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Sample records for adjacent continental regions

  1. Evidence of low density sub-crustal underplating beneath western continental region of India and adjacent Arabian Sea: Geodynamical considerations

    NASA Astrophysics Data System (ADS)

    Pandey, O. P.; Agrawal, P. K.; Negi, J. G.

    1996-07-01

    The known high mobility of the Indian subcontinent during the period from 80 to 53 Ma has evoked considerable interest in recent times. It appears to have played an important role in shaping the subcontinental structures of western India and the adjoining Arabian Sea. During this period, a major catastrophic event took place in the form of Deccan volcanism, which coincides with the biological mass extinction at the K-T boundary, including the death of dinosaurs. The origin of Deccan volcanism is still being debated. Geophysically, western India and its offshore regions exhibit numerous prominent anomalies which testify to the abnormal nature of the underlying crust-lithosphere. In this work, we develop a two-dimensional structural model of these areas along two long profiles extending from the eastern basin of the Arabian Sea to about 1000 km inland. The model, derived from the available gravity data in the oceanic and continental regions, is constrained by seismic and other relevant information in the area, and suggests, for the first time, the presence of an extensive low-density (2.95-3.05 g/cm 3) sub-crustal underplating. Such a layer is found to occur between depths of 11 and 20 km in the eastern basin of the Arabian Sea, and betweeen 45 and 60 km in the continental region where it is sandwiched in the lower lithosphere. The low density may have been caused as a result of serpentinization or fractionation of magma by a process related in some way to the Deccan volcanic event. Substantial depletion of both oceanic and continental lithosphere is indicated. We hypothesize that the present anatomy of the deformed lithosphere of the region at the K-T boundary is the result of substantial melt generated owing to frictional heat possibly giving rise to a hot cell like condition at the base of the lithosphere, resulting from the rapid movement of the Indian subcontinent between 80 and 53 Ma.

  2. The speciation of marine particulate iron adjacent to active and passive continental margins

    NASA Astrophysics Data System (ADS)

    Lam, Phoebe J.; Ohnemus, Daniel C.; Marcus, Matthew A.

    2012-03-01

    We use synchrotron-based chemical-species mapping techniques to compare the speciation of suspended (1-51 μm) marine particulate iron collected in two open ocean environments adjacent to active and passive continental margins. Chemical-species mapping provides speciation information for heterogeneous environmental samples, and is especially good for detecting spectroscopically distinct trace minerals and species that could not be detectable by other methods. The average oxidation state of marine particulate iron determined by chemical-species mapping is comparable to that determined by standard bulk X-ray Absorption Near Edge Structure spectroscopy. Using chemical-species mapping, we find that up to 43% of particulate Fe in the Northwest Pacific at the depth of the adjacent active continental margin is in the Fe(II) state, with the balance Fe(III). In contrast, particulate iron in the eastern tropical North Atlantic, which receives the highest dust deposition on Earth and is adjacent to a passive margin, is dominated by weathered and oxidized Fe compounds, with Fe(III) contributing 90% of total iron. The balance is composed primarily of Fe(II)-containing species, but we detected individual pyrite particles in some samples within an oxygen minimum zone in the upper thermocline. Several lines of evidence point to the adjacent Mauritanian continental shelf as the source of pyrite to the water column. The speciation of suspended marine particulate iron reflects the mineralogy of iron from the adjacent continental margins. Since the solubility of particulate iron has been shown to be a function of its speciation, this may have implications for the bioavailability of particulate iron adjacent to passive compared to active continental margins.

  3. Historic surface faulting in continental United States and adjacent parts of Mexico

    USGS Publications Warehouse

    Bonilla, M.G.

    1967-01-01

    This report summarizes geometric aspects of approximately 35 instances of historic faulting of the ground surface in the continental United States and adjacent parts of Mexico. This information is of immediate importance in the selection and evaluation of sites for vital structures such as nuclear power plants. The data are presented in a table and graphs which show the quantitative relations between various aspects of the faulting. Certain items in the table that are uncertain, poorly known, or not in the published literature are briefly described in the text.

  4. Regional magnetic anomaly constraints on continental rifting

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

    1985-01-01

    Radially polarized MAGSAT anomalies of North and South America, Europe, Africa, India, Australia and Antarctica demonstrate remarkably detailed correlation of regional magnetic lithospheric sources across rifted margins when plotted on a reconstruction of Pangea. These major magnetic features apparently preserve their integrity until a superimposed metamorphoric event alters the magnitude and pattern of the anomalies. The longevity of continental scale magnetic anomalies contrasts markedly with that of regional gravity anomalies which tend to reflect predominantly isostatic adjustments associated with neo-tectonism. First observed as a result of NASA's magnetic satellite programs, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans. Accordingly, satellite magnetic observations provide a further tool for investigating continental drift to compliment other lines of evidence in paleoclimatology, paleontology, paleomagnetism, and studies of the radiometric ages and geometric fit of the continents.

  5. Cyclic growth in Atlantic region continental crust

    NASA Technical Reports Server (NTRS)

    Goodwin, A. M.

    1986-01-01

    Atlantic region continental crust evolved in successive stages under the influence of regular, approximately 400 Ma-long tectonic cycles. Data point to a variety of operative tectonic processes ranging from widespread ocean floor consumption (Wilson cycle) to entirely ensialic (Ampferer-style subduction or simple crustal attenuation-compression). Different processes may have operated concurrently in some or different belts. Resolving this remains the major challenge.

  6. The Alegre Lineament and its role over the tectonic evolution of the Campos Basin and adjacent continental margin, Southeastern Brazil

    NASA Astrophysics Data System (ADS)

    Calegari, Salomão Silva; Neves, Mirna Aparecida; Guadagnin, Felipe; França, George Sand; Vincentelli, Maria Gabriela Castillo

    2016-08-01

    The structural framework and tectonic evolution of the sedimentary basins along the eastern margin of the South American continent are closely associated with the tectonic framework and crustal heterogeneities inherited from the Precambrian basement. However, the role of NW-SE and NNW-SSE structures observed at the outcropping basement in Southeastern Brazil and its impact over the development of those basins have not been closely investigated. In the continental region adjacent to the Campos Basin, we described a geological feature with NNW-SSE orientation, named in this paper as the Alegre Fracture Zone (AFZ), which is observed in the onshore basement and can be projected to the offshore basin. The main goal of this work was to study this structural lineament and its influence on the tectonic evolution of the central portion of the Campos Basin and adjacent mainland. The onshore area was investigated through remote sensing data joint with field observations, and the offshore area was studied through the interpretation of 2-D seismic data calibrated by geophysical well logs. We concluded that the AFZ occurs in both onshore and offshore as a brittle deformation zone formed by multiple sets of fractures that originated in the Cambrian and were reactivated mainly as normal faults during the rift phase and in the Cenozoic. In the Campos Basin, the AFZ delimitates the western side of the Corvina-Parati Low, composing a complex fault system with the NE-SW faults and the NW-SE transfer faults.

  7. ON THE WIND-INDUCED EXCHANGE BETWEEN INDIAN RIVER BAY, DELAWARE AND THE ADJACENT CONTINENTAL SHELF. (R826945)

    EPA Science Inventory

    The structure of the wind-induced exchange between Indian River Bay, Delaware and the adjacent continental shelf is examined based on current measurements made at the Indian River Inlet which represents the only conduit of exchange between the bay and the coastal ocean. Local ...

  8. Sea-floor drainage features of Cascadia Basin and the adjacent continental slope, northeast Pacific Ocean

    USGS Publications Warehouse

    Hampton, M.A.; Karl, Herman A.; Kenyon, Neil H.

    1989-01-01

    Sea-floor drainage features of Cascadia Basin and the adjacent continental slope include canyons, primary fan valleys, deep-sea valleys, and remnant valley segments. Long-range sidescan sonographs and associated seismic-reflection profiles indicate that the canyons may originate along a mid-slope escarpment and grow upslope by mass wasting and downslope by valley erosion or aggradation. Most canyons are partly filled with sediment, and Quillayute Canyon is almost completely filled. Under normal growth conditions, the larger canyons connect with primary fan valleys or deep-sea valleys in Cascadia Basin, but development of accretionary ridges blocks or re-routes most canyons, forcing abandonment of the associated valleys in the basin. Astoria Fan has a primary fan valley that connects with Astoria Canyon at the fan apex. The fan valley is bordered by parallel levees on the upper fan but becomes obscure on the lower fan, where a few valley segments appear on the sonographs. Apparently, Nitinat Fan does not presently have a primary fan valley; none of the numerous valleys on the fan connect with a canyon. The Willapa-Cascadia-Vancouver-Juan de Fuca deep-sea valley system bypasses the submarine fans and includes deeply incised valleys to broad shallow swales, as well as within-valley terraces and hanging-valley confluences. ?? 1989.

  9. Subsurface geology of upper Tertiary and Quaternary deposits, coastal Louisiana and adjacent Continental Shelf

    SciTech Connect

    McFarlan, E. Jr.; Leroy, D.O.

    1988-09-01

    Upper Tertiary and Quaternary deposits thicken seaward from a feather edge on the outcrop in the uplands of southern Louisiana to more than 7000 ft (2134 m) beneath the middle continental shelf. Through a study of cores and cuttings from 100 control wells and electric-log pattern correlations from 350 water and petroleum industry wells with seismic corroboration in the offshore area, these deposits have been divided into six major time-stratigraphic units, four of which correlate to outcropping terraces. This investigation presents a regional stratigraphic framework of the major upper Tertiary and Quaternary units from their updip pinch-outs in and beneath the terraced uplands, into the subsurface, across the coastal plain to the Louisiana offshore area.

  10. Late Quaternary Paleoenvironmental History of the Peru-Chile Current System and Adjacent Continental Chile

    NASA Astrophysics Data System (ADS)

    Lamy, F.; Hebbeln, D.; Kaiser, J.; Mohtadi, M.; Ninnemann, U.

    2004-12-01

    A combined analysis of terrigenous and biogenic compounds in marine sediments from the Chilean continental margin allows detailed reconstructions of the paleoclimatic and paleoceanographic history of this region during the last ca. 120,000 years. Based on several sediment cores recovered during two German cruises and ODP Leg 202 (Site 1233), we found evidence for changes both in continental rainfall, most likely induced by latitudinal shifts of the Southern Westerlies, and marine productivity as well as sea surface temperature and salinity changes within the Peru-Chile Current system on time scales ranging from Milankovitch to centennial-scale. On Milankovitch time-scales, we found strong evidence for precession-controlled shifts of the Southern Westerlies implying for example generally more humid conditions during the LGM and a trend towards more arid climates during the deglaciation culminating in the early Holocene. These shifts are paralleled by paleoceanographic changes indicating generally higher productivity during the LGM mainly caused by increased advection of nutrients from the south through an enhanced Peru-Chile current. North of 33°S, these general productivity patterns are complicated by additional impacts from the tropics resulting in maximum paleoproductivity during the deglaciation and prior to the LGM. On shorter time-scales, extremely high resolution sediment cores from the southern Chilean margin provide evidence of significant short-term Holocene climate variability with bands of variability centred at ca. 900 and 1500 years, periodicities also well known from Northern Hemisphere records. Recently drilled ODP Site 1233 allowed to prolong these records into the last glacial. The available data show millennial-scale SST changes that closely follow the temperature pattern known from Antarctic ice-cores. Including other records from the Southern Hemisphere mid-latitudes, our data suggest a quasi-hemisphere-wide response that is consistent with the

  11. The stoichiometric ratio during biological removal of inorganic carbon and nutrient in the Mississippi River plume and adjacent continental shelf

    NASA Astrophysics Data System (ADS)

    Huang, W.-J.; Cai, W.-J.; Powell, R. T.; Lohrenz, S. E.; Wang, Y.; Jiang, L.-Q.; Hopkinson, C. S.

    2012-02-01

    The stoichiometric ratios of dissolved inorganic carbon (DIC) and nutrients during biological removal have been widely assumed to follow the Redfield ratios (especially the C/N ratio) in large river plume ecosystems. However, this assumption has not been systematically examined and documented because DIC and nutrients are rarely studied simultaneously in a river plume area, a region in which they can be affected by strong river-ocean mixing as well as intense biological activity. We examined stoichiometric ratios of DIC, total alkalinity (TA), and nutrients (NO3, PO43- and Si(OH)4) data during biological removal in the Mississippi River plume and adjacent continental shelf in June 2003 and August 2004 with biological removals defined as the difference between measured values and values predicted on the basis of conservative mixing determined using a multi-endmember mixing model. Despite complex physical and biogeochemical influences, relationships between DIC and nutrients were strongly dependent on salinity range and geographic location, and influenced by biological removal. Lower C/Si and N/Si ratios in one nearshore area were attributed to a potential silicate source induced by water exchange with coastal salt marshes. When net biological uptake was separated from river-ocean mixing and the impact of marshes and bays excluded, stoichiometric ratios of C/N/Si were similar to the Redfield ratios, thus supporting the applicability of the Redfield-type C/N/Si ratios as a principle in river-plume biogeochemical models.

  12. Empires and percolation: stochastic merging of adjacent regions

    NASA Astrophysics Data System (ADS)

    Aldous, D. J.; Ong, J. R.; Zhou, W.

    2010-01-01

    We introduce a stochastic model in which adjacent planar regions A, B merge stochastically at some rate λ(A, B) and observe analogies with the well-studied topics of mean-field coagulation and of bond percolation. Do infinite regions appear in finite time? We give a simple condition on λ for this hegemony property to hold, and another simple condition for it to not hold, but there is a large gap between these conditions, which includes the case λ(A, B) ≡ 1. For this case, a non-rigorous analytic argument and simulations suggest hegemony.

  13. Stress pattern in Portugal mainland and the adjacent Atlantic region, West Iberia

    NASA Astrophysics Data System (ADS)

    Ribeiro, A.; Cabral, J.; Baptista, R.; Matias, L.

    1996-06-01

    The Portuguese mainland territory is located close to the Azores-Gibraltar plate boundary, in a tectonic setting responsible for significant neotectonic and seismic activities. However, few data concerning the present regional lithospheric stress field were available, as testified by recently published maps of stress indicators for the Europe and Mediterranean regions. One of the authors already presented a synthesis on this subject [Cabral, 1993], where geological and geophysical stress indicators were considered. In this paper we introduce new information, mainly a considerable amount of borehole breakout data. The updated data set comprises 32 reliable stress indicators showing a mean azimuth of 145° (standard deviation 21°) for the maximum horizontal stress direction (SHmax). On the average, the geological data are rotated clockwise and the focal mechanism data deviated anticlockwise to that azimuth, while the borehole elongation results are consistent with the mean SHmax trend. These differences in stress trend suggest a regional progressive rotation of the SHmax direction from NNW-SSE to WNW-ESE since the upper Pliocene. To estimate stress trajectories, new and published stress indicators in the adjacent Atlantic area and northern Africa were also investigated, showing a very uniform NW-SE SHmax trend in west Iberia. A high level of horizontal compressive stress acting oblique to the western Portuguese continental margin is inferred and interpreted in view of a proposed regional geodynamical model, of activation of this passive margin, with the nucleation of a subduction zone in the Atlantic SW of Iberia, at the Gorringe submarine bank, which is propagating northward along the base of the continental slope, at the transition between thinned and normal continental crust.

  14. Causes of long-term landscape evolution of "passive" margins and adjacent continental segments at the South Atlantic Ocean.

    NASA Astrophysics Data System (ADS)

    Glasmacher, Ulrich Anton; Hackspacher, Peter C.

    2013-04-01

    During the last 10 years research efforts have been devoted to understand the coupling between tectonic and surface processes in the formation of recent topography. Quantification of the rate at which landforms adapt to a changing tectonic, heat flow, and climate environment in the long term has become an important research object and uses intensively data revealed by low-temperature thermochronology, terrigenous cosmogenic nuclides, and geomorphological analyses. The influence of endogenic forces such as mantle processes as one of the causes for "Dynamic Topography Evolution" have been explored in a few studies, recently. In addition, the increased understanding how change in surface topography, and change in the amount of downward moving cold surface water caused by climate change affects warping isotherms in the uppermost crust allows further interpretation of low-temperature thermochronological data. "Passive" continental margins and adjacent continental segments especially at the South Atlantic ocean are perfect locations to quantify exhumation and uplift rates, model the long-term landscape evolution, and provide information on the influence of mantle processes on a longer time scale. This climate-continental margin-mantle process-response system is caused by the interaction between endogenic and exogenic forces that are related to the mantle-process driven rift - drift - "passive" continental margin evolution of the South Atlantic, and the climate change since the Early/Late Cretaceous climate maximum. Furthermore, the influence of major transform faults (also called: transfer zones, Fracture Zones (FZ)) on the long-term evolution of "passive" continental margins is still very much in debate. The presentation will provide insight in possible causes for the differentiated long-term landscape evolution along the South Atlantic Ocean.

  15. Gas-particle partitioning of polycyclic aromatic hydrocarbons in urban, adjacent coastal, and continental background sites of western Greece.

    PubMed

    Terzi, Eleni; Samara, Constantini

    2004-10-01

    Particle- and gas-phase polycyclic aromatic hydrocarbons (PAHs) were collected from an urban, an adjacent coastal, and a continental background site located in Eordea basin, western Greece, to investigate their gas/ particle distributions. Thirteen two- to six-ring PAHs, included in the U.S. EPA priority pollutant list, were determined in 24-h integrated glass fiber filters and polyurethane foam samples. At the prevailing ambient temperature levels, the three-ringed species (phenanthrene, anthracene) and the four-ringed fluoranthene and pyrene were primarily found in the gas phase. Conversely, the five- and six-ring PAHs were mainly associated with the particle phase. Gas/particle partitioning coefficients, Kp, were calculated, and their relationship with the subcooled liquid vapor pressure p degrees L of individual PAHs was investigated. Despite the large variability among samples, a good linear relationship between log Kp and log p degrees L was obtained for all sampling sites following the equation log Kp = m(r) log p degrees L + b(r). In the majority of sampling events, particularly in the adjacent coastal and the continental background sites, slopes (m(r)) were found to be shallower than the value of -1, which has been suggested as reflecting equilibrium partitioning. The deviations from predicted aerosol behavior observed in the present study may be attributed to several reasons, such as the presence of nonexchangeable PAH fraction, nonequilibrium as well as different particle characteristics.

  16. Trend and dynamic cause of sediment particle size on the adjacent continental shelf of the Yangtze Estuary

    NASA Astrophysics Data System (ADS)

    Yang, Yun-ping; Zhang, Ming-jin; Li, Yi-tian; Fan, Yong-yang

    2016-12-01

    Based on the measured data in recent 20 years, the variation trends of the median grain size of the surface sediment, the sand-silt boundary and the mud area on the adjacent continental shelf of the Yangtze Estuary were analyzed in depth, and the effects of natural mechanism and human activities were discussed. The results show that: (1) In recent years (2006-2013), the median grain size of sediment and the distribution pattern of grouped sediments in the adjacent continental shelf area to the Yangtze Estuary have presented no obvious change compared with those before 2006; (2) The median diameter of the surface sediment in the continental shelf area displayed a coarsening trend with the decrease of sediment discharge from the basin and the drop in suspended sediment concentration in the shore area; (3) In 2004-2007, the sand-silt boundary in the north part (31°30'N) of the continental shelf area presented no significant changes, while that in the south part (31°30'S) moved inwards; In 2008-2013, both the sand-silt boundaries in the north and south parts of the continental shelf area moved inwards, mainly due to the fact that in the dry season, a relatively enhanced hydrodynamic force of the tides was generated in the Yangtze River, as well as a decreased suspended sediment concentration and a flow along the banks in North Jiangsu; (4) The mud area where the maximum deposition rate is found in the Yangtze Estuary, tends to shrink due to the drop in sediment discharge from the basin, and the decrease in suspended sediment concentration in the shore area and erosion in the delta. Moreover, it tended to shift to the south at the same time because the implement of the training works on the deep-water channel of the North Passage changed the split ratio between the North and South Passages with an increase in the power of the discharged runoff in the South Passage.

  17. iSIMM (Integrated Seismic Imaging and Modelling of Margins): Seismic Acquisition on the Faroes Shelf, Hatton Bank and adjacent Continental Margins

    NASA Astrophysics Data System (ADS)

    White, B.; Kusznir, N.; Christie, P.; Roberts, A. M.; Lunnon, Z.; Roberts, A. W.; Hurst, N.; Smith, L.; Parkin, C.; Surendra, A.; Davies, A.

    2002-12-01

    The iSIMM project is using state-of-the art seismic techniques with long-offset and wide-angle data, to image the crust formed on volcanic continental margins in parallel with developing and testing new quantitative models of rifted margin formation, incorporating heterogeneous stretching, the effects of melt generation and emplacement and varying thermal anomalies in the mantle. During June-July 2002, we used RRS Discovery to acquire wide angle and normal incidence seismic data on the Faroes Shelf and adjacent continental margin, Hatton-Rockall Basin, Hatton Bank and the adjacent oceanic crust using OBS and MCS. In August 2002, WesternGeco's Topaz used three single-sensor, Q-Marine streamers, 12km plus two 4km, to overshoot the wide-angle profiles on the Faroes Shelf and adjacent continental margin. In the Faroes region we deployed 85 4-component ocean bottom seismometers (OBS) and 5 vertical arrays along a 350km-long profile extending from the Faroes-Shetland Channel across the Faroes Shelf and continental margin into the oceanic crust of the Norwegian Sea. The entire profile was shot twice. First with a 6,300 cubic inch airgun array towed at 20 m depth and tuned to enhance the initial peak output pressure pulse. Second, with the airguns reconfigured to enhance the low-frequency bubble waveform, producing a source rich in low frequency energy (centred on 10-12 Hz), and with a broad bandwidth. Shots were spaced at either 75 m or 100 m, giving shot repetition rates in excess of 60 secs, thus avoiding contaminating with wrap-round energy from the previous shot. The Q-Marine acquisition used a 48-gun, 10,170 cu. in. airgun array, also tuned to enhance the low-frequency bubble signature, shooting at 50m/20s intervals and recorded on individual sensors for optimal grouping. The streamer configuration provides swath coverage at shorter offsets, while the long offsets record diving waves and wide-angle reflections. Shot-by-shot source signature recording will facilitate

  18. Heavy metal distribution in surface sediments from the continental shelf adjacent to Nazaré canyon

    NASA Astrophysics Data System (ADS)

    Oliveira, A.; Palma, C.; Valença, M.

    2011-12-01

    The continental shelf surface sediments around the Nazaré canyon have been analyzed for heavy metal contamination. Organic carbon content and grain size were also determined. The shelf area around the Nazaré canyon shows mean concentrations of Cr, Cu, Hg, Ni, Pb and Zn within the limits recommended by OSPAR (2008). Some enrichment and human impact was found for Cr and especially Pb. Local rivers, mainly the Mondego and southern creeks seem to be the major sources of heavy metals for the Nazaré area, showing similar contamination levels. A set of reference values for non-contaminated fine surface sediments (<63 μm) in the North-Eastern Atlantic are proposed for As, Al, Cd, Cr, Cu, Fe, Hg, Li, Mn, Ni, Pb and Zn.

  19. Phaneorozoic sequence stratigraphy of Bolivia and adjacent regions

    SciTech Connect

    Sempere, T. )

    1993-02-01

    Phaneorozoic sequence stratigraphy of the Pacific margin of western South America, particularly the Bolivian section, has been completed and new interpretations and hypotheses have been proposed as a result of data analyses of this information. The Paleozoic margin was initially passive (late Cambrian-Llanvirn, [open quotes]Puna aulacogen[close quotes]), but became active during a middle Ordovician compressional episode. Most of late Cambrian to early Triassic Bolivian rocks are of marine origin, with dark shale units recording sea level rises, whereas middle Triassic to Recent rocks were mainly deposited in continental environments (except six restricted-marine ingressions in the late Cretaceous-Danian, and one in the late Miocene, all with hydrocarbon potential). A noteworthy similarity exists between the Devonian to Jurassic stratigraphies of Bolivia and the Parana basin, suggesting that Bolivia behaved as part of the Brazilian craton from late Cambrian to late Jurassic, when it was captured into the Pacific margin geotectonic system. Organic-rich units correlate with Paleozoic highstand deposits and younger ingressions. The Bolivian Phanerozoic strata is characterized by thick layers, partly due to middle Ordovician-Carboniferous and late Cretaceous-Cenozoic foreland basins. Paleozoic foreland geometries include northeastern onlaps and, potentially, stratigraphic traps. Hydrocarbon generation, migration and trapping mainly depended on Cenozoic structural loading and burial and on propagation of Andean deformation which are comprised of Paleozoic shale decollements. Precise knowledge of the evolution of the Phanerozoic geodynamic contexts and basin geometries through sedimentation and subsequent deformations is crucial for hydrocarbon exploration strategies in these regions.

  20. Metal elements in the bottom sediments of the Changjiang Estuary and its adjacent continental shelf of the East China Sea.

    PubMed

    Cao, Lu; Hong, Gi Hoon; Liu, Sumei

    2015-06-15

    The metal elements (Al, Fe, Mn, Cr, Co, Ni, Cu, Zn, As, Pb and Ca) in the bottom sediment of the Changjiang Estuary and its adjacent continental shelf of the East China Sea were studied to map their spatial distribution and to assess their potential risk to the marine biota. These metal concentrations except Ca were generally higher in the inner shelf and northeastern part, and were found to decrease from the coast to the offshore of the Changjiang Estuary. Sedimentary Ca was most abundant in the outer shelf sediments and decreased in inner shelf. Arsenic (As) appeared to be contaminated due to economic development from 1980s in the inner shelf overall, but the potential ecological risk from the selected metals was low in the coastal sea off the Changjiang.

  1. Regional Jurassic geologic framework of Alabama coastal waters area and adjacent Federal waters area

    USGS Publications Warehouse

    Mink, R.M.; Bearden, B.L.; Mancini, E.A.

    1989-01-01

    To date, numerous Jurassic hydrocarbon fields and pools have been discovered in the Cotton Valley Group, Haynesville Formation, Smackover Formation and Norphlet Formation in the tri-state area of Mississippi, Alabama and Florida, and in Alabama State coastal waters and adjacent Federal waters area. Petroleum traps are basement highs, salt anticlines, faulted salt anticlines and extensional faults associated with salt movement. Reservoirs include continental and marine sandstones, limestones and dolostones. Hydrocarbon types are oil, condensate and natural gas. The onshore stratigraphic and structural information can be used to establish a regional geologic framework for the Jurassic for the State coastal waters and adjacent Federal waters areas. Evaluation of the geologic information along with the hydrocarbon data from the tri-state area indicates that at least three Jurassic hydrocarbon trends (oil, oil and gas condensate, and deep natural gas) can be identified onshore. These onshore hydrocarbon trends can be projected into the Mobile area in the Central Gulf of Mexico and into the Pensacola, Destin Dome and Apalachicola areas in the Eastern Gulf of Mexico. Substantial reserves of natural gas are expected to be present in Alabama State waters and the northern portion of the Mobile area. Significant accumulations of oil and gas condensate may be encountered in the Pensacola, Destin Dome, and Apalachicola areas. ?? 1989.

  2. Distribution of Pasiphaea japonica larvae in submarine canyons and adjacent continental slope areas in Toyama Bay, Sea of Japan

    NASA Astrophysics Data System (ADS)

    Nanjo, Nobuaki; Katayama, Satoshi

    2014-09-01

    The horizontal and vertical distribution of Pasiphaea japonica larvae, which included larval stages and postlarval or later stages, were investigated in Toyama Bay located in central Japan. The horizontal distributions in the inner part of the bay were investigated by oblique hauls from 10 m above the sea-bottom to the surface using a Remodeled NORPAC net (LNP net) in May, August, November 2005, January, March, April, July, September, December 2006, March-September, November-December 2007, and January-March 2008. The vertical distributions were investigated by concurrent horizontal hauls at the depths of 0, 50, 100, 150, 200, and 250 m using a Motoda net (MTD net) in January, March, April, July, September, and December 2006. Mean density of larvae was higher in submarine canyons which dissect the continental shelf and run to the mouth of river, than adjacent continental slope areas. Larvae densely aggregated in the canyon head. Vertical distribution of the larval stages concentrated in the depth range of 100-150 m in both daytime and nighttime, and larvae in the postlarval or later stages showed diel vertical distribution over a wider depth range than larval stages. Our results indicate the possibility of a larval aggregation in energy-rich habitats, and indicated two important roles of submarine canyons, which were larval retention and high food supply.

  3. Best Merge Region Growing Segmentation with Integrated Non-Adjacent Region Object Aggregation

    NASA Technical Reports Server (NTRS)

    Tilton, James C.; Tarabalka, Yuliya; Montesano, Paul M.; Gofman, Emanuel

    2012-01-01

    Best merge region growing normally produces segmentations with closed connected region objects. Recognizing that spectrally similar objects often appear in spatially separate locations, we present an approach for tightly integrating best merge region growing with non-adjacent region object aggregation, which we call Hierarchical Segmentation or HSeg. However, the original implementation of non-adjacent region object aggregation in HSeg required excessive computing time even for moderately sized images because of the required intercomparison of each region with all other regions. This problem was previously addressed by a recursive approximation of HSeg, called RHSeg. In this paper we introduce a refined implementation of non-adjacent region object aggregation in HSeg that reduces the computational requirements of HSeg without resorting to the recursive approximation. In this refinement, HSeg s region inter-comparisons among non-adjacent regions are limited to regions of a dynamically determined minimum size. We show that this refined version of HSeg can process moderately sized images in about the same amount of time as RHSeg incorporating the original HSeg. Nonetheless, RHSeg is still required for processing very large images due to its lower computer memory requirements and amenability to parallel processing. We then note a limitation of RHSeg with the original HSeg for high spatial resolution images, and show how incorporating the refined HSeg into RHSeg overcomes this limitation. The quality of the image segmentations produced by the refined HSeg is then compared with other available best merge segmentation approaches. Finally, we comment on the unique nature of the hierarchical segmentations produced by HSeg.

  4. Contrasts Between Precipitation over Mediterranean Sea and Adjacent Continental Areas Based on Decadal Scale Satellite Estimates

    NASA Technical Reports Server (NTRS)

    Smith, Eric A.

    2007-01-01

    Most knowledge concerning the last century's climatology and climate dynamics of precipitation over the Mediterranean Sea basin is based on observations taken from rain gauges surrounding the sea itself. In turn, most of the observations come from Southern Europe, with many fewer measurements taken from widely scattered sites situated over North Africa, the Middle East, and the Balkans. This aspect of research on the Mediterranean Sea basin is apparent in a recent compilation of studies presented in book form concerning climate variability of the Mediterranean region [Lionello, P., P. Malanotte-Rizzoli, and R. Boscolo (eds.), 2006: Mediterranean Climate Variability. Elsevier, Amsterdam, 9 chapters.] In light of this missing link to over-water observations, this study (in conjunction with four companion studies by Z. Haddad, A. Mugnai, T. Nakazawa, and G. Stephens) will contrast the nature of precipitation variability directly over the Mediterranean Sea to precipitation variability over the surrounding land areas based on three decades of satellite-based precipitation estimates which have stood up well to validation scrutiny. The satellite observations are drawn from the Global Precipitation Climatology Project (GPCP) dataset extending back to 1979 and the TRMM Merged Algorithm 3b42 dataset extending back to 1998. Both datasets are mostly produced from microwave measurements, excepting the period from 1979 to mid-1987 when only infrared satellite measurements were available for the GPCP estimates. The purpose of this study is to emphasize how the salient properties of precipitation variability over land and sea across a hierarchy of space and time scales, and the salient differences in these properties, might be used in guiding short-term climate models to better predictions of future climate states under different regional temperature-change scenarios.

  5. A catalog of moisture sources for continental climatic regions

    NASA Astrophysics Data System (ADS)

    Nieto, Raquel; Castillo, Rodrigo; Drumond, Anita; Gimeno, Luis

    2014-06-01

    This technical note describes a catalog of moisture sources for two sets of continental climatic regions: one based on regions with similar late 20th century mean climate and similar projected late 21st century precipitation changes, and the other widely used in IPCC assessment reports. By illustrating with one region by classification, the European one was selected and we identify and characterize all the major sources of moisture, and analyze their interannual variability and the role of the three dominant modes of global climate variability, including the El Niño-Southern Oscillation (ENSO) and the Northern and Southern Annular Modes (NAM, SAM). We also estimate the influence of those oceanic regions that will see the greatest increases in evaporation rate in future years.

  6. Characterization of rat c-myc and adjacent regions.

    PubMed Central

    Hayashi, K; Makino, R; Kawamura, H; Arisawa, A; Yoneda, K

    1987-01-01

    Rat genomic regions covering c-myc were cloned from the DNA of both normal liver and two lines of Morris hepatomas, one of which had c-myc amplification. The three restriction maps showed perfect agreement within the overlapping regions. The 7 kb regions, which included the entire normal rat c-myc and the region 2.2 kb upstream, and one from the hepatomas, were sequenced and found to be identical. The coding regions of exons 2 and 3 were highly conserved between rat, mouse and man, but some differences in amino acids were noted. Exon 1 and the non-coding region of exon 3 showed limited homology between the three species. Rat exon 1 contained several nonsense codons in each frame and no ATG codon, indicating there to be no coding capacity in this exon. The 2.2 kb upstream regions and the introns compared showed unusual conservation between the rat and human genes. Some motifs, previously proposed as having a functional role in human c-myc, were also found in equivalent positions of the rat sequence. Nucleas S1 protection mapping revealed the second promoter to be preferentially used in most tissues or in hepatoma cells, and the second poly A addition signal to be the only one functional in all the RNA sources examined. Images PMID:3306601

  7. High resolution regional seismic attenuation tomography in eastern Tibetan Plateau and adjacent regions

    NASA Astrophysics Data System (ADS)

    Bao, Xueyang; Sandvol, Eric; Ni, James; Hearn, Thomas; Chen, Yongshun John; Shen, Yang

    2011-08-01

    The Q of regional seismic phases Lg and Pg within the crust is assumed as a proxy for crustal Qβ and Qα, which is used as a constraint of crustal rheology. We measure regional-phase Q of the eastern Tibetan Plateau and adjacent areas. This method eliminates contributions from source and site responses and is an improvement on the Two-Station Method (TSM). We have generated tomographic images of crustal attenuation anomalies with resolution as high as 1°. In general we observe low Q in the northernmost portions of the Tibetan Plateau and high Q in the more tectonically stable regions such as the interior of the Qaidam basin. The calculated site responses appear to correlate with topography or sediment thickness. Furthermore the relationship between earthquake magnitudes and calculated source terms suggest that the RTM method effectively removes the source response and may be used as an alternative to source magnitude.

  8. Geologic framework of the offshore region adjacent to Delaware

    USGS Publications Warehouse

    Benson, R.N.; Roberts, J.H.

    1989-01-01

    postrift sediments that cover the more deeply buried rift basins are estimated to be of Middle Jurassic age (Bajocian-Bathonian), the probable time of opening of the Atlantic Ocean basin and onset of continental drift about 175-180 m.y. ago. By late Oxfordian-early Kimmeridgian time, the less deeply buried basins nearshore Delaware had been covered. A time-temperature index of maturity plot of one of the basins indicates that only dry gas would be present in reservoirs in synrift rocks buried by more than 6000 m of postrift sediments and in the oldest (Bathonian?-Callovian?) postrift rocks. Less deeply buried synrift rocks landward of the basin modeled might still be within the oil generation window. ?? 1989.

  9. Post-Gondwanan continental sedimentaiton, Limpopo region, southeastern Africa

    NASA Astrophysics Data System (ADS)

    Botha, G. A.; De Wit, M. C. J.

    1996-08-01

    The post-Karoo age sedimentary succession known formerly as the Malvernia Formation, is currently termed the Malonga Formation, 'Formaçao de Sena', 'Formaçao de Singuédeze/Elefantes' and Gona-re-Zhou Plateau Beds in the Limpopo Basin region where South Africa, Mozambique and Zimbabwe have common borders. These rocks represent continental, taphrogenic sedimentation on the eastern margin of the emergent African continent after the breakup of Gondwana. The wide occurrence of this system along the northern Lebombo mountains and within the tectonically active Limpopo and Zambezi valleys, suggests the existence of a peidmont landsurface comprising coalesced alluvial fans and major fluvial channel/floodplain systems close to the continental margin during the Late Mesozoic to Early Cainozoic era. Sedimentation followed the long period of eustatic uplift associated with Karoo vulcanicity and the extensional tectonics and rifting along the continental margin and within the proto-Limpopo and Zambezi valleys. The Malonga Formation exposed near Pafuri in the extreme NW of South Africa shows an eastward lithological change from homogeneous, poorly-sorted, thinly-bedded sandstones and conglomerates, deposited by sheetflood action, to a sequence of fining-upward units comprising clast-supported pebble to boulder grade conglomerate and overlying planar bedded silt and sand, deposited in fluvial channel and floodplain environments. The homogeneous, silty succession exposed in the Olifants River valley, east of the Lebombo mountains in Mozambique, possibly represents the distal reaches of this system. Calcareous palaeosols developed within the sedimentary units suggest periodic geomorphic stability on the broad alluvial plain. Further north in southeastern Zimbabwe, laterally continuous depositional units comprising thinly-bedded, poorly-sorted, matrix-supported conglomerate, interbedded with very coarse-grained sandstone, is consistent with deposition on an alluvial fan complex

  10. Degrading permafrost and gas hydrate under the Beaufort Shelf and marine gas hydrate on the adjacent continental slope

    NASA Astrophysics Data System (ADS)

    Paull, C. K.; Dallimore, S. R.; Hughes Clarke, J. E.; Blasco, S.; Melling, H.; Lundsten, E.; Vagle, S.; Collett, T. S.

    2011-12-01

    The sub-seafloor under the Arctic Shelf is arguably the part of the Earth that is undergoing the most dramatic warming. In the southern Beaufort Sea, the shelf area was terrestrially exposed during much of the Quaternary period when sea level was ~120m lower than present. As a consequence, many areas are underlain by >600m of ice-bonded permafrost that conditions the geothermal regime such that the base of the methane hydrate stability can be >1000m deep. Marine transgression has imposed a change in mean annual surface temperature from -15°C or lower during periods of terrestrial exposure, to mean annual sea bottom temperatures near 0°C. The thermal disturbance caused by transgression is still influencing the upper km of subsurface sediments. Decomposition of gas hydrate is inferred to be occurring at the base and the top of the gas hydrate stability zone. As gas hydrate and permafrost intervals degrade, a range of processes occur that are somewhat unique to this setting. Decomposition of gas hydrate at depth can cause sediment weakening, generate excess pore water pressure, and form free gas. Similarly, thawing permafrost can cause thaw consolidation, liberate trapped gas bubbles in ice bonded permafrost. Understanding the connection between deep subsurface processes generated by transgression, surficial sediment processes near the seafloor, and gas flux into the ocean and atmosphere is important to assessing geohazard and environmental conditions in this setting. In contrast, conditions for marine gas hydrate formation occur on the adjacent continental slope below ~270m water depths. In this paper, we present field observations of gas venting from three geologically distinct environments in the Canadian Beaufort Sea, two on the shelf and one on the slope. A complimentary paper by Dallimore et al reviews the geothermal changes conditioning this environment. Vigorous methane venting is occurring over Pingo-Like-Features (PLF) on the mid-shelf. Diffuse venting of

  11. Cloud-to-ground lightning over Mexico and adjacent oceanic regions: a preliminary climatology using the WWLLN dataset

    NASA Astrophysics Data System (ADS)

    Kucieńska, B.; Raga, G. B.; Rodríguez, O.

    2010-11-01

    This work constitutes the first climatological study of lightning over Mexico and adjacent oceanic areas for the period 2005-2009. Spatial and temporal distributions of cloud to ground lightning are presented and the processes that contribute to the lightning variability are analysed. The data are retrieved from the World Wide Lightning Location Network (WWLLN) dataset. The current WWLL network includes 40 stations which cover much of the globe and detect very low frequency radiation ("spherics") associated with lightning. The spatial distribution of the average yearly lightning over the continental region of Mexico shows the influence of orographic forcing in producing convective clouds with high lightning activity. However, a very high number of strikes is also observed in the States of Tabasco and Campeche, which are low-lying areas. This maximum is related to the climatological maximum of precipitation for the country and it may be associated with a region of persistent low-level convergence and convection in the southern portion of the Gulf of Mexico. The maps of correlation between rainfall and lightning provide insight into the microphysical processes occurring within the clouds. The maritime clouds close to the coastline exhibit similar properties to continental clouds as they produce very high lightning activity. The seasonal cycle of lightning registered by WWLLN is consistent with the LIS/OTD dataset for the selected regions. In terms of the annual distribution of cloud-to-ground strikes, July, August and September exhibit the highest number of strikes over continental Mexico. The diurnal cycle indicates that the maximum number of strikes over the continent is observed between 6 and 9 p.m. LT. The surrounding oceanic regions were subdivided into four distinct sectors: Gulf of Mexico, Caribbean, Sub-tropical Pacific and Tropical Pacific. The Gulf of Mexico has the broadest seasonal distribution, since during winter lightning associated with mid

  12. Regional tectonics of Myanmar (Burma) and adjacent areas

    SciTech Connect

    Everett, J.R.; Russell, O.R.; Staskowski, R.J.; Loyd, S.P.; Tabbutt, V.M. ); Dolan, Stein, A. )

    1990-05-01

    Analysis of 38 contiguous Landsat Multispectral Scanner scenes acquired over Myanmar (Burma) reveals numerous large-scale features associated with margins of the Burman plate, previously unidentified northeast-southwest-trending discontinuities, important extensions of previously mapped fault trends, and numerous structural features that appear favorable for petroleum exploration. A mosaic of these scenes at 1:1,000,000 scale shows a large number of tectonic elements and their spatial relationships. Within the area of investigation are portions of the Indian, Burman, Lhasa, and Shan-Thai plates, and perhaps other, smaller plates. The Himalayan front and Indo-Burman Ranges manifest effects of current and recently past plate movement. The complexity of the kinematic history accounts for the diversity of structural features in the area. The last major event in this long and violent saga, which began in middle Miocene (approximately 11 Ma) time and continues to the present, is the recent change from a collisional to a right-lateral strike-slip transform margin between the Indian and Burman plates. The complexity of the structures visible is the product of multiple plate collisions, rotation of the Indian plate and parts of the Asian plate, and long-continued convergence that changed velocity and direction tbrough time. The most obvious evidence of this complexity, which is immediately apparent on geologic maps or the Landsat mosaic of the region, is the almost right-angle relationship of the folds of the Indo-Burman Ranges and the frontal thrusts and suture zones of the Himalaya. These two sets of compressive features imply maximum compressive stress axes that lie at right angles to each other. The implications are either that the orientation of the stress field changes rapidly over a short distance or that the stress field has changed through time. Both occurrences seem to be true.

  13. Nd isotopic variation of Paleozoic-Mesozoic granitoids from the Da Hinggan Mountains and adjacent areas, NE Asia: Implications for the architecture and growth of continental crust

    NASA Astrophysics Data System (ADS)

    Yang, Qidi; Wang, Tao; Guo, Lei; Tong, Ying; Zhang, Lei; Zhang, Jianjun; Hou, Zengqian

    2017-02-01

    There is a long-standing controversy regarding the tectonic division, composition and structure of the continental crust in the Da Hinggan Mountains and adjacent areas, which are mainly part of the southeastern Central Asian Orogenic Belt (CAOB). This paper approaches these issues via neodymium isotopic mapping of Paleozoic-Mesozoic (480 to 100 Ma) granitoids. On the basis of 943 published and 8 new whole-rock Nd isotopic data, the study area can be divided into four Nd isotopic provinces (I, II, III and IV). Province I (the youngest crust, Nd model ages (TDM) = 0.8-0.2 Ga) is a remarkable region of Phanerozoic crustal growth, which may reflect a major zone for closures of the Paleo-Asian Ocean. Province II (slightly juvenile crust, TDM = 1.0-0.8 Ga), the largest Nd isotopic province in the southeastern CAOB, is considered to reflect the recycling of the initial crustal material produced during the early stage (Early Neoproterozoic) evolution of the Paleo-Asian Ocean. Province III (slightly old crust, TDM = 1.6-1.1 Ga) is characterized by ancient crustal blocks, such as the central Mongolian, Erguna, Dariganga and Hutag Uul-Xilinhot blocks, which represent micro-continents and Precambrian basements in the southeastern CAOB. Several parts of Province III are located along the northern margin of the North China Craton (NCC), which is interpreted as a destroyed cratonic margin during the Paleozoic and Mesozoic. Province IV (the oldest crust, TDM = 2.9-1.6 Ga) mainly occurs within the NCC and reflects its typical Precambrian nature. These mapping results indicate that the boundary between Provinces II and III (the northern margin of the NCC) along the Solonker-Xar Moron Fault can be regarded as the lithospheric boundary between the CAOB and NCC. Provinces I and II account for 20% and 44% of the area of the southeastern CAOB, respectively, and therefore the ratio of continental growth is 64% from the Neoproterozoic to the Mesozoic, which is typical for this part of the

  14. Reassessment of stable continental regions of Southeast Asia

    USGS Publications Warehouse

    Wheeler, R.L.

    2011-01-01

    Probabilistic seismic-hazard assessments of the central and eastern United States (CEUS) require estimates of the size of the largest possible earthquake (Mmax). In most of the CEUS, sparse historical seismicity does not provide a record of moderate and large earthquakes that is sufficient to constrain Mmax. One remedy for the insufficient catalog is to combine the catalog of moderate to large CEUS earthquakes with catalogs from other regions worldwide that are tectonically analogous to the CEUS (stable continental regions, or SCRs). After the North America SCR, the largest contribution of earthquakes to this global SCR catalog comes from a Southeast Asian SCR that extends from Indochina to southeasternmost Russia. Integration and interpretation of recently published geological and geophysical results show that most of these Southeast Asian earthquakes occurred in areas exposing abundant alkaline igneous rocks and extensional faults, both of Neogene age (last 23 million years). The implied Neogene extension precludes classification of the areas as SCR crust. The extension also reduces the number of moderate and large Southeast Asian historical earthquakes that are available to constrain CEUS Mmax by 86 percent, from 43 to six.

  15. Temporal evolution of continental lithospheric strength in actively deforming regions

    USGS Publications Warehouse

    Thatcher, W.; Pollitz, F.F.

    2008-01-01

    It has been agreed for nearly a century that a strong, load-bearing outer layer of earth is required to support mountain ranges, transmit stresses to deform active regions and store elastic strain to generate earthquakes. However the dept and extent of this strong layer remain controversial. Here we use a variety of observations to infer the distribution of lithospheric strength in the active western United States from seismic to steady-state time scales. We use evidence from post-seismic transient and earthquake cycle deformation reservoir loading glacio-isostatic adjustment, and lithosphere isostatic adjustment to large surface and subsurface loads. The nearly perfectly elastic behavior of Earth's crust and mantle at the time scale of seismic wave propagation evolves to that of a strong, elastic crust and weak, ductile upper mantle lithosphere at both earthquake cycle (EC, ???10?? to 103 yr) and glacio-isostatic adjustment (GIA, ???103 to 104 yr) time scales. Topography and gravity field correlations indicate that lithosphere isostatic adjustment (LIA) on ???106-107 yr time scales occurs with most lithospheric stress supported by an upper crust overlying a much weaker ductile subtrate. These comparisons suggest that the upper mantle lithosphere is weaker than the crust at all time scales longer than seismic. In contrast, the lower crust has a chameleon-like behavior, strong at EC and GIA time scales and weak for LIA and steady-state deformation processes. The lower crust might even take on a third identity in regions of rapid crustal extension or continental collision, where anomalously high temperatures may lead to large-scale ductile flow in a lower crustal layer that is locally weaker than the upper mantle. Modeling of lithospheric processes in active regions thus cannot use a one-size-fits-all prescription of rheological layering (relation between applied stress and deformation as a function of depth) but must be tailored to the time scale and tectonic

  16. Geoacoustic models of the Donghae-to-Gangneung region in the Korean continental margin of the East Sea

    NASA Astrophysics Data System (ADS)

    Ryang, Woo Hun; Kim, Seong Pil; Hahn, Jooyoung

    2016-04-01

    Geoacoustic model is to provide a model of the real seafloor with measured, extrapolated, and predicted values of geoacoustic environmental parameters. It controls acoustic propagation in underwater acoustics. In the Korean continental margin of the East Sea, this study reconstructed geoacoustic models using geoacoustic and marine geologic data of the Donghae-to-Gangneung region (37.4° to 37.8° in latitude). The models were based on the data of the high-resolution subbottom and air-gun seismic profiles with sediment cores. The Donghae region comprised measured P-wave velocities and attenuations of the cores, whereas the Gangneung region comprised regression values using measured values of the adjacent areas. Geoacoustic data of the cores were extrapolated down to a depth of the geoacoustic models. For actual modeling, the P-wave speed of the models was compensated to in situ depth below the sea floor using the Hamilton method. These geoacoustic models of this region probably contribute for geoacoustic and underwater acoustic modelling reflecting vertical and lateral variability of acoustic properties in the Korean continental margin of the western East Sea. Keywords: geoacoustic model, environmental parameter, East Sea, continental margin Acknowledgements: This research was supported by the research grants from the Agency of Defense Development (UD140003DD and UE140033DD).

  17. New species of Amanita from the eastern Himalaya and adjacent regions.

    PubMed

    Yang, Zhu L; Weiß, M; Oberwinkler, F

    2004-01-01

    Four new species of Amanita, Amanita-ceae (Agaricales) are described from the eastern Himalaya and adjacent regions of southwestern China. Amanita altipes and A. parvipantherina are members of section Amanita, while A. orientifulva and A. liquii are representatives of section Vaginatae. They are compared with similar species and illustrated with line drawings.

  18. Seismic Hazard Assessment in Stable Continental Regions of Northen Eurasia

    NASA Astrophysics Data System (ADS)

    Levshenko, V.; Yunga, S.

    2009-04-01

    Assessment of the seismic potential and related risk level of stable continental regions (SCR) is a highly complex problem, as the applicability of techniques developed for seismically active areas to the areas that have no or limited seismic records is still under discussion. The seismotectonic data of the SCR are very poor because of low seismic activity and an insufficient seismological monitoring system. On the other hand, the geological knowledge is rather good owing to extensive geological and geophysical surveys held during the past decades. Digital data base is compiled from all collected data. Procedure of its interpretation use current internationally recognized methods and criteria and include several stages. 1) Microearthquake detection on the base of seismograms which used polarization analysis, artificial intellect method, wavelet analysis. 2) Paleoearthquakes, prehistorical, historical and instrumentally recorded earthquakes are investigated. 3) The faults capability are analyzed and appropriate seismotectonic model is created. 4) Amplitudes of neotectonic vertical movements, basement and Moho boundaries are interpreted numerically in terms of deformation of earth crust in the investigated region through curvatures calculations. 5) Seismotectonic deformation rate (seismic strain release) are estimated analytically and thus it dependence from maximum earthquake magnitude (Mmax) and the seismic activity parameters are derived. 6) Maximum earthquake potential Mmax of capable faults is evaluated on the base of comparison of geological and seismic deformation. Magnitude of design basis earthquake is estimated using recurrence plot. 7) Engineering Seismology Studies included estimation of peak ground acceleration (PGA) and duration of strong shaking. The PGA is derived from the regional attenuation lows for ground motion versus distance. We apply the above approach to the several critical facilities which have been investigated during last years. The

  19. Seismic Monitoring Capabilities of the Caribbean and Adjacent Regions Tsunami Warning System

    NASA Astrophysics Data System (ADS)

    Saurel, Jean-Marie; von Hillebrandt-Andrade, Christa; Crespo, Hector; McNamara, Dan; Huerfano, Victor

    2014-05-01

    Over 75 tsunamis have been documented in the Caribbean and Adjacent Regions during the past 500 years. Since 1500, at least 4484 people are reported to have perished in these killer waves. Hundreds of thousands are currently threatened along the Caribbean coastlines. In 2005 the Intergovernmental Coordination Group for the Tsunami and other Coastal Hazards Warning System for the Caribbean and Adjacent Regions (CARIBE EWS) was established. It recommended the following minimum seismic performance standards for the detection and analysis of earthquakes: 1) Earthquake detection within 1 minute, 2) Minimum magnitude threshold = M4.5, and 3) Initial hypocenter error of <30 km. The implementation plan of the CARIBE EWS currently includes 115 seismic stations in the Caribbean and Adjacent Regions. The NOAA National Weather Service Caribbean Tsunami Warning Program prepares and distributes monthly reports on real time and archived seismic data availability of the contributing stations at the US Tsunami Warning Centers, the Puerto Rico Seismic Network and IRIS. As of early 2014, 99 of the proposed stations are being contributed by national, regional and international seismological institutions. Recent network additions (Nicaragua, Colombia, Mexico, Cayman Islands, and Venezuela) have reduced detection threshold, time and location error throughout much of the Caribbean region and Central America. Specifically, earthquakes (>M4.0) can be detected within 1 minute throughout much of the Caribbean. The remaining exceptions to this standard for detection are portions of northern South America and Mexico. Another performance criterion is 90% data availability. Currently 60-70% of the stations meet this standard. The presentation will further report on the status of the CARIBE EWS seismic capability for the timely and accurate detection and analysis of earthquakes for tsunami warning purposes for the Caribbean and Adjacent Regions.

