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At least 793 records · Page 44Linked to original sources
USGS2005

Contrasting Proterozoic basement complexes near the truncated margin of Laurentia, northwestern Sonora–Arizona international border region

We utilize new geological mapping, conventional isotope dilution–thermal ionization mass spectrometry (ID-TIMS) and sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon analyses, and whole-rock radiogenic isotope characteristics to distinguish two contrasting Proterozoic basement complexes in the international border region southeast of Yuma, Arizona. Strategically located near the truncated southwest margin of Laurentia, these Proterozoic exposures are separated by a northwest-striking Late Cretaceous batholith. Although both complexes contain strongly deformed Paleoproterozoic granitoids (augen gneisses) intruded into fine-grained host rocks, our work demonstrates marked differences in age, host rock composition, and structure between the two areas. The Western Complex reveals a >5-km-thick tilted section of finely banded felsic, intermediate, and mafic orthogneiss interspersed with tabular intrusive bodies of medium-grained leucocratic biotite granite (1696 ± 11 Ma; deepest level), medium-grained hornblende-biotite granodiorite (1722 ± 12 Ma), and coarse-grained porphyritic biotite granite (1725 ± 19 Ma; shallowest level). Penetrative ductile deformation has converted the granites to augen gneisses and caused isoclinal folding and transposition of primary contacts. Exposed in a belt of northwest-trending folds, these rocks preserve southwest-vergent shear fabric annealed during amphibolite facies metamorphism, when crystalloblastic textures developed. Deformation and regional metamorphism occurred before emplacement of 1.1 Ga(?) mafic dikes. Throughout the Eastern Complex, meta-arkose, quartzite, biotite schist, and possible felsic metavolcanic rocks comprise the country rocks of strongly foliated medium- and coarse-grained biotite granite augen gneisses that yield mean 207 Pb/ 206 Pb ages of 1646 ± 10 Ma, 1642 ± 19 Ma, and 1639 ± 15 Ma. Detrital zircons from four samples of host sandstone are isotopically disturbed; nevertheless, the data indicate a restricted provenance (ca. 1665 Ma to 1650 Ma), with two older grains (1697 and 1681 Ma). The pervasively recrystallized Paleoproterozoic map units strike parallel to foliation and are repeated in south-trending folds that are locally refolded about easterly hinges. Southeasterly lineation developed in augen gneiss and host strata becomes penetrative in local domains of L-tectonite. Regional metamorphism associated with this tectonism persisted until ca. 1590 Ma, as recorded by metamorphic growths within some zircon grains. Mesoproterozoic intrusions that crosscut the Paleoproterozoic metasediments and augen gneisses include coarsely porphyritic biotite granite (1432 ± 6 Ma) and diabase dikes (1.1 Ga?). Emplacement of the granite was accompanied by secondary high-U overgrowths, dated at 1433 ± 8 Ma, on some of the Paleoproterozoic detrital zircons, and apparently was also responsible for resetting the whole-rock Pb isotopic systematics (1441 ± 39 Ma) within these Eastern Complex augen gneisses. Younger plutons emplaced into both Proterozoic basement complexes include medium-grained quartz diorite (73.4 ± 3.3 Ma and 72.8 ± 1.7 Ma), Late Cretaceous hornblende-biotite granodiorite, and Paleogene leucocratic biotite granite. Neogene sedimentary and volcanic strata overlie basement along unconformities that are tilted to the northeast, southeast, or southwest. A brittle normal fault, dipping gently northeast, juxtaposes Tertiary andesite with Paleoproterozoic metasandstone. These relationships suggest that the area shares a common history of mid-Tertiary extension with southwestern Arizona. Later influence of the southern San Andreas fault system is implied by multiple dextral offsets of pre-Tertiary units across northwest-trending valleys. Our structural, geochronologic, and isotopic data provide new information to constrain pre–750 Ma Rodinia reconstructions involving southwestern Laurentia. Whole-rock U-Th-Pb and Rb-Sr isotopic systematics in both Paleoproterozoic gneiss complexes are disturbed, however, well-behaved Sm-Nd analyses preserve depleted initial ε Nd values (+2 to +4) that are distinct from the Mojave crustal province, but overlapping with the Yavapai and Mazatzal Provinces of Arizona. The Eastern Complex has the appropriate age and Nd isotopic signature to be part of the Mazatzal Province, but records major tectonism and metamorphism at ca. 1.6 Ga that postdates the Mazatzal orogeny. Deformed granitoids of the Western Complex have “Yavapai-type” ages and ε Nd but display structures discordant to the southwesterly Yavapai trend in central Arizona. The Western Complex lies along-strike with similar-age rocks (1.77 Ga to 1.69 Ga) of the “Caborca block” that have only been studied in detail near Quitovac and south of Caborca. Collectively, these rocks form a northwest-trending strip of basement situated at the truncated edge of Laurentia. The present-day basement geography may reflect an original oroclinal bend in the Yavapai orogenic belt. Alternatively, the western Proterozoic belt of Sonora may represent displaced fragments of basement juxtaposed against the Yavapai-Mazatzal Provinces along a younger sinistral transform fault (e.g., the Late Jurassic Mojave-Sonora megashear or the Permian Coahuila transform). Crustal blocks with these specific petrologic, geochronologic, and isotopic characteristics can be found in south-central and northeastern portions of the Australian Proterozoic basement, further supporting a connection between the two continents prior to breakup of the Rodinian supercontinent.

