New Geologic Maps in Northern Nevada: Mount Rose NW and Herder Creek Quadrangles

 

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Preliminary Geologic Map of the South Half of the Mount Rose NW Quadrangle, Washoe County, Nevada

 Authors: Nicholas H. Hinz and Alan R. Ramelli
Year: 2016
Series: Open-File Report 16-6
Format: plate: 35 x 29 inches, color; text: 3 pages, b/w
Scale: 1:24,000
View/Download/Buy: http://pubs.nbmg.unr.edu/Geol-south-half-Mount-Rose-NW-p/of2016-06.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 this quadrangle. This quadrangle also encompasses part of the rural community along Thomas Creek in the southeast quarter, and segments of the Steamboat irrigation ditch and part of the City of Reno urban area fall within the northeast corner.

The bedrock exposures in the quadrangle consist of Mesozoic granitic basement and Tertiary volcanic and sedimentary rocks. The Tertiary section includes a complex section of lavas, intrusions, and volcanic sedimentary rocks. Many of these volcanic and sedimentary rocks were derived from a ~6-7 Ma ancestral Cascades volcanic center in the Mount Rose quadrangle, directly south of this quadrangle. Plio-Pleistocene basaltic andesite lavas and rhyolite domes locally rest on the late Miocene volcanic rocks in the middle part of the quadrangle. Principal surficial deposits include late Pliocene to modern alluvial fan and fluvial deposits, Quaternary glacial deposits, and 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 were observed on the east side of the range and west-facing Quaternary fault scarps were observed on the west side of the range.

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

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Preliminary Geologic Map of the Herder Creek Quadrangle, Elko County, Nevada
Author: Seth Dee and Michael W. Ressel
Year: 2016
Series: Open-File Report 16-5
Format: plate: 33 x 29 inches, color; text: 5 pages, b/w
Scale: 1:24,000
View/Download/Buy: http://pubs.nbmg.unr.edu/Prel-geol-Herder-Creek-quad-p/of2016-05.htm

The map area covers part of Starr Valley, the upper reaches of the Humboldt River, and the northwest part of the East Humboldt Range.

The Ruby Mountains–East Humboldt Range metamorphic core complex is exposed in the high-relief range front in the southeast part of the quadrangle. In this area, the core complex is comprised of intensely metamorphosed and highly attenuated Neoarchean through Mississippian(?) strata, thought to be part of the platform facies of the Proterozoic through Paleozoic passive margin. Contractional structures exposed in the map area are complex and difficult to discern due to overprinted extensional deformation but are likely part of the Winchell Lake nappe (WLN), a kilometer scale, southward-closing recumbent fold-nappe mapped in adjacent quadrangles to the east. Overturned Devonian to Neoproterozoic(?) meta-sedimentary strata exposed at the highest structural levels are interpreted to be in thrust contact with an underlying, upright sequence of Cambrian to Neoproterozoic(?) paragneiss and Paleoproterozoic to Neoarchean(?) orthogneiss in the core of the fold. This structural interpretation matches those from the adjacent Welcome quadrangle (McGrew and Snoke, 2015; NBMG Map 184). Rocks in the upper part of the metamorphic core complex are pervasively overprinted by a WNW-directed mylonitic shear fabric, which records middle to late Cenozoic extensional exhumation from mid-crustal depths. Abundant sills and lenses of less deformed Oligocene to Cretaceous garnet-muscovite leucogranite and biotite monzogranite intrude all metamorphic rocks in the quadrangle.

The west side of the East Humboldt Range is bound by the active, W-dipping Ruby Mountains frontal fault zone, which extends for more than 60 km to the southwest. A west step-over in the Ruby Mountains fault south of the Herder Creek drainage results in a broad, hanging wall uplift underlain by middle-Miocene to Pliocene strata comprised of NE-dipping to flat-lying tuffaceous sandstone, shale, and conglomerate of the Humboldt Formation and younger units. A tephra in the uppermost exposed section yielded a 40Ar/39Ar age on feldspar of 5.15 ± 1.82 Ma.

Repeated late Quaternary surface-rupturing earthquakes along active traces of the frontal fault are recorded by increased uplift and dissection of Quaternary surfaces as a function of relative age. Fault scarps in Holocene deposits have up to 2.5 m of vertical separation while glacial outwash deposits from the two most recent Pleistocene glacial advances have scarp heights ranging from 6 to 32 m. The upper reaches of several drainages have well-preserved glacial moraine deposits that record the Angel Lake and Lamoille glacial advances. Adjacent to the Humboldt River, in the northwest corner of the quadrangle, 3 sets of abandoned terrace surfaces are preserved, including a broad surface comprised of gravel-rich alluvium that was likely deposited during a period of increased discharge during the latest Pleistocene.

