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At least 1,405 records · Page 78Linked to original sources
USGS2003

Field guide to hydrothermal alteration in the White River altered area and in the Osceola Mudflow, Washington

The Cenozoic Cascades arcs of southwestern Washington are the product of long-lived, but discontinuous, magmatism beginning in the Eocene and continuing to the present (for example, Christiansen and Yeats, 1992). This magmatism is the result of subduction of oceanic crust beneath the North American continent. The magmatic rocks are divided into two subparallel, north-trending continental-margin arcs, the Eocene to Pliocene Western Cascades, and the Quaternary High Cascades, which overlies, and is east of, the Western Cascades. Both arcs are calc-alkaline and are characterized by voluminous mafic lava flows (mostly basalt to basaltic andesite compositions) and scattered large stratovolcanoes of mafic andesite to dacite compositions. Silicic volcanism is relatively uncommon. Quartz diorite to granite plutons are exposed in more deeply eroded parts of the Western Cascades Arc (for example, Mount Rainier area and just north of Mt. St. Helens). Hydrothermal alteration is widespread in both Tertiary and Quaternary igneous rocks of the Cascades arcs. Most alteration in the Tertiary Western Cascades Arc resulted from hydrothermal systems associated with small plutons, some of which formed porphyry copper and related deposits, including copper-rich breccia pipes, polymetallic veins, and epithermal gold-silver deposits. Hydrothermal alteration also is present on many Quaternary stratovolcanoes of the High Cascades Arc. On some High Cascades volcanoes, this alteration resulted in severely weakened volcanic edifices that were susceptible to failure and catastrophic landslides. Most notable is the sector collapse of the northeast side of Mount Rainier that occurred about 5,600 yr. B.P. This collapse resulted in formation of the clay-rich Osceola Mudflow that traveled 120 km down valley from Mount Rainier to Puget Sound covering more than 200 km2. This field trip examines several styles and features of hydrothermal alteration related to Cenozoic magmatism in the Cascades arcs. The morning of the trip will examine the White River altered area, which includes high-level alteration related to a large, early Miocene magmatic-hydrothermal system exposed about 10 km east of Enumclaw, Washington. Here, vuggy silica alteration is being quarried for silica and advanced argillic alteration has been prospected for alunite. Clay-filled fractures and sulfide-rich, fine-grained sedimentary rocks of hydrothermal origin locally are enriched in precious metals. Many hydrothermal features common in high-sulfidation gold-silver deposits and in advanced argillic alteration zones overlying porphyry copper deposits (for example, Gustafson and Hunt, 1975; Hedenquist and others, 2000; Sillitoe, 2000) are exposed, although no economic base or precious metal mineralized rock has been discovered to date. The afternoon will be spent examining two exposures of the Osceola Mudflow along the White River. The Osceola Mudflow contains abundant clasts of altered Quaternary rocks from Mount Rainier that show various types of hydrothermal alteration and hydrothermal features. The mudflow matrix contains abundant hydrothermal clay minerals that added cohesiveness to the debris flow and helped allow it to travel much farther down valley than other, noncohesive debris flows from Mount Rainier (Crandell, 1971; Vallance and Scott, 1997). The White River altered area is the subject of ongoing studies by geoscientists from Weyerhaeuser Company and the U.S. Geological Survey (USGS). The generalized descriptions of the geology, geophysics, alteration, and mineralization presented here represent the preliminary results of this study (Ashley and others, 2003). Additional field, geochemical, geochronologic, and geophysical studies are underway. The Osceola Mudflow and other Holocene debris flows from Mount Rainier also are the subject of ongoing studies by the USGS (for example, Breit and others, 2003; John and others, 2003; Plumlee and others, 2003, Sisson and others, 2003; Vallance and others, 2003). Studies of hydrothermal alteration in the Osceola Mudflow are being used to better understand fossil hydrothermal systems on Mount Rainier and potential hazards associated with this alteration.