Arizona, California, Nevada, Sonora↗
USGS2011

National Climate Change and Wildlife Science Center project accomplishments: highlights

The National Climate Change and Wildlife Science Center (NCCWSC) has invested more than $20M since 2008 to put cutting-edge climate science research in the hands of resource managers across the Nation. With NCCWSC support, more than 25 cooperative research initiatives led by U.S. Geological Survey (USGS) researchers and technical staff are advancing our understanding of habitats and species to provide guidance to managers in the face of a changing climate. Projects focus on quantifying and predicting interactions between climate, habitats, species, and other natural resources such as water. Spatial scales of the projects range from the continent of North America, to a regional scale such as the Pacific Northwest United States, to a landscape scale such as the Florida Everglades. Time scales range from the outset of the 20th century to the end of the 21st century. Projects often lead to workshops, presentations, publications and the creation of new websites, computer models, and data visualization tools. Partnership-building is also a key focus of the NCCWSC-supported projects. New and on-going cooperative partnerships have been forged and strengthened with resource managers and scientists at Federal, tribal, state, local, academic, and non-governmental organizations. USGS scientists work closely with resource managers to produce timely and relevant results that can assist managers and policy makers in current resource management decisions. This fact sheet highlights accomplishments of five NCCWSC projects.

Fact Sheet↗
USGS1992

Geologic framework of pre-Cretaceous rocks in the Southern Ute Indian Reservation and adjacent areas, southwestern Colorado and northwestern New Mexico

This report is a discussion and summary of Jurassic and older rocks in the Southern Ute Indian Reservation and adjacent areas, southwestern Colorado and northwestern New Mexico, and is based on analysis of geophysical logs and observations of outcrops. The Reservation, which is located in the northern San Juan Basin, has been the site of deposition of sediments for much of the Phanerozoic. Geologic times represented on the Reservation are the Precambrian, Cambrian, Devonian, Mississippian, Pennsylvanian, Permian, Triassic, Jurassic, Cretaceous, Tertiary, and Quaternary. Rocks of Ordovician and Silurian age have not been reported in this region. Thicknesses of pre-Cretaceous sedimentary rocks range from about 750 feet (229 meters) on the Archuleta arch, east of the Reservation, to more than 8,300 feet (2,530 meters) just northwest of the Reservation. About 5,500 feet (1,676 meters) of pre-Cretaceous sedimentary rocks occur in the central part of the Reservation, near Ignacio. At Ignacio the top of the Jurassic lies at a depth of 7,600 feet (2,316 meters) below the surface, which is composed of Tertiary rocks. As much as 2,500 feet (762 meters) of Tertiary rocks occur in the area. More than 10,000 feet (3,048 meters) of Cretaceous and younger rocks, and 15,600 feet (4,755 meters) of all Phanerozoic sedimentary rocks occur in the vicinity of the Reservation. In the early Paleozoic the area that includes the Southern Ute Reservation was on the stable western shelf of the craton. During this time sediments that compose the following shallow-marine clastic and carbonate rocks were deposited: the Upper Cambrian Ignacio Quartzite (0-150 feet; 0-46 meters), Upper Devonian Elbert Formation (50-200 feet; 15-61 meters), Upper Devonian Ouray Limestone (10-75 feet; 3-23 meters), and Mississippian Leadville Limestone (0-250 feet; 0-76 meters). Mixed carbonate and clastic deposition, which was punctuated by a unique episode of deposition of evaporite sediments, continued through the Pennsylvanian after a significant episode of erosion at the end of the Mississippian. Pennsylvanian rocks on the Reservation are the Molas Formation (20-100 feet; 6-30 meters) and Hermosa Group (400-2,800 feet; 122-853 meters), which consists of the Pinkerton Trail Formation (40-120 feet; 12-36 meters), Paradox Formation and equivalent rocks (200-1,800 feet; 61-549 meters), and Honaker Trail Formation (200-1,300 feet; 61-396 meters). A unit that is transitional between the Pennsylvanian and Permian is the Rico Formation, which is about 200 feet (61 meters) thick across most of the Reservation area. The close of the Paleozoic Era was marked by a great influx of arkosic clastic sediments from uplifted highlands to the north of the Reservation area during the Permian. Near the paleomountain front the Cutler Formation (presently as thick as 8,000 feet; 2,438 meters) formed as a result of deposition of arkosic sediments; however, the original thickness of the Cutler is unknown due to an unconformity at its top. In the area of the Reservation the Cutler has group status and has been divided into several formations: the Halgaito Formation (350-800 feet; 107-244 meters), Cedar Mesa Sandstone and equivalent rocks (150-350 feet; 46-107 meters), Organ Rock Formation (500-900 feet; 152-274 meters), and De Chelly Sandstone (0-100 feet; 0-30 meters). The sediments of these formations were deposited in a variety of environments, including eolian, mud-flat, and fluvial systems. Following an episode of erosion in the Early and Middle(?) Triassic, deposition in the area of the Southern Ute Reservation continued during the Mesozoic. Sediments of the Upper Triassic Dolores and correlative Chinle Formations were deposited in fluvial, lacustrine, and minor eolian environments. On the Reservation the Dolores is 500-1,200 feet (152-366 meters) thick. Lower Jurassic eolian and fluvial deposits may have been present in much of the Reservation area but have been removed