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

New Geologic Maps in Clark County: Boulder City and Apex Quadrangles

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Preliminary Geologic Map of the Boulder City Quadrangle, Clark County, Nevada

Authors: Seth Dee, Nicholas H. Hinz, R. Ernie Anderson, and Racheal Johnsen
Year: 2016
Series: Open-File Report 16-4
Format: plate: 39 x 29 inches, color; text: 6 pages, some color
Scale: 1:24,000
View/Download/Buy: http://pubs.nbmg.unr.edu/Prel-geol-Boulder-City-quad-p/of2016-04.htm

 A 1:24,000 scale preliminary geologic map of the Boulder City 7.5-minute quadrangle in Clark County, Nevada. This quadrangle covers portions of the southeastern River Mountains, the northern Eldorado Mountains and straddles a segment of the drainage divide between the hydrologically closed Eldorado Valley and the through-flowing Colorado River Basin. Boulder City is located in the northern part of the quadrangle, as is the in-progress Interstate 11, Boulder City Bypass. This publication includes a combination of new mapping and integration with existing mapping by Ernie Anderson.

The bedrock exposures in the quadrangle are dominated by Tertiary plutonic, volcanic, and sedimentary rocks with lesser Proterozoic metamorphic rocks and Paleozoic sedimentary rocks. In the northern Eldorado Mountains the basal volcanic section includes the early to middle Miocene, intermediate to felsic composition Patsy Mine volcanics. The Patsy Mine volcanics are locally intruded by the composite, middle Miocene Boulder City pluton. This pluton is variably hydrothermally altered with actinolite present in altered groundmass and fracture-fill veins. Both the Boulder City pluton and the Patsy Mine volcanics are locally overlain by the middle Miocene Mount Davis volcanics which consist of a syn-extensional, bimodal sequence of lavas and tuffaceous sediments. In the southeastern River Mountains, the Tertiary strata are dominated by the middle Miocene, intermediate to felsic composition Red Mountain volcanics. These rocks are intruded by a middle Miocene granitic stock, which is probably related to widespread hydrothermal alteration of the Red Mountain volcanics. Locally overlying the Red Mountain volcanics are the less altered, intermediate to silicic, volcanics of Bootleg Wash, and unaltered Mount Davis volcanics.

The bedrock in the northern Eldorado Mountains is faulted by numerous north-striking, down-to-east and down-to-west normal faults. The northeast-striking, sinistral Hemenway Wash fault transects the northwest quarter of the quadrangle, separating the Eldorado Mountains from the River Mountains. The Hemenway Wash fault is one of the faults that makes up the >100 km-long, Lake Mead Fault System. In the northernmost Eldorado Mountains, fault strikes curve from N-S to NW and to E-W as they approach the Hemenway Wash fault zone, possibly due to oroclinal flexure. Provisional analysis of new geochronologic and geochemical data acquired in this study indicate that the plutonic and volcanic strata exposed in the southeastern River Mountains may correlate directly to strata in the northern Eldorado Mountain, providing a means to evaluate a range of possible displacements across the Hemenway Wash fault.

Surficial sediments in the quadrangle are largely alluvial fan and pediment deposits ranging from historic to Pliocene in age. Early Pleistocene to late Pliocene surficial deposits are characterized by 2+ m thick pedogenic carbonate horizons, which form resistant geomorphic surfaces on the east side of the Eldorado basin and cap many of the bedrock highlands in the Eldorado range. Fan deposits eroded from altered Boulder City plutonic rocks or from Miocene basin sediments may contain redistributed actinolite-bearing clasts. One possible fault scarp was observed in a late to middle Pleistocene aged fan. No other evidence for Quaternary faulting was recognized in the quadrangle.