Washington↗
USGS1915

Springs of California

In 1903 the United States Geological Survey began an investigation of the underground water of California, generally with financial cooperation on the part of the State. Since that year ten papers on the underground water of the State have been issued by the Survey, each representing an investigation that has been completed. The field work which is to serve as the basis for two additional papers has also been done and the reports are in preparation. Investigations have been begun in two other areas in the State and their results will eventually be assembled and published. Since a period soon after the inception of the California work those responsible for its conduct have realized the desirability of a special study of the springs, particularly those which yield mineral waters and which are utilized to a greater or less extent by citizens of the State and by tourists as recreation and health resorts. It did not become practicable to begin this work until the summer of 1908, when Mr. G. A. Waring, who had assisted in some of the earlier California studies and had investigated for the Survey certain areas in southern Oregon and Washington, was assigned to the task of collecting and assembling the necessary data. California, with an area of 158,000 square miles, is the second largest State in the Union. It exhibits wide geographic diversity, since it includes the lowest area in the United States Death Valley, 276 feet below sea level and the highest Mount Whitney, 14,501 feet above the sea; and accompanying this geographic diversity there is a corresponding range in scenic effects, climate, and vegetation. The records obtained at meteorological stations in the Salton Sink indicate a maximum temperature of 130° in the shade, the highest of record within the continental United States. It is probable that minimum temperatures on the higher peaks, like Mount Whitney and Mount Shasta, approach the minimum within our boundaries. Rainfall records in the most arid sections of the southern deserts of the State represent the extreme of aridity in the United States, with averages of less than 3 inches per annum and periods of 12 months or more with only traces of rain, whereas the precipitation in northwestern California is very heavy, an annual average of close to 100 inches being recorded at a few stations in Mendocino and Del Norte counties. The immensity of the area of the State has made the collection of the field data required for the report a task of considerable magnitude, though its diversity has added greatly to the interest of the work. In the original plan it was estimated that two years of field studies would prove sufficient. Mr. Waring succeeded in visiting the more important localities during this period, although some of his examinations were, of necessity, rather cursory. In midsummer, 1910, after the completion of the field work and the assembling of the greater portion of his data in manuscript form he was called by the Government of Brazil to take charge of general water supply investigations in the northeastern arid portion of that South American republic. The task of reviewing, editing, and supplementing in some respects, the results of his studies was thus unavoidably left to others. This task was rendered light by the systematic form in which Mr. Waring's material was left. It was a matter of regret to Mr. Waring, as it has been to those associated with him, that the financial limitations which controlled his work made it impracticable to procure the large number of new analyses which are particularly important in a paper of this type, in which waters of unusual chemical characteristics are discussed. Such analyses as are available have been assembled from all possible sources and combined with those which were prepared especially in connection with this investigation. The result, although it is in some respects unsatisfactory, furnishes a basis for a general view of the characteristics of the spring waters and serves to permit, their classification in a general way. Mr. Herman Stabler has reviewed the chemical data and rearranged and interpreted the available analyses. It is hoped that the report, setting forth as it does the results of impartial observations upon one of the important present and more important prospective resources of the State, will prove of value to its citizens as well as to its visitors, and that the assembled material will not be without interest to physicians, chemists, geologists, and teachers who may have especial need for the information contained in the volume.

California↗
USGS2014

Hydrogeologic framework and groundwater/surface-water interactions of the South Fork Nooksack River Basin, northwestern Washington

