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Sediment distribution and hydrologic conditions of the Potomac aquifer in Virginia and parts of Maryland and North Carolina

Sediments of the heavily used Potomac aquifer broadly contrast across major structural features of the Atlantic Coastal Plain Physiographic Province in eastern Virginia and adjacent parts of Maryland and North Carolina. Thicknesses and relative dominance of the highly interbedded fluvial sediments vary regionally. Vertical intervals in boreholes of coarse-grained sediment commonly targeted for completion of water-supply wells are thickest and most widespread across the central and southern parts of the Virginia Coastal Plain. Designated as the Norfolk arch depositional subarea, the entire sediment thickness here functions hydraulically as a single interconnected aquifer. By contrast, coarse-grained sediment intervals are thinner and less widespread across the northern part of the Virginia Coastal Plain and into southern Maryland, designated as the Salisbury embayment depositional subarea. Fine-grained intervals that are generally avoided for completion of water-supply wells are increasingly thick and widespread northward. Fine-grained intervals collectively as thick as several hundred feet comprise two continuous confining units that hydraulically separate three vertically spaced subaquifers. The subaquifers are continuous northward but merge southward into the single undivided Potomac aquifer. Lastly, far southeastern Virginia and northeastern North Carolina are designated as the Albemarle embayment depositional subarea, where both coarse- and fine-grained intervals are of only moderate thickness. The entire sediment thickness functions hydraulically as a single interconnected aquifer. A substantial hydrologic separation from overlying aquifers is imposed by the upper Cenomanian confining unit. Potomac aquifer sediments were deposited by a fluvial depositional complex spanning the Virginia Coastal Plain approximately 100 to 145 million years ago. Westward, persistently uplifted granite and gneiss source rocks sustained a supply of coarse-grained sand and gravel. Immature, high-gradient braided streams deposited longitudinal bars and channel fills across the Norfolk arch subarea. By contrast, across the Salisbury and Albemarle embayment subareas, mature, medium- to low-gradient meandering streams deposited medium- to coarse-grained channel fills and point bars segregated from fine-grained overbank deposits. The Virginia depositional complex merged northward across the Salisbury embayment subarea with another complex in Maryland. Here, additional sediments were received from schist source rocks that underwent three cycles of initial uplift and rapid erosion followed by crustal stability and erosional leveling. Because of the predominance of coarse-grained sediments, transmissivity, hydraulic conductivity, and regional velocities of lateral flow through the Potomac aquifer are greatest across the Norfolk arch depositional subarea, but decrease progressively northward with increasingly fine-grained sediments. Confining units hydraulically separate the Potomac aquifer from overlying aquifers, as indicated by large vertical hydraulic gradients. By contrast, most of the Potomac aquifer internally functions hydraulically as a single interconnected aquifer, as indicated by uniformly small vertical gradients. Most fine-grained sediments within the aquifer do not hydraulically separate overlying and underlying coarse-grained sediments. Across the Salisbury embayment depositional subarea, however, hydraulic separation among the vertically spaced subaquifers is imposed by the intervening confining units. The Potomac aquifer is the largest and most heavily used source of groundwater in the Virginia Coastal Plain. Water-level declines as great as 200 feet create the potential for saltwater intrusion. Conventional stratigraphic correlation has been generally ineffective at accurately characterizing complexly distributed fluvial sediments that compose the Potomac aquifer. Consequently, the aquifer’s internal hydraulic connectivity and overall hydrologic function have not been well understood. Water-supply planning and development efforts have been hampered, and interpretations of regulatory criteria for allowable water-level declines have been ambiguous. An investigation undertaken during 2010–11 by the U.S. Geological Survey, in cooperation with the Virginia Department of Environmental Quality, provides a comprehensive regional description of the spatial distribution of Potomac aquifer sediments and their relation to hydrologic conditions. Altitudes and thicknesses of 2,725 vertical sediment intervals represent the spatial distribution of Potomac aquifer sediments in the Virginia Coastal Plain and adjacent parts of Maryland and North Carolina. Sediment intervals are designated as either dominantly coarse or fine grained and were determined by interpretation of geophysical logs and ancillary information from 456 boreholes. Sediment-interval and borehole summary statistical data indicate regional trends in sediment lithology and stratigraphic continuity, upon which three structurally based and hydrologically distinct sediment depositional subareas are designated. Broad patterns of sediment deposition over time are inferred from published sediment pollen-age data. Discrepancies in previously drawn hydrostratigraphic relations between southeastern Virginia and northeastern North Carolina are partly resolved based on borehole geophysical logs and a recently documented geologic map and corehole. A conceptual model theorizes the depositional history of the sediments and geologically accounts for their distribution. Documented pumping tests of the Potomac aquifer at 197 locations produced 336 values of transmissivity and 127 values of storativity. Based on effective aquifer thicknesses, 296 values of sediment hydraulic conductivity and 113 values of sediment specific storage are calculated. Vertical hydraulic gradients are calculated from 9,479 pairs of water levels measured between November 17, 1953, and October 4, 2011, in 129 closely spaced pairs of wells. Borehole sediment-interval and related data provide a means to achieve high yielding production wells in the Potomac aquifer by site-specific targeting of drilling operations toward water-bearing coarse-grained sand and gravel. Advance knowledge of the potential of different parts of the aquifer also aids in planning optimal groundwater-development areas. Depositional subareas further provide a possible context for resource management. Current (2013) regulatory limits on water-level declines are relative to top surfaces of subdivided upper, middle, and lower Potomac aquifers across the entire Virginia Coastal Plain, but have the potential to exceed the same limit relative to a single undivided Potomac aquifer. By contrast, designation of the sediments as a single aquifer in the Norfolk arch and Albemarle embayment subareas—and as a series of vertically spaced subaquifers and intervening confining units in the Salisbury embayment subarea—best reflects understanding of the Potomac aquifer and can avoid the potential for excessive water-level declines. Simulation modeling to evaluate effects of groundwater withdrawals could be designed similarly, including vertical discretization and (or) zonation of the Potomac aquifer based on depositional subareas and a geostatistical distribution of aquifer properties derived from borehole sediment-interval data. Further resource-management information needs extend beyond the developed part of the Potomac aquifer, particularly across the Northern Neck and Middle Peninsula where only the shallowest part of the aquifer is known, and include structural aspects such as faults, basement bedrock, and the Chesapeake Bay impact crater.