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

apexPreliminary Geologic Map of the Apex Quadrangle, Clark County, Nevada

Author: Robert G. Bohannon
Year: 2016
Series: Open-File Report 16-3
Format: plate: 31 x 32 inches, color; text: 5 pages, color
Scale: 1:24,000
View/Download/Buy: http://pubs.nbmg.unr.edu/Prelim-geol-Apex-quad-p/of2016-03.htm

The Apex quadrangle (1:24,000 scale) is centered approximately 22.5 km northeast of downtown Las Vegas in Clark County, Nevada. Rocks in the quadrangle are exclusively sedimentary and include a mostly conformable sequence of Paleozoic continental shelf and platform rocks in its north half. The south half of the quadrangle is mostly Miocene interior-continental-basin deposits. Dissected alluvial deposits of Quaternary and latest Tertiary age, only the oldest of which are consolidated, discontinuously cover large lowland parts of the quadrangle. The Paleozoic rocks are deformed and in some places overturned by Mesozoic thrust faults associated with the Late Cretaceous Sevier Orogenic disturbance. A large east-vergent thrust fault with a northeast orientation, the Dry Lake Thrust, cuts the eastern half of the quadrangle, where it is mostly concealed by post-Cretaceous deposits. The thrust juxtaposes lower Paleozoic shelf rocks in the hanging wall above upper Paleozoic continental platform rocks in the footwall. Tertiary normal faults are also common and are mostly oriented northeast where they cut Paleozoic rocks. The Miocene beds, most of which post-date the northeast normal faults, are deformed by a few east-west or east-northeast-oriented faults and numerous small folds that are associated with them. The younger faults might be associated with very late-stage movement on the Las Vegas Valley shear zone which projects into the quadrangle from beneath Las Vegas Valley to the east, but the shear zone is otherwise concealed by the Miocene deposits.

Preliminary Geologic Map of the Sloan Quadrangle, Clark County, Nevada


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Authors:
Nicholas H. Hinz, Alan R. Ramelli, and Seth Dee
Year: 2015
Series: Open-File Report 15-7
Format: plate: 37 x 26 inches, color, includes 1 cross section; text: 4 pages, b/w
Scale: 1:24,000

A 1:24,000 scale, preliminary geologic map of the Sloan 7.5-minute quadrangle in Clark County, Nevada. This quadrangle straddles Interstate Highway 15 along the south side of Las Vegas Valley and abuts the drainage divide with Ivanpah Valley. The actively managed Sloan Quarry is located in the NW quarter of the quadrangle. The north half of the quadrangle includes new housing developments in the City of Henderson, the Henderson Executive Airport, and new developments in the unincorporated communities of Paradise, Enterprise, and Sloan. The southeastern margin of this map area covers the north end of Hidden Valley and contains parts of each of the following land use features: the Sloan Canyon National Conservation Area, the Sloan Canyon Rock Art Site, and the Sloan Rock Art Area of Critical Environmental Concern.

The bedrock exposures in the quadrangle consist of Paleozoic carbonate basement and Tertiary volcanic and sedimentary rocks. The Paleozoic stratigraphy includes the Early to Middle Devonian Sultan Limestone, the Late Devonian to Early Mississippian Crystal Pass Limestone, the Mississippian Monte Cristo Group, and the Late Mississippian to Early Permian Bird Spring Formation. Four sub-units in the commonly undivided lower part the Bird Spring Formation were distinguished in the Sloan quadrangle. The Tertiary section includes a complex section of fluvial gravels and volcanic rocks. The fluvial gravels reach 350 m thick, fill a previously unrecognized paleovalley segment with as much as 500 m of preserved paleotopography. The volcanic rocks include middle Miocene basalt, basaltic andesite, andesite, and dacite that were locally erupted. The lower-most volcanic rocks are intercalated with the uppermost fluvial gravels. The Paleozoic section was initially deformed during the Sevier and/or Laramide orogenies and were displaced along reverse faults, thrust faults, and strike-slip faults. Normal faults associated with Basin and Range extension cut the Paleozoic strata and the lower half of the Tertiary section. Faults were not observed cutting the upper half of the Tertiary strata or the Quaternary surficial deposits.

This map was prepared as a part of the STATEMAP component of the National Cooperative Geologic Mapping Program in cooperation with the U.S. Geological Survey.

View or purchase here:
http://pubs.nbmg.unr.edu/Prel-geol-Sloan-quad-p/of2015-07.htm

New Geologic Map: Mount Rose Quadrangle with shaded relief

Open-File Report 14-7
Preliminary geologic map of the Mount Rose quadrangle, Washoe County, Nevada

by Nicholas H. Hinz, Alan R. Ramelli, and James E. Faulds, 2014

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A 1:24,000-scale, preliminary geologic map of the Mount Rose 7.5-minute quadrangle in Washoe County, Nevada.  This quadrangle straddles the northern Carson Range directly north of Lake Tahoe and includes much of Incline Village, the Mount Rose Highway, three north Lake Tahoe ski areas, part of the Tahoe Rim Trail, Mount Rose proper, and numerous major tributary drainages to the Truckee River and Lake Tahoe. Mapping of this quadrangle has important implications for understanding earthquake and landslide hazards in the Reno–Carson City–Lake Tahoe region.