A hydrogeologic framework of the South Fork (SF) Nooksack River Basin in northwestern Washington was developed and hydrologic data were collected to characterize the groundwater-flow system and its interaction with surface‑water features. In addition to domestic, agricultural, and commercial uses of groundwater within the SF Nooksack River Basin, groundwater has the potential to provide ecological benefits by maintaining late-summer streamflows and buffering stream temperatures. Cold-water refugia, created and maintained in part by groundwater, have been identified by water-resource managers as key elements to restore the health and viability of threatened salmonids in the SF Nooksack River. The SF Nooksack River drains a 183-square mile area of the North Cascades and the Puget Lowland underlain by unconsolidated glacial and alluvial sediments deposited over older sedimentary, metamorphic, and igneous bedrock. The primary aquifer that interacts with the SF Nooksack River was mapped within unconsolidated glacial outwash and alluvial sediment. The lower extent of this unit is bounded by bedrock and fine-grained, poorly sorted unconsolidated glaciomarine and glaciolacustrine sediments. In places, these deposits overlie and confine an aquifer within older glacial sediments. The extent and thickness of the hydrogeologic units were assembled from mapped geologic units and lithostratigraphic logs of field-inventoried wells. Generalized groundwater-flow directions within the surficial aquifer were interpreted from groundwater levels measured in August 2012; and groundwater seepage gains and losses to the SF Nooksack River were calculated from synoptic streamflow measurements made in the SF Nooksack River and its tributaries in September 2012. A subset of the field-inventoried wells was measured at a monthly interval to determine seasonal fluctuations in groundwater levels during water year 2013. Taken together, these data provide the foundation for a future groundwater-flow model of the SF Nooksack River Basin that may be used to investigate the potential effects of future climate change, land use, and groundwater pumping on water resources in the study area. Site-specific hydrologic data, including time series of longitudinal temperature profiles measured with a fiber-optic distributed temperature sensor and continuous monitoring of stream stage and water levels measured in wells in adjacent wetlands and aquifers, also were measured to characterize the interaction among the SF Nooksack River, surficial aquifers, and riparian wetlands.

Washington↗
USGS2008

Modeling landslide recurrence in Seattle, Washington, USA

To manage the hazard associated with shallow landslides, decision makers need an understanding of where and when landslides may occur. A variety of approaches have been used to estimate the hazard from shallow, rainfall-triggered landslides, such as empirical rainfall threshold methods or probabilistic methods based on historical records. The wide availability of Geographic Information Systems (GIS) and digital topographic data has led to the development of analytic methods for landslide hazard estimation that couple steady-state hydrological models with slope stability calculations. Because these methods typically neglect the transient effects of infiltration on slope stability, results cannot be linked with historical or forecasted rainfall sequences. Estimates of the frequency of conditions likely to cause landslides are critical for quantitative risk and hazard assessments. We present results to demonstrate how a transient infiltration model coupled with an infinite slope stability calculation may be used to assess shallow landslide frequency in the City of Seattle, Washington, USA. A module called CRF (Critical RainFall) for estimating deterministic rainfall thresholds has been integrated in the TRIGRS (Transient Rainfall Infiltration and Grid-based Slope-Stability) model that combines a transient, one-dimensional analytic solution for pore-pressure response to rainfall infiltration with an infinite slope stability calculation. Input data for the extended model include topographic slope, colluvial thickness, initial water-table depth, material properties, and rainfall durations. This approach is combined with a statistical treatment of rainfall using a GEV (General Extreme Value) probabilistic distribution to produce maps showing the shallow landslide recurrence induced, on a spatially distributed basis, as a function of rainfall duration and hillslope characteristics.

Washington↗
USGS2009

Updating the 2001 National Land Cover Database land cover classification to 2006 by using Landsat imagery change detection methods

The recent release of the U.S. Geological Survey (USGS) National Land Cover Database (NLCD) 2001, which represents the nation's land cover status based on a nominal date of 2001, is widely used as a baseline for national land cover conditions. To enable the updating of this land cover information in a consistent and continuous manner, a prototype method was developed to update land cover by an individual Landsat path and row. This method updates NLCD 2001 to a nominal date of 2006 by using both Landsat imagery and data from NLCD 2001 as the baseline. Pairs of Landsat scenes in the same season in 2001 and 2006 were acquired according to satellite paths and rows and normalized to allow calculation of change vectors between the two dates. Conservative thresholds based on Anderson Level I land cover classes were used to segregate the change vectors and determine areas of change and no-change. Once change areas had been identified, land cover classifications at the full NLCD resolution for 2006 areas of change were completed by sampling from NLCD 2001 in unchanged areas. Methods were developed and tested across five Landsat path/row study sites that contain several metropolitan areas including Seattle, Washington; San Diego, California; Sioux Falls, South Dakota; Jackson, Mississippi; and Manchester, New Hampshire. Results from the five study areas show that the vast majority of land cover change was captured and updated with overall land cover classification accuracies of 78.32%, 87.5%, 88.57%, 78.36%, and 83.33% for these areas. The method optimizes mapping efficiency and has the potential to provide users a flexible method to generate updated land cover at national and regional scales by using NLCD 2001 as the baseline.