  20. Beta-blockade improves adjacent regional sympathetic innervation during postinfarction remodeling.

    PubMed

    Kramer, C M; Nicol, P D; Rogers, W J; Seibel, P S; Park, C S; Reichek, N

    1999-10-01

    The effect of beta-blockade on left ventricular (LV) remodeling, when added to angiotensin-converting enzyme inhibition (ACEI) after anterior myocardial infarction (MI), is incompletely understood. On day 2 after coronary ligation-induced anteroapical infarction, 17 sheep were randomized to ramipril (ACEI, n = 8) or ramipril and metoprolol (ACEI-beta, n = 9). Magnetic resonance imaging was performed before and 8 wk after MI to measure changes in LV end-diastolic, end-systolic, and stroke volume indexes, LV mass index, ejection fraction (EF), and regional percent intramyocardial circumferential shortening. (123)I-labeled m-iodobenzylguanidine (MIBG) and fluorescent microspheres before and after adenosine were infused before death at 8 wk post-MI for quantitation of sympathetic innervation, blood flow, and blood flow reserve in adjacent and remote noninfarcted regions. Infarct size, regional blood flow, blood flow reserve, and the increase in LV mass and LV end-diastolic and end-systolic volume indexes were similar between groups. However, EF fell less over the 8-wk study period in the ACEI-beta group (-13 +/- 11 vs. -22 +/- 4% in ACEI, P < 0.05). The ratio of adjacent to remote region (123)I-MIBG uptake was greater in ACEI-beta animals than in the ACEI group (0.93 +/- 0.06 vs. 0.86 +/- 0.07, P < 0.04). When added to ACE inhibition after transmural anteroapical MI, beta-blockade improves EF and adjacent regional sympathetic innervation but does not alter LV size.

  1. Habitat use and preferences of cetaceans along the continental slope and the adjacent pelagic waters in the western Ligurian Sea

    NASA Astrophysics Data System (ADS)

    Azzellino, A.; Gaspari, S.; Airoldi, S.; Nani, B.

    2008-03-01

    The physical habitat of cetaceans occurring along the continental slope in the western Ligurian Sea was investigated. Data were collected from two different sighting platforms, one of the two being a whale-watching boat. Surveys, conducted from May to October and from 1996 to 2000, covered an area of approximately 3000 km 2 with a mean effort of about 10,000 km year -1. A total of 814 sightings was reported, including all the species occurring in the area: Stenella coeruleoalba, Balaenoptera physalus, Physeter macrocephalus, Globicephala melas, Grampus griseus, Ziphius cavirostris, Tursiops truncatus, Delphinus delphis. A Geographic Information System was used to integrate sighting data to a set of environmental characteristics, which included bottom gradient, area between different isobaths, and length and linearity of the isobaths within a cell unit. Habitat use was analysed by means of a multi-dimensional scaling, MDS, analysis. Significant differences were found in the habitat preference of most of the species regularly occurring in the area. Bottlenose dolphin, Risso's dolphin, sperm whale and Cuvier's beaked whale were found strongly associated to well-defined depth and slope gradient characteristics of the shelf-edge and the upper and lower slope. The hypothesis of habitat segregation was considered for Risso's dolphin, sperm whale and Cuvier's beaked whale. Canonical discriminant functions using depth and slope as predictors outlined clear and not overlapping habitat preferences for Risso's dolphin and Cuvier's beaked whale, whereas a partial overlapping of the habitat of the other two species was observed for sperm whale. Such a partitioning of the upper and lower slope area may be the result of the common feeding habits and suggests a possible competition of these three species. A temporal segregation in the use of the slope area was also observed for sperm whales and Risso's dolphins. Fin whales, and the occasionally encountered common dolphin and long

  2. Downscaling Reanalysis over Continental Africa with a Regional Model: NCEP Versus ERA Interim Forcing

    NASA Technical Reports Server (NTRS)

    Druyan, Leonard M.; Fulakeza, Matthew B.

    2013-01-01

    Five annual climate cycles (1998-2002) are simulated for continental Africa and adjacent oceans by a regional atmospheric model (RM3). RM3 horizontal grid spacing is 0.44deg at 28 vertical levels. Each of 2 simulation ensembles is driven by lateral boundary conditions from each of 2 alternative reanalysis data sets. One simulation downs cales National Center for Environmental Prediction reanalysis 2 (NCPR2) and the other the European Centre for Medium Range Weather Forecasts Interim reanalysis (ERA-I). NCPR2 data are archived at 2.5deg grid spacing, while a recent version of ERA-I provides data at 0.75deg spacing. ERA-I-forced simulations are recomrp. ended by the Coordinated Regional Downscaling Experiment (CORDEX). Comparisons of the 2 sets of simulations with each other and with observational evidence assess the relative performance of each downscaling system. A third simulation also uses ERA-I forcing, but degraded to the same horizontal resolution as NCPR2. RM3-simulated pentad and monthly mean precipitation data are compared to Tropical Rainfall Measuring Mission (TRMM) data, gridded at 0.5deg, and RM3-simulated circulation is compared to both reanalyses. Results suggest that each downscaling system provides advantages and disadvantages relative to the other. The RM3/NCPR2 achieves a more realistic northward advance of summer monsoon rains over West Africa, but RM3/ERA-I creates the more realistic monsoon circulation. Both systems recreate some features of JulySeptember 1999 minus 2002 precipitation differences. Degrading the resolution of ERA-I driving data unrealistically slows the monsoon circulation and considerably diminishes summer rainfall rates over West Africa. The high resolution of ERA-I data, therefore, contributes to the quality of the downscaling, but NCPR2laterai boundary conditions nevertheless produce better simulations of some features.

  3. Digital depth horizon compilations of the Alaskan North Slope and adjacent Arctic regions

    USGS Publications Warehouse

    Saltus, Richard W.; Bird, Kenneth J.

    2003-01-01

    Data have been digitized and combined to create four detailed depth horizon grids spanning the Alaskan North Slope and adjacent offshore areas. These map horizon compilations were created to aid in petroleum system modeling and related studies. Topography/bathymetry is extracted from a recent Arctic compilation of global onshore DEM and satellite altimetry and ship soundings offshore. The Lower Cretaceous Unconformity (LCU), the top of the Triassic Shublik Formation, and the pre-Carboniferous acoustic basement horizon grids are created from numerous seismic studies, drill hole information, and interpolation. These horizons were selected because they mark critical times in the geologic evolution of the region as it relates to petroleum. The various horizons clearly show the major tectonic elements of this region including the Brooks Range, Colville Trough, Barrow Arch, Hanna Trough, Chukchi Platform, Nuwuk Basin, Kaktovik Basin, and Canada Basin. The gridded data are available in a variety of data formats for use in regional studies.

  4. Regional, Continental, and Global Mobility to an Emerging Economy: The Case of South Africa

    ERIC Educational Resources Information Center

    Lee, Jenny J.; Sehoole, Chika

    2015-01-01

    This study examined mobility within the understudied region of southern Africa and particularly, the factors that drive and shape educational migration toward South Africa as a regional, continental, and global destination. Based on a survey administered to international students across seven South African universities, the findings revealed…

  5. Tsunami Ready Recognition Program for the Caribbean and Adjacent Regions Launched in 2015

    NASA Astrophysics Data System (ADS)

    von Hillebrandt-Andrade, C.; Hinds, K.; Aliaga, B.; Brome, A.; Lopes, R.

    2015-12-01

    Over 75 tsunamis have been documented in the Caribbean and Adjacent Regions over the past 500 years with 4,561 associated deaths according to the NOAA Tsunami Database. The most recent devastating tsunamis occurred in 1946 in Dominican Republic; 1865 died. With the explosive increase in residents, tourists, infrastructure, and economic activity along the coasts, the potential for human and economic loss is enormous. It has been estimated that on any day, more than 500,000 people in the Caribbean could be in harm's way just along the beaches, with hundreds of thousands more working and living in the tsunamis hazard zones. In 2005 the UNESCO Intergovernmental Oceanographic Commission established the Intergovernmental Coordination Group for the Tsunami and other Coastal Hazards Warning System for the Caribbean and Adjacent Regions (ICG CARIBE EWS) to coordinate tsunami efforts among the 48 participating countries in territories in the region. In addition to monitoring, modeling and communication systems, one of the fundamental components of the warning system is community preparedness, readiness and resilience. Over the past 10 years 49 coastal communities in the Caribbean have been recognized as TsunamiReady® by the US National Weather Service (NWS) in the case of Puerto Rico and the US Virgin Islands and jointly by UNESCO and NWS in the case of the non US jurisdictions of Anguilla and the British Virgin Islands. In response to the positive feedback of the implementation of TsunamiReady, the ICG CARIBE EWS in 2015 recommended the approval of the guidelines for a Community Performance Based Recognition program. It also recommended the adoption of the name "Tsunami Ready", which has been positively consulted with the NWS. Ten requirements were established for recognition and are divided among Preparedness, Mitigation and Response elements which were adapted from the proposed new US TsunamiReady guidelines and align well with emergency management functions. Both a

  6. Regional prospectivity of Mesozoic and Tertiary in the eastern Adriatic and adjacent area

    SciTech Connect

    Scott, J.; Dolan, P.; Lunn, G. )

    1988-08-01

    Post-Hercynian deposits in the eastern Adriatic and the adjacent external zones of the Dinarides and Albanian Hellenides may be subdivided into four facies groups. (1) Permian-Lower Triassic clastics and carbonates with some evaporites, (2) Middle Triassic-lower Tertiary carbonate platform facies with associated continental margin deeper marine sequences, (3) Upper Cretaceous-lower Tertiary flysch, and (4) middle Tertiary molasse and postorogenic Neogene sediments. The Permian to lower Tertiary section was deposited during the complex Alpine cycle, while the upper Tertiary section is the product of post-Alpine deposition. This depositional history during markedly different tectonic regimes creates two groups of petroleum plays in the eastern Adriatic: (1) Alpine cycle plays in the Permian to lower Tertiary in the thrust-faulted and folded foreland of Adria and (2) post-Alpine plays in upper Tertiary postorogenic or late synorogenic basins. Around the Adriatic, the post-Alpine plays have so far proved the most successful. Major production occurs in the onshore Po basin and its extension beneath the Adriatic. Some of this production is from deep Alpine-cycle reservoirs, but the bulk is from the upper Tertiary-Quaternary. Similar horizons produce onshore and offshore the central-southern Adriatic coast of Italy. Major Tertiary production also occurs to the northeast in the Pannonian basin of Yugoslavia and Hungary from Miocene and younger sequences. Onshore Albania produces significant quantities of hydrocarbons; although data are scarce, much of this production is presumably from upper Tertiary molasse or lower Tertiary flysch.

  7. Integrating regional and continental scale comparisons of tree composition in Amazonian terra firme forests

    NASA Astrophysics Data System (ADS)

    Honorio Coronado, E. N.; Baker, T. R.; Phillips, O. L.; Pitman, N. C. A.; Pennington, R. T.; Vásquez Martínez, R.; Monteagudo, A.; Mogollón, H.; Dávila Cardozo, N.; Ríos, M.; García-Villacorta, R.; Valderrama, E.; Ahuite, M.; Huamantupa, I.; Neill, D. A.; Laurance, W. F.; Nascimento, H. E. M.; Soares de Almeida, S.; Killeen, T. J.; Arroyo, L.; Núñez, P.; Freitas Alvarado, L.

    2009-01-01

    We contrast regional and continental-scale comparisons of the floristic composition of terra firme forest in South Amazonia, using 55 plots across Amazonia and a subset of 30 plots from northern Peru and Ecuador. Firstly, we examine the floristic patterns using both genus- or species-level data and find that the species-level analysis more clearly distinguishes different plot clusters. Secondly, we compare the patterns and causes of floristic differences at regional and continental scales. At a continental scale, ordination analysis shows that species of Lecythidaceae and Sapotaceae are gradually replaced by species of Arecaceae and Myristicaceae from eastern to western Amazonia. These floristic gradients are correlated with gradients in soil fertility and to dry season length, similar to previous studies. At a regional scale, similar patterns are found within north-western Amazonia, where differences in soil fertility distinguish plots where species of Lecythidaceae, characteristic of poor soils, are gradually replaced by species of Myristicaceae on richer soils. The main coordinate of this regional-scale ordination correlates mainly with concentrations of available calcium and magnesium. Thirdly, we ask at a regional scale within north-western Amazonia, whether soil fertility or other distance dependent processes are more important for determining variation in floristic composition. A Mantel test indicates that both soils and geographical distance have a similar and significant role in determining floristic similarity across this region. Overall, these results suggest that regional-scale variation in floristic composition can rival continental scale differences within Amazonian terra firme forests, and that variation in floristic composition at both scales is dependent on a range of processes that include both habitat specialisation related to edaphic conditions and other distance-dependent processes. To fully account for regional scale variation in continental

  8. A geodynamic model of the evolution of the Arctic basin and adjacent territories in the Mesozoic and Cenozoic and the outer limit of the Russian Continental Shelf

    NASA Astrophysics Data System (ADS)

    Laverov, N. P.; Lobkovsky, L. I.; Kononov, M. V.; Dobretsov, N. L.; Vernikovsky, V. A.; Sokolov, S. D.; Shipilov, E. V.

    2013-01-01

    The tectonic evolution of the Arctic Region in the Mesozoic and Cenozoic is considered with allowance for the Paleozoic stage of evolution of the ancient Arctida continent. A new geodynamic model of the evolution of the Arctic is based on the idea of the development of upper mantle convection beneath the continent caused by subduction of the Pacific lithosphere under the Eurasian and North American lithospheric plates. The structure of the Amerasia and Eurasia basins of the Arctic is shown to have formed progressively due to destruction of the ancient Arctida continent, a retained fragment of which comprises the structural units of the central segment of the Arctic Ocean, including the Lomonosov Ridge, the Alpha-Mendeleev Rise, and the Podvodnikov and Makarov basins. The proposed model is considered to be a scientific substantiation of the updated Russian territorial claim to the UN Commission on the determination of the Limits of the Continental Shelf in the Arctic Region.

  9. A climatology and oceanographic analysis of the California Pacific Outer Continental Shelf region. Final report

    SciTech Connect

    Williams, R.G.; Reeves, R.W.; Godshall, F.A.; Fehler, S.W.; Pytlowany, P.J.

    1980-09-01

    The results of an environmental study of the California Pacific Offshore Continental Shelf (CPOCS) region are presented. The CPOCS region is defined as the area between the Mexican border to the Oregon State boundary and seaward to the shelf edge or 200 km. A larger region was examined in several components of the study to describe conditions upstream and downstream of potential leasing areas. Individual chapters focus on meteorological factors, ocean circulation, water masses and physical properties, nutrient chemistry and water elevations.

  10. Tectonic origin of Lower Mesozoic regional unconformities: Southern Colorado Plateau and adjacent Basin and Range

    SciTech Connect

    Marzolf, J.E. )

    1990-05-01

    Palinspastic restoration of Basin and Range structural blocks to early Mesozoic positions relative to the Colorado Plateau permits correlation of lower Mesozoic regional unconformities of the Colorado Plateau across the southern Basin and Range. These unconformities correlate with tectonic reconfiguration of sedimentary basins in which enclosed depositional sequences were deposited. Lesser recognized intraformational unconformities are related to relative sea level change. The Tr-1 unconformity developed on subaerially exposed, karsted, and deeply incised Leonardian carbonates. The overlying Lower Triassic Moenkopi Formation and equivalent strata display a narrow, north-south aligned, passive-margin-type architecture subdivided by Smithian and Spathian intraformational unconformities into three depositional sequences. From basinal to inner shelf facies, Tr-1 truncates folds in Permian rocks. Initial deposition of the lowest sequence began with sea level at the base of the continental slope. Basal conglomerates of the Upper Triassic Chinle Formation were deposited in northward-trending paleovalleys incised within and parallel to the Early Triassic shelf. Distribution of fluvial deposition, orientation of paleovalleys, paleocurrent indicators, and provenance indicate change from the passive-margin-bordered Early Triassic basin to an offshore active-margin basin. Continental and marine facies suggest two depositional sequences separated by an early Norian type 2( ) sequence boundary. The J-O unconformity at the base of the Lower Jurassic Glen Canyon Group marks a major change in tectonic setting of western North America as evidenced by (1) progressive southwestward downcutting of the unconformity to deformed Paleozoic rocks and Precambrian basement, (2) coincidence in time and space with Late Triassic to Early Jurassic thrust faults, and (3) initiation of calcalkaline volcanism.

  11. Quantifying 10 years of Improvements in Earthquake and Tsunami Monitoring in the Caribbean and Adjacent Regions

    NASA Astrophysics Data System (ADS)

    von Hillebrandt-Andrade, C.; Huerfano Moreno, V. A.; McNamara, D. E.; Saurel, J. M.

    2014-12-01

    The magnitude-9.3 Sumatra-Andaman Islands earthquake of December 26, 2004, increased global awareness to the destructive hazard of earthquakes and tsunamis. Post event assessments of global coastline vulnerability highlighted the Caribbean as a region of high hazard and risk and that it was poorly monitored. Nearly 100 tsunamis have been reported for the Caribbean region and Adjacent Regions in the past 500 years and continue to pose a threat for its nations, coastal areas along the Gulf of Mexico, and the Atlantic seaboard of North and South America. Significant efforts to improve monitoring capabilities have been undertaken since this time including an expansion of the United States Geological Survey (USGS) Global Seismographic Network (GSN) (McNamara et al., 2006) and establishment of the United Nations Educational, Scientific and Cultural Organization (UNESCO) Intergovernmental Coordination Group (ICG) for the Tsunami and other Coastal Hazards Warning System for the Caribbean and Adjacent Regions (CARIBE EWS). The minimum performance standards it recommended for initial earthquake locations include: 1) Earthquake detection within 1 minute, 2) Minimum magnitude threshold = M4.5, and 3) Initial hypocenter error of <30 km. In this study, we assess current compliance with performance standards and model improvements in earthquake and tsunami monitoring capabilities in the Caribbean region since the first meeting of the UNESCO ICG-Caribe EWS in 2006. The three measures of network capability modeled in this study are: 1) minimum Mw detection threshold; 2) P-wave detection time of an automatic processing system and; 3) theoretical earthquake location uncertainty. By modeling three measures of seismic network capability, we can optimize the distribution of ICG-Caribe EWS seismic stations and select an international network that will be contributed from existing real-time broadband national networks in the region. Sea level monitoring improvements both offshore and

  12. Regional Hydrothermal Cooling During the Initiation of Continental Rifting

    NASA Astrophysics Data System (ADS)

    Buck, W. R.

    2001-12-01

    Thermochronologic data from the uplifted flanks of the Red Sea clearly indicate at least two distinct phases of regional cooling: the first at about 32 Ma and the second at about 21 Ma according to Omar and Steckler (1995). The latter phase correlates well with the rapid subsidence in the rift and uplift of the flanks. Thus this cooling data is generally interpreted to result from tectonic denudation. The earlier cooling is more problematic, since sediments of the same age are not clearly identified in rift basins. A different explanation for the early cooling episode is suggested by numerical models of lithospheric stretching. Those models show that rift initiation can result in a very broad region of lithospheric downbending. This bending produces small magnitude (several percent) surface extension of the sides of the rift. Eventually, these rift flanks are bent in the opposite sense and uplifted. The earlier phase of extensional strain may create a system of cracks and faults of sufficient permeability to allow significant water circulation. Hydrothermal flow could produce cooling of rocks as deep as 5-10 km. The cooling would be recorded in low-temperature thermochrologic systems such as apatite fission tracks. Model thermal histories for different rift and hydrothermal flow histories are compared to fission track data from the Red Sea region.

  13. The importance of GRM gravity observations in continental regions

    NASA Technical Reports Server (NTRS)

    Mckenzie, D. P.

    1985-01-01

    Altimetric satellites showed the existence of gravity anomalies with wavelengths between 1500 km and 3000 km which correlated with residual depth anomalies. It was suggested that there is also an even smaller scale convective circulation with a wavelength of less than 500 km. Numerical experiments and SEASAT profiles demonstrate that similar small scale circulation must also exist near fracture zones. The mantle therefore must contain at least three scales of circulation: (1) comparable to the plate dimensions, the large scale circulation, which returns material from the Island arcs to the ridges; (2) an intermediate scale comparable to the depth of the upper mantle; and (3) a small scale comparable to the thickness of the asthenosphere. This picture was established by observations of gravity and bathymetry in oceanic regions.

  14. Modeling fluvial erosion on regional to continental scales

    NASA Technical Reports Server (NTRS)

    Howard, Alan D.; Dietrich, William E.; Seidl, Michele A.

    1994-01-01

    The fluvial system is a major concern in modeling landform evolution in response to tectonic deformation. Three stream bed types (bedrock, coarse-bed alluvial, and fine-bed alluvial) differ in factors controlling their occurrence and evolution and in appropriate modeling approaches. Spatial and temporal transitions among bed types occur in response to changes in sediment characteristics and tectonic deformation. Erosion in bedrock channels depends upon the ability to scour or pluck bed material; this detachment capacity is often a power function of drainage area and gradient. Exposure of bedrock in channel beds, due to rapid downcutting or resistant rock, slows the response of headwater catchments to downstream baselevel changes. Sediment routing through alluvial channels must account for supply from slope erosion, transport rates, abrasion, and sorting. In regional landform modeling, implicit rate laws must be developed for sediment production from erosion of sub-grid-scale slopes and small channels.

  15. Seasonal variations of transport time of freshwater exchanges between Changjiang Estuary and its adjacent regions

    NASA Astrophysics Data System (ADS)

    Wang, Ya; Shen, Jian; He, Qing; Zhu, Lei; Zhang, Dai

    2015-05-01

    Seasonal variations of transport time of freshwater between the Changjiang Estuary (CJE) and its adjacent regions, Hangzhou Bay (HZB) and Jiangsu Coast (JSC), are investigated. The freshwater exchange between the CJE and HZB is controlled by the strength of the secondary plume, which initiates from the South Passage of the southernmost waterway of CJE. The transport time varies seasonally and is modulated by spring-neap tides. The water exchange between CJE and HZB exhibits a high spatial variation. A large water age is observed in the region near the southern coast of the HZB, which corresponds to high pollutant deposition and low water quality conditions observed in the field. A large exchange occurs in summer between CJE and HZB. The freshwater transported into the HZB is accumulated in the deep channel near the western shoreline of the HZB and weak horizontal exchange occurs in the southern region near the southern shoreline, resulting in an increase of water age in the southern region. Due to the increase of northerly and northwesterly winds in winter and fall, more horizontal exchange occurs, resulting in a decrease of water age. The transport time from Xuliujing to the Hangzhou Bay ranges from 30 to 60 days near Jinshanwei, and ranges from 100 to 140 days in the southern region. The advective transport is the dominant transport mechanism to move water out of the HZB, while shear-induced exchange flow transports freshwater into the HZB. Net flux is out of HZB in winter and fall, but into the HZB in summer when Changjiang discharge is high. A weak transport of freshwater between the CJE and Subei Coast exists. A portion of a freshwater plume transports freshwater northward during summer and fall. It takes approximately 60-140 days for the freshwater from Xuliujing to be transported to the Subei Coast.

  16. Biodiversity of the Deep-Sea Continental Margin Bordering the Gulf of Maine (NW Atlantic): Relationships among Sub-Regions and to Shelf Systems

    PubMed Central

    Kelly, Noreen E.; Shea, Elizabeth K.; Metaxas, Anna; Haedrich, Richard L.; Auster, Peter J.

    2010-01-01

    Background In contrast to the well-studied continental shelf region of the Gulf of Maine, fundamental questions regarding the diversity, distribution, and abundance of species living in deep-sea habitats along the adjacent continental margin remain unanswered. Lack of such knowledge precludes a greater understanding of the Gulf of Maine ecosystem and limits development of alternatives for conservation and management. Methodology/Principal Findings We use data from the published literature, unpublished studies, museum records and online sources, to: (1) assess the current state of knowledge of species diversity in the deep-sea habitats adjacent to the Gulf of Maine (39–43°N, 63–71°W, 150–3000 m depth); (2) compare patterns of taxonomic diversity and distribution of megafaunal and macrofaunal species among six distinct sub-regions and to the continental shelf; and (3) estimate the amount of unknown diversity in the region. Known diversity for the deep-sea region is 1,671 species; most are narrowly distributed and known to occur within only one sub-region. The number of species varies by sub-region and is directly related to sampling effort occurring within each. Fishes, corals, decapod crustaceans, molluscs, and echinoderms are relatively well known, while most other taxonomic groups are poorly known. Taxonomic diversity decreases with increasing distance from the continental shelf and with changes in benthic topography. Low similarity in faunal composition suggests the deep-sea region harbours faunal communities distinct from those of the continental shelf. Non-parametric estimators of species richness suggest a minimum of 50% of the deep-sea species inventory remains to be discovered. Conclusions/Significance The current state of knowledge of biodiversity in this deep-sea region is rudimentary. Our ability to answer questions is hampered by a lack of sufficient data for many taxonomic groups, which is constrained by sampling biases, life

  17. Analysis of regional deformation and strain accumulation data adjacent to the San Andreas fault

    NASA Technical Reports Server (NTRS)

    Turcotte, Donald L.

    1991-01-01

    A new approach to the understanding of crustal deformation was developed under this grant. This approach combined aspects of fractals, chaos, and self-organized criticality to provide a comprehensive theory for deformation on distributed faults. It is hypothesized that crustal deformation is an example of comminution: Deformation takes place on a fractal distribution of faults resulting in a fractal distribution of seismicity. Our primary effort under this grant was devoted to developing an understanding of distributed deformation in the continental crust. An initial effort was carried out on the fractal clustering of earthquakes in time. It was shown that earthquakes do not obey random Poisson statistics, but can be approximated in many cases by coupled, scale-invariant fractal statistics. We applied our approach to the statistics of earthquakes in the New Hebrides region of the southwest Pacific because of the very high level of seismicity there. This work was written up and published in the Bulletin of the Seismological Society of America. This approach was also applied to the statistics of the seismicity on the San Andreas fault system.

  18. Regional Lg attenuation for the continental United States

    USGS Publications Warehouse

    Benz, H.M.; Frankel, A.; Boore, D.M.

    1997-01-01

    Measurements of the Fourier amplitude spectra of Lg phases recorded at high frequency (0.5 to 14.0 Hz) by broadband seismic stations are used to determine regional attenuation relationships for southern California, the Basin and Range Province, the central United States, and the northeastern United States and southeastern Canada. Fourier spectral amplitudes were measured every quarter octave from Lg phases windowed between 3.0 and 3.7 km sec-1 and recorded in the distance range of 150 to 1000 km. Attenuation at each frequency is determined by assuming a geometrical spreading exponent of 0.5 and inverting for Q and source and receiver terms. Both southern California and the Basin and Range Province are well described by low Lg Q and frequency-dependent attenuation. Lg spectral amplitudes in southern California are fit at low frequencies (0.625 to 0.875 Hz) by a constant Lg Q of 224 and by a frequency-dependent Lg Q function Q = 187-7+7 f0.55(??0.03) in the frequency band 1.0 to 7.0 Hz. The Basin and Range Province is characterized by a constant Lg Q of 192 for frequencies of 0.5 to 0.875 Hz and by the frequency-dependent Lg Q function Q = 235-11+11 f0.56(??0.04) in the frequency band 1.0 to 5.0 Hz. A change in frequency dependence above 5.0 Hz is possible due to contamination of the Lg window by Pn and Sn phases. Lg spectral amplitudes in the central United States are fit by a mean frequency-independent Lg Q of 1291 for frequencies of 1.5 to 7.0 Hz, while a frequency-dependent Lg Q of Q = 1052-83+91(f/1.5)0.22(??0.06) fits the Lg spectral amplitudes for the northeastern United States and southeastern Canada over the passband 1.5 to 14.0 Hz. Attenuation measurements for these areas were restricted to frequencies >1.5 Hz due to larger microseismic noise levels at the lower frequencies.

  19. Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Bouyahiaoui, B.; Sage, F.; Abtout, A.; Klingelhoefer, F.; Yelles-Chaouche, K.; Schnürle, P.; Marok, A.; Déverchère, J.; Arab, M.; Galve, A.; Collot, J. Y.

    2015-06-01

    We determine the deep structure of the eastern Algerian basin and its southern margin in the Annaba region (easternmost Algeria), to better constrain the plate kinematic reconstruction in this region. This study is based on new geophysical data collected during the SPIRAL cruise in 2009, which included a wide-angle, 240-km-long, onshore-offshore seismic profile, multichannel seismic reflection lines and gravity and magnetic data, complemented by the available geophysical data for the study area. The analysis and modelling of the wide-angle seismic data including refracted and reflected arrival travel times, and integrated with the multichannel seismic reflection lines, reveal the detailed structure of an ocean-to-continent transition. In the deep basin, there is an ˜5.5-km-thick oceanic crust that is composed of two layers. The upper layer of the crust is defined by a high velocity gradient and P-wave velocities between 4.8 and 6.0 km s-1, from the top to the bottom. The lower crust is defined by a lower velocity gradient and P-wave velocity between 6.0 and 7.1 km s-1. The Poisson ratio in the lower crust deduced from S-wave modelling is 0.28, which indicates that the lower crust is composed mainly of gabbros. Below the continental edge, a typical continental crust with P-wave velocities between 5.2 and 7.0 km s-1, from the top to the bottom, shows a gradual seaward thinning of ˜15 km over an ˜35-km distance. This thinning is regularly distributed between the upper and lower crusts, and it characterizes a rifted margin, which has resulted from backarc extension at the rear of the Kabylian block, here represented by the Edough Massif at the shoreline. Above the continental basement, an ˜2-km-thick, pre-Messinian sediment layer with a complex internal structure is interpreted as allochthonous nappes of flysch backthrusted on the margin during the collision of Kabylia with the African margin. The crustal structure, moreover, provides evidence for Miocene

  20. The influence of surface waves on water circulation in a mid-Atlantic continental shelf region

    NASA Technical Reports Server (NTRS)

    Whitlock, C. H.; Talay, T. A.

    1974-01-01

    The importance of wave-induced currents in different weather conditions and water depths (18.3 m and 36.6 m) is assessed in a mid-Atlantic continental-shelf region. A review of general circulation conditions is conducted. Factors which perturb the general circulation are examined using analytic techniques and limited experimental data. Actual wind and wave statistics for the region are examined. Relative magnitudes of the various currents are compared on a frequency of annual occurrence basis. Results indicated that wave-induced currents are often the same order of magnitude as other currents in the region and become more important at higher wind and wave conditions. Wind-wave and ocean-swell characteristics are among those parameters which must be monitored for the analytical computation of continental-shelf circulation.

  1. Processes on the continental slope off North Carolina with special reference to the Cape Hatteras region

    NASA Astrophysics Data System (ADS)

    Rhoads, Donald C.; Hecker, Barbara

    Historical data from the slope off Cape Hatteras show this environment to be atypical of the rest of the Atlantic slope in terms of high rates of sedimentation and high benthic/demersal standing stocks. This paper focuses on identifying potential sources for sediments and nutrients on the Hatteras slope and on likely transport mechanisms. Sediments consist mainly of subequal mixtures of sand, silt, and clay and contain an average of 1% carbon. This pool of carbon represents weathered organic matter containing polyunsaturated fatty acids (PUFA) and sterols typical of relatively refractory shelf/estuarine sediments. The labile organic fraction is derived from phytoplankton and zooplankton as reflected in short chain fatty acids (continental slope. The inventory of organic nitrogen is much higher on the mid-slope (800-1 000 m) than shallower or deeper bottom areas as predicted from plots of organic nitrogen versus grain-size for the U.S. Atlantic continental margin. The midslope region is the major focusing area for sedimentation. Bioturbation is an important diagenetic process that has profound influence on sediment profiles of sulphate, methane, fatty acids, sterols, chlorophyll a, viable diatoms, and metals. The low inventory of relatively refractory carbon (1%) stands in contrast to high measured rates of organic carbon sedimentation (28-121 g organic C m -2 year -1). This paradox is probably related to high remineralization rates in the water column and on the bottom. The refractory nature of the small residual pool of deposited organic matter may define the trophic niche filled by those benthos found on this slope that are more typically encountered on the shelf (e.g. oligochaetes and opportunistic polychaetes). A likely mechanism for high input rates of both organic and inorganic particulates to the Hatteras slope may be attributed to

  2. Teleseismic tomography of the southern Puna plateau in Argentina and adjacent regions

    NASA Astrophysics Data System (ADS)

    Bianchi, M.; Heit, B.; Jakovlev, A.; Yuan, X.; Kay, S. M.; Sandvol, E.; Alonso, R. N.; Coira, B.; Brown, L.; Kind, R.; Comte, D.

    2013-02-01

    We performed a teleseismic P wave tomography study using seismic events at both teleseismic and regional distances, recorded by a temporary seismic array in the Argentine Puna Plateau and adjacent regions. The tomographic images show the presence of a number of positive and negative anomalies in a depth range of 20-300 km beneath the array. The most prominent of these anomalies corresponds to a low-velocity body, located in the crust, most clearly seen in the center of the array (27°S, 67°W) between the Cerro Peinado volcano, the Cerro Blanco caldera and the Farallon Negro in the east. This anomaly (southern Puna Magmatic Body) extends from the northern most part of the array and follows the line with the highest density of stations towards the south where it becomes smaller. It is flanked by high velocities on the west and the east respectively. On the west, the high velocities might be related to the subducted Nazca plate. On the northeast the high velocity block coincides with the position of the Hombre Muerto basin in the crust and could be indicating an area of lithospheric delamination where we detected a high velocity block at 100 km depth on the eastern border of the Puna plateau, north of Galan. This block might be related to a delamination event in an area with a thick crust of Paleozoic metamorphic rocks at the border between Puna and Eastern Cordillera. In the center of the array the Southern Puna magmatic body is also flanked by high velocities but the most prominent region is located on the east and is interpreted as part of the Sierras Pampeanas lithosphere with high velocities. The position of the Sierras Pampeanas geological province is key in this area as it appears to limit the extension of the plateau towards the south.

  3. Identification guide to skates (Family Rajidae) of the Canadian Atlantic and adjacent regions

    USGS Publications Warehouse

    Sulak, Kenneth J.; MacWhirter, P. D.; Luke, K.E.; Norem, A.D.; Miller, J.M.; Cooper, J.A.; Harris, L.E.

    2009-01-01

    Ecosystem-based management requires sound information on the distribution and abundance of species both common and rare. Therefore, the accurate identification for all marine species has assumed a much greater importance. The identification of many skate species is difficult as several are easily confused and has been found to be problematic in both survey data and fisheries data collection. Identification guides, in combination with training and periodic validation of taxonomic information, improve our accuracy in monitoring data required for ecosystem-based management and monitoring of populations. This guide offers a comparative synthesis of skate species known to occur in Atlantic Canada and adjacent regions. The taxonomic nomenclature and descriptions of key morphological features are based on the most up-to-date understanding of diversity among these species. Although this information will aid the user in accurate identification, some features vary geographically (such as colour) and others with life stage (most notably the proportion of tail length to body length; the presence of spines either sharper in juveniles or in some cases not yet present; and also increases in the number of tooth rows as species grow into maturity). Additional information on juvenile features are needed to facilitate problematic identifications (e.g. L. erinacea vs. L. ocellata). Information on size at maturity is still required for many of these species throughout their geographic distribution.

  4. Glacial erosion and expected permafrost thickness of Fennoscandia and adjacent regions

    NASA Astrophysics Data System (ADS)

    Amantov, Aleksey

    2013-04-01

    Linked geological, geomorphological and tectonic features of Fennoscandia with adjacent regions of East-European plain and Barents-Kara shelf indirectly influenced the history of glacial grows and decays. The first-order bedrock landscape elements (often created or exhumed during pre-glacial Cenozoic stages) were the major factors that could partly control centers of ice nucleation and basal velocities, serve natural barriers shaping ice sheet margin during some time intervals, etc. On the hand, many landforms were powerfully modified by glacial and periglacial processes, in particular by strong glacial erosion with lithological and structural control. Quantitative estimation of Plio-Pleistocene erosion and deposition was performed combining regional geological-geomorphological analysis (GA) and modeling with rate-based time-scale reconstructions (RR), and mass-balance control. Of special GA importance was to compare and extract changes of preserved elements of pre-glacial Neogene topography from areas that underwent different duration of glacial activity, in comparison with bordering non-glaciated ones. More distinct radial glacial erosion pattern and larger basal ice velocities seem likely at the beginning of the early ice-age stage, with partial widening of pre-glacial drainage elements. Few wide lowlands with meandering rivers in permafrost condition could provoke early stage onset of topographic ice-streams. Over time, further complication of the pattern from radial to "spider web" is expected due to developing of topographic ice-streams. Worth to mention is progressive exhumation of resistant formations, additional complications of the pattern by fluvioglacial activity and glacial sedimentation, "pendulum" principle, with increasing amount of glacial and interglacial sedimentation in eroded material. Approximated variable permafrost distribution seems to be additional weighty aspect, changing erosion rates at some time intervals. To estimate mean annual

  5. Crustal and upper mantle structure of stable continental regions in North America and northern Europe

    USGS Publications Warehouse

    Masse, R.P.

    1987-01-01

    From an analysis of many seismic profiles across the stable continental regions of North America and northern Europe, the crustal and upper mantle velocity structure is determined. Analysis procedures include ray theory calculations and synthetic seismograms computed using reflectivity techniques. The P wave velocity structure beneath the Canadian Shield is virtually identical to that beneath the Baltic Shield to a depth of at least 800 km. Two major layers with a total thickness of about 42 km characterize the crust of these shield regions. Features of the upper mantle of these region include velocity discontinuities at depths of about 74 km, 330 km, 430 km and 700 km. A 13 km thick P wave low velocity channel beginning at a depth of about 94 km is also present. A number of problems associated with record section interpretation are identified and a generalized approach to seismic profile analysis using many record sections is described. The S wave velocity structure beneath the Canadian Shield is derived from constrained surface wave data. The thickness of the lithosphere beneath the Canadian and Baltic Shields is determined to be 95-100 km. The continental plate thickness may be the same as the lithospheric thickness, although available data do not exclude the possibility of the continental plate being thicker than the lithosphere. ?? 1987 Birkha??user Verlag.

  6. 76 FR 53481 - Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf, Alaska OCS Region... Continental Shelf (OCS) Oil and Gas Lease Sale 193, Chukchi Sea, Alaska (OCS EIS/EA BOEMRE 2011-041)....

  7. Russian aeromagnetic surveys of the Prince Charles Mountains and adjacent regions into the 21st century

    NASA Astrophysics Data System (ADS)

    Golynsky, Alexander; Golynsky, Dmitry; Kiselev, Alexander; Masolov, Valery

    2014-05-01

    Russian aeromagnetic investigations in the Prince Charles Mountains (PCM) and surrounding areas, seek to contribute data on the tectonics of Precambrian igneous belts and cratonic fragments, the crustal structure of the Lambert Rift system and other major aspects of Antarctic geology, critical to understanding continental growth processes (Golynsky et al., 2006). Over the past decade, the Polar Marine Geoscience Expedition projects acquired approximately 77,400 line-km of aeromagnetic data over the largely ice-covered regions of MacRobertson Land and Princess Elizabeth Land. The airborne surveys were performed with a standard profile spacing of 5 km and tie-line interval of 15-25 km. The total amount of the Russian aeromagnetic data collected in this region exceeded more than 165,000 line-km. Together with the PCMEGA and AGAP surveys (Damaske and McLean, 2005; Ferraccioli et al., 2011) the PMGE dataset forms the longest transect ever mapped in East Antarctica exceeding 1950 km in length. Several distinct crustal subdivisions are clearly differentiated in the magnetic data. The high-amplitude positive anomalies that extend around the Vestfold Hills and Rauer Islands are likely be attributed to the southern boundary of high-grade metamorphic Late Archean craton. The northern PCM that are composed by ~1 Ga orthogneiss and charnockite display a predominantly northeasterly trending magnetic fabric that continues to the eastern shoulder of the Lambert Rift. The aeromagnetic data from the Southern PCM reveal the spatial boundary of the Archaean Ruker Terrane that is characterized by a short-wavelength anomalies and the prominent Ruker Anomaly that is associated with a banded iron formation. The prominent alternating system of linear NE-SW positive and negative anomalies over the eastern shoulder of the Lambert Rift may reflect the western boundary of the Princess Elizabeth Land cratonic(?) block, although its relationships and tectonic origin remained largely ambiguous

  8. Seasonal variations and horizontal distribution of precipitation over extratropical continental regions in CMIP5

    NASA Astrophysics Data System (ADS)

    Hamada, A.; Hirota, N.; Takayabu, Y. N.

    2012-12-01

    Seasonal variations and horizontal distribution of precipitation over extratropical continental regions by the CMIP5 climate models in their historical runs are evaluated, in comparison with GPCP, CMAP, daily gridded gauge data APHRODITE, and with various reanalysis data. Eight regions are selected over the Eastern Europe, northwestern Russia, Mongolia, northeastern Russia, Alaska, western US, eastern Canada, and eastern US. It is shown that precipitation reproducibility over extratropical continental regions in climate models widely varies depending on regions and seasons, probably attributed to the matching of the precipitation characteristics and treatments of physical processes in the climate models. In some regions, additional treatments of physical processes such as those implemented in the Earth System Models improve the result, while in other regions, horizontal resolution looks essential for the improvements. The reproducibility also varies depending on seasons in a same region, for example, differs between summer and winter in the Eastern Europe. It is also noted that estimated rain amounts considerably vary among GPCP, CMAP, and APHRODITE. Acknowledgment: This study is supported by the 6th GPM/TRMM RA of JAXA, Green Network of Excellence (GRENE) Program by the Ministry of Education, Culture, Sports, Science and Technology, Japan, and Environment Research and Technology Development Fund (A-1201) of the Ministry of the Environment, Japan.

  9. An updated global earthquake catalogue for stable continental regions: reassessing the correlation with ancient rifts

    NASA Astrophysics Data System (ADS)

    Schulte, Saskia M.; Mooney, Walter D.

    2005-06-01

    We present an updated global earthquake catalogue for stable continental regions (SCRs; i.e. intraplate earthquakes) that is available on the Internet. Our database contains information on location, magnitude, seismic moment and focal mechanisms for over 1300 M (moment magnitude) >= 4.5 historic and instrumentally recorded crustal events. Using this updated earthquake database in combination with a recently published global catalogue of rifts, we assess the correlation of intraplate seismicity with ancient rifts on a global scale. Each tectonic event is put into one of five categories based on location: (i) interior rifts/taphrogens, (ii) rifted continental margins, (iii) non-rifted crust, (iv) possible interior rifts and (v) possible rifted margins. We find that approximately 27 per cent of all events are classified as interior rifts (i), 25 per cent are rifted continental margins (ii), 36 per cent are within non-rifted crust (iii) and 12 per cent (iv and v) remain uncertain. Thus, over half (52 per cent) of all events are associated with rifted crust, although within the continental interiors (i.e. away from continental margins), non-rifted crust has experienced more earthquakes than interior rifts. No major change in distribution is found if only large (M>= 6.0) earthquakes are considered. The largest events (M>= 7.0) however, have occurred predominantly within rifts (50 per cent) and continental margins (43 per cent). Intraplate seismicity is not distributed evenly. Instead several zones of concentrated seismicity seem to exist. This is especially true for interior rifts/taphrogens, where a total of only 12 regions are responsible for 74 per cent of all events and as much as 98 per cent of all seismic moment released in that category. Of the four rifts/taphrogens that have experienced the largest earthquakes, seismicity within the Kutch rift, India, and the East China rift system, may be controlled by diffuse plate boundary deformation more than by the presence

  10. An updated global earthquake catalogue for stable continental regions: Reassessing the correlation with ancient rifts

    USGS Publications Warehouse

    Schulte, S.M.; Mooney, W.D.

    2005-01-01

    We present an updated global earthquake catalogue for stable continental regions (SCRs; i.e. intraplate earthquakes) that is available on the Internet. Our database contains information on location, magnitude, seismic moment and focal mechanisms for over 1300 M (moment magnitude) ??? 4.5 historic and instrumentally recorded crustal events. Using this updated earthquake database in combination with a recently published global catalogue of rifts, we assess the correlation of intraplate seismicity with ancient rifts on a global scale. Each tectonic event is put into one of five categories based on location: (i) interior rifts/taphrogens, (ii) rifted continental margins, (iii) non-rifted crust, (iv) possible interior rifts and (v) possible rifted margins. We find that approximately 27 per cent of all events are classified as interior rifts (i), 25 per cent are rifted continental margins (ii), 36 per cent are within non-rifted crust (iii) and 12 per cent (iv and v) remain uncertain. Thus, over half (52 per cent) of all events are associated with rifted crust, although within the continental interiors (i.e. away from continental margins), non-rifted crust has experienced more earthquakes than interior rifts. No major change in distribution is found if only large (M ??? 6.0) earthquakes are considered. The largest events (M ??? 7.0) however, have occurred predominantly within rifts (50 per cent) and continental margins (43 per cent). Intraplate seismicity is not distributed evenly. Instead several zones of concentrated seismicity seem to exist. This is especially true for interior rifts/taphrogens, where a total of only 12 regions are responsible for 74 per cent of all events and as much as 98 per cent of all seismic moment released in that category. Of the four rifts/taphrogens that have experienced the largest earthquakes, seismicity within the Kutch rift, India, and the East China rift system, may be controlled by diffuse plate boundary deformation more than by the

  11. Hydrology, geochemistry and geothermal aspects of the thermal waters from Switzerland and adjacent alpine regions

    NASA Astrophysics Data System (ADS)

    Vuataz, François-David

    1983-11-01

    Waters of 19 thermal areas in Switzerland and adjacent alpine regions were studied to acquire a better knowledge of their deep thermal circulation, geochemistry and low-temperature geothermal potential. A systematic multisampling and multitracing program was executed over a complete hydrologic cycle for each of the 19 thermal areas. Pertinent physical, chemical and isotopic parameters were measured and analyzed on thermal and nonthermal waters during nine sampling periods. Thermal water occurrences are generally related either to Triassic evaporites or to the weathered and fractured zone between crystalline basements (or ranges) and their sedimentary cover. Emergence areas are located in faulted or overthrust zones. Sulfate and calcium are the two principal ions responsible for the mineralization of most thermal waters. Actually, gypsum and anhydrite are more often encountered in Triassic evaporites than halite. Many variations of the water geochemistry, caused by seasonal changes, have been recorded during the hydrologic cycle. From mineralization, temperature and discharge variations, it has been possible to distinguish fast or delayed responses to rain or snow-melt events and mixing between deep-thermal and shallow-cold waters. Chemical geothermometers were tested on these warm waters. The chalcedony and Na-K-Ca geothermometers seem to be the only ones which display calculated temperatures in reasonable agreement with known local geothermal gradients or bottom-hole temperatures. The majority of inferred reservoir temperatures ranges from 40° to 60°C. Oxygen-18 and deuterium results show that most thermal waters fit along the meteoric water line, with some exceptions due to Mediterranean precipitation, possible water-rock isotopic exchange or mixing with connate waters. A regional oxygen-18 gradient has been established with altitude in order to locate and determine the elevation of intake areas. Tritium is very useful in the detection of mixing between deep

  12. Late cenozoic uplift of the southwestern colorado plateau and adjacent lower colorado river region

    USGS Publications Warehouse

    Lucchitta, I.

    1979-01-01

    Rocks deposited near sea level under marine, estuarine, and lacustrine conditions, and located along the course of the lower Colorado River from the mouth of the Grand Canyon as far as the Mexican border, have been displaced to present positions as high as 880 m a.s.l. and as low as 1600 m b.s.l. The rocks include the marine and estuarine Bouse Formation and the lacustrine or marine Hualapai Limestone Member of the Muddy Creek Formation. A profile joining spot elevations that represent the highest erosional remnants of these rocks preserved at any one locality gives an approximation (in most cases a minimum value) for the uplift or downdropping of the region relative to sea level since about 5.5 m.y. ago, the K/Ar age of the most widespread and critical unit. The profile shows that most of the lower Colorado region has risen at least 550 m through broad and rather uniform upwarping and at an average rate of about 100 m/m.y. In addition to these 550 m, the nearby Colorado Plateau has risen by discrete movement along Wheeler fault, which is parallel to and about 8 km west of the plateau's edge, to a total uplift of at least 880 m, at a rate that may be as high as 160 m/m.y. Before warping and faulting, the top of the plateau was about 1100 m above the fill of adjacent basins; the top of this fill probably was at or a little below sea level. p]The profile shows two major south-facing rises in slope. The bigger one, near Yuma, occurs where the profile intersects the northwest-trending San Andreas-Salton trough system of faults; it is interpreted as rifting resulting from transcurrent movement along the faults. At the Mexican border, the base of the Bouse Formation is 1600 m b.s.l., which corresponds to a rate of subsidence since the beginning of Bouse time that may be as high as 290 m/.m.y. The top of the Bouse is at 1000 m b.s.l., corresponding to a rate of subsidence of about 180 m/m.y. In this area, the "older marine sedimentary rocks" of Olmsted et al., (1973

  13. Explaining darker deep convective clouds over the western Pacific in comparison to tropical continental regions

    NASA Astrophysics Data System (ADS)

    Sohn, B.; Choi, M.

    2013-12-01

    A recent study, based on analysis of Moderate Resolution Imaging Spectroradiometer (MODIS) solar channel measurements, reports that deep convective clouds (DCCs) over the western Pacific are found to be darker than DCCs over continental tropical regions such as Africa and South America. This phenomenon is quite interesting although an immediate attempt to explain the reason may be the different cloud microphysics within the deep convective clouds between land and ocean. However, in fact, attempt has not made what causes such difference. In this study, aiming at understanding why DCCs over the western Pacific show generally lower reflectivity in comparison to tropical African and South American regions, regional differences in optical properties of DCCs are examined using Cloud Profile Radar (CPR) onboard CloudSat and Cloud Aerosol Lidar Infrared Pathfinder Satellite Observation (CALIPSO) measurements. Analysis of four January months of 2007-2010, demonstrates that there are distinct difference in ice water path (IWP) between the western Pacific and other two continental regions. Also found is small but meaningful differences in the effective radius. Results lead to a conjecture that smaller IWP over the western Pacific is the main cause inducing smaller reflectance. Radiative transfer experiments investigating what optical parameters of DCCs are responsible for the darker clouds over the western Pacific make it clear that smaller ice water content available in the western Pacific is the main cause.