The bedrock exposures in the quadrangle consist of Mesozoic crystalline basement and Tertiary volcanic and sedimentary rocks.  The Mesozoic rocks are dominantly granitic with local metamorphic roof pendants.  The Tertiary section includes a complex section of lavas, intrusions, and volcanic sedimentary rocks.  Much of these volcanic and sedimentary rocks were derived from a Miocene ancestral Cascades volcanic center in the northwest quarter of this quadrangle.  Principle surficial deposits include late Pliocene to modern alluvial fan and fluvial deposits, Quaternary glacial deposits, and late Quaternary mass wasting deposits.  Notable deep-seated landslide complexes reside in the Whites Creek, Gray Creek, and First Creek drainages.  The Tertiary section is cut by a system of north-northwest to north-northeast-striking normal and dextral-normal faults with both down-to-west and down-to-east sense of displacement, kinematically linked with a system of northeast to east-northeast-striking sinistral-normal faults.  Detailed mapping of Quaternary fault scarps associated with the Incline Village fault zone benefited greatly from publicly available, high-resolution LiDAR data for the Tahoe basin.

This publication was prepared as part of the STATEMAP component of the National Cooperative Geologic Mapping Program in cooperation with the U.S. Geological Survey.

Open-File Report 14-7, scale 1:24,000, 39 x 28 inches, color; 4-page text, b/w; folded or rolled, $18.00       

Be sure and check out the new shaded relief format on this map of Mount Rose.

Available free on the Web or purchase here: http://www.nbmg.unr.edu/sales/pbsdtls.php?sku=OF14-%207

New Geologic Map: Minden Quadrangle

Map 182
Geologic map of the Minden quadrangle, Douglas County, Nevada and Alpine County, California

by Alan R. Ramelli, James C. Yount, David A. John, and Larry J. Garside, 2014

M182

A 1:24,000-scale, color geologic map of the Minden 7.5-minute quadrangle in Douglas County, Nevada and Alpine County, California with descriptions of 37 geologic units and two cross sections. Accompanying text includes full unit descriptions and references. This quadrangle includes portions of the Genoa fault, which ruptured in a major earthquake several hundred years ago.  The Minden quadrangle also includes extensive deposits of the Carson River; understanding the distribution of these deposits helps in assessing flood hazards for populated areas in the Carson Valley.

This map was prepared as part of the COGEOMAP and STATEMAP components of the National Cooperative Geologic Mapping Program in cooperation with the U.S. Geological Survey.

This map supersedes Open-File Report 2003-13: Preliminary Geologic Map of the Minden Quadrangle, Nevada (2nd ed., 2009).

Map 182, one 33×27-inch color map, scale 1:24,000; 8-page text, b/w; folded or rolled, $20.00

Available free on the Web or purchase here: http://www.nbmg.unr.edu/sales/pbsdtls.php?sku=M182

New Geologic Map – Terrill Mountains quadrangle

Preliminary geologic map of the Terrill Mountains quadrangle, Churchill and Mineral counties, Nevada, by Chad W. Carlson, 2014

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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 Pliocene 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 to early Miocene 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, completed through the EDMAP component of the National Cooperative Geologic Mapping Program in cooperation with the U.S. Geological Survey, has provided a robust foundation for ongoing and future structural, paleomagnetic, and geochronologic investigations in the region.

Open-File Report 14-4, scale 1:24,000, 33 x 27 inches, color, $15.00 or free on the Web: http://www.nbmg.unr.edu/dox/of144.pdf

NBMG Information Video—Now Available!

The Nevada Bureau of Mines and Geology conducts cutting edge, societally relevant science that fosters economic development and public safety and involves training of the next generation of geoscientists. Major projects include earthquake hazard studies in the nation’s third most seismically active state, mineral and geothermal resource assessments, and regional tectonic studies of Nevada’s rapidly evolving landscape.

Learn how the Nevada Bureau of Mines and Geology serves the citizens of Nevada in this informative and beautiful video with audio (produced in cooperation with WebsEdge):