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At least 1,099 records · Page 61Linked to original sources
USGS2010

Mercury in Indiana watersheds: Retrospective for 2001–2006

Information about total mercury and methylmercury concentrations in water samples and mercury concentrations in fish-tissue samples was summarized for 26 watersheds in Indiana that drain most of the land area of the State. Mercury levels were interpreted with information on streamflow, atmospheric mercury deposition, mercury emissions to the atmosphere, mercury in wastewater, and landscape characteristics. Unfiltered total mercury concentrations in 411 water samples from streams in the 26 watersheds had a median of 2.32 nanograms per liter (ng/L) and a maximum of 28.2 ng/L. When these concentrations were compared to Indiana water-quality criteria for mercury, 5.4 percent exceeded the 12-ng/L chronic-aquatic criterion, 59 percent exceeded the 1.8-ng/L Great Lakes human-health criterion, and 72.5 percent exceeded the 1.3-ng/L Great Lakes wildlife criterion. Mercury concentrations in water were related to streamflow, and the highest mercury concentrations were associated with the highest streamflows. On average, 67 percent of total mercury in streams was in a particulate form, and particulate mercury concentrations were significantly lower downstream from dams than at monitoring stations not affected by dams. Methylmercury is the organic fraction of total mercury and is the form of mercury that accumulates and magnifies in food chains. It is made from inorganic mercury by natural processes under specific conditions. Unfiltered methylmercury concentrations in 411 water samples had a median of 0.10 ng/L and a maximum of 0.66 ng/L. Methylmercury was a median 3.7 percent and maximum 64.8 percent of the total mercury in 252 samples for which methylmercury was reported. The percentages of methylmercury in water samples were significantly higher downstream from dams than at other monitoring stations. Nearly all of the total mercury detected in fish tissue was assumed to be methylmercury. Fish-tissue samples from the 26 watersheds had wet-weight mercury concentrations that exceeded the 0.3 milligram per kilogram (mg/kg) U.S. Environmental Protection Agency (USEPA) methylmercury criterion in 12.4 percent of the 1,731 samples. The median wet-weight concentration in the fish-tissue samples was 0.13 mg/kg, and the maximum was 1.07 mg/kg. A coarse-scale analysis of all fish-tissue data in each watershed and a fine-scale analysis of data within 5 kilometers (km) of the downstream end of each watershed showed similar results overall. Mercury concentrations in fish-tissue samples were highest in the White River watershed in southern Indiana and the Fall Creek watershed in central Indiana. In fish-tissue samples within 5 km of the downstream end of a watershed, the USEPA methylmercury criterion was exceeded by 45 percent of mercury concentrations from the White River watershed and 40 percent of the mercury concentration from the Fall Creek watershed. A clear relation between mercury concentrations in fish-tissue samples and methylmercury concentrations in water was not observed in the data from watersheds in Indiana. Average annual atmospheric mercury wet-deposition rates were mapped with data at 156 locations in Indiana and four surrounding states for 2001–2006. These maps revealed an area in southeastern Indiana with high mercury wet-deposition rates—from 15 to 19 micrograms per square meter per year (µg/m 2 /yr). Annual atmospheric mercury dry-deposition rates were estimated with an inferential method by using concentrations of mercury species in air samples at three locations in Indiana. Mercury dry deposition-rates were 5.6 to 13.6 µg/m 2 /yr and were 0.49 to 1.4 times mercury wet-deposition rates. Total mercury concentrations were detected in 96 percent of 402 samples of wastewater effluent from 50 publicly owned treatment works in the watersheds; the median concentration was 3.0 ng/L, and the maximum was 88 ng/L. When these concentrations were compared to Indiana water-quality criteria for mercury, 12 percent exceeded the 12-ng/L chronic-aquatic criterion, 68 percent exceeded the 1.8-ng/L Great Lakes human-health criterion, and 81 percent exceeded the 1.3-ng/L Great Lakes wildlife criterion. Annual stream mercury yields were calculated with a model by using the mercury concentrations in water samples and daily average streamflows for 2002–2006, normalized to the watershed drainage areas. The average annual total mercury stream yields ranged from 0.73 to 45.2 µg/m 2 /yr and were highest in two White River watersheds in central Indiana. Median methylmercury stream yield was 1.9 percent of the median total mercury stream yield. In most watersheds, average annual stream yields of total mercury were a fraction of the combined average annual atmospheric mercury wet-deposition and estimated annual dry-deposition loading rates, indicating that much of the stream mercury was attributable to atmospheric deposition. In two watersheds, average annual stream yields of total mercury were approximately twice the atmospheric mercury loading, indicating that some of the stream mercury apparently was not attributable to atmospheric deposition. Rather, some of the stream mercury yield potentially was contributed by mercury in wastewater discharges. Land-cover type corresponded with the mercury levels in three watersheds: (1) A watershed of the White River in central Indiana with a high percentage of urban land cover had some of the highest total mercury concentrations and stream mercury yields. The urban land cover and numerous permitted wastewater outfalls with mercury in treated effluent potentially contributed mercury to this watershed. (2) A monitoring station on the Maumee River in northeastern Indiana, downstream from a large area of urban land cover, recorded the highest stream mercury concentrations. The urban land cover and mercury detected in treated effluent potentially contributed to the high mercury concentrations at this station. (3) A watershed of the Patoka River in southern Indiana with a high percentage of forest land cover had the highest atmospheric mercury dry-deposition rate. The high dry-deposition rate from the forest land cover potentially contributed to the high mercury concentrations in this watershed. From a retrospective view, mercury concentrations in Indiana watersheds routinely exceeded criteria protective of humans and commonly exceeded criteria protective of wildlife. Atmospheric mercury wet deposition was a predominant factor, but not the single factor, affecting mercury in Indiana watersheds. Mercury in wastewater discharges and atmospheric mercury dry deposition apparently contributed a substantial part of the mercury yield from some watersheds. Dams and impoundments increased the percentage of methylmercury in downstream waters. Long-term monitoring of mercury in wet and dry atmospheric deposition, and in streams and reservoirs, coordinated with monitoring of mercury in fish, will be needed to detect whether mercury levels in Indiana watersheds change in the future.