Professional Paper↗
USGS2009

Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991-2008

Several shutdown-rebound tests have been conducted at the Henderson Road Superfund Site, which has been on the U.S. Environmental Protection Agency's National Priorities List since 1984. For a given test, the extraction wells are turned off, and water samples are collected from selected monitor wells at regular intervals before and during cessation of pumping to monitor for changes in chemical concentrations. A long-term shutdown-rebound test began on July 17, 2006. In support of this test, the U.S. Geological Survey conducted this study to determine the effects of shutting down on-site extraction wells on concentrations of selected contaminants and water levels. Concentrations were compared to ARARs (applicable relevant and appropriate requirements), which were set as remediation goals in the Henderson Road Site Record of Decision. Water from 10 wells in and near the source area and to the north, northeast, and northwest of the source area sampled in 2008 exceeded the 5.52 ug/L (micrograms per liter) ARAR for benzene. The greatest changes in benzene concentration between pre-shutdown samples collected in July 2006 and samples collected in February and March 2008 (19 months after the shutdown) were for wells in and north of the source area; increases in benzene concentration ranged from 1.5 to 164 ug/L. Water from five wells in the source area and to the north and northwest of the source area sampled in 2008 exceeded the 60 ug/L ARAR for chlorobenzene. The greatest changes in chlorobenzene concentration between pre-shutdown samples collected in July 2006 and samples collected in February and March 2008 were for wells north of the source area; increases in chlorobenzene concentration ranged from 6.9 to 99 ug/L. The highest concentrations of chlorobenzene were near or outside the northern site boundary, indicating chlorobenzene may have moved north away from the source area; however, no monitor well clusters are on the northern side of the Pennsylvania Turnpike, which is about 190 feet north of the source area. A much larger area was affected by chlorobenzene than benzene. Chlorobenzene concentrations decreased in the source area and increased at and beyond the site boundary. Water from four wells in and northeast of the source area sampled in 2008 exceeded the 5.06 ug/L ARAR for 1,1-dichloroethane (1,1-DCA). Increases in 1,1-DCA concentration between pre-shutdown samples collected in July 2006 and samples collected in February 2008 ranged from 0.4 to 20 ug/L. Water from two wells in the source area sampled in 2008 exceeded the 175 ug/L ARAR for total xylene. The 1,1-DCA and xylene plumes appear to extend in an east-northeast direction from the source area. Large drawdowns in the Upper Merion Reservoir during droughts in 1998 and 2001 affected water levels in the Chester Valley and at the Henderson Road Site, except for well HR-17-170. After the drought of 2001, water levels in the Chester Valley showed a protracted recovery lasting from September 2001 until June 2005 (46 months). Water-level data were evaluated temporally for 1997-2008 and spatially for (1) June 16, 2003, when the extraction wells were pumping at the full rate prior to the start of the June 2003 shutdown test; (2) July 10, 2006, during the period of reduced pumping after the June 2003 shutdown test; and (3) February 25-29, 2008, when the extraction wells were not pumping. Except for well HR-5-195, wells were categorized as shallow, intermediate-depth, and deep wells. The potentiometric surface for shallow wells did not appear to be affected by pumping of the extraction wells. The general direction of ground-water flow was to the north. The potentiometric surface for intermediate-depth wells showed a cone of depression when the extraction wells were pumping at the full rate but did not show a cone of depression when the extraction wells were pumping at the reduced rate. The ground-water-flow direction was toward the north and northeast, similar to

Scientific Investigations Report↗
USGS2018

Revised groundwater-flow model of the glacial aquifer system north of Aberdeen, South Dakota, through water year 2015

The city of Aberdeen, in northeastern South Dakota, requires an expanded and sustainable supply of water to meet current and future demands. Conceptual and numerical models of the glacial aquifer system in the area north of Aberdeen were developed by the U.S. Geological Survey in cooperation with the City of Aberdeen in 2012. The U.S. Geological Survey, in cooperation with the City of Aberdeen, completed a study to revise the original numerical groundwater-flow model using data through water year (WY) 2015 to aid the City of Aberdeen in their development of plans and strategies for a sustainable water supply and to increase understanding of the glacial aquifer system and groundwater-flow system near Aberdeen. The original model was revised to improve the fit between model-simulated values and observed (measured or estimated) data, provide greater insight into surface-water interactions, and improve the usefulness of the model for water-supply planning. The revised groundwater-flow model (hereafter referred to as the “revised model”) presented in this report supersedes the original model. The purpose of this report is to describe a revised groundwater-flow model including data collection, model calibration, and model results for the glacial aquifer system including the Elm, Middle James, and Deep James aquifers north of Aberdeen, South Dakota, using updated hydrologic data through WY 2015. The original numerical model was revised in several ways. The model was modified by adding four new layers, which included a surficial layer, two intervening confining layers, and a shale bedrock layer. The revised model provides an improved understanding of the groundwater-flow system in comparison to the original model. The principal aquifers of the model area include portions of the Elm, Middle James, and Deep James aquifers. The lithologic information used to define and describe the aquifers in the model area was unaltered; however, aquifer properties and boundary conditions were reviewed and updated using geological information reported by the South Dakota Department of Environmental and Natural Resources and information obtained from geophysical investigations for this study. The horizontal extent of the Elm, Middle James, and Deep James aquifers was unaltered from the original model. The thickness of the Deep James aquifer was modified based on interpretations from the geophysical investigations. In general, groundwater in the Elm aquifer flowed from northwest to southeast and locally towards rivers and streams. Similarly, in the Middle James and Deep James aquifers, groundwater also typically flowed southeast. The revisions made to the original model include use of the following MODFLOW stress packages: Recharge, Evapotranspiration, Time-Variant Specified Head, Wells, Drains, and Stream Flow Routing, all of which were updated from the original model except for the Stream Flow Routing Package, which replaced the River Package used in the original model. Model calibration is the process of estimating model parameters to minimize the differences, or residuals, between observed data and simulated values; therefore, Parameter ESTimation (PEST) software was used to optimize model input parameters by matching model-simulated values to observed data. Calibration parameters included horizontal hydraulic conductivity, vertical hydraulic conductivity, specific yield, specific storage, and vertical streambed conductance for stream and drain cells. Multipliers were used to calibrate the recharge and evapotranspiration stresses. Evapotranspiration extinction depth also was adjusted during model calibration. Comparisons to the original model are described to highlight the changes made in the revised model. In general, the revised model adequately simulates the natural system and compares favorably with observed hydrologic data. Simulated water levels were evaluated by comparing them to single water-level observations at selected well locations. The selected wells were the same wells used in the original model. The coefficient of determination value between simulated and observed water levels for the revised model was 0.89 and included simulated and observed values from October 1, 1974 (WY 1975), through September 30, 2015 (WY 2015). The coefficient of determination value for the original model was 0.94 and included simulated and observed values from October 1, 1974, through September 30, 2009. The difference may indicate that the original model could have been overfit to hydraulic head observations because base flow was not simulated. The additional data used in the revised model included some climatically wetter, more extreme periods, such as 2011, in which annual precipitation was 30.9 inches. Average annual precipitation for the original model timeframe, which included data from WYs 1975–2009, was 20.26 inches. Additional precipitation data for WYs 2010–15, included in the revised model timeframe, resulted in an average annual precipitation for WYs 1975–2015 in the model area of 20.6 inches. The larger variability in climate data coupled with the additional water-level data could explain the lower coefficient of determination for water levels in the revised model. The revised model was used to calculate various groundwater-budget components for steady-state and transient conditions for WYs 1975–2015. The time-variant specified-head cells in the revised model had the largest change when compared to the original steady-state model for inflows and outflows. Comparing the transient budget components between the original and the revised models indicated that inflow from recharge and time-variant specified-head cells had the greatest effect on groundwater inflows, and outflow from storage had the greatest effect on groundwater outflows. The simulated potentiometric contours from the revised model were compared with (1) the observed (interpreted) potentiometric surface (layer 2) and the hydraulic head values (layers 4 and 6) and (2) the simulated contours from the original model. The simulated hydraulic gradients and general direction of groundwater flow in the Elm aquifer in the revised model generally matched the observed potentiometric contours, the simulated potentiometric contours from the original model, and general flow directions interpreted to be perpendicular to the contours. Minor discrepancies between simulated potentiometric contours from the revised model and the observed potentiometric contours may be due to the lack of observed data in the model area. The revised model was designed to reduce the limitations of the original model. The revisions were validated by comparing the results of the original model with the revised model. A primary benefit of the revised model is the inclusion of the surficial deposits and the confining units as explicit layers in the model. The addition of the surficial layer was beneficial for three primary reasons: (1) more accurate representation of recharge from precipitation, (2) more accurate representation of groundwater evapotranspiration, and (3) more accurate representation of groundwater and surface-water interactions. The groundwater model is a numeric approximation of a complex physical hydrologic system, and the revised model data were interpolated in regions with sparse data. Additionally, model discretization included averaged and interpolated values for water use, withdrawal rates, and hydraulic conductivity. The revised model provides a useful estimate for hydraulic gradients, groundwater-flow directions, and aquifer response to groundwater withdrawals.