  14. Lake nutrient stoichiometry is less predictable than nutrient concentrations at regional and sub-continental scales.

    PubMed

    Collins, Sarah M; Oliver, Samantha K; Lapierre, Jean Francois; Stanley, Emily H; Jones, John R; Wagner, Tyler; Soranno, Patricia A

    2017-03-31

    Production in many ecosystems is co-limited by multiple elements. While a known suite of drivers associated with nutrient sources, nutrient transport, and internal processing controls concentrations of phosphorus (P) and nitrogen (N) in lakes, much less is known about whether the drivers of single nutrient concentrations can also explain spatial or temporal variation in lake N:P stoichiometry. Predicting stoichiometry might be more complex than predicting concentrations of individual elements because some drivers have similar relationships with N and P, leading to a weak relationship with their ratio. Further, the dominant controls on elemental concentrations likely vary across regions, resulting in context dependent relationships between drivers, lake nutrients and their ratios. Here, we examine whether known drivers of N and P concentrations can explain variation in N:P stoichiometry, and whether explaining variation in stoichiometry differs across regions. We examined drivers of N:P in ~2,700 lakes at a sub-continental scale and two large regions nested within the sub-continental study area that have contrasting ecological context, including differences in the dominant type of land cover (agriculture vs. forest). At the sub-continental scale, lake nutrient concentrations were correlated with nutrient loading and lake internal processing, but stoichiometry was only weakly correlated to drivers of lake nutrients. At the regional scale, drivers that explained variation in nutrients and stoichiometry differed between regions. In the Midwestern US region, dominated by agricultural land use, lake depth and the percentage of row crop agriculture were strong predictors of stoichiometry because only phosphorus was related to lake depth and only nitrogen was related to the percentage of row crop agriculture. In contrast, all drivers were related to N and P in similar ways in the Northeastern US region, leading to weak relationships between drivers and stoichiometry. Our

  15. A revision of the continental species of Copa Simon, 1885 (Araneae, Corinnidae) in the Afrotropical Region

    PubMed Central

    Haddad, Charles Richard

    2013-01-01

    Abstract The cryptic ground-dwelling castianeirine genus Copa Simon, 1885 (Araneae: Corinnidae) is revised in the continental Afrotropical Region. The type species of the genus, Copa flavoplumosa Simon, 1885, is redescribed and considered a senior synonym of Copa benina Strand, 1916 syn. n. and Copa benina nigra Lessert, 1933 syn. n. It is widespread throughout the Afrotropical Region but has not been introduced to any of the associated regional islands. A new species, Copa kei sp. n., is described from South Africa. Copa agelenina Simon, 1910, originally described from a subadult female from southern Botswana, is considered a nomen dubium. Copa flavoplumosa is a characteristic species of leaf litter spider assemblages and is particularly prevalent in savanna habitats on the continent, but also occurs in various forest types, grasslands, fynbos and semi-arid Nama Karoo habitats. In contrast, Copa kei sp. n. has only been recorded from Afromontane and coastal forests in south-eastern South Africa. PMID:23794814

  16. Changes in Climate over the South China Sea and Adjacent Regions: Response to and Feedback on Global Climate Change

    NASA Astrophysics Data System (ADS)

    Yang, Song

    2016-04-01

    El Niño-Southern Oscillation and the Asian monsoon have experienced significant long-term changes in the past decades. These changes, together with other factors, have in turn led to large climate change signals over the South China Sea and adjacent regions including Southeast Asia, the western Pacific, and the tropical Indian Ocean. An attribution analysis of the feedback processes of these signals indicate the predominant importance of water vapor and cloud radiative feedbacks. Experiments with multiple earth system models also show that these regional climate change signals exert significant influences on global climate. The increases in atmospheric heating over Southeast Asia and sea surface temperature in the adjacent oceans in the past decades have weakened the Indian and African monsoons, led to a drying effect over East Asia, and generated wave-train patterns in both the northern and southern hemispheres, explaining several prominent climate features in and outside Southeast Asia.

  17. Diets and food-web relationships of seabirds in the Gulf of Alaska and adjacent marine regions

    SciTech Connect

    Sanger, G.A.

    1983-01-01

    Overall diets of 39 species of marine birds (four procellariiforms, three cormorants, six sea ducks, one phalarope, two jaegers, 17 gulls, two terns, and 13 alcids) inhabiting the Gulf of Alaska and adjacent marine regions are summarized with food-web diagrams, tables, and text. Diets of the Northern Fulmar, Sooty and Short-tailed Shearwaters, Pelagic Cormorant, Black-legged Kittiwake, Common and Thick-billed Murres, Marbled and Kittlitz's Murrelets, and Horned and Tufted Puffins are compared among seasons and geographic regions.

  18. Continental crust in deep-water basins of East Arctic region

    NASA Astrophysics Data System (ADS)

    Artyushkov, Eugene; Belyaev, Igor; Chekhovich, Peter; Poselov, Victor

    2013-04-01

    The nature of the crust in deep-water basins (1.5-4 km) in East Arctic is a matter of debates. The occurrence of continental crust has been demonstrated by deep-sea drilling only for the central part of the Lomonosov Ridge. Many authors suggest that the Mendeleev High and the Makarov and Podvodnikov basins in the Amerasian Basin are underlain by oceanic crust. In these regions the mean P-wave velocities in the consolidated crust are higher than in most continental areas. However, the thickness of this layer is several times larger (15-30 km) than that of the oceanic crust (7 km) and it includes a thin granitic layer (2-5 km). To explain this anomalous structure and thickness of the crust it is commonly supposed that in the Late Jurassic and Cretaceous the oceanic crust was formed in the above regions by sea-floor spreading accompanies by melting out of large masses of crustal material on a hot spot like on the present Iceland hot spot. Other investigators consider the crust in the above regions as a continental one. An important argument is the evolution of the subsidence in time which is quite different from a square root of time that typical of oceanic crust. Thus, according to the dredging data, the Mendeleev High remained near to sea level for 170 Myr since the Late Silurian and until the Early Permian. This would be absolutely impossible for a cooling hot spot on the oceanic crust. Furthermore, the structure of consolidated crust in these areas is similar to that in some ultradeep basins within the continents and on their passive margins, e.g., in the East Barents, North Caspian and North Chukchi basins which were originally formed on continental crust. To produce the water loaded subsidence by 1.5-4 km by lithospheric stretching, the lithosphere should be stretched by 1.5-4 times. However, in most of the seismic reflection profiles, no large tensile deformations can be observed. Under such circumstances the transformation of gabbro in the lower crust into

  19. Effects of biogenic nitrate chemistry on the NOx lifetime in remote continental regions

    NASA Astrophysics Data System (ADS)

    Browne, E. C.; Cohen, R. C.

    2012-12-01

    We present an analysis of the NOx budget in conditions of low NOx (NOx = NO + NO2) and high biogenic volatile organic compound (BVOC) concentrations that are characteristic of most continental boundary layers. Using a steady-state model, we show that below 500 pptv of NOx, the NOx lifetime is extremely sensitive to organic nitrate (RONO2) formation rates. We find that even for RONO2 formation values that are an order of magnitude smaller than is typical for continental conditions significant reductions in NOx lifetime, and consequently ozone production efficiency, are caused by nitrate forming reactions. Comparison of the steady-state box model to a 3-D chemical transport model (CTM) confirms that the concepts illustrated by the simpler model are a useful approximation of predictions provided by the full CTM. This implies that the regional and global budgets of NOx, OH, and ozone will be sensitive to assumptions regarding organic nitrate chemistry. Changes in the budgets of these species affect the representation of processes important to air quality and climate. Consequently, CTMs must include an accurate representation of organic nitrate chemistry in order to provide accurate assessments of past, present, and future air quality and climate. These findings suggest the need for further experimental constraints on the formation and fate of biogenic RONO2.

  20. Deformation Rates in the Snake River Plain and Adjacent Basin and Range Regions Based on GPS Measurements

    NASA Astrophysics Data System (ADS)

    Payne, S. J.; McCaffrey, R.; King, R. W.; Kattenhorn, S. A.

    2012-12-01

    We estimate horizontal velocities for 405 sites using Global Positioning System (GPS) phase data collected from 1994 to 2010 within the Northern Basin and Range Province, U.S.A. The velocities reveal a slowly-deforming region within the Snake River Plain in Idaho and Owyhee-Oregon Plateau in Oregon separated from the actively extending adjacent Basin and Range regions by shear. Our results show a NE-oriented extensional strain rate of 5.6 ± 0.7 nanostrain/yr in the Centennial Tectonic Belt and an ~E-oriented extensional strain rate of 3.5 ± 0.2 nanostrain/yr in the Great Basin. These extensional rates contrast with the very low strain rate within the 125 km x 650 km region of the Snake River Plain and Owyhee-Oregon Plateau which is not distinguishable from zero (-0.1 ± 0.4 x nanostrain/yr). Inversions of Snake River Plain velocities with dike-opening models indicate that rapid extension by dike intrusion in volcanic rift zones, as previously hypothesized, is not currently occurring. GPS data also disclose that rapid extension in the surrounding regions adjacent to the slowly-deforming region of the Snake River Plain drives shear between them. We estimate right-lateral shear with slip rates of 0.3-1.5 mm/yr along the northwestern boundary adjacent to the Centennial Tectonic Belt and left-lateral oblique extension with slip rates of 0.5-1.5 mm/yr along the southeastern boundary adjacent to the Intermountain Seismic Belt. The fastest lateral shearing evident in the GPS occurs near the Yellowstone Plateau where earthquakes with right-lateral strike-slip focal mechanisms are within a NE-trending zone of seismicity. The regional velocity gradients are best fit by nearby poles of rotation for the Centennial Tectonic Belt, Snake River Plain, Owyhee-Oregon Plateau, and eastern Oregon, indicating that clockwise rotation is not locally driven by Yellowstone hotspot volcanism, but instead by extension to the south across the Wasatch fault possibly due to gravitational

  1. Moving from a regional to a continental perspective of Phragmites australis invasion in North America

    PubMed Central

    Kettenring, Karin M.; de Blois, Sylvie; Hauber, Donald P.

    2012-01-01

    Aims We use a regional comparison of Phragmites australis (common reed) subsp. americanus, P. australis subsp. berlandieri and introduced P. australis (possibly five sublineages) in the Chesapeake Bay, the St Lawrence River, Utah and the Gulf Coast to inform a North American perspective on P. australis invasion patterns, drivers, impacts and research needs. Findings and research needs Our regional assessments reveal substantial diversity within and between the three main lineages of P. australis in terms of mode of reproduction and the types of environment occupied. For introduced P. australis, the timing of introduction also differed between the regions. Nevertheless, a common finding in these regions reinforces the notion that introduced P. australis is opportunistic and thrives in disturbed habitats. Thus, we expect to see substantial expansion of introduced P. australis with increasing anthropogenic disturbances in each of these regions. Although there have been some studies documenting the negative impacts of introduced P. australis, it also plays a beneficial role in some regions, and in some cases, the purported negative impacts are unproven. There is also a broader need to clarify the genetic and ecological relationships between the different introduced sublineages observed in North America, and their relative competitive ability and potential for admixture. This may be done through regional studies that use similar methodologies and share results to uncover common patterns and processes. To our knowledge, such studies have not been performed on P. australis in spite of the broad attention given to this species. Such research could advance theoretical knowledge on biological invasion by helping to determine the extent to which the patterns observed can be generalized or are sublineage specific or region specific. Synthesis Given what appears to be sometimes idiosyncratic invasion patterns when interpreted in isolation in the regions that we analysed, it may

  2. The Bay of Bengal and the Statement of Understanding Concerning the Establishment of the Outer Edge of the Continental Margin: Regional Implications for Delimiting the Juridical Continental Shelf

    NASA Astrophysics Data System (ADS)

    Mridha, M.; Varma, H.; Macnab, R.

    2005-12-01

    The Bay of Bengal is the site of massive depositions of sediment from the Ganga-Brahmaputra river systems, which discharge an estimated 2300 million tons of material into the Indian Ocean every year. The accumulated material comprises an enormous fan that extends some 4000 km from the Mouths of the Ganges, a delta system which encompasses the entire coast of Bangladesh and a segment of the coast of India. The major tectonic elements of the Bay of Bengal and surrounding areas are: the passive eastern continental margin of India; the 85E Ridge; the Ninetyeast Ridge; the intervening basin buried beneath deep sediment; and the Sunda Arc system with the associated back-arc Andaman Basin. Except for the Nikitin Seamounts which rise above the seabed just south of the Equator, the 85E Ridge is totally covered by thick sediment. The Ninetyeast Ridge, on the other hand, protrudes above the seabed as far north as 10N, where it plunges beneath the thickening sediment and separates the deposits into the Bengal Fan and the smaller Nicobar Fan. The 85E and Ninetyeast Ridges present the most significant relief in the crystalline basement underlying the Bay of Bengal, and should therefore figure substantially in any analysis of sediment thickness pursuant to the delimitation of the outer continental shelf. In this region, the sediment thickness provision of Article 76 has been modified by a Statement of Understanding in Annex II of the Final Act of the Third UN Conference on the Law of the Sea. To avoid a perceived inequity that might arise from the application of the standard one percent sediment thickness formula of Article 76, the Statement introduced a new formula: a qualified State in this region, even if it has a narrow physiographic continental shelf, may establish the outer edge of its continental margin by a line where the thickness of sedimentary rock is not less than one km. This presentation will describe the development of a joint formula line for the States that

  3. Continental-Margin Processes Recorded in Shelf and Canyon Sediments. Sediment Deposition, Erosion and Accumulation on a Tidal Flat Adjacent to a River Mouth

    DTIC Science & Technology

    2007-01-01

    Sequence Stratigraphy , IAS Spec. Pub. 37, Blackwell Publishing, Oxford, 549 pp. (2007). C.A. Nittrouer, J.A. Austin, M.E. Field, J.H. Kravitz, J.P.M...Continental Margin Sedimentation: From Sediment Transport to Sequence Stratigraphy , IAS Spec. Pub. 37, Blackwell Publishing, Oxford, 1-48 (2007... Stratigraphy , IAS Spec. Pub. 37, Blackwell Publishing, Oxford, 157-212 (2007). L.F. Pratson, C.A. Nittrouer, P.L.Wiberg, M.S. Steckler, J.B. Swenson

  4. Schottky barrier amorphous silicon solar cell with thin doped region adjacent metal Schottky barrier

    DOEpatents

    Carlson, David E.; Wronski, Christopher R.

    1979-01-01

    A Schottky barrier amorphous silicon solar cell incorporating a thin highly doped p-type region of hydrogenated amorphous silicon disposed between a Schottky barrier high work function metal and the intrinsic region of hydrogenated amorphous silicon wherein said high work function metal and said thin highly doped p-type region forms a surface barrier junction with the intrinsic amorphous silicon layer. The thickness and concentration of p-type dopants in said p-type region are selected so that said p-type region is fully ionized by the Schottky barrier high work function metal. The thin highly doped p-type region has been found to increase the open circuit voltage and current of the photovoltaic device.

  5. Pelagic fishes in the Marguerite Bay region of the West Antarctic Peninsula continental shelf

    NASA Astrophysics Data System (ADS)

    Donnelly, Joseph; Torres, Joseph J.

    2008-02-01

    Pelagic fishes in the Marguerite Bay region of the western Antarctic Peninsula (WAP) continental margin were sampled using a 10-m 2 MOCNESS as part of the Southern Ocean Global Ocean Ecosystems Dynamics (SO GLOBEC) program. Sixty-two tows were completed during the course of four cruises conducted during the austral fall and winter, 22 each during the austral fall, and 9 each during the austral winter. Six thousand and sixty individuals of 34 species representing 13 families were collected in the fall, while 672 individuals of 22 species from 10 families were collected in the winter. Nearly all of the notothenioid specimens collected (families Artedraconidae, Bathydraconidae, Channichthyidae, and Nototheniidae) were either larvae or young juveniles (0-2 years). Conversely, except for the paralepidid Notolepis coatsi and the occasional juveniles of the bathylagid Bathylagus antarcticus, the gonostomatid Cyclothone kobayashii, or the myctophid Electrona antarctica, the non-notothenioid specimens collected were predominantly adults. In the fall, the nototheniids Pleuragramma antarcticum and Trematomus scotti, and the myctophid E. antarctica numerically dominated the overall assemblage, collectively accounting for 89.7% of the total catch. In the winter, E. antarctica, Cyclothone microdon, and B. antarcticus were the numerical dominants, each contributing 14-20% of the total. The pelagic fish community within the Marguerite Bay region of the WAP continental shelf is a variable mixture of mesopelagic and neritic fauna. At one extreme is an oceanic assemblage exhibiting high-diversity indices and characterized by the genera Electrona, Gymnoscopelus, Protomyctophum, Bathylagus, Cyclothone, and Notolepis. Minor components of this group include numerous less common mesopelagic genera (e.g., Paradiplospinus, Lampanyctus, Benthalbella, Borostomias) and the occasional larval/juvenile notothenioid. At the other extreme is a coastal assemblage with low-diversity indices dominated

  6. Reproducibility of precipitation distributions over extratropical continental regions in the CMIP5

    NASA Astrophysics Data System (ADS)

    Hirota, Nagio; Takayabu, Yukari

    2013-04-01

    Reproducibility of precipitation distributions over extratropical continental regions in the CMIP5 Nagio Hirota1,2 and Yukari N. Takayabu2 (1) National Institute of Polar Research (NIPR) (2) Atmosphere and Ocean Research Institute (AORI), the University of Tokyo Reproducibility of precipitation distributions over extratropical continental regions by CMIP5 climate models in their historical runs are evaluated, in comparison with GPCP(V2.2), CMAP(V0911), daily gridded gauge data APHRODITE. Surface temperature, cloud radiative forcing, and atmospheric circulations are also compared with observations of CRU-UEA, CERES, and ERA-interim/ERA40/JRA reanalysis data. It is shown that many CMIP5 models underestimate and overestimate summer precipitation over West and East Eurasia, respectively. These precipitation biases correspond to moisture transport associated with a cyclonic circulation bias over the whole continent of Eurasia. Meanwhile, many models underestimate cloud over the Eurasian continent, and associated shortwave cloud radiative forcing result in a significant warm bias. Evaporation feedback amplify the warm bias over West Eurasia. These processes consistently explain the precipitation biases over the Erasian continent in summer. We also examined reproducibility of winter precipitation, but robust results are not obtained yet due to the large uncertainty in observation associated with the adjustment of snow measurement in windy condition. Better observational data sets are necessary for further model validation. Acknowledgment: This study is supported by the PMM RA of JAXA, Green Network of Excellence (GRENE) Program by the Ministry of Education, Culture, Sports, Science and Technology, Japan, and Environment Research and Technology Development Fund (A-1201) of the Ministry of the Environment, Japan.

  7. Apparatus and methods for impingement cooling of an undercut region adjacent a side wall of a turbine nozzle segment

    DOEpatents

    Burdgick, Steven Sebastian; Itzel, Gary Michael

    2001-01-01

    A gas turbine nozzle segment has outer and inner bands. Each band includes a side wall, a cover and an impingement plate between the cover and nozzle wall defining two cavities on opposite sides of the impingement plate. Cooling steam is supplied to one cavity for flow through apertures of the impingement plate to cool the nozzle wall. The side wall of the band and inturned flange define with the nozzle wall an undercut region. The inturned flange has a plurality of apertures for directing cooling steam to cool the side wall between adjacent nozzle segments.

  8. Thorium concentrations in the lunar surface. IV - Deconvolution of the Mare Imbrium, Aristarchus, and adjacent regions

    NASA Technical Reports Server (NTRS)

    Etchegaray-Ramirez, M. I.; Metzger, A. E.; Haines, E. L.; Hawke, B. R.

    1983-01-01

    Several fields of orbital gamma ray spectroscopy data have been deconvolved in order to model the distribution of Th over the Mare Imbrium and northern Oceanus Procellarum portions of the Apollo 15 lunar ground track, which in combination with a prior study of the Apenninus region covers a continuous swath from 10 deg E to 60 deg W in the northwest quadrant. The crater of the Aristarchus region dominates the Th distribution, with a concentration of 20 ppm, and substantial enhancements are also found in the mare regions around Brayley and at the ejecta blankets of Timocharis and Lambert. The existence of enhanced Th concentrations in mare basalt regions suggests that reservoirs of some late stage mare basalts incorporated KREEP-rich material during formation or transit.

  9. Regions of strongly enhanced perpendicular electric fields adjacent to auroral arcs

    NASA Astrophysics Data System (ADS)

    Opgenoorth, H. J.; Haggstrom, I.; Williams, P. J. S.; Jones, G. O. L.

    1990-08-01

    A joint campaign involving EISCAT, the Cornell University Portable Radar Interferometer (CUPRI), and sounding rockets has observed short-lived elevations of E-region electron temperatures, indicating the presence of strong electric fields. The use of a new pulse-code technique has considerably improved the EISCAT data in regions of low ionospheric electron densities. It has been found that strong and apparently short-lived enhancements of electric fields and associated E-region electron temperatures occur more commonly than long-lived ones. However, earlier EISCAT data with simultaneous optical recordings (and also some CUPRI radar data from the ERRRIS campaign) indicate that many of these events are, in fact, not short-lived, but occur in localized regions and are associated with drifting auroral forms.

  10. Population Health in Regions Adjacent to the Semipalatinsk Nuclear Test Site

    DTIC Science & Technology

    1998-09-01

    The surplus cancer mortality in this group to archived material at Dispensary Number 4 be- was 6.6 x 106 cases and coincides with biological cause...type, with feather-grass, wild oats, desert East Kazakhstan region, Semipalatinsk region, timothy-grass, and different kinds of wormwood . southern part...Ust’- tons were provided. The limits on fats, fish, vege- Kamenogorsk, severe contamination of the atmos- tables, sweets , cookies, and other products

  11. Continental magnetic anomaly constraints on continental reconstruction

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

    1985-01-01

    Crustal magnetic anomalies mapped by the MAGSAT satellite for North and South America, Europe, Africa, India, Australia and Antarctica and adjacent marine areas were adjusted to a common elevation of 400 km and differentially reduced to the radial pole of intensity 60,000 nT. These radially polarized anomalies are normalized for differential inclination, declination and intensity effects of the geomagnetic field, so that in principle they directly reflected the geometric and magnetic polarization attributes of sources which include regional petrologic variations of the crust and upper mantle, and crustal thickness and thermal perturbations. Continental anomalies demonstrate remarkably detailed correlation of regional magnetic sources across rifted margins when plotted on a reconstruction of Pangea. Accordingly, they suggest further fundamental constraints on the geologic evolution of the continents and their reconstructions.

  12. Vesicomyinae (Bivalvia: Vesicomyidae) of the Kuril-Kamchatka Trench and adjacent abyssal regions

    NASA Astrophysics Data System (ADS)

    Krylova, Elena M.; Kamenev, Gennady M.; Vladychenskaya, Irina P.; Petrov, Nikolai B.

    2015-01-01

    Representatives of the subfamily Vesicomyinae (Bivalvia, Vesicomyidae) are tiny deep-sea molluscs distributed worldwide and reaching huge abundances of hundreds and thousands of specimens in trawl catches. During the German-Russian deep-sea expedition KuramBio (R/V Sonne, 2012) for the first time two vesicomyin species were collected from the abyssal plain adjacent to the Kuril-Kamchatka Trench from the depths of 4861-5787 m, Vesicomya pacifica (Smith, 1885) and "Vesicomya" filatovae sp.n. Two species of vesicomyins, V. sergeeviFilatova, 1971 and V. profundiFilatova, 1971, which were previously reported from the hadal of the Kuril-Kamchatka Trench, were not collected at the abyssal depth despite of the close geographical proximity of the sampling area to their distribution ranges. Altogether nine species of vesicomyins are recorded now from the West and Indo-West Pacific; data on distribution and morpho-anatomical characters of these species are provided. Taxonomic description of V. pacifica is revised including information on its soft part anatomy, new localities and COI sequences. For the first time for a vesicomyin bivalve molecular data is given for a species with an explicit morphological description and unambiguous taxonomic affiliation. Molecular analysis of 160 published COI sequences of vesicomyids and newly obtained molecular data on V. pacifica showed that V. pacifica and two undescribed vesicomyin species forming a monophyletic clade which exhibits sister relationships with the Pliocardiinae, the group of chemosymbiotic vesicomyids. "Vesicomya" filatovae sp.n. is provisionally assigned to the genus Vesicomya (s.l.) until additional morphological and molecular data are obtained. It differs from Vesicomya s.s. by a broader hinge margin with more radiating teeth and the presence of only one pair of demibranchs.

  13. Thorium concentrations in the lunar surface: IV. Deconvolution of the mare imbrium, aristarchus, and adjacent regions

    SciTech Connect

    Etchegaray-Ramirez, M.I.; Metzger, A.E.; Haines, E.L.; Hawke, B.R.

    1983-02-15

    The distribution of Th over the Mare Imbrium and northern Oceanus Procellarum portions of the Apollo 15 lunar ground track has been modeled by deconvolving several fields of orbital gamma ray spectroscopy data. Including a prior study of the Apenninus region, a continuous swath from 10/sup 0/E to 60/sup 0/W in the northwest quadrant has now been analyzed. In the Aristarchus region, the crater dominates the Th distribution with a concentration of 20 ppm. Other enhancements are seen on the Aristarchus Plateau and south of the plateau. The concentration across the Aristarchus Plateau is not uniform. The average Th concentration in Oceanus Procellarum is less to the west than to the east of the Aristarchus Plateau. Substantial enhancements are found in mare regions around Brayley, and at the ejecta blankets of Timocharis and Lambert. Th in the Eratosthenian mare regions is generally low with one notable exception lying rouhgly between the craters Euler and Carlini. The existence of enhanced Th concentrations in mare basalt regions suggests that reservoirs of some late stage mare basalts incorporated KREEP-rich material during formation or transit.

  14. Ground-water resources in the tri-state region adjacent to the Lower Delaware River

    USGS Publications Warehouse

    Barksdale, Henry C.; Greenman, David W.; Lang, Solomon Max; Hilton, George Stockbridge; Outlaw, Donald E.

    1958-01-01

    The maximum beneficial utilization of the ground-water resources cannot be accomplished in haphazard fashion. It must be planned and controlled on the basis of sound, current information about the hydrology of the various aquifers. Continued and, in some areas, intensified investigations of the ground-water resources of the region should form the basis for such planning and control.

  15. Aquifer systems in the Great Basin region of Nevada, Utah, and adjacent states; a study plan

    USGS Publications Warehouse

    Harrill, James R.; Welch, A.H.; Prudic, D.E.; Thomas, J.M.; Carman, R.L.; Plume, R.W.; Gates, J.S.; Mason, J.L.

    1983-01-01

    The Great Basin Regional Aquifer Study includes about 140,000 square miles in parts of Nevada, Utah, California, Idaho, Oregon , and Arizona within which 240 hydrographic areas occupy structural depressions formed primarily by basin-and-range faulting. The principal aquifers are in basin-fill deposits; however, significant carbonate-rock aquifers underlie much of eastern Nevada and western Utah. In October 1980, the U.S. Geological Survey started a 4-year study to: (1) describe the ground-water systems, (2) analyze the changes that have led to the systems ' present conditions, (3) tie the results of this and previous studies together in a regional analysis, and (4) provide means by which effects of future ground-water development can be estimated. A plan of work is presented that describes the general approach to be taken. It defines the major tasks necessary to meet objectives and defines constraints on the scope of work. The approach has been influenced by the diverse nature of ground water flow systems and the large number of basins. A detailed appraisal of 240 individual areas would require more resources than are available. Consequently, the general approach is to study selected ' typical ' areas and key hydrologic processes. Effort during the first three years will be directed toward describing the regional hydrology, conducting detailed studies of ' type ' areas and studying selected hydrologic processes. Effort during the final year will be directed toward developing a regional analysis of results. Special studies will include evaluation of regional geochemistry , regional hydrogeology, recharge, ground-water discharge, and use of remote sensing. Areas to be studied using ground-water flow models include the regional carbonate-rock province in eastern Nevada and western Utah, six valleys--Las Vegas, Carson, Paradise, Dixie, Smith Creek, and Stagecoach--Nevada, plus Jordan Valley, the Millford area, and Tule Valley in Utah. The results will be presented in a

  16. 76 FR 30956 - Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-27

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193 AGENCY: Bureau of Ocean Energy...

  17. 75 FR 63504 - Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-15

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193 AGENCY: Bureau of Ocean Energy...

  18. 77 FR 18260 - Outer Continental Shelf (OCS), Alaska OCS Region, Cook Inlet Planning Area, Proposed Oil and Gas...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-27

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS), Alaska OCS Region, Cook Inlet Planning... of Ocean Energy Management (BOEM), Interior. ACTION: Request for Interest (RFI). SUMMARY: The... Federal OCS offshore area has been limited in the past decade, recently there has been renewed interest...

  19. 78 FR 60892 - Outer Continental Shelf (OCS), Alaska OCS Region, Chukchi Sea Planning Area, Proposed Oil and Gas...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-02

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS), Alaska OCS Region, Chukchi Sea Planning Area, Proposed Oil and Gas Lease Sale 237 (Lease Sale 237) MMAA104000 AGENCY: Bureau of Ocean Energy... addressed in this Call (``Program Area'') is located offshore Alaska in the Chukchi Sea Planning Area....

  20. Maximizing species conservation in continental Ecuador: a case of systematic conservation planning for biodiverse regions

    PubMed Central

    Lessmann, Janeth; Muñoz, Jesús; Bonaccorso, Elisa

    2014-01-01

    Ecuador has the largest number of species by area worldwide, but also a low representation of species within its protected areas. Here, we applied systematic conservation planning to identify potential areas for conservation in continental Ecuador, with the aim of increasing the representation of terrestrial species diversity in the protected area network. We selected 809 terrestrial species (amphibians, birds, mammals, and plants), for which distributions were estimated via species distribution models (SDMs), using Maxent. For each species we established conservation goals based on conservation priorities, and estimated new potential protected areas using Marxan conservation planning software. For each selected area, we determined their conservation priority and feasibility of establishment, two important aspects in the decision-making processes. We found that according to our conservation goals, the current protected area network contains large conservation gaps. Potential areas for conservation almost double the surface area of currently protected areas. Most of the newly proposed areas are located in the Coast, a region with large conservation gaps and irreversible changes in land use. The most feasible areas for conservation were found in the Amazon and Andes regions, which encompass more undisturbed habitats, and already harbor most of the current reserves. Our study allows defining a viable strategy for preserving Ecuador's biodiversity, by combining SDMs, GIS-based decision-support software, and priority and feasibility assessments of the selected areas. This approach is useful for complementing protected area networks in countries with great biodiversity, insufficient biological information, and limited resources for conservation. PMID:25360277

  1. Maximizing species conservation in continental Ecuador: a case of systematic conservation planning for biodiverse regions.

    PubMed

    Lessmann, Janeth; Muñoz, Jesús; Bonaccorso, Elisa

    2014-06-01

    Ecuador has the largest number of species by area worldwide, but also a low representation of species within its protected areas. Here, we applied systematic conservation planning to identify potential areas for conservation in continental Ecuador, with the aim of increasing the representation of terrestrial species diversity in the protected area network. We selected 809 terrestrial species (amphibians, birds, mammals, and plants), for which distributions were estimated via species distribution models (SDMs), using Maxent. For each species we established conservation goals based on conservation priorities, and estimated new potential protected areas using Marxan conservation planning software. For each selected area, we determined their conservation priority and feasibility of establishment, two important aspects in the decision-making processes. We found that according to our conservation goals, the current protected area network contains large conservation gaps. Potential areas for conservation almost double the surface area of currently protected areas. Most of the newly proposed areas are located in the Coast, a region with large conservation gaps and irreversible changes in land use. The most feasible areas for conservation were found in the Amazon and Andes regions, which encompass more undisturbed habitats, and already harbor most of the current reserves. Our study allows defining a viable strategy for preserving Ecuador's biodiversity, by combining SDMs, GIS-based decision-support software, and priority and feasibility assessments of the selected areas. This approach is useful for complementing protected area networks in countries with great biodiversity, insufficient biological information, and limited resources for conservation.

  2. Isotopic evidence for continental ice sheet in mid-latitude region in the supergreenhouse Early Cretaceous

    PubMed Central

    Yang, Wu-Bin; Niu, He-Cai; Sun, Wei-Dong; Shan, Qiang; Zheng, Yong-Fei; Li, Ning-Bo; Li, Cong-Ying; Arndt, Nicholas T.; Xu, Xing; Jiang, Yu-Hang; Yu, Xue-Yuan

    2013-01-01

    Cretaceous represents one of the hottest greenhouse periods in the Earth's history, but some recent studies suggest that small ice caps might be present in non-polar regions during certain periods in the Early Cretaceous. Here we report extremely negative δ18O values of −18.12‰ to −13.19‰ for early Aptian hydrothermal zircon from an A-type granite at Baerzhe in northeastern China. Given that A-type granite is anhydrous and that magmatic zircon of the Baerzhe granite has δ18O value close to mantle values, the extremely negative δ18O values for hydrothermal zircon are attributed to addition of meteoric water with extremely low δ18O, mostly likely transported by glaciers. Considering the paleoaltitude of the region, continental glaciation is suggested to occur in the early Aptian, indicating much larger temperature fluctuations than previously thought during the supergreenhouse Cretaceous. This may have impact on the evolution of major organism in the Jehol Group during this period. PMID:24061068

  3. Isotopic evidence for continental ice sheet in mid-latitude region in the supergreenhouse Early Cretaceous.

    PubMed

    Yang, Wu-Bin; Niu, He-Cai; Sun, Wei-Dong; Shan, Qiang; Zheng, Yong-Fei; Li, Ning-Bo; Li, Cong-Ying; Arndt, Nicholas T; Xu, Xing; Jiang, Yu-Hang; Yu, Xue-Yuan

    2013-01-01

    Cretaceous represents one of the hottest greenhouse periods in the Earth's history, but some recent studies suggest that small ice caps might be present in non-polar regions during certain periods in the Early Cretaceous. Here we report extremely negative δ(18)O values of -18.12‰ to -13.19‰ for early Aptian hydrothermal zircon from an A-type granite at Baerzhe in northeastern China. Given that A-type granite is anhydrous and that magmatic zircon of the Baerzhe granite has δ(18)O value close to mantle values, the extremely negative δ(18)O values for hydrothermal zircon are attributed to addition of meteoric water with extremely low δ(18)O, mostly likely transported by glaciers. Considering the paleoaltitude of the region, continental glaciation is suggested to occur in the early Aptian, indicating much larger temperature fluctuations than previously thought during the supergreenhouse Cretaceous. This may have impact on the evolution of major organism in the Jehol Group during this period.

  4. Wild Boar Tissue Levels of Cadmium, Lead and Mercury in Seven Regions of Continental Croatia

    PubMed Central

    Sedak, Marija; Đokić, Maja; Šimić, Branimir

    2010-01-01

    Concentrations of cadmium, mercury and lead were analysed by atomic absorption spectrometry in the kidney and muscle of free-living wild boar (n = 169) from hunting grounds in seven counties of continental Croatia. Mean levels of metals (mg/kg) in muscle and kidney of boars ranged as follows: Cd: 0.005–0.016 and 0.866–4.58, Pb: 0.033–0.15 and 0.036–0.441, Hg: 0.004–0.012 and 0.04–0.152. In all seven regions, concentrations exceeded the permitted values (muscle and kidney mg/kg: cadmium 0.05/1; lead 0.1/0.5; mercury 0.03/0.1) in 13.6% and 71.6% of samples (muscle and kidney, respectively) for cadmium; 13.6% and 8.9% for lead; 19.5% and 2.4% for mercury. There were significant differences among the regions. Vukovar-Srijem and Virovitica-Podravina Counties were highly contaminated with cadmium, Sisak-Moslavina and Virovitica-Podravina Counties with lead and Brod-Posavina County had highest mercury concentrations. These results suggest a detailed investigation of physiological and environmental factors contributing to accumulation of metals in boars. PMID:20405101

  5. Apparatus for impingement cooling a side wall adjacent an undercut region of a turbine nozzle segment

    DOEpatents

    Burdgick, Steven Sebastian

    2002-01-01

    A gas turbine nozzle segment has outer and inner bands and vanes therebetween. Each band includes a side wall, a cover and an impingement plate between the cover and nozzle wall defining two cavities on opposite sides of the impingement plate. Cooling steam is supplied to one cavity for flow through apertures of the impingement plate to cool the nozzle wall. The side wall of the band and inturned flange define with the nozzle wall an undercut region. Slots are formed through the inturned flange along the nozzle side wall. A plate having through-apertures extending between opposite edges thereof is disposed in each slot, the slots and plates being angled such that the cooling medium exiting the apertures in the second cavity lie close to the side wall for focusing and targeting cooling medium onto the side wall.

  6. Subduction-driven recycling of continental margin lithosphere.

    PubMed

    Levander, A; Bezada, M J; Niu, F; Humphreys, E D; Palomeras, I; Thurner, S M; Masy, J; Schmitz, M; Gallart, J; Carbonell, R; Miller, M S

    2014-11-13

    Whereas subduction recycling of oceanic lithosphere is one of the central themes of plate tectonics, the recycling of continental lithosphere appears to be far more complicated and less well understood. Delamination and convective downwelling are two widely recognized processes invoked to explain the removal of lithospheric mantle under or adjacent to orogenic belts. Here we relate oceanic plate subduction to removal of adjacent continental lithosphere in certain plate tectonic settings. We have developed teleseismic body wave images from dense broadband seismic experiments that show higher than expected volumes of anomalously fast mantle associated with the subducted Atlantic slab under northeastern South America and the Alboran slab beneath the Gibraltar arc region; the anomalies are under, and are aligned with, the continental margins at depths greater than 200 kilometres. Rayleigh wave analysis finds that the lithospheric mantle under the continental margins is significantly thinner than expected, and that thin lithosphere extends from the orogens adjacent to the subduction zones inland to the edges of nearby cratonic cores. Taking these data together, here we describe a process that can lead to the loss of continental lithosphere adjacent to a subduction zone. Subducting oceanic plates can viscously entrain and remove the bottom of the continental thermal boundary layer lithosphere from adjacent continental margins. This drives surface tectonics and pre-conditions the margins for further deformation by creating topography along the lithosphere-asthenosphere boundary. This can lead to development of secondary downwellings under the continental interior, probably under both South America and the Gibraltar arc, and to delamination of the entire lithospheric mantle, as around the Gibraltar arc. This process reconciles numerous, sometimes mutually exclusive, geodynamic models proposed to explain the complex oceanic-continental tectonics of these subduction zones.

  7. Evidence that local land use practices influence regional climate, vegetation, and stream flow patterns in adjacent natural areas

    USGS Publications Warehouse

    Stohlgren, T.J.; Chase, T.N.; Pielke, R.A.; Kittel, T.G.F.; Baron, J.S.

    1998-01-01

    We present evidence that land use practices in the plains of Colorado influence regional climate and vegetation in adjacent natural areas in the Rocky Mountains in predictable ways. Mesoscale climate model simulations using the Colorado State University Regional Atmospheric Modelling System (RAMS) projected that modifications to natural vegetation in the plains, primarily due to agriculture and urbanization, could produce lower summer temperatures in the mountains. We corroborate the RAMS simulations with three independent sets of data: (i) climate records from 16 weather stations, which showed significant trends of decreasing July temperatures in recent decades; (ii) the distribution of seedlings of five dominant conifer species in Rocky Mountain National Park, Colorado, which suggested that cooler, wetter conditions occurred over roughly the same time period; and (iii) increased stream flow, normalized for changes in precipitation, during the summer months in four river basins, which also indicates cooler summer temperatures and lower transpiration at landscape scales. Combined, the mesoscale atmospheric/land-surface model, short-term in regional temperatures, forest distribution changes, and hydrology data indicate that the effects of land use practices on regional climate may overshadow larger-scale temperature changes commonly associated with observed increases in CO2 and other greenhouse gases.

  8. Climate change in the four corners and adjacent regions: Implications for environmental restoration and land-use planning

    SciTech Connect

    Waugh, W.J.

    1995-09-01

    This document contains the workshop proceedings on Climate Change in the Four Corners and Adjacent Regions: Implications for Environmental Restoration and Land-Use Planning which took place September 12-14, 1994 in Grand Junction, Colorado. The workshop addressed three ways we can use paleoenvironmental data to gain a better understanding of climate change and its effects. (1) To serve as a retrospective baseline for interpreting past and projecting future climate-induced environmental change, (2) To differentiate the influences of climate and humans on past environmental change, and (3) To improve ecosystem management and restoration practices in the future. The papers presented at this workshop contained information on the following subjects: Paleoclimatic data from the Pleistocene and Holocene epochs, climate change and past cultures, and ecological resources and environmental restoration. Selected papers are indexed separately for inclusion in the Energy Science and Technology Database.

  9. Subduction of continental lithosphere in the Banda Sea region: Combining evidence from full waveform tomography and isotope ratios

    NASA Astrophysics Data System (ADS)

    Fichtner, Andreas; De Wit, Maarten; van Bergen, Manfred

    2010-09-01

    We provide new insight into the subduction of old continental lithosphere to depths of more than 100 km beneath the Banda arc, based on a spatial correlation of full waveform tomographic images of its lithosphere with He, Pb, Nd and Sr isotope signatures in its arc volcanics. The thickness of the subducted lithosphere of around 200 km coincides with the thickness of Precambrian lithosphere as inferred from surface wave tomography. While the deep subduction of continental material in continent-continent collisions is widely recognised, the analogue process in the arc-continent collision of the Banda region is currently unique. The integrated data suggest that the late Jurassic ocean lithosphere north of the North Australian craton was capable of entraining large volumes of continental lithosphere. The Banda arc example demonstrates that continental lithosphere in arc-continent collisions is not generally preserved, thus increasing the complexity of tectonic reconstructions. In the particular case of Timor, the tomographic images indicate that this island is not located directly above the northern margin of the North Australian craton, and that decoupled oceanic lithosphere must be located at a considerable distance north of Timor, possibly as far north as the northern margin of the volcanically extinct arc sector. The tomographic images combined with isotope data suggest that subduction of the continental lithosphere did not lead to the delamination of its complete crust. A plausible explanation involves delamination within the continental crust, separating upper from lower crustal units. This interpretation is consistent with the existence of a massive accretionary complex on Timor island, with evidence from Pb isotope analysis for lower-crust involvement in arc volcanism; and with the approximate gravitational stability of the subducted lithosphere as inferred from the tomographic images. The subduction of continental lithosphere including crustal material beneath

  10. Reclamation by tubewell drainage in Rechna Doab and adjacent areas, Punjab region, Pakistan

    USGS Publications Warehouse

    Malmberg, Glenn T.

    1975-01-01

    Around the turn of the century, a network of more than 40,000 miles of canals was constructed to divert water from the Indus River and its tributaries to about 23 million acres of largely unused desert in the Punjab region of Pakistan. The favorable climate and the perennial supply of irrigation water made available through the canals instituted the beginning of intensive farming. However, because of generally poor drainage and the high rate of canal leakage, the water table began to rise. As the population increased and agriculture expanded, the demand for irrigation water soon exceeded the available supply. Spreading of the canal supply to meet the expanded needs locally created shortages that prevented adequate leaching. Increased evaporation from the rising water table further contributed to the progressive accumulation of soluble salts in the soil. By the late 1930's the combined effect of waterlogging and salinity had reduced the agricultural productivity of the region to one of the lowest in the world. In 1954, after several unsuccessful projects were undertaken to reclaim affected areas and to stop the progressive encroachment of waterlogging and salinization, the Government of Pakistan in cooperation with the U.S. International Cooperation Administration undertook a study of the geology and hydrology of the Indus Plain that ultimately resulted in the formulation of a ground-water reclamation program. The principal feature of the program is the utilization of a network of deep wells spaced about a mile apart for the dual purpose of lowering the water table and for providing supplemental irrigation water. Through financial assistance and technical and engineering support principally from the United States, construction began in 1960 on the first of 18 proposed reclamation projects that eventually will include 21 million acres and more than 28,000 wells having an installed capacity of more than 100,000 cubic feet per second. An area of about 1.3 million acres

  11. Regional Heat Flow Map and the Continental Thermal Isostasy Understanding of México

    NASA Astrophysics Data System (ADS)

    Espinoza-Ojeda, O. M.; Harris, R. N.

    2014-12-01

    The first heat flow values made in Mexico were reported by Von Herzen [Science, 1963] for the marine environment and Smith [EPSL, 1974] for the continent. Since that time the number of measurements has increased greatly but are mostly from oil and gas exploration and in and around geothermal areas. We have compiled published values of conductive heat flow for Mexico and the Gulf of California to generate a new regional heat flow map consisting of 261 values. In addition to those original values, published heat flow sources include, Lee and Henyey [JGR, 1975], Lawver and Williams [JGR, 1979] Smith et al. [JGR, 1979], Lachenbruch et al. [JGR, 1985], and Ziagos et al. [JGR, 1985]. Although the geographic distribution is uneven, heat flow data are present in each of the eight main tectonic provinces. Our new compilation indicates relatively high regional heat flow averages in the Gulf Extensional Province (n=114, 92±22 mW/m2) and Mexican Basin and Range (n=21, 82±20 mW/m2) and are consistent with geologic estimates of extension. Lower regional averages are found in the Baja California Microplate (n=91, 75±19 mW/m2), the Sierra Madre Occidental (n=9, 75±12 mW/m2), the Sierra Madre Oriental (n=4, 68±15 mW/m2) and Mesa Central (n=X 77±23 mW/m2). In contrast low and variable heat flow value characterize the forearc region of the Middle America Trench (n=6, 35±16 mW/m2). A higher mean heat flow is associated with the Trans-Mexican Volcanic Belt (n=6, 78±26 mW/m2). Continental elevation results from a combination of buoyancy (i.e. compositional and thermal) and geodynamic forces. We combine these regional heat flow values with estimates of crustal thickness and density for each tectonic province and compute the thermal and compositional buoyancy following the approach of Hasterok and Chapman [JGR, 2007a,b]. We find that within uncertainties most provinces lie near the theoretical isostatic relationship with the exception of the Mesa Central and Sierra Madre del Sur

  12. Surficial sediment character of the Louisiana offshore continental shelf region: a GIS compilation

    USGS Publications Warehouse

    Williams, S. Jeffress; Arsenault, Matthew A.; Buczkowski, Brian J.; Reid, Jane A.; Flocks, James; Kulp, Mark A.; Penland, Shea; Jenkins, Chris J.

    2007-01-01

    switching by the Mississippi River and its distributaries over the past ~10,000 years that resulted in laterally overlapping deltaic depocenters. The interactions among riverine, coastal, and inner shelf processes have been superimposed on the Holocene transgression resulting in distinctive landforms and sedimentary sequences. Four Holocene shelf-phase delta complexes have been identified using seismic reflection data and vibracores. Each delta complex is bounded by transgressive surfaces. Following each cycle of deposition and abandonment, the delta lobes undergo regional subsidence and marine reworking that forms transgressive coastal systems and barrier islands. Ultimately, the distal end of each of the abandoned delta lobes is marked by submerged marine sand bodies representing drowned barriers. These sand bodies (e.g. Ship Shoal, Outer Shoal, Trinity Shoal, Tiger Shoal, St. Bernard Shoal) offer the largest volumes and highest quality sand for beach nourishment and shoreline and wetlands restoration. These four large sand shoals on inner continental shelf, representing the reworked remnants of former prograded deltaic headlands that existed on the continental shelf at lower sea level, were generated in the retreat path of the Mississippi River delta plain during the Holocene transgression. Penland and others (1989) have shown these sand bodies represent former shoreline positions associated with lower still stands in sea level. Short periods of rapid relative sea-level rise led to the transgressive submergence of the shorelines which today can be recognized at the -10 m to -20 m isobaths on the Louisiana continental shelf. Trinity Shoal and Ship Shoal represent the -10 m middle-to-late Holocene shoreline trend, whereas Outer Shoal and the St. Bernard Shoals define the -20 m early Holocene shoreline trend (Penland and others, 1989). Collectively, these sand shoals constitute a large volume of high quality sandy sediment potentially suitable for barrier island nourishment

  13. H.R. 73: A Bill to protect the ecologically fragile coastal resources of south Florida by prohibiting offshore oil and gas activities and by cancelling Federal leases in the area of the Outer Continental Shelf adjacent to the south Florida coast. Introduced in the House of Representatives, One Hundred Fourth Congress, First session

    SciTech Connect

    1995-12-31

    This document contains H.R. 73, A Bill to protect the ecologically fragile coastal resources of south Florida by prohibiting offshore oil and gas activities and by cancelling Federal leases in the area of the Outer Continental Shelf adjacent to south Florida. This Bill was introduced in the House of Representatives, 104th Congress, First Session, January 4, 1995.

  14. High regional climate sensitivity over continental China constrained by glacial-recent changes in temperature and the hydrological cycle

    PubMed Central

    Eagle, Robert A.; Risi, Camille; Mitchell, Jonathan L.; Eiler, John M.; Seibt, Ulrike; Neelin, J. David; Li, Gaojun; Tripati, Aradhna K.

    2013-01-01

    The East Asian monsoon is one of Earth’s most significant climatic phenomena, and numerous paleoclimate archives have revealed that it exhibits variations on orbital and suborbital time scales. Quantitative constraints on the climate changes associated with these past variations are limited, yet are needed to constrain sensitivity of the region to changes in greenhouse gas levels. Here, we show central China is a region that experienced a much larger temperature change since the Last Glacial Maximum than typically simulated by climate models. We applied clumped isotope thermometry to carbonates from the central Chinese Loess Plateau to reconstruct temperature and water isotope shifts from the Last Glacial Maximum to present. We find a summertime temperature change of 6–7 °C that is reproduced by climate model simulations presented here. Proxy data reveal evidence for a shift to lighter isotopic composition of meteoric waters in glacial times, which is also captured by our model. Analysis of model outputs suggests that glacial cooling over continental China is significantly amplified by the influence of stationary waves, which, in turn, are enhanced by continental ice sheets. These results not only support high regional climate sensitivity in Central China but highlight the fundamental role of planetary-scale atmospheric dynamics in the sensitivity of regional climates to continental glaciation, changing greenhouse gas levels, and insolation. PMID:23671087

  15. High regional climate sensitivity over continental China constrained by glacial-recent changes in temperature and the hydrological cycle.

    PubMed

    Eagle, Robert A; Risi, Camille; Mitchell, Jonathan L; Eiler, John M; Seibt, Ulrike; Neelin, J David; Li, Gaojun; Tripati, Aradhna K

    2013-05-28

    The East Asian monsoon is one of Earth's most significant climatic phenomena, and numerous paleoclimate archives have revealed that it exhibits variations on orbital and suborbital time scales. Quantitative constraints on the climate changes associated with these past variations are limited, yet are needed to constrain sensitivity of the region to changes in greenhouse gas levels. Here, we show central China is a region that experienced a much larger temperature change since the Last Glacial Maximum than typically simulated by climate models. We applied clumped isotope thermometry to carbonates from the central Chinese Loess Plateau to reconstruct temperature and water isotope shifts from the Last Glacial Maximum to present. We find a summertime temperature change of 6-7 °C that is reproduced by climate model simulations presented here. Proxy data reveal evidence for a shift to lighter isotopic composition of meteoric waters in glacial times, which is also captured by our model. Analysis of model outputs suggests that glacial cooling over continental China is significantly amplified by the influence of stationary waves, which, in turn, are enhanced by continental ice sheets. These results not only support high regional climate sensitivity in Central China but highlight the fundamental role of planetary-scale atmospheric dynamics in the sensitivity of regional climates to continental glaciation, changing greenhouse gas levels, and insolation.