Maryland, North Carolina, Virginia↗

Geologic and geophysical maps and volcanic history of the Kelton Pass SE and Monument Peak SW Quadrangles, Box Elder County, Utah

The Kelton Pass SE and Monument Peak SW 7.5' quadrangles are located in Box Elder County, northwestern Utah (figure 1; plate 1). The northern boundary of the map area is 8.5 miles (13.7 km) south of the Utah-Idaho border, and the southern boundary reaches the edge of mud flats at the north end of Great Salt Lake. Elevations range from 4218 feet (1286 m) along the mud flats to 5078 feet (1548 m) in the Wildcat Hills. Deep Creek forms a prominent drainage between the Wildcat Hills and Cedar Hill. The closest towns are the ranching communities of Snowville, Utah (10 miles [16 km] to the northeast) (figure 1), and Park Valley, Utah (10 miles [16 km] to the west). The Kelton Pass SE and Monument Peak SW 7.5' quadrangles are located entirely within southern Curlew Valley, which drains south into Great Salt Lake, and extends north of the area shown on figure 1 into Idaho. Curlew Valley is bounded on the west by the Raft River Mountains and on the east by the Hansel Mountains (figure 1). Sedimentary and volcanic bedrock exposures within the quadrangles form the Wildcat Hills, Cedar Hill, and informally named Middle Shield (figure 1). Exposed rocks and deposits are Permian to Holocene in age, and include the Permian quartz sandstone and orthoquartzite of the Oquirrh Formation (Pos), tuffaceous sedimentary rocks of the Miocene Salt Lake Formation (Ts), Pliocene basaltic lava flows (Tb) and dacite (Tdw), Pleistocene rhyolite (Qrw) and basalt (Qb), and Pleistocene and Holocene surficial deposits of alluvial, lacustrine, and eolian origin. Structurally, the map area is situated in the northeastern Basin and Range Province, and is inferred to lie within the hanging wall of the late Miocene detachment faults exposed in the Raft River Mountains to the northwest (e.g., Wells, 1992, 2009; figure 1). This mapping project was undertaken to produce a comprehensive, large-scale geologic map of the Wildcat Hills, as well as to improve understanding of the volcanic and tectonic evolution of southern Curlew Valley. The resultant publication includes a geologic map of the Kelton Pass SE and Monument Peak SW quadrangles (plate 1), two interpretive geologic cross sections (plate 2), new geophysical data and interpretations, and new geochronology data for volcanic units within and near the quadrangles.

Utah↗

Selected ground-water information for the Columbia Plateau Regional Aquifer System, Washington and Oregon, 1982-1985; Volume III, Ground-water quality data

The data report presents ground-water information collected and analyzed as part of the U.S. Geological Survey's Columbia Plateau Regional Aquifer-System Analysis Program. The information was gathered from July 1982 through September 1985 in the part of the aquifer system located in central and eastern Washington and north-central and northeastern Oregon. The report consists of three volumes: volume I, geohydrology; volume II, water levels; and volume III, ground-water quality. This volume, III, presents ground-water quality data gathered from about 570 wells during the study.

Open-File Report↗

Hydrogeologic framework, groundwater movement, and water budget in the Chimacum Creek basin and vicinity, Jefferson County, Washington

This report presents information used to characterize the groundwater flow system in the Chimacum Creek basin. It includes descriptions of the geology and hydrogeologic framework; groundwater recharge and discharge; groundwater levels and flow directions; seasonal fluctuations in groundwater level; interactions between aquifers and the surface-water system; and a groundwater budget. The study area covers 124 square miles in northeastern Jefferson County, Washington, and includes the Chimacum Creek basin, which drains an area of about 37 square miles. The area is underlain by a north-thickening sequence of unconsolidated glacial and interglacial deposits that overlie sedimentary and igneous bedrock units that crop out along the margins and western interior of the study area. Six hydrogeologic units consisting of unconsolidated aquifers and confining units, along with an underlying bedrock unit, were identified. A surficial hydrogeologic map was developed and used with well information from 187 drillers' logs to construct 4 hydrogeologic sections, and maps showing the extent and thickness of the units. Natural recharge was estimated using precipitation-recharge relation regression equations developed for western Washington, and estimates were calculated for return flow from data on domestic indoor and outdoor use and irrigated agriculture. Results from synoptic streamflow measurements and water table elevations determined from monthly measurements at monitoring wells are presented and compared with those from a study conducted during 2002-03. A water budget was calculated comprising long-term average recharge, domestic public-supply withdrawals and return flow, self-supplied domestic withdrawals and return flow, and irrigated agricultural withdrawals and return flow.

Washington↗

Characteristics of water, sediment, and benthic communities of the Wolf River, Menominee Indian Reservation, Wisconsin, water years 1986-98

