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.

Geologic Map of the Independence Valley NW Quadrangle, Elko County, Nevada

Authors: Andrew V. ZuzaSeth DeeChristopher D. Henry, Michael W. Ressel, and Charles H. Thorman
Year: 2019
Series: Open-File Report 2019-03
Version: partially supersedes Open-File Report 2017-06
Format: plate: 40.5 x 28.5 inches, color; text: 18 pages, color
Scale: 1:24,000

View, download, or purchase the Independence Valley NW Quadrangle map.

The Independence Valley NW 7.5-minute quadrangle covers a part of the western Pequop Mountains and adjacent Independence Valley in eastern Elko County. The east-tilted Pequop Mountains have newly recognized Carlin-type gold deposits in a geographic and geologic setting distinct from similar deposits elsewhere in Nevada. Southeast-dipping Cambrian through Ordovician sedimentary rocks are exposed in the range front along the eastern edge of the map area. Eocene rhyolite dikes and sills, and Cretaceous granitic sills and pods locally intrude the oldest Cambrian stratigraphy. The Eocene intrusions may be part of a magmatic system that produced the heat source for the nearby Carlin-type mineralization. The range front is bound on the west by two west-dipping normal fault systems that accommodated late Cenozoic exhumation. Exposed in the hanging wall of the eastern fault system are late Cenozoic basin deposits that uncomfortably overlie Cambrian through Ordovician sedimentary rocks. Logs from three boreholes drilled into the Paleozoic rocks of the hanging wall during mineral exploration were used to help develop cross section A–A”. One of the boreholes encountered an approximately 60-m-thick zone of fault gouge and a fault sliver with repeated Ordovician stratigraphy. This fault zone may be correlative with the enigmatic Pequop fault observed in adjacent quadrangles. Another borehole advanced through the eastern range-front fault constrains its dip to 34° west. Correlation of stratigraphy across the eastern range-front fault suggests approximately 4 km of total dip-slip displacement during Cenozoic exhumation.

The oldest Cenozoic basin deposits exposed between the two range-front fault systems are Miocene tuffaceous sediments with a maximum measured bedding dip of 34° east. New 40Ar/39Ar dates bracket the age of the deposit between approximately 6 Ma and 10.8 Ma. The tuffaceous sediments are overlain by a megabreccia landslide deposit with individual bedrock blocks over 200 m long. The individual blocks have lithologic and textural characteristics similar to rocks exposed along the western flank of the modern Pequop Mountains, which may have been the source of these megabreccia deposits. The megabreccia is overlain by Pliocene fanglomerate deposits with nearly horizontal bedding. New 40Ar/39Ar dates from detrital sanidine grains constrain the age of the fanglomerate to younger than ca. 4.8 Ma. New dating of the Cenozoic basin deposits records the timing of the east-tilting of the range along range-bounding faults.

The western range-front fault, named the Independence Valley fault zone, has evidence for late Quaternary activity. In the footwall of the fault, alluvial-fan deposits of probable middle Pleistocene age are beveled onto the Cenozoic sediments. Late Quaternary displacement along the Independence Valley fault zone has uplifted these fan deposits a minimum of 30 m. The youngest fan deposits offset by the fault zone are of probable latest Pleistocene age, and are displaced by fault scarps up to 3 m high. In Independence Valley, lacustrine gravels are deposited on shorelines, beach bars, and spits recording the highstand and recessional stages of latest Pleistocene Lake Clover. An older lacustrine gravel deposit with a well-developed pedogenic carbonate soil horizon was mapped topographically above the latest Pleistocene shorelines along the western edge of the map area.

This map completes a suite of three new geologic maps in the Pequop Mountains including the Independence Valley NE and Pequop Summit 7.5-minute quadrangles. Together these maps and associated analytical datasets build upon prior research to address basic (characteristics and timing of major contraction, metamorphism, and extension) and applied (origin of Carlin-type gold deposits) geologic research questions. Contraction and metamorphism, which had been attributed to either the Jurassic Elko or Cretaceous Sevier orogenies, is likely Jurassic because of a newly mapped lamprophyre sill that intruded along the major thrust of the range. Although the lamprophyre that intruded the thrust is not yet dated, our dating of similar mafic intrusions across the range all yielded similar ca. 160 Ma ages. Furthermore, a continuous metamorphic gradient from amphibolite-grade Cambrian rocks to non-metamorphosed Permian rocks in the lower plate of the thrust raises questions about previous interpretations of overlying thrust plates that buried rocks to great depths and pressures. New thermochronology reveals three significant overprinting thermal pulses that affected the range—Middle Jurassic, Late Cretaceous, and Eocene—that resulted in the metamorphism and economic mineralization.

