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Sample records for central west greenland

  1. Gyrfalcon diet in central west Greenland during the nestling period

    USGS Publications Warehouse

    Booms, Travis; Fuller, Mark R.

    2003-01-01

    We studied food habits of Gyrfalcons (Falco rusticolus) nesting in central west Greenland in 2000 and 2001 using three sources of data: time-lapse video (3 nests), prey remains (22 nests), and regurgitated pellets (19 nests). These sources provided different information describing the diet during the nesting period. Gyrfalcons relied heavily on Rock Ptarmigan (Lagopus mutus) and arctic hares (Lepus arcticus). Combined, these species contributed 79-91% of the total diet, depending on the data used. Passerines were the third most important group. Prey less common in the diet included waterfowl, arctic fox pups (Alopex lagopus), shorebirds, gulls, alcids, and falcons. All Rock Ptarmigan were adults, and all but one arctic hare were young of the year. Most passerines were fledglings. We observed two diet shifts, first from a preponderance of ptarmigan to hares in mid-June, and second to passerines in late June. The video-monitored Gyrfalcons consumed 94-110 kg of food per nest during the nestling period, higher than previously estimated. Using a combination of video, prey remains, and pellets was important to accurately document Gyrfalcon diet, and we strongly recommend using time-lapse video in future diet studies to identify biases in prey remains and pellet data.

  2. Gyrfalcon diet in central west Greenland during the nesting period

    USGS Publications Warehouse

    Booms, T.L.; Fuller, M.R.

    2003-01-01

    We studied food habits of Gyrfalcons (Falco rusticolus) nesting in central west Greenland in 2000 and 2001 using three sources of data: time-lapse video (3 nests), prey remains (22 nests), and regurgitated pellets (19 nests). These sources provided different information describing the diet during the nesting period. Gyrfalcons relied heavily on Rock Ptarmigan (Lagopus mutus) and arctic hares (Lepus arcticus). Combined, these species contributed 79-91% of the total diet, depending on the data used. Passerines were the third most important group. Prey less common in the diet included waterfowl, arctic fox pups (Alopex lagopus), shorebirds, gulls, alcids, and falcons. All Rock Ptarmigan were adults, and all but one arctic hare were young of the year. Most passerines were fledglings. We observed two diet shifts, first from a preponderance of ptarmigan to hares in mid-June, and second to passerines in late June. The video-monitored Gyrfalcons consumed 94-110 kg of food per nest during the nestling period, higher than previously estimated. Using a combination of video, prey remains, and pellets was important to accurately document Gyrfalcon diet, and we strongly recommend using time-lapse video in future diet studies to identify biases in prey remains and pellet data.

  3. Paleoceanography and Ice Sheet-Ocean Interactions on the Central West Greenland Margin, LGM through Deglaciation

    NASA Astrophysics Data System (ADS)

    Jennings, A. E.; Andrews, J. T.; Ó Cofaigh, C.; St-Onge, G.; Belt, S. T.; Cabedo-Sanz, P.; Dowdeswell, J. A.

    2014-12-01

    Hemipelagic sediments in several central West Greenland trough mouth fan cores are critical for testing whether an ice shelf covered Baffin Bay during the late LGM and H1 (core HU2008029-12PC) and to investigate the role of ocean warming in initiating and/or sustaining retreat of the Greenland Ice Sheet from the shelf edge (cores JR175-VC29 & -VC46). We use benthic and planktic foram assemblages, IP25 sea ice biomarker, ice-rafted detritus (IRD), lithofacies and quantitative mineralogy to reconstruct paleoceanographic conditions. HU2008029-12PC comprises bioturbated, thin turbidites and hemipelagic sediments with Greenlandic provenance from >19.2 to 16.7 cal ka BP. Abundance spikes of planktic forams provide the radiocarbon dates in this interval and coincide with abundance spikes of benthic foram species indicative of chilled Atlantic Water and episodic marine productivity. IRD and IP25 are rare in this interval. These characteristics are consistent with the ice margin at the shelf edge meeting a heavily sea-ice covered ocean with chilled Atlantic Water at depth, rather than an ice shelf-covered ocean. Initial deglaciation from the West Greenland margin began c. 16.7 ka BP, as recorded by a lithofacies shift from turbidites to bioturbated mud with dispersed IRD and continued presence of Atlantic Water benthic species. After 16.7 ka BP, IP25, large diatoms and benthic forams indicative of sea-ice edge productivity show warming conditions. By 15.2 ka BP Greenlandic IRD and meltwater species, Elphidium excavatum, reflect accelerated ice sheet ablation. By 14.4 ka BP a strong rise in IP25 content, introduction of key Atlantic Water species Cassidulina neoteretis, and IRD spikes rich in detrital carbonate with a northern Baffin Bay provenance provide evidence for increased advection of West Greenland Current, collapse of the LIS ice streams, and formation of an IRD belt along the W. Greenland margin during the Bølling-Allerod and early Holocene warm intervals.

  4. Spacing and physical habitat selection patterns by peregrine falcons in central West Greenland

    USGS Publications Warehouse

    Wightman, C.; Fuller, Mark R.

    2005-01-01

    We examined nest-site spacing and selection of nesting cliffs by Peregrine Falcons (Falco peregrinus) in central West Greenland. Our sample included 67 nesting cliffs that were occupied at least once between 1972 and 1999 and 38 cliffs with no known history of Peregrine Falcon occupancy. We measured 29 eyrie, cliff, and topographical features at each occupied nesting cliff and unused cliff in 1998a??1999 and used them to model the probability of peregrines occupying a cliff for a breeding attempt. Nearest-neighbor distance was significantly greater than both nearest-cliff distance and nearest-occupied distance (the distance between an occupied cliff and one occupied at least once, 1972a??1999). Thus, spacing among occupied cliffs was probably the most important factor limiting nesting-cliff availability, and, ultimately, peregrine nesting densities. Although some unused cliffs were unavailable in a given year because of peregrine spacing behavior, physical characteristics apparently made some cliffs unsuitable, regardless of availability. We confirmed the importance of several features common to descriptions of peregrine nesting habitat and found that peregrines occupied tall nesting cliffs with open views. They chose nesting cliffs with eyrie ledges that provided a moderate degree of overhang protection and that were inaccessible to ground predators. Overall, we concluded that certain features of a cliff were important in determining its suitability as a nest site, but within a given breeding season there also must be sufficient spacing between neighboring falcon pairs. Our habitat model and information on spacing requirements may be applicable to other areas of Greenland and the Arctic, and can be used to test the generalities about features of Peregrine Falcon nesting cliffs throughout the species' widespread distribution.

  5. Gyrfalcon feeding behavior during the nestling period in central west Greenland

    USGS Publications Warehouse

    Booms, Travis; Fuller, Mark R.

    2003-01-01

    We studied gyrfalcon (Falco rusticolus) food delivery and feeding behavior during the nestling period in central West Greenland during the 2000 and 2001 field seasons. We used time-lapse video cameras installed at three nests to record 2677.25 hours of nestling video. Ptarmigan delivered to nests were usually plucked prior to delivery and included the breast and superior thoracic vertebrae. Arctic hare leverets were rarely plucked and often delivered in parts. The most commonly delivered leveret part was the hind legs attached to the lower back. Passerines were rarely plucked and usually delivered whole. After feeding the young, adults removed 20.9% of prey items from the nest, which included items both with and without obvious muscle still attached. Prey delivery rates were similar among nests and increased as nestlings aged. Prey delivery frequency peaked in the morning and evening, with a distinct lull in the late evening and early morning hours. Male and female adults delivered a similar number of prey, though males typically delivered smaller prey than females. Gyrfalcons cached and re-delivered at least 9.1% of all items delivered, and one item was cached and retrieved three times.

  6. Paleoecology and paleoclimatology of a late holocene peat deposit from Braendevinsskaer, Central West Greenland

    SciTech Connect

    Bennike, O. )

    1992-08-01

    The macroscopical plant and animal remains of a nearshore peat deposit in West Greenland are described and documented. The assemblages contain a mixture of limnic, terrestrial, and marine plants and animals. These are divided into four local macrofossil assemblage zones, of which zone 3, ca. A.D. 950 to ca. A.D. 1760, represents a wet phase which is correlated in part with the Little Ice Age.

  7. Seismic architecture and evolution of the Disko Bay trough-mouth fan, central West Greenland margin

    NASA Astrophysics Data System (ADS)

    Hofmann, Julia C.; Knutz, Paul C.; Nielsen, Tove; Kuijpers, Antoon

    2016-09-01

    The present study is the first to document the large-scale glacigenic evolution of a West Greenland trough-mouth fan (TMF) system, i.e. the Disko Bay TMF, from onset of shelf-based glaciation to present. We have constrained the paleo-ice sheet configuration in the Disko Bay region and determine the controlling factors of ice-stream development using 2D- and 3D-seismic reflection data, seabed bathymetry and stratigraphic information from two exploration wells. This has revealed three stages of the Disko Bay TMF development. The early stage, probably of Pliocene-early Pleistocene age, marks the onset of a central depocentre located below the modern mid-shelf and constructed by sediment progradation delivered through at least two erosive pathways related to fast-flowing, grounded ice. At that time, ice-stream routing in the Disko Bay shelf region was strongly controlled by the pre-glacial topography and structural boundaries associated with fracture zones and deep-seated faults. During the middle evolutionary stage, the focus of deposition shifted from the mid-shelf to two elongate areas fringing the outer margin. The marginal depocentres were not only related to glacial processes but also alongslope deposition by contour currents, which may have developed as a consequence of basin subsidence surrounding the Davis Strait High and the Kangerluk Structure. The late stage of TMF development, presumably representing the late Pleistocene to Holocene, is characterized by the marginal depocentres becoming less significant and sediment aggradation occurring over wide parts of the mid-outer shelf, while features of subglacial erosion are generally absent. In contrast to the inferred fast-flowing ice streams of the early-middle evolutionary stages, this points to the existence of a rather thin and "lightly" grounded ice sheet, i.e. at the threshold of floatation. The "lightly" grounded ice sheet scenario, applying to the late Pleistocene interval of the Disko Bay TMF, was

  8. 3D-seismic observations of Late Pleistocene glacial dynamics on the central West Greenland margin

    NASA Astrophysics Data System (ADS)

    Hofmann, Julia; Knutz, Paul; Cofaigh, Colm Ó.

    2016-04-01

    suggesting the transition between grounded ice and a glacimarine setting. The back-stepping scarps are suggestive of slide scars that were created as a result of mass movement induced by instabilities along the NW slope. The buried section contains morphologies indicating an asymmetric feature with a steeper side facing south. It comprises a thickness of c. 100 m and a length of c. 28 km. The detailed surface observations and seismic geometries suggest that the northern area represents a relict grounding-zone wedge (GZW). The wedge is covered by stratified deposits suggesting that it was at least occasionally submarine after its formation and may have served as pinning-point for floating ice shelves during periods of the Late TMF Stage. Important implications of the study are the intermittent development of floating ice shelves during the course of the Late Stage of TMF development and the presence of shelf-edge terminating grounded Late Weichselian ice outside of the troughs. Hofmann, J.C., Knutz, P.C., Nielsen, T., Kuijpers, A., submitted. Seismic architecture and evolution of the Disko Bay trough-mouth fan, central West Greenland margin. Quaternary Science Reviews.

  9. 10Be dating reveals early-middle Holocene age of the Drygalski Moraines in central West Greenland

    NASA Astrophysics Data System (ADS)

    Cronauer, Sandra L.; Briner, Jason P.; Kelley, Samuel E.; Zimmerman, Susan R. H.; Morlighem, Mathieu

    2016-09-01

    We reconstruct the history of the Greenland Ice Sheet margin on the Nuussuaq Peninsula in central West Greenland through the Holocene using lake sediment analysis and cosmogenic 10Be exposure dating of the prominent Drygalski Moraines. Erratics perched on bedrock outboard of the Drygalski Moraines constrain local deglaciation to ∼9.9 ± 0.6 ka (n = 2). Three Drygalski Moraine crests yield mean 10Be ages of 8.6 ± 0.4 ka (n = 2), 8.5 ± 0.2 ka (n = 3), and 7.6 ± 0.1 ka (n = 2) from outer to inner. Perched erratics between the inner two moraines average 7.8 ± 0.1 ka (n = 2) and are consistent with the moraine ages. Sediments from a proglacial lake with a catchment area extending an estimated 2 km beneath (inland of) the present ice sheet terminus constrain an ice sheet minimum extent from 5.4 ka to 0.6 ka. The moraine chronology paired with the lake sediment stratigraphy reveals that the ice margin likely remained within ∼2 km of its present position from ∼9.9 to 5.4 ka. This unexpected early Holocene stability, preceded by rapid ice retreat and followed by minimum ice extent between ∼5.4 and 0.6 ka, contrasts with many records of early Holocene warmth and the Northern Hemisphere summer insolation maximum. We suggest ice margin stability may instead be tied to adjacent ocean temperatures, which reached an optimum in the middle Holocene.

  10. Influence of habitat heterogeneity on distribution, occupancy patterns, and productivity of breeding peregrine falcons in central west Greenland

    USGS Publications Warehouse

    Wightman, C.; Fuller, Mark R.

    2006-01-01

    We used occupancy and productivity data collected at 67 cliffs used for nesting from 1972 to 1999 to assess patterns of distribution and nest-site selection in an increasing population of Peregrine Falcons (Falco peregrinus) in central West Greenland. Peregrine Falcons breeding at traditionally occupied cliffs used for nesting had significantly lower variation in productivity and thus these cliffs were better quality sites. This indicates that Peregrine Falcons occupied cliffs according to a pattern of despotic distribution. Falcons breeding at cliffs that were consistently occupied during the breeding season had higher average productivity and lower variation in productivity than falcons at inconsistently occupied cliffs, and thus consistent occupancy also was indicative of cliff quality. Features of high quality habitat included tall cliffs, greater change in elevation from the lowest point within 3 km of the cliff to the cliff top (elevation gain), and protection from weather on the eyrie ledge. Spacing of suitable and occupied cliffs also was an important feature, and the best cliffs generally were more isolated. Increased spacing was likely a mechanism for reducing intraspecific competition. Our results suggest that Peregrine Falcons use a resource defense strategy to compete for better quality habitats and may use spacing and physical features of a nest site to identify good quality breeding habitat.

  11. Influence of habitat heterogeneity on distribution, occupancy patterns, and productivity of breeding peregrine falcons in central West Greenland

    USGS Publications Warehouse

    Wightman, C.S.; Fuller, M.R.

    2006-01-01

    We used occupancy and productivity data collected at 67 cliffs used for nesting from 1972 to 1999 to assess patterns of distribution and nest-site selection in an increasing population of Peregrine Falcons (Falco peregrinus) in central West Greenland. Peregrine Falcons breeding at traditionally occupied cliffs used for nesting had significantly lower variation in productivity and thus these cliffs were better quality sites. This indicates that Peregrine Falcons occupied cliffs according to a pattern of despotic distribution. Falcons breeding at cliffs that were consistently occupied during the breeding season had higher average productivity and lower variation in productivity than falcons at inconsistently occupied cliffs, and thus consistent occupancy also was indicative of cliff quality. Features of high quality habitat included tall cliffs, greater change in elevation from the lowest point within 3 km of the cliff to the cliff top (elevation gain), and protection from weather on the eyrie ledge. Spacing of suitable and occupied cliffs also was an important feature, and the best cliffs generally were more isolated. Increased spacing was likely a mechanism for reducing intraspecific competition. Our results suggest that Peregrine Falcons use a resource defense strategy to compete for better quality habitats and may use spacing and physical features of a nest site to identify good quality breeding habitat. ?? The Cooper Ornithological Society 2006.

  12. Ice stream retreat following the LGM and onset of the west Greenland current in Uummannaq Trough, west Greenland

    NASA Astrophysics Data System (ADS)

    Sheldon, Christina; Jennings, Anne; Andrews, John T.; Ó Cofaigh, Colm; Hogan, Kelly; Dowdeswell, Julian A.; Seidenkrantz, Marit-Solveig

    2016-09-01

    The deglacial history and oceanography of Uummannaq Trough, central West Greenland continental shelf, was investigated using foraminiferal, sedimentological, and bathymetric records together with a radiocarbon chronology, providing a timeline for the retreat of glacial ice after the Last Glacial Maximum (LGM). To map ice stream retreat, data were collected from cores from the outer (JR175-VC45 and JR175-VC43) and inner (JR175-VC42) Uummannaq Trough. A large ice stream, fed by confluent glaciers draining the interior of the Greenland Ice Sheet, extended across the outer shelf during the LGM and was in retreat by 15.0 cal kyr BP. Foraminiferal data indicate that the 'warm' West Greenland Current (WGC) was established prior to 14.0 cal kyr BP, which is the hitherto earliest record of Atlantic Water found on the West Greenland shelf. For each of the cores, foraminifera indicate that ice sheet retreat was followed quickly by incursion of the WGC, suggesting that the warm water may have enhanced ice retreat. Prior to the Younger Dryas cold event, the radiocarbon chronology indicates that the ice sheet retreated to the mid-shelf, where it subsequently stabilised and formed a large grounding-zone wedge (GZW). After the Younger Dryas, around 11.5 cal kyr BP, the ice retreated rapidly from the GZW and into the fjords.

  13. The multifaceted West Greenland passive margin

    NASA Astrophysics Data System (ADS)

    Breuer, Sonja; Damm, Volkmar; Block, Martin; Schreckenberger, Bernd; Heyde, Ingo; Nelson, Catherine; Kouwe, Wim

    2013-04-01

    The Baffin Bay located between Greenland and Canada, is the northward extension of the Labrador Sea. The Davis Strait High separates these two marine basins. The evolution of these basins is closely linked, and is as well affiliated to the opening of the North Atlantic Ocean. The opening history started in the Cretaceous with the formation of several terrestrial rift basins with a block-faulted, metamorphic Precambrian basement. The further opening of the Baffin Bay coincides with the volcanic activity (60.9-52.5 Ma) along the West Greenland margin (Storey et al., 1998). The subsequent seafloor spreading in the Baffin Bay is linked to the Labrador Sea by the Ungava Fault Zone (UFZ), which is the most prominent transform fault in this region. Two main problems are still unsolved: 1) There are clear indications for normal seafloor spreading in the Baffin Bay like the seaward dipping reflectors (SDRs) on the Canadian side (Skaarup et al., 2006) and on the Greenland side based on our data. On the other hand, associated magnetic spreading anomalies are not yet discovered in the Baffin Bay or are not formed. These findings may either point to slow or ultraslow spreading or underlying strongly extended continental crust and/or serpentinised mantle. 2) The Greenlandic margin is much wider than the Canadian. In addition, a breakup unconformity can only be traced on the Greenland side and is not reported for the Canadian side. Which process causes this asymmetric margin and differences in shelf width? Is it a result of asymmetric spreading or connected to volcanic activity during breakup processes? In summer 2008, a marine geoscientific expedition (MSM09/03) was conducted with the research vessel "Maria S. Merian" in the Davis Strait and southern Baffin Bay. Approximately 1800 km of multichannel reflection seismic data were acquired. To supplement the database, a subsequent marine geoscientific expedition ARK-XXV/3 with RV POLARSTERN in summer 2010 was conducted. In our

  14. Buoyant Currents West and East of Greenland

    NASA Astrophysics Data System (ADS)

    Aksenov, Y.; Bacon, S.; Nurser, G.; Coward, A.

    2014-12-01

    Low salinity buoyant polar waters exit the Arctic Ocean into the Nordic Seas and the North Atlantic, affecting deep convection in the Nordic and Labrador Seas with potential impacts on the meridional overturning circulation. The pathways of the polar water in Davis Strait, Fram Strait and then to the south are well documented by observations and model simulations. In contrast, measurements upstream of Fram Strait are too sparse to allow us to explain what causes the outflows to exit either west or east of Greenland or to attribute the variability in the Arctic outflows to atmospheric or oceanic mechanisms. Two high-resolution global ocean general circulation models (OGCM), NEMO-ORCA025, of ~12 km resolution, and NEMO-ORCA12, of ~4 km resolution, have been used to examine the dynamics and seasonal variability of the outflow west and east of Greenland. Montgomery potential analysis is used to investigate the dynamics of the currents in the area. The model results suggest wind as a driving mechanism for the seasonal variability of the ocean circulation in the area.

  15. Crustal Structure in Central-Eastern Greenland

    NASA Astrophysics Data System (ADS)

    Shulgin, A.; Thybo, H.

    2013-12-01

    We present the seismic structure in the interior of Greenland based on the first measurements by the seismic refraction/wide angle reflection method. Previous seismic surveys have only been carried out offshore and near the coast of Greenland, where the crustal structure is affected by oceanic break-up and may not be representative of the interior of the island. Acquisition of geophysical data onshore Greenland is logistically complicated by the presence of an up to 3.4 km thick ice sheet, permanently covering most of the land mass. The seismic data was acquired by a team of six people during a two-month long experiment in summer of 2011 on the ice cap in the interior of central-eastern Greenland. The EW-trending profile extends 310 km inland from the approximate edge of the stable ice cap near Scoresby Sund across the centre of the ice cap. The planned extension of the profile by use of OBSs and air gun shooting in Scoresbysund Fjord to the east coast of Greenland was unfortunately cancelled, because navigation was prevented by ice drift. 350 Reftek Texan receivers recorded high-quality seismic data from 8 equidistant shots along the profile. Explosive charge sizes were 1 ton at the ends and ca. 500 kg along the profile, loaded with about 100 kg at 35-85 m depth in individual boreholes. Two-dimensional velocity model based on forward ray tracing and tomography modelling shows a decrease of crustal thickness from 47 km below the centre of Greenland in the western part to 40 km in the eastern part of the profile. Earlier studies show that crustal thickness further decreases eastward to ca. 30 km below the fjord system, but details of the changes are unknown. Relatively high lower crustal velocities (Vp 6.8 - 7.3) in the western part of the TopoGreenland profile may indicate past collision tectonics or may be related or to the passage of the Iceland mantle plume. The origin of the pronounced circum-Atlantic mountain ranges in Norway and eastern Greenland, which have

  16. West and Central Africa.

    PubMed

    Lydie, N; Robinson, N J

    1998-01-01

    This article reviews scientific and other literature during the 1990s that links migration and mobility with the spread of sexually transmitted diseases (STDs), including HIV/AIDS. The focus is on key population groups linked to the spread of HIV and STDs in West and Central Africa: migrant laborers, truck drivers, itinerant traders, commercial sex workers (CSWs), and refugees. Countries with high emigration and immigration tend to have high levels of HIV infection, with the exception of Senegal. The main destination of immigrants are Senegal, Nigeria, and Cote d'Ivoire in West Africa and Cameroon, Congo, Gabon, and Congo in Central Africa. The risk of infection and the spread of HIV is variable among migrants. There is little in the literature that substantiates hypotheses about the strong association between migration and HIV-positive status. Information is needed on the duration, frequency of return visits, living conditions, sexual activities with multiple partners, and information before departure, along the routes, at final destination, and at the time of returns. Action-based research in five West African countries (Burkina Faso, Cote d'Ivoire, Mali, Niger, and Senegal) should produce results in late 1998. Comparable studies in Central Africa are unknown. Regional studies should be complemented by local studies. Prevention would benefit from studies on the relative size of these five population groups by geographic location.

  17. Central Greenland Holocene Deuterium Excess Variability

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Jouzel, J.; Falourd, S.; Cattani, O.; Dahl-Jensen, D.; Johnsen, S.; Sveinbjornsdottir, A. E.; White, J. W. C.

    Water stable isotopes (oxygen 18 and deuterium) have been measured along the Holocene part of two deep ice cores from central Greenland, GRIP and North GRIP. Theoretical studies have shown that the second-order isotopic parameter, the deu- terium excess (d=dD-8d18O), is an indicator of climatic changes at the oceanic mois- ture source reflecting at least partly changes in sea-surface-temperature. The two deu- terium excess records from GRIP and North GRIP show a long term increasing trend already observed in Antarctic deep ice cores and related to changes in the Earth's obliquity during the Holocene : an decreased obliquity is associated with a larger low to high latitude annual mean insolation gradient, warmer tropics, colder poles, and a more intense atmospheric transport from the tropics to the poles, resulting in a higher moisture source temperature and higher deuterium excess values. Superimposed onto this long term trend, central Greenland deuterium excess records also exhibit small abrupt events (8.2 ka BP and 4.5 ka BP) and a high frequency variability.

  18. Force balance along Isunnguata Sermia, west Greenland

    NASA Astrophysics Data System (ADS)

    Meierbachtol, Toby; Harper, Joel; Johnson, Jesse

    2016-09-01

    Ice flows when gravity acts on gradients in surface elevation, producing driving stresses. In the Isunnguata Sermia and Russel Glacier catchments of western Greenland, a 50% decline in driving stress along a flow line is juxtaposed with increasing surface flow speed. Here, these circumstances are investigated using modern observational data sources and an analysis of the balance of forces. Stress gradients in the ice mass and basal drag which resist the local driving stress are computed in order to investigate the underlying processes influencing the velocity and stress regimes. Our results show that the largest resistive stress gradients along the flowline result from increasing surface velocity. However, the longitudinal coupling stresses fail to exceed 15 kPa, or 20% of the local driving stress. Consequently, computed basal drag declines in proportion to the driving stress. In the absence of significant resistive stress gradients, other mechanisms are therefore necessary to explain the observed velocity increase despite declining driving stress. In the study area, the observed velocity - driving stress feature occurs at the long-term mean position of the equilibrium line of surface mass balance. We hypothesize that this position approximates the inland limit where surface meltwater penetrates the bed, and that the increased surface velocity reflects enhanced basal motion associated with seasonal meltwater perturbations.

  19. Crustal structure of the West Greenland margin in North Baffin Bay

    NASA Astrophysics Data System (ADS)

    Damm, V.; Block, M.; Berglar, K.; Ehrhardt, A.; Heyde, I.; Schnabel, M.; Schreckenberger, B.; Altenbernd, T.; Suckro, S.

    2012-04-01

    The tectonic and geodynamic evolution of the Baffin Bay is interpreted to be closely associated with mantle dynamics and plume activity. The initial opening of the Baffin Bay coincides with the volcanic activity along the West Greenland margin between 60.7 and 59.4 Ma (Storey at al., 1998), attributed to the arrival of the Iceland plume beneath Greenland (Lawver and Müller, 1994, Larsen and Saunders, 1998). Rifting in the Baffin Bay is linked to oceanic spreading in the Labrador Sea, but there is no consensus about the nature of the underlying crust in central Baffin Bay. The geodynamic evolution of the Baffin Bay and plate tectonic reconstructions for Greenland relative to North America are still a matter of debate though they are of special importance in the circum-Arctic geodynamic framework. Due to lack of data the plate boundary between the North American plate and the Greenland plate is not well defined and the nature of the continent-ocean transition zone is widely unknown. Evidence indicating that the deep sea area of the Baffin Bay crust is oceanic has been provided by Keen and Barrett (1972) based on seismic refraction data. However, Reid and Jackson (1997) did not find evidence for layered oceanic crust and interpreted the deep part of Baffin Bay as serpentinized mantle material. They suggest that rifting was amagmatic and separation of passive continental margins was comparable to ultra-slow spreading ridges. Linear magnetic anomaly patterns in this region were not clearly identified. The position of the extinct spreading axis was defined by a northwest-trending linear gravity anomaly of central Baffin Bay (Chalmers and Pulvertaft, 2001). Spreading in the Baffin Bay took obviously place in Paleocene and Eocene times in two phases which may be distinguished by a reorientation of the directions of plate motion for Greenland starting about 55 Ma ago (Chalmers and Pulvertaft, 2001). It is not fully explained how a postulated major transform fault

  20. The diel cycle of water vapor in west Greenland

    NASA Astrophysics Data System (ADS)

    Kopec, B. G.; Lauder, A. M.; Posmentier, E. S.; Feng, X.

    2014-08-01

    We present a study of the dynamics of small-scale (~100 km) atmospheric circulation in west Greenland which is dominated by interactions of marine and continental air masses. Water vapor concentration and isotopic ratios measured continuously over a 25 day period in Kangerlussuaq, Greenland were used to monitor the convergence of easterly katabatic winds and westerly sea breezes that form a front between the dry, isotopically depleted, glacial air mass and the moist, isotopically enriched, marine air mass. During the latter 16 days of the measurement period, an interval with no large-scale synoptic interference, the inland penetration of the sea breeze controlled the largest day-to-day humidity and vapor isotopic variations. Kangerlussuaq experienced sea breezes in the afternoon on 9 days, consistent with the long-term average of such occurrences on 56% of days in July and August. The inland position of the sea breeze front is controlled by the katabatic wind strength, which is stronger during times of reduced cloud coverage and/or higher-pressure gradient between the coast and the Greenland ice sheet. The position and movement of the front will likely respond to changes in the general atmospheric circulation and regional radiation balance resulting from global warming, which will, in turn, impact the local hydrological cycle and ecosystem processes.

  1. Paleomagnetism and multi-model stereo photogrammetry of the West Greenland flood volcanic province

    NASA Astrophysics Data System (ADS)

    Riisager, J.; Riisager, P.; Pedersen, A. K.

    2002-12-01

    We present new paleomagnetic and multi-model photogrammetry data from the West Greenland part of the North Atlantic igneous province (NAIP). During fieldwork the paleomagnetic sampling sites were photographed from helicopter with stereoscopic overlap and in colour. The photographs have been set up for multi-model photogrammetry allowing three-dimensional lithological mapping, giving us important information for interpreting the paleomagnetic data in their stratigraphic context. Another advantage of the multi-model photogrammetry coverage is that individual lavas can be traced in three-dimensional space allowing very precise measurements of the attitude of strata (+/-0.5°) to be made for tectonic correction of the paleomagnetic data. The paleomagnetic study is based on a large collection of 586 oriented paleomagnetic drill cores collected from 81 lava flows. All sampled flows carry stable thermoremanent magnetization of reversed polarity. The earliest part of the volcanic sequence (i.e. Vaigat Fm.) is characterized by several consecutive flows recording statistically indistinguishable paleomagnetic field directions. The thickest Vaigat Fm. directional group consists of 37 lava flows (combined thickness 104 meter), which based on photogrammetry and XRF observations we interpret to represent a single flow field (i.e. one eruption consisting of several lavas erupted in a short period of time). If Paleocene paleosecular variation was similar to Holocene variations, the thick directional groups would form within 100 years implying an extreme volcanic activity at the onset of NAIP volcanism on West Greenland. Based on directional groups we obtain a new well-defined paleomagnetic pole for Greenland, which is statistically similar to a recently published NAIP pole from Faroe Islands (Riisager et al., 2002) rotated to Greenland. The corresponding paleolatitude of the central NAIP in Paleocene is ~20° south of the present latitude of the Iceland hotspot, indicating that the

  2. Vegetation phenology gradients along the west and east coasts of Greenland from 2001 to 2015.

    PubMed

    Karami, Mojtaba; Hansen, Birger Ulf; Westergaard-Nielsen, Andreas; Abermann, Jakob; Lund, Magnus; Schmidt, Niels Martin; Elberling, Bo

    2017-02-01

    The objective of this paper is to characterize the spatiotemporal variations of vegetation phenology along latitudinal and altitudinal gradients in Greenland, and to examine local and regional climatic drivers. Time-series from the Moderate Resolution Imaging Spectroradiometer (MODIS) were analyzed to obtain various phenological metrics for the period 2001-2015. MODIS-derived land surface temperatures were corrected for the sampling biases caused by cloud cover. Results indicate significant differences between West and East Greenland, in terms of both observed phenology during the study period, as well as the climatic response. The date of the start of season (SOS) was significantly earlier (24 days), length of season longer (25 days), and time-integrated NDVI higher in West Greenland. The sea ice concentration during May was found to have a significant effect on the date of the SOS only in West Greenland, with the strongest linkage detected in mid-western parts of Greenland.

  3. Levels and temporal trends of HCH isomers in ringed seals from West and East Greenland.

    PubMed

    Rigét, Frank; Vorkamp, Katrin; Dietz, Rune; Muir, Derek C G

    2008-08-01

    Levels and temporal trends of the hexachlorocyclohexane isomers alpha-, beta- and gamma-HCH were analysed in blubber of juvenile ringed seals from West Greenland (1994 to 2006) and juvenile and adult ringed seals from East Greenland (1986 to 2006). No significant differences in the concentration levels in the juvenile seals were found between East and West Greenland for any of the three isomers. alpha-HCH concentrations were not significantly different between juvenile and adult ringed seals from East Greenland, whereas beta- and gamma-HCH concentrations were significantly higher in adult ringed seals. alpha- and beta-HCH in Greenland ringed seals were approximately a factor two lower than in the Canadian Arctic, and alpha-HCH was a factor 2-3 higher than in ringed seals from an area east of Svalbard, Norway. Annual decreases in ringed seals from Greenland during the study periods were detected to be 9.1-11.7%, 1.4-3.9% and 6.0-6.4% for alpha-, beta- and gamma-HCH, respectively, being quite similar in both East and West Greenland. Similar levels and trends in East and West Greenland support the general understanding of the pathways of HCH isomers to and in the Arctic.

  4. Divergent parasite faunas in adjacent populations of West Greenland caribou: suggested natural and anthropogenic influences

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Gastrointestinal parasite diversity was characterized for two adjacent populations of west Greenland caribou (Rangifer tarandus groenlandicus) through examinations of abomasa and small intestines of adult and subadult females collected during late winter. Three trichostrongyline (Trichostrongylina: ...

  5. Anomalous subglacial heat flow in central Greenland induced by the Iceland plume.

    NASA Astrophysics Data System (ADS)

    Petrunin, Alexey G.; Rogozhina, Irina; Kaban, Mikhail K.; Vaughan, Alan P. M.; Steinberger, Bernhard; Johnson, Jesse; Koulakov, Ivan; Thomas, Maik

    2013-04-01

    3000 m of ice sheet thickness has ensured that central Greenland has kept it geothermal heat flow (GHF) distribution enigmatic. Some few direct ice temperature measurements from deep ice cores reveal a GHF of 50 to 60 mW/m² in the Summit region and this is noticeably above what would be expected for the underlying Early Proterozoic lithosphere. In addition, indirect estimates from zones of rapid basal melting suggest extreme anomalies 15 to 30 times continental background. Subglacial topography indicates caldera like topographic features in the zones hinting at possible volcanic activity in the past [1], and all of these observations combined hint at an anomalous lithospheric structure. Further supporting this comes from new high-resolution P-wave tomography, which shows a strong thermal anomaly in the lithosphere crossing Greenland from east to west [2]. Rock outcrops at the eastern and western end of this zone indicate significant former magmatic activity, older in the east and younger in the west. Additionally, plate modelling studies suggest that the Greenland plate passed over the mantle plume that is currently under Iceland from late Cretaceous to Neogene times, consistent with the evidence from age of magmatism. Evidence of rapid basal melt revealed by ice penetrating radar along the hypocentre of the putative plume track indicates that it continues to affect the Greenland continental geotherm today. We analyse plume-induced thermal disturbance of the present-day lithosphere and their effects on the central Greenland ice sheet by using a novel evolutionary model of the climate-ice-lithosphere-upper mantle system. Our results indicate that mantle plume-induced erosion of the lithosphere has occurred, explaining caldera-type volcanic structures, the GHF anomaly, and requiring dyke intrusion into the crust during the early Cenozoic. The residual thermo-mechanical effect of the mantle plume has raised deep-sourced heat flow by over 25 mW/m² since 60 Ma and

  6. Measurement campaign for wind power potential in west Greenland

    NASA Astrophysics Data System (ADS)

    Rønnow Jakobsen, Kasper

    2013-04-01

    Experiences and results from a wind resource exploring campaign 2003- in west Greenland. Like many other countries, Greenland is trying to reduce its dependency of fossil fuel by implementing renewable energy. The main challenge is that the people live on the coast in scattered settlements, without power infrastructure. Based on this a wind power potential project was established in 2002, funded by the Greenlandic government and the Technical University of Denmark. We present results and experiences of the campaign. 1 Field campaign There were only a few climate stations in or close to settlements and due to their positioning and instrumentation, they were not usable for wind resource estimation. To establish met stations in Arctic areas with complex topography, there are some challenges to face; mast positioning in complex terrain, severe weather conditions, instrumentation, data handling, installation and maintenance budget. The terrain in the ice free and populated part, mainly consists of mountains of different heights and shapes, separated by deep fjords going from the ice cap to the sea. With a generally low wind resource the focus was on the most exposed positions close to the settlements. Data from the nearest existing climate stations was studied for background estimations of predominant wind directions and extreme wind speeds, and based on that the first 10m masts were erected in 2003. 2 Instruments The first installations used standard NRG systems with low cost NRG instruments. For most of the sites this low cost setup did a good job, but there were some problems with the first design, including instrument and boom strains. In subsequent years, the systems were updated several times to be able to operate in the extreme conditions. Different types of instruments, data logger and boom systems were tested to get better data quality and reliability. Today 11 stations with heights ranging from 10-50m are installed and equipped according to the IEC standard

  7. Temporal trends of mercury in marine biota of west and northwest Greenland.

    PubMed

    Rigét, Frank; Dietz, Rune; Born, Erik W; Sonne, Christian; Hobson, Keith A

    2007-01-01

    Temporal trends in mercury concentrations ([Hg]) during the last two to three decades were determined in liver of shorthorn sculpin, ringed seal and Atlantic walrus from northwest Greenland (NWG, 77 degrees N) and in liver of shorthorn sculpin and ringed seal from central west Greenland (CWG, 69 degrees N) during the last decade. Stable-nitrogen (delta(15)N) and carbon (delta(13)C) isotope values were determined in muscle of ringed seals to provide insight into potential trophic level changes through time. Log-linear regressions on annual median [Hg] did not reveal any temporal trend in shorthorn sculpin from CWG and NWG and walrus from NWG. In ringed seals from NWG, an increase in [Hg] of 7.8% per year was observed. When based on delta(15)N-adjusted [Hg] this rate increased to 8.5% but was still non-significant. In ringed seal from CWG no trend was found in [Hg] during the period 1994-2004. However, during the last part of the period (1999-2004) the [Hg] increased significantly. Including tissue delta(15)N values as a covariate had a marked effect on these results. The annual changes in delta(15)N-adjusted [Hg] was estimated to -5.0% for the whole period and 2.2% during the last 5 years compared to -1.3% and 12.4%, respectively, for the non-adjusted [Hg].

  8. Surface and sub-surface multi-proxy reconstruction of middle to late Holocene palaeoceanographic changes in Disko Bugt, West Greenland

    NASA Astrophysics Data System (ADS)

    Moros, Matthias; Lloyd, Jeremy M.; Perner, Kerstin; Krawczyk, Diana; Blanz, Thomas; de Vernal, Anne; Ouellet-Bernier, Marie-Michele; Kuijpers, Antoon; Jennings, Anne E.; Witkowski, Andrzej; Schneider, Ralph; Jansen, Eystein

    2016-01-01

    We present new surface water proxy records of meltwater production (alkenone derived), relative sea surface temperature (diatom, alkenones) and sea ice (diatoms) changes from the Disko Bugt area off central West Greenland. We combine these new surface water reconstructions with published proxy records (benthic foraminifera - bottom water proxy; dinocyst assemblages - surface water proxy), along with atmospheric temperature from Greenland ice core and Greenland lake records. This multi-proxy approach allows us to reconstruct centennial scale middle to late Holocene palaeoenvironmental evolution of Disko Bugt and the Western Greenland coastal region with more detail than previously available. Combining surface and bottom water proxies identifies the coupling between ocean circulation (West Greenland Current conditions), the atmosphere and the Greenland Ice Sheet. Centennial to millennial scale changes in the wider North Atlantic region were accompanied by variations in the West Greenland Current (WGC). During periods of relatively warm WGC, increased surface air temperature over western Greenland led to ice sheet retreat and significant meltwater flux. In contrast, during periods of cold WGC, atmospheric cooling resulted in glacier advances. We also identify potential linkages between the palaeoceanography of the Disko Bugt region and key changes in the history of human occupation. Cooler oceanographic conditions at 3.5 ka BP support the view that the Saqqaq culture left Disko Bugt due to deteriorating climatic conditions. The cause of the disappearance of the Dorset culture is unclear, but the new data presented here indicate that it may be linked to a significant increase in meltwater flux, which caused cold and unstable coastal conditions at ca. 2 ka BP. The subsequent settlement of the Norse occurred at the same time as climatic amelioration during the Medieval Climate Anomaly and their disappearance may be related to harsher conditions at the beginning of the

  9. Crustal structure of the Central-Eastern Greenland: results from the TopoGreenland refraction profile

    NASA Astrophysics Data System (ADS)

    Shulgin, Alexey; Thybo, Hans

    2014-05-01

    Until present, seismic surveys have only been carried out offshore and near the coasts of Greenland, where the crustal structure is affected by oceanic break-up. We present the deep seismic structure of the crust of the interior of Greenland, based on the new and the only existing so far seismic refraction/wide-angle reflection profile. The seismic data was acquired by a team of six people during a two-month long experiment in summer of 2011 on the ice cap in the interior of central-eastern Greenland. The presence of an up to 3.4 km thick ice sheet, permanently covering most of the land mass, made acquisition of geophysical data logistically complicated. The profile extends 310 km inland in E-W direction from the approximate edge of the stable ice cap near the Scoresby Sund across the center of the ice cap. 350 Reftek Texan receivers recorded high-quality seismic data from 8 equidistant shots along the profile. Explosive charge sizes were 1 ton at the ends and ca. 500 kg along the profile, loaded with about 125 kg at 35-85 m depth in individual boreholes. Given that the data acquisition was affected by the thick ice sheet, we questioned the quality of seismic records in such experiment setup. We have developed an automatic routine to check the amplitudes and spectra of the selected seismic phases and to check the differences/challenges in making seismic experiments on ice and the effects of ice on data interpretation. Using tomographic inversion and forward ray tracing modelling we have obtained the two-dimensional velocity model down to a 50 km depth. The model shows a decrease of crustal thickness from 47 km below the centre of Greenland in the western part of the profile to 40 km in its eastern part. Relatively high lower crustal velocities (Vp 6.8 - 7.3 km/s) in the western part of the TopoGreenland profile may result from past collision tectonics or, alternatively, may be related to the speculated passage of the Iceland mantle plume. Comparison of our results

  10. Assessment of Undiscovered Oil and Gas Resources of the West Greenland-East Canada Province, 2008

    USGS Publications Warehouse

    Schenk, Christopher J.; Bird, Kenneth J.; Brown, Philip J.; Charpentier, Ronald R.; Gautier, Donald L.; Houseknecht, David W.; Klett, Timothy R.; Pawlewicz, Mark J.; Shah, Anjana; Tennyson, Marilyn E.

    2008-01-01

    The U.S. Geological Survey (USGS) recently assessed the undiscovered oil and gas potential of the West Greenland?East Canada Province as part of the USGS Circum-Arctic Oil and Gas Resource Appraisal effort. The West Greenland?East Canada Province is essentially the offshore area between west Greenland and east Canada and includes Baffin Bay, Davis Strait, Lancaster Sound, and Nares Strait west of and including Kane Basin. The tectonic evolution of the West Greenland?East Canada Province led to the formation of several major structural domains that are the geologic basis for the five assessment units (AU) defined in this study. The five AUs encompass the entire province. Each AU was assessed in its entirety for undiscovered, technically recoverable (assuming absence of sea ice) oil and gas resources, but the assessment results reported here are only for those portions of each AU that are north of the Arctic Circle, as that latitude defines the area of the Circum-Arctic oil and gas assessment.

  11. Observed runoff, jokulhlaups and suspended sediment load from the Greenland ice at Kangerlussuaq, West Greenland, 2007 and 2008

    SciTech Connect

    Mernild, Sebastian Haugard; Hasholt, Bent

    2009-01-01

    This study fills the gap in hydrologic measurements of runoff exiting a part of the Greenland Ice Sheet (GrIS), the Kangerlussuaq drainage area, West Greenland. The observations are of value for obtaining knowledge about the terrestrial freshwater and sediment output from part of the GrIS and the strip of land between the GrIS and the ocean, in the context of varying ice sheet surface melt and influx entering the ocean. High-resolution stage, discharge and suspended sediment load show a decrease in runoff of {approx} 25% and in sediment load of {approx} 40% from 2007 to 2008 in response to a decrease in the summer accumulated number of positive degree days. During the 2007 and 2008 runoff season, joekulhlaups are observed at Kangerlussuaq, drained from an ice-dammed lake at the margin of the GrIS.

  12. One million years of glaciation and denudation history in west Greenland

    NASA Astrophysics Data System (ADS)

    Strunk, Astrid; Knudsen, Mads Faurschou; Egholm, David L.; Jansen, John D.; Levy, Laura B.; Jacobsen, Bo H.; Larsen, Nicolaj K.

    2017-01-01

    The influence of major Quaternary climatic changes on growth and decay of the Greenland Ice Sheet, and associated erosional impact on the landscapes, is virtually unknown beyond the last deglaciation. Here we quantify exposure and denudation histories in west Greenland by applying a novel Markov-Chain Monte Carlo modelling approach to all available paired cosmogenic 10Be-26Al bedrock data from Greenland. We find that long-term denudation rates in west Greenland range from >50 m Myr-1 in low-lying areas to ~2 m Myr-1 at high elevations, hereby quantifying systematic variations in denudation rate among different glacial landforms caused by variations in ice thickness across the landscape. We furthermore show that the present day ice-free areas only were ice covered ca. 45% of the past 1 million years, and even less at high-elevation sites, implying that the Greenland Ice Sheet for much of the time was of similar size or even smaller than today.

  13. One million years of glaciation and denudation history in west Greenland

    PubMed Central

    Strunk, Astrid; Knudsen, Mads Faurschou; Egholm, David L.; Jansen, John D.; Levy, Laura B.; Jacobsen, Bo H.; Larsen, Nicolaj K.

    2017-01-01

    The influence of major Quaternary climatic changes on growth and decay of the Greenland Ice Sheet, and associated erosional impact on the landscapes, is virtually unknown beyond the last deglaciation. Here we quantify exposure and denudation histories in west Greenland by applying a novel Markov-Chain Monte Carlo modelling approach to all available paired cosmogenic 10Be-26Al bedrock data from Greenland. We find that long-term denudation rates in west Greenland range from >50 m Myr−1 in low-lying areas to ∼2 m Myr−1 at high elevations, hereby quantifying systematic variations in denudation rate among different glacial landforms caused by variations in ice thickness across the landscape. We furthermore show that the present day ice-free areas only were ice covered ca. 45% of the past 1 million years, and even less at high-elevation sites, implying that the Greenland Ice Sheet for much of the time was of similar size or even smaller than today. PMID:28098141

  14. Chapter 41: Geology and petroleum potential of the West Greenland-East Canada Province

    USGS Publications Warehouse

    Schenk, C.J.

    2011-01-01

    The US Geological Survey (USGS) assessed the potential for undiscovered oil and gas resources of the West Greenland-East Canada Province as part of the USGS Circum-Arctic Resource Appraisal programme. The province lies in the offshore area between western Greenland and eastern Canada and includes Baffin Bay, Davis Strait, Lancaster Sound and Nares Strait west of and including part of Kane Basin. A series of major tectonic events led to the formation of several distinct structural domains that are the geological basis for defining five assessment units (AU) in the province, all of which are within the Mesozoic-Cenozoic Composite Petroleum System. Potential petroleum source rocks include strata of Ordovician, Lower and Upper Cretaceous, and Palaeogene ages. The five AUs defined for this study - the Eurekan Structures AU, NW Greenland Rifted Margin AU, NE Canada Rifted Margin AU, Baffin Bay Basin AU and the Greater Ungava Fault Zone AU - encompass the entire province and were assessed for undiscovered technically recoverable resources. The mean volumes of undiscovered resources for the West Greenland-East Canada Province are 10.7 ?? 109 barrels of oil, 75 ?? 1012 cubic feet of gas, and 1.7 ?? 109 barrels of natural gas liquids. For the part of the province that is north of the Arctic Circle, the estimated mean volumes of these undiscovered resources are 7.3 ?? 109 barrels of oil, 52 ?? 1012 cubic feet of natural gas, and 1.1 ?? 109 barrels of natural gas liquids. ?? 2011 The Geological Society of London.

  15. Abrupt Holocene climate change as an important factor for human migration in West Greenland.

    PubMed

    D'Andrea, William J; Huang, Yongsong; Fritz, Sherilyn C; Anderson, N John

    2011-06-14

    West Greenland has had multiple episodes of human colonization and cultural transitions over the past 4,500 y. However, the explanations for these large-scale human migrations are varied, including climatic factors, resistance to adaptation, economic marginalization, mercantile exploration, and hostile neighborhood interactions. Evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of Holocene temperature derived from ice cores atop the Greenland ice sheet. Here we present high-resolution records of temperature over the past 5,600 y based on alkenone unsaturation in sediments of two lakes in West Greenland. We find that major temperature changes in the past 4,500 y occurred abruptly (within decades), and were coeval in timing with the archaeological records of settlement and abandonment of the Saqqaq, Dorset, and Norse cultures, which suggests that abrupt temperature changes profoundly impacted human civilization in the region. Temperature variations in West Greenland display an antiphased relationship to temperature changes in Ireland over centennial to millennial timescales, resembling the interannual to multidecadal temperature seesaw associated with the North Atlantic Oscillation.

  16. New insights into West Greenland ice sheet/stream dynamics during the last glacial cycle.

    NASA Astrophysics Data System (ADS)

    Roberts, David; Lane, Tim; Rea, Brice; Cofaigh, Colm O.; Jamieson, Stewart; Vieli, Andreas; Rodes, Angel

    2015-04-01

    Onshore and offshore geomorphological mapping and deglacial chronologies from West Greenland constrain the nature and magnitude of ice advance and decay of the Greenland Ice Sheet (GrIS) during the last glacial cycle. Several ice stream troughs are known to have fed ice to the shelf edge during the last glacial cycle. Their offshore expression suggests that many were coalescent systems fed by smaller outlet glaciers and ice streams onshore but their central flow pathways were also controlled by geology and preglacial topography. The bed morphology of these large ice streams shows they operated over soft, deforming beds with drumlins, mega-scale glacial lineations and grounding zone wedges marking an offshore transition from predominant areal scour onshore. Records of offshore deglacial chronology remain sparse but the Uummannaq and Disko Bugt ice stream corridors are now well constrained. The Uummannaq ice stream (UIS) completely deglaciated from the continental shelf between 14.8 ka and 11.0 ka in response to rising air temperatures, increasing JJA solar radiation and sea-level rise, but temporary standstills and the asynchronous retreat history of its feeder zones suggest that topography/bathymetry strongly modulated retreat rates as ice became 'locked' back into the coastal fjord system. Initial reconstructions of behaviour UIS discounted an oceanic role in early deglaciation and favoured retreat from the mid-shelf and inner-shelf prior to the Younger Dryas but both these concepts remain under investigation. In Disko Bugt, Jakobshavn Isbrae deglaciated later than the UIS and remained on the outer shelf during the Younger Dyras stadial (12.8 - 11.7 cal. kyrs BP) only reaching in the inner coast fjords at approximately 10.0 ka. The later deglaciation of the Disko system (despite similar external forcing mechanisms) was controlled by regional topographic/bathymetric contrasts in their respective trough morphologies. This hypothesis is supported by recent model

  17. Deglaciation of a major palaeo-ice stream in Disko Trough, West Greenland

    NASA Astrophysics Data System (ADS)

    Hogan, Kelly A.; Ó Cofaigh, Colm; Jennings, Anne E.; Dowdeswell, Julian A.; Hiemstra, John F.

    2016-09-01

    Recent work has confirmed that grounded ice reached the shelf break in central West Greenland during the Last Glacial Maximum (LGM). Here we use a combination of marine sediment-core data, including glacimarine lithofacies and IRD proxy records, and geomorphological and acoustic facies evidence to examine the nature of and controls on the retreat of a major outlet of the western sector of the Greenland Ice Sheet (GrIS) across the shelf. Retreat of this outlet, which contained the ancestral Jakobshavns Isbræ ice stream, from the outer shelf in Disko Trough was rapid and progressed predominantly through iceberg calving, however, minor pauses in retreat (tens of years) occurred on the middle shelf at a trough narrowing forming subtle grounding-zone wedges. By 12.1 cal kyr BP ice had retreated to a basalt escarpment and shallow banks on the inner continental shelf, where it was pinned and stabilised for at least 100 years. During this time the ice margin appears to have formed a calving bay over the trough and melting became an important mechanism of ice-mass loss. Fine-grained sediments (muds) were deposited alternately with IRD-rich sediments (diamictons) forming a characteristic deglacial lithofacies that may be related to seasonal climatic cycles. High influxes of subglacial meltwater, emanating from the nearby ice margins, deposited muddy sediments during the warmer summer months whereas winters were dominated by iceberg calving leading to the deposition of the diamictons. This is the first example of this glacimarine lithofacies from a continental-shelf setting and we suggest that the calving-bay configuration of the ice margin, plus the switching between calving and melting as ablation mechanisms, facilitated its deposition by channelling meltwater and icebergs through the inner trough. The occurrence of a major stillstand on the inner shelf in Disko Trough demonstrates that the ice-dynamical response to local topography was a crucial control on the behaviour

  18. Outbreak of trichinellosis associated with consumption of game meat in West Greenland.

    PubMed

    Møller, Lone Nukâraq; Petersen, Eskild; Kapel, Christian M O; Melbye, Mads; Koch, Anders

    2005-09-05

    The Inuit population of the Arctic has always been at risk of acquiring trichinellosis and severe outbreaks have been recorded in Alaska and Canada. In West Greenland, a number of large outbreaks took place during the 1940s and 1950s; they involved total 420 cases including 37 deaths. Since then only sporadic cases have been reported. Here, we describe an outbreak of infection with Trichinella spp. after consumption of infected meat presumably from walrus or polar bear caught in western Greenland. Six persons who had eaten of the walrus and polar bear meat were two males and four females, age range 6--47 years. Using ELISA and Western blot analysis (Trichinella-specific IgG antibodies against excreted/secreted antigen and synthetic tyvelose antigen, respectively) four of these persons were found to be sero-positive for Trichinella antibodies, with three of these having clinical symptoms compatible with trichinellosis. On re-test, 12--14 months later one of the two sero-negative persons had sero-converted, probably due to a new, unrelated infection. This study demonstrates that acquiring Trichinella from the consumption of marine mammals remains a possibility in Greenland, and that cases may go undetected. Trichinellosis in Greenland can be prevented by the implementation of public health measures.

  19. Mapping and classifying the seabed of the West Greenland continental shelf

    NASA Astrophysics Data System (ADS)

    Gougeon, S.; Kemp, K. M.; Blicher, M. E.; Yesson, C.

    2017-03-01

    Marine benthic habitats support a diversity of marine organisms that are both economically and intrinsically valuable. Our knowledge of the distribution of these habitats is largely incomplete, particularly in deeper water and at higher latitudes. The western continental shelf of Greenland is one example of a deep (more than 500 m) Arctic region with limited information available. This study uses an adaptation of the EUNIS seabed classification scheme to document benthic habitats in the region of the West Greenland shrimp trawl fishery from 60°N to 72°N in depths of 61-725 m. More than 2000 images collected at 224 stations between 2011 and 2015 were grouped into 7 habitat classes. A classification model was developed using environmental proxies to make habitat predictions for the entire western shelf (200-700 m below 72°N). The spatial distribution of habitats correlates with temperature and latitude. Muddy sediments appear in northern and colder areas whereas sandy and rocky areas dominate in the south. Southern regions are also warmer and have stronger currents. The Mud habitat is the most widespread, covering around a third of the study area. There is a general pattern that deep channels and basins are dominated by muddy sediments, many of which are fed by glacial sedimentation and outlets from fjords, while shallow banks and shelf have a mix of more complex habitats. This first habitat classification map of the West Greenland shelf will be a useful tool for researchers, management and conservationists.

  20. Geologic Assessment of Undiscovered Oil and Gas Resources of the West Greenland-East Canada Province

    USGS Publications Warehouse

    Schenk, Christopher J.

    2010-01-01

    The U.S. Geological Survey (USGS) recently assessed the potential for undiscovered oil and gas resources of the West Greenland-East Canada Province as part of the USGS Circum-Arctic Resource Appraisal program. The province lies in the offshore area between western Greenland and eastern Canada and includes Baffin Bay, Davis Strait, Lancaster Sound, and Nares Strait west of and including part of Kane Basin. A series of major tectonic events led to the formation of several distinct structural domains that are the geologic basis for defining five assessment units (AU) in the province, all of which are within the Mesozoic-Cenozoic Composite Total Petroleum System (TPS). Potential petroleum source rocks within the TPS include strata of Ordovician, Early and Late Cretaceous, and Paleogene ages. The five AUs defined for this study-the Eurekan Structures AU, Northwest Greenland Rifted Margin AU, Northeast Canada Rifted Margin AU, Baffin Bay Basin AU, and the Greater Ungava Fault Zone AU-encompass the entire province and were assessed for undiscovered, technically recoverable resources.

  1. Runoff simulations from the Greenland ice sheet at Kangerlussuaq from 2006-2007 to 2007/08. West Greenland

    SciTech Connect

    Mernild, Sebastian Haugard; Hasholt, Bent; Van Den Broeke, Michiel; Liston, Glen

    2009-01-01

    This study focuses on runoff from a large sector of the Greenland Ice Sheet (GrIS) - the Kangerlussuaq drainage area, West Greenland - for the runoff observation period 2006/07 to 2007/08. SnowModel, a state-of-the-art snow-evolution modeling system, was used to simulate winter accumulation and summer ablation processes, including runoff. Independent in situ end-of-winter snow depth and high-resolution runoff observations were used for validation of simulated accumulation and ablation processes. Runoff was modeled on both daily and hourly time steps, filling a data gap of runoff exiting part of the GrIS. Using hourly meteorological driving data instead of smoothed daily-averaged data produced more realistic meteorological conditions in relation to snow and melt threshold surface processes, and produced 6-17% higher annual cumulative runoff. The simulated runoff series yielded useful insights into the present conditions of inter-seasonal and inter-annual variability of Kangerlussuaq runoff, and provided an acceptable degree of agreement between simulated and observed runoff. The simulated spatial runoff distributions, in some areas of the GrIS terminus, were as high as 2,750 mm w.eq. of runoff for 2006/07, while only 900 mm w.eq was simulated for 2007/08. The simulated total runoff from Kangerlussuaq was 1.9 km{sup 3} for 2006/07 and 1.2 km{sup 3} for 2007/08, indicating a reduction of 35-40% caused by the climate conditions and changes in the GrIS freshwater storage. The reduction in runoff from 2006/07 to 2007/08 occurred simultaneously with the reduction in the overall pattern of satellite-derived GrIS surface melt from 2007 to 2008.

  2. Alkenone and Isotopic Records of Holocene Climatic and Environmental Change From Laminated West Greenland Lakes

    NASA Astrophysics Data System (ADS)

    D'Andrea, W. J.; Huang, Y.

    2004-12-01

    Long chain alkenones (LCAs) are a key class of biomarkers for paleotemperature reconstructions. These compounds are ubiquitous in ocean sediments, but rare in lake sediments. Here we report the first discovery of LCAs in a downcore profile and surface sediments of five Greenland lakes. The concentrations of LCAs in surface sediments of these lakes are one to two orders of magnitude higher than those reported previously in other lake surface sediments around the world. Alkenones are present in five Greenland lakes with elevated salinity, but absent from five freshwater lakes. The alkenones have exceptionally low \\delta13C values ranging from -40 to -43\\permil, and are depleted by 10 to 15\\permil relative to short-chain fatty acids and sterols within the same samples. These \\delta13C values are the lowest ever reported for alkenones in a natural setting and have important implications for tracing the alkenone producers in lakes. Using the published calibration for lake sediments, the alkenone unsaturation indices in the surface sediments of the Greenland lakes record late spring/early summer temperature when algal blooms occur, suggesting the applicability of lacustrine alkenones as a paleotemperature proxy. LCA unsaturation indices and \\deltaD from sediment cores taken from these Greenland lakes will help elucidate the environmental controls on these sedimentary parameters, and will aid the reconstruction of Holocene climate variability in West Greenland. Ongoing work on the saline lakes includes determining high resolution alkenone unsaturation ratios/abundances and bulk/compound-specific isotopic values from sediment cores, algal culturing, and establishing microbial community structure in the saline lakes using DNA/RNA fingerprinting. Up-to-date results will be presented in the meeting.

  3. Surface exposure dating of Little Ice Age ice cap advances on Disko Island, West Greenland

    NASA Astrophysics Data System (ADS)

    Lane, Timothy; Jomelli, Vincent; Rinterknecht, Vincent; Brunstein, Daniel; Schimmelpfennig, Irene; Swingedouw, Didier; Favier, Vincent; Masson-Delmotte, Valerie

    2015-04-01

    Little Ice Age (LIA: 1200-1920 AD) glacier advances in Greenland often form the most extensive positions of Greenland Ice Sheet (GrIS) ice cap and margins since the Early Holocene. Across Greenland these advances are commonly represented by un-vegetated moraines, usually within 1-5 km of the present ice margin. However, chronological constraints on glacier advances during this period are sparse, meaning that GrIS and ice cap behavior and advance/retreat chronology remains poorly understood during this period. At present the majority of ages are based on historical accounts, ice core data, and radiocarbon ages from proglacial threshold lakes. However, developments in the accuracy and precision of surface exposure methods allow dating of LIA moraine boulders, permitting an opportunity to better understand of ice dynamics during this period. Geomorphological mapping and surface exposure dating (36Cl) were used to interpret moraine deposits from the Lyngmarksbræen on Disko Island, West Greenland. A Positive Degree Day (PDD) model was used to estimate Equilibrium Line Altitude (ELA) and mass balance changes for two distinct paleo-glacial extents. Three moraines (M1, M2, and M3) were mapped in the field, and sampled for 36Cl surface exposure dating. The outermost moraine (M1) was of clearly different morphology to the inner moraines, and present only in small fragments. M2 and M3 were distinct arcuate termino-lateral moraines within 50 m of one another, 1.5 km from the present ice margin. The weighted average of four 36Cl ages from M1 returned an early Holocene age of 8.4 ± 0.6 ka. M2 (four samples) returned an age of 0.57 ± 0.04 ka (1441 AD) and M3 (four samples) returned an age of 0.28 ± 0.02 ka (1732 AD). These surface exposure ages represent the first robustly dated Greenlandic ice cap moraine sequence from the LIA. The two periods of ice cap advance and marginal stabilisation are similar to recorded periods of LIA GrIS advance in west Greenland, constrained

  4. Simulating Ice-Flow and Calving on Store Glacier, West Greenland, with a 3D Full Stokes Model

    NASA Astrophysics Data System (ADS)

    Todd, J.; Christoffersen, P.; Zwinger, T.; Luckman, A. J.; Benn, D.

    2015-12-01

    The mass balance and long-term stability of the ice sheets in Greenland and Antarctica depend heavily on the dynamics of their ice-ocean margins. Iceberg calving accounts for the majority of the net annual loss of ice in Antarctica and around half of that from Greenland. Furthermore, climate driven changes to dynamics at these calving margins can be transmitted far inland. Thus, predicting future sea level contribution from the cryosphere requires an improved understanding of calving, and the processes which link it to climate and ice-sheet flow. We present results from a new 3D calving model coupled to a full-Stokes, time evolving glacier dynamic model, implemented for Store Glacier, a 5-km-wide calving glacier in the Uummannaq region of West Greenland, which flows at a rate of 20 m/day at its terminus. The model is developed using the open source finite element package Elmer/Ice, with the criterion that calving occurs when surface and basal crevasses meet. Crevasses open in response to tensile stresses near the terminus and water pressure at the bed. When the model was applied in 2D for the central flowline of Store Glacier, we found that basal topography exerts overarching control on the long term position of the calving front, while ice mélange buttressing allows the seasonal extension of a floating tongue, which collapses in early summer. New results emerging from implementation of calving in a 3D model indicate significant spatial heterogeneity in calving dynamics because the northern half of the terminus is grounded whereas the southern half is floating. This contrasting setting affects calving dynamics, further underlining the importance of geometry and basal topography, and suggesting that lower dimensional calving models may miss important aspects of calving dynamics. Our results also suggest that implementing grounding line dynamics is important for modelling calving, even for glaciers which are, for the most part, firmly grounded.

  5. Identifying potential seasonal and historical drivers of marine-terminating glacier retreat in Disko and Uummannaq Bays, West Greenland

    NASA Astrophysics Data System (ADS)

    York, A.; Frey, K. E.; Das, S. B.

    2015-12-01

    The variability in outlet glacier termini positions is an important indicator of overall glacier health and the net effects of ice-ocean-atmosphere interactions. Glacier margins fluctuate on both seasonal and interannual time scales and satellite imagery provides a critical spatially- and temporally-extensive resource for monitoring glacier behavior. Outlet glaciers have generally been retreating globally over recent decades, but the magnitude of seasonal variation, overall retreat, and foremost drivers have proven unique to each glacier. The outlet glaciers in central West Greenland are generally experiencing the same regional atmospheric forcing, yet previous studies have shown varying magnitudes of retreat over the last forty years. In this study, we utilize Landsat imagery between the years 1985 and 2014 to digitize a time series of glacier front positions of 18 marine-terminating outlet glaciers in the Disko and Uummannaq Bay regions of West Greenland. We examine potential drivers of trends in outlet glacier retreat through satellite observations of adjacent sea ice concentrations and sea surface temperatures. Additionally, reanalysis data and long-term automatic weather station measurements are investigated to contextualize the role of atmospheric drivers at both a regional and local scale. Results indicate retreat of all glaciers in the region over the study period and no indication of a south to north trend in magnitude of retreat on either a seasonal or long-term scale. The 11 glaciers in Uummannaq Bay retreated between 25 m and 3.5 km, an average of 1.22 ± 1.20 km over the entire study period. The retreat of 7 glaciers in Disko Bay ranged from 181 m to 2.3 km, an average of 1.0 ± 0.78 km over the period. Although the mean terminus retreat rate between the two bays is comparable, there remains a wide range of total retreat amounts among the glaciers. We investigate the degree of seasonal variation in terminus position as an indicator of longer

  6. Sm-Nd age of the Fiskenaesset Anorthosite Complex, West Greenland

    NASA Technical Reports Server (NTRS)

    Ashwal, Lewis D.; Goldstein, Steven J.; Jacobsen, Stein B.; Myers, John S.; Kalsbeek, Feiko

    1989-01-01

    A Sm-Nd isotopic study on samples from the Fiskenaesset Anorthosite Complex in West Greenland was conducted to estimate the age of crystallization of the complex. A five-point isochron, including data for whole-rock samples of anorthosite, metagabbro, metaperidotite, and separates of calcic plagioclase and mafic matrix from a coarse megacrystic leucogabbro, corresponds to an age of 2.86 + or - 0.05 Ga, with initial sigma(Nd) of +2.9 + or - 0.4. This implies a relatively short time interval, on the order of 70 Ma, during which anorthosite formation, tonalite emplacement, and high-grade metamorphism took place.

  7. Study of subaqueous melting of Store Glacier, West Greenland using ocean observations and numerical simulations

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Rignot, E. J.; Menemenlis, D.; van den Broeke, M. R.

    2012-12-01

    Ice discharge from the Greenland Ice Sheet is mainly through tidewater glaciers that terminate in the ocean and melt in contact with ocean waters. Subaqueous melting at the calving front is a direct mechanism for mass loss and a potential trigger for glacier acceleration. We present an analysis of oceanographic data collected in the fjord of Store Glacier, West Greenland during August 2010 and 2012. Using these data, we calculate the subaqueous melt rates. Independently, we employ the Massachusetts Institute of Technology general circulation model (MITgcm), modified to include melting at the calving front and outflow of subglacial water to model the ice melt rates of Store Glacier. Previous 2-D sensitivity studies showed that the subaqueous melt rate reaches several meters per day during the summer, increases non-linearly with subglacial runoff and linearly with ocean thermal forcing, and ceases when subglacial discharge is off during winter. We present new 3-D simulations at very high resolution, with measured oceanic temperature/salinity as boundary conditions, and subglacial runoff from the University of Utrecht's Regional Atmospheric Climate Model outputs on different years and seasons. We compare the ocean observations and numerical simulations and discuss the seasonal and inter-annual variations of subaqueous melting. This study helps evaluate the impact of the ocean on the subaqueous melting of Greenland tidewater glaciers and in turn on glacier mass balance. This work was carried out at University of California, Irvine and at the Jet Propulsion Laboratory under contract with NASA Cryosphere Science Program.

  8. Monitoring South-West Greenland's ice sheet melt with ambient seismic noise

    NASA Astrophysics Data System (ADS)

    Mordret, Aurélien; Mikesell, Dylan; Harig, Christopher; Lipovsky, Brad; Prieto, German

    2016-04-01

    The Greenland ice sheet (GIS) accounts for ~ 70% of global ice sheet mass loss and contributes to sea level rise at a rate of 0.7 mm/yr. Therefore, the GIS needs to be carefully monitored. The spaceborne techniques commonly used to monitor the GIS mass balance contain inherent uncertainties. These uncertainties can be reduced by comparing independent datasets and techniques. However, spaceborne methods remain inadequate in the sense that they offer low spatial and/or temporal resolution. This fact highlights the need for other complementary methods to monitor the GIS more accurately and with greater resolution. Here we use a seismic method: the correlation of seismic noise recorded at South-West Greenland seismic stations to show that the GIS seasonal melt produces significant variations of seismic wave speed in the Greenland crust. The amplitudes of the measured velocity variations during 2012-2013 correlate with the total ice plus atmospheric mass variations measured by the GRACE (Gravity Recovery and Climate Experiment) satellite mission. We explain the phase delay between mass maxima and velocity minima ( 50 days) using a non-linear poroelastic model that includes a 55 cm-thick layer of till between the ice sheet and the bedrock. We, thus, interpret the velocity variations as pore pressure variations in the bedrock resulting from the loading and unloading of the overlying glacier and atmosphere. This method provides a new and independent way to monitor in near real-time the first-order state of the GIS, giving new constraints on its evolution and its contribution to the global sea level rise. By increasing the density of seismic stations in the region it will be possible to increase the spatial and temporal resolution of the method and create detailed maps of ice-mass variations across Greenland.

  9. Monitoring South-West Greenland's ice sheet melt with ambient seismic noise

    NASA Astrophysics Data System (ADS)

    Mordret, A.; Mikesell, T. D.; Harig, C.; Lipovsky, B.; Prieto, G. A.

    2015-12-01

    The Greenland ice sheet (GIS) accounts for ~ 70% of global ice sheet mass loss and contributes to sea level rise at a rate of 0.7 mm/yr. Therefore, the GIS needs to be carefully monitored. The spaceborne techniques commonly used to monitor the GIS mass balance contain inherent uncertainties. These uncertainties can be reduced by comparing independent datasets and techniques. However, spaceborne methods remain inadequate in the sense that they offer low spatial and/or temporal resolution. This fact highlights the need for other complimentary methods to monitor the GIS more accurately and with greater resolution. Here we use a seismic method: the correlation of seismic noise recorded at South-West Greenland seismic stations to show that the GIS seasonal melt produces significant variations of seismic wave speed in the Greenland crust. The amplitudes of the measured velocity variations during 2012-2013 correlate with the total ice plus atmospheric mass variations measured by the GRACE (Gravity Recovery and Climate Experiment) satellite mission. We explain the phase delay between mass maxima and velocity minima ( 50 days) using a non-linear poroelastic model that includes a 55 cm-thick layer of till between the ice sheet and the bedrock. We, thus, interpret the velocity variations as pore pressure variations in the bedrock resulting from the loading and unloading of the overlying glacier and atmosphere. This method provides a new and independent way to monitor in near real-time the first-order state of the GIS, giving new constraints on its evolution and its contribution to the global sea level rise. By increasing the density of seismic stations in the region it will be possible to increase the spatial and temporal resolution of the method and create detailed maps of ice-mass variations across Greenland.

  10. Cenozoic uplift on the West Greenland margin: active sedimentary basins in quiet Archean terranes.

    NASA Astrophysics Data System (ADS)

    Jess, Scott; Stephenson, Randell; Brown, Roderick

    2016-04-01

    The North Atlantic is believed by some authors to have experienced tectonically induced uplift within the Cenozoic. Examination of evidence, onshore and offshore, has been interpreted to imply the presence of kilometre scale uplift across the margins of the Barents Sea, North Sea, Baffin Bay and Greenland Sea. Development of topography on the West Greenland margin (Baffin Bay), in particular, has been subject to much discussion and dispute. A series of low temperature thermochronological (AFT and AHe) studies onshore and interpretation of seismic architecture offshore have suggested uplift of the entire margin totalling ~3km. However, challenges to this work and recent analysis on the opposing margin (Baffin Island) have raised questions about the validity of this interpretation. The present work reviews and remodels the thermochronological data from onshore West Greenland with the aim of re-evaluating our understanding of the margin's history. New concepts within the discipline, such as effect of radiation damage on Helium diffusivity, contemporary modelling approaches and denudational mapping are all utilised to investigate alternative interpretations to this margins complex post rift evolution. In contrast to earlier studies our new approach indicates slow protracted cooling across much of the region; however, reworked sedimentary samples taken from the Cretaceous Nuussuaq Basin display periods of rapid reheating and cooling. These new models suggest the Nuussuaq Basin experienced a tectonically active Cenozoic, while the surrounding Archean basement remained quiet. Faults located within the basin appear to have been reactivated during the Palaeocene and Eocene, a period of well-documented inversion events throughout the North Atlantic, and may have resulted in subaerial kilometre scale uplift. This interpretation of the margin's evolution has wider implications for the treatment of low temperature thermochronological data and the geological history of the North

  11. Links between central Greenland stable isotopes, blocking and extreme climate variability over Europe at decadal to multidecadal time scales

    NASA Astrophysics Data System (ADS)

    Rimbu, N.; Lohmann, G.; Werner, M.; Ionita, M.

    2016-10-01

    The link between central Greenland stable oxygen isotopes, atmospheric blocking frequency and cold temperature extremes at decadal to multidecadal time scales is investigated using observed and proxy data as well as model experiments. A composite analysis reveals that positive stable isotope anomalies in central Greenland are associated with enhanced blocking activity in the Atlantic European region. Several indices of blocking activity in the Atlantic European region are higher correlated with central Greenland stable isotope time series than with the North Atlantic Oscillation indices both in observations and model simulation. Furthermore, the blocking frequency anomaly pattern associated with central Greenland stable isotope variability is similar to the blocking anomaly pattern associated with the Atlantic Multidecadal Oscillation. A composite analysis reveals that stable isotope variations in central Greenland are related to a large-scale pattern in the frequency of extreme low temperature events with significant positive anomalies over Europe and a southwest to northeast dipolar pattern over Asia. During observational period central Greenland isotope records, blocking and extreme temperature indices over Europe show enhanced variability 10-30 and 50-70 years. Similar quasi-periodicities dominate the spectrum of central Greenland isotope variability during the last millennium. We argue that long-term variations of climate extreme indices over Europe and Asia, as derived from observational data, can be put into a long-term perspective using central Greenland stable isotope ice core records.

  12. Helicopter-based Photography for use in SfM over the West Greenland Ablation Zone

    NASA Astrophysics Data System (ADS)

    Mote, T. L.; Tedesco, M.; Astuti, I.; Cotten, D.; Jordan, T.; Rennermalm, A. K.

    2015-12-01

    Results of low-elevation high-resolution aerial photography from a helicopter are reported for a supraglacial watershed in West Greenland. Data were collected at the end of July 2015 over a supraglacial watershed terminating in the Kangerlussuaq region of Greenland and following the Utrecht University K-Transect of meteorological stations. The aerial photography reported here were complementary observations used to support hyperspectral measurements of albedo, discussed in the Greenland Ice sheet hydrology session of this AGU Fall meeting. A compact digital camera was installed inside a pod mounted on the side of the helicopter together with gyroscopes and accelerometers that were used to estimate the relative orientation. Continuous video was collected on 19 and 21 July flights, and frames extracted from the videos are used to create a series of aerial photos. Individual geo-located aerial photos were also taken on a 24 July flight. We demonstrate that by maintaining a constant flight elevation and a near constant ground speed, a helicopter with a mounted camera can produce 3-D structure of the ablation zone of the ice sheet at unprecedented spatial resolution of the order of 5 - 10 cm. By setting the intervalometer on the camera to 2 seconds, the images obtained provide sufficient overlap (>60%) for digital image alignment, even at a flight elevation of ~170m. As a result, very accurate point matching between photographs can be achieved and an extremely dense RGB encoded point cloud can be extracted. Overlapping images provide a series of stereopairs that can be used to create point cloud data consisting of 3 position and 3 color variables, X, Y, Z, R, G, and B. This point cloud is then used to create orthophotos or large scale digital elevation models, thus accurately displaying ice structure. The geo-referenced images provide a ground spatial resolution of approximately 6 cm, permitting analysis of detailed features, such as cryoconite holes, evolving small

  13. Use of Glacial Fronts by Narwhals (Monodon monoceros) in West Greenland

    NASA Astrophysics Data System (ADS)

    Laidre, K. L.