South Dakota↗
USGS1999

Geohydrology and numerical simulation of the ground-water flow system of Kona, Island of Hawaii

Prior to the early 1990's, ground-water in the Kona area, which is in the western part of the island of Hawaii, was withdrawn from wells located within about 3 mi from the coast where water levels were less than 10 feet above sea level. In 1990, exploratory drilling in the uplands east of the existing coastal wells first revealed the presence of high water levels (greater than 40 feet above sea level) in the Kona area. Measured water levels from 16 wells indicate that high water levels exist in a zone parallel to and inland of the Kona coast, between Kalaoa and Honaunau. Available hydrologic and geophysical evidence is generally consistent with the concept that the high ground-water levels are associated with a buried dike complex. A two-dimensional (areal), steady-state, freshwater-saltwater, sharp-interface ground-water flow model was developed for the Kona area of the island of Hawaii, to enhance the understanding of (1) the distribution of aquifer hydraulic properties, (2) the conceptual framework of the ground-water flow system, and (3) the regional effects of ground-water withdrawals on water levels and coastal discharge. The model uses the finite-difference code SHARP. To estimate the hydraulic characteristics, average recharge, withdrawals, and water-level conditions for the period 1991-93 were simulated. The following horizontal hydraulic-conductivity values were estimated: (1) 7,500 feet per day for the dike-free volcanic rocks of Hualalai and Mauna Loa, (2) 0.1 feet per day for the buried dike complex of Hualalai, (3) 10 feet per day for the northern marginal dike zone (north of Kalaoa), and (4) 0.5 feet per day for the southern marginal dike zone between Palani Junction and Holualoa. The coastal leakance was estimated to be 0.05 feet per day per foot. Measured water levels indicate that ground water generally flows from inland areas to the coast. Model results are in general agreement with the limited set of measured water levels in the Kona area. Model results indicate, however, that water levels do not strictly increase in an inland direction and that a ground-water divide exists within the buried dike complex. Data are not available, however, to verify model results in the area near and inland of the model-calculated ground-water divide. Three simulations to determine the effects of proposed withdrawals from the high water-level area on coastal discharge and water levels, relative to model-calculated, steady-state coastal discharge and water levels for 1997 withdrawal rates, show that the effects are widespread. During 1997, the total withdrawal of ground water from the high water-level area between Palani Junction and Holualoa was about 1 million gallons per day. Model results indicate that it may not be possible to withdraw 25.6 million gallons per day of freshwater from this area between Palani Junction and Holualoa, but that it may be possible to withdraw between 5 to 8 million gallons per day from the same area. For a proposed withdrawal rate of 5.0 million gallons per day uniformly distributed to 12 sites between Palani Junction and Holualoa, the model-calculated drawdown of 0.01 foot or more extends about 9 miles north-northwest and about 7 miles south of the proposed well sites. In all scenarios, freshwater coastal discharge is reduced by an amount equal to the additional freshwater withdrawal. Additional data needed to improve the understanding of the ground-water flow system in the Kona area include: (1) a wider spatial distribution and longer temporal distribution of water levels, (2) improved information about the subsurface geology, (3) independent estimates of hydraulic conductivity, (4) improved recharge estimates, and (5) information about the vertical distribution of salinity in ground water.