Analyses and interpretation of water quality, sediment, and biological data from water years 1986 through 1998 indicated that land use and other human activities have had only minimal effects on water quality in the Wolf River upstream from and within the Menominee Indian Reservation in northeastern Wisconsin. Relatively high concentrations of calcium and magnesium (natural hardness), iron, manganese, and aluminum were measured in Wolf River water samples during water years 1986-98 from the three sampled sites and attributed to presence of highly mineralized geologic materials in the basin. Average calcium and magnesium concentrations varied from 22-26 milligrams per liter (mg/L) and 11-13 mg/L, respectively. Average iron concentrations ranged from 290-380 micrograms per liter ( μ g/L); average manganese concentrations ranged from 53-56 mg/L. Average aluminum concentrations ranged from 63-67 μ g/L. Mercury was present in water samples but concentrations were not at levels of concern. Levels of Kjeldahl nitrogen, ammonia, nitrite plus nitrate, total phosphorus, and orthophosphorus in water samples were often low or below detection limits (0.01- 0.10 mg/L). Trace amounts of atrazine (maximum concentration of 0.031 μ g/L), deethylatrazine (maximum 0.032 μ g/L), and alachlor (maximum of 0.002 μ g/L) were detected. Low concentrations of most trace elements were found in streambed sediment. Tissues of fish and aquatic invertebrates collected once each year from 1995 through 1998 at the Langlade and Keshena sites, near the northern and southern boundaries of the Reservation, respectively, were low in concentrations of most trace elements. Arsenic and silver in fish livers from both sites were less than or equal to 2 μ g/g arsenic and less than 1 μ g/g silver for dry weight analysis, and concentrations of antimony, beryllium, cadmium, cobalt, lead, nickel, and uranium were all below detection limits (less than 1 μ g/g dry weight). Concentrations of most other trace elements in fish were low, with the exceptions of chromium, copper, mercury, and selenium; however, these concentrations are not at levels of concern. Concentrations of all trace elements analyzed in whole caddisfly larvae also were low compared to those reported in the literature. During 1998, a total of 48 species of macroinvertebrates were identified at each of two sampled sites, with similar numbers of genera represented at both: 41 at Keshena and 44 at Langlade. The percentage EPT (Ephemeroptera, Plecoptera, and Trichoptera) was 52 at Keshena and 77 at Langlade; these relatively large percentages suggest very good to excellent water quality at these sites. A total of 52 algal taxa were identified at the Wolf River near Langlade. Diatoms made up 96 percent of the algal biomass. A total of 58 algal taxa were identified at Keshena, including 48 diatom taxa (83 percent). Although diatoms accounted for just 22 percent of the algal relative abundance, in cells per square centimeter, diatoms contributed 91 percent of the total algal biomass. The overall biological integrity of the Keshena and Langlade sites, based on diversity, siltation, and pollution indexes for diatoms is excellent.

Wisconsin↗

Water resources of the Lake Traverse Reservation, South and North Dakota, and Roberts County, South Dakota

In 1994, the U.S. Geological Survey, in cooperation with the Sisseton-Wahpeton Sioux Tribe; Roberts County; and the South Dakota Department of Environment and Natural Resources, Geological Survey Program, began a 6-year investigation to describe and quantify the water resources of the area within the 1867 boundary of the Lake Traverse Reservation and adjacent parts of Roberts County. Roberts County is located in extreme northeastern South Dakota, and the 1867 boundary of the Lake Traverse Reservation encompasses much of Roberts County and parts of Marshall, Day, Codington, and Grant Counties in South Dakota and parts of Richland and Sargent Counties in southeast North Dakota. This report includes descriptions of the quantity, quality, and availability of surface and ground water, the extent of the major glacial and bedrock aquifers and named outwash groups, and surface- and ground-water uses within the 1867 boundary of the Lake Traverse Reservation and adjacent parts of Roberts County. The surface-water resources within the 1867 boundary of the Lake Traverse Reservation and adjacent parts of Roberts County include rivers, streams, lakes, and wetlands. The Wild Rice and Bois de Sioux Rivers are tributaries of the Red River within the Souris-Red-Rainy River Basin; the Little Minnesota, Jorgenson, and North Fork Whetstone Rivers are tributaries of the Minnesota River within the Upper Mississippi River Basin, and the James and Big Sioux Rivers are tributaries within the Missouri River Basin. Several of the larger lakes within the study area have been developed for recreation, while many of the smaller lakes and wetlands are used for livestock watering or as wildlife production areas. Statistical summaries are presented for the water-quality data of six selected streams within the study area, and the dominant chemical species are listed for 17 selected lakes within the study area. The glacial history of the study area has led to a rather complex system of glacial aquifers. The boundaries of 11 aquifers and 6 named outwash groups were delineated based on hydrogeologic cross sections, water levels, and water-quality similarities/dissimilarities. The glacial aquifers include Coteau Lakes system, Big Sioux, Alta-mont, Revillo, James, Veblen system, Spiritwood, Hankinson, Rosholt, Milnor Channel, and Fairmount; the bedrock aquifer included in this report is the Dakota. Named outwash groups include the Prairie Coteau, Lonesome Lake, Marday, Eden, Roslyn, and Wilmot. A summary of the character-istics of each of the major aquifers and outwash groups and a summary of selected chemical analyses for each aquifer and outwash group are presented. All aquifers and outwash groups in the study area have either moderately hard or very hard water and are considered fresh to slightly saline. One or more water samples from some of the aquifers and outwash groups have a constituent that was above the recommended or mandatory limit for drinking water. Most aquifers and outwash groups have dissolved solids and sulfate contents above the recommended levels of 500 and 250 mg/L (milligrams per liter), respectively. The Dakota aquifer was the only one to have a mean chloride concentration above the recommended level of 250 mg/L. Nitrate concentrations greater than the mandatory limit of 10 mg/L were found in the Big Sioux aquifer and the Coteau Lakes and Veblen aquifer systems. Concentrations of arsenic greater than 10 ?g/L (micrograms per liter) were found in the Coteau Lakes and Veblen aquifer systems, and in the Rosholt and Fairmount aquifers. Municipalities and rural water systems currently provide most of the water used in the study area-nearly all of it from ground-water sources. Surface-water use is limited to livestock watering. About 55 percent of the total water used in Roberts County is for domestic purposes, with most domestic users served by a public supply system. Irrigation accounts for about 10 percent of the total water used. All