    2015-12-01

    Glacial fronts in Greenland are known to be important summer habitat for narwhals (Monodon monoceros), as freshwater runoff and sediment discharge may aggregate prey at the terminus. We investigated the importance of glacial habitat characteristics in determining narwhal visitation. Narwhals (n=18) were instrumented with satellite transmitters in September 1993-1994 and 2006-2007 in Melville Bay, West Greenland. Daily narwhal locations were interpolated using a correlated random walk based on observed filtered locations and associated positional error. We also compiled a database on physical features of 41 glaciers along the northwest Greenland coast. This covered the entire coastal region with narwhal activity. Parameters included glacier ice velocity (km/yr) from radar satellite data, glacier front advance and retreat, and glacier width (km) at the ice-ocean interface derived using front position data digitized from 20-100m resolution radar image mosaics and Landsat imagery. We also quantified relative volumes and extent of glacial ice discharge, thickness of the glacial ice at the terminus (m), and water depth at the terminus (m) from gravity and airborne radar data, sediment flux from satellite-based analysis, and freshwater runoff from a regional atmospheric climate model (RACMO2.3). We quantified whale visits to glaciers at three distances (5, 7, and 10 km) and conducted proximity analyses on annual and monthly time steps. We estimated 1) narwhal presence or absence, 2) the number of 24 h periods spent at glaciers, and 3) the fraction of study animals that visited each glacier. The use of glacial habitat by narwhals expanded to the north and south between the 1990s (n=9 unique glaciers visited) and the 2000s (n=30 visited), likely due to loss of summer fast ice and later fall freeze-up trends (3.5 weeks later since 1979). We used a generalized linear mixed effects framework to quantify the glacier and fjord habitat characteristics preferred by narwhals.

  14. Geomicrobiology of subglacial meltwater samples from Store Landgletscher and Russell Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Cameron, K. A.; Dieser, M.; Choquette, K.; Christner, B. C.; Hagedorn, B.; Harrold, Z.; Liu, L.; Sletten, R. S.; Junge, K.

    2012-12-01

    The melting of the Greenland Ice Sheet provides direct connections between atmospheric, supraglacial and subglacial environments. The intraglacial hydrological pathways that result are believed to accommodate the microbial colonization of subglacial environments; however, little is known about the abundance, diversity and activity of microorganisms within these niches. The Greenland Ice Sheet (1.7 million square kilometers) and its associated surpaglacial and subglacial ecosystems may contribute significantly to biogeochemical cycling processes. We analyzed subglacial microbial assemblages in subglacial outflows, near Thule and Kangerlussuaq, West Greenland. The investigative approach included correlating microbial diversity, inferred function, abundance, melt water chemistry, O-18 water isotope ratios, alkalinity and sediment load. Using Illumina sequencing, bacterial small subunit ribosomal RNA hypervariable regions have been targeted and amplified from both extracted DNA and reverse transcribed rRNA. Over 3 billion sequence reads have been generated to create a comprehensive diversity profile. Total abundances ranged from 2.24E+04 to 1.58E+06 cells mL-1. In comparison, the total abundance of supraglacial early season snow samples ranged from 3.35E+02 to 2.8E+04 cells mL-1. 65 % of samples incubated with cyano ditoyl tetrazolium chloride (CTC), used to identify actively respiring cells, contained CTC-positive cells. On average, these cells represented 1.9 % of the estimated total abundance (1.86E+02 to 2.19E+03 CTC positive cells mL-1; 1.39E+03 cells mL-1 standard deviation); comparative to those measured in temperate freshwater lakes. The overarching objective of our research is to provide data that indicates the role of microbial communities, associated with ice sheets, in elemental cycling and in the release of biomass and nutrients to the surrounding marine biome.

  15. Snowmelt and runoff modelling of an Arctic hydrological basin in west Greenland

    NASA Astrophysics Data System (ADS)

    Bøggild, C. E.; Knudby, C. J.; Knudsen, M. B.; Starzer, W.

    1999-09-01

    This paper compares the performance of a conceptual modelling system and several physically-based models for predicting runoff in a large hydrological basin, Tasersuaq, in west Greenland. This basin, which is typical of many Greenland basins, is interesting because of the fast hydrological response to changing conditions. Due to the predominance of exposed bedrock surface and only minor occurrence of sediments and organic soils, there is little restraint to run-off, making the treatment of the snowmelt component of primary importance.Presently a conceptual modelling system, HBV, is applied in Greenland and also in most of the arctic regions of Scandinavia for operational forecasting. A general wish to use hydrological models for other purposes, such as to improve data collection and to gain insight into the hydrological processes has promoted interest in the more physically-based hydrological models. In this paper, two degree-day models, the Danish version of the physically-based SHE distributed hydrological modelling system (MIKE SHE) and the conceptual HBV model are compared with a new model that links MIKE SHE and a distributed energy balance model developed for this study, APUT.The HBV model performs the best overall simulation of discharge, which presently makes it most suited for general forecasting. The combination of MIKE SHE and APUT i.e. a physically based modelling system shows promising results by improving the timing of the initiation of spring flood, but does not perform as well throughout the remaining part of the snowmelt season. The modelling study shows that local parameters such as the snow depletion curve, the temporal snow albedo and perhaps also melt water storage need to be more precisely determined from field studies before physically-based modelling can be improved.

  16. The early archaean crustal history of West Greenland as recorded by detrital zircons

    NASA Technical Reports Server (NTRS)

    Kinny, P. D.; Compston, W.; Mcgregor, V. R.

    1988-01-01

    The isotope systematics of some of the oldest samples on Earth from both Greenland and Australia was discussed. The antiquity was confirmed of the 4.1 to 4.2 Ga zircons from Western Australia; the model Lu-Hf age of these zircons, as measured with the ANU ion probe is 4.14 + or - 0.24 Ga, although the oldest preserved rock units there are anorthosites with a Lu-Hf model age of about 3.73 Ga. U-Pb ion probe ages of detrital zircons ranging between 2.87 and 3.89 Ga from an Akilia association quartzite was reported, whose age of deposition is probably around 3.8 Ga. It was argued that the younger age in this range are discordant because of late Pb-loss, probably associated with a high grade metamorphic event at about 3.6 Ga. It was also argued that the earliest crust in West Greenland and elsewhere is about 3.9 Ga, but in some places, such as Western Australia, crustal evolution took place much earlier, perhaps starting as far back as 4.3 Ga. This would account for the presence in that terrane of abundant K rich granitoid, the paucity of tonalitic and trondhjemitic materials, and the existence of Eu anomalies in early Archean sediments.

  17. Significance of the late Archaean granulite facies terrain boundaries, Southern West Greenland

    NASA Technical Reports Server (NTRS)

    Friend, C. R. L.; Nutman, A. P.; Mcgregor, V. R.

    1988-01-01

    Three distinct episodes and occurrences of granulite metamorphism in West Greenland are described: (1) the oldest fragmentary granulites occur within the 3.6-Ga Amitsoq gneisses and appear to have formed 200 Ma after the continental crust in which they lie (Spatially associated rapakivi granites have zircon cores as old as 3.8 Ga, but Rb-Sr, whole-rock Pb-Pb, and all other systems give 3.6 Ga, so these granulites apparently represent a later metamorphic event); (2) 3.0-Ga granulites of the Nordlandet Peninsula NW of Godthaab, developed immediately after crustal formation in hot, dry conditions, are carbonate-free, associated with voluminous tonalite, and formed at peak metamorphic conditions of 800 C and 7 to 8 kbar (Synmetamorphic trondhjemite abounds and the activity of H2O has been indicated by Pilar to have varied greatly); and (3) 2.8-Ga granulites south of Godthaab, lie to the south of retrogressed amphibolite terranes. Prograde amphibolite-granulite transitions are clearly preserved only locally at the southern end of this block, near Bjornesund, south of Fiskenaesset. Progressively deeper parts of the crust are exposed from south to north as a major thrust fault is approached. Characteristic big hornblende pegmatites, which outcrop close to the thrust in the east, have been formed by replacement of orthopyroxene. Comparable features were not seen in South Indian granulites. It was concluded that no one mechanism accounts for the origin of all granulites in West Greenland. Various processes have interacted in different ways, and what happened in individual areas must be worked out by considering all possible processes.

  18. High-resolution, terrestrial radar velocity observations and model results reveal a strong bed at stable, tidewater Rink Isbræ, West Greenland

    NASA Astrophysics Data System (ADS)

    Bartholomaus, T. C.; Walker, R. T.; Stearns, L. A.; Fahnestock, M. A.; Cassotto, R.; Catania, G. A.; Felikson, D.; Fried, M.; Sutherland, D.; Nash, J. D.; Shroyer, E.

    2015-12-01

    At tidewater Rink Isbræ, on the central west coast of Greenland, satellite observations reveal that glacier velocities and terminus positions have remained stable, while the lowest 25 km have thinned 30 m since 1985. Over this same time period, other tidewater glaciers in central west Greenland have retreated, thinned and accelerated. Here we present field observations and model results to show that the flow of Rink Isbræ is resisted by unusually high basal shear stresses. Terrestrial radar interferometry (TRI) observations over 9 days in summer 2014 demonstrate weak velocity response to 4 km wide, full thickness calving events. Velocities at the terminus change by +/- 10% in response to rising and falling tides within a partial-width, 2.5-km-long floating ice tongue; however these tidal perturbations damp out within 2 km of the grounding line. Inversions for basal shear stress and force balance analyses together show that basal shear stresses in excess of 300 kPa support the majority of the driving stress at thick, steep Rink Isbræ. These observational and modeling results tell a consistent story in which a strong bed may limit the unstable tidewater glacier retreats observed elsewhere. Rink Isbræ has an erosion resistant quartzite bed with low fracture density. We hypothesize that this geology may play a major role in the bed strength.

  19. Recent changes in North West Greenland climate documented by NEEM shallow ice core data and simulations, and implications for past temperature reconstructions

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Steen-Larsen, H. C.

    2014-12-01

    Stack records of accumulation, d18O and deuterium excess were produced from up to 4 shallow ice cores at NEEM (North-West Greenland), spanning 1724-2007 and updated to 2011 using pit water stable isotope data. Signal-to-noise ratio is high for d18O (1.3) and accumulation (1.2) but is low for deuterium excess (0.4). No long-term trend is observed in the accumulation record. By contrast, NEEM d18O shows multi-decadal increasing trends in the late 19th century and since the 1980s. Decadal d18O and accumulation variability is in phase with Atlantic Multi-decadal Oscillation indices, and enhanced at the beginning of the 19th century. Large-scale spatial coherency is detected between NEEM and other Greenland ice core and temperature records, strongest for North-West Greenland d18O and summer South-West coastal temperature instrumental records. The strength of correlations with the North Atlantic Oscillation is smaller than in central or south Greenland. The strongest positive d18O values are recorded at NEEM in 2010, followed by 1928, while maximum accumulation occurs in 1933. The coldest/driest decades are depicted at NEEM in 1815-1825 and 1836-1836. The spatial structure of these warm/ wet years and cold/dry decades is investigated using all available Greenland ice cores. During the period 1958-2011, the NEEM accumulation and d18O records are highly correlated with simulated precipitation, temperature and d18O from simulations performed with MAR, LMDZiso and ECHAM5iso atmospheric models, nudged to atmospheric reanalyses. Model-data agreement is better using ERA reanalyses than NCEP/NCAR and 20CR ones. Model performance is poor for deuterium excess. Gridded temperature reconstructions, instrumental data and model outputs at NEEM are used to estimate the d18O-temperature relationship for the strong warming period in 1979-2007. The estimated slope of this relationship is 1.1±0.2‰ per °C, about twice larger than previously used to estimate last interglacial temperature

  20. The use of electromagnetic induction methods for establishing quantitative permafrost models in West Greenland

    NASA Astrophysics Data System (ADS)

    Ingeman-Nielsen, Thomas; Brandt, Inooraq

    2010-05-01

    The sedimentary settings at West Greenlandic town and infrastructural development sites are dominated by fine-grained marine deposits of late to post glacial origin. Prior to permafrost formation, these materials were leached by percolating precipitation, resulting in depletion of salts. Present day permafrost in these deposits is therefore very ice-rich with ice contents approaching 50-70% vol. in some areas. Such formations are of great concern in building and construction projects in Greenland, as they loose strength and bearing capacity upon thaw. It is therefore of both technical and economical interest to develop methods to precisely investigate and determine parameters such as ice-content and depth to bedrock in these areas. In terms of geophysical methods for near surface investigations, traditional methods such as Electrical Resistivity Tomography (ERT) and Refraction Seismics (RS) have generally been applied with success. The Georadar method usually fails due to very limited penetration depth in the fine-grained materials, and Electromagnetic Induction (EMI) methods are seldom applicable for quantitative interpretation due to the very high resistivities causing low induced currents and thus small secondary fields. Nevertheless, in some areas of Greenland the marine sequence was exposed relatively late, and as a result the sediments may not be completely leached of salts. In such cases, layers with pore water salinity approaching that of sea water, may be present below an upper layer of very ice rich permafrost. The saline pore water causes a freezing-point depression which results in technically unfrozen sediments at permafrost temperatures around -3 °C. Traditional ERT and VES measurements are severely affected by equivalency problems in these settings, practically prohibiting reasonable quantitative interpretation without constraining information. Such prior information may be obtained of course from boreholes, but equipment capable of drilling

  1. View of West end of central lift span truss web ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of West end of central lift span truss web of Tensaw River Bridge, showing web brace of lift girder superstructure, looking west - Tensaw River Lift Bridge, Spanning Tensaw River at U.S. Highway 90, Mobile, Mobile County, AL

  2. General view of central and west wings with loading dock ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    General view of central and west wings with loading dock from north - National Home for Disabled Volunteer Soldiers, Pacific Branch, Mess Hall, 11301 Wilshire Boulevard, West Los Angeles, Los Angeles County, CA

  3. Accumulation rates during 1311-2011 CE in North Central Greenland derived from air-borne radar data

    NASA Astrophysics Data System (ADS)

    Karlsson, Nanna; Eisen, Olaf; Dahl-Jensen, Dorthe; Freitag, Johannes; Kipfstuhl, Sepp; Lewis, Cameron; Nielsen, Lisbeth; Paden, John; Winter, Anna; Wilhelms, Frank

    2016-11-01

    Radar-detected internal layering contains information on past accumulation rates and patterns. In this study, we assume that the radar layers are isochrones, and use the layer stratigraphy in combination with ice-core measurements and numerical methods to retrieve accumulation information for the northern part of central Greenland. Measurements of the dielectric properties of an ice core from the NEEM (North Greenland Eemian Ice Drilling) site, allow for correlation of the radar layers with volcanic horizons to obtain an accurate age of the layers. We obtain accumulation patterns averaged over 100 a for the period 1311-2011. Our results show a clear trend of high accumulation rates west of the ice divide and low accumulation rates east of the ice divide. At the NEEM site the accumulation pattern is persistent during our study period and only small temporal variations occur in the accumulation rate. However, from approximately 200 km south of the NEEM drill site, the accumulation rate shows temporal variations based on our centennial averages. We attribute this variation to shifts in the location of the high-low accumulation boundary that usually is aligned with the ice divide, but appears to have moved across the divide in the past.

  4. A synthesis of the ongoing seasonal work in a west Greenland tidewater outlet glacier fjord, Godthåbsfjord

    NASA Astrophysics Data System (ADS)

    Mortensen, J.; Bendtsen, J.; Rysgaard, S.

    2015-12-01

    The coastal waters off west Greenland is subjected to significant temperature fluctuations which might affect the mass loss from local tidewater outlet glaciers from the Greenland Ice Sheet in different ways. We present a comprehensive hydrographic data set from a west Greenland fjord, Godthåbsfjord, a fjord in contact with the Greenland Ice Sheet through tidewater outlet glaciers. We analyze with respect to water masses, dynamics, seasonal and interannual hydrographic variability. Through seasonal observations of hydrographic and moored observations we recognize a seasonal pattern in the fjords circulation system, where an intermediate baroclinic circulation mode driven by tidal currents at the fjord entrance is associated as an important local heat source for the fjord. Four distinct circulation modes are observed in the fjord of which all can contribute to glacial ice melt. In water observation of a subglacial plume core will be presented and discussed with respect to vertical distribution of water masses and local heat budget in the fjord. The example of the extreme case of subglacial plume will be discussed (ice-dammed lake drainage).

  5. Accumulation rates from central North Greenland during the past 700 year

    NASA Astrophysics Data System (ADS)

    Karlsson, Nanna B.; Eisen, Olaf; Nielsen, Lisbeth T.; Kipfstuhl, Sepp; Freitag, Johannes; Paden, John D.; Dahl-Jensen, Dorthe; Winter, Anna; Wilhelms, Frank

    2016-04-01

    A key variable when interpreting the evolution and mass loss from polar ice sheets is the input from the surface mass balance. While ice core records contain information on past accumulation rates, they always only provide information for a single location. Here, we present spatially distributed accumulation rates from central northern Greenland, specifically the area between the NEEM (North Greenland Eemian Drilling) and NGRIP (North Greenland Ice Core Project) ice core drill sites. The accumulation rates have been reconstructed using ice-penetrating radar, firn core measurements and inverse methods, and we are able to retrieve both spatial and temporal changes in the accumulation over an area spanning 300 km by 300 km. We investigate the stability of the accumulation pattern over the past several hundred years, and we address the question of how well the measured accumulation rates at the ice core sites capture the regional variations in accumulation. We find that while the accumulation rates at NEEM have been stable for the past 700 years, the NGRIP site has experienced fluctuations in accumulation rate. We interpret this as an indication of shifts in the dominating weather pattern over the ice divide in central North Greenland.

  6. Variability of subglacial discharge recorded with thermal infrared timelapse of a tidewater glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Byers, L. C.; Stearns, L. A.; Brunsell, N. A.; Catania, G. A.; Fried, M.; Bartholomaus, T.; Felikson, D.; Sutherland, D.; Carroll, D.; Shroyer, E.; Nash, J. D.; Walker, R. T.; Finnegan, D. C.; LeWinter, A.

    2015-12-01

    Subglacial hydrology and the dynamics therein are important modulators of ice flow in the Greenland Ice Sheet. At tidewater outlet glaciers the characteristics of proglacial discharge affect fjord circulation, sediment deposition, submarine melt rates, and iceberg calving. Information about the spatio-temporal variability of discharge is limited by the challenges of in situ data collection at tidewater glaciers. Here, we present summertime measurements of subglacial discharge variability using a thermal infrared (7.5μm to 13μm) camera and intervalometer at Kangerlussuup Sermia (KS), a ~4km wide outlet glacier in the Uummannaq Bay region of West Greenland (71.46 N, 51.43 W). KS has an advantageous geometry for this investigation because of its shallow grounding zone and well-entrenched subglacial hydrologic system. In tandem, these characteristics promote buoyant freshwater to rise to the fjord surface from discrete outlets at the glacier's base. We investigate the timing of plume activity at these outlets and discuss potential controls on outlet switching. Raw camera measurements cannot be accurately converted to surface temperature without correcting for environmental variables and scene geometry, both of which are time-evolving during data acquisition. Our processing methodology relies on a variety of existing techniques -- image segmentation, ray casting, atmospheric radiative transfer modeling, Monte Carlo simulations -- and a variety of ancillary data products -- satellite imagery, atmospheric reanalysis, meteorologic and hydrologic measurements -- to produce the final results. What is gained is an unprecedented view into interactions between the cryosphere, hydrosphere, and atmosphere that control the dynamic and sensitive terminus region of a tidewater outlet glacier.

  7. Modelled and observed present-day state of the Jakobshavn Isbræ, west Greenland

    NASA Astrophysics Data System (ADS)

    Khan, S. A.; Muresan, I. S.; Aschwanden, A.; Khroulev, C.

    2014-12-01

    Jakobshavn Isbræ located in west Greenland drains approximately 7.5 % of the area of the Greenland ice sheet (GrIS). Understanding its sensitivity to climatic forcing is critical for assessing mass balance of the GrIS. Here we use a high-resolution, three dimensional and time-dependent regional outlet glacier model developed as part of the Parallel Ice Sheet Model (PISM) forced by climatology datasets from RACMO2 to model present-day state of Jakobshavn Isbræ. Our choice of modelling consists of a forward integration in time (hindcasting) for 1990-2012 with monthly climatic forcing. To assess the modeled mass change, we use observed ice volume change from airborne and satellite laser altimetry from ATM, ICESat, and LVIS during 1997-2013 and convert to mass change. However, the airborne and satellite measurements are conducted few times per year, and may provide yearly mass loss rates only. To assess weekly to monthly scale mass variability, we use measurements of bedrock displacement from permanent GPS sites during 2005-2013. The GPS data provide daily to monthly scale estimates of bedrock displacements caused by the earth's elastic response to ice mass change from Jakobshavn Isbræ. Additionally, we assess modeled ice velocities (and velocity changes) with observed velocities obtained from measurements of ice motion by satellite interferometric synthetic-aperture radar (InSAR) data from the RADARSAT-1 satellite.Our results show good agreement between modeled and observed mass change and velocity change from weekly to long-term timespan. Both model and observations show huge mass loss anomalies in 2010 and 2012 caused by enhanced melting during summer months.

  8. The Holocene sedimentary history of the Kangerlussuaq Fjord-valley fill, West Greenland

    NASA Astrophysics Data System (ADS)

    Storms, Joep E. A.; de Winter, Ilja L.; Overeem, Irina; Drijkoningen, Guy G.; Lykke-Andersen, Holger

    2012-03-01

    West Greenland has been intensively studied to reconstruct and better understand past relative sea level changes and deglacial history. This study extends these efforts by linking sea level and deglacial history to the sedimentary infill successions of Kangerlussuaq Fjord and associated landward valleys. Based on published and new land- and sea-based geophysical data, radiocarbon dates and geological observations we have characterized the infill and reconstructed the sedimentation history during the Holocene. Based on a revised sea level curve and data presented in this paper we defined three depositional phases. Phase I (>7000 yr BP) is represented by dominant glaciomarine deposition associated with a tide-water glacier system. As the Greenland Ice Sheet (GIS) continued to retreat it became land based. During phase II (7000-1500 yr BP) two separate depocenters formed. Keglen delta depocenter arose from a temporary stabilization phase of the GIS and prograded rapidly over the glaciomarine deposits of Phase I. Further inland, proglacial lake formation and subsequent sedimentary infill associated with the ongoing GIS retreat is represents the second depocenter. The Watson River connected both depocenters by a flood plain which transferred sediment from the GIS to the Keglen delta. Ongoing sea level fall due to glacio-isostastic uplift combined with a gradually cooler and dryer climate resulted in terrace formation along the Watson River flood plain. Around 4000 yr BP, the GIS margin reached its most landward location and began to advance to its present location. The final phase (Phase III; <1500 yr BP) is represented by a stabilized GIS position and a relative sea level rise which led to aggrading conditions near the present-day delta plain of Watson River. Simultaneously, subaqueous channels were formed at the delta front by hyperpycnal flows associated with jökulhlaup events.

  9. The Subglacial Access and Fast Ice Research Experiment - SAFIRE - on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Christoffersen, P.; Hubbard, B. P.; Doyle, S. H.; Young, T. J.; Hofstede, C. M.; Bougamont, M. H.; Todd, J.; Toberg, N.; Nicholls, K. W.; Box, J.; Walter, J. I.; Hubbard, A.

    2015-12-01

    Marine-terminating outlet glaciers drain 90 percent of the Greenland Ice Sheet and are responsible for about half of the ice sheet's net annual mass loss, which currently raises global sea level by 1 mm per year. The basal controls on these fast-flowing glaciers are, however, poorly understood, with the implication that numerical ice sheet models needed to predict future dynamic ice loss from Greenland relies on uncertain and often untested basal parameterizations. The Subglacial Access and Fast Ice Research Experiment - SAFIRE - is addressing this paucity of observational constraints by drilling to the bed of Store Glacier, a fast-flowing outlet glacier terminating in Uummannaq Fjord, West Greenland. In 2014, we gained access to the bed in four boreholes drilled to depths of 603-616 m near the center of the glacier, 30 km inland from the calving terminus where ice flows at a rate of 700 m/year. A seismic survey showed the glacier bed to consist of water-saturated, soft sediment. The water level in all four boreholes nevertheless dropped rapidly to 80 m below the ice surface when the drill connected with a basal water system, indicating effective drainage over a sedimentary bed. We were able to install wired sensor strings at the bed (water pressure, temperature, electrical conductivity and turbidity) and within the glacier (temperature and tilt) in three boreholes. The sensors operated for up to 80+ days before cables stretched and ultimately snapped due to high internal strain. The data collected during this sensor deployment show ice as cold as -21 degrees Celcius; yet, temperature of water in the basal water system was persistently above the local freezing point. With diurnal variations detected in several sensor records, we hypothesise that surface water lubricates the ice flow while also warming basal ice. The fast basal motion of Store Glacier not only occurs by basal sliding, but from high rates of concentrated strain in the bottom third of the glacier

  10. 13C-Depleted carbon microparticles in >3700-Ma sea-floor sedimentary rocks from west greenland

    PubMed

    Rosing

    1999-01-29

    Turbiditic and pelagic sedimentary rocks from the Isua supracrustal belt in west Greenland [more than 3700 million years ago (Ma)] contain reduced carbon that is likely biogenic. The carbon is present as 2- to 5-micrometer graphite globules and has an isotopic composition of delta13C that is about -19 per mil (Pee Dee belemnite standard). These data and the mode of occurrence indicate that the reduced carbon represents biogenic detritus, which was perhaps derived from planktonic organisms.

  11. Arctic Outflow West Of Greenland: Nine Years Of Volume And Freshwater Transports From Observations In Davis Strait

    NASA Astrophysics Data System (ADS)

    Curry, B.; Lee, C.; Petrie, B.; Moritz, R. E.; Kwok, R.

    2014-12-01

    Recent Arctic changes suggest alterations in the export of freshwater from the Arctic to the North Atlantic, with conceivable impacts on the Atlantic Meridional Overturning circulation. Approximately 50% of the Arctic outflow exits west of Greenland, traveling through the Canadian Arctic Archipelago (CAA) and into Baffin Bay before crossing Davis Strait. The CAA outflow contributes over 50% of the net southward freshwater outflow through Davis Strait. The remainder is deeper outflow from Baffin Bay, flow from the West Greenland Current and runoff from West Greenland and CAA glaciers. Since September 2004, an observational program in Davis Strait has quantified volume and freshwater transport variability. The year-round program includes velocity, temperature and salinity measurements from 15 moorings spanning the full width (330 km) of the strait accompanied by autonomous Seagliders surveys (average profile separation = 4 km) and autumn ship-based hydrographic sections. Over the shallow Baffin Island and West Greenland shelves, moored instrumentation provides temperature and salinity measurements near the ice-ocean interface. From 2004-2013, the average net volume and liquid freshwater transports are -1.6 ± 0.2 Sv, -94 ± 7 mSv, respectively (salinity referenced to 34.8 and negative indicates southward transport); sea ice contributes an additional -10 ± 1 mSv. Over this period, volume and liquid freshwater transports show significant interannual variability and no clear trends, but a comparison with reanalyzed 1987-90 data indicate a roughly 40% decrease in net southward liquid volume transport and a corresponding an almost 30% decrease in freshwater transport. Connections between the Arctic are also captured, e.g., a unique yearlong Davis Strait freshening event starting September 2009 that was likely driven by an earlier freshening (January 2009 - April/May 2010) in the Canadian Arctic. The Davis Strait autumn 2009 salinity minimum was fresher (by about 0

  12. INTERIOR FIRST FLOOR WEST CENTRAL ELEVATOR LOBBY DETAIL VIEW, FACING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR FIRST FLOOR WEST CENTRAL ELEVATOR LOBBY DETAIL VIEW, FACING SOUTHEAST. - NASA Industrial Plant, Systems Integration & Checkout Facility, 12214 Lakewood Boulevard, Downey, Los Angeles County, CA

  13. Modelling of subglacial hydrological development during a rapid lake drainage event, West Greenland

    NASA Astrophysics Data System (ADS)

    Dow, C. F.; Kulessa, B.; Pimentel, S.; Tsai, V. C.; Doyle, S. H.; Rutt, I. C.; Jones, G. A.; Booth, A. D.; Hubbard, A.

    2012-12-01

    We present results from a local-scale model of subglacial hydrological development during a rapid lake drainage event on the Russell Glacier catchment in West Greenland. Previous models applied to rapid lake drainage events include a turbulent radial model (Tsai and Rice, 2010) and a 1-D flowband model (Pimentel and Flowers, 2011). Both models have limitations for application to lake drainage events. For the former, the radial extent of water flow is restricted to several ice thicknesses and no provision is made for the development of basal channels. For the latter model, the input of water directly from the lake to the bed without modulation by englacial flow, together with the fact that lateral basal flux is neglected, causes unrealistic subglacial pressure levels. To resolve these limitations, we link the two models together, thus allowing both local radial flux and downstream development of a coupled efficient and distributed drainage system. Our model is constrained by inputs from fieldwork completed in summer 2010 at a rapid lake drainage site in the land-terminating region of West Greenland. Passive seismic records indicate the region of basal water injection. Reflection seismic amplitude vs. angle (AVA) surveys allow analysis of the basal material characteristics. Lake drainage rate and differential GPS vertical and horizontal motion records are used as constraints for our model outputs. Our preliminary results suggest that large basal channels do not necessarily form during the rapid drainage of supraglacial lakes. A lack of an efficient drainage system has an impact on the local ice dynamics and the treatment of lake drainage events in larger-scale dynamic models. References: Pimentel, S and Flowers, G. (2011). A numerical study of hydrologically driven glacier dynamics and subglacial flooding, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science, 467 (2126): doi: 10.1098/rspa.2010.0211. Tsai, V.C. and Rice, J.R. (2010). A

  14. Two years of Irminger Ring observations offshore of the West Greenland Shelf

    NASA Astrophysics Data System (ADS)

    Femke de Jong, M.; Bower, Amy S.; Furey, Heather; Lilly, Jonathan M.

    2013-04-01

    Anti-cyclonic eddies, called Irminger Rings, shed from the boundary current along the west coast of Greenland, transport warm and saline Irminger Current water into the interior Labrador Sea. The transport of heat and salt by Irminger Rings into the relatively fresh and cold Labrador Sea is thought to be important in the restratification of the basin after convection. However, since there are few observations, recent estimates of the importance of Irminger Rings are mostly based on models. This study shows new data from a mooring deployed offshore of the west Greenland shelf near the local maximum of eddy kinetic energy associated with the shedding of Irminger Rings. The mooring was deployed between September 2007 and September 2009. It recorded the hydrographic properties and current velocities of the water column, thus obtaining a time series of passing Irminger Rings. During the 2 year mooring deployment 12 eddies fitting the description of an Irminger Ring were observed to pass the mooring location. The Irminger Ring core properties show a seasonal cycle in temperature and salinity with a range of about 2°C and 0.05 psu, with maxima observed in late fall. This results in larger heat and salt contribution estimates compared to observations in literature, which were either taken earlier in the year or further downstream sampling older modified Irminger Rings. Some inter-annual variability was also observed. Most of the 12 Irminger Rings described here were observed during the first year. The decrease in the number of observed eddies during the second year of deployment appears to be due to a change in boundary current strength, as determined from satellite altimetry and surveys of the AR7W section. The resulting change in the circulation pattern was evident in the current meter records at the mooring site. More information about the seasonal to inter-annual variability is needed to fully understand the exchange between the boundary current and the interior

  15. Precipitation zones of west-central Nevada

    USGS Publications Warehouse

    Lopes, Thomas J.; Medina, Rose L.

    2007-01-01

    Whether Nevada can sustain its fast rate of growth depends in part on accurately quantifying the amount of water that is available, including precipitation. The Precipitation-Zone Method (PZM) is a way of estimating mean annual precipitation at any point. The PZM was developed using data from west-central Nevada and northeastern California, but preliminary analysis indicates it can be applied to the entire state. Patterns in the spatial distribution of precipitation were identified by mapping station locations and plotting 1971-2000 precipitation normals versus station elevation. Precipitation zones are large areas where precipitation is linearly related to elevation. Four precipitation zones with different linear relations were delineated; these zones cover much of west-central Nevada. Regression equations with adjusted R2 values of 0.89 to 0.95 were developed for each zone. All regression equations estimate similar precipitation rates at 4,000 feet, but the slopes of the regression equations become progressively shallower to the south. A geographic information system, 30-meter digital elevation model, and the regression equations were used to estimate the distribution and volumes of precipitation in each zone and in hydrographic areas of the Walker River Basin. Comparison between the PZM and Parameter-elevation Regressions on Independent Slopes Model (PRISM) indicate PRISM estimates are linearly related to elevation at low elevations in each zone, but PRISM estimates become non-linear at high elevations and are up to 2.5 times greater than the normals. However, PRISM under-estimates more than it over-estimates precipitation compared to the PZM. The PZM estimated the same or larger volumes of precipitation compared to PRISM in three of the zones, and the larger volumes mostly were from areas that receive greater than 15 inches/year of precipitation. Additional work is needed to accurately estimate mean annual precipitation throughout Nevada.

  16. Ice Sheet Meltwater Impacts on Biological Productivity in High-Latitude Coastal Zones - Observations and Model Results for West Antarctica and Southwest Greenland

    NASA Astrophysics Data System (ADS)

    Yager, P. L.; Oliver, H.; Sherrell, R. M.; Stammerjohn, S. E.; St-Laurent, P.; Hofmann, E. E.; Mote, T. L.; Castelao, R. M.; Rennermalm, A. K.; Tedesco, M.; Arrigo, K. R.

    2015-12-01

    Surface mass balance observations and models confirm that both the west Antarctic and Greenland Ice Sheets have undergone accelerating ice mass losses during the past decade. These losses enhance freshwater discharge to the ocean and have important implications for ocean circulation and sea level, but they can also impact marine ecosystems and carbon cycling. High-latitude primary productivity is limited by light or nutrients (or both), and phytoplankton access to these limiting factors can be altered by freshwater additions. Mechanisms for delivering meltwater to the ocean are complex and depend in part on whether the melt occurs at the ice-atmosphere or ice-ocean interface. Marine-terminus glaciers may generate buoyant plumes at depth, similar to upwelling whereas runoff from glacial termini on land will behave more like a riverine point source at the ocean surface. Here, we present preliminary results from two ongoing efforts to understand these impacts: one from the Amundsen Sea Polynya (ASP) in west Antarctica (NSF-funded INSPIRE), and another from NASA-IDS Ice Sheet Impact Study in coastal Greenland. Field observations from the Amundsen Sea Polynya International Research Expedition (ASPIRE) showed how the enormous phytoplankton bloom in the central ASP depends on an iron supply from the Dotson Ice Shelf (DIS). This outcome implied a three-dimensional pathway for iron, from the DIS cavity to the euphotic zone of the ASP bloom region located 20-100 km offshore. Such a pathway differs from the traditional one-dimensional view, where nutrients are injected into the euphotic zone by vertical mixing. Mesoscale structures and eddies may play a central role. A ROMS model is used to investigate key physical and biogeochemical processes in the ASP region. A similar effort is underway to investigate the fate of extreme melt from Greenland and its impact on primary productivity. In coastal Greenland, meltwater is modeled as surface runoff and the resulting shallower

  17. 1. General view to west along Central Street. Photo shows ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. General view to west along Central Street. Photo shows Calvin T. Call House (HABS No. NH-224), with Thompson House to right. - William Thompson House, 45 Central Street, Franklin, Merrimack County, NH

  18. Quantitative reconstruction of Holocene sea ice and sea surface temperature off West Greenland from the first regional diatom data set

    NASA Astrophysics Data System (ADS)

    Krawczyk, D. W.; Witkowski, A.; Moros, M.; Lloyd, J. M.; Høyer, J. L.; Miettinen, A.; Kuijpers, A.

    2017-01-01

    Holocene oceanographic conditions in Disko Bay, West Greenland, were reconstructed from high-resolution diatom records derived from two marine sediment cores. A modern data set composed of 35 dated surface sediment samples collected along the West Greenland coast accompanied by remote sensing data was used to develop a diatom transfer function to reconstruct April sea ice concentration (SIC) supported by July sea surface temperature (SST) in the area. Our quantitative reconstruction shows that oceanographic changes recorded throughout the last 11,000 years reflect seasonal interplay between spring (April SIC) and summer (July SST) conditions. Our records show clear correlation with climate patterns identified from ice core data from GISP2 and Agassiz-Renland for the early to middle Holocene. The early Holocene deglaciation of western Greenland Ice Sheet was characterized in Disko Bay by initial strong centennial-scale fluctuations in April SIC with amplitude of over 40%, followed by high April SIC and July SST. These conditions correspond to a general warming of the climate in the Northern Hemisphere. A decrease in April SIC and July SST was recorded during the Holocene Thermal Optimum reflecting more stable spring-summer conditions in Disko Bay. During the late Holocene, high April SIC characterized the Medieval Climate Anomaly, while high July SST prevailed during the Little Ice Age, supporting previously identified antiphase relationship between surface waters in West Greenland and climate in NW Europe. This antiphase pattern might reflect seasonal variations in regional oceanographic conditions and large-scale fluctuations within the North Atlantic Oscillation and Atlantic Meridional Overturning Circulation.

  19. Lu-Hf total-rock age for the Amitsoq gneisses, West Greenland

    NASA Technical Reports Server (NTRS)

    Pettingill, H. S.; Patchett, P. J.

    1981-01-01

    Lu-Hf total-rock data for the Amitsoq gneisses of West Greenland yield an age of 3.55 + or - 0.22 billion years, based on the decay constant for Lu-176 of 1.96 x 10 to the -11th/year, and an initial Hf-176/Hf-177 ratio of 0.280482 + or - 33. The result is in good agreement with Rb-Sr total-rock and U-Pb zircon ages. In spite of severe metamorphism of the area at 2.9 billion years, zircons from two of the samples have remained on the total-rock line, and define points close to the initial Hf ratio. The initial Hf-176/Hf-177 lies close to a chondritic Hf isotopic evolution curve from 4.55 billion years to present. This is consistent with the igneous precursors to the Amitsoq gneisses having been derived from the mantle at or shortly before 3.6 billion years. Anomalous relationships between Hf concentration and the Lu-176/Hf-177 ratio may suggest that trace element abundances in the Amitsoq gneisses are partly controlled by processes related to metamorphism.

  20. Biogeochemical data from terrestrial and aquatic ecosystems in a periglacial catchment, West Greenland

    NASA Astrophysics Data System (ADS)

    Lindborg, Tobias; Rydberg, Johan; Tröjbom, Mats; Berglund, Sten; Johansson, Emma; Löfgren, Anders; Saetre, Peter; Nordén, Sara; Sohlenius, Gustav; Andersson, Eva; Petrone, Johannes; Borgiel, Micke; Kautsky, Ulrik; Laudon, Hjalmar

    2016-09-01

    Global warming is expected to be most pronounced in the Arctic where permafrost thaw and release of old carbon may provide an important feedback mechanism to the climate system. To better understand and predict climate effects and feedbacks on the cycling of elements within and between ecosystems in northern latitude landscapes, a thorough understanding of the processes related to transport and cycling of elements is required. A fundamental requirement to reach a better process understanding is to have access to high-quality empirical data on chemical concentrations and biotic properties for a wide range of ecosystem domains and functional units (abiotic and biotic pools). The aim of this study is therefore to make one of the most extensive field data sets from a periglacial catchment readily available that can be used both to describe present-day periglacial processes and to improve predictions of the future. Here we present the sampling and analytical methods, field and laboratory equipment and the resulting biogeochemical data from a state-of-the-art whole-ecosystem investigation of the terrestrial and aquatic parts of a lake catchment in the Kangerlussuaq region, West Greenland. This data set allows for the calculation of whole-ecosystem mass balance budgets for a long list of elements, including carbon, nutrients and major and trace metals. The data set is freely available and can be downloaded from PANGAEA: doi:10.1594/PANGAEA.860961.

  1. A new Eimeria species (Protozoa: Eimeriidae) from caribou in Ameralik, West Greenland.

    PubMed

    Skirnisson, K; Cuyler, C

    2016-04-01

    Fecal samples of 11 calves shot in the Ameralik area, West Greenland, in August-September 2014 were examined for coccidian parasites. The calves belonged to a population of interbreeding indigenous caribou Rangifer tarandus groenlandicus and feral semi-domestic Norwegian reindeer Rangifer tarandus tarandus. Two coccidian species were found: Eimeria rangiferis and a coccidium that was identified and described as a new species. The latter's sporulated oocyst is spherical or slightly subspherical. Average size is 25.6 × 24.8 μm. The oocyst has two distinct walls. Wall thickness is ∼1.4 μm. The unicolored outer wall is brown, the inner wall is dark gray. The oocysts contain a small polar granule but are devoid of a microphyle. The oocysts enclose four ovoid-shaped sporocysts with a rounded end opposite to the Stieda body. The average size of sporocysts is 15.2 × 7.8 μm. Sporocysts contain a granular sporocyst residuum that forms a spherical cluster between the sporocysts, one large refractile body is present in each sporozoite. The spherical form easily distinguishes oocysts of the new species from the seven previously described eimerid species in R. tarandus. This is the first eimerid described as a new species to the sciences from caribou in the Nearctic.

  2. Zinc, cadmium, mercury and selenium in polar bears (Ursus maritimus) from Central East Greenland

    SciTech Connect

    Dietz, R.; Born, E.W.; Agger, C.T.; Nielsen, C.O.

    1995-02-01

    Muscle, liver, and kidney tissues from 38 polar bears (Ursus maritimus) caught in the Scoresby Sound area, Central East Greenland, were analysed for zinc, cadmium, mercury and selenium. In general, cadmium concentrations were low in muscle, liver and kidney tissue. This finding can be explained by low cadmium levels in the blubber of ringed seals. The concentration of mercury in muscle tissue was low, whereas concentrations in liver and kidney tissue were relatively high. Mercury and cadmium were positively correlated with age in liver and kidney. Zinc was positively correlated with in kidney, and selenium was correlated with age in liver. Contrary to other marine mammals, polar bears had higher mercury levels in the kidneys than in the liver. In all three tissues polar bears had significantly lower cadmium levels than ringed seals from the same area. Mercury levels were significantly lower in the muscle tissue of polar bears than in ringed seals, where-as levels in the liver and kidney were significantly higher. The previous geographic trend for cadmium and mercury found in Canadian polar bears could be extended to cover East Greenland as well. Hence cadmium levels were higher in Greenland than in Canada, while the opposite was the case for mercury. Greenland polar bears had higher mercury and cadmium contents in livers and kidneys than polar bears from Svalbard. The mercury levels in muscle and liver tissue from polar bears from East Greenland were twice as high as found in bears from western Alaska, but half the levels found in northern Alaska. Cadmium and zinc were partially correlated in kidney tissue, and this was found for mercury and selenium as well. Cadmium and zinc showed molar ratios close to unity with the highest concentrations occurring in kidney tissue, while the levels of zinc exceeded cadmium in muscle and liver tissue by up to several decades. Mercury and selenium showed molar ratios close to unity in liver and kidneys. 56 refs., 5 figs., 6 tabs.

  3. Meltwater flux and runoff modeling in the abalation area of jakobshavn Isbrae, West Greenland

    SciTech Connect

    Mernild, Sebastian Haugard; Chylek, Petr; Liston, Glen; Steffen, Konrad

    2009-01-01

    The temporal variability in surface snow and glacier melt flux and runoff were investigated for the ablation area of lakobshavn Isbrae, West Greenland. High-resolution meteorological observations both on and outside the Greenland Ice Sheet (GrIS) were used as model input. Realistic descriptions of snow accumulation, snow and glacier-ice melt, and runoff are essential to understand trends in ice sheet surface properties and processes. SnowModel, a physically based, spatially distributed meteorological and snow-evolution modeling system was used to simulate the temporal variability of lakobshavn Isbrre accumulation and ablation processes for 2000/01-2006/07. Winter snow-depth observations and MODIS satellite-derived summer melt observations were used for model validation of accumulation and ablation. Simulations agreed well with observed values. Simulated annual surface melt varied from as low as 3.83 x 10{sup 9} m{sup 3} (2001/02) to as high as 8.64 x 10{sup 9} m{sup 3} (2004/05). Modeled surface melt occurred at elevations reaching 1,870 m a.s.l. for 2004/05, while the equilibrium line altitude (ELA) fluctuated from 990 to 1,210 m a.s.l. during the simulation period. The SnowModel meltwater retention and refreezing routines considerably reduce the amount of meltwater available as ice sheet runoff; without these routines the lakobshavn surface runoff would be overestimated by an average of 80%. From September/October through May/June no runoff events were simulated. The modeled interannual runoff variability varied from 1.81 x 10{sup 9} m{sup 3} (2001/02) to 5.21 x 10{sup 9} m{sup 3} (2004/05), yielding a cumulative runoff at the Jakobshavn glacier terminus of {approx}2.25 m w.eq. to {approx}4.5 m w.eq., respectively. The average modeled lakobshavn runoff of {approx}3.4 km{sup 3} y{sup -1} was merged with previous estimates of Jakobshavn ice discharge to quantify the freshwater flux to Illulissat Icefiord. For both runoff and ice discharge the average trends are

  4. Modeling the West Antarctic and Greenland ice sheets: New dynamic, thermodynamic, and isostatic insights

    NASA Astrophysics Data System (ADS)

    Parizek, Byron R.

    Numerical simulations indicate that the apparent long-term persistence and short-term variability of the Ross ice streams in West Antarctica are tied to regional thermal conditions and local basal lubrication. Modelling results suggest that the flux of latent heat in a throughgoing hydrologic system fed by melt beneath thick inland ice maintains the lubrication of the ice streams despite their tendency to freeze to the bed, and would allow additional thinning and grounding-line retreat. However, the efficiency of basal water distribution may be a constraint on the system. Because local thermal deficits promote basal freeze-on (especially on topographic highs), observed short-term variability is likely to persist. Furthermore, simulations indicate that the ice streams have experienced only small deglacial thickness changes and are thinning more rapidly than their beds are rising isostatically. Thickness changes of O (100)m are modelled at the modern grounding line through the last glacial cycle. Coupled ice and bedrock models indicate isostatic rebound is raising the ice sheet at the modern grounding line faster than the rising sea level is submerging it. While, in and of itself, this could potentially lead to a grounding-line re-advance, ice flow is modelled to respond to recent changes in temperature, accumulation rate, and basal processes more rapidly than it does to bedrock-elevation and/or sea-level fluctuations. Future projections of the Greenland ice sheet indicate a faster contribution to sea-level rise in a warming world than previously believed, based on numerical modelling using a parameterization of recent results showing surface-meltwater lubrication of Greenland ice flow (Zwally et al., 2002). Numerous simulations were conducted to test a wide range of parameter space linking surface melt with a new sliding law based on Zwally et al. data under different global warming scenarios. Comparisons to reconstructions generated with a traditional sliding

  5. Paleomagnetism of large igneous provinces: case-study from West Greenland, North Atlantic igneous province

    NASA Astrophysics Data System (ADS)

    Riisager, Janna; Riisager, Peter; Pedersen, Asger Ken

    2003-09-01

    We present new paleomagnetic and multi-model stereo photogrammetry data from lava sequences in the West Greenland part of the North Atlantic igneous province (NAIP). The joint analyses of paleomagnetic and photogrammetric data yield a well-defined paleomagnetic pole located at Lat=73.6°N, Long=160.5°E ( N=44, α95=6.2°, K=13.1; age ˜61-55 Ma), which is statistically indistinguishable from a pole recently obtained for the Eurasian part of the NAIP on Faroe Islands [Riisager et al., Earth Planet. Sci. Lett. 201 (2002) 261-276]. Combining the two datasets we obtain a joint NAIP paleomagnetic pole in Greenland coordinates: Lat=71.1°N, Long=161.1°E ( N=87, α95=4.3°, K=13.6; age ˜61-54 Ma). The results presented here represent the first study in which photogrammetry profiles were photographed at the exact same locations where paleomagnetic fieldwork was carried out, and a direct flow-to-flow comparison of the two datasets is possible. Photogrammetry is shown to be particularly useful because of (i) highly precise dip/strike measurements and (ii) detailed 'field observations' that can be made in the laboratory. Highly precise determination of the structural attitude of well-exposed Kanisut Mb lava sequences demonstrates that their apparently reliable in-field dip/strike measurements typically are up to ˜6° wrong. Erroneous dip/strike readings are particularly problematic as they offset paleomagnetic poles without affecting their confidence limits. Perhaps more important for large igneous provinces is the recognition of a variable temporal relationship between consecutive lava flows. We demonstrate how correct interpretation of paleosecular variation, facilitated by the detailed photogrammetry analysis, is crucial for the rapidly emplaced Vaigat Formation lavas. Inaccurate tectonic correction, non-averaged paleosecular variation and unrecognized excursional directions may, perhaps, explain why coeval paleomagnetic poles from large igneous provinces are often

  6. Modeling of Ice Flow and Internal Layers Along a Flow Line Through Swiss Camp in West Greenland

    NASA Technical Reports Server (NTRS)

    Wang, W. L.; Zwally, H. Jay; Abdalati, W.; Luo, S.; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    An anisotropic ice flow line model is applied to a flow line through Swiss Camp (69.57 N, 49.28 W) in West Greenland to estimate the dates of internal layers detected by Radio-Echo Sounding measurements. The effect of an anisotropic ice fabric on ice flow is incorporated into the steady state flow line model. The stress-strain rate relationship for anisotropic ice is characterized by an enhancement factor based on the laboratory observations of ice deformation under combined compression and shear stresses. By using present-day data of accumulation rate, surface temperature, surface elevation and ice thickness along the flow line as model inputs, a very close agreement is found between the isochrones generated from the model and the observed internal layers with confirmed dates. The results indicate that this part of Greenland ice sheet is primarily in steady state.

  7. Larval outbreaks in West Greenland: Instant and subsequent effects on tundra ecosystem productivity and CO2 exchange.

    PubMed

    Lund, Magnus; Raundrup, Katrine; Westergaard-Nielsen, Andreas; López-Blanco, Efrén; Nymand, Josephine; Aastrup, Peter

    2017-02-01

    Insect outbreaks can have important consequences for tundra ecosystems. In this study, we synthesise available information on outbreaks of larvae of the noctuid moth Eurois occulta in Greenland. Based on an extensive dataset from a monitoring programme in Kobbefjord, West Greenland, we demonstrate effects of a larval outbreak in 2011 on vegetation productivity and CO2 exchange. We estimate a decreased carbon (C) sink strength in the order of 118-143 g C m(-2), corresponding to 1210-1470 tonnes C at the Kobbefjord catchment scale. The decreased C sink was, however, counteracted the following years by increased primary production, probably facilitated by the larval outbreak increasing nutrient turnover rates. Furthermore, we demonstrate for the first time in tundra ecosystems, the potential for using remote sensing to detect and map insect outbreak events.

  8. Estimating ice-melange properties with repeat UAV surveys over Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Toberg, Nick; Ryan, Johnny; Christoffersen, Poul; Snooke, Neal; Todd, Joe; Hubbard, Alun

    2016-04-01

    In the past decade, tidewater outlet glaciers of the Greenland ice sheet (GrIS) have thinned and retreated when compared to the 1980s when the ice sheet was in a state of dynamic balance. With a growing amount of ice discharged into the sea by tidewater glaciers as well as more ice melting on the surface, the Greenland Ice Sheet has become the single largest cryospheric source of global sea level rise. Today, the ice sheet causes sea level rise of 1 mm per year, highlighting the need to understand the ice sheet's response to climate change. Atmospheric warming will inevitably continue to increase surface meltwater production, but the dynamic response, which includes hundreds of fast-flowing tidewater glaciers, is largely unknown. To develop new understanding of ice sheet dynamics, we investigated the mechanism whereby icebergs break off tidewater glaciers and form a proglacial ice melange. This melange is rigid in winter when sea ice and friction along the sidewalls of the fjord, or even at the sea floor, hold it together. The result is a resistive force, which reduces the rate of iceberg calving when the ice melange is rigid and is lost when the melange disappears in the summer. From early May to late July 2014, we launched unmanned aerial vehicles (UAVs) from a basecamp on a bluff overlooking the calving front of Store Glacier, a 5 km wide tidewater glacier flowing into Uummannaq Fjord in West Greenland. The Skywalker X8 UAVs had a wing-span of 2.1m and a payload containing a high resolution camera, an autopilot system and a GPS data logger. We generated almost 70,000 georeferenced images during 63 sorties over the glacier during a 10 week field season starting 13 May 2014. The images were used to construct orhorectified mosaics and digital elevation models of the proglacial melange with Photoscan structure-from-motion software. The imagery and the DEMs were analysed statistically to understand the spatial characteristics of the ice melange. By combining the

  9. The Archean geology of the Godthabsfjord Region, southern west Greenland (includes excursion guide)

    NASA Technical Reports Server (NTRS)

    Mcgregor, V. R.; Nutman, A. P.; Friend, C. R. L.

    1986-01-01

    The part of the West Greenland Archean gneiss complex centered around Godthabsfjord and extending from Isukasia in the north to south Faeringehavn is studied. Extensive outcrops of 3800 to 3400 Ma rocks can provide some direct evidence of conditions and processes that operated on the Earth in the early Archean. However, the ways in which primary characteristics have been modified by later deformation, metamorphism, and chemical changes are first taken into account. The rocks exposed are the products of two major phases of accretion of continental crust, at 3800 to 3700 Ma and 3100 to 29 Ma. The main features of these two accretion phases are similar, but careful study of the least modified rocks may reveal differences related to changes in the Earth in the intervening period. The combination of excellent exposure over an extensive area, relatively detailed geological mapping of much of the region, and a considerable volume of isotopic and other geochemical data gives special insights into processes that operated at moderately deep levels of the crust in the Archean. Of particular interest is the effect of late Archean granulite facies metamorphism on early Archean rocks, especially the extent to which isotope systems were disturbed. Similar processes may well have partly or wholly destroyed evidence of more ancient components of other high grade terrains. This account does not attempt to be an exhaustive review of all work carried out on the geology of the region. Rather, it attempts to summarize aspects of the geology and some interest in the context of early crustal genesis.

  10. Influence of the Little Ice Age on the biological structure of lakes in South West Greenland

    NASA Astrophysics Data System (ADS)

    McGowan, S.; Hogan, E. J.; Jones, V.; Anderson, N. J.; Simpson, G.

    2013-12-01

    Arctic lakes are considered to be particularly sensitive to environmental change, with biological remains in lake sediment records being interpreted as reflecting climate forcing. However the influence that differences in catchment properties and lake morphometries have on the sedimentary record is rarely considered. We investigated sediment cores from three lakes located close to the inland ice sheet margin in the Kangerlussuaq area of South West Greenland but within a few kilometres of one another. This regional replication allowed for direct comparisons of biological change in lakes exposed to identical environmental pressures (cooling, increased wind speeds) over the past c.2000 years. Sedimentary pigments were used as a proxy for whole-lake production and to investigate differences in phytoplankton community structure whilst fossil diatom assemblages were studied to determine differences in ecological responses during this time. We noted several major effects of the Little Ice Age cooling (LIA, c. 1400-1850AD). The organic content of sediments in all three lakes declined, and this effect was most pronounced in lakes closest to the inland ice sheet margin, which suggests that aeolian inputs derived from the glacial outwash plains (sandurs), and wind-scouring of the thin catchment soils by strong katabatic winds associated with the regional cooling might have both contributed to this sedimentary change. During the LIA total algal production (as indicated by chlorophyll and carotenoid pigments) was lower in all three lakes, most likely because of extended ice-cover and shorter growing seasons, and the ratio of planktonic: benthic diatom taxa increased, possibly because of lower light availability or fertilization from loess material. Despite this coherence in lake response to the LIA, diatom community composition changes in individual lakes differed, reflecting individual lake morphometry and catchment characteristics. These findings highlight the importance of

  11. Molecular diversity patterns among various phytoplankton size-fractions in West Greenland in late summer

    NASA Astrophysics Data System (ADS)

    Elferink, Stephanie; Neuhaus, Stefan; Wohlrab, Sylke; Toebe, Kerstin; Voß, Daniela; Gottschling, Marc; Lundholm, Nina; Krock, Bernd; Koch, Boris P.; Zielinski, Oliver; Cembella, Allan; John, Uwe

    2017-03-01

    Arctic regions have experienced pronounced biological and biophysical transformations as a result of global change processes over the last several decades. Current hypotheses propose an elevated impact of those environmental changes on the biodiversity, community composition and metabolic processes of species. The effects on ecosystem function and services, particularly when invasive or toxigenic harmful species become dominant, can be expressed over a wide range of temporal and spatial scales in plankton communities. Our study focused on the comparison of molecular biodiversity of three size-fractions (micro-, nano-, picoplankton) in the coastal pelagic zone of West Greenland and their association with environmental parameters. Molecular diversity was assessed via parallel amplicon sequencing the 28S rRNA hypervariable D1/D2 region. We showed that biodiversity distribution within the area of Uummannaq Fjord, Vaigat Strait and Disko Bay differed markedly within and among size-fractions. In general, we observed a higher diversity within the picoplankton size fraction compared to the nano- and microplankton. In multidimensional scaling analysis, community composition of all three size fractions correlated with cell size, silicate and phosphate, chlorophyll a (chl a) and dinophysistoxin (DTX). Individually, each size fraction community composition also correlated with other different environmental parameters, i.e. temperature and nitrate. We observed a more homogeneous community of the picoplankton across all stations compared to the larger size classes, despite different prevailing environmental conditions of the sampling areas. This suggests that habitat niche occupation for larger-celled species may lead to higher functional trait plasticity expressed as an enhanced range of phenotypes, whereas smaller organisms may compensate for lower potential plasticity with higher diversity. The presence of recently identified toxigenic harmful algal bloom (HAB) species (such

  12. The impact of local topography on glacial geomorphological records in West Greenland

    NASA Astrophysics Data System (ADS)

    Adamson, Kathryn; Lane, Tim

    2015-04-01

    The Holocene glacial record of Lyngmarksbræen, an ice cap in West Greenland, has been used to explore the impacts of local topography on landform generation and preservation. It is well-established that glacial response to regional climate drivers may be locally modulated by local-scale topography, but there has been little systematic investigation of its impacts on the geomorphological record. Establishing the relative influence of regional and local-scale drivers on landform development is important as it will allow us to make more robust reconstructions of past ice dynamics. Detailed geomorphological analysis of seven outlet valleys from Lyngmarksbræen, Disko Island has been undertaken. Satellite imagery and field mapping have been used to explore the topographic variations of neighbouring valleys, and the resulting geomorphological record. Comparisons between valleys are made on the basis of existing morphostratigraphic correlations (Ingólfsson, 1990) and recent surface exposure ages (Lane et al., In prep), which indicate that the majority of the landforms were deposited during the Little Ice Age (LIA). The valleys draining Lyngmarksbræen vary considerably in terms of geometry, landform characteristics (type, size, location), and ice extent (Holocene to present day). This allows us to explore geomorphological dynamics in contrasting, but geographically proximal, settings. During the LIA, ice extended up to 3 km beyond the present ice margins. In all outlets, glacial landforms are confined to the radial valleys and there is only limited evidence of deposition in the larger trunk valleys. To the north and east of Lyngmarksbræen, large latero-frontal moraines are well-preserved and often impound small proglacial lakes. In the west, the LIA and present day ice margins are more diffuse, and there is evidence of ice-cored moraine, kettle holes, and buried ice. To the south of the ice cap, landform preservation is limited. We discuss the extent to which these

  13. Fatty Acid Composition of Muscle, Adipose Tissue and Liver from Muskoxen (Ovibos moschatus) Living in West Greenland

    PubMed Central

    Alves, Susana P.; Raundrup, Katrine; Cabo, Ângelo; Bessa, Rui J. B.; Almeida, André M.

    2015-01-01

    Information about lipid content and fatty acid (FA) composition of muskoxen (Ovibos moschatos) edible tissues is very limited in comparison to other meat sources. Thus, this work aims to present the first in-depth characterization of the FA profile of meat, subcutaneous adipose tissue and liver of muskoxen living in West Greenland. Furthermore, we aim to evaluate the effect of sex in the FA composition of these edible tissues. Samples from muscle (Longissimus dorsi), subcutaneous adipose tissue and liver were collected from female and male muskoxen, which were delivered at the butchery in Kangerlussuaq (West Greenland) during the winter hunting season. The lipid content of muscle, adipose tissue and liver averaged 284, 846 and 173 mg/g of dry tissue, respectively. This large lipid contents confirms that in late winter, when forage availability is scarce, muskoxen from West Greenland still have high fat reserves, demonstrating that they are well adapted to seasonal feed restriction. A detailed characterization of FA and dimethylacetal composition of muskoxen muscle, subcutaneous adipose tissue and liver showed that there are little differences on FA composition between sexes. Nevertheless, the 18:1cis-9 was the most abundant FA in muscle and adipose tissue, reaching 43% of total FA in muscle. The high content of 18:1cis-9 suggests that it can be selectively stored in muskoxen tissues. Regarding the nutritional composition of muskoxen edible tissues, they are not a good source of polyunsaturated FA; however, they may contribute to a higher fat intake. Information about the FA composition of muskoxen meat and liver is scarce, so this work can contribute to the characterization of the nutritional fat properties of muskoxen edible tissues and can be also useful to update food composition databases. PMID:26678792

  14. Origin of cratonic lithospheric mantle roots: A geochemical study of peridotites from the North Atlantic Craton, West Greenland

    NASA Astrophysics Data System (ADS)

    Wittig, N.; Pearson, D. G.; Webb, M.; Ottley, C. J.; Irvine, G. J.; Kopylova, M.; Jensen, S. M.; Nowell, G. M.

    2008-09-01

    A critical examination of the extent to which geodynamic information on the initial mantle depletion and accretion event(s) is preserved in kimberlite-borne cratonic SCLM peridotite xenoliths is attempted by using new major and trace element data of whole-rock peridotites ( n = 55) sampled across the North Atlantic Craton (NAC; West Greenland). We also present additional whole-rock trace element data of mantle xenoliths from Somerset Island, the Slave and Kaapvaal cratons for comparison. Peridotites comprising the West Greenland SCLM are distinctly more olivine-rich and orthopyroxene-poor than most other cratonic peridotites, in particular those from the Kaapvaal craton. The West Greenland peridotites have higher Mg/Si but lower Al/Si, Al 2O 3 and CaO than cratonic mantle from the Kaapvaal Craton. We suggest that the more orthopyroxene depleted, harzburgite to dunite character of the NAC peridotites reflects more of the original melting history than peridotites from other cratons and in that sense may be more typical of cratonic lithosphere compositions prior to extensive modification. Despite this, some modal and cryptic metasomatism has clearly taken place in the West Greenland lithosphere. The insensitivity of major elements to pressure of melting at high degrees of melt extraction combined with the ease with which these elements may be changed by modal metasomatism mean that we cannot confidently constrain the depth of melting of peridotites using this approach. Mildly incompatible trace elements offer much more promise in terms of providing geodynamic information about the original Archean melting regime. The very low, systematically varying heavy REE abundances in NAC whole-rock peridotites and in peridotites from all other cratons where high-quality data are available provide ubiquitous evidence for a shallow melting regime in the absence of, or to the exhaustion of garnet. This finding explicitly excludes large extents of deep (iso- and polybaric) melting

  15. 100. DETAIL OF PATCHBOARD LOCATED CENTRALLY ON WEST SIDE OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    100. DETAIL OF PATCHBOARD LOCATED CENTRALLY ON WEST SIDE OF LANDLINE INSTRUMENTATION ROOM. Two rows of equipment cabinets west of (behind) patchboard are not accessible for photography. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Operations Building, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  16. 88. 451 MADISON AVENUE, LIBRARY, SOUTH WALL, WEST CENTRAL SECTION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    88. 451 MADISON AVENUE, LIBRARY, SOUTH WALL, WEST CENTRAL SECTION SHOWING WINDOW AND RADIATOR (Pair with NY-5635-89) - Villard Houses, 451-457 Madison Avenue & 24 East Fifty-first Street, New York County, NY

  17. 13. View of west entrance to central corridor of filtration ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. View of west entrance to central corridor of filtration bed building. - Lake Whitney Water Filtration Plant, Filtration Plant, South side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

  18. Automated Ground-based Time-lapse Camera Monitoring of West Greenland ice sheet outlet Glaciers: Challenges and Solutions

    NASA Astrophysics Data System (ADS)

    Ahn, Y.; Box, J. E.; Balog, J.; Lewinter, A.

    2008-12-01

    Monitoring Greenland outlet glaciers using remotely sensed data has drawn a great attention in earth science communities for decades and time series analysis of sensory data has provided important variability information of glacier flow by detecting speed and thickness changes, tracking features and acquiring model input. Thanks to advancements of commercial digital camera technology and increased solid state storage, we activated automatic ground-based time-lapse camera stations with high spatial/temporal resolution in west Greenland outlet and collected one-hour interval data continuous for more than one year at some but not all sites. We believe that important information of ice dynamics are contained in these data and that terrestrial mono-/stereo-photogrammetry can provide theoretical/practical fundamentals in data processing along with digital image processing techniques. Time-lapse images over periods in west Greenland indicate various phenomenon. Problematic is rain, snow, fog, shadows, freezing of water on camera enclosure window, image over-exposure, camera motion, sensor platform drift, and fox chewing of instrument cables, and the pecking of plastic window by ravens. Other problems include: feature identification, camera orientation, image registration, feature matching in image pairs, and feature tracking. Another obstacle is that non-metric digital camera contains large distortion to be compensated for precise photogrammetric use. Further, a massive number of images need to be processed in a way that is sufficiently computationally efficient. We meet these challenges by 1) identifying problems in possible photogrammetric processes, 2) categorizing them based on feasibility, and 3) clarifying limitation and alternatives, while emphasizing displacement computation and analyzing regional/temporal variability. We experiment with mono and stereo photogrammetric techniques in the aide of automatic correlation matching for efficiently handling the enormous

  19. Measurements of supraglacial lake drainage and surface streams over West Greenland and effects on ice dynamics

    NASA Astrophysics Data System (ADS)

    Tedesco, M.; Willis, I. C.; Alexander, P. M.; Banwell, A. F.

    2011-12-01

    During the summer of 2011 we measured the filling and draining of two surface lakes in the Paakitsoq region of the West Greenland Ice Sheet (49.79 W, 69.57 N), together with the level of streams flowing into the basins feeding the lakes. We also used GPS to record the horizontal and vertical movement of the ice sheet surface at five locations surrounding the lakes for a two week period (overlapping the draining of the two lakes). In this talk we report results concerning the processes of lake filling and draining between the two lakes. 'Lake Half Moon', with a smaller catchment area, filled slowly at a steady rate over several days, then drained gradually over a 24 hour period as an existing moulin located outside the bottom of the lake became active; the lake level continued to drop very slowly over the remaining week as the surface stream leading from the lake to the moulin incised. 'Lake Ponting', with the larger catchment area, filled more rapidly and at an accelerating rate as depressions upstream of the lake filled with water, overflowed and delivered increasing volumes of water to the lake. Lake Ponting drained by hydrofracture following a particularly rapid rise in water level, generating a new ~ 800m long extensional crevasse on the ice sheet surface. The entire ~ 3 x 106 m3 lake drained within a few hours. For the Lake Pointing, we show, for the first time, a movie of the lake draining, showing many features that we observed right after its drainage. The rate of lake level lowering during the drainage varied; initially moderately rapid while the fractures formed and accommodated the water, then exceptionally rapid as the fractures reached the bed allowing the lake to drain completely. The analysis of the GPS data suggest that the different styles of lake draining affect the vertical and horizontal movement of the ice sheet in different ways. We also anticipate that the effect of the draining of Lake Ponting was affecting the GPS sensors in a different

  20. Regime Change of Ice Draft in Nares Strait to the West of Greenland 2003 to 2009

    NASA Astrophysics Data System (ADS)

    Ryan, P. A.; Muenchow, A.; Huntley, H.

    2014-12-01

    The last of remaining multi-year ice exits the Arctic Ocean via Nares Strait to the west of northern Greenland. Measuring ice draft and velocity directly, we maintained moored sensors in Nares Strait from 2003 through 2009. Two ice profiling sonars measured acoustic travel times from about 100-m depth to the bottom of the sea ice. Estimates of ice draft result, if vertically averaged density, speed of sound, and depth of the sensor are known. We use concurrently measured temperature, salinity, and pressure at nearby mooring locations for those properties at daily time scales. Sensitivity tests reveal that our ice draft estimates are accurate to within 0.1 m. With ice drafts sampled at 15 second intervals, we construct ice draft probability density functions to define ice categories and to compare these at inter-annual and seasonal time sales. Categories are open water (no ice), thin ice (< 0.5 m), first year ice (0.5- 2 m; FYI), multi year ice (>2 m; MYI). FYI dominated the ice draft distribution from 2003 to 2006 when it was observed about half of the time. It diminished to ~20% from 2006 to 2009 when much FYI was replaced by a combination of thin ice and MYI. We interpret this finding as a transition towards a more dynamic and advective ice regime in Nares Strait. At seasonal time scales we found the largest ice drafts always during the period prior to prolonged periods of zero ice velocity, that is, the onset of landfast ice conditions. The duration of this landfast season reduced from more than 180 days per year on average for the 2003-06 period to less than 20 days per year on average for the 2006-09 period. Implications on ice flux are profound as the transition from landfast to mobile ice conditions enhances both local wind forcing, local ice formation (thin ice), and ice export. We emphasize that this transition precedes the record setting Arctic ice minimum in the summer of 2007.

  1. Modeling experiments on the deceleration and reactivation of Kangerlussuup Sermusa, West Greenland

    NASA Astrophysics Data System (ADS)

    Rezvanbehbahani, S.; Stearns, L. A.; van der Veen, C. J.; Catania, G. A.

    2015-12-01

    Seasonal variations in outlet glacier velocity due to basal sliding are well-documented and typically involve acceleration early in the melt season due to enhanced sliding as a result of inefficient drainage of surface water reaching the bed. However, velocity observations from Kangerlussuup Sermusa (KS) in West Greenland contradict this pattern. Instead, ice velocity at KS shows no significant change in early spring compared with the previous winter. This sluggish response of the glacier to spring melt is often followed by an extreme, and short-lived, deceleration. For example, in August 2010, the lower 20 km of the trunk decelerated from about 1600 m a-1 to less than 250 m a-1; this event was followed by a rapid reactivation back to the previous velocity in less than 60 days. Available records since 2006 show that the sequence of steady spring velocity, followed by summer deceleration, and rapid fall reactivation occurs annually; however, the magnitudes of deceleration vary. In this regard, the response of KS to regional environmental forcings is unique compared to its neighboring glaciers. In this study, we investigate whether the unique behavior of KS can be explained by the interaction between changes in basal conditions and the local geometry of the glacier. We model the glacier flow by solving full-Stokes equations using the finite element method in the open-source FEniCS framework. Assuming isothermal ice within the lower trunk, we run experiments on the mechanical properties and boundary conditions of the glacier. These experiments include spatio-temporal changes in basal slipperiness, periodic melt-water influx to the bed, and ice viscosity variations due to changes in melt-water supply to the bed. We also conduct sensitivity analyses on the glacier flow with different ice geometries (e.g. thickness and surface slope) to investigate conditions under which we can produce the unique seasonal behavior of KS. Finally, we assess the impact of the combination

  2. Parasites as biological tags to track an ontogenetic shift in the feeding behaviour of Gadus morhua off West and East Greenland.

    PubMed

    Münster, Julian; Klimpel, Sven; Fock, Heino O; MacKenzie, Ken; Kuhn, Thomas

    2015-07-01

    Parasites, being an integral part of every ecosystem and trophically transmitted along the food webs, can provide detailed insights into the structure of food webs and can close the information gap between short-term stomach content analyses and long-term fish otolith analyses. They are useful for tracking ontogenetic shifts in the host's diet, the occurrence of specific organisms or migratory behaviour of their hosts, even in inaccessible environments. In the present study, stomach content analyses and parasitological examinations were performed on 70 Atlantic cod Gadus morhua, one of the most important high-level predators of small fish in the North Atlantic, caught during one research vessel cruise from West and East Greenlandic waters. Analyses revealed significant differences in fish size with higher values for East Greenland (average total length (TL) of 50.5 cm) compared to West Greenland (average TL of 33.3 cm). Clear differences were also present in prey and parasite composition. Crustacea was the main food source for all fish (IRI = 10082.70), while the importance of teleosts increased with fish size. With a prevalence of 85 % in West Greenland and 100 % in East Greenland, Nematoda were the most abundant parasite group. The results indicate an ontogenetic shift in the diet, which are discussed in the context of the common distribution theory, stock dynamics and migratory behaviour.

  3. Hydrogeochemistry of Groundwater as Part of the Greenland Analogue Project in an Area of Continuous Permafrost Adjacent to the Greenland Ice Sheet, Kangerlussuaq, West Greenland

    NASA Astrophysics Data System (ADS)

    Henkemans, E.; Frape, S.; Ruskeeniemi, T.; Claesson-Liljedahl, L.; Lehtinen, A.; Annable, W. K.

    2011-12-01

    Studying groundwater in areas of continuous permafrost is often limited to studies of springs and open pingos (eg. Pollard et al. 1999 and Allen et al. 1976). Boreholes in such locations are expensive, risky and logistically challenging (eg. Stotler et al. 2011) resulting in a limited understanding of the interaction between continental scale ice sheets and groundwater. Continental ice sheet models are often coupled to groundwater flow systems; however, there is a lack of modern field data with which to compare the results of models and their treatment of groundwater flow systems under the influence of glaciation. The Greenland Analogue Project (GAP) aims to eliminate some of the uncertainties in modeling ice sheets by using the Greenland ice sheet as a modern analogue for past glaciations. Since 2009, 3 boreholes have been drilled, 2 of which contain sampling systems. DH-GAP01 is a 191 m deep borehole drilled at an angle into a talik and has been sampled and studied since 2009. DH-GAP04 is a 632 m deep, angled borehole that intersects the groundwater flow system directly beneath Isunguata Sermia and is producing preliminary groundwater samples. Additional information on groundwater in the Kangerlussuaq area comes from a spring located directly in front of the Leverett ice lobe. Geochemical and isotopic (δ18O, δ2H, δ37Cl, 87Sr/86Sr, and δ34S and δ18O of SO4) tools are used to interpret geochemical processes acting on groundwaters and provide insight into groundwater flow. Analyses of δ18O and δ2H in groundwaters from DH-GAP01 show the borehole waters fall along the Global Meteoric Water Line (GMWL). Evaporation is an important process affecting the δ18O-δ2H of surface waters in the region causing lakes to plot along a local evaporation line (Leng and Anderson, 2003). The waters from the Leverett spring plot to the right of the GMWL as possibly a mixture of groundwater and surface evaporated fluids. However, both the waters from DH-GAP01 and the Leverett

  4. 3. VIEW OF CENTRAL AVENUE LOOKING WEST FROM JUST EAST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. VIEW OF CENTRAL AVENUE LOOKING WEST FROM JUST EAST OF THE INTERSECTION OF CENTRAL AVENUE AND THE EAST PERIMETER ROAD. THE ROCKY FLATS PLANT IS ABOUT 16 MILES NORTHWEST OF DENVER ON A PLATEAU AT THE EASTERN EDGE OF THE FRONT RANGE OF THE ROCKY MOUNTAINS. - Rocky Flats Plant, Bounded by Indiana Street & Routes 93, 128 & 72, Golden, Jefferson County, CO

  5. Coeval dust accumulation minima in Greenland and East Central Europe over 31-23 ka

    NASA Astrophysics Data System (ADS)

    Újvári, Gábor; Stevens, Thomas; Varga, György; Kovács, János; Molnár, Mihály

    2016-04-01

    As reflected in δ18O values in ice cores, the North Atlantic area experienced a series of abrupt, dramatic climatic fluctuations over the last glacial during which oceanic and atmospheric conditions alternated between full glacial (stadial) and relatively mild (interstadial) conditions [1,2]. Beyond the δ18O profiles, calcium ion concentration data (hereafter [Ca2+]) also exhibit particularly clear stadial/interstadial contrasts [3]. The Ca2+/dust concentration records are considered as a proxy for the amount of terrestrial dust reaching the ice sheet [4] and/or changing dust storm activity in the source areas around the Northern Hemisphere, mainly in East Asia [5,6]. The mode of the dust size distributions is thought to reflect transit times during transport, with larger modes indicating shorter transit times and transport routes, i.e. changed atmospheric circulation patterns [5]. However, based on clay mineralogy and Sr-Nd isotopic compositions of loess sediments Újvári, et al. [7] suggested that Central European dust cannot be excluded as a potential source of Greenland dust. As such, it is vital to analyze dust deposition in the key dust depocentres of Eastern Europe. As a record of Carpathian Basin dust source activity, we therefore studied loess sedimentation and grain size changes in the Dunaszekcsö loess sequence in Southern Hungary. For this record, we developed the highest resolution geochronological dataset for European loess based on 61 AMS 14C dates from molluscs and charcoal fragments. This allowed us to establish a uniquely high precision Bayesian age-depth model, with the mean 95% confidence ranges that vary between 119 and 798 yr. Sedimentation rates (SR) calculated from the age-depth model vary between 0.36-1.7 mm yr-1 and the estimated bulk dust mass accumulation rates (MAR) range from 551 to 2525 g m-2 yr-1. Both the SR and MAR display millennial/sub-millennial scale variations, visible uniquely due to the high precision dating, together

  6. Variations of the glacio-marine air mass front in West Greenland through water vapor isotopes

    NASA Astrophysics Data System (ADS)

    Kopec, B. G.; Lauder, A. M.; Posmentier, E. S.; Feng, X.