Indiana↗
USGS2026

Apatite (U-Th)/He thermochronology from Marsh Creek anticline reconciles Cenozoic and Holocene strain patterns and elucidates the Cenozoic canning displacement zone of Arctic Alaska

The northeastern Brooks Range is a vast fold-thrust belt that records the northernmost expression of Cenozoic deformation in Alaska, likely with complex dynamic linkages to distant tectonic elements. The principal focus of this manuscript is the Marsh Creek anticline (MCA), which is a large and recently active structure within the broader northeastern Brooks Range. The MCA is a complex, polyphase structure mostly buried beneath the Arctic coastal plain. We present apatite (U-Th)/He (AHe) dates from six outcrop samples, all near the structural crest of the anticline, as well as supporting detrital zircon U/Pb (ZUPb) age spectra from five outcrop samples. The AHe sample transect spans ~3 km of structural relief. The four shallowest AHe samples are not reset. However, the two deepest samples exhibit low intrasample variability among replicates and strong date versus grain radius correlations, suggesting post-depositional burial heating to within the AHe partial retention zone. Inverse thermal history modeling of these data resolves a protracted phase of exhumational cooling that began around 33–28 Ma. Detrital ZUPb age spectra from Paleogene strata support an interpretation of diverse inherited thermal histories recorded by the AHe data, and they are also consistent with extant reconstructions of Paleogene sediment dispersal. Placed into regional context, the results constrain a phase of increasing structural relief in the northeastern Brooks Range fold-thrust belt that began by the Eocene. The relief developed in a zone characterized by diminishing structural relief to the west called the Canning displacement zone. Although this zone was active since the Eocene, several structures including the studied part of the MCA were rapidly exhumed in the Oligocene. Lastly, we argue for kinematic compatibility between Cenozoic contraction and active strike-slip in the northeastern Brooks Range, with the temporal change in strain style likely reflecting the increase in structural relief and topography.

Alaska↗
USGS2003

SHRIMP U-Pb geochronology of Neoproterozoic Windermere Supergroup, central Idaho: Implications for rifting of western Laurentia and synchroneity of Sturtian glacial deposits

In central Idaho roof pendants, a northwest-trending belt of metamorphosed strata, correlative with the Windermere Supergroup, links northern and southern segments of the western Laurentia Neoproterozoic rift belt. Nine newly named formations within the Gospel Peaks sequence-A through Gospel Peaks sequence-D record Cryogenian preglacial, rift-glacial, and postglacial events as well as Neoproterozoic III glacial and rift events. The Edwardsburg Formation of Gospel Peaks sequence B includes interfingered bimodal rift-related volcanic and glaciogenic diamictite strata. Zircons from a rhyodacite flow in the lower Edwardsburg Formation and from a rhyolite flow at its top, dated by using the sensitive high-resolution ion microprobe (SHRIMP), yielded a weighted average of 685 ± 7 Ma and 684 ± 4 Ma. Reevaluation of geochronology and correlations indicates that Cryogenian rifting may have been (1) protracted between 780 and 685 Ma, (2) diachronous along the Cordillera, and/or (3) stepwise with a Cordilleran-wide event at ca. 685 Ma that initiated the formation of the Cordilleran miogeocline and set its geometry. Reevaluation of the Cryogenian glacial record indicates that (1) two associated ca. 685 Ma glacial intervals in the Edwardsburg Formation correlate with the Rapitan glaciation, (2) the Sturtian snowball Earth event must be reevaluated on the basis of revision of Rapitan glaciation from 750–700 Ma to ca. 685 Ma, and (3) there were older Cryogenian glaciations or Cryogenian glaciations were not globally synchronous. New dates and correlations significantly impact the number and synchroneity of possible snowball Earth events and the paleolatitudes of Cryogenian glaciations. Western Laurentian events at ca. 685 Ma particularily affect Neoproterozoic paleocontinental reconstructions by indicating diachronous and multi step breakup of supercontinent Rodinia.

