Job Announcements from BLM

blm-logo

Message from BLM:  We are pleased to announce new, exciting positions available at BLM – BUREAU OF LAND MANAGEMENT.   It is our hope that qualified, career oriented individuals at your organization or other professionals known to you will actively consider this position and apply accordingly.  Efforts on your part to disseminate this information are greatly appreciated.

Position Information:
Job Description:  Mining Engineer;
Announcement Number:  CO-DEU-2015-0052;
Location(s) of position:  Lakewood, CO, US;
Salary:  $75,333 – $116,453;
Applications will be accepted until:  08/04/2015.
For additional information on this job posting, please click here.

Position Information:
Job Description:  Soil Scientist;
Announcement Number:  OR-DEU-2015-0171;
Location(s) of position:  Eugene, OR, US;
Salary:  $48,403 – $76,131;
Applications will be accepted until:  07/17/2015.
For additional information on this job posting, please click here. 

Position Information:
Job Description:  Purchasing Agent;
Announcement Number:  OR-DEU-2015-0170;
Location(s) of position:  Salem, OR, US;
Salary:  $51,027 – $66,332;
Applications will be accepted until:  07/13/2015.
For additional information on this job posting, please click here.

New Server for NBMG Website—please note new links

The NBMG website has been moved to a new web server. This web server migration was critical since the old server was running the Microsoft Server 2003 operating system, which becomes unsupported on July 14, 2015.

The URLs have changed for the “Free Downloads” links on the Publications page, so please be sure to update your bookmarks. Here is an example of the new URL format (for Nevada Mineral Industry 2013):

Old URL: http://www.nbmg.unr.edu/freedownloads/mi/mi2013.zip  (no longer works)
New URL: http://data.nbmg.unr.edu/public/freedownloads/mi/mi2013.zip

You can locate these Free Downloads links by clicking on the blue publication title on the listing of NBMG publications on the shopping cart. When you click on the title, you will then be on the publication landing page which includes options to purchase the item or download it for free if that option is available. If there is no Free Downloads tab to the right of the Description tab on the landing page, then there is no free download available. The Description and Free Downloads tabs are located on top of the gray text box under the thumbnail images.

Note that some pages in our website have moved as a result of this server migration, particularly from our cleanup and organization of the web server files in order to make updating the website more efficient. We also had to eliminate php code in order to move our website to the University’s server.

Here are some of the main pages affected by the changes:

There is limited space on the new web server, so to organize our data and ensure there is plenty of room for growth we moved our large static data (mining district scans, historical air photos, etc.) to a new location that includes “http://data.nbmg.unr.edu” in the first part of the URLs. While data.nbmg.unr.edu is not an open server to browse through, all public data that sits at data.nbmg.unr.edu is accessible through links in various web pages throughout our website and interactive web applications.

If you have any questions about this migration, please contact Jennifer Vlcan, Manager, NBMG Cartography & GIS group
mauldin@unr.edu
Phone (775) 682-8759

New Geologic Map—Welcome Quadrangle

Welcome

Title:  Geologic map of the Welcome quadrangle and an adjacent part of the Wells quadrangle, Elko County, Nevada
Author:  Allen J. McGrew[udayton.edu] and Arthur W. Snoke[uwyo.edu]
Year:  2015
Series:  Map 184
Format:  plate: 51 x 32.5 inches, color; text: 40 pages, color
Scale:  1:24,000; inset: 1:12,000

Located in central Elko County, the Welcome quadrangle and an adjacent part of the Wells quadrangle expose a remarkable array of critical relationships for understanding the geologic history of the state of Nevada and the interior of the southwestern U.S. Cordillera. Covering the northern end of the East Humboldt Range and adjacent Clover Valley and Clover Hill, this map includes the northern terminus of the Ruby Mountains–East Humboldt Range metamorphic core complex.

The oldest rocks in the state of Nevada (the gneiss complex of Angel Lake), and Nevada’s only exposures of Archean rock, form the core of a multi-kilometer scale, southward-closing recumbent fold-nappe, the Winchell Lake nappe (WLN). Although intensely metamorphosed and profoundly ductilely attenuated, the WLN folds a series of pre-metamorphic thrust allochthons that collectively form an essentially complete sequence of Paleoproterozoic to Mississippian metasedimentary rocks. The WLN transported what may be Nevada’s most deeply exhumed rocks, with peak pressures ranging to 10 kb, peak temperatures in excess of 750 ºC, and widespread partial melting and stromatic migmatization, all related to Late Cretaceous to Paleocene tectonism.