Hawaii↗
USGS2007

Geologic map of Wupatki National Monument and vicinity, Coconino County, Northern Arizona

Introduction The geologic map of Wupatki National Monument is a cooperative effort between the U.S. Geological Survey, the National Park Service, and the Navajo Nation to provide geologic information for resource management officials of the National Park Service, U.S. Forest Service, Navajo Indian Reservation (herein the Navajo Nation), and visitor information services at Wupatki National Monument, Arizona. Funding for the map was provided in part by the Water Rights Branch of the Water Resources Division of the National Park Service. Field work on the Navajo Nation was conducted under a permit from the Navajo Nation Minerals Department. Any persons wishing to conduct geologic investigations on the Navajo Nation must first apply for, and receive, a permit from the Navajo Nation Minerals Department, P.O. Box 1910, Window Rock, Arizona 86515, telephone (928)-871-6587. Wupatki National Monument lies within the USGS 1:24,000-scale Wupatki NE, Wupatki SE, Wupatki SW, Gray Mountain, East of SP Mountain, and Campbell Francis Wash quadrangles in northern Arizona. The map is bounded approximately by longitudes 111? 16' to 111? 32' 30' W. and latitudes 35? 30' to 35? 37' 40' N. The map area is in Coconino County on the southern part of the Colorado Plateaus geologic province (herein Colorado Plateau). The map area is locally subdivided into three physiographic parts, the Coconino Plateau, the Little Colorado River Valley, and the San Francisco Volcanic Field as defined by Billingsley and others (1997) [fig. 1]. Elevations range from 4,220 ft (1,286 m) at the Little Colorado River near the northeast corner of the map area to about 6,100 ft (1,859 m) at the southwest corner of the map area. The small community of Gray Mountain is about 16 mi (26 km) northwest of Wupatki National Monument Visitor Center, and Flagstaff, Arizona, the nearest metropolitan area, is about 24 mi (38 km) southwest of the Visitor Center (fig. 1). U.S. Highway 89 provides access to the west entrance of Wupatki National Monument. A paved Coconino County road provides a loop from Wupatki National Monument south to Sunset Crater National Monument and back to U.S. Highway 89 about 10 mi (16 km) north of Flagstaff, Arizona. Access to Coconino National Forest is via dirt roads maintained by the National Forest Service. Several unimproved dirt roads on Babbitt Ranch lands provide limited access to remote areas north of Wupatki National Monument. Travel is mostly restricted to paved roads within Wupatki National Monument, and a dirt road that crosses the Little Colorado River provides access to the Navajo Nation area east and northeast of the Little Colorado River. The Little Colorado River crossing is not bridged and can be impassable when the river is flowing. Four-wheel-drive vehicles are recommended but not necessary for travel in remote parts of the Navajo Nation. Extra food and water are highly recommended for travel in this sandy area. Land ownership north of Wupatki National Monument forms a checkerboard pattern between private and State land. Coconino National Forest manages lands south of Wupatki National Monument and the National Park Service manages Wupatki National Monument. The Leupp and Tolani Lake Chapters of the Navajo Nation manage the area northeast and east of the Little Colorado River (see land management boundaries on map). The geologic map of Wupatki National Monument provides updated geologic framework information for this part of the Colorado Plateau. The geologic information supports Federal, State, and private land managers when conducting geologic, biologic, and hydrologic investigations and will support future and ongoing geologic and associated scientific investigations of all disciplines within the Wupatki National Monument area.

Arizona↗
USGS1970

Thermal infrared investigations, Arbuckle Mountains, Oklahoma

Thermal-infrared images obtained on flights over the Tishomingo anticline and South Flank areas near Mill Creek in the Arbuckle Mountains, Oklahoma, were used to study the possibility of identifying some common rock types from their diagnostic reflection and emission characteristics, and to evaluate the usefulness of infrared images in structural geologic investigations. The areas flown are underlain by folded and faulted Paleozoic dolomite, limestone, sandstone, shale, and Precambrian granite. Images were obtained at 6:00 a.m., 11:00 a.m., and 2:00 p.m. The predawn (6:00 a.m.) image is the most useful in distinguishing rock types. Of particular interest is a thermal contrast of dolomite (warm) and limestone (cool), sufficient to distinguish those rock types and to reveal facies changes between them. Theoretical considerations indicate that this thermal contrast arises from a combination of albedo and thermal-inertia characteristics distinctive of dolomites and limestones in many areas. The daytime images display much stratigraphic and structural detail. Small-scale bedding detail is enhanced in the morning images of low-relief areas, and contrasts of alternating formations that form hogbacks and valleys are enhanced in the afternoon images of higher relief areas. The difference in features displayed in morning and afternoon images appears to be a function of the insolation on sunward and shadowed slopes of differing scale. Fault or fracture zones are best displayed in the predawn image; they appear cooler than surrounding ground, because of greater water content and concomitant evaporation. The abundance and throughgoing nature of lineaments (which coincide for the most part with joint systems) are more obvious in the infrared images than in aerial photographs. Lineaments striking northwest are preferentially enhanced in the morning images, and lineaments striking northeast are preferentially shown in the afternoon images. This enhancement cannot be ascribed to the effects of topography, insolation, or wind; it may relate to a combination of ground-water and vegetation effects.