Idaho↗
USGS2020

Minimal stratigraphic evidence for coseismic coastal subsidence during 2000 yr of megathrust earthquakes at the central Cascadia subduction zone

Lithology and microfossil biostratigraphy beneath the marshes of a central Oregon estuary limit geophysical models of Cascadia megathrust rupture during successive earthquakes by ruling out >0.5 m of coseismic coastal subsidence for the past 2000 yr. Although the stratigraphy in cores and outcrops includes as many as 12 peat-mud contacts, like those commonly inferred to record subsidence during megathrust earthquakes, mapping, qualitative diatom analysis, foraminiferal transfer function analysis, and 14 C dating of the contacts failed to confirm that any contacts formed through subsidence during great earthquakes. Based on the youngest peat-mud contact’s distinctness, >400 m distribution, ∼0.6 m depth, and overlying probable tsunami deposit, we attribute it to the great 1700 CE Cascadia earthquake and(or) its accompanying tsunami. Minimal changes in diatom assemblages from below the contact to above its probable tsunami deposit suggest that the lower of several foraminiferal transfer function reconstructions of coseismic subsidence across the contact (0.1–0.5 m) is most accurate. The more limited stratigraphic extent and minimal changes in lithology, foraminifera, and(or) diatom assemblages across the other 11 peat-mud contacts are insufficient to distinguish them from contacts formed through small, gradual, or localized changes in tide levels during river floods, storm surges, and gradual sea-level rise. Although no data preclude any contacts from being synchronous with a megathrust earthquake, the evidence is equally consistent with all contacts recording relative sea-level changes below the ∼0.5 m detection threshold for distinguishing coseismic from nonseismic changes.

British Columbia, California, Oregon, Washington↗
USGS2012

Eruptive history of Mount Katmai, Alaska

Mount Katmai has long been recognized for its caldera collapse during the great pyroclastic eruption of 1912 (which vented 10 km away at Novarupta in the Valley of Ten Thousand Smokes), but little has previously been reported about the geology of the remote ice-clad stratovolcano itself. Over several seasons, we reconnoitered all parts of the edifice and sampled most of the lava flows exposed on its flanks and caldera rim. The precipitous inner walls of the 1912 caldera remain too unstable for systematic sampling; so we provide instead a photographic and interpretive record of the wall sequences exposed. In contrast to the several andesite-dacite stratovolcanoes nearby, products of Mount Katmai range from basalt to rhyolite. Before collapse in 1912, there were two overlapping cones with separate vent complexes and craters; their products are here divided into eight sequences of lava flows, agglutinates, and phreatomagmatic ejecta. Latest Pleistocene and Holocene eruptive units include rhyodacite and rhyolite lava flows along the south rim; a major 22.8-ka rhyolitic plinian fall and ignimbrite deposit; a dacite-andesite zoned scoria fall; a thick sheet of dacite agglutinate that filled a paleocrater and draped the west side of the edifice; unglaciated leveed dacite lava flows on the southeast slope; and the Horseshoe Island dacite dome that extruded on the caldera floor after collapse. Pre-collapse volume of the glaciated Katmai edifice was ∼30 km 3 , and eruptive volume is estimated to have been 57±13 km 3 . The latter figure includes ∼40±6 km 3 for the edifice, 5±2 km 3 for off-edifice dacite pyroclastic deposits, and 12±5 km 3 for the 22.8-ka rhyolitic pyroclastic deposits. To these can be added 13.5 km 3 of magma that erupted at Novarupta in 1912, all or much of which is inferred to have been withdrawn from beneath Mount Katmai. The oldest part of the edifice exposed is a basaltic cone, which gave a 40 Ar/ 39 Ar plateau age of 89 ± 25 ka. The seismic record of caldera collapse includes 14 earthquakes of magnitude 6.0–7.0. By combining the times of earthquakes, the hours of downwind plinian-fall episodes from Novarupta, and the stratigraphic record of hydrothermal explosion breccia and phreatic mud layers ejected around the caldera rim and intercalated within the Novarupta pumice-fall sequence, it can be inferred that collapse began in the 11th hour of the 60-h-long eruption and continued fitfully for 3.5 days. Several big landslides and pumiceous debris flows shaken loose by the collapse-related seismicity are bracketed in time by their levels of intercalation within the Novarupta pumice-fall sequence. An intracaldera lake was ∼10 m deep by 1916, drained away in 1923, and has since deepened progressively to ∼250 m today. Compositionally, products of Mount Katmai represent an ordinary medium-K arc array, both tholeiitic and calcalkaline, that extends from 51.6% to 72.3% SiO 2 . Values of 87 Sr/ 86 Sr range from 0.70335 to 0.70372, correlating loosely with fractionation indices. The 5–6 km 3 of continuously zoned andesite-dacite magma (58%–68% SiO 2 ) that erupted at Novarupta in 1912 was withdrawn from beneath Mount Katmai and bears close compositional affinity with products of that edifice, not with pre-1912 products of the adjacent Trident cluster. Evidence is presented that the 7–8 km 3 of high-silica rhyolite (77% SiO 2 ) released in 1912 is unlikely to have been stored under Novarupta or Trident. Pre-eruptive contiguity with the andesite-dacite reservoir is suggested by (1) eruption of ∼3 km 3 of rhyolite magma first, followed by mutual mingling in fluctuating proportions; (2) thermal and redox continuity of the whole zoned sequence despite the wide compositional gap; (3) Nd, Sr, O isotopic, and rare earth element (REE) affinities of the whole array; (4) compositional continuity of the nearly aphyric rhyolite with the glass (melt) phase of the phenocryst-rich dacite; and (5) phase-equilibrium experiments that indicate similar shallow pre-eruptive storage depths (3–6 km) for rhyolite, dacite, and andesite.