Remote Sensing of Environment↗
USGS2004

Chapter G: Tentative Correlation Between CIPW Normin pl (Total Plagioclase) and Los Angeles Wear in Precambrian Midcontinental Granites-Examples from Missouri and Oklahoma, with Applications and Limitations for Use

The normative chemical classification of Cross, Iddings, Pirsson, and Washington (CIPW) is commonly used in igneous petrology to distinguish igneous rocks by comparing their magmatic chemistries for similar and dissimilar components. A potential use for this classification other than in petrologic studies is in the rapid assessment of aggregate sources, possibly leading to an economic advantage for an aggregate producer or user, by providing the opportunity to determine whether further physical testing of an aggregate is warranted before its use in asphalt or concrete pavement. However, the CIPW classification currently should not be substituted for the physical testing required in specifications by State departments of transportation. Demands for physical testing of aggregates have increased nationally as users seek to maximize the quality of the aggregate they purchase for their pavements. Concrete pavements are being laid with increased thicknesses to withstand increasing highway loads. New pavement mixes, most notably Superior Performance Asphalt Pavement ('Superpave'), are designed for additional service life. For both concrete and asphalt, the intent is to generate a durable pavement with a longer service life that should decrease overall life-cycle costs. Numerous aggregate producers possess chemical-composition data available for examination to answer questions from the potential user. State geological surveys also possess chemical-composition data for stone sources. Paired with the results of physical testing, chemical- composition data provide indicative information about stone durability and aggregate strength. The Missouri Department of Transportation has noted a possible relation among coarse-grained Precambrian granites of the midcontinental region, correlating the results of abrasion testing with the contents of normative minerals, also known as normins, calculated from chemical composition data. Thus, normin pl ( total plagioclase) can predict, by way of simple regression, the Los Angeles wear for granite samples collected in Missouri. The results of this abrasion testing were extended to another granite in Oklahoma where normin pl predicted Los Angeles wear to within 0.6 percent. This relation may also exist for granitic rocks outside the Oklahoma-Missouri region, as well as for other igneous-rock types.

Bulletin↗
USGS2008

Late orogenic mafic magmatism in the North Cascades, Washington: Petrology and tectonic setting of the Skymo layered intrusion

The Skymo Complex in the North Cascades, Washington, is a layered mafic intrusion within the Ross Lake fault zone, a major orogen-parallel structure at the eastern margin of the Cascades crystalline core. The complex is composed dominantly of troctolite and gabbro, both with inclusions of primitive olivine gabbro. Low-pressure minerals in the metasedimentary contact aureole and early crystallization of olivine + plagioclase in the mafic rocks indicate the intrusion was emplaced at shallow depths (<12 km). The Skymo rocks have trace-element characteristics of arc magmas, but the association of Mg-rich olivine (Fo88-80) with relatively sodic plagioclase (An75-60) and the Al/Ti ratios of clinopyroxene are atypical of arc gabbros and more characteristic of rift-related gabbros. A Sm-Nd isochron indicates crystallization in the early Tertiary (ca. 50 Ma), coeval with the nearby Golden Horn alkaline granite. Mantle melting to produce Skymo magma likely occurred in a mantle wedge with a long history of arc magmatism. The Skymo mafic complex and the Golden Horn granite were emplaced during regional extension and collapse of the North Cascades orogen and represent the end of large-scale magmatism in the North Cascades continental arc. ?? 2008 Geological Society of America.

Geological Society of America Bulletin↗
USGS1976

New molluscan assemblages from the upper member of the Twin River Formation, western Washington: Significance in Neogene chronostratigraphy

New molluscan assemblages of provincial early Miocene age from a previously unrecognized fossiliferous interval of 400 to 500 metres in the uppermost part of the Twin River Formation, western Washington, are referable to the upper part of the "Blakeley" [or Matlockian] Stage. The new biostratigraphic data provide, for the first time, definition of the uppermost part of the "Blakeley" Stage and the boundary between it and an unnamed stage of late early Miocene age represented by the Clallam Formation and its megafauna. In contradistinction to earlier studies, the upper boundary of the "Blakeley" Stage does not coincide with the upper boundary of the Zemorrian Stage of the foraminiferal chronology, the "Blakeley" boundary being at least 45 m higher and possibly much more. Nearly 60 species of mollusks from the upper few hundred metres of the Twin River Formation are recognized herein, and 40 of these are illustrated. Six species are previously undescribed.