North Dakota, South Dakota↗

Meeting the Science Needs of the Nation in the Wake of Hurricane Sandy-- A U.S. Geological Survey Science Plan for Support of Restoration and Recovery

n late October 2012, Hurricane Sandy came ashore during a spring high tide on the New Jersey coastline, delivering hurricane-force winds, storm tides exceeding 19 feet, driving rain, and plummeting temperatures. Hurricane Sandy resulted in 72 direct fatalities in the mid-Atlantic and northeastern United States, and widespread and substantial physical, environmental, ecological, social, and economic impacts estimated at near $50 billion. Before the landfall of Hurricane Sandy, the USGS provided forecasts of potential coastal change; collected oblique aerial photography of pre-storm coastal morphology; deployed storm-surge sensors, rapid-deployment streamgages, wave sensors, and barometric pressure sensors; conducted Light Detection And Ranging (lidar) aerial topographic surveys of coastal areas; and issued a landslide alert for landslide prone areas. During the storm, Tidal Telemetry Networks provided real-time water-level information along the coast. Long-term network and rapid-deployment real-time streamgages and water-quality monitors reported on river levels and changes in water quality. Immediately after the storm, the USGS serviced real-time instrumentation, retrieved data from over 140 storm-surge sensors, and collected other essential environmental data, including more than 830 high-water marks mapping the extent and elevation of the storm surge. Post-storm lidar surveys documented storm impacts to coastal barriers informing response and recovery and providing a new baseline to assess vulnerability of the reconfigured coast. The USGS Hazard Data Distribution System served storm related information from many agencies on the Internet on a daily basis. This science plan was developed immediately following Hurricane Sandy to coordinate continuing USGS activities with other agencies and to guide continued data collection and analysis to ensure support for recovery and restoration efforts. The data, information, and tools that are produced by implementing this plan will: (1) further characterize impacts and changes, (2) guide mitigation and restoration of impacted communities and ecosystems, (3) inform a redevelopment strategy aimed at developing resilient coastal communities and ecosystems, (4) improve preparedness and responsiveness to the next hurricane or similar coastal disaster, and (5) enable improved hazard assessment, response, and recovery for future storms along the hurricane prone shoreline of the United States. The activities outlined in this plan are organized in five themes based on impact types and information needs. These USGS science themes are: Theme 1: Coastal topography and bathymetry. Theme 2: Impacts to coastal beaches and barriers. Theme 3: Impacts of storm surge and estuarine and bay hydrology. Theme 4: Impacts on environmental quality and persisting contaminant exposures. Theme 5: Impacts to coastal ecosystems, habitats, and fish and wildlife. A major emphasis in the implementation of this plan will be on interacting with stakeholders to better understand their specific data and information needs, to define the best way to make information available, and to support applications of USGS science and expertise to decisionmaking.

Connecticut;Delaware;Maine;Maryl;Massachusetts;New↗

Geologic map of the Littlefield Quadrangle, northern Mohave County, Arizona

The Littlefield 7.5' quadrangle lies in the extreme northwestern corner of Mohave County, Arizona (fig. 1). Elevations range from about 536.5 m (1,760 ft) at the Virgin River (south-central edge of quadrangle) to 975 m (3,200 ft) in the Beaver Dam Mountains (northeastern corner of quadrangle). Interstate Arizona Highway 15 and U.S. Highway 91 provides a general access to the quadrangle while several unimproved dirt roads lead to remote areas of the quadrangle. The community of Littlefield, Arizona is just southeast of Interstate 15 along the west bank of the Virgin River, and the community of Beaver Dam, Arizona is just northwest of Interstate 15 in the valley of Beaver Dam Wash (fig. 1). Population of both communities is about 300 people. The environment, topography, and geography is typical of the Mohave Desert of Nevada and California. There are about 9 sections of private land in the quadrangle and 5 sections belonging to the state of Arizona. The balance is public land administrated by the U.S. Bureau of Land Management, Arizona Strip District in St. George, Utah. The area supports sparse growth of desert shrubs, mainly creosote bush and cactus. Dense growths of tamerisk (Salt Cedar), cottonwood, and willow trees thrive along the alluvial terraces and banks of the Virgin River. A variety of water loving plants thrive in warm spring waters on the east side of the Virgin River near the Interstate 15 bridge, and in Beaver Dam Wash, northwest corner of the quadrangle.

Arizona↗

Assessment of streamflow trends in the eastern Dakotas, water years 1960–2019

Hydrologic extremes, whether periods of drought or flooding, are occurring more frequently with greater severity and can have substantial economic impacts. Along with flooding, the timing and volume of streamflow also is changing across the United States. The focus of this report is to characterize a unique trend in mean annual streamflow occurring in eastern North and South Dakota, hereafter referred to as the eastern Dakotas, that is not being observed anywhere else in the conterminous United States. Streamflow records for 1,853 U.S. Geological Survey streamgages obtained from the U.S. Geological Survey National Water Information System database with a continuous record of mean annual streamflow during water years 1960–2019 were included in this study. Using a Kendall tau statistical test ( p -value less than or equal to 0.10), 573 streamgages had a statistically significant upward trend in mean annual streamflow and are primarily located in the Midwest and northeastern United States. Of the streamgages, 182 had a statistically significant downward trend and are located primarily in the western and southeastern States. Several sites had increases in streamflow between 100 and 500 percent. Most of the streamgages with the highest increases in mean annual streamflow are along the same rivers in the eastern Dakotas, regardless of basin size. A comparison of mean annual streamflow of the last decade (2010–19) to the first decade (1960–69) of the study period shows that the largest increases in annual streamflow volumes in the United States also are in the eastern Dakotas. Among all 1,853 streamgages in the United States, the Sheyenne River near Warwick, North Dakota (U.S. Geological Survey station 05056000), has the greatest percent change, with an increase of 486 percent. Several factors may be contributing to increasing trends in streamflow in the eastern Dakotas and may include, in part, precipitation changes owing to climatic variation within the region, geologic makeup of the subsurface, and land-use changes. A better understanding of these research areas will help producers, resource managers, and infrastructure engineers to make more informed environmental and economic decisions.