Alaska↗
USGS2016

Re-Os systematics and age of pyrite associated with stratiform Zn-Pb mineralization in the Howards Pass district, Yukon and Northwest Territories, Canada

Stratiform Zn-Pb deposits hosted in unmetamorphosed carbonaceous and siliceous mudstones of the Ordovician to Silurian Duo Lake Formation define the Howards Pass district in Yukon Territory and Northwest Territories, western Canada. Collectively, the deposits are amongst the largest in the world, containing drill-indicated and inferred resources of 423 Mt at 4.84 % Zn and 1.59 % Pb. Sulphide textures include (a) fine-scale laminations of sphalerite, galena, and pyrite from <0.05 mm to 1 cm thick, interbedded with carbonaceous sedimentary rock; (b) layers of coarse sulphide that are structurally controlled by microfolds; and (c) veins that cut bedding and sulphide laminations. The finely interlaminated nature of sulphides with mudstone has been used as evidence for syngenetic mineralizing processes, whereas paleomagnetic data determined on coarse layered sulphides suggest a Middle Jurassic age of mineralization. Here, we present new rhenium-osmium (Re-Os) isotopic data for 12 pyrite separates obtained from 4 laminated sulphide-rich samples from the XY Central (XYC) and Don (DON) deposits and for 1 unmineralized organic-rich mudstone ∼20 m stratigraphically below the sulphide-bearing zone. Pyrite separates that lack mudstone inclusions (“pure”) from the XYC deposit contain 2.2 to 4.0 ppb Re and 93.4 to 123.4 ppt Os; pure pyrite from the DON deposit is significantly more enriched in Re and Os (34–37 ppb Re; 636.8–694.9 ppt Os). The 187 Re/ 188 Os values of pure pyrite separates from the XYC and DON deposits range from 137.6 to 197 and 182.1 to 201.4, respectively. Regression of all pure pyrite Re-Os data from both deposits yields an isochron age of 442 ± 14 Ma (MSWD = 7.4) and an initial 187 Os/ 188 Os (Os i ) value of 0.71 ± 0.07. The Re-Os age indicates that the early phase of pyrite precipitation (and by inference, sphalerite and galena) occurred during the early Silurian, consistent with biostratigraphic ages of the host rocks. The Os i value of ∼0.8 for earliest Silurian seawater recorded from organic-rich shale in the basal Silurian Global Stratotype Section and Point (GSSP) at Dobs Linn, Scotland is very similar to that provided by the Howards Pass pyrite regression and hence suggests a hydrogenous (seawater) source of Os for the pyrite. Therefore, two possible sources of Os are (1) the Zn- and Pb-bearing hydrothermal fluid that leached Os from footwall sedimentary rocks, which were deposited in seawater, or (2) directly from seawater during precipitation of the pyrite, which suggests that the Os content of the hydrothermal fluid was minor relative to that of seawater.