    2012-12-01

    While the isotopic distribution of precipitation has been widely used for research in hydrology, paleoclimatology, and ecology for decades, intensive isotopic studies of atmospheric water vapor has only recently been made possible by spectral-based technology. New instrumentation based on this technology opens up many opportunities to investigate short-term atmospheric dynamics involving the water cycle and moisture transport. We deployed a Los Gatos Water Vapor Isotope Analyzer (WVIA) at Kangerlussuaq, Greenland from July 21 to August 15, and measured the water vapor concentration and its isotopic ratios continuously at 10s intervals. A Danish Meteorological Institute site is located about 1 km from the site of the deployment, and meteorological data is collected at 30 min intervals. During the observation period, the vapor concentration of the ambient air ranges from 5608.4 to 11189.4 ppm; dD and d18O range from -254.5 to -177.7 ‰ and -34.2 to -23.2 ‰, respectively. The vapor content (dew point) and the isotopic ratios are both strongly controlled by the wind direction. The easterly winds are associated with dry, isotopically depleted air masses formed over the glacier, while westerly winds are associated with moist and isotopically enriched air masses from the marine/fjord surface. This region typically experiences katabatic winds off of the ice sheet to the east. However, during some afternoons, the wind shifts 180 degrees, blowing off the fjord to the west. This wind switch marks the onset of a sea breeze, and significant isotopic enrichment results. Enrichment in deuterium is up to 60 ‰ with a mean of 15‰, and oxygen-18 is enriched by 3‰ on average and up to 8 ‰. Other afternoons have no change in wind, and only small changes in humidity and vapor isotopic ratios. The humidity and isotopic variations suggest the local atmosphere circulation is dominated by relatively high-pressure systems above the cold glaciers and cool sea surface, and diurnal

  7. Gravity Data for west-central Colorado

    DOE Data Explorer

    Zehner, Richard

    2012-04-06

    Modeled Bouger Gravity data was extracted from the Pan American Center for Earth and Environmental Studies Gravity Database of the U.S. at http://irpsrvgis08.utep.edu/viewers/Flex/GravityMagnetic/GravityMagnetic_CyberShare/ on 2/29/2012. The downloaded text file was opened in an Excel spreadsheet. This spreadsheet data was then converted into an ESRI point shapefile in UTM Zone 13 NAD27 projection, showing location and gravity (in milligals). This data was then converted to grid and then contoured using ESRI Spatial Analyst. This dataset contains the original spreadsheet data, a point shapefile showing gravity station locations and Bouger gravity, and a line shapefile showing 1 milligal contours. Projection: UTM Zone 13 NAD27 Gravity Contour Shapefile Extent: West -108.366690 East -105.478730 North 40.932318 South 36.961606 Gravity Point Shapefile Extent: West -108.366692 East -105.478847 North 40.932361 South 36.961606 Data from From University of Texas: Pan American Center for Earth and Environmental Studies

  8. Longitudinal Inter-Comparison of Modeled and Measured West Greenland Ice Sheet Meltwater Runoff Losses (2004-2014)

    NASA Astrophysics Data System (ADS)

    Moustafa, S.; Rennermalm, A. K.; Tedesco, M.; Mote, T. L.; Koenig, L.; Smith, L. C.; Hagedorn, B.; Overeem, I.; Sletten, R. S.; Mikkelsen, A. B.; Hasholt, B.; Hall, D. K.

    2015-12-01

    Increased surface meltwater runoff, that exits the Greenland ice sheet (GrIS) margin via supra-, en-, and sub-glacial drainage networks into fjords, pro-glacial lakes and rivers, accounts for half or more of total mass loss. Despite its importance, modeled meltwater runoff fluxes are poorly constrained, primarily due to a lack of direct in situ observations. Here, we present the first ever longitudinal (north-south) inter-comparison of a multi-year dataset (2004-2014) of discharge for four drainage basins - Watson, Akuliarusiarsuup Kuua, Naujat Kuat, and North Rivers - along West Greenland. These in situ hydrologic measurements are compared with modeled runoff output from Modèle Atmosphérique Régional (MAR) regional climate model, and the performance of the model is examined. An analysis of the relationship between modeled and actual ice sheet runoff patterns is assessed, and provides insight into the model's ability to capture inter-annual and intra-annual variability, spatiotemporal patterns, and extreme melt events. This study's findings will inform future development and parameterization of ice sheet surface mass balance models.

  9. Analysis of Arctic outflows west and east of Greenland in an eddying global sea ice-ocean model

    NASA Astrophysics Data System (ADS)

    Aksenov, Yevgeny; Bacon, Sheldon; Regan, Heather; Nurser, George; Coward, Andrew

    2014-05-01

    Low salinity buoyant polar waters exit the Arctic Ocean into the Nordic Seas and the North Atlantic, affecting deep convection in the Nordic and Labrador Seas with potential impacts on the meridional overturning circulation. The pathways of the polar water in Davis Strait, Fram Strait and then to the south are well documented by observations and model simulations. In contrast, measurements upstream of Fram Strait are too sparse to allow us to explain what causes the outflows to exit either west or east of Greenland or to attribute the variability in the Arctic outflows to atmospheric or oceanic mechanisms. A high-resolution global ocean general circulation model, NEMO-ORCA12, has been used to examine the dynamics of the outflow north of Greenland, above the Belgica Bank and in Nares Strait. Montgomery potential analysis is used to investigate the dynamics of the currents in the area. The model results suggest wind as a driving mechanism for the variability of the ocean circulation in these areas.

  10. A modeling study of the effect of runoff variability on the effective pressure beneath Russell Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Fleurian, Basile; Morlighem, Mathieu; Seroussi, Helene; Rignot, Eric; Broeke, Michiel R.; Kuipers Munneke, Peter; Mouginot, Jeremie; Smeets, Paul C. J. P.; Tedstone, Andrew J.

    2016-10-01

    Basal sliding is a main control on glacier flow primarily driven by water pressure at the glacier base. The ongoing increase in surface melting of the Greenland Ice Sheet warrants an examination of its impact on basal water pressure and in turn on basal sliding. Here we examine the case of Russell Glacier, in West Greenland, where an extensive set of observations has been collected. These observations suggest that the recent increase in melt has had an equivocal impact on the annual velocity, with stable flow on the lower part of the drainage basin but accelerated flow above the Equilibrium Line Altitude (ELA). These distinct behaviors have been attributed to different evolutions of the subglacial draining system during and after the melt season. Here we use a high-resolution subglacial hydrological model forced by reconstructed surface runoff for the period 2008 to 2012 to investigate the cause of these distinct behaviors. We find that the increase in meltwater production at low elevation yields a more efficient drainage system compatible with the observed stagnation of the mean annual flow below the ELA. At higher elevation, the model indicates that the drainage system is mostly inefficient and is therefore strongly sensitive to an increase in meltwater availability, which is consistent with the observed increase in ice velocity.

  11. Bathymetry data reveal glaciers vulnerable to ice-ocean interaction in Uummannaq and Vaigat glacial fjords, west Greenland

    NASA Astrophysics Data System (ADS)

    Rignot, E.; Fenty, I.; Xu, Y.; Cai, C.; Velicogna, I.; Cofaigh, C. Ó.; Dowdeswell, J. A.; Weinrebe, W.; Catania, G.; Duncan, D.

    2016-03-01

    Marine-terminating glaciers play a critical role in controlling Greenland's ice sheet mass balance. Their frontal margins interact vigorously with the ocean, but our understanding of this interaction is limited, in part, by a lack of bathymetry data. Here we present a multibeam echo sounding survey of 14 glacial fjords in the Uummannaq and Vaigat fjords, west Greenland, which extends from the continental shelf to the glacier fronts. The data reveal valleys with shallow sills, overdeepenings (>1300 m) from glacial erosion, and seafloor depths 100-1000 m deeper than in existing charts. Where fjords are deep enough, we detect the pervasive presence of warm, salty Atlantic Water (AW) (>2.5°C) with high melt potential, but we also find numerous glaciers grounded on shallow (<200 m) sills, standing in cold (<1°C) waters in otherwise deep fjords, i.e., with reduced melt potential. Bathymetric observations extending to the glacier fronts are critical to understand the glacier evolution.

  12. The metamorphic record of subduction-accretion processes in the Neoarchaean: the Nuuk region, southern West Greenland.

    NASA Astrophysics Data System (ADS)

    Dziggel, Annika; Kolb, Jochen

    2013-04-01

    The Nuuk region of southern West Greenland exposes an exceptionally well preserved section through Archaean mid- to lower continental crust, and therefore provides a natural laboratory to study the tectonic processes in the Archaean. The area mainly consists of amphibolite to granulite facies TTG gneisses, narrow supracrustal belts, and minor late-tectonic granites. It is made up of several distinct terranes, including, from NW to SE, the Færingehavn, Tre Brødre, and Tasiusarsuaq terranes. Extensive high-grade metamorphism and a clockwise PT evolution of the Færingehavn terrane in the Neoarchaean (2.72-2.71 Ga) have been interpreted as a result of crustal thickening and thrusting of the Tasiusarsuaq terrane on top of the Tre Brødre and Færingehavn terranes (Nutman and Friend, 2007). Prior to final collision, the Tasiusarsuaq terrane (the upper plate in a plate tectonic model) underwent a prolonged period of compressive deformation between 2.8 and 2.72 Ga (Kolb et al., 2012). The structural evolution was associated with near-isobaric cooling from medium-pressure granulite facies conditions of ca. 850°C and 7.5 kbar to amphibolite facies conditions of ca. 700°C and 6.5-7 kbar (Dziggel et al., 2012). Despite this long period of crustal convergence, there is no evidence for exhumation and/or loading, pointing to a rheologically weak and unstable Archaean crust perhaps due to low density differences and ongoing melt extraction. Rocks of the structurally underlying Færingehavn terrane record a distinctly different metamorphic evolution. Although generally more strongly retrogressed, relict higher-pressure mineral assemblages in mafic granulites and felsic gneisses record conditions of > 8-9 kbar and >= 750°C, indicating burial to depths of at least 30 km along an apparent geothermal gradient of 20-25°C/km. The peak of metamorphism was followed by isothermal decompression at ca. 2.715 Ga (Nutman and Friend, 2007), indicating rapid exhumation of lower crustal

  13. The effect of long range nitrogen deposition on nutrient limitation of phytoplankton growth in lakes in South West Greenland

    NASA Astrophysics Data System (ADS)

    Hogan, E. J.; Mcgowan, S.; Anderson, N. J.

    2011-12-01

    There is growing evidence of ecological change in Arctic lakes. The majority of this evidence comes from lake sediment records which suggest that the composition of algal communities has changed, and that algal productivity has increased in the past 150 years. This change has commonly been attributed to a change in climate. However, such interpretation often ignores other drivers of change such as long range nitrogen (N) deposition, which has been shown to occur over a similar period of time. The region of South West Greenland is typical of much of the Arctic in terms of lake density, precipitation patterns and vegetation. It also provides a unique opportunity to investigate long range N deposition as a possible driver of ecological change as it has not experienced rapid 20th century warming which has been observed elsewhere in the Arctic. There is also evidence from ice core records that long range N deposition has increased in Greenland during the past 150 years. The effect of N deposition on nutrient limitation of phytoplankton growth was investigated in 20 freshwater lakes situated in 3 study regions in South West Greenland. The three regions span a gradient of increasing precipitation (and predicted N deposition) from the inland ice sheet margin to the coast. Nutrient limitation was investigated 3 times between August 2010 and July 2011, allowing both seasonal and regional differences to be explored. Phytoplankton growth was assessed over 14 days following in vivo fluorescence of sub-surface water samples treated with one of six nutrient additions: control (no addition), P (6 μM NaH2PO4), NH4+ (90 μM NH4Cl), NO3- (90 μM NaNO3), P + NH4+ (final concentrations as before), P + NO3- (final concentrations as before). A clear response to nutrient addition was found in 95 % of all bioassays, and of these, co-nutrient limitation was most commonly recorded (70 %). Regardless of region, phytoplankton growth appeared to show a seasonal change in nutrient limitation

  14. 4. VIEW LOOKING WEST DOWN CENTRAL AVENUE AT THE INTERSECTION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. VIEW LOOKING WEST DOWN CENTRAL AVENUE AT THE INTERSECTION WITH SEVENTH STREET. THE PLANT HAS MOST OF THE AMENITIES OF A SMALL TOWN - WATER SUPPLY, WASTE WATER TREATMENT, POLICE FORCE, FIRE DEPARTMENT, FOOD SERVICES, HOSPITAL, COMMUNICATIONS NETWORK, STEAM GENERATION, VEHICLE MAINTENANCE, TRANSPORTATION, AND A GOVERNMENT. - Rocky Flats Plant, Bounded by Indiana Street & Routes 93, 128 & 72, Golden, Jefferson County, CO

  15. 3. VIEW LOOKING NORTH WEST OVER CENTRAL ATLANTIC WITH ATLANTIC ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. VIEW LOOKING NORTH WEST OVER CENTRAL ATLANTIC WITH ATLANTIC OCEAN IN THE FOREGROUND. DENNIS HOTEL, BLENHEIM HOTEL, AND MARLBOROUGH HOTEL (LEFT TO RIGHT) ARE LOCATED IN THE CENTER OF THE PHOTOGRAPH. THE CLARIDGE HOTEL IS THE HIGHRISE IMMEDIATELY TO THE RIGHT OF THE MARLBOROUGH HOTEL - Marlborough, Blenheim & Dennis Hotels (aerial views), Between Park Place, Michigan Avenue & Boardwalk, Atlantic City, Atlantic County, NJ

  16. 15. View west of central corridor between filtration beds which ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. View west of central corridor between filtration beds which are located to the left and right of the photograph. - Lake Whitney Water Filtration Plant, Filtration Plant, South side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

  17. 16. View west from center of central corridor between filtration ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    16. View west from center of central corridor between filtration beds which are located to the left and right of the photograph. - Lake Whitney Water Filtration Plant, Filtration Plant, South side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

  18. Palynology of the late Holocene in Disko Bugt, West Greenland: evidence for centennial variability in sea-surface conditions.

    NASA Astrophysics Data System (ADS)

    Allan, Estelle; de Vernal, Anne; Matthias, Moros; Marie-Michèle, Ouellet-Bernier

    2016-04-01

    The palynological analyses of a sediment core collected in Disko Bay (core 343310; 68° 38,861'N, 53° 49,493'W) provide a dinocyst record of the last 1500 years with 5-30 year time resolution and thus permit reconstruction of changes in surface water, including sea-ice cover, temperature and salinity. Dinocyst assemblages are characterized by high taxonomic diversity (18 taxa) with dominance of Islandinium minutum, Pentapharsodinium dalei, Brigantedinium spp. and Islandinium? cezare and by very high concentrations (>105 cysts.cm-3) leading to calculate fluxes of the order of (>104 cysts.cm-2.years-1). The modern analogue technique (MAT) was applied to dinocyst assemblages to quantitatively reconstruct paleo-sea-surface conditions. The seasonal sea ice cover shows large amplitude variations from 2 to 8 months.yr-1(sea ice coverage >50%), with maxima at 1050-1300 AD, 1400-1500 AD, 1550-1600 AD and 1770-1800 AD, which reflect episodic cooling during the last millennium. In the overall record, sea ice cover and salinity variation are correlated with increase sea ice extent corresponding with decrease salinity and vice versa, which suggests strong linkages between the regional freshwater/meltwater budget and winter sea ice. Relationship between sea ice cover and the North Atlantic Oscillation (NAO) is also possible. The increased sea ice being associated with dominant NAO+ mode can be linked with change of the regional properties of the West Greenland Current, the marked by lower influence of warm and saline Atlantic waters relative to an increase influence of the polar and low salinity in Arctic waters from East Greenland Current under NAO+ situation.

  19. Nuuk, Greenland

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Nuuk (or Gadthab) is the capital and largest city of Greenland. It is located at the mouth of the Nuup Kangerlua inlet on the west coast of Greenland. It has a population of about 15,000. The site has a long history of different inhabitation: first by the Inuit people around 2000 B.C., later by Viking explorers in the 10th century. Inuit and Vikings lived together for about 500 years until about 1500, when human habitation suddenly stopped, most likely due to change in climate and vegetation.

    The image was acquired August 2, 2004, covers an area of 22.7 x 26 km, and is located at 64.2 degrees north latitude, 51.8 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  20. Middle to late Holocene fluctuations of the Vindue glacier, an outlet glacier of the Greenland Ice Sheet, central East Greenland.

    NASA Astrophysics Data System (ADS)

    Levy, L.; Hammer, S. K.; Kelly, M. A.; Lowell, T. V.; Hall, B. L.; Howley, J. A.; Wilcox, P.; Medford, A.

    2014-12-01

    The margins of the Greenland Ice Sheet are currently responding to present-day climate changes. Determining how the ice sheet margins have responded to past climate changes provides a means to understand how they may respond in the future. Here we present a multi-proxy record used to reconstruct the Holocene fluctuations of the Vindue glacier, an ice sheet outlet glacier in eastern Greenland. Lake sediment cores from Qiviut lake (informal name), located ~0.75 km from the present-day Vindue glacier margin contain a sharp transition from medium sand/coarse silt to laminated gyttja just prior to 6,340±130 cal yr BP. We interpret this transition to indicate a time when the Vindue glacier retreated sufficiently to cease glacial sedimentation into the lake basin. Above this contact the core contains laminated gyttja with prominent, ~0.5 cm thick, silt layers. 10Be ages of boulders on bedrock located between Qiviut lake and the present-day ice margin date to 6.81 ± 0.67 ka (n = 3), indicating the time of deglaciation. These ages also agree well with the radiocarbon age of the silt-gyttja transition in Qiviut lake cores. 10Be ages on boulders on bedrock located more proximal to the ice margin (~0.5 km) yield ages of 2.67 ± 0.18 ka (n = 2). These ages indicate either the continued recession of the ice margin during the late Holocene or an advance at this time. Boulders on the historical moraines show that ice retreated from the moraine by AD 1620 ± 20 yrs (n = 2). These results are in contrast with some areas of the western margin of the ice sheet where 10Be ages indicate that the ice sheet was behind its Historical limit from the middle Holocene (~6-7 ka) to Historical time. This may indicate that the eastern margin may have responded to late Holocene cooling more sensitively or that the advance associated with the Historical moraines overran any evidence of late Holocene fluctuations along the western margin of the ice sheet.

  1. Modelling the dynamic response of Jakobshavn Isbræ, West Greenland, to calving rate perturbations

    NASA Astrophysics Data System (ADS)

    Bondzio, J. H.; Seroussi, H.; Morlighem, M.; Kleiner, T.; Rückamp, M.; Humbert, A.; Larour, E.

    2015-10-01

    Calving is a major means of ice discharge of the Antarctic and Greenland Ice Sheets. The breaking off of icebergs changes the ice front configuration of marine terminating glaciers, which affects the stress regime of their upstream areas. Recent observations show the close correlation between the ice front position and the behaviour of many outlet glaciers. However, modelling of a glacier subject to calving poses various challenges. No universal calving rate parametrisation is known, and tracking of a moving ice front and the related boundary conditions in two or three spatial dimensions is non-trivial. Here, we present the theoretical and technical framework for a Level-Set Method, an implicit boundary tracking scheme, which we implemented into the Ice Sheet System Model (ISSM). The scheme allows us to study the dynamic response of a drainage basin to user-defined front ablation rates. We apply the method in a suite of experiments to Jakobshavn Isbræ, a major marine terminating outlet glacier of the western Greenland Ice Sheet. The model robustly reproduces the high sensitivity of the glacier to frontal ablation in form of calving. We find that enhanced calving is able to trigger significant acceleration of the ice stream. Upstream acceleration is sustained through a combination of various feedback mechanisms. However, lateral stress and ice influx into the trough are able to stabilise the ice stream. This study contributes to the present discussion on causes and effects of the continued changes occurring at Jakobshavn Isbræ, and emphasises that the incorporation of seasonal calving and dynamic lateral effects is key for realistic model projections of future global sea level rise on centennial time scales.

  2. Tidewater Dynamics at Store Glacier, West Greenland from Daily Repeat UAV Survey

    NASA Astrophysics Data System (ADS)

    Hubbard, A., II; Ryan, J.; Toberg, N.; Todd, J.; Christoffersen, P.; Snooke, N.; Box, J. E.

    2015-12-01

    A significant component of the Greenland ice sheet's mass wasteage to sea level rise is attributed to the acceleration and dynamic thinning at its tidewater margins. To improve understanding of the rapid mass loss processes occurring at large tidewater glaciers, we conducted a suite of daily repeat aerial surveys across the terminus of Store Glacier, a large outlet draining the western Greenland Ice Sheet, from May to July 2014 (https://www.youtube.com/watch?v=-y8kauAVAfE). A suite flock of Unmanned Aerial Vehicles (UAVs) were equipped with digital cameras, which, in combination with onboard GPS, enabled production of high spatial resolution orthophotos and digital elevation models (DEMs) using standard structure-from-motion techniques. These data provide insight into the short-term dynamics of Store Glacier surrounding the break-up of the sea-ice mélange that occurred between 4 and 7 June. Feature tracking of the orthophotos reveals that mean speed of the terminus is 16 - 18 md-1, which was independently verified against a high temporal resolution time-series derived from an expendable/telemetric GPS deployed at the terminus. Differencing the surface area of successive orthophotos enable quantification of daily calving rates, which significantly increase just after melange break-up. Likewise, by differencing bulk freeboard volume of icebergs through time we could also constrain the magnitude and variation of submarine melt. We calculate a mean submarine melt rate of 0.18 md-1 throughout the spring period with relatively little supraglacial runoff and no active meltwater plumes to stimulate fjord circulation and upwelling of deeper, warmer water masses. Finally, we relate calving rates to the zonation and depth of water-filled crevasses, which were prominent across parts of the terminus from June onwards.

  3. Subglacial Meltwater Drainage at Paakitsoq, West Greenland: Insights From a Distributed, Physically Based Numerical Model

    NASA Astrophysics Data System (ADS)

    Long, S. M.; Willis, I.; Arnold, N.; Ahlstrom, A. P.

    2008-12-01

    Recent results indicate that surface melting influences the dynamics of the Greenland Ice Sheet margin through meltwater input to a subglacial drainage system, but the hydrological characteristics of this drainage system and the degree to which variations in subglacial water pressure enhance or impede ice flow remain uncertain. Investigating the hydrology of this relatively inaccessible subglacial system requires a numerical modeling approach in which spatial and temporal variations in subglacial water pressures are calculated in response to the main controlling variables (subglacial drainage system structure and morphology and surface water inputs). We present the preliminary findings of such a study for the Paakitsoq region of W. Greenland, north of Jakobshavn Isbrae. Recent airborne radar data are used to construct surface and bed DEMs of the region from which patterns of subglacial hydraulic potential are derived. These are used to define the subglacial drainage system structure (the location, alignment and interconnection of major drainage pathways). Water flow along these pathways is modeled using a component of the United States Environmental Protection Agency's Storm Water Management Model (SWMM) modified to allow for enlargement and closure of ice walled channels (cf. Arnold et al., Hydrol. Processes, 12, 1998). We assess the model's ability to deal with two types of input: rapid lake drainage events, and diurnally varying melt inputs calculated from a degree-day model. We perform sensitivity tests to determine the effects of model parameters on modeled channel cross-sectional area, water pressure and subglacial flow. Finally, we simulate drainage beneath the ice sheet for a summer melt season and compare the results with measured proglacial stream discharges. Preliminary results suggest that channelized flow is only possible close to the ice sheet margin where ice is thin and water inputs are large. Distributed drainage is predicted beneath thicker inland

  4. Rerouting of subglacial water flow between neighboring glaciers in West Greenland

    NASA Astrophysics Data System (ADS)

    Chu, Winnie; Creyts, Timothy T.; Bell, Robin E.

    2016-05-01

    Investigations of the Greenland ice sheet's subglacial hydrological system show that the connectivity of different regions of the system influences how the glacier velocity responds to variations in surface melting. Here we examine whether subglacial water flow paths can be rerouted beneath three outlet glaciers in the ablation zone of western Greenland. We use Lamont-Doherty and Center for Remote Sensing of Ice Sheets of University of Kansas (CReSIS) ice-penetrating radar data to create a new ice thickness map. We then use a simple subglacial water flow model to examine whether flow paths can be rerouted and identify the topographic conditions that are sensitive to subglacial rerouting. By varying water pressures within an observationally constrained range, we show that moderate changes in pressure can cause flow paths to reroute and exchange water from one subglacial catchment to another. Flow across subglacial overdeepenings is particularly sensitive to rerouting. These areas have low hydraulic gradients driving flow, so subtle water pressure variations have a strong influence on water flow direction. Based on correlations between water flow paths and ice velocity changes, we infer that water piracy between neighboring catchments can result in a different spatial pattern of hydrologically induced ice velocity speedup depending on the amount and timing of surface melt. The potential for subglacial water to reroute across different catchments suggests that multiple hydrographs from neighboring glaciers are likely necessary to accurately ascertain melt budgets from proglacial point measurements. The relationship between surface runoff, ice dynamics, and proglacial discharge can be altered by rerouting of subglacial water flow within and across outlet glaciers.

  5. Regional flood-frequency relations for west-central Florida

    USGS Publications Warehouse

    Seijo, M.A.; Giovannelli, R.F.; Turner, J.F.

    1979-01-01

    This report presents regional relations for estimating the magnitude and frequency of floods on streams in west-central Florida. Flood prediction equations derived cover 20, 5-, 25-, 100-, 200-, and 500-year recurrence intervals. Annual floods for three geographic areas of west-central Florida were found to relate significantly to basin characteristics. Basin characteristics include drainage area, soils index, slope, and lake area. The average standard error of estimate for regional flood relations ranged from 38.4 to 52.1 percent with a mean of 43.5 percent. The average multiple correlation coefficient if 0.94. Regional relations apply to gaged and ungaged sites whose drainage areas are greater than 10 but less than 2,500 square miles. Tables of maximum known floods for 64 streamflow stations used in the analysis are included. Tables comparing station, weighted, and regional flood-peak discharges are also included. (Kosco-USGS)

  6. Microfossils from oolites and pisolites of the Upper Proterozoic Eleonore Bay Group, Central East Greenland

    NASA Technical Reports Server (NTRS)

    Green, J. W.; Knoll, A. H.; Swett, K.

    1988-01-01

    Silicified oolites and pisolites from Bed 18 of the Upper Proterozoic (about 700-800 Ma) Limestone-Dolomite "Series" of the Eleonore Bay Group, central East Greenland, contain a diverse suite of organically preserved microfossils that is, for the most part. [Of the] assemblages previously described from Proterozoic cherts and shales. Three principal assemblages occur in these rocks: 1) a class bound assemblage found in detrital carbonate grains (now silicified) that served as nuclei for ooid and pisoid growth, as well as in uncoated mud and mat clasts that were carried into the zone of ooid and pisoid deposition; 2) an epilithic and interstitial assemblage consisting of microorganisms that occurred on top of and between grains; and 3) a euendolithic assemblage composed of microbes that actively bored into coated grains. The Upper Proterozoic euendolithic assemblage closely resembles a community of euendolithic cyanobacteria found today in shallow marine ooid sands of the Bahama Banks. Thirteen species are described, of which eight are new, five representing new genera: Eohyella dichotoma n. sp., Eohyella endoatracta n. sp., Eohyella rectoclada n. sp., Thylacocausticus globorum n. gen. and sp., Cunicularius halleri n. gen. and sp., Graviglomus incrustus n. gen. and sp., Perulagranum obovatum n. gen. and sp., and Parenchymodiscus endolithicus n. gen. and sp.

  7. Paleobiology of distinctive benthic microfossils from the upper Proterozoic Limestone-Dolomite "Series," central East Greenland

    NASA Technical Reports Server (NTRS)

    Green, J. W.; Knoll, A. H.; Golubic, S.; Swett, K.

    1987-01-01

    Populations of Polybessurus bipartitus Fairchild ex Green et al., a large morphologically distinctive microfossil, occur in silicified carbonates of the Upper Proterozoic (700-800 Ma) Limestone-Dolomite "Series," central East Greenland. Large populations of well-preserved individuals permit reconstruction of P. bipartitus as a coccoidal unicell that "jetted" upward from the sediment by the highly unidirectional secretion of extracellular mucopolysaccharide envelopes. Reproduction by baeocyte formation is inferred on the basis of clustered envelope stalks produced by small cells. Sedimentological evidence indicates that P. bipartitus formed surficial crusts locally within a shallow peritidal carbonate platform. Among living microorganisms a close morphological, reproductive, and behavioral counterpart to Polybessurus is provided by populations of an as yet underscribed cyanobacterium found in coastal Bahamian environments similar to those in which the Proterozoic fossils occur. In general morphology and "jetting" behavior, this population resembles species of the genus Cyanostylon, Geitler (1925), but reproduces via baeocyte formation. Polybessurus is but one of the more than two dozen taxa in the richly fossiliferous biota of the Limestone-Dolomite "Series." This distinctive population, along with co-occurring filamentous cyanobacteria and other microfossils, contributes to an increasingly refined picture of ecological heterogeneity in late Proterozoic oceans.

  8. Microfossils from silicified stromatolitic carbonates of the Upper Proterozoic Limestone-Dolomite 'Series', central East Greenland

    NASA Technical Reports Server (NTRS)

    Green, J. W.; Knoll, A. H.; Swett, K.

    1989-01-01

    Silicified flake conglomerates and in situ stratiform stromatolites of the Upper Proterozoic (c. 700-800 Ma) Limestone-Dolomite 'Series', central East Greenland, contain well preserved microfossils. Five stratigraphic horizons within the 1200 m succession contain microbial mat assemblages, providing a broad palaeontological representation of late Proterozoic peritidal mat communities. Comparison of assemblages demonstrates that the taxonomy and diversity of mat builder, dweller, and allochthonous populations all vary considerably within and among horizons. The primary mat builder in most assemblages is Siphonophycus inornatum, a sheath-forming prokaryote of probable but not unequivocally established cyanobacterial affinities. An unusual low diversity unit in Bed 17 is dominated by a different builder, Tenuofilum septatum, while a thin cryptalgal horizon in Bed 18 is built almost exclusively by Siphonophycus kestron. Although variable taphonomic histories contribute to observed assemblage variation, most differences within and among horizons appear to reflect the differential success or failure of individual microbial populations in colonizing different tidal flat microenvironments. Twenty-two taxa are recognized, of which two are described as new: Myxococcoides stragulescens n.sp. and Scissilisphaera gradata n. sp.

  9. The crust and upper mantle of central East Greenland - implications for continental accretion and rift evolution

    NASA Astrophysics Data System (ADS)

    Schiffer, Christian; Balling, Niels; Ebbing, Jörg; Holm Jacobsen, Bo; Bom Nielsen, Søren

    2016-04-01

    The geological evolution of the North Atlantic Realm during the past 450 Myr, which has shaped the present-day topographic, crustal and upper mantle features, was dominated by the Caledonian orogeny and the formation of the North Atlantic and associated igneous activity. The distinct high altitude-low relief landscapes that accompany the North Atlantic rifted passive margins are the focus of a discussion of whether they are remnant and modified Caledonian features or, alternatively, recently uplifted peneplains. Teleseismic receiver function analysis of 11 broadband seismometers in the Central Fjord Region in East Greenland indicates the presence of a fossil subduction complex, including a slab of eclogitised mafic crust and an overlying wedge of hydrated mantle peridotite. This model is generally consistent with gravity and topography. It is shown that the entire structure including crustal thickness variations and sub-Moho heterogeneity gives a superior gravity and isostatic topographic fit compared to a model with a homogeneous lithospheric layer (1). The high topography of >1000 m in the western part of the area is supported by the c. 40 km thick crust. The eastern part requires buoyancy from the low velocity/low density mantle wedge. The geometry, velocities and densities are consistent with structures associated with a fossil subduction zone. The spatial relations with Caledonian structures suggest a Caledonian origin. The results indicate that topography is isostatically compensated by density variations within the lithosphere and that significant present-day dynamic topography seems not to be required. Further, this structure is suggested to be geophysically very similar to the Flannan reflector imaged north of Scotland, and that these are the remnants of the same fossil subduction zone, broken apart and separated during the formation of the North Atlantic in the early Cenozoic (2). 1) Schiffer, C., Jacobsen, B.H., Balling, N., Ebbing, J. and Nielsen, S

  10. Evolution of a trough-fan system: Scoresby Sund fjord, central-east Greenland

    NASA Astrophysics Data System (ADS)

    Pérez, Lara F.; Nielsen, Tove; Knutz, Paul C.; Kuijpers, Antoon; Damm, Volkmar

    2016-04-01

    The continental shelf along the east margin of Greenland is shaped by several, glacially carved transverse troughs that constitute the oceanward extension of the major fjords. Scoresby Sund is the most prominent fjord of central-east Greenland and separates Liverpool Land, to the north, from Blosseville Kyst to the south. Offshore of Scoresby Sund a large glacial trough mouth fan (TMF) has been built through successive phases of glacial advances. Morpho-structural and seismo-stratigraphic analyses of the Scoresby Sund TMF have been done using all Multichannel Seismic (MCS) profiles available in the area. The ODP site 987 of the leg 162 is located in the abyssal plain offshore of Scoresby Sund and was used for age estimations. The width of the continental shelf in the study area ranges from a 65 km narrow part along the Blosseville Kyst to 120 km off Scoresby Sund. The average water depth is shallower than 300 m, deepening to 600 m along Scoresby Sund glacial trough. Oceanwards a steep slope, seafloor falls into the 2250 m deep abyssal plain of the south Greenland Sea. The sedimentary cover displays maximum thickness along the middle continental shelf (2.8 s TWTT on average). Seven major stratigraphic discontinuities could be identified within the sedimentary record. They restrict eight major seismic units, named from 8 to 1, in upward stratigraphic order. The distribution and seismic facies of these units reveal the evolutionary sequence of the study area from early Cenozoic to Present. The lowest unit, Unit 8, is post-basalt to middle-late Miocene age and represents a pre-glacial depositional stage when tectonic events controlled the sedimentation. Deposition of Unit 7 occurred by late Miocene, revealing glacial-related deposits and ice-stream along Scoresby Sund fjord. Unit 6 was formed during early Pliocene by glacial advance over the continental shelf leading to strong erosive surfaces in the shelf area and Mass Transport Deposits (MTDs) in the northern abyssal

  11. Subglacial Meltwater Drainage at Paakitsoq, West Greenland: Insights from a Distributed, Physically Based Numerical Model

    NASA Astrophysics Data System (ADS)

    Banwell, Alison; Willis, Ian; Arnold, Neil; Ahlstrom, Andreas

    2010-05-01

    Recent studies indicate that surface meltwater is reaching the bed of the Greenland Ice Sheet (GrIS) and modulating glacier sliding rates at the ice sheet margin. However, the hydrological characteristics of this drainage system and the degree to which variations in subglacial water pressure enhance or impede ice flow remain uncertain. As the subglacial hydrological system beneath the GrIS is physically inaccessible and beyond the resolution of geophysical imaging techniques, numerical models are an important tool for investigating the stability of plausible hydrological systems. We present preliminary results of a numerical model that investigates theoretically-constructed hydrological systems of the Paakitsoq region of W. Greenland, north of Jakobshavn Isbrae. Subglacial drainage system structures (the location, alignment and interconnection of major drainage channels) are defined from patterns of subglacial hydrological potential derived from surface and bed DEMs. Discharge and hydraulic head within subglacial channels are modelled using a component of the US EPA Storm Water Management Model (SWMM), modified to allow for enlargement and closure of ice walled channels (Arnold et al., Hydrol. Processes, 12, 1998). We assess the model's ability to deal with two types of input: rapid lake drainage events; and diurnally varying melt inputs calculated from a degree-day model. We perform sensitivity tests to determine the effects of individual model parameters on modelled channel cross-sectional area, water pressure and subglacial flow. Finally, we simulate drainage beneath the ice sheet for a summer melt season and compare the results with measured proglacial stream discharges. Through a recent code modification allowing subglacial water pressures to reach values in excess of ice overburden pressures, we find that consistently high inland subglacial water pressures assist with keeping marginal conduits full and counteract the effects of creep closure, allowing

  12. Recognition of > or = 3850 Ma water-lain sediments in West Greenland and their significance for the early Archaean Earth.

    PubMed

    Nutman, A P; Mojzsis, S J; Friend, C R

    1997-01-01

    A layered body of amphibolite, banded iron formation (BIF), and ultramafic rocks from the island of Akilia, southern West Greenland, is cut by a quartz-dioritic sheet from which SHRIMP zircon 206Pb/207Pb weighted mean ages of 3865 +/- 11 Ma and 3840 +/- 8 Ma (2 sigma) can be calculated by different approaches. Three other methods of assessing the zircon data yield ages of >3830 Ma. The BIFs are interpreted as water-lain sediments, which with a minimum age of approximately 3850 Ma, are the oldest sediments yet documented. These rocks provide proof that by approximately 3850 Ma (1) there was a hydrosphere, supporting the chemical sedimentation of BIF, and that not all water was stored in hydrous minerals, and (2) that conditions satisfying the stability of liquid water imply surface temperatures were similar to present. Carbon isotope data of graphitic microdomains in apatite from the Akilia island BIF are consistent with a bio-organic origin (Mojzsis et al. 1996), extending the record of life on Earth to >3850 Ma. Life and surface water by approximately 3850 Ma provide constraints on either the energetics or termination of the late meteoritic bombardment event (suggested from the lunar cratering record) on Earth.

  13. Recognition of > or = 3850 Ma water-lain sediments in West Greenland and their significance for the early Archaean Earth

    NASA Technical Reports Server (NTRS)

    Nutman, A. P.; Mojzsis, S. J.; Friend, C. R.; Bada, J. L. (Principal Investigator)

    1997-01-01

    A layered body of amphibolite, banded iron formation (BIF), and ultramafic rocks from the island of Akilia, southern West Greenland, is cut by a quartz-dioritic sheet from which SHRIMP zircon 206Pb/207Pb weighted mean ages of 3865 +/- 11 Ma and 3840 +/- 8 Ma (2 sigma) can be calculated by different approaches. Three other methods of assessing the zircon data yield ages of >3830 Ma. The BIFs are interpreted as water-lain sediments, which with a minimum age of approximately 3850 Ma, are the oldest sediments yet documented. These rocks provide proof that by approximately 3850 Ma (1) there was a hydrosphere, supporting the chemical sedimentation of BIF, and that not all water was stored in hydrous minerals, and (2) that conditions satisfying the stability of liquid water imply surface temperatures were similar to present. Carbon isotope data of graphitic microdomains in apatite from the Akilia island BIF are consistent with a bio-organic origin (Mojzsis et al. 1996), extending the record of life on Earth to >3850 Ma. Life and surface water by approximately 3850 Ma provide constraints on either the energetics or termination of the late meteoritic bombardment event (suggested from the lunar cratering record) on Earth.

  14. Modeling of ocean-induced ice melt rates of five west Greenland glaciers over the past two decades

    NASA Astrophysics Data System (ADS)

    Rignot, E.; Xu, Y.; Menemenlis, D.; Mouginot, J.; Scheuchl, B.; Li, X.; Morlighem, M.; Seroussi, H.; den Broeke, M. van; Fenty, I.; Cai, C.; An, L.; Fleurian, B. de

    2016-06-01

    High-resolution, three-dimensional simulations from the Massachusetts Institute of Technology general circulation model ocean model are used to calculate the subaqueous melt rate of the calving faces of Umiamako, Rinks, Kangerdlugssup, Store, and Kangilerngata glaciers, west Greenland, from 1992 to 2015. Model forcing is from monthly reconstructions of ocean state and ice sheet runoff. Results are analyzed in combination with observations of bathymetry, bed elevation, ice front retreat, and glacier speed. We calculate that subaqueous melt rates are 2-3 times larger in summer compared to winter and doubled in magnitude since the 1990s due to enhanced subglacial runoff and 1.6 ± 0.3°C warmer ocean temperature. Umiamako and Kangilerngata retreated rapidly in the 2000s when subaqueous melt rates exceeded the calving rates and ice front retreated to deeper bed elevation. In contrast, Store, Kangerdlugssup, and Rinks have remained stable because their subaqueous melt rates are 3-4 times lower than their calving rates, i.e., the glaciers are dominated by calving processes.

  15. Trans-generational and neonatal humoral immune responses in West Greenland sledge dogs (Canis familiaris) exposed to organohalogenated environmental contaminants.

    PubMed

    Sonne, Christian; Larsen, Hans Jørgen S; Kirkegaard, Maja; Letcher, Robert J; Dietz, Rune

    2010-11-01

    Previous investigations in the Arctic have suggested OHC (organohalogen contaminant) induced immune toxic effects on e.g. polar bears (Ursus maritimus). We therefore studied the dietary impact from minke whale blubber (Balaenoptera acutorostrata), rich in polyunsaturated fatty acids and OHCs, on the humoral immunity of 7 captive West Greenland sledge dog (Canis familiaris) bitches and their 4 pups constituting a sentinel model species for polar bears. A control group was composed of 8 bitches and their 5 pups all fed pork (Suis scrofa) fat. The study included serum IgG measurements (bitches and pups) and specific immune responses towards tetanus toxoid (bitches) and diphtheria toxoid (pups) as well as influenza virus (pups). The analyses showed that IgG concentrations were non-significantly lowest in exposed bitches and pups (t-test: all p>0.05). In addition, significant lower antibody response was detected in exposed pups immunized with influenza virus at age 3 months (t-test: both p<0.05). No clear group differences were found for tetanus toxoid in bitches and diphtheria toxoid in pups. The results suggest that the humoral immune system of sledge dogs may be suppressed by the dietary blubber composition of OHCs and polyunsaturated fatty acids while a larger follow-up study is recommended in order to investigate this relationship further.

  16. Multi-Year Elevation Changes Near the West Margin of the Greenland Ice Sheet from Satellite Radar Altimetry

    NASA Technical Reports Server (NTRS)

    Lingle, Craig S.; Brenner, Anita C.; Zwally, H. Jay; DiMarzio, John P.

    1991-01-01

    Mean changes in the surface elevation near the west margin of the Greenland ice sheet are measured using Seasat altimetry and altimetry from the Geosat Exact Repeat Mission (ERM). The Seasat data extend from early July through early October 1978. The ERM data extend from winter 1986-87 through fall 1988. Both seasonal and multi-year changes are measured using altimetry referenced to GEM T2 orbits. The possible effects of orbit error are minimized by adjusting the orbits into a common ocean surface. Seasonal mean changes in the surface height are recognizable during the Geosat ERM. The multi-year measurements indicate the surface was lower by 0.4 +/- 0.4 m on average in late summer 1987 than in late summer 1978. The surface was lower by 0.2 +/- 0.5 m on average in late summer 1988 than in late summer 1978. As a control case, the computations art also carried out using altimetry referenced to orbits not adjusted into a common ocean surface.

  17. Multi-year elevation changes near the west margin of the Greenland ice sheet from satellite radar altimetry

    SciTech Connect

    Lingle, C.S.; Brenner, A.C.; Zwally, H.J.; DiMarzio, J.P.

    1992-03-01

    Mean changes in the surface elevation near the west margin of the Greenland ice sheet are measured using Seasat altimetry and altimetry from the Geosat Exact Repeat Mission (ERM). The Seasat data extend from early July through early October 1978. The ERM data extend from winter 1986-87 through fall 1988. Both seasonal and multi-year changes are measured using altimetry referenced to GEM T2 orbits. The possible effects of orbit error are minimized by adjusting the orbits into a common ocean surface. Seasonal mean changes in the surface height are recognizable during the Geosat ERM. The multi-year measurements indicate the surface was lower by 0.4 +/- 0.4 m on average in late summer 1987 than in late summer 1978. The surface was lower by 0.2 +/- 0.5 m on average in late summer 1988 than in late summer 1978. As a control case, the computations are also carried out using altimetry referenced to orbits not adjusted into a common ocean surface.

  18. Epidemiological study of viral hepatitis types A, B, C, D and E among Inuits in West Greenland.

    PubMed

    Langer, B C; Frösner, G G; von Brunn, A

    1997-09-01

    A descriptive study was performed to evaluate the relative frequencies and molecular epidemiological features of viral hepatitis types A to E among the Inuit population in West Greenland. Serum samples were collected from 503 Inuits (186 males and 317 females; mean age 35 years; range 7-79 years) and were tested for markers of viral hepatitis infection. The hepatitis A prevalence averaged 54%, with a significant rise from 9% to 50% between the second and third decade of life. As for hepatitis B, 42% of the total study population showed serological evidence of current or past hepatitis B virus (HBV) infection and 7% were hepatitis B surface antigen (HBsAg) carriers. Among the carriers, 6% were also positive for hepatitis B e antigen (HBeAg), and HBV DNA could be detected in 49% of carriers by polymerase chain reaction. Typing of the HBV isolates revealed genomic group D in 83% (serotype ayw2) and group A in 17% (serotype adw 2). Less than 1% of the study population had antibodies to the hepatitis C virus. None were positive for HCV RNA. Serological evidence of hepatitis D infection was found in 7% of those with hepatitis B helper virus infection markers and in 40% of the HBsAg carriers. As for hepatitis E, 3% of the Inuits showed reactivity in an enzyme immunoassay that detected hepatitis E virus antibody. HEV RNA could not be detected.

  19. Comparison of remote sensing reflectance from above-water and in-water measurements west of Greenland, Labrador Sea, Denmark Strait, and west of Iceland.

    PubMed

    Garaba, Shungudzemwoyo P; Zielinski, Oliver

    2013-07-01

    The need to obtain ocean color essential climate variables (OC-ECVs) using hyperspectral technology has gained increased interest in recent years. Assessing ocean color on a large scale in high latitude environments using satellite remote sensing is constrained by polar environmental conditions. Nevertheless, on a small scale we can assess ocean color using above-water and in-water remote sensing. Unfortunately, above-water remote sensing can only determine apparent optical properties leaving the sea surface and is susceptible to near surface environmental conditions for example sky and sunglint. Consequently, we have to rely on accurate in-water remote sensing as it can provide both synoptic inherent and apparent optical properties of seawater. We use normalized water leaving radiance LWN or the equivalent remote sensing reflectance RRS from 27 stations to compare the differences in above-water and in-water OC-ECVs. Analysis of above-water and in-water RRS spectra provided very good match-ups (R2 > 0.97, MSE < 1.8*10(-7)) for all stations. The unbiased percent differences (UPD) between above-water and in-water approaches were determined at common OC-ECVs spectral bands (410, 440, 490, 510 and 555) nm and the classic band ratio (490/555) nm. The spectral average UPD ranged (5 - 110) % and band ratio UPD ranged (0 - 12) %, the latter showing that the 5% uncertainty threshold for ocean color radiometric products is attainable. UPD analysis of these stations West of Greenland, Labrador Sea, Denmark Strait and West of Iceland also suggests that the differences observed are likely a result of environmental and instrumental perturbations.

  20. U-Pb Zircon Provenance of Metasedimentary Basement of the Northwestern Terrane, Svalbard: A central East Greenland correlation

    NASA Astrophysics Data System (ADS)

    Petterssen, C.; Frei, D.; Pease, V.

    2007-12-01

    Svalbard's Caledonian and older bedrock consists of three main exotic terranes separated by north-south trending strike-slip faults. Early in the 19-century Kulling (1930, 1934) noted the striking similarity between the Neoproterozoic and Early Paleozoic sedimentary rocks from East Greenland and Svalbard's Eastern Terrane. After this pioneering work Harland et al. (1969) documented their remarkable similarities through detailed stratigraphic correlation of Neoproterozoic and Early Paleozoic sedimentary rocks. Recent work in the Northwestern and the eastern part of the Eastern terrane shows that this metasedimentary basement has a strong resemblance to the Krummedal and Smallefjord sequences of central East Greenland, with Grenville age (sensu lato) granitoid intrusion followed by Caledonian migmatization and granite genesis. We present the first LA-ICP-MS U-Pb zircon provenance study on quartzites and mica schists from the Kongsfjorden Group of the Northwestern Terrane of Svalbard. These results indicate a strong correlation with the Krummedal of central East Greenland and help to constrain paleogeographic reconstructions of the Northwestern Terrane. References: Kulling, O. 1930. Stratigraphic studies of the geology of Northeast Greenland. Meddelelser on Gronland, 74, 317- 346. Kulling, O. 1934. Scientific results of the Swedish-Norwegian Arctic Expedition in the summer of 1931. Part XI, The "Hecla Hoek Formation" round Hinlopenstredet. Geografiska Annaler, 16, 161-254. Gee, D. G. and Tebenkov, A. M., 2004. Svalbard: a fragment of the Laurentian margin.? In: Gee, D. G. and Pease, V. (eds) The Neoproterozoic Timanide Orogen of eastern Baltica. Geological Society, London, Memoirs, 30, 191- 206. Harland, W. B. 1969. Contribution of Spitsbergen to understanding of tectonic evolution of North Atlantic region. North Atlantic Geology and Continental Drift. Memoirs of the American Association of Petroleum Geologists, 12, 817-851.

  1. Transformation of landforms and sediments in the periglacial setting of West Greenland

    NASA Astrophysics Data System (ADS)

    Česnulevičius, Algimantas; Šeirienė, Vaida

    2009-06-01

    The article deals with the cryogenic processes taking place in the terminal zone of the recessing glacier of SW Greenland, which modify the sediment layers and transform the landforms. The sediment horizons were examined in natural outcrops and in trenches. Structural analysis of periglacial sediments in the slopes has shown that subdued evaporation and shallow permafrost favour the development of cryoturbations. In relief declensions, the formation of polygonal surfaces is predetermined by shallow beds of magmatic rocks, permafrost and especially slow evaporation during short warm seasons. Aeolian processes are most active in the valleys sculptured by glaciofluvial flows where cold arid winds blow out or rework inequigranular deposits. Dust is blown out by wind erosion, whereas the coarse-grained material is transported by creeping or saltation. Sand ripple and embryo dune terrains are widespread in glaciofluvial valleys. Wind erosion processes forming pebble-boulder deflation pavements take place in relief declensions. Outcrops sized 10-60 m2 and niches develop in the hill slopes. Diatoms indicate that sedimentation in small closed basins took place under cold, oligotrophic, acidophilous conditions.

  2. Gravity survey of Dixie Valley, west-central Nevada

    USGS Publications Warehouse

    Schaefer, Donald H.

    1983-01-01

    Dixie Valley, a northeast-trending structural trough typical of valleys in the Basin and Range Province, is filled with a maximum of about 10,000 feet of alluvial and lacustrine deposits , as estimated from residual-gravity measurements obtained in this study. On the basis of gravity measurements at 300 stations on nine east-west profiles, the gravity residuals reach a maximum of 30 milligals near the south-central part of the valley. Results from a three-dimensional inversion model indicate that the central depression of the valley is offset to the west of the geographic axis. This offset is probably due to major faulting along the west side of the valley adjacent to the Stillwater Range. Comparison of depths to bedrock obtained during this study and depths obtained from a previous seismic-refraction study indicates a reasonably good correlation. A heterogeneous distribution of densities within the valley-fill deposits would account for differing depths determined by the two methods. (USGS)

  3. Preliminary results from hot-water drilling and borehole instrumentation on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Doyle, S. H.; Christoffersen, P.; Hubbard, B. P.; Young, T. J.; Hofstede, C. M.; Box, J.; Todd, J.; Bougamont, M. H.; Hubbard, A.

    2015-12-01

    As part of the Subglacial Access and Fast Ice Research Experiment (SAFIRE) pressurised hot water was used to drill four 603-616 m-long boreholes to the bed of the Greenland Ice Sheet at a site located 30 km from the calving front of fast-flowing, marine-terminating Store Glacier (70° N, ~1000 m elevation). Despite the boreholes freezing within hours, 4 wired sensor strings were successfully deployed in three of the boreholes. These included a thermistor string to obtain the englacial temperature profile installed in the same borehole as a string of tilt sensors to measure borehole deformation, and two sets of water pressure, electrical conductivity and turbidity sensors installed just above the bed in separate, adjacent boreholes. The boreholes made a strong hydrological connection to the bed during drilling, draining rapidly to ~80 m below the ice surface. The connection of subsequent boreholes was observed as a perturbation in water pressure and temperature recorded in neighbouring boreholes, indicating an effective hydrological sub- or en-glacial connection between them. The sensors, which were all connected to loggers at the surface by cables, operated for between ~30 and 80+ days before indications suggest that the cables stretched and then snapped - with the lowermost sensors failing first. The records obtained from these sensors reveal (i) high and increasing water pressure varying diurnally close to overburden albeit of a small magnitude (~ 0.3 m H2O), (ii) a minimum extrapolated englacial temperature of -21°C with above-freezing temperatures at the bed, and (iv) high rates of internal deformation and strain increasing towards the bed as evinced by increasing tilt with depth. These borehole observations are complemented by GPS measurements of ice motion, meteorological data, and seismic and radar surveys.

  4. Petrology of the Plutonic Rocks of west-central Alaska

    USGS Publications Warehouse

    Miller, Thomas P.

    1970-01-01

    A series of plutons in west-central Alaska defines the Hogatza plutonic belt which extends for about 200 miles in an east-west direction from the northeastern Seward Peninsula to the Koyukuk River. The plutonic rocks have an aggregate area of about 1,200 square miles and their composition, distribution, and possible petrogenesis are discussed for the first time in this report. Field, petrographic and chemical data supported by K/Ar age dating indicate the plutonic rocks are divisible into two suites differing in age, location, and composition. The western plutons are mid-Cretaceous (~100 m.y.) in age and consist of a heterogeneous assemblage of monzonite, syenite, quartz monzonite. Associated with these granitic rocks is a group of alkaline sub-silicic rocks that forma belt of intrusive complexes extending for a distance of at least 180 miles from west-central Alaska to the Bering Sea. The complex at Granite Mountain shows a rare example of zoning from an alkaline rim to a quartz-bearing core. The occurrence of a similar complex at Cape Dezhnev on the easternmost tip of Siberia suggests the alkaline province may extend into Siberia. The easternmost plutons are Late Cretaceous (180 m.y.) in age and composed primarily of granodiorite and quartz monzonite similar to calc-alkaline plutons found throughout the North America Cordillera. The plutons are epizonal and intrude deformed but unmetamorphosed Lower Cretaceous andesitic volcanics and volcanic graywacke which constitute the highly mobile Yukon-Koyukuk volcanogenic province of west-central Alaska. No older rocks have been found within the confines of this vast tract; the occurrence of a bounding ophiolite sequence has lead to the suggestion that the province was formed by large-scale rifting and is underlain by oceanic crust. The possibility of no juvenile sialic crust over much of the area suggests that the potassium-rich magma now represented by the alkaline rocks originated in the mantle. The distribution of the

  5. 9 CFR 93.320 - Horses from Central America and the West Indies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 9 Animals and Animal Products 1 2014-01-01 2014-01-01 false Horses from Central America and the... PRODUCTS; REQUIREMENTS FOR MEANS OF CONVEYANCE AND SHIPPING CONTAINERS Horses Central America and the West Indies 17 § 93.320 Horses from Central America and the West Indies. Horses from Central America and...

  6. 9 CFR 93.320 - Horses from Central America and the West Indies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 9 Animals and Animal Products 1 2011-01-01 2011-01-01 false Horses from Central America and the... PRODUCTS; REQUIREMENTS FOR MEANS OF CONVEYANCE AND SHIPPING CONTAINERS Horses Central America and the West Indies 17 § 93.320 Horses from Central America and the West Indies. Horses from Central America and...

  7. 9 CFR 93.320 - Horses from Central America and the West Indies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 1 2012-01-01 2012-01-01 false Horses from Central America and the... PRODUCTS; REQUIREMENTS FOR MEANS OF CONVEYANCE AND SHIPPING CONTAINERS Horses Central America and the West Indies 17 § 93.320 Horses from Central America and the West Indies. Horses from Central America and...

  8. 9 CFR 93.320 - Horses from Central America and the West Indies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Horses from Central America and the... PRODUCTS; REQUIREMENTS FOR MEANS OF CONVEYANCE AND SHIPPING CONTAINERS Horses Central America and the West Indies 17 § 93.320 Horses from Central America and the West Indies. Horses from Central America and...

  9. 9 CFR 93.320 - Horses from Central America and the West Indies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 9 Animals and Animal Products 1 2013-01-01 2013-01-01 false Horses from Central America and the... PRODUCTS; REQUIREMENTS FOR MEANS OF CONVEYANCE AND SHIPPING CONTAINERS Horses Central America and the West Indies 17 § 93.320 Horses from Central America and the West Indies. Horses from Central America and...

  10. Floods of May 1981 in west-central Montana

    USGS Publications Warehouse

    Parrett, Charles; Omang, R.J.; Hull, J.A.; Fassler, John W.

    1982-01-01

    Extensive flooding occurred in west-central Montana during May 22-23, 1981, as a result of a series of rainstorms. Flooding was particularly severe in the communities of East Helena, Belt, and Deer Lodge. Although no lives were lost, total flood damages were estimated by the Montana Disaster Emergency Services Division to be in excess of $30 million. Peak discharges were determined at 75 sites in the flooded area. At 25 sites the May 1981 peak discharge exceeded the computed 100-year frequency flood, and at 29 sites, where previous flow records are available, the May 1981 peak discharge exceeded the previous peak of record. (USGS)

  11. Geologic Map of the Nulato Quadrangle, West-Central Alaska

    USGS Publications Warehouse

    Patton, W.W.; Moll-Stalcup, E. J.

    2000-01-01

    Introduction The Nulato quadrangle encompasses approximately 17,000 km2 (6,500 mi2) of west-central Alaska within the Yukon River drainage basin. The quadrangle straddles two major geologic features-the Yukon-Koyukuk sedimentary basin, a huge triangle-shaped Cretaceous depression that stretches across western Alaska from the Brooks Range to the Yukon delta; and the Ruby geanticline,a broad uplift of pre-Cretaceous rocks that borders the Yukon-Koyukuk basin on the southeast. The Kaltag Fault crosses the quadrangle diagonally from northeast to southwest and dextrally offsets all major geologic features as much as 130 km.

  12. Volume and Freshwater Flux to the West of Greenland: Nares Strait from 2003 to 2009

    NASA Astrophysics Data System (ADS)

    Muenchow, A.; Melling, H.

    2014-12-01

    Nares Strait is a 30-40 km wide channel between northern Greenland and Canada where we collected time series observation of velocity, subsurface pressure, and salinity from 2003 to 2009 to quantify volume and freshwater flux. Direct sub-surface observations are augmented by ice velocity and dynamical constraints to interpolate observations to the surface. Measurements indicate a mean volume flux of 1.0 +/- 0.08 Sv (Sv=10^6 m^3/s) and a mean freshwater flux of 62 mSv from the Arctic Ocean through Nares Strait to the south. About 20% of the volume and 50% of the freshwater flux reside in the top 30-m of the water column. Flux variability peaks at a 20-day time scale and correlates strongly with along-channel pressure gradients which explain more than 80% of the flux variance. Seasonal volume flux variations have an amplitude of about 0.1 Sv and a phase that result in maximal and minimal southward transports in March and November, respectively. Ice cover is usually land-fast in March and mobile in November suggesting that the frictional dynamics in a surface layer under the ice are secondary in importance to the along-channel pressure gradient that peaks in early spring with high sea level in the Arctic and low sea level in the more southerly Baffin Bay. Observed changes in the duration of land-fast ice conditions impact ocean stratification and flux through Nares Strait. For example, volume and freshwater fluxes increased by 50% and 100% in years when the ice was mobile almost year-round from 2006 through 2010 as compared to the 2003 to 2006 period when the ice was not mobile for more than 6 month per year on average. Local winds explain almost 50% of the variance during the 2007 to 2009 period of year-round mobile ice when a southern ice arch did not form. This ice arch returned to southern Nares Strait in 2011 resulting in long periods of land-fast ice cover and, we hypothesize, reduced ocean flux.

  13. Ocean properties, ice-ocean interactions, and calving front morphology at two major west Greenland glaciers

    NASA Astrophysics Data System (ADS)

    Chauché, N.; Hubbard, A.; Gascard, J.-C.; Box, J. E.; Bates, R.; Koppes, M.; Sole, A.; Patton, H.

    2013-11-01

    Warm sub-polar mode water (SPMW) has been identified as a primary driver of mass loss of marine terminating glaciers draining the Greenland Ice Sheet (GrIS) yet, the specific mechanisms by which SPMW interacts with these tidewater termini remain uncertain. We present oceanographic data from Rink Glacier (RG) and Store Glacier (SG) fjords, two major marine outlets draining the western sector of the GrIS into Baffin Bay over the contrasting melt-seasons of 2009 and 2010. Submarine melting occurs wherever ice is in direct contact with warmer water and the consistent presence of 2.8 °C SPMW adjacent to both ice fronts below 400 m throughout all surveys indicates that melting is maintained by a combination of molecular diffusion and large scale, weak convection, diffusional (hereafter called ubiquitous) melting. At shallower depths (50-200 m), cold, brine-enriched water (BEW) formed over winter appears to persist into the summer thereby buffering this melt by thermal insulation. Our surveys reveal four main modes of glacier-ocean interaction, governed by water depth and the rate of glacier runoff water (GRW) injected into the fjord. Deeper than 200 m, submarine melt is the only process observed, regardless of the intensity of GRW or the depth of injection. However, between the surface and 200 m depth, three further distinct modes are observed governed by the GRW discharge. When GRW is weak (≲1000 m3 s-1), upward motion of the water adjacent to the glacier front is subdued, weak forced or free convection plus diffusional submarine melting dominates at depth, and seaward outflow of melt water occurs from the glacier toe to the base of the insulating BEW. During medium intensity GRW (∼1500 m3 s-1), mixing with SPMW yields deep mixed runoff water (DMRW), which rises as a buoyant plume and intensifies local submarine melting (enhanced buoyancy-driven melting). In this case, DMRW typically attains hydrostatic equilibrium and flows seaward at an intermediate depth of

  14. Ground Magnetic Data for west-central Colorado

    DOE Data Explorer

    Zehner, Richard

    2012-03-08

    Ground Magnetic Data for west-central Colorado Modeled ground magnetic data was extracted from the Pan American Center for Earth and Environmental Studies database at http://irpsrvgis08.utep.edu/viewers/Flex/GravityMagnetic/GravityMagnetic_CyberShare/ on 2/29/2012. The downloaded text file was then imported into an Excel spreadsheet. This spreadsheet data was converted into an ESRI point shapefile in UTM Zone 13 NAD27 projection, showing location and magnetic field strength in nano-Teslas. This point shapefile was then interpolated to an ESRI grid using an inverse-distance weighting method, using ESRI Spatial Analyst. The grid was used to create a contour map of magnetic field strength. This dataset includes the raw spreadsheet data, an ESRI point shapefile showing magnetic sample locations and magnetic field strength, and an ESRI line shapefile showing magnetic contours. Projection: UTM Zone 13 NAD27 Magnetic Contour Shapefile Extent: West -108.698836 East -105.283977 North 41.048206 South 36.950086 Magnetic Point Shapefile Extent: West -108.698832 East -105.283908 North 41.048142 South 36.950086

  15. 22. AERIAL VIEW LOOKING EAST DOWN CENTRAL AVENUE FROM WEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. AERIAL VIEW LOOKING EAST DOWN CENTRAL AVENUE FROM WEST OF THE ADMINISTRATIVE AND SUPPORT AREA OF THE PLANT. ON THE LEFT (NORTH) SIDE OF THE STREET IN THE FOREGROUND OF THE PHOTOGRAPH IS BUILDING 111, THE GENERAL ADMINISTRATION BUILDING. TO THE EAST OF BUILDING 111 IS BUILDING 112, THE CAFETERIA. FURTHER TO THE EAST IS BUILDING 331, THE VEHICLE MAINTENANCE GARAGE AND FIRE DEPARTMENT; BUILDING 333, THE PAINT SHOP; BUILDING 334, THE ELECTRICAL AND GENERAL MAINTENANCE SHOP; AND BUILDING 551, THE GENERAL WAREHOUSE. ON THE RIGHT (SOUTH) SIDE OF CENTRAL AVENUE, IN THE FOREGROUND IS BUILDING 121, FIREARMS REPAIR. BEHIND BUILDING 121 IS BUILDING 122, EMERGENCY MEDICAL SERVICES, AND BUILDING 123, HEALTH PHYSICS LABORATORY. BUILDING 441, THE PRODUCTION ... - Rocky Flats Plant, Bounded by Indiana Street & Routes 93, 128 & 72, Golden, Jefferson County, CO

  16. Metamorphism of the ca. 3800 Ma supracrustal rocks at Isua, West Greenland: implications for early Archaean crustal evolution

    NASA Astrophysics Data System (ADS)

    Boak, Jeremy L.; Dymek, Robert F.

    1982-06-01

    A detailed mineralogical and petrological study has been carried out on samples from two clastic metasedimentary lithologies from the ˜ 3800 Ma Isua Supracrustal Belt, West Greenland. Semipelitic to pelitic "garnet-biotite schist" contains the limiting AKFM assemblage: muscovite-biotite-garnet-staurolite (+ quartz + plagioclase + ilmenite), whereas "muscovite-biotite gneiss", derived from felsic volcanogenic graywacke, locally contains kyanite (+ quartz+ plagioclase + Ca-, Mn-rich garnet). Temperatures calculated from Fe-Mg partitioning between coexisting garnet- biotite indicate equilibration for garnet coresat T ˜550°C, and ˜460°C for garnet rims. We interpret the higher T as a minimum estimate for prograde regional metamorphism which we argue occurred before 3600 Ma, whereas the lower T reflects later retrogression as indicated by the development of chlorite ± sericite in many samples. The presence of kyanite as the stable aluminosilicate polymorph, combined with phase assemblage data, indicate P ˜5 kbar during prograde metamorphism, and a depthof burial of at least 15 km. The Isua supracrustals are the oldest comprehensively dated rocks on Earth, and the metamorphic mineral assemblages reported here constitute the earliest direct record of thermal regimes in Archaean crust. Therefore, characterization of the metamorphic history of the Isua region places an important constraint on models of early Earth history. Our data and observations indicate that prograde regional metamorphism at Isua occurred at conditions which are considered "normal" for an orogenic system, with a metamorphic thermal gradient ˜35°C/km. Moreover, our results contraindicate the universal occurrence of "thin" Archaean crust and excessively "steep" crustal thermal gradients as proposed by some investigators. Such conclusion appears at odds with estimates for higher terrestrial heat production during the early Archaean, but can be resolved by appealing to more rapid convection and

  17. Mesoarchean melting and Neoarchean to Paleoproterozoic metasomatism during the formation of the cratonic mantle keel beneath West Greenland

    NASA Astrophysics Data System (ADS)

    van Acken, D.; Luguet, A.; Pearson, D. G.; Nowell, G. M.; Fonseca, R. O. C.; Nagel, T. J.; Schulz, T.

    2017-04-01

    Highly siderophile element (HSE) concentration and 187Os/188Os isotopic heterogeneity has been observed on various scales in the Earth's mantle. Interaction of residual mantle peridotite with infiltrating melts has been suggested to overprint primary bulk rock HSE signatures originating from partial melting, contributing to the heterogeneity seen in the global peridotite database. Here we present a detailed study of harzburgitic xenolith 474527 from the Kangerlussuaq suite, West Greenland, coupling the Re-Os isotope geochemistry with petrography of both base metal sulfides (BMS) and silicates to assess the impact of overprint induced by melt-rock reaction on the Re-Os isotope system. Garnet harzburgite sample 474527 shows considerable heterogeneity in the composition of its major phases, most notably olivine and Cr-rich garnet, suggesting formation through multiple stages of partial melting and subsequent metasomatic events. The major BMS phases show a fairly homogeneous pentlandite-rich composition typical for BMS formed via metasomatic reaction, whereas the 187Os/188Os compositions determined for 17 of these BMS are extremely heterogeneous ranging between 0.1037 and 0.1981. Analyses by LA-ICP-MS reveal at least two populations of BMS grains characterized by contrasting HSE patterns. One type of pattern is strongly enriched in the more compatible HSE Os, Ir, and Ru over the typically incompatible Pt, Pd, and Re, while the other type shows moderate enrichment of the more incompatible HSE and has overall lower compatible HSE/incompatible HSE composition. The small-scale heterogeneity observed in these BMS highlights the need for caution when utilizing the Re-Os system to date mantle events, as even depleted harzburgite samples such as 474527 are likely to have experienced a complex history of metasomatic overprinting, with uncertain effects on the HSE.

  18. Changes in ice geometry and supraglacial hydrology, Sermeq Avannarleq ablation zone, West Greenland

    NASA Astrophysics Data System (ADS)

    McLamb, W. S.; Colgan, W.; Phillips, T. P.; Abdalati, W.; Steffen, K.; Motyka, R. J.; Rajaram, H.

    2010-12-01

    distribution. We also manually extracted major supraglacial lakes from both the 1985 map and 2009 imagery. No significant difference was found in lake locations or area distribution over the study interval. From this we hypothesize that despite an increase in melt water production, Sermeq Avannarleq’s supraglacial lakes have experienced an acceleration in their filling and draining cycle over the study period. Generally, the high rates of thinning (reaching a maximum of 5.79 ± 1.29 m/a) are too great to be explained by surface balance and along-flow ice flux alone. We suggest that an increase in across-flow ice flux, associated with the acceleration of Jakobshavn Isbrae to the south, has resulted in significant dynamic thinning. The observations of marginal recession of land-terminating ice and a thinning and steepening of the ablation zone are also consistent with model predictions the Greenland Ice Sheet’s dynamic response to a warming climate.

  19. The diorite at West Warren, south-central Massachusetts

    USGS Publications Warehouse

    Pomeroy, John S.

    1974-01-01

    Follated, syntectonic, concordant intrusive bodies of mostly diorite and meladiorite with less abundant quartz diorite and norite have been mapped in the West Warren area of south-central Massachusetts. The rocks of the pluton range from a medium colored phase of diorite and quartz diorite to a dark colored phase of meladiorite and norite. Major minerals In the dioritic rocks are calcic andesine, green hornblende, brown biotite, and hypersthene. Igneous textures are dominant, and retrograde or deuteric effects are generally minor. Silica and alumina contents of the dioritic rocks are somewhat higher than for average diorites; conversely, the oxides of iron, magnesium, and calcium are generally lower. Normative quartz, albite, and anorthite are higher and orthoclase is lower in the samples than In the average diorite. Sizeable plutons of diorite-norite are uncommon in central Massachusetts. The West Warren body, roughly 26 km2 (10 square miles) in area, bears little petrochemical relation to adjacent rock units. The pluton can be construed as belonging to a belt of intrusive mafic rocks which stretches from southeastern New York to coastal Maine.

  20. Status of the Topeka shiner in west-central Iowa

    USGS Publications Warehouse

    Pierce, Clay; Bakevich, Bryan D.; Quist, Michael C.

    2015-01-01

    The Topeka shiner Notropis topeka is a federally endangered fish species that is estimated to occupy only 20% of its historic range. In Iowa Topeka shiners have been in decline for decades. Our goal was to determine the present distribution of Topeka shiners in the west-central portion of their range in Iowa and to characterize the extent of its decline. We compared the current distribution to distributions generated from earlier collections. We found Topeka shiners in six of 22 watersheds where they occurred historically. Status of Topeka shiners was judged to be stable in 27% of the watersheds, at risk in 45% of the watersheds, and possibly extirpated in 27% of the watersheds. None were classified as increasing. Based on comparison of the historical distribution with more recent ones, Topeka shiners in west-central Iowa showed a 27% decline a decade ago and currently exhibits a 73% decline in their distribution. The collective evidence from four of five other states in the species’ range reveals similar declines. This study provides further information on the local distribution and extent of decline for this federally endangered species with a greatly reduced and fragmented overall distribution.

  1. Geology and total petroleum systems of the West-Central Coastal province (7203), West Africa

    USGS Publications Warehouse

    Brownfield, Michael E.; Charpentier, Ronald R.

    2006-01-01

    The West-Central Coastal Province of the Sub-Saharan Africa Region consists of the coastal and offshore areas of Cameroon, Equatorial Guinea, Gabon, Democratic Republic of the Congo, Republic of the Congo, Angola (including the disputed Cabinda Province), and Namibia. The area stretches from the east edge of the Niger Delta south to the Walvis Ridge. The West-Central Coastal Province includes the Douala, Kribi-Campo, Rio Muni, Gabon, Congo, Kwanza, Benguela, and Namibe Basins, which together form the Aptian salt basin of equatorial west Africa. The area has had significant exploration for petroleum; more than 295 oil fields have been discovered since 1954. Since 1995, several giant oil fields have been discovered, especially in the deep-water area of the Congo Basin. Although many total petroleum systems may exist in the West-Central Coastal Province, only four major total petroleum systems have been defined. The area of the province north of the Congo Basin contains two total petroleum systems: the Melania-Gamba Total Petroleum System, consisting of Lower Cretaceous source and reservoir rocks, and the Azile-Senonian Total Petroleum System, consisting of Albian to Turonian source rocks and Cretaceous reservoir rocks. Two assessment units are defined in the West-Central Coastal Province north of the Congo Basin: the Gabon Subsalt and the Gabon Suprasalt Assessment Units. The Congo Basin contains the Congo Delta Composite Total Petroleum System, consisting of Lower Cretaceous to Tertiary source and reservoir rocks. The Central Congo Delta and Carbonate Platform and the Central Congo Turbidites Assessment Units are defined in the Congo Delta Composite Total Petroleum System. The area south of the Congo Basin contains the Cuanza Composite Total Petroleum System, consisting of Lower Cretaceous to Tertiary source and reservoir rocks. The Cuanza-Namibe Assessment Unit is defined in the Cuanza Composite Total Petroleum System. The U.S. Geological Survey (USGS) assessed the

  2. Mantle Sources, Mantle Melting and the Genesis of the Central East Greenland Plateau Lavas

    NASA Astrophysics Data System (ADS)

    Brown, E. L.; Barfod, G. H.; Lesher, C. E.

    2006-12-01

    The Central East Greenland (CEG) plateau lavas (56-54 Ma) contain a very complete geochemical record of the opening of the North Atlantic basin in response to the breakup of Pangaea. This record provides an unique opportunity for identifying the mantle source compositions and melting processes involved in the genesis of the North Atlantic Igneous Province (NAIP). The plateau lavas consist of three compositional suites: the volumetrically dominant high-Ti suite (TiO2 ca. 1.67 - 4 wt. %) (HTS) and the minor low-Ti (TiO2 < 1.96 wt. %) and very high-Ti (TiO2 ca. 4 - 6 wt. %) suites (LTS and VHTS, respectively). We present detailed Hf-Nd-Sr data and trace element data for VHTS and LTS lavas closely associated within the lava succession. These uncontaminated lava suites represent the extreme compositional ranges of the plateau lavas and show limited variability in ɛHf (9.58 - 10.96 [VHTS] and 14.39 - 14.68 [LTS]) and a somewhat broader variation in ɛNd (5.42 - 6.73 [VHTS] and 8.29 - 9.68 [LTS]). The LTS and VHTS source compositions bracket the chemical range observed for the HTS lavas. Drawing from the model of [1], we propose that the mantle sources for the VHTS and LTS were intimately associated within the mantle melting regime beneath CEG and were present throughout the generation of the plateau lavas. Correlations between trace element and isotopic data can be accounted for by a forward melting model involving a heterogeneous source containing fusible eclogite and refractory peridotite. These findings are in contrast to the model of [2] proposing that temporal sampling of three distinct and isolated mantle domains within a zoned plume is the dominant control on plateau lava chemistry. Our study highlights the importance of combining isotope and trace element data in understanding melt production in the NAIP and elsewhere. (1) Tegner et al., 1998, Nature, v 395, p 591-594; (2) Barker et al., 2006, Geology, v 34, p 481-484

  3. 9 CFR 93.423 - Ruminants from Central America and the West Indies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 9 Animals and Animal Products 1 2013-01-01 2013-01-01 false Ruminants from Central America and the... PRODUCTS; REQUIREMENTS FOR MEANS OF CONVEYANCE AND SHIPPING CONTAINERS Ruminants Central America and West Indies 9 § 93.423 Ruminants from Central America and the West Indies. (a) Ruminants intended...

  4. 9 CFR 93.423 - Ruminants from Central America and the West Indies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 1 2012-01-01 2012-01-01 false Ruminants from Central America and the... PRODUCTS; REQUIREMENTS FOR MEANS OF CONVEYANCE AND SHIPPING CONTAINERS Ruminants Central America and West Indies 9 § 93.423 Ruminants from Central America and the West Indies. (a) Ruminants intended...

  5. 9 CFR 93.423 - Ruminants from Central America and the West Indies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 9 Animals and Animal Products 1 2011-01-01 2011-01-01 false Ruminants from Central America and the... PRODUCTS; REQUIREMENTS FOR MEANS OF CONVEYANCE AND SHIPPING CONTAINERS Ruminants Central America and West Indies 9 § 93.423 Ruminants from Central America and the West Indies. (a) Ruminants intended...

  6. 9 CFR 93.423 - Ruminants from Central America and the West Indies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 9 Animals and Animal Products 1 2014-01-01 2014-01-01 false Ruminants from Central America and the... PRODUCTS; REQUIREMENTS FOR MEANS OF CONVEYANCE AND SHIPPING CONTAINERS Ruminants Central America and West Indies 9 § 93.423 Ruminants from Central America and the West Indies. (a) Ruminants intended...

  7. Seasonal and regional variability in dissolved and particulate iron fluxes via glacial runoff along the West Greenland coast

    NASA Astrophysics Data System (ADS)

    Choquette, K.; Hagedorn, B.; Sletten, R. S.; Harrold, Z.; Liu, L.; Dieser, M.; Cameron, K. A.; Christner, B. C.; Junge, K.