North Dakota, South Dakota↗

Self-potential investigations of a gravel bar in a restored river corridor

Self-potentials (SP) are sensitive to water fluxes and concentration gradients in both saturated and unsaturated geological media, but quantitative interpretations of SP field data may often be hindered by the superposition of different source contributions and time-varying electrode potentials. Self-potential mapping and close to two months of SP monitoring on a gravel bar were performed to investigate the origins of SP signals at a restored river section of the Thur River in northeastern Switzerland. The SP mapping and subsequent inversion of the data indicate that the SP sources are mainly located in the upper few meters in regions of soil cover rather than bare gravel. Wavelet analyses of the time-series indicate a strong, but non-linear influence of water table and water content variations, as well as rainfall intensity on the recorded SP signals. Modeling of the SP response with respect to an increase in the water table elevation and precipitation indicate that the distribution of soil properties in the vadose zone has a very strong influence. We conclude that the observed SP responses on the gravel bar are more complicated than previously proposed semi-empiric relationships between SP signals and hydraulic head or the thickness of the vadose zone. We suggest that future SP monitoring in restored river corridors should either focus on quantifying vadose zone processes by installing vertical profiles of closely spaced SP electrodes or by installing the electrodes within the river to avoid signals arising from vadose zone processes and time-varying electrochemical conditions in the vicinity of the electrodes.

Lake Constance, Neunforn, Thur catchment, Thur val↗

Late quaternary geology and frost phenomena along Alaska Highway, Northern British Columbia and Southeastern Yukon

Reconnaissance field work along the Alaska Highway in northern British Columbia and southeastern Yukon furnishes preliminary data on the later Quaternary history of the region, and on the processes and results of intensive frost action. Extensive erosion surfaces were developed prior to glaciation, such as the Alberta Plateau of northeastern British Columbia and the Yukon Plateau in southern Yukon . In the region from Dawson Creek to Fort Nelson, British Columbia , the drift is dominantly a slightly weathered bouldery clay till of Wisconsin age, deposited by ice that came from the east. In the northern Rocky Mountains, the last eastward advance of the Wisconsin glaciers to the mountain front preceded the maximum westward advance of the ice sheets. In the foothills belt west of the Highway , the tills of these two advances are separated by lake deposits. Much of the drift is probably pre-Altamont in age and was subjected to vigorous frost action during the Altamont substage. The climate ameliorated perhaps with the advent of the post-glacial optimum and possibly coincident with the development of prairies. A recent change from prairie to forest perhaps indicates a slight cooling in recent time. In the northern Rocky Mountains, four substages of Wisconsin glaciation are recognized tentatively on the basis of morainal deposits and outwash terraces. The upper Liard basin is characterized by extensive pitted outwash plains, probably of late Wisconsin age. From Teslin Lake to Whitehorse, the Highway is bordered by extensive terraces of gravel and sand deposited in ice-marginal streams and lakes. Intensive frost action has modified pre-existing land forms and has produced a wide variety of features, such as talus, blockfields, stone rings, stone stripes, and terraces. Long smooth slopes, chiefly due to mass movements such as solifluction, are characteristic of the landscapes. These slopes and ancient soil structures extend down into forested areas and probably developed prior to the advent of forests, doubtless prior to the post-glacial optimum. Phenomena resulting from intensive frost action at the present time are restricted largely to areas above timber line.

Alaska, Yukon, British Columbia↗

Timing, distribution, amount, and style of Cenozoic extension in the northern Great Basin

This field trip examines contrasting lines of evidence bearing on the timing and structural style of Cenozoic (and perhaps late Mesozoic) extensional deformation in northeastern Nevada. Studies of metamorphic core complexes in this region report extension beginning in the early Cenozoic or even Late Cretaceous, peaking in the Eocene and Oligocene, and being largely over before the onset of “modern” Basin and Range extension in the middle Miocene. In contrast, studies based on low-temperature thermochronology and geologic mapping of Eocene and Miocene volcanic and sedimentary deposits report only minor, localized extension in the Eocene, no extension at all in the Oligocene and early Miocene, and major, regional extension in the middle Miocene. A wealth of thermochronologic and thermobarometric data indicate that the Ruby Mountains–East Humboldt Range metamorphic core complex (RMEH) underwent ~170 °C of cooling and 4 kbar of decompression between ca. 85 and ca. 50 Ma, and another 450 °C cooling and 4–5 kbar decompression between ca. 50 and ca. 21 Ma. These data require ~30 km of exhumation in at least two episodes, accommodated at least in part by Eocene to early Miocene displacement on the major west-dipping mylonitic zone and detachment fault bounding the RMEH on the west (the mylonitic zone may also have been active during an earlier phase of crustal extension). Meanwhile, Eocene paleovalleys containing 45–40 Ma ash-flow tuffs drained eastward from northern Nevada to the Uinta Basin in Utah, and continuity of these paleovalleys and infilling tuffs across the region indicate little, if any deformation by faults during their deposition. Pre–45 Ma deformation is less constrained, but the absence of Cenozoic sedimentary deposits and mappable normal faults older than 45 Ma is also consistent with only minor (if any) brittle deformation. The presence of ≤1 km of late Eocene sedimentary—especially lacustrine—deposits and a low-angle angular unconformity between ca. 40 and 38 Ma rocks attest to an episode of normal faulting at ca. 40 Ma. Arguably the greatest conundrum is how much extension occurred between ca. 35 and 17 Ma. Major exhumation of the RMEH is interpreted to have taken place in the late Oligocene and early Miocene, but rocks of any kind deposited during this interval are scarce in northeastern Nevada and absent in the vicinity of the RMEH itself. In most places, no angular unconformity is present between late Eocene and middle Miocene rocks, indicating little or no tilting between the late Eocene and middle Miocene. Opinions among authors of this report differ, however, as to whether this indicates no extension during the same time interval. The one locality where Oligocene deposits have been documented is Copper Basin, where Oligocene (32.5–29.5 Ma) conglomerates are ~500 m thick. The contact between Oligocene and Eocene rocks in Copper Basin is conformable, and the rocks are uniformly tilted ~25° NW, opposite to a normal fault system dipping ~35° SE. Middle Miocene rhyolite (ca. 16 Ma) rests nonconformably on the metamorphosed lower plate of this fault system and appears to rest on the tilted upper-plate rocks with angular unconformity, but the contact is not physically exposed. Different authors of this report interpret geologic relations in Copper Basin to indicate either (1) significant episodes of extension in the Eocene, Oligocene, and middle Miocene or (2) minor extension in the Eocene, uncertainty about the Oligocene, and major extension in the middle Miocene. An episode of major middle Miocene extension beginning at ca. 16–17 Ma is indicated by thick (up to 5 km) accumulations of sedimentary deposits in half-graben basins over most of northern Nevada, tilting and fanning of dips in the synextensional sedimentary deposits, and apatite fission-track and (U-Th)/He data from the southern Ruby Mountains and other ranges that indicate rapid middle Miocene cooling through near-surface temperatures (~120–40 °C). Opinions among authors of this report differ as to whether this period of extension was merely the last step in a long history of extensional faulting dating back at least to the Eocene, or whether it accounts for most of the Cenozoic deformation in northeastern Nevada. Since 10–12 Ma, extension appears to have slowed greatly and been accommodated by high-angle, relatively wide-spaced normal faults that give topographic form to the modern ranges. Despite the low present-day rate of extension, normal faults are active and have generated damaging earthquakes as recently as 2008.