  16. Seismic structure beneath the Gulf of Aqaba and adjacent areas based on the tomographic inversion of regional earthquake data

    NASA Astrophysics Data System (ADS)

    El Khrepy, Sami; Koulakov, Ivan; Al-Arifi, Nassir; Petrunin, Alexey G.

    2016-06-01

    We present the first 3-D model of seismic P and S velocities in the crust and uppermost mantle beneath the Gulf of Aqaba and surrounding areas based on the results of passive travel time tomography. The tomographic inversion was performed based on travel time data from ˜ 9000 regional earthquakes provided by the Egyptian National Seismological Network (ENSN), and this was complemented with data from the International Seismological Centre (ISC). The resulting P and S velocity patterns were generally consistent with each other at all depths. Beneath the northern part of the Red Sea, we observed a strong high-velocity anomaly with abrupt limits that coincide with the coastal lines. This finding may indicate the oceanic nature of the crust in the Red Sea, and it does not support the concept of gradual stretching of the continental crust. According to our results, in the middle and lower crust, the seismic anomalies beneath the Gulf of Aqaba seem to delineate a sinistral shift (˜ 100 km) in the opposite flanks of the fault zone, which is consistent with other estimates of the left-lateral displacement in the southern part of the Dead Sea Transform fault. However, no displacement structures were visible in the uppermost lithospheric mantle.

  17. Two regimes of cloud water over the Okhotsk Sea and the adjacent regions around Japan in summer

    NASA Astrophysics Data System (ADS)

    Shimada, Teruhisa; Iwasaki, Toshiki

    2015-03-01

    This study derived two regimes of cloud water with a dipole structure between over the Okhotsk Sea and over the adjacent regions around Japan in summer by using a climate index for cool summer. When the Okhotsk high develops, clouds are confined to a thin low-level layer owing to the enhanced stability in the lower atmosphere induced by the downward motion associated with the Okhotsk high. The resulting optically thin clouds allow more downward shortwave radiation to reach the surface of the Okhotsk Sea. In contrast, the low-level easterly winds blowing toward the Japanese Islands and the Eurasian continent enhance cloud formation. This is due to the convergence of the water vapor flux induced by the easterly winds associated with the Okhotsk high and the southerly winds associated with the Baiu frontal zone and the Pacific high and due to the orographic uplift of air mass. When a cyclonic circulation occurs over the Okhotsk Sea, a thick layer of low-level clouds extending close to the sea surface is formed. The convergence of the water vapor flux over the subarctic sea surface temperature (SST) frontal zone and the cool SST promote fog formation, and upward motion associated with the cyclonic circulation supports the high cloud water content from the lower to the upper troposphere. The resulting optically thick clouds reduce the downward shortwave radiation at the surface of the Okhotsk Sea. Over the regions around Japan, water vapor flux diverges owing to dry air originating from land and cloud water decreases.

  18. Paleoseismicity of two historically quiescent faults in Australia: Implications for fault behavior in stable continental regions

    USGS Publications Warehouse

    Crone, A.J.; De Martini, P. M.; Machette, M.M.; Okumura, K.; Prescott, J.R.

    2003-01-01

    Paleoseismic studies of two historically aseismic Quaternary faults in Australia confirm that cratonic faults in stable continental regions (SCR) typically have a long-term behavior characterized by episodes of activity separated by quiescent intervals of at least 10,000 and commonly 100,000 years or more. Studies of the approximately 30-km-long Roopena fault in South Australia and the approximately 30-km-long Hyden fault in Western Australia document multiple Quaternary surface-faulting events that are unevenly spaced in time. The episodic clustering of events on cratonic SCR faults may be related to temporal fluctuations of fault-zone fluid pore pressures in a volume of strained crust. The long-term slip rate on cratonic SCR faults is extremely low, so the geomorphic expression of many cratonic SCR faults is subtle, and scarps may be difficult to detect because they are poorly preserved. Both the Roopena and Hyden faults are in areas of limited or no significant seismicity; these and other faults that we have studied indicate that many potentially hazardous SCR faults cannot be recognized solely on the basis of instrumental data or historical earthquakes. Although cratonic SCR faults may appear to be nonhazardous because they have been historically aseismic, those that are favorably oriented for movement in the current stress field can and have produced unexpected damaging earthquakes. Paleoseismic studies of modern and prehistoric SCR faulting events provide the basis for understanding of the long-term behavior of these faults and ultimately contribute to better seismic-hazard assessments.

  19. NEON: Developing a Platform for Regional to Continental Scale Biological Inquiry

    NASA Astrophysics Data System (ADS)

    Goldman, J.

    2004-05-01

    Climate variation, introductions of alien species, and patterns of land use are some of the important interacting drivers of biological change that are affecting our nation's ecosystems. Many of these drivers operate over large spatial and temporal scales, and our understanding of how these phenomena interact to drive biological change is limited by our inability to link traditionally local and short-term ecological approaches to larger and longer scales. Similarly, our ability to forecast such changes and respond to their consequences is constrained. The National Ecological Observatory Network (NEON) is a proposed shared-use research and education platform intended to improve our capacity to understand and predict biological phenomena operating from regional to continental scales. NEON is envisioned as a system of field and laboratory-based facilities distributed across the United States, which will provide the physical infrastructure and human capabilities necessary to coordinate and integrate research and education campaigns on the following types of issues: (1) biodiversity, species composition, and ecosystem functioning; (2) ecological aspects of biogeochemical cycles; (3) ecological implications of climate change; (4) ecology and evolution of infectious disease; (5) invasive species; and (6) land use and habitat alteration. Themes such as data sharing, multidisciplinary collaboration, and the development of technologies for sensing, forecasting, and visualizing biological information are central to the NEON concept. Development of the NEON science plan and the design of the network itself are proceeding through a variety of workshops and community planning meetings. A national project office is expected to form toward the end of 2004 to lead the development and creation of NEON. Ultimately, the project office will reside within an independent national organization devoted to the coordinated operation of NEON for the scientific community.

  20. Association between dental implants in the posterior region and traumatic occlusion in the adjacent premolars: a long-term follow-up clinical and radiographic analysis

    PubMed Central

    2016-01-01

    Purpose The aim of this retrospective study was to determine the association between dental implants in the posterior region and traumatic occlusion in the adjacent premolars, using data collected during from 2002 to 2015. Methods Traumatic occlusion in the adjacent premolars was assessed by examining clinical parameters (bleeding on probing, probing pocket depth, fremitus, and tooth mobility) and radiographic parameters (loss of supporting bone and widening of the periodontal ligament space) over a mean follow-up of 5 years. Clinical factors (gender, age, implant type, maxillary or mandibular position, opposing teeth, and duration of functional loading) were evaluated statistically in order to characterize the relationship between implants in the posterior region and traumatic occlusion in the adjacent premolars. Results The study inclusion criteria were met by 283 patients, who had received 347 implants in the posterior region. The incidence of traumatic occlusion in the adjacent premolars was significantly higher for splinted implants (P=0.004), implants in the maxillary region (P<0.001), and when implants were present in the opposing teeth (P<0.001). The other clinical factors of gender, age, and duration of functional loading were not significantly associated with traumatic occlusion. Conclusions This study found that the risk of traumatic occlusion in the adjacent premolars increased when splinted implants were placed in the maxillary molar region and when the teeth opposing an implant also contained implants. PMID:28050317

  1. Seismic hazard and seismic risk assessment based on the unified scaling law for earthquakes: Himalayas and adjacent regions

    NASA Astrophysics Data System (ADS)

    Nekrasova, A. K.; Kossobokov, V. G.; Parvez, I. A.

    2015-03-01

    For the Himalayas and neighboring regions, the maps of seismic hazard and seismic risk are constructed with the use of the estimates for the parameters of the unified scaling law for earthquakes (USLE), in which the Gutenberg-Richter law for magnitude distribution of seismic events within a given area is applied in the modified version with allowance for linear dimensions of the area, namely, log N( M, L) = A + B (5 - M) + C log L, where N( M, L) is the expected annual number of the earthquakes with magnitude M in the area with linear dimension L. The spatial variations in the parameters A, B, and C for the Himalayas and adjacent regions are studied on two time intervals from 1965 to 2011 and from 1980 to 2011. The difference in A, B, and C between these two time intervals indicates that seismic activity experiences significant variations on a scale of a few decades. With a global consideration of the seismic belts of the Earth overall, the estimates of coefficient A, which determines the logarithm of the annual average frequency of the earthquakes with a magnitude of 5.0 and higher in the zone with a linear dimension of 1 degree of the Earth's meridian, differ by a factor of 30 and more and mainly fall in the interval from -1.1 to 0.5. The values of coefficient B, which describes the balance between the number of earthquakes with different magnitudes, gravitate to 0.9 and range from less than 0.6 to 1.1 and higher. The values of coefficient C, which estimates the fractal dimension of the local distribution of epicenters, vary from 0.5 to 1.4 and higher. In the Himalayas and neighboring regions, the USLE coefficients mainly fall in the intervals of -1.1 to 0.3 for A, 0.8 to 1.3 for B, and 1.0 to 1.4 for C. The calculations of the local value of the expected peak ground acceleration (PGA) from the maximal expected magnitude provided the necessary basis for mapping the seismic hazards in the studied region. When doing this, we used the local estimates of the

  2. Successful Aging among Elders Living in the Mani Continental Region vs. Insular Areas of the Mediterranean: the MEDIS Study

    PubMed Central

    Mariolis, Anargiros; Foscolou, Alexandra; Tyrovolas, Stefanos; Piscopo, Suzanne; Valacchi, Giuseppe; Tsakountakis, Nikos; Zeimbekis, Akis; Bountziouka, Vassiliki; Gotsis, Efthimios; Metallinos, George; Tyrovola, Dimitra; Tur, Josep-Antoni; Matalas, Antonia-Leda; Lionis, Christos; Polychronopoulos, Evangelos; Panagiotakos, Demosthenes

    2016-01-01

    To evaluate the role of geography i.e., continental vs. insular Mediterranean, on successful aging among older inhabitants. During 2005-2014, 2693 elderly (aged 65 to 100 years) individuals from 21 Mediterranean islands in Greece, Italy and Spain as well as Cyprus, Malta, and the rural region of Mani (southeast continental region of Greece keeping old-time traditions), were voluntarily recruited. Successful aging was evaluated using a validated index composed of 10 health-related socio-lifestyle and clinical characteristics. After accounting for age, sex, body mass index (BMI), physical activity, smoking habits, MedDietScore and access to health care services, the older inhabitants of islands were found to have a higher level of the successful aging index when compared to their counterparts in Mani (Beta=0.174, p<0.001); moreover, islanders exhibited slightly more years of “good” health (68.7 vs 68.4 years for Mani residents (p=0.99)). However, compared to the residents of Mani, islanders had 1.64 times higher odds (95%CI, 1.08-2.48) for having hypertension, 2.4-times higher odds (95%CI, 1.34-4.21) for having diabetes and 1.52 times higher odds (95%CI, 0.97-2.38) for having hypercholesterolemia. Engaging in physical activities and healthy dietary habits were the major determinants of healthy aging, among islanders as compared to their counterparts of continental Mani region. Elder residents of the continental Mani area enjoyed a better health status, whereas elder islanders had a higher level of successful aging; a finding which could be attributed to differences in lifestyle among elders. PMID:27330843

  3. Identification of an extended N-acetylated sequence adjacent to the protein-linkage region of fibroblast heparan sulphate.

    PubMed Central

    Lyon, M; Steward, W P; Hampson, I N; Gallagher, J T

    1987-01-01

    The distribution of N-sulphate groups within fibroblast heparan sulphate chains was investigated. The detergent-extractable heparan sulphate proteoglycan from adult human skin fibroblasts, radiolabelled with [3H]glucosamine and [35S]sulphate, was coupled to CNBr-activated Sepharose 4B. After partial depolymerization of the heparan sulphate with nitrous acid, the remaining Sepharose-bound fragments were removed by treatment with alkali. These fragments, of various sizes, but all containing an intact reducing xylose residue, were fractionated on Sephacryl S-300 and the distribution of the 3H and 35S radiolabels was analysed. A decreased degree of sulphation was observed towards the reducing termini of the chains. After complete nitrous acid hydrolysis of the Sepharose-bound proteoglycan, analysis of the proximity of N-sulphation to the reducing end revealed the existence of an extended N-acetylated sequence directly adjacent to the protein-linkage sequence. The size of this N-acetylated domain was estimated by gel filtration to be approximately eight disaccharide units. This domain appears to be highly conserved, being present in virtually all the chains derived from this proteoglycan, implying the existence of a mechanism capable of generating such a non-random sequence during the post-polymeric modification of heparan sulphate. Comparison with the corresponding situation in heparin suggests that different mechanisms regulate polymer N-sulphation in the vicinity of the protein-linkage region of these chemically related glycosaminoglycans. PMID:2954540

  4. Identification of Triplophysa species from the Qinghai-Tibetan Plateau (QTP) and its adjacent regions through DNA barcodes.

    PubMed

    Li, Jiuxuan; Wang, Ying; Jin, Huifang; Li, Wujiao; Yan, Chaochao; Yan, Pengfei; Zhang, Xiuyue; He, Shunping; Song, Zhaobin

    2017-03-20

    The genus Triplophysa is the largest and most difficult to identity morphologically fish group of superfamily Cobitoidea with 140 currently valid species, and is mainly distributed in the Qinghai-Tibetan Plateau (QTP) and adjacent regions. Most species within this genus possess highly similar morphological characteristics for adaption to the highland environment and are very difficult to be identified only based on morphology. The traditional species identification, mainly based on external morphological diagnostic characters, leads to inconsistent results in many cases. Herein, we provided a molecular method based on mitochondrial cytochrome c subunit I (COI) for the identification of Triplophysa fishes. Thirty-three Triplophysa species, 244 individuals, were used to determine whether barcoding was effective in discriminating species for this genus. The mean intraspecific and interspecific K2P distances ranged from 0 to 14.9% (mean, 2.9%) and 0 to 23.4% (mean, 9.7%), respectively. The tree-based analysis displayed most of species formed discrete clusters with strong bootstrap support values (>90%). The results showed that most of Triplophysa species could be identified by DNA barcode and indicated DNA barcode could be used as a molecular marker for these species.

  5. Virio- and bacterioplankton in the estuary zone of the Ob River and adjacent regions of the Kara Sea shelf

    NASA Astrophysics Data System (ADS)

    Kopylov, A. I.; Sazhin, A. F.; Zabotkina, E. A.; Romanenko, A. V.; Romanova, N. D.

    2017-01-01

    The distribution of structural and functional characteristics of virioplankton in the north of the Ob River estuary and the adjacent Kara Sea shelf (between latitudes 71°44'44″ N and 73°45'24″ N) was studied with consideration of the spatial variations in the number ( N B) and productivity ( P B) of bacteria and water properties (temperature, salinity, density) by analyzing samples taken in September 2013. The number of plankton viruses ( N V), the occurrence of visible infected bacteria cells, virus-induced mortality of bacteria, and virioplankton production in the studied region varied within (214-2917) × 103 particles/mL, 0.3-5.6% of NB, 2.2-64.4% of P B, and (6-17248) × 103 particles/(mL day), respectively. These parameters were the highest in water layers with a temperature of +7.3-7.5°C, salinity of 3.75-5.41 psu, and conventional density (στ) of 2.846-4.144. The number of bacterioplankton was (614-822) × 103 cells/mL, and the N V/ N B ratio was 1.1-4.5. A large amount of virus particles were attached to bacterial cells and suspended matter. The data testify to the considerable role of viruses in controlling the number and production of heterotrophic bacterioplankton in the interaction zone of river and sea waters.

  6. The genus Xestoleberis (Ostracoda: Xestoleberididae) in the Northern, Northeastern and Eastern regions of the Brazilian continental shelf.

    PubMed

    Da Luz, Nathália Carvalho; Coimbra, João Carlos

    2015-06-22

    The analysis of 359 samples from three regions of the Brazilian continental shelf (Northern, Northeastern and Eastern) resulted in the recognition of six species of the genus Xestoleberis. One of these species was already described, X. umbonata Whatley et al. 1998, four species are new and herein described, X. inesae sp. nov., X. amazonica sp. nov., X. subtriangularis sp. nov. and X. virilis sp. nov., and one was maintained in open nomenclature, Xestoleberis sp. The species X. inesae sp. nov. is widely distributed in the study area, occurring in all mentioned regions, while X. amazonica sp. nov. is restricted to the Northern region. Xestoleberis subtriangularis sp. nov., X. virilis sp. nov. and Xestoleberis sp. occur in the Northeastern and Eastern regions. Xestoleberis umbonata was recorded in this study only in the southernmost part of the Eastern region.

  7. Upper mantle anisotropy beneath Indochina block and adjacent regions from shear wave splitting analysis of Vietnam array data

    NASA Astrophysics Data System (ADS)

    Bai, L.; Iidaka, T.; Kawakatsu, H.; Morita, Y.; Dzung, N.

    2007-12-01

    Indochina block is located at the junction of Eurasia, Indian and Pacific plates. It has a close relationship with the uplift of Tibet plateau and the spreading of South China Sea basin in the geological evolution histories. The anisotropy is considered to directly relate to deformation in the mantle, and therefore provide constraints on tectonic and geodynamic processes. In this study, we present upper mantle anisotropy beneath Indochina block and adjacent regions from shear wave splitting analysis of Vietnam array and IRIS data. The data used here recorded by Vietnam array during the period between February 2000 and October 2005. The array consists of 6 broadband seismometers. We employed a compact HDD for data storage, which enables long-term and stable observation. We also used data form three IRIS stations around Vietnam for the same period. All records are band-pass filtered between 0.02 and 1.0 Hz to eliminate background noise. The dominant time windows used are 10-15 s around SKS phases based on the predicted travel times from the iasp91 model. We used the methodology of Silver and Chan (1991) as modified by Walker (2004) to determine the fast polarization direction and the delay time between the fast and slow components. In order to find the best splitting parameters, a grid search over possible values is performed to linearize the shear wave particle motion when the effect of the anisotropy if removed. The error estimation of each combination of splitting parameters is given by 95 percent confidence level of F test. We are able to characterize the splitting patterns in greater detail because of the use of new data. The average value of delay times in Indochina block is about 1.35 s, larger than that in adjacent regions. Tomographic studies also revealed low velocity anomalies in upper mantle beneath study area (Lebedev and Nolet, 2003). We estimate that the Indochina block might be affected by the mantle convection produced by the spreading of the South

  8. Vestiges of a continental margin ophiolite type in the Novo Oriente region, Borborema Province, NE Brazil

    NASA Astrophysics Data System (ADS)

    Pitombeira, João Paulo Araújo; Amaral, Wagner da Silva; Uchôa Filho, Evilarde Carvalho; Fuck, Reinhardt Adolfo; Dantas, Elton Luiz; Parente, Clóvis Vaz; da Costa, Felipe Grandjean; Veríssimo, César Ulisses Vieira

    2017-01-01

    The Novo Oriente Group is a restricted well-preserved metasedimentary sequence, composed of two tectonic-stratigraphic sequences in the southwestern portion of the Ceará Central Domain, NE Brazil. The Bonsucesso Formation comprises mainly quartzite and metamafic rocks and the Caraúbas Formation is dominantly metapelitic, with chemical sedimentary contribution, metamafic and metaultramafic rocks. New integrated field, geochemical data and Sm-Nd isotopes of the metaultramafic and metamafic rocks of the two formations have been investigated in order to determine their tectonic setting. The metaultramafic rocks are dominantly composed of deformed and undeformed serpentinites, chloritites, actinolitites, talc-chlorite schists, serpentine-talc schists, talc-rich siliceous rocks and subordinated listwänites. Geochemical data indicate that the serpentinites correspond to rocks resulting from the alteration of dunites depleted in HREE, similar to the pattern presented by subduction-zone serpentinites generated from exhumed sub-continental peridotites and hydrated during ocean-continent transition (OCT) rifting. The metamafic rocks, represented by metagabbros, hornblende metagabbros and metabasalts, consist of basic rocks of basaltic and tholeiitic affinity with signatures between E- and N-MORB and variable contamination by crustal components similar to the rocks formed from the interaction between mantle plumes and heavily thinned continental crust. Isotopic analysis indicates crustal assimilation with negative ɛNd and Paleoproterozoic TDM ages. The data suggest that metaultramafic and metamafic rocks correspond, respectively, to continental sub-lithospheric mantle exhumed in an area of ocean-continent transition (OCT), and mafic magmatism associated with the development of a magma-poor passive margin generated by the break-up of the Rodinia Supercontinent, which was later dismembered by the Brasiliano/Pan-African Orogeny collisional phase and preserved as a Continental

  9. Imaging the Subduction of Continental Lithosphere in the Banda Sea Region

    NASA Astrophysics Data System (ADS)

    Fichtner, A.; De Wit, M.; van Bergen, M.

    2014-12-01

    We present a 3D tomographic model of Australasia obtained by full seismic waveform inversion. Our model features a sharp lateral velocity contrast extending to >200 km depth, coincident with the abrupt transition from low to high Helium ratios in arc volcanics near 123°E (see figure). The joint analysis of the tomographic model and isotope data (for He, Pb, Nd, Sr) suggests that the North Australian craton subducted beneath the Banda Sea to around 100 km depth. The continuous increase of computing power combined with advances in numerical seismology allow us to develop full waveform inversion techniques that translate complete seismograms into 3D Earth models. The natural incorporation of any type of body and surface waves in full waveform inversion improves tomographic resolution in terms of both resolution length and amplitude recovery. We applied full waveform inversion to Australasia, including the Sunda and Banda arcs. The correlation of the tomographic model with isotope signatures of arc volcanics supports the shallow-angle subduction of North Australian lithosphere. The integrated data suggest that the late Jurassic ocean lithosphere north of the North Australian craton was capable of entraining large volumes of continental lithosphere. A plausible explanation involves delamination within the continental crust, separating upper from lower crustal units. This interpretation is consistent with the existence of a massive accretionary complex on Timor island, with evidence from Pb isotope analysis for lower-crust involvement in arc volcanism; and with the approximate gravitational stability of the subducted lithosphere as inferred from the tomographic images. The Banda arc example demonstrates that continental lithosphere in arc-continent collisions may not generally be preserved, thus increasing the complexity of tectonic reconstructions and models of recycling continental crust.

  10. Present-day Focal Mechanisms and Stress Field of the Sichuan-Yunnan Active Block and Its Adjacent Region

    NASA Astrophysics Data System (ADS)

    zhao, cuiping; luo, jun; zhou, lianqing

    2013-04-01

    Focal mechanism solutions together with the depths of 66 M 3.5 moderate earthquakes occurred in the Sichuan Yunnan active block and its adjacent regions from Aug.1st, 2007 to Sep.15th, 2012was obtained by CAP method. Furthermore, by combining the results with the focal mechanism solutions from Harvard University, we investigated the characteristics of the stress field in the study area. We discussed the spatial distribution of the focal mechanisms and the focal depths, and then analyzed its dynamics. Four conclusions are drawn as follows. (1)Focal mechanism solutions show zoning characteristic. Along the ANH-ZMH-XJ faults(the eastern border of Sichuan-Yunnan block), the earthquakes are mostly left-lateral strike-slip mechanism. Along the HSH fault, the earthquakes are mostly right-lateral strike-slip mechanism. Around the XGLL block and in its interior, there exists remarkable normal fault mechanism with different fault striking and direction of P and T stress axis. Along the arc boundary of Sichuan-Yunnan block with the Sichuan basin, the earthquakes are reverse fault mechanism. (2) The inversed regional stress field shows complicated local feature. On and to the east side of the eastern border of Sichuan-Yunnan block, the stress field is similar with the stress field of the Eastern China block, which is from the relative motion of Philippine plate towards the Urasia plate. Whereas to the west side of the eastern border of Sichuan-Yunnan block, the stress field is much more complicated, indicting the strong influence of local structures to the stress field, especially the NE striking of JPS-YL over-thrusting tectonic structure located in the interior of Sichuan-Yunnan block.(3)The moment center depths of events occurred in the Sichuan-Yunnan active block are within 15km deep, and mostly among 5~15km, suggesting that the brittle seismic layer is among the depth of 5~15km in the upper and middle crust.

  11. Fluid-induced Crystallization of Majoritic Garnet During Deep Continental Subduction (Western Gneiss Region, Norway)

    NASA Astrophysics Data System (ADS)

    Scambelluri, M.; Pettke, T.; van Roermund, H. L.

    2008-12-01

    In ultrahigh pressure (UHP) rocks, garnet containing pyroxene exsolutions derives from breakdown of majorite crystallized at depths > 200 km. Presence of microdiamonds in some of these rocks [1], including those of the Western Gneiss Region (WGR) of Norway [2], may suggest a fluid-bearing environment for the genesis of majorite. The WGR UHP gneisses host garnet peridotite and websterite recording uplift from extraordinary depths prior to uptake in a subducting slab [2]. These ultramafic rocks (islands of Otrøy and Bardane) derive from depleted Archean transition-zone mantle (350 km depth) upwelled and accreted to a cratonic lithosphere (M2 stage). Evidence for this are decimetric garnets (grt) preserved in Otrøy, hosting up to 20 volume% orthopyroxene (opx) and clinopyroxene (cpx) exsolved from precursor majoritic garnet (M1 stage). The pyroxene lamellae (20-30 ¥ìm thick, hundreds of ¥ìm long) [3] were exsolved under high-T, as shown by the garnet/cpx REE distribution [4]. This Archean-mid Proterozoic record is overprinted by the 425- 390 Ma Scandian continental subduction (M3 stage), forming new grt + cpx + opx + phlogopite (phl) + spinel (sp) that contain diamond-bearing micro-inclusions witnessing deep COH subduction fluids [2]. Here we document formation of new majoritic garnet in the M3 assemblage and in veins at Bardane [5]. Textural characteristics, together with the LREE and LILE enrichments of the M3 minerals, indicate that the new majorite is linked to infiltration of subduction fluids during renewed burial towards sub-lithospheric depths. It represents the deepest occurrence of fluid-related microstructures in mantle rocks. The new majoritic garnet crystallized at grain boundaries and in micro-veins at 7 Gpa and 900-1000 °C. It hosts thin pyroxene needles (5 mm thick, 100 mm long) exsolved under comparatively low-T, as indicated by the garnet/cpx REE distribution. The trace element signature of the majorite-bearing subduction assemblage is LREE

  12. Comparison of vesicular-arbuscular mycorrhizae in plants from disturbed and adjacent undisturbed regions of a coastal salt marsh in Clinton, Connecticut, USA

    NASA Astrophysics Data System (ADS)

    Cooke, John C.; Lefor, Michael W.

    1990-01-01

    Roots of salt marsh plant species Spartina alterniflora, S. patens, Distichlis spicata, and others were examined for the presence of vesicular-arbuscular mycorrhizal (VAM) fungi. Samples were taken from introduced planted material in a salt marsh restoration project and from native material in adjacent marsh areas along the Indian River, Clinton, Connecticut, USA. After ten years the replanted area still has sites devoid of vegetation. The salt marsh plants introduced there were devoid of VAM fungi, while high marsh species from the adjacent undisturbed region showed consistent infection, leading the authors to suggest that VAM fungal infection of planting stocks may be a factor in the success of marsh restoration.

  13. Inherent gravitational instability of thickened continental crust with regionally developed low- to medium-pressure granulite facies metamorphism

    NASA Astrophysics Data System (ADS)

    Gerya, Taras V.; Maresch, Walter V.; Willner, Arne P.; Van Reenen, Dirk D.; Smit, C. Andre

    2001-08-01

    Petrological arguments show that regionally developed low- to medium-pressure, high-temperature granulite facies metamorphism may critically enhance the lowering of crustal density with depth. This leads to gravitational instability of homogeneously thickened continental crust, mainly due to changes in mineral assemblages and the thermal expansion of minerals in conjunction with the exponential lowering of the effective viscosity of rocks with increasing temperature. It is argued that crustal processes of gravitational redistribution (crustal diapirism) contributing to the exhumation of granulite facies rocks may be activated in this way.

  14. Correlation between Focal Nodular Low Signal Changes in Hoffa's Fat Pad Adjacent to Anterior Femoral Cartilage and Focal Cartilage Defect Underlying This Region and Its Possible Implication

    PubMed Central

    Ng, Wuey Min

    2016-01-01

    Purpose. This study investigates the association between focal nodular mass with low signal in Hoffa's fat pad adjacent to anterior femoral cartilage of the knee (FNMHF) and focal cartilage abnormality in this region. Method. The magnetic resonance fast imaging employing steady-state acquisition sequence (MR FIESTA) sagittal and axial images of the B1 and C1 region (described later) of 148 patients were independently evaluated by two reviewers and categorized into four categories: normal, FNMHF with underlying focal cartilage abnormality, FNMHF with normal cartilage, and cartilage abnormality with no FNMHF. Results. There was a significant association (p = 0.00) between FNMHF and immediate adjacent focal cartilage abnormality with high interobserver agreement. The absence of focal nodular lesions next to the anterior femoral cartilage has a very high negative predictive value for chondral injury (97.8%). Synovial biopsy of focal nodular lesion done during arthroscopy revealed some fibrocollagenous tissue and no inflammatory cells. Conclusion. We postulate that the FNMHF adjacent to the cartilage defects is a form of normal healing response to the cartilage damage. One patient with FHMHF and underlying cartilage abnormality was rescanned six months later. In this patient, the FNMHF disappeared and normal cartilage was observed in the adjacent region which may support this theory. PMID:27213085

  15. Variants in Adjacent Oxytocin/Vasopressin Gene Region and Associations with ASD Diagnosis and Other Autism Related Endophenotypes

    PubMed Central

    Francis, Sunday M.; Kistner-Griffin, Emily; Yan, Zhongyu; Guter, Stephen; Cook, Edwin H.; Jacob, Suma

    2016-01-01

    Background: There has been increasing interest in oxytocin (peptide: OT, gene: OXT) as a treatment pathway for neurodevelopmental disorders such as Autism Spectrum Disorder (ASD). Neurodevelopmental disorders affect functional, social, and intellectual abilities. With advances in molecular biology, research has connected multiple gene regions to the clinical presentation of ASD. Studies have also shown that the neuropeptide hormones OT and arginine vasopressin (AVP) influence mammalian social and territorial behaviors and may have treatment potential for neurodevelopmental disorders. Published data examining molecular and phenotypic variation in ASD, such as cognitive abilities, are limited. Since most studies have focused on the receptors in the OT-AVP system, we investigated genetic variation within peptide genes for association with phenotypic ASD features that help identify subgroups within the spectrum. Methods: In this study, TDT analysis was carried out utilizing FBAT in 207 probands (156 trios) and a European Ancestry (EA) subsample (108 trios).The evolutionarily related and adjacent genes of OXT and AVP were studied for associations between the tagged single nucleotide polymorphisms and ASD diagnosis, social abilities, restrictive and repetitive behaviors, and IQ for cognitive abilities. Additionally, relationships with whole blood serotonin (WB5HT) were explored because of the developmental relationships connecting plasma levels of OT and WB5HT within ASD. Results: Results indicate significant association between OXT rs6084258 (p = 0.001) and ASD. Associations with several endophenotypes were also noted: OXT rs6133010 was associated with IQ (full scale IQ, p = 0.008; nonverbal IQ, p = 0.010, verbal IQ, p = 0.006); and OXT rs4813625 and OXT rs877172 were associated with WB5HT levels (EA, p = 0.027 and p = 0.033, respectively). Additionally, we measured plasma OT (pOT) levels in a subsample (N = 54). Results show the three polymorphisms, OXT rs6084258, OXT

  16. Quantitative woody cover reconstructions from eastern continental Asia of the last 22 kyr reveal strong regional peculiarities

    NASA Astrophysics Data System (ADS)

    Tian, Fang; Cao, Xianyong; Dallmeyer, Anne; Ni, Jian; Zhao, Yan; Wang, Yongbo; Herzschuh, Ulrike

    2016-04-01

    We present a calibration-set based on modern pollen and satellite-based Advanced Very High Resolution Radiometer (AVHRR) observations of woody cover (including needleleaved, broadleaved and total tree cover) in eastern continental Asia, which shows good performance under cross-validation with the modern analogue technique (all the coefficients of determination between observed and predicted values are greater than 0.65). The calibration-set is used to reconstruct woody cover from a taxonomically harmonized and temporally standardized fossil pollen dataset (including 274 cores) with 500-year resolution over the last 22 kyr. The spatial range of forest has not noticeably changed in eastern continental Asia during the last 22 kyr, although woody cover has, especially at the margin of the eastern Tibetan Plateau and in the forest-steppe transition area of north-central China. Vegetation was sparse during the LGM in the present forested regions, but woody cover increased markedly at the beginning of the Bølling/Allerød period (B/A; ca. 14.5 ka BP) and again at the beginning of the Holocene (ca. 11.5 ka BP), and is related to the enhanced strength of the East Asian Summer Monsoon. Forest flourished in the mid-Holocene (ca. 8 ka BP) possibly due to favourable climatic conditions. In contrast, cover was stable in southern China (high cover) and arid central Asia (very low cover) throughout the investigated period. Forest cover increased in the north-eastern part of China during the Holocene. Comparisons of these regional pollen-based results with simulated forest cover from runs of a global climate model (for 9, 6 and 0 ka BP (ECHAM5/JSBACH ∼1.125° spatial resolution)) reveal many similarities in temporal change. The Holocene woody cover history of eastern continental Asia is different from that of other regions, likely controlled by different climatic variables, i.e. moisture in eastern continental Asia; temperature in northern Eurasia and North America.

  17. Glacial-interglacial organic carbon record from the Makassar Strait, Indonesia: Implications for regional changes in continental vegetation

    USGS Publications Warehouse

    Visser, K.; Thunell, R.; Goni, M.A.

    2004-01-01

    Recent studies convincingly show that climate in the Western Pacific Warm Pool and other equatorial/tropical regions was significantly colder (by ???3-4??C) during glacial periods, prompting a reexamination of the late Pleistocene paleoenvironments of these regions. This study examines changes in continental vegetation during the last two deglaciations (Terminations I and II) using a sediment core (MD9821-62) recovered from the Makassar Strait, Indonesia. Evidence based on the lignin phenol ratios suggests that vegetation on Borneo and other surrounding islands did not significantly change from tropical rainforest during the last two glacial periods relative to subsequent interglacial periods. This supports the hypothesis that the winter monsoon increased in strength during glacial periods, allowing Indonesia to maintain high rainfall despite the cooler conditions. ?? 2003 Elsevier Ltd. All rights reserved.

  18. Seismic patterns of the Guerrero-Oaxaca, Mexico region, and its relationship to the continental margin structure

    NASA Astrophysics Data System (ADS)

    Yamamoto, Jaime; González-Moran, Tomas; Quintanar, Luis; Zavaleta, Ana B.; Zamora, Araceli; Espindola, Victor H.

    2013-01-01

    The main purpose of this paper is to enhance awareness on the seismic evidences that suggest a possible segmentation of the continental margin at the Guerrero-Oaxaca, Mexico region. Data from a recent 7 months survey of microseismicity carried out from 2008 December to 2009 June at Ometepec, Guerrero area, using a portable broad-band digital seismographs network added with data of a previous survey and the aftershocks distribution of the 1982 and 1995 major earthquakes permit to infer the characteristics of the seismic patterns of the Acapulco-Pinotepa Nacional portion of the southern Mexico subduction region. Two different seismic regimens are apparent, one in the Acapulco-Marquelia and the other in the Marquelia-Pinotepa Nacional areas. In the Acapulco-Marquelia portion, the seismicity is broader and dispersed starting at the coast up to 160 km inland approximately. Seismicity in the Marquelia-Pinotepa portion, on the other hand, is narrower and concentrates near the coast. The two seismic regimens are separated by a narrow band or strip of low seismic activity, nearly perpendicular to the coast and trench axis. The apparent low seismicity strip that separates the seismic regimens may trace the position either of a seismically inactive fracture zone or a seismic gap. Moreover, careful observation of the epicentres distribution of the Marquelia-Pinotepa segment reveals two clusters of events separated by another low seismicity strip. Thus, the two observed low activity strips, located near the northern tip of the Ometepec submarine canyon and Punta Maldonado, respectively, are interpreted in this paper as corresponding to disruptions of the continental margin. Other low seismic activity strips probably exist but these two are the most conspicuous. Supplementary information on fault mechanisms available for this area seems to substantiate additionally this interpretation. The observations reported are important to understand the mechanics of the major earthquakes

  19. Multi-regional synthesis of temporal trends in biotic assemblages in streams and rivers of the continental United States

    USGS Publications Warehouse

    Miller, Matthew P.; Brasher, Anne M.D.; Keenen, Jonathan G.

    2013-01-01

    Biotic assemblages in aquatic ecosystems are excellent integrators and indicators of changing environmental conditions within a watershed. Therefore, temporal changes in abiotic environmental variables often can be inferred from temporal changes in biotic assemblages. Algae, macroinvertebrate, and fish assemblage data were collected from 91 sampling sites in 4 geographic regions (northeastern/north-central, southeastern, south-central, and western), collectively encompassing the continental United States, from 1993 to 2009 as part of the U.S. Geological Survey National Water-Quality Assessment Program. This report uses a multivariate approach to synthesize temporal trends in biotic assemblages and correlations with relevant abiotic parameters as a function of biotic assemblage, geographic region, and land use. Of the three groups of biota, algal assemblages had temporal trends at the greatest percentage of sites. Of the regions, a greater percentage of sites in the northeastern/north-central and western regions had temporal trends in biotic assemblages. In terms of land use, a greater percentage of watersheds draining agricultural, urban, and undeveloped areas had significant temporal changes in biota, as compared to watersheds with mixed use. Correlations between biotic assemblages and abiotic variables indicate that, in general, macroinvertebrate assemblages correlated with water quality and fish assemblages correlated with physical habitat. Taken together, results indicate that there are regional differences in how individual biotic assemblages (algae, macroinvertebrates, and fish) respond to different abiotic drivers of change.

  20. Factors affecting stream nutrient loads: A synthesis of regional SPARROW model results for the continental United States

    USGS Publications Warehouse

    Preston, Stephen D.; Alexander, Richard B.; Schwarz, Gregory E.; Crawford, Charles G.

    2011-01-01

    We compared the results of 12 recently calibrated regional SPARROW (SPAtially Referenced Regressions On Watershed attributes) models covering most of the continental United States to evaluate the consistency and regional differences in factors affecting stream nutrient loads. The models - 6 for total nitrogen and 6 for total phosphorus - all provide similar levels of prediction accuracy, but those for major river basins in the eastern half of the country were somewhat more accurate. The models simulate long-term mean annual stream nutrient loads as a function of a wide range of known sources and climatic (precipitation, temperature), landscape (e.g., soils, geology), and aquatic factors affecting nutrient fate and transport. The results confirm the dominant effects of urban and agricultural sources on stream nutrient loads nationally and regionally, but reveal considerable spatial variability in the specific types of sources that control water quality. These include regional differences in the relative importance of different types of urban (municipal and industrial point vs. diffuse urban runoff) and agriculture (crop cultivation vs. animal waste) sources, as well as the effects of atmospheric deposition, mining, and background (e.g., soil phosphorus) sources on stream nutrients. Overall, we found that the SPARROW model results provide a consistent set of information for identifying the major sources and environmental factors affecting nutrient fate and transport in United States watersheds at regional and subregional scales. ?? 2011 American Water Resources Association. This article is a U.S. Government work and is in the public domain in the USA.

  1. Marginal continental and within-plate neoproterozoic granites and rhyolites of Wrangel Island, Arctic region

    NASA Astrophysics Data System (ADS)

    Luchitskaya, M. V.; Moiseev, A. V.; Sokolov, S. D.; Tuchkova, M. I.; Sergeev, S. A.; O'Sullivan, P. B.; Verzhbitskii, V. E.; Malyshev, N. A.

    2017-01-01

    The paper presents new data on the U-Pb zircon age, as well as results of isotopic geochemical analysis, of granites and rhyolites from Wrangel Island. The U-Pb age estimates of granites and rhyolites are grouped into two clusters ( 690-730 and 590-610 Ma), which imply that these rocks crystallized in the Late Neoproterozoic. Granitic rocks dated back to 690-730 Ma are characterized by negative ɛNd( t) values and Paleoproterozoic Sm-Nd model age. The older inherited zircons corroborate the ancient age of their crustal source. The granitic rocks pertain to involved peraluminous granites of type I, which form at a continental margin of the Andean type and can be compared with coeval granites and orthogneisses from the Seward Peninsula in Alaska. Rhyolites and granites 590-610 Ma in age are distinguished by a moderately positive ɛNd( t) and Mesoproterozoic model age. It is suggested that they have a heterogeneous magma source comprising crustal and mantle components. The geochemical features of granites and rhyolites correspond to type A granites. Together with coeval OIB-type basalts, they make up a riftogenic bimodal association of igneous rocks, which are comparable with orthogneisses (565 Ma) and gabbroic rocks (540 Ma) of Seward Peninsula in Alaska.

  2. HyFlux - Part I: Regional Modeling of Methane Flux From Near-Seafloor Gas Hydrate Deposits on Continental Margins

    NASA Astrophysics Data System (ADS)

    MacDonald, I. R.; Asper, V.; Garcia, O. P.; Kastner, M.; Leifer, I.; Naehr, T.; Solomon, E.; Yvon-Lewis, S.; Zimmer, B.

    2008-12-01

    HyFlux - Part I: Regional modeling of methane flux from near-seafloor gas hydrate deposits on continental margins MacDonald, I.R., Asper, V., Garcia, O., Kastner, M., Leifer, I., Naehr, T.H., Solomon, E., Yvon-Lewis, S., and Zimmer, B. The Dept. of Energy National Energy Technology Laboratory (DOE/NETL) has recently awarded a project entitled HyFlux: "Remote sensing and sea-truth measurements of methane flux to the atmosphere." The project will address this problem with a combined effort of satellite remote sensing and data collection at proven sites in the Gulf of Mexico where gas hydrate releases gas to the water column. Submarine gas hydrate is a large pool of greenhouse gas that may interact with the atmosphere over geologic time to affect climate cycles. In the near term, the magnitude of methane reaching the atmosphere from gas hydrate on continental margins is poorly known because 1) gas hydrate is exposed to metastable oceanic conditions in shallow, dispersed deposits that are poorly imaged by standard geophysical techniques and 2) the consumption of methane in marine sediments and in the water column is subject to uncertainty. The northern GOM is a prolific hydrocarbon province where rapid migration of oil, gases, and brines from deep subsurface petroleum reservoirs occurs through faults generated by salt tectonics. Focused expulsion of hydrocarbons is manifested at the seafloor by gas vents, gas hydrates, oil seeps, chemosynthetic biological communities, and mud volcanoes. Where hydrocarbon seeps occur in depths below the hydrate stability zone (~500m), rapid flux of gas will feed shallow deposits of gas hydrate that potentially interact with water column temperature changes; oil released from seeps forms sea-surface features that can be detected in remote-sensing images. The regional phase of the project will quantify verifiable sources of methane (and oil) the Gulf of Mexico continental margin and selected margins (e.g. Pakistan Margin, South China Sea

  3. Contribution of the upper river, the estuarine region, and the adjacent sea to the heavy metal pollution in the Yangtze Estuary.

    PubMed

    Yin, Su; Wu, Yuehan; Xu, Wei; Li, Yangyang; Shen, Zhenyao; Feng, Chenghong

    2016-07-01

    To determine whether the discharge control of heavy metals in the Yangtze River basin can significantly change the pollution level in the estuary, this study analyzed the sources (upper river, the estuarine region, and the adjacent sea) of ten heavy metals (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, and Zn) in dissolved and particulate phases in the surface water of the estuary during wet, normal, and dry seasons. Metal sources inferred from section fluxes agree with those in statistical analysis methods. Heavy metal pollution in the surface water of Yangtze Estuary primarily depends on the sediment suspension and the wastewater discharge from estuary cities. Upper river only constitutes the main source of dissolved heavy metals during the wet season, while the estuarine region and the adjacent sea (especially the former) dominate the dissolved metal pollution in the normal and dry seasons. Particulate metals are mainly derived from sediment suspension in the estuary and the adjacent sea, and the contribution of the upper river can be neglected. Compared with the hydrologic seasons, flood-ebb tides exert a more obvious effect on the water flow directions in the estuary. Sediment suspension, not the upper river, significantly affects the suspended particulate matter concentration in the estuary.

  4. High-resolution ensemble projections of near-term regional climate over the continental United States

    DOE PAGES

    Ashfaq, Moetasim; Rastogi, Deeksha; Mei, Rui; ...

    2016-09-01

    We present high-resolution near-term ensemble projections of hydro-climatic changes over the contiguous U.S. using a regional climate model (RegCM4) that dynamically downscales 11 Global Climate Models from the 5th phase of Coupled Model Inter-comparison Project at 18km horizontal grid spacing. All model integrations span 41 years in the historical period (1965 – 2005) and 41 years in the near-term future period (2010 – 2050) under Representative Concentration Pathway 8.5 and cover a domain that includes the contiguous U.S. and parts of Canada and Mexico. Should emissions continue to rise, surface temperatures in every region within the U.S. will reach amore » new climate norm well before mid 21st century regardless of the magnitudes of regional warming. Significant warming will likely intensify the regional hydrological cycle through the acceleration of the historical trends in cold, warm and wet extremes. The future temperature response will be partly regulated by changes in snow hydrology over the regions that historically receive a major portion of cold season precipitation in the form of snow. Our results indicate the existence of the Clausius-Clapeyron scaling at regional scales where per degree centigrade rise in surface temperature will lead to a 7.4% increase in precipitation from extremes. More importantly, both winter (snow) and summer (liquid) extremes are projected to increase across the U.S. These changes in precipitation characteristics will be driven by a shift towards shorter and wetter seasons. Altogether, projected changes in the regional hydro-climate can have substantial impacts on the natural and human systems across the U.S.« less

  5. High-resolution ensemble projections of near-term regional climate over the continental United States

    SciTech Connect

    Ashfaq, Moetasim; Rastogi, Deeksha; Mei, Rui; Kao, Shih -Chieh; Gangrade, Sudershan; Naz, Bibi S.; Touma, Danielle

    2016-09-01

    We present high-resolution near-term ensemble projections of hydro-climatic changes over the contiguous U.S. using a regional climate model (RegCM4) that dynamically downscales 11 Global Climate Models from the 5th phase of Coupled Model Inter-comparison Project at 18km horizontal grid spacing. All model integrations span 41 years in the historical period (1965 – 2005) and 41 years in the near-term future period (2010 – 2050) under Representative Concentration Pathway 8.5 and cover a domain that includes the contiguous U.S. and parts of Canada and Mexico. Should emissions continue to rise, surface temperatures in every region within the U.S. will reach a new climate norm well before mid 21st century regardless of the magnitudes of regional warming. Significant warming will likely intensify the regional hydrological cycle through the acceleration of the historical trends in cold, warm and wet extremes. The future temperature response will be partly regulated by changes in snow hydrology over the regions that historically receive a major portion of cold season precipitation in the form of snow. Our results indicate the existence of the Clausius-Clapeyron scaling at regional scales where per degree centigrade rise in surface temperature will lead to a 7.4% increase in precipitation from extremes. More importantly, both winter (snow) and summer (liquid) extremes are projected to increase across the U.S. These changes in precipitation characteristics will be driven by a shift towards shorter and wetter seasons. Altogether, projected changes in the regional hydro-climate can have substantial impacts on the natural and human systems across the U.S.

  6. High-resolution ensemble projections of near-term regional climate over the continental United States

    NASA Astrophysics Data System (ADS)

    Ashfaq, Moetasim; Rastogi, Deeksha; Mei, Rui; Kao, Shih-Chieh; Gangrade, Sudershan; Naz, Bibi S.; Touma, Danielle

    2016-09-01

    We present high-resolution near-term ensemble projections of hydroclimatic changes over the contiguous U.S. using a regional climate model (RegCM4) that dynamically downscales 11 global climate models from the fifth phase of Coupled Model Intercomparison Project at 18 km horizontal grid spacing. All model integrations span 41 years in the historical period (1965-2005) and 41 years in the near-term future period (2010-2050) under Representative Concentration Pathway 8.5 and cover a domain that includes the contiguous U.S. and parts of Canada and Mexico. Should emissions continue to rise, surface temperatures in every region within the U.S. will reach a new climate norm well before mid 21st century regardless of the magnitudes of regional warming. Significant warming will likely intensify the regional hydrological cycle through the acceleration of the historical trends in cold, warm, and wet extremes. The future temperature response will be partly regulated by changes in snow hydrology over the regions that historically receive a major portion of cold season precipitation in the form of snow. Our results indicate the existence of the Clausius-Clapeyron scaling at regional scales where per degree centigrade rise in surface temperature will lead to a 7.4% increase in precipitation from extremes. More importantly, both winter (snow) and summer (liquid) extremes are projected to increase across the U.S. These changes in precipitation characteristics will be driven by a shift toward shorter and wetter seasons. Overall, projected changes in the regional hydroclimate can have substantial impacts on the natural and human systems across the U.S.

  7. Constrained Regional Recovery of Continental Water Mass Time-variations from GRACE-based Geopotential Anomalies over South America

    NASA Astrophysics Data System (ADS)

    Ramillien, G. L.; Seoane, L.; Frappart, F.; Biancale, R.; Gratton, S.; Vasseur, X.; Bourgogne, S.

    2012-09-01

    We propose a "constrained" least-squares approach to estimate regional maps of equivalent-water heights by inverting GRACE-based potential anomalies at satellite altitude. According to the energy integral method, the anomalies of difference of geopotential between the two GRACE vehicles are derived from along-track K-Band Range-Rate (KBRR) residuals that correspond mainly to the continental water storage changes, once a priori known accelerations (i.e. static field, polar movements, atmosphere and ocean masses including tides) are removed during the orbit adjustment process. Newton's first law merely enables the Difference of Potential Anomalies from accurate KBRR data and the equivalent-water heights to be recovered. Spatial constraints versus spherical distance between elementary surface tiles are introduced to stabilize the linear system to cancel the effects of the north-south striping. Unlike the "mascons" approach, no basis of orthogonal functions (e.g., spherical harmonics) is used, so that the proposed regional method does not suffer from drawbacks related to any spectrum truncation. Time series of 10-day regional maps over South America for 2006-2009 also prove to be consistent with independent data sets, namely the outputs of hydrological models, "mascons" and global GRACE solutions.

  8. Mapping seismic moment and b-value within the continental-collision orogenic-belt region of the Iranian Plateau

    NASA Astrophysics Data System (ADS)

    Mousavi, S. Mostafa

    2017-01-01

    In this paper, high-resolution map of the Gutenberg-Richter b-value and seismic moment-release are provided for the Iranian Plateau using the unified and homogeneous part of the seismicity record of the region (January 1995-July 2016). We use these parameters as stressmeters and qualitatively explore their correlations with the GPS velocity field, strain rate, faulting mechanism, attenuation, and structure of the region. Our goal is to reveal the correlations and anomalous patterns that can help to better understand the seismotectonics and the state of present-day crustal stress within the region. A negative correlation between b-value and seismic moment release as well as convergence rates is found. Correlation between geodetic measurements and seismic observations might indicate the existence of a strong mechanical coupling between the basement and the sediment cover across Zagros. High geodetic strain rates east of the Hormuz strait, southern central Alborz, and along the north Tabriz fault correspond to low b-value anomalies at these areas. A strong low b-value anomaly is observed at the major tectonic discontinuity between the Zagros continental collision and the oceanic Makran subduction.