Oklahoma↗
USGS2016

Automated mapping of persistent ice and snow cover across the western U.S. with Landsat

We implemented an automated approach for mapping persistent ice and snow cover (PISC) across the conterminous western U.S. using all available Landsat TM and ETM+ scenes acquired during the late summer/early fall period between 2010 and 2014. Two separate validation approaches indicate this dataset provides a more accurate representation of glacial ice and perennial snow cover for the region than either the U.S. glacier database derived from US Geological Survey (USGS) Digital Raster Graphics (DRG) maps (based on aerial photography primarily from the 1960s–1980s) or the National Land Cover Database 2011 perennial ice and snow cover class. Our 2010–2014 Landsat-derived dataset indicates 28% less glacier and perennial snow cover than the USGS DRG dataset. There are larger differences between the datasets in some regions, such as the Rocky Mountains of Northwest Wyoming and Southwest Montana, where the Landsat dataset indicates 54% less PISC area. Analysis of Landsat scenes from 1987–1988 and 2008–2010 for three regions using a more conventional, semi-automated approach indicates substantial decreases in glaciers and perennial snow cover that correlate with differences between PISC mapped by the USGS DRG dataset and the automated Landsat-derived dataset. This suggests that most of the differences in PISC between the USGS DRG and the Landsat-derived dataset can be attributed to decreases in PISC, as opposed to differences between mapping techniques. While the dataset produced by the automated Landsat mapping approach is not designed to serve as a conventional glacier inventory that provides glacier outlines and attribute information, it allows for an updated estimate of PISC for the conterminous U.S. as well as for smaller regions. Additionally, the new dataset highlights areas where decreases in PISC have been most significant over the past 25–50 years.

ISPRS Journal of Photogrammetry and Remote Sensing↗
USGS2000

System of gigantic valleys northwest of Tharsis, Mars: Latent catastrophic flooding, northwest watershed, and implications for northern plains ocean

Mars Orbiter Laser Altimeter (MOLA) reveals a system of gigantic valleys to the northwest of the huge martian shield volcano, Arsia Mons, in the western hemisphere of Mars. These newly identified northwestern slope valleys (NSVs) potentially signify previously undocumented martian catastrophic floods and may corroborate the northern ocean hypotheses. These features, which generally correspond spatially to gravity lows, were previously obscurred in Mariner and Viking Orbiter imagery by veneers of materials, including volcanic lava flows and air fall deposits. Geologic investigations of the Tharsis region suggest that the NSVs were mainly carved prior to the construction of Arsia Mons and its associated Late Hesperian and Amazonian age lava flows, concurrent with the early development of the outflow channels that debouch into Chryse Planitia.

Geophysical Research Letters↗
USGS2011

Popular myths about flooding in Western Washington

Floods are the most destructive natural hazard in the Nation, causing more deaths and financial loss in the 20th century than any other natural disaster. The most significant 20 riverine floods of the 20th century for which data are available have killed more than 1,843 people and caused more than $50 billion (uninflated) in damages (Perry, 2000). One of the most common means of describing the severity of a flood is a comparison to the "100-year flood." In the last decade, increasing attention has been paid to the fact that some regions, notably the Pacific Northwest, have experienced numerous so-called "100-year" floods in the span of a few years. Part of the confusion stems from the statistical nature of the "100-year flood" (Greene, 1996); however, another part of the confusion is the fact that the statistics are calculated for specific sites (streamgages) on specific rivers, rather than for a region as a whole. Scientists with the U.S. Geological Survey have begun to investigate how the likelihood of flooding may be determined on a regional basis (Troutman and Karlinger, 2003).

Washington↗
USGS2022

Geologic maps of the Stephenson and Winchester quadrangles, Frederick and Clarke Counties, Virginia, and Inwood and White Hall quadrangles, Berkeley and Jefferson Counties, West Virginia

The study area consists of four contiguous 7.5-minute quadrangles and is located in Frederick and Clarke Counties, Virginia, and Berkeley and Jefferson Counties, West Virginia. The individual quadrangles are Stephenson, Winchester, Inwood, and White Hall. The study area lies within the Great Valley subprovince of the Valley and Ridge physiographic province where about 23,000 feet (ft) (7,000 meters [m]) of Middle Cambrian to Upper Devonian sedimentary rocks are exposed and are overlain by Holocene and older surficial deposits. The area of the four maps is divided into three geologic regions based on the following primary lithologies: (1) Cambrian and Ordovician carbonate rocks of the Great Valley southeast of the North Mountain fault zone and east and west of the core of the Massanutten synclinorium; (2) shale, graywacke, and calcareous shale of the Ordovician Martinsburg Formation of the Great Valley and Massanutten synclinorium; and (3) Ordovician through Devonian clastic rocks and minor limestone and dolostone northwest of and within the North Mountain fault zone. Rocks of all three regions were folded and faulted during the late Paleozoic Alleghanian orogeny (roughly 320 to 250 million years before present). The terrain of this portion of the Great Valley generally is gently to moderately rolling with low local relief with elevations in the study area ranging from about 425 ft (130 m) where Opequon Creek flows out of the eastern edge of the Inwood quadrangle to about 950 ft (290 m) adjacent to Round Hill in the western part of the Winchester quadrangle. Sinkholes and other karst features are common in the carbonate rocks of the Great Valley. The area west of the North Mountain fault zone is underlain by middle Paleozoic strata and consists of a series of ridges and valleys with higher local relief, with elevations ranging from about 785 ft (240 m) in the vicinity of Green Spring in the central part of the White Hall quadrangle to about 1,435 ft (437 m) at the summit of North Mountain in the northeastern part of the White Hall quadrangle.