This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under STATEMAP award number G16AC00186 (2017) and G18AC00198 (2019).

Geologic map of the Terrill Mountains quadrangle, Churchill and Mineral counties, Nevada


Author: Chad W. Carlson
Year: 2018
Series: Map 187
Version: supersedes Open-File Report 2014-04
Format: plate: 33 x 27 inches, color; text: 16 pages, color
Scale: 1:24,000
View/download/purchase:

http://pubs.nbmg.unr.edu/Geol-Terrill-Mountains-quad-p/m187.htm

GIS version:

http://pubs.nbmg.unr.edu/CDP-Geol-Terrill-Mountains-quad-p/m187z.htm

The Terrill Mountains 7.5-minute quadrangle is located about 45 km south of Fallon and incorporates the bulk of the Terrill Mountains, southern Calico Hills, northwest Red Ridge, and part of the Rawhide Flats valley just east of U.S. Highway 95. The Terrill Mountains quadrangle has significant relevance to understanding the evolving tectonic framework of the region, as it straddles a major domain boundary in the Walker Lane. Positioned between the Sierra Nevada microplate and Basin and Range, the Walker Lane accommodates ~20% of the right-lateral transform motion between the North American and Pacific plates. This motion is accommodated on NW-striking right-lateral and ENE to E-W-striking left-lateral fault systems. The Terrill Mountains lie at the northern terminus of right-lateral fault zones translating crustal-blocks of the central Walker Lane and at the southeastern edge of left-lateral faults accommodating clockwise-rotation of blocks in the northern Walker Lane. As the mechanisms of strain transfer between these disparate fault systems are poorly understood, the thick Oligocene to latest Miocene volcanic strata of the Terrill Mountains make it an ideal site for studying the transfer of strain between regions undergoing differing styles of deformation and yet both accommodating right-lateral motions. Further, it contains several major Quaternary faults capable of producing large earthquakes and the Camp Terrill mining district.

Detailed geologic mapping of the Terrill Mountains quadrangle was completed to help elucidate the Neogene styles of, and changes in, strain accommodation for this region of the Walker Lane. The mapped Tertiary strata include at least nine late Oligocene ash-flow tuffs. Several tuffs, not previously identified in the Terrill Mountains, are tentatively correlated to regionally extensive units in the western Great Basin, including the 25.3 Ma Nine Hill Tuff. A distinct ~23 Ma paleosol is locally preserved below the tuff of Toiyabe and provides an important marker bed. This paleosol is offset ~6 km across a strand of the NW-striking, right-lateral Benton Springs fault that bounds the NE flank of the Terrill Mountains. Strain at the northernmost Terrill Mountains appears to be transferred from a system of NW-striking right-lateral faults to a system of ~E-W striking left-lateral faults with associated clockwise flexure. The northern Terrill Mountains may represent a localized region of strain transfer analogous to the greater transition between the central and northern Walker Lane.

The detailed mapping of the Terrill Mountains quadrangle was completed through the EDMAP component of the National Cooperative Geologic Mapping Program in cooperation with the U.S. Geological Survey (Agreement No. G13AC00106), and supported by a grant from the National Science Foundation (EAR1419724). This mapping has provided a robust foundation for structural, paleomagnetic, and geochronologic investigations in the region.

Award-winning map!
Chad Carlson won first place in the 2014 Student Geologic Map Competition at the annual meeting of the Geological Society of America in Vancouver on October 21, 2014 for his Geologic Map of the Terrill Mountains, Western Nevada.