  9. A new interpretation of deformation rates in the Snake River Plain and adjacent basin and range regions based on GPS measurements

    NASA Astrophysics Data System (ADS)

    Payne, S. J.; McCaffrey, R.; King, R. W.; Kattenhorn, S. A.

    2012-04-01

    Within the Northern Basin and Range Province, USA, we estimate horizontal velocities for 405 sites using Global Positioning System (GPS) phase data collected from 1994 to 2010. The velocities, together with geologic, volcanic, and earthquake data, reveal a slowly deforming region within the Snake River Plain in Idaho and Owyhee-Oregon Plateau in Oregon separated from the actively extending adjacent Basin and Range regions by shear. Our results show a NE-oriented extensional strain rate of 5.6 ± 0.7 × 10-9 yr-1 in the Centennial Tectonic Belt and an ˜E-oriented extensional strain rate of 3.5 ± 0.2 × 10-9 yr-1 in the Great Basin. These extensional rates contrast with the very low strain rate within the 125 km × 650 km region of the Snake River Plain and Owyhee-Oregon Plateau, which is indistinguishable from zero (-0.1 ± 0.4 × 10-9 yr-1). Inversions of the velocities with dyke-opening models indicate that rapid extension by dyke intrusion in volcanic rift zones, as previously hypothesized, is not currently occurring in the Snake River Plain. This slow internal deformation, in contrast to the rapidly extending adjacent Basin and Range regions, indicates shear along the boundaries of the Snake River Plain. We estimate right-lateral shear with slip rates of 0.3-1.4 mm yr-1 along the northwestern boundary adjacent to the Centennial Tectonic Belt and left-lateral oblique extension with slip rates of 0.5-1.5 mm yr-1 along the southeastern boundary adjacent to the Intermountain Seismic Belt. The fastest lateral shearing evident in the GPS occurs near the Yellowstone Plateau where strike-slip focal mechanisms and faults with observed strike-slip components of motion are documented. The regional velocity gradients are best fit by nearby poles of rotation for the Centennial Tectonic Belt, Snake River Plain, Owyhee-Oregon Plateau, and eastern Oregon, indicating that clockwise rotation is not locally driven by Yellowstone hotspot volcanism, but instead by extension to the

  10. SEASONAL AND REGIONAL VARIATIONS OF PRIMARY AND SECONDARY ORGANIC AEROSOLS OVER THE CONTINENTAL UNITED STATES: SEMI-EMPIRICAL ESTIMATES AND MODEL EVALUATION

    EPA Science Inventory

    Seasonal and regional variations of primary (OCpri) and secondary (OCsec) organic carbon aerosols across the continental U.S. for the year 2001 were examined by a semi-empirical technique using observed OC and elemental carbon (EC) data from 142 routine moni...

  11. Regional Climate and Variability of the Summertime Continental United States in Reanalyses

    NASA Technical Reports Server (NTRS)

    Bosilovich, M G.; Robertson, F. R.; Roberts, B.

    2013-01-01

    Understanding climate variability at regional scales is an important for research and societal needs. Atmospheric retrospective-analyses (or reanalyses) integrate multitudes of observing systems with numerical models to produce continuous data that include variables not easily observed, if at all. The breadth of variables as well as observational influence included in reanalyses make them ideal for investigating climate variability. In this paper, we assess NASA s Modern Era Retrospective-analysis for Research and Application (MERRA) regional variability in North America, specifically the United States, in conjunction with current satellite data reanalyses. Emphasis is placed on summertime precipitation because 1) it is a difficult parameter to capture in the most difficult season, 2) significant observational resources exist to benchmark comparisons, and 3) accurate assessment of precipitation variability is crucial to a multitude of sectors and applications. Likewise, we have also begun to evaluate surface air temperature. While precipitation biases are identified, year to year variability of the precipitation variations, in many cases, are quite reasonable. However, some spurious long term trends and sudden shifts in the time series are also identified. In surface air temperature, analysis of station observations provides ERA Interim a clear overall advantage. However, in a number of regions, all the reanalyses are quite comparable in variability and trend. In other regions, significant precipitation biases may occur, which has implications for the ancillary process data in a reanalysis, such as surface fluxes. We also characterize the reanalyses ability to capture variability related to ENSO. In general, the summertime variations of precipitation in the reanalyses are more highly correlated (positively) to ENSO (using ENSO34) than are the observations. The Northwestern US shows the largest positive correlations to ENSO34, and reanalyses agree with that, and

  12. Surficial sediment character of the New York-New Jersey offshore continental shelf region: a GIS compilation

    USGS Publications Warehouse

    Williams, S. Jeffress; Arsenault, Matthew A.; Poppe, Lawrence J.; Reid, Jane A.; Reid, Jamey M.; Jenkins, Chris J.

    2007-01-01

    Broad continental shelf regions such as the New York Bight are the product of a complex geologic history and dynamic oceanographic processes, dominated by the Holocene marine transgression (>100 m sea-level rise) following the end of the last Pleistocene ice advance ~ 20,000 years ago. The area of the U.S. Exclusive Economic Zone (U.S. EEZ) territory, extending 200 nautical miles seaward from the coast, is larger than the continental U.S. and contains submerged landforms that provide a variety of natural functions and societal benefits, such as: critical habitats for fisheries, ship navigation and homeland security, and engineering activities (i.e. oil and gas platforms, pipeline and cable routes, potential wind-energy-generation sites). Some parts of the continental margins, particularly inner-continental shelf regions, also contain unconsolidated hard-mineral deposits such as sand and gravel that are regarded as potential aggregate resources to meet or augment needs not met by onshore deposits (Williams, 1992). The present distribution of surficial sediment off the northeastern United States is shaped from the deposits left by the last glaciation and reflects the cumulative effects of sediment erosion, transport, sorting, and deposition by storm and tidal processes during the Holocene rise in sea level. As a result, the sediments on the sea floor represent both an historical record of former conditions and a guide to possible future sedimentary environments. The U.S. Geological Survey (USGS) through the Coastal and Marine Geology Program, in cooperation with the University of Colorado and other partners, has compiled extant sediment character and textural data as well as other geologic information on the sea floor from all regions around the U.S. into the usSEABED data system (Reid and others, 2005; Buczkowski and others, 2006; Reid and others, 2006). The usSEABED system, which contains information on sediment grain size and lithology for more than 340

  13. The mantle transition zone beneath the Afar Depression and adjacent regions: implications for mantle plumes and hydration

    NASA Astrophysics Data System (ADS)

    Reed, C. A.; Gao, S. S.; Liu, K. H.; Yu, Y.

    2016-06-01

    The Afar Depression and its adjacent areas are underlain by an upper mantle marked by some of the world's largest negative velocity anomalies, which are frequently attributed to the thermal influences of a lower-mantle plume. In spite of numerous studies, however, the existence of a plume beneath the area remains enigmatic, partially due to inadequate quantities of broad-band seismic data and the limited vertical resolution at the mantle transition zone (MTZ) depth of the techniques employed by previous investigations. In this study, we use an unprecedented quantity (over 14 500) of P-to-S receiver functions (RFs) recorded by 139 stations from 12 networks to image the 410 and 660 km discontinuities and map the spatial variation of the thickness of the MTZ. Non-linear stacking of the RFs under a 1-D velocity model shows robust P-to-S conversions from both discontinuities, and their apparent depths indicate the presence of an upper-mantle low-velocity zone beneath the entire study area. The Afar Depression and the northern Main Ethiopian Rift are characterized by an apparent 40-60 km depression of both MTZ discontinuities and a normal MTZ thickness. The simplest and most probable interpretation of these observations is that the apparent depressions are solely caused by velocity perturbations in the upper mantle and not by deeper processes causing temperature or hydration anomalies within the MTZ. Thickening of the MTZ on the order of 15 km beneath the southern Arabian Plate, southern Red Sea and western Gulf of Aden, which comprise the southward extension of the Afro-Arabian Dome, could reflect long-term hydration of the MTZ. A 20 km thinning of the MTZ beneath the western Ethiopian Plateau is observed and interpreted as evidence for a possible mantle plume stem originating from the lower mantle.

  14. Environmental controls on storm intensity and charge structure in multiple regions of the continental United States

    NASA Astrophysics Data System (ADS)

    Fuchs, Brody R.; Rutledge, Steven A.; Bruning, Eric C.; Pierce, Jeffrey R.; Kodros, John K.; Lang, Timothy J.; MacGorman, Donald R.; Krehbiel, Paul R.; Rison, William

    2015-07-01

    A database consisting of approximately 4000 storm observations has been objectively analyzed to determine environmental characteristics that produce high radar reflectivities above the freezing level, large total lightning flash rates on the order of 10 flashes per minute, and anomalous vertical charge structures (most notably, dominant midlevel positive charge). The storm database is drawn from four regions of the United States featuring distinct environments, each with coinciding Lightning Mapping Array (LMA) network data. LMAs are able to infer total lightning flash rates using flash clustering algorithms, such as the one implemented in this study. Results show that anomalous charge structures inferred from LMA data, significant lightning flash rates, and increased radar reflectivities above the freezing level tend to be associated with environments that have high cloud base heights (approximately 3 km above ground level) and large atmospheric instability, quantified by normalized convective available potential energy (NCAPE) near 0.2 m s-2. Additionally, we infer that aerosols may affect storm intensity. Maximum flash rates were observed in storms with attributed aerosol concentrations near 1000 cm-3, while total flash rates decrease when aerosol concentrations exceed 1500 cm-3, consistent with previous studies. However, this effect is more pronounced in regions where the NCAPE and cloud base height are low. The dearth of storms with estimated aerosol concentrations less than 700 cm-3 (approximately 1% of total sample) does not provide a complete depiction of aerosol invigoration.

  15. Imaging the continental lithosphere: Perspectives from global and regional anisotropic seismic tomography

    NASA Astrophysics Data System (ADS)

    Lebedev, Sergei; Schaeffer, Andrew

    2016-04-01

    Azimuthal seismic anisotropy, the dependence of seismic wave speeds on propagation azimuth, is largely due to fabrics within the Earth's crust and mantle, produced by deformation. It thus provides constraints on the distribution and evolution of deformation within the upper mantle. Lateral variations in isotropic-average seismic velocities reflect variations in the temperature of the rocks at depth. Seismic tomography thus also provides a proxy for lateral changes in the temperature and thickness of the lithosphere. It can map the deep boundaries between tectonic blocks with different properties and age of the lithosphere. Our new global, anisotropic, 3D tomographic models of the upper mantle and the crust are constrained by an unprecedentedly large global dataset of broadband waveform fits (over one million seismograms) and provide improved resolution of the lithosphere at the global scale, compared to other available models. The most prominent high-velocity anomalies, seen down to around 200 km depths, indicate the cold, thick, stable mantle lithosphere beneath Precambrian cratons. The tomography resolves the deep boundaries of the cratons even where they are not exposed and difficult to map at the surface. Our large waveform dataset, with complementary large global networks and high-density regional array data, also produces improved resolution of azimuthal anisotropy patterns, so that regional-scale variations related to lithospheric deformation and mantle flow can be resolved, in particular in densely sampled regions. The depth of the boundary between the cold, rigid lithosphere (preserving ancient, frozen anisotropic fabric) and the rheologically weak asthenosphere (characterized by fabric developed recently) can be inferred from the depth layering of seismic anisotropy and its comparison to the past and present plate motions. Beneath oceans, the lithosphere-asthenosphere boundary (LAB) is defined clearly by the layering of anisotropy, with a dependence on

  16. Boundary Values for Regional to Continental Scale Greenhouse Gas Flux Estimation

    NASA Astrophysics Data System (ADS)

    Andrews, A. E.; Basu, S.; Benmergui, J. S.; Dlugokencky, E. J.; Karion, A.; Masarie, K. A.; Michalak, A. M.; Mountain, M. E.; Nehrkorn, T.; Stein, A. F.; Sweeney, C.; Tans, P. P.; Thoning, K. W.; Trudeau, M.; Yadav, V.

    2015-12-01

    Errors in prescribed boundary values can bias estimates of surface fluxes in data-assimilation and inverse modeling studies of regional greenhouse gas budgets. Sensitivity to boundary value errors is particularly important for CO2, since strong seasonally opposing fluxes result in comparatively small net annual uptake. We have developed empirical boundary value products for North America for CO2, CH4, N2O and other long-lived gases using data from aircraft profiles and marine boundary layer sites in NOAA's Global Greenhouse Gas Reference Network. The influence of each aircraft sample is mapped forward and backward from the measurement location using trajectories generated with NOAA's HYSPLIT model driven by meteorological fields from the North American Regional Reanalysis system. These data and influence functions are used to create free-tropospheric reference surfaces that describe monthly scale variability as a function of longitude, latitude, altitude, and time. Data from remote marine boundary layer sites are used to generate Atlantic and Pacific marine boundary layer reference surfaces that vary with latitude, altitude and time. Taken together, the free-troposphere and marine boundary layer reference surfaces provide 4-dimensional boundary values for the continent. This product has been significantly improved compared to earlier versions used in several published studies. We have also developed a related framework for simultaneous optimization of boundary values and surface fluxes in the NOAA CarbonTracker-Lagrange regional inverse modeling system, which uses surface and boundary value footprints from the WRF-STILT model. In this case, we adjust a prior estimate for the boundary values such as can be obtained from the global Eulerian CarbonTracker modeling system or another global model. Vertically resolved data from aircraft and/or from a combination of surface and column measurements are needed to reliably separate surface and boundary influences. We will

  17. Valles caldera region, New Mexico, and the emerging continental scientific drilling program

    SciTech Connect

    Goff, F.; Gardner, J.N.

    1988-06-10

    Valles caldera is best known in recent years as an excellent example of a resurgent caldera and as the site of a high-temperature geothermal system. However, Valles caldera and the surrounding Jemez Mountains volcanic field possess a rich history of geologic research that dates back to the late 1880s. Through the years, the research focus has changed as different economic and scientific factors have exerted their influence. Early work emphasized mining activity, while modern work has stressed volcanology and, later, geothermal development. Only in the last 5 years has it been possible to view the region as a dynamic, integrated magma-hydrothermal system having a complex evolution lasting more than 13 m.y.

  18. U-Pb isotopic evidence for the accretion of a continental microplate in the Zalm region of the Saudi Arabian Shield.

    USGS Publications Warehouse

    Stacey, J.S.; Agar, R.A.

    1985-01-01

    This area includes three of the main tectonic units of the Arabian Shield: the Afif continental terrain, the Nabitah suture with its associated mobile belt, and the Asir ensimatic arc terrain. U/Pb zircon data from a pelitic garnet-sillimanite gneiss show that the Kabib formation in the S of the Afif terrain may be as old as 1770 m.y. Pb and Rb/Sr isotopic data in the Zalm region reveal a change in the nature of the underlying crust, from continental basement in the NE to less radiogenic marginal arc rocks in the SW. Miogeosynclinal continental shelf facies of the Siham group lie unconformably over the Kabid formation. U/Pb zircon age determinations show that this 'Andean' continental margin developed before approx 720 m.y. and the emplacement of calc-alkaline plutonic rocks continued until approx 690 m.y. During the period 685-640 m.y. the continental Afif microplate collided with the Asir terrain as part of the Nabitah orogeny. At approx 640 m.y. age the Najd strike-slip faulting commenced, with a dextral phase that controlled emplacement of granite plutons as well as the development of large pull-apart grabens. Some of the latter were floored by new oceanic crust and filled with volcanosedimentary rocks of the Bani Ghayy group.-R.A.H.

  19. On the tectonic problems of the southern East China Sea and adjacent regions: Evidence from gravity and magnetic data

    NASA Astrophysics Data System (ADS)

    Shang, Luning; Zhang, Xunhua; Han, Bo; Du, Runlin

    2016-02-01

    In this paper, two sets of gravity and magnetic data were used to study the tectonics of the southern East China Sea and Ryukyu trench-arc system: one data set was from the `Geological-geophysical map series of China Seas and adjacent areas' database and the other was newly collected by R/V Kexue III in 2011. Magnetic and gravity data were reorganized and processed using the software MMDP, MGDP and RGIS. In addition to the description of the anomaly patterns in different areas, deep and shallow structure studies were performed by using several kinds of calculation, including a spectrum analysis, upward-continuation of the Bouguer anomaly and horizontal derivatives of the total-field magnetic anomaly. The depth of the Moho and magnetic basement were calculated. Based on the above work, several controversial tectonic problems were discussed. Compared to the shelf area and Ryukyu Arc, the Okinawa Trough has an obviously thinned crust, with the thinnest area having thickness less than 14 km in the southern part. The Taiwan-Sinzi belt, which terminates to the south by the NW-SE trending Miyako fault belt, contains the relic volcanic arc formed by the splitting of the paleo Ryukyu volcanic arc as a result of the opening of the Okinawa Trough. As an important tectonic boundary, the strike-slip type Miyako fault belt extends northwestward into the shelf area and consists of several discontinuous segments. A forearc terrace composed of an exotic terrane collided with the Ryukyu Arc following the subduction of the Philippine Sea Plate. Mesozoic strata of varying thicknesses exist beneath the Cenozoic strata in the shelf basin and significantly influence the magnetic pattern of this area. The gravity and magnetic data support the existence of a Great East China Sea, which suggests that the entire southern East China Sea shelf area was a basin in the Mesozoic without alternatively arranged uplifts and depressions, and might have extended southwestward and connected with the

  20. Assessment of Aerosol Radiative Impact over Oceanic Regions Adjacent to Indian Subcontinent using Multi-Satellite Analysis

    SciTech Connect

    Satheesh, S. K.; Vinoj, V.; Krishnamoorthy, K.

    2010-10-01

    Using data from Ozone Monitoring Instrument (OMI) and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments, we have retrieved regional distribution of aerosol column single scattering albedo (parameter indicative of the relative dominance of aerosol absorption and scattering effects), a most important, but least understood aerosol property in assessing its climate impact. Consequently we provide improved assessment of short wave aerosol radiative forcing (ARF) (on both regional and seasonal scales) estimates over this region. Large gradients in north-south ARF were observed as a consequence of gradients in single scattering albedo as well as aerosol optical depth. The highest ARF (-37 W m-2 at the surface) was observed over the northern Arabian Sea during June to August period (JJA). In general, ARF was higher over northern Bay of Bengal (NBoB) during winter and pre-monsoon period, whereas the ARF was higher over northern Arabian Sea (NAS) during the monsoon and post- monsoon period. The largest forcing observed over NAS during JJA is the consequence of large amounts of desert dust transported from the west Asian dust sources. High as well as seasonally invariant aerosol single scattering albedos (~0.98) were observed over the southern Indian Ocean region far from continents. The ARF estimates based on direct measurements made at a remote island location, Minicoy (8.3°N, 73°E) in the southern Arabian Sea are in good agreement with the estimates made following multisatellite analysis.

  1. Crustal structure beneath Liaoning province and the Bohai Sea and its adjacent region in China based on ambient noise tomography

    NASA Astrophysics Data System (ADS)

    Pang, Guang-hua; Feng, Ji-Kun; Lin, Jun

    2017-03-01

    The velocity structure of the crust beneath Liaoning province and the Bohai sea in China was imaged using ambient seismic noise recorded by 73 regional broadband stations. All available three-component time series from the 12-month span between January and December 2013 were cross-correlated to yield empirical Green's functions for Rayleigh and Love waves. Phase-velocity dispersion curves for the Rayleigh waves and the Love waves were measured by applying the frequency-time analysis method. Dispersion measurements of the Rayleigh wave and the Love wave were then utilized to construct 2D phase-velocity maps for the Rayleigh wave at 8-35 s periods and the Love wave at 9-32 s periods, respectively. Both Rayleigh and Love phase-velocity maps show significant lateral variations that are correlated well with known geological features and tectonics units in the study region. Next, phase dispersion curves of the Rayleigh wave and the Love wave extracted from each cell of the 2D Rayleigh wave and Love wave phase-velocity maps, respectively, were inverted simultaneously to determine the 3D shear wave velocity structures. The horizontal shear wave velocity images clearly and intuitively exhibit that the earthquake swarms in the Haicheng region and the Tangshan region are mainly clustered in the transition zone between the low- and high-velocity zones in the upper crust, coinciding with fault zones, and their distribution is very closely associated with these faults. The vertical shear wave velocity image reveals that the lower crust downward to the uppermost mantle is featured by distinctly high velocities, with even a high-velocity thinner layer existing at the bottom of the lower crust near Moho in central and northern the Bohai sea along the Tanlu fault, and these phenomena could be caused by the intrusion of mantle material, indicating the Tanlu fault could be just as the uprising channel of deep materials.

  2. Density and magnetic suseptibility values for rocks in the Talkeetna Mountains and adjacent region, south-central Alaska

    USGS Publications Warehouse

    Sanger, Elizabeth A.; Glen, Jonathan M.G.

    2003-01-01

    This report presents a compilation and statistical analysis of 306 density and 706 magnetic susceptibility measurements of rocks from south-central Alaska that were collected by U.S. Geological Survey (USGS) and Alaska Division of Geological and Geophysical Surveys (ADGGS) scientists between the summers of 1999 and 2002. This work is a product of the USGS Talkeetna Mountains Transect Project and was supported by USGS projects in the Talkeetna Mountains and Iron Creek region, and by Bureau of Land Management (BLM) projects in the Delta River Mining District that aim to characterize the subsurface structures of the region. These data were collected to constrain potential field models (i.e., gravity and magnetic) that are combined with other geophysical methods to identify and model major faults, terrane boundaries, and potential mineral resources of the study area. Because gravity and magnetic field anomalies reflect variations in the density and magnetic susceptibility of the underlying lithology, these rock properties are essential components of potential field modeling. In general, the average grain density of rocks in the study region increases from sedimentary, felsic, and intermediate igneous rocks, to mafic igneous and metamorphic rocks. Magnetic susceptibility measurements performed on rock outcrops and hand samples from the study area also reveal lower magnetic susceptibilities for sedimentary and felsic intrusive rocks, moderate susceptibility values for metamorphic, felsic extrusive, and intermediate igneous rocks, and higher susceptibility values for mafic igneous rocks. The density and magnetic properties of rocks in the study area are generally consistent with general trends expected for certain rock types.

  3. Spring onset variations and trends in the continental United States: past and regional assessment using temperature-based indices

    USGS Publications Warehouse

    Schwartz, Mark D.; Ault, Toby R.; Betancourt, Julio L.

    2012-01-01

    Phenological data are simple yet sensitive indicators of climate change impacts on ecosystems, but observations have not been made routinely or extensively enough to evaluate spatial and temporal patterns across most continents, including North America. As an alternative, many studies use weather-based algorithms to simulate specific phenological responses. Spring Indices (SI) are a set of complex phenological models that have been successfully applied to evaluate variations and trends in the onset of spring across the Northern Hemisphere’s temperate regions. To date, SI models have been limited by only producing output in locations where both the plants’ chilling and warmth requirements are met. Here, we develop an extended form of the SI (abbreviated SI-x) that expands their application into the subtropics by ignoring chilling requirements while still retaining the utility and accuracy of the original SI (now abbreviated SI-o). The validity of the new indices is tested, and regional SI anomalies are explored across the data-rich continental United States. SI-x variations from 1900 to 2010 show an abrupt and sustained delay in spring onset of about 4–8 d (around 1958) in parts of the Southeast and southern Great Plains, and a comparable advance of 4–8 d (around 1984) in parts of the northern Great Plains and the West. Atmospheric circulation anomalies, linked to large-scale modes of variability, exert modest but significant roles in the timing of spring onset across the United States on interannual and longer timescales. The SI-x are promising metrics for tracking spring onset variations and trends in mid-latitudes, relating them to relevant ecological, hydrological, and socioeconomic phenomena, and exploring connections between atmospheric drivers and seasonal timing.

  4. Influence of tectonic terranes adjacent to Precambrian Wyoming province of petroleum source and reservoir rock stratigraphy in northern Rocky Mountain region

    SciTech Connect

    Tonnsen, J.J.

    1984-07-01

    The perimeter of the Archean Precambrian Wyoming province can be generally defined. A Proterozoic suture belt separates the province from the Archean Superior province to the east. The western margin of the Precambrian rocks lies under the western Overthrust belt, but the Precambrian province extends at least as far west as southwest Montana and southeast Idaho. The province is bounded on the north and south by more regionally extensive Proterozoic mobile belts. In the northern belt, Archean rocks have been remobilized by Proterozoic tectonic events, but the southern belt does not appear to contain rocks as old as Archean. The tectonic response of these Precambrian terranes to cratonic and continental margin vertical and horizontal forces has exerted a profound influence on Phanerozoic sedimentation and stratigraphic facies distributions. Petroleum source rock and reservoir rock stratigraphy of the Northern Rocky Mountain region has been correlated with this structural history. In particular, the Devonian, Permian, and Jurassic sedimentation patterns can be shown to have been influenced by articulation among the different terranes comprising the ancient substructure. Depositional patterns in the Chester-Morrow carbonate and clastic sequence in the Central Montana trough are also related to this substructure. Further, a correlation between these tectonic terranes and the localization of regional hydrocarbon accumulations has been observed and has been useful in basin analyses for exploration planning.

  5. Fault Intersections as Stress Concentrators for Current Stable Continental Region Seismicity in New Madrid and Middleton Place Summerville Seismic Zones in Eastern United States

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, A.; Talwani, P.

    2006-05-01

    Evaluation of seismic hazard in the eastern United States is being constantly debated primarily because of our inadequate understanding of the seismicity and deformation patterns in such stable continental interiors, which are characterized by low strain rates. In the pursuit of a better understanding of the dynamics of these regions, multidisciplinary data from 20 stable continental regions worldwide that had hosted 39 earthquakes (M >= 5) were synthesized. The results showed that fault intersections are spatially associated with the observed seismicity in majority of the regions. Simple 2D mechanical models of two major stable continental regions in the eastern U.S., namely, New Madrid Seismic Zone (NMSZ) and Middleton Place Summerville Seismic Zone (MPSSZ) supported a causal association. However, three-dimensional representation and analyses of these regions are more realistic and allow for adequate demonstration of vertical tectonics. This research is directed towards developing three-dimensional mechanical models of NMSZ and MPSSZ so as to better demonstrate the causal associations of fault intersections with stable continental region earthquakes. Numerical modeling using a Distinct Element Method was performed and the program used for the purpose is called 3DEC. The models comprise of the structural framework of the concerned region represented by a set of blocks with the faults within them treated as joints or discontinuities. The blocks and the faults are assigned elastic properties conforming to the known geology, and subjected to tectonic loading along the direction of maximum regional compression (SHmax) at a rate similar to the ambient plate velocity measured from GPS studies. The stresses and displacements of the blocks and along the faults are then observed at the end of the loading period. The results of the modeling indicate that locations of stress build-up in three-dimensions correlate well with those of the instrumental seismicity in these

  6. Multi-Scale Interactions Associated with the Monsoon Onset Over South China Sea and Adjacent Regions during SCSMEX-98

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Li, X.; Wu, H.-T.

    1999-01-01

    Using data collected during The South China Sea Monsoon Experiment (SCSMEX) (1998) as well as from the TRMM Microwave-Imager (TMI) and precipitation radar (PR), we have studied the multi-scale interactions (meso-synoptic-intraseasonal) associated with monsoon onset over South China Sea (SCS) and its subsequent evolution. Results show that the monsoon onset (defined by development of steady wind direction and heavy precipitation) over the northern SCS occurred around May 15 -17. Prevailing southerlies and southwesterlies developed over the central SCS after May 20. Shortly after, monsoon convection developed over the whole SCS region around May 23-27. The entire onset process appeared to be delayed by about a week to 10 days compared with climatology. During late spring of 1998, mid-latitude frontal systems were particularly active. These systems strongly impacted the northern SCS convection and may have been instrumental in triggering the onset of the SCS monsoon. The Tropical Oceans and Global Atmosphere (TOGA) and Bureau of Meteorology Research Centre (BMRC) radar showed a wide variety of convective systems over the Intensive Flux Array, from frontal bands to shear-banded structure, deep convection, pop-corn type shallow convection, slow moving "fine lines" to water spout. Analysis of SSM/I wind and moisture data suggested that the delayed convective activity over the SCS may be linked to the weakened northward propagation of monsoon rain band, hence contributing to a persistence of the rainband south of the Yangtze River and the disastrous flood that occurred over this region during mid to late June, 1998.

  7. Petrology and geochronology of crustal xenoliths from the Bering Strait region: Linking deep and shallow processes in extending continental crust

    USGS Publications Warehouse

    Akinin, V.V.; Miller, E.L.; Wooden, J.L.

    2009-01-01

    Petrologic, geochemical, and metamorphic data on gneissic xenoliths derived from the middle and lower crust in the Neogene Bering Sea basalt province, coupled with U-Pb geochronology of their zircons using sensitive high-resolution ion microprobe-reverse geometry (SHRIMP-RG), yield a detailed comparison between the P-T-t and magmatic history of the lower crust and magmatic, metamorphic, and deformational history of the upper crust. Our results provide unique insights into the nature of lithospheric processes that accompany the extension of continental crust. The gneissic, mostly maficxenoliths (constituting less than two percent of the total xenolith population) from lavas in the Enmelen, RU, St. Lawrence, Nunivak, and Seward Peninsula fields most likely originated through magmatic fractionation processes with continued residence at granulite-facies conditions. Zircon single-grain ages (n ??? 125) are interpreted as both magmatic and metamorphic and are entirely Cretaceous to Paleocene in age (ca. 138-60 Ma). Their age distributions correspond to the main ages of magmatism in two belts of supracrustal volcanic and plutonic rocks in the Bering Sea region. Oscillatory-zoned igneous zircons, Late Cretaceous to Paleocene metamorphic zircons and overgrowths, and lack of any older inheritance in zircons from the xenoliths provide strong evidence for juvenile addition of material to the crust at this time. Surface exposures of Precambrian and Paleozoic rocks locally reached upper amphibolite-facies (sillimanite grade) to granulite-facies conditions within a series of extension-related metamorphic culminations or gneiss domes, which developed within the Cretaceous magmatic belt. Metamorphic gradients and inferred geotherms (??30-50 ??C/km) from both the gneiss domes and xenoliths aretoo high to be explained by crustal thickening alone. Magmatic heat input from the mantle is necessary to explain both the petrology of the magmas and elevated metamorphic temperatures. Deep

  8. Genetic Structure and Evolutionary History of Three Alpine Sclerophyllous Oaks in East Himalaya-Hengduan Mountains and Adjacent Regions

    PubMed Central

    Feng, Li; Zheng, Qi-Jian; Qian, Zeng-Qiang; Yang, Jia; Zhang, Yan-Ping; Li, Zhong-Hu; Zhao, Gui-Fang

    2016-01-01

    The East Himalaya-Hengduan Mountains (EH-HM) region has a high biodiversity and harbors numerous endemic alpine plants. This is probably the result of combined orographic and climate oscillations occurring since late Tertiary. Here, we determined the genetic structure and evolutionary history of alpine oak species (including Quercus spinosa, Quercus aquifolioides, and Quercus rehderiana) using both cytoplasmic-nuclear markers and ecological niche models (ENMs), and elucidated the impacts of climate oscillations and environmental heterogeneity on their population demography. Our results indicate there were mixed genetic structure and asymmetric contemporary gene flow within them. The ENMs revealed a similar demographic history for the three species expanded their ranges from the last interglacial (LIG) to the last glacial maximum (LGM), which was consistent with effective population sizes changes. Effects of genetic drift and fragmentation of habitats were responsible for the high differentiation and the lack of phylogeographic structure. Our results support that geological and climatic factors since Miocene triggered the differentiation, evolutionary origin and range shifts of the three oak species in the studied area and also emphasize that a multidisciplinary approach combining molecular markers, ENMs and population genetics can yield deep insights into diversification and evolutionary dynamics of species. PMID:27891142

  9. Genetic Structure and Evolutionary History of Three Alpine Sclerophyllous Oaks in East Himalaya-Hengduan Mountains and Adjacent Regions.

    PubMed

    Feng, Li; Zheng, Qi-Jian; Qian, Zeng-Qiang; Yang, Jia; Zhang, Yan-Ping; Li, Zhong-Hu; Zhao, Gui-Fang

    2016-01-01

    The East Himalaya-Hengduan Mountains (EH-HM) region has a high biodiversity and harbors numerous endemic alpine plants. This is probably the result of combined orographic and climate oscillations occurring since late Tertiary. Here, we determined the genetic structure and evolutionary history of alpine oak species (including Quercus spinosa, Quercus aquifolioides, and Quercus rehderiana) using both cytoplasmic-nuclear markers and ecological niche models (ENMs), and elucidated the impacts of climate oscillations and environmental heterogeneity on their population demography. Our results indicate there were mixed genetic structure and asymmetric contemporary gene flow within them. The ENMs revealed a similar demographic history for the three species expanded their ranges from the last interglacial (LIG) to the last glacial maximum (LGM), which was consistent with effective population sizes changes. Effects of genetic drift and fragmentation of habitats were responsible for the high differentiation and the lack of phylogeographic structure. Our results support that geological and climatic factors since Miocene triggered the differentiation, evolutionary origin and range shifts of the three oak species in the studied area and also emphasize that a multidisciplinary approach combining molecular markers, ENMs and population genetics can yield deep insights into diversification and evolutionary dynamics of species.

  10. Sedimentary and crustal thicknesses and Poisson's ratios for the NE Tibetan Plateau and its adjacent regions based on dense seismic arrays

    NASA Astrophysics Data System (ADS)

    Wang, Weilai; Wu, Jianping; Fang, Lihua; Lai, Guijuan; Cai, Yan

    2017-03-01

    The sedimentary and crustal thicknesses and Poisson's ratios of the NE Tibetan Plateau and its adjacent regions are estimated by the h- κ stacking and CCP image of receiver functions from the data of 1,317 stations. The horizontal resolution of the obtained results is as high as 0.5° × 0.5°, which can be used for further high resolution model construction in the region. The crustal thicknesses from Airy's equilibrium are smaller than our results in the Sichuan Basin, Qilian tectonic belt, northern Alxa block and Qaidam Basin, which is consistent with the high densities in the mantle lithosphere and may indicate that the high-density lithosphere drags crust down overall. High Poisson's ratios and low velocity zones are found in the mid- and lower crust beneath eastern Qilian tectonic belt and the boundary areas of the Ordos block, indicating that partial melting may exist in these regions. Low Poisson's ratios and low-velocity anomalies are observed in the crust in the NE Tibetan Plateau, implying that the mafic lower crust is thinning or missing and that the mid- and lower crust does not exhibit melting or partial melting in the NE Tibetan Plateau, and weak flow layers are not likely to exist in this region.

  11. The Application of DNA Barcodes for the Identification of Marine Crustaceans from the North Sea and Adjacent Regions.

    PubMed

    Raupach, Michael J; Barco, Andrea; Steinke, Dirk; Beermann, Jan; Laakmann, Silke; Mohrbeck, Inga; Neumann, Hermann; Kihara, Terue C; Pointner, Karin; Radulovici, Adriana; Segelken-Voigt, Alexandra; Wesse, Christina; Knebelsberger, Thomas

    2015-01-01

    During the last years DNA barcoding has become a popular method of choice for molecular specimen identification. Here we present a comprehensive DNA barcode library of various crustacean taxa found in the North Sea, one of the most extensively studied marine regions of the world. Our data set includes 1,332 barcodes covering 205 species, including taxa of the Amphipoda, Copepoda, Decapoda, Isopoda, Thecostraca, and others. This dataset represents the most extensive DNA barcode library of the Crustacea in terms of species number to date. By using the Barcode of Life Data Systems (BOLD), unique BINs were identified for 198 (96.6%) of the analyzed species. Six species were characterized by two BINs (2.9%), and three BINs were found for the amphipod species Gammarus salinus Spooner, 1947 (0.4%). Intraspecific distances with values higher than 2.2% were revealed for 13 species (6.3%). Exceptionally high distances of up to 14.87% between two distinct but monophyletic clusters were found for the parasitic copepod Caligus elongatus Nordmann, 1832, supporting the results of previous studies that indicated the existence of an overlooked sea louse species. In contrast to these high distances, haplotype-sharing was observed for two decapod spider crab species, Macropodia parva Van Noort & Adema, 1985 and Macropodia rostrata (Linnaeus, 1761), underlining the need for a taxonomic revision of both species. Summarizing the results, our study confirms the application of DNA barcodes as highly effective identification system for the analyzed marine crustaceans of the North Sea and represents an important milestone for modern biodiversity assessment studies using barcode sequences.

  12. The Application of DNA Barcodes for the Identification of Marine Crustaceans from the North Sea and Adjacent Regions

    PubMed Central

    Raupach, Michael J.; Barco, Andrea; Steinke, Dirk; Beermann, Jan; Laakmann, Silke; Mohrbeck, Inga; Neumann, Hermann; Kihara, Terue C.; Pointner, Karin; Radulovici, Adriana; Segelken-Voigt, Alexandra; Wesse, Christina; Knebelsberger, Thomas

    2015-01-01

    During the last years DNA barcoding has become a popular method of choice for molecular specimen identification. Here we present a comprehensive DNA barcode library of various crustacean taxa found in the North Sea, one of the most extensively studied marine regions of the world. Our data set includes 1,332 barcodes covering 205 species, including taxa of the Amphipoda, Copepoda, Decapoda, Isopoda, Thecostraca, and others. This dataset represents the most extensive DNA barcode library of the Crustacea in terms of species number to date. By using the Barcode of Life Data Systems (BOLD), unique BINs were identified for 198 (96.6%) of the analyzed species. Six species were characterized by two BINs (2.9%), and three BINs were found for the amphipod species Gammarus salinus Spooner, 1947 (0.4%). Intraspecific distances with values higher than 2.2% were revealed for 13 species (6.3%). Exceptionally high distances of up to 14.87% between two distinct but monophyletic clusters were found for the parasitic copepod Caligus elongatus Nordmann, 1832, supporting the results of previous studies that indicated the existence of an overlooked sea louse species. In contrast to these high distances, haplotype-sharing was observed for two decapod spider crab species, Macropodia parva Van Noort & Adema, 1985 and Macropodia rostrata (Linnaeus, 1761), underlining the need for a taxonomic revision of both species. Summarizing the results, our study confirms the application of DNA barcodes as highly effective identification system for the analyzed marine crustaceans of the North Sea and represents an important milestone for modern biodiversity assessment studies using barcode sequences. PMID:26417993

  13. Correlative anatomy for the electrophysiologist: ablation for atrial fibrillation. Part II: regional anatomy of the atria and relevance to damage of adjacent structures during AF ablation.

    PubMed

    Macedo, Paula G; Kapa, Suraj; Mears, Jennifer A; Fratianni, Amy; Asirvatham, Samuel J

    2010-07-01

    Ablation procedures for atrial fibrillation have become an established and increasingly used option for managing patients with symptomatic arrhythmia. The anatomic structures relevant to the pathogenesis of atrial fibrillation and ablation procedures are varied and include the pulmonary veins, other thoracic veins, the left atrial myocardium, and autonomic ganglia. Exact regional anatomic knowledge of these structures is essential to allow correlation with fluoroscopy and electrograms and, importantly, to avoid complications from damage of adjacent structures within the chest. We present this information as a series of 2 articles. In a prior issue, we have discussed the thoracic vein anatomy relevant to paroxysmal atrial fibrillation. In the present article, we focus on the atria themselves, the autonomic ganglia, and anatomic issues relevant for minimizing complications during atrial fibrillation ablation.

  14. Regional based modeling approach for rainfall-induced debris flows in the continental-climatic Northern Tien Shan (SE Kazakhstan)

    NASA Astrophysics Data System (ADS)

    Fischer, Thomas; Küfmann, Carola; Haas, Florian; Baume, Otfried; Becht, Michael

    2013-04-01

    The high mountain systems of Central Asia (Hindukush, Pamir and Tien Shan) are dominated by continental-climatic conditions. Nevertheless, westerly maritime air circulation and convective rainfalls during the summer season result in high rainfall intensities. In combination with a high availability of unconsolidated material rainfall triggered debris flows are prominent and intensive geomorphologic processes in these mountain areas. The presented study aims to figure out a regional based modeling approach for rainfall-induced debris flow processes based on combination of a disposition model for debris flow starting zones with process-flow models. The investigation area has a size of about 700 square kilometers and is situated in the Northern Tien Shan mountains in SE Kazakhstan (investigation areas: valleys of Prochadnaja, Big Almatinka, Little Almatinka and Left Talgar). The area is characterized by mountain forest zone, alpine meadows and high-alpine glaciated areas with the highest peaks at 4500m. In a first step the disposition (point of process triggering) of actual debris flows was analyzed. Due to different triggering mechanisms, the processes were divided into channel-type and slope-type debris flows. Detailed mapping of actual debris flows initiation areas and a GIS-based geostatistical disposition analysis are used to identify the main geofactor-variables and geofactor combinations which enhance the triggering of rainfall-induced debris flows. It can be shown that both, longtime variable geofactors (such as local geomorphology and hydrology) plays a significant role for triggering debris flows, as well as mid- and short time variable geofactors. Especially actual permafrost distribution and degradation plus glacier retreat comes into the focus of interest. This is most notably for rainfall induced slope-type debris flows which primarily are triggered in the discontinuous and continuous permafrost areas eroding younger unconsolidated material from actual

  15. Geology, geochronology, and paleogeography of the southern Sonoma volcanic field and adjacent areas, northern San Francisco Bay region, California

    USGS Publications Warehouse

    Wagner, D.L.; Saucedo, G.J.; Clahan, K.B.; Fleck, R.J.; Langenheim, V.E.; McLaughlin, R.J.; Sarna-Wojcicki, A. M.; Allen, J.R.; Deino, A.L.

    2011-01-01

    Recent geologic mapping in the northern San Francisco Bay region (California, USA) supported by radiometric dating and tephrochronologic correlations, provides insights into the framework geology, stratigraphy, tectonic evolution, and geologic history of this part of the San Andreas transform plate boundary. There are 25 new and existing radiometric dates that define three temporally distinct volcanic packages along the north margin of San Pablo Bay, i.e., the Burdell Mountain Volcanics (11.1 Ma), the Tolay Volcanics (ca. 10-8 Ma), and the Sonoma Volcanics (ca. 8-2.5 Ma). The Burdell Mountain and the Tolay Volcanics are allochthonous, having been displaced from the Quien Sabe Volcanics and the Berkeley Hills Volcanics, respectively. Two samples from a core of the Tolay Volcanics taken from the Murphy #1 well in the Petaluma oilfield yielded ages of 8.99 ?? 0.06 and 9.13 ?? 0.06 Ma, demonstrating that volcanic rocks exposed along Tolay Creek near Sears Point previously thought to be a separate unit, the Donnell Ranch volcanics, are part of the Tolay Volcanics. Other new dates reported herein show that volcanic rocks in the Meacham Hill area and extending southwest to the Burdell Mountain fault are also part of the Tolay Volcanics. In the Sonoma volcanic field, strongly bimodal volcanic sequences are intercalated with sediments. In the Mayacmas Mountains a belt of eruptive centers youngs to the north. The youngest of these volcanic centers at Sugarloaf Ridge, which lithologically, chemically, and temporally matches the Napa Valley eruptive center, was apparently displaced 30 km to the northwest by movement along the Carneros and West Napa faults. The older parts of the Sonoma Volcanics have been displaced at least 28 km along the RodgersCreek fault since ca. 7 Ma. The Petaluma Formation also youngs to the north along the Rodgers Creek-Hayward fault and the Bennett Valley fault. The Petaluma basin formed as part of the Contra Costa basin in the Late Miocene and was

  16. On the mass and salt budgets for a region of the continental shelf in the southern Mid-Atlantic Bight

    SciTech Connect

    Kim, Yoo Yin; Weatherly, Georges L.; Pietrafesa, Leonard J.

    2001-12-01

    Two field studies were conducted across and along the continental shelf, one from February to May 1996 (deployment 1) and the other from July to October 1996 (deployment 2), in part to determine the mass and salt budgets of shelf water from south of Cape Henry to north of Cape Hatteras, the southernmost portion of the Mid-Atlantic Bight. The temporal means of current meter records indicated that most of the water enters the region across its northern boundary near the shelf break as part of a southward, alongshore current and exits the southeast corner as a southeastward flowing current. Estimates of the volume transports indicated that not all the transport across the northern boundary was accounted for by transport across the southern boundary, and that the remainder occurred as a broad, diffusive flow across the eastern boundary at the shelf break. Time series of volume transport across northern and southern boundaries were very similar and associated with variations in the alongshore wind stress and sea level, indicative of a geostrophic balance. Examination of the individual current meter records indicated these fluctuations were very barotropic even during deployment 2, which included the stratified summer season. Time series of the volume transport across the eastern boundary at the shelf break strongly mirrored the volume transport across the northern boundary minus that across the southern boundary, suggesting that the inferred eastern boundary transport was real and accommodated whatever the southern boundary could not. The turbulent salt flux across each boundary contributes very little to the net respective mass fluxes because the salt fluxes are almost governed by current velocity fields. The instantaneous and mean salt fluxes across each boundary were very well approximated by the instantaneous and mean volume transports across the boundary times the deployment average salinity across that boundary, respectively. The Ocean Margins Program (OMP) moored

  17. Integrating surface and mantle constraints for palaeo-ocean evolution: a tour of the Arctic and adjacent regions (Arne Richter Award for Outstanding Young Scientists Lecture)

    NASA Astrophysics Data System (ADS)

    Shephard, Grace E.

    2016-04-01

    Plate tectonic reconstructions heavily rely on absolute motions derived from hotspot trails or palaeomagnetic data and ocean-floor magnetic anomaies and fracture-zone geometries to constrain the detailed history of ocean basins. However, as oceanic lithosphere is progressively recycled into the mantle, kinematic data regarding the history of these now extinct-oceans is lost. In order to better understand their evolution, novel workflows, which integrate a wide range of complementary yet independent geological and geophysical datasets from both the surface and deep mantle, must be utilised. In particular, the emergence of time-dependent, semi or self-consistent geodynamic models of ever-increasing temporal and spatial resolution are revealing some critical constraints on the evolution and fate of oceanic slabs. The tectonic evolution of the circum-Arctic is no exception; since the breakup of Pangea, this enigmatic region has seen major plate reorganizations and the opening and closure of several ocean basins. At the surface, a myriad of potential kinematic scenarios including polarity, timing, geometry and location of subduction have emerged, including for systems along continental margins and intra-oceanic settings. Furthermore, recent work has reignited a debate about the origins of 'anchor' slabs, such as the Farallon and Mongol-Okhotsk slabs, which have been used to refine absolute plate motions. Moving to the mantle, seismic tomography models reveal a region peppered with inferred slabs, however assumptions about their affinities and subduction location, timing, geometry and polarity are often made in isolation. Here, by integrating regional plate reconstructions with insights from seismic tomography, satellite derived gravity gradients, slab sinking rates and geochemistry, I explore some Mesozoic examples from the palaeo-Arctic, northern Panthalassa and western margin of North America, including evidence for a discrete and previously undescribed slab under

  18. Wave refraction diagrams for the Baltimore Canyon region of the mid-Atlantic continental shelf computed by using three bottom topography approximation techniques

    NASA Technical Reports Server (NTRS)

    Poole, L. R.

    1976-01-01

    The Langley Research Center and Virginia Institute of Marine Science wave refraction computer model was applied to the Baltimore Canyon region of the mid-Atlantic continental shelf. Wave refraction diagrams for a wide range of normally expected wave periods and directions were computed by using three bottom topography approximation techniques: quadratic least squares, cubic least squares, and constrained bicubic interpolation. Mathematical or physical interpretation of certain features appearing in the computed diagrams is discussed.

  19. Characterization of strong polar mutations in a region immediately adjacent to the L-arabinose operator in Escherichia coli B-r.

    PubMed

    Eleuterio, M; Griffin, B; Sheppard, D E

    1972-08-01

    Seven l-arabinose-negative mutations are described that map in three genetically distinct regions immediately adjacent to the araO (operator) region of the l-arabinose operon. All seven mutants revert spontaneously, exhibit a cis-dominant, trans-recessive polarity effect upon the expression of l-arabinose isomerase (gene araA), and fail to respond to amber, ochre, or UGA suppressors. Three of these mutants exhibit absolute polarity and are not reverted by the mutangens 2-aminopurine, diethyl sulfate, and ICR-191. These may have arisen as a consequence of an insertion mutation in gene araB or in the initiator region of the l-arabinose operon. The four remaining mutants exhibit strong but not absolute polarity on gene araA and respond to the mutagens diethyl sulfate and ICR-191. Three of these mutants are suppressible by two independently isolated suppressors that fail to suppress known nonsense codons. Partially polar Ara(+) revertants with lesions linked to ara are obtained from three of the same four mutants. These polar mutants, their external suppressors, and their partially polar revertants are discussed in terms of the mechanism of initiation of expression of the l-arabinose operon.

  20. An oilspill risk analysis for the Gulf of Mexico outer continental shelf lease area; regional environmental impact statement

    USGS Publications Warehouse

    LaBelle, R.P.

    1982-01-01

    An oilspill risk analysis was conducted for the Gulf of Mexico Outer Continental Shelf (OCS)lease area region. Results of the analysis can be used to determine relative risks associated with oil production in different regions to be offered in OCS Lease Sales 72, 74, and 79. The analysis considered the probability of spill occurrences based on historical trends; likely movement of oil slicks based on a climatological model; and locations of major environmental resources which could be vulnerable to spilled oil. The times between spill occurrence and contact with resources were estimated to aid in estimating slick characteristics. Critical assumptions made for this particular analysis were (1) that oil exists in the lease area, and (2) that oil will be, found and produced from tracts sold in sales 72, 74, and 79. On the basis of a most likely resource estimate of 241 million barrels of oil to be produced over an 18-year production life from sales to be held in 1983 (sales 72, 74, 79), it was calculated that approximately one oilspill of 1,000 barrels or larger will occur. The estimated probability that one or more oilspills of 1,000 barrels or larger will occur and contact land after being at sea less than 30 days is 41-percent. For a high resource estimate case of sales to be held in 1983, 717 million barrels are estimated to be produced over an 18-year production life with an 83-percent chance of one or more spills of 1,000 barrels or larger occurring and contacting land within 30 days. These results depend upon the routes and methods chosen to transport oil from OCS platforms to shore. Given a total development scenario in which 5.6 billion barrels of oil are estimated to be present and produced, it was calculated that 18 oilspills of 1,000 barrels or larger will occur over the 40-year production life of the proposed lease area. The estimated probability that one or more oilspills of 1,000 barrels or larger will occur and contact land after being at sea less than

  1. A new interpretation of deformation rates in the Snake River Plain and adjacent basin and range regions based on GPS measurements

    SciTech Connect

    S.J. Payne; R. McCaffrey; R.W. King; S.A. Kattenhorn

    2012-04-01

    We evaluate horizontal Global Positioning System (GPS) velocities together with geologic, volcanic, and seismic data to interpret extension, shear, and contraction within the Snake River Plain and the Northern Basin and Range Province, U.S.A. We estimate horizontal surface velocities using GPS data collected at 385 sites from 1994 to 2009 and present an updated velocity field within the Stable North American Reference Frame (SNARF). Our results show an ENE-oriented extensional strain rate of 5.9 {+-} 0.7 x 10{sup -9} yr{sup -1} in the Centennial Tectonic belt and an E-oriented extensional strain rate of 6.2 {+-} 0.3 x 10{sup -9} yr{sup -1} in the Intermountain Seismic belt combined with the northern Great Basin. These extensional strain rates contrast with the regional north-south contraction of -2.6 {+-} 1.1 x 10{sup -9} yr{sup -1} calculated in the Snake River Plain and Owyhee-Oregon Plateau over a 125 x 650 km region. Tests that include dike-opening reveal that rapid extension by dike intrusion in volcanic rift zones does not occur in the Snake River Plain at present. This slow internal deformation in the Snake River Plain is in contrast to the rapidly-extending adjacent Basin and Range provinces and implies shear along boundaries of the Snake River Plain. We estimate right-lateral shear with slip rates of 0.5-1.5 mm/yr along the northwestern boundary adjacent to the Centennial Tectonic belt and left-lateral oblique extension with slip rates of <0.5 to 1.7 mm/yr along the southeastern boundary adjacent to the Intermountain Seismic belt. The fastest lateral shearing occurs near the Yellowstone Plateau where strike-slip focal mechanisms and faults with observed strike-slip components of motion are documented. The regional GPS velocity gradients are best fit by nearby poles of rotation for the Centennial Tectonic belt, Idaho batholith, Snake River Plain, Owyhee-Oregon Plateau, and central Oregon, indicating that clockwise rotation is driven by extension to the

  2. Crustal seismicity and the earthquake catalog maximum moment magnitudes (Mcmax) in stable continental regions (SCRs): correlation with the seismic velocity of the lithosphere

    USGS Publications Warehouse

    Mooney, Walter D.; Ritsema, Jeroen; Hwang, Yong Keun

    2012-01-01

    A joint analysis of global seismicity and seismic tomography indicates that the seismic potential of continental intraplate regions is correlated with the seismic properties of the lithosphere. Archean and Early Proterozoic cratons with cold, stable continental lithospheric roots have fewer crustal earthquakes and a lower maximum earthquake catalog moment magnitude (Mcmax). The geographic distribution of thick lithospheric roots is inferred from the global seismic model S40RTS that displays shear-velocity perturbations (δVS) relative to the Preliminary Reference Earth Model (PREM). We compare δVS at a depth of 175 km with the locations and moment magnitudes (Mw) of intraplate earthquakes in the crust (Schulte and Mooney, 2005). Many intraplate earthquakes concentrate around the pronounced lateral gradients in lithospheric thickness that surround the cratons and few earthquakes occur within cratonic interiors. Globally, 27% of stable continental lithosphere is underlain by δVS≥3.0%, yet only 6.5% of crustal earthquakes with Mw>4.5 occur above these regions with thick lithosphere. No earthquakes in our catalog with Mw>6 have occurred above mantle lithosphere with δVS>3.5%, although such lithosphere comprises 19% of stable continental regions. Thus, for cratonic interiors with seismically determined thick lithosphere (1) there is a significant decrease in the number of crustal earthquakes, and (2) the maximum moment magnitude found in the earthquake catalog is Mcmax=6.0. We attribute these observations to higher lithospheric strength beneath cratonic interiors due to lower temperatures and dehydration in both the lower crust and the highly depleted lithospheric root.