    2012-12-01

    Subglacial weathering, due to biogeochemical and physical weathering processes, can affect the chemical evolution of subglacial waters and release dissolved and particulate iron via glacial runoff. Iron is a growth limiting nutrient and plays a critical role in the biogeochemical cycles of coastal and marine waters. More recently, dissolved and colloidal iron derived from subglacial sources have been considered an important contributor of Fe fluxes to the ocean; however, their dependency on lithology, grain size, and microbial activity is not well understood. This study characterizes the solute chemistry, in particular iron mineralogy and dissolved iron concentrations, released from beneath the Greenland Ice Sheet (GrIS), from two locations along the West Greenland coast, Thule (76°N, 68°W) and Kangerlussuaq (67°N, 50°W). We hypothesize that the subglacial lithology has a control on Fe fluxes from the GrIS to coastal and marine systems. The underlying bedrock in Thule is the Precambrian Dundas and Narssarssuk sedimentary formations which include sandstone, siltstone, and shale. The bedrock in Kangerlussuaq is dominated by Archean granodioritic gneiss and amphibolite within the Nagssugtoqidian Orogen. Supra and subglacial meltwater samples were collected directly in front of the Ice Sheet over an entire melt season in 2011 (North River, Thule) and 2012 (Akuliarusiarsuup Kuua River, Kangerlussuaq). In situ parameters such as temperature, pH, dissolved oxygen, and electrical conductivity were recorded in order to interpret meltwater chemistry. Dissolved Fe(II) and Fe(III) species were fixed immediately and analyzed within 24 hours after sampling in the field laboratory using a spectrophotometer and 10 cm cell. Total dissolved iron (FeT) of different size fractions (<0.22 and <0.05 μm) of iron were determined back in the home laboratory using reaction cell ICP MS. Preliminary results demonstrate that subglacial meltwater of North River has average Fe

  8. Climatic factors influencing triatomine occurrence in Central-West Brazil

    PubMed Central

    Pereira, Joyce Mendes; de Almeida, Paulo Silva; de Sousa, Adair Vieira; de Paula, Aécio Moraes; Machado, Ricardo Bomfim; Gurgel-Gonçalves, Rodrigo

    2013-01-01

    We estimated the geographic distributions of triatomine species in Central-West Region of Brazil (CW) and analysed the climatic factors influencing their occurrence. A total of 3,396 records of 27 triatomine species were analysed. Using the maximum entropy method, ecological niche models were produced for eight species occurring in at least 20 municipalities based on 13 climatic variables and elevation. Triatoma sordida and Rhodnius neglectus were the species with the broadest geographic distributions in CW Brazil. The Cerrado areas in the state of Goiás were found to be more suitable for the occurrence of synanthropic triatomines than the Amazon forest areas in the northern part of the state of Mato Grosso. The variable that best explains the evaluated models is temperature seasonality. The results indicate that almost the entire region presents climatic conditions that are appropriate for at least one triatomine species. Therefore, it is recommended that entomological surveillance be reinforced in CW Brazil. PMID:23778666

  9. Multiresolution quantification of deciduousness in West Central African forests

    NASA Astrophysics Data System (ADS)

    Viennois, G.; Barbier, N.; Fabre, I.; Couteron, P.

    2013-04-01

    The characterization of leaf phenology in tropical forests is of major importance and improves our understanding of earth-atmosphere-climate interactions. The availability of satellite optical data with a high temporal resolution has permitted the identification of unexpected phenological cycles, particularly over the Amazon region. A primary issue in these studies is the relationship between the optical reflectance of pixels of 1 km or more in size and ground information of limited spatial extent. In this paper, we demonstrate that optical data with high to very-high spatial resolution can help bridge this scale gap by providing snapshots of the canopy that allow discernment of the leaf-phenological stage of trees and the proportions of leaved crowns within the canopy. We also propose applications for broad-scale forest characterization and mapping in West Central Africa over an area of 141 000 km2. Eleven years of the Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) data were averaged over the wet and dry seasons to provide a dataset of optimal radiometric quality at a spatial resolution of 250 m. Sample areas covered at a very-high (GeoEye) and high (SPOT-5) spatial resolution were used to identify forest types and to quantify the proportion of leaved trees in the canopy. The dry season EVI was positively correlated with the proportion of leaved trees in the canopy. This relationship allowed the conversion of EVI into canopy deciduousness at the regional level. On this basis, ecologically important forest types could be mapped, including young secondary, open Marantaceae, Gilbertiodendron dewevrei and swamp forests. We show that in west central African forests, a large share of the variability in canopy reflectance, as captured by the EVI, is due to variation in the proportion of leaved trees in the upper canopy, thereby opening new perspectives for biodiversity and carbon-cycle applications.

  10. Multiresolution quantification of deciduousness in West-Central African forests

    NASA Astrophysics Data System (ADS)

    Viennois, G.; Barbier, N.; Fabre, I.; Couteron, P.

    2013-11-01

    The characterization of leaf phenology in tropical forests is of major importance for forest typology as well as to improve our understanding of earth-atmosphere-climate interactions or biogeochemical cycles. The availability of satellite optical data with a high temporal resolution has permitted the identification of unexpected phenological cycles, particularly over the Amazon region. A primary issue in these studies is the relationship between the optical reflectance of pixels of 1 km or more in size and ground information of limited spatial extent. In this paper, we demonstrate that optical data with high to very-high spatial resolution can help bridge this scale gap by providing snapshots of the canopy that allow discernment of the leaf-phenological stage of trees and the proportions of leaved crowns within the canopy. We also propose applications for broad-scale forest characterization and mapping in West-Central Africa over an area of 141 000 km2. Eleven years of the Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) data were averaged over the wet and dry seasons to provide a data set of optimal radiometric quality at a spatial resolution of 250 m. Sample areas covered at a very-high (GeoEye) and high (SPOT-5) spatial resolution were used to identify forest types and to quantify the proportion of leaved trees in the canopy. The dry-season EVI was positively correlated with the proportion of leaved trees in the canopy. This relationship allowed the conversion of EVI into canopy deciduousness at the regional level. On this basis, ecologically important forest types could be mapped, including young secondary, open Marantaceae, Gilbertiodendron dewevrei and swamp forests. We show that in West-Central African forests, a large share of the variability in canopy reflectance, as captured by the EVI, is due to variation in the proportion of leaved trees in the upper canopy, thereby opening new perspectives for biodiversity and

  11. Substantial contribution to sea-level rise during the last interglacial from the Greenland ice sheet

    PubMed

    Cuffey; Marshall

    2000-04-06

    During the last interglacial period (the Eemian), global sea level was at least three metres, and probably more than five metres, higher than at present. Complete melting of either the West Antarctic ice sheet or the Greenland ice sheet would today raise sea levels by 6-7 metres. But the high sea levels during the last interglacial period have been proposed to result mainly from disintegration of the West Antarctic ice sheet, with model studies attributing only 1-2 m of sea-level rise to meltwater from Greenland. This result was considered consistent with ice core evidence, although earlier work had suggested a much reduced Greenland ice sheet during the last interglacial period. Here we reconsider the Eemian evolution of the Greenland ice sheet by combining numerical modelling with insights obtained from recent central Greenland ice-core analyses. Our results suggest that the Greenland ice sheet was considerably smaller and steeper during the Eemian, and plausibly contributed 4-5.5 m to the sea-level highstand during that period. We conclude that the high sea level during the last interglacial period most probably included a large contribution from Greenland meltwater and therefore should not be interpreted as evidence for a significant reduction of the West Antarctic ice sheet.

  12. Ice-Ocean Interactions to the North-West of Greenland: Glaciers, Straits, Ice Bridges, and the Rossby Radius (Invited)

    NASA Astrophysics Data System (ADS)

    Muenchow, A.; Falkner, K. K.; Melling, H.; Johnson, H. L.; Huntley, H. S.; Ryan, P.; Friends Of Petermann

    2010-12-01

    Petermann Glacier at 81 N latitude is a major outlet glacier adjacent to Nares Strait. It terminates in a long (70 km), narrow (16 km) and thin (50 m) floating tongue and has a grounding line more than 500 m below sea level. A calving event in 2010 reduced the floating area by 25% and produced a single 240 km2 ice island currently moving south in Nares Strait where it will likely interact with island to potentially create a temporary polynya in Nares Strait. The 2010 calving from Petermann Glacier contributes <10% to its mass balance as more than 80% is lost due to basal melting by the ocean. Hence the largely unexplored physics at the ice-ocean interface determine how a changing climate impacts this outlet glacier. Conducting exploratory surveys inside Petermann Fjord in 2003, 2007, and 2009, we find a 1100 m deep fjord connected to Nares Strait via a sill at 350-450 m depth. The fjord receives about 3 times the amount of heat required for the basal melt rates. Furthermore, limited data and analytical modeling suggests a 3-dimensional circulation over the upper 300-m of the water column with a coastally trapped buoyant outflow. We integrate these findings with more complete oceanic time series data from an array moored in Nares Strait from 2003 through 2009 near 80.5 N. In the past Nares Strait and Petermann Fjord were covered by land fast sea ice during the 9-10 month long winter season. Archeological and remotely sensed records indicate that an ice bridge formed regularly at the southern end of Nares Strait creating the North-Water polynya near 79 N latitude. Since 2006 this ice bridge has largely failed to form, leading, perhaps, to the occasional formation of a secondary ice bridge 300 km to the north where Nares Strait connects to the Arctic Ocean. However, this ice bridge appears to form for shorter periods only. Consequently Arctic sea ice can now exit the Arctic in winter via pathways to the west of Greenland all year. We speculate that this changed ocean

  13. Plate Tectonics at 3.8-3.7 Ga: Field Evidence from the Isua Accretionary Complex, Southern West Greenland.

    PubMed

    Komiya; Maruyama; Masuda; Nohda; Hayashi; Okamoto

    1999-09-01

    A 1&rcolon;5000 scale mapping was performed in the Isukasia area of the ca. 3.8-Ga Isua supracrustal belt, southern West Greenland. The mapped area is divided into three units bounded by low-angle thrusts: the Northern, Middle, and Southern Units. The Southern Unit, the best exposed, is composed of 14 subunits (horses) with similar lithostratigraphy, bound by layer-parallel thrusts. Duplex structures are widespread in the Isua belt and vary in scale from a few meters to kilometers. Duplexing proceeded from south to north and is well documented in the relationship between link- and roof-thrusts. The reconstructed lithostratigraphy of each horse reveals a simple pattern, in ascending order, of greenstone with low-K tholeiitic composition with or without pillow lava structures, chert/banded iron-formation, and turbidites. The cherts and underlying low-K tholeiites do not contain continent- or arc-derived material. The lithostratigraphy is quite similar to Phanerozoic "oceanic plate stratigraphy," except for the abundance of mafic material in the turbidites. The evidence of duplex structures and oceanic plate stratigraphy indicates that the Isua supracrustal belt is the oldest accretionary complex in the world. The dominantly mafic turbidite composition suggests that the accretionary complex was formed in an intraoceanic environment comparable to the present-day western Pacific Ocean. The duplex polarity suggests that an older accretionary complex should occur to the south of the Isua complex. Moreover, the presence of seawater (documented by a thick, pillow, lava unit at the bottom of oceanic plate stratigraphy) indicates that the surface temperature was less than ca. 100 degrees C in the Early Archean. The oceanic geotherm for the Early Archean lithosphere as a function of age was calculated based on a model of transient half-space cooling at given parameters of surface and mantle temperatures of 100 degrees and 1450 degrees C, respectively, suggesting that the

  14. Past sea-level data from Lakse Bugt, Disko Island, West Greenland from ground-penetrating radar data

    NASA Astrophysics Data System (ADS)

    Souza, Priscila E.; Nielsen, Lars; Kroon, Aart; Clemmensen, Lars B.

    2016-04-01

    Beach-ridge deposits have been used as sea-level indicators in numerous studies from temperate coastal regions. However, their present surface morphology in artic regions may not accurately correspond to past sea-level, because subsequent surface erosion, solifluction processes and/or later sediment deposition may have altered the surface significantly. The internal structure of these beach ridges, however, is often well-preserved and thus constitutes an important key to reconstruction of past sea levels as seen elsewhere. In the present study, high-resolution reflection GPR data and high-precision topographic data were collected at Lakse Bugt (Disko Island, West Greenland) using a shielded 250 MHz antennae system and a RTK-Trimble R8 DGPS, respectively. Three transects were collected across a sequence of fossil, raised beach ridge deposits, and two transects were obtained across modern beach deposits at the shoreline of the mesotidal regime. Along all radar profiles we observed downlap reflection points, which we interpret to represent the boundary between sediments deposited on the beachface and sediments deposited in the upper shoreface regime. Both the upper shoreface and the beachface deposits exhibit reflection patterns dipping in the seaward direction. The beachface deposits show the strongest dip. At or just below the downlap points strong diffractions are often observed indicating the presence of a layer containing stones. These stones are large enough to generate significant signal scattering. At the present day beach a sharp transition defined by the presence of large stones is observed near the low tide water level: cobbles characterize the seaside, while the land side is characterized by sand and gravel. Therefore, it seems reasonable to conclude that downlap points observed in the GPR data serve as indicators of past low-tide levels (at the time of deposition). The downlap points show a consistent offset with respect to present surface topography

  15. Ordovician sponges from west-central and east-central Alaska and western Yukon Territory, Canada

    USGS Publications Warehouse

    Rigby, J.K.; Blodgett, R.B.; Britt, B.B.

    2008-01-01

    Moderate collections of fossil sponges have been recovered over a several-year period from a few scattered localities in west-central and east-central Alaska, and from westernmost Yukon Territory of Canada. Two fragments of the demosponge agelasiid cliefdenellid, Cliefdenella alaskaensis Stock, 1981, and mostly small unidentifiable additional fragments were recovered from a limestone debris flow bed in the White Mountain area, McGrath A-4 Quadrangle in west-central Alaska. Fragments of the agelasiid actinomorph girtyocoeliids Girtyocoeliana epiporata (Rigby & Potter, 1986) and Girtyocoelia minima n. sp., plus a specimen of the vaceletid colospongiid Corymbospongia amplia Rigby, Karl, Blodgett & Baichtal, 2005, were collected from probable Ashgillian age beds in the Livengood B-5 Quadrangle in east-central Alaska. A more extensive suite of corymbospongiids, including Corymbospongia betella Rigby, Potter & Blodgett, 1988, C. mica Rigby & Potter, 1986, and C.(?) perforata Rigby & Potter, 1986, along with the vaceletiid colospongiids Pseudo-imperatoria minima? (Rigby & Potter, 1986), and Pseudoimperatoria media (Rigby & Potter, 1986), and with the heteractinid Nucha naucum? Pickett & Jell, 1983, were recovered from uppermost part of the Jones Ridge Limestone (Ashgillian), on the south flank of Jones Ridge, in the Sheep Mountain Quadrangle, in westernmost Yukon Territory, Canada. The fossil sponges from the McGrath A-4 and Livengood B-5 quadrangles were recovered from attached Siberian terranes, and those from the Sheep Mountain Quadrangle were recovered from an allochthonous Laurentian terrane in the Yukon Territory.

  16. Deglaciation and postglacial vegetation history of the West Mountains, west-central Idaho, USA

    USGS Publications Warehouse

    Doerner, J.P.; Carrara, P.E.

    1999-01-01

    The West Mountains, west-central Idaho, were deglaciated before ca. 11,500 BP, as indicated by radiocarbon ages and Glacier Peak tephra, at several sites in cirques. Pollen analysis of a sediment core, and plant macrofossils from sediments recovered from the cirque at the head of Van Wyck Creek, indicate that a closed spruce-pine forest surrounded the site from ca. 11,500 to 9800 BP. Early in this period, spruce (probably krummholz) was already growing near the present-day altitudinal limit of large upright spruce. Hence, the climate during this period was significantly warmer than before 11,500 BP. Between ca. 9800 and 3200 BP the climate was warmer and drier than present. Pollen data indicate that from ca. 9300 to the time of Mazama tephra deposition (ca. 6700 BP), the climate was warmer and drier than at any time since 11,500 BP. From ca. 6700 to 3200 BP there was a small decrease in temperature with a minor increase in effective moisture. Beginning ca. 3200 BP, the climate was characterized by cooler temperatures and more mesic conditions. Modern plant communities were established by ca. 1500 BP.

  17. Levels and trends of radioactive contaminants in the Greenland environment.

    PubMed

    Dahlgaard, Henning; Eriksson, Mats; Nielsen, Sven P; Joensen, Hans Pauli

    2004-09-20

    Levels of radioactive contaminants in various Greenland environments have been assessed during 1999-2001. The source of 137Cs, 90Sr and (239,240)Pu in terrestrial and fresh water environments is mainly global fallout. In addition, the Chernobyl accident gave a small contribution of 137Cs. Reindeer and lamb contain the largest observed 137Cs concentrations in the terrestrial environment--up to 80 Bq kg(-1) fresh weight have been observed in reindeer. Due to special environmental conditions, 137Cs is transferred to landlocked Arctic char with extremely high efficiency in South Greenland leading to concentrations up to 100 Bq kg(-1) fresh weight. In these cases very long ecological half-lives are seen. Concentrations of 99Tc, 137Cs and 90Sr in seawater and in marine biota decrease in the order North-East Greenland and the coastal East Greenland current > South-West Greenland > Central West Greenland and North-West Greenland > Irmiger Sea-Faroe Islands. The general large-scale oceanic circulation combined with European coastal discharges and previous contamination of the Arctic Ocean causes this. As the same tendency is seen for the persistent organic pollutants (POPs) DDT and PCB in marine biota, it is suggested that long-distance oceanic transport by coastal currents is a significant pathway also for POPs in the Greenland marine environment. The peak 99Tc discharge from Sellafield 1994-1995 has only been slightly visible in the present survey year 2000. The concentrations are expected to increase in the future, especially in East Greenland. The Bylot Sound at the Thule Airbase (Pituffik) in North-West Greenland was contaminated with plutonium and enriched uranium in a weapons accident in 1968. Biological activity has mixed accident plutonium efficiently into the new sediments resulting in continued high surface sediment concentrations three decades after the accident. Transfer of plutonium to benthic biota is low--and lower than observed in the Irish Sea. This is

  18. The hydrology of Lake Rousseau, west-central Florida

    USGS Publications Warehouse

    German, E.R.

    1978-01-01

    Lake Rousseau, about 4 miles southwest of Inglis, Florida, was formed in 1909 by impoundment of the Withlacooche River by Inglis Dam, west of Dunnellon, Florida. The lake was to have been part of the Cross-Florida Barge Canal; a lock and channel associated with the presently inactive project were completed in 1969. Lake Rousseau is about 11 miles long, covers about 4,000 acres, and contains about 34,000 acre-feet of water at the normal pool elevation of 27.5 feet above mean sea level. Inflow to the lake is relatively constant and responds slowly to rainfall. The estimated 100-year peak inflow, 10,400 cubic feet per second, is only 19 percent higher than the 100-year high monthly inflow. Water in Lake Rousseau is a calcium-bicarbonate type and is hard. Mean total phosphorus and organic nitrogen concentrations are considerably lower in Lake Rousseau than in north-central Florida lakes which have been considered to be eutrophic by other investigators, however, the lake supports of prolific aquatic plant community. Dissolved-oxygen concentrations near the water surface are occasionally less than 3 mg/liter. (Woodard-USGS)

  19. Silurian gastropoda from southeastern and west-central Alaska

    USGS Publications Warehouse

    Rohr, D.M.; Blodgett, R.B.; Fryda, J.

    2008-01-01

    Additional Silurian (Ludlovian) gastropods are described from the Heceta Formation in the Alexander terrane on Prince of Wales Island, southeastern Alaska. Species include Spinicharybdis krizi n. sp., Spinicharybdis boucoti n. sp., Morania wagneri n. sp., Haplospira craigi n. sp., Australonema sp., Pachystrophia cf. gotlandica (Lindstro??m, 1884), and Medfrazyga gilmulli n. sp. An additional new Silurian species, Morania nixonforkensis n. sp., is described from the Nixon Fork subterrane of the Farewell terrane of west-central Alaska. The spine-bearing Spinicharybdis is placed into a new subfamily Spinicharybdiinae together with Hystricoceras Jahn, 1894. Joint occurrences of genera Beraunia, Coelocaulus, and Morania, as well as members of subfamily Spinicharybdiinae in the gastropod fauna from the Heceta Formation, support its close relationship with gastropod fauna of Bohemia. Additionally, the occurrence of the genus Medfrazyga suggests a faunal link between the Alexander and Farewell terranes of Alaska. Medfrazyga gilmulli n. sp. is the oldest known and the only early Paleozoic member of the family Palaeozygopleuridae. Copyright ?? 2008, The Paleontological Society.

  20. Stable isotopes differentiate bottlenose dolphins off west-central Florida

    USGS Publications Warehouse

    Barros, Nélio B.; Ostrom, P. H.; Stricker, Craig A.; Wells, R.S.

    2010-01-01

    Distinguishing discrete population units among continuously distributed coastal small cetaceans is challenging and crucial to conservation. We evaluated the utility of stable isotopes in assessing group membership in bottlenose dolphins (Tursiops truncatus) off west-central Florida by analyzing carbon, nitrogen, and sulfur isotope values (δ13C, δ15N, and δ34S) of tooth collagen from stranded dolphins. Individuals derived from three putative general population units: Sarasota Bay (SB), nearshore Gulf of Mexico (GULF), and offshore waters (OFF). Animals of known history (SB) served to ground truth the approach against animals of unknown history from the Gulf of Mexico (GULF, OFF). Dolphin groups differed significantly for each isotope. Average δ13C values from SB dolphins (−10.6‰) utilizing sea grass ecosystems differed from those of GULF (−11.9‰) and OFF (−11.9‰). Average δ15N values of GULF (12.7‰) and OFF (13.2‰) were higher than those of SB dolphins (11.9‰), consistent with differences in prey trophic levels. δ34S values showed definitive differences among SB (7.1‰), GULF (11.3‰), and OFF (16.5‰) dolphins. This is the first application of isotopes to population assignment of bottlenose dolphins in the Gulf of Mexico and results suggest that isotopes may provide a powerful tool in the conservation of small cetaceans.

  1. Increasing Freshwater Runoff and Tidal Action Influences on Spatial Mixing Patterns in Søndre Strømfjord, West Greenland

    NASA Astrophysics Data System (ADS)

    Smiley, C. R.; Kamenos, N.; Hoey, T.; Cottier, F.; Ellam, R. M.

    2014-12-01

    Greenland Ice Sheet melt has the potential to affect global sea levels and the strength of the thermohaline circulation (THC). Investigating spatial mixing patterns of seawater in Greenlandic fjords can help reveal characteristics of changes in runoff from the GrIS; for example higher runoff may be associated with lower salinity within GrIS fjords, which can be recorded by palaeoenvironmental proxies (Kamenos et al 2012). The Kangerlussuaq Drainage Basin mirrors melt patterns of the whole GrIS and drains into Søndre Strømfjord, a 170km long fjord on the west coast of Greenland. Temperature and salinity profiles to 40m depth were obtained at 11 stations along Søndre Strømfjord during the 2014 melt season. Each station was sampled twice once at high KDB runoff and once at low KDB runoff. With increasing freshwater runoff, salinity decreases by 1.65 - 2.91 at each station over a 7 hour time period. Higher salinities occur at low run-off. In addition, with increasing run-off, the disparity between surface and deeper water (30m) becomes greater with a 19.3 difference between the surface and 30m. With higher KDB runoff temperature increases by 0.47oC - 2.34oC. This information will be integrated with oxygen and deuterium isotope patterns to pinpoint the exact source of the runoff causing salinity reductions. Our data show a relationship between KDB runoff and salinity of Søndre Strømfjord, data that will enable further calibration of marine proxies of GrIS melt.

  2. Strontium and neodymium isotopic variations in early Archean gneisses affected by middle to late Archean high-grade metamorphic processes: West Greenland and Labrador

    NASA Technical Reports Server (NTRS)

    Collerson, K. D.; Mcculloch, M. T.; Bridgwater, D.; Mcgregor, V. R.; Nutman, A. P.

    1986-01-01

    Relicts of continental crust formed more than 3400 Ma ago are preserved fortuitously in most cratons. The cratons provide the most direct information about crust and mantle evolutionary processes during the first billion years of Earth history. In view of their polymetamorphic character, these terrains are commonly affected by subsequent tectonothermal events. Hence, their isotope systematics may be severely disturbed as a result of bulk chemical change or local isotopic homogenization. This leads to equivocal age and source information for different components within these terrains. The Sr and Nd isotopic data are presented for early Archean gneisses from the North Atlantic Craton in west Greenland and northern Labrador which were affected by younger metamorphic events.

  3. Increasing freshwater runoff and tidal action influences on spatial mixing patterns in Søndre Strømfjord, West Greenland.

    NASA Astrophysics Data System (ADS)

    Smiley, Crystal; Kamenos, Nick; Hoey, Trevor; Cottier, Finlo; Ellam, Rob

    2015-04-01

    Greenland Ice Sheet melt has the potential to affect global sea levels and the strength of the thermohaline circulation (THC). Investigating spatial mixing patterns of seawater in Greenlandic fjords can help reveal characteristics of changes in runoff from the GrIS; for example higher runoff may be associated with lower salinity within GrIS fjords, which can be recorded by palaeoenvironmental proxies (Kamenos et al 2012). The Kangerlussuaq Drainage Basin mirrors melt patterns of the whole GrIS and drains into Søndre Strømfjord, a 170km long fjord on the west coast of Greenland. Temperature and salinity profiles to 40m depth were obtained at 11 stations along Søndre Strømfjord during the 2014 melt season. Each station was sampled twice once at high KDB runoff and once at low KDB runoff. With increasing freshwater runoff, salinity decreased by 1.65 - 2.91 and temperature increased by 0.47oC- 2.34oC at each station over a 7 hour time period. Higher salinities occurred at low run-off. In addition, with increasing run-off, the disparity between surface and deeper water (30m) salinity became greater with a 19.3 difference between the surface and 30m. This information was integrated with oxygen and deuterium isotopic signatures collected at 10 m depth from each station to pinpoint the exact source of the runoff causing salinity reductions. With increasing freshwater runoff, the chemistry of the fjord exhibits an enrichment of the heavier isotope. δ18Ovsmow values enrich by 7.40 permil while δDvsmow enrich 53.26 permil. Our data shows a relationship between KDB runoff, salinity, and oxygen, hydrogen isotopic chemistry of Søndre Strømfjord, data that will enable further calibration of marine proxies of GrIS melt. References Kamenos, N.A, Hoey, T.B, Nienow, P., Fallick, A.E., & Claverie, T., 2012: Reconstructing Greenland Ice Sheet runoff using coralline algae; Geological Society of America, Geology, doi: 10.1130/G33405.1

  4. Fagaceae pollen from the early Cenozoic of West Greenland: revisiting Engler's and Chaney's Arcto-Tertiary hypotheses.

    PubMed

    Grímsson, Friðgeir; Zetter, Reinhard; Grimm, Guido W; Pedersen, Gunver Krarup; Pedersen, Asger Ken; Denk, Thomas

    In this paper we document Fagaceae pollen from the Eocene of western Greenland. The pollen record suggests a remarkable diversity of the family in the early Cenozoic of Greenland. Extinct Fagaceae pollen types include Eotrigonobalanus, which extends at least back to the Paleocene, and two ancestral pollen types with affinities to the Eurasian Quercus Group Ilex and the western North American Quercus Group Protobalanus. In addition, modern lineages of Fagaceae are unambiguously represented by pollen of Fagus, Quercus Group Lobatae/Quercus, and three Castaneoideae pollen types. These findings corroborate earlier findings from Axel Heiberg Island that Fagaceae were a dominant element at high latitudes during the early Cenozoic. Comparison with coeval or older mid-latitude records of modern lineages of Fagaceae shows that modern lineages found in western Greenland and Axel Heiberg likely originated at lower latitudes. Further examples comprise (possibly) Acer, Aesculus, Alnus, Ulmus, and others. Thus, before fossils belonging to modern northern temperate lineages will have been recovered from older (early Eocene, Paleocene) strata from high latitudes, Engler's hypothesis of an Arctic origin of the modern temperate woody flora of Eurasia, termed 'Arcto-Tertiary Element', and later modification by R. W. Chaney and H. D. Mai ('Arcto-Tertiary Geoflora') needs to be modified.

  5. The speed and timing of climate change: Detailed ice core stable isotope records from NorthGRIP, Greenland and Mt. Moulton, West Antarctica

    NASA Astrophysics Data System (ADS)

    Popp, Trevor J.

    Objective projections of future climate change require a detailed understanding of the natural variability and behavior of the climate system observed in the past. This dissertation endeavors to characterize the speed and timing of past climate changes on both orbital and extremely abrupt time scales from new high-resolution stable isotope time series from ice cores collected at NorthGRIP in Greenland and Mt. Moulton in West Antarctica. Greenland ice cores are uniquely suited for study of abrupt climate events because relatively high snow accumulation rates allow single years to be identified well into the last glacial period. Deuterium (deltaD) and deuterium excess time series at near annual resolution or better across the three major abrupt transitions of the last glacial termination are examined from the precisely dated NGRIP ice core. These records have been synchronized to within a few years or less to similar isotopic series developed from the GISP2 ice core which was collected 320 km SSE of the NGRIP site. 300-500 year time intervals were examined in detail at the end of the Younger Dryas (YD, 11.7 ka), the beginning of the YD (12.9 ka), and at the onset of Bolling (14.7 ka). Transition timing, duration and amplitudes were determined for each transition at both sites via a statistical ramp fitting approach. At each transition a complete mode shift between two climate states recorded by deltaD or excess, or both, was detected in as little as a single year with one exception at the cooling at the onset of the YD at GISP2. NGRIP and GISP2 share much common variance, sometimes in remarkable detail, in the timing and evolution of the climate transitions. Complete mode shifts in excess were synchronous to within a year or better between NGRIP and GISP2 for the two cold-to-warm transitions and represent a significant regional reorganization of atmospheric circulation delivering moisture from lower latitude source regions to the high latitudes of Greenland. At the

  6. Melting at the base of the Greenland ice sheet explained by Iceland hotspot history

    NASA Astrophysics Data System (ADS)

    Rogozhina, Irina; Petrunin, Alexey G.; Vaughan, Alan P. M.; Steinberger, Bernhard; Johnson, Jesse V.; Kaban, Mikhail K.; Calov, Reinhard; Rickers, Florian; Thomas, Maik; Koulakov, Ivan

    2016-05-01

    Ice-penetrating radar and ice core drilling have shown that large parts of the north-central Greenland ice sheet are melting from below. It has been argued that basal ice melt is due to the anomalously high geothermal flux that has also influenced the development of the longest ice stream in Greenland. Here we estimate the geothermal flux beneath the Greenland ice sheet and identify a 1,200-km-long and 400-km-wide geothermal anomaly beneath the thick ice cover. We suggest that this anomaly explains the observed melting of the ice sheet’s base, which drives the vigorous subglacial hydrology and controls the position of the head of the enigmatic 750-km-long northeastern Greenland ice stream. Our combined analysis of independent seismic, gravity and tectonic data implies that the geothermal anomaly, which crosses Greenland from west to east, was formed by Greenland’s passage over the Iceland mantle plume between roughly 80 and 35 million years ago. We conclude that the complexity of the present-day subglacial hydrology and dynamic features of the north-central Greenland ice sheet originated in tectonic events that pre-date the onset of glaciation in Greenland by many tens of millions of years.

  7. Hydrogeology of McMullen Valley, west-central Arizona

    USGS Publications Warehouse

    Pool, D.R.

    1987-01-01

    The geohydrology of McMullen Valley, west-central Arizona, was investigated using geologic, geophysical, and hydrologic data and a numerical model of the groundwater system. Interpretation of geologic and geophysical information indicates that the main structure of McMullen Valley is a syncline that has been normal faulted on the southeast side. Basin fill that accumulated in the structural depression during late Miocene to Pleistocene time is the main aquifer and is divided into upper and lower units on the basis of lithologic information. The upper unit is a thin layer of coarse-grained sediments and generally is not saturated. The lower unit is 3,000 to 4,000 ft thick, includes a fine-grained facies in the upper 1,000 ft, and is the main source of water. The fine-grained facies is found in the southwest half of the basin and is further divided into upper and lower parts. The lower part of the fine-grained facies has: a higher percentage of silt and clay than the upper part, contains evaporites, does not yield water to wells, and separates the aquifer into shallow and deep systems. A numerical model was used to analyze the groundwater system for both steady-state and transient conditions. The transient model was used to analyze system response to pumping stress. The transient system is one of storage depletion, and water level declines are controlled by pumping and specific yield distributions. Water level declines are also influenced by hydraulic properties and areal extent of the fine-grained facies. Significant water level declines may extend to aquifer boundaries in most of the basin; in one area, impermeable boundary greatly influences declines. The location of the nearby boundary was estimated through gravity data modeling. Several hydrologic components, including hydraulic properties and areal extent of the fine-grained facies , storage properties, and aquifer boundaries, need better definition in order to develop a more accurate model of the groundwater

  8. Karrat REE mineralization on Niaqornakavsak and extension on Umiamako Nuna, West Greenland: mineralogic, geochronologic, and carbon and oxygen isotope constraints on the origin

    NASA Astrophysics Data System (ADS)

    Mott, A.; Bird, D. K.; Grove, M.; Bernstein, S.; Mackay, H.; Rose, N.

    2011-12-01

    The Karrat rare earth element (REE) mineralization is located in the Niaqornakavsak (NIAQ) area of Qeqertarssuaq Island in Greenland (~72°N). A mineralized horizon occurs as a single distinct layer (35-40° dip) within an amphibolite host rock of the Qeqertarssuaq Formation: a member of the Paleoproterozoic Karrat Group sequence. Average Yttrium + REE-oxide (YREEO) concentration is ~1.0 wt. % with concentrations up to 2.59 wt. % over one meter intervals. Eight drill holes across three locations on NIAQ allow for an estimated true thickness of REE enrichment (YREEO ≥ 0.2 wt. %) of 29-38m in the east and central area, and a fault restricted thickness at the site in the west of 16m (at surface) to 28m (at depth). Two distinct metasomatic reaction zones comprise the mineralized horizon and are universal across NIAQ: the upper unit (CCA ~1.5 %YREEO) has a primary mineralogy of calcite + ankerite + fluorite (>50%), grunerite, cummingtonite, magnetite, fergusonite, bastnasite, allanite, and monazite, while the lower unit (BLC) consists of biotite (>50%), calcite, ilmenite, magnetite, allanite, fergusonite, and monazite. An extension of the Karrat REE deposit outcrops 7 km to the east on Umiamako Nuna. Hand samples from Umiamako Nuna similar to CCA (YREEO up to 2.4 wt. %) have been collected, but two exploratory drill holes revealed the majority of the REE enriched zone is comparable to the mineralogy of the incomplete reaction zone around CCA on NIAQ with concentrations of YREEO ranging from 0.5-1.0 wt. % with an estimated thickness of 15m. The mineralization consists of Ca-amphiboles, biotite, calcite, pyrite, albite, and garnet. Enrichment of REE continues to a depth of 60m from vein mineralization. In addition, a secondary occurrence at depth can be found on Umiamako Nuna tens of meters below the primary mineralized horizon, which is characterized by high modal concentrations of calcite, fluorite, and amphiboles. Carbon and oxygen isotope analyses of 145 carbonate

  9. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 1. Programme of investigation on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Christoffersen, Poul; Hubbard, Bryn; Bougamont, Marion; Doyle, Samuel; Young, Tun Jan; Hofstede, Coen; Nicholls, Keith; Todd, Joe; Box, Jason; Ryan, Johnny; Toberg, Nick; Walter, Jacob; Hubbard, Alun

    2015-04-01

    Marine-terminating outlet glaciers drain 90 percent of the Greenland Ice Sheet and are responsible for about half of the ice sheet's net annual mass loss, which currently raises global sea level by almost 1 mm per year. Understanding the processes that drive the fast flow of these glaciers is crucial because a growing body of evidence points to a strong, but spatially varied and often complex, response to oceanographic as well as atmospheric forcing. While the bed of glaciers elsewhere is known to strongly influence the flow of ice, no observations have ever been made at the bed of a marine-terminating glacier in Greenland. The flow of ice in numerical models of the Greenland Ice Sheet consequently rely on untested basal parameterisations, which form a likely and potentially significant source of error in the prediction of sea level rise over the coming decades and century. The Subglacial Access and Fast Ice Research Experiment (SAFIRE) is addressing this paucity of observational constraints by gaining access to the bed of Store Glacier, a marine-terminating outlet of the Greenland Ice Sheet which has a drainage basin of 35,000 square kilometres and terminates in Uummannaq Fjord. In 2014, the SAFIRE programme drilled four boreholes in a region where ice flows at a rate of 700 m per year and where a seismic survey revealed a bed consisting of soft sediment. (See joint abstract by Hofstede et al. for details.) The boreholes were 603-616 m deep and direct access to the bed was confirmed by a clear hydrological connectivity with a basal water system. (See joint abstract by Doyle et al. for details.) With sensors deployed englacially (temperature and tilt) and at the bed (water pressure, turbidity, electrical conductivity), the SAFIRE will inform the ratio of internal ice deformation and basal slip, vertical strain, ice temperature, and fluctuations in water pressure linked to supraglacial lake drainage as well as diurnal drainage into moulins. In 2015, we plan to

  10. Seasonal and Intra-Seasonal Variability of Surface Streams Over the West Greenland Ice Sheet from High Resolution Satellite Optical Data.

    NASA Astrophysics Data System (ADS)

    Brown, M. G.; Tedesco, M.

    2014-12-01

    The surface hydrology of the Greenland ice sheet plays a crucial role on surface energy and mass balance, as well as on the englacial and sub-glacial environments. The spatial distribution of these surface streams is poorly understood and their temporal variability is (to our knowledge) unknown. One of the reasons for the lack of knowledge on the temporal variability of such streams is related to the historical unavailability of satellite data that could spatially resolve the presence and associated properties of the streams. In recent years, however, multi-spectral commercial satellite data in the visible and infra-red bands have been made available to the scientific community. These newly accessible data sets are provided at spatial resolutions of the order of 1-2 meters, therefore, allowing to perform accurate spatial and temporal analysis of surface streams (and small lakes and ponds that cannot be resolved with sensors such as MODIS or LANDSAT). In this study, we report results concerning the seasonal and intra-seasonal variability of surface streams over a selected area on the west Greenland ice sheet. Using a combination of ENVI® and ArcGIS® software packages applied to multispectral high resolution imagery from World View 2 and Quickbird satellites, surface streams are identified through multiple approaches (either based on unsupervised classifications, band combinations, band ratio thresholds, or digitization) and vector maps of the surface hydrology network were created. Stream networks created during one melting season (at three different stages of the season) were compared and discussed as well as the networks mapped between two consecutive years for proximate dates.

  11. Seasonal and Intra-Seasonal Variability of Surface Streams over the West Greenland Ice Sheet from High Resolution Satellite Optical Data.

    NASA Astrophysics Data System (ADS)

    Brown, Michael G.; Tedesco, Marco

    2015-04-01

    The surface hydrology of the Greenland ice sheet plays a crucial role on surface energy and mass balance, as well as on the en-glacial and sub-glacial environments. The spatial distribution of these surface streams is poorly understood and their temporal variability is (to our knowledge) unknown. One of the reasons for the lack of knowledge on the temporal variability of such streams is related to the historical unavailability of satellite data that could spatially resolve the presence and associated properties of the streams. In recent years, however, multi-spectral commercial satellite data in the visible and infra-red bands have been made available to the scientific community. These newly accessible data sets are provided at spatial resolutions of the order of 1-2 meters, therefore, allowing to perform accurate spatial and temporal analysis of surface streams (and small lakes and ponds that cannot be resolved with sensors such as MODIS or LANDSAT). In this study, we report results concerning the seasonal and intra-seasonal variability of surface streams over a selected area on the west Greenland ice sheet. Using ArcGIS® software applied to multispectral high resolution imagery from World View 2 and Quickbird satellites, surface streams were identified through band math, threshold classifications, and morphological operations. Raster and vector maps of the surface hydrology network were created. Stream networks created during multiple melt seasons (at several different stages of the season) were compared and discussed as well as the networks mapped between consecutive years for proximate dates.

  12. Modelling Greenland Outlet Glaciers

    NASA Technical Reports Server (NTRS)

    vanderVeen, Cornelis; Abdalati, Waleed (Technical Monitor)

    2001-01-01

    The objective of this project was to develop simple yet realistic models of Greenland outlet glaciers to better understand ongoing changes and to identify possible causes for these changes. Several approaches can be taken to evaluate the interaction between climate forcing and ice dynamics, and the consequent ice-sheet response, which may involve changes in flow style. To evaluate the icesheet response to mass-balance forcing, Van der Veen (Journal of Geophysical Research, in press) makes the assumption that this response can be considered a perturbation on the reference state and may be evaluated separately from how this reference state evolves over time. Mass-balance forcing has an immediate effect on the ice sheet. Initially, the rate of thickness change as compared to the reference state equals the perturbation in snowfall or ablation. If the forcing persists, the ice sheet responds dynamically, adjusting the rate at which ice is evacuated from the interior to the margins, to achieve a new equilibrium. For large ice sheets, this dynamic adjustment may last for thousands of years, with the magnitude of change decreasing steadily over time as a new equilibrium is approached. This response can be described using kinematic wave theory. This theory, modified to pertain to Greenland drainage basins, was used to evaluate possible ice-sheet responses to perturbations in surface mass balance. The reference state is defined based on measurements along the central flowline of Petermann Glacier in north-west Greenland, and perturbations on this state considered. The advantage of this approach is that the particulars of the dynamical flow regime need not be explicitly known but are incorporated through the parameterization of the reference ice flux or longitudinal velocity profile. The results of the kinematic wave model indicate that significant rates of thickness change can occur immediately after the prescribed change in surface mass balance but adjustments in flow

  13. A review of structural patterns and melting processes in the Archean craton of West Greenland: Evidence for crustal growth at convergent plate margins as opposed to non-uniformitarian models

    NASA Astrophysics Data System (ADS)

    Polat, Ali; Wang, Lu; Appel, Peter W. U.

    2015-11-01

    The Archean craton of West Greenland consists of many fault-bounded Eoarchean to Neoarchean tectonic terranes (crustal blocks). These tectonic terranes are composed mainly of tonalite-trondhjemite-granodiorite (TTG) gneisses, granitic gneisses, metavolcanic-dominated supracrustal belts, layered anorthositic complexes, and late- to post-tectonic granites. Rock assemblages and geochemical signatures in these terranes suggest that they represent fragments of dismembered oceanic island arcs, consisting mainly of TTG plutons, tholeiitic to calc-alkaline basalts, boninites, picrites, and cumulate layers of ultramafic rocks, gabbros, leucogabbros and anorthosites, with minor sedimentary rocks. The structural characteristics of the terrane boundaries are consistent with the assembly of these island arcs through modern style of horizontal tectonics, suggesting that the Archean craton of West Greenland grew at convergent plate margins. Several supracrustal belts that occur at or near the terrane boundaries are interpreted as relict accretionary prisms. The terranes display fold and thrust structures and contain numerous 10 cm to 20 m wide bifurcating, ductile shear zones that are characterized by a variety of structures including transposed and redistributed isoclinal folds. Geometrically these structures are similar to those occurring on regional scales, suggesting that the Archean craton of West Greenland can be interpreted as a continental scale accretionary complex, such as the Paleozoic Altaids. Melting of metavolcanic rocks during tectonic thickening in the arcs played an important role in the generation of TTGs. Non-uniformitarian models proposed for the origin of Archean terranes have no analogs in the geologic record and are inconsistent with structural, lithological, petrological and geochemical data collected from Archean terranes over the last four decades. The style of deformation and generation of felsic rocks on outcrop scales in the Archean craton of West

  14. Geographic distribution of phlebotomine sandfly species (Diptera: Psychodidae) in Central-West Brazil.

    PubMed

    Almeida, Paulo Silva de; Andrade, Andrey José de; Sciamarelli, Alan; Raizer, Josué; Menegatti, Jaqueline Aparecida; Hermes, Sandra Cristina Negreli Moreira; Carvalho, Maria do Socorro Laurentino de; Gurgel-Gonçalves, Rodrigo

    2015-06-01

    This study updates the geographic distributions of phlebotomine species in Central-West Brazil and analyses the climatic factors associated with their occurrence. The data were obtained from the entomology services of the state departments of health in Central-West Brazil, scientific collections and a literature review of articles from 1962-2014. Ecological niche models were produced for sandfly species with more than 20 occurrences using the Maxent algorithm and eight climate variables. In all, 2,803 phlebotomine records for 127 species were analysed. Nyssomyia whitmani, Evandromyia lenti and Lutzomyia longipalpis were the species with the greatest number of records and were present in all the biomes in Central-West Brazil. The models, which were produced for 34 species, indicated that the Cerrado areas in the central and western regions of Central-West Brazil were climatically more suitable to sandflies. The variables with the greatest influence on the models were the temperature in the coldest months and the temperature seasonality. The results show that phlebotomine species in Central-West Brazil have different geographical distribution patterns and that climate conditions in essentially the entire region favour the occurrence of at least one Leishmania vector species, highlighting the need to maintain or intensify vector control and surveillance strategies.

  15. Geographic distribution of phlebotomine sandfly species (Diptera: Psychodidae) in Central-West Brazil

    PubMed Central

    de Almeida, Paulo Silva; de Andrade, Andrey José; Sciamarelli, Alan; Raizer, Josué; Menegatti, Jaqueline Aparecida; Hermes, Sandra Cristina Negreli Moreira; de Carvalho, Maria do Socorro Laurentino; Gurgel-Gonçalves, Rodrigo

    2015-01-01

    This study updates the geographic distributions of phlebotomine species in Central-West Brazil and analyses the climatic factors associated with their occurrence. The data were obtained from the entomology services of the state departments of health in Central-West Brazil, scientific collections and a literature review of articles from 1962-2014. Ecological niche models were produced for sandfly species with more than 20 occurrences using the Maxent algorithm and eight climate variables. In all, 2,803 phlebotomine records for 127 species were analysed. Nyssomyia whitmani, Evandromyia lenti and Lutzomyia longipalpis were the species with the greatest number of records and were present in all the biomes in Central-West Brazil. The models, which were produced for 34 species, indicated that the Cerrado areas in the central and western regions of Central-West Brazil were climatically more suitable to sandflies. The variables with the greatest influence on the models were the temperature in the coldest months and the temperature seasonality. The results show that phlebotomine species in Central-West Brazil have different geographical distribution patterns and that climate conditions in essentially the entire region favour the occurrence of at least one Leishmania vector species, highlighting the need to maintain or intensify vector control and surveillance strategies. PMID:26018450

  16. CHARACTER AND REGIONAL SIGNIFICANCE OF GREAT FALLS TECTONIC ZONE, EAST-CENTRAL IDAHO AND WEST-CENTRAL MONTANA.

    USGS Publications Warehouse

    O'Neill, J. Michael; Lopez, David A.

    1985-01-01

    The Great Falls tectonic zone, here named, is a belt of diverse northeast-trending geologic features that can be traced from the Idaho batholith in the Cordilleran miogeocline, across thrust-belt structures and basement rocks of west-central and southwestern Montana, through cratonic rocks of central Montana, and into southwestern-most Saskatchewan, Canada. Geologic mapping in east-central Idaho and west-central Montana has outlined a continuous zone of high-angle faults and shear zones. Recurrent fault movement in this zone and strong structural control over igneous intrusion suggest a fundamental tectonic feature that has influenced the tectonic development of the Idaho-Montana area from a least middle Proterozoic time to the present. Refs.

  17. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 2. High magnitude englacial strain detected with autonomous phase-sensitive FMCW radar on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Young, Tun Jan; Christoffersen, Poul; Nicholls, Keith; Bun Lok, Lai; Doyle, Samuel; Hubbard, Bryn; Stewart, Craig; Hofstede, Coen; Bougamont, Marion; Todd, Joseph; Brennan, Paul; Hubbard, Alun

    2016-04-01

    Fast-flowing outlet glaciers terminating in the sea drain 90% of the Greenland Ice Sheet. It is well-known that these glaciers flow rapidly due to fast basal motion, but its contributing processes and mechanisms are, however, poorly understood. In particular, there is a paucity of data to quantify the extent to which basal sliding and internal ice deformation by viscous creep contribute to the fast motion of Greenland outlet glaciers. To study these processes, we installed a network of global positioning system (GPS) receivers around an autonomous phase-sensitive radio-echo sounder (ApRES) capable of imaging internal reflectors and the glacier bed. The ApRES system, including antennas, were custom-designed to monitor and image ice sheets and ice shelves in monostatic and multiple-input multiple-output (MIMO) modes. Specifically, the system transmits a frequency-modulated continuous-wave (FMCW) that increases linearly from 200 to 400 MHz over a period of 1 second. We installed this system 30 km up-flow of the tidewater terminus of Store Glacier, which flows into Uummannaq Fjord in West Greenland, and data were recorded every hour from 06 May to 16 July 2014 and every 4 hours from 26 July to 11 December 2014. The same site was used to instrument 600 m deep boreholes drilled to the bed as part of the SAFIRE research programme. With range and reflector distances captured at high temporal (hourly) and spatial (millimetre) resolutions, we obtained a unique, 6-month-long time series of strain through the vertical ice column at the drill site where tilt was independently recorded in a borehole. Our results show variable, but persistently high vertical strain. In the upper three-fourths of the ice column, we have calculated strain rates on the order of a few percent per year, and the strain regime curiously shifts from vertical thinning in winter to vertical thickening at the onset of summer melt. In the basal ice layer we observed high-magnitude vertical strain rates on

  18. Bathymetry of Walker Lake, West-Central Nevada

    USGS Publications Warehouse

    Lopes, Thomas J.; Smith, J. LaRue

    2007-01-01

    Walker Lake lies within a topographically closed basin in west-central Nevada and is the terminus of the Walker River. Much of the streamflow in the Walker River is diverted for irrigation, which has contributed to a decline in lake-surface altitude of about 150 feet and an increase in dissolved solids from 2,500 to 16,000 milligrams per liter in Walker Lake since 1882. The increase in salinity threatens the fresh-water ecosystem and survival of the Lahontan cutthroat trout, a species listed as threatened under the Endangered Species Act. Accurately determining the bathymetry and relations between lake-surface altitude, surface area, and storage volume are part of a study to improve the water budget for Walker Lake. This report describes the updated bathymetry of Walker Lake, a comparison of results from this study and a study by Rush in 1970, and an estimate of the 1882 lake-surface altitude. Bathymetry was measured using a single-beam echosounder coupled to a differentially-corrected global positioning system. Lake depth was subtracted from the lake-surface altitude to calculate the altitude of the lake bottom. A Lidar (light detection and ranging) survey and high resolution aerial imagery were used to create digital elevation models around Walker Lake. The altitude of the lake bottom and digital elevation models were merged together to create a single map showing land-surface altitude contours delineating areas that are currently or that were submerged by Walker Lake. Surface area and storage volume for lake-surface altitudes of 3,851.5-4,120 feet were calculated with 3-D surface-analysis software. Walker Lake is oval shaped with a north-south trending long axis. On June 28, 2005, the lake-surface altitude was 3,935.6 feet, maximum depth was 86.3 feet, and the surface area was 32,190 acres. The minimum altitude of the lake bottom from discrete point depths is 3,849.3 feet near the center of Walker Lake. The lake bottom is remarkably smooth except for mounds near

  19. Hydrogeology and Analysis of Aquifer Characteristics in West-Central Pinellas County, Florida

    DTIC Science & Technology

    1999-01-01

    the Study Area Pinellas County is a peninsula in west-central Florida bounded by Tampa Bay to the east and the Gulf of Mexico to the west (fig. 1). The...packstones. The foraminiferal limestones in the unit commonly contain benthic foraminifera , bryozoan, echinoid, and mollusk fossils. The Ocala Limestone...county is part of the Gulf Coastal Lowlands physiographic region described by White (1970) which consists of low angle scarps and terraces formed

  20. Average sedimentary rock rare Earth element patterns and crustal evolution: Some observations and implications from the 3800 Ma ISUA supracrustal belt, West Greenland

    NASA Technical Reports Server (NTRS)

    Dymek, R. F.; Boak, J. L.; Gromet, L. P.

    1983-01-01

    Rare earth element (REE) data is given on a set of clastic metasediments from the 3800 Ma Isua Supracrustal belt, West Greenland. Each of two units from the same sedimentary sequence has a distinctive REE pattern, but the average of these rocks bears a very strong resemblance to the REE pattern for the North American Shale Composite (NASC), and departs considerably from previous estimates of REE patterns in Archaean sediments. The possibility that the source area for the Isua sediments resembled that of the NASC is regarded as highly unlikely. However, REE patterns like that in the NASC may be produced by sedimentary recycling of material yielding patterns such as are found at Isua. The results lead to the following tentative conclusions: (1) The REE patterns for Isua Seq. B MBG indicate the existence of crustal materials with fractionated REE and negative Eu anomalies at 3800 Ma, (2) The average Seq. B REE pattern resembles that of the North American Shale Composite (NASC), (3) If the Seq. B average is truly representative of its crustal sources, then this early crust could have been extensively differentiated. In this regard, a proper understanding of the NASC pattern, and its relationship to post-Archaean crustal REE reservoirs, is essential, (4) The Isua results may represent a local effect.

  1. Formation of native iron in sediment-contaminated magma: I. A. case study of the Hanekammen Complex on Disko Island, West Greenland

    SciTech Connect

    Ulff-Moller, F. )

    1990-01-01

    For the first time a compositional range of native iron bodies is described in a cogenetic series of sediment-contaminated volcanic rocks from the Tertiary West Greenland Basalt Province. The iron-bearing rocks occur in a high-level composite intrusion, the Hanekammen Complex. Reaction between a tholeiitic parent magma with >11% MgO and carbonaceous Al{sub 2}O{sub 3}-rich shale took place in a reservoir >3 km below the paleosurface and created magmatic layering with basaltic magma overlain by less dense andesitic magma. The contaminated rock series bears a strong imprint of assimilation but very little fractional crystallization, which implies that the two processes were not intimately coupled in the present in basalt and andesite form a general trend, defined by Co versus Ni concentrations, that reflects the degree of assimilation, the amount of immiscible sulfide liquid, and the degree of reduction (in order of decreasing importance). The zoning of single iron grains reflects the dynamics of their growth and, to some extent, subsequent homogenization and reaction with magma. Weakly zoned iron spherules in viscous andesite were formed and remained in situ, whereas iron grains in basalt settled through the layered magma and developed strong zoning. All iron types contain Co-rich domains (<1 mm in diameter); their conservation implies a residence time for the iron at magmatic temperatures on the order of a month or less before the emplacement in the subvolcanic intrusions.

  2. Pb isotopes as tracers of mining-related Pb in lichens, seaweed and mussels near a former Pb-Zn mine in West Greenland.

    PubMed

    Søndergaard, Jens; Asmund, Gert; Johansen, Poul; Elberling, Bo

    2010-05-01

    Identification of mining-related contaminants is important in order to assess the spreading of contaminants from mining as well as for site remediation purposes. This study focuses on lead (Pb) contamination in biota near the abandoned 'Black Angel Mine' in West Greenland in the period 1988-2008. Stable Pb isotope ratios and total Pb concentrations were determined in lichens, seaweed and mussels as well as in marine sediments. The results show that natural background Pb ((207)Pb/(206)Pb: 0.704-0.767) and Pb originating from the mine ore ((207)Pb/(206)Pb: 0.955) have distinct isotopic fingerprints. Total Pb in lichens, seaweed, and mussels was measured at values up to 633, 19 and 1536 mg kg(-1) dry weight, respectively, and is shown to be a mixture of natural Pb and ore-Pb. This enables quantification of mining-related Pb and shows that application of Pb isotope data is a valuable tool for monitoring mining pollution.

  3. Long-term response of an arctic fiord system to lead-zinc mining and submarine disposal of mine waste (Maarmorilik, West Greenland).

    PubMed

    Søndergaard, Jens; Asmund, Gert; Johansen, Poul; Rigét, Frank

    2011-06-01

    Contamination by lead (Pb) and zinc (Zn) was studied in seawater, sediments, seaweeds and blue mussels near the former Black Angel Pb-Zn Mine in Maarmorilik, West Greenland. The mine operated during the period 1973-90 when mine waste (tailings and later waste rock) was discharged directly into the sea. Metal concentrations peaked during the mining period and Pb and Zn in seawater within the discharge area were measured up to 440 and 790 μg L⁻¹, respectively. Pb in fiord sediments, seaweeds and blue mussels just outside the discharge area were measured in concentrations up to 190, 84 and 2650 and Zn up to 300, 360 and 1190 μg g⁻¹ dry wt., respectively. Within the discharge area, seawater metal concentrations (especially Pb) decreased abruptly after mine closure. Metals concentrations in sediments and biota, however, decreased more slowly and two decades after mine closure seaweeds and blue mussels were still contaminated 12 km from the mine.

  4. Deciphering the Ecology of Key Diatom Taxa to Understand Climate-Induced Changes in West Greenland Lakes over the Holocene

    NASA Astrophysics Data System (ADS)

    Saros, J. E.; Northington, R.; Malik, H.; Anderson, N. J.

    2014-12-01

    Paleolimnological records from southwest Greenland reveal that diatom communities have not changed in a similar way to other regions of the Arctic, and in general, do not show synchronous change across this area. There are a number of cases in which lakes in close proximity to each other show opposite community changes over the Holocene. These changes in diatom fossil profiles have been difficult to interpret due to a lack of explicit ecological information for key species. The objective of this project is to decipher the ecology of key diatom species that are abundant across these paleolimnological records. We hypothesize that climate-driven changes in nutrients and water column stability (via its effects on light availability) are key factors shaping diatom community structure in these lakes. We assessed the requirements of particular taxa for nutrients and light through comparative lake sampling and resource bioassays. A whole-lake manipulation in which water column stability was reduced through enhanced water circulation was also conducted to assess the response of key taxa to this change. We found that the relative abundances of key diatom taxa are under complex control by the interactive effects of nutrients and light. We discuss how these results will enhance interpretation of climate-induced changes in Arctic lakes in this region.

  5. Interregional comparison of karst disturbance: west-central Florida and southeast Italy.

    PubMed

    North, Leslie A; van Beynen, Philip E; Parise, Mario

    2009-04-01

    The karst disturbance index (KDI) consists of 31 environmental indicators contained within the five broad categories: geomorphology, hydrology, atmosphere, biota, and cultural. The purpose of this research is to apply the KDI to two distinct karst areas, west Florida, USA, and Apulia, Italy. Through its application, the utility of the index can be validated and other important comparisons can be made, such as differences in the karst legislations implemented in each region and the effect of time exposure to human occupation to each karst terrain. Humans have intensively impacted the karst of southeast Italy for thousands of years compared to only decades in west-central Florida. However, west-central Florida's higher population density allows the region to reach disturbance levels comparable to those reached over a longer period in Apulia. Similarly, Italian karst is more diverse than the karst found in west-central Florida, creating an opportunity to test all the KDI indicators. Overall, major disturbances for southeast Italy karst include quarrying, stone clearing, and the dumping of refuse into caves, while west-central Florida suffers most from the infilling of sinkholes, soil compaction, changes in the water table, and vegetation removal. The application of the KDI allows a benchmark of disturbance to be established and later revisited to determine the changing state of human impact for a region. The highlighting of certain indicators that recorded high levels of disturbance also allows regional planners to allocate resources in a more refined manner.

  6. Autosomal and mtDNA Markers Affirm the Distinctiveness of Lions in West and Central Africa.

    PubMed

    Bertola, Laura D; Tensen, Laura; van Hooft, Pim; White, Paula A; Driscoll, Carlos A; Henschel, Philipp; Caragiulo, Anthony; Dias-Freedman, Isabela; Sogbohossou, Etotépé A; Tumenta, Pricelia N; Jirmo, Tuqa H; de Snoo, Geert R; de Iongh, Hans H; Vrieling, Klaas

    2015-01-01

    The evolutionary history of a species is key for understanding the taxonomy and for the design of effective management strategies for species conservation. The knowledge about the phylogenetic position of the lion (Panthera leo) in West/Central Africa is largely based on mitochondrial markers. Previous studies using mtDNA only have shown this region to hold a distinct evolutionary lineage. In addition, anthropogenic factors have led to a strong decline in West/Central African lion numbers, thus, the conservation value of these populations is particularly high. Here, we investigate whether autosomal markers are concordant with previously described phylogeographic patterns, and confirm the unique position of the West/Central African lion. Analysis of 20 microsatellites and 1,454 bp of the mitochondrial DNA in 16 lion populations representing the entire geographic range of the species found congruence in both types of markers, identifying four clusters: 1) West/Central Africa, 2) East Africa, 3) Southern Africa and 4) India. This is not in line with the current taxonomy, as defined by the IUCN, which only recognizes an African and an Asiatic subspecies. There are no indications that genetic diversity in West/Central Africa lions is lower than in either East or Southern Africa, however, given this genetic distinction and the recent declines of lion numbers in this region, we strongly recommend prioritization of conservation projects in West/Central Africa. As the current taxonomic nomenclature does not reflect the evolutionary history of the lion, we suggest that a taxonomic revision of the lion is warranted.

  7. Autosomal and mtDNA Markers Affirm the Distinctiveness of Lions in West and Central Africa

    PubMed Central

    Bertola, Laura D.; Tensen, Laura; van Hooft, Pim; White, Paula A.; Driscoll, Carlos A.; Henschel, Philipp; Caragiulo, Anthony; Dias-Freedman, Isabela; Sogbohossou, Etotépé A.; Tumenta, Pricelia N.; Jirmo, Tuqa H.; de Snoo, Geert R.

    2015-01-01

    The evolutionary history of a species is key for understanding the taxonomy and for the design of effective management strategies for species conservation. The knowledge about the phylogenetic position of the lion (Panthera leo) in West/Central Africa is largely based on mitochondrial markers. Previous studies using mtDNA only have shown this region to hold a distinct evolutionary lineage. In addition, anthropogenic factors have led to a strong decline in West/Central African lion numbers, thus, the conservation value of these populations is particularly high. Here, we investigate whether autosomal markers are concordant with previously described phylogeographic patterns, and confirm the unique position of the West/Central African lion. Analysis of 20 microsatellites and 1,454 bp of the mitochondrial DNA in 16 lion populations representing the entire geographic range of the species found congruence in both types of markers, identifying four clusters: 1) West/Central Africa, 2) East Africa, 3) Southern Africa and 4) India. This is not in line with the current taxonomy, as defined by the IUCN, which only recognizes an African and an Asiatic subspecies. There are no indications that genetic diversity in West/Central Africa lions is lower than in either East or Southern Africa, however, given this genetic distinction and the recent declines of lion numbers in this region, we strongly recommend prioritization of conservation projects in West/Central Africa. As the current taxonomic nomenclature does not reflect the evolutionary history of the lion, we suggest that a taxonomic revision of the lion is warranted. PMID:26466139

  8. Colonization history and clonal richness of asexual Daphnia in periglacial habitats of contrasting age in West Greenland.

    PubMed

    Haileselasie, Tsegazeabe H; Mergeay, Joachim; Weider, Lawrence J; Jeppesen, Erik; De Meester, Luc

    2016-07-01

    Due to climate change, Arctic ice sheets are retreating. This leads to the formation of numerous new periglacial ponds and lakes, which are being colonized by planktonic organisms such as the water flea Daphnia. This system provides unique opportunities to test genotype colonization dynamics and the genetic assemblage of populations. Here, we studied clonal richness of the Daphnia pulex species complex in novel periglacial habitats created by glacial retreat in the Jakobshavn Isbrae area of western Greenland. Along a 10 km transect, we surveyed 73 periglacial habitats out of which 61 were colonized by Daphnia pulex. Hence, for our analysis, we used 21 ponds and 40 lakes in two clusters of habitats differing in age (estimated <50 years vs. >150 years). We tested the expectation that genetic diversity would be low in recently formed (i.e. young), small habitats, but would increase with increasing age and size. We identified a total of 42 genetically distinct clones belonging to two obligately asexual species of the D. pulex species complex: D. middendorffiana and the much more abundant D. pulicaria. While regional clonal richness was high, most clones were rare: 16 clones were restricted to a single habitat and the five most widespread clones accounted for 68% of all individuals sampled. On average, 3·2 clones (range: 1-12) coexisted in a given pond or lake. There was no relationship between clonal richness and habitat size when we controlled for habitat age. Whereas clonal richness was statistically higher in the cluster of older habitats when compared with the cluster of younger ponds and lakes, most young habitats were colonized by multiple genotypes. Our data suggest that newly formed (periglacial) ponds and lakes are colonized within decades by multiple genotypes via multiple colonization events, even in the smallest of our study systems (4 m(2) ).

  9. Ilheus Virus Isolation in the Pantanal, West-Central Brazil

    PubMed Central

    Pauvolid-Corrêa, Alex; Kenney, Joan L.; Couto-Lima, Dinair; Campos, Zilca M. S.; Nogueira, Rita M. R.; Brault, Aaron C.; Komar, Nicholas

    2013-01-01

    The wetlands of the Brazilian Pantanal host large concentrations of diverse wildlife species and hematophagous arthropods, conditions that favor the circulation of zoonotic arboviruses. A recent study from the Nhecolândia sub-region of Pantanal reported serological evidence of various flaviviruses, including West Nile virus and Ilheus virus (ILHV). According to the age of seropositive horses, at least three flaviviruses, including ILHV, circulated in the Brazilian Pantanal between 2005 and 2009. To extend this study, we collected 3,234 adult mosquitoes of 16 species during 2009 and 2010 in the same sub-region. Mosquito pool homogenates were assayed for infectious virus on C6/36 and Vero cell monolayers and also tested for flaviviral RNA by a group-specific real-time RT-PCR. One pool containing 50 non-engorged female specimens of Aedes scapularis tested positive for ILHV by culture and for ILHV RNA by real-time RT-PCR, indicating a minimum infection rate of 2.5 per 1000. Full-length genomic sequence exhibited 95% identity to the only full genome sequence available for ILHV. The present data confirm the circulation of ILHV in the Brazilian Pantanal. PMID:23875051

  10. Phytoplankton Productivity in an Arctic Fjord (West Greenland): Estimating Electron Requirements for Carbon Fixation and Oxygen Production

    PubMed Central

    Hancke, Kasper; Dalsgaard, Tage; Sejr, Mikael Kristian; Markager, Stiig; Glud, Ronnie Nøhr

    2015-01-01

    Accurate quantification of pelagic primary production is essential for quantifying the marine carbon turnover and the energy supply to the food web. Knowing the electron requirement (Κ) for carbon (C) fixation (ΚC) and oxygen (O2) production (ΚO2), variable fluorescence has the potential to quantify primary production in microalgae, and hereby increasing spatial and temporal resolution of measurements compared to traditional methods. Here we quantify ΚC and ΚO2 through measures of Pulse Amplitude Modulated (PAM) fluorometry, C fixation and O2 production in an Arctic fjord (Godthåbsfjorden, W Greenland). Through short- (2h) and long-term (24h) experiments, rates of electron transfer (ETRPSII), C fixation and/or O2 production were quantified and compared. Absolute rates of ETR were derived by accounting for Photosystem II light absorption and spectral light composition. Two-hour incubations revealed a linear relationship between ETRPSII and gross 14C fixation (R2 = 0.81) during light-limited photosynthesis, giving a ΚC of 7.6 ± 0.6 (mean ± S.E.) mol é (mol C)−1. Diel net rates also demonstrated a linear relationship between ETRPSII and C fixation giving a ΚC of 11.2 ± 1.3 mol é (mol C)−1 (R2 = 0.86). For net O2 production the electron requirement was lower than for net C fixation giving 6.5 ± 0.9 mol é (mol O2)−1 (R2 = 0.94). This, however, still is an electron requirement 1.6 times higher than the theoretical minimum for O2 production [i.e. 4 mol é (mol O2)−1]. The discrepancy is explained by respiratory activity and non-photochemical electron requirements and the variability is discussed. In conclusion, the bio-optical method and derived electron requirement support conversion of ETR to units of C or O2, paving the road for improved spatial and temporal resolution of primary production estimates. PMID:26218096

  11. 40 CFR 81.96 - West Central Florida Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 18 2012-07-01 2012-07-01 false West Central Florida Intrastate Air Quality Control Region. 81.96 Section 81.96 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) DESIGNATION OF AREAS FOR AIR QUALITY PLANNING PURPOSES Designation of Air Quality Control Regions § 81.96...

  12. 40 CFR 81.96 - West Central Florida Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 17 2010-07-01 2010-07-01 false West Central Florida Intrastate Air Quality Control Region. 81.96 Section 81.96 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) DESIGNATION OF AREAS FOR AIR QUALITY PLANNING PURPOSES Designation of Air Quality Control Regions § 81.96...

  13. 40 CFR 81.96 - West Central Florida Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 18 2013-07-01 2013-07-01 false West Central Florida Intrastate Air Quality Control Region. 81.96 Section 81.96 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) DESIGNATION OF AREAS FOR AIR QUALITY PLANNING PURPOSES Designation of Air Quality Control Regions § 81.96...

  14. 40 CFR 81.96 - West Central Florida Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 17 2011-07-01 2011-07-01 false West Central Florida Intrastate Air Quality Control Region. 81.96 Section 81.96 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) DESIGNATION OF AREAS FOR AIR QUALITY PLANNING PURPOSES Designation of Air Quality Control Regions § 81.96...

  15. 40 CFR 81.96 - West Central Florida Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 18 2014-07-01 2014-07-01 false West Central Florida Intrastate Air Quality Control Region. 81.96 Section 81.96 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) DESIGNATION OF AREAS FOR AIR QUALITY PLANNING PURPOSES Designation of Air Quality Control Regions § 81.96...

  16. Effects of climate variations and soil conservation on sedimentation of a west-central Oklahoma reservoir

    Technology Transfer Automated Retrieval System (TEKTRAN)

    During the second half of the 20th century, extensive soil conservation practices were implemented on the Fort Cobb Reservoir watershed in West-Central Oklahoma. Sediment and flow observations were made on major tributaries in 1943-1950 (pre-conservation time period), and again in 2004-2008 (post-co...

  17. Association analysis of photoperiodic flowering genes in West and Central African sorghum [Sorghum bicolor (L.) Moench

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Photoperiod-sensitive flowering is a key adaptive trait for sorghum (Sorghum bicolor) in West and Central Africa. In this study we performed an association analysis to investigate the effect of polymorphisms within the genes putatively related to variation in flowering time on photoperiod sensitive ...

  18. Origin and Role of Recycled Crust in Flood Basalt Magmatism: Case Study of the Central East Greenland Rifted Margin

    NASA Astrophysics Data System (ADS)

    Brown, E.; Lesher, C. E.

    2015-12-01

    Continental flood basalts (CFB) are extreme manifestations of mantle melting derived from chemically/isotopically heterogeneous mantle. Much of this heterogeneity comes from lithospheric material recycled into the convecting mantle by a range of mechanisms (e.g. subduction, delamination). The abundance and petrogenetic origins of these lithologies thus provide important constraints on the geodynamical origins of CFB magmatism, and the timescales of lithospheric recycling in the mantle. Basalt geochemistry has long been used to constrain the compositions and mean ages of recycled lithologies in the mantle. Typically, this work assumes the isotopic compositions of the basalts are the same as their mantle source(s). However, because basalts are mixtures of melts derived from different sources (having different fusibilities) generated over ranges of P and T, their isotopic compositions only indirectly represent the isotopic compositions of their mantle sources[1]. Thus, relating basalts compositions to mantle source compositions requires information about the melting process itself. To investigate the nature of lithologic source heterogeneity while accounting for the effects of melting during CFB magmatism, we utilize the REEBOX PRO forward melting model[2], which simulates adiabatic decompression melting in lithologically heterogeneous mantle. We apply the model to constrain the origins and abundance of mantle heterogeneity associated with Paleogene flood basalts erupted during the rift-to-drift transition of Pangea breakup along the Central East Greenland rifted margin of the North Atlantic igneous province. We show that these basalts were derived by melting of a hot, lithologically heterogeneous source containing depleted, subduction-modified lithospheric mantle, and <10% recycled oceanic crust. The Paleozoic mean age we calculate for this recycled crust is consistent with an origin in the region's prior subduction history, and with estimates for the mean age of

  19. Evaluation of the use of common sculpin (Myoxocephalus scorpius) organ histology as bioindicator for element exposure in the fjord of the mining area Maarmorilik, West Greenland

    SciTech Connect

    Sonne, Christian; Bach, Lis; Søndergaard, Jens; Rigét, Frank F.; Dietz, Rune; Mosbech, Anders; Leifsson, Pall S.; Gustavson, Kim

    2014-08-15

    The former Black Angel lead–zinc mine in Maarmorilik, West Greenland, is a historic example of how mining activity may result in a significant impact on the surrounding fjord system in terms of elevated concentrations of especially lead (Pb) and zinc (Zn) in seawater, sediments and surrounding biota. In order to shed light on the present contamination and possible effects in the fjord we initiated a range of studies including a pilot study on gill and liver morphology of common sculpins (Myoxocephalus scorpius) around Maarmorilik. Sculpins were caught and sampled at five different stations known to represent a gradient of Pb concentrations. Fish livers from all specimens were analyzed for relevant elements in the area: Fe, Zn, As, Cu, Se, Cd, Pb, Ag, Hg, Co and Ni. Lead, As and Hg showed significant differences among the five stations. For 20% of the sculpins, Hg concentrations were in the range of lowest observed effect dose (LOED) of 0.1–0.5 μg/g ww for toxic threshold on reproduction and subclinical endpoints. Likewise LOEDs for tissue lesions, LOEDs for biochemistry, growth, survival and reproduction were exceeded for Cd (0.42–1.8 μg/g ww) and for As (11.6 μg/g ww) in 28% and 85% of the sculpins, respectively. Similar to this, the no observed effect dose (NOED) for biochemistry was exceeded for Pb (0.32 μg/g ww) and for growth, mortality and reproduction for Zn (60–68 μg/g ww) in 33% and 24% of the sculpins, respectively. For all sculpins, females were significantly larger than males and for five of the elements (Fe, Co, Ni, Cu, Se) females had higher concentrations. The chronic lesions observed in liver (mononuclear cell infiltrates, necrosis, vacuolar hepatocytes, portal fibrosis, bile duct hyperplasia, active melanomacrophage centers) and gills (fusion and edema of secondary lamellae, laminar telangiectasis, mononuclear cell infiltrates, blebs) were similar to those in the literature studies for both wild and laboratory exposed sculpins and

  20. Photobiology of sea ice algae during initial spring growth in Kangerlussuaq, West Greenland: insights from imaging variable chlorophyll fluorescence of ice cores.

    PubMed

    Hawes, Ian; Lund-Hansen, Lars Chresten; Sorrell, Brian K; Nielsen, Morten Holtegaard; Borzák, Réka; Buss, Inge

    2012-06-01

    We undertook a series of measurements of photophysiological parameters of sea ice algae over 12 days of early spring growth in a West Greenland Fjord, by variable chlorophyll fluorescence imaging. Imaging of the ice-water interface showed the development of ice algae in 0.3-0.4 mm wide brine channels between laminar ice crystals in the lower 4-6 mm of the ice, with a several-fold spatial variation in inferred biomass on cm scales. The maximum quantum yield of photosynthesis, F(v) /F(m), was initially low (~0.1), though this increased rapidly to ~0.5 by day 6. Day 6 also saw the onset of biomass increase, the cessation of ice growth and the time at which brine had reached <50 psu and >-2 °C. We interpret this as indicating that the establishment of stable brine channels at close to ambient salinity was required to trigger photosynthetically active populations. Maximum relative electron transport rate (rETR(max)), saturation irradiance (E(k)) and photosynthetic efficiency (α) had also stabilised by day 6 at 5-6 relative units, ~30 μmol photons m⁻² s⁻¹ and 0.4-0.5 μmol photons m⁻²s⁻¹, respectively. E(k) was consistent with under-ice irradiance, which peaked at a similar value, confirming that daytime irradiance was adequate to facilitate photosynthetic activity throughout the study period. Photosynthetic parameters showed no substantial differences with depth within the ice, nor variation between cores or brine channels suggesting that during this early phase of ice algal growth cells were unaffected by gradients of environmental conditions within the ice. Variable chlorophyll fluorescence imaging offers a tool to determine how this situation may change over time and as brine channels and algal populations evolve.

  1. Trends of lead and zinc in resident and transplanted Flavocetraria nivalis lichens near a former lead-zinc mine in West Greenland.

    PubMed

    Søndergaard, Jens; Johansen, Poul; Asmund, Gert; Rigét, Frank

    2011-09-01

    This study investigated spatial and temporal trends of lead (Pb) and zinc (Zn) in resident and transplanted Flavocetraria nivalis lichens near the former Black Angel Mine in Maarmorilik, West Greenland. The objectives of the study were to evaluate resident and transplanted lichens for monitoring dust contamination and investigate trends in mine-related dust contamination near the mine. The mine operated between 1973 and 1990 and lichens were regularly sampled between 1986 and 2009. When the mine operated, elevated concentrations of Pb, Zn and other elements were observed in resident lichens up to 35 km from Maarmorilik. In the period after mine closure, Pb and Zn concentrations in resident lichens decreased with 1-11% and 0-6% per year, respectively. From 1996 to 2009, lichens were transplanted into the study area from an uncontaminated site and collected the following year. After 1 year, transplanted lichens showed elevated concentrations of Pb and Zn but contained consistently less Pb and Zn compared to resident lichens (24±23% and 63±37%, respectively). During the most recent sampling in 2009, transplanted lichens still showed significantly elevated Pb concentrations (up to a factor 270) within a distance of 20 km from Maarmorilik. Zinc concentrations were only significantly elevated at sites within 5 km from the mine. Time-series regression analyses showed no significant decreases in Pb and Zn in transplanted lichens at any of the sites during the period 1996-2009. In conclusion, our study showed that resident F. nivalis lichens could not be used to evaluate the recent annual dust contamination in Maarmorilik. Lichen transplants, however, were considered adequate for assessing spatial and temporal trends in Pb and Zn contamination from recently deposited dust. The continuous dispersal of contaminated dust in Maarmorilik almost 20 years after mine closure reveals a slow recovery from mining contamination in this arctic area.