Overprinting the metamorphic core is a WNW-directed kilometer-scale shear zone that, together with the detachment fault that forms its roof, accommodated tens of kilometers of extensional displacement in mid- to late Cenozoic time, diachronously exhuming the terrain from mid-crustal depths by late Miocene time. In addition, the high-grade rocks are extensively intruded by one of the Nevada’s most diverse suites of magmatic rocks, ranging in age from Archean to Miocene and in composition from mafic to felsic. On the west flank of Clover Hill, a west-dipping detachment-fault system separates the high-grade metamorphic core from an overlying plexus of brittlely deformed, partly correlative but lower grade to non-metamorphosed Paleozoic rocks. In turn, a sequence of partly syntectonic volcanic and sedimentary rocks ranging in age from Eocene to Miocene structurally overlie the fault-bounded Paleozoic units. The Cenozoic sequence includes late Eocene and Oligocene ignimbrites and volcaniclastic rocks, Miocene sedimentary rocks and megabreccias, a Miocene rhyolite complex, and younger sedimentary rocks and vitric tuffs. The presence of the most distal northeasterly exposure of a key Oligocene volcanic marker, the 29 Ma tuff of Campbell Creek, suggests that a broad, low-relief (unfaulted) terrain was dissected by paleovalleys that extended at least 200 km to the west. Bracketed between the tuff of Campbell Creek and a 15.5 Ma tuffaceous sandstone at the base of the Miocene Humboldt Formation is a proximal sedimentary sequence known as the sedimentary sequence of Clover Creek that includes conglomerate, sedimentary breccia, sandstone, and megabreccia as well as intercalations of fossiliferous lacustrine strata. The megabreccias consist of unmetamorphosed mid-Paleozoic rocks (chiefly Upper Devonian Guilmette Formation) interpreted as rock-avalanche deposits shed from evolving normal-fault scarps inferred to have bounded the basin to the east. Disconformably overlying the sedimentary sequence of Clover Creek is a thick sequence of Miocene Humboldt Formation that is tilted steeply down against the detachment fault system, documenting large-scale displacement on the detachment system extending to at least as young ca. 9 Ma.

Finally, bounding the range today on both east and west are large, normal-fault systems that were active in Quaternary time, including the Clover Hill fault, which may represent a southerly extension of the blind fault that caused the 2008 Mw 6.0 Wells earthquake.

This map was prepared with support from the Geological Society of Nevada; National Science Foundation; University of Wyoming, Laramie; and the University of Dayton, Dayton, Ohio.

View or purchase Map 184 here: http://pubs.nbmg.unr.edu/product-p/m184.htm

New Geologic Map—Heelfly Creek Quadrangle

Heelfly

Title: Preliminary geologic map of the Heelfly Creek quadrangle and adjacent parts of the Tent Mountain, Soldier Peak, and Secret Valley quadrangles, Elko County, Nevada
Author: Seth M. Dee, Gregory M. Dering, and Christopher D. Henry
Year: 2015
Series: Open-File Report 15-4
Format: plate: 31 x 33 inches, color; text: 5 pages, b/w
Scale: 1:24,000

A 1:24,000-scale geologic map of the Heelfly Creek 7.5-minute quadrangle and adjacent parts of the Tent Mountain, Soldier Peak, and Secret Valley quadrangles, Elko County, Nevada. The map area covers the westernmost part of the East Humboldt Range, foothills west of the range front, and lowlands of Starr Valley. The quadrangle is traversed by numerous creeks flowing from the high topography in the east across lowlands occupied by ranching and farming communities toward the Humboldt River. New mapping has been integrated with data from previous bedrock and neotectonic studies to elucidate the structural and stratigraphic framework of the region. The relative timing and varying modes of Cenozoic extension documented here provide context for seismic hazard assessment as well as hydrocarbon and metallic mineral exploration.

Middle Proterozoic through Devonian sedimentary and metamorphic rocks (Ely Formation, Diamond Peak Formation, Guilmette Formations, Eureka Quartzite, Horse Creek assemblage and Proterozoic crystalline basement) are exposed along the high relief East Humboldt range front. These rocks are part of the Ruby Mountains–East Humboldt Range metamorphic core complex, a package of complexly deformed Proterozoic orthogneiss interfolded with Paleozoic metasedimentary rocks exhumed from mid-crustal depths along several low-angle faults during Tertiary extension. The crystalline and Paleozoic sedimentary rocks of the East Humboldt Range front are juxtaposed against middle Miocene sedimentary and volcanic rock along a north-striking, high-angle normal fault. The fault is locally buried by a mega-landslide deposit of presumed mid-Pleistocene age. Activity on this fault likely ended in the middle Pleistocene when uplift stepped 4–5 km west to the currently active frontal fault trace. Late Quaternary uplift along the active frontal fault trace exposed a section of largely northeast-dipping tuffaceous sandstone, shale and conglomerate of the Miocene Humboldt Formation. The stratigraphically lowest Cenozoic deposits, exposed near the southern map boundary in a broad anticline, may be as old as Eocene and equivalent to the Elko Formation. The Miocene sediments are locally overlain by coarsely porphyritic lavas chemically correlated with Jarbidge Rhyolite, which is widely distributed across northeastern Nevada.