Here is a YouTube video of the students at GSA talking about their winning posters:

https://www.youtube.com/watch?v=9_MA-757UK4

Preliminary geologic map of the Independence Valley NE quadrangle, Elko County, Nevada

Authors: Andrew V. Zuza, Christopher D. Henry, Michael W. Ressel, Charles H. Thorman, Seth Dee, and Jeffrey E. Blackmon
Year: 2018
Series: Open-File Report 2018-04
Format: plate: 39 x 31 inches, color; text: 12 pages, b/w
Scale: 1:24,000
View/download/purchase:

http://pubs.nbmg.unr.edu/Prel-geol-Indep-Valley-NE-p/of2018-04.htm

The Independence Valley NE 7.5-minute quadrangle encompasses the northern Pequop Mountains and adjacent Goshute Valley in eastern Elko County. Active mining in the northeast corner of the quadrangle is focused on newly recognized Carlin-type gold deposits in the east-tilted Pequop Mountains that are hosted in a geographic and geologic setting distinct from similar deposits elsewhere in Nevada. Mapping was conducted in 2017 and 2018.

The northern Pequop Mountains are comprised of east-southeast-dipping Cambrian through Permian sedimentary rocks. Cambrian and Ordovician rocks are metamorphosed and strongly foliated. Although contacts on the geologic map suggest a parallel undeformed stratigraphy, the lower and middle Paleozoic units are variably deformed with local boudinage development, shearing, thrust faulting, and folding. Upper Paleozoic rocks exhibit open folds. This deformation is strongly partitioned to the mechanically weaker horizons, with some beds completely undeformed. Well-developed lineations and asymmetric shear fabrics across the range suggest top-southeast shear. A large thrust fault, named the Independence thrust, cuts across the western and central parts of the map area, juxtaposing lower Paleozoic rocks over younger Paleozoic rocks with an apparent southeast transport direction (present-day orientation). Total offset along this thrust fault is a minimum of two kilometers, based on mapped cutoff relationships. Sparse Jurassic sills and dikes intrude the Paleozoic stratigraphy, including the Independence thrust, which requires this structure to be older.

In the northern map area, the Pequop structural plate consists of Devonian rocks thrust over Pennsylvanian-Permian strata, which are juxtaposed over Ordovician rocks along the enigmatic Pequop fault. This fault has been regarded as a thrust (Thorman, 1970) or a low-angle normal fault (Camilleri, 2010). We interpret that the Pequop plate consists of the structurally highest part of the Independence thrust system—i.e., hanging wall Devonian rocks thrust over footwall Permian strata—that was faulted over Ordovician rocks via the low-angle Pequop normal fault system during an unconstrained phase of post-Jurassic extension. Eastward tilting and exhumation of the entire range was accommodated by late Cenozoic high-angle normal fault activity on the western flank of the range.

In Goshute Valley, lacustrine gravels are deposited in beach bars, and spits recording the high-stand and recessional stages of latest Pleistocene Lake Clover (Munroe and Laabs, 2013). Lacustrine sediments are buttressed against Pleistocene fan deposits (Qfi) along a lake high-stand shoreline at an elevation of approximately 1765 m.

This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under STATEMAP award number G17AC00212, 2018.

Read about the authors

Mike Ressel, author of two of these newly released maps, was featured in the Geological Society of Nevada “Faces of GSN” in November. You can read his story here:

http://www.gsnv.org/about/faces-of-gsn.php?face=mressel

http://www.gsnv.org/about/faces-of-gsn.php

NBMG staff pages

You can also read about the other geologic mappers and their work on the individual NBMG staff pages:

http://www.nbmg.unr.edu/Staff.html

Preliminary geologic map of the Ravens Nest quadrangle, Elko and Eureka counties, Nevada

Authors: Michael W. Ressel and Seth Dee

Year: 2018

Series: Open-File Report 2018-05

Format: plate: 37 x 30 inches, color, 2 cross sections; text: 20 pages, color

Scale: 1:24,000

View/download/purchase:

