporal change signals. We focus on the main points in ZW24 and demonstrate that its arguments are problematic in many aspects and do not diminish the credibility of YSR21 or other related works by Yang and Song in support of the IC differential rotation.

Seismological Research Letters↗

USGS1951

Stratigraphy and structure of the upper Siksikpuk - Nanushuk Rivers area

Structural and stratigraphic studies of tha rocks in the Siksikpuk and Nanushuk Rivers area were conducted by Navy Oil Unit party 2 during the summer field season of 1950. The field party consisted of two geologists, two field assistants, a cook, and a weasel mechanic. Three weasels were used for transportation of equipment and personnel. The area examined covers approximately 1,000 square miles of the Arctic Foothills province and lies between the Itkillik River on the east and the Chandler River on the west. The area is drained by the Itkillik, Nanushuk, Anaktuvuk, Siksikpuk, and Chandler Rivers. The mapped area adjoins the Okpikruak and Kiruktagiak Rivers area 1/ to the west. The primary objective of the geologic work in this area was detailed stratigraphic study of pre-Nanushuk group rocks in the Southern Foothills belt as a supplement to the Work begun in the Okpikruak and Kiruktagiak Rivers area in 1949. A secondary objective was areal mapping and structural studies for the purpose of delimiting structures favorable for drilling tests of the Lisburne limestone. Parts of this area had been reconnoitered by members of the U. S. Geological Survey in previous years. In 1901 F. C. Schrader traversed the Anaktuvuk River, In 1945 R. E. Fellows, R. M. Chapman, and C. T. Bressler visited outcrops along the northern margin of the area in the vicinity of the Anaktuvuk River and Kanayut Creek. E. J. Webber and R. L. Detterman examined a few of the cutbanks along the Nanushuk River in 1947; and in 1949 A. L. Bowsher, Sr., and J. T. Dutro mapped an outlier of Lisburne limestone north of Nanushuk Lake.

Alaska↗

USGS2009

Seasonal Flux and Assemblage Composition of Planktic Foraminifera from the Northern Gulf of Mexico

A year-long sediment-trap experiment was conducted in the northern Gulf of Mexico (GOM) between January and December 2008 to study the flux and assemblage composition of planktic foraminifera from the region for comparison with concurrent hydrographic and climatic measurements. Ten species, or varieties, of planktic foraminifera constitute >80 percent of the assemblage: Globigerinoides ruber (pink and white varieties), Gs. sacculifer, Globigerina calida, Globigerinella aequilateralis, Globorotalia menardii group, Gt. crassaformis, Gt. truncatulinoides, Pulleniatina spp., and Neogloboquadrina dutertrei. The mean daily flux is about 200 tests per meter square per day (m-2 day-1) with the maximum fluxes of >600 tests m-2 day-1 occurring during October-March and minimum fluxes of <30 tests m-2 day-1 during April-June. The annual flux is weighted toward October-March; approximately 73.2 percent of the total annual flux is produced during this period, while the April-June and July-September fluxes make up 14 percent and 12 percent, respectively. During 2008, Gs. ruber (white) contributed ~1.5 percent to the total annual flux and averaged 4.5 percent during April-September, the period of highest fluxes for this species. Results from previous work in the GOM show Gs. ruber (white) contributing 20-30 percent of the late Holocene sediment record.

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