  3. Sediment and Lower Water Column Oxygen Consumption in the Seasonally-hypoxic Region of the Louisiana Continental Shelf

    EPA Science Inventory

    We report sediment and bottom water respiration rates from 10 cruises from 2003-2007 on the Louisiana Continental Shelf (LSC) where summer hypoxia regularly occurs. Cruises were conducted during spring (5 cruises), summer (3 cruises) and fall (2 cruises). Cruise average sediment ...

  4. U-Pb isotopic evidence for accretion of a continental microplate in the Zalm region of the Saudi Arabian Shield

    USGS Publications Warehouse

    Stacey, J.S.; Agar, R.A.

    1986-01-01

    U-Pb zircon age determinations show that this "Andean" continental margin developed before about 720 Ma, and emplacement of calc-alkaline plutonic rocks continued until about 690 Ma. During the period 690-640 Ma, the continental Afif microplate collided with the Asir terrane as part of the Nabitah orogeny. At approximately 640 Ma ago, the Najd strike-slip orogen commenced with a dextral phase that controlled the emplacement of granitic plutons as well as the development of a series of large pull-apart grabens. Some of these grabens were floored by new oceanic crust and were filled with volcano-sedimentary rocks of the Bani Ghayy group. Subsequently, the Najd fault system changed to sinistral strike slip motion at about 620 Ma ago.

  5. Upper mantle anisotropy beneath Indochina block and adjacent regions from shear-wave splitting analysis of Vietnam broadband seismograph array data

    NASA Astrophysics Data System (ADS)

    Bai, Ling; Iidaka, Takashi; Kawakatsu, Hitoshi; Morita, Yuichi; Dzung, N. Q.

    2009-09-01

    The Indochina block is located at the junction of four major plates. It has a close relationship with the uplift of Tibet plateau and the sea-floor spreading of the South China Sea in the geological evolution histories. We deployed a temporary broadband seismograph array in Vietnam from February 2000 to October 2005, and measured shear-wave splitting of core-refracted phases to investigate the upper mantle anisotropy beneath the Indochina block and adjacent regions. The observed delay times of up to 1.5 s are large, indicating a mantle source for the anisotropy. Two distinct regimes of seismic anisotropy are revealed. The fast polarization directions in the northern Indochina block with a main trend of N100°E are almost consistent with the direction of both the surface displacement and the absolute plate motion. These observations suggest the anisotropy is possibly generated by the present-day asthenospheric flow caused by the India-Eurasia collision. The fast polarization directions in the southern Indochina block and the Hainan island are nearly N60°E. The anisotropy in this area may reflect a combination of the India-Eurasia collision and the past orogenies in the lithosphere, or an abrupt variation in the asthenospheric flow.

  6. Seismicity and S-wave velocity structure of the crust and the upper mantle in the Baikal rift and adjacent regions

    NASA Astrophysics Data System (ADS)

    Seredkina, Alena; Kozhevnikov, Vladimir; Melnikova, Valentina; Solovey, Oksana

    2016-12-01

    Correlations between seismicity, seismotectonic deformation (STD) field and velocity structure of the crust and the upper mantle in the Baikal rift and the adjacent areas of the Siberian platform and the Mongol-Okhotsk fold belt have been investigated. The 3D S-wave velocity structure up to the depths of 500 km has been modeled using a representative sample of Rayleigh wave group velocity dispersion curves (about 3200 paths) at periods from 10 to 250 s. The STD pattern has been reconstructed from mechanisms of large earthquakes, and is in good agreement with GPS and structural data. Analysis of the results has shown that most of large shallow earthquakes fall in regions of low S-wave velocities in the uppermost mantle (western Mongolia and areas of recent mountain building in southern Siberia) and in zones of their relatively high lateral variations (northeastern flank of the Baikal rift). In the first case the dominant STD regime is compression manifested in a mixture of thrust and strike-slip deformations. In the second case we observe a general predominance of extension.

  7. Plant molecular phylogeography in China and adjacent regions: Tracing the genetic imprints of Quaternary climate and environmental change in the world's most diverse temperate flora.

    PubMed

    Qiu, Ying-Xiong; Fu, Cheng-Xing; Comes, Hans Peter

    2011-04-01

    The Sino-Japanese Floristic Region (SJFR) of East Asia harbors the most diverse of the world's temperate flora, and was the most important glacial refuge for its Tertiary representatives ('relics') throughout Quaternary ice-age cycles. A steadily increasing number of phylogeographic studies in the SJFR of mainland China and adjacent areas, including the Qinghai-Tibetan-Plateau (QTP) and Sino-Himalayan region, have documented the population histories of temperate plant species in these regions. Here we review this current literature that challenges the oft-stated view of the SJFR as a glacial sanctuary for temperate plants, instead revealing profound effects of Quaternary changes in climate, topography, and/or sea level on the current genetic structure of such organisms. There are three recurrent phylogeographic scenarios identified by different case studies that broadly agree with longstanding biogeographic or palaeo-ecological hypotheses: (i) postglacial re-colonization of the QTP from (south-)eastern glacial refugia; (ii) population isolation and endemic species formation in Southwest China due to tectonic shifts and river course dynamics; and (iii) long-term isolation and species survival in multiple localized refugia of (warm-)temperate deciduous forest habitats in subtropical (Central/East/South) China. However, in four additional instances, phylogeographic findings seem to conflict with a priori predictions raised by palaeo-data, suggesting instead: (iv) glacial in situ survival of some hardy alpine herbs and forest trees on the QTP platform itself; (v) long-term refugial isolation of (warm-)temperate evergreen taxa in subtropical China; (vi) 'cryptic' glacial survival of (cool-)temperate deciduous forest trees in North China; and (vii) unexpectedly deep (Late Tertiary/early-to-mid Pleistocene) allopatric-vicariant differentiation of disjunct lineages in the East China-Japan-Korea region due to past sea transgressions. We discuss these and other consequences

  8. A conceptual review of regional-scale controls on the composition of clastic sediment and the co-evolution of continental blocks and their sedimentary cover.

    PubMed

    Cox, R; Lowe, D R

    1995-01-02

    Both sediment recycling and first-cycle input influence the composition of clastic material in sedimentary systems. This paper examines conceptually the roles played by these processes in governing the composition of clastic sediment on a regional scale by outlining the expected effects on sediment composition of protracted sediment recycling and of continuous first-cycle input on a maturing continental block. Generally speaking, long-term recycling tends to enrich sediments in the most chemically and mechanically stable components: quartz in the sand and silt size fractions, and illite among the clay minerals. Sandstones trend towards pure quartz arenites, and mudrocks become more potassic and aluminous. The average grain size of clastic sediment decreases by a combination of progressive attrition of sand grains and ongoing breakdown of primary silicate minerals to finer-grained clay minerals and oxides. Sandstones derived by continuous first-cycle input from an evolving continental crustal source also become increasingly rich in quartz, but in addition become more feldspathic as the proportion of granitic material in the upper continental crust increases during crustal stabilization. Associated mudrocks also become richer in potassium and aluminum, but will have higher K2O/Al2O3 ratios than recycled muds. The average grain size of the sediment may increase with time as the proportion of sand-prone granitic source rocks increases at the expense of more mud-prone volcanic sources. In general, except in instances where chemical weathering is extreme, first-cycle sediments lack the compositional maturity of recycled detritus, and are characterized by the presence of a variety of primary silicate minerals. Sedimentary systems are not usually completely dominated by either recycling or first-cycle detritus. Generally, however, sedimentary systems associated with the earliest phases of formation and accretion of continental crust are characterized by first-cycle input

  9. The emergence of the climate change signal in the hydrodynamic and ecosystem properties of the different regions of the northwest European continental shelf

    NASA Astrophysics Data System (ADS)

    Wakelin, Sarah; Artioli, Yuri; Holt, Jason; Butenschon, Momme

    2015-04-01

    Climate change on the northwest European continental shelf is forced by a combination of atmospheric, oceanic and terrestrial changes. The impact of changes in the atmosphere is experienced across the shelf, whereas the relative impacts of the oceanic and terrestrial changes vary depending on the proximity to land and to the edge of the continental shelf. All are modulated by the underlying regional hydrodynamics. In previous work for the North Sea Region Climate Change Assessment (NOSCCA) we used time-slice simulations and analysed the differences between average conditions in future and past time periods. Here, using a transient simulation, we study the evolution of climate change and use present day variability to investigate the emergence of the climate change signal from the present day climate. We use a 120-year simulation (1980-2099) of the coupled hydrodynamics-ecosystem model NEMO-ERSEM for the northwest European continental shelf. The model is driven by atmospheric forcing from a CMIP5 OAGCM (HADGEM2, under a high emissions scenario RCP8.5) and ocean/ecosystem boundary forcing from a global NEMO-MEDUSA model (ORCA1, forced by HADGEM2 under RCP8.5). We compare the emerging climate change signal of the North Sea to that of other regions of the European shelf. Some changes, such as increasing temperature and decreasing salinity, occur throughout the simulation timeframe and across the shelf. The projected ecosystem response is more complex with different regions showing different time-varying responses; e.g. after initial decreases in some regions, zooplankton biomass generally increases by 2099, while phytoplankton biomass decreases in the more northern regions of the shelf and increases elsewhere. The present-day European shelf is a sink for atmospheric CO2 and, in the future projection, the uptake of CO2 from the atmosphere increases in the southern North Sea and the western shelf regions (west of the UK, Ireland and France) but decreases elsewhere on the

  10. Climatic stress events in the source region of modern man - Matching the last 20 ka of the Chew Bahir climate record with occupation history of adjacent refugia

    NASA Astrophysics Data System (ADS)

    Foerster, Verena; Vogelsang, Ralf; Junginger, Annett; Asrat, Asfawossen; Lamb, Henry F.; Viehberg, Finn; Trauth, Martin H.; Schaebitz, Frank

    2014-05-01

    A rapidly changing environment is considered an important driver not just for human evolution but also for cultural and technological innovation and migration. To evaluate the impact that climatic shifts on different timescales might have had on the living conditions of prehistoric humans is one of the cornerstones in current research, but continuous paleo-climate records in the vicinity of archaeological sites are still rare. As a contribution towards a better understanding of this human-climate interaction we here present a match between the last 20 ka of the just recently developed paleo-climate record from Chew Bahir in southern Ethiopia and the settlement history of adjacent possible refugia. The Chew Bahir basin, as a newly explored reliable climatic archive, lies in a biogeographically highly sensitive transition zone between the Main Ethiopian Rift and the Omo-Turkana basin and hence represents an ideal site to study climatic variability in the source region of modern man. The climatic history with a temporal resolution of up to 3 years is showing besides orbitally driven long-term transitions in and out of favourable living conditions several short abrupt excursions towards drier or wetter episodes. Comparing the frequency of archaeological findings as a parameter for human occupation to this close-by climate record that allows us to outline how complex the interplay between humans and environment during the last 20 ka really was, which dynamics might have been involved and which role the temporal dimension of environmental changes could have played for the adaption of humans.

  11. Rapid climatic changes and resilient vegetation during the Lateglacial and Holocene in a continental region of south-western Europe

    NASA Astrophysics Data System (ADS)

    Aranbarri, Josu; González-Sampériz, Penélope; Valero-Garcés, Blas; Moreno, Ana; Gil-Romera, Graciela; Sevilla-Callejo, Miguel; García-Prieto, Eduardo; Di Rita, Federico; Mata, M. Pilar; Morellón, Mario; Magri, Donatella; Rodríguez-Lázaro, Julio; Carrión, José S.

    2014-03-01

    Palynological, sedimentological and geochemical analyses performed on the Villarquemado paleolake sequence (987 m a.s.l, 40°30‧N; 1°18‧W) reveal the vegetation dynamics and climate variability in continental Iberia over the last 13,500 cal yr BP. The Lateglacial and early Holocene periods are characterized by arid conditions with a stable landscape dominated by pinewoods and steppe until ca. 7780 cal yr BP, despite sedimentological evidence for large paleohydrological fluctuations in the paleolake. The most humid phase occurred between ca. 7780 and 5000 cal yr BP and was characterized by the maximum spread of mesophytes (e.g., Betula, Corylus, Quercus faginea type), the expansion of a mixed Mediterranean oak woodland with evergreen Quercus as dominant forest communities and more frequent higher lake level periods. The return of a dense pinewood synchronous with the depletion of mesophytes characterizes the mid-late Holocene transition (ca. 5000 cal yr BP) most likely as a consequence of an increasing aridity that coincides with the reappearance of a shallow, carbonate wetland environment. The paleohydrological and vegetation evolution shows similarities with other continental Mediterranean areas of Iberia and demonstrates a marked resilience of terrestrial vegetation and gradual responses to millennial-scale climate fluctuations. Human impact is negligible until the Ibero-Roman period (ca. 2500 cal yr BP) when a major deforestation occurred in the nearby pine forest. The last 1500 years are characterized by increasing landscape management, mainly associated with grazing practices shaping the current landscape.

  12. Continental shelves

    SciTech Connect

    Postma, H.; Zijlstra

    1987-01-01

    Continental shelves form a relatively narrow fringe, of varying width, around the continents. Altogether they take up only about 7% of the ocean's surface and less than 0.2% if its volume. Nevertheless, their specific biological characteristics and economical importance justify a separate discussion in this series. Ecosystems of the World. The specific biological characteristics are due to the position of continental shelves between the land masses on one side and the oceans on the other, to their relative shallowness and variable sea-floor texture and to the fact that, besides residual currents, tidal streams exert a great influence on the movements of water bodies.

  13. Imaging upper mantle structures in regional, continental and global scales using long-period surface waves (50-300 sec) from ambient noise

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Xie, J.

    2014-12-01

    Most of ambient noise tomography studies performed to date exploit surface waves at periods shorter than 40/50 sec. Two natural questions one may ask are (1) whether longer-period surface wave (>50 s) can also be extracted from ambient noise and (2) whether long-period dispersion curves from ambient noise are accurate enough for tomography to constrain upper-mantle structures. In this study, we investigate the capability of using teleseismic long-period surface waves from ambient noise in regional-, continental- and global-scale surface wave tomography and also evaluate the accuracy of long-period dispersion measurements at periods up to 300 sec. For regional and continental scale studies, we process ambient noise data from USArray to extract inter-station long-period surface wave dispersion curves and then perform surface wave tomography using the dispersion curves. For the global scale studies, we process ambient noise data from more than 1000 stations distributed around the globe, including both permanent FDSN stations and a number of PASSCAL transportable arrays. We observe clear, strong, and coherent long-period surface waves at 50-300 sec periods at both regional and teleseismic inter-station distances. Using long-period dispersion curves from ambient noise, we generate phase velocity maps at 50-300 sec periods and then compare them with those generated from earthquake data. The results show that long-period dispersion measurements from ambient noise are compatible with those from earthquake data and phase velocity maps from ambient noise data and earthquake data are similar to each other, verifying the feasibility and validity of using long-period surface waves from ambient noise in regional, continental and global surface wave tomography. Long-period surface waves from ambient noise are complementary to those from earthquakes. The inclusion of them in regional and global surface wave tomography could significantly increase both lateral and azimuthal path

  14. The Continental Crust.

    ERIC Educational Resources Information Center

    Burchfiel, B. Clark

    1983-01-01

    Continental crust underlies the continents, their margins, and also small shallow regions in oceans. The nature of the crust (much older than oceanic crust) and its dynamics are discussed. Research related to and effects of tectonics, volcanism, erosion, and sedimentation on the crust are considered. (JN)

  15. Regional methamphetamine use among U.S. Army personnel stationed in the continental United States and Hawaii: a six-year retrospective study (2000-2005).

    PubMed

    Lacy, Benjamin W; Ditzler, Thomas F; Wilson, Raymond S; Martin, Thomas M; Ochikubo, Jon T; Roussel, Robert R; Pizarro-Matos, Jose M; Vazquez, Raymond

    2008-04-01

    Substance use disorders constitute a serious and persistent threat to military readiness and to the health and safety of military personnel and their families. Methamphetamine is among the most addictive and damaging of commonly abused drugs; this is of great concern for military health providers in Hawaii due to the unusually high prevalence in the local community. The effect of regional drug use on active duty subpopulations has not been previously studied. This study includes a 6-year retrospective sample of laboratory-confirmed methamphetamine-, cocaine-, and marijuana-positive drug tests among Army soldiers stationed in Hawaii and western and eastern continental U.S. installations. The findings suggest that active duty members are significantly affected by the local drug climate. However, current military drug policies also deter use as evidenced by low absolute drug-positive rates even in regions of high civilian prevalence.

  16. Allosteric modulation of the HIV-1 gp120-gp41 association site by adjacent gp120 variable region 1 (V1) N-glycans linked to neutralization sensitivity.

    PubMed

    Drummer, Heidi E; Hill, Melissa K; Maerz, Anne L; Wood, Stephanie; Ramsland, Paul A; Mak, Johnson; Poumbourios, Pantelis

    2013-01-01

    The HIV-1 gp120-gp41 complex, which mediates viral fusion and cellular entry, undergoes rapid evolution within its external glycan shield to enable escape from neutralizing antibody (NAb). Understanding how conserved protein determinants retain functionality in the context of such evolution is important for their evaluation and exploitation as potential drug and/or vaccine targets. In this study, we examined how the conserved gp120-gp41 association site, formed by the N- and C-terminal segments of gp120 and the disulfide-bonded region (DSR) of gp41, adapts to glycan changes that are linked to neutralization sensitivity. To this end, a DSR mutant virus (K601D) with defective gp120-association was sequentially passaged in peripheral blood mononuclear cells to select suppressor mutations. We reasoned that the locations of suppressors point to structural elements that are functionally linked to the gp120-gp41 association site. In culture 1, gp120 association and viral replication was restored by loss of the conserved glycan at Asn¹³⁶ in V1 (T138N mutation) in conjunction with the L494I substitution in C5 within the association site. In culture 2, replication was restored with deletion of the N¹³⁹INN sequence, which ablates the overlapping Asn¹⁴¹-Asn¹⁴²-Ser-Ser potential N-linked glycosylation sequons in V1, in conjunction with D601N in the DSR. The 136 and 142 glycan mutations appeared to exert their suppressive effects by altering the dependence of gp120-gp41 interactions on the DSR residues, Leu⁵⁹³, Trp⁵⁹⁶ and Lys⁶⁰¹. The 136 and/or 142 glycan mutations increased the sensitivity of HIV-1 pseudovirions to the glycan-dependent NAbs 2G12 and PG16, and also pooled IgG obtained from HIV-1-infected individuals. Thus adjacent V1 glycans allosterically modulate the distal gp120-gp41 association site. We propose that this represents a mechanism for functional adaptation of the gp120-gp41 association site to an evolving glycan shield in a

  17. Isoxazole moiety in the linker region of HDAC inhibitors adjacent to the Zn-chelating group: effects on HDAC biology and antiproliferative activity.

    PubMed

    Tapadar, Subhasish; He, Rong; Luchini, Doris N; Billadeau, Daniel D; Kozikowski, Alan P

    2009-06-01

    A series of hydroxamic acid based histone deacetylase inhibitors 6-15, containing an isoxazole moiety adjacent to the Zn-chelating hydroxamic acid, is reported herein. Some of these compounds showed nanomolar activity in the HDAC isoform inhibitory assay and exhibited micro molar inhibitory activity against five pancreatic cancer cell lines.

  18. Raising the continental crust

    NASA Astrophysics Data System (ADS)

    Campbell, Ian H.; Davies, D. Rhodri

    2017-02-01

    The changes that occur at the boundary between the Archean and Proterozoic eons are arguably the most fundamental to affect the evolution of Earth's continental crust. The principal component of Archean continental crust is Granite-Greenstone Terranes (GGTs), with granites always dominant. The greenstones consist of a lower sequence of submarine komatiites and basalts, which erupted onto a pre-existing Tonalite-Trondhjemite-Granodiorite (TTG) crust. These basaltic rocks pass upwards initially into evolved volcanic rocks, such as andesites and dacites and, subsequently, into reworked felsic pyroclastic material and immature sediments. This transition coincides with widespread emplacement of granitoids, which stabilised (cratonised) the continental crust. Proterozoic supra-crustal rocks, on the other hand, are dominated by extensive flat-lying platform sequences of mature sediments, which were deposited on stable cratonic basements, with basaltic rocks appreciably less abundant. The siliceous TTGs cannot be produced by direct melting of the mantle, with most hypotheses for their origin requiring them to be underlain by a complimentary dense amphibole-garnet-pyroxenite root, which we suggest acted as ballast to the early continents. Ubiquitous continental pillow basalts in Archean lower greenstone sequences require the early continental crust to have been sub-marine, whereas the appearance of abundant clastic sediments, at higher stratigraphic levels, shows that it had emerged above sea level by the time of sedimentation. We hypothesise that the production of komatiites and associated basalts, the rise of the continental crust, widespread melting of the continental crust, the onset of sedimentation and subsequent cratonisation form a continuum that is the direct result of removal of the continent's dense amphibole-garnet-pyroxenite roots, triggered at a regional scale by the arrival of a mantle plume at the base of the lithosphere. Our idealised calculations suggest

  19. Low temperature thermochronology and topographic evolution of the South Atlantic passive continental margin in the region in eastern Argentina

    NASA Astrophysics Data System (ADS)

    Pfister, Sabrina; Kollenz, Sebastian; Glasmacher, Ulrich A.

    2014-05-01

    To understand the evolution of the passive continental margin in Argentina low temperature thermochronology is an appropriate method, which will lead to new conclusions in this area. The Tandilia System, also called Sierras Septentrionales, is located south of the Río de la Plato Craton in eastern Argentina in the state of Buenos Aires. North of the hills Salado basin is located whereas the Claromecó basin is situated south of the mountain range. In contrary to most basins along the southamerican passive continental margin the Tandilia-System and the neighbouring basins trend perpendicular to the coast line. The topography is fairly flat with altitudes of. The igneous-metamorphic basement is pre-proterozoic in age and build up of mainly granitic-tonalitic gneisses, migmatites, amphibolites, some ultramafic rocks and granitoid plutons it is overlain by a series of Neoproterozoic to early Paleozoic sediments (Cingolani, 2010), like siliciclastics, dolostones, shales and limestones (Demoulin et al., 2005). The aim of the study is to quantify the long-term landscape evolution of the passive continental margin in eastern Argentina in terms of thermal history, exhumation and tectonic activities. For that purpose, samples were taken from the Sierra Septentrionales and analyzed with the apatite fission-track method. Further 2-D thermokinematic modeling was conducted with the computer code HeFTy (Ketcham, 2005; Ketcham 2007; Ketcham et al., 2009). The results indicate apatite fission track ages between 101.6 (9.4) to 228.9 (22.3) Ma, what means all measured ages are younger as their formation age. That shows all samples have been reset. Six samples accomplished enough confined tracks and were used to test geological t-T models against the AFT data set. These models give a more detailed insight on the cooling history and tectonic activities in the research area. References: Cingolani C. A. (2010): The Tandilia System of Argentina as a southern extension of the Río de la

  20. Physiography, surficial sediments and Quaternary stratigraphy of the inner continental shelf and nearshore region of the Gulf of Maine

    USGS Publications Warehouse

    Kelley, J.T.; Belknap, D.F.

    1991-01-01

    The western margin of the Gulf of Maine is a bedrock-framed, glaciated continental shelf that has only recently been geologically mapped. The bathymetry is divisible into four physiographic areas: nearshore basins, shelf valleys, rocky zones, and outer basins. The nearshore basins are largely floored by mud except near rock outcrops where shelly gravel occurs. Shelf valleys extend seaward from nearshore basins and estuaries and generally possess less sediment than nearshore basins. Abundant exposures of Pleistocene sediment with rippled substrates suggest that contemporary reworking is occurring. Rocky zones are the most abundant physiographic area and include both exposed bedrock and glacial gravel outcrops. Shell material produced by organisms living on or near rocks is common both in the rocky zones and in abutting environments. The outer basin begins at a depth of about 60 m and extends beyond the 100 m isobath. This area is occasionally bordered on its landward side by the late Quaternary lowstand shoreline. Below this shoreline thicker deposits of sediment exist, while all environments landward were reworked by a regression and transgression of the sea. ?? 1991.

  1. Horizontal coherence of low-frequency fixed-path sound in a continental shelf region with internal-wave activity.

    PubMed

    Duda, Timothy F; Collis, Jon M; Lin, Ying-Tsong; Newhall, Arthur E; Lynch, James F; DeFerrari, Harry A

    2012-02-01

    Sound at 85 to 450 Hz propagating in approximately 80-m depth water from fixed sources to a joint horizontal/vertical line array (HLA/VLA) is analyzed. The data are from a continental shelf area east of Delaware Bay (USA) populated with tidally generated long- and short-wavelength internal waves. Sound paths are 19 km in the along-shore (along internal-wave crest) direction and 30 km in the cross-shore direction. Spatial statistics of HLA arrivals are computed as functions of beam steering angle and time. These include array gain, horizontally lagged spatial correlation function, and coherent beam power. These quantities vary widely in magnitude, and vary over a broad range of time scales. For example, correlation scale can change rapidly from forty to five wavelengths, and correlation-scale behavior is anisotropic. In addition, the vertical array can be used to predict correlation expected for adiabatic propagation with cylindrical symmetry, forming a benchmark. Observed variations are in concert with internal-wave activity. Temporal variations of three coherence measures, horizontal correlation length, array gain, and ratio of actual correlation length to predicted adiabatic-mode correlation length, are very strong, varying by almost a factor of ten as internal waves pass.

  2. Was the exposed continental shelf a long-distance colonization route in the ice age? The Southeast Asia origin of Hainan and Taiwan partridges.

    PubMed

    Chen, De; Chang, Jiang; Li, Shou-Hsien; Liu, Yang; Liang, Wei; Zhou, Fang; Yao, Cheng-Te; Zhang, Zhengwang

    2015-02-01

    Research on island biotas has greatly contributed to the development of modern evolutionary and biogeographic theories. Until now, most studies have suggested that continental islands received their biotas directly from the adjacent mainland. However, only a few studies have indicated that species on continental islands might originate from other distantly non-adjacent regions. Here, we used the hill partridges (genus Arborophila) that are widely distributed in the southwest and southeast China mainland, Indochina, Hainan and Taiwan islands to test whether species on continental islands might originate from distant regions rather than the adjacent mainland. Based on molecular phylogenies inferred from three mitochondrial fragments and three nuclear introns, together with ancestral area reconstruction, we found that the ancestors of the endemic Hainan and Taiwan partridges (A. ardens and A. crudigularis) likely originated from Indochina, rather than the nearby southeast China mainland. The divergence time estimates demonstrate that their ancestors likely colonized Hainan and Taiwan islands using the long exposed continental shelf between Indochina, Hainan and Taiwan islands during glacial periods, which had not been demonstrated before. Thus, integrating distribution data with phylogenetic information can shed new lights on the historical biogeography of continental islands and surrounding mainland regions.

  3. Transport of Australian Continental Dust to Australia's Great Barrier Reef Region: First Results From Sampling, Remote Sensing, Synoptic and Trajectory Analyses

    NASA Astrophysics Data System (ADS)

    Tapper, N.; O'Loingsigh, T.; de Deckker, P.; Cohen, D.

    2009-04-01

    As part of a large multi-disciplinary project funded by the Australian Research Council and in collaboration with the Australian Nuclear Science and Technology Organisation, we established in mid-2008 three PM 2.5 samplers in eastern Australia to determine possible transport of continental dust from the major dust source region of the Lake Eyre Basin (LEB). These samplers were located at Fowlers Gap, New South Wales [NSW] (31.09S, 141.70E), Mount Stromlo, NSW (35.30S, 149.00E) and Heron Island, Queensland (23.44S, 151.83E). The latter location is of particular significance because of its proximity to the World Heritage Great Barrier Reef (GBR) and to the tropical rainforest of coastal North Queensland. In previous studies, dust and associated organic material of African origin has been associated with rainforest fertilisation in Amazonia and coral bleaching in the Carribean. In this presentation three case studies of continental dust transport to Heron Island that occurred in the first four months of sampling are examined. In each case transport of soil material from the LEB region and/or western NSW is confirmed by the nature of material sampled, by remote sensing of the dust, by forward and backward air parcel trajectory analysis and by synoptic analysis. In each case the dust arrived over Heron Island 3-7 days after passing over the southern samplers, generally having followed an anti-clockwise curved path to approach Heron Island from the southeast. The potential significance of this finding for the GBR is briefly discussed.

  4. Insights into the evolution of the uppermost continental mantle from xenolith localities on and near the Colorado Plateau and regional comparisons

    NASA Astrophysics Data System (ADS)

    Smith, D.

    2000-07-01

    The interplay between the evolution of mantle and crust has been investigated by textural and electron probe analysis of Cr-diopside spinel peridotite xenoliths from six localities and by comparisons to a database of mineral compositions. The six localities are on a 300-km transect from the Colorado Plateau into the adjoining Rio Grande rift. Typical xenolith populations from the Colorado Plateau province have magnesian olivine (average Fo90.5) and Ti- and Na-poor clinopyroxene. In contrast, typical xenolith populations from the Rio Grande rift and the Basin and Range are characterized by more Fe-rich olivine (average Fo89.6) and clinopyroxene with a range of Ti and Na (average 0.44wt%TiO2). The contrast between the xenoliths from these adjacent provinces documents that the Colorado Plateau has a depleted mantle root that helps to stabilize it. At Mount Taylor, however, a locality high on a composite volcano within the eastern Colorado Plateau, most xenoliths are not depleted, and the Fe-rich olivine (Fo86-Fo88) in them may characterize mantle affected by silicate melt metasomatism at high melt/rock ratios. Low-Al orthopyroxene occurs at two of the six transect localities, and part of a large porphyroblast contains only 0.13wt%Al2O3 because of the unusual compositions and textures, water-rock reactions are inferred to have been important in parts of the refractory continental mantle. Zonation of Ca and Al in orthopyroxene provides constraints on the temperature histories of the unusual pyroxenes. Equilibration temperatures for xenoliths from Lunar Crater, Nevada, average 1270°C, much higher than the average of 1012°C for others from the Basin and Range; Lunar Crater xenoliths may be samples of a plume or asthenosphere emplaced recently into the uppermost mantle.

  5. The regional structural setting of the 2008 Wells earthquake and Town Creek Flat Basin: implications for the Wells earthquake fault and adjacent structures

    USGS Publications Warehouse

    Henry, Christopher S.; Colgan, Joseph P.

    2011-01-01

    The 2008 Wells earthquake occurred on a northeast-striking, southeast-dipping fault that is clearly delineated by the aftershock swarm to a depth of 10-12 km below sea level. However, Cenozoic rocks and structures around Wells primarily record east-west extension along north- to north-northeast-striking, west-dipping normal faults that formed during the middle Miocene. These faults are responsible for the strong eastward tilt of most basins and ranges in the area, including the Town Creek Flat basin (the location of the earthquake) and the adjacent Snake Mountains and western Windermere Hills. These older west-dipping faults are locally overprinted by a younger generation of east-dipping, high-angle normal faults that formed as early as the late Miocene and have remained active into the Quaternary. The most prominent of these east-dipping faults is the set of en-échelon, north-striking faults that bounds the east sides of the Ruby Mountains, East Humboldt Range, and Clover Hill (about 5 km southwest of Wells). The northeastern-most of these faults, the Clover Hill fault, projects northward along strike toward the Snake Mountains and the approximately located surface projection of the Wells earthquake fault as defined by aftershock locations. The Clover Hill fault also projects toward a previously unrecognized, east-facing Quaternary fault scarp and line of springs that appear to mark a significant east-dipping normal fault along the western edge of Town Creek Flat. Both western and eastern projections may be northern continuations of the Clover Hill fault. The Wells earthquake occurred along this east-dipping fault system. Two possible alternatives to rupture of a northern continuation of the Clover Hill fault are that the earthquake fault (1) is antithetic to an active west-dipping fault or (2) reactivated a Mesozoic thrust fault that dips east as a result of tilting by the west-dipping faults along the west side of the Snake Mountains. Both alternatives are

  6. Crust structure of the Northern Margin of North China Craton and adjacent region from Sinoprobe-02 North China seismic WAR/R experiment

    NASA Astrophysics Data System (ADS)

    Li, W.; Gao, R.; Keller, G. R.; Li, Q.; Cox, C. M.; Hou, H.; Guan, Y.

    2011-12-01

    The Central Asian Orogen Belt (CAOB) or Altaids, situated between the Siberian craton(SC) to the north and north China craton (NCC) with tarim to the south, is one of the world's largest accretionary orogens formed by subduction and accretion of juvenile material from the Neoproterozoic through the Paleozoic. The NCC is the oldest craton in China, which suffered Yanshan intercontinental orogenic process and lithosphere thinning in Mesozoic. In the past 20 years, remarkable studies about this region have been carried out and different tectonic models were proposed, however, some crucial geologic problems remain controversial. In order to obtain better knowledge of deep structure and properties of crust on the northern margin of north China craton, a 450 km long WAR/R section was completed jointly by Institute of Geology, CAGS and University of Oklahoma. Our 450 km long NW-SE WAR/R line extends from west end of the Yanshan orogen, across the Bainaimiao arc, Ondor sum subduction accretion complex to the Solonker suture zone. The recording of seismic waves from 8 explorations was conducted in 4 deployments of 300 reftek-125A records and single-channel 4.5Hz geophones with station spacing of 1km. The shooting procedure was employ 500 or 1500kg explosives in 4-5 or 15-23 boreholes at 40-45m depth. The sampling rate was 100 HZ, and recording time window was 1200s. The P wave field on the sections got high quality data for most part of the profile, but have low signal-to-noise for the south end, where closed to Beijing with a lot of ambient noise from traffic, industry and human activity. Arrivals from of refracted and reflected waves from sediments and basement (Pg), intracrust (Pcp, Plp) and Moho (Pmp) were typically observed, but Pn phase through the upper most mantle was only observed for 2 shots. Identification and correlation of seismic phases was done manually on computer screen Zplot software. Each trace has been bandpass filtered (1-20Hz) and normalized with AGC

  7. Nitrogen isotopes in thermal fluids of a forearc region (Jalisco Block, Mexico): Evidence for heavy nitrogen from continental crust

    NASA Astrophysics Data System (ADS)

    Inguaggiato, S.; Taran, Y.; Grassa, F.; Capasso, G.; Favara, R.; Varley, N.; Faber, E.

    2004-12-01

    The Jalisco Block (JB) is a geologically and tectonically complex part of northwestern Mexico characterized by active subduction-type volcanism, rifting, and old stable structures. Thermal springs and groups of springs are widely distributed over JB. Bubbling gas from seven thermal springs located within different tectonic environments of the JB was analyzed for He, 20Ne, and N2 concentrations and δ15N ratios. All gases are N2-dominant (>84%) with the exception of one sample (Rió Purificación), which has a significant CH4 content (about 50%). All collected gas samples are relatively high in He, up to 1500 ppm vol and with 3He/4He values ranging from 0.6 to 4.5 Ra. All measured nitrogen isotope ratios are heavier than air with δ15N values ranging from 0.5 to 5.0‰. The relative N2 excess with respect to air-saturated water computed on the basis of N2 and 20Ne contents indicates the contribution of a nonatmospheric N2 source. All the samples show a good correlation between δ15N and the relative excess of N2 with δ15N ˜ +5.3‰ for the maximum N2 excess of 100%. Due to a presumed lack of seafloor sediment involved in the subduction process, such a δ15N positive value seems to reflect the addition to the fluids of a heavy nitrogen originating from metamorphism processes of rocks occurring within the overlying continental crust.

  8. Developing of a VS30 map for addressing site effects for Portugal: evaluation of the effectiveness of using VS30-proxies for stable continental regions.

    NASA Astrophysics Data System (ADS)

    Vilanova, Susana; Narciso, Joao; Carvalho, Joao; Pinto, Carlos; Lopes, Isabel; Nemser, Eliza; Borges, Jose; Oliveira, Carlos

    2014-05-01

    - Sand deposits and clays, terrace deposits of Pleistocene age; and S6 - Alluvium, mud, sands, clay, silt and sand dune of Holocene age. The time-average shear-wave velocity in the upper 30m (Vs30) from the database sites range from 123m/s to 1870m/s. The variance of the distribution of Vs30 values varies significantly with the generalized geological unit, being larger S1 and S2 units. The use of proxies based either on the geological-geographical units developed for California by Wills and Clahan (2006) or on correlations with the topographic slope for stable continental regions (Wald and Allen, 2007) shows relatively unbiased total residual distributions of the logarithm of Vs30, although with a large variance. However, the performance of both methods varies significantly with the generalized geological unit analyzed. Both methods are highly biased towards lower values of Vs30 for unit S1 (hard rock). The topographic-slope method shows inconsistent bias for each generalized unit. These results are not in agreement with those of Lemoine et al. (2012) who concluded that, for stable continental regions, the topographic-slope method performance was best for rock sites (A/B NERPH class). This discrepancy points to the limitations of the database on near-surface site-conditions used in project SHARE in what concerns stable continental regions.

  9. Phytoplankton Communities in Louisiana coastal waters and the continental shelf

    EPA Science Inventory

    Louisiana coastal waters and the adjacent continental shelf receive large freshwater and nutrient inputs from the Mississippi and Atchafalaya Rivers, creating favorable conditions for increased phytoplankton productivity. To examine inshore-offshore patterns in phytoplankton comm...

  10. Ants of three adjacent habitats of a transition region between the cerrado and caatinga biomes: the effects of heterogeneity and variation in canopy cover.

    PubMed

    Neves, F S; Queiroz-Dantas, K S; da Rocha, W D; Delabie, J H C

    2013-06-01

    Habitat heterogeneity and complexity associated with variations in climatic conditions are important factors determining the structure of ant communities in different terrestrial ecosystems. The objective of this study was to describe the horizontal and vertical distribution patterns of the ant community associated with three adjacent habitats in a transition area between the Cerrado and Caatinga biomes at the Pandeiros River, state of Minas Gerais, Brazil. We tested the following hypotheses: (1) the richness and composition of ant species and functional group structure changes between different habitats and strata; (2) habitats with higher tree species richness and density support higher ant species richness; and (3) habitats with lower variation in canopy cover support higher ant species richness. Sampling was conducted in three adjacent habitats and at three vertical strata. Ant species richness was significantly different among vertical strata. Ant species composition was different among both habitats and vertical strata and functional group structure was divergent among habitats. Partitioning of the diversity revealed that the diversity for the three components was statistically different from the one expected by the null model; α and β 2 were higher and β 1 was lower than the values expected by chance. Tree density and variation in canopy cover negatively affected ant species richness. The occurrence of different species and the changing of functional group structures in different habitats and strata suggest an ecological-evolutionary relationship between ants and their habitats and emphasize the need to implement local conservation strategies in the ecotones between biomes.

  11. Evaluation of the performance of SiBcrop model in predicting carbon fluxes and crop yields in the croplands of the US mid continental region

    NASA Astrophysics Data System (ADS)

    Lokupitiya, E.; Denning, S.; Paustian, K.; Corbin, K.; Baker, I.; Schaefer, K.

    2008-12-01

    The accurate representation of phenology, physiology, and major crop variables is important in the land- atmosphere carbon models being used to predict carbon and other exchanges of the man-made cropland ecosystems. We evaluated the performance of SiBcrop model (which is the Simple Biosphere model (SiB) with a new scheme for crop phenology and physiology) in predicting carbon exchanges of the US mid continental region which has several major crops. The use of the new phenology scheme within SiB remarkably improved the prediction of LAI and carbon fluxes for corn, soybean, and wheat crops as compared with the observed data at several Ameriflux eddy covariance flux tower sites with those crops. SiBcrop better predicted the onset and end of the growing season, harvest, interannual variability associated with crop rotation, day time carbon draw down, and day to day variability in the carbon exchanges. The model has been coupled with RAMS, the regional Atmospheric Modeling System (developed at Colorado State University), and the coupled SiBcrop-RAMS has predicted better carbon and other fluxes compared to the original SiB-RAMS. SiBcrop also predicted daily variation in biomass in different plant pools (i.e. roots, leaves, stems, and products). In this study, we further evaluated the performance of SiBcrop by comparing the yield estimates based on the grain/seed biomass at harvest predicted by SiBcrop for relevant major crops, against the county-level crop yields reported by the US National Agricultural Statistics Service (NASS). Initially, the model runs were based on crop maps scaled at 40 km resolution; the maps were used to derive the fraction of corn, soybean, and wheat at each grid cell across the US Mid Continental Intensive (MCI) region under the North American Carbon Program (NACP). The yield biomass carbon values (at harvest) predicted for each grid cell by SiBcrop were extrapolated to derive the county-level yield biomass carbon values, which were then

  12. Petrofabrics and Water Contents of Peridotites from the Western Gneiss Region (Norway): Implications for Fabric Transition of Olivine in Continental Subduction Zones

    NASA Astrophysics Data System (ADS)

    Wang, Q.; Xia, Q.; O'Reilly, S.; Griffin, W. L.; Beyer, E.

    2010-12-01

    The Western Gneiss Region (WGR) of Norway lies within the Caledonian collision zone, which was subjected to the eclogites-facies metamorphism during the Silurian-Devonian continental collision of Baltica and Laurentia. Exhumed from depths of 80-200 km, the peridotites enclosed in Proterozoic gneisses in the WGR can be divided into two groups: garnet-free Archean dunites with extremely depleted compositions, and garnet-bearing peridotites that resulted from refertilization of the dunites during the Proterozoic time (Beyer et al., 2006). Therefore peridotites from the WGR provide a unique window to investigate petrofabrics of the upper mantle with different compositions and deformation history. Using the electron backscatter diffraction (EBSD) technique, we measured lattice-preferred orientations of 10 peridotite samples from the WGR. The water contents of olivine were determined by Fourier transform infrared spectroscopy in Paterson’s calibration (1982). For dunites from Almklovdalen in the southern WGR, one sample with water content of 0.5 ppm H2O displays the [100](010) (the A-type) olivine fabric, while the other two samples with water contents of 5-7 ppm H2O developed [001](010) (the B-type) fabric. In contrast, garnet lherzolites and wehrlites with various water content of 0.2-7 ppm H2O from Almklovdalen and Gurskøy yield the B-type fabric. The [001](100) (the C-type) fabric of olivine was observed in garnet harzburgite with very low water content (1.4 ppm H2O) from Otrøy in the northern WGR, where coesite, majoritic garnet and microdiamond were found by previous studies. Compared with the fabric diagram of olivine proposed by Jung and Karato (2001), all 10 peridotite samples came from dry conditions, under which the A-type or the D-type fabric is expected at low or high stress, respectively. Clearly, our results indicate that water is not the key to producing the different fabrics in the WGR peridotites, and the Proterozoic refertilization did not

  13. Regional Variation of Lg Coda Q in the Continental United States and its Relation to Crustal Structure and Evolution

    NASA Astrophysics Data System (ADS)

    Baqer, S.; Mitchell, B. J.

    Records from broadband digital stations have allowed us to map regional variations of Lg coda Q across almost the entire United States. Using a stacked ratio method we obtained estimates of Q0 (Lg coda Q at 1 Hz) and its frequency dependence, , for 218 event-station pairs. Those sets of estimates were inverted using a back-projection method to obtain tomographic images showing regional variations of Q0 and . Q0 is lowest (250-300) in the California coastal regions and the western part of the Basin and Range province, and highest (650-750) in the northern Appalachians and a portion of the Central Lowlands. Intermediate values occur in the Colorado Plateau (300-500), the Columbia Plateau (300-400), the Rocky Mountains (450-550), the Great Plains (500-650), the Gulf Coastal Plain and the southern portion of Atlantic Coastal Plain (400-500), and the portions of the Central Lowlands surrounding the high-Q region (500-550). The pattern of Q0 variations suggests that the United States can be divided into two large Q provinces. One province spans the area from the Rocky Mountains to the Atlantic coast, is tectonically stable, and exhibits relatively high Q0 . The other extends westward from the approximate western margin of the Rocky Mountains to the Pacific coast, is tectonically active, and exhibits low Q0 . The transition from high to low Lg coda Q in the western United States lies further to the west than does an upper mantle transition for Q and electrical resistivity found in earlier studies. The difference in Q0 between the western and eastern United States can be attributed to a greater amount of interstitial crustal fluids in the west. Regions of moderately reduced Q within the stable platform often occur where there are accumulations of Mesozoic and younger sediments. Reduced Q0 in the southeastern United States may not be due to anelasticity but may rather be explained by a gradational velocity increase at the crust-mantle boundary that causes shear

  14. Estimation of continental precipitation recycling

    NASA Technical Reports Server (NTRS)

    Brubaker, Kaye L.; Entekhabi, Dara; Eagleson, P. S.

    1993-01-01

    The total amount of water that precipitates on large continental regions is supplied by two mechanisms: 1) advection from the surrounding areas external to the region and 2) evaporation and transpiration from the land surface within the region. The latter supply mechanism is tantamount to the recycling of precipitation over the continental area. The degree to which regional precipitation is supplied by recycled moisture is a potentially significant climate feedback mechanism and land surface-atmosphere interaction, which may contribute to the persistence and intensification of droughts. Gridded data on observed wind and humidity in the global atmosphere are used to determine the convergence of atmospheric water vapor over continental regions. A simplified model of the atmospheric moisture over continents and simultaneous estimates of regional precipitation are employed to estimate, for several large continental regions, the fraction of precipitation that is locally derived. The results indicate that the contribution of regional evaporation to regional precipitation varies substantially with location and season. For the regions studied, the ratio of locally contributed to total monthly precipitation generally lies between 0. 10 and 0.30 but is as high as 0.40 in several cases.

  15. Comparison between simulated and observed chemical composition of fine aerosols in Paris (France) during springtime: contribution of regional versus continental emissions

    NASA Astrophysics Data System (ADS)

    Sciare, J.; D'Argouges, O.; Sarda-Estève, R.; Gaimoz, C.; Gros, V.; Zhang, Q. J.; Beekmann, M.; Sanchez, O.

    2010-07-01

    Hourly concentrations of inorganic salts (ions) and carbonaceous material in fine aerosols (aerodynamic diameter, A.D.<2.5 μm) have been determined experimentally from fast measurements performed for a 3-week period in spring 2007 in Paris (France). The sum of these two chemical components (ions and carbonaceous aerosols) has shown to account for most of the fine aerosol mass (PM2.5). This time-resolved dataset allowed investigating the factors controlling the levels of PM2.5 in Paris and showed that polluted periods with PM2.5<15 μg/m3 were characterized by air masses of continental (North-Western Europe) origin and chemical composition made by 75% of ions. By contrast, periods with clean marine air masses have shown the lowest PM2.5 concentrations (typically of about 10 μg/m3); carbonaceous aerosols contributing for most of this mass (typically 75%). In order to better discriminate between regional and continental contributions to the observed chemical composition and concentrations of PM2.5 over Paris, a comparative study was performed between this time-resolved dataset and the outputs of a chemistry transport model (CHIMERE), showing a relatively good capability of the model to reproduce the time-limited intense maxima observed in the field for PM2.5 and ion species. Different model scenarios were then investigated switching off regional and European (North-Western and Central) emissions. Results of these scenarios have clearly shown that most of the ions observed over Paris during polluted periods, were either transported or formed in-situ from gas precursors transported from Northern Europe. By opposite, long-range transport from Europe appeared to poorly contribute to the levels of carbonaceous aerosols observed over Paris. The model failed to properly account for the concentration levels and variability of secondary organic aerosols (SOA) determined experimentally by the EC-tracer method. The abundance of SOA (relatively to organic aerosol, OA) was as

  16. Regional 3D Numerical Modeling of the Lithosphere-Mantle System: Implications for Continental Rift-Parallel Surface Velocities

    NASA Astrophysics Data System (ADS)

    Stamps, S.; Bangerth, W.; Hager, B. H.

    2014-12-01

    The East African Rift System (EARS) is an active divergent plate boundary with slow, approximately E-W extension rates ranging from <1-6 mm/yr. Previous work using thin-sheet modeling indicates lithospheric buoyancy dominates the force balance driving large-scale Nubia-Somalia divergence, however GPS observations within the Western Branch of the EARS show along-rift motions that contradict this simple model. Here, we test the role of mantle flow at the rift-scale using our new, regional 3D numerical model based on the open-source code ASPECT. We define a thermal lithosphere with thicknesses that are systematically changed for generic models or based on geophysical constraints in the Western branch (e.g. melting depths, xenoliths, seismic tomography). Preliminary results suggest existing variations in lithospheric thicknesses along-rift in the Western Branch can drive upper mantle flow that is consistent with geodetic observations.