Quaternary deposits in the map area include numerous inset Pleistocene surfaces beveled onto the Miocene sediments, early Pleistocene to Tertiary lacustrine and fluvial basin deposits, glacial outwash likely from the Lamoille and Angel Lake glaciations, and several inset late Pleistocene through Holocene alluvial fan and fluvial terrace deposits. Repeated late Quaternary surface-rupturing earthquakes along the active trace of the frontal fault system are recorded by increased uplift of Quaternary surfaces as a function of relative age.

This map was prepared with support from the Nevada Division of Minerals.

View or purchase Open-File Report 15-4 here: http://pubs.nbmg.unr.edu/product-p/of2015-04.htm

New Geologic Map—Robinson Mountain Volcanic Field / NW Huntington Valley

of2015-2_plate1

Title: Preliminary geologic map of Cenozoic units of the central Robinson Mountain volcanic field and northwestern Huntington Valley, Elko County, Nevada
Author: Jens-Erik Lund Snee[earth.stanford.edu] and Elizabeth L. Miller[earth.stanford.edu]
Year: 2015
Series: Open-File Report 15-2
Format: two color plates and color text; plate 1 (geologic map): 41 x 54 inches, plate 2 (cross sections): 43 x 21 inches, text: 42 pages
Scale: 1:24,000

Huntington Valley is situated east of the Piñon Range, in the hanging wall of a shallowly west-dipping detachment system bounding the west side of the Ruby Mountains–East Humboldt Range (RMEH) metamorphic core complex. This geologic map of Cenozoic sedimentary, volcanic, and subvolcanic rocks of the central Robinson Mountain volcanic field and northwestern Huntington Valley provides important information about the history of Cenozoic crustal extension, magmatism, sedimentation, and paleogeography near the RMEH.

Depositional rates in the Elko Basin were minor from Cretaceous to Oligocene time, and became rapid in the middle Miocene. Late Cretaceous(?)–Eocene(?) conglomerate, sandstone, siltstone, and limestone “redbeds” (TKcs) and limestone (TKl) are exposed at the base of the Cenozoic section in places, where they each reach thicknesses of ~600 m, but they are not exposed at all in other locations. The overlying Eocene Elko Formation is only ~180 m thick at its greatest in the map area. Detrital zircon geochronology conducted on two samples collected near its base yields a maximum depositional age of ~45.9 ± 1.0 Ma, and a third sample collected near the top of this unit yields a maximum depositional age of 37.9 ± 0.5 Ma.

The calcic to calc-alkalic Robinson Mountain volcanic field records early peraluminous to weakly metaluminous “ignimbrite flare-up” volcanism of basaltic andesite to trachydacite and rhyolite composition, which occurred mostly between about 38.5 and 36.8 Ma. Early eruptions were roughly synchronous with the end of deposition of the Elko Formation, and no significant unconformity is observed beneath the volcanic units. The only Eocene–Oligocene sedimentary rocks exposed above the Eocene Elko Formation are thin, fluviolacustrine deposits interbedded within the volcanic rocks. For this reason, the “Indian Well Formation” name for Eocene–Oligocene volcanic and sedimentary rocks has been abandoned. The rhyolitic, Oligocene-age tuff of Hackwood Ranch is significantly younger than the Eocene deposits of the Robinson Mountain volcanic field. This tuff was erupted at ~31.1 Ma, which coincides with a lull in regional volcanism, but could represent far-traveled deposits from a distant volcanic center.

Significant, approximately westward tilting developed a shallow angular unconformity between ~37.3 and 33.9 Ma (10–15°). Subsequently, between ~31.1 and 24.4 Ma or later, 10–15° additional westward tilting occurred. These westward tilting events were likely associated with slip on east-dipping normal faults in the Piñon Range. Following the second episode of westward tilting, a basin rapidly developed near the present-day RMEH, as recorded by thick deposits of the mostly Miocene Humboldt Formation that dip gently eastward toward the RMEH. Greater than 1 km of the sedimentary strata previously mapped as Eocene–Oligocene age has been reassigned to the Miocene Humboldt Formation as a result of our geologic mapping and supporting geochronology.

Detrital zircon geochronology yielded a coherent age group at ~24.4 Ma for one tuffaceous pebble conglomerate and sandstone sample at the base of the Humboldt Formation, but it is unlikely that this maximum depositional age constrains the timing of the start of basin sedimentation. Deposition accelerated at ~16–15 Ma, when most of Humboldt Formation pebble conglomerate, sandstone, siltstone, marl, and air-fall tuff were deposited in Huntington Valley. Locally, pre-Tertiary rocks were exposed by faulting by ~16 Ma (although this depositional age is not well constrained), and RMEH provenance is not detected until ~14 Ma, suggesting that the metamorphic core complex was not exposed until about this time. Greater than 2100 m of Humboldt Formation strata were deposited in the study area alone (thickening further eastward toward the RMEH), and deposition continued until at least ~8.2 Ma, but the rate apparently decreased before ~12 Ma.