Northern Great Basin↗

Paleozoic and Precambrian rocks of Alaska and their role in its structural evolution

Acknowledging that there are large gaps in the knowledge of the geology of Alaska, the following threefold subdivision of Alaska into Paleozoic tectonic elements is proposed: Southern Alaska--the Alaska Range and farther south--is the northern end of the Paleozoic Cordilleran geosyncline that rims the eastern Pacific. Northern Alaska--the northeastern Brooks Range and the Arctic Coastal Plain--is underlain by a pre-Upper Devonian fold belt that may continue around the rim of the Canada Basin into the Franklinian geosyncline of the Canadian Arctic Islands. East-central Alaska, with a thinner, mainly carbonate rock section, seems to be a western extension of the Yukon shelf that separates the circum-Arctic geosynclinal trend from the Cordilleran geosyncline along the Pacific margin of southern Alaska.

Alaska↗

Estimation of Streamflow Characteristics for Charles M. Russell National Wildlife Refuge, Northeastern Montana

Charles M. Russell National Wildlife Refuge (CMR) encompasses about 1.1 million acres (including Fort Peck Reservoir on the Missouri River) in northeastern Montana. To ensure that sufficient streamflow remains in the tributary streams to maintain the riparian corridors, the U.S. Fish and Wildlife Service is negotiating water-rights issues with the Reserved Water Rights Compact Commission of Montana. The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, conducted a study to gage, for a short period, selected streams that cross CMR, and analyze data to estimate long-term streamflow characteristics for CMR. The long-term streamflow characteristics of primary interest include the monthly and annual 90-, 80-, 50-, and 20-percent exceedance streamflows and mean streamflows (Q.90, Q.80, Q.50, Q.20, and QM, respectively), and the 1.5-, 2-, and 2.33- year peak flows (PK1.5, PK2, and PK2.33, respectively). The Regional Adjustment Relationship (RAR) was investigated for estimating the monthly and annual Q.90, Q.80, Q.50, Q.20, and QM, and the PK1.5, PK2, and PK2.33 for the short-term CMR gaging stations (hereinafter referred to as CMR stations). The RAR was determined to provide acceptable results for estimating the long-term Q.90, Q.80, Q.50, Q.20, and QM on a monthly basis for the months of March through June, and also on an annual basis. For the months of September through January, the RAR regression equations did not provide acceptable results for any long-term streamflow characteristic. For the month of February, the RAR regression equations provided acceptable results for the long-term Q.50 and QM, but poor results for the long-term Q.90, Q.80, and Q.20. For the months of July and August, the RAR provided acceptable results for the long-term Q.50, Q.20, and QM, but poor results for the long-term Q.90 and Q.80. Estimation coefficients were developed for estimating the long-term streamflow characteristics for which the RAR did not provide acceptable results. The RAR also was determined to provide acceptable results for estimating the PK1.5., PK2, and PK2.33 for the three CMR stations that lacked suitable peak-flow records. Methods for estimating streamflow characteristics at ungaged sites also were derived. Regression analyses that relate individual streamflow characteristics to various basin and climatic characteristics for gaging stations were performed to develop regression equations to estimate streamflow characteristics at ungaged sites. Final equations for the annual Q.50, Q.20, and QM are reported. Acceptable equations also were developed for estimating QM for the months of February, March, April, June, and July, and Q.50, Q.20, and QM on an annual basis. However, equations for QM for the months of February, March, April, June, and July were determined to be less consistent and reliable than the use of estimation coefficients applied to the regression equation results for the annual QM. Acceptable regression equations also were developed for the PK1.5, PK2, and PK2.33.

Scientific Investigations Report↗

Beach-ridge development and lake-level variation in southern Lake Michigan

The most accurate source of information on lake-level fluctuations in the Great Lakes is the historical record from lake-level gauges. Although it can be semiquantitatively extended back into the late 1700's, the historical record is too short to recognize long-term patterns of lake-level behavior. To extend the historical record, information must be obtained from the Great Lakes geologic record. Such information includes the elevation and age of geomorphic features and stratigraphic sequences. One of the longest geologic records of late Holocene lake-level variation is preserved in a beach-ridge complex along the southern shore of Lake Michigan called the Toleston Beach. This strandplain contains over 150 beach ridges that arc across northwestern Indiana and fan out into northeastern Illinois. Each ridge was formed during the fall from a high lake level, and the elevation of the foreshore deposits in each ridge provides information on the upper physical limit of lake level over the past 4000 years. Three scales of quasi-periodic lake-level variation were determined by radiocarbon-dating basal peats of wetlands between the ridges and by measuring the elevation of foreshore (swash) deposits within ridges. These three scales are: (1) a short-term and small-scale fluctuation of 25 to 35 years with a range of about 0.5 to 0.6 m; (2) an intermediate-term and meso-scale fluctuation of 140 to 160 years and a range of about 0.8 to 0.9 m; and (3) a long-term and large-scale fluctuation of 500 to 600 years and a range of 1.8 to 3.7 m. The short-term and intermediate-term fluctuations are reflected in the historical record. An increase in the rate of shoreline progradation from east to west across Indiana's shoreline causes differential preservation of the lake-level fluctuations. That is, groups of four to six ridges in the western part of the strandplain that formed in response to the small-scale fluctuations combine eastward into single ridges and groups of ridges representing the meso-scale fluctuations. The large-scale fluctuations produced the most dramatic response in the western part of the Toleston Beach. Here, following each high stand, individual spits prograded southward off of a bedrock headland. The successive spit extensions created several small lakes landward of the spits and started the 20 km eastward stream-mouth deflection of the Grand Calumet River across Indiana's western lakeshore.