Washington↗
USGS2007

Arc-parallel extension and fluid flow in an ancient accretionary wedge: The San Juan Islands, Washington

Structural analysis of the Lopez Structural Complex, a major Late Cretaceous terrane-bounding fault zone in the San Juan thrust system, reveals a sequence of events that provides insight into accretionary wedge mechanics and regional tectonics. After formation of regional ductile flattening and shear-related fabrics, the area was crosscut by brittle structures including: (1) southwest-vergent thrusts, (2) extension veins and normal faults related to northwest-southeast extension, and (3) conjugate strike-slip structures that record northwest-southeast extension and northeast-southwest shortening. Aragonite-bearing veins are associated with thrust and normal faults, but only rarely with strike-slip faults. High-pressure, low-temperature (HP-LT) minerals constrain the conditions for brittle deformation to ???20 km and <250 ??C. The presence of similar structures elsewhere indicates that the brittle structural sequence is typical of the San Juan nappes. Sustained HP-LT conditions are possible only if structures formed in an accretionary prism during active subduction, which suggests that these brittle structures record internal wedge deformation at depth and early during uplift of the San Juan nappes. The structures are consistent with orogen-normal shortening and vertical thickening followed by vertical thinning and along-strike extension. The kinematic evolution may be related initially to changes in wedge strength, followed by response to overthickening of the wedge in an unbuttressed, obliquely convergent setting. The change in vein mineralogy indicates that exhumation occurred prior to the strike-slip event. The pressure and temperature conditions and spatial and temporal extent of small faults associated with fluid flow suggest a link between these structures and the silent earthquake process. ?? 2007 Geological Society of America.

Geological Society of America Bulletin↗
USGS2003

Pleistocene tephrostratigraphy and paleogeography of southern Puget Sound near Olympia, Washington

Our detailed mapping in the south Puget Sound basin has identified two tephras that are tentatively correlated to tephras from Mount St. Helens and Mount Rainier dated ca. 100-200 ka and 200 ka, respectively. This, plus the observation that fluvial and lacustrine sediments immediately underlying the Vashon Drift of latest Wisconsin age are nearly everywhere radiocarbon infinite, suggests that glacial and nonglacial sediments of more than the past five oxygen-isotope stages are exposed above sea level. Distal lacustrine advance outwash equivalent to the Lawton Clay in the Seattle area is conspicuously absent. Instead, a thick (>120 ft) glaciolacustrine silt below the Vashon sediments contains dropstones and is radiocarbon infinite. Elsewhere, coarsegrained advance Vashon outwash rests unconformably on radiocarbon-infinite non-glacial sediments. These relationships may imply that late Pleistocene tectonic activity has modified the paleotopography and stratigraphy of the south Puget Sound area.

Washington↗
USGS1980

Mount St. Helens eruptive behavior during the past 1500 yr

During the past 1,500 yr Mount St. Helens, Washington, has repeatedly erupted dacite domes, tephra, and pyroclastic flows as well as andesite lava flows and tephra. Two periods of activity prior to 1980, each many decades long, were both initiated by eruptions of volatile-rich dacite which were followed by andesite, then by dacite. A third eruptive period was characterized by the eruption of volatile-poor dacite that formed a dome and minor pyroclastic flows. The prolonged duration of some previous eruptive periods suggests that the current activity could continue for many years. The volatile-rich dacite that has been erupted to date probably will be followed by gas-poor magma, but it cannot yet be predicted whether a more mafic magma will be extruded during the current eruptive period.