Miocene or later fault slip occurred along a well preserved, east-dipping normal fault system exposed at the east side of the Piñon Range, partially synchronous with faulting at the RMEH. Uplift and erosion of Eocene- to Quaternary-age sedimentary and volcanic deposits on the west side of Huntington Valley support a significant magnitude of slip on west-dipping normal faults west of the study area during or after Miocene time. Open folding of the Humboldt Formation occurred during or after the middle–late Miocene, perhaps due to normal fault slip offsetting underlying Paleozoic basement.

This geologic mapping study thus supports the hypothesis that surface-breaking extensional faulting in and near the mapped area was minor from the Late Cretaceous(?) through the early Miocene, and that most surface-breaking extension and sediment deposition occurred in middle Miocene time.

This map covers all of the following 1:24,000-scale quadrangles: Robinson Mountain, Cedar Ridge, and Red Spring and a portion of the following quadrangles: Bailey Mountain, Bullion, and West of Lee.

This map was prepared as part of the EDMAP component of the National Cooperative Geologic Mapping Program in cooperation with the U.S. Geological Survey and with support from the Geological Society of Nevada.

View or purchase Open-File Report 15-2 here: http://pubs.nbmg.unr.edu/product-p/of2015-02.htm

New Interactive Mining District Map

Rachel (Wearne) Micander, GIS Specialist with the NBMG Cart/GIS group, has created a new interactive mining district map, and you can view the beta test of that map here.

New: Beta test of the interactive mining districts web mapping application and how-to guide.

Please send any comments and suggestions that you may have to Rachel Micander: rwearne@unr.edu

Creation of map services and interactive maps are an important component of the Nevada Bureau of Mines and Geology mission. Interactive maps are developed as a tool for users who may not have access to their own datasets or GIS software. Users can download specific databases, excel files and PDF’s, search layer information, and view updated data without any special skill other than internet familiarity.

The Mining District Files consist largely of historical and current maps, reports, articles, photographs, correspondence, assays, production reports, and reserve information on all aspects of mining in Nevada. These have largely been donated to the NBMG over the years from individuals, companies, and other government agencies.

Over the last several years, Nevada Bureau of Mines and Geology has undertaken the digital conversion of these paper documents into scanned images. The files contained in the mining district files are in PDF file format. The digital file conversion project at NBMG is ongoing. Some records are copyrighted and have no link associated with them in the search results. However, these documents are available for viewing at NBMG’s Great Basin Science Sample and Records Library.

See other interactive maps created by the NBMG Cart/GIS group here:
http://www.nbmg.unr.edu/Mapping/InteractiveMaps.html

Take a five minute vacation with this geologic photo tour of Nevada:
http://nbmg.maps.arcgis.com/apps/MapTour/?appid=32bc91f8e5b84522828663f9b6516410#[nbmg.maps.arcgis.com]

Job Announcements from BLM

blm-logo Message from BLM:  We are pleased to announce new, exciting positions available at BLM – BUREAU OF LAND MANAGEMENT.   It is our hope that qualified, career oriented individuals at your organization or other professionals known to you will actively consider this position and apply accordingly.  Efforts on your part to disseminate this information are greatly appreciated. Position Information: Job Description:  Civil Engineer; Announcement Number:  OR-DEU-2015-0169; Location(s) of position:  Eugene, OR, US; Salary:  $58,562 – $76,131; Applications will be accepted until:  07/07/2015. For additional information on this job posting, please click here. Position Information: Job Description:  General Engineer; Announcement Number:  AZ DEU-2015-0039; Location(s) of position:  Phoenix, AZ, US; Salary:  $71,791 – $93,333; Applications will be accepted until:  07/09/2015. For additional information on this job posting, please click here. Position Information: Job Description:  Archeologist; Announcement Number:  OR-DEU-2015-0168; Location(s) of position:  Roseburg, OR, US; Salary:  $70,192 – $91,255; Applications will be accepted until:  06/30/2015. For additional information on this job posting, please click here. Position Information: Job Description:  Contact Representative; Announcement Number:  OR-DEU-2015-0164; Location(s) of position:  Eugene, OR, US; Salary:  $39,570 – $51,437; Applications will be accepted until:  07/07/2015. For additional information on this job posting, please click here.  Position Information: Job Description:  Range Technician (ESI Team); Announcement Number:  OR-DEU-2015-0157; Location(s) of position:  Vale, OR, US; Salary:  $39,570 – $51,437; Applications will be accepted until:  07/01/2015. For additional information on this job posting, please click here. 

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