Geologic Map of the Granite Peak Quadrangle, Washoe County, Nevada

Author: Seth Dee
Year: 2019
Series: Open-File Report 2019-05
Version: supersedes Open-File Report 1987-08
Format: plate: 28 x 32.5 inches, color; text: 5 pages, color
Scale: 1:24,000

View, download, or purchase the Granite Peak Quadrangle map.

The Granite Peak 7.5-minute quadrangle is located immediately north of Reno, and abuts the Nevada-California state line in an area known as the ‘North Valleys’. The quadrangle includes the summits of Petersen Mountain and Granite Peak, and portions of Red Rock Valley and Cold Springs valley. The bedrock exposures in the quadrangle consist primarily of Cretaceous granitic rocks related to the Sierra Nevadan batholith. The granitic rocks include three distinct lithologies with relative ages constrained by clear crosscutting relationships. Miocene to Pliocene clastic and fluvio-lacustrine sediments are deposited in a shallow basin west of Freds Mountain in the easternmost part of the quadrangle. On the western flank of Petersen Mountain, west-dipping Oligocene ash-flow tuff deposits nonconformably overlie Cretaceous granite. Quaternary sediments largely consist of alluvial fans and several large landslide deposits (up to 2.7 sq. km.).

The quadrangle is bisected by the Petersen Mountain fault zone. The fault zone consists of two subparallel traces (western and eastern) that extend from Cold Springs valley in the south to Seven Lakes Mountain in the north. The western trace of the fault strikes generally north-south along the eastern range front of Petersen Mountain, dips steeply east, and locally displaces surficial deposits as young as Holocene. The eastern trace consists of several north-south striking strands that displace surficial deposits as young as late Pleistocene and locally forms a narrow graben infilled by faulted fanglomerate material. Fault surfaces on the eastern trace have subhorizontal slickenlines demonstrating a history of dextral-oblique motion. Long-term late Cenozoic normal displacement across the western trace is demonstrated by the high relief of the Petersen Mountain range front (>500 m) as well as the accumulation of Miocene-Pliocene sediments to the east that were likely deposited into a basin controlled by early displacement along the fault. This is in contrast to the eastern strand, which has been active since at least the middle Pleistocene but for much of its length does not bound basins with significant accumulations of late Cenozoic deposits. These map relationships suggest the Petersen Mountain fault zone initially developed as a Basin and Range extensional structure with displacement primarily along the western fault trace, and has evolved into a Walker Lane structure with dextral-oblique motion focused on the eastern trace.

This geologic map was funded by the USGS National Cooperative Geologic Mapping Program under STATEMAP award number G18AC00198, 2019.

Geologic Map of the Washoe City Quadrangle, Washoe County, Nevada

Authors: Chad W. Carlson, Richard D. Koehler, and Christopher D. Henry
Year: 2019
Series: Open-File Report 2019-04
Version: supersedes Urban Maps UM5Ag and UM5Ak
Format: plate: 34.5 x 37 inches, color; text: 7 pages, b/w
Scale: 1:24,000

View, download, or purchase the Washoe City Quadrangle map.

This quadrangle encompasses Washoe Valley, an internally drained basin located between the Reno/Sparks and Carson City urban areas in northern Nevada. The seismically active eastern range front of the Sierra Nevada (Carson Range) extends along the western side of the quadrangle. Washoe Lake, a popular recreational area, extends from the south into the central part of the quadrangle. The eastern side of the quadrangle contains the rural communities of New Washoe City and Pleasant Valley, located along the western foothills of the Virginia Range. Major infrastructure within the quadrangle includes Interstate 580 concurrent with U.S. Highway 395, which extends north-south through the quadrangle west of Washoe Lake, and the ~73 megawatt Steamboat Hills geothermal power plants, with expansion plans for an additional 20 megawatts, occupying the northeasternmost part of the quadrangle.