Northwest Territories, Yukon↗
USGS2014

Little late Holocene strain accumulation and release on the Aleutian megathrust below the Shumagin Islands, Alaska

Can a predominantly creeping segment of a subduction zone generate a great ( M &thinsp;>&thinsp;8) earthquake? Despite Russian accounts of strong shaking and high tsunamis in 1788, geodetic observations above the Aleutian megathrust indicate creeping subduction across the Shumagin Islands segment, a well-known seismic gap. Seeking evidence for prehistoric great earthquakes, we investigated Simeonof Island, the archipelago's easternmost island, and found no evidence for uplifted marine terraces or subsided shorelines. Instead, we found freshwater peat blanketing lowlands, and organic-rich silt and tephra draping higher glacially smoothed bedrock. Basal peat ages place glacier retreat prior to 10.4&thinsp;ka and imply slowly rising (<0.2&thinsp;m/ka) relative sea level since ~3.4&thinsp;ka. Storms rather than tsunamis probably deposited thin, discontinuous deposits in coastal sites. If rupture of the megathrust beneath Simeonof Island produced great earthquakes in the late Holocene, then coseismic uplift or subsidence was too small (&le;0.3&thinsp;m) to perturb the onshore geologic record.

Alaska↗
USGS2002

Paleoecological insights on fixed tree island development in the Florida Everglades: I. environmental controls

Palynological and geochemical analyses of sediment cores collected on two tree islands in the Florida Everglades indicate long-term hydrologic and chemical differences between tree islands and surrounding marshes and sloughs. Gumbo Limbo and Nuthouse tree islands are elongate, teardrop-shaped islands in Water Conservation Area 3B. Prior to tree island formation at both sites, pollen records indicate that sites on modern tree island heads were covered with sawgrass marshes with abundant weedy annuals. Such vegetation is characteristic of moderate water depths and hydroperiods with frequent droughts or disturbances. Contemporaneously deposited sediments on tree island tails indicate progressively deeper water conditions with increasing distance from the head; wetlands surrounding tree islands were covered by sloughs with deep water and long hydroperiods. Tree island formation occurred at about 1200 BC on Gumbo Limbo Island, with mature tree island vegetation established by about 800 AD. On Nuthouse Island, tree island formation occurred around 300 AD, shifting to mature tree island vegetation around 1400 AD. Thus, tree island formation began on these islands between 3.2 Ka and 1.7 Ka. Maturation of tree islands took between 1,000 and 2,000 years, and vegetation on these tree islands has been relatively stable for the last 600–1,200 years. Phosphorus levels on tree island heads have been extremely high (approximately six times greater than baseline levels in marshes) throughout the history of the sites, and phosphorus content in tree island tails began increasing when tree island formation occurred. Elevated phosphorus content may reflect the long-term presence of wading birds at these sites and provide a proxy for reconstructing the historic distribution of wading bird populations.

Florida↗
USGS2014

Geochemistry of a marine phosphate deposit: A signpost to phosphogenesis

The Permian age Phosphoria Formation in southeastern Idaho and adjoining states represents possibly the largest marine phosphate deposit in the world. The Meade Peak Member, which contains the highest concentrations and amount of carbonate fluorapatite in the formation, was not significantly altered by mechanical reworking during deposition or subsequently by chemical weathering. Thus, its present composition reflects properties of the Phosphoria Sea that were critical to its accumulation and possibly to the accumulation of most major marine phosphate deposits. These properties included the chemistry of the water column, the hydrography, and the level of primary productivity. Calculated accumulation rates of the PO 4 3− and trace nutrients – Cd, Cu, Ni, and Zn – recorded a dynamic upwelling rate of c. 30 m year −1 that supported primary productivity of 2g C m −2 day −1 . High accumulation rates of the hydrogenous redox-sensitive trace metals – Cr, Mo, U, and V – reflect bottom-water redox conditions that were dominantly suboxic, maintained by a balance between the oxidation of ~ 8% of the organic detritus that settled out of the photic zone and advection of bottom water with a residence time of c .10 years. A limited flux into the basin of siliciclastic lithogenous debris contributed further to elevated concentrations of the seawater-derived sediment fractions.

Book chapter↗
USGS2014

Discussion of “The relation of geology to dry weather stream flow in Ohio”

The concepts presented in this paper are of great value to the ground‐water hydrologist. They indicate one way to analyze and conveniently use the vast accumulation of stream‐flow records collected by governmental agencies as a tool for geophysical reconnaisance. To be usable as a method of geophysical prospecting for ground water, stream‐flow records must first be transformed into flow‐duration curves. Then, by means of the 90 per cent index, chosen by Cross, or other, more suitable indices, the ground‐water storage characteristics of the surficial deposits of drainage basins can readily be determined. Where there is good indication of extensive groundwater storage, it is probable that large supplies of ground water can be developed for use.