Illinois, Indiana↗

Geologic framework and hydrogeology of the middle Carson River Basin, Eagle, Dayton, and Churchill Valleys, West-Central Nevada

Changes in land use and water use and increasing development of water resources in the middle Carson River basin may affect flow of the river and, in turn, affect downstream water users dependent on sustained river flows to Lahontan Reservoir. The U.S. Geological Survey, in cooperation with the Bureau of Reclamation, began a study in 2008 of the middle Carson River basin, extending from Eagle Valley to Churchill Valley. Various types of geologic and hydrologic data were compiled from previous studies, collected for this study, and compiled and analyzed to provide a framework for development of a numerical model of the groundwater and surface-water flow systems of the basin. Geologic units that are assumed to have similar hydrologic characteristics were grouped into hydrogeologic units comprised of consolidated rocks of pre-Cenozoic age that underlie a unit of consolidated volcanic rock and semi-consolidated sediments of Tertiary age. The principal aquifer in the study area is comprised of unconsolidated sediments of Quaternary age. The Quaternary sediments include alluvial fan, fluvial, and lake sediments, and were grouped into a basin-fill hydrogeologic unit that overlies the pre-Cenozoic and Tertiary hydrologic units. The thickness of the combined section of Tertiary volcanic and sedimentary rocks and Quaternary basin-fill deposits previously was estimated to range from zero where pre-Cenozoic rocks are exposed to greater than 10,000 feet in the Bull Canyon subbasin, and greater than 6,000 feet on the western side of Churchill Butte and beneath the Desert Mountains. The thickness of Quaternary basin-fill sediments was estimated using gravity data and lithologic descriptions from driller’s logs. The most permeable parts of basin-fill sediments are greater than 1,000 feet thick in the Carson Plains subbasin, greater than 800 feet and 600 feet thick in the western and northeastern parts of the Stagecoach subbasin, and greater than 1,000 feet and 800 feet thick in the northern and southern parts of Churchill Valley, respectively. The distribution of aquifer properties was estimated for basin-fill sediments using slug-test and aquifer test data, and the lithologic descriptions of previously mapped geologic units. Slug-test data show hydraulic conductivity is greater than 10 to greater than 100 feet per day for fluvial sediments near the flood plain, less than 10 feet per day for basin-fill sediments outside the flood plain, and less than 1 foot per day for consolidated rocks. Estimates of transmissivity exceed 20,000 feet squared per day near the Carson River in Dayton, Churchill, and western Lahontan Valleys and in the northern part of the Stagecoach subbasin, and exceed 10,000 feet squared per day in the western part of Churchill Valley. A transmissivity of 90,000 feet squared per day was estimated from results of an aquifer test in the Carson Plains subbasin, indicating that permeable gravel and cobble zones at depths greater than 400 feet supplied water to the pumping well. Estimates of specific yield ranged from less than 1 to 2 percent for most consolidated rocks, from 1 to 15 percent for semi-consolidated Tertiary sediments, and from 10 to 40 percent for unconsolidated basin-fill sediments. Water-level altitude maps based on measurements at about 300 wells in 2009 show water levels have declined as much as 70 feet since 1964 on the northwestern side of Eagle Valley, about 10 feet since 1995 near Dayton in the Carson Plains subbasin, and from 5 to 10 feet since 1982 in the western and northeastern parts of the Stagecoach subbasin and the northwestern part of Churchill Valley. The declines are likely the result of municipal and agricultural pumping. The maps show a groundwater divide between the Carson Plains and Stagecoach subbasins, and a continuous hydraulic gradient between the Stagecoach subbasin and Churchill Valley. Groundwater flow directions are uncertain beneath parts of the boundary of Churchill Valley. The altitude of the top of pre-Cenozoic rocks shows thick sections of saturated Tertiary rocks and sediments south of the Dead Camel Mountains and beneath the eastern part of the Desert Mountains through which groundwater flow between Churchill Valley, Mason Valley, and Lahontan Valley may take place. North of Lahontan reservoir, beneath the Dead Camel Mountains, and beneath the southern part of Adrian Valley, the altitude of pre-Cenozoic rocks indicates groundwater flow between the three valleys is minimal. Streamflow measurements, supported by data on the deuterium content and specific conductance of surface-water samples, indicate a loss of Carson River streamflow in the Riverview subbasin, streamflow gains in the Moundhouse subbasin and the eastern part of the Carson Plains subbasin, and streamflow losses in the Bull Canyon subbasin. Comparisons of fluctuations in groundwater levels to those in stream stage in the Carson Plains subbasin indicate that streamflow lost to infiltration from the Carson River, from irrigation ditches, and from irrigated fields is an important source of groundwater recharge. Fluctuations in groundwater levels compared with the stage of Lahontan Reservoir in Churchill Valley indicate losses to infiltration from the reservoir during high stage and groundwater seepage to the reservoir during low stage.