http://pubs.nbmg.unr.edu/Prel-geol-Ravens-Nest-p/of2018-05.htm

The Ravens Nest 7.5-minute quadrangle is located in the northern Piñon Range south of the town of Carlin in north-central Nevada. Mapping at Ravens Nest was undertaken to address several components of the complex geology of north-central Nevada, including the nature of sedimentation and deformation associated with the Early Mississippian Antler orogeny, the effects of post-Antler contractional deformation, development of the Eocene Elko Basin and slightly younger Robinson Mountain volcanic field, and deformation associated with Cenozoic extension in the hanging wall of the Ruby Mountains–East Humboldt Range metamorphic core complex. Importantly, the northern Piñon Range lies within the southern segment of the Carlin trend gold belt, which is one of the premier gold mining jurisdictions in the world. Gold produced from disseminated, sedimentary rock-hosted deposits, or Carlin-type deposits, in Nevada comprised about 90.5% of Nevada’s production and about 73.6% of U.S. production in 2016 (Muntean et al., 2017). The southern Carlin trend in the vicinity of the Ravens Nest quadrangle has seen several new Carlin-type gold discoveries since 2010 in non-traditional Paleozoic host strata. The Piñon Range and flanking Pine and Huntington valleys are also important areas for conventional and unconventional hydrocarbon resources. The Blackburn and Tomera Ranch oil fields in Pine Valley produce from Cenozoic and Paleozoic rocks widely distributed in the Ravens Nest quadrangle, and the Elko Basin has seen assessment of its oil-bearing shale by the U.S. Bureau of Mines in the 1970s and in 2012-15 for its hydrofracture potential by energy companies.

Mapping shows that three principal Paleozoic structural-stratigraphic domains exist at Ravens Nest. In particular, Late Devonian to Early Mississippian strata, which straddle the leading edge of the Roberts Mountains allochthon, are interpreted to comprise: 1) the deformed base of the allochthon, 2) the incipiently deformed foreland basin, and 3) the least-deformed passive margin. The allochthonous rocks are separated from rocks of the passive margin by a west-dipping thrust or thrusts. In addition, a fourth domain, the Antler overlap sequence, consists of relatively undeformed Late Mississippian through Permian strata widespread at Ravens Nest, which overlies all three other Paleozoic domains. The Early Mississippian Chainman Shale, previously mapped as a component of all three domains, is herein restricted to an allochthonous shale-dominant Lower Mississippian facies that occurs in the western half of the Ravens Nest quadrangle. The Chainman along with underlying deformed units of the Webb and Woodruff Formations were thrust upon a coarse chert- and quartzite-grain sandstone and fine conglomerate formerly assigned to the Chainman Shale by Smith and Ketner (1978) but herein attributed to the Melandco Sandstone. Two key Early Mississippian units, the Webb of allochthon derivation, and the Tripon Pass of passive margin derivation, straddle allochthon, foreland basin, and passive margin, and thus, provide important ties between Antler tectonic domains. Late south-vergent reverse faults cut some Lower Mississippian rocks, indicative of a change from Antler east vergence that may reflect either post-Early Mississippian (i.e., post-Antler) contraction, or local variation of Antler deformation through time and space.

Rocks of the Eocene Elko Basin unconformably overlie Paleozoic rocks at Ravens Nest. The basin developed as primarily lacustrine sedimentation from ~45 Ma to 38 Ma, and only a small part of the lacustrine facies is present in the far northeast corner of the Ravens Nest quadrangle. An Eocene basal fluvial-alluvial gravel is present in many places in and near Ravens Nest quadrangle, which in previous mapping was commonly assigned a Paleozoic age (Hollingsworth et al., 2017). By ~40 Ma at Ravens Nest, significant volcanic input is evident in strata of the Elko Basin, as distally derived small-volume ash-flow tuff and tephra. By ~38.5 Ma, significant local volcanic input began, and lacustrine deposition completely ceased by ~38 Ma, during major deposition of volcanic products of the nearby Robinson Mountain volcanic field (RMVF). Activity associated with the RMVF was short-lived, with abundant rhyolite and dacite lavas and domes with lesser tuff emplaced between ~38.5 and 37.5 Ma. Coeval with calc-alkaline volcanism was the emplacement of the Bullion granodiorite to high-silica rhyolite intrusion in the Railroad district as well as other smaller stocks and swarms of silicic to intermediate sills and dikes. The intrusions of the Railroad district are responsible for polymetallic skarn and carbonate-hosted replacement deposits. In addition, widespread marble and hornfels occurs over 40 km2 in the southern half of the quadrangle, indicative of a much larger underlying pluton. Carlin-type gold deposits are coeval with Eocene intrusions and occur peripherally to them and higher-temperature polymetallic deposits (Henry et al., 2015; Hollingsworth et al., 2017).