Ohio↗
USGS1992

On the age of the penultimate full glaciation of New England

Tills that discontinuously underlie the late Wisconsinan till throughout New England represent the penultimate full glaciation of the region. In southern New England, the late Wisconsinan till and the tills that locally underlie it are informally referred to as upper and lower tills, respectively. For the most part, the ages of the lower tills are not firmly established, and regional correlations between occurrences of lower till, including those on Long Island, New York, are tenuous. Where a lower till underlies deposits having limiting middle Wisconsinan radiocarbon ages (e.g., the Montauk till member of the Manhassett Formation on Long Island at Port Washington, New York, and the lower till at New Sharon, Maine), many workers have assigned the till an early Wisconsinan age. However, lower tills throughout much of New England may be Illinoian or older in age and may correlate with a lower till exposed at Sankaty Head, Nantucket Island, Massachusetts, that is pre-Sangamonian in age. The till at Sankaty Head lies below marine beds containing marine faunas indicative of sea-water temperatures both warmer and slightly cooler than those off Nantucket today and that have uranium-thorium and amino-acid racemization (AAR) age estimates suggesting a Sangamonian age (marine oxygen-isotope stage 5). The lower till at Sankaty Head and the Montauk till member on Long Island were deposited during a full glaciation of New England that was at least as extensive as the late Wisconsinan advance of the Laurentide ice. Global ice-volume data from the marine oxygen-isotope record and the late Pleistocene eustatic sea-level record inferred from raised coral terraces support an advance of this magnitude during marine oxygenisotope stage 6, but not during stage 4. An early Wisconsinan age of the southern New England lower tills and, hence, of the penultimate glaciation there is problematic in terms of the pre-Sangamonian age of the lower till on Nantucket, and in terms of the late Pleistocene global ice-volume and sea-level records. An Illinoian age for the tills and for the penultimate full glaciation of New England is compatible with all the available evidence except some equivocal radiocarbon ages and AAR age estimates.

GSA Special Papers↗
USGS2001

The STRATAFORM Project: U.S. Geological Survey geotechnical studies

This report presents physical property logs of core samples from an offshore area near Eureka, CA. The cores were obtained as part of the STRATAFORM Program (Nittrouer and Kravitz, 1995, 1996), a study investigating how present sedimentation and sediment transport processes influence long-term stratigraphic sequences preserved in the geologic record. The core samples were collected during four separate research cruises to the northern California study area, and data shown in the logs of the cores were collected using a multi-sensor whole core logger. The physical properties collected are useful in identifying stratigraphic units, ground-truthing acoustic imagery and sub-bottom profiles, and in understanding mass movement processes. STRATA FOR mation on M argins was initiated in 1994 by the Office of Naval Research, Marine Geology and Geophysics Department as a coordinated multi-investigator study of continental-margin sediment transport processes and stratigraphy (Nittrouer and Kravitz, 1996). The program is investigating the stratigraphic signature of the shelf and slope parts of the continental margins, and is designed to provide a better understanding of the sedimentary record and a better prediction of strata. Specifically, the goals of the STRATAFORM Program are to (Nittrouer and Kravitz, 1995): - determine the geological relevance of short-term physical processes that erode, transport, and deposit particles and those processes that subsequently rework the seabed over time scales <10 2 years. - improve capabilities for identifying the processes that form the strata observed within the upper ~100 m of the seabed commonly representing 104-106 years of sedimentation. - synthesize this knowledge and bridge the gap between time scales of sedimentary processes and those of sequence stratigraphy. The STRATAFORM Program is divided into studies of the continental shelf and the continental slope; the geotechnical group within the U.S. Geological Survey provides support to both parts of the project.

California↗
USGS2007

Holocene oceanographic and climatic variability of the Vega Drift deduced through foraminiferal interpretation

A sediment sequence recovered from the Vega Drift, Antarctica was analyzed for benthic foraminifera to determine Holocene oceanographic and climatic variability of the northern Antarctic Peninsula margin. Core NBP0003-JPC38, collected during cruise 00-03 of the R.V. Nathaniel B. Palmer recovered 20.53 meters of Holocene glacio-marine sediments. Samples were collected every 4 cm for foraminiferal analyses. The data were analyzed using principal component and cluster analyses. Results of these analyses show significant stratigraphic changes in the benthic foraminiferal record of the Vega Drift. Three assemblages characterize the core, including the Miliammina arenacea, Textulariawiesneri, and Stainforthia fusiformis assemblages. Most agglutinated forms tend to decrease downcore, and comparisons to modern analogues imply post-depositional disintegration, while calcareous taxa indicate non-corrosive bottom waters. The lower to middle Holocene Vega Drift sediments are characterized by the calcareous S. fusiformis assemblage and glacial plume sediments. This assemblage is characterized by calcareous forms including Globocassidulina biora, G. subglobosa, and Nonionella iridea. The planktic species Neogloboquadrina pachyderma is associated with the S. fusiformis assemblage. The S. fusiformis assemblage is faunally similar to assemblages described in fjords of the western Antarctic Peninsula and indicates non-corrosive bottom water. Sediments of the mid to upper Holocene interval are characterized by the T. wiesneri and M. arenacea assemblages and indicate the presence of Hyper Saline Shelf Water. These assemblages are similar to modern assemblages directly to the south in the Prince Gustav Channel. The upper Holocene is marked by several small intervals with taxonomic characteristics similar to the S. fusiformis assemblage, indicating periodic introduction of non-corrosive bottom water to the Vega Drift