Geology↗
USGS2010

Zircon reveals protracted magma storage and recycling beneath Mount St. Helens

Current data and models for Mount St. Helens volcano (Washington, United States) suggest relatively rapid transport from magma genesis to eruption, with no evidence for protracted storage or recycling of magmas. However, we show here that complex zircon age populations extending back hundreds of thousands of years from eruption age indicate that magmas regularly stall in the crust, cool and crystallize beneath the volcano, and are then rejuvenated and incorporated by hotter, young magmas on their way to the surface. Estimated dissolution times suggest that entrained zircon generally resided in rejuvenating magmas for no more than about a century. Zircon elemental compositions reflect the increasing influence of mafic input into the system through time, recording growth from hotter, less evolved magmas tens of thousands of years prior to the appearance of mafic magmas at the surface, or changes in whole-rock geochemistry and petrology, and providing a new, time-correlated record of this evolution independent of the eruption history. Zircon data thus reveal the history of the hidden, long-lived intrusive portion of the Mount St. Helens system, where melt and crystals are stored for as long as hundreds of thousands of years and interact with fresh influxes of magmas that traverse the intrusive reservoir before erupting. ?? 2010 Geological Society of America.

Geology↗
USGS2015

Water levels of the Ozark aquifer in northern Arkansas, 2013

The Ozark aquifer is the largest aquifer, both in area of outcrop and thickness, and the most important source of freshwater in the Ozark Plateaus physiographic province, supplying water to northern Arkansas, southeastern Kansas, southern Missouri, and northeastern Oklahoma. The study area includes 16 Arkansas counties lying completely or partially within the Ozark Plateaus of the Interior Highlands major physiographic division. The U.S. Geological Survey, in cooperation with the Arkansas Natural Resources Commission and the Arkansas Geological Survey, conducted a study of water levels in the Ozark aquifer within Arkansas. This report presents a potentiometric-surface map of the Ozark aquifer within the Ozark Plateaus of northern Arkansas, representing water-level conditions for the early spring of 2013 and selected water-level hydrographs. The Ozark aquifer in Arkansas is composed of dolomites, limestones, sandstones, and shales of Late Cambrian to Middle Devonian age and ranges in thickness from approximately 1,100 feet (ft) in northwestern Arkansas to more than 4,000 ft in the west-central part of Arkansas. Most wells completed in the aquifer yield between 50 and 100 gallons per minute (gal/min), although some wells may yield as much as 600 gal/min. Water-level measurements were made in wells completed in the Ozark aquifer from February to May 2013. Hydrographs were constructed for nine wells that have water-level measurements with a minimum 20-year period of record. Water-level altitudes in wells used to construct the potentiometric-surface map range from about 1,159 ft to 313 ft above National Geodetic Vertical Datum of 1929 (NGVD 29). The highest water-level altitudes occur in Carroll and Washington Counties while water-level altitudes of less than 400 ft above NGVD 29 are mapped along the eastern and southeastern part of the study area in Independence, Lawrence, Randolph, and Sharp Counties. The lowest water level of 313 ft above NGVD 29 was measured in southwestern Randolph County. The direction of groundwater flow generally is affected by local topography, flowing from high altitudes toward stream valleys. In southern Baxter, eastern Fulton, Independence, eastern Izard, Lawrence, Randolph, and Sharp Counties, the groundwater flow is generally to the south and southeast. In western Fulton and Izard Counties, the groundwater flow is generally to the southwest. In Boone, Marion, Newton, Searcy, and Stone Counties, the groundwater flow is generally to the east and northeast. In eastern Benton, Carroll, Madison, and eastern Washington Counties, the groundwater flow is generally to the north and northeast. In western Benton and western Washington Counties, the groundwater flow is generally to the west and northwest. The general level and shape of the potentiometric surface has changed little since predevelopment. A comparison of the predevelopment potentiometric surface and the 2007, 2010, and 2013 potentiometric surfaces indicate general agreement between the mapped surfaces with the exception of parts of Benton, Boone, Marion, and Washington Counties. In Boone and northern Marion Counties in 2013, water levels have declined when compared to the predevelopment potentiometric surface, although the direction of flow is still to the northeast and north. In southern Marion County, water levels have declined when compared to the predevelopment, 2007, and 2010 potentiometric surfaces, although the direction of flow is towards and along the stream valleys. In western Benton and northwestern Washington Counties, water levels are similar when compared to the predevelopment potentiometric surface, and the direction of flow is to the west and northwest, similar to the predevelopment direction of flow. The mapped 2007 and 2010 potentiometric surfaces are very different from the mapped 2013 potentiometric surface in western Benton and northwestern Washington Counties. The mapped 2013 potentiometric surface in western Benton and northwestern Washington Counties follows the contours of the top of the formation, similar to the predevelopment potentiometric surface. Since 1975, water use in the Ozark aquifer has declined 45 percent, while water levels in Benton, Boone, Marion, and Washington Counties continue to decline. Nine hydrographs were selected as representative of the water-level conditions in their respective counties. Wells in Fulton, Izard, and Newton Counties (station names 20N08W27ABD1, 18N09W15BCB1, and 16N21W34ABC1, respectively) have water levels that are within the usual range of values for their respective counties. Wells in Boone, Marion, and Washington Counties (station names 18N19W19BCC1, 19N15W20ACC1, and 16N32W09ABD1, respectively) have water levels that have recently declined or are declining for the period of record. Wells in Benton, Carroll, and Sharp Counties (station names 19N29W07DAA1, 21N26W17BCC1, and 15N05W06DDD1, respectively) have water levels that have been rising recently.