  17. Declining water budget in a deep regional aquifer assessed by geostatistical simulations of stable isotopes: Case study of the Saharan "Continental Intercalaire"

    NASA Astrophysics Data System (ADS)

    Gonçalvès, Julio; Vallet-Coulomb, Christine; Petersen, Jade; Hamelin, Bruno; Deschamps, Pierre

    2015-12-01

    The stable isotopes of water were used to improve the determination of the groundwater budget of the deep Saharan "Continental Intercalaire" (CI), a deep confined aquifer. Mixing processes between the CI and shallower aquifers have been described in several regional studies over the last few decades, based on observed isotopic differences between local water masses. Here, we improve the quantitative determination of the discharge flux of this aquifer in one of its main outlet regions, the Djeffara plain in Tunisia, based on geostatistics and a simple mass balance mixing model, applied before and after the beginning of extensive pumping in the 1970s. First, the average values of δ18O and δ2H were precisely documented in the mixing zone between CI water and the local recharge, based on conditional simulations using spatially distributed isotopic data. Together with the available estimate of local recharge and conservative hypotheses on the isotopic end-members, we estimate the discharge flux of the CI in the Djeffara plain at 1.78 ± 1.03 m3 s-1 in 1970, probably near natural steady-state, reduced to 1.02 ± 0.58 m3 s-1 in 2004 under strong anthropogenic pressure, related to the drastic increase in pumping rates in the deep CI aquifer during this period. Considering the general groundwater budget over the entire CI aquifer, we estimate a recharge value of 5.13 m3 s-1, or 6.5 mm yr-1 over the 25,000 km2 of recharge area in the Saharan Atlas. This value is in line with the evaluation of 2.1 mm yr-1 obtained recently from the GRACE satellite gravity data for the overall outcrops considering that recharge occurs mostly in the Atlas region.

  18. PTt path in metamorphic rocks of the Khoy region (northwest Iran) and their tectonic significance for Cretaceous Tertiary continental collision

    NASA Astrophysics Data System (ADS)

    Azizi, H.; Moinevaziri, H.; Mohajjel, M.; Yagobpoor, A.

    2006-06-01

    Metamorphic rocks in the Khoy region are exposed between obducted ophiolites to the southwest and sedimentary rocks of Precambrian-Paleozoic age to the northeast. The Qom formation (Oligocene-Miocene) with a basal conglomerate transgressively overlies all of these rocks. The metamorphic rocks consist of both metasediments and metabasites. The metasediments are micaschist, garnet-staurolite schist and garnet-staurolite sillimanite schist with some meta-arkose, marble and quartzite. The metabasites are metamorphosed to greenschist and amphibolite facies from a basaltic and gabbroic protolith of tholeiitic and calc-alkaline rocks. Geothermobarometry based on the equivalence of minerals stability and their paragenesis in these rocks and microprobe analyses by several different methods indicate that metamorphism occurred in a temperature range between 450 and 680 °C at 5.5 and 7.5 kb pressure. Rims of minerals reveal a considerable decrease of pressure (<2 kb) and insignificant decrease of temperature. The PTt path of this metamorphism is normal. The MFG line passes above the triple junction of Al 2SiO 5 polymorphs, and the average geothermal gradient during metamorphism was from 27 to 37 °C/km, which is more concordant with the temperature regime of collision zones. We infer that crustal thickening during post-Cretaceous (possibly Eocene) collision of the Arabian plate and the Azerbaijan-Albourz block was the main factor that caused the metamorphism in the studied area.

  19. Crustal structure of the Altiplano from broadband regional waveform modeling: Implications for the composition of thick continental crust

    NASA Astrophysics Data System (ADS)

    Swenson, Jennifer L.; Beck, Susan L.; Zandt, George

    2000-01-01

    We have modeled the full waveforms from six intermediate-depth and two shallow earthquakes recorded at regional distances by the BANJO Broadband Andean Joint Experiment (BANJO) and Seismic Exploration of the Deep Altiplano (SEDA) portable seismic networks in the central Andes. In this study we utilize data from those BANJO and SEDA stations located within the Altiplano and Eastern Cordillera. We used reflectivity synthetic seismograms and a grid search to constrain four parameters of the Altiplano-Eastern Cordillera lithosphere: crustal thickness, average crustal velocity (Vp), and crustal and upper mantle Poisson's ratios (σcrust and σmantle). Using our grid search, we investigated the crustal and upper mantle structure along 36 individual event station paths and applied forward modeling to 56 event station paths. Robust models for the Altiplano that provide the best overall fit between the data and synthetic seismograms are characterized by an average Vp of 5.75-6.25 km/s, crustal thicknesses of 60-65 km, σcrust = 0.25, and σmantle = 0.27-0.29. We find a north-south variation in the structure of the Altiplano, with the crust south of the BANJO transect characterized by either lower than average crustal P wave velocities or a slightly higher σcrust relative to crust north of the BANJO transect. These results are consistent with a model of crustal thickening caused predominantly by tectonic shortening of felsic crust, rather than by underplating or magmatic intrusion from the mantle.

  20. Electron microscopic analysis of synaptic inputs from the median preoptic nucleus and adjacent regions to the supraoptic nucleus in the rat.

    PubMed

    Armstrong, W E; Tian, M; Wong, H

    1996-09-16

    The median preoptic nucleus (MnPo) is critical for normal fluid balance, mediating osmotically evoked drinking and neurohypophysial hormone secretion. The influence of the MnPo on vasopressin and oxytocin release is in part through direct connections to the supraoptic and paraventricular nucleus. In the present investigation the synaptic contacts between the MnPo and supraoptic neurons were investigated in rats by ultrastructural examination of terminals labeled anterogradely with the tracers Phaseolus vulgaris-leucoagglutinin or biotinylated dextran. At the light microscopic level, labeled fibers within the supraoptic nucleus branched frequently, were punctuated by varicosities, and were distributed throughout the nucleus without preference for the known distributions of oxytocin and vasopressin neurons. At the ultrastructural level, synapses were associated with many of these varicosities. The ratio of labeled axodendritic to axosomatic synapses encountered was roughly consistent with a uniform innervation of dendrites and somata. The great majority of synapses were characterized by symmetrical contacts. Similar results were found for a few injections made in the organum vasculosum of the lamina terminalis, just rostral to the MnPo, and in the immediately adjacent periventricular preoptic area. Coupled with other recent anatomical and electrophysiological evidence, these results suggest there is a strong monosynaptic pathway from structures along the ventral lamina terminalis to the supraoptic nucleus.

  1. Late Cretaceous intraplate silicic volcanism in the Lake Chad region: incipient continental rift volcanism vs. Cameroon Line volcanism

    NASA Astrophysics Data System (ADS)

    Shellnutt, G.; Lee, T. Y.; Torng, P. K.; Yang, C. C.

    2015-12-01

    The crustal evolution of west-central Africa during the Cretaceous was directly related to plate motion associated with the opening of the central Atlantic Ocean. Late Cretaceous (~66 Ma) to recent magmatism related to the Cameroon Line stretches from Northern Cameroon (i.e. Golda Zuelva) to the Gulf of Guinea (i.e. Pagalu) and is considered to be due to mantle-crust interaction. The volcanic rocks at Hadjer el Khamis, west-central Chad, are considered to be amongst the oldest volcanic rocks of the Cameroon Line but their relationship is uncertain because they erupted during a period of a regional extension associated with the opening of the Late Cretaceous (~75 Ma) Termit basin. The silicic volcanic rocks can be divided into a peraluminous group and a peralkaline group with both rock types having similar chemical characteristics as within-plate granitoids. In situ U/Pb zircon dating yielded a mean 206Pb/238U age of 74.4 ± 1.3 Ma and indicates the rocks erupted ~10 million years before the next oldest eruption attributed to the Cameroon Line. The Sr isotopes (i.e. ISr = 0.7050 to 0.7143) show a wide range but the Nd isotopes (i.e. 143Nd/144Ndi = 0.51268 to 0.51271) are more uniform and indicate that the rocks were derived from a moderately depleted mantle source. Major and trace elemental modeling show that the silicic rocks likely formed by shallow fractionation of a mafic parental magma where the peraluminous rocks experienced crustal contamination and the peralkaline rocks did not. The silicic rocks are more isotopically similar to Late Cretaceous basalts in the Doba and Bongor basins (i.e. ISr = 0.7040 to 0.7060; 143Nd/144Ndi = 0.51267 to 0.51277) of southern Chad than to rocks of the Cameroon Line (i.e. ISr = 0.7026 to 0.7038; 143Nd/144Ndi = 0.51270 to 0.51300). Given the age and isotopic compositions, it is likely that the silicic volcanic rocks of the Lake Chad area are related to Late Cretaceous extensional tectonics rather than to Cameroon Line magmatism.

  2. Thyroid abnormality trend over time in northeastern regions of Kazakstan, adjacent to the Semipalatinsk nuclear test site: a case review of pathological findings for 7271 patients.

    PubMed

    Zhumadilov, Z; Gusev, B I; Takada, J; Hoshi, M; Kimura, A; Hayakawa, N; Takeichi, N

    2000-03-01

    From 1949 through 1989 nuclear weapons testing carried out by the former Soviet Union at the Semipalatinsk Nuclear Test Site (SNTS) resulted in local fallout affecting the residents of Semipalatinsk, Ust-Kamenogorsk and Pavlodar regions of Kazakstan. To investigate the possible relationship between radiation exposure and thyroid gland abnormalities, we conducted a case review of pathological findings of 7271 urban and rural patients who underwent surgery from 1966-96. Of the 7271 patients, 761 (10.5%) were men, and 6510 (89.5%) were women. The age of the patients varied from 15 to 90 years. Overall, a diagnosis of adenomatous goiter (most frequently multinodular) was found in 1683 patients (63.4%) of Semipalatinsk region, in 2032 patients (68.6%) of Ust-Kamenogorsk region and in 1142 patients (69.0%) of Pavlodar region. In the period 1982-96, as compared before, there was a noticeable increase in the number of cases of Hashimoto's thyroiditis and thyroid cancer. Among histological forms of thyroid cancer, papillary (48.1%) and follicular (33.1%) predominated in the Semipalatinsk region. In later periods (1987-96), an increased frequency of abnormal cases occurred among patients less than 40 years of age, with the highest proportion among patients below 20 in Semipalatinsk and Ust-Kamenogorsk regions of Kazakstan. Given the positive findings of a significant cancer-period interaction, and a significant trend for the proportion of cancer to increase over time, we recommend more detailed and etiologic studies of thyroid disease among populations exposed to radiation fallout from the SNTS in comparison to non-exposed population.

  3. A comparison of recent Earth gravitational models with emphasis on their contribution in refining the gravity and geoid at continental or regional scale

    NASA Astrophysics Data System (ADS)

    Arabelos, D. N.; Tscherning, C. C.

    2010-11-01

    Since the publication of the Earth gravitational model (EGM)96 considerable improvements in the observation techniques resulted in the development of new improved models. The improvements are due to the availability of data from dedicated gravity mapping missions (CHAMP, GRACE) and to the use of 5' × 5' terrestrial and altimetry derived gravity anomalies. It is expected that the use of new EGMs will further contribute to the improvement of the resolution and accuracy of the gravity and geoid modeling in continental and regional scale. To prove this numerically, three representative Earth gravitational models are used for the reduction of several kinds of data related to the gravity field in different places of the Earth. The results of the reduction are discussed regarding the corresponding covariance functions which might be used for modeling using the least squares collocation method. The contribution of the EIGEN-GL04C model in most cases is comparable to that of EGM96. However, the big difference is shown in the case of EGM2008, due not only to its quality but obviously to its high degree of expansion. Almost in all cases the variance and the correlation length of the covariance functions of data reduced to this model up to its maximum degree are only a few percentages of corresponding quantities of the same data reduced up to degree 360. Furthermore, the mean value and the standard deviation of the reduced gravity anomalies in extended areas of the Earth such as Australia, Arctic region, Scandinavia or the Canadian plains, vary between -1 and +1 and between 5 and 10 × 10-5 ms-2, respectively, reflecting the homogenization of the gravity field on a regional scale. This is very important in using least squares collocation for regional applications. However, the distance to the first zero-value was in several cases much longer than warranted by the high degree of the expansion. This is attributed to errors of medium wavelengths stemming from the lack of, e

  4. Modes of continental decretion in western Canada

    NASA Astrophysics Data System (ADS)

    Cook, F. A.

    2010-12-01

    Between the Archean Slave Province and the Pacific Ocean, the North American continent in Canada appears to have ‘grown’ westward during Paleoproterozoic (Wopmay) and Paleozoic-Mesozoic (Cordilleran) orogenesis. However, results from geological observations combined with regional geophysical surveys lead to interpretations in which pre-orogenic basement in both the Wopmay and the Cordillera projects far beneath proposed ‘accreted’ terranes. In the Wopmay orogen (1.89-1.84 Ga), deep geophysical images indicate that Archean Slave basement projects in the subsurface up to 50 km west of the Medial zone (formerly Wopmay fault), a boundary that was previously interpreted as the transition from Slave basement to accreted terrane basement. The Slave basement appears as a west-tapering tectonic wedge into accreted(?) rocks, consistent with an interpretation by Hildebrand and Bowring (Geology, 1999) that the Archean lithosphere that was formerly west of the wedge broke off and was recycled. In the Cordillera, cross sections of the lithosphere illustrate that lower crustal and upper mantle rocks as much as 2/3 of the distance across the orogen can be stratigraphically, geologically and seismically correlated to the ancient cratonic margin. Retrodeformation of rocks that were deposited on or adjacent to the craton leads to the conclusion that, prior to the onset of terrane accretion, the North American margin and associated rocks projected even farther west (today’s coordinates) - at least as far as the modern margin. Apparently, as flakes of terranes were added to the surface in the western regions of the Cordillera, the North American lithosphere, which may have been foreshortened during contraction, was tectonically and/or thermally eroded from below. As a result, terrane accretion in the Cordillera apparently resulted in a net decretion of continental lithosphere. Together, these observations lead to the interpretation that the processes responsible for

  5. Regional long-term model of radioactivity dispersion and fate in the Northwestern Pacific and adjacent seas: application to the Fukushima Dai-ichi accident.

    PubMed

    Maderich, V; Bezhenar, R; Heling, R; de With, G; Jung, K T; Myoung, J G; Cho, Y-K; Qiao, F; Robertson, L

    2014-05-01

    The compartment model POSEIDON-R was modified and applied to the Northwestern Pacific and adjacent seas to simulate the transport and fate of radioactivity in the period 1945-2010, and to perform a radiological assessment on the releases of radioactivity due to the Fukushima Dai-ichi accident for the period 2011-2040. The model predicts the dispersion of radioactivity in the water column and in sediments, the transfer of radionuclides throughout the marine food web, and subsequent doses to humans due to the consumption of marine products. A generic predictive dynamic food-chain model is used instead of the biological concentration factor (BCF) approach. The radionuclide uptake model for fish has as a central feature the accumulation of radionuclides in the target tissue. The three layer structure of the water column makes it possible to describe the vertical structure of radioactivity in deep waters. In total 175 compartments cover the Northwestern Pacific, the East China and Yellow Seas and the East/Japan Sea. The model was validated from (137)Cs data for the period 1945-2010. Calculated concentrations of (137)Cs in water, bottom sediments and marine organisms in the coastal compartment, before and after the accident, are in close agreement with measurements from the Japanese agencies. The agreement for water is achieved when an additional continuous flux of 3.6 TBq y(-1) is used for underground leakage of contaminated water from the Fukushima Dai-ichi NPP, during the three years following the accident. The dynamic food web model predicts that due to the delay of the transfer throughout the food web, the concentration of (137)Cs for piscivorous fishes returns to background level only in 2016. For the year 2011, the calculated individual dose rate for Fukushima Prefecture due to consumption of fishery products is 3.6 μSv y(-1). Following the Fukushima Dai-ichi accident the collective dose due to ingestion of marine products for Japan increased in 2011 by a

  6. Molecular Dissection of the 5' Region of no-on-transientA of Drosophila melanogaster Reveals cis-Regulation by Adjacent dGpi1 Sequences.

    PubMed Central

    Sandrelli, F; Campesan, S; Rossetto, M; Benna, C; Zieger, E; Megighian, A; Couchman, M; Kyriacou, C; Costa, R

    2001-01-01

    The nonA gene of Drosophila melanogaster is important for normal vision, courtship song, and viability and lies approximately 350 bp downstream of the dGpi1 gene. Full rescue of nonA mutant phenotypes can be achieved by transformation with a genomic clone that carries approximately 2 kb of 5' regulatory material and that encodes most of the coding sequence of dGpi1. We have analyzed this 5' region by making a series of deleted fragments, fusing them to yeast GAL4 sequences, and driving UAS-nonA expression in a mutant nonA background. Regions that both silence and enhance developmental tissue-specific expression of nonA and that are necessary for generating optomotor visual responses are identified. Some of these overlap the dGpi1 sequences, revealing cis-regulation by neighboring gene sequences. The largest 5' fragment was unable to rescue the normal electroretinogram (ERG) consistently, and no rescue at all was observed for the courtship song phenotype. We suggest that sequences within the nonA introns that were missing in the UAS-nonA cDNA may carry enhancer elements for these two phenotypes. Finally, we speculate on the striking observation that some of the cis-regulatory regions of nonA appear to be embedded within the coding regions of dGpi1. PMID:11156995

  7. The 1987 estimate of undiscovered uranium endowment in solution-collapse breccia pipes in the Grand Canyon region of northern Arizona and adjacent Uta

    SciTech Connect

    Finch, W.I.; Sutphin, H.B.; Pierson, C.T.; McCammon, R.B.; Wenrich, K.J.

    1990-01-01

    This book is based on a new method published in U.S. Geological Survey Circular 994 and is the second assessment made in accordance with the 1984 Memorandum of Understanding between the U.S. Department of the Interior and the U.S. Department of Energy. The first estimate was published as U.S. Geological Survey Open-File Report 80-2. The endowment estimates are reported for 26 areas in the following 1{degrees} {times} 2{degrees} guadrangles: Grand Canyon, Marble Canyon, Williams, Flagstaff, Prescott, Holbrook, and St. Johns, Ariz., and Cedar City, Utah. The total uranium endowment is about eight times larger than reported in 1980 by the Department of Energy. The Grand Canyon region has the potential of becoming the second most important domestic uranium producer after the most production San Juan Basin uranium region in New Mexico.

  8. Limited Flow of Continental Crust at UHP Depths: Coupled Age and Trace-Element Analyses of Titanite in the Western Gneiss Region, Norway

    NASA Astrophysics Data System (ADS)

    Garber, J. M.; Hacker, B. R.; Kylander-Clark, A. R.

    2015-12-01

    Coupled age and trace-element data from titanites in the Western Gneiss Region (WGR) of Norway suggest that continental crust underwent limited recrystallization and ductile flow through ~40 My of deep subduction and subsequent exhumation. Precambrian igneous titanites in granitic to tonalitic orthogneisses from the WGR were metastably preserved though Caledonian ultrahigh-pressure (UHP) metamorphism and variably recrystallized through subsequent amphibolite-facies metamorphism from ~420-385 Ma. The inherited Precambrian titanites are not present everywhere but rather cluster primarily in a cooler "southern domain" (peak T ~650oC) and a hotter "northern domain" (peak T ~750-800oC).Titanite data were collected using LASS (laser-ablation split stream inductively-coupled plasma mass spectrometry) at UCSB, and a principal component analysis (PCA) was used to define age and trace-element populations. These data indicate that inherited titanites are LREE-enriched, HFSE-enriched, and have higher Th/U, consistent with Precambrian neocrystallization from a granitic melt. In contrast, the recrystallized titanites have generally lower Th/U and flat, LREE-depleted, or hump-shaped trace-element patterns. These data suggest that (1) Caledonian titanite recrystallization occurred in the presence of LREE-depleted melts or fluids, or that (2) recrystallization was accompanied by a "typical" granitic melt, but that titanite/bulk-rock distribution coefficients are different for neo- and recrystallization; on-going whole-rock analyses will clarify these hypotheses. Critically, the geochemical signature of recrystallized titanite in felsic orthogneisses is comparable across the entire WGR - emphasizing that the petrologic process of titanite recrystallization was similar orogen-wide, but was less extensive in the domains where inherited titanite was preserved. In this case, large volumes of crust outside of the "old domains" may also have retained metastable titanite during subduction

  9. Climatic Factors Drive Population Divergence and Demography: Insights Based on the Phylogeography of a Riparian Plant Species Endemic to the Hengduan Mountains and Adjacent Regions

    PubMed Central

    Wang, Zhi-Wei; Chen, Shao-Tian; Nie, Ze-Long; Zhang, Jian-Wen; Zhou, Zhuo; Deng, Tao; Sun, Hang

    2015-01-01

    Quaternary climatic factors have played a significant role in population divergence and demography. Here we investigated the phylogeography of Osteomeles schwerinae, a dominant riparian plant species of the hot/warm-dry river valleys of the Hengduan Mountains (HDM), Qinling Mountains (QLM) and Yunnan-Guizhou Plateau (YGP). Three chloroplast DNA (cpDNA) regions (trnD-trnT, psbD-trnT, petL-psbE), one single copy nuclear gene (glyceraldehyde 3-phosphate dehydrogenase; G3pdh), and climatic data during the Last Interglacial (LIG; c. 120–140 ka), Last Glacial Maximum (LGM; c. 21 ka), and Current (c. 1950–2000) periods were used in this study. Six cpDNA haplotypes and 15 nuclear DNA (nDNA) haplotypes were identified in the 40 populations of O. schwerinae. Spatial Analysis of Molecular Variance, median-joining networks, and Bayesian phylogenetic trees based on the cpDNA and nDNA datasets, all suggested population divergence between the QLM and HDM-YGP regions. Our climatic analysis identified significant heterogeneity of the climatic factors in the QLM and HDM-YGP regions during the aforementioned three periods. The divergence times based on cpDNA and nDNA haplotypes were estimated to be 466.4–159.4 ka and 315.8–160.3 ka, respectively, which coincide with the time of the weakening of the Asian monsoons in these regions. In addition, unimodal pairwise mismatch distribution curves, expansion times, and Ecological Niche Modeling suggested a history of population expansion (rather than contraction) during the last glaciation. Interestingly, the expansion times were found being well consistent with the intensification of the Asian monsoons during this period. We inferred that the divergence between the two main lineages is probably caused by disruption of more continuous distribution because of weakening of monsoons/less precipitation, whilst subsequent intensification of the Asian monsoons during the last glaciation facilitated the expansion of O. schwerinae

  10. Intraplate volcanism controlled by back-arc and continental structures in NE Asia inferred from transdimensional Bayesian ambient noise tomography

    NASA Astrophysics Data System (ADS)

    Kim, Seongryong; Tkalčić, Hrvoje; Rhie, Junkee; Chen, Youlin

    2016-08-01

    Intraplate volcanism adjacent to active continental margins is not simply explained by plate tectonics or plume interaction. Recent volcanoes in northeast (NE) Asia, including NE China and the Korean Peninsula, are characterized by heterogeneous tectonic structures and geochemical compositions. Here we apply a transdimensional Bayesian tomography to estimate high-resolution images of group and phase velocity variations (with periods between 8 and 70 s). The method provides robust estimations of velocity maps, and the reliability of results is tested through carefully designed synthetic recovery experiments. Our maps reveal two sublithospheric low-velocity anomalies that connect back-arc regions (in Japan and Ryukyu Trench) with current margins of continental lithosphere where the volcanoes are distributed. Combined with evidences from previous geochemical and geophysical studies, we argue that the volcanoes are related to the low-velocity structures associated with back-arc processes and preexisting continental lithosphere.

  11. Ordovician of the Sauk megasequence in the Ozark region of northern Arkansas and parts of Missouri and adjacent states: Chapter 11

    USGS Publications Warehouse

    Ethington, Raymond L.; Repetski, John E.; Derby, James R.

    2012-01-01

    The oldest formation that crops out in the region is the Jefferson City Dolomite, which may be present in outcrops along incised river valleys near the Missouri-Arkansas border. Rare fossil gastropods, bivalves, brachiopods, conodonts, and trilobites permit correlation of the Cotter through Powell Dolomites with Ibexian strata elsewhere in Laurentia. Conodonts in the Black Rock Limestone Member of the Smithville Formation and the upper part of the Powell Dolomite confirm regional relationships that have been suggested for these units; those of the Black Rock Limestone Member are consistent with deposition under more open marine conditions than existed when older and younger units were forming. Brachiopods and conodonts from the overlying Everton Formation assist in interpreting complex facies within that formation and its correlation to equivalent rocks elsewhere. The youngest conodonts in the Everton Formation provide an age limit for the Sauk-Tippecanoe unconformity near the southern extremity of the great American carbonate bank. The correlation to coeval strata in the Ouachita Mountains of central Arkansas and in the Arbuckle Mountains of Oklahoma and to rocks penetrated in wells drilled in the Reelfoot rift basin has been improved greatly in recent years by integration of biostratigraphic data with lithologic information.

  12. The Enhancer of Split Complex and Adjacent Genes in the 96f Region of Drosophila Melanogaster Are Required for Segregation of Neural and Epidermal Progenitor Cells

    PubMed Central

    Schrons, H.; Knust, E.; Campos-Ortega, J. A.

    1992-01-01

    The Enhancer of split complex [E(spl)-C] of Drosophila melanogaster is located in the 96F region of the third chromosome and comprises at least seven structurally related genes, HLH-mδ, HLH-mγ, HLH-mβ, HLH-m3, HLH-m5, HLH-m7 and E(spl). The functions of these genes are required during early neurogenesis to give neuroectodermal cells access to the epidermal pathway of development. Another gene in the 96F region, namely groucho, is also required for this process. However, groucho is not structurally related to, and appears to act independently of, the genes of the E(spl)-C; the possibility is discussed that groucho acts upstream to the E(spl)-C genes. Indirect evidence suggests that a neighboring transcription unit (m4) may also take part in the process. Of all these genes, only gro is essential; m4 is a dispensable gene, the deletion of which does not produce detectable morphogenetic abnormalities, and the genes of the E(spl)-C are to some extent redundant and can partially substitute for each other. This redundancy is probably due to the fact that the seven genes of the E(spl)-C encode highly conserved putative DNA-binding proteins of the bHLH family. The genes of the complex are interspersed among other genes which appear to be unrelated to the neuroepidermal lineage dichotomy. PMID:1427039

  13. Revision of Errhomeninae and Aphrodinae (Hemiptera, Cicadomorpha) in Italy with remarks on their variability and distribution in adjacent regions and description of three new taxa.

    PubMed

    Guglielmino, Adalgisa; Bückle, Christoph

    2015-01-15

    A revision of the subfamilies Errhomeninae and Aphrodinae in Italy is presented. Two new species, Anoscopus gorloppus and Anoscopus carlebippus, and one new subspecies Anoscopus albifrons mappus are described. Anoscopus dubius Gębicki & Bednarzyk is established as subspecies of Anoscopus flavostriatus (Donovan) (stat. nov.), Aphrodes siracusae (Matsumura) is transferred to the genus Anoscopus (comb. nov.). Anoscopus samuricus Tshmir is recorded in Italy for the first time. Information concerning ecology and regional distribution is given for all taxa present in Italy. Genital morphology and variability of colouration are figured for many taxa. A morphometric analysis based on measurements of aedeagus and body is conducted for the taxa of the Aphrodes bicincta group. Keys for the Italian species of Aphrodes and Anoscopus are given. Distribution and specific characters of Anoscopus assimilis (Signoret) and Anoscopus alpinus (Wagner) are presented. Differences between Italian populations and conspecific ones in other European regions, and reasons for the particularly high variability in the Alpine areas of Italy are discussed. A list of 19 species and two subspecies, presently recorded from Italy is given. 

  14. Spreading and slope instability at the continental margin offshore Mt Etna, imaged by high-resolution 2D seismic data

    NASA Astrophysics Data System (ADS)

    Gross, Felix; Krastel, Sebastian; Behrmann, Jan-Hinrich; Papenberg, Cord; Geersen, Jacob; Ridente, Domenico; Latino Chiocci, Francesco; Urlaub, Morelia; Bialas, Jörg; Micallef, Aaron

    2015-04-01

    Mount Etna is the largest active volcano in Europe. Its volcano edifice is located on top of continental crust close to the Ionian shore in east Sicily. Instability of the eastern flank of the volcano edifice is well documented onshore. The continental margin is supposed to deform as well. Little, however, is known about the offshore extension of the eastern volcano flank and its adjacent continental margin, which is a serious shortcoming in stability models. In order to better constrain the active tectonics of the continental margin offshore the eastern flank of the volcano, we acquired and processed a new marine high-resolution seismic and hydro-acoustic dataset. The data provide new detailed insights into the heterogeneous geology and tectonics of shallow continental margin structures offshore Mt Etna. In a similiar manner as observed onshore, the submarine realm is characterized by different blocks, which are controlled by local- and regional tectonics. We image a compressional regime at the toe of the continental margin, which is bound to an asymmetric basin system confining the eastward movement of the flank. In addition, we constrain the proposed southern boundary of the moving flank, which is identified as a right lateral oblique fault movement north of Catania Canyon. From our findings, we consider a major coupled volcano edifice instability and continental margin gravitational collapse and spreading to be present at Mt Etna, as we see a clear link between on- and offshore tectonic structures across the entire eastern flank. The new findings will help to evaluate hazards and risks accompanied by Mt Etna's slope- and continental margin instability and will be used as a base for future investigations in this region.

  15. Micropaleontological Record of Post-glacial History in Lake Champlain and Adjacent Regions: Implications for Glacial Lake Drainage and Abrupt Climate Events

    NASA Astrophysics Data System (ADS)

    Cronin, T. M.; Manley, P. L.; Guilbault, J.; Berke, M.; Rayburn, J. A.; Franzi, D. A.; Knuepfer, P. L.

    2005-12-01

    Post-glacial lacustrine and marine sediments of the Lake Champlain region range from 20 to >50 meters in thickness presenting an opportunity to assess the timing of North American glacial lake drainage at multidecadal timescales and evaluate its effect on North Atlantic salinity and abrupt climate events 13.5 to 10 kyr B.P. High-resolution analysis of foraminifera and ostracodes from cores taken onshore in the Plattsburgh, N.Y. vicinity and southern Quebec and offshore in southern Lake Champlain reveal complex changes in salinity during and after the transition from pro-glacial Lake Vermont (Lake Candona in Canada) to marine sedimentation in the Champlain Sea. The microfaunal sequence (bottom to top) includes: non-marine ostracodes ( Candona) in lacustrine varves, foraminiferal assemblages (common Cassidulina reniforme), another interval of Candona-bearing sediments (sometimes containing foraminifera), and, finally, sediments from the main phase of the Champlain sea episode containing diverse foraminiferal and marine ostracode assemblages. A decrease in salinity during the Champlain Sea is also in evidence from the shift in dominance of distinct variants of Elphidium in the deep basin. The marine episode ended with a progressive salinity decrease and the formation of Lake Champlain about 10 kyr B.P. Observed salinity changes could be caused by catastrophic fresh-water influx from large glacial lakes west of the Lake Champlain region, meltwater from the retreating Laurentide Ice Sheet margin, diminished influx of marine water from the St. Lawrence due to changes in the position of the ice sheet margin and isostatic adjustment, or a combination of factors. The ages of these events were determined by estimating the reservoir effect on radiocarbon dates on marine shells through comparison with AMS dates on plant material and palynology, and shed light on the hypothesis that glacial lake discharges catalyzed abrupt climate events.

  16. Transient regional climate change: analysis of the summer climate response in a high-resolution, century-scale, ensemble experiment over the continental United States

    PubMed Central

    Diffenbaugh, Noah S.; Ashfaq, Moetasim; Scherer, Martin

    2013-01-01

    Integrating the potential for climate change impacts into policy and planning decisions requires quantification of the emergence of sub-regional climate changes that could occur in response to transient changes in global radiative forcing. Here we report results from a high-resolution, century-scale, ensemble simulation of climate in the United States, forced by atmospheric constituent concentrations from the Special Report on Emissions Scenarios (SRES) A1B scenario. We find that 21st century summer warming permanently emerges beyond the baseline decadal-scale variability prior to 2020 over most areas of the continental U.S. Permanent emergence beyond the baseline annual-scale variability shows much greater spatial heterogeneity, with emergence occurring prior to 2030 over areas of the southwestern U.S., but not prior to the end of the 21st century over much of the southcentral and southeastern U.S. The pattern of emergence of robust summer warming contrasts with the pattern of summer warming magnitude, which is greatest over the central U.S. and smallest over the western U.S. In addition to stronger warming, the central U.S. also exhibits stronger coupling of changes in surface air temperature, precipitation, and moisture and energy fluxes, along with changes in atmospheric circulation towards increased anticylonic anomalies in the mid-troposphere and a poleward shift in the mid-latitude jet aloft. However, as a fraction of the baseline variability, the transient warming over the central U.S. is smaller than the warming over the southwestern or northeastern U.S., delaying the emergence of the warming signal over the central U.S. Our comparisons with observations and the Coupled Model Intercomparison Project Phase 3 (CMIP3) ensemble of global climate model experiments suggest that near-term global warming is likely to cause robust sub-regional-scale warming over areas that exhibit relatively little baseline variability. In contrast, where there is greater

  17. Phylogeographic Structure of a Tethyan Relict Capparis spinosa (Capparaceae) Traces Pleistocene Geologic and Climatic Changes in the Western Himalayas, Tianshan Mountains, and Adjacent Desert Regions

    PubMed Central

    Wang, Qian; Zhang, Ming-Li; Yin, Lin-Ke

    2016-01-01

    Complex geological movements more or less affected or changed floristic structures, while the alternation of glacials and interglacials is presumed to have further shaped the present discontinuous genetic pattern of temperate plants. Here we consider Capparis spinosa, a xeromorphic Tethyan relict, to discuss its divergence pattern and explore how it responded in a stepwise fashion to Pleistocene geologic and climatic changes. 267 individuals from 31 populations were sampled and 24 haplotypes were identified, based on three cpDNA fragments (trnL-trnF, rps12-rpl20, and ndhF). SAMOVA clustered the 31 populations into 5 major clades. AMOVA suggests that gene flow between them might be restricted by vicariance. Molecular clock dating indicates that intraspecific divergence began in early Pleistocene, consistent with a time of intense uplift of the Himalaya and Tianshan Mountains, and intensified in mid-Pleistocene. Species distribution modeling suggests range reduction in the high mountains during the Last Glacial Maximum (LGM) as a result of cold climates when glacier advanced, while gorges at midelevations in Tianshan appear to have served as refugia. Populations of low-altitude desert regions, on the other hand, probably experienced only marginal impacts from glaciation, according to the high levels of genetic diversity. PMID:27314028

  18. Phylogeographic Structure of a Tethyan Relict Capparis spinosa (Capparaceae) Traces Pleistocene Geologic and Climatic Changes in the Western Himalayas, Tianshan Mountains, and Adjacent Desert Regions.

    PubMed

    Wang, Qian; Zhang, Ming-Li; Yin, Lin-Ke

    2016-01-01

    Complex geological movements more or less affected or changed floristic structures, while the alternation of glacials and interglacials is presumed to have further shaped the present discontinuous genetic pattern of temperate plants. Here we consider Capparis spinosa, a xeromorphic Tethyan relict, to discuss its divergence pattern and explore how it responded in a stepwise fashion to Pleistocene geologic and climatic changes. 267 individuals from 31 populations were sampled and 24 haplotypes were identified, based on three cpDNA fragments (trnL-trnF, rps12-rpl20, and ndhF). SAMOVA clustered the 31 populations into 5 major clades. AMOVA suggests that gene flow between them might be restricted by vicariance. Molecular clock dating indicates that intraspecific divergence began in early Pleistocene, consistent with a time of intense uplift of the Himalaya and Tianshan Mountains, and intensified in mid-Pleistocene. Species distribution modeling suggests range reduction in the high mountains during the Last Glacial Maximum (LGM) as a result of cold climates when glacier advanced, while gorges at midelevations in Tianshan appear to have served as refugia. Populations of low-altitude desert regions, on the other hand, probably experienced only marginal impacts from glaciation, according to the high levels of genetic diversity.

  19. Assessment of heavy metals contamination in sediments from three adjacent regions of the Yellow River using metal chemical fractions and multivariate analysis techniques.

    PubMed

    Ma, Xiaoling; Zuo, Hang; Tian, Mengjing; Zhang, Liyang; Meng, Jia; Zhou, Xuening; Min, Na; Chang, Xinyuan; Liu, Ying

    2016-02-01

    Metal chemical fractions obtained by optimized BCR three-stage extraction procedure and multivariate analysis techniques were exploited for assessing 7 heavy metals (Cr, Pb, Cd, Co, Cu, Zn and Ni) in sediments from Gansu province, Ningxia and Inner Mongolia Autonomous Regions of the Yellow River in Northern China. The results indicated that higher susceptibility and bioavailability of Cr and Cd with a strong anthropogenic source were due to their higher availability in the exchangeable fraction. A portion of Pb, Cd, Co, Zn, and Ni in reducible fraction may be due to the fact that they can form stable complexes with Fe and Mn oxides. Substantial amount of Pb, Co, Ni and Cu was observed as oxidizable fraction because of their strong affinity to the organic matters so that they can complex with humic substances in sediments. The high geo-accumulation indexes (I(geo)) for Cr and Cd showed their higher environmental risk to the aquatic biota. Principal component analysis (PCA) revealed that high toxic Cr and Cd in polluted sites (Cd in S10, S11 and Cr in S13) may be contributed to anthropogenic sources, it was consistent with the results of dual hierarchical clustering analysis (DHCA), which could give more details about contributing sources.

  20. Mantle plumes and continental tectonics.

    PubMed

    Hill, R I; Campbell, I H; Davies, G F; Griffiths, R W

    1992-04-10

    Mantle plumes and plate tectonics, the result of two distinct modes of convection within the Earth, operate largely independently. Although plumes are secondary in terms of heat transport, they have probably played an important role in continental geology. A new plume starts with a large spherical head that can cause uplift and flood basalt volcanism, and may be responsible for regional-scale metamorphism or crustal melting and varying amounts of crustal extension. Plume heads are followed by narrow tails that give rise to the familiar hot-spot tracks. The cumulative effect of processes associated with tail volcanism may also significantly affect continental crust.

  1. The northern Egyptian continental margin

    NASA Astrophysics Data System (ADS)

    Badawy, Ahmed; Mohamed, Gad; Omar, Khaled; Farid, Walid

    2015-01-01

    Africa displays a variety of continental margin structures, tectonics and sedimentary records. The northern Egyptian continental margin represents the NE portion of the North African passive continental margin. Economically, this region is of great importance as a very rich and productive hydrocarbon zone in Egypt. Moreover, it is characterized by remarkable tectonic setting accompanied by active tectonic processes from the old Tethys to recent Mediterranean. In this article, seismicity of the northern Egyptian continental margin has been re-evaluated for more than 100-years and the source parameters of three recent earthquakes (October 2012, January 2013 and July 2013) have been estimated. Moment tensor inversions of 19th October 2012 and 17th January 2013 earthquakes reveal normal faulting mechanism with strike-slip component having seismic moment of 3.5E16 N m and 4.3E15 N m respectively. The operation of the Egyptian National Seismic Network (ENSN) since the end of 1997 has significantly enhanced the old picture of earthquake activity across northern Egyptian continental margin whereas; the record-ability (annual rate) has changed from 2-events/year to 54-event/year before and after ENSN respectively. The spatial distribution of earthquakes foci indicated that the activity tends to cluster at three zones: Mediterranean Ridge (MR), Nile Cone (NC) and Eratosthenes Seamount (ERS). However, two seismic gaps are reported along Levant Basin (LEV) and Herodotus Basin (HER).

  2. Toward regional- to continental-scale estimates of vegetation canopy height: An empirical approach based on data from the Shuttle Radar Topography Mission

    NASA Astrophysics Data System (ADS)

    Walker, Wayne S.

    This dissertation investigates the feasibility of exploiting interferometric synthetic aperture radar (InSAR) data acquired during the 2000 Shuttle Radar Topography Mission (SRTM) for the purpose of obtaining regional- to continental-scale estimates of vegetation canopy height. The specific objectives were to (1) assess the quality of SRTM C- and X-band data in the context of canopy height retrieval with an emphasis on vertical accuracy and horizontal resolution, (2) determine the extent to which SRTM C-band data could be used to develop empirical models for canopy height prediction, and (3) develop a robust SRTM-based approach for generating a year-2000 baseline map of canopy height for the conterminous U.S. The assessment of SRTM data quality revealed the presence of a vegetation signal sufficient to support canopy height retrieval. In the vertical dimension, signal quality was found to be most affected by error attributed to residual phase noise, and a novel strategy for error mitigation was developed. In the horizontal dimension, the resolution of the SRTM C- and X-band data was estimated at approximately 45 meters. Pilot studies conducted in Georgia and California demonstrated that empirical estimates of canopy height could be obtained from the SRTM C-band vegetation signal in conjunction with the National Elevation Dataset assuming the availability of sufficient field reference data and an appropriate level of error mitigation. The studies also revealed the importance of stand-level characteristics, including stand size and shape in the context of phase noise reduction and stand structure where regression model development is concerned. Supported by an unprecedented confluence of national geospatial data layers as well as an extensive national reference data network, a proof-of-concept study was designed to evaluate a novel, empirical approach for broad-scale SRTM-based canopy height mapping. The study produced the first-ever InSAR-based map of canopy height

  3. Sea ice and oceanic processes on the Ross Sea continental shelf

    NASA Technical Reports Server (NTRS)

    Jacobs, S. S.; Comiso, J. C.

    1989-01-01

    The spatial and temporal variability of Antarctic sea ice concentrations on the Ross Sea continental shelf have been investigated in relation to oceanic and atmospheric forcing. Sea ice data were derived from Nimbus 7 scanning multichannel microwave radiometer (SMMR) brightness temperatures from 1979-1986. Ice cover over the shelf was persistently lower than above the adjacent deep ocean, averaging 86 percent during winter with little month-to-month of interannual variability. The large spring Ross Sea polynya on the western shelf results in a longer period of summer insolation, greater surface layer heat storage, and later ice formation in that region the following autumn.

  4. Physical oceanography of continental shelves

    SciTech Connect

    Allen, J.S.; Beardlsey, R.C.; Blanton, J.O.; Boicourt, W.C.; Butman, B.; Coachman, L.K.; Huyer, A.; Kinder, T.H.; Royer, T.C.; Schumacher, J.D.

    1983-06-01

    Knowledge of the physical oceanography of continental shelves has increased tremendously in recent years, primarily as a result of new current and hydrographic measurements made in locations where no comparable measurements existed previously. In general, observations from geographically distinct continental shelves have shown that the nature of the flow may vary considerably from region to region. Although some characteristics, such as the response of currents to wind forcing, are common to many shelves, the relative importance of various physical processes in influencing the shelf flow field frequently is different. In the last several years, the scientific literature on shelf studies has expanded rapidly, with that for separate regions, to some extent, developing independently because of the variable role played by different physical effects. Consequently, it seems that a simultaneous review of progress in physical oceanographic research in different shelf regions would be especially useful at this time in order to help assess the overall progress in the field. This multi-author report has been compiled as a result. Included are sections on the physical oceanography of continental shelves, in or off of, the eastern Bering Sea, northern Gulf of Alaska, Pacific Northwest, southern California, west Florida, southeastern US, Middle Atlantic Bight, Georges Bank and Peru. These discussions clearly point to the diverse nature of the dominant physics in several of the regions, as well as to some of the dynamical features they share in common. 390 references, 23 figures.

  5. Joint geophysical and petrological models for the lithosphere structure of the Antarctic Peninsula continental margin

    NASA Astrophysics Data System (ADS)

    Yegorova, Tamara; Bakhmutov, Vladimir; Janik, Tomasz; Grad, Marek

    2011-01-01

    The Antarctic Peninsula (AP) is a composite magmatic arc terrane formed at the Pacific margin of Gondwana. Through the late Mesozoic and Cenozoic subduction has stopped progressively from southwest to northeast as a result of a series of ridge trench collisions. Subduction may be active today in the northern part of the AP adjacent to the South Shetland Islands. The subduction system is confined by the Shackleton and Hero fracture zones. The magmatic arc of the AP continental margin is marked by high-amplitude gravity and magnetic anomaly belts reaching highest amplitudes in the region of the South Shetland Islands and trench. The sources for these anomalies are highly magnetic and dense batholiths of mafic bulk composition, which were intruded in the Cretaceous, due to partial melting of upper-mantle and lower-crustal rocks. 2-D gravity and magnetic models provide new insights into crustal and upper-mantle structure of the active and passive margin segments of the northern AP. Our models incorporate seismic refraction constraints and physical property data. This enables us to better constrain both Moho geometry and petrological interpretations in the crust and upper mantle. Model along the DSS-12 profile crosses the AP margin near the Anvers Island and shows typical features of a passive continental margin. The second model along the DSS-17 profile extends from the Drake Passage through the South Shetland Trench/Islands system and Bransfield Strait to the AP and indicates an active continental margin linked to slow subduction and on-going continental rifting in the backarc region. Continental rifting beneath the Bransfield Strait is associated with an upward of hot upper mantle rocks and with extensive magmatic underplating.

  6. Permian to Triassic I to S-type magmatic switch in the northeast Sierra Nevada de Santa Marta and adjacent regions, Colombian Caribbean: Tectonic setting and implications within Pangea paleogeography

    NASA Astrophysics Data System (ADS)

    Cardona, A.; Valencia, V.; Garzón, A.; Montes, C.; Ojeda, G.; Ruiz, J.; Weber, M.

    2010-10-01

    The Late Paleozoic to Triassic tectonics of northwestern South America have major implications for the understanding of Laurentia-Gondwana interactions that formed Pangea, and the origin of several tectonostratigraphic terranes dispersed by the break-up of this supercontinent during the formation of the Caribbean. Two mylonitic and orthogneissic granitoid suites have been recognized in the northeastern segment of the Sierra Nevada de Santa Marta, the lower Magdalena basin and the Guajira Serranias, within the Caribbean region of Colombia. For the Santa Marta region U/Pb LAM-ICP-MS analysis yielded zircon crystallization ages of 288.1 ± 4.5 Ma, 276.5 ± 5,1 Ma and 264.9 ± 4.0 Ma, related to the magmatic intrusion. Geochemical and modal variations show a compositional spectrum between diorite and granite, whereas LREE enrichment, Ti and Nb anomalies and geochemical discrimination suggest that this granitoid suite was formed within a magmatic arc setting. Inherited zircons suggest that this Early Permian plutonism was formed with the participation of Neoproterozoic and Grenvillian basement proximal to the South American continent. Evidence of a superimposed Early Triassic (ca. 250 Ma) deformational event in Santa Marta, together with a well defined S-type magmatism in the basement rocks from the adjacent lower Magdalena Valley and Guajira Peninsula regions are related to a major shift in the regional tectonic evolution. It's envisioned that this event records either terrane accretion or strong plate coupling during the final stages of Pangea agglutination. Connections with the main Alleghanian-Ouachitan Pangean orogen are precluded due to their timing differences. The plutons temporally and compositionally correlate with an arc found in the northern Andes and Mexican Gondwana terranes, and represent a broader magmatic event formed at the proto-Pacific margin, outside the nucleus of the Laurentia-Gondwana Alleghanian-Oachitan orogens. Evidence of lower temperature

  7. Freshly brewed continental crust

    NASA Astrophysics Data System (ADS)

    Gazel, E.; Hayes, J. L.; Caddick, M. J.; Madrigal, P.

    2015-12-01

    Earth's crust is the life-sustaining interface between our planet's deep interior and surface. Basaltic crusts similar to Earth's oceanic crust characterize terrestrial planets in the solar system while the continental masses, areas of buoyant, thick silicic crust, are a unique characteristic of Earth. Therefore, understanding the processes responsible for the formation of continents is fundamental to reconstructing the evolution of our planet. We use geochemical and geophysical data to reconstruct the evolution of the Central American Land Bridge (Costa Rica and Panama) over the last 70 Ma. We also include new preliminary data from a key turning point (~12-6 Ma) from the evolution from an oceanic arc depleted in incompatible elements to a juvenile continental mass in order to evaluate current models of continental crust formation. We also discovered that seismic P-waves (body waves) travel through the crust at velocities closer to the ones observed in continental crust worldwide. Based on global statistical analyses of all magmas produced today in oceanic arcs compared to the global average composition of continental crust we developed a continental index. Our goal was to quantitatively correlate geochemical composition with the average P-wave velocity of arc crust. We suggest that although the formation and evolution of continents may involve many processes, melting enriched oceanic crust within a subduction zone, a process probably more common in the Achaean where most continental landmasses formed, can produce the starting material necessary for juvenile continental crust formation.

  8. Apatite fission track dating and long-term landscape evolution of the South Atlantic passive continental margin in the region of the Sierras Septentrionales in eastern Argentina

    NASA Astrophysics Data System (ADS)

    Pfister, S.; Glasmacher, P. A.; Kollenz, S.

    2013-12-01

    To understand the evolution of the passive continental margin in Argentina apatite fission track dating is an appropriate method, which will lead to new conclusions in this area. The Tandilia System, also called Sierras Septentrionales, is located south of the Río de la Plato Craton in eastern Argentina in the state of Buenos Aires. North of the hills Salado basin is orientated whereas the Claromeó basin is located south of the mountain range. In contrary to most basins along the southamerican passive continental margin the Tandilia-System and the neighbouring basins trend perpendicular to the coast line. The topography ranges between 50 and 250m within the study area and is therefore fairly flat. The igneous-metamorphic basement is pre-proterozoic in age build up of mainly granitic-tonalitic gneisses, migmatites, amphibolites, some ultramafic rocks and granitoid plutons and is overlain by a series of Neoproterozoic to early Paleozoic sediments (Cingolani, 2010). The aim of the study is to evaluate the long-term landscape evolution of the passive continental margin in eastern Argentina in terms of thermal history and exhumation. For that purpose samples were taken from the Sierra Septentrionales basement analyzed for the apatite-FT method. The results so far indicate apatite fission track ages between 146.2 (10.1) Ma and 200.4 (12.7) Ma, which shows all samples have been reseted. Still ongoing length measurements will lead to 2D thermo kinematic Hefty (Ketcham, 2005; Ketcham et al., 2009; Ketcham, 2007) models. This will leads to further more insights on the cooling history and tectonic activities in the research area. References: Cingolani C. A. (2010): The Tandilia System of Argentina as a southern extension of the Río de la Plata craton: an overview. Int. J. Earth Sci. (Geol. Rundsch.) (2011) 100:221-242, doi 10.1007/s00531-010-0611-5. Ketcham, R. A. (2005): Forward and inverse modeling of low-temperature thermochronometry data, in Low

  9. Subduction-Driven Recycling of Continental Margin Lithosphere

    NASA Astrophysics Data System (ADS)

    Levander, Alan; Bezada, Maximiliano; Niu, Fenglin; Palomeras, Imma; Humphreys, Eugene; Carbonell, Ramon; Gallart, Josep; Schmitz, Michael; Miller, Meghan

    2016-04-01

    Subduction recycling of oceanic lithosphere, a central theme of plate tectonics, is relatively well understood. Recycling continental lithosphere is more difficult to recognize, can take a number of different forms, and appears to require an external trigger for initiation. Delamination and localized convective downwelling are two processes invoked to explain the removal of lithospheric mantle under or adjacent to orogenic belts. We describe a related process that can lead to the loss of continental lithosphere adjacent to a subduction zone: Subducting oceanic plates can entrain and recycle lithospheric mantle from an adjacent continent and disrupt the continental lithosphere far inland from the subduction zone. Body wave tomograms from dense broadband seismograph arrays in northeastern South America (SA) and the western Mediterranean show larger than expected volumes of positive velocity anomalies which we identify as the subducted Atlantic slab under northeastern SA, and the Alboran slab beneath the Gibraltar arc (GA). The positive anomalies lie under and are aligned with the continental margins at sublithospheric depths. The continental margins along which the subduction zones have traversed, i.e. the northeastern SA plate boundary and east of GA, have significantly thinner lithosphere than expected. The thinner than expected lithosphere extends inland as far as the edges of nearby cratons as determined from receiver function images and surface wave tomography. These observations suggest that subducting oceanic plates viscously entrain and remove continental mantle lithosphere from beneath adjacent continental margins, modulating the surface tectonics and pre-conditioning the margins for further deformation. The latter can include delamination of the entire lithospheric mantle and include the lower crust, as around GA, inferred by results from active and passive seismic experiments. Viscous removal of continental margin lithosphere creates LAB topography leading

  10. Application of Global Positioning Measurements to Continental Collision in the Pamir-Tien Shan Region, Central Asia and GPS Survey of the Western Tien Shan

    NASA Technical Reports Server (NTRS)

    Hamburger, Michael W.; Reilinger, Robert E.; Hager, Bradford H.; Molnar, Peter

    1997-01-01

    In this report, we summarize what we have accomplished with five years of funding from NASA under its DOSE program, and with a comparable level of funding from NSF. We describe the development of a GPS network in the Tien Shan of Kyrgyzstan and Kazakhstan of the former Soviet Union, the analysis of data, and the main results. This discussion presents the state of the current network, which has grown significantly since the termination of our DOSE grants, with continued support both from NSF through its continental dynamics program and from NASA's SENH program. Although grants from NASA's DOSE program did not support this growth not directly, it did so indirectly by building the infrastructure that has enabled further expansion in an area where otherwise there would be only a small GPS presence. We note how the network has grown over time, but the emphasis of this discussion is on the quantity and quality of measurements that we have made.