Bedrock exposures in the quadrangle consist of Jurassic to Triassic metasedimentary and metavolcanic rocks of the Gardnerville Formation, Cretaceous granite and granodiorite, and Tertiary volcanic and sedimentary rocks. The Tertiary section includes Oligocene ash-flow tuffs and a complex section of Miocene volcanic rocks, intrusions, and volcaniclastic sedimentary rocks. Miocene volcanic rocks are basaltic to dacitic lavas and breccias interfingering across the northern parts of the quadrangle. The volcanic rocks were part of an ancestral Cascades arc that consisted of two recognized pulses in the Washoe City quadrangle: ~5.5–7.1 Ma lavas and breccias that extend east from the Mount Rose quadrangle into the Steamboat Hills and ~15 Ma lavas and breccias that extend west from the Virginia City quadrangle. Quaternary, 1.2 Ma rhyolite lava and tuff and 2.2 Ma basaltic andesite lava in the Steamboat Hills are some of the youngest volcanic rocks in western Nevada. Holocene sinter is being deposited by the active Steamboat geothermal system.

Principle Quaternary surficial deposits include middle Pleistocene to modern alluvial fan, landslide, and debris-flow deposits, middle to late Pleistocene glacial outwash and moraine deposits, late Pleistocene to modern lacustrine and eolian deposits, as well as active alluvial and colluvial deposits. A major debris flow complex sourced from the flank of Slide Mountain (Mount Rose) occupies the Ophir Creek canyon and is associated with at least five distinct flows including the 1983 debris flow, which caused significant damage to residential structures and infrastructure. Numerous other debris-flow deposits occur within smaller drainages of the eastern Carson Range. A massive landslide deposit along the northeastern side of Pleasant Valley is associated with large intact blocks of bedrock. The Mount Rose fan complex sourced from Jones, Whites, and Galena creeks records a long history of fan deposition (early to late Pleistocene) that includes fan deposits eroded from the Cascades arc volcanic rocks and multiple pulses of glacial outwash.

The east-dipping Carson Range fault bounds the eastern flank of the Carson Range and displaces Quaternary alluvial-fan, debris-flow, and glacial deposits across east-facing scarps that range in height from 2 to over 60 m. North of Washoe Valley, the Carson Range fault becomes distributed and is characterized by a broad zone of west- and east-facing scarps and grabens. The east-dipping Little Valley fault within the Carson Range displaces glacial outwash and moraines. A component of right-lateral displacement along the Little Valley fault is suggested by offset drainages along the eastern flank of Slide Mountain. West-dipping faults mapped and interpreted from gravity data along the eastern boundary of Washoe Valley similarly diffuse and anastamose with east-dipping faults in the northern part of the quadrangle to develop a structural accommodation zone occupied by the Steamboat Hills geothermal power plants.

This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under STATEMAP award number G18AC00198, 2019.

Nevada Active Mines and Energy Producers

Authors: John L. Muntean and David A. Davis
Year: 2019
Series: Open-File Report 2019-01
Version: supersedes Open-File Report 2017-01, Open-File Report 2014-01 (first and second editions), Open-File Report 2010-05, and Map 170
Format: 31 x 34.5 inches, color
Scale: compilation at 1:1,000,000

View/download:
http://pubs.nbmg.unr.edu/NV-active-mines-and-energy-2019-p/of2019-01.htm

GIS version:
http://pubs.nbmg.unr.edu/CDP-NV-active-mines-2019-p/of2019-01z.htm

Reduced-size version (11×17 inches):
http://pubs.nbmg.unr.edu/NV-active-mines-2019-11×17-p/e064.htm

Site locations and information on this map were obtained from a variety of published and non-published sources with the last updates made in January 2019. All sites shown on this map have had some form of production activity during 2017.

This map was prepared in cooperation with the Nevada Division of Minerals.

Radon in Nevada—the Silent Killer

“In Nevada, one in four homes tested has elevated radon concentrations.”
http://www.unce.unr.edu/programs/sites/radon/testing/

You can test your home or business by obtaining a radon test kit from the Nevada Radon Education Program (University of Nevada Cooperative Extension):
http://www.unce.unr.edu/programs/sites/radon/results/
“Select an area on the map or click on a link below to get radon test results by zip code.”