  2. Recent changes in north-west Greenland climate documented by NEEM shallow ice core data and simulations, and implications for past temperature reconstructions

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Steen-Larsen, H. C.; Ortega, P.; Swingedouw, D.; Popp, T.; Vinther, B. M.; Oerter, H.; Sveinbjornsdottir, A. E.; Gudlaugsdottir, H.; Box, J. E.; Falourd, S.; Fettweis, X.; Gallée, H.; Garnier, E.; Jouzel, J.; Landais, A.; Minster, B.; Paradis, N.; Orsi, A.; Risi, C.; Werner, M.; White, J. W. C.

    2015-01-01

    Combined records of snow accumulation rate, δ18O and deuterium excess were produced from several shallow ice cores and snow pits at NEEM (north-west Greenland), covering the period from 1724 to 2007. They are used to investigate recent climate variability and characterize the isotope-temperature relationship. We find that NEEM records are only weakly affected by inter-annual changes in the North Atlantic Oscillation. Decadal δ18O and accumulation variability is related to North Atlantic SST, and enhanced at the beginning of the 19th century. No long-term trend is observed in the accumulation record. By contrast, NEEM δ18O shows multi-decadal increasing trends in the late 19th century and since the 1980s. The strongest annual positive δ18O anomaly values are recorded at NEEM in 1928 and 2010, while maximum accumulation occurs in 1933. The last decade is the most enriched in δ18O (warmest), while the 11-year periods with the strongest depletion (coldest) are depicted at NEEM in 1815-1825 and 1836-1846, which are also the driest 11-year periods. The NEEM accumulation and δ18O records are strongly correlated with outputs from atmospheric models, nudged to atmospheric reanalyses. Best performance is observed for ERA reanalyses. Gridded temperature reconstructions, instrumental data and model outputs at NEEM are used to estimate the multi-decadal accumulation-temperature and δ18O-temperature relationships for the strong warming period in 1979-2007. The accumulation sensitivity to temperature is estimated at 11 ± 2% °C-1 and the δ18O-temperature slope at 1.1 ± 0.2‰ °C-1, about twice larger than previously used to estimate last interglacial temperature change from the bottom part of the NEEM deep ice core.

  3. Tuna Longline Fishing around West and Central Pacific Seamounts

    PubMed Central

    Morato, Telmo; Hoyle, Simon D.; Allain, Valerie; Nicol, Simon J.

    2010-01-01

    Background Seamounts have been identified as aggregating locations for pelagic biodiversity including tuna; however the topography and prevailing oceanography differ between seamounts and not all are important for tuna. Although a relatively common feature in oceanic ecosystems, little information is available that identifies those that are biologically important. Improved knowledge offers opportunities for unique management of these areas, which may advance the sustainable management of oceanic resources. In this study, we evaluate the existence of an association between seamounts and tuna longline fisheries at the ocean basin scale, identify significant seamounts for tuna in the western and central Pacific Ocean, and quantify the seamount contribution to the tuna longline catch. Methodology/Principal Findings We use data collected for the Western and Central Pacific Ocean for bigeye, yellowfin, and albacore tuna at the ocean basin scale. GLMs were applied to a coupled dataset of longline fisheries catch and effort, and seamount location information. The analyses show that seamounts may be associated with an annual longline combined catch of 35 thousand tonnes, with higher catch apparent for yellowfin, bigeye, and albacore tuna on 17%, 14%, and 14% of seamounts respectively. In contrast 14%, 18%, and 20% of seamounts had significantly lower catches for yellowfin, bigeye and albacore tuna respectively. Studying catch data in relation to seamount positions presents several challenges such as bias in location of seamounts, or lack of spatial resolution of fisheries data. Whilst we recognize these limitations the criteria used for detecting significant seamounts were conservative and the error in identification is likely to be low albeit unknown. Conclusions/Significance Seamounts throughout the study area were found to either enhance or reduce tuna catch. This indicates that management of seamounts is important Pacific-wide, but management approaches must take

  4. Upper mantle structure of central and West Antarctica from array analysis of Rayleigh wave phase velocities

    NASA Astrophysics Data System (ADS)

    Heeszel, David S.; Wiens, Douglas A.; Anandakrishnan, Sridhar; Aster, Richard C.; Dalziel, Ian W. D.; Huerta, Audrey D.; Nyblade, Andrew A.; Wilson, Terry J.; Winberry, J. Paul

    2016-03-01

    The seismic velocity structure of Antarctica is important, both as a constraint on the tectonic history of the continent and for understanding solid Earth interactions with the ice sheet. We use Rayleigh wave array analysis methods applied to teleseismic data from recent temporary broadband seismograph deployments to image the upper mantle structure of central and West Antarctica. Phase velocity maps are determined using a two-plane wave tomography method and are inverted for shear velocity using a Monte Carlo approach to estimate three-dimensional velocity structure. Results illuminate the structural dichotomy between the East Antarctic Craton and West Antarctica, with West Antarctica showing thinner crust and slower upper mantle velocity. West Antarctica is characterized by a 70-100 km thick lithosphere, underlain by a low-velocity zone to depths of at least 200 km. The slowest anomalies are beneath Ross Island and the Marie Byrd Land dome and are interpreted as upper mantle thermal anomalies possibly due to mantle plumes. The central Transantarctic Mountains are marked by an uppermost mantle slow-velocity anomaly, suggesting that the topography is thermally supported. The presence of thin, higher-velocity lithosphere to depths of about 70 km beneath the West Antarctic Rift System limits estimates of the regionally averaged heat flow to less than 90 mW/m2. The Ellsworth-Whitmore block is underlain by mantle with velocities that are intermediate between those of the West Antarctic Rift System and the East Antarctic Craton. We interpret this province as Precambrian continental lithosphere that has been altered by Phanerozoic tectonic and magmatic activity.

  5. Post-Industrial Revolution changes in large-scale atmospheric pollution of the northern hemisphere by heavy metals as documented in central Greenland snow and ice

    NASA Astrophysics Data System (ADS)

    Candelone, Jean-Pierre; Hong, Sungmin; Pellone, Christian; Boutron, Claude F.

    1995-08-01

    Pb, Zn, Cd and Cu have been measured using ultraclean procedures in various sections of a 70.3-m snow/ice core covering the past 220 years (including the Industrial Revolution) drilled at Summit, central Greenland. These time series are the first reliable ones ever published for Zn, Cd, and Cu; for Pb they are the first verification of the pioneering data published more than two decades ago by C. Patterson and his coworkers [Murozumi et al., 1969]. For all four heavy metals, concentrations are found to have markedly increased up until the 1960s and 1970s before decreasing significantly during the following few decades. The timing and the amplitude of the observed changes differ significantly however from one metal to another. Comparison with concentration values obtained by analyzing ancient Holocene ice dated 7760 years B.P., that is, before humans started to impact on the atmosphere, show that no detectable increase occurred for Zn, Cd, and Cu before the Industrial Revolution. On the other hand, Pb concentrations were already one order of magnitude above natural values in late 18th century ice. Cumulative deposition of heavy metals to the whole Greenland ice cap since the Industrial Revolution ranges from 3200 t for Pb to 60 t for Cd.

  6. Summary of reported agriculture and irrigation water use in west-central Arkansas counties, 1991

    USGS Publications Warehouse

    Holland, T.W.; Manning, C.A.; Stafford, K.L.

    1993-01-01

    This report summarizes the 1991 water-use reporting through the Conservation District Offices in the following west-central Arkansas counties: Conway, Crawford, Faulkner, Franklin, Johnson, Logan, Perry, Pope, Scott, Sebastian, and Yell. The number of withdrawal registrations for west-central Arkansas counties was 307 (90 groundwater and 217 surface water). Water withdrawals reported during the registration process total 1.00 Mgal/d (0.15 Mgal/d groundwater and 0.85 Mgal/d surface water) for agriculture and 32.07 Mgal/d (5.67 Mgal/d groundwater and 26.40 Mgal/d surface water) for irrigation. The registration reports for 1991 indicate that this water was applied to 22,856 acres of land to irrigate rice, corn, sorghum, soybeans, wheat, cash grains, hay, milo, vegetables, sod, berries, grapes, and fruit trees as well as for the agricultural uses of catfish and ducks.

  7. Simulation of the soil water balance of an undeveloped prairie in west-central Florida

    USGS Publications Warehouse

    Bidlake, W.R.; Boetcher, P.F.

    1996-01-01

    A one-dimensional numerical model was developed to simulate the soil water balance of a densely vegetated prairie site in west-central Florida. Transient simulations of the soil water balance were performed using field-measured soil and vegetation properties. Simulated and measured soil water content generally agreed to within 0.04; however, simulated water storage and recharge were sensitive to air-entry soil-water pressure potential and depth to the water table.

  8. Generalized thickness and configuration of the top of the intermediate aquifer, west-central Florida

    USGS Publications Warehouse

    Corral, Miguel A.; Wolansky, Richard M.

    1984-01-01

    Generalized map show the thickness and top of the intermediate aquifer in west-central Florida within the boundaries of the Southwest Florida Water Management District. The intermediate aquifer consists of a series of water-bearing units and confining beds between the surficial aquifer (water table) and the Floridan aquifer. This aquifer contains from one to several water-bearing units in west-central Florida. The aquifer and confining beds consist of the Tamiami and Hawthorn Formations of late and middle Miocene age and parts of the Tampa Limestone of early Miocene age. The top of the intermediate aquifer is about 100 feet above sea level in the north and slopes to about 100 feet below sea level in the south. The thickness ranges from zero in the north to more than 600 feet in the south. Despite the high mineral content of the water in some areas, the intermediate aquifer offers the best source of ground water to the coastal and southern areas of west-central Florida. (USGS)

  9. Integration of remotely-sensed geobotanical and structural methods for hydrocarbon exploration in West-Central West Virginia. Quartery report, May 1, 1996--July 31, 1996

    SciTech Connect

    1997-06-01

    Progress is reported on hydrocarbon exploration in West-Central West Virginia. In this period, the following tasks were carried out: a reconnaissance soil gas geochemical survey was performed at the Volcano test site and at the Lewis County test site; a geobotanical analysis of the September imagery was carried out in order to highlight spectral anomalies that appear to be associated with the historic volcano field and the Lewis County test site; and multi-temporal spectral reflectance measurements continued.

  10. West-east lithostratigraphic cross section of Cretaceous rocks from central Utah to western Kansas

    USGS Publications Warehouse

    Anna, Lawrence O.

    2012-01-01

    A west-east lithostratigraphic cross section of the Cretaceous rocks from central Utah to western Kansas was prepared as part of the former Western Interior Cretaceous (WIK) project, which was part of the Global Sedimentary Geology Program started in 1989. This transect is similar to that published by Dyman and others (1994) as a summary paper of the WIK project but extends further east and is more detailed. Stratigraphic control was provided by 32 geophysical logs and measured sections tied to ammonite and Inoceramus faunal zones. A variable datum was used, including the base of the Castlegate Sandstone for the western part of the section, and the fossil ammonite zone Baculites obtusus for the middle and eastern section. Lower Cretaceous units and the Frontier Formation and Mowry Shale are shown as undifferentiated units. Cretaceous strata along the transect range in thickness from more than 7,000 ft in the structural foredeep of the western overthrust belt in central Utah, to about 11,000 ft near the Colorado-Utah border as a result of considerable thickening of the Mesaverde Group, to less than 3,500 ft in the eastern Denver Basin, Kansas resulting in a condensed section. The basal Mancos Shale rises stepwise across the transect becoming progressively younger to the west as the Western Interior Seaway transgressed westward. The section illustrates large scale stratigraphic relations for most of the area covered by the seaway, from central Utah, Colorado, to west-central Kansas. These strata are predominantly continental and shoreline deposits near the Sevier thrust belt in Utah, prograding and regressive shorelines to the east with associated flooding surfaces, downlapping mudstones, and transgressive parasequences (shoreface) that correlate to condensed zones across the seaway in central Colorado and eastern Denver Basin.

  11. A tectonically controlled basin-fill within the Valle del Cauca, West-Central Colombia

    SciTech Connect

    Rine, J.M.; Keith, J.F. Jr.; Alfonso, C.A.; Ballesteros, I.; Laverde, F.; Sacks, P.E.; Secor, D.T. Jr. ); Perez, V.E.; Bernal, I.; Cordoba, F.; Numpaque, L.E. )

    1993-02-01

    Tertiary strata of the Valle del Cauca reflect a forearc/foreland basin tectonic history spanning a period from pre-uplift of the Cordillera Central to initiation of uplift of the Cordillera Occidental. Stratigraphy of the Valle del Cauca begins with Jurassic-Cretaceous rocks of exotic and/or volcanic provenance and of oceanic origin. Unconformably overlying these are Eocene to Oligocene basal quartz-rich sandstones, shallow marine algal limestones, and fine-grained fluvial/deltaic mudstones and sandstones with coalbeds. These Eocene to Oligocene deposits represent a period of low tectonic activity. During late Oligocene to early Miocene, increased tectonic activity produced conglomeratic sediments which were transported from east to west, apparently derived from uplift of the Cordillera Central, and deposited within a fluvial to deltaic setting. East-west shortening of the Valle del Cauca basin folded the Eocene to early Miocene units, and additional uplift of the Cordillera Central during the later Miocene resulted in syn-tectonic deposition of alluvial fans. After additional fold and thrust deformation of the total Eocene-Miocene basin-fill, tectonic activity abated and Pliocene-Quaternary alluvial and lacustrine strata were deposited. Within the framework of this depositional and tectonic history of the Valle del Cauca, hydrocarbon exploration strategies can be formulated and evaluated.

  12. Emsian (late Early Devonian) sponges from west-central and south-central Alaska

    USGS Publications Warehouse

    Rigby, J.K.; Blodgett, R.B.; Anderson, N.K.

    2009-01-01

    Relatively common specimens of the hypercalcified agelasiid sponge Hormospongia labyrinthica Rigby and Blodgett, 1983 and specimens of associated species of Hormospongia have been previously reported from Emsian and Eifelian stratigraphic units at several localities in south-central and southeastern Alaska (Rigby and Blodgett, 1983). Those sponges were first described from the type section of the Eifelian Cheeneetnuk Limestone in the McGrath A-5 quadrangle. Since then several additional specimens of Hormospongia labyrinthica have also been collected from a new locality in the Talkeetna C-6 quadrangle in southcentral Alaska (Figs. 1, 2.1), and are documented here.

  13. Time trend by region of suicides and suicidal thoughts among Greenland Inuit

    PubMed Central

    Bjerregaard, Peter; Larsen, Christina Viskum Lytken

    2015-01-01

    Background Suicides remain a major public health problem in Greenland. Their increase coincides with the modernization since 1950. Serious suicidal thoughts are reported by a significant proportion of participants in countrywide surveys. Objective To analyze the time trend by region of suicides and suicidal thoughts among the Inuit in Greenland. Design Data included the Greenland registry of causes of death for 1970–2011 and 2 cross-sectional health surveys carried out in 1993–1994 and 2005–2010 with 1,580 and 3,102 Inuit participants, respectively. Results Suicide rates were higher among men than women while the prevalence of suicidal thoughts was higher among women. Suicide rates for men and women together increased from 1960 to 1980 and have remained around 100 per 100,000 person-years since then. The regional pattern of time trend for suicide rates varied with an early peak in the capital, a continued increase to very high rates in remote East and North Greenland and a slow increase in villages relative to towns on the West Coast. Suicidal thoughts followed the regional pattern for completed suicides. Especially for women there was a noticeable increasing trend in the villages. The relative risk for suicide was highest among those who reported suicidal thoughts, but most suicides happened outside this high-risk group. Conclusion Suicide rates and the prevalence of suicidal thoughts remain high in Greenland but different regional trends point towards an increased marginalization between towns on the central West Coast, villages and East and North Greenland. Different temporal patterns call for different regional strategies of prevention. PMID:25701279

  14. New Argentine Central-West Line taps rich Neuquen gas field

    SciTech Connect

    Watts, J.

    1982-02-01

    Argentina's Centro-Oeste (Central-West) Gas Pipeline is now a reality, carrying gas from the extensive Loma de la Lata (Hill of Tin) field in Neuquen State to cities which had been relying on bottled gas. The project is impressive, but hardly seems unique. A pipeline consisting of 697 miles of 30-in. line and 451 miles of smaller diameter gathering and distribution lines is a big project but nothing that has not been done before. Sometimes figures and statistics hide more than they reveal. A discussion is provided of project financing, logistics, pipeline outlets, treatment plants, route, construction, other lines, compressor stations, and suppliers.

  15. New Argentine Central-West line taps rich Neuquen gas field

    SciTech Connect

    Watts, J.

    1982-02-01

    Argentina's new Central-West gas pipeline consists of 697 miles of 30-in. line and 451 miles of smaller gathering and distribution lines that link the rich Neuquen gas field with cities to the north. A financing package drawn up by 21 banks in the US and Europe allowed Cogasco S.A. to build the line for Gas del Estado across the roadless pampas east of the Andes. Primarily an agricultural country, Argentina had to import all the equipment and materials for the project. Site work began in July, 1980 with 800 workers employed on three spreads; the line was commissioned in November, 1981, 15 months ahead of the contract schedule.

  16. Sedimentary Record and Morphological Effects of a Landslide-Generated Tsunami in a Polar Region: The 2000 AD Tsunami in Vaigat Strait, West Greenland

    NASA Astrophysics Data System (ADS)

    Szczucinski, W.; Rosser, N. J.; Strzelecki, M. C.; Long, A. J.; Lawrence, T.; Buchwal, A.; Chague-Goff, C.; Woodroffe, S.

    2012-12-01

    To date, the effects of tsunami erosion and deposition have mainly been reported from tropical and temperate climatic zones yet tsunamis are also frequent in polar zones, particularly in fjord settings where they can be generated by landslides. Here we report the geological effects of a landslide-triggered tsunami that occurred on 21st November 2000 in Vaigat, northern Disko Bugt in west Greenland. To characterise the typical features of this tsunami we completed twelve detailed coastal transects in a range of depositional settings: cliff coasts, narrow to moderate width coastal plains, lagoons and a coastal lake. At each setting we completed a detailed map using a laser scanner and DGPS survey. The tsunami deposits were described from closely spaced trenches and, from the lake, by a series of sediment cores . At each setting we examined the sedimentological properties of the deposits, as well as their bulk geochemistry and diatom content. Selected specimens of arctic willow from inundated and non-inundated areas were collected to assess the impact of the event in their growth ring records. Samples of sediments beneath the AD 2000 deposit were studied for 137Cs to confirm the age of the tsunami and to assess the extent of erosion. Offshore sediment samples, modern beach and soils/sediments underlying the AD 2000 tsunami deposits were sampled to determine tsunami deposit sources. The observed tsunami run-up exceeded 20 m next to the tsunami trigger - a rock avalanche at Paatuut - and up to 10 m on the opposite coast of the fjord. The inland inundation distance ranged from several tens of meters to over 300 m. The wave was recorded as far as 180 km away from the source. The tsunami inundated the coast obliquely to the shoreline in all locations studied. The tsunami frequently caused erosion of existing beach ridges whilst erosional niches were formed inland. The tsunami deposits mainly comprise gravels and very coarse sand. They are over 30 cm thick close to the

  17. In-situ Measurements of Sedimentary Graphites and Sulfides in Early Archean (>3.7 Ga) Banded Iron-Formations from West Greenland: Biological and Atmospheric Influences

    NASA Astrophysics Data System (ADS)

    Mojzsis, S. J.

    2001-05-01

    might atmospheric and biological evolutionary links be evaluated by studying the carbon and sulfur isotope compositions of ancient sediments? New data reveal well-resolved non-mass-dependent Δ 33S anomalies in an early Archean [3.77-3.83 Ga] banded iron-formation and a metapelite from West Greenland [total range in Δ 33S=+1.10+/-0.07‰ to +1.23+/-0.05‰ , 2σ ] previously analyzed for carbon isotopes. Data from sulfides in a diverse collection of stromatolithic cherts, banded iron-formation and shales of Proterozoic to late Archean age [1.8-3.2 Ga] displayed only mass-dependent [Δ 33S ~0‰ ] sulfur isotope relationships within the precision of the measurements [typically +/-0.06‰ , 2σ ]. Results reveal that non-mass-dependent sulfur isotope anomalies [i.e. Δ 33S>0] are preserved in sulfide phases contained in the oldest known rocks of sedimentary origin. That these rocks contain a record of gas-phase reactions in an early atmosphere would support the interpretation that atmospheric partial pressures of oxygen were low and the effects of UV-photolysis on atmospheric sulfur from a UV-active young Sun were widespread and commonplace on the Archean Earth. This might also be reflected in the long-term [billion-year timescale] changes to the isotope composition of bioorganic carbon. Further studies warrant coupling sulfur, carbon [and nitrogen] measurements in ancient sediments to explore this relationship.

  18. Geodetic long-term studies (1991-2011) in ice dynamics and in mass balance in the Paakitsoq area (West Greenland)

    NASA Astrophysics Data System (ADS)

    Stober, M.; Rawiel, P.; Hepperle, J.

    2012-12-01

    Ice flow velocity, deformation, elevation change and mass balance are essential properties required for modeling ice sheets and correlation with climate change. Since 1991 until 2011 now 11 campaigns had been carried out in order to study ice flow velocity, surface deformation and elevation change respectively mass balance of the inland ice in the Paakitsoq area, West Greenland. It is a long-term project with terrestrial GPS observations of stake networks in two research areas. One area is situated at the Swiss-Camp in an altitude of 1170 m, where the former position of the equilibrium line was supposed. The second research area, called ST2, is located in the flow line in an altitude of 1000 m, and situated close to the automatic weather station JAR1 of the GC-Net. The ST2 network was established in 2004. In 2004, 2005, 2006, 2008 and 2011 here now 5 campaigns have been performed. The results in elevation change very clearly show the increased lowering of the ice surface. At Swiss-Camp we started in the period 1991 until 2002 with -0.25 m/year, in 2002 - 2006 with -0.60 m/year and in 2006 - 2011 with -1.10 m/year. At ST2 in 2004 - 2006 we find a lowering of -0.34 m/year and in 2006 - 2011 of -1.31 m/year. The elevation decrease is directly correlated with altitude. In general, the recent ice thickness loss is more than three times greater than the long-term trend in former years. The elevation changes are converted into mass balance results between the measuring dates. They are compared to meteorological parameters with data from the AWS of the GC-net. Elevation changes are also derived by digital terrain models from the research areas. It is shown that systematic local height change anomalies occur in all years indicating local variations of melting, probably caused by albedo variations. From the horizontal deformation of the stake network the local horizontal strain rates were derived. In connection with the incompressibility condition of ice, the vertical strain

  19. Evaluation of the use of common sculpin (Myoxocephalus scorpius) organ histology as bioindicator for element exposure in the fjord of the mining area Maarmorilik, West Greenland.

    PubMed

    Sonne, Christian; Bach, Lis; Søndergaard, Jens; Rigét, Frank F; Dietz, Rune; Mosbech, Anders; Leifsson, Pall S; Gustavson, Kim

    2014-08-01

    The former Black Angel lead-zinc mine in Maarmorilik, West Greenland, is a historic example of how mining activity may result in a significant impact on the surrounding fjord system in terms of elevated concentrations of especially lead (Pb) and zinc (Zn) in seawater, sediments and surrounding biota. In order to shed light on the present contamination and possible effects in the fjord we initiated a range of studies including a pilot study on gill and liver morphology of common sculpins (Myoxocephalus scorpius) around Maarmorilik. Sculpins were caught and sampled at five different stations known to represent a gradient of Pb concentrations. Fish livers from all specimens were analyzed for relevant elements in the area: Fe, Zn, As, Cu, Se, Cd, Pb, Ag, Hg, Co and Ni. Lead, As and Hg showed significant differences among the five stations. For 20% of the sculpins, Hg concentrations were in the range of lowest observed effect dose (LOED) of 0.1-0.5 μg/g ww for toxic threshold on reproduction and subclinical endpoints. Likewise LOEDs for tissue lesions, LOEDs for biochemistry, growth, survival and reproduction were exceeded for Cd (0.42-1.8 μg/g ww) and for As (11.6 μg/g ww) in 28% and 85% of the sculpins, respectively. Similar to this, the no observed effect dose (NOED) for biochemistry was exceeded for Pb (0.32 μg/g ww) and for growth, mortality and reproduction for Zn (60-68 μg/g ww) in 33% and 24% of the sculpins, respectively. For all sculpins, females were significantly larger than males and for five of the elements (Fe, Co, Ni, Cu, Se) females had higher concentrations. The chronic lesions observed in liver (mononuclear cell infiltrates, necrosis, vacuolar hepatocytes, portal fibrosis, bile duct hyperplasia, active melanomacrophage centers) and gills (fusion and edema of secondary lamellae, laminar telangiectasis, mononuclear cell infiltrates, blebs) were similar to those in the literature studies for both wild and laboratory exposed sculpins and other fish

  20. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, May 2006

    USGS Publications Warehouse

    Ortiz, A.G.

    2007-01-01

    Introduction Hydrologic Conditions in West-Central Florida The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2006. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 50.23 inches for west-central Florida (from June 2005 through May 2006) was 2.82 inches below the historical cumulative average of 53.05 inches (Southwest Florida Water Management District, 2006). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water

  1. Depositional environments and paleogeography of the Upper Miocene Wassuk Group, west-central Nevada

    USGS Publications Warehouse

    Golia, R.T.; Stewart, John H.

    1984-01-01

    Fluvial and lacustrine deposits of the Miocene Wassuk Group, exposed in Coal Valley, west-central Nevada, are divided into five lithofacies: (1) diatomite, claystone, siltstone, and carbonaceous siltstone deposited in a lake with paludal conditions at the margin; (2) upward-coarsening sequences of sandstone deposited on a delta and fan-delta; (3) channel-form sandstone deposited on a distal braided alluvial plain; (4) clast-supported conglomerate deposited on a proxial braided alluvial plain or distal alluvial fan; and (5) matrix-supported conglomerate deposited on a distal to middle alluvial fan. Petrographic analysis records an upsection change from a predominantly andesitic to a predominantly plutonic provenance. This change, combined with the overall upward-coarsening of the Wassuk Group and the great thickness (2400 m) of the sequence, suggests active uplift and rapid subsidence during deposition of the group. Facies relationships and paleocurrent directions indicate source areas to the south, southeast and west of Coal Valley. The Miocene Wassuk Group was deposited in an intra-arc basin with penecontemporaneous volcanism and tectonic activity. Syndepositional faulting at the southern margin of Coal Valley between 13 and 11 m.y. ago suggests an early episode of northeast-southwest extension prior to the onset of east-west basin and range extension. ?? 1984.

  2. Central and South West Services (CSWS) transmission system studies: (Rio Grande Valley FACTS studies). Final report

    SciTech Connect

    Arabi, S.; Hamadanizadeh, H.

    1998-12-01

    Stability limitations impose constraints on power imports into the Rio Grande Valley, the southern region of Central Power and Light`s (CPL) system. CPL`s parent company, Central and South West Services, sought to identify viable plans for eliminating these constraints to enable power transfers via two 345-kV transmission lines. This project conducted assessment studies of the CPL system, using applications from EPRI`s Power System Analysis Package, and identified two scenarios as the most likely remedial measures required. These consisted of the addition of generating units and the use of series compensation of the two transmission lines, in conjunction with shunt compensation. While Flexible AC Transmission System (FACTS) devices were not indicated in this study phase, the researchers indicated a Thyristor Controlled Series Compensation device could be considered to address a potential subsynchronous resonance issue.

  3. Anthropogenic influence on recent bathymetric change in west-central San Francisco Bay

    USGS Publications Warehouse

    Barnard, Patrick L.; Kvitek, Rikk G.

    2010-01-01

    Two multibeam sonar surveys of west-central San Francisco Bay, California, were conducted in 1997 and 2008. Bathymetric change analysis between the two surveys indicates a loss of 14.1 million cubic meters (-3.1 cm/yr-1) of sediment during this time period, representing an approximately three-fold acceleration of the rate that was observed from prior depth change analysis from 1947 to 1979 for all of Central Bay, using more spatially coarse National Ocean Service (NOS) soundings. The portions of the overlapping survey areas between 1997 and 2008 designated as aggregate mining lease sites lost sediment at five times the rate of the remainder of west-central San Francisco Bay. Despite covering only 28% of the analysis area, volume change within leasing areas accounted for 9.2 million cubic meters of sediment loss, while the rest of the area lost 4.9 million cubic meters of sediment. The uncertainty of this recent analysis is more tightly constrained due to more stringent controls on vertical and horizontal position via tightly coupled, inertially aided differential Global Positioning Systems (GPS) solutions for survey vessel trajectory that virtually eliminate inaccuracies from traditional tide modeling and vessel motion artifacts. Further, quantification of systematic depth measurement error can now be calculated through comparison of static surfaces (e.g., bedrock) between surveys using seafloor habitat maps based on acoustic backscatter measurements and ground-truthing with grab samples and underwater video. Sediment loss in the entire San Francisco Bay Coastal System during the last half-century,as estimated from a series of bathymetric change studies, is 240 million cubic meters, and most of this is believed to be coarse sediment (i.e., sand and gravel) from Central Bay and the San Francisco Bar, which is likely to limit the sand supply to adjacent, open-coast beaches. This hypothesis is supported by a calibrated numerical model in a related study that indicates

  4. Measuring bioavailable metals using diffusive gradients in thin films (DGT) and transplanted seaweed (Fucus vesiculosus), blue mussels (Mytilus edulis) and sea snails (Littorina saxatilis) suspended from monitoring buoys near a former lead-zinc mine in West Greenland.

    PubMed

    Søndergaard, Jens; Bach, Lis; Gustavson, Kim

    2014-01-15

    Measuring loads of bioavailable metals is important for environmental assessment near mines and other industrial sources. In this study, a setup of monitoring buoys was tested to assess loads of bioavailable metals near a former Pb-Zn mine in West Greenland using transplanted seaweed, mussels and sea snails. In addition, passive DGT samplers were installed. After a 9-day deployment period, concentrations of especially Pb, Zn and Fe in the species were all markedly elevated at the monitoring sites closest to the mine. Lead concentrations in all three species and the DGT-Pb results showed a significant linear correlation. Zinc and Fe concentrations were less correlated indicating that the mechanisms for Zn and Fe accumulation in the three species are more complex. The results show that there is still a significant load of metals from the mine and that such buoys can be an adequate method to assess present loads of bioavailable metals.

  5. Potentiometric surface of the Upper Floridan aquifer, west-central Florida, September 2010

    USGS Publications Warehouse

    Ortiz, A.G.

    2011-01-01

    This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2010. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when groundwater levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 53.17 inches for west-central Florida (from October 2009 through September 2010) was 0.41 inches above the historical cumulative average of 52.76 inches (Southwest Florida Water Management District, 2010). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District.

  6. A Precambrian cratonic block in the west-central Chihuahua - The Sierra del Nido cratonic block

    SciTech Connect

    Goodell, P.C. . Dept. of Geological)

    1993-02-01

    Precambrian rocks in west-central Chihuahua have been recognized by Denison (1969) and Mauger et al. (1983), on the basis of radiometric dating. The rocks are rhyolite clasts, and an allucthonous block, respectively, however their source direction and vergence can be measured. They point back to and are on the edge of a large, uniform, negative Bouguer gravity anomaly, having values greater than 200 milligals. The isotopic geochemical character of several Tertiary felsic fields within this anomalous are has been determined, and initial strontium isotopic ratios are all greater than 0.7055. Outside the anomalous area these ratios are lower, and Basin and Range extension tectonism is more evident. It is proposed that a Precambrian cratonic block, the Sierra del Nido, is present in the crust in west-central Chihuahua. It is reasonable to propose that it was decreted from North America during a Precambrian extensional (1.1. By ) event, from somewhere along the Arizona Transition Zone-Texas Linament region. The Sierra del Nido Block is separated form the ATZ-TL by a region of disrupted craton and extended crust, the Basin and Range Province. Implications of the pressure of the Sierra del Nido Block on other regional tectonic events will be discussed.

  7. Hydrologic maps of Ogallala Aquifer, west-central Kansas, 1979-81

    USGS Publications Warehouse

    Spinazola, Joseph M.

    1982-01-01

    A mathematical technique, called kriging, was programmed for a computer to interpolate hydrologic data based on a network of measured values in west-central Kansas. The computer program generated estimated values at the center of each 1-mile section in the Western Kansas Groundwater Management District No. 1 and facilitated contouring of selected hydrologic data that are needed in the effective management of ground water for irrigation. The kriging technique produced various maps that illustrated hydrologic conditions in the Ogallala aquifer, the principal source of water in west-central Kansas. Maps of the aquifer, which use a 3-year average, included the 1979-81 water-table altitudes, which ranged from about 2,580 to 3,720 feet; the 1979-81 saturated thicknesses, which ranged from about 0 to 250 feet; and the percentage changes in saturated thickness from 1950 to 1979-81, which ranged from about a 40-percent increase to a 100-percent decrease. A map showing errors of estimate also was provided as a measure of reliability for the 1979-81 water-table altitudes. Errors of estimate ranged from 2 to 24 feet. (USGS)

  8. Tracing the origin of the east-west population admixture in the Altai region (Central Asia).

    PubMed

    González-Ruiz, Mercedes; Santos, Cristina; Jordana, Xavier; Simón, Marc; Lalueza-Fox, Carles; Gigli, Elena; Aluja, Maria Pilar; Malgosa, Assumpció

    2012-01-01

    A recent discovery of Iron Age burials (Pazyryk culture) in the Altai Mountains of Mongolia may shed light on the mode and tempo of the generation of the current genetic east-west population admixture in Central Asia. Studies on ancient mitochondrial DNA of this region suggest that the Altai Mountains played the role of a geographical barrier between West and East Eurasian lineages until the beginning of the Iron Age. After the 7th century BC, coinciding with Scythian expansion across the Eurasian steppes, a gradual influx of East Eurasian sequences in Western steppes is detected. However, the underlying events behind the genetic admixture in Altai during the Iron Age are still unresolved: 1) whether it was a result of migratory events (eastward firstly, westward secondly), or 2) whether it was a result of a local demographic expansion in a 'contact zone' between European and East Asian people. In the present work, we analyzed the mitochondrial DNA lineages in human remains from Bronze and Iron Age burials of Mongolian Altai. Here we present support to the hypothesis that the gene pool of Iron Age inhabitants of Mongolian Altai was similar to that of western Iron Age Altaians (Russia and Kazakhstan). Thus, this people not only shared the same culture (Pazyryk), but also shared the same genetic east-west population admixture. In turn, Pazyryks appear to have a similar gene pool that current Altaians. Our results further show that Iron Age Altaians displayed mitochondrial lineages already present around Altai region before the Iron Age. This would provide support for a demographic expansion of local people of Altai instead of westward or eastward migratory events, as the demographic event behind the high population genetic admixture and diversity in Central Asia.

  9. Ocean climate data for user community in West and Central Africa: Needs, opportunities, and challenges

    NASA Technical Reports Server (NTRS)

    Ojo, S. O.

    1992-01-01

    The urgent need to improve data delivery systems needed by scientists studying ocean role in climate and climate characteristics has been manifested in recent years because of the unprecedented climatic events experienced in many parts of the world. Indeed, there has been a striking and growing realization by governments and the general public indicating that national economies and human welfare depend on climate and its variability. In West and Central Africa, for instance climatic events, which have resulted in floods and droughts, have caused a lot of concern to both governments and people of the region. In particular, the droughts have been so widespread that greater awareness and concern have become generated for the need to find solutions to the problems created by the consequences of the climatic events. Particularly in the southern border regions of the Sahara Desert as well as in the Sahel region, the drought episodes considerably reduced food production and led to series of socioeconomic problems, not only in the areas affected by the droughts, but also in the other parts of West Africa. The various climatic variabilities which have caused the climatic events are no doubt related to the ocean-atmosphere interactions. Unfortunately, not much has been done on the understanding of these interactions, particularly as they affect developing countries. Indeed, not much has been done to develop programs which will reflect the general concerns and needs for researching into the ocean-atmosphere systems and their implications on man-environmental systems in many developing countries. This is for example, true of West and Central Africa, where compared with the middle latitude countries, much less is known about the characteristics of the ocean-atmosphere systems and their significance on man-environmental systems of the area.

  10. Aponogeton pollen from the Cretaceous and Paleogene of North America and West Greenland: Implications for the origin and palaeobiogeography of the genus☆

    PubMed Central

    Grímsson, Friðgeir; Zetter, Reinhard; Halbritter, Heidemarie; Grimm, Guido W.

    2014-01-01

    The fossil record of Aponogeton (Aponogetonaceae) is scarce and the few reported macrofossil findings are in need of taxonomic revision. Aponogeton pollen is highly diagnostic and when studied with light microscopy (LM) and scanning electron microscopy (SEM) it cannot be confused with any other pollen types. The fossil Aponogeton pollen described here represent the first reliable Cretaceous and Eocene records of this genus worldwide. Today, Aponogeton is confined to the tropics and subtropics of the Old World, but the new fossil records show that during the late Cretaceous and early Cenozoic it was thriving in North America and Greenland. The late Cretaceous pollen record provides important data for future phylogenetic and phylogeographic studies focusing on basal monocots, especially the Alismatales. The Eocene pollen morphotypes from North America and Greenland differ in morphology from each other and also from the older Late Cretaceous North American pollen morphotype, indicating evolutionary trends and diversification within the genus over that time period. The presence of Aponogeton in the fossil record of North America and Greenland calls for a reconsideration of all previous ideas about the biogeographic history of the family. PMID:24926107

  11. Aponogeton pollen from the Cretaceous and Paleogene of North America and West Greenland: Implications for the origin and palaeobiogeography of the genus.

    PubMed

    Grímsson, Friðgeir; Zetter, Reinhard; Halbritter, Heidemarie; Grimm, Guido W

    2014-01-01

    The fossil record of Aponogeton (Aponogetonaceae) is scarce and the few reported macrofossil findings are in need of taxonomic revision. Aponogeton pollen is highly diagnostic and when studied with light microscopy (LM) and scanning electron microscopy (SEM) it cannot be confused with any other pollen types. The fossil Aponogeton pollen described here represent the first reliable Cretaceous and Eocene records of this genus worldwide. Today, Aponogeton is confined to the tropics and subtropics of the Old World, but the new fossil records show that during the late Cretaceous and early Cenozoic it was thriving in North America and Greenland. The late Cretaceous pollen record provides important data for future phylogenetic and phylogeographic studies focusing on basal monocots, especially the Alismatales. The Eocene pollen morphotypes from North America and Greenland differ in morphology from each other and also from the older Late Cretaceous North American pollen morphotype, indicating evolutionary trends and diversification within the genus over that time period. The presence of Aponogeton in the fossil record of North America and Greenland calls for a reconsideration of all previous ideas about the biogeographic history of the family.

  12. Melt anomalies on the Greenland Ice Sheet and large scale modes of atmospheric circulation

    NASA Astrophysics Data System (ADS)

    Huff, Russell

    The relationships between inter annual melt variability in Greenland and large scale atmospheric circulation are explored based on an empirical orthogonal function (EOF) analysis of melt in Greenland derived from passive microwave satellite observations. The first EOF of the melt anomalies was found to be highly representative of the spatial and temporal distribution of melt anomalies accounting for over 34% of the variability and the principal component (PC) time series is 98% correlated with the annual total melt extent time series. The leading melt PC is highly correlated with key features of the large scale atmospheric circulation both in the vicinity of Greenland and regions that are well removed. Some aspects of the atmospheric pressure anomaly fields related to melt in Greenland are congruent with the summer expression of the AO/NAO including the main center of action east of Greenland, however there are features of the melt related anomaly field that are not. During peak melt years there is a decrease in the pressure gradient between the Bearing Sea and more southerly latitudes resulting in a redistribution of the central Arctic low pressure toward the Pacific side of the Arctic basin. This pattern is expressed as a 50% correlation between melt in Greenland and the phase of planetary pressure wave #1 and #2 north of 50° N. The storm tracks related to increased melt in Greenland result in increased summer storm activity to the south and west of Greenland balanced by decreased cyclonic activity to the east and north. Comparison with the NAO related storm track highlights key differences relative to the melt related atmospheric circulation that lead to increased southerly flow directly into Greenland during years with increased melt. The pattern of summer sea ice concentration anomalies linked to the melt PC is remarkably similar to the spatial pattern of recent sea ice decline. The pattern of circulation anomalies associated with increased melt in Greenland

  13. Population Structure of Clinical Pseudomonas aeruginosa from West and Central African Countries

    PubMed Central

    Cholley, Pascal; Ka, Roughyatou; Guyeux, Christophe; Thouverez, Michelle; Guessennd, Nathalie; Ghebremedhin, Beniam; Frank, Thierry; Bertrand, Xavier; Hocquet, Didier

    2014-01-01

    Background Pseudomonas aeruginosa (PA) has a non-clonal, epidemic population with a few widely distributed and frequently encountered sequence types (STs) called ‘high-risk clusters’. Clinical P. aeruginosa (clinPA) has been studied in all inhabited continents excepted in Africa, where a very few isolates have been analyzed. Here, we characterized a collection of clinPA isolates from four countries of West and Central Africa. Methodology 184 non-redundant isolates of clinPA from hospitals of Senegal, Ivory Coast, Nigeria, and Central African Republic were genotyped by MLST. We assessed their resistance level to antibiotics by agar diffusion and identified the extended-spectrum β-lactamases (ESBLs) and metallo-β-lactamases (MBLs) by sequencing. The population structure of the species was determined by a nucleotide-based analysis of the entire PA MLST database and further localized on the phylogenetic tree (i) the sequence types (STs) of the present collection, (ii) the STs by continents, (iii) ESBL- and MBL-producing STs from the MLST database. Principal Findings We found 80 distinct STs, of which 24 had no relationship with any known STs. ‘High-risk’ international clonal complexes (CC155, CC244, CC235) were frequently found in West and Central Africa. The five VIM-2-producing isolates belonged to CC233 and CC244. GES-1 and GES-9 enzymes were produced by one CC235 and one ST1469 isolate, respectively. We showed the spread of ‘high-risk’ international clonal complexes, often described as multidrug-resistant on other continents, with a fully susceptible phenotype. The MBL- and ESBL-producing STs were scattered throughout the phylogenetic tree and our data suggest a poor association between a continent and a specific phylogroup. Conclusions ESBL- and MBL-encoding genes are borne by both successful international clonal complexes and distinct local STs in clinPA of West and Central Africa. Furthermore, our data suggest that the spread of a ST could be

  14. Hydrologic reconnaissance of the southern Great Salt Lake Desert and summary of the hydrology of west-central Utah

    USGS Publications Warehouse

    Gates, Joseph S.; Kruer, Stacie A.

    1981-01-01

    This report is the last of 19 hydrologic reconnaissances of the basins in western Utah. The purposes of this series of studies are (1) to analyze available hydrologic data and describe the hydrologic system, (2) to evaluate existing and potential water-resources development, and (3) to identify additional studies that might be needed. Part 1 of this report gives an estimate of recharge and discharge, an estimate of the potential for water-resources development, and a statement on the quality of water in the southern Great Salt Lake Desert part of west-central Utah. Part 2 deals with the same aspects of west-central Utah as a whole. Part 2 also summarizes the evidence of interbasin ground-water flow in west-central Utah and presents a theory for the origin of the water discharged from Fish Springs.

  15. Potentiometric surface of the upper Floridan aquifer, west-central Florida, May 2011

    USGS Publications Warehouse

    Ortiz, Anita G.

    2011-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2011. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when groundwater levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 45.74 inches for west-central Florida (from June 2010 through May 2011) was 6.85 inches below the historical cumulative average of 52.59 inches (Southwest Florida Water Management District, 2011). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September from 1975 through 2010. Water-level data are collected in May and September each year to

  16. Potentiometric surface of the Upper Floridan aquifer, west-central Florida, September 2005

    USGS Publications Warehouse

    Ortiz, A.G.

    2006-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District (SWFWMD) and is used for major public supply, domestic use, irrigation, and brackish-water desalination in coastal communties (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2005. The potentiometric surface is an imaginary surface, connecting points of equal altitude to which water will rise in a tightly cased well that taps a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 55.19 inches for west-central Florida (from October 2004 through September 2005) was 2.00 inches above the historical cumulative average of 53.19 inches (Southwest Florida Water Management District, 2005). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to the most recent calendar year) and are updated monthly by the SWFWMD. This report, prepared by the U.S. Geological Survey (USGS) in cooperation with the SWFWMD, is part of a semiannual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water

  17. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, May 2007

    USGS Publications Warehouse

    Ortiz, A.G.

    2008-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2007. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 41.21 inches for west-central Florida (from June 2006 through May 2007) was 11.63 inches below the historical cumulative average of 52.84 inches (Southwest Florida Water Management District, 2007). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the

  18. Potentiometric Surface of the Upper Floridan Aquifer, West-central Florida, May 2010

    USGS Publications Warehouse

    Ortiz, A.G.

    2010-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2010. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when groundwater levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 55.21 inches for west-central Florida (from June 2009 through May 2010) was 2.55 inches above the historical cumulative average of 52.66 inches (Southwest Florida Water Management District, 2010). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the

  19. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, September 2006

    USGS Publications Warehouse

    Ortiz, A.G.

    2007-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2006. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 46.06 inches for west-central Florida (from October 2005 through September 2006) was 6.91 inches below the historical cumulative average of 52.97 inches (Southwest Florida Water Management District, 2006). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each

  20. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, September 2008

    USGS Publications Warehouse

    Ortiz, Anita G.

    2009-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2008. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 50.63 inches for west-central Florida (from October 2007 through September 2008) was 2.26 inches below the historical cumulative average of 52.89 inches (Southwest Florida Water Management District, 2008). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each

  1. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, September 2007

    USGS Publications Warehouse

    Ortiz, A.G.

    2008-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2007. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 39.50 inches for west-central Florida (from October 2006 through September 2007) was 13.42 inches below the historical cumulative average of 52.92 inches (Southwest Florida Water Management District, 2007). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each

  2. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, May 2008

    USGS Publications Warehouse

    Ortiz, A.G.

    2008-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2008. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 46.95 inches for west-central Florida (from June 2007 through May 2008) was 5.83 inches below the historical cumulative average of 52.78 inches (Southwest Florida Water Management District, 2008). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the

  3. Magnetic signature of North-East Greenland, the Morris Jesup Rise, the Yermak Plateau, the central Fram Strait: Constraints for the rift/drift history between Greenland and Svalbard since the Eocene

    NASA Astrophysics Data System (ADS)

    Jokat, Wilfried; Lehmann, Paul; Damaske, Detlef; Bradley Nelson, J.

    2016-11-01

    A compilation of several aeromagnetic surveys across North Greenland and the Fram Strait area is presented. Across North Greenland, the data are related to the known onshore geology. The correlation between the geological structure and the large-scale magnetic anomalies is excellent. Along the North Greenland coast, the data indicate that the Late Mesozoic Kap Washington volcanics might have a larger areal extent than known from onshore geological mapping. The submarine Morris Jesup Rise is characterized by strong positive magnetic anomalies, and the anomalies across the plateau indicate the presence of distinct volcanic centers. This massive magmatism has occurred latest in conjunction with the Oligocene initial stages of plate divergence between Svalbard and North Greenland that led to the development of Fram Strait. Both plateaux, the Morris Jesup Rise and the Yermak Plateau, are interpreted to be of continental origin and, in the initial rift stage of the Eurasia Basin around 56 Ma, to have been contiguous with the Lomonosov Ridge. More toward the east in the Fram Strait interpretations of seismic and bathymetric data indicate the presence of an active segment of mid-ocean ridge, the Lena Trough. This approximately 280-km-long segment terminates in the south at the NW-SE striking Spitsbergen Fracture Zone, while in the north it bends to connect with the Gakkel Ridge. A shallow water pathway along the line of the trough might have existed between those times and 21 Ma, above the propagating rift system in the north and, further south, over extending and subsiding continental crust of the Svalbard and North-East Greenland margins. Magnetic anomaly identifications indicate that the Lena Trough has remained an ultraslow spreading system, or possibly even all of the magnetic lineations may be signals of serpentinized exhumed mantle rocks rather than of basaltic crust.

  4. Precipitation, streamflow, and base flow in west-central Texas, December 1974 through March 1977

    USGS Publications Warehouse

    Kuniansky, Eve L.

    1989-01-01

    Precipitation, streamflow, and base-flow data were analyzed for December 1974 through March 1977 as a part of the Edwards-Trinity Regional Aquifer-System Analysis in west-central Texas. The period of record analyzed corresponds to the calibrating period of a digital groundwater-flow model of the aquifer system currently (1988) being developed. Precipitation at individual stations ranged from 6 to 45 in/yr. Precipitation normally (1951-80) ranged from 10 to 32 in/year from east to west in the study area. Precipitation was near normal over most of the area and above normal in the southeastern part of the study area. Streamflow ranged from less than 1 in/year in the western part of the study area to 13 in/yr in the southeastern part. Streamflow was 8 in/yr above normal in the southeast. Base flow ranged from less than 0.1 in/yr in the western part of the study area to 6 in/yr in the southeastern part. (USGS)

  5. From Arctic greenhouse to icehouse: the Cenozoic development of the West Greenland-Baffin Bay margin and the case for scientific drilling

    NASA Astrophysics Data System (ADS)

    Knutz, Paul; Gregersen, Ulrik; Hopper, John R.; Dybkjær, Karen; Nøhr-Hansen, Henrik; Sheldon, Emma; Huuse, Mads

    2016-04-01

    The long-term evolution of glaciated margins plays an essential role in understanding the driving forces and interactions that determine the build-up and decay of ice sheets. The Greenland continental margin towards Baffin Bay is densely covered by industry seismic data and several exploration wells have been drilled, providing a regional stratigraphic framework for the sedimentary successions. This presentation provides an overview of the major depositional units and stratigraphy of the mid-late Cenozoic (since mid-Eocene), with examples demonstrating the different processes that have formed this margin. A sedimentary succession up to 3.5 km thick, of mid-Eocene to mid-Miocene age (mega-unit D), infills the pronounced ridge-basin structures of the rifted and tectonically inverted margin. The lower part of this interval, presumably late Eocene-Oligocene in age, is interpreted as basin-floor fan deposits, while the upper section, of early-middle Miocene age, is mainly marine mudstone. The basin infilling strata are overlain by a late Miocene-Pliocene succession consisting of two mega-units (B and C), with typical thicknesses of 0.5-1 km. The units are characterised by upslope-climbing sediment waves and along-slope trending sedimentary prisms reminiscent of giant contourite drifts. The borehole data associates the prism accumulations with a deep shelf environment influenced by strong marine currents and nearby fluvial sources. On the slope and in the deep basin of Baffin Bay the late Neogene succession is strongly influenced by mass wasting correlated with erosional scars updip. The uppermost seismic mega-unit (A) is dominated by aggradational wedges and prograding fan deposits displaying depocentres >3 km thick, formed at the terminus of palaeo-ice streams. Borehole information associates this interval with deposition of primarily diamict sediments and suggests a late Pliocene onset of major shelf based glaciations on the NW Greenland margin. The southwest margin

  6. Physical characteristics of stream subbasins in the Chippewa River basin, west-central Minnesota

    USGS Publications Warehouse

    Sanocki, C.A.; Krumrie, J.R.

    1994-01-01

    Data that describe the physical characteristics of stream subbasins upstream from selected points on streams in the Chippewa River Basin, located in west-central Minnesota, are presented in this report The physical characteristics are the drainage area of the subbasin, the percentage area of the subbasin covered only by lakes, the percentage area of the subbasin covered by both lakes and wetlands, the main-channel length, and the main-channel slope. The points on the stream include outlets of subbasins of at least 5 square miles, outlets of sewage treatment plants, and locations of U.S. Geological Survey low-flow, high-flow, and continuous-record gaging stations.

  7. Physical characteristics of stream subbasins in the Pomme de Terre River Basin, west-central Minnesota

    USGS Publications Warehouse

    Lorenz, D.L.; Payne, G.A.

    1994-01-01

    Data describing the physical characteristics of stream subbasins upstream from selected points on streams in the Pomme de Terre River Basin, located in west-central Minnesota, are presented in this report. The physical characteristics are the drainage area of the subbasin, the percentage area of the subbasin covered only by lakes, the percentage area of the subbasin covered by both lakes and wetlands, the main-channel length, and the main-channel slope. The points on the stream include outlets of subbasins of at least 5 square miles, outfalls of sewage treatment plants, and locations of U.S. Geological Survey low-flow, high-flow, and continuous-record gaging stations.

  8. Prevalence of hepatitis C virus infection among recyclable waste collectors in Central-West Brazil.

    PubMed

    Marinho, Thaís Augusto; Lopes, Carmen Luci Rodrigues; Teles, Sheila Araújo; Reis, Nádia Rúbia Silva; Carneiro, Megmar Aparecida dos Santos; de Andrade, Andreia Alves; Martins, Regina Maria Bringel

    2013-06-01

    The prevalence of hepatitis C virus (HCV) in a population of recyclable waste collectors (n = 431) was assessed using a cross-sectional survey in all 15 cooperatives in the city of Goiânia, Central-West Brazil. The HCV prevalence was 1.6% (95% confidence interval: 0.6-3.6) and a history of sexually transmitted infections was independently associated with this infection. HCV RNA (corresponding to genotype 1; subtypes 1a and 1b) was detected in five/seven anti-HCV-positive samples. Although the study population reported a high rate (47.3%) of sharps and needle accidents, HCV infection was not more frequent in recyclable waste collectors than in the general Brazilian population.

  9. Possible new constraints on late Miocene depositional patterns in west-central California

    NASA Astrophysics Data System (ADS)

    Liniecki-Laporte, Margaret; Andersen, David W.

    1988-03-01

    In the San Francisco Bay area, estuarine, lacustrine, and fluvial depositional environments existed contemporaneously within the Mulholland Formation, which was deposited in the Contra Costa basin from 7.7 to 6.5 Ma. The estuarine facies is differentiated from the nonmarine facies on the bases of ostracodes and sedimentology. Presence of the estuarine facies in the Mulholland Formation demonstrates that the Contra Costa basin was at sea level, the western part of the basin being a marine embayment for about 1 m.y. Absence of fresh Sierra Nevada-derived material in the lower Mulholland Formation indicates that a topographically elevated area existed east of the Contra Costa basin, effectively deflecting the Sierran debris, which is represented by the coeval Neroly Formation found in the eastern central Coast Ranges. To the west of the Contra Costa basin, some gaps in the Coast Ranges allowed connection with the Pacific Ocean.

  10. Flood of May 6, 2007, Willow Creek, west-central Iowa

    USGS Publications Warehouse

    Fischer, Edward E.; Eash, David A.

    2008-01-01

    Major flooding occurred May 6, 2007, in the Willow Creek drainage basin in Harrison County following severe thunderstorm activity over west-central Iowa. More than 7 inches of rain were recorded for the 72-hour period ending 7 a.m., May 6, at the Logan, Iowa weather station. The peak discharge in Willow Creek at Medford Avenue near Missouri Valley, Iowa, was 17,000 cubic feet per second. The recurrence interval of the flood is 160 years, which was estimated using regional regression equations. Information about the basin, the storms, the flooding, and a profile of high-water marks measured at 10 locations along Willow Creek between the mouth at the Boyer River and State Highway 37 in Monona County, a distance of almost 33 river miles, are presented in this report.

  11. Chlorinated pesticide residues in sediments from the Arabian Sea along the central west coast of India

    SciTech Connect

    Sarkar, A.; Gupta, R.S.

    1987-12-01

    The problem of environmental contamination by persistent chlorinated pesticides still evokes major concern due to the presence of their residues in the environment and in human tissues. In developing countries like India organochlorine insecticides, especially DDT are extensively being used in agriculture and vector control programs. Few data are available on their levels of concentration from the seas around India. Persistent pesticides residues can be expected to accumulate in marine sediments. However, very little data on this are available along the Indian coast. An attempt has been made in the present communication to identify and quantify some of the chlorinated pesticides residues in the marine sediments collected from different region along the central west coast of India. This is a part of our ongoing project to monitor and map pollutants within the exclusive economic zone of India.

  12. Near-surface water balance of an undeveloped upland site in west-central Florida

    USGS Publications Warehouse

    Bidlake, W.R.; Boetcher, P.F.

    1996-01-01

    A study was made to examine the near-surface water balance of a dry prairie site in west-central Florida. The water balance, which was defined on a unit area basis and for a depth of 5.5 meters, was described for the period June 1991 to October 1992. Precipitation during the 498 days of field measurements was 2,245 millimeters. Evapotranspiration, the second largest component, was 1,419 millimeters. Water yield was 808 millimeters and the change in soil water storage was 19 millimeters. Computed vertical water flux was less than 4 percent of evapotranspiration because of the small hydraulic conductivity of a clay layer that began at a depth of 5.5 meters.

  13. Geophysical Framework Investigations Influencing Ground-Water Resources in East-Central Nevada and West-Central Utah

    USGS Publications Warehouse

    Watt, Janet T.; Ponce, David A.

    2007-01-01

    A geophysical investigation was undertaken as part of an effort to characterize the geologic framework influencing ground-water resources in east-central Nevada and west-central Utah. New gravity data were combined with existing aeromagnetic, drill-hole, and geologic data to help determine basin geometry, infer structural features, estimate depth to pre-Cenozoic basement rocks, and further constrain the horizontal extents of exposed and buried plutons. In addition, a three-dimensional (3D) geologic model was constructed to help illustrate the often complex geometries of individual basins and aid in assessing the connectivity of adjacent basins. In general, the thirteen major valleys within the study area have axes oriented north-south and frequently contain one or more sub-basins. These basins are often asymmetric and typically reach depths of 2 km. Analysis of gravity data helped delineate geophysical lineaments and accommodation zones. Structural complexities may further compartmentalize ground-water flow within basins and the influence of tectonics on basin sedimentation further complicates their hydrologic properties. The horizontal extent of exposed and, in particular, buried plutons was estimated over the entire study area. The location and subsurface extents of these plutons will be very important for regional water resource assessments, as these features may act as either barriers or pathways for groundwater flow. A previously identified basement gravity low strikes NW within the study area and occurs within a highly extended terrane between the Butte and Confusion synclinoria. Evidence from geophysical, geologic, and seismic reflection data suggests relatively lower density plutonic rocks may extend to moderate crustal depths and rocks of similar composition may be the source of the entire basement gravity anomaly.

  14. Climate Change and Baleen Whale Trophic Cascades in Greenland

    DTIC Science & Technology

    2008-01-01

    species in West Greenland. We use a multidisciplinary approach by combining observations of foraging ecology and phenology collected by satellite and...feeding in each site and the phenology of the use of the focal areas. These data are related to long-term physical and biological monitoring program...in Nuuk Fjord and on the coast of West Greenland, where long-term fishery data are collected to quantify seasonal and inter-annual variations in the

  15. Drug Development and Conservation of Biodiversity in West and Central Africa: Performance of Neurochemical and Radio Receptor Assays of Plant Extracts Drug Discovery for the Central Nervous System

    DTIC Science & Technology

    2004-09-01

    7) Hui, D.; Sao-Xing, C. J. Nat. Prod. 1998, 61, 142-144. (8) Aldrich Libray of 13C and 1H FT NMR spectra 1992, 2, 326A. (9) Kadota, S .; Hui, D...Biodiversity in West and Central Africa: Performance of Neurochemical and Radio Receptor Assays of Plant Extracts Drug Discovery for the Central... s ) and should not be construed as an official Department of the Army position, policy or decision unless so designated by other documentation

  16. Evaluation of Statistical Rainfall Disaggregation Methods Using Rain-Gauge Information for West-Central Florida

    SciTech Connect

    Murch, Renee Rokicki; Zhang, Jing; Ross, Mark; Ganguly, Auroop R; Nachabe, Mahmood

    2008-01-01

    Rainfall disaggregation in time can be useful for the simulation of hydrologic systems and the prediction of floods and flash floods. Disaggregation of rainfall to timescales less than 1 h can be especially useful for small urbanized watershed study, and for continuous hydrologic simulations and when Hortonian or saturation-excess runoff dominates. However, the majority of rain gauges in any region record rainfall in daily time steps or, very often, hourly records have extensive missing data. Also, the convective nature of the rainfall can result in significant differences in the measured rainfall at nearby gauges. This study evaluates several statistical approaches for rainfall disaggregation which may be applicable using data from West-Central Florida, specifically from 1 h observations to 15 min records, and proposes new methodologies that have the potential to outperform existing approaches. Four approaches are examined. The first approach is an existing direct scaling method that utilizes observed 15 min rainfall at secondary rain gauges, to disaggregate observed 1 h rainfall at more numerous primary rain gauges. The second approach is an extension of an existing method for continuous rainfall disaggregation through statistical distributional assumptions. The third approach relies on artificial neural networks for the disaggregation process without sorting and the fourth approach extends the neural network methods through statistical preprocessing via new sorting and desorting schemes. The applicability and performance of these methods were evaluated using information from a fairly dense rain gauge network in West-Central Florida. Of the four methods compared, the sorted neural networks and the direct scaling method predicted peak rainfall magnitudes significantly better than the remaining techniques. The study also suggests that desorting algorithms would also be useful to randomly replace the artificial hyetograph within a rainfall period.

  17. Metamorphism and fluid flow related to Mesozoic thrusting in west-central Arizona

    SciTech Connect

    Martinez, S.L.; Peacock, S.M.; Reynolds, S.J. . Dept. of Geology)

    1993-04-01

    Petrologic, fluid inclusion, and stable isotope investigations are being conducted on rocks from the Granite Wash mountains (GWM) and the Harquahala Mountains (HM), located in west-central Arizona, to constrain fluid flow paths and metamorphism during basement-involved thrusting. Regional south-vergent thrusting in west-central Arizona resulted in widespread greenschist-facies metamorphism. In the GWM, upper greenschist-facies metamorphic conditions are indicated by (1) the presence of kyanite and andalusite in aluminum-rich metavolcanic rocks, (2) the presence of calcic amphibole in metabasites, and (3) the absence of garnet in pelitic units. In the HM, higher P-T conditions are indicated by the assemblage kyanite + staurolite + garnet in metasedimentary lithologies. A complex fluid history is recorded by fluid inclusions from both ranges. Individual microfractures from quartz veins parallel to the thrust-related fabric contain either liquid-rich, vapor-rich, or three phase inclusions, representing several stages of fluid flow. A C-O-H fluid was present during thrusting based on the occurrence of three-phase inclusions in quartz veins, CO[sub 2]-bearing inclusions in kyanite crystals related to the thrusting event, and the formation of chlorite and calcite in upper plate granite of the Hercules thrust in the GWM. Homogenization temperatures of [approximately]270 C, which constrain minimum temperatures of the fluid, are common for the liquid-rich inclusions; vapor-rich and three-phase inclusions homogenize at higher temperatures. Preliminary stable isotope analyses suggest large volumes of isotopically light fluid may have flowed preferentially along thrust surfaces.

  18. Legume Diversity Patterns in West Central Africa: Influence of Species Biology on Distribution Models

    PubMed Central

    de la Estrella, Manuel; Mateo, Rubén G.; Wieringa, Jan J.; Mackinder, Barbara; Muñoz, Jesús

    2012-01-01

    Objectives Species Distribution Models (SDMs) are used to produce predictions of potential Leguminosae diversity in West Central Africa. Those predictions are evaluated subsequently using expert opinion. The established methodology of combining all SDMs is refined to assess species diversity within five defined vegetation types. Potential species diversity is thus predicted for each vegetation type respectively. The primary aim of the new methodology is to define, in more detail, areas of species richness for conservation planning. Methodology Using Maxent, SDMs based on a suite of 14 environmental predictors were generated for 185 West Central African Leguminosae species, each categorised according to one of five vegetation types: Afromontane, coastal, non-flooded forest, open formations, or riverine forest. The relative contribution of each environmental variable was compared between different vegetation types using a nonparametric Kruskal-Wallis analysis followed by a post-hoc Kruskal-Wallis Paired Comparison contrast. Legume species diversity patterns were explored initially using the typical method of stacking all SDMs. Subsequently, five different ensemble models were generated by partitioning SDMs according to vegetation category. Ecological modelers worked with legume specialists to improve data integrity and integrate expert opinion in the interpretation of individual species models and potential species richness predictions for different vegetation types. Results/Conclusions Of the 14 environmental predictors used, five showed no difference in their relative contribution to the different vegetation models. Of the nine discriminating variables, the majority were related to temperature variation. The set of variables that played a major role in the Afromontane species diversity model differed significantly from the sets of variables of greatest relative important in other vegetation categories. The traditional approach of stacking all SDMs indicated overall

  19. Flood of July 9-11, 1993, in the Raccoon River basin, west-central Iowa

    USGS Publications Warehouse

    Eash, D.A.; Koppensteiner, B.A.

    1997-01-01

    Water-surface-elevation profiles and peak discharges for the flood of July 9-11, 1993, in the Raccoon River Basin, west-central Iowa, are presented in this report. The profiles illustrate the 1993 flood along the Raccoon, North Raccoon, South Raccoon, and Middle Raccoon Rivers and along Brushy and Storm Creeks in the west-central Iowa counties of Carroll, Dallas, Greene, Guthrie, and Polk. Water-surface-elevation profiles for the floods of June 1947, March 1979, and June 29- July 1, 1986, in the Raccoon River Basin also are included in the report for comparative purposes. The July 9-11, 1993, flood is the largest known peak discharge at gaging stations Brushy Creek near Templeton (station number 05483318) 19,000 cubic feet per second, Middle Raccoon River near Bayard (station number 05483450) 27,500 cubic feet per second, Middle Raccoon River at Panora (station number 05483600) 22,400 cubic feet per second, South Raccoon River at Redfield (station number 05484000) 44,000 cubic feet per second, and Raccoon River at Van Meter (station number 05484500) 70,100 cubic feet per second. The peak discharges were, respectively, 1.5, 1.3, 1.1,1.2, and 1.3 times larger than calculated 100-year recurrence-interval discharges. The report provides information on flood stages and discharges and floodflow frequencies for streamflow-gaging stations in the Raccoon River Basin using flood information collected through 1996. A flood history summarizes rainfall conditions and damages for floods that occurred during 1947, 1958, 1979, 1986, 1990, and 1993. Information on temporary bench marks and reference points established in the Raccoon River Basin during 1976-79 and 1995-97 also is included in the report.

  20. Selenium status in Greenland Inuit.

    PubMed

    Hansen, Jens C; Deutch, Bente; Pedersen, Henning Sloth

    2004-09-20

    In Greenland, the human intake of selenium has always been relatively high and is closely connected to intake of the traditional food of marine origin. Analyses of historic and present day human and animal hair samples have indicated that the selenium level in the marine environment has been constant over time, while the levels in humans have declined corresponding to a decrease in intake of traditional food. The Inuit population in Greenland is in dietary transition where western-style food will increasingly dominate. As a consequence, the ample supply of selenium may not be sustained in the future. We report here the selenium status in three Greenlandic population groups, Ittoqqortoormiit and Tasiilaq on the east coast and Uummannaq on the west coast. Mean whole blood concentrations ranged from 178 microg/l in Tasiilaq men to 488 microg/l in Uummannaq men. Plasma concentrations ranged from 79 microg/l in Tasiilaq women to 113 microg/l in Uummannaq men. With increasing Se concentrations in whole blood, the plasma concentrations increased but tended to stabilise a level approximately 140 microg/l. Selenium blood levels were highly significantly correlated with long chain marine fatty acids. Dietary survey and food composition data from the west coast showed that whale skin, muktuk, is the main source of Se followed by birds, seal meat and organs, and fish. Terrestrial animals contributed only insignificantly to the selenium intake. In West Greenland, daily Se intake (235 microg/day) was estimated by dietary survey; it corresponded well with a calculated intake (220 microg/day) based on the mean blood concentration.

  1. Age and provenance of Triassic to Cenozoic sediments of West and Central Sarawak, Malaysia

    NASA Astrophysics Data System (ADS)

    Breitfeld, H. Tim; Galin, Thomson; Hall, Robert

    2015-04-01

    Sarawak is located on the northern edge of Sundaland in NW Borneo. West and Central Sarawak include parts of the Kuching and Sibu Zones. These contain remnants of several sedimentary basins with ages from Triassic to Cenozoic. New light mineral, heavy mineral and U-Pb detrital zircon ages show differences in provenance reflecting the tectonic evolution of the region. The oldest clastic sediments are Triassic (Sadong Formation and its deep marine equivalent Kuching Formation). They were sourced by a Triassic (Carnian to Norian) volcanic arc and reworked Paleoproterozoic detritus derived from Cathaysialand. The Upper Jurassic to Cretaceous Pedawan Formation is interpreted as forearc basin fill with distinctive zircon populations indicating subduction beneath present-day West Sarawak which initiated in the Late Jurassic. Subsequent subduction until the early Late Cretaceous formed the Schwaner Mountains magmatic arc. After collision of SW Borneo and other microcontinental fragments with Sundaland in the early Late Cretaceous, deep marine sedimentation (Pedawan Formation) ceased, and there was uplift forming the regional Pedawan-Kayan unconformity. Two episodes of extension followed and were responsible for basin development on land in West Sarawak from the latest Cretaceous onwards, probably in a pull-apart setting. The first episode is associated with sediments of the Kayan Group, deposited in the Latest Cretaceous (Maastrichtian) to Eocene, and the second episode with Upper Eocene sediments of the Ketungau Basin. Zircon ages indicate volcanic activity throughout the Early Cenozoic in NW Borneo, and inherited zircon ages indicate reworking of Triassic and Cretaceous rocks. A large deep marine basin, the Rajang Basin, was north of the Lupar Line Fault in Central Sarawak (Sibu Zone) from the Late Cretaceous to the Late Eocene. Zircons from sediments of the Rajang Basin indicate they have similar ages and provenance to contemporaneous terrestrial sediments of the Kayan

  2. Potentiometric surface of the Upper Floridan aquifer, west-central Florida, May 2005

    USGS Publications Warehouse

    Ortiz, A.G.; Blanchard, R.A.

    2006-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is a highly productive aquifer and supplies more than 10 times the amount of water pumped from either the surficial aquifer system or the intermediate aquifer system in most of the study area (Duerr and others, 1988). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2005. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in a tightly cased well that taps a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 67.27 inches for west-central Florida (from June 2004 through May 2005) was 14.20 inches above the historical cumulative average of 53.07 inches (Southwest Florida Water Management District (SWFWMD), 2005). The above average precipitation is attributed to the active hurrican season for Florida in 2004. Historical cumulative averages are calculated from regional rainfall summary reports (1915 to the most recent completed calendar year) and are updated monthly by the SWFWMD. This report, prepared by the U.S. Geological Survey (USGS) in cooperation with the SWFWMD, is part of a semiannual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to

  3. Intra- and Inter-Seasonal Supra-glacial Water Variability over the West Greenland Ice Sheet as Estimated from Combining High Resolution Satellite Optical Data and a Digital Elevation Model

    NASA Astrophysics Data System (ADS)

    Brown, M. G.; Tedesco, M.; Smith, L. C.; Rennermalm, A. K.; Yang, K.

    2015-12-01

    The supra-glacial hydrology of the Greenland Ice Sheet (GrIS) plays a crucial role on the surface energy and mass balance budgets of the ice sheet as a whole. The surface hydrology network variability of small streams in the ablation zone of Greenland is poorly understood both spatially and temporally. Using satellites that can spatially resolve the presence and associated properties of small streams, the scientific community is now able to be provided with accurate spatial and temporal analysis of surface hydrology on the ice sheet (that could not have been resolved with other sensors such as those on board MODIS or LANDSAT). In this study we report mapped supra-glacial water networks over a region of the West GrIS (approximately 164 km2) derived from high resolution multispectral satellite imagery from the Quickbird and WorldView - 2 satellites in tandem with a 2 meter stereographic SETSM DEM (digital elevation model). The branching complexity of the identified surface streams is computed from the available DEM as well as the intra- and inter seasonal changes observed in the hydrological system. The stream networks created during the melt season (at several different stages of melting) are compared and discussed as well as the networks mapped between consecutive years for proximate dates. Also, depth and volume estimations for the surface water features identified were extracted via band math algorithms, threshold classifications, and morphological operations. Our results indicate that the higher stream orders have the largest amount of stored surface water per km but the lower stream orders, specifically 1st order with widths of ~ 2 meters, hold more stored surface water overall. We also employ and compare runoff data from the numerical model MAR (Modèle Atmosphérique Régional) to the estimations found using imagery and the DEM.

  4. Integration of Remotely-Sensed Geobotanical and Structural Methods for Hydrocarbon Exploration in West-Central West Virginia

    SciTech Connect

    1997-01-26

    This report covers the first of the two years covered in the DOE grant to investigate structural and geobotanical features of hydrocarbon reservoirs in western West Virginia. The reader is referred to the three previous Quarterly reports for greater detail on tasks originally described in those reports. The progress of the project will be discussed with reference to the tasks identified for the project.

  5. Hydrogeologic framework of Antelope Valley and Bedell Flat, Washoe County, west-central Nevada

    USGS Publications Warehouse

    Berger, D.L.; Ponce, D.A.; Ross, W.C.

    2001-01-01

    Description of the hydrogeologic framework of Antelope Valley and Bedell Flat in west-central Nevada adds to the general knowledge of regional ground-water flow north of the Reno-Sparks metropolitan area. The hydrogeologic framework is defined by the rocks and deposits that transmit ground water or impede its movement and by the combined thickness of Cenozoic deposits. When data are lacking about the subsurface geology of an area, geophysical methods can be used to provide additional information. In this study, gravimetric and seismic-refraction methods were used to infer the form of structural features and to estimate the thickness of Cenozoic deposits in each of the two valleys. In Antelope Valley, the thickness of these deposits probably does not exceed about 300 feet, suggesting that ground-water storage in the basin-fill aquifer is limited. Beneath Bedell Flat is an elongated, northeast-trending structural depression in the pre-Cenozoic basement; the maximum thickness of Cenozoic deposits is about 2,500 feet beneath the south-central part of the valley. Shallow ground water in the northwest corner of Bedell Flat may be a result of decreasing depth to the pre-Cenozoic basement.

  6. Raccoon (Procyon lotor) diurnal den use within an intensively managed forest in central West Virginia

    USGS Publications Warehouse

    Owen, Sheldon F.; Berl, Jacob L.; Edwards, John W.; Ford, W. Mark; Wood, Petra Bohall

    2015-01-01

    Intensive forest management may influence the availability of suitable den sites for large den-seeking species, such as Procyon lotor (Raccoon). As part of a Raccoon ecology study on an industrial forest in the Allegheny Mountains of central West Virginia, we radio-tracked 32 Raccoons to 175 diurnal den sites to determine relative use of dens that included cavity trees, rock dens, log piles, slash piles, and exposed limbs. Patterns of den use significantly differed between sexes and among seasons. Overall, we recorded 58 cavity dens in 12 tree species with 7 maternal dens found in 5 tree species. Raccoons selected larger-diameter den trees than available cavity trees and non-cavity trees. Because the abundance of suitable tree cavities is known to influence Raccoon densities and recruitment at fine spatial scales and female Raccoons in this study used tree cavities as maternal den sites, the continued harvest of large-diameter trees (i.e., those capable of developing den cavities) without replacement may impact Raccoon recruitment within intensively managed forests throughout the central Appalachians.

  7. Lower and middle Guadalupian shelf carbonates, eastern margin of Central Basin platform, Permian basin, west Texas

    SciTech Connect

    Ward, R.F.; Chalcraft, R.G.

    1988-01-01

    Lower and middle Guadalupian shelf carbonates serve as the reservoir for a nearly continuous band of oil fields extending 100 mi along the eastern margin of the Central Basin platform of west Texas. Approximately 5 billion bbl of oil have been produced from stratigraphic-structural traps within the Upper Permian (Gaudalupian Series) dolomites of the San Andrea and Grayburg Formations in Upton, Crane, Ector, Pecos, and Andrews Counties, Texas. The San Andrea and Grayburg Formations are cyclical shallowing-upward carbonate sequences of open shelf through sabkha facies whose depositional strike parallels the eastern margin of the Central Basin platform. Porosity and permeability of reservoir rock are governed by diagenetic processes such as dolomitization, anhydrite porosity occlusion, leaching, silicification, and authigenic clay formation. Self sediments are primarily burrowed wackestones and packstones that locally contain pelletal, skeletal, and ooid grainstones. Typical subtidal shelf sediments are capped by algal-laminated dolomite, nodular anhydritic dolomite, and bedded anhydrite. The fauna is normally sparse and dominated by foraminifera and algae. Less common faunal components include pelecypods, crinoids, sponges, Bryozoa, brachiopods, gastropods, and coral that are associated with the development of small scattered patch reefs. Lowering the sea level during the early Guadalpian initiated basinward progradation of San Andres carbonate facies with hydrocarbon reservoirs best developed in shallow self fusulinid wackestones to packstone and oolitic grainstone. Reservoir dolomites of the Grayburg formation are present east of San Andres fields with optimal reservoir properties occurring near the San Andreas outer shelf margin.

  8. Environmental characteristics and water quality of hydrologic benchmark network stations in the west-central United States, 1963-95

    USGS Publications Warehouse

    Clark, Melanie L.; Eddy-Miller, C. A.; Mast, M. Alisa

    2000-01-01

    This report describes the environmental characteristics and water-quality characteristics of 14 benchmark basins in the west-central United States. The information was compiled to aide in the interpretation and application of historical water-quality data collected through the Hydrologic Benchmark Network Program.