Open-File Report↗
USGS1999

Effects of historical land-cover changes on flooding and sedimentation, North Fish Creek, Wisconsin

North Fish Creek, a Wisconsin tributary to Lake Superior, is an important recreational fishery that is potentially limited by the loss of aquatic habitat caused by accelerated flooding and sedimentation. A study of the historical flooding and sedimentation characteristics of North Fish Creek was done to determine how North Fish Creek responded to human-caused changes in land cover since European settlement of the region in the 1870's. Geomorphic field evidence combined with hydrologic and sediment-transport modeling indicate that historical clear-cut logging, followed by agricultural activity, significantly altered the hydrologic and geomorphic conditions of North Fish Creek. The geomorphic responses to land-cover changes were especially sensitive to the location of the reaches along the main stem and on the timing of large floods. On the basis of geomorphic evidence in flood-plain deposits and abandoned channels, the size of floods and sediment loads also increased in North Fish Creek after conversion of forested land to cropland and pasture. Changes in channel characteristics were particularly noticeable after record floods in 1941 and 1946. The upper main stem channel bed eroded downward at least 3 meters and the channel capacity at least doubled after European settlement. In the lower stem, the post-settlement sedimentation rate on the flood plain and in the channel is 4 to 6 times pre-settlement rates. The water table also appears to be rising near the mouth of North Fish Creek, perhaps consistent with (1) elevated local streambed elevations caused by sedimentation and (2) a slow relative rise in the local level of Lake Superior due to crustal rebound from glaciation. Along a transitional reach of the main stem between the upper and lower main stem, there is evidence of accelerated flood-plain sedimentation initially following European settlement. Since at least the 1940's, however, the channel bed in the transitional reach has eroded about 1 meter and the channel capacity has at least doubled. Results from hydrologic and sediment-transport modeling indicate that modern flood peaks and sediment loads in North Fish Creek may be double that expected under pre-settlement forest cover. During maximum agricultural activity in the mid-1920's to mid-1930's, flood peaks probably were about 3 times larger and sediment loads were about 5 times larger than expected under pre-settlement forest cover. These results indicate that future changes from pasture or cropland to forest will help reduce flood peaks, thereby reducing erosion and sedimentation. The addition of detention basins (to decrease flood peaks) on tributaries to North Fish Creek, or bank and instream restoration (to decrease erosion) in the upper main stem, also may help reduce the contribution of sediment from the upper main stem to the transitional section and lower main stem of the creek.

Wisconsin↗
USGS2022

A novel method for conducting a geoenvironmental assessment of undiscovered ISR-amenable uranium Resources: Proof-of-concept in the Texas Coastal Plain

A geoenvironmental assessment methodology was developed to estimate waste quantities and disturbances that could be associated with the extraction of undiscovered uranium resources and identify areas on the landscape where uranium and other constituents of potential concern (COPCs) that may co-occur with uranium deposits in this region are likely to persist, if introduced into the environment. Prior to this work, a method was lacking to quantitively assess the environmental aspects associated with potential development of undiscovered uranium resources at a scale of a uranium resource assessment. The mining method of in situ recovery (ISR) was historically used to extract uranium from deposits in the Goliad Sand of the Texas Coastal Plain. For this reason, the study’s methodology projected the following types of wastes and disturbances commonly associated with ISR based on historical ISR mining records: the mine area, affected aquifer volume, mine pore volume, water pumped and disposed during uranium extraction and restoration, and radon emissions. Within the tract permissive for the occurrence of undiscovered uranium resources, maps and statistics of factors were derived that indicate the potential contaminant pathways. The percentage of days meeting the criteria for air stagnation indicate the potential for radon accumulation; the geochemical mobility of COPCs in groundwater in combination with effective recharge indicates the potential for infiltration of surface-derived COPCs; the geochemical mobility of COPCs in groundwater combined with hydraulic conductivity indicates the propensity for transmitting fluids away from contaminated or mined aquifers; and finally, geochemical mobility of COPCs in surface water combined with the factor for climatic erosivity (R factor) indicates the potential for COPCs to persist in surface waters due to runoff. This work resulted in a new methodology that can be applied to any undiscovered mineral resource to better understand possible wastes and disturbances associated with extraction and identify areas on the landscape where COPCs are likely to persist.