The mid-Miocene Humboldt Basin partly overlapped the Elko Basin in the vicinity of the Ravens Nest quadrangle. However, extensive areas of lacustrine shale and siltstone, tuff, and fluvial and alluvial gravels occur over a large area in the southwest part of the quadrangle where lacustrine deposition postdated emplacement of the Palisade Rhyolite (Wallace et al., 2008). Strata of the Humboldt Basin were faulted against Paleozoic bedrock along north striking normal faults on the eastern margin of Pine Valley. Pliocene and younger gravels and extensive tuffaceous lacustrine deposits of the Hay Ranch Formation were deposited synextensionally into a hydrologically closed Pine Valley. Quaternary normal faulting along the western margin of the Piñon Range has continued at least into the middle Pleistocene. The effects of the stream capture of Pine Creek and integration of Pine Valley into the Humboldt River watershed during the middle Pleistocene include deeply incised drainages, oversteepened hillslopes and extensive landslide deposits.

This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under STATEMAP award number G17AC00212, 2018.

Read about the authors

Mike Ressel, author of two of these newly released maps, was featured in the Geological Society of Nevada “Faces of GSN” in November. You can read his story here:

http://www.gsnv.org/about/faces-of-gsn.php?face=mressel

http://www.gsnv.org/about/faces-of-gsn.php

NBMG staff pages

You can also read about the other geologic mappers and their work on the individual NBMG staff pages:

http://www.nbmg.unr.edu/Staff.html

Preliminary geologic map of the Mount Rose NW quadrangle, Washoe County, Nevada


Authors:
Nicholas H. Hinz, Alan R. Ramelli, and Christopher D. Henry
Year:
2018
Series:
Open-File Report 2018-03
Version:
supersedes Open-File Report 2016-06
Format: plate: 35 x 29 inches, color; text: 4 pages, B/W
Scale:
1:24,000
View/download/purchase:

http://pubs.nbmg.unr.edu/Prel-geol-Mount-Rose-NW-p/of2018-03.htm

This quadrangle straddles the north end of the Carson Range directly west-southwest of Reno and abuts the Nevada-California border. The Truckee River and Interstate 80 transect the northwest quarter of the quadrangle. Parts of the City of Reno urban area and Steamboat irrigation ditch fall within the northern part of the quadrangle, and part of a rural community along Thomas Creek is in the southeast quarter.

The bedrock exposures in the quadrangle consist of Mesozoic granitic and metamorphic basement, and Tertiary volcanic and sedimentary rocks. The Tertiary section includes a complex section of lavas, intrusions, and volcanic sedimentary rocks. Tertiary volcanic and sedimentary rocks in the northern part of the quadrangle are part of an ~1112 Ma ancestral Cascades volcanic center. Generally north-dipping Miocene basalt (~10 Ma) and fluvial-lacustrine sediments rest on the ~11–12 Ma volcanic rocks. Many of the volcanic and sedimentary rocks in the southern part of the quadrangle were derived from a ~6–7 Ma volcanic center in the Mount Rose quadrangle, directly south of this quadrangle. Plio-Pleistocene basaltic andesite lavas locally rest on these late Miocene volcanic rocks in the middle part of the quadrangle. Principal surficial deposits include late Pliocene to modern alluvial fan and fluvial deposits, deposits of the Truckee River, Quaternary glacial deposits, and extensive late Quaternary mass wasting deposits. Notable deep-seated landslide complexes reside in all major drainages—including Thomas Creek, Hunter Creek, Bronco Creek, and the smaller catchments along the west edge of the quadrangle. Most of the Carson Range is west-tilted with west-dipping Cenozoic strata. However, within the Mount Rose NW quadrangle, the dip domain flips and most all the Cenozoic strata dips east with numerous west-dipping normal faults. These west-dipping normal faults are cut by younger east-dipping normal faults of the Mount Rose fault zone on the east side of the range. East-facing Quaternary fault scarps occur on the east side of the range, west-facing Quaternary fault scarps occur on the west side of the range, and the crest of the range is cut by a complex zone of mostly west-facing faults.

This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under STATEMAP award numbers G15AC00240, 2016, and G17AC00212, 2018.