  9. REGIONAL EMISSIONS OF NITRIC OXIDE (NO) AND CARBON DIOXIDE (CO2) IN AGROECOSYSTEMS IN CENTRAL WEST REGION, BRAZIL.

    EPA Science Inventory

    The Central West Region in Brazil has been the focus of intense agricultural expansion since the 1970s and, nowadays, a large area of native cerrado has been converted to agricultural use. The expansion was accompanied by intensive use of fertilizer, irrigation and management pra...

  10. Seawater-like trace element signatures (REE + Y) of Eoarchaean chemical sedimentary rocks from southern West Greenland, and their corruption during high-grade metamorphism

    NASA Astrophysics Data System (ADS)

    Friend, C. R. L.; Nutman, A. P.; Bennett, V. C.; Norman, M. D.

    2008-02-01

    Modern chemical sediments display a distinctive rare earth element + yttrium (REE + Y) pattern involving depleted LREE, positive La/La*SN, Eu/Eu*SN, and YSN anomalies (SN = shale normalised) that is related to precipitation from circumneutral to high pH waters with solution complexation of the REEs dominated by carbonate ions. This is often interpreted as reflecting precipitation from surface waters (usually marine). The oldest broadly accepted chemical sediments are c. 3,700 Ma amphibolite facies banded iron-formation (BIF) units in the Isua supracrustal belt, Greenland. Isua BIFs, including the BIF international reference material IF-G are generally considered to be seawater precipitates, and display these REE + Y patterns (Bolhar et al. in Earth Planet Sci Lett 222:43 60, 2004). Greenland Eoarchaean BIF metamorphosed up to granulite facies from several localities in the vicinity of Akilia (island), display REE + Y patterns identical to Isua BIF, consistent with an origin by chemical sedimentation from seawater and a paucity of clastic input. Furthermore, the much-debated magnetite-bearing siliceous unit of “earliest life” rocks (sample G91/26) from Akilia has the same REE + Y pattern. This suggests that sample G91/26 is also a chemical sediment, contrary to previous assertions (Bolhar et al. in Earth Planet Sci Lett 222:43 60, 2004), and including suggestions that the Akilia unit containing G91/26 consists entirely of silica-penetrated, metasomatised, mafic rock (Fedo and Whitehouse 2002a). Integration of our trace element data with those of Bolhar et al. (Earth Planet Sci Lett 222:43 60, 2004) demonstrates that Eoarchaean siliceous rocks in Greenland, with ages from 3.6 to 3.85 Ga, have diverse trace element signatures. There are now geographically-dispersed, widespread examples with Isua BIF-like REE + Y signatures, that are interpreted as chemically unaltered, albeit metamorphosed, chemical sediments. Other samples retain remnants of LREE depletion but

  11. Depositional environments and sedimentary tectonics of subsurface Cotton Valley group (upper Jurassic), west-central Mississippi

    SciTech Connect

    Sydboten, B.D. Jr.; Bowen, R.L.

    1987-09-01

    Study of data from 65 selected wells in a 6-county area (about 60 by 60 mi) north and west of Jackson, Mississippi, discloses that Cotton Valley strata, now within the axial trough of the Mississippi embayment, display thickness variations which demonstrate that Late Jurassic sedimentation was strongly controlled by maximum subsidence along the same trough axis. Examination of well logs, other records, and cutting sets from 38 wells has resulted in preparation of dip and strike cross sections that permit information definition of lower, middle, and upper parts of the Cotton Valley Group throughout the area evaluated. Within these lithostratigraphic diversions, lithofacies are discriminable that represent alluvial, upper delta plain, lower delta plain, and prodeltaic environments. These facies display a general variation from coarse, commonly red, oxidized sediments on the north and east, to mudrocks, locally calcareous and carbonaceous, on the southwest. Within the Cotton Valley Group examined, two persistent clastic lobes demonstrate relative environmental stability while deposits ranging in thickness from 1500 ft (northwestern corner of study area) to 4500 ft (axial depocenter on the south) accumulated. During Cotton Valley deposition, west-central Mississippi was the site of a two-toed birdfoot delta within which lignites were deposited. Major sediment supply was from the east and north; a minor source was to the northwest (Ouachita-Ozarks). Irregulatories in both rates of supply of clastics and of shelf subsidence permitted intermittent shallow, clear-water, marine incursions from the south during which thin carbonate beds were deposited, interfingering with the clastics. Thus, potential source and host rocks for hydrocarbon traps are closely associated, for thick, organic-rich, interlobate mudrocks pass laterally and vertically into fluvial sands of the delta lobes.

  12. Apatite Fission Track Constraints On The Denudational History Of The Bielsa And Millares Plutons, West-Central Pyrenees, Spain

    NASA Astrophysics Data System (ADS)

    Schwabe, E.; Fitzgerald, P. G.; Munoz, J. A.; Baldwin, S. L.

    2006-12-01

    The Pyreneean orogen extends for ~ 440 km from the Bay of Biscay to the Mediterranean Sea, forming a WNW-ESE topographic barrier between France and Spain. The mountain belt, formed by the Late Cretaceous-Early Miocene oblique collision and partial subduction of the Iberian Plate beneath the European Plate. Restored and balanced cross sections show a decrease in crustal shortening from ~165 km in the central Pyrenees to ~ 50 km in the Cantabrian margin, further to the west. The variation in shortening and crustal style is due to the decrease westward in convergence and differences in inherited geometry of pre- existing extensional faults. We propose the variation must also be reflected in the denudation record, with relative timing of the main denudational events younging to the west, as well as the magnitude and rates of denudation decreasing westward. In this study we analyze AFT data collected from vertical profiles on the southern flank of the mountains in the west-central Pyrenees. The results constrain the relative timing of structures between the central and west-central Pyrenees. AFTT data from the Bielsa and Millares massifs, located in the Bielsa and Millares thrust sheets on the southern flank of the axial zone, west-central Pyrenees yield AFT ages from 30 to 20 Ma. The data, including constraints from inverse thermal modeling, indicate denudation at rates ca. 300 m/my underway in the middle Oligocene, slowing in the Miocene. Denudation is likely related to erosion following thrusting during which the granites were transported within the south-vergent Bielsa and Millares thrust sheets. The Late Oligocene-Early Miocene AFT PAZ has since been exhumed to its present elevation. In form, results are similar to those from the central Pyrenees (Fitzgerald et al., 1999) but that Oligocene denudation in the west-central Pyrenees occurred later, was slower, and of reduced magnitude when compared to extremely rapid Oligocene denudation recorded ~50 km east in the

  13. Potential for water-quality degradation of interconnected aquifers in west-central Florida

    USGS Publications Warehouse

    Metz, P.A.; Brendle, D.L.

    1996-01-01

    Thousands of deep artesian wells were drilled into the Upper Floridan aquifer in west-central Florida prior to well-drilling regulations adopted in the 1970's. The wells were usually completed with a short length of casing through the unconsolidated sediments and were left open to multiple aquifers containing water of varying quality. These open boreholes serve as a potential source of water-quality degradation within the aquifers when vertical internal borehole flow is induced by hydraulic-head differences. Thispotential for water-quality degradation exists in west-central Florida where both the intermediate aquifer system and Upper Floridan aquifer exist. Measurements of caliper, temperature, gamma, fluid conductivity, and flow were obtained in 87 wells throughout west-central Florida to determine the occurrence of interaquifer borehole flow between the intermediate aquifer system and the Upper Floridan aquifer. Flow measurements were made using an impeller flowmeter, a heat-pulse flowmeter, and a video camera with an impeller flowmeter attachment. Of the 87 wells measured with the impeller flowmeter, 17 had internal flow which ranged from 10 to 300 gallons per minute. A heat-pulse flowmeter was used in 19 wells in which flow was not detected using the impeller flowmeter. Of these 19 wells, 18 had internal flow which ranged from 0.3 to 10gallons per minute. Additionally, water-quality samples were collected from specific contributing zones in wells that had internal flow. Analysis of geophysical and water-quality data indicates degradation of water quality has occurred from mineralized ground water flowing upward from the Upper Floridan aquifer into the intermediate aquifer system through both uncased boreholes and corroded black-iron well casings. In areas where there is a downward component of flow, data indicate that potable water from the intermediate aquifer system is artificially recharging the Upper Floridan aquifer through open boreholes. A geographical

  14. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, May 2009

    USGS Publications Warehouse

    Ortiz, Anita G.

    2009-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2009. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 48.53 inches for west-central Florida (from June 2008 through May 2009) was 4.12 inches below the historical cumulative average of 52.65 inches (Southwest Florida Water Management District, 2009). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the

  15. Early Pleistocene Glacial Lake Lesley, West Branch Susquehanna River valley, central Pennsylvania

    NASA Astrophysics Data System (ADS)

    Ramage, Joan M.; Gardner, Thomas W.; Sasowsky, Ira D.

    1998-02-01

    Laurentide glaciers extended into north central Pennsylvania repeatedly during at least the last 2 million years. Early Pleistocene glaciation extended farther south into central Pennsylvania than any subsequent glaciation, reaching the West Branch Susquehanna River (WBSR) valley. Early Pleistocene ice dammed the northeast-flowing West Branch Susquehanna River at Williamsport, forming Glacial Lake Lesley, a 100-km-long proglacial lake. In this paper, we present compelling evidence for the lake and its age. Maximum lake volume (˜ 100 km 3) was controlled by the elevation of the lowest drainage divide, ˜ 340 m above sea level at Dix, Pennsylvania. Stratified deposits at McElhattan and Linden are used to reconstruct depositional environments in Glacial Lake Lesley. A sedimentary section 40 m thick at McElhattan fines upward from crossbedded sand to fine, wavy to horizontally laminated clay, consistent with lake deepening and increasing distance from the sediment source with time. At Linden, isolated cobbles, interpreted as dropstones, locally deform glacio-lacustrine sediment. We use paleomagnetism as an age correlation tool in the WBSR valley to correlate contemporaneous glaciofluvial and proglacial lacustrine sediments. Reversed remanent polarity in finely-laminated lacustrine clay and silt at McElhattan ( I = 20.4°, D = 146.7°, α95 = 17.7°) and in interbedded silt and sand at Linden ( I = 55.3°, D = 175.2°, α95 = 74.6°) probably corresponds to the latter part of the Matuyama Reversed Polarity Chron, indicating an age between ˜ 770 and ˜ 970 ka. At McElhattan, a diamicton deformed the finely laminated silt and clay by loading and partial fluidization during or soon after lake drainage. As a result, the deformed clay at McElhattan lacks discrete bedding and records a different characteristic remanent magnetism from underlying, undeformed beds. This difference indicates that the characteristic remanent magnetism is detrital. An electrical resistivity

  16. Geochemical differences between along-arc and across-arc volcanics in west-central Nicaragua

    NASA Astrophysics Data System (ADS)

    Geilert, Sonja; Freundt, Armin; Wörner, Gerhard; Kutterolf, Steffen

    2012-04-01

    The La Paz Centro - Malpaisillo Lineament (LPML) in west-central Nicaragua is a north-south striking, 20 km long chain of maars and cinder cones, which intersects the northwest-southeast striking main volcanic front. A tectonic control of LPML volcanism is likely but only evident for the Malpaisillo fissure at the northern end of the LPML. Previous work demonstrated geochemical variations implying changes in mantle-source composition (i.e., added slab components) along the Central American Volcanic Arc at spatial scales of some 10's of kilometers. Our study of the LPML shows that minor but systematic changes also occur across the arc within 20 km distance. Variations in trace element ratios such as Zr/Nb, Ba/Th, Ba/La, Th/Zr, U/La and La/Yb along the LPML, i.e. across the volcanic front indicate little change in the degree of partial melting but an increase particularly in the hemipelagic sediment component in the mantle source from the fore arc towards the arc front, followed by a decrease behind the arc. Interestingly, the slab component is most prominent just in front of the arc. About 60 km southeast of the LPML, the Nejapa-Miraflores volcanic and tectonic lineament, which marks a 20 km north-south offset in the arc, differs substantially from the LPML. There is a wide scatter in incompatible trace element ratios indicating a heterogeneous mantle source at small spatial scales (c. 1 km). This mantle heterogeneity may represent vertical rather than across-arc variations and is probably related to the arc offset, because in the absence of such offset at the LPML mantle source conditions vary much less but more systematically.

  17. Complex climate controls on 20th century oak growth in Central-West Germany.

    PubMed

    Friedrichs, Dagmar A; Büntgen, Ulf; Frank, David C; Esper, Jan; Neuwirth, Burkhard; Löffler, Jörg

    2009-01-01

    We analyze interannual to multi-decadal growth variations of 555 oak trees from Central-West Germany. A network of 13 pedunculate oak (Quercus robur L.) and 33 sessile oak (Quercus petraea (Matt.) Liebl.) site chronologies is compared with gridded temperature, precipitation, cloud-cover, vapor pressure and drought (i.e., Palmer Drought Severity Index, PDSI) fluctuations. A hierarchic cluster analysis identifies three groups for each oak species differentiated by ecologic settings. When high precipitation is primarily a characteristic for one Q. robur and one Q. petraea cluster, the other clusters are more differentiated by prevailing temperature conditions. Correlation analysis with precipitation and vapor pressure reveals statistically significant (P < or = 0.05) correlations for June (r = 0.51) and annual (r = 0.43) means. Growth of both species at dry sites correlates strongly with PDSI (r = 0.39, P < or = 0.05), and weakly with temperature and cloud-cover. In natural stands, Q. robur responds more strongly to water depletion than Q. petraea. Twenty-one-year moving correlations show positive significant growth response to both PDSI and precipitation throughout the 20th century, except for the 1940s - an anomalously warm decade during which all oak sites are characterized by an increased growth and an enhanced association with vapor pressure and temperature. We suggest that the wider oak rings that are exhibited during this period may be indicative of a nonlinear or threshold-induced growth response to drought and vapor pressure, and run counter to the general response of oak to drought and precipitation that normally would result in suppressed growth in a warmer and drier environment. As the wide rings are formed during the severe drought period of the 20th century, a complex model seems to be required to fully explain the widespread oak growth. Our results indicate uncertainty in estimates of future growth trends of Central European oak forests in a warming and

  18. Paleoenvironment of the Ogallala (Neogene) Formation in west-central Kansas

    SciTech Connect

    Twiss, P.C.; McCahon, T.J.; Oviatt, C.G. . Geology Dept.)

    1993-02-01

    At Lake Scott (Scott County) in west-central Kansas, the Ogallala Formation unconformably overlies the Niobrara Formation (Cretaceous) and forms the bluffs of the north-trending Ladder Creek valley. Two sections (Devil's Backbone, 23 m thick; Suicide Bluff, 45 m thick) contain fluvial sands that grade upward into probable eolian sands. The lower sections contain poorly cemented, moderately sorted, arkosic sand, some mud gravel, and poorly defined fluvial channels. In the lower part of Devil's Backbone, cross-bedded sand is capped by mud drapes. At Suicide Bluff, beds of cross-bedded and better sorted sand occur high in the section. Paleosols and secondary calcite and opal dominate the sections. Pedogenic calcretes with more than 52% CaCO[sub 3] are especially abundant and range up to morphologic Stage VI. The [delta][sup 13]C and [delta][sup 18]O in the calcretes range from [minus]4.8 to [minus]6.5 and [minus]8.2 to [minus]6.7 per mil (PDB), respectively. Opal-A has replaced most rhizoliths of the Ogallala. Silicified fossil seeds (Celtis sp., Biorbia sp.) and probable fossil mammal burrows also occur in the sections. Rhyolitic tephra, about 10 Ma, occurs 12 m below the calcrete caprock of Suicide Bluff. A massive layer of opal occurs about 8 m above the tephra and below a diatomaceous bed. Siliceous cement occurs throughout each section, possibly originating from opal phytoliths, tephra, and/or diatoms. These sections afford the potential for understanding the stratigraphic succession and paleoclimate during the late Miocene to possibly early Pliocene in the central High Plains region.

  19. Hydrogeologic framework, groundwater movement, and water budget of the Kitsap Peninsula, west-central Washington

    USGS Publications Warehouse

    Welch, Wendy B.; Frans, Lonna M.; Olsen, Theresa D.

    2014-01-01

    This report presents information used to characterize the groundwater-flow system on the Kitsap Peninsula, and includes descriptions of the geology and hydrogeologic framework, groundwater recharge and discharge, groundwater levels and flow directions, seasonal groundwater-level fluctuations, interactions between aquifers and the surface‑water system, and a water budget. The Kitsap Peninsula is in the Puget Sound lowland of west-central Washington, is bounded by Puget Sound on the east and by Hood Canal on the west, and covers an area of about 575 square miles. The peninsula encompasses all of Kitsap County, the part of Mason County north of Hood Canal, and part of Pierce County west of Puget Sound. The peninsula is surrounded by saltwater and the hydrologic setting is similar to that of an island. The study area is underlain by a thick sequence of unconsolidated glacial and interglacial deposits that overlie sedimentary and volcanic bedrock units that crop out in the central part of the study area. Geologic units were grouped into 12 hydrogeologic units consisting of aquifers, confining units, and an underlying bedrock unit. A surficial hydrogeologic unit map was developed and used with well information from 2,116 drillers’ logs to construct 6 hydrogeologic sections and unit extent and thickness maps. Unconsolidated aquifers typically consist of moderately to well-sorted alluvial and glacial outwash deposits of sand, gravel, and cobbles, with minor lenses of silt and clay. These units often are discontinuous or isolated bodies and are of highly variable thickness. Unconfined conditions occur in areas where aquifer units are at land surface; however, much of the study area is mantled by glacial till, and confined aquifer conditions are common. Groundwater in the unconsolidated aquifers generally flows radially off the peninsula in the direction of Puget Sound and Hood Canal. These generalized flow patterns likely are complicated by the presence of low

  20. Numerical simulation of the groundwater-flow system of the Kitsap Peninsula, west-central Washington

    USGS Publications Warehouse

    Frans, Lonna M.; Olsen, Theresa D.

    2016-05-05

    A groundwater-flow model was developed to improve understanding of water resources on the Kitsap Peninsula. The Kitsap Peninsula is in the Puget Sound lowland of west-central Washington, is bounded by Puget Sound on the east and by Hood Canal on the west, and covers an area of about 575 square miles. The peninsula encompasses all of Kitsap County, Mason County north of Hood Canal, and part of Pierce County west of Puget Sound. The peninsula is surrounded by saltwater, and the hydrologic setting is similar to that of an island. The study area is underlain by a thick sequence of unconsolidated glacial and interglacial deposits that overlie sedimentary and volcanic bedrock units that crop out in the central part of the study area. Twelve hydrogeologic units consisting of aquifers, confining units, and an underlying bedrock unit form the basis of the groundwater-flow model.Groundwater flow on the Kitsap Peninsula was simulated using the groundwater-flow model, MODFLOW‑NWT. The finite difference model grid comprises 536 rows, 362 columns, and 14 layers. Each model cell has a horizontal dimension of 500 by 500 feet, and the model contains a total of 1,227,772 active cells. Groundwater flow was simulated for transient conditions. Transient conditions were simulated for January 1985–December 2012 using annual stress periods for 1985–2004 and monthly stress periods for 2005–2012. During model calibration, variables were adjusted within probable ranges to minimize differences between measured and simulated groundwater levels and stream baseflows. As calibrated to transient conditions, the model has a standard deviation for heads and flows of 47.04 feet and 2.46 cubic feet per second, respectively.Simulated inflow to the model area for the 2005–2012 period from precipitation and secondary recharge was 585,323 acre-feet per year (acre-ft/yr) (93 percent of total simulated inflow ignoring changes in storage), and simulated inflow from stream and lake leakage was 43

  1. Ground-water levels in selected well fields and in west-central Florida, May 1981

    USGS Publications Warehouse

    Yobbi, D.K.; Woodham, W.M.

    1981-01-01

    The water table in the surficial aquifer and the potentiometric surface of the Floridan aquifer in a 1,200-square-mile area in west-central Florida are mapped semi-annually by the U.S. Geological Survey. Maps are based on water levels measured in wells each May to coincide with seasonal low levels and each September to coincide with seasonal high levels. The mapped area shows 14 well fields that supplied 200.7 million gallons to municipalities on May 18, 1981. The water is withdrawn from the Floridan aquifer, the major aquifer in Florida. The effect of localized withdrawal on ground water is shown on the maps as depressions in both the potentiometric and water-table surfaces. Water levels were lower in May 1981 than in May and September 1980. Annual change of water levels ranged from decreases of 19 feet at Sun City well field to less than 1 foot at Eldridge-Wilde well field. (USGS)

  2. Ground-water levels in selected well fields and in west-central Florida, May 1980

    USGS Publications Warehouse

    Yobbi, D.K.; Mills, L.R.; Woodham, W.M.

    1980-01-01

    The water table in the surficial aquifer and the potentiometric surface of the Floridan aquifer in a 1,200-square-mile area in west-central Florida are mapped semiannually by the U.S. Geological Survey. Maps are prepared showing water levels measured in wells each May to coincide with seasonal low levels and each September to coincide with seasonal high levels. The mapped area shows 14 well-field areas that supplied 155 million gallons to municipalities on May 12, 1980. The water is withdrawn from the Floridan aquifer, the major aquifer in Florida. The effect of localized withdrawal of ground water is shown on the maps as depressions in both the potentiometric and water-table surfaces. Water levels were lower in May 1980 than in September 1979 and a little higher than the average May levels. Change of water levels ranged from a decrease of 12 feet at Verna well field to an increase of 7 feet at Eldridge-Wilde well field. (USGS)

  3. Ground-water levels in selected well fields and in west-central Florida, September 1980

    USGS Publications Warehouse

    Yobbi, D.K.; Mills, L.R.; Woodham, W.M.

    1980-01-01

    The water table in the surficial aquifer and the potentiometric surface of the Floridan aquifer in a 1,200-square-mile area in west-central Florida are mapped semiannually by the U.S. Geological Survey. Maps are based on water levels measured in wells each May to coincide with seasonal low levels and each September to coincide with seasonal high levels. The mapped area shows 14 well fields that supplied 141.8 million gallons to municipalities on September 18, 1980. The water is withdrawn from the Floridan aquifer, the major aquifer in Florida. The effect of localized withdrawal of ground water is shown on the maps as depressions in both the potentiometric and water-table surfaces. Potentiometric levels in the Floridan aquifer were higher in September 1980 than in May 1980 and generally lower than in September 1979. Annual change of water levels ranged from a decrease of 6 feet at Morris Bridge well field to an increase of 2 feet at Eldridge-Wilde well field. (USGS)

  4. Evapotranspiration from areas of native vegetation in west-central Florida

    USGS Publications Warehouse

    Bidlake, W.R.; Woodham, W.M.; Lopez, M.A.

    1993-01-01

    A study was made to examine the suitability of three different micrometeorological methods for estimating evapotranspiration from selected areas of native vegetation in west-central Florida and to estimate annual evapotranspiration from those areas. Evapotranspiration was estimated using the energy- balance Bowen ratio and eddy correlation methods. Potential evapotranspiration was computed using the Penman equation. The energy-balance Bowen ratio method was used to estimate diurnal evapotrans- piration at unforested sites and yielded reasonable results; however, measurements indicated that the magnitudes of air temperature and vapor-pressure gradients above the forested sites were too small to obtain reliable evapotranspiration measurements with the energy balance Bowen ratio system. Analysis of the surface energy-balance indicated that sensible and latent heat fluxes computed using standard eddy correlation computation methods did not adequately account for available energy. Eddy correlation data were combined with the equation for the surface energy balance to yield two additional estimates of evapotranspiration. Daily potential evapotranspiration and evapotranspira- tion estimated using the energy-balance Bowen ratio method were not correlated at a unforested, dry prairie site, but they were correlated at a marsh site. Estimates of annual evapotranspiration for sites within the four vegetation types, which were based on energy-balance Bowen ratio and eddy correlation measurements, were 1,010 millimeters for dry prairie sites, 990 millimeters for marsh sites, 1,060 millimeters for pine flatwood sites, and 970 millimeters for a cypress swamp site.

  5. Soilscape of west-central Taiwan: Its pedogenesis and geomorphic implications

    NASA Astrophysics Data System (ADS)

    Tsai, Heng; Hseu, Zeng-Yei; Kuo, Hung-Yu; Huang, Wen-Shu; Chen, Zueng-Sang

    2016-02-01

    Five different soil types, including Entisol, Inceptisol, Alfisol, Ultisol and Oxisol, are distributed across west-central Taiwan. These soils cover the surfaces of three geological terrains, namely, the Pleistocene anticline, the Holocene coastal plain, and the modern alluvial fan. These soils developed from the similar parent materials, facilitating the analysis of soil diversity and the processes of pedogenesis. The soil chronosequence of Entisol → Inceptisol (Endoaquept) → reddish Inceptisol (Dystrudept) → Ultisol → Oxisol with increasing age is suggested for the progressive pathway of soil development. The degree of pedogenesis was quantified using a weighted profile development index (WPDI), which indicates that the soils from the tropics develop faster than those in temperate and/or Mediterranean climates, but was not as fast as those documented in the published literature. Moreover, the distribution of soils during pedogenesis conformed to the order of landform formation. Soil genesis and the way in which the different soils evolve illustrate the paleo-environments of the fluvial system in the area.

  6. Reservoir geology and paleoenvironmental reconstruction of Yates Formation, Central Basin Platform, West Texas

    SciTech Connect

    Casavant, R.R.

    1988-01-01

    Computer slice maps and proprietary three-dimensional interactive graphics were used to reconstruct the paleodeposition and to map reservoir variations within the Yates Formation of west Texas. The prolific Yates Formation is a major reservoir in the North Ward Estes field, Ward County, Texas. The Upper Permian (Guadalupian) Yates Formation is an overall regressive shallowing-upward package containing variable sequences of subtidal, intertidal, and supratidal strata. Sediment types include various siliciclastics mixed with sabkha-type carbonates and evaporites. The types of rocks and their structures indicate that these sediments were deposited in a prograding tidal flat-lagoonal setting located behind a shelf margin edge on the western flank of the positive Central Basin platform during the Guadalupian. The cyclic nature of the Yates is largely the result of lagoonal expansion and construction that caused environmental belts on both sides of the lagoon to converge and diverge. These rapid migrations of facies coupled with diagenetic processes created the heterogeneities that characterize this large reservoir.

  7. Concentrations of Heavy Metals in Commercially Important Oysters from Goa, Central-West Coast of India.

    PubMed

    Shenai-Tirodkar, Prachi S; Gauns, Mangesh U; Ansari, Zakir A

    2016-12-01

    The major beds of oyster along the central-west coast of India are exposed to different anthropogenic activities and are severely exploited for human consumption. In this viewpoint, tissues of oyster Crassostrea madrasensis, C. gryphoides and Saccostrea cucullata were analyzed for Cu, Ni, Cd and Pb concentrations (dry weight) from Chicalim Bay, Nerul Creek and Chapora Bay in pre-monsoon, monsoon and post-monsoon seasons. A higher concentration of Cu (134.4-2167.9 mg kg(-1)) and Cd (7.1-88.5 mg kg(-1)) was found, which is greater than the recommended limits in all the three species (and sites). Moreover, significant (p < 0.05) variations were observed for all the metals concentrations among the species, seasons and sites. The high concentrations of Cd and Cu in tissues of edible oyster pose a threat to human health. Therefore, continuous monitoring, people awareness and a stringent government policy should be implemented to mitigate the metal pollution along the studied sites.

  8. Traits associated with winter wheat grain yield in Central and West Asia.

    PubMed

    Lopes, Marta Silva; Saglam, Didem; Ozdogan, Mutlu; Reynolds, Matthew

    2014-07-01

    Improved adaptation of winter wheat (Triticum aestivum L.) to drought and heat may be influenced by days to heading, plant height, biomass, canopy temperature (CT) at grain filling, and rate of senescence. This study shows that, under supplemental irrigation or rainfed conditions, days to heading and plant height together explain up to 68% of grain yield (GY) variation, and these associations were further confirmed in several locations across West and Central Asia. Days to heading can be slightly reduced below that of check line Karahan to further improve GY while avoiding the effect of late frosts. Plant height has been decreased in recent germplasm, but further reductions below that of check line Karahan could still improve GY in a wide range of environments. However, in Iranian sites, taller genotypes showed better adaptation with higher biomass and increased reserves for grain filling. Canopy temperature and rate senescence were not associated with GY. A normalized difference vegetation index, used to estimate biomass (Feekes stages 4-5), had intermediate heritability across environments and correlated positively with GY under low plant density and should be explored further as a tool for early selection.

  9. Reproductive biology of yellowfin tuna T. albacares in the west-central Indian Ocean

    NASA Astrophysics Data System (ADS)

    Zhu, Guoping; Xu, Liuxiong; Zhou, Yingqi; Song, Liming

    2008-08-01

    Survey of yellowfin tuna in the west-central Indian Ocean was conducted on board of Chinese longliners during 2003, 2004 and 2005, which is a part of Chinese Tuna Fishery Scientific Observer Program (CTFSOP). The reproductive biology has been investigated. A total of 1 023 samples are collected including 417 ovaries and 606 testes. Spawning activities of yellowfin tuna have been studied for both male and female from January to June. The data showed that the average monthly sex ratio is 0.59, and the minimum length at sexual maturity is 101 cm for female and 110 cm for male respectively. Length at 50% sexual maturity is estimated at 113.77 cm for female and 120.20 cm for male, whereas maturation rate is 0.066 cm-1 for female and 0.091 cm-1 for male. Sex ratio by length class indicates that the proportion of male is higher than female’s along with size increasing; for instance, in the group of the body length longer than 145 cm, some females have their body length from 145 to 160 cm and males have their body length at 160 cm and even longer. Statistically, yellowfin tuna has a significant seasonal reproduction.

  10. New evidence for hybrid zones of forest and savanna elephants in Central and West Africa.

    PubMed

    Mondol, Samrat; Moltke, Ida; Hart, John; Keigwin, Michael; Brown, Lisa; Stephens, Matthew; Wasser, Samuel K

    2015-12-01

    The African elephant consists of forest and savanna subspecies. Both subspecies are highly endangered due to severe poaching and habitat loss, and knowledge of their population structure is vital to their conservation. Previous studies have demonstrated marked genetic and morphological differences between forest and savanna elephants, and despite extensive sampling, genetic evidence of hybridization between them has been restricted largely to a few hybrids in the Garamba region of northeastern Democratic Republic of Congo (DRC). Here, we present new genetic data on hybridization from previously unsampled areas of Africa. Novel statistical methods applied to these data identify 46 hybrid samples--many more than have been previously identified--only two of which are from the Garamba region. The remaining 44 are from three other geographically distinct locations: a major hybrid zone along the border of the DRC and Uganda, a second potential hybrid zone in Central African Republic and a smaller fraction of hybrids in the Pendjari-Arli complex of West Africa. Most of the hybrids show evidence of interbreeding over more than one generation, demonstrating that hybrids are fertile. Mitochondrial and Y chromosome data demonstrate that the hybridization is bidirectional, involving males and females from both subspecies. We hypothesize that the hybrid zones may have been facilitated by poaching and habitat modification. The localized geography and rarity of hybrid zones, their possible facilitation from human pressures, and the high divergence and genetic distinctness of forest and savanna elephants throughout their ranges, are consistent with calls for separate species classification.

  11. Public health professionals’ perceptions of mental health services in Equatorial Guinea, Central-West Africa

    PubMed Central

    Reuter, Peter Robert; McGinnis, Shannon Marcail; Reuter, Kim Eleanor

    2016-01-01

    Introduction Mental health disorders constitute 13% of global disease burden, the impacts of which are disproportionality felt in sub-Saharan Africa. Equatorial Guinea, located in Central-West Africa, has the highest per-capita investment in healthcare on the African continent, but only two studies have discussed mental health issues in the country and none of have examined the perspective of professionals working in the field. The purpose of this study was to gain a preliminary understanding of Equatoguinean health care professionals' perspectives on the mental health care system. Methods Nine adult participants (directors or program managers) were interviewed in July 2013 in Malabo, Equatorial Guinea from government agencies, aid organizations, hospitals, and pharmacies. Interviews were designed to collect broad information about the mental healthcare system in Equatorial Guinea including the professionals' perspectives and access to resources. This research was reviewed and approved by an ethical oversight committee. Results All individuals interviewed indicated that the mental health system does not currently meet the needs of the community. Professionals cited infrastructural capacity, stigmatization, and a lack of other resources (training programs, knowledgeable staff, medications, data) as key factors that limit the effectiveness of mental healthcare. Conclusion This study provides a preliminary understanding of the existing mental health care needs in the country, highlighting opportunities for enhanced healthcare services. PMID:28293352

  12. Chronic morbidity in women, namely in pregnancy. (Comparative study between West, Central and East European centres).

    PubMed

    Kukla, L; Bouchalova, M; Shkiriak-Nyzhnyk, Z; Chyslovska, N; Golding, J; Goodfellow, S; Ignatjeva, R

    2008-01-01

    18 chronic diseases were investigated in a population of 13,115 women living in six settings of West- (Avon UK, the Isle of Man), Central- (the Czech Republic and the Slovak Republic) and East-Europe (the Ukraine and Russia), that collaborate in the European Longitudinal Study of Pregnancy and Childhood (ELSPAC project). In prenatal questionnaires filled in after the first half of pregnancy, women reported 25,795 chronic diseases they ever suffered, out of them 11,188 having in present pregnancies. In the whole sample, lifelong prevalence was 11,2%, and prevalence in pregnancy 4,8% which means that 43,4% of all chronic diseases recurred in pregnancy. Up to mean age of 255 years in the whole sample, 39,6% women reported ever having indigestion, 29% back pains, 22,6% migraine, about 16% haemorrhoids, hay fever and eczema, about 10% varicose veins, anorexia nervosa, heavy depression and kidney diseases, over 5% rheumatism and 4% asthma. Less prevalent were infections of pelvic organs, febrile convulsions, joint inflammations, stomach ulcers, psoriasis and epilepsy. Lifetime prevalence of chronic diseases and their prevalence in pregnancy were the highest in the western zone and decreased eastwards, but recurrence grew in the opposite direction, being the highest in the eastern zone. The variation of each morbidity indicator is followed in all diseases between geographical zones as well as between individual study centres.

  13. An exploration of nitrate concentrations in groundwater aquifers of central-west region of Bangladesh.

    PubMed

    Majumder, Ratan K; Hasnat, Mohammad A; Hossain, Shahadat; Ikeue, Keita; Machida, Masato

    2008-11-30

    Groundwater and river water samples were collected from the study area to investigate the spatial distribution of nitrate (NO(3)(-)) in the central-west region of Bangladesh. The shallow and deep groundwater nitrate concentrations ranged from <0.10 to 75.12 and <0.10 to 40.78 mg/L, respectively. Major river water NO(3)(-) concentrations were ranged from 0.98 to 2.32 mg/L with an average of 1.8 mg/L. The average Cl(-)/NO(3)(-) ratio (4.9) of major river water has been considered as reference point to delineate denitrification processes. The alluvial fan, alluvial, deltaic and coastal deposits shallow groundwater having C1(-)/NO(3)(-) values less than that of the average river water value (4.9), suggested denitrification processes within the aquifers. On the other hand, denitrification processes are insignificant in the Pleistocene terraces area aquifers related to relatively higher concentrations of nitrate. Iron pyrite has been found as insignificant effect on denitrification.

  14. Origin of tonalites from the Boil Mountain ophiolitic complex, west-central Maine

    SciTech Connect

    Chow, J.S. . Geology Dept.)

    1993-03-01

    The Boil Mountain ophiolitic complex, west-central Maine, marks the suture between the Boundary Mountain and Gander terranes that became amalgamated in the late Cambrian during a pre-Taconic collisional event known as the Penobscottian orogeny. This even formed a composite terrane that is believed to have collided with the proto-North American margin during the Ordovician Taconic orogeny. The ophiolite is unusual in that there is no associated tectonized ultramafic section; there is a lack of a sheeted dike sequence; and an intrusive tonalite layer comprises a significant volume of the complex. Preliminary major and trace element geochemical analysis of the tonalites indicates that this unit is derived by partial melting of the associated mafic volcanics. This melting may have been induced by stopping water-rich hydrothermally altered basalts into subcrustal magma chambers. The association of arc-like volcanics and plutonics of the Boil Mountain ophiolite with the adjacent Hurricane melange suggests that the Boil Mountain may be a fragment of a forearc supra-subduction zone complex. Similar interpretations have been made recently for the Late Proterozoic Bou Azzer ophiolite in Morocco and the Coast Range ophiolite.

  15. Hydrology of the Floral City Pool of Tsala Apopka Lake, west-central Florida

    USGS Publications Warehouse

    Bradner, L.A.

    1988-01-01

    Tsala Apopka Lake, in west-central Florida, has an area of about 19,000 acres and is divided into three water-management pools, with the Floral City Pool, the most upgradient. The Floral City Pool, which has a surface area of approximately 4,750 acres, contains an extensive combination of lakes, wetlands, and connecting canals. The Pool receives inflow from the Withlacoochee River through two canals. Outflow is through one manmade canal and one natural slough. Canal flow is partially controlled by manmade structures. A cumulative deficit of 19.4 inches of rainfall from August 1984 through May 1985 reduced surface-water inflow to the Floral City Pool to about 0.5 cu ft/sec by May 1985. During May 1985, pool levels declined approximately 0.04 ft/day. By the end of May, there was no observable outflow. From June 1985 through September 1985, 39.8 inches of rainfall caused above-average inflow to the Floral City Pool and a pool-level increase of 6.2 ft. The inflow of 340 CFS nearly equaled the outflow of 338 CFS by the end of September. (USGS)

  16. Geologic interpretation of an aeromagnetic map of the west-central Columbia Plateau, Washington and Oregon

    USGS Publications Warehouse

    Swanson, Donald A.; Wright, Thomas L.; Zietz, Isidore

    1976-01-01

    A low altitude, total intensity aeromagnetic map of the ?west-central Columbia Plateau, underlain principally by the Yakima Basalt,. shows Positive and negative anomalies that stand out from a moderate intensity .background reflecting .interbedded flows of normal and reversed magnetic polarity. One set of anomalies is related to anticlinal ridges, nother follows the traces of known or inferred faults, and a third set coincides with a swarm of feeder dikes for the Ice Harbor flows of Swanson and others (1975b), the youngest unit of basalt in the area. A fourth set of narrow, sinuous anomalies is related to flows that filled ancient valleys during the late stage of Yakima volcanism. The magnetic map suggests that the Ice Harbor dike swarm is offset by left-lateral strike-slip displacement along the Rattlesnake-Wallula fault, a segment of the Olympic-Wallowa lineament. The aeromagnetic map is of great help in delineating the extent of the dike swarm, mapping the ancient drainage system, and understanding the structural history of this part of the Columbia Plateau.

  17. Brevetoxicosis in seabirds naturally exposed to Karenia brevis blooms along the central west coast of Florida.

    PubMed

    Fauquier, Deborah A; Flewelling, Leanne J; Maucher, Jennifer M; Keller, Martha; Kinsel, Michael J; Johnson, Christine K; Henry, Michael; Gannon, Janet G; Ramsdell, John S; Landsberg, Jan H

    2013-04-01

    Harmful algal bloom events caused by the dinoflagellate Karenia brevis occurred along the central west Florida, USA, coast from February 2005 through December 2005 and from August 2006 through December 2006. During these events, from 4 February 2005 through 28 November 2006, live, debilitated seabirds admitted for rehabilitation showed clinical signs that included disorientation, inability to stand, ataxia, and seizures. Testing of blood, biologic fluids, and tissues for brevetoxin by enzyme-linked immunosorbent assay found toxin present in 69% (n=95) of rehabilitating seabirds. Twelve of the 19 species of birds had evidence of brevetoxin exposure. Commonly affected species included Double-crested Cormorants (Phalacrocorax auritus), Brown Pelicans (Pelecanus occidentalis), Great Blue Herons (Ardea herodias), and Common Loons (Gavia immer). Serial blood and fecal samples taken from several live seabirds during rehabilitation showed that brevetoxin was cleared within 5-10 days after being admitted to the rehabilitation facility, depending on the species tested. Among seabirds that died or were euthanized, the highest brevetoxin concentrations were found in bile, stomach contents, and liver. Most dead birds had no significant pathologic findings at necropsy, thereby supporting brevetoxin-related mortality.

  18. Geothermal potential of West-Central New Mexico from geochemical and thermal gradient data

    SciTech Connect

    Levitte, D.; Gambill, D.T.

    1980-11-01

    To study the low temperature and Hot Dry Rock (HDR) geothermal potential of west-central New Mexico, 46 water samples were collected and geothermal gradient measurements were made in 29 wells. Water chemistry data indicate that all the samples collected are meteoric waters. High temperatures of samples taken from wells between Gallup and Tohatchi indicate these wells may derive water from a warm aquifer below the depth of the wells. The chemistries of the samples farther south on the Zuni Indian reservation suggest these waters are not circulating below 600 m of the surface. Geothermometry calculations support the conclusion that the waters sampled are meteoric. The geothermometry also indicates that the deep reservoir between Gallup and Tohatchi may be greater than 60/sup 0/C. Thermal gradient data indicate an area of high gradient on the Zuni Indian Reservation with a measured maximum of 67/sup 0/C/km between 181 m and 284 m. This high probably is not hydrologically controlled. The maximum gradients in the study area are 76/sup 0/C/km and 138/sup 0/C/km, measured just east of Springerville, Arizona. These gradients are undoubtedly controlled by circulating water, possibly heated by a magmatic source at depth and circulating back to the surface.

  19. Thermal springs in the Payette River basin, west-central Idaho

    USGS Publications Warehouse

    Lewis, R.E.; Young, H.W.

    1980-01-01

    The Payette River basin, characterized by steep, rugged mountains and narrow river valleys, occupies an area of about 3 ,300 square miles in west-central Idaho. Predominant rock types in the basin include granitic rocks of the Idaho batholith and basalt flows of the Columbia River Basalt Group. Waters from thermal springs in the basin, temperatures of which range from 34 to 86 degrees Celsius, are sodium bicarbonate types and are slightly alkaline. Dissolved-solids concentrations range from 173 to 470 milligrams per liter. Reservoir temperatures determined from the sodium-potassium-calcium and silicic acid-corrected silica geothermometers range from 53 to 143 degrees Celsius. Tritium, present in concentrations between 0 and 2 tritium units, indicate sampled thermal waters are at least 100 years old and possibly more than 1,000 years old. Stable isotope data indicate it is unlikely any of the nonthermal waters sampled are representative of precipitation that recharges the thermal springs in the basin. Thermal springs discharged about 5,700 acre-feet of water in 1979. Associated convective heat flux is 1.1x10 to the 7th power calories per second. (USGS)

  20. Mobile pastoralists in Central and West Africa: between conflict, mobile telephony and (im)mobility.

    PubMed

    De Bruijn, M; Amadou, A; Lewa Doksala, E; Sangaré, B

    2016-11-01

    The livelihoods of the Fulani mobile pastoralists in the Sahel, West and Central Africa are characterised by mobility (related to the needs of their animals), extensive social networks, and a focus on social ties as the basis of status and influence ('wealth in people'). The Sahel environment in which many Fulani nomads live has become embroiled in jihadism, conflict, and violence; at the same time, this region has experienced an increase in opportunities to connect through the wireless mobile communication system. This paper analyses the triangle of mobility, communication, and insecurity in order to understand the present-day situation of the nomadic and semi-nomadic Fulani pastoralists and their identity dynamics. The Fulani find themselves caught in between these conflicts, which end their mobility and often lead to the loss of their herds. Will they be able to keep their mobile lifestyle and identity? This article is based on qualitative case studies and the biographical narratives of nomadic and semi-nomadic pastoralists who have lived through conflict and violence in Cameroon, Chad and Mali. These case studies show that, despite the fact that mobile pastoralism has become difficult as a consequence of the conflicts and loss of cattle, the 'mobile' identity is very present and reinforced with the help of mobile telephony, through which social networks and 'wealth in people' are sustained.

  1. Low-flow frequency analyses for streams in west-central Florida

    USGS Publications Warehouse

    Hammett, K.M.

    1985-01-01

    The log-Pearson type III distribution was used for defining low-flow frequency at 116 continuous-record streamflow stations in west-central Florida. Frequency distributions were calculated for 1, 3, 7, 14, 30, 60, 90, 120, and 183 consecutive-day periods for recurrence intervals of 2, 5, 10, and 20 years. Discharge measurements at more than 100 low-flow partial-record stations and miscellaneous discharge-measurement stations were correlated with concurrent daily mean discharge at continuous-record stations. Estimates of the 7-day, 2-year; 7-day, 10-year; 30-day, 2-year; and 30-day, 10-year discharges were made for most of the low-flow partial-record and miscellaneous discharge-measurement stations based on those correlations. Multiple linear-regression analysis was used in an attempt to mathematically relate low-flow frequency data to basin characteristics. The resulting equations showed an apparent bias and were considered unsatisfactory for use in estimating low-flow characteristics. Maps of the 7-day, 10-year and 30-day, 10-year low flows are presented. Techniques that can be used to estimate low-flow characteristics at an ungaged site are also provided. (USGS)

  2. Floods of November 1978 to March 1979 in Arizona and west-central New Mexico

    USGS Publications Warehouse

    Aldridge, B.N.; Hales, T.A.

    1983-01-01

    Widespread rainfall of 3 to 9 inches in the mountains area of Arizona and West-Central New Mexico during December 17-20, 1978, caused maximum known discharges on the Gila River in New Mexico and on several streams in Arizona. At Phoenix, the Salt River was the highest since 1920 but was only slightly higher than the flood in March 1978. The Agua Fria River was the highest since 1919. The floods caused 12 deaths and more than $150 million in damage. Damage of $51.8 million occurred in Maricopa County, Arizona. Ten counties in Arizona and three counties in New Mexico wer declared disaster areas. Unusually high volumes of runoff occurred on the Salt, Verde, and Agua Fria Rivers upstream from reservoirs. Overflow from the reservoir systems caused flooding downstream. Storage in the reservoirs on the Salt and Verde River reduced the peak discharge of the Salt River at Phoenix from a potential of about 234,000 cubic feet per second to 126,00 cubic feet per second and greatly reduced the duration of the flood. (USGS)

  3. Assessment of processes affecting low-flow water quality of Cedar Creek, west-central Illinois

    USGS Publications Warehouse

    Schmidt, Arthur R.; Freeman, W.O.; McFarlane, R.D.

    1989-01-01

    Water quality and the processes that affect dissolved oxygen, nutrient (nitrogen and phosphorus species), and algal concentrations were evaluated for a 23.8-mile reach of Cedar Creek near Galesburg, west-central Illinois, during periods of warm-weather, low-flow conditions. Water quality samples were collected and stream conditions were measured over a diel (24 hour) period on three occasions during July and August 1985. Analysis of data from the diel-sampling periods indicates that concentrations of iron, copper, manganese, phenols, and total dissolved-solids exceeded Illinois ' general-use water quality standards in some locations. Dissolved-oxygen concentrations were less than the State minimum standard throughout much of the study reach. These data were used to calibrate and verify a one-dimensional, steady-state, water quality model. The computer model was used to assess the relative effects on low-flow water quality of processes such as algal photosynthesis and respiration, ammonia oxidation, biochemical oxygen demand, sediment oxygen demand, and stream reaeration. Results from model simulations and sensitivity analysis indicate that sediment oxygen demand is the principal cause of low dissolved-oxygen concentrations in the creek. (USGS)

  4. Paleobiogeographic affinities of emsian (late early devonian) gastropods from farewell terrane (west-central Alaska)

    USGS Publications Warehouse

    Fryda, J.; Blodgett, R.B.

    2008-01-01

    The vast majority of Emsian gastropods from Limestone Mountain, Medfra B-4 quadrangle, west-central Alaska (Farewell terrane) belong to species with lecithotrophic larval strategy. The present data show that there is no significant difference in the paleobiogeo-graphic distribution of Emsian gastropod genera with lecithotrophic and planktotrophic larval strategies. Numerical analysis of the faunal affinities of the Emsian gastropod fauna from the Farewell terrane reveals that this terrane has much stronger faunal connections to regions like Variscan Europe, eastern Australia, and the Alexander terrane of southeast Alaska than to cratonic North America (Laurentia). The Canadian Arctic Islands is the only region of cratonic North America (Laurentia) that shows significant faunal affinities to the Emsian gastropod faunas of the Farewell terrane. The analysis also indicates a close faunal link between the Farewell and Alexander terranes. Published paleontological and geological data suggest that the Farewell and Alexander terranes represents tectonic entities that have been rifted away from the Siberia, Baltica, or the paleo-Pacific margin of Australia. The results of the present numerical analysis are not in conflict with any of these possibilities. However, the principle of spatial continuity of the wandering path prefers Siberia as the most probable "parental" paleocontinent for the derivation of both the Farewell and Alexander terranes. ?? 2008 The Geological Society of America.

  5. Ground-water levels in selected well fields and in west-central Florida, May 1982

    USGS Publications Warehouse

    Barr, G.L.

    1982-01-01

    The water table in the surficial aquifer and the potentiometric surface of the Floridan aquifer in a 1,700-square-mile area in west-central Florida are mapped semiannually by the U.S. Geological Survey. Maps are based on water levels measured in wells each May to coincide with the seasonal low levels and each September to coincide with seasonal high levels. The mapped area shows 14 well fields that supplied 181.1 million gallons to municipalities on May 10, 1982. The water is withdrawn from the Floridan aquifer, the major aquifer in Florida. The effect of localized withdrawal on ground water is shown on the maps as depressions in both the potentiometric and water-table surfaces. In May 1982, ground-water levels were lower than those of September 1981. Seasonal recharge from above-average rainfall and reduced pumpage aided in the water-level recovery from record to near record levels of May 1981. (USGS)

  6. Ground-water levels in selected well fields and in west-central Florida, September 1979

    USGS Publications Warehouse

    Yobbi, D.K.; Mills, L.R.; Woodham, W.M.

    1980-01-01

    The water table in the surficial aquifer and the potentiometric surface of the Floridan aquifer in a 1,200-square-mile area in west-central Florida are mapped semiannually by the U.S. Geological Survey. Maps are based on water levels measured in wells each May to coincide with seasonal low levels, and each September to coincide with seasonal high levels. The mapped area shows 16 well fields which supplied 123.7 million gallons to municipalities on September 18, 1979. The water is withdrawn from the Floridan aquifer, the major aquifer in Florida. The effect of localized withdrawal of ground water is shown on the maps as depressions in both the potentiometric and water-table surfaces. Water levels were generally higher in September 1979 than in May 1979 and higher than the average September levels. Change of water levels ranged from an increase of 15 feet at Cosme well field to a decrease of 9 feet at Verna well field. (USGS)

  7. Ground-water levels in selected well fields and in west-central Florida, September 1981

    USGS Publications Warehouse

    Yobbi, D.K.; Barr, G.L.

    1982-01-01

    The water table in the surficial aquifer and the potentiometric surface of the Floridan aquifer in a 1,200-square-mile area in west-central Florida are mapped semiannually by the U.S. Geological Survey. Maps are based on water levels measured in wells each May to coincide with seasonal low levels and each September to coincide with seasonal high levels. The mapped area shows 14 well fields that supplied 140.3 million gallons to municipalities on September 21, 1981. The water is withdrawn from the Floridan aquifer, the major aquifer in Florida. The effect of localized withdrawal on ground water is shown on the maps as depressions in both the potentiometric and water-table surfaces. In September 1981, ground-water levels were significantly higher than those of May 1981 and were unchanged or within a few feet of those in September 1980. Seasonal recharge from summer rains and reduced pumpage are factors in the water-level recovery from record and near record low levels of May 1981. (USGS)

  8. Subsurface Glen Rose reef trend in east Texas and west-central Louisiana

    SciTech Connect

    Adams, G.S.

    1983-03-01

    The subsurface Glen Rose reef trend in east Texas and west-central Louisiana (Lower Cretaceous Comanchean) is a regressive carbonate complex deposited on a broad shallow water shelf. The Glen Rose reef trend can be differentiated into two separate reef tracts that prograded seaward over a slowly subsiding shelf. It remains to be seen whether the Glen Rose reefs are actual framework reefs or mounds of transported material. Reef facies include poorly sorted caprinidcoral grainstones, moderately sorted peloid and oncolite packstones and grainstones, and well-sorted, very fine grained skeletal grainstones. Coated grains, abraded skeletal fragments, scoured bedding surfaces, and minor cross-beds are evidence for deposition of the reef facies in a high-energy shoal setting. The reefal buildups grade laterally into low-energy shallow water wackestones and mudstones containing toucasids, orbitolinids, and serpulid burrows. Porosities associated with the reefal buildups appear facies controlled. Caprinid-coral packstones and grainstones exhibit intraparticle, moldic, and vuggy porosities of 10 to 15%. Pinpoint microporosity of 5 to 10% are found within the finegrained skeletal grainstones. Fracture porosity enhances permeability in several facies. Moldic and vuggy porosity types are generally secondary whereas intraparticle porosity may be preserved primary. Coarse equant calcite commonly occludes intraparticle, moldic, vuggy, and fracture porosities. Dolomitization within the reef limestones may have acted to create or preserve porosities. Poor production from the Glen Rose reef trend has been attributed to the lack of structural closure.

  9. Geothermal gradients in the Missoula and Bitterroot Valleys, west-central Montana

    USGS Publications Warehouse

    Leonard, Robert B.; Wood, Wayne A.

    1980-01-01

    Temperature-depth profiles of six cased test holes in the Missoula and Bitterroot Valleys, west-central Montana, consist of linear segments, the intersections of which commonly correspond with lithologic boundaries. Geothermal gradients commonly decreased with depth, probably as a result of compaction and higher quartz content of the deeper sedimentary deposits. There is no evidence for hydrothermal discharge. A maximum temperature of 31.7 degrees Celsius was measured at a depth of 869 meters. Estimated temperatures at a depth of 1 kilometer at the drill sites ranged from about 34 to 63 degrees Celsius. Temperatures exceeding 90 degrees Celsius probably would not occur at depths less than 1,500 meters. Values of thermal conductivity needed to maintain an assumed regional heat flow of about 2.1 heat flow units along the measured geothermal gradients generally exceeded published values for the rock and soil penetrated by the wells. Laboratory determinations of the thermal conductivity of cores and cuttings would be useful to refine the estimates and to test the conclusion that the measured temperatures are not hotter than normal. (USGS)

  10. Streamflow simulation studies of the Hillsborough, Alafia, and Anclote Rivers, west-central Florida

    USGS Publications Warehouse

    Turner, J.F.

    1979-01-01

    A modified version of the Georgia Tech Watershed Model was applied for the purpose of flow simulation in three large river basins of west-central Florida. Calibrations were evaluated by comparing the following synthesized and observed data: annual hydrographs for the 1959, 1960, 1973 and 1974 water years, flood hydrographs (maximum daily discharge and flood volume), and long-term annual flood-peak discharges (1950-72). Annual hydrographs, excluding the 1973 water year, were compared using average absolute error in annual runoff and daily flows and correlation coefficients of monthly and daily flows. Correlations coefficients for simulated and observed maximum daily discharges and flood volumes used for calibrating range from 0.91 to 0.98 and average standard errors of estimate range from 18 to 45 percent. Correlation coefficients for simulated and observed annual flood-peak discharges range from 0.60 to 0.74 and average standard errors of estimate range from 33 to 44 percent. (Woodard-USGS)

  11. Hydrogeological framework of the Edwards-Trinity aquifer system, west-central Texas

    USGS Publications Warehouse

    Barker, Rene A.; Ardis, Ann F.

    1996-01-01

    The Edwards-Trinity aquifer system underlies about 42,000 square miles of west-central Texas, where mostly gently dipping Lower Cretaceous strata comprise three regional aquifers and two regional confining units. The aquifers are the Edwards Aquifer of the Balcones fault zone, the Trinity Aquifer of the Balcones fault zone and Hill County, and the Edwards-Trinity Aquifer of the Edwards Plateau and Trans-Pecos. The Navarro-Del Rio confining unit confines the downdip part of the Edwards Aquifer, and the Hammett confining unit confines the updip, basal part of the Trinity Aquifer and a small southeastern fringe of the Edwards-Trinity Aquifer. Transmissivity averages less than 10,000 feet squared per day throughout more than 90 percent of the study area as the result of widespread cementation and secondary mineral growth. However, in fractured and leached rocks in the Balcones fault zone, transmissivity averages about 750,000 feet squared per day in the Edwards aquifer, which occupies less than 10 percent of the area.

  12. Potentiometric surface of the upper Floridan Aquifer, west-central Florida, September 1985

    USGS Publications Warehouse

    Barr, G.L.

    1985-01-01

    The potentiometric surface is the level to which water will rise in tightly cased wells that tap the Upper Floridan aquifer. The surface is mapped by determining the altitude of water levels in a network of wells and is represented on maps by contours that connect points of equal altitude. Maps of the potentiometric surface of the Upper Floridan aquifer in west-central Florida are prepared semiannually by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District. Maps for May and September show, respectively, the potentiometric surfaces of the normally expected annual low and high water level conditions. The potentiometric surface of the Upper Floridan aquifer is shown for September 1985. Most of the water level data were collected during September 9-13. Supplemental data were collected by other agencies and companies. The map represents water level conditions near the end of the summer rainy season when groundwater withdrawals for agricultural use are low. Hence, the potentiometric surface is near its highest level for the year. (Lantz-PTT)

  13. Potentiometric surface of the Upper Floridan Aquifer, west-central Florida, September 1987

    USGS Publications Warehouse

    Lewelling, B.R.

    1987-01-01

    The potentiometric surface in the Upper Floridan aquifer was mapped by determining the altitude of water levels in a network of wells and is represented on maps by contours that connect points of equal altitude. Maps of the potentiometric surface of the Upper Floridan aquifer in west-central Florida are prepared semiannually by the U.S. Geological Survey. Maps for May and September show, respectively, the potentiometric surface of the normally expected annual low and high water level conditions. Potentiometric surface maps have been prepared for January 1964, May 1969, May 1971 to 1974, and for each May and September since 1975. The potentiometric surface of the Upper Floridan aquifer is shown for September 1987. Most of the water level data were collected by the U.S. Geological Survey during the period of September 14-18. Supplemental data were collected by other agencies and companies. This map represents water level conditions near the end of the summer rainy season when groundwater withdrawals for agricultural use are low and therefore, when the potentiometric surface is near its highest level for the year. (See also W88-03126) (Lantz-PTT)

  14. Population structure and skeletal variation in the Late Woodland of west-central Illinois.

    PubMed

    Conner, M D

    1990-05-01

    This paper analyzes nonmetric trait variation in 11 late Late Woodland (ca. AD 700-1000) and one Mississippian (AD 1000-1300) skeletal samples from west-central Illinois from a population-structure perspective. Most of the sites are of the Bluff phase of Late Woodland in the lower Illinois River valley; others are from a nearby, contemporary archaeological phase. Late Woodland as a whole era (ca. AD 250-1000) was a period of marked population growth and expansion into new regional environments, trends that accompanied horticultural intensification in the area. Overall variation between sites was low, but males, females, and the total sample exhibited a significant geographic component to variation due to interregional morphological differences. The Bluff sites tended to group together relative to the non-Bluff sites. However, there was no significant geographic component to variation among the Bluff sites. The results are only partially consistent with archaeological data suggesting population growth and expansion through fissioning. Previous studies have demonstrated significant heterogeneity for nonmetric trait frequencies among Middle Woodland (ca. 100 BC to AD 250) sites, suggesting a Middle to Late Woodland change in population structure that lowered levels of morphological variation. This supports a model of increased intra- and interregional interaction from Middle to Late Woodland times developed from ceramic data by Braun and by Braun and Plog.

  15. Adventure Learning @ Greenland

    NASA Astrophysics Data System (ADS)

    Miller, B. G.; Cox, C. J.; Hougham, J.; Walden, V. P.; Eitel, K.; Albano, A.

    2013-12-01

    Summit (ICECAPS) project (Shupe et al. 2012; http://www.esrl.noaa.gov/psd/arctic/observatories/summit/). ICECAPS is an atmospheric observatory focused on obtaining high temporal resolution measurements of clouds from ground-based remote sensors including radar, lidar, infrared spectra and others. ICECAPS also launches radiosondes twice daily. This large suite of complementary observations are providing an important baseline understanding of cloud and atmospheric conditions over the central Greenland ice sheet and are supporting Arctic climate research on cloud processes and climate model validation. ICECAPS measures parameters that are associated with those identified in student misconceptions, for example, different types of atmospheric radiation, the effect of greenhouse gases, and climate versus weather (see also Haller et al., 2011). Thus, ICECAPS research and the AL@GL project combined to create a learning environment and educational activities that sought to increase climate literacy in high school students as well as communicate important atmospheric research to a broader audience.

  16. Surface-water radon-222 distribution along the west-central Florida shelf

    USGS Publications Warehouse

    Smith, C.G.; Robbins, L.L.

    2012-01-01

    In February 2009 and August 2009, the spatial distribution of radon-222 in surface water was mapped along the west-central Florida shelf as collaboration between the Response of Florida Shelf Ecosystems to Climate Change project and a U.S. Geological Survey Mendenhall Research Fellowship project. This report summarizes the surface distribution of radon-222 from two cruises and evaluates potential physical controls on radon-222 fluxes. Radon-222 is an inert gas produced overwhelmingly in sediment and has a short half-life of 3.8 days; activities in surface water ranged between 30 and 170 becquerels per cubic meter. Overall, radon-222 activities were enriched in nearshore surface waters relative to offshore waters. Dilution in offshore waters is expected to be the cause of the low offshore activities. While thermal stratification of the water column during the August survey may explain higher radon-222 activities relative to the February survey, radon-222 activity and integrated surface-water inventories decreased exponentially from the shoreline during both cruises. By estimating radon-222 evasion by wind from nearby buoy data and accounting for internal production from dissolved radium-226, its radiogenic long-lived parent, a simple one-dimensional model was implemented to determine the role that offshore mixing, benthic influx, and decay have on the distribution of excess radon-222 inventories along the west Florida shelf. For multiple statistically based boundary condition scenarios (first quartile, median, third quartile, and maximum radon-222 inshore of 5 kilometers), the cross-shelf mixing rates and average nearshore submarine groundwater discharge (SGD) rates varied from 100.38 to 10-3.4 square kilometers per day and 0.00 to 1.70 centimeters per day, respectively. This dataset and modeling provide the first attempt to assess cross-shelf mixing and SGD on such a large spatial scale. Such estimates help scale up SGD rates that are often made at 1- to 10-meter

  17. Occult hepatitis B virus infection among injecting drug users in the Central-West Region of Brazil

    PubMed Central

    de Matos, Márcia Alves Dias; Ferreira, Renata Carneiro; Rodrigues, Fabiana Perez; Marinho, Tamíris Augusto; Lopes, Carmen Luci Rodrigues; Novais, Antônia Carlos Magalhães; Motta-Castro, Ana Rita Coimbra; Teles, Sheila Araújo; Souto, Francisco José Dutra; Martins, Regina Maria Bringel

    2013-01-01

    The prevalence of occult hepatitis B virus (HBV) infection was investigated in 149 hepatitis B surface antigen (HBsAg) negative injecting drug users (IDUs) in the Central-West Region of Brazil. Of these individuals, 19 were positive for HBV DNA, resulting in an occult HBV infection prevalence of 12.7% (19/149); six of these 19 individuals had anti-HBV core and/or anti-HBV surface antibodies and 13 were negative for HBV markers. All IDUs with occult hepatitis B reported sexual and/or parenteral risk behaviours. All HBV DNA-positive samples were successfully genotyped. Genotype D was the most common (17/19), followed by genotype A (2/19). These findings reveal a high prevalence of occult HBV infection and the predominance of genotype D among IDUs in Brazil's Central-West Region. PMID:23778654

  18. The North West African Margin Magnetic Anomaly revisited : implications for the initial evolution of the Central Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Sahabi, M.; Olivet, J.-L.; Aslanian, D.; Patriat, M.; Géli, L.; Matias, L.; Réhault, J.-P.; Malod, J.; Bouabdelli, M.

    2003-04-01

    Due to the lack of data from the North West African margin, the Mesozïc evolution of the Central Atlantic is still controversial. Existing plate kinematics (Le Pichon et al, 1977), Wissmann and Roger (1982), Olivet et al, 1984, Klitgord and Schouten, 1986) reconstructions do not explain the characteristics of the S1 Magnetic Anomaly, nor the the presence and geometry of salt basins on the margins off NW Marocco and off Mauritania. We present a new magnetic compilation detailing the correspondance between the different conjugated magnetic anomalies that exist on each side of the Central Atlantic : the East Coast (ECMA), Brunswick (BMA) and Blake Spur (BSMA) Magnetic Anomalies on the American side, and the S1 and West African Coast (WACMA) magnetic anomalies on the African side. In addition, using all available, academic, seismic data, we mapped the ocenawards extension of the salt province of the 200 Ma old Seine Abyssal Plain basin, off Marocco, which is considered as autochtonous.

  19. Percentage change in saturated thickness of the High Plains Aquifer, west-central Kansas, 1950 to average 1980-82

    USGS Publications Warehouse

    Pabst, Marilyn E.

    1982-01-01

    A statistical technique, called kriging, was programmed for a computer to interpolate hydrologic data based on a network of 296 measured values in west-central Kansas and eastern Colorado. The computer program generated estimated values of selected hydrologic data at the center of each 1-mile section in the Western Kansas Groundwater Management District No. 1. This program facilitated contouring of the data that are needed to aid in the management of ground water for irrigation. The kriging technique produced a map that illustrates the percentage change in saturated thickness of the High Plains aquifer from 1950 to average 1980-82 in west-central Kansas. Estimated changes in saturated thickness of the aquifer, as shown on the map, range from about a 50% increase to a 100% decrease. (USGS)

  20. Estimating the magnitude and frequency of floods for streams in west-central Florida, 2001

    USGS Publications Warehouse

    Hammett, Kathleen M.; DelCharco, Michael J.

    2005-01-01

    Flood discharges were estimated for recurrence intervals of 2, 5, 10, 25, 50, 100, 200, and 500 years for 94 streamflow stations in west-central Florida. Most of the stations are located within the 10,000 square-mile, 16-county area that forms the Southwest Florida Water Management District. All stations had at least 10 years of homogeneous record, and none have flood discharges that are significantly affected by regulation or urbanization. Guidelines established by the U.S. Water Resources Council in Bulletin 17B were used to estimate flood discharges from gaging station records. Multiple linear regression analysis was then used to mathematically relate estimates of flood discharge for selected recurrence intervals to explanatory basin characteristics. Contributing drainage area, channel slope, and the percent of total drainage area covered by lakes (percent lake area) were the basin characteristics that provided the best regression estimates. The study area was subdivided into four geographic regions to further refine the regression equations. Region 1 at the northern end of the study area includes large rivers that are characteristic of the rolling karst terrain of northern Florida. Only a small part of Region 1 lies within the boundaries of the Southwest Florida Water Management District. Contributing drainage area and percent lake area were the most statistically significant basin characteristics in Region 1; the prediction error of the regression equations varied with the recurrence interval and ranged from 57 to 69 percent. In the three other regions of the study area, contributing drainage area, channel slope, and percent lake area were the most statistically significant basin characteristics, and are the three characteristics that can be used to best estimate the magnitude and frequency of floods on most streams within the Southwest Florida Water Management District. The Withlacoochee River Basin dominates Region 2; the prediction error of the regression

  1. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 2. Preliminary outcomes from hot-water drilling and borehole instrumentation on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Doyle, Samuel; Hubbard, Bryn; Christoffersen, Poul; Young, Tun Jan; Hofstede, Coen; Todd, Joe; Bougamont, Marion; Hubbard, Alun

    2015-04-01

    As part of the SAFIRE research programme, pressurised hot water was used to drill four 603-616 m-long boreholes to the bed of the Greenland Ice Sheet at a site located 30 km from the calving front of marine-terminating Store Glacier (70° N, ~1000 m elevation). Despite the boreholes freezing within hours, 4 wired sensor strings were successfully deployed in three of the boreholes. These included a thermistor string to obtain the englacial temperature profile installed in the same borehole as a string of tilt sensors to measure borehole deformation, and two sets of water pressure, electrical conductivity and turbidity sensors installed just above the bed in separate, adjacent boreholes. The boreholes made a strong hydrological connection to the bed during drilling, draining rapidly to ~80 m below the ice surface. The connection of subsequent boreholes was observed as a perturbation in water pressure and temperature recorded in neighbouring boreholes, indicating an effective hydrological sub- or en-glacial connection between them. The short (week long) records obtained from these sensors in summer 2014 tentatively reveal (i) water pressure varying diurnally close to overburden albeit of a small magnitude (~0.3 m H2O), (ii) a minimum extrapolated englacial temperature of -21° C, (iii) and thermistors in the lowest 10 m of the borehole recorded temperatures above the pressure melting point indicating the presence of water. Data loggers were left running and longer records should become available in the near future. Differential drilling and instrument installation depths together with observations of discrete, diurnal turbidity events provisionally suggest the presence of sediment at the bed. These preliminary borehole observations will be complemented by GPS measurements of ice motion, meteorological data, and seismic and radar surveys to be undertaken over the next two years.

  2. Recent changes in north-west Greenland climate documented by NEEM shallow ice core data and simulations, and implications for past-temperature reconstructions

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Steen-Larsen, H. C.; Ortega, P.; Swingedouw, D.; Popp, T.; Vinther, B. M.; Oerter, H.; Sveinbjornsdottir, A. E.; Gudlaugsdottir, H.; Box, J. E.; Falourd, S.; Fettweis, X.; Gallée, H.; Garnier, E.; Gkinis, V.; Jouzel, J.; Landais, A.; Minster, B.; Paradis, N.; Orsi, A.; Risi, C.; Werner, M.; White, J. W. C.

    2015-08-01

    Combined records of snow accumulation rate, δ18O and deuterium excess were produced from several shallow ice cores and snow pits at NEEM (North Greenland Eemian Ice Drilling), covering the period from 1724 to 2007. They are used to investigate recent climate variability and characterise the isotope-temperature relationship. We find that NEEM records are only weakly affected by inter-annual changes in the North Atlantic Oscillation. Decadal δ18O and accumulation variability is related to North Atlantic sea surface temperature and is enhanced at the beginning of the 19th century. No long-term trend is observed in the accumulation record. By contrast, NEEM δ18O shows multidecadal increasing trends in the late 19th century and since the 1980s. The strongest annual positive δ18O values are recorded at NEEM in 1928 and 2010, while maximum accumulation occurs in 1933. The last decade is the most enriched in δ18O (warmest), while the 11-year periods with the strongest depletion (coldest) are depicted at NEEM in 1815-1825 and 1836-1846, which are also the driest 11-year periods. The NEEM accumulation and δ18O records are strongly correlated with outputs from atmospheric models, nudged to atmospheric reanalyses. Best performance is observed for ERA reanalyses. Gridded temperature reconstructions, instrumental data and model outputs at NEEM are used to estimate the multidecadal accumulation-temperature and δ18O-temperature relationships for the strong warming period in 1979-2007. The accumulation sensitivity to temperature is estimated at 11 ± 2 % °C-1 and the δ18O-temperature slope at 1.1 ± 0.2 ‰ °C-1, about twice as large as previously used to estimate last interglacial temperature change from the bottom part of the NEEM deep ice core.

  3. Hydrogeology and analysis of aquifer characteristics in west-central Pinellas County, Florida

    USGS Publications Warehouse

    Broska, J.C.; Barnette, H.L.

    1999-01-01

    The U.S. Geological Survey, in cooperation with Pinellas County, Florida, conducted an investigation to describe the hydrogeology and analyze the aquifer characteristics in west-central Pinellas County. A production test well and four monitor wells were constructed in Pinellas County at Walsingham Park during 1996-97. Water-quality sampling, static and dynamic borehole geophysical surveys, and hydraulic tests were conducted at the wells to delineate the hydrogeology at Walsingham Park. A 9-day aquifer test was conducted to determine the hydraulic characteristics of the aquifer system and observe the changes in water quality due to pumping. A numerical model was constructed to simulate the aquifer test and calculate values for hydraulic conductivity and storage coefficient for permeable zones and confining units at Walsingham Park. Final calibrated values for hydraulic conductivity for the different permeable zones and confining units at the test site were 18 feet per day for Upper Zone A, 750 feet per day for Lower Zone A, 1 foot per day for Zone B, 1x10-4 feet per day for the intermediate confining unit, and 10 feet per day for the semiconfining unit separating Upper Zone A and Lower Zone A. Final calibrated values for storage coefficient were 3.1x10-4 for Upper Zone A, 8.6x10-5 for Lower Zone A, 2.6x10-5 for Zone B, 3.1x10-4 for the intermediate confining unit, and 4.3x10-5 for the semiconfining unit separating Upper Zone A and Lower Zone A. Estimates of transmissivity for Upper Zone A and Lower Zone A were about 2,500 and 37,500 feet squared per day, respectively.

  4. Integrated biostratigraphy of the upper Oligocene-middle Miocene successions in west central Sinai, Egypt

    NASA Astrophysics Data System (ADS)

    Hewaidy, Abdel Galil A.; Farouk, Sherif; Ayyad, Haitham M.

    2014-12-01

    The nannofossil and planktonic foraminiferal biostratigraphy in four upper Oligocene-middle Miocene sections are examined in Nukhul-Sudr area of west central Sinai, Egypt. The integration of calcareous nannofossils and planktonic foraminifera is used to verify the ages and determine the biozones of the upper Oligocene-middle Miocene units in the studied area. This target is important in the light of the great lithofacies changes during the time interval. The detailed examination of the nannofossil and planktonic foraminiferal contents in these sections led to identification of 86 calcareous nannofossil species belonging to 22 genera, 10 families and 3 orders, in addition to 64 planktonic foraminiferal species belonging to 11 genera, 4 families and 2 superfamilies. The identified nannofossil and planktonic foraminiferal assemblages allow to distinguish five calcareous nannofossil biozones and six planktonic foraminiferal biozones. The biostratigraphic integration suggested the Chattian-Aquitanian age for the Nukhul Formation where the Globigerina ciperoensis Zone (P22) and Globigerinoides primordius Zone (M1a) correspond to calcareous nannofossil Sphenolithus ciperoensis Zone (NP25) and Discoaster druggii Zone (NN2), respectively. The Rudeis Formation is assigned to the Burdigalian-Langhian age depending on correspondence of Catpsydrax dissimilis Zone (M2), Globigerinoides bisphericus Zone (M4b) and Praeorbulina sicana Zone (M5) with Discoaster druggii zone (NN2), Sphenolithus belemnos Zone (NN3) and Helicosphaera ampliaperta Zone (NN4). The Somar Formation is found barren ofany microfossils, but it contains index pectens and oysters of Burdigalian age which may be equivalent to the lower part of the Rudeis Formation. The Kareem and Sarbut El-Gamal formations are represented by evaporitic and conglomeratic succession, where no foraminifera or nannofossils are recorded and assigned to the Langhian age according to their stratigraphic position. The Belayim Formation

  5. The morphology and migration of transverse bars off the west-central Florida coast

    USGS Publications Warehouse

    Gelfenbaum, G.; Brooks, G.R.

    2003-01-01

    A series of migrating shore-normal sandbars with wavelengths of 75-120 m and heights up to 2 m have been identified off the northern tip of Anna Maria Island, a barrier island on the west-central Florida coast. Similar features have been described elsewhere since the 1930s and termed 'transverse bars'. The transverse bars identified off Anna Maria Island are found for about 3 km along the coast and extend 4 km offshore, well outside the normal surf-zone width. No cusps or any other associated beach expression is evident despite the fact that the bars come to within about 75 m of the beach. Sediments on the crests of the bars are a well-sorted fine quartz sand, whereas sediments in the troughs are a poorly sorted coarse carbonate shell hash. Historical aerial photographs and repeated high-resolution bathymetric surveys provide a means of quantifying the migration of the transverse bars. Analyses of orthorectified aerial photographs from the early 1940s through the mid 1990s clearly show movement or migration taking place in the bar field. In the 40-yr period from 1951 to 1991, the southern edge of the bar field moved 200-350 m to the south, with an average long-term migration rate of 8 m/yr. Repeated bathymetric surveys over an 8-month period give an average short-term migration rate of 21 m/yr to the south. Wave and current measurements suggest that southerly winds associated with the passage of cold fronts drive near-bed currents to the south that are strong enough to initiate sediment transport and cause the southerly migration of the transverse bars.

  6. Soil-gas radon analyses in the Mt. Rose and Lovelock areas, west-central Nevada

    SciTech Connect

    Ramelli, A.R.; Rigby, J.G.; LaPointe, D.D. )

    1993-04-01

    Soil-gas radon has been sampled and analyzed in two area of differing surficial geology in west-central Nevada. Elevated levels of indoor radon have been found in both area. The Mt. Rose alluvial fan complex, located just southwest of Reno, is an alluvial fan/pediment formed by flow from major drainages in the Carson Range. The surface of the Mt. Rose fan is dominated by glacial outwash deposits believed to be of Donner Lake and Tahoe age. These two units have somewhat differing lithologies and degrees of soil development. The Donner Lake outwash is dominated by volcanic clasts and typically has a thick argillic B-horizon and a moderately to strongly developed duripan. The Tahoe outwash has a mixture of volcanic and granitic clasts and typically has a thinner argillic B-horizon and no duripan. Soil-gas radon levels are generally higher in the Tahoe outwash, probably reflecting either greater emanation from granitic clasts or differences in soil gas permeability. Radon levels along Holocene faults cutting these outwash deposits are fairly typical for the study area and minor differences may be due to the faults' effects on soil gas permeability. Lovelock, about 90 miles northeast of Reno, is located within the Humboldt Sink, one of the lowest parts of the pluvial Lake Lahontan basin. Surficial geology in this area is dominated by fine-grained lacustrine deposits and overbank alluvium from the Humboldt River. During interpluvial periods, this is commonly a marshy area resulting from Humboldt River flow into the basin. Elevated radon levels are likely due to uranium accumulation in black, organic-rich clay layers.