Arkansas↗
USGS2023

Fluvial delivery and wave resuspension of sediment in a sheltered, urbanized Pacific Northwest estuary

The sequence and timing of sediment delivery and redistribution in coastal systems is important for shoreline stability, ecosystem services, and remediation planning. In temperate estuaries, understanding the role of fluvial sediment delivery and dispersal relative to wind and wave remobilization processes is particularly important to address the fate of contaminants, many of which adsorb to fine particles, and to assess changes in coastal systems under projected changes in climate. Here we present an integrated analysis of observations at multiple timescales to evaluate sediment dynamics and the sedimentary coupling between fluvial and oceanographic processes within Bellingham Bay, Washington, USA, an urban estuary. Time-series data of currents, waves, and turbidity at four moorings along with geochemical data from grab samples and cores of seabed sediment from across the bay are contrasted with the dynamics of the Nooksack River, its fluvial sediment source. Even during large (5-yr return interval) river-flood events, water-column suspended-sediment concentration (SSC) near the bed on the outer delta topset was not correlated with Nooksack River runoff and was instead closely correlated with local wind-wave height. In contrast, near-surface SSC was strongly correlated with fluvial discharge, suggesting intense water-column suspended-sediment stratification during flood events. Grain-size and geochemical ( 7 "> 7 Be and excess 210 "> 210 Pb) results from seabed-sediment samples and historical bathymetric measurements of the subaqueous Nooksack River delta reveal spatial gradients of fluvial and wave influence and sediment-accumulation rates. Analysis of historical bathymetric surveys of the Nooksack River delta combined with the geochemical data reveal that about 75% of the fluvial sediment load can be accounted for in the Bellingham Bay receiving system. Studies of this type in urbanized coastal settings can help address ecological and geological questions regarding the risks from contaminants associated with fine-grained sediment, predict longer-term delta morphological evolution, and inform managers planning future coastal restoration efforts

Washington↗
USGS2019

Contaminant baselines and sediment provenance along the Puget Sound Energy Transport Corridor, 2015

The transport of coal and oil can result in contaminated soil, water, and organisms from unintended releases. Trains carrying coal and crude oil regularly pass through Puget Sound, Washington, and an increase in the number of coal and oil trains is expected in the future. This study characterized levels of potentially toxic contaminants in sediment in September 2015: arsenic, metals, and polycyclic aromatic hydrocarbons (PAHs) at four sites with fine-grained sediment (Chuckanut Bay, Padilla Bay, Snohomish River Delta, Nisqually River Delta) adjacent to the Burlington Northern Santa Fe (BNSF) rail line in the Puget Sound region. Arsenic (As) and metals levels were compared to those measured at a fifth site, urban Saltwater State Park, which was expected to show contaminants associated with urbanization but not rail transport of coal and oil because it is not adjacent to the BNSF rail line. Knowledge about current properties of soil and sediment is essential for quantifying impacts of spills and other releases, and for setting remediation or restoration targets. For the sampling effort and timing of this study, all five sites had fine sediment contents of cadmium (Cd), mercury (Hg), lead (Pb), and zinc (Zn) below minimal effects levels. Pb and Zn appeared to be urban sourced. Median As, chromium (Cr), copper (Cu), and nickel (Ni) levels were in the range where adverse biological effects would possibly occur; however, Cr and Ni were geologically sourced and unlikely to be bioavailable to organisms. As, Cu, and antimony (Sb) levels were highly correlated, an association that is characteristic of legacy smelting operations; however, total sediment contents of these three elements, along with Hg and As/Sb ratios, were near natural levels and could indicate river-borne inputs. Median total PAH concentrations were highest at Snohomish River Delta, but were below minimal effects levels at all sites. Diagnostic PAH ratios were indicative of PAHs sourced from petroleum combustion and coal/biomass burning, rather than from spilled petroleum or coal. Rare earth element patterns were distinct among watersheds with Cascade volcanoes, granitic rocks, or non-volcanic sediments, making them promising sediment provenance indicators. Knowledge about sediment sources and contaminant distributions could provide unique insights about sediment-bound contaminant sourcing, delivery, and dispersal in nearshore regions.