Virginia, West Virginia↗
USGS2004

Combined impacts of Black-crowned Night-Heron predation/disturbance and various management activities on Roseate Tern productivity in 2003, and testing of a video surveillance system for recording the diurnal and nocturnal behavior of terns and night-herons at Falkner Island, Stewart B. McKinney National Wildlife Refuge, Connecticut, in 2004: Report to U.S. Fish and Wildlife Service, Stewart B. McKinney National Wildlife Refuge, Westbrook, Connecticut and U.S. Fish and Wildlife Service, Region 5 Regional Office, Hadley, Massachusetts

Falkner Island (FICT), a unit of the U.S. Fish and Wildlife Service's Stewart B. McKinney National Wildlife Refuge (SBMNWR) since 1985, is located in Long Island Sound 5 km south of Guilford, CT. For more than three decades it has been the site of the only large breeding colony in Connecticut of the federally endangered Northwest Atlantic population of Roseate Terns (Sterna dougallii) and the state's largest colony of Common Terns (S. hirundo). Both species have been studied at this site since 1978 as part of the Falkner Island Tern Project (FITP), and since 1987 also as part of a regional Cooperative Roseate Tern Metapopulation Dynamics and Ecology Project (CRTMP), both coordinated by Dr. Jeffrey A. Spendelow of the U.S. Geological Survey's Patuxent Wildlife Research Center (USGS-PWRC). From 1997-2002 the Roseate Tern breeding population at this site declined by more than 50% from about 150 to about 70 nesting pairs, mostly as a result of the nocturnal predation and disturbance of tern chicks and eggs by Black-crowned Night-Herons (Nycticorax nycticorax). Here we report the results of research done with the goal of improving management of nocturnal predators and developing new practices/structures to reduce losses of tern eggs and chicks so as to prevent the abandonment of this site by Roseate Terns. Notification of release of the USGS 'Quick Response Funds' (QRF) that were to be used to support the part of this study entitled 'Nocturnal behavior/interactions of endangered Roseate Terns and Black-crowned Night-Herons', and final approval of the Study Plan for this research did not occur until after the breeding season in 2003 was well underway. As a result, some work will need to be completed during the 2004 field season. There are two major objectives of this study. The first is to collect basic information (a) on the nocturnal behavior and interactions of Roseate (and Common) Terns with predatory Black-crowned Night-Herons, and (b) on how the behavior of the night-herons and the behavior and productivity of the terns are affected by the activities of management personnel (or researchers) that may be moving around the island at night. The second objective is to develop new structures (or to modify existing ones) that can be used by adult Roseate Terns for nesting sites and/or by chicks as hiding sites so that tern eggs and chicks will be less susceptible to night-heron predation. Work on the development and comparative use of various man-made structures began prior to the start of the 2003 nesting season; work on the evaluation and testing of a video surveillance system to study the nocturnal behavior of the terns and night-herons began in June 2003. Reported here are (1) the results of work on the placement and use by Roseate Terns of several types of structures in different habitats, and (2) a description of the set-up, testing, and evaluation of a multi-camera video system to record tern and predator behavior during both day and night. Also given here is some additional information on other factors that affected the productivity of the Roseate Terns at FICT collected as part of the CRTMP which served as the underlying foundation for the additional work done with support of the 2003 Quick Response Funds.

Book↗
USGS2011

Faulted terrace risers place new constraints on the late Quaternary slip rate for the central Altyn Tagh fault, northwest Tibet

The active, left-lateral Altyn Tagh fault defines the northwestern margin of the Tibetan Plateau in western China. To clarify late Quaternary temporal and spatial variations in slip rate along the central portion of this fault system (85°–90°E), we have more than doubled the number of dated offset markers along the central Altyn Tagh fault. In particular, we determined offset-age relations for seven left-laterally faulted terrace risers at three sites (Kelutelage, Yukuang, and Keke Qiapu) spanning a 140-km-long fault reach by integrating surficial geologic mapping, topographic surveys (total station and tripod–light detection and ranging [T-LiDAR]), and geochronology (radiocarbon dating of organic samples, 230 Th/U dating of pedogenic carbonate coatings on buried clasts, and terrestrial cosmogenic radionuclide exposure age dating applied to quartz-rich gravels). At Kelutelage, which is the westernmost site (37.72°N, 86.67°E), two faulted terrace risers are offset 58 ± 3 m and 48 ± 4 m, and formed at 6.2–6.1 ka and 5.9–3.7 ka, respectively. At the Yukuang site (38.00°N, 87.87°E), four faulted terrace risers are offset 92 ± 12 m, 68 ± 6 m, 55 ± 13 m, and 59 ± 9 m and formed at 24.2–9.5 ka, 6.4–5.0 ka, 5.1–3.9 ka, and 24.2–6.4 ka, respectively. At the easternmost site, Keke Qiapu (38.08°N, 88.12°E), a faulted terrace riser is offset 33 ± 6 m and has an age of 17.1–2.2 ka. The displacement-age relationships derived from these markers can be satisfied by an approximately uniform slip rate of 8–12 mm/yr. However, additional analysis is required to test how much temporal variability in slip rate is permitted by this data set.

Central Altyn Tagh fault↗
USGS1965

Geology and ground water in Russian River Valley areas and in Round, Laytonville, and Little Lake Valleys, Sonoma and Mendocino Counties, California

This report describes the occurrence, availability, and quality of ground water in seven valley areas along the course of the Russian River in Sonoma and Mendocino Counties, Calif., and in three valleys in the upper drainage reach of the Eel River in Mendocino County. Except for the westward-trending lower Russian River valley, the remaining valley areas along the Russian River (Healdsburg, Alexander, Cloverdale, Sanel, Ukiah, and Potter Valleys) lie in northwest-trending structurally controlled depressions formed in marine rocks of Jurassic and Cretaceous age. The principal aquifer in all the valleys is the alluvium of Recent age, which includes highly permeable channel deposits of gravel and sand. Water for domestic, irrigation, industrial, and other uses is developed by (1) direct diversion from the Russian River and its tributaries, (2) withdrawal of ground water and river water from shallow wells near the river, and (3) withdrawals of ground water from wells in alluvial deposits at varying distances from the river. Surface water in the Russian River and most tributaries is of good chemical quality. The water is a calcium magnesium bicarbonate type and contains 75,200 parts per million of dissolved solids. Ground water is also of good chemical quality throughout most of the drainage basin, but the concentration of dissolved solids (100-300 parts per million) is somewhat higher than that in the surface water. Round, Laytonville, and Little Lake Valleys are in central and northern Mendocino County in the drainage basin of the northwestward flowing Eel River. In Round Valley the alluvium of Recent age yields water of good chemical quality in large quantities. Yields are lower and the chemical quality poorer in Laytonville Valley. Ground water in Little Lake Valley is relatively undeveloped. Selected descriptions of wells, drillers' logs, chemical analyses, and hydrographs showing water-level fluctuations are included in the report. Accompanying maps show the distribution of water-bearing formations and the location of wells.