  7. Current developments in understanding of West Nile virus central nervous system disease

    PubMed Central

    Tyler, Kenneth L.

    2014-01-01

    Purpose of review West Nile virus (WNV) is the most important cause of epidemic encephalitis in the United States. We review articles published in the last 18 months related to the epidemiology, immunology, clinical features, and treatment of this disease. Recent findings There was a resurgence in WNV disease in the United States in 2012. The WNV strain now predominant in the United States (NA/WN02) differs from the initial emergent isolate in 1999 (NY99). However, differences in the genetics of currently circulating United States WNV strains do not explain variations in epidemic magnitude or disease severity. Innate and acquired immunity are critical in control of WNV, and in some cases pathways are central nervous system specific. The clinical features of infection are now well understood, although nonconfirmed observations of chronic viral excretion in urine remain controversial. There is no specific antiviral therapy for WNV, but studies of antivirals specific for other flaviviruses may identify agents with promise against WNV. Phase I and II human WNV vaccine clinical trials have established that well tolerated and immunogenic WNV vaccines can be developed. Summary WNV remains an important public health problem. Although recent studies have significantly increased our understanding of host immune and genetic factors involved in control of WNV infection, no specific therapy is yet available. Development of a well tolerated, immunogenic, and effective vaccine against WNV is almost certainly feasible, but economic factors and the lack of predictability of the magnitude and location of outbreaks are problematic for designing phase III trials and ultimate licensure. PMID:24722324

  8. Ichthyoplankton assemblages of coastal west-central Lake Erie and associated habitat characteristics

    USGS Publications Warehouse

    McKenna, J.E.; Davis, B.M.; Fabrizio, M.C.; Savino, J.F.; Todd, T.N.; Bur, M.

    2008-01-01

    Early life stage survival often determines fish cohort strength and that survival is affected by habitat conditions. The structure and dynamics of ichthyoplankton assemblages can tell us much about biodiversity and fish population dynamics, but are poorly understood in nearshore areas of the Great Lakes, where most spawning and nursery habitats exist. Ichthyoplankton samples were collected with a neuston net in waters 2-13 m deep weekly or biweekly from mid-April through August, during 3 years (2000-2002) as part of a study of fish assemblages in west-central Lake Erie. A suite of abiotic variables was simultaneously measured to characterize habitat. Cluster and ordination analyses revealed several distinct ichthyoplankton assemblages that changed seasonally. A lake whitefish (Coregonus clupeaformis) dominated assemblage appeared first in April. In May, assemblages were dominated by several percid species. Summer assemblages were overwhelmingly dominated by emerald shiner (Notropis atherinoides), with large gizzard shad (Dorosoma cepedianum) and alewife (Alosa pseudoharengus) components. This seasonal trend in species assemblages was also associated with increasing temperature and water clarity. Water depth and drift processes may also play a role in structuring these assemblages. The most common and widely distributed assemblages were not associated with substratum type, which we characterized as either hard or soft. The timing of hatch and larval growth separated the major groups in time and may have adaptive significance for the members of each major assemblage. The quality and locations (with reference to lake circulation) of spawning and nursery grounds may determine larval success and affect year class strength.

  9. Contrasting Genetic Structure among Populations of Two Amphidromous Fish Species (Sicydiinae) in the Central West Pacific

    PubMed Central

    Taillebois, Laura; Castelin, Magalie; Ovenden, Jennifer R.; Bonillo, Céline; Keith, Philippe

    2013-01-01

    Both present-day and past processes can shape connectivity of populations. Pleistocene vicariant events and dispersal have shaped the present distribution and connectivity patterns of aquatic species in the Indo-Pacific region. In particular, the processes that have shaped distribution of amphidromous goby species still remain unknown. Previous studies show that phylogeographic breaks are observed between populations in the Indian and Pacific Oceans where the shallow Sunda shelf constituted a geographical barrier to dispersal, or that the large spans of open ocean that isolate the Hawaiian or Polynesian Islands are also barriers for amphidromous species even though they have great dispersal capacity. Here we assess past and present genetic structure of populations of two amphidromous fish (gobies of the Sicydiinae) that are widely distributed in the Central West Pacific and which have similar pelagic larval durations. We analysed sections of mitochondrial COI, Cytb and nuclear Rhodospine genes in individuals sampled from different locations across their entire known range. Similar to other Sicydiinae fish, intraspecific mtDNA genetic diversity was high for all species (haplotype diversity between 0.9–0.96). Spatial analyses of genetic variation in Sicyopus zosterophorum demonstrated strong isolation across the Torres Strait, which was a geologically intermittent land barrier linking Australia to Papua New Guinea. There was a clear genetic break between the northwestern and the southwestern clusters in Si. zosterophorum (φST = 0.67502 for COI) and coalescent analyses revealed that the two populations split at 306 Kyr BP (95% HPD 79–625 Kyr BP), which is consistent with a Pleistocene separation caused by the Torres Strait barrier. However, this geographical barrier did not seem to affect Sm. fehlmanni. Historical and demographic hypotheses are raised to explain the different patterns of population structure and distribution between these species. Strategies

  10. Diagenesis of the Cambro-Ordovician sedimentary rocks of west-central Wisconsin

    SciTech Connect

    Carpenter, T.L.; Hooper, R.L. . Dept. of Geology)

    1994-04-01

    Shales and siltstones of the Cambro-Ordovician sedimentary rocks of west-central Wisconsin record a complex history of diagenesis. This study examined clays and other minerals within clay-rich layers from fresh surface outcrops of the Cambro-Ordovician sedimentary rocks using XRD and SEM/EDX. Feldspar authigenesis in the base of the Mt. Simon Fm. represents the earliest recorded period of authigenesis. These early formed feldspars ([approximately] 60[mu]M in size) have been completely pseudomorphed by kaolinite. These feldspathization and kaolinization events are limited to the lower 80 feet of the Mt. Simon Fm. Later periods of authigenesis resulted in corrosion of the kaolinite, feldspar authigenesis and illitization with production of I/S ([approximately] 90%I) and minor neoformed filamentous illite throughout the section from the base of the Mt Simon Fm. to at least the Glenwood Fm. In rare instances the filamentous illites have been replaced by kaolinite during a second period of kaolinization. Some of the shales contain abundant authigenic pyrite and at least two generations of authigenic gypsum. Complete dissolution of K-feldspars within some of the samples is evidenced by the presence of small euhedral pits in phosphatic brachiopod shells and suggests that organic acids may have played a role in the diagenesis. The complexity of the authigenic relationships identified in these rocks indicates that they have been subjected to multiple periods of diagenesis with fluids of divergent compositions. This is most readily explained if the rocks behaved as an open system with periodic flushing of K-rich and K-poor fluids.

  11. Geophysical Investigation of Avon Valley, West-Central Montana, using Gravity and Seismic Reflection Profiling

    NASA Astrophysics Data System (ADS)

    Knatterud, L.; Mosolf, J.; Speece, M. A.; Zhou, X.

    2014-12-01

    The Avon Valley and adjacent mountains in west-central Montana lie within the Lewis and Clark Line, a major system of WNW-striking faults and folds that transect the more northerly structural grain of the northern Rockies and represent alternating episodes of transtensional and transpressional deformation. The northwest-trending valley has been previously interpreted as an extensional half graben filled with Tertiary sedimentary and volcanic deposits; however, little-to-no geophysical constraints on basin architecture or the thickness of Tertiary fill have been reported. A major northwest-striking fault with significant normal displacement clearly bounds the valley to the northeast, juxtaposing Tertiary sedimentary deposits against Proterozoic-Mesozoic units deformed by shortening structures and crosscut by Cretaceous granitic intrusions. Tertiary volcanic deposits unconformably overlying faulted and folded Phanerozoic-Proterozoic sequences in the eastern Garnet Range bound the valley to the southwest, but in the past no faults had been mapped along this margin. New mapping by the Montana Bureau of Mines and Geology (MBMG) has identified a system of high-angle, northwest- and northeast-striking, oblique-slip faults along the southwest border of the Avon calling into question if the valley is a half, full, or asymmetrical graben. Geophysical data has recently been acquired by Montana Tech to help define the structural architecture of the Avon Valley and the thickness of its Tertiary fill. Gravity data and a short seismic reflection profile have been collected and a preliminary interpretation of these data indicates a half graben with a series of normal faults bounding the western side of the valley. Ongoing gravity data collection throughout 2014 should refine this interpretation by better defining the bedrock-Tertiary interface at depth.

  12. Seeking new potential in the early-late Permian Gharif Play, West Central Oman

    SciTech Connect

    Guit, F.; Al-Lawati, M.; Nederlof, P.

    1995-08-01

    West Central Oman is a relatively underexplored area where the hydrocarbons found to date occur mainly within the Early-Late Permian Gharif Formation. Structural definition of the low relief closures is hampered by seismic velocity variations caused by dune terrain. Recent exploration activity resulted in several Gharif discoveries, but highlighted reservoir distribution problems. The Gharif Formation, which consists of fluvio-marine sediments, conformably overlies the glacio-lacustine sediments of the Early Permian Al Khlata Formation. It is overlain by shallow marine carbonates of the Late Permian Khuff Formation, the main regional seal. The area is located distally from the main sediment sources to the east. Reservoir development and lateral continuity are seen as the main risk. Most reservoirs are beyond seismic resolution, only the stacked sandstones of the incised valley fills could provide sufficient acoustic contrast to be recognized on seismic. Geochemical typing indicates that the hydrocarbons in the Gharif can be grouped in two main families: the Huqf and Q-hydrocarbons, which are believed to originate from Cambrian to Precambrian source rocks. Although the two hydrocarbon families are sometimes found in one well, they have very different spatial distributions. The Q-oils form continuous strings of accumulations below the main regional seal, whereas the Huqf hydrocarbons occur scattered throughout the area. Mixed accumulations are found where cross-faults or salt domes intercept a Q-oil fairway. Future exploration activities will be guided by refined sedimentological, stratigraphical and hydrocarbon migration models and by the continued efforts to recognize incised valley fills on seismic.

  13. Displacement transfer system linking the Furnace Creek and Walker Lane fault systems, west-central Nevada

    SciTech Connect

    Kohler, G.; Oldow, J.S.; Sisson, V.B.; Donelick, R.A. . Dept. of Geology and Geophysics)

    1993-04-01

    Late Cenozoic (10 Ma to recent) strike-slip displacements on the northwest-striking Walker Lane fault system (WLF) and Furnace Creek fault (FCF) are kinematically linked by east-northeast high-angle and low-angle extensional faults in west-central Nevada. At least 35 km of right-slip is accommodated by the northwest-striking FCF which stretches 250 km from eastern California to its northern terminus in Fish Lake Valley of western Nevada. High-angle fault trajectories at the northern end of the FCF swing easterly forming a broad belt of east-northeast striking faults. The apexes of the curved faults are the locus of greatest extension and correspond to deep, prismatic basins of the Mina deflection. Within the Silver Peak-Lone Mountain extensional complex (SPLM), a widespread detachment fault separates deformed late Miocene clastic and relatively unmetamorphosed lower Paleozoic rocks from an underlying assemblage of amphibolite facies metamorphic tectonites formed during earlier episode of regional deformation. The detachment is warped in northwest domes and basins but when active dipped shallowly to the northwest. Displacement began in the mid-Miocene and continued into the late Miocene to early Pliocene. Fission-track length analysis of apatite from the lower-plate metamorphic rocks indicate cooling through 100--120 C at about 5 Ma. Strike-slip transfer resulted in northwesterly extension on the SPLM. Northwest-trending warps in the SPLM detachment fault formed during transpressional deformation of the transfer zone during northwest-directed simple shear.

  14. Historic impact of watershed change and sedimentation to reefs along west-central Guam

    USGS Publications Warehouse

    Prouty, Nancy G.; Storlazzi, Curt D.; McCutcheon, Amanda L.; Jenson, John W.

    2014-01-01

    Using coral growth parameters (extension, density, calcification rates, and luminescence) and geochemical measurements (barium to calcium rations; Ba/Ca) from coral cores collected in west-central Guam, we provide a historic perspective on sediment input to coral reefs adjacent to the Piti-Asan watershed. The months of August through December are dominated by increased coral Ba/Ca values, corresponding to the rainy season. With river water enriched in barium related to nearshore seawater, coral Ba/Ca ratios are presented as a proxy for input of fine-grained terrigenous sediment to the nearshore environment. The century-long Ba/Ca coral record indicates that the Asan fore reef is within the zone of impact from discharged sediments transported from the Piti-Asan watershed and has experienced increased terrestrial sedimentation since the 1940s. This abrupt shift in sedimentation occurred at the same time as both the sudden denudation of the landscape by military ordinance and the immediate subsequent development of the Asan area through the end of the war, from 1944 through 1945. In response to rapid input of sediment, as determined from coral Ba/Ca values, coral growth rates were reduced for almost two decades, while calcification rates recovered much more quickly. Furthermore, coral luminescence is decoupled from the Ba/Ca record, which is consistent with degradation of soil organic matter through disturbance by forest fires, suggesting a potential index of fire history and degradation of soil organic matter. These patterns were not seen in the cores from nearby reefs associated with watersheds that have not undergone the same degree of landscape denudation. Taken together, these records provide a valuable tool for understanding the compounding effects of land-use change on coral reef health.

  15. Evaluation of methodology for delineation of protection zones around public-supply wells in west-central Florida

    USGS Publications Warehouse

    Vecchioli, John; Hunn, J.D.; Aucott, W.R.

    1989-01-01

    Public-supply wells in the west-central Florida area of Citrus, Hernando, Pasco, Hillsborough, and Pinellas Counties derive their supply solely from the Floridan aquifer system. In much of this area, the Floridan is at or near land surface and vulnerable to contamination. Recognizing this potential threat to the aquifer, the Florida Department of Environmental Regulation (FDER) recently promulgated regulations providing for the delineation of protection zones around public-supply wells that tap vulnerable aquifers, such as the Floridan in west-central Florida. This report evaluates the methodology for delineation of protection zones for public supply wells in west-central Florida in accordance with the methods detailed in the FDER regulations. Protection zones were delineated for public supply wells or well fields that are permitted an average daily withdrawal of 100,000 gal or more from the Floridan aquifer system where it is unconfined or leaky confined. Leaky confined, as used in FDER regulations describe conditions such that the time for a particle of water to travel vertically from the water table to the top of the Floridan is 5 years or less. Protection zones were delineated by using a radial volumetric-displacement model that simulated 5 years of permitted-rate withdrawal. Where zones overlapped, such as for well fields, composite protection zones in shapes that varied according to the configuration of well arrays were delineated on maps. (USGS)

  16. The Swansea Plutonic Suite: Synextensional magmatism in the Buckskin and Rawhide Mountains, west-central Arizona

    SciTech Connect

    Bryant, B.; Nealey, L.D. . Denver Federal Center); Wooden, J.L. )

    1993-04-01

    About 200 km[sup 2] of the crystalline rocks exposed below the Buckskin-Rawhide detachment fault in west-central Arizona consists of gabbro to granite of the 20--30 Ma Swansea Plutonic Suite. Gabbro is only locally mylonitized and is intruded by more felsic rocks of the suite. The felsic rocks have a well-developed mylonitic texture and northeast-trending mineral lineation formed by ductily deformed quartz grains and aggregates. The felsic rocks are generally fine to medium grained except for a distinctive porphyritic phase, in which K-feldspar phenocrysts (now porphyroclasts) are as much as 3 cm in diameter. The suite is calcic to alkali calcic, metaluminous to weakly peraluminous (A/CNK = 0.7--1), and has average Th/U of 4.8 and Rb/Sr of 0.11. It shows a wide range in total rare-earth abundances (REE = 132--393 ppm), light to heavy REE enrichment (chondrite normalized [CN] La/Yb = 3--52), and heavy REE enrichment (CN Yb = 2.6--24.5). Intermediate and silicic members are depleted in HREE compared with mafic members, indicating magmatic control by clinopyroxene with or without amphibole or garnet. The porphyritic phase has the highest total REE and HREE abundances. Lead isotope ratios cluster in tight groups between reference lines for the Mohave and central Arizona crustal provinces. Lead in the porphyritic phase is distinctly less radiogenic than in the other phases. U-Pb zircon age of a granite in the suite is 21 [+-] 1.5 Ma. Upper intercept of the discordia line is 1,420 [+-] 54 Ma, indicating that 1,400-Ma rock dominates the source region for at least the felsic rocks of the suite. The suite was emplaced during the beginning and early phases of crustal extension and was probably pulled southwest out from beneath the Colorado Plateau transition zone as extension progressed. Thus the suite may represent roots of subaerial volcanic centers at the margin of the transition zone, which chemically resemble rocks of the suite in major-element chemistry.

  17. Lu-Hf garnet geochronology of the Salmon River Suture Zone, West-Central Idaho

    NASA Astrophysics Data System (ADS)

    Wilford, D. E.; Vervoort, J. D.; Lewis, R.; Tikoff, B.

    2011-12-01

    The Salmon River Suture Zone (SRSZ) in west-central Idaho records the accretion of island arc terranes to North America. It is modified by the Western Idaho Shear Zone (WISZ), a high strain zone within the SRSZ, which defines the present-day boundary between old continental North America and the accreted oceanic assemblages. Timing of the onset of deformation on the WISZ is not well established, primarily due to a poorly constrained metamorphic history. Existing garnet geochronologic studies of units within the SRSZ, using the Sm-Nd isotope system, have provided a framework towards a progressive accretion of arc-derived rocks to North America [1,2]. In this study, we report on the application of the Lu-Hf isotope system to provide ages of garnet growth within the suture zone. This system has the advantage of being insensitive to light rare earth element (LREE)-rich inclusions in garnet, which can complicate Sm-Nd geochronology. Samples were taken from several locations from both along and perpendicular to the suture zone. We report results on two of these samples, within and east of the WISZ. First, a garnet bearing leucocratic layer in a gneissic meta-sedimentary screen near Cascade, Idaho, yields a garnet age of 98 ± 2.0 Ma (2SD). The screen occurs completely within the orthogneisses of the WISZ, and displays similar fabrics and kinematics. Second, a biotite quartzo-feldspathic garnet gneiss from Elk City, Idaho, yields an age 100 ± 2.9 Ma (2SD). This location is ~35 km east of the WISZ, on a sub-parallel deformation zone that was active at the same time. Both samples were single-stage garnet fractions consisting of inclusion-free to inclusion-bearing fragments and whole rock pairs. These ages provide two important implications for the Mesozoic evolution of the western edge of North America. First, transpressional deformation in the WISZ occurred simultaneously with deformation on parallel structures in central Idaho, indicating that a wide zone of deformation

  18. Serosurvey Reveals Exposure to West Nile Virus in Asymptomatic Horse Populations in Central Spain Prior to Recent Disease Foci.

    PubMed

    Abad-Cobo, A; Llorente, F; Barbero, M Del Carmen; Cruz-López, F; Forés, P; Jiménez-Clavero, M Á

    2016-05-08

    West Nile fever/encephalitis (WNF) is an infectious disease affecting horses, birds and humans, with a cycle involving birds as natural reservoirs and mosquitoes as transmission vectors. It is a notifiable disease, re-emerging in Europe. In Spain, it first appeared in horses in the south (Andalusia) in 2010, where outbreaks occur every year since. However, in 2014, an outbreak was declared in horses in central Spain, approximately 200 km away from the closest foci in Andalusia. Before that, evidence of West Nile virus (WNV) circulation in central Spain had been obtained only from wildlife, but never in horses. The purpose of this work was to perform a serosurvey to retrospectively detect West Nile virus infections in asymptomatic horses in central Spain from 2011 to 2013, that is before the occurrence of the first outbreaks in the area. For that, serum samples from 369 horses, collected between September 2011 and November 2013 in central Spain, were analysed by ELISA (blocking and IgM) and confirmed by virus neutralization, proving its specificity using parallel titration with another flavivirus (Usutu virus). As a result, 10 of 369 horse serum samples analysed gave positive results by competitive ELISA, 5 of which were confirmed as positive to WNV by virus neutralization (seropositivity rate: 1.35%). One of these WNV seropositive samples was IgM-positive. Chronologically, the first positive samples, including the IgM-positive, corresponded to sera collected in 2012 in Madrid province. From these results, we concluded that WNV circulated in asymptomatic equine populations of central Spain at least since 2012, before the first disease outbreak reported in this area.

  19. Floods of November 1978 to March 1979 in Arizona and west-central New Mexico

    USGS Publications Warehouse

    Aldridge, Byron Neil; Hales, T.A.

    1984-01-01

    Severe flooding occurred in parts of the Little Colorado and Gila River basins as a result of a storm that occurred December 17-20, 1978. The central highlands received 3 to 10 inches of precipitation that was augmented by snowmelt to altitudes of 10,000 feet. The storm was preceded by extremely large amounts of rainfall and runoff in November and was followed by other periods of high runoff in January and March 1979. In some areas flood peaks in November, January, or March were higher than the peak of December 1978. At Winslow, the discharge of the Little Colorado River in December 1978 was the highest since at least 1952. The discharge of the Gila River above the San Francisco River was probably the highest since at least 1891, and in the Safford Valley, the peak was the highest since 1916. The Agua Fria River below Waddell Dam had the highest discharge since 1919. The flood of December 1978 caused 12 deaths and caused damage that was probably in excess of $150 million in Arizona and west-central New Mexico. Damage was estimated to be $51.8 million in Maricopa County, Arizona. Floods caused extensive agricultural damage along the Gila River in Virden Valley in New Mexico and in Duncan, York, and Safford Valleys in Arizona. Duncan, Arizona, was flooded with as much as 7 feet of water. The flood crest on the Gila River in December 1978 moved from Redrock, New Mexico, to Duncan, Arizona, in about 6 hours, which is more rapid than during other recent floods but is comparable to the travel-time recorded in 1941. Travel-time in the reach varies with discharge and is about 14 hours for discharges of 10,000 cubic feet per second and 5 hours for discharges of more than 40,000 cubic feet per second. Water-conservation reservoirs on the Gila, Salt, Verde, and Agua Fria Rivers and a flood-control reservoir on the Gila River had a major influence on the magnitude of floods downstream from the reservoirs. All runoff from the Gila River basin upstream from Coolidge Dam, Arizona

  20. Changes in the velocity structure of the Greenland Ice Sheet.

    PubMed

    Rignot, Eric; Kanagaratnam, Pannir

    2006-02-17

    Using satellite radar interferometry observations of Greenland, we detected widespread glacier acceleration below 66 degrees north between 1996 and 2000, which rapidly expanded to 70 degrees north in 2005. Accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year. As more glaciers accelerate farther north, the contribution of Greenland to sea-level rise will continue to increase.

  1. Effective elastic thickness and crustal thickness variations in west central Africa inferred from gravity data

    SciTech Connect

    Poudjom Djomani, Y.H.; Nnange, J.M.; Ebinger, C.J.

    1995-11-10

    This report uses coherence function analysis of 32,000 gravity and topography points from Cameroon west Africa to determine the relationship between the plate tectonic and flexural rigidity of the lithosphere in terms of the crusts effective elastic thickness.

  2. Overwintering of Uranotaenia Unguiculata Adult Females in Central Europe: A Possible Way of Persistence of the Putative New Lineage of West Nile Virus?

    PubMed

    Rudolf, Ivo; Šebesta, Oldřich; Straková, Petra; Betášová, Lenka; Blažejová, Hana; VEnclíková, Kristýna; Seidel, Bernhard; Tóth, Sandor; Hubálek, Zdeněk; Schaffner, Francis

    2015-12-01

    We report the overwintering of Uranotaenia unguiculata adult females in Central Europe (Czech Republic, Hungary, Austria). This finding suggests a potential mode of winter persistence of putative novel lineage of West Nile virus in the temperate regions of Europe.

  3. Detrital zircon evidence for progressive underthrusting in Franciscan metagraywackes, west-central California

    USGS Publications Warehouse

    Snow, C.A.; Wakabayashi, J.; Ernst, W.G.; Wooden, J.L.

    2010-01-01

    central Coast Ranges is a classic accretionary prism, where younger, structurally lower allochthons are exposed on the west, and older, structurally higher allochthons occur to the east, in the heavily studied San Francisco Bay area. ?? 2009 Geological Society of America.

  4. Facies development in the Lower Freeport coal bed, west-central Pennsylvania, U.S.A.

    USGS Publications Warehouse

    Pierce, B.S.; Stanton, R.W.; Eble, C.F.

    1991-01-01

    The Lower Freeport coal bed in west-central Pennsylvania is interpreted to have formed within a lacustrine-mire environment. Conditions of peat formation, caused by the changing chemical and physical environments, produced five coal facies and two mineral-rich parting facies within the coal bed. The coal bed facies are compositionally unique, having developed under varying conditions, and are manifested by megascopic, petrographic, palynologic and quality characteristics. The initial environment of the Lower Freeport peat resulted in a coal facies that is relatively high in ash yield and contains large amounts of lycopod miospores and moderate abundances of cryptotelinite, crypto-gelocollinite, inertinite and tree fern miospores. This initial Lower Freeport peat is interpreted to have been a topogenous body that was low lying, relatively nutrient rich (mesotrophic to eutrophic), and susceptible to ground water and to sediment influx from surface water. The next facies to form was a ubiquitous, clay-rich durain parting which is attributed to a general rise in the water table accompanied by widespread flooding. Following formation of the parting, peat accumulation resumed within an environment that inhibited clastic input. Development of doming in this facies restricted deposition of the upper shale parting to the margins of the mire and allowed low-ash peat to form in the interior of the mire. Because this environment was conducive to preservation of cellular tissue, this coal facies also contains large amounts of crypto-telinite. This facies development is interpreted to have been a transitional phase from topogenous, planar peat formation to slightly domed, oligotrophic (nutrient-poor) peat formation. As domed peat formation continued, fluctuations in the water table enabled oxidation of the peat surface and produced high inertinite concentrations toward the top of the coal bed. Tree ferns became an increasingly important peat contributor in the e upper facies

  5. Surface-Water and Groundwater Interactions along the Withlacoochee River, West-Central Florida

    USGS Publications Warehouse

    Trommer, J.T.; Yobbi, D.K.; McBride, W.S.

    2009-01-01

    A study of the Withlacoochee River watershed in west-central Florida was conducted from October 2003 to March 2007 to gain a better understanding of the hydrology and surface-water and groundwater interactions along the river. The Withlacoochee River originates in the Green Swamp area in north-central Polk County and flows northerly through seven counties, emptying into the Gulf of Mexico. This study includes only the part of the watershed located between the headwaters in the Green Swamp and the U.S. Geological Survey gaging station near Holder, Florida. The Withlacoochee River within the study area is about 108 miles long and drains about 1,820 square miles. The Withlacoochee River watershed is underlain by thick sequences of carbonate rock that are covered by thin surficial deposits of unconsolidated sand and sandy clay. The clay layer is breached in many places because of the karst nature of the underlying limestone, and the degree of confinement between the Upper Florida aquifer and the surficial aquifer is highly variable throughout the watershed. The potential for movement of water from the surface or shallow deposits to deeper deposits, or from deeper deposits to the shallow deposits, exists throughout the Withlacoochee River watershed. Water levels were higher in deeper Upper Floridan aquifer wells than in shallow Upper Floridan aquifer wells or surficial aquifer wells at 11 of 19 paired or nested well sites, indicating potential for discharge to the surface-water system. Water levels were higher in shallow Upper Floridan aquifer or surficial aquifer wells than in deeper Upper Floridan aquifer wells at five other sites, indicating potential for recharge to the deeper Upper Floridan aquifer. Water levels in the surficial aquifer and Upper Floridan aquifer wells at the remaining three sites were virtually the same, indicating little or no confinement at the sites. Potentiometric-surface maps of the Upper Floridan aquifer indicate the pattern of groundwater

  6. Genetic evidence of enzootic leishmaniasis in a stray canine and Texas mouse from sites in west and central Texas

    PubMed Central

    Kipp, Evan J; Mariscal, Jacqueline; Armijos, Rodrigo X; Weigel, Margaret; Waldrup, Kenneth

    2016-01-01

    We detected Leishmania mexicana in skin biopsies taken from a stray canine (Canis familiaris) and Texas mouse (Peromyscus attwateri) at two ecologically disparate sites in west and central Texas using polymerase chain reaction (PCR). A single PCR-positive dog was identified from a sample of 96 stray canines and was collected in a peri-urban area in El Paso County, Texas. The PCR-positive P. attwateri was trapped at a wildlife reserve in Mason County, Texas, from a convenience sample of 20 sylvatic mammals of different species. To our knowledge, this represents the first description of L. mexicana in west Texas and extends the known geographic range of the parasite to an area that includes the arid Chihuahuan Desert. Our finding of L. mexicana in P. attwateri represents a new host record and is the first description of the parasite in a wild peromyscid rodent in the United States. PMID:27759765

  7. Geologic Map of the Denver West 30' x 60' Quadrangle, North-Central Colorado

    USGS Publications Warehouse

    Kellogg, Karl S.; Shroba, Ralph R.; Bryant, Bruce; Premo, Wayne R.

    2008-01-01

    The Denver West quadrangle extends east-west across the entire axis of the Front Range, one of numerous uplifts in the Rocky Mountain region in which Precambrian rocks are exposed. The history of the basement rocks in the Denver West quadrangle is as old as 1,790 Ma. Along the east side of the range, a sequence of sedimentary rocks as old as Pennsylvanian, but dominated by Cretaceous-age rocks, overlies these ancient basement rocks and was upturned and locally faulted during Laramide (Late Cretaceous to early Tertiary) uplift of the range. The increasingly coarser grained sediments up section in rocks of latest Cretaceous to early Tertiary age record in remarkable detail this Laramide period of mountain building. On the west side of the range, a major Laramide fault (Williams Range thrust) places Precambrian rocks over Cretaceous sedimentary rocks. The geologic history of the quadrangle, therefore, can be divided into four major periods: (1) Proterozoic history, (2) Pennsylvanian to pre-Laramide, Late Cretaceous history, (3) Late Cretaceous to early Tertiary Laramide mountain building, and (4) post-Laramide history. In particular, the Quaternary history of the Denver West quadrangle is described in detail, based largely on extensive new mapping.

  8. New and revisited paleomagnetic data from Permian-Triassic red beds: Two kinematic domains in the west-central Pyrenees

    NASA Astrophysics Data System (ADS)

    Oliva-Urcia, Belén; Pueyo, Emilio L.; Larrasoaña, Juan Cruz; Casas, Antonio M.; Román-Berdiel, Teresa; Van der Voo, Rob; Scholger, Robert

    2012-02-01

    New paleomagnetic results of Permian-Triassic red beds from Bielsa, Aure and Somport-Anayet sectors in the Pyrenean Axial Zone are presented and combined with revisited and reviewed paleomagnetic data from the west-central Pyrenees. The paleomagnetic data from the red beds vary between different sectors that share similar structural position; i.e. whilst all sectors share the existence of a characteristic prefolding component, a Cenozoic postfolding component is found only in one area but not in other areas with similar structural position and kinematics. Previous paleomagnetic data to the west of the studied zone reveal a pre-Turonian remagnetization component, but this secondary component is not found in an area that shares a similar structural position (Aure). This variability suggests that the paleomagnetic behavior is the result of a series of factors related to the particular tectonic history of the region (sedimentation, burial, and deformation during basin inversion) and therefore paleomagnetic data demands careful assessment in order to unravel the kinematics of areas with equivalent structural positions in orogens. However, important kinematic implications that hold in the Pyrenees can be inferred from the restoration of the Permian-Triassic characteristic magnetizations to positions previous to the paleomagnetic rotations recorded by Cretaceous or Cenozoic paleomagnetic data. The restoration reveals on one hand the lack of large rotations in the South Pyrenenan Zone except in the Nogueras area, according to Bates (1989), and on the other hand, the contrasting rotations recorded to the west of the studied zone, in the Paleozoic Basque Massifs (PBM) and the South-Pyrenean Zone, indicating the existence of two different tectonic domains in the west-central sector of the Pyrenees. The strong clockwise rotations postdating the Early Cretaceous remagnetization that are recorded in the PBM and in the North Pyreneean Zone, suggest a late dextral shear

  9. Forest pricing and concession policies: Managing the high forest of west and central Africa. World Bank technical paper; Politique de redevances et de concessions forestieres: gestion des futaies en afrique occidentale et centrale

    SciTech Connect

    Grut, M.; Gray, J.A.; Egli, N.

    1993-12-01

    This French edition describes forest revenue systems and concession policies in the tropical moist hardwood forests of West and Central Africa. The paper reviews current issues in silviculture, tenure, concession management, and biological and financial sustainable development. Until the fledgling forestry departments of governments in West and Central Africa are strengthened, the report concludes that a simple system of forest fees should be implemented. The report recommends that such a system emphasize bidding and concession fees.

  10. First record of Taenia ovis krabbei muscle cysts in muskoxen from Greenland.

    PubMed

    Raundrup, Katrine; Al-Sabi, Mohammad Nafi Solaiman; Kapel, Christian Moliin Outzen

    2012-03-23

    A first record of Taenia ovis krabbei muscle cysts in a muskoxen (Ovibos moschatus) from the Kangerlussuaq population in West Greenland suggests that introduced muskoxen now contributes to the transmission of this parasite in addition to previous observations from caribou (Rangifer tarandus). Muskoxen and caribou are the only wild ungulates in Greenland.

  11. Mineralization in the Uyaijah-Thaaban area, west-central part of the Uyaijah ring structure, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Dodge, F.C.; Helaby, A.M.

    1975-01-01

    Anomalous amounts of tungsten, molybdenum, and bismuth were found previously in surficial debris collected from the Uyaijah-Thaaban area in the west-central part of the Precambrian Al Uyaijah ring structure. The area is mostly underlain by quartz monzonite. Countless quartz veins ranging from a knife edge to more than 3 m in thickness cut the quartz monzonite; many of these veins contain molybdenite. Detailed mapping and intensive sampling of the molybdenite-bearing quartz veins indicate that their grade and quantity are probably inadequate to permit present-day mining; however, they represent a potential future resource. The tungsten of the area appears to be negligible.

  12. Paleomagnetic and structural evidence for middle Tertiary counterclockwise block rotation in the Dixie Valley region, west-central Nevada

    SciTech Connect

    Hudson, M.R.; Geissman, J.W.

    1987-07-01

    Paleomagnetic data from late Oligocene to early Miocene ash-flow tuffs at four localities in the northern Dixie Valley region, west-central Nevada, indicate that parts of the crust have rotated counterclockwise by at least 25/sup 0/ and perhaps significantly more in late Cenozoic time. Field relations in White Rock Canyon, Stillwater Range, suggest that rotation (1) was accommodated by right-lateral slip on northwest-trending faults, (2) spanned ash-flow tuff emplacement, and (3) probably ceased before eruption of overlying middle Miocene basalts. Accurate estimates of Cenozoic extension, as well as evaluation of earlier Mesozoic structures, must include the strain partitioned into rotation in the area.

  13. West Nile virus epizootiology, central Red River Valley, North Dakota and Minnesota, 2002-2005.

    PubMed

    Bell, Jeffrey A; Brewer, Christina M; Mickelson, Nathan J; Garman, Gabriel W; Vaughan, Jefferson A

    2006-08-01

    West Nile virus (WNV) epizootiology was monitored from 2002 through 2005 in the area surrounding Grand Forks, North Dakota. Mosquitoes were tested for infection, and birds were surveyed for antibodies. In 2003, WNV was epidemic; in 2004, cool temperatures precluded WNV amplification; and in 2005, immunity in passerines decreased, but did not preclude, WNV amplification.

  14. West Nile Virus Epizootiology, Central Red River Valley, North Dakota and Minnesota, 2002–2005

    PubMed Central

    Bell, Jeffrey A.; Brewer, Christina M.; Mickelson, Nathan J.; Garman, Gabriel W.

    2006-01-01

    West Nile virus (WNV) epizootiology was monitored from 2002 through 2005 in the area surrounding Grand Forks, North Dakota. Mosquitoes were tested for infection, and birds were surveyed for antibodies. In 2003, WNV was epidemic; in 2004, cool temperatures precluded WNV amplification; and in 2005, immunity in passerines decreased, but did not preclude, WNV amplification. PMID:16965705

  15. Geology of the Northern Part of the Harcuvar Complex, West-Central Arizona

    USGS Publications Warehouse

    Bryant, Bruce; Wooden, J.L.

    2008-01-01

    In west-central Arizona near the northeast margin of the Basin and Range Province, the Rawhide detachment fault separates Tertiary and older rocks lacking significant effects of Tertiary metamorphism from Precambrian, Paleozoic, and Mesozoic rocks in the Harcuvar metamorphic core complex below. Much of the northern part of the Harcuvar complex in the Buckskin and eastern Harcuvar Mountains is layered granitic gneiss, biotite gneiss, amphibolite, and minor pelitic schist that was probably deformed and metamorphosed in Early Proterozoic time. In the eastern Buckskin Mountains, Early and Middle Proterozoic plutons having U-Pb zircon ages of 1,683?6.4 mega-annum (Ma) and 1,388?2.3 Ma, respectively, intruded the layered gneiss. Small plutons of alkaline gabbro and diorite intruded in Late Jurassic time. A sample of mylonitized diorite from this unit has a U-Pb zircon age of 149?2.8 Ma. In the Early Cretaceous, amphibolite facies regional metamorphism was accompanied by partial melting and formation of migmatite. Zircon from a granitic layer in migmatitic gneiss in the eastern Harcuvar Mountains has a U-Pb age of 110?3.7 Ma. In the Late Cretaceous, sills and plutons of the granite of Tank Pass were emplaced in both the Buckskin and eastern Harcuvar Mountains. In the Buckskin Mountains those intrusions are locally numerous enough to form an injection migmatite. A pluton of this granite crops out over almost half the area of the eastern Harcuvar Mountains. Paleozoic and Mesozoic sedimentary rocks were caught as slices along south-vergent Cretaceous thrusts related to the Maria fold and thrust belt and were metamorphosed beneath a thick sheet of Proterozoic crustal rocks. Inception of volcanism and basin formation in upper-plate rocks indicates that regional extension started at about 26 Ma, in late Oligocene. The Swansea Plutonic Suite, composed of rocks ranging from gabbro to granite, intruded the lower-plate rocks in the Miocene and Oligocene(?). Granite and a gabbro

  16. Hydrologic description of the Braden River watershed, west-central Florida

    USGS Publications Warehouse

    DelCharco, M.J.; Lewelling, B.R.

    1997-01-01

    The Braden River watershed drains an 83-square mile area in west-central Florida and is the largest tributary to the Manatee River. The hydrology of the Braden River was altered in 1936 when the city of Bradenton created Ward Lake, a reservoir with an 838-foot broad-crested weir 6 miles upstream from the mouth. In 1985 the reservoir, which is the sole source of drinking water for the city of Bradenton, was expanded and supplies an annual average of 5.7 million gallons of water per day. The Braden River can be hydrologically divided into three distinct sections that include an 8.6-mile reach of naturally incised, free-flowing channel; a 6.4-mile reach of impounded river created by the Ward Lake reservoir and weir; and a 6-mile reach of tidal estuary. Ten first-order and two second-order tributaries that flow into the Braden River were examined in this report. The Braden River watershed is dominated by low topographic relief. The two physiographic zones that contain the Braden River watershed, the Gulf Coast Lowlands and De Soto Plain, are both poorly drained and have numerous depressional features. The climate is subtropical with an annual average rainfall of 56 inches, annual average temperatures of 72 degrees Fahrenheit, and estimated annual lake evaporation of 52 inches. The soil series in the watershed are predominantly Myakka-Cassia and the EauGallie-Floridana; these series are characterized as nearly level and poorly drained soils. Land use within the watershed is the fastest changing characteristic that affects the hydrology of the system. The western half of the watershed is typically urban and includes parts of the city of Bradenton. Land use in the eastern half of the watershed is predominantly agricultural, but the explosive population growth of the area is driving the development of medium to high-density residential communities. The three major aquifers underlying the Braden River watershed are the surficial, intermediate, and Floridan aquifer systems

  17. The Origin of Andesite in the Deep Crust: Evidence from the West-Central Mexican Arc

    NASA Astrophysics Data System (ADS)

    Lange, R. A.; Ownby, S.; Delgado Granados, H.; Hall, C. M.

    2011-12-01

    Although it has long been recognized that andesite is one of the most common magma types erupted at subduction zones and is relatively rare at other tectonic settings, there continues to be a confusing array of different models to explain both its origin and its unique abundance at convergent margins. End-member processes that are most frequently invoked include: (1) crystal fractionation of hydrous basalt (in the upper, middle, and/or lower crust); (2) partial melting of hydrated, mafic lower crust; (3) magma mixing of basalt with rhyolite/dacite; and (4) assimilation of granitoid upper crust by basalt/basaltic andesite. In this study, we test the relative importance of the four end-member differentiation mechanisms to form andesite by examining a segment of the west-central Mexican arc (Michoacán-Guanajuato), which spans ~200 km of arc length and is notable for the scarcity of Quaternary dacite and rhyolite, despite a crustal thickness of ~40-45 km. This arc segment is further remarkable for the relative scarcity of large volcanoes and is instead characterized by >380 small shields (median: <2 km3) and >1000 monogenetic cones and flows. We focused our study on the Tancítaro-Nueva Italia region (~4400 km2), which spans ~80 km of arc length along the volcanic front. On the basis of 65 40Ar/39Ar ages, mapping, and ArcGIS tools, we show that ~326 ± 57 km3 of magma has erupted from > 200 vents since 1.2 Ma. The total proportions of erupted lava types are 6-7% basalt, ~18% basaltic andesite, and ~74-76% andesite. One of the most striking features of this volcanic field is the phenocryst-poor character of lavas erupted from peripheral vents (1-25% crystals) compared to those erupted from the main vent, Volcán Tancítaro (30-45% crystals). Another key observation is that the bulk composition of the crystal-rich andesites are very similar to the most crystal-poor (<5%) andesites, which leads to two conclusions: (1) andesite occurs as a liquid composition, as evidenced

  18. Late Mississippian gastropods of the Chainman Shale, west-central Utah

    USGS Publications Warehouse

    Gordon, Mackenzie; Yochelson, Ellis L.

    1987-01-01

    The Chainman Shale of Mississippian (Osagean to late Chesterian) age, well exposed in the Confusion Range of western Utah, has yielded a profusion of fossils during investigations conducted by the U.S. Geological Survey in the past 30 years. Conspicuous among these fossils are gastropods, which range in age from latest Meramecian to late Chesterian. In west-central Utah, not far from the State boundary, the Chainman outcrop belt stretches from Granite Mountain south to the northern part of the Needle Range, a distance of69 miles (110 km). The Chainman thickens from north to south; the section at Granite Mountain is 1,315 feet (401 m) thick and that at Jensen Wash in the Burbank Hills, 2,203 feet (671 m). The rocks of the Chainman Shale record a general though irregular shallowing of the area from moderate depths of 330 feet (100 m) or so to quite shallow depths of perhaps locally little more than 3-6 feet (1-2 m). Most of the gastropods occur with ammonoids in a facies of shale or shale containing phosphatic limestone concretions, In this lutaceous facies, Glabrocingulum is predominant and Lunulazona and Retispira are common; these genera are represented by a succession of species. A thick limestone unit is present in some areas in the upper part of the formation, particularly in the vicinity of Skunk Spring, where it is 318 feet (97 m) thick. This limestone unit represents a calcareous shoal facies having an entirely different gastropod fauna, characterized by Catazona and species of Naticopsis. The Chainman Shale could be easily zoned by gastropods, but we are not proposing such azonation. A framework of ammonoid and foraminiferal zones already is available, and we prefer to regard the gastropod assemblages as part of this framework. The assemblages are confined to the major ammonoid and foraminiferal zones, and only three of the gastropod species seem to range across major zonal boundaries. These species are Bellerophon (Bellerophon vespertinus Gordon and

  19. Regression Analysis of Stage Variability for West-Central Florida Lakes

    USGS Publications Warehouse

    Sacks, Laura A.; Ellison, Donald L.; Swancar, Amy

    2008-01-01

    -water exchange in controlling the stage of karst lakes in Florida. Regression equations were used to predict lake-stage variability for the recent period for 12 additional lakes, and the median difference between predicted and observed values ranged from 11 to 23 percent. Coefficients of determination for the historical period were considerably lower (maximum R2 of 0.28) than for the recent period. Reasons for these low R2 values are probably related to the small number of lakes (20) with stage data for an equivalent time period that were unaffected by ground-water pumping, the similarity of many of the lake types (large surface-water drainage lakes), and the greater uncertainty in defining historical basin characteristics. The lack of lake-stage data unaffected by ground-water pumping and the poor regression results obtained for that group of lakes limit the ability to predict natural lake-stage variability using this method in west-central Florida.

  20. Tectonic inversion in the Wandel Sea Basin: A new structural model of Kilen (eastern North Greenland)

    NASA Astrophysics Data System (ADS)

    Svennevig, Kristian; Guarnieri, Pierpaolo; Stemmerik, Lars

    2016-12-01

    The seminunatak Kilen in eastern North Greenland, with its complexly deformed Carboniferous-Cretaceous strata, is a key area to understand the tectonic history of the transform plate boundary between eastern North Greenland and Svalbard. Detailed 3-D geological mapping from oblique photogrammetry along with limited ground fieldwork and interpretation of previously published data forms the basis for a new structural model of Kilen. Previous structural models interpreted rhombic-shaped fault patterns as the evidence for strike-slip tectonics. These structures are here interpreted to be the result of a post-Coniacian NE-SW extension with NW-SE trending normal faults followed by later, N-S compression of presumable Paleocene-Eocene age, folding the faults passively and suggesting the presence of a basal detachment. Furthermore, two thrust sheets have been distinguished on Kilen: a lower Kilen Thrust Sheet and an upper Hondal Elv Thrust Sheet separated by a subhorizontal fault: the Central Detachment. The style of deformation and the structures described are interpreted as the result of Paleocene-Eocene N-S directed compression resulting in basin inversion with strike-slip faults only having minor status. This indicates that the Greenland margin as exposed on Kilen and the conjugate Svalbard margin in the West Spitsbergen fold-and-thrust belt are more similar than previously anticipated.

  1. A synthesis of the basal thermal state of the Greenland Ice Sheet

    USGS Publications Warehouse

    MacGregor, Joseph A; Fahnestock, Mark A; Catania, Ginny A; Aschwanden, Andy; Clow, Gary D.; Colgan, William T.; Gogineni, Prasad S.; Morlighem, Mathieu; Nowicki, Sophie M .J.; Paden, John D; Price, Stephen F.; Seroussi, Helene

    2016-01-01

    The basal thermal state of an ice sheet (frozen or thawed) is an important control upon its evolution, dynamics and response to external forcings. However, this state can only be observed directly within sparse boreholes or inferred conclusively from the presence of subglacial lakes. Here we synthesize spatially extensive inferences of the basal thermal state of the Greenland Ice Sheet to better constrain this state. Existing inferences include outputs from the eight thermomechanical ice-flow models included in the SeaRISE effort. New remote-sensing inferences of the basal thermal state are derived from Holocene radiostratigraphy, modern surface velocity and MODIS imagery. Both thermomechanical modeling and remote inferences generally agree that the Northeast Greenland Ice Stream and large portions of the southwestern ice-drainage systems are thawed at the bed, whereas the bed beneath the central ice divides, particularly their west-facing slopes, is frozen. Elsewhere, there is poor agreement regarding the basal thermal state. Both models and remote inferences rarely represent the borehole-observed basal thermal state accurately near NorthGRIP and DYE-3. This synthesis identifies a large portion of the Greenland Ice Sheet (about one third by area) where additional observations would most improve knowledge of its overall basal thermal state.

  2. A synthesis of the basal thermal state of the Greenland Ice Sheet.

    PubMed

    MacGregor, Joseph A; Fahnestock, Mark A; Catania, Ginny A; Aschwanden, Andy; Clow, Gary D; Colgan, William T; Gogineni, S Prasad; Morlighem, Mathieu; Nowicki, Sophie M J; Paden, John D; Price, Stephen F; Seroussi, Hélène

    2016-08-10

    The basal thermal state of an ice sheet (frozen or thawed) is an important control upon its evolution, dynamics and response to external forcings. However, this state can only be observed directly within sparse boreholes or inferred conclusively from the presence of subglacial lakes. Here we synthesize spatially extensive inferences of the basal thermal state of the Greenland Ice Sheet to better constrain this state. Existing inferences include outputs from the eight thermomechanical ice-flow models included in the SeaRISE effort. New remote-sensing inferences of the basal thermal state are derived from Holocene radiostratigraphy, modern surface velocity and MODIS imagery. Both thermomechanical modeling and remote inferences generally agree that the Northeast Greenland Ice Stream and large portions of the southwestern ice-drainage systems are thawed at the bed, whereas the bed beneath the central ice divides, particularly their west-facing slopes, is frozen. Elsewhere, there is poor agreement regarding the basal thermal state. Both models and remote inferences rarely represent the borehole-observed basal thermal state accurately near NorthGRIP and DYE-3. This synthesis identifies a large portion of the Greenland Ice Sheet (about one third by area) where additional observations would most improve knowledge of its overall basal thermal state.

  3. Mitochondrial DNA variability in Giraffa camelopardalis: consequences for taxonomy, phylogeography and conservation of giraffes in West and central Africa.

    PubMed

    Hassanin, Alexandre; Ropiquet, Anne; Gourmand, Anne-Laure; Chardonnet, Bertrand; Rigoulet, Jacques

    2007-03-01

    The giraffe (Giraffa camelopardalis) still survives in four countries of West and central Africa. The populations of Niger and Cameroon are generally assigned to the subspecies peralta, but those of Chad and the Central African Republic are taxonomically problematic, as they are referred to as either peralta, or antiquorum, or congoensis. In this study, a mitochondrial fragment of 1765 nucleotide sites, covering the complete cytochrome b gene, three transfer RNAs and a large part of the control region, was sequenced to assess the relationships between several populations of giraffe. The phylogenetic analyses performed on the 12 identified haplotypes indicate that northern giraffes constitute a natural group, distinct from that of southern giraffes. Surprisingly, the giraffes of Niger are found to be more closely related to the giraffes of East Africa (subspecies rothschildi and reticulata) than to those of central Africa. We conclude therefore that the subspecies peralta contains only the Niger giraffes, whereas the subspecies antiquorum includes all populations living in Cameroon, Chad, the Central African Republic, and southwestern Sudan. We suggest that the ancestor of the Nigerian giraffe dispersed from East to North Africa during the Quaternary period and thereafter migrated to its current Sahelian distribution in West Africa, in response to the development of the Sahara desert. This hypothesis implies that Lake Mega-Chad acted as a strong geographical barrier during the Holocene, preventing any contact between the subspecies peralta and antiquorum. Our study has direct implications for conservation management, as we show that no subspecies peralta is represented in any European zoos, only in Niger, with a small population of less than 200 individuals.

  4. Retrospective seasonal prediction of summer monsoon rainfall over West Central and Peninsular India in the past 142 years

    NASA Astrophysics Data System (ADS)

    Li, Juan; Wang, Bin; Yang, Young-Min

    2016-06-01

    Prediction of Indian summer (June-September) rainfall on regional scales remains an open issue. The operational predictions of West Central Indian summer rainfall (WCI-R) and Peninsular Indian summer rainfall (PI-R) made by the Indian Meteorological Department (IMD) had no skills during 2004-2012. This motivates the present study aiming at better understanding the predictability sources and physical processes governing summer rainfall variability over these two regions. Analysis of 133 year data reveal that although the lower boundary forcing that associated with enhanced WCI-R and PI-R featured a similar developing La-Nina and "east high west low" sea-level pressure (SLP) dipole pattern across the Indo-Pacific, the anomalous high sea surface temperature (SST) over the northern Indian Ocean and weak low pressure over northern Asia tended to enhance PI-R but reduce WCI-R. Based on our understanding of physical linkages with the predictands, we selected four and two causative predictors for predictions of the WCI-R and PI-R, respectively. The intensified summer WCI-R is preceded by (a) Indian Ocean zonal dipole-like SST tendency (west-warming and east-cooling), (b) tropical Pacific zonal dipole SST tendency (west-warming and east-cooling), (c) central Pacific meridional dipole SST tendency (north-cooling and south-warming), and (d) decreasing SLP tendency over northern Asia in the previous season. The enhanced PI-R was lead by the central-eastern Pacific cooling and 2-m temperature cooling tendency east of Lake Balkhash in the previous seasons. These causative processes linking the predictors and WCI-R and PI-R are supported by ensemble numerical experiments using a coupled climate model. For the period of 1871-2012, the physics-based empirical (P-E) prediction models built on these predictors result in cross-validated forecast temporal correlation coefficient skills of 0.55 and 0.47 for WCI-R and PI-R, respectively. The independent forecast skill is significantly

  5. Analysis of variables affecting unemployment rate and detecting for cluster in West Java, Central Java, and East Java in 2012

    NASA Astrophysics Data System (ADS)

    Samuel, Putra A.; Widyaningsih, Yekti; Lestari, Dian

    2016-02-01

    The objective of this study is modeling the Unemployment Rate (UR) in West Java, Central Java, and East Java, with rate of disease, infant mortality rate, educational level, population size, proportion of married people, and GDRP as the explanatory variables. Spatial factors are also considered in the modeling since the closer the distance, the higher the correlation. This study uses the secondary data from BPS (Badan Pusat Statistik). The data will be analyzed using Moran I test, to obtain the information about spatial dependence, and using Spatial Autoregressive modeling to obtain the information, which variables are significant affecting UR and how great the influence of the spatial factors. The result is, variables proportion of married people, rate of disease, and population size are related significantly to UR. In all three regions, the Hotspot of unemployed will also be detected districts/cities using Spatial Scan Statistics Method. The results are 22 districts/cities as a regional group with the highest unemployed (Most likely cluster) in the study area; 2 districts/cities as a regional group with the highest unemployed in West Java; 1 district/city as a regional groups with the highest unemployed in Central Java; 15 districts/cities as a regional group with the highest unemployed in East Java.

  6. Application of ground-penetrating radar methods in determining hydrogeologic conditions in a karst area, west-central Florida

    USGS Publications Warehouse

    Barr, G.L.

    1993-01-01

    Ground-penetrating radar (GPR) is useful as a surface geophysical method for exploring geology and subsurface features in karst settings. Interpretation of GPR data was used to infer lithology and hydrogeologic conditions in west-central Florida. This study demonstrates how GPR methods can be used to investigate the hydrogeology of an area. GPR transmits radio- frequency electromagnetic waves into the ground and receives reflected energy waves from subsurface interfaces. Subsurface profiles showing sediment thickness, depth to water table and clay beds, karst development, buried objects, and lake-bottom structure were produced from GPR traverses obtained during December 1987 and March 1990 in Pinellas, Hillsborough, and Hardee Counties in west-central Florida. Performance of the GPR method is site specific, and data collected are principally affected by the sediment and pore fluids, conductances and dielectric constants. Effective exploration depths of the GPR surveys through predominately unsaturated and saturated sand and clay sediments at five study sites ranged from a few feet to greater than 50 feet below land surface. Exploration depths were limited when high conductivity clay was encountered, whereas greater exploration depths were possible in material composed of sand. Application of GPR is useful in profiling subsurface conditions, but proper interpretation depends upon the user's knowledge of the equipment and the local hydrogeological setting, as well as the ability to interpret the graphic profile.

  7. Association analysis of photoperiodic flowering time genes in west and central African sorghum [Sorghum bicolor (L.) Moench

    PubMed Central

    2012-01-01

    Background Photoperiod-sensitive flowering is a key adaptive trait for sorghum (Sorghum bicolor) in West and Central Africa. In this study we performed an association analysis to investigate the effect of polymorphisms within the genes putatively related to variation in flowering time on photoperiod-sensitive flowering in sorghum. For this purpose a genetically characterized panel of 219 sorghum accessions from West and Central Africa was evaluated for their photoperiod response index (PRI) based on two sowing dates under field conditions. Results Sorghum accessions used in our study were genotyped for single nucleotide polymorphisms (SNPs) in six genes putatively involved in the photoperiodic control of flowering time. Applying a mixed model approach and previously-determined population structure parameters to these candidate genes, we found significant associations between several SNPs with PRI for the genes CRYPTOCHROME 1 (CRY1-b1) and GIGANTEA (GI). Conclusions The negative values of Tajima's D, found for the genes of our study, suggested that purifying selection has acted on genes involved in photoperiodic control of flowering time in sorghum. The SNP markers of our study that showed significant associations with PRI can be used to create functional markers to serve as important tools for marker-assisted selection of photoperiod-sensitive cultivars in sorghum. PMID:22394582

  8. Factors associated with the occurrence of Triatoma sordida (Hemiptera: Reduviidae) in rural localities of Central-West Brazil

    PubMed Central

    Rossi, Juliana Chedid Nogared; Duarte, Elisabeth C; Gurgel-Gonçalves, Rodrigo

    2015-01-01

    This study estimates the factors of artificial environments (houses and peridomestic areas) associated with Triatoma sordida occurrence. Manual searches for triatomines were performed in 136 domiciliary units (DUs) in two rural localities of Central-West Brazil. For each DU, 32 structural, 23 biotic and 28 management variables were obtained. Multiple logistic regression analysis was performed in order to identify statistically significant variables associated with occurrence of T. sordida in the study areas. A total of 1,057 specimens (99% in peridomiciles, mainly chicken coops) of T. sordida were collected from 63 DUs (infestation: 47%; density: ~8 specimens/DU; crowding: ~17 specimens/infested DU; colonisation: 81%). Only six (0.6%) out of 945 specimens examined were infected with Trypanosoma cruzi. The final adjusted logistic regression model indicated that the probability of T. sordida occurrence was higher in DU with wooden chicken coops, presence of > 30 animals in wooden corrals, presence of wood piles and presence of food storeroom. The results show the persistence of T. sordida in peridomestic habitats in rural localities of Central-West Brazil. However, the observed low intradomestic colonisation and minimal triatomine infection rates indicate that T. sordida has low potential to sustain high rates of T. cruzi transmission to residents of these localities. PMID:25946242

  9. Depositional environments and sequence architecture of the Raha and Abu Qada formations (Cenomanian-Turonian), west central Sinai, Egypt

    NASA Astrophysics Data System (ADS)

    Anan, Tarek I.; El-Shahat, Adam; Genedi, Adel; Grammer, Michael

    2013-06-01

    Cenomanian-Turonian deposits are important reservoirs for many oil fields in the Western Desert and the Gulf of Suez region of Egypt. Study of the Raha and Abu Qada formations (Cenomanian-Turonian), from five dip-oriented outcrop locations in west central Sinai; indicates deposition of a mixed siliciclastic-carbonate system on a ramp setting. The inner ramp facies (bivalve and benthonic foraminiferal wackestone) grades northward to the mid ramp facies (echinoderm calcisphere packstone, and oyster floatstone), and outer ramp facies (planktonic foraminiferal wackestone and calcisphere wackestone). The two studied formations comprise one second-order depositional sequence (duration of approximately 10 Million years). This large scale sequence includes four third-order depositional sequences, three of which are observed in the Raha Formation, with the other one recorded in the Abu Qada Formation. Because west central Sinai was tectonically stable during the Cenomanian and Turonian, the main factor controlling the lateral and vertical distribution of facies tracts is likely due to changes in the relative sea level. The Cenomanian-Turonian boundary event is known as the largest oceanic anoxic event during the Cretaceous. This global event has been documented in three of the studied sections. The recorded δ13C excursions range from +3.04‰ to +5.24‰. These high positive excursions in δ13C are associated with highly negative values of δ18O (values range from -6.01‰ to -1.38‰).

  10. Application of a cave inventory system to stimulate development of management strategies: the case of west-central Florida, USA.

    PubMed

    Harley, Grant L; Polk, Jason S; North, Leslie A; Reeder, Philip P

    2011-10-01

    The active management of air-filled cave systems is virtually non-existent within the karst landscape of west-central Florida. As in every karst landscape, caves are important because they contain a wide variety of resources (e.g., biota, speleothems) and can act as direct connections between surface and subsurface hydrological processes, potentially exacerbating the pollution of groundwater. Before sound management policies can be drafted, implemented, and enforced, stakeholders must first have knowledge of the management requirements of each cave. However, there is an informational disconnect between researchers, stakeholders, and the recreational caving community. Here, we present a cave inventory system that simplifies the dissemination of resource knowledge to stakeholders so that cave management and protection policies can be drafted and implemented at the state and local level. We inventoried 36 caves in west-central Florida, located on both public and private land, and analyzed cave resource data to provide insights on cave sensitivity and disturbance using two standardized indices. The data revealed that both public and private caves exhibit a wide range of sensitivity and disturbance, and before management strategies can be drafted, the ownership of each cave must be considered. Our inventory geodatabase serves as a link between researchers, landowners, and the public. To ensure the conservation and protection of caves, support from county or state government, combined with cave inventory data, is crucial in developing sound management policy.

  11. Changes in Intense Precipitation Events in West Africa and the central U.S. under Global Warming

    SciTech Connect

    Cook, Kerry H.; Vizy, Edward

    2016-02-08

    The purpose of the proposed project is to improve our understanding of the physical processes and large-scale connectivity of changes in intense precipitation events (high rainfall rates) under global warming in West Africa and the central U.S., including relationships with low-frequency modes of variability. This is in response to the requested subject area #2 “simulation of climate extremes under a changing climate … to better quantify the frequency, duration, and intensity of extreme events under climate change and elucidate the role of low frequency climate variability in modulating extremes.” We will use a regional climate model and emphasize an understanding of the physical processes that lead to an intensification of rainfall. The project objectives are as follows: 1. Understand the processes responsible for simulated changes in warm-season rainfall intensity and frequency over West Africa and the Central U.S. associated with greenhouse gas-induced global warming 2. Understand the relationship between changes in warm-season rainfall intensity and frequency, which generally occur on regional space scales, and the larger-scale global warming signal by considering modifications of low-frequency modes of variability. 3. Relate changes simulated on regional space scales to global-scale theories of how and why atmospheric moisture levels and rainfall should change as climate warms.

  12. Percentage change in saturated thickness of the High Plains aquifer, west-central Kansas, 1950 to average 1985-87

    USGS Publications Warehouse

    Dague, Barbara J.

    1987-01-01

    Continuing studies are being made in west-central Kansas to provide up-to-date information that will aid in the management of groundwater for irrigation. This report presents the results of the seventh in a series of studies that uses a statistical technique, called kriging, to produce hydrologic maps. The kriging technique interpolates water-level altitudes at the center of each 1-square-mile section in the study area on the basis of water-level measurements from 164 observation wells. These interpolated altitudes (1859 in all), along with bedrock-surface and base-year water-level altitudes were used to prepare a hydrologic map that illustrates percentage change in saturated thickness. Saturated thickness, as used in this report , is the thickness of the High Plains Aquifer between the groundwater surface, as indicated by water-level altitudes, and the bedrock surface. Because irrigation development in west-central Kansas was minimal prior to 1950, the saturated thickness during 1950 represented a nearly static condition in the aquifer. Thus, the decrease in saturated thickness of the aquifer since 1950 is related to the effects of irrigation withdrawals on the volume of water in storage. In general, percentage change in saturated thickness indicates the degree of stress on the aquifer in most areas resulting from irrigation pumpage. (Shidler-PTT)

  13. Percentage change in saturated thickness of the High Plains aquifer, west-central Kansas, 1950 to average 1983-85

    USGS Publications Warehouse

    Dague, Barbara J.

    1985-01-01

    Continuing studies are being made in west-central Kansas to provide up-to-date information to aid in the management of groundwater for irrigation. This report presents the fifth in a series of studies that uses a statistical technique, called kriging, to produce hydrologic maps that are used as management tools. Kriging is a statistical technique that was used to interpolate water level altitudes at the center of each 1 sq mi section in the study area based on measured water levels at 165 observation wells. These interpolation altitudes (1,859 in all), along with bedrock surface and base year water table altitudes, were used to prepare a geohydrologic map illustrating percentage change in saturated thickness. Saturated thickness, as used in this report, is the thickness of the High Plains aquifer between the groundwater surface indicated by water table altitudes and the bedrock surface. Because irrigation development in west-central Kansas was minimal prior to 1950, the saturated thickness during 1950 represented a nearly static condition in the aquifer. Apparent increases in saturated thickness generally occurred in areas of sparse data or thin saturated thickness, and large errors were possible; therefore, zero and negative-change areas were not contoured. A decrease in saturated thickness of 100% may indicate that: (1) the aquifer has been dewatered, or (2) no saturated thickness occurred in that area during 1950. In general, percentage change in saturated thickness indicates the degree of stress on the aquifer in most areas due to irrigation pumpage. (Lantz-PTT)

  14. Percentage change in saturated thickness of the High Plains Aquifer, west-central Kansas, 1950 to average 1984-86

    USGS Publications Warehouse

    Dague, Barbara J.

    1986-01-01

    Continuing studies are being made in west-central Kansas to provide up-to-date information that will aid in the management of groundwater for irrigation. The results are presented of the sixth in a series of studies that used a statistical technique called kriging, to produce hydrologic maps. The kriging technique interpolates water level altitudes at the center of each 1 sq mi section in the study area on the basis of water level measurements from 169 observation wells. For this study, measurements made at each site during the winter months of 1984, 1985, and 1986 were averaged. These interpolated altitudes (1 ,859 in all), along with bedrock-surface and base yr water level altitudes, were used to prepare a hydrologic map that illustrates percentage change in saturated thickness. Saturated thickness is the thickness of the High Plains aquifer between the groundwater surface, as indicated by water level altitudes, and the bedrock surface. Because irrigation development in west-central Kansas was minimal prior to 1950, the saturated thickness during 1950 represented a nearly static condition in the aquifer. Thus, the decrease in saturated thickness of the aquifer since 1950 is related to the effects of irrigation withdrawals on the volume of water in storage. (Lantz-PTT)

  15. Disease-Bearing Mosquitoes of North and Central America, the West Indies, and the Philippine Islands

    DTIC Science & Technology

    1913-11-01

    April in Old Calabar (Annett). James reports it experimentally positive to malaria, but not found infected in nature, and Christoph<’r 1 says that...frag- ments of aquatic plants. l Boyce, Sir Rubert. The Prevalence , Distribution, and Significance of Stegomyiafasciata in West Africa. Bull. Ento...these mountain or hill streams free of grass and weeds, and the current running strongl.y, did not control certain mosquitoes, and that the prevalence

  16. Stratigraphic framework of Cambrian and Ordovician rocks in the central Appalachian Basin from Medina County, Ohio, through southwestern and south-central Pennsylvania to Hampshire County, West Virginia

    USGS Publications Warehouse

    Ryder, Robert T.; Harris, Anita G.; Repetski, John E.; revised and digitized by Crangle, Robert D.

    2003-01-01

    A 275-mi-long restored stratigraphic cross section from Medina County, Ohio, through southwestern and south-central Pennsylvania to Hampshire County, W. Va., provides new details on Cambrian and Ordovician stratigraphy in the central Appalachian basin and the structure of underlying Precambrian basement rocks. From west to east, the major structural elements of the block-faulted basement in this section are (1) the relatively stable, slightly extended craton, which includes the Wooster arch, (2) the fault-controlled Ohio-West Virginia hinge zone, which separates the craton from the adjoining Rome trough, (3) the Rome trough, which consists of an east-facing asymmetric graben and an overlying sag basin, and (4) a positive fault block, named here the South-central Pennsylvania arch, which borders the eastern margin of the graben part of the Rome trough. Pre-Middle Ordovician structural relief on Precambrian basement rocks across the down-to-the-west normal fault that separates the Rome trough and the adjoining South-central Pennsylvania arch amounted to between 6,000 and 7,000 ft. The restored cross section shows eastward thickening of the Cambrian and Ordovician sequence from about 3,000 ft near the crest of the Wooster arch at the western end of the section to about 5,150 ft at the Ohio-West Virginia hinge zone adjoining the western margin of the Rome trough to about 19,800 ft near the depositional axis of the Rome trough. East of the Rome trough, at the adjoining western edge of the South-central Pennsylvania arch, the Cambrian and Ordovician sequence thins abruptly to about 13,500 ft and then thins gradually eastward across the arch to about 12,700 ft near the Allegheny structural front and to about 10,150 ft at the eastern end of the restored section. In general, the Cambrian and Ordovician sequence along this section consists of four major lithofacies that are predominantly shallow marine to peritidal in origin. In ascending stratigraphic order, the lithofacies

  17. Hydrologic Setting and Conceptual Hydrologic Model of the Walker River Basin, West-Central Nevada

    USGS Publications Warehouse

    Lopes, Thomas J.; Allander, Kip K.

    2009-01-01

    The Walker River is the main source of inflow to Walker Lake, a closed-basin lake in west-central Nevada. Between 1882 and 2008, agricultural diversions resulted in a lake-level decline of more than 150 feet and storage loss of 7,400,000 acre-ft. Evaporative concentration increased dissolved solids from 2,500 to 17,000 milligrams per liter. The increase in salinity threatens the survival of the Lahontan cutthroat trout, a native species listed as threatened under the Endangered Species Act. This report describes the hydrologic setting of the Walker River basin and a conceptual hydrologic model of the relations among streams, groundwater, and Walker Lake with emphasis on the lower Walker River basin from Wabuska to Hawthorne, Nevada. The Walker River basin is about 3,950 square miles and straddles the California-Nevada border. Most streamflow originates as snowmelt in the Sierra Nevada. Spring runoff from the Sierra Nevada typically reaches its peak during late May to early June with as much as 2,800 cubic feet per second in the Walker River near Wabuska. Typically, 3 to 4 consecutive years of below average streamflow are followed by 1 or 2 years of average or above average streamflow. Mountain ranges are comprised of consolidated rocks with low hydraulic conductivities, but consolidated rocks transmit water where fractured. Unconsolidated sediments include fluvial deposits along the active channel of the Walker River, valley floors, alluvial slopes, and a playa. Sand and gravel deposited by the Walker River likely are discontinuous strata throughout the valley floor. Thick clay strata likely were deposited in Pleistocene Lake Lahontan and are horizontally continuous, except where strata have been eroded by the Walker River. At Walker Lake, sediments mostly are clay interbedded with alluvial slope, fluvial, and deltaic deposits along the lake margins. Coarse sediments form a multilayered, confined-aquifer system that could extend several miles from the shoreline

  18. First Younger Dryas moraines in Greenland

    NASA Astrophysics Data System (ADS)

    Funder, Svend; Larsen, Nicolaj K.; Linge, Henriette; Möller, Per; Schomacker, Anders; Fabel, Derek; Kjær, Kurt H.; Xu, Sheng

    2016-04-01

    Over the Greenland ice sheet the Younger Dryas (YD) cold climate oscillation (12.9-11.7 kaBP) began with up to 10°C drop in temperatures and ended with up to 12°C abrupt warming. In the light of the present warming and melting of the ice sheet, and its importance for future climate change, the ice sheet's response to these dramatic changes in the past is of great interest. However, even though much effort has gone into charting YD ice margin behaviour around Greenland in recent years, no clear-cut signal of response to the oscillation has been uncovered. Here we show evidence to suggest that three major outlets from a local ice cap at Greenland's north coast advanced and retreated synchronously during YD. The evidence comprises OSL (optically stimulated luminescence) dates from a marine transgression of the coastal valleys that preceded the advance, and exposure ages from boulders on the moraines, formed by glaciers that overrode the marine sediment. The OSL ages suggest a maximum age of 12.4 ±0.6 kaBP for the marine incursion, and 10 exposure ages on boulders from the three moraines provide an average minimum age of 12.5 ±0.7 kaBP for the moraines, implying that the moraines were formed within the interval 11.8-13.0 kaBP. Elsewhere in Greenland evidence for readvance has been recorded in two areas. Most notably, in the East Greenland fjord zone outlet glaciers over a stretch of 800 km coast advanced through the fjords. In Scoresby Sund, where the moraines form a wide belt, an extensive 14C and exposure dating programme has shown that the readvance here probably culminated before YD, while cessation of moraine formation and rapid retreat from the moraine belt did not commence until c. 11.5 kaBP, but no moraines have so far been dated to YD. Readvance is also seen in Disko Bugt, the largest ice sheet outlet in West Greenland. However, here the advance and retreat of the ice stream took place in mid YD times, and lasted only a few hundred years, while YD in

  19. Diachronous retreat of the Greenland ice sheet during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Sinclair, G.; Carlson, A. E.; Mix, A. C.; Lecavalier, B. S.; Milne, G.; Mathias, A.; Buizert, C.; DeConto, R.

    2016-08-01

    The last deglaciation is the most recent interval of large-scale climate change that drove the Greenland ice sheet from continental shelf to within its present extent. Here, we use a database of 645 published 10Be ages from Greenland to document the spatial and temporal patterns of retreat of the Greenland ice sheet during the last deglaciation. Following initial retreat of its marine margins, most land-based deglaciation occurred in Greenland following the end of the Younger Dryas cold period (12.9-11.7 ka). However, deglaciation in east Greenland peaked significantly earlier (13.0-11.5 ka) than that in south Greenland (11.0-10 ka) or west Greenland (10.5-7.0 ka). The terrestrial deglaciation of east and south Greenland coincide with adjacent ocean warming. 14C ages and a recent ice-sheet model reconstruction do not capture this progression of terrestrial deglacial ages from east to west Greenland, showing deglaciation occurring later than observed in 10Be ages. This model-data misfit likely reflects the absence of realistic ice-ocean interactions. We suggest that oceanic changes may have played an important role in driving the spatial-temporal ice-retreat pattern evident in the 10Be data.

  20. Late Oligocene glacimarine sedimentation of the central Ross Sea and implications for the evolution of the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Kraus, C.; Mckay, R. M.; Naish, T.; Levy, R. H.; Kulhanek, D. K.

    2015-12-01

    Today the West Antarctic Ice Sheet (WAIS) is grounded mostly below sea level, making it sensitive to oceanic temperature and circulation changes. However, recent reconstructions of the Cenozoic bedrock topographic evolution of West Antarctica have suggested that the West Antarctic Ice Sheet (WAIS) may have first formed as a terrestrial ice sheet at the Eocene-Oligocene boundary (33 Ma), when there was up to 20% more land area in West Antarctica. At some point during the Oligocene or Miocene (23 - 5 Ma) vast areas of West Antarctica became an over-deepened marine-based continental shelf, as is observed today. The evolution of the WAIS through this transition is largely unconstrained, but as atmospheric CO2 fluctuated between 600 and 200 ppm over the past 34 Ma, determining the development of a marine-based WAIS is critical in the context of understanding the sensitivity of ice sheet systems to environmental change. Our research re-examines the sediment cores recovered from the central Ross Sea, a principal drainage area of the WAIS, at Deep Sea Drilling Project Site 270 (77°26.48'S, 178°30.19'W). These cores contain a glacimarine sequence of late Oligocene age (28 - 23.1 Ma). Sedimentological (visual core description, facies, grain size analysis), geochemical (x-ray fluorescence), geophysical (seismic) techniques, and physical properties (magnetic susceptibility) are used to construct a sedimentation model of this sequence, in order to track the late Oligocene evolution of the WAIS. The late Oligocene warming (25 - 23 Ma) is examined in detail because proximal Antarctic geological records of ice sheet extent, proxy environmental data, and atmospheric CO2 appear to be at odds with the composite δ18O record of global temperature and ice volume at this time. Moreover, our research provides insights into the sensitivity of marine-based ice sheets, and supports the hypothesis that they are unstable above a CO2 threshold of 400 ppm. Our preliminary results also

  1. West Nile virus: an infectious viral agent to the central nervous system.

    PubMed

    Farrar, Francisca

    2013-06-01

    This article reviews the growing epidemic of West Nile virus (WNV), clinical manifestations of the 2 primary groups of WNV, diagnostic tests, critical nursing management, risk factors, and prevention of WNV. Critical care nursing management is based on symptom management and supportive therapy for neuroinvasive disease complications. Nursing management for complications such as altered level of consciousness, mechanical ventilator respiratory support, high fever, cerebral edema, increased intracranial pressure, seizures, and neuropsychiatric issues is outlined. Preventive measures for WNV, such as surveillance programs, personal protective measures, source reduction, mosquito programs, and vaccine development, are discussed.

  2. Sediment-starved sand ridges on a mixed carbonate/siliciclastic inner shelf off west-central Florida

    USGS Publications Warehouse

    Harrison, S.E.; Locker, S.D.; Hine, A.C.; Edwards, J.H.; Naar, D.F.; Twichell, D.C.; Mallinson, D.J.