“You can also view an interactive map of “Radon in Nevada” from Nevada Bureau of Mines and Geology’s MyHazards website. Once there, click on the “Radon” symbol and then you can view geologic units representing possible radon risk combined with radon potential and average maps for Nevada.”
https://gisweb.unr.edu/MyHAZARDS/

New Geologic Map—Red Ridge Area, Churchill and Mineral Counties

Preliminary Geologic Map of the Red Ridge Area, Churchill and Mineral Counties, Nevada
Author: Chad W. Carlson
Year: 2017
Series: Open-File Report 2017-02
Format: plate: 35.5 x 28 inches, color; text: 7 pages, color
Scale: 1:24,000
Free download/purchase: http://pubs.nbmg.unr.edu/Prel-geol-Red-Ridge-area-p/of2017-02.htm

The Walker Lane accommodates dextral motion between the northwest translating Sierra Nevada microplate to the west and Basin and Range extension to the east. A significant portion of dextral shear in the central Walker Lane is accommodated on left-stepping, en echelon, northwest-striking fault systems that compose the Walker Lake domain. Northwest of these dextral faults, strain is transferred to sinistral faults accommodating oroclinal flexure and clockwise-rotation of blocks in the Carson domain of the northern Walker Lane. Positioned at the northern terminus of the Walker Lake domain, the Red Ridge area resides southeast and in right-lateral separation across the Benton Spring fault from the Terrill Mountains. The thick Oligocene to late Miocene volcanic strata of the Red Ridge area provide opportunity to examine Tertiary strata and styles of deformation and correlate to results of recent geologic mapping completed in the adjacent Terrill Mountains quadrangle. Detailed geologic mapping of the Red Ridge area was completed to help elucidate the Neogene styles of, and transitions in, strain accommodation for this region of the Walker Lane.

Geologic mapping of the Red Ridge area greatly elucidated the stratigraphic and structural framework of Red Ridge and expanded understanding of deformation at the northern termination of the Walker Lake domain. The Tertiary strata included late Oligocene ash-flow tuffs and Miocene volcanic rocks correlated to, and dextrally offset from, Terrill Mountains stratigraphy. Several ash-flow tuffs correlate with regionally extensive units and provide opportunity for future paleomagnetic study. Similar to the southern Terrill Mountains, northeasterly-striking normal faults appear kinematically linked to major northwest-striking dextral faults and accommodate diffusion of dextral strain and basin development. The detailed mapping of the Red Ridge area has provided a firm foundation for future structural analysis and paleomagnetic study of the region.

This map was partially funded by the National Science Foundation.

New Geologic Map—Bradys Geothermal Area, Churchill County

Preliminary Geologic Map of the Bradys Geothermal Area, Churchill County, Nevada
Authors: James E. Faulds, Alan R. Ramelli, Mark F. Coolbaugh, Nicholas H. Hinz, Larry J. Garside, and John H. Queen
Year: 2017
Series: Open-File Report 2017-04
Format: plate: 51 x 39 inches, color, with cross sections; text: 6 pages, color
Scale: 1:12,000
Free download/purchase: http://pubs.nbmg.unr.edu/Prel-geol-Bradys-geothermal-p/of2017-04.htm

The Bradys geothermal field lies in the northern Hot Springs Mountains ~80 km northeast of Reno in Churchill County, Nevada.  The field has a reservoir temperature of 180-193°C at 1- to 2-km depth and currently supports a combined dual flash and binary geothermal power plant with a total installed capacity of 26 MWe, as well as a vegetable dehydration plant.  The power plant has been in operation since 1992.  The detailed geologic map and cross sections of the Bradys geothermal field illustrate the linkages between permeability and a complex structural setting dominated by a left step in a normal fault zone but also including several fault intersections within a broader accommodation zone.  Seismic reflection data and re-logging of cuttings and core from 34 wells were incorporated into the cross sections.  A previously published 1:24,000-scale geologic map of the Desert Peak quadrangle only included the easternmost part of the Bradys geothermal field.  The purpose of this map is to show the entire geothermal field at a finer scale (1:12,000) sufficient to illustrate multiple geothermal features, such as the complex faulting, sinter, warm ground, and fumaroles.  Unpublished versions of this map and cross sections have served as the foundation for previously published, 3D structural modeling and 3D gravity inversion of the Bradys geothermal field.

This project was supported by the U.S. Department of Energy, Ormat Technologies, Inc., and the U.S. Geological Survey STATEMAP Program.