Washington↗
USGS1996

Tectonic model explaining divergent contraction directions along the Cascadia subduction margin, Washington

Differential motion across the central Cascadia subduction boundary in Washington results in a complex pattern of folds and faults within the shelf and onshore parts of the accretionary margin. Faults and folds above a coastal, north-northwest–trending thrust system provide evidence of ongoing subduction-related contraction. South of this coastal thrust system many fold axes and thrust faults trend east-northeast, in the direction of convergence. These structures are not consistent with a simple subduction system undergoing northeastward convergence. This deformation, adjacent to the boundary between the subduction complex and the Siletz terrane, may be driven by relative convergence between the northward-translating Siletz terrane and the subduction complex. The regional pattern of modern uplift rates is consistent with ongoing north-south contraction across this boundary and the north-south compressional stress field in the area.

Geology↗
USGS1938

Dolomite and jasperoid in the Metaline District, northeastern Washington

The replacement ore bodies of the Metaline zinc-lead district, in northeastern Washington are limited to the greatly disturbed fault block through which the Pend Oreille River flows and are associated with the major faults but are not in them. They are mostly near the top of the Metaline limestone, of Middle Cambrian age, and below black Ordovician slate. The ores are generally in jasperoid and are surrounded by a shell of crystalline dolomite. Outside of the dolomite is a shell of coarse-grained calcite that in places was deposited along solution channels long distances from known ore bodies. Jasperoid, crystalline dolomite, and, to a less extent, coarse-grained calcite are therefore favorable but not infallible signs of the presence of ore nearby. The Metaline limestone was dolomitized regionally before the ore was introduced, and this early dolomitization is independent of the ore.

Washington↗
USGS2017

Are the benches at Mormon Point, Death Valley, California, USA, scarps or strandlines?

The benches and risers at Mormon Point, Death Valley, USA, have long been interpreted as strandlines cut by still-stands of pluvial lakes correlative with oxygen isotope stage (OIS) 5e/6 (120,000-186,000 yr B.P.) and OIS-2 (10,000-35,000 yr B.P.). This study presents geologic mapping and geomorphic analyses (Gilbert's criteria, longitudinal profiles), which indicate that only the highest bench at Mormon Point (~90 m above mean sea level (msl)) is a lake strandline. The other prominent benches on the north-descending slope immediately below this strandline are interpreted as fault scarps offsetting a lacustrine abrasion platform. The faults offsetting the abrasion platform most likely join downward into and slip sympathetically with the Mormon Point turtleback fault, implying late Quaternary slip on this low-angle normal fault. Our geomorphic reinterpretation implies that the OIS-5e/6 lake receded rapidly enough not to cut strandlines and was ~90 m deep. Consistent with independent core studies of the salt pan, no evidence of OIS-2 lake strandlines was found at Mormon Point, which indicates that the maximum elevation of the OIS-2 lake surface was -30 m msl. Thus, as measured by pluvial lake depth, the OIS-2 effective precipitation was significantly less than during OIS-5e/6, a finding that is more consistent with other studies in the region. The changed geomorphic context indicates that previous surface exposure dates on fault scarps and benches at Mormon Point are uninterpretable with respect to lake history. ?? 2002 University of Washington.

Quaternary Research↗