    2003-01-01

    High-resolution side-scan mosaics, sediment analyses, and physical process data have revealed that the mixed carbonate/siliciclastic, inner shelf of west-central Florida supports a highly complex field of active sand ridges mantled by a hierarchy of bedforms. The sand ridges, mostly oriented obliquely to the shoreline trend, extend from 2 km to over 25 km offshore. They show many similarities to their well-known counterparts situated along the US Atlantic margin in that both increase in relief with increasing water depth, both are oriented obliquely to the coast, and both respond to modern shelf dynamics. There are significant differences in that the sand ridges on the west-central Florida shelf are smaller in all dimensions, have a relatively high carbonate content, and are separated by exposed rock surfaces. They are also shoreface-detached and are sediment-starved, thus stunting their development. Morphological details are highly distinctive and apparent in side-scan imagery due to the high acoustic contrast. The seafloor is active and not a relict system as indicated by: (1) relatively young AMS 14C dates (< 1600 yr BP) from forams in the shallow subsurface (1.6 meters below seafloor), (2) apparent shifts in sharply distinctive grayscale boundaries seen in time-series side-scan mosaics, (3) maintenance of these sharp acoustic boundaries and development of small bedforms in an area of constant and extensive bioturbation, (4) sediment textural asymmetry indicative of selective transport across bedform topography, (5) morphological asymmetry of sand ridges and 2D dunes, and (6) current-meter data indicating that the critical threshold velocity for sediment transport is frequently exceeded. Although larger sand ridges are found along other portions of the west-central Florida inner shelf, these smaller sand ridges are best developed seaward of a major coastal headland, suggesting some genetic relationship. The headland may focus and accelerate the N-S reversing

  3. Summertime Extremes in the Arctic Climate System: Understanding the 2012 Extreme Greenland Melt in the Context of the 1889 Episode

    NASA Astrophysics Data System (ADS)

    Neff, W. D.; Compo, G. P.; Webb, R. S.

    2013-12-01

    The last melting of the high Greenland ice sheet prior to 2012 occurred in 1889 and prior to that a number of times during the Medieval Warm Anomaly. In the case of the 2012 episode, key factors in the summer melt episode were a combination of 1) Central North American drought andheat wave, 2) Amplification of a polar trough-ridge pattern, 3) A positive excursion of the Atlantic Multi-Decadal Oscillation (AMO), and 4) Advection of warm moist air northward along the west coast of Greenland and thence over the ice sheet as an elevated thin liquid cloud layer. In both episodes, transport over the western Atlantic to Greenland in the form of 'Atmospheric Rivers,' thin filaments of high water vapor air, are observed in both the 20CR (which uses only historic global surface pressure measurements and sea-surface temperatures back to 1871) and satellite imagery. In the 2012 case, air mass changes associated with these transport events over Greenland were marked by rapid changes in observed isotope time series (Personal communications, Masson-Delmotte and Steen-Hansen). In this presentation, we use the 2012 episode to 'calibrate' the 20CR as a tool to examine past extreme events involving mid-latitude and northern ice sheet interaction. Of particular importance is determining the limits on 20CR-derived back-trajectory analyses: While the 2012 back-trajectories from modern reanalyses are fairly convincing in documenting the various transport paths, in 1889 the interpretation is complicated by the interplay of the propagation of ridge-trough patterns versus material transport coupled with the relatively coarse resolution of the 20CR. What we found in 1889 were two potential melt-inducing episodes in July. These episodes have many of the key factors seen in 2012: a positive AMO, moisture transport along the U.S. east coast, and warm-air transport from the west with some trajectories originating in the drought-stricken Dakota Territory.

  4. Late Jurassic to Early Cretaceous transpression, Pine Nut and Luning-Fencemaker fault system, west-central Nevada

    SciTech Connect

    Oldow, J.S. . Dept. of Geology and Geophysics)

    1993-04-01

    Recent studies of the Mesozoic tectonic evolution of the western U.S. Cordillera have called for substantial transcurrent displacement between the Sierra Nevada and the western Great Basin. The location, timing, and sense of shear of the postulated transcurrent fault system(s) are controversial, and to a larger degree the controversy has centered on the Pine Nut fault (PNF) of western Nevada. The northwest-trending Pine Nut fault juxtaposes two coeval assemblages of the Mesozoic marine province of the northwestern Great Basin that have distinctly different structural histories. On the east, Mesozoic rocks are deformed in the late Mesozoic Luning-Fencemaker fold and thrust belt (LFT). To the west, coeval rocks are not involved in structures of the LFT but rather share a structural history with the eastern Sierra Nevada. A segment of the PNF is expressed as a brittle shear zone, up to 3 km wide, mapped discontinuously for over 50 km in the eastern Wassuk Range in west-central Nevada. Cataclasites of the brittle fault zone are superposed on ductility deformed lower Mesozoic layered and intrusive rocks with structures indicating top to the east shear. The ductile deformation, which predated post-kinematic plutons dated by U-Pb as 169 Ma, was accompanied by metamorphism ranging from lower greenschist to amphibolite-facies conditions. The PNF and LFT formed during sinistral transpression and represent components of oblique plate-convergence along the late Mesozoic Sierran are system.

  5. Spatio-Temporal Identification of Areas Suitable for West Nile Disease in the Mediterranean Basin and Central Europe.

    PubMed

    Conte, Annamaria; Candeloro, Luca; Ippoliti, Carla; Monaco, Federica; De Massis, Fabrizio; Bruno, Rossana; Di Sabatino, Daria; Danzetta, Maria Luisa; Benjelloun, Abdennasser; Belkadi, Bouchra; El Harrak, Mehdi; Declich, Silvia; Rizzo, Caterina; Hammami, Salah; Ben Hassine, Thameur; Calistri, Paolo; Savini, Giovanni

    2015-01-01

    West Nile virus (WNV) is a mosquito-transmitted Flavivirus belonging to the Japanese encephalitis antigenic complex of the Flaviviridae family. Its spread in the Mediterranean basin and the Balkans poses a significant risk to human health and forces public health officials to constantly monitor the virus transmission to ensure prompt application of preventive measures. In this context, predictive tools indicating the areas and periods at major risk of WNV transmission are of paramount importance. Spatial analysis approaches, which use environmental and climatic variables to find suitable habitats for WNV spread, can enhance predictive techniques. Using the Mahalanobis Distance statistic, areas ecologically most suitable for sustaining WNV transmission were identified in the Mediterranean basin and Central Europe. About 270 human and equine clinical cases notified in Italy, Greece, Portugal, Morocco, and Tunisia, between 2008 and 2012, have been considered. The environmental variables included in the model were altitude, slope, night time Land Surface Temperature, Normalized Difference Vegetation Index, Enhanced Vegetation Index, and daily temperature range. Seasonality of mosquito population has been modelled and included in the analyses to produce monthly maps of suitable areas for West Nile Disease. Between May and July, the most suitable areas are located in Tunisia, Libya, Egypt, and North Cyprus. Summer/Autumn months, particularly between August and October, characterize the suitability in Italy, France, Spain, the Balkan countries, Morocco, North Tunisia, the Mediterranean coast of Africa, and the Middle East. The persistence of suitable conditions in December is confined to the coastal areas of Morocco, Tunisia, Libya, Egypt, and Israel.

  6. Greenland Ice Flow

    NASA Video Gallery

    Greenland looks like a big pile of snow seen from space using a regular camera. But satellite radar interferometry helps us detect the motion of ice beneath the snow. Ice starts flowing from the fl...

  7. Hydrogeology of the Hanford Site Central Plateau – A Status Report for the 200 West Area

    SciTech Connect

    Last, George V.; Thorne, Paul D.; Horner, Jacob A.; Parker, Kyle R.; Bjornstad, Bruce N.; Mackley, Rob D.; Lanigan, David C.; Williams, Bruce A.

    2009-08-27

    The Remediation Decisions Support (RDS) function of the Soil and Groundwater Remediation Project (managed by CH2M HILL Plateau Remediation Company [CHPRC]) is responsible for facilitating the development of consistent data, parameters, and conceptual models to resolve technical issues and support efforts to estimate contaminant migration and impacts (i.e., the assessment process). In particular, the RDS function is working to update electronic data sources and conceptual models of the geologic framework and associated hydraulic and geochemical parameters to facilitate traceability, transparency, defensibility, and consistency in support of environmental assessments. This report summarizes the efforts conducted by Pacific Northwest National Laboratory (PNNL) scientists in fiscal year 2008 (FY08) that focused primarily on the 200 West Area, as well as a secondary effort initiated on the 200 East Area.

  8. Interaction of Rahaliya-Ekhedhur groundwater with the aquifer rock, West Razzaza Lake, Central Iraq

    NASA Astrophysics Data System (ADS)

    Al-Dabbas, Moutaz A.

    2016-09-01

    The groundwater of Dammam aquifer in Rahaliya-Ekhedhur area, West Razzaza, Iraq, was studied to identify the main hydrogeochemical processes and the groundwater-rock interaction. The results indicated that Na+ and SO4 2- are the dominant ions in the groundwater. The average contribution of cations in the aquifer is Na+ + K+ (24.7 %), Ca2+ (13.9 %), and Mg2+ (11.4 %), while anions contribution is SO4 2- (23.0 %), Cl- (20.7 %), and HCO3 - (6.3 %). The groundwater characterized by neutral to slightly alkaline hard water, excessively mineralized, and slightly brackish water type. Rock-water interaction processes are identified to include dissolution of carbonates, sulfates, halite, and clay minerals, leaching, and cation exchanges, with little impact of evaporation.

  9. Bathymetry of the west-central slope of the island of Hawaii

    USGS Publications Warehouse

    Chadwick, William W.; Moore, James G.; Fox, Christopher G.

    1994-01-01

    This map shows the topography of a small part of the subaerial western part of the Island of Hawaii as well as modern multibeam bathymetry of the west submarine flank, which covers a total area of about 8,500 km2 ( see index map). The map area includes part of the submerged flanks of the active Mauna Loa and Hualalai Volcanoes, which last erupted in 1984 and 1801 respectively. The steep and irregular submarine slope is shaped by several giant submarine landslides. They were first identified during surveys from the U.S. Geological Survey research vessel S.P. Lee in 1976 and 1978 (Normark and others, 1979) and later mapped in more detail during a swath-sonar survey (GLORIA) of the United States Hawaiian Exclusive Economic Zone in 1986 to 1991 (Lipman and others, 1988; Moore and others, 1989) as part of a cooperative venture of the U.S. Geological Survey and the British Institute of Oceanographic Sciences.

  10. Comparison of automated satellite systems with conventional systems for hydrologic data collection in west-central Florida

    USGS Publications Warehouse

    Woodham, W.M.

    1982-01-01

    This report provides results of reliability and cost-effective studies of the goes satellite data-collection system used to operate a small hydrologic data network in west-central Florida. The GOES system, in its present state of development, was found to be about as reliable as conventional methods of data collection. Benefits of using the GOES system include some cost and manpower reduction, improved data accuracy, near real-time data availability, and direct computer storage and analysis of data. The GOES system could allow annual manpower reductions of 19 to 23 percent with reduction in cost for some and increase in cost for other single-parameter sites, such as streamflow, rainfall, and ground-water monitoring stations. Manpower reductions of 46 percent or more appear possible for multiple-parameter sites. Implementation of expected improvements in instrumentation and data handling procedures should further reduce costs. (USGS)

  11. Geometeorological data collected by the USGS Desert Winds Project at Desert Wells, Sonoran Desert, central-west Arizona, 1981 - 1996

    USGS Publications Warehouse

    Helm, Paula J.; Breed, Carol S.; Tigges, Richard; Creighton, Shawn

    1998-01-01

    The data in this report were obtained by instruments deployed on a GOES-satellite data collection station operated by the U.S. Geological Survey Desert Winds Project at Desert Wells (latitude 33° 42' 08" N, longitude 113° 48' 40" W), La Paz County, west-central Arizona. The elevation is 344 m (1,130 ft). From January 9, 1981 through May 31, 1995 the station recorded eight parameters: wind direction, wind speed, peak gust, air temperature, precipitation, humidity, barometric pressure, and soil temperature. On June 1, 1995, the station was upgraded by adding a SENSIT sand-flux sensor, which records grain impacts concurrently with wind speed and wind direction measurements. Included with the data is descriptive text on the geology, soils, climate, vegetation, and land use at the site, as well as text on data format, date retrieval software and instructions, and metadata

  12. Abundance, composition, and distribution of crustacean zooplankton in relation to hypolimnetic oxygen depletion in west-central Lake Erie

    USGS Publications Warehouse

    Heberger, Roy F.; Reynolds, James B.

    1977-01-01

    Samples of crustacean zooplankton were collected monthly in west-central Lake Erie in April and June to October 1968, and in July and August 1970, before and during periods of hypolimnetic dissolved oxygen (DO) depletion. The water column at offshore stations was thermally stratified from June through September 1968, and the hypolimnion contained no DO in mid-August of 1968 or 1970. Composition, abundance, and vertical distribution of crustacean zooplankton changed coincidentally with oxygen depletion. From July to early August, zooplankton abundance dropped 79% in 1968 and 50% in 1970. The declines were attributed largely to a sharp decrease in abundance of planktonic Cyclops bicuspidatus thomasi. Zooplankton composition shifted from mainly cyclopoid copepods in July to mainly cladocerans and copepod nauplii in middle to late August. We believe that mortality of adults and dormancy of copepodites in response to anoxia was the probable reason for the late summer decline in planktonic C. b. thomasi.

  13. An integrtated approach to the use of Landsat TM data for gold exploration in west central Nevada

    NASA Technical Reports Server (NTRS)

    Mouat, D. A.; Myers, J. S.; Miller, N. L.

    1987-01-01

    This paper represents an integration of several Landsat TM image processing techniques with other data to discriminate the lithologies and associated areas of hydrothermal alteration in the vicinity of the Paradise Peak gold mine in west central Nevada. A microprocessor-based image processing system and an IDIMS system were used to analyze data from a 512 X 512 window of a Landsat-5 TM scene collected on June 30, 1984. Image processing techniques included simple band composites, band ratio composites, principal components composites, and baseline-based composites. These techniques were chosen based on their ability to discriminate the spectral characteristics of the products of hydrothermal alteration as well as of the associated regional lithologies. The simple band composite, ratio composite, two principal components composites, and the baseline-based composites separately can define the principal areas of alteration. Combined, they provide a very powerful exploration tool.

  14. Thanetian transgressive-regressive sequences based on foraminiferal paleobathymetry at Gebel Matulla, west-central Sinai, Egypt

    NASA Astrophysics Data System (ADS)

    Farouk, Sherif; Elamri, Zaineb; El-Sorogy, Abdelbaset

    2016-09-01

    Qualitative and quantitative analysis of Thanetian foraminiferal assemblages at Gebel Matulla in west-central Sinai has been carried out. Three benthic foraminiferal assemblages are recorded from shallowest to deepest as Cibicidoides pseudoacutus, Angulogavelinella avnimelechi, Gavelinella danica witch evidences of fluctuations from middle neritic to upper bathyal environments. Changes in the foraminiferal population enabled us to classify the Thanetian succession into two fourth order transgressive-regressive (T-R) sequences. Three sequence boundaries are identified, at the Selandian/Thanetian (S/T) boundary, within the Thanetian succession, and the Paleocene/Eocene (P/E) boundary. It occurs at the top part of the maximum regression associated with major discontinuities and changes in depositional regimes as well as vertical facies changes. Broad correlation with eustatic records based upon integrated microplanktonic biostratigraphy suggests that the fluctuations of foraminiferal population were controlled by global sea-level changes.

  15. Ground-water data for the alluvial, buried channel, Basel Pleistocene and Dakota aquifer in West-Central Iowa

    USGS Publications Warehouse

    Hunt, Pamela K.B.; Runkle, Donna L.

    1985-01-01

    The purpose of this investigation was to determine the availability, quantity and quality of groundwater from three principal aquifers in West-Central Iowa, the alluvial, buried channel, Basal Pleistocene and the Dakota aquifers. Specific objectives were to: (1) determine the location, extent and the nature of these aquifers; (2) evaluate the occurrence and movement of groundwater, including the sources of recharge and discharge; (3) estimate the quantities of water stored in the aquifers; (4) estimate the potential yields of wells tapping the aquifers; (5) estimate the water use; and (6) describe the chemical quality of the groundwater. This report is the compilation of the data collected during the investigation and has the purpose of providing a reference for an interpretive report describing groundwater resources and a bedrock topography map of the study area.

  16. Genetic composition of contemporary swine influenza viruses in the West Central region of the United States of America

    PubMed Central

    Evseenko, Vasiliy A.; Boon, Adrianus C. M.; Brockwell‐Staats, Christy; Franks, John; Rubrum, Adam; Daniels, Curt S.; Gramer, Marie R.; Webby, Richard J.

    2011-01-01

    Please cite this paper as: Evseenko et al. (2011) Genetic composition of contemporary swine influenza viruses in the West Central region of the United States of America. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2010.00189.x. Background  Because of continuous circulation in different animal species and humans, influenza viruses have host‐specific phenotypic and genetic features. Reassortment of the genome segments can significantly change virus phenotype, potentially generating virus with pandemic potential. In 2009, a new pandemic influenza virus emerged. Objectives  In this study, we attempted to find precursor viruses or genes of pandemic H1N1 influenza 2009 among 25 swine influenza viruses, isolated in the West Central region of the United States of America (USA), between 2007 and 2009. The Phylogenetically Similar Triple‐Reassortant Internal Genes (PSTRIG) cassette of all the viruses studied here as well as the PSTRIG cassette of pandemic H1N1 viruses have close but equidistant phylogenetic relationships to the early triple‐reassortant swine H3N2 influenza A isolated in the USA in 1998. Methods  Samples (nasal swabs and lung tissue lavage) were taken from swine with or without clinical signs of respiratory disease via farmer‐funded syndromic surveillance. All studied viruses were isolated in Madin–Darby Canine Kidney cell cultures from the above‐mentioned samples according to standard protocols recommended for influenza virus isolation. Sequences were obtained using BigDye Terminator v3.1 Cycle Sequencing kit. Phylogenetic trees were built with MEGA 4.0 software using maximum composite likelihood algorithm and neighbor‐joining method for tree topology reconstruction. Results  Among the 25 viruses studied, we have not found any gene segments of Eurasian origin. Our results suggest that pandemic H1N1 viruses diverged and are not directly descended from swine viruses that have been circulating in USA since 1998

  17. West Meets East in Central Asia: Competing Discourses on Secondary Education Reform in the Kyrgyz Republic.

    ERIC Educational Resources Information Center

    De Young, Alan J.

    The Kyrgyz Republic--a remote mountainous region--is one of five former Soviet states in central Asia. This case study begins with a brief overview of the political and economic situation of the Kyrgyz Republic and its relation to aims of Soviet schooling in the 20th century. A critique of the Soviet schooling model by foreign academics before and…

  18. Tectonic Map of the Ellesmerian and Eurekan deformation belts on Svalbard, North Greenland and the Queen Elizabeth Islands (Canadian Arctic)

    NASA Astrophysics Data System (ADS)

    Piepjohn, Karsten; von Gosen, Werner; Tessensohn, Franz; Reinhardt, Lutz; McClelland, William C.; Dallmann, Winfried; Gaedicke, Christoph; Harrison, Christopher

    2016-04-01

    The tectonic map presented here shows the distribution of the major post-Ellesmerian and pre-Eurekan sedimentary basins, parts of the Caledonian Orogen, the Ellesmerian Fold-and-Thrust Belt, structures of the Cenozoic Eurekan deformation, and areas affected by the Eurekan overprint. The present continental margin of North America towards the Arctic Ocean between the Queen Elizabeth Islands and Northeast Greenland and the present west margin of the Barents Shelf are characterized by the Paleozoic Ellesmerian Fold-and-Thrust Belt, the Cenozoic Eurekan deformation, and, in parts, the Caledonian Orogen. In many areas, the structural trends of the Ellesmerian and Eurekan deformations are more or less parallel, and often, structures of the Ellesmerian Orogeny are affected or reactivated by the Eurekan deformation. While the Ellesmerian Fold-and-Thrust Belt is dominated by orthogonal compression and the formation of wide fold-and-thrust zones on Ellesmere Island, North Greenland and Spitsbergen, the Eurekan deformation is characterized by a complex network of regional fold-and-thrust belts (Spitsbergen, central Ellesmere Island), large distinct thrust zones (Ellesmere Island, North Greenland) and a great number of strike-slip faults (Spitsbergen, Ellesmere Island). The Ellesmerian Fold-and-Thrust Belt was most probably related to the approach and docking of the Pearya Terrane (northernmost part of Ellesmere Island) and Spitsbergen against the north margin of Laurasia (Ellesmere Island/North Greenland) in the earliest Carboniferous. The Eurekan deformation was related to plate tectonic movements during the final break-up of Laurasia and the opening of Labrador Sea/Baffin Bay west, the Eurasian Basin north, and the Norwegian/Greenland seas east of Greenland. The tectonic map presented here shows the German contribution to the Tectonic Map of the Arctic 1:5,000,000 (TeMAr) as part of the international project "Atlas of geological maps of Circumpolar Arctic at 1

  19. The preliminary results of new submarine caldera on the west of Kume-jima island, Central Ryukyu Arc, Japan

    NASA Astrophysics Data System (ADS)

    Harigane, Y.; Ishizuka, O.; Shimoda, G.; Sato, T.

    2014-12-01

    The Ryukyu Arc occurs between the islands of Kyushu and Taiwan with approximately 1200 km in the full length. This volcanic arc is caused by subduction of the Philippine Sea plate beneath the Eurasia Plate along the Ryukyu trench, and is composed of forearc islands, chains of arc volcanoes, and a back-arc rift called Okinawa Trough. The Ryukyu Arc is commonly divided into three segments (northern, central and southern) that bounded by the Tokara Strait and the Kerama Gap, respectively (e.g., Konishi 1965; Kato et al., 1982). Sato et al. (2014) mentioned that there is no active subaerial volcano in the southwest of Iotori-shima in the Central Ryukyu Arc whereas the Northern Ryukyu Arc (i.e., the Tokara Islands) has active frontal arc volcanoes. Therefore, the existence of volcanoes and volcanotectonic history of active volcanic front in the southwestern part of the Central Ryukyu Arc are still ambiguous. Detailed geophysical and geological survey was mainly conducted using R/V Kaiyou-maru No.7 during GK12 cruise operated by the Geological Survey of Japan/National Institute of Advanced Industrial Science and Technology, Japan. As a result, we have found a new submarine volcanic caldera on the west of Kume-jima island, where located the southwestern part of Central Ryukyu Arc. Here, we present (1) the bathymetrical feature of this new submarine caldera for the first time and (2) the microstructural and petrological observations of volcanic rocks (20 volcanic samples in 13 dredge sites) sampled from the small volcanic cones of this caldera volcano. The dredged samples from the caldera consist of mainly rhyolite pumice with minor andesites, Mn oxides-crust and hydrothermally altered rocks. Andesite has plagioclase, olivine and pyroxene phenocrysts. Key words: volcanic rock, caldera, arc volcanism, active volcanic front, Kume-jima island, Ryukyu Arc

  20. Swath-bathymetric Mapping of Glacial Landforms in the Central Pine Island Trough, West Antarctica

    NASA Astrophysics Data System (ADS)

    Jakobsson, M.; Anderson, J. B.; Nitsche, F. O.; Gyllencreutz, R.; Kirshner, A. E.; Kirchner, N.; O'regan, M. A.; Mohammad, R.; Eriksson, B.

    2011-12-01

    The Pine Island Glacier drains the West Antarctic Ice Sheet into the Amundsen Sea. During the Last Glacial Maximum (LGM), the Pine Island Glacier extended nearly 500 km from its present location, across the continental shelf to the shelf break. The Oden-Southern-Ocean 2009/2010 (OSO0910) expedition with Swedish icebreaker Oden carried out swath-bathymetric mapping and chirp sonar profiling of the mid-shelf section of Pine Island Trough. Since the bay was virtually ice free during the 2010 austral summer, the swath-bathymetric mapping could be conducted as a systematic survey which covered a coherent area of 4,140 km^2 of the mid-shelf glacial trough. The swath-bathymetric mapping and chirp sonar profiling were carried out with Oden's hull-mounted Kongsberg 12 kHz EM122 1°x1° multibeam echo sounder and integrated SBP 120 3°x3° chirp sonar. From these data we present new insights into to the glacial dynamics during the deglaciation of the mid-continental shelf since LGM. The landforms imaged in Pine Island Trough indicate stepwise retreat of the Pine Island Ice Stream punctuated by periods of grounding line stability and a minor advance followed by episodes of rapid retreat. Notably, directions of mapped mega scale lineations clearly show that the Pine Island Ice Stream changed its flow path during the advance. This advance followed a massive ice shelf break-up and grounding line retreat inferred from mapped corrugation ridges and iceberg plow ridges previously reported by Jakobsson et al., (2011). The periods of grounding line stability during the deglaciation are marked by sediment accumulations in the form of grounding zone wedges. Some of these wedges are here mapped to their full extents and in sufficient detail to characterize spatial dimensions and to estimate the volume of deposited sediment. Considering a range of sediment flux rates from the paleo-Pine Island Ice Stream we estimate that the largest and most clearly defined grounding zone wedge located

  1. Structural style of the Cuyo-Bolsones basin complex of west-central Argentina

    SciTech Connect

    Gollop, I.G. )

    1991-03-01

    The Cuyo-Bolsones basin complex is part of a mosaic of basinal features that lie in the eastern Andean foreland. Sedimentary section ranges from Ordovician to Tertiary in age with the main petroleum source and reservoir potential in Carboniferous to Triassic clastics. Thick conglomerate units and widespread unconformities of both Permo-Carboniferous and Triassic age as well as localized volcanics indicate several periods of violent tectonic activity during late Paleozoic to early Mesozoic times. Triassic and older sediments are affected by normal faulting which in basins directly south extends up into the Lower Cretaceous. In the Cuyo-Bolsones basinal area, however this ancient tensional regime is entirely overprinted by relatively recent thrusting. This thrusting is late Tertiary in age, generally from east to west with very substantial relief. These thrust sheets are cut in places by later northeast-southwest strike-slip fault zones producing some localized flower structures. Nearly all the oil discovered in the Cuyo basin is produced from Triassic clastic reservoirs in compressional anticlines related to this thrusting. The major thrusts are well defined seismically, and seismic interpretations fit easily on balanced sections.

  2. Relationship between Mesozoic and Cenozoic tectonic features in west central Arizona and adjacent southeastern California

    SciTech Connect

    Spencer, J.E.; Reynolds, S.J. )

    1990-01-10

    The Maria fold-and-thrust belt (MFTB) is a narrow belt of Mesozoic crustal shortening that is characterized by generally south vergent folds and thrusts that commonly displace Proterozoic crystalline rocks over deformed and metamorphosed Paleozoic and Mesozoic strata. The MFTB is cut by a south to southeast trending belt of mid-Tertiary extensional deformation. Extension was characterized by large displacements on low-angle normal faults, known as detachment faults, and by isostatic uplift of mylonitic midcrustal rocks now exposed in metamorphic core complexes. The geometry and style of extensional deformation change along the extensional belt and reveal the influence of the MFTB. Several extensional features are spatially coincident with the root zone of MFTB thrusts: (1) an areally extensive west-northwest trending belt of denuded Tertiary mylonitic fabrics in the Whipple and Harcuvar metamorphic core complexes, (2) a style of extension characterized by minimum extensional dismemberment of the upper plate and maximum denudation and uplift of deep-seated lower plate rocks, (3) an abrupt bend in the belt of arched, uplifted rocks below detachment faults, and (4) an abrupt bend in the trend of the breakaway zone of the detachment faults and an associated lateral ramp in the detachment fault system.

  3. Water resources on the Pueblo of Laguna, west-central New Mexico

    USGS Publications Warehouse

    Risser, D.W.; Lyford, F.P.

    1983-01-01

    This study evaluates the quality and quantity of water available on the Pueblo of Laguna, New Mexico. Groundwater for public supply occurs in the valley fill along the Rio San Jose, in the Paguate and Encinal areas, and possibly in the northern part of the Sedillo Grant. The valley fill in the Rio San Jose will supply 50 to 450 gallons per minute of potable water to properly constructed wells. In the alluvium along Rio Paguate, additional development of as much as 250 gallons per minute is possible. Groundwater for irrigation is restricted by available yields and quality to the valley fill along the Rio San Jose and possibly the western part of the Major 's Ranch area. In the Rio San Jose valley yields of 50 to 450 gallons per minute of water containing 500 to 3,000 milligrams per liter are possible. Digital-model simulations of the valley-fill aquifer west of the Village of Laguna show a potential salvage of as much as 900 acre-feet per year of evapotranspiration losses if water levels are lowered. Model studies also indicate that the winter flow of the Rio San Jose could be used to recharge groundwater stored in the valley. (USGS)

  4. Seasonal dynamics of four potential West Nile vector species in north-central Texas.

    PubMed

    Bolling, Bethany G; Kennedy, James H; Zimmerman, Earl G

    2005-12-01

    A population survey was conducted from April through September 2002 on mosquito species occurring on the Ray Roberts Greenbelt, a riparian corridor used for public recreation on the Elm Fork of the Trinity River, in Denton County, TX. Geographic information system software was used to set up a stratified random sampling design based on habitat parameters. Mosquitoes were collected using light traps, gravid traps, and resting boxes. A total of 29 species was collected during this study belonging to the following genera: Aedes, Anopheles, Coquillettidia, Culex, Mansonia, Ochlerotatus, Orthopodomyia, Psorophora, and Uranotaenia. The four most common species collected during this study were Aedes vexans, Culex erraticus, Culex salinarius, and Psorophora columbiae. West Nile virus (WNV) has been detected in these species in the United States, and they may serve as important vector species in Denton County. Collections were analyzed by the Texas Department of Health for arboviruses. One pool consisting of both Cx. erraticus and Cx. salinarius, collected in August 2002, tested positive for WNV, making it the first mosquito pool to test positive for WNV in Denton County. Canonical correspondence analysis was performed using abundance data of dominant species with selected weather variables and habitat parameters. Important factors for determining dominant species abundance were temperature, precipitation, dew point, and canopy coverage. Spatial and temporal patterns of these species are discussed.

  5. Hydrogeology of the Buffalo aquifer, Clay and Wilkin Counties, West-Central Minnesota

    USGS Publications Warehouse

    Wolf, R.J.

    1981-01-01

    The Buffalo aquifer is the principal source of ground-water supplies in the Moorhead, Minnesota area. The aquifer is an elongate deposit of sand and gravel, which locally contains water under confined conditions. Although the Buffalo aquifer contains about 270 billion gallons of water in storage, only 120 billion gallons could be withdrawn. Largest well yields occur along the deep trough in the center of the aquifer. Induced streambed infiltration may be possible in certain areas where the stream overlies the aquifer and where the intervening lake sediments are thin or absent. A numerical model constructed for aquifer evaluation has shown that a considerable amount of ground water is discharged through the confining bed to the stream or leaves the area as underflow to the west. Water from the Buffalo aquifer generally is very hard and of the calcium bicarbonate type. The average discharge of the Buffalo River for the base period 1946-78 ranges from 0.229 cubic foot per second per square mile near Hawley to 0.108 cubic foot per second per square mile at Sabin. Surface water in the Buffalo River drainage system is dominantly a calcium bicarbonate type similar to ground water of the area, especially at low flow in the upper reaches of the tributaries.

  6. Jurassic crustal deformation in west-central part of Colorado Plateau

    SciTech Connect

    Peterson, F.

    1985-05-01

    Although the Jurassic Period is commonly thought of as a time of tectonic quiescence, updated isopach maps and new sedimentologic information indicate that it was a time of notable crustal deformation on the Colorado Plateau. A significant change in structural style occurred in Middle Jurassic time, especially during the erosion interval that produced the J-3 unconformity. Prior to late Middle Jurassic time, the region had been tilted westward and structural troughs formed in the area of the present-day Circle Cliffs uplift and in the vicinity of the Circle Cliffs and Black Mesa regions were uplifted and the nearby Henry and Kaiparowits regions began to be downwarped as troughs or basins. It cannot be determined if or how the present-day monoclines flexed during the Jurassic. However, the direction of structural tilt across these areas changed from west side down to east side down during the late Middle and early Late Jurassic. The Monument region, the largest and most persistent structural element in the region, changed from a structural bench to a positive structure in the early Late Jurassic. In most cases the positive structures subsided more slowly than adjacent downwarps. Two exceptions during the Late Jurassic are the Black Mesa and Emery uplifts. These are the only uplifts that actually rose above the level of sediment accumulation. Jurassic rocks are not known to contain significant hydrocarbon resources in this region, but their tectonic history may offer clues to the structural history of underlying Paleozoic strata, which are the primary hydrocarbon exploration targets.

  7. An assessment of the occupational and environmental health needs in seven Southeastern European and West-Central Asian countries.

    PubMed

    Coman, Alexandru; Cherecheş, Răzvan M; Ungureanu, Marius I; Marton-Vasarhelyi, Emanuela O; Valentine, Marissa A; Sabo-Attwood, Tara; Gray, Gregory C

    2015-12-01

    Eastern European and Central Asian countries are undergoing rapid socioeconomic and political reforms. Many old industrial facilities are either abandoned, or use outdated technologies that severely impact the environment. Emerging industries have less regulation than in developed countries and environmental and occupational problems seem to be increasing. Under a US National Institutes of Health pilot grant, we developed an interdisciplinary One Health research network in Southeastern Europe and West-Central Asia to identify environmental and occupational problems. From 2012 to 2014, this GeoHealth Hub engaged 11 academic centers and 16 public health institutions in eight different countries: Albania, Armenia, Georgia, Kazakhstan, Kyrgyzstan, Moldova, Romania, and the United States with a goal of strengthening environmental and occupational research and training capacities. Employing face-to-face interviews and large group meetings, we conducted an evidenced-based needs and opportunities assessment focused on aquatic health, food safety, and zoonotic diseases. Comprehensive reviews of the published literature yielded priority research areas for each of the seven GeoHealth Hub countries including heavy metal and pesticide contamination, tick-borne diseases, rabies, brucellosis, and inadequate public health surveillance.

  8. Surficial geology of the sea floor in west-central Long Island Sound as shown by sidescan-sonar imagery

    USGS Publications Warehouse

    McMullen, K.Y.; Poppe, L.J.; DiGiacomo-Cohen, M. L.; Moser, M.S.; Christman, E.B.

    2005-01-01

    We used sidescan-sonar imagery detailing almost 300 km2 of the sea floor in west-central Long Island Sound in conjunction with bathymetry, sediment samples, bottom video, and seismic data to interpret the area's surficial geology. The distribution of sediments and sedimentary environments interpreted from these data sets represents the Quaternary geology, regional bathymetry, and effects of modern tidal- and wave-driven currents. Four distinct sedimentary environments consisting of 1) fine-grained deposition, 2) sorting and reworking, 3) coarse-grained bedload transport, and 4) erosion or nondeposition, were identified and mapped. Relatively low-energy environments prevail where deposition of clayey silts occurs in deeper water throughout the central part of the study area, and in the protected areas of the far northeastern corner. As low-energy environments transition to relatively high-energy environments, sorting and reworking of sand, silty sand, and sand-silt-clay takes place on the flanks of the shoals and over smaller bathymetric highs. Environments of coarse-grained bedload transport, distinguished by sandy sediments with current-derived bedforms, are located on an unnamed shoal in the northwestern part of the study area and directly to the south of this on Stratford Shoal. High-energy conditions are reflected by environments of erosion or nondeposition, which occur on bathymetric highs where gravel and gravelly sediments are present.

  9. An Assessment of the Occupational and Environmental Health Needs in Seven Southeastern European and West-Central Asian Countries

    PubMed Central

    Coman, Alexandru; Cherecheş, Răzvan M.; Ungureanu, Marius I.; Vasarhelyi, Emanuela O. Marton; Valentine, Marissa A.; Sabo-Attwood, Tara; Gray, Gregory C.

    2015-01-01

    Eastern European and Central Asian countries are undergoing rapid socioeconomic and political reforms. Many old industrial facilities are either abandoned, or use outdated technologies that severely impact the environment. Emerging industries have less regulation than in developed countries and environmental and occupational problems seem to be increasing. Under a US National Institutes of Health pilot grant, we developed an interdisciplinary One Health research network in Southeastern Europe and West-Central Asia to identify environmental and occupational problems. From 2012–2014, this GEOHealth Hub engaged 11 academic centers and 16 public health institutions in eight different countries: Albania, Armenia, Georgia, Kazakhstan, Kyrgyzstan, Moldova, Romania, and the United States with a goal of strengthening environmental and occupational research and training capacities. Employing face-to-face interviews and large group meetings, we conducted an evidenced-based needs and opportunities assessment focused on aquatic health, food safety, and zoonotic diseases. Comprehensive reviews of published literature yielded priority research areas for each of the seven GeoHealth Hub countries including heavy metal and pesticide contamination, tick-borne diseases, rabies, brucellosis, and inadequate public health surveillance. PMID:25963604

  10. Flying Low over Southeast Greenland

    NASA Video Gallery

    Few of us ever get to see Greenland's glaciers from 500 meters above the ice. But in this video — recorded on April 9,2013 in southeast Greenland using a cockpit camera installed and operated by ...

  11. Hydrothermal-metasomatic and tectono-metamorphic processes in the Isua supracrustal belt (West Greenland): a multi-isotopic investigation of their effects on the earth's oldest oceanic crustal sequence

    NASA Astrophysics Data System (ADS)

    Frei, Robert; Rosing, Minik T.; Waight, Tod E.; Ulfbeck, David G.

    2002-02-01

    Despite superimposed metamorphic overprinting and metasomatic alterations, primary volcanic features remain preserved in low-strain domains of mafic volcanic sequences in the western Isua supracrustal belt (ISB, West Greenland). These basaltic successions represent the hitherto oldest known fragments of oceanic crust on Earth. Early Archean metasomatic fluids, rich in light rare earth elements (LREE), Th, U, Pb, Ba, and alkalies, invaded the supracrustal package and distinctively altered the basaltic sequences. Field relationships, source characteristics traced by Pb isotopes, and geochronological results provide indications that these fluids were genetically related to the emplacement of tonalite sheets into the ISB between 3.81 and 3.74 Ga ago. Subsequent early Archean metamorphism homogenized the mixed primary and metasomatic mineral parageneses of these metavolcanic rocks. Allanite occurs as the most characteristic and critical secondary metasomatic-metamorphic phase and is developed in macroscopically discernible zones of increased metsomatic alteration, even in domains of low strain. Because of its high concentration of LREE, Th, and U, this secondary mineral accounts for much of the disturbances recorded by the Sm-Nd and Th-U-Pb isotope systematics of the pillowed metabasalts. The supracrustal sequences were tectono-metamorphically affected to varying degrees during a late Archean, ˜2.6- to 2.8-Ga-old event, also recognized in the adjacent gneiss terranes of the Isuakasia area. The degree to which bulk rocks were isotopically reequilibrated is directly dependent on the different relative contributions of allanite-hosted parent-daughter elements to the overall whole-rock mass budget of the respective isotope systems. Although low-strained (initially only weakly metasomatized) pillow basalts remained more or less closed with respect to the U-Pb and Rb-Sr systems since ˜3.74 Ga, the Sm-Nd system appears to have been partially opened on a whole-rock scale

  12. Late Paleozoic tectonic evolution and concentrated mineralization in Balkhash and West Junggar, western part of the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Dong, Shuwen; Chen, Xuanhua; Chen, Zhengle

    2016-04-01

    The Central Asia Orogenic Belt (CAOB) is an important area with significant growth of the crust and metallogeny in the Late Paleozoic. The Balkhash-Junggar tectono-metallogenic belt consists of the Balkhash, the West Junggar, and the East Junggar tectono-metallogenic belts in western part of the Central Asian Orogenic Belt (CAOB). According to the structural geological relationship, the East Junggar, the West Junggar, and the Balkhash belts are considered to be once a continuous E-W-trending tectono-metallogenic belt in Late Carboniferous. The West Junggar belt is featured with NE-trending left-lateral strike-slip faulting tectonic system (WJTS), while the left-lateral strike-slip faults are E-W-trending in the Balkhash belt. The WJTS consists of the Darabut, the Mayile, and the Baerluke faults, and the blocks among them. All these left-lateral strike-slip faults are forming due to the transition of tectonic settings from syn-collisional orogeny to post-collisional extension during the closure of the ocean (the Junggar Sea) in Late Carboniferous, with significant intrusion of batholiths and crust growth occurred in this period. These faults are truncated by the right-lateral strike-slip faults, such as the Chingiz-Junggar fault, and the Central Balkhash fault in Mesozoic. The Balkhash-Junggar tectono-metallogenic belt is important for the occurrence of many well-known super-large and large porphyry Cu-Mo deposits (such as the Kounrad, the Aktogai, the Borly, and the Baogutu deposits), large skarn Cu deposits (in the Sayak ore-filed), large rare metal deposits (such as the East Kounrad, the Zhanet, and the Akshatau deposits), and large gold deposits (such as the Hatu deposit). Zircon U-Pb ages, Re-Os isotopic dating of molybdenites, 40Ar/39Ar thermochronology of hornblendes, muscovites, biotites, and K-feldspars, and zircon and apatite fission track (FT) and (U-Th)/He dating and thermal history modeling, provide a multidisciplinary approach to constrain the whole

  13. Community Problems in Five West Central Counties. Report No. 7 of a Series on Quality of Life and Development in Northwestern Wisconsin, February 1976.

    ERIC Educational Resources Information Center

    Lambert, Virginia; Linn, Gary

    As part of a study on development and the quality of life in northwestern Wisconsin, questions concerning important problems, public services, and environmental issues were asked of samples of 150 people in each of 4 west central counties (Clark, Dunn, Eau Claire, and Polk) in 1974. Responses to similar questions asked in a 1973 study of St. Croix…

  14. Multibeam Data and Socio-Economic Issues in West-Central San Francisco Bay, California

    USGS Publications Warehouse

    Chin, John L.; Carlson, Paul R.; Wong, Florence L.; Cacchione, David A.

    1998-01-01

    San Francisco Bay is the largest estuary on the conterminous U.S. Pacific Coast and is one of the world's largest natural harbors. It is a biologically productive and diverse environment. San Francisco Bay has a maritime economy that annually generates over $7.5 billion, handles 50 million tons of cargo, and involves thousands of jobs. Recent investigations by the USGS in this estuary help address both socio-economic and scientific issues: *Trimming pinnacles may prevent a calamitous oil spill. *Can San Francisco Bay accept more dredge spoil? *Bay floor biological habitats are quite varied. *How thick and how variable is the sediment fill in central San Francisco Bay?

  15. Spatio-Temporal Identification of Areas Suitable for West Nile Disease in the Mediterranean Basin and Central Europe

    PubMed Central

    Conte, Annamaria; Candeloro, Luca; Ippoliti, Carla; Monaco, Federica; De Massis, Fabrizio; Bruno, Rossana; Di Sabatino, Daria; Danzetta, Maria Luisa; Benjelloun, Abdennasser; Belkadi, Bouchra; El Harrak, Mehdi; Declich, Silvia; Rizzo, Caterina; Hammami, Salah; Ben Hassine, Thameur; Calistri, Paolo; Savini, Giovanni

    2015-01-01

    West Nile virus (WNV) is a mosquito-transmitted Flavivirus belonging to the Japanese encephalitis antigenic complex of the Flaviviridae family. Its spread in the Mediterranean basin and the Balkans poses a significant risk to human health and forces public health officials to constantly monitor the virus transmission to ensure prompt application of preventive measures. In this context, predictive tools indicating the areas and periods at major risk of WNV transmission are of paramount importance. Spatial analysis approaches, which use environmental and climatic variables to find suitable habitats for WNV spread, can enhance predictive techniques. Using the Mahalanobis Distance statistic, areas ecologically most suitable for sustaining WNV transmission were identified in the Mediterranean basin and Central Europe. About 270 human and equine clinical cases notified in Italy, Greece, Portugal, Morocco, and Tunisia, between 2008 and 2012, have been considered. The environmental variables included in the model were altitude, slope, night time Land Surface Temperature, Normalized Difference Vegetation Index, Enhanced Vegetation Index, and daily temperature range. Seasonality of mosquito population has been modelled and included in the analyses to produce monthly maps of suitable areas for West Nile Disease. Between May and July, the most suitable areas are located in Tunisia, Libya, Egypt, and North Cyprus. Summer/Autumn months, particularly between August and October, characterize the suitability in Italy, France, Spain, the Balkan countries, Morocco, North Tunisia, the Mediterranean coast of Africa, and the Middle East. The persistence of suitable conditions in December is confined to the coastal areas of Morocco, Tunisia, Libya, Egypt, and Israel. PMID:26717483

  16. Hydrologic and water-quality conditions in the Horse Creek Basin, west-central Florida, October 1992-February 1995

    USGS Publications Warehouse

    Lewelling, B.R.

    1997-01-01

    A baseline study of the 241-square-mile Horse Creek basin was undertaken from October 1992 to February 1995 to assess the hydrologic and water-quality conditions of one of the last remaining undeveloped basins in west-central Florida. During the period of the study, much of the basin remained in a natural state, except for limited areas of cattle and citrus production and phosphate mining. Rainfall in 1993 and 1994 in the Horse Creek basin was 8 and 31 percent, respectively, above the 30-year long-term average. The lowest and highest maximum instantaneous peak discharge of the six daily discharge stations occurred at the Buzzard Roost Branch and the Horse Creek near Arcadia stations with 185 to 4,180 cubic feet per second, respectively. The Horse Creek near Arcadia station had the lowest number of no-flow days with zero days and the Brushy Creek station had the highest number with 113 days. During the study, the West Fork Horse Creek subbasin had the highest daily mean discharge per square mile with 30.6 cubic feet per second per square mile, and the largest runoff coefficient of 43.7 percent. The Buzzard Roost Branch subbasin had the lowest daily mean discharge per square mile with 5.05 cubic feet per second per square mile, and Brushy Creek and Brandy Branch shared the lowest runoff coefficient of 0.6 percent. Brandy Branch had the highest monthly mean runoff in both 1993 and 1994 with 11.48 and 19.28 inches, respectively. During the high-baseflow seepage run, seepage gains were 8.87 cubic feet per second along the 43-mile Horse Creek channel. However, during the low-baseflow seepage run, seepage losses were 0.88 cubic foot per second. Three methods were used to estimate average annual ground-water recharge in the Horse Creek basin: (1) well hydrograph, (2) chloride mass balance, and (3) streamflow hydrograph. Estimated average annual recharge using these three methods ranged from 3.6 to 8.7 inches. The high percentage of carbonate plus bicarbonate analyzed at

  17. East Meets West: An Earthquake in India Helps Hazard Assessment in the Central United States

    USGS Publications Warehouse

    ,

    2002-01-01

    Although geographically distant, the State of Gujarat in India bears many geological similarities to the Mississippi Valley in the Central United States. The Mississippi Valley contains the New Madrid seismic zone that, during the winter of 1811-1812, produced the three largest historical earthquakes ever in the continental United States and remains the most seismically active region east of the Rocky Mountains. Large damaging earthquakes are rare in ‘intraplate’ settings like New Madrid and Gujarat, far from the boundaries of the world’s great tectonic plates. Long-lasting evidence left by these earthquakes is subtle (fig. 1). Thus, each intraplate earthquake provides unique opportunities to make huge advances in our ability to assess and understand the hazards posed by such events.

  18. Geophysical evidence of Cretaceous volcanics in Logone Birni Basin (Northern Cameroon), Central Africa, and consequences for the West and Central African Rift System

    NASA Astrophysics Data System (ADS)

    Loule, Jean-Pierre; Pospisil, Lubomil

    2013-01-01

    Detailed analyses and interpretation realized by combining existing 2D reflection seismic and Gravity/Magnetic data of the Logone Birni Basin (LBB) in the West and Central African Rift System (WCAS) have revealed the distribution of the main buried volcanic bodies as well as their relationships with the structural and tectonic evolution of this basin. The volcanic activity in the LBB is restricted to the Cretaceous period. Three main volcanic episodes are identified and are associated to the Neocomian, Late Albian and Cenomanian-Turonian rifting phases respectively. The volcanic bodies within the Lower Cretaceous are either lying directly on basement or are mainly interbedded with the contemporaneous sediments whereas the Upper Cretaceous bodies are morphologically expressed in the forms of dykes and sills. The volcanic activity was more intense in the western region of the central LBB (Zina sub-basin) along the Cameroon-Nigeria border whereas it was scanty and scattered in the other parts of the basin. The main volcanic dykes are found on the flanks of the major faults bounding basement horsts or in crestal positions in association with syndepositional faults. Although WCAS is associated with large amount of crustal extension and minor volcanism, the intense volcanic activity observed in LBB during the Cretaceous suggests that the intrusive zone during this period was confined to the basement beneath the study area flanked respectively to the north, south and southwest by the Lake Chad, Poli and Chum triple junctions. Tensional stresses generated by this localized domal uplift accounts for most of the observed tectonic structures where major faults transected the entire lithosphere, thus providing conduits for magma migration.

  19. Recent Intermediate Depth Earthquakes in El Salvador, Central Mexico, Cascadia and South-West Japan

    NASA Astrophysics Data System (ADS)

    Lemoine, A.; Gardi, A.; Gutscher, M.; Madariaga, R.

    2001-12-01

    We studied occurence and source parameters of several recent intermediate depth earthquakes. We concentrated on the Mw=7.7 salvadorian earthquake which took place on January 13, 2001. It was a good example of the high seismic risk associated to such kind of events which occur closer to the coast than the interplate thrust events. The Salvadorian earthquake was an intermediate depth downdip extensional event which occured inside the downgoing Cocos plate, next to the downdip flexure where the dip increases sharply before the slab sinks more steeply. This location corresponds closely to the position of the Mw=5.7 1996 and Mw=7.3 1982 downdip extensional events. Several recent intermediate depth earthquakes occured in subduction zones exhibiting a ``flat slab'' geometry with three distinct flexural bends where flexural stress may be enhanced. The Mw=6.7 Geiyo event showed a downdip extensional mechanism with N-S striking nodal planes. This trend was highly oblique to the trench (Nankai Trough), yet consistent with westward steepening at the SW lateral termination of the SW Japan flat slab. The Mw=6.8 Olympia earthquake in the Cascadia subduction zone occured at the downdip termination of the Juan de Fuca slab, where plate dip increases from about 5o to over 30o. The N-S orientation of the focal planes, parallel to the trench indicated downdip extension. The location at the downdip flexure corresponds closely to the estimated positions of the 1949 M7.1 Olympia and 1965 M6.5 Seattle-Tacoma events. Between 1994 and 1999, in Central Mexico, an unusually high intermediate depth seismicity occured where several authors proposed a flat geometry for the Cocos plate. Seven events of magnitude between Mw=5.9 and Mw=7.1 occured. Three of them were downdip compressional and four where down-dip extensional. We can explain these earthquakes by flexural stresses at down-dip and lateral terminations of the supposed flat segment. Even if intermediate depth earthquakes occurence could

  20. Glaciers of Greenland

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1995-01-01

    Landsat imagery, combined with aerial photography, sketch maps, and diagrams, is used as the basis for a description of the geography, climatology, and glaciology, including mass balance, variation, and hazards, of the Greenland ice sheet and local ice caps and glaciers. The Greenland ice sheet, with an estimated area of 1,736,095+/-100 km2 and volume of 2,600,000 km3, is the second largest glacier on the planet and the largest relict of the Ice Age in the Northern Hemisphere. Greenland also has 48,599+/-100 km2 of local ice caps and other types of glaciers in coastal areas and islands beyond the margin of the ice sheet.

  1. Permian of Norwegian-Greenland sea margins: future exploration target

    SciTech Connect

    Surlyk, F.; Hurst, J.M.; Piasecki, S.; Rolle, F.; Stemmerik, L.; Thomsen, E.; Wrang, P.

    1984-09-01

    Oil and gas exploration in the northern North Sea and the southern Norwegian shelf has mainy been concentrated on Jurassic and younger reservoirs with Late Jurassic black shale source rocks. New onshore investigations in Jameson Land, central East Greenland, suggest that the Permian of the Norwegian-Greenland Sea margins contains relatively thick sequences of potential oil source rocks interbedded with carbonate reefs. The East Greenland, Upper Permian marine basin is exposed over a length of 400 km (250 mi) from Jameson Land in the south to Wollaston Forland in the north, parallel with the continental margin. The Upper Permian black shale is relatively thick, widely distributed, has a high organic carbon content, and a favorable kerogen type. Consequently, the possibilities for a Permian play in the northern part of the Norwegian shelf and along parts of the Norwegian-Greenland Sea margins are worth evaluating.

  2. Large quaternary landslides in the central appalachian valley and ridge province near Petersburg, West Virginia

    USGS Publications Warehouse

    Scott, Southworth C.

    1988-01-01

    Geological mapping and photointerpretation of side-looking airborne radar images and color-infrared aerial photographs reveal two large Quaternary landslides in the Valley and Ridge province of the central Appalachians near Petersburg, W. Va. The Elkhorn Mountain rock avalanche occurs on the thrust-faulted northwestern flank of the Elkhorn Mountain anticlinorium. A minimum of 7 ?? 106 m3 of quartzite colluvium was transported more than 3 km from a 91 m high escarpment of Silurian Tuscarora Quartzite. The extensively vegetated deposit may owe, in part, its transport and weathering to periglacial conditions during the Pleistocene. In contrast, the Gap Mountain rock block slide is a single allochthonous block that is 1.2 km long, 0.6 km wide, and at least 60 m thick. The 43 ?? 106 m3 block is composed of limestone of the Helderberg Group and the Oriskany Sanstone of Early Devonian age. Planar detachment probably occurred along a dissolution bedding plane near the Shriver Chert and the Oriskany Sandstone contact. Failure probably was initiated by downcutting of the South Branch Potomac River during the Pleistocene. Landslides of this magnitude suggest accelerated erosion during periglacial climates in the Pleistocene. The recognition of these large slope failures may provide evidence of paleoclimatic conditions and, thereby, increase our understanding of the geomorphologic development of the Valley and Ridge province. ?? 1988.

  3. Potentiometric surfaces of the intermediate aquifer system, west-central Florida, May, 1993

    USGS Publications Warehouse

    Mularoni, R.A.

    1994-01-01

    The intermediate aquifer system underlies a 5000-sq-mi area including De Soto, Sarasota, Hardee, Manatee, and parts of Charlotte, Hillsborough, Highlands, and Polk Counties, Florida. It is overlain by the surf@cial aquifer system and underlain by the Floridan aquifer system. The potentiometric surface of the intermediate aquifer system was mapped by determining the altitude of water levels in a network of wells and represented on a map by contours that connect points of equal altitude. This map represents water-level conditions near the end of the spring dry season when ground- water withdrawals for agricultural use were high. The cumulative rainfall for the study area was 4.84 inches above normal for the period from June 1992 to May 1993. Hydrographs for selected wells indicated that the annual and seasonal fluctuations of the water levels were generally large (greater than 15 feet) in the central interior region where water demand for irrigation is high during the fall and spring. Seasonal fluctuations were smaller in the northern recharge area where water use is predominantly for public supply. Water levels measured in May 1993 for the composite intermediate aquifer potentiometric surface were lower than those measured in May or September 1992. A cone of depression exists in the potentiometric surface for the composite aquifer system at Warm Mineral Springs, which is a natural discharge point from this system.

  4. Hydrothermal uranium deposits containing molybdenum and fluorite in the Marysvale volcanic field, west-central Utah

    USGS Publications Warehouse

    Cunningham, C.G.; Rasmussen, J.D.; Steven, T.A.; Rye, R.O.; Rowley, P.D.; Romberger, S.B.; Selverstone, J.

    1998-01-01

    Uranium deposits containing molybdenum and fluorite occur in the Central Mining Area, near Marysvale, Utah, and formed in an epithermal vein system that is part of a volcanic/hypabyssal complex. They represent a known, but uncommon, type of deposit; relative to other commonly described volcanic-related uranium deposits, they are young, well-exposed and well-documented. Hydrothermal uranium-bearing quartz and fluorite veins are exposed over a 300 m vertical range in the mines. Molybdenum, as jordisite (amorphous MoS2, together with fluorite and pyrite, increase with depth, and uranium decreases with depth. The veins cut 23-Ma quartz monzonite, 20-Ma granite, and 19-Ma rhyolite ash-flow tuff. The veins formed at 19-18 Ma in a 1 km2 area, above a cupola of a composite, recurrent, magma chamber at least 24 ?? 5 km across that fed a sequence of 21- to 14-Ma hypabyssal granitic stocks, rhyolite lava flows, ash-flow tuffs, and volcanic domes. Formation of the Central Mining Area began when the intrusion of a rhyolite stock, and related molybdenite-bearing, uranium-rich, glassy rhyolite dikes, lifted the fractured roof above the stock. A breccia pipe formed and relieved magmatic pressures, and as blocks of the fractured roof began to settle back in place, flat-lying, concave-downward, 'pull-apart' fractures were formed. Uranium-bearing, quartz and fluorite veins were deposited by a shallow hydrothermal system in the disarticulated carapace. The veins, which filled open spaces along the high-angle fault zones and flat-lying fractures, were deposited within 115 m of the ground surface above the concealed rhyolite stock. Hydrothermal fluids with temperatures near 200??C, ??18OH2O ~ -1.5, ?? -1.5, ??DH2O ~ -130, log fO2 about -47 to -50, and pH about 6 to 7, permeated the fractured rocks; these fluids were rich in fluorine, molybdenum, potassium, and hydrogen sulfide, and contained uranium as fluoride complexes. The hydrothermal fluids reacted with the wallrock resulting in

  5. Late Proterozoic reconstructions of North-West Scotland and Central Canada: Magnetic fabrics, paleomagnetism and tectonics

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham J.; Geneviciene, Ieva

    2008-12-01

    vectors were rotated into Laurentian coordinates for comparison with Canadian Proterozoic palaeopoles. The Stoer Group was magnetized in a normal polarity geomagnetic field whereas the Torridon Group was magnetized in a reversed polarity epoch. However, both sequences include at least one polarity transition, indicating long duration chemical magnetizations successfully averaging secular variation. At a minimum, red-bed magnetization processes exceeded 0.1 Ma and may have encompassed several million years. During Stoer Group magnetization, the Hebridean craton was at paleolatitudes of 26-44°N; when the Torridon Group magnetized it was at 23-27°S. Accepting published ages, this defines a minimum southward latitudinal displacement rate of 27-40 km/Ma. Restored Stoer Group paleopoles lie in the present-day north-central Pacific Ocean (˜190E/25N); corresponding to the Laurentian APWP dated at between 1090 and 1109 Ma. Torridon Group paleopoles lie in the south-central Pacific (˜210E/25S) near the poorly documented (<900 Ma) southernmost part of the Laurentian APWP.

  6. The central west Saharan dust hotspot and its relation to African easterly waves and extratropical disturbances

    NASA Astrophysics Data System (ADS)

    Knippertz, Peter; Todd, Martin C.

    2010-05-01

    A vast, arid, and virtually uninhabited region covering eastern Mauritania and northern Mali appears in many satellite estimates of dust loading as the global maximum during boreal summer. Here the complex meteorological conditions that create this central western Sahara (CWS) dust hotspot are investigated on the basis of regression analyses and case study examples using a wide range of satellite analysis products (TOMS, OMI, MISR, SEVIRI). The results confirm the importance of African easterly waves (AEWs), previously hypothesized on the basis of case studies. The main ingredients to create this connection are: (I) Strengthened southerlies to the east of an AEW trough advect moist air into the southern Sahara. Daytime heating and orography trigger moist convection in this airmass. Strong evaporation in dry midlevel air generates extended cold pools and haboob dust storms. (II) Vertical mixing brings dust into the upper parts of the deep Saharan boundary layer, from where it can be advected back into the CWS region with the northerlies ahead of the next AEW trough. (III) If the associated surface vortex is strong enough, more dust emission occurs within or just upstream of the CWS. (IV) High-amplitude waves in the subtropics enhance the meridional flow associated with the AEW. Although there is a considerable case-to-case variability, it can be concluded that AEWs in concert with extratropical disturbances substantially contribute to the hotspot creation both through emission and the organization of transport. Disagreement between different satellite products and the presence of clouds complicate the analysis and underline the necessity for improved in-situ observations.

  7. Genetic diversity, introgression and relationships among West/Central African cattle breeds

    PubMed Central

    Ibeagha-Awemu, Eveline Mengwi; Jann, Oliver Carl; Weimann, Christina; Erhardt, Georg

    2004-01-01

    Genetic diversity, introgression and relationships were studied in 521 individuals from 9 African Bos indicus and 3 Bos taurus cattle breeds in Cameroon and Nigeria using genotype information on 28 markers (16 microsatellite, 7 milk protein and 5 blood protein markers). The genotypes of 13 of the 16 microsatellite markers studied on three European (German Angus, German Simmental and German Yellow) and two Indian (Nelore and Ongole) breeds were used to assess the relationships between them and the African breeds. Diversity levels at microsatellite loci were higher in the zebu than in the taurine breeds and were generally similar for protein loci in the breeds in each group. Microsatellite allelic distribution displayed groups of alleles specific to the Indian zebu, African taurine and European taurine. The level of the Indian zebu genetic admixture proportions in the African zebus was higher than the African taurine and European taurine admixture proportions, and ranged from 58.1% to 74.0%. The African taurine breed, Muturu was free of Indian zebu genes while its counter Namchi was highly introgressed (30.2%). Phylogenic reconstruction and principal component analysis indicate close relationships among the zebu breeds in Cameroon and Nigeria and a large genetic divergence between the main cattle groups – African taurine, European taurine and Indian zebu, and a central position for the African zebus. The study presents the first comprehensive information on the hybrid composition of the individual cattle breeds of Cameroon and Nigeria and the genetic relationships existing among them and other breeds outside of Africa. Strong evidence supporting separate domestication events for the Bos species is also provided. PMID:15496287

  8. Foraminifera and paleoenvironments in the Etchegoin and lower San Joaquin Formations, west-central San Joaquin valley, California

    SciTech Connect

    Lagoe, M.B.; Tenison, J.A.; Buehring, R. )

    1991-02-01

    The Etchegoin and San Joaquin formations preserve a rich stratigraphic record of paleoenvironments, deposition, and tectonics during the late Miocene-Pliocene development of the San Joaquin basin. The distribution of foraminifera within these formations can help constrain this record, which includes final filling of the basin, facies responses to sea level changes, and active movement on the San Andreas fault system. The distribution of foraminifera in core samples is analyzed from seven wells along the west-central San joaquin basin - four from Buena Vista oil field, one from western Elk Hills oil field, and two from an area just south of South Belridge oil field. A model of modern, shallow- to marginal-marine foraminiferal biofacies is used to interpret the Etchegoin-San Joaquin faunal distributions. This modern model distinguishes marsh, tidal channel, intertidal, lagoonal, littoral, and shallow sublittoral environments. Ongoing work calibrating this foraminiferal record to the lithologic and macrofossil records in addition to interpreted depositional systems within these formations will further define relationships between paleoenvironments, relative sea level, and tectonics.

  9. Selenium in soil, water, sediment, and biota of the lower Sun River area, West-Central Montana

    USGS Publications Warehouse

    Nimick, David A.; Lambing, John H.; Palawski, Donald U.

    1993-01-01

    A U.S. Department of the Interior study started in 1990 examined the source, movement, fate, and possible biological effects of selenium associated with irrigation drainage from the Sun River Irrigation Project in west-central Montana. Concentrations of total selenium in soil samples ranged from 0.1 to 8.5 micrograms per gram; the maximum concentrations were measured in nonirrigated areas overlying geologic formations containing seleniferous shale. In irrigated areas, concentrations of dissolved selenium in ground water flowing toward Freezeout Lake ranged from less than 1 to 18 micrograms per liter (??g/L) in terrace gravel and from 1 to 190 ??g/L in glacial deposits derived from seleniferous shale. Concentrations of total selenium ranged from less than 1 to 180 ??g/L in surface irrigation drainage, and from less than 1 to 1,000 ??g/L in natural flows from nonirrigated land. Selenium concentrations in water from lakes generally were less than the aquatic-life criterion for chronic toxicity. The range of selenium concentrations in bottom sediment of lakes was similar to that of local soils. However, biological samples indicate that selenium is accumulating through the aquatic food chain. Selenium concentrations indicative of biological risk were exceeded in at least 80 percent of the freshwater-invertebrate, bird-egg, and bird-liver samples collected from all wetland sites.

  10. Sampling strategies and variability in fruit pulp micronutrient contents of west and central african bananas and plantains (Musa species).

    PubMed

    Davey, Mark W; Stals, Ellen; Ngoh-Newilah, Gérard; Tomekpe, Kodjo; Lusty, Charlotte; Markham, Richard; Swennen, Rony; Keulemans, Johan

    2007-04-04

    The variability in fruit micronutrient contents in a selection of Central and West African Musa varieties cultivated under standardized field conditions was studied. Analysis of the within-fruit, within-hand, and within-plant as well as the between-plant variations demonstrated that both provitamin A carotenoids (pVACs) and mineral micronutrient (Fe, Zn) contents vary significantly across all sample groups. The variations in pVACs contents appear to be at least partly related to differences in the developmental status of the fruit, but the observed trends were genotype-specific. The mean pVACs concentrations per genotype indicated that there is substantial genetic variation in the fruit pVACs contents between Musa cultivars, with orange-fleshed plantain varieties (AAB) having generally higher fruit pVACs contents than dessert bananas (AAA). It was not possible to identify consistent trends between the sampling position and fruit Fe/Zn contents. Once the within-bunch micronutrient variability has been accounted for, the mean variations in fruit micronutrient contents between individual plants of a variety generally fell to within acceptable limits. Results are discussed within the framework of standardizing sampling and developing strategies to screen for the nutritional values of new and existing Musa varieties.

  11. Foods of American badgers in west-central Minnesota and southeastern North Dakota during the duck nesting season

    USGS Publications Warehouse

    Sovada, M.A.; Roaldson, J.M.; Sargeant, A.B.

    1999-01-01

    Although the American badger (Taxidea taxus) is common in grasslands and preys on a wide diversity of foods including birds, little is known about badger diet in areas where nesting ducks are common. Small mammals, primarily Muridae and Geomyidae, were the most common food items in the diet of badgers collected from west-central Minnesota and southeastern North Dakota during April-July 1987 through 1990, based on analysis of gastrointestinal tracts of 47 adult ( 1/4 -y-old) and 5 juvenile (<6-mo-old) badgers. Remains of mammals occurred in 98% of samples from adult badgers. Small quantities of insects were found in 40% of adult samples. Bird remains were in 32% of adult samples, most birds identified as Anatidae; ducks or ducklings occurred in 27% and duck eggs in 60% of those samples. Remains of reptiles, amphibians and mollusks were present, but were less common than other foods. Insects and bird eggs were more common during spring (April-May) than summer (June-July). Birds were more frequent in diets of adults than juvenile badgers.

  12. Cryptomyrus: a new genus of Mormyridae (Teleostei, Osteoglossomorpha) with two new species from Gabon, West-Central Africa.

    PubMed

    Sullivan, John P; Lavoué, Sébastien; Hopkins, Carl D

    2016-01-01

    We use mitochondrial and nuclear sequence data to show that three weakly electric mormyrid fish specimens collected at three widely separated localities in Gabon, Africa over a 13-year period represent an unrecognized lineage within the subfamily Mormyrinae and determine its phylogenetic position with respect to other taxa. We describe these three specimens as a new genus containing two new species. Cryptomyrus, new genus, is readily distinguished from all other mormyrid genera by a combination of features of squamation, morphometrics, and dental attributes. Cryptomyrus ogoouensis, new species, is differentiated from its single congener, Cryptomyrus ona, new species, by the possession of an anal-fin origin located well in advance of the dorsal fin, a narrow caudal peduncle and caudal-fin lobes nearly as long as the peduncle. In Cryptomyrus ona, the anal-fin origin is located only slightly in advance of the dorsal fin, the caudal peduncle is deep and the caudal-fin lobes considerably shorter than the peduncle. Continued discovery of new taxa within the "Lower Guinea Clade" of Mormyridae highlights the incompleteness of our knowledge of fish diversity in West-Central Africa. We present a revised key to the mormyrid genera of Lower Guinea.

  13. Brevetoxin in blood, biological fluids, and tissues of sea turtles naturally exposed to Karenia brevis blooms in central west Florida.

    PubMed

    Fauquier, Deborah A; Flewelling, Leanne J; Maucher, Jennifer; Manire, Charles A; Socha, Victoria; Kinsel, Michael J; Stacy, Brian A; Henry, Michael; Gannon, Janet; Ramsdell, John S; Landsberg, Jan H

    2013-06-01

    In 2005 and 2006, the central west Florida coast experienced two intense Karenia brevis red tide events lasting from February 2005 through December 2005 and August 2006 through December 2006. Strandings of sea turtles were increased in the study area with 318 turtles (n = 174, 2005; n = 144, 2006) stranding between 1 January 2005 and 31 December 2006 compared to the 12-yr average of 43 +/- 23 turtles. Live turtles (n = 61) admitted for rehabilitation showed clinical signs including unresponsiveness, paresis, and circling. Testing of biological fluids and tissues for the presence of brevetoxin activity by enzyme-linked immunosorbent assay found toxin present in 93% (52 of 56) of live stranded sea turtles, and 98% (42 of 43) of dead stranded sea turtles tested. Serial plasma samples were taken from several live sea turtles during rehabilitation and toxin was cleared from the blood within 5-80 days postadmit depending upon the species tested. Among dead animals the highest brevetoxin levels were found in feces, stomach contents, and liver. The lack of significant pathological findings in the majority of animals necropsied supports toxin-related mortality.

  14. Chemical composition of red, brown and green macroalgae from Buarcos bay in Central West Coast of Portugal.

    PubMed

    Rodrigues, Dina; Freitas, Ana C; Pereira, Leonel; Rocha-Santos, Teresa A P; Vasconcelos, Marta W; Roriz, Mariana; Rodríguez-Alcalá, Luís M; Gomes, Ana M P; Duarte, Armando C

    2015-09-15

    Six representative edible seaweeds from the Central West Portuguese Coast, including the less studied Osmundea pinnatifida, were harvested from Buarcos bay, Portugal and their chemical characterization determined. Protein content, total sugar and fat contents ranged between 14.4% and 23.8%, 32.4% and 49.3% and 0.6-3.6%. Highest total phenolic content was observed in Codium tomentosum followed by Sargassum muticum and O. pinnatifida. Fatty acid (FA) composition covered the branched chain C13ai to C22:5 n3 with variable content in n6 and n3 FA; low n6:n3 ratios were observed in O. pinnatifida, Grateloupia turuturu and C. tomentosum. Some seaweed species may be seen as good sources of Ca, K, Mg and Fe, corroborating their good nutritional value. According to FTIR-ATR spectra, G. turuturu was associated with carrageenan seaweed producers whereas Gracilaria gracilis and O. pinnatifida were mostly agar producers. In the brown algae, S. muticum and Saccorhiza polyschides, alginates and fucoidans were the main polysaccharides found.

  15. Aquifer tests at the Jackpile-Paguate uranium mine, Pueblo of Laguna, west-central New Mexico

    USGS Publications Warehouse

    Risser, D.W.; Davis, P.A.; Baldwin, J.A.; McaAda, D.P.

    1984-01-01

    The transmissivity of the Jackpile sandstone bed in the Brushy Basin Shale Member of the Morrison Formation, west-central New Mexico, was determined to be 24 sq ft/day at well M2 and 47 sq ft/day at well M3 from constant-discharge aquifer tests conducted at the Jackpile-Paguate Uranium Mine. The storage coefficient of the Jackpile sandstone bed was estimated to be 0.00018 at well M2 and 0.00029 at well M3 from the same tests. An aquifer test conducted at well M21 indicated the transmissivity of the Jackpile sandstone bed was 2.0 sq ft/day and the storage coefficient was 0.00002. The transmissivity of an unnamed sandstone bed in the Brushy Basin Shale Member of the Morrison Formation was estimated from ' slug-test ' results to be about 20 sq ft/day. Water levels in this sandstone probably did not change due to pumping from the overlying Jackpile sandstone bed for 88 hours at an average discharge of 15.3 gallons/min. A constant discharge aquifer test at well M4C indicated that the transmissivity of the alluvium at this location was about 430 sq ft/day. Water levels in the underlying Jackpile sandstone bed began declining within 15 minutes after withdrawals of groundwater from the alluvial aquifer began. (USGS)

  16. Serological markers and risk factors related to hepatitis B virus in dentists in the Central West region of Brazil

    PubMed Central

    de Paiva, Enilza Maria Mendonça; Tiplle, Anaclara Ferreira Veiga; de Paiva Silva, Eliane; de Paula Cardoso, Divina das Dores

    2008-01-01

    The hepatitis B virus (HBV) has been considered the major occupational risk agent for dentists. The Central West region of Brazil is considered an intermediate endemic pattern area, but currently there is no information about the HBV prevalence in dentists of Goiânia, Goiás. This study aimed at the detection of the HBV infection rate and risk factors for dentists of Goiânia and the comparison of the obtained data with the general population and other groups. A randomized sample of 680 professionals participated in this study. All dentists gave written consent for the procedure and filled out a questionnaire about risk factors. The HBV serological markers were analyzed using ELISA test and the presence of anti-HBc was observed in 41 (6.0%) of the dentists. None of them was HBsAg positive. Significant relationships with HBV positivity were observed with gender, the time working as a dentist and the use of incomplete personal protective equipment (PPE). The HBV prevalence found in this group of dentists was lower than the endemic pattern of the general population, other health care workers of the region and the dentists from other regions in Brazil. These results may indicate a positive impact of vaccination considering the high adherence of the dentists to the immunization program (98.4%). Finally, the use of complete PPE by the majority as well as other standard precautions recommended for health care workers could be responsible for the low HBV seroprevalence. PMID:24031211

  17. Terminal Pleistocene to early Holocene volcanic eruptions at Zuni Salt Lake, west-central New Mexico, USA

    NASA Astrophysics Data System (ADS)

    Onken, Jill; Forman, Steven

    2017-01-01

    Zuni Salt Lake (ZSL) is a large maar in the Red Hill-Quemado volcanic field located in west-central New Mexico in the southwestern USA. Stratigraphic analysis of sections in and around the maar, coupled with optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) 14C dating, indicate that ZSL volcanic activity occurred between ˜13.4 and 9.9 ka and was most likely confined to a ≤500-year interval sometime between ˜12.3 and 11.0 ka. The basal volcanic unit consists of locally widespread basaltic ash fallout interpreted to represent a violent or wind-aided strombolian eruption tentatively attributed to Cerro Pomo, a scoria cone ˜10 km south of ZSL. Subsequent eruptions emanated from vents near or within the present-day ZSL maar crater. Strombolian eruptions of multiple spatter and scoria cones produced basaltic lava and scoria lapilli fallout. Next, a phreatomagmatic eruption created the maar crater and surrounding tephra rim and apron. ZSL eruptions ended with strombolian eruptions that formed three scoria cones on the crater floor. The revised age range of ZSL is younger and more precise than the 190-24 ka 2-sigma age range derived from previous argon dating. This implies that other morphologically youthful, argon-dated volcanoes on the southern margin of the Colorado Plateau might be substantially younger than previously reported.

  18. An unusual occurrence of arsenic-bearing pyrite in the Upper Freeport coal bed, West-Central Pennsylvania

    USGS Publications Warehouse

    Ruppert, L.F.; Minkin, J.A.; McGee, J.J.; Cecil, C.B.

    1992-01-01

    Scanning electron microscopy and electron microprobe analysis were used to identify a rare type of As-bearing pyrite in selected specific gravity separates from the Pennsylvanian age Upper Freeport coal bed, west-central Pennsylvania. Arsenic was detected mainly in cell-wall replacement pyrite where concentrations ranged from nondetectable to 1.9 wt %. Although the majority of arsenic-bearing pyrite in the Upper Freeport coal bed is concentrated in massive and late diagenetic pyrite morphologies, the rarer As-bearing cell-replacement pyrite was observed in both light and heavy gravity separates from the three coal facies examined. Arsenic was occasionally detected in cell-filling replacement pyrite, but this As appears to be an artifact produced by signals from underlying and/or adjacent As-bearing cell-wall replacement pyrite. It is postulated that some plants of the Upper Freeport paleoswamp may have biomethylated As, which later could have been converted to dimethylarsine or other volatile organoarsenic compounds by either biologically or chemically driven processes. Once liberated, the arsenic may have been incorporated into pyrite during pyritization of the cell walls. The As incorporation occurred early, before significant compaction of the peat, because the pyritized cell walls are not compacted.

  19. The west-central Florida inner shelf and coastal system: A geologic conceptual overview and introduction to the special issue

    USGS Publications Warehouse

    Hine, A.C.; Brooks, G.R.; Davis, R.A.; Duncan, D.S.; Locker, S.D.; Twichell, D.C.; Gelfenbaum, G.

    2003-01-01

    This paper provides an overview for this special publication on the geologic framework of the inner shelf and coastal zone of west-central Florida. This is a significant geologic setting in that it lies at the center of an ancient carbonate platform facing an enormous ramp that has exerted large-scale control on coastal geomorphology, the availability of sediments, and the level of wave energy. In order to understand the Holocene geologic history of this depositional system, a regional study defined by natural boundaries (north end of a barrier island to the apex of a headland) was undertaken by a group of government and university coastal geologists using a wide variety of laboratory and field techniques. It is the purpose of this introductory paper to define the character of this coastal/inner shelf system, provide a historical geologic perspective and background of environmental information, define the overall database, present the collective objectives of this regional study, and very briefly present the main aspects of each contribution. Specific conclusions are presented at the end of each paper composing this volume. ?? 2003 Elsevier B.V. All rights reserved.

  20. Simulated changes in ground-water levels resulting from proposed phosphate mining, west-central Florida; preliminary results

    USGS Publications Warehouse

    Wilson, William Edward

    1977-01-01

    A digital model of two-dimensional ground-water flow was used to simulate projected changes in the Floridan aquifer potentiometric surface in 1985 and 2000, resulting from proposed ground-water developments by the phosphate mining industry in west-central Florida. The .model was calibrated under steady-state conditions to simulate the S