Nevada↗

Geohydrology of bedrock aquifers in the Northern Great Plains in parts of Montana, North Dakota, South Dakota, and Wyoming

Rocks of Paleozoic and Mesozoic age underlie the entire northern Great Plains of the United States. These rocks form 5 artesian aquifer systems that are recharged in the mountainous areas of Montana, South Dakota, and Wyoming and extend more than 600 miles to discharge areas in the northeastern part of North Dakota and in the Canadian Province of Manitoba. Generally, the principal direction of flow in each aquifer is deflected to the north and south around the Williston basin. Flow through the Williston basin is restricted because of geologic structure, and decreased permeability of rocks in the deeper parts of the basin. Major fracture systems or lineaments traverse the geologic section and are either vertical or horizontal conduits, or barriers to, groundwater flow. Vertical leakage from the aquifers is restricted by shale of minimal permeability, halite beds, and stratigraphic traps or minimal-permeability zones associated with petroleum accumulations. Interaquifer leakage appears to occur through and along some of the major lineaments. During the Pleistocene Epoch, thick ice sheets completely covered the discharge areas of the bedrock aquifers. This effectively blocked flow northeastward from the system and, at some locations, it may have caused a reversal of flow. The existing flow, system therefore, may not have reached hydrologic equilibrium with the stress of the last glacial period. (USGS)

Professional Paper↗

Sea lamprey mark type, wounding rate, and parasite-host preference and abundance relationships for lake trout and other species in Lake Ontario

We examined how the frequency of attacks by Sea Lamprey on fishes in Lake Ontario varied in response to Sea Lamprey abundance and preferred host abundance (Lake Trout >432mm). For this analysis we assembled seven data sets. Two fishery independent surveys for Lake Trout: US Geological Survey (USGS)/New York State Department of Environmental Conservation (NYSDEC) south shore September gillnet assessment of adult Lake Trout (USGS/NYSDEC SGNS)( Lantry and Lantry 2011); and Ontario Ministry of Natural Resources (OMNR) monthly June-November community index gillnetting in northeastern Lake Ontario (OMNR CIS) (Ontario Ministry of Natural Resources 2011). One angler survey: NYSDEC April-September Fishing Boat Survey data collected along the south shore for Chinook and Coho salmon, and Rainbow and Brown trout (NYSDEC FBS) ( Lantry and Eckert 2012). Two spawning run datasets: OMNR north shore data including spring spawning runs of Rainbow Trout in the Ganaraska River and electroshocking data for fall spawning runs of Chinook and Coho salmon in the Credit River (Ontario Ministry of Natural Resources 2011); and NYSDEC data from the Salmon River on the southeastern shore including October spawning runs of Chinook and Coho salmon. One Sea Lamprey spawning survey: Department of Fisheries and Oceans Canada (DFO)/US Fish and Wildlife Service (USFWS) data for spawning-phase Sea Lamprey abundance collected from known spawning streams distributed throughout the Lake Ontario drainage basin (Mullet et al. 2003). One assessment of the abundance of dead Lake Trout: USGS/NYSDEC October-November bottom trawl collection of Lake Trout carcasses (Schneider et al. 1996). Annual patterns in A1, A2 and A3 wound stages did not track well in plots of wounding rates for the USGS/NYSDEC SGNS and correlations between A1 and later stages did not exist. A1 rates were not correlated to either Lake Trout abundance or Sea Lamprey numbers when considered alone, but were strongly correlated to the ratio between Sea Lamprey numbers and Lake Trout abundance (parasite/host ratio). While A2 and A3 rates were correlated to each other, neither was consistently correlated to any of the Lake Trout abundance or Sea Lamprey abundance parameters and sums of A1 to A3 rates did not improve correlations over those for A1 rates considered alone. Our analysis of the strain-specific susceptibility of Lake Trout to attack by Sea Lampreys extended the previous Schneider et al. (1996) analysis of three strains (SUP, CWL, and SEN) and 11 years of data 1982-1992 to an analysis of seven strains (SUP, CWL, SEN, JEN, LEW, ONT, and OXS) and two groups of unmarked fish (1983-1995 and 1996-2010) and included 18 more years of data through 2010. The susceptibility to attack for CWLs and SENs were below SUPs and nearly identical to the earlier values, new values for LEWs were greater than SUPS and values of unmarked Lake Trout prior to 1996 were unexpectedly greater than SUPs. By reexamining the Schneider et al. (1996) regression relationship between A1 wounding on Lake Trout and the incidence of Lake Trout carcasses recovered in fall bottom trawls (including three additional years of data), and substituting A1 wounding rate for total numbers of A1s observed which was used as the independent variable in the previous version, we were able to increase the variance explained by the relationship from an r2 of 0.60 to 0.88. Healing rate of wounds was explored by examining the monthly incidence of A1 and A2 wounds on Lake Trout from the OMNR CIS. Because wounding intensity varied between years and monthly sample size was frequently low, the ratio of A2 to A1s wounds was used to index how wounds accumulated or disappeared from the Lake Trout populations across seasons. The A2/A1 ratio decreased between June/July and October. A simple wounding model for Lake Trout was constructed to simulate the pattern of ratios by inflicting wounds on the population each month according to a predetermined distribution and including parameters for lethality (fixed distribution) and healing rate of A1 and A2 wounds (discretely varied between simulations). The best simulated representation (ratio size and monthly pattern) of the OMNR CIS data came from an A1 healing rate of 0.5 months and an A2 rate of 2 months. To examine whether alternate hosts provided reliable data to index damage caused by Sea Lampreys we compared September values of abundance and A1 wounding rates on Lake Trout, Sea Lamprey abundance, and the parasite/host ratio with NYSDEC Creel data for observations of Sea lampreys attached to sport-caught salmonids and to wounding observations for salmonids sampled in OMNR and NYSDEC spawning run assessments. Attachment frequency on NYSDEC Creel Chinook Salmon, Brown Trout, and Rainbow Trout were strongly correlated to all measures of Lake Trout abundance and wounding and to the parasite/host ratio. Chinook Salmon and Coho Salmon wounding observations for the NYSDEC Salmon River spawning run assessments and Rainbow Trout from the OMNR Ganaraska River spawning run assessment were strongly correlated to wounding measures for nearly all salmonids and to the parasite/host ratio.

Lake Ontario↗