Water Supply Paper↗
USGS2008

Tracking the Archean-Proterozoic suture zone in the northeastern Great Basin, Nevada and Utah

It is important to know whether major mining districts in north-central Nevada are underlain by crust of the Archean Wyoming craton, known to contain major orogenic gold deposits or, alternatively, by accreted crust of the Paleoproterozoic Mojave province. Determining the location and orientation of the Archean-Proterozoic suture zone between these provinces is also important because it may influence subsequent patterns of sedimentation, deformation, magmatism, and hydrothermal activity. The suture zone is exposed in northeastern Utah and south-western Wyoming and exhibits a southwest strike. In the Great Basin, the suture zone strike is poorly constrained because it is largely concealed below a Neoproterozoic-Paleozoic miogeocline and Cenozoic basin fill. Two-dimensional resistivity modeling of three regional north-south magnetotelluric sounding profiles in western Utah, north-central Nevada, and northeastern Nevada, and one east-west profile in northeastern Nevada, reveals a deeply penetrating (>10 km depth), broad (tens of kilometers) conductor (1-20 ohm-meters) that may be the Archean-Proterozoic suture zone, which formed during Early Proterozoic rifting of the continent and subsequent Proterozoic accretion. This major crustal conductor changes strike direction from southwest in Utah to northwest in eastern Nevada, where it broadens to ???100 km width that correlates with early Paleozoic rifting of the continent. Our results suggest that the major gold belts may be over-isolated blocks of Archean crust, so Phanerozoic mineral deposits in this region may be produced, at least in part, from recycled Archean gold. Future mineral exploration to the east may yield large gold tonnages. ?? 2008 Geological Society of America.

Geosphere↗
USGS2017

Confirmation of the southwest continuation of the Cat Square terrane, southern Appalachian Inner Piedmont, with implications for middle Paleozoic collisional orogenesis

Detailed geologic mapping, U-Pb zircon geochronology and whole-rock geochemical analyses were conducted to test the hypothesis that the southwestern extent of the Cat Square terrane continues from the northern Inner Piedmont (western Carolinas) into central Georgia. Geologic mapping revealed the Jackson Lake fault, a ∼15 m-thick, steeply dipping sillimanite-grade fault zone that truncates lithologically distinct granitoids and metasedimentary units, and roughly corresponds with a prominent aeromagnetic lineament hypothesized to represent the southern continuation of the terrane-bounding Brindle Creek fault. Results of U-Pb SHRIMP geochronology indicate Late Ordovician to Silurian granitoids (444–439 Ma) occur exclusively northwest of the fault, whereas Devonian (404–371 Ma) granitoids only occur southeast of the fault. The relatively undeformed Indian Springs granodiorite (three individual bodies dated 317–298 Ma) crosscuts the fault and occurs on both sides, which indicates the Jackson Lake fault is a pre-Alleghanian structure. However, detrital zircon signatures from samples southeast of the Jackson Lake fault reveal dominant Grenville provenance, in contrast to Cat Square terrane detrital zircon samples from the northern Inner Piedmont, which include peri-Gondwanan (600–500 Ma) and a prominent Ordovician-Silurian (∼430 Ma) signature. We interpret the rocks southeast of the Jackson Lake fault to represent the southwestern extension of the Cat Square terrane primarily based on the partitioning of granitoid ages and lithologic distinctions similar to the northern Inner Piedmont. Data suggest Cat Square terrane metasedimentary rocks were initially deposited in a remnant ocean basin setting and developed into an accretionary prism in front of the approaching Carolina superterrane, ultimately overridden by it in Late Devonian to Early Mississippian time. Burial to >20 km resulted in migmatization of lower plate rocks, forming an infrastructure beneath the Carolina superterrane suprastructure. Provenance patterns support ∼250 km of Devonian dextral translation of the composite Inner Piedmont, which places the northern portion of the Inner Piedmont adjacent to a suite of ∼430 Ma plutons in the Virginia Blue Ridge during deposition. The megascopic thrust-nappe structural style of the northern Inner Piedmont, combined with southwest-directed lateral extrusion at mid-crustal depths, may reconcile differences in timing of metamorphism between the Carolina and central Georgia Inner Piedmont and structural contrasts between the Brindle Creek and Jackson Lake faults.

American Journal of Science↗
USGS1955

Phosphate deposits in northern Alaska

Deposits of low and medium grade phosphate rock were found recently at seven localities on the Arctic slope of Alaska. They were reported by field parties of the U.S. Geological Survey during the mapping of Naval Petroleum Reserve No. 4 and adjacent areas. The deposits are sedimentary in origin and are confined to a thin zone in the Lisburne group of Mississippian age. Six of the localities are in a narrow belt along the north front of the Brooks gang between the Anaktuvuk and Okokmilaga rivers. The seventh is near the Ipnavik River about 100 miles northwest of the Okokmilaga River. At all but two of these localities the zone of soft phosphatic rocks does not crop out extensively and samples of phosphate rock were collected chiefly from float or talus. Little or nothing is known about the thickness and extent of the deposits. Near Chandler Lake on the upper Kiruktagiak River and 11 miles west of at the head of Tiglukpuk Creek, the phosphatic zone is well-exposed. This paper is a preliminary report on the results of a detailed examination of the phosphatic zone in these two areas during the summer of 1953.

Alaska↗