Texas↗
USGS2025

Variable partitioning of lithium in rhyolitic melt during decompression and ascent

The partitioning behavior of Li in magmatic systems is increasingly being investigated due to the economic importance of Li in the transition to sustainable energy resources (e.g., batteries). However, at upper crustal pressures, it remains uncertain whether Li preferentially partitions into the vapor or liquid (brine) phase or remains in the silicate melt. This complicates our ability to determine where Li resides—silicate melt, minerals, or fluid phase—upon eruption, a crucial factor for understanding its postdepositional movement and concentration into a brine or volcano-sedimentary deposit. Here, we present a novel investigation into the behavior of Li within natural evolved melts during continuous magma decompression and ascent using melt embayments (open melt inclusions). Mineral-hosted melt embayments preserve records of the evolving composition of the exterior melt, including degassing pathways and ascent timescales, when paired with appropriate diffusion coefficients. Lithium concentration profiles were measured in quartz-hosted melt embayments from the rapidly quenched eruptive phases of five rhyolitic, caldera-forming eruptions to investigate the behavior of Li during magma decompression and ascent, where vapor partitioning and ascent dynamics were previously established by investigating H 2 O and CO 2 profiles. We find that in four systems, embayments contain lower interior Li concentrations than the coerupted melt inclusions; the fifth system contains the same Li concentrations in embayments and melt inclusions. However, many of these embayments contain gradients, with 84 % preserving Li enrichment near the melt-bubble interface, as compared to their interior concentration. We interpret these characteristics to represent two distinct stages of Li partitioning during magma decompression and ascent, in contrast to existing literature that proposes only one type of partitioning behavior. The first stage is interpreted as melt depletion of Li, likely driven by partitioning into an exsolved supercritical fluid phase, supported by the strong correlation between the extent of Li depletion and Cl concentration in the melt, as well as the decompression rate. This behavior then fundamentally shifts, where Li reenriches in the melt, postulated to be driven by the unmixing of the supercritical fluid phase at shallow pressures. For the one system that did not develop Li gradients through decompression, we attribute this to the lower values of Na and Cl in the melt, potentially inhibiting the partitioning of Li into a fluid phase. Importantly, the behavior of Li during decompression is not consistent within or between volcanic centers, highlighting the need for systematic experimental investigation in variable composition melts at pressures relevant to conduit dynamics. This knowledge would improve our ability to model Li profiles to understand magma decompression, and predict where Li resides (e.g., stored in volcanic glass, gas, or crystals) upon eruption prior to any later extraction.

Economic Geology↗
USGS2019

Geology of the Mineral and Lake Anna West Quadrangles, Virginia

This map product is a cooperator series publication and, as such, does not have a specific abstract. Geologic mapping for this map product was completed between 2014 and 2017, with most of the field work occurring between January 2016 and May 2017. Numerous foot traverses were completed along creeks and roads throughout the field area; the shore of Lake Anna was accessed by kayak to provide additional data. Distributions of soil units were considered when assigning bedrock type in areas where outcrop was lacking and helped to distinguish fluvial terrace deposits. Hill-shade raster images created from LiDAR datasets and geophysical data sets proved useful in the field to trace bedrock and surficial units. GPS location control and field data were collected and recorded in digital databases using a variety of geologic mapping applications for an iPad 3rd Gen Model A1403 and Motion C5v tablet using Fieldmove 2013.1. Structural measurements were also plotted on field maps. Data collected included lithology and the orientation of foliations, folds, lineations, joints, and faults. Representative rock samples of significant formations were thin-sectioned for petrographic analysis; a few samples from these and surrounding quadrangles were analyzed for zircon U-Pb geochronology and geochemistry.

Virginia↗
USGS2014

Loess records

Loess is aeolian sediment, dominated by silt-sized particles, that is identifiable in the field as a distinct sedimentary body. It covers a significant portion of the land surface of the Earth and as such constitutes one of the most important archives of long-term dust deposition. Large tracts of loess cover Europe, Asia, South America, and North America, and smaller loess bodies are found covering parts of Africa, the Middle East, New Zealand, and Australia. Loess thickness, particle size, and carbonate content decrease downwind from sources, trends that are powerful tools for reconstructing paleowinds. Many loess sections consist of relatively thick deposits of mostly unaltered sediment with intercalated paleosols. Paleosols represent periods of landscape stability when loess deposition ceased or at least slowed significantly. Studies from several continents show that loess in most regions was deposited during glacial periods and paleosols formed during interglacial and interstadial periods.

Book chapter↗