  11. Mean hydrography on the continental shelf from 26 repeat glider deployments along Southeastern Australia

    PubMed Central

    Schaeffer, Amandine; Roughan, Moninya; Austin, Tim; Everett, Jason D.; Griffin, David; Hollings, Ben; King, Edward; Mantovanelli, Alessandra; Milburn, Stuart; Pasquer, Benedicte; Pattiaratchi, Charitha; Robertson, Robin; Stanley, Dennis; Suthers, Iain; White, Dana

    2016-01-01

    Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern Australia. Typically these missions have spanned the continental shelf on the inshore edge of the East Australian Current from 29.5–33.5°S. This comprehensive dataset of over 33,600 CTD profiles from the surface to within 10 m of the bottom in water depths ranging 25–200 m provides new and unprecedented high resolution observations of the properties of the continental shelf waters adjacent to a western boundary current, straddling the region where it separates from the coast. The region is both physically and biologically significant, and is also in a hotspot of ocean warming. We present gridded mean fields for temperature, salinity and density, but also dissolved oxygen and chlorophyll-a fluorescence indicative of phytoplankton biomass. This data will be invaluable for understanding shelf stratification, circulation, biophysical and bio-geochemical interactions, as well as for the validation of high-resolution ocean models or serving as teaching material. PMID:27575831

  12. Mean hydrography on the continental shelf from 26 repeat glider deployments along Southeastern Australia.

    PubMed

    Schaeffer, Amandine; Roughan, Moninya; Austin, Tim; Everett, Jason D; Griffin, David; Hollings, Ben; King, Edward; Mantovanelli, Alessandra; Milburn, Stuart; Pasquer, Benedicte; Pattiaratchi, Charitha; Robertson, Robin; Stanley, Dennis; Suthers, Iain; White, Dana

    2016-08-30

    Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern Australia. Typically these missions have spanned the continental shelf on the inshore edge of the East Australian Current from 29.5-33.5°S. This comprehensive dataset of over 33,600 CTD profiles from the surface to within 10 m of the bottom in water depths ranging 25-200 m provides new and unprecedented high resolution observations of the properties of the continental shelf waters adjacent to a western boundary current, straddling the region where it separates from the coast. The region is both physically and biologically significant, and is also in a hotspot of ocean warming. We present gridded mean fields for temperature, salinity and density, but also dissolved oxygen and chlorophyll-a fluorescence indicative of phytoplankton biomass. This data will be invaluable for understanding shelf stratification, circulation, biophysical and bio-geochemical interactions, as well as for the validation of high-resolution ocean models or serving as teaching material.

  13. Mean hydrography on the continental shelf from 26 repeat glider deployments along Southeastern Australia

    NASA Astrophysics Data System (ADS)

    Schaeffer, Amandine; Roughan, Moninya; Austin, Tim; Everett, Jason D.; Griffin, David; Hollings, Ben; King, Edward; Mantovanelli, Alessandra; Milburn, Stuart; Pasquer, Benedicte; Pattiaratchi, Charitha; Robertson, Robin; Stanley, Dennis; Suthers, Iain; White, Dana

    2016-08-01

    Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern Australia. Typically these missions have spanned the continental shelf on the inshore edge of the East Australian Current from 29.5-33.5°S. This comprehensive dataset of over 33,600 CTD profiles from the surface to within 10 m of the bottom in water depths ranging 25-200 m provides new and unprecedented high resolution observations of the properties of the continental shelf waters adjacent to a western boundary current, straddling the region where it separates from the coast. The region is both physically and biologically significant, and is also in a hotspot of ocean warming. We present gridded mean fields for temperature, salinity and density, but also dissolved oxygen and chlorophyll-a fluorescence indicative of phytoplankton biomass. This data will be invaluable for understanding shelf stratification, circulation, biophysical and bio-geochemical interactions, as well as for the validation of high-resolution ocean models or serving as teaching material.

  14. The Wide Bay Canyon system: A case study of canyon morphology on the east Australian continental margin

    NASA Astrophysics Data System (ADS)

    Yu, P. W.; Hubble, T.; Airey, D.; Gallagher, S. J.; Clarke, S. L.

    2014-12-01

    A voyage was conducted aboard the RV Southern Surveyor in early 2013 to investigate the east Australian continental margin. From the continental slope of the Wide Bay region offshore Fraser Island, Queensland, Australia, remote sensing data and sediment samples were collected. Bathymetric data reveals that the continental slope of the region presents a mature canyon system. Eight dredge samples were recovered from the walls of Wide Bay Canyon and the adjacent, relatively intact continental slope along the entire length of the slope, from the start of the shelf break to the toe, in water depths ranging from 1100-2500 m. For these samples, sediment composition, biostratigraphic age, and bulk mineralogy data are reported. These slope-forming sediments are primarily comprised of calcareous sandy-silts. Occasional terrestrial plant fossils and minerals can be found in a mostly marine-fossiliferous composition, suggesting minor but significant riverine and aeolian input. Biostratigraphic dates extracted from the foraminiferal contents of these samples indicate that the intra-canyon and slope material was deposited between Middle Miocene to Pliocene, implying that the incision of this section of the margin and formation of the erosional features took place no earlier than the Pliocene. In conjunction with bathymetric data of the local continental slope, the depositional origins of this section of the east Australian continental margin, and the timing of major morphological events such as slope failure and canyon incision can be interpreted. The Wide Bay Canyon system can serve as a representative case study of local canyon formation, allowing a better understanding of the past or ongoing processes that are shaping the margin and giving way to similar morphologies.

  15. Dynamics of continental accretion.

    PubMed

    Moresi, L; Betts, P G; Miller, M S; Cayley, R A

    2014-04-10

    Subduction zones become congested when they try to consume buoyant, exotic crust. The accretionary mountain belts (orogens) that form at these convergent plate margins have been the principal sites of lateral continental growth through Earth's history. Modern examples of accretionary margins are the North American Cordilleras and southwest Pacific subduction zones. The geologic record contains abundant accretionary orogens, such as the Tasmanides, along the eastern margin of the supercontinent Gondwana, and the Altaïdes, which formed on the southern margin of Laurasia. In modern and ancient examples of long-lived accretionary orogens, the overriding plate is subjected to episodes of crustal extension and back-arc basin development, often related to subduction rollback and transient episodes of orogenesis and crustal shortening, coincident with accretion of exotic crust. Here we present three-dimensional dynamic models that show how accretionary margins evolve from the initial collision, through a period of plate margin instability, to re-establishment of a stable convergent margin. The models illustrate how significant curvature of the orogenic system develops, as well as the mechanism for tectonic escape of the back-arc region. The complexity of the morphology and the evolution of the system are caused by lateral rollback of a tightly arcuate trench migrating parallel to the plate boundary and orthogonally to the convergence direction. We find geological and geophysical evidence for this process in the Tasmanides of eastern Australia, and infer that this is a recurrent and global phenomenon.

  16. Dynamics of continental accretion

    NASA Astrophysics Data System (ADS)

    Moresi, L.; Betts, P. G.; Miller, M. S.; Cayley, R. A.

    2014-04-01

    Subduction zones become congested when they try to consume buoyant, exotic crust. The accretionary mountain belts (orogens) that form at these convergent plate margins have been the principal sites of lateral continental growth through Earth's history. Modern examples of accretionary margins are the North American Cordilleras and southwest Pacific subduction zones. The geologic record contains abundant accretionary orogens, such as the Tasmanides, along the eastern margin of the supercontinent Gondwana, and the Altaïdes, which formed on the southern margin of Laurasia. In modern and ancient examples of long-lived accretionary orogens, the overriding plate is subjected to episodes of crustal extension and back-arc basin development, often related to subduction rollback and transient episodes of orogenesis and crustal shortening, coincident with accretion of exotic crust. Here we present three-dimensional dynamic models that show how accretionary margins evolve from the initial collision, through a period of plate margin instability, to re-establishment of a stable convergent margin. The models illustrate how significant curvature of the orogenic system develops, as well as the mechanism for tectonic escape of the back-arc region. The complexity of the morphology and the evolution of the system are caused by lateral rollback of a tightly arcuate trench migrating parallel to the plate boundary and orthogonally to the convergence direction. We find geological and geophysical evidence for this process in the Tasmanides of eastern Australia, and infer that this is a recurrent and global phenomenon.

  17. Dynamics of Continental Accretion

    NASA Astrophysics Data System (ADS)

    Moresi, L. N.; Betts, P. G.; Miller, M. S.

    2013-12-01

    Subduction zones become congested when they try to swallow buoyant exotic crust. Accretionary mountain belts (orogens) that form at these convergent plate margins are the principal sites of lateral continental growth through Earth's history. Modern examples of accretionary margins are the North and South American Cordilleras and southwest Pacific. The geologic record is riddled with accretionary orogens, such as the Tasmanides along the eastern margin of the supercontinent Gondwana and the Altaides that formed on the southern margin of Laurasia. Both the modern and ancient examples are characterised by episodic switches between extension and shortening associated with transitions from collision of exotic crust and subduction related rollback. We present three-dimensional dynamic models that show for the first time how accretionary margins evolve from the initial collision, through a period of plate margin instability, to re-establishment of a stable convergent margin. The models illustrate how significant curvature of the orogenic system develops, as well as the mechanism for tectonic escape of the back arc region. The complexity of the morphology and evolution of the system are driven by lateral rollback of a tightly arcuate trench migrating parallel to the plate boundary and orthogonal to the convergence direction. We find geological and geophysical evidence for this process in the Tasmanides of eastern Australia, but infer that this is a global phenomena throughout Earth's evolution.

  18. Modeling the dynamics of continental shelf carbon.

    PubMed

    Hofmann, Eileen E; Cahill, Bronwyn; Fennel, Katja; Friedrichs, Marjorie A M; Hyde, Kimberly; Lee, Cindy; Mannino, Antonio; Najjar, Raymond G; O'Reilly, John E; Wilkin, John; Xue, Jianhong

    2011-01-01

    Continental margin systems are important contributors to global nutrient and carbon budgets. Effort is needed to quantify this contribution and how it will be modified under changing patterns of climate and land use. Coupled models will be used to provide projections of future states of continental margin systems. Thus, it is appropriate to consider the limitations that impede the development of realistic models. Here, we provide an overview of the current state of modeling carbon cycling on continental margins as well as the processes and issues that provide the next challenges to such models. Our overview is done within the context of a coupled circulation-biogeochemical model developed for the northeastern North American continental shelf region. Particular choices of forcing and initial fields and process parameterizations are used to illustrate the consequences for simulated distributions, as revealed by comparisons to observations using quantitative statistical metrics.

  19. A regional assessment of potential environmental hazards to and limitations on petroleum development of the Southeastern United States Atlantic continental shelf, slope, and rise, offshore North Carolina

    USGS Publications Warehouse

    Popenoe, Peter; Coward, E.L.; Cashman, K.V.

    1982-01-01

    More than 11,000 km of high-resolution seismic-reflection data, 325 km of mid-range sidescan-sonar data, and 500 km of long-range sidescan-sonar data were examined and used to construct an environmental geology map of the Continental Shelf, Slope, and Rise for the area of the U.S. Atlantic margin between lats. 32?N. and 37?N. Hardgrounds and two faults described in previous literature also are shown on the map. On the Continental Shelf, at least two faults, the Helena Banks fault and the White Oak lineament, appear to be tectonic in origin. However, a lack of historical seismicity associated with these faults indicates that they are probably not active at the present time. Hardgrounds are widely scattered but are most abundant in Onslow Bay. Although paleostream channels are common nearshore, they do not appear to be common on the central and outer shelf except off Albemarle Sound where extensive Pleistocene, Pliocene, and late Miocene channels extend across the shelf. Mobile bottom sediments are confined mainly to the shoals off Cape Romain, Cape Fear, Cape Lookout, and Cape Hatteras. Elsewhere the sand cover is thin, and older more indurated rocks are present in subcrop. No slope-instability features were noted on the Florida-Hatteras slope off North Carolina. The lack of features indicates that this slope is relatively stable. Evidence for scour by strong currents is ubiquitous on the northern Blake Plateau although deep-water reefs are sparse. The outer edge of the plateau is dominated by a major growth fault and numerous splay and antithetic faults. These faults are the product of salt tectonism in the Carolina trough and thus are not associated with seismicity. Displacements observed near the sea floor and breached diapirs offshore indicate that the main fault is still moving. Associated with the faults are collapse features that are interpreted to be caused by karst solution and cavernous porosity in Eocene and Oligocene limestones at depth. Major slumps

  20. Geochemistry and geochronology of the Late Permian mafic intrusions along the boundary area of Jiamusi and Songnen-Zhangguangcai Range massifs and adjacent regions, northeastern China: Petrogenesis and implications for the tectonic evolution of the Mudanjiang Ocean

    NASA Astrophysics Data System (ADS)

    Dong, Yu; Ge, Wen-chun; Yang, Hao; Xu, Wen-liang; Bi, Jun-hui; Wang, Zhi-hui

    2017-01-01

    This paper presents zircon U-Pb ages, whole-rock major and trace element data, and Hf isotope data for the metagabbros from the Zhushan pluton and gabbros from the Taiping pluton along the boundary area of Jiamusi and Songnen-Zhangguangcai Range massifs and adjacent regions, which will not only place important constraints on the rock-forming ages, source characteristics and tectonic setting of these gabbros, but will also provide insights into understanding the Permian tectonic evolution between the Jiamusi Massif and the Songnen-Zhangguangcai Range Massif. Zircon U-Pb dating, determined using laser ablation-inductively coupled plasma-mass spectrometry and secondary-ion mass spectrometry, indicates that the magmatic zircons from the Zhushan and Taiping plutons yield 206Pb/238U ages of 256 ± 2 Ma and 259 ± 3 Ma, respectively, interpreted as the emplacement ages of the intrusions. The metagabbros from the Zhushan pluton display the geochemical characteristics of calc-alkaline series rocks, and are enriched in light rare earth and large ion lithophile elements, and depleted in Nb, Ta, P, Zr and Hf. The εHf(t) values of magmatic zircons in these metagabbros vary from - 5.47 to + 0.74. All these geochemical features indicate that the primary magma of the Zhushan pluton was derived from an enriched lithospheric mantle source that was metasomatized by subducted slab-derived fluids. The gabbros from the Taiping pluton are also enriched in large ion lithophile elements (e.g., Rb, Ba and U) relative to high field strength elements, and have negative Nb-Ta-P anomalies, with εHf(t) values of - 4.02 to - 1.70. It is inferred that they also formed from a primary magma generated by the partial melting of enriched lithospheric mantle that was metasomatized by subducted slab-derived fluids. The rocks from the Zhushan and Taiping plutons have similar petrogenetic processes, but their primary magmas are likely to be derived from two distinct magma sources based on geochemical and

  1. Comparison between simulated and observed chemical composition of fine aerosols in Paris (France) during springtime: contribution of regional versus continental emissions

    NASA Astrophysics Data System (ADS)

    Sciare, J.; D'Argouges, O.; Zhang, Q. J.; Sarda-Estève, R.; Gaimoz, C.; Gros, V.; Beekmann, M.; Sanchez, O.

    2010-12-01

    Hourly concentrations of inorganic salts (ions) and carbonaceous material in fine aerosols (aerodynamic diameter, A.D. <2.5 μm) have been determined experimentally from fast measurements performed for a 3-week period in spring 2007 in Paris (France). The sum of these two chemical components (ions and carbonaceous aerosols) has shown to account for most of the fine aerosol mass (PM2.5). This time-resolved dataset allowed investigating the factors controlling the levels of PM2.5 in Paris and showed that polluted periods with PM2.5 > 15 μg m-3 were characterized by air masses of continental (North-Western Europe) origin and chemical composition made by 75% of ions. By contrast, periods with clean marine air masses have shown the lowest PM2.5 concentrations (typically of about 10 μg m-3); carbonaceous aerosols contributing for most of this mass (typically 75%). In order to better discriminate between local and continental contributions to the observed chemical composition and concentrations of PM2.5 over Paris, a comparative study was performed between this time-resolved dataset and the outputs of a chemistry transport model (CHIMERE), showing a relatively good capability of the model to reproduce the time-limited intense maxima observed in the field for PM2.5 and ion species. Different model scenarios were then investigated switching off local and European (North-Western and Central) emissions. Results of these scenarios have clearly shown that most of the ions observed over Paris during polluted periods, were either transported or formed in-situ from gas precursors transported from Northern Europe. On the opposite, long-range transport from Europe appeared to weakly contribute to the levels of carbonaceous aerosols observed over Paris. The model failed to properly account for the concentration levels and variability of secondary organic aerosols (SOA) determined experimentally by the EC-tracer method. The abundance of SOA (relatively to organic aerosol, OA) was as

  2. The paradox of cooling streams in a warming world: regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States

    USGS Publications Warehouse

    Arismendi, Ivan; Johnson, Sherri; Dunham, Jason B.; Haggerty, Roy; Hockman-Wert, David

    2012-01-01

    Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream temperature. Here, we examined the evidence for this using long-term stream temperature data from minimally and highly human-impacted sites located across the Pacific continental United States. Based on hypothesized climate impacts, we predicted that we should find warming trends in the maximum, mean and minimum temperatures, as well as increasing variability over time. These predictions were not fully realized. Warming trends were most prevalent in a small subset of locations with longer time series beginning in the 1950s. More recent series of observations (1987-2009) exhibited fewer warming trends and more cooling trends in both minimally and highly human-influenced systems. Trends in variability were much less evident, regardless of the length of time series. Based on these findings, we conclude that our perspective of climate impacts on stream temperatures is clouded considerably by a lack of long-termdata on minimally impacted streams, and biased spatio-temporal representation of existing time series. Overall our results highlight the need to develop more mechanistic, process-based understanding of linkages between climate change, other human impacts and stream temperature, and to deploy sensor networks that will provide better information on trends in stream temperatures in the future.

  3. Carbon Burial Rates in Sediments and a Carbon Mass Balance for the Herbert River Region of the Great Barrier Reef Continental Shelf, North Queensland, Australia

    NASA Astrophysics Data System (ADS)

    Brunskill, G. J.; Zagorskis, I.; Pfitzner, J.

    2002-04-01

    The largest century scale carbon reservoir in the Herbert River sector of the Great Barrier Reef continental shelf is carbonate carbon. This carbonate carbon is produced by corals, coralline algae, and other benthic organisms, and is stored on less than 13% of the area of the shelf. Maximum organic carbon burial rates (1-28 mol m -2 yr -1) occur within a wind-protected <20 m water depth embayment (<1% area of the shelf), where the highest bulk sedimentation rates (1-12 kg m -2 yr -1) were determined from 210Pb and 137 Cs profiles in 1-4 m cores. Sediment, organic carbon (OC), and carbonate carbon (CC) accumulation rates are very low in the Great Barrier Reef lagoon shelf and slope, where most annual productivity (8-15 mol OC m -2 yr -1) is decomposed by algal and microbial respiration. A carbon mass balance indicated that approximately 1% of combined river and marine organic carbon production was preserved in across-shelf sedimentation, but 3% of river and mangrove organic carbon input was preserved in this small wind-protected embayment. An across-shelf carbon mass balance model predicted average shelf organic matter respiration correctly, and the ratio of organic carbon fixation to respiration (corrected for burial losses) was 1·06.

  4. Continental crust beneath southeast Iceland

    PubMed Central

    Torsvik, Trond H.; Amundsen, Hans E. F.; Trønnes, Reidar G.; Doubrovine, Pavel V.; Gaina, Carmen; Kusznir, Nick J.; Steinberger, Bernhard; Corfu, Fernando; Ashwal, Lewis D.; Griffin, William L.; Werner, Stephanie C.; Jamtveit, Bjørn

    2015-01-01

    The magmatic activity (0–16 Ma) in Iceland is linked to a deep mantle plume that has been active for the past 62 My. Icelandic and northeast Atlantic basalts contain variable proportions of two enriched components, interpreted as recycled oceanic crust supplied by the plume, and subcontinental lithospheric mantle derived from the nearby continental margins. A restricted area in southeast Iceland—and especially the Öræfajökull volcano—is characterized by a unique enriched-mantle component (EM2-like) with elevated 87Sr/86Sr and 207Pb/204Pb. Here, we demonstrate through modeling of Sr–Nd–Pb abundances and isotope ratios that the primitive Öræfajökull melts could have assimilated 2–6% of underlying continental crust before differentiating to more evolved melts. From inversion of gravity anomaly data (crustal thickness), analysis of regional magnetic data, and plate reconstructions, we propose that continental crust beneath southeast Iceland is part of ∼350-km-long and 70-km-wide extension of the Jan Mayen Microcontinent (JMM). The extended JMM was marginal to East Greenland but detached in the Early Eocene (between 52 and 47 Mya); by the Oligocene (27 Mya), all parts of the JMM permanently became part of the Eurasian plate following a westward ridge jump in the direction of the Iceland plume. PMID:25825769

  5. Continental crust beneath southeast Iceland.

    PubMed

    Torsvik, Trond H; Amundsen, Hans E F; Trønnes, Reidar G; Doubrovine, Pavel V; Gaina, Carmen; Kusznir, Nick J; Steinberger, Bernhard; Corfu, Fernando; Ashwal, Lewis D; Griffin, William L; Werner, Stephanie C; Jamtveit, Bjørn

    2015-04-14

    The magmatic activity (0-16 Ma) in Iceland is linked to a deep mantle plume that has been active for the past 62 My. Icelandic and northeast Atlantic basalts contain variable proportions of two enriched components, interpreted as recycled oceanic crust supplied by the plume, and subcontinental lithospheric mantle derived from the nearby continental margins. A restricted area in southeast Iceland--and especially the Öræfajökull volcano--is characterized by a unique enriched-mantle component (EM2-like) with elevated (87)Sr/(86)Sr and (207)Pb/(204)Pb. Here, we demonstrate through modeling of Sr-Nd-Pb abundances and isotope ratios that the primitive Öræfajökull melts could have assimilated 2-6% of underlying continental crust before differentiating to more evolved melts. From inversion of gravity anomaly data (crustal thickness), analysis of regional magnetic data, and plate reconstructions, we propose that continental crust beneath southeast Iceland is part of ∼350-km-long and 70-km-wide extension of the Jan Mayen Microcontinent (JMM). The extended JMM was marginal to East Greenland but detached in the Early Eocene (between 52 and 47 Mya); by the Oligocene (27 Mya), all parts of the JMM permanently became part of the Eurasian plate following a westward ridge jump in the direction of the Iceland plume.

  6. Seismicity in Azerbaijan and Adjacent Caspian Sea

    SciTech Connect

    Panahi, Behrouz M.

    2006-03-23

    So far no general view on the geodynamic evolution of the Black Sea to the Caspian Sea region is elaborated. This is associated with the geological and structural complexities of the region revealed by geophysical, geochemical, petrologic, structural, and other studies. A clash of opinions on geodynamic conditions of the Caucasus region, sometimes mutually exclusive, can be explained by a simplified interpretation of the seismic data. In this paper I analyze available data on earthquake occurrences in Azerbaijan and the adjacent Caspian Sea region. The results of the analysis of macroseismic and instrumental data, seismic regime, and earthquake reoccurrence indicate that a level of seismicity in the region is moderate, and seismic event are concentrated in the shallow part of the lithosphere. Seismicity is mostly intra-plate, and spatial distribution of earthquake epicenters does not correlate with the plate boundaries.

  7. Continental drift before 1900.

    PubMed

    Rupke, N A

    1970-07-25

    The idea that Francis Bacon and other seventeenth and eighteenth century thinkers first conceived the notion of continental drift does not stand up to close scrutiny. The few authors who expressed the idea viewed the process as a catastrophic event.

  8. Geomorphology of the Iberian Continental Margin

    NASA Astrophysics Data System (ADS)

    Maestro, Adolfo; López-Martínez, Jerónimo; Llave, Estefanía; Bohoyo, Fernando; Acosta, Juan; Hernández-Molina, F. Javier; Muñoz, Araceli; Jané, Gloria

    2013-08-01

    The submarine features and processes around the Iberian Peninsula are the result of a complex and diverse geological and oceanographical setting. This paper presents an overview of the seafloor geomorphology of the Iberian Continental Margin and the adjacent abyssal plains. The study covers an area of approximately 2.3 million km2, including a 50 to 400 km wide band adjacent to the coastline. The main morphological characteristics of the seafloor features on the Iberian continental shelf, continental slope, continental rise and the surrounding abyssal plains are described. Individual seafloor features existing on the Iberian Margin have been classified into three main groups according to their origin: tectonic and/or volcanic, depositional and erosional. Major depositional and erosional features around the Iberian Margin developed in late Pleistocene-Holocene times and have been controlled by tectonic movements and eustatic fluctuations. The distribution of the geomorphological features is discussed in relation to their genetic processes and the evolution of the margin. The prevalence of one or several specific processes in certain areas reflects the dominant morphotectonic and oceanographic controlling factors. Sedimentary processes and the resulting depositional products are dominant on the Valencia-Catalán Margin and in the northern part of the Balearic Promontory. Strong tectonic control is observed in the geomorphology of the Betic and the Gulf of Cádiz margins. The role of bottom currents is especially evident throughout the Iberian Margin. The Galicia, Portuguese and Cantabrian margins show a predominance of erosional features and tectonically-controlled linear features related to faults.

  9. Synchronous oceanic spreading and continental rifting in West Antarctica

    NASA Astrophysics Data System (ADS)

    Davey, F. J.; Granot, R.; Cande, S. C.; Stock, J. M.; Selvans, M.; Ferraccioli, F.

    2016-06-01

    Magnetic anomalies associated with new ocean crust formation in the Adare Basin off north-western Ross Sea (43-26 Ma) can be traced directly into the Northern Basin that underlies the adjacent morphological continental shelf, implying a continuity in the emplacement of oceanic crust. Steep gravity gradients along the margins of the Northern Basin, particularly in the east, suggest that little extension and thinning of continental crust occurred before it ruptured and the new oceanic crust formed, unlike most other continental rifts and the Victoria Land Basin further south. A preexisting weak crust and localization of strain by strike-slip faulting are proposed as the factors allowing the rapid rupture of continental crust.

  10. Geometries of hyperextended continental crust in northeastern continental brazilian margin: insights from potential field and seismic interpretation

    NASA Astrophysics Data System (ADS)

    Magalhães, José; Barbosa, José; Ribeiro, Vanessa; Oliveira, Jefferson; Filho, Osvaldo; Buarque, Bruno

    2016-04-01

    The study region encompasses a set of three basins located at Northeast Brazilian continental margin: Pernambuco (south sector), Paraíba and Natal platform (north sector). These basins were formed during the last stage of separation between South America and African plates during Cretaceous. The continental breakup in these regions occurred probably during the Middle-Upper Albian (~102 m.y). The adjacent basement rocks belong to Borborema Province (BP), which was formed due a complex superposition between Pre-Cambrian orogenic cycles. The structural framework of BP is dominated by large shear zones that divided this province in three main tectonic domains: South, Central and North. The Pernambuco Basin is located in the South Domain and the Paraíba and Natal platform basins are related to the Central Domain. The tectonic and magmatic evolution of the Pernambuco Basin was influenced by oblique rifting (~ 35° to rift axis) and a thermal anomaly probably caused by the Santa Helena hotspot. The north sector represents a continental shelf characterized by basement high with a narrow platform and an abrupt shelf break on transition to the abyssal plain. The continental platform break of this sector was parallel to the rift axis. In this way, we present a regional structural interpretation of these sectors of Brazilian rifted margin based on interpretation and 2D forward modeling of potential field and 2D seismic data. The magnetic maps (Reduction to magnetic pole and Analytic signal) revealed the influence of an alternating pattern of large narrow magnetic and non-magnetic lineaments, oriented NE-SW, E-W and NW-SE. In the Pernambuco Basin these lineaments (NE-SW and E-W) are related to shear zones in the hyperextended basement which is interpreted as a continuation of the granitic-gneissic and metasedimentary rocks of the South Domain of BP. The Paraíba and Natal platform basins show a slight change in the orientation of structures trending E-W (shear zones in

  11. 30 CFR 282.6 - Disclosure of data and information to an adjacent State.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Disclosure of data and information to an adjacent State. 282.6 Section 282.6 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE OPERATIONS IN THE OUTER CONTINENTAL SHELF FOR MINERALS OTHER THAN OIL, GAS, AND...

  12. Decadal evaluation of regional climate, air quality, and their interactions over the continental US and their interactions using WRF/Chem version 3.6.1

    NASA Astrophysics Data System (ADS)

    Yahya, Khairunnisa; Wang, Kai; Campbell, Patrick; Glotfelty, Timothy; He, Jian; Zhang, Yang

    2016-02-01

    The Weather Research and Forecasting model with Chemistry (WRF/Chem) v3.6.1 with the Carbon Bond 2005 (CB05) gas-phase mechanism is evaluated for its first decadal application during 2001-2010 using the Representative Concentration Pathway 8.5 (RCP 8.5) emissions to assess its capability and appropriateness for long-term climatological simulations. The initial and boundary conditions are downscaled from the modified Community Earth System Model/Community Atmosphere Model (CESM/CAM5) v1.2.2. The meteorological initial and boundary conditions are bias-corrected using the National Center for Environmental Protection's Final (FNL) Operational Global Analysis data. Climatological evaluations are carried out for meteorological, chemical, and aerosol-cloud-radiation variables against data from surface networks and satellite retrievals. The model performs very well for the 2 m temperature (T2) for the 10-year period, with only a small cold bias of -0.3 °C. Biases in other meteorological variables including relative humidity at 2 m, wind speed at 10 m, and precipitation tend to be site- and season-specific; however, with the exception of T2, consistent annual biases exist for most of the years from 2001 to 2010. Ozone mixing ratios are slightly overpredicted at both urban and rural locations with a normalized mean bias (NMB) of 9.7 % but underpredicted at rural locations with an NMB of -8.8 %. PM2.5 concentrations are moderately overpredicted with an NMB of 23.3 % at rural sites but slightly underpredicted with an NMB of -10.8 % at urban/suburban sites. In general, the model performs relatively well for chemical and meteorological variables, and not as well for aerosol-cloud-radiation variables. Cloud-aerosol variables including aerosol optical depth, cloud water path, cloud optical thickness, and cloud droplet number concentration are generally underpredicted on average across the continental US. Overpredictions of several cloud variables over the eastern US result in

  13. The basins on the Argentine continental margin

    SciTech Connect

    Urien, C.M.

    1996-08-01

    After the stabilization of the central Gondwana Craton, orogenic belts were accreted, as a result of convergence events and an extensive passive margin developed in southwestern Gondwana. Thermal subsidence in Parana, Karoo-Ventania basins and the Late Paleozoic-Early Mesozoic rifts, were modified by the Gondwana breakup and the South Atlantic opening. Early Paleozoic marine transgressions deposited the Table Mountain Group in Ventania. In southwestern Patagonia foreland clastics were deposited. Magmatic arcs and marine units indicate a tectonic trough was formed, alternating with continental sequences, over Late Paleozoic metamorphics and intrusives, resulting from plastered terrains along the Gondwana margin. In Patagonia, Permo-Carboniferous continental and glacio marine clastics infill the basins, while in Ventania, paralic sequences, grade from neritic to continental to the northeast, extending beneath the continental margin. The Triassic-Jurassic rift basins progressed onto regional widespread acid lavas and were infilled by lagoonal organic-rich sequences. Early drift phase built basins transverse to the margin, with fluvio-lacustrine sequences: Salado, Colorado, Valdes-Rawson, San Julian and North Malvinas intracratonic basins, which underwent transtensional faulting. Post-Oxfordian to Neocomian brackish sequences, onlapped the conjugate basins during the margin`s drift, with petroleum systems, as in Austral and Malvinas. In the Valanginian, basic extrusions commenced to form on the continental border, heralding the oceanic phase. Due to thermal subsidence, offlaping sediments prograded onto the remaining half-grabens. Several petroleum systems, proven and hypothetical, are identified in this region.

  14. GPS constraints on the kinematics of continental deformation

    USGS Publications Warehouse

    Thatcher, W.

    2003-01-01

    Recent GPS observations from the western United States, New Zealand, central Greece, and Japan indicate that present-day continental deformation is typically focused in narrow deforming zones whose extent is much smaller than the intervening largely inactive regions. However, these narrow zones are heterogeneously distributed, reflecting the inherent heterogeneity of continental lithospheric strength and internal buoyancy. Plate driving and resisting forces stress plate boundary zones and plate interiors and drive deformation. These forces change continuously and discontinuously, leading to continental deformation that typically evolves and migrates with time. Magmatic and tectonic processes alter lithospheric rheology and internal buoyancy and also contribute to the time-varying character of continental deformation.

  15. Electromagnetic study of the active continental margin in northern Chile

    NASA Astrophysics Data System (ADS)

    Echternacht, Friedrich; Tauber, Sebastian; Eisel, Markus; Brasse, Heinrich; Schwarz, Gerhard; Haak, Volker

    1997-06-01

    Magnetotelluric and geomagnetic deep sounding measurements were carried out in the magmatic arc and forearc regions of northern Chile between 19.5° and 22°S to study the electrical conductivity structures of this active continental margin. The instruments used covered a very broad period range from 10 -4 s to approx. 2 × 10 4 s and thus enabled a resolution of deep as well as shallow structures. In this paper we focus on the interpretation of data from an east-west profile crossing Chile from the Pacific coast to the Western Cordillera at 20.5°S. A decomposition of the impedance tensors using the Groom-Bailey decomposition scheme shows that a two-dimensional interpretation is possible. The resulting regional strike direction is N9°W. Two-dimensional models were calculated in this coordinate frame and include the significant bathymetry of the trench as well as the topography of the Andes. The final model shows a generally high resistivity in the forearc and a very good conductor below the Precordillera. Unlike earlier models from areas further south, a good conductor is not observed below the magmatic arc itself. This correlates with the so-called Pica gap in the volcanic chain and a higher age of volcanic activity compared with adjacent areas.

  16. Regional assessment of sediment contamination from marshes to the continental shelf: Results of the western component of the US EPA National Coastal Assessment

    EPA Science Inventory

    The US EPA National Coastal Assessment (NCA) program on the U.S. West Coast was designed as a pilot project to explore assessment of new components of coastal resources not previously incorporated in the NCA. The Western Regional component of the NCA program began with a two yea...

  17. PIXE analysis of elements in gastric cancer and adjacent mucosa

    NASA Astrophysics Data System (ADS)

    Liu, Qixin; Zhong, Ming; Zhang, Xiaofeng; Yan, Lingnuo; Xu, Yongling; Ye, Simao

    1990-04-01

    The elemental regional distributions in 20 resected human stomach tissues were obtained using PIXE analysis. The samples were pathologically divided into four types: normal, adjacent mucosa A, adjacent mucosa B and cancer. The targets for PIXE analysis were prepared by wet digestion with a pressure bomb system. P, K, Fe, Cu, Zn and Se were measured and statistically analysed. We found significantly higher concentrations of P, K, Cu, Zn and a higher ratio of Cu compared to Zn in cancer tissue as compared with normal tissue, but statistically no significant difference between adjacent mucosa and cancer tissue was found.

  18. Elephant teeth from the atlantic continental shelf.

    PubMed

    Whitmore, F C; Emery, K O; Cooke, H B; Swift, D J

    1967-06-16

    Teeth of mastodons and mammoths have been recovered by fishermen from at least 40 sites on the continental shelf as deep as 120 meters. Also present are submerged shorelines, peat deposits, lagoonal shells, anz relict sands. Evidently elephants and other large mammals ranged this region during the glacial stage of low sea level of the last 25,000 years.

  19. Elephant teeth from the atlantic continental shelf

    USGS Publications Warehouse

    Whitmore, F.C.; Emery, K.O.; Cooke, H.B.S.; Swift, D.J.P.

    1967-01-01

    Teeth of mastodons and mastodons have been recovered by fishermen from at least 40 sites on the continental shelf as deep as 120 meters. Also present are submerged shorelines, peat deposits, lagoonal shells, and relict sands. Evidently elephants and other large mammals ranged this region during the glacial stage of low sea level of the last 25.000 years.

  20. Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: implications for the regional sediment budget and long-term shoreline response

    USGS Publications Warehouse

    Denny, Jane F.; Schwab, William C.; Baldwin, Wayne E.; Barnhardt, Walter A.; Gayes, Paul T.; Morton, R.A.; Warner, John C.; Driscoll, Neal W.; Voulgaris, George

    2013-01-01

    High-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget. The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain ~67 M m3 of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack of any significant modern fluvial input of sand to the region, the Holocene deposits are likely derived from reworking of relict Pleistocene and older inner-shelf deposits during the Holocene marine transgression. The Holocene sediments are concentrated in the southern part of the study area, due to a combination of ancestral drainage patterns, a regional shift in sediment supply from the northeast to the southwest in the late Pleistocene, and proximity to modern inlet systems. Where sediment is limited, only small, low relief ridges have formed and Pleistocene and older deposits are exposed on the seafloor. The low-relief ridges are likely the result of a thin, mobile veneer of sediment being transported across an irregular, erosional surface formed during the last transgression. Sediment textural trends and seafloor morphology indicate a long-term net transport of sediment to the southwest. This is supported by oceanographic studies that suggest the long-term sediment transport direction is controlled by the frequency and intensity of storms that pass through the region, where low pressure systems yield net along-shore flow to the southwest and a weak onshore component. Current sediment budget estimates for the Grand Strand yield a deficit for the region. Volume calculations of Holocene deposits on the

  1. [Ecology and the genetic structure of sympatric leishmania species circulating in the intra-continental deserts of the south Palaearctic region].

    PubMed

    Strelkova, M V; Shendrik, A G; El Fari, M; Schonian, G

    2003-01-01

    A PCR fingerprinting approach with single non-specific primers--(GTG)5 and T3B--was apply to investigate variations in the genotyping of three species of Leishmania species within the Rhombomys opimus area. Forty-three strains of Leishmania major, L. turanica, and L. gerbilli circulating among great gerbils in Turkmenistan, Uzbekistan, Kazakhstan, and Mongolia were examined. PCR fingerprint revealed a high genetic intraspecific heterogeneity among L. turanica strains. Three groups of strains were clearly identified. The strains from Mongolia greatly differed from other L. turanica ones. The second group was formed by strains from Kazakhstan, they also demonstrated rather different patterns. L. turanica strains from Turkmenistan and Uzbekistan showed only minor differences, but greatly different from those from Kazakhstan and Mongolia. The groups identified by the PCR fingerprint correlate with the conditions of circulation: the duration of a transmission season and as the result of different periods of retention of Leishmania in the skin of great gerbils, as well as the presence or absence of L. major as coexisting species. There were no differences between L. turanica strains isolated from different hosts in the same geographical region, as well as between L. turanica strains isolated in the hyper- or meso and hypoendemic foci. There was no correlation between the genotypic and phenotypic characteristics of L. turanica. No intraspecific polymorphism was found among L. major and L. gerbilli strains from different geographical regions within the great gerbil area.

  2. Cenozoic continental climatic evolution of Central Europe.

    PubMed

    Mosbrugger, Volker; Utescher, Torsten; Dilcher, David L

    2005-10-18

    Continental climate evolution of Central Europe has been reconstructed quantitatively for the last 45 million years providing inferred data on mean annual temperature and precipitation, and winter and summer temperatures. Although some regional effects occur, the European Cenozoic continental climate record correlates well with the global oxygen isotope record from marine environments. During the last 45 million years, continental cooling is especially pronounced for inferred winter temperatures but hardly observable from summer temperatures. Correspondingly, Cenozoic cooling in Central Europe is directly associated with an increase of seasonality. In contrast, inferred Cenozoic mean annual precipitation remained relatively stable, indicating the importance of latent heat transport throughout the Cenozoic. Moreover, our data support the concept that changes in atmospheric CO2 concentrations, although linked to climate changes, were not the major driving force of Cenozoic cooling.

  3. Site-condition map for Portugal, Western Iberia: methodology and constraints on the performance of Vs30 proxies for stable continental regions in Europe.

    NASA Astrophysics Data System (ADS)

    Vilanova, S. P.; Narciso, J.; Carvalho, J. P.; Cancela, C.; Lopes, I.; Nemser, E. S.; Borges, J.

    2014-12-01

    Information on the amplification characteristics of the near-surface formations in a regional sense is essential to adequately represent both seismic hazard maps and ground shaking maps. Due to the scarceness of shear-wave velocity data in most regions, several methods have been proposed in order to obtain first order representations of Vs30. These include the surface geology method and the topographic slope method. The latter method has become the standard way for incorporating site effects into regional studies worldwide given the convenience provided by the global Vs30 Internet server. In the framework of project SCENE we developed a shear wave velocity database for Portugal. The database consists of 87 shear-wave velocity depth profiles from a variety of lithological and geological formations. We used an iterative three-step procedure to develop the Vs30 based site-condition map: 1) to define a preliminary set of geologically defined units based on the literature; 2) to calculate the distribution of Vs30 for each unit; and 3) to perform statistical tests in order to estimate the significance of the difference in the Vs30 distribution characteristics between the units. The units were merged according to the results of the statistical tests and the procedure was repeated. We started by classifying the sites into six generalized geological units. The final set consists of three units only: F1 (igneous, metamorphic and old sedimentary rocks); F2 (Neogene and Pleistocene formations); and F3 (Holocene deposits). We used the database to evaluate the performance of Vs30 proxies. The use of proxies based either on geological units or on correlations with the topographic slope shows relatively unbiased total residual distributions of the logarithm of Vs30. However, the performance of the methods varies significantly with the generalized geological unit analyzed. Both methods are biased towards lower values of Vs30 for rock formations. The topographic-slope method is

  4. Convective Removal of Continental Margin Lithosphere at the Edges of Subducting Oceanic Plates

    NASA Astrophysics Data System (ADS)

    Levander, A.; Bezada, M. J.; Palomeras, I.; Masy, J.; Humphreys, E.; Niu, F.

    2013-12-01

    Although oceanic lithosphere is continuously recycled to the deeper mantle by subduction, the rates and manner in which different types of continental lithospheric mantle are recycled is unclear. Cratonic mantle can be chemically reworked and essentially decratonized, although the frequency of decratonization is unclear. Lithospheric mantle under or adjacent to orogenic belts can be lost to the deeper mantle by convective downwellings and delamination phenomena. Here we describe how subduction related processes at the edges of oceanic plates adjacent to passive continental margins removes the mantle lithosphere from beneath the margin and from the continental interior. This appears to be a widespread means of recycling non-cratonic continental mantle. Lithospheric removal requires the edge of a subducting oceanic plate to be at a relatively high angle to an adjacent passive continental margin. From Rayleigh wave and body wave tomography, and receiver function images from the BOLIVAR and PICASSO experiments, we infer large-scale removal of continental margin lithospheric mantle from beneath 1) the northern South American plate margin due to Atlantic subduction, and 2) the Iberian and North African margins due to Alboran plate subduction. In both cases lithospheric mantle appears to have been removed several hundred kilometers inland from the subduction zones. This type of ';plate-edge' tectonics either accompanies or pre-conditions continental margins for orogenic activity by thinning and weakening the lithosphere. These processes show the importance of relatively small convective structures, i.e. small subducting plates, in formation of orogenic belts.

  5. Dynamics of Intra-Continental Convergence Between the Western Tarim Basin and Central Tien Shan Constrained by Centroid Moment Tensors of Regional Earthquakes

    NASA Astrophysics Data System (ADS)

    Huang, Guo-chin Dino; Roecker, Steven W.; Levin, Vadim; Wang, Haitao; Li, Zhihai

    2016-11-01

    Among the outstanding tectonic questions regarding the convergence between the Tien Shan and Tarim basin in northwestern China are the manner in which deformation is accommodated within their lithospheres, and the extent that the Tarim lithosphere underthrusts the Tien Shan. In particular, the amount and type of deformation within the Tarim basin is poorly understood. It is also uncertain if the convergence between the Tarim and the Tien Shan takes place mainly along a discrete boundary, or if the Tarim lithosphere simply indents into the Kazach shield, forming the Tien Shan through crustal thickening accommodated by a distributed series of thrust faults. In this study we use hypocenters from published earthquake catalogs and waveforms recorded by regional seismic networks to determine earthquake source parameters through regional centroid moment tensor inversion. The entire dataset consists of 160 earthquakes that occurred between 1969 and 2009 and with moment magnitudes between 3.5 and 7 distributed throughout the central Tien Shan and northwestern Tarim Basin. The estimated focal depths of these earthquakes range from the near-surface to about 44 km. Focal mechanisms throughout much of the Tien Shan indicate active deformation accommodated by thrust faults from at least the upper crust to 30 km depth. South of the Tien Shan, the Jia-shi earthquake sequence within the Tarim basin suggests that both crustal shortening and localized flexure are part of a complicated process involving rotational convergence. Inside the Tarim basin, two earthquakes with thrust faulting mechanisms near the crust-mantle boundary beneath the Bachu uplift imply a brittle rheology of the lower crust. High-angle thrust events occur broadly across the Tien Shan, suggesting that the Tarim lithosphere as a whole is strong and indents into the Kazach shield to create the mountain range.

  6. Zambezi continental margin: compartmentalized sediment transfer routes to the abyssal Mozambique Channel

    NASA Astrophysics Data System (ADS)

    Wiles, E.; Green, A. N.; Watkeys, M. K.; Jokat, W.

    2017-03-01

    Sediment delivery to the abyssal regions of the oceans is an integral process in the source to sink cycle of material derived from adjacent continents and islands. The Zambezi River, the largest in southern Africa, delivers vast amounts of material to the inner continental shelf of central Mozambique. The aim of this contribution is to better constrain sediment transport pathways to the abyssal plains using the latest, regional, high-resolution multibeam bathymetry data available, taking into account the effects of bottom water circulation, antecedent basin morphology and sea-level change. Results show that sediment transport and delivery to the abyssal plains is partitioned into three distinct domains; southern, central and northern. Sediment partitioning is primarily controlled by changes in continental shelf and shelf-break morphology under the influence of a clockwise rotating shelf circulation system. However, changes in sea-level have an overarching control on sediment delivery to particular domains. During highstand conditions, such as today, limited sediment delivery to the submarine Zambezi Valley and Channel is proposed, with increased sediment delivery to the deepwater basin being envisaged during regression and lowstand conditions. However, there is a pronounced along-strike variation in sediment transport during the sea-level cycle due to changes in the width, depth and orientation of the shelf. This combination of features outlines a sequence stratigraphic concept not generally considered in the strike-aligned shelf-slope-abyssal continuum.

  7. Regional stratigraphy and petroleum geology, North Africa-Middle East

    SciTech Connect

    Peterson, J.A. )

    1991-03-01

    The North Africa-Middle East petroleum provinces are part of the broad sedimentary platform that occupied the northern and northeastern borders of the African-Arabian craton adjacent to the ancestral Hercynian (late Paleozoic) and subsequent Tethyan-Alpine oceans. Carbonate-clastic-evaporite sediments of infra-Cambrian through Holocene age were cyclically deposited in a relatively continuous belt around the eastern and northern borders of the craton, mainly on a broad, shallow-water platform adjacent to the proto-Tethys and Tethys seaway. The Paleozoic section reaches a substantial thickness in the subsurface of the Middle East and in northern Africa adjacent to the Mediterranean Sea, but all or part of it is absent because of nondeposition or erosion over much of the region. Post-Paleozoic deposition was more or less continuous across the entire craton border region in the Middle East and along the northern border of the Sahara platform in North Africa and in Somalia and eastern Ethiopia. Similar marine and associated sedimentary rock facies are present in all of these regions, although paleotectonic-stratigraphic interrelationships and continental paleolatitude positions have greatly affected petroleum generation and accumulation in the specific provinces along the craton border. A series of regional stratigraphic-sedimentary environment, and continental position, layer maps illustrates the relative influence of these factors through geologic time with respect to the relationship between petroleum reservoirs, source rocks, and confining rock facies.

  8. Developing Bottom-Up Estimates of Net Carbon Flux Using Survey Data, Remote Sensing, and Economic Modeling: A Case Study for Agricultural Lands in the U.S. Mid-Continental Region

    NASA Astrophysics Data System (ADS)

    West, T. O.; Brandt, C. C.; de La Torre Ugarte, D.; Larson, J. A.; Hellwinkle, C.; Wilson, B.; Marland, G.

    2005-12-01

    Estimates of net carbon-equivalent (Ceq) flux of greenhouse gases to the atmosphere from agricultural lands in the U.S. can be made on an annual basis using existing survey data and remote sensing. Integrating these data sets with the POLYSYS agricultural economics model will allow for estimates of future changes in land use and Ceq emissions that will be associated with carbon management incentives or changes in land-use policies (e.g., Farm Bill and land conservation policies). We are examining carbon sinks and Ceq sources for agricultural lands at the county scale and at a resolution commensurate with remotely sensed land-use data. Carbon sinks and sources include changes in soil carbon stocks; CO2 and N2O emissions associated with the production, transport, and application of agricultural inputs; carbon uptake by crops; and emissions from livestock. This presentation places emphasis on the development and structure of the accounting framework, on the data inputs, and on the mechanisms that will be used to update these inputs on a regular basis. Different accounting methods that may be implemented in the framework to account for either on-site net emissions or first order, upstream emissions associated with new land-use practices will also be discussed. Results are presented for the U.S. mid-continental region in a manner that can be compared to atmospheric top-down modeling approaches for estimating net carbon flux from terrestrial ecosystems.

  9. Recent acoustic studies of western Canadian continental margin

    SciTech Connect

    Bornhold, B.D.; Brandon, M.T.; Clowes, R.M.; Currie, R.G.; Davis, E.E.; Hussong, D.M.; Hyndman, R.D.; Riddihough, R.P.; Rogers, G.C.; Yorath, C.J.

    1986-07-01

    A regional survey of the western Canadian continental margin from the central Queen Charlotte Island, 52/sup 0/40'N, to the Strait of Juan de Fuca, 47/sup 0/40'N, has been completed with the acoustic imaging system SeaMARC II. These data, combined with single-channel and multichannel seismic reflection data, reveal many new insights concerning the deep structure of the subduction margin off Vancouver Island. Clearly evident in the imagery are the deformation of sediments at the base of the slope, the surface expression of seismically active faults, the mass wasting of sediment frequently observed at the base of the slope, and the erosional canyons and sediment transport channels on the slope and adjacent abyssal plain. The variability in the surficial and deep structures along the length of the margin is great and corresponds well with the postulated variations in the local ocean/continent motion vectors: motion along the southern Queen Charlotte Islands margin is primarily transform (about 55 mm/year) with a small component of convergence (about 10 mm/year); motion south of the triple junction at the Wilson Knolls is convergent but at a very slow rate (about 10 mm/year); and motion along the central and southern Vancouver Island margin is nearly orthogonal to the coast and more rapid (about 40 mm/year).

  10. Brazilian continental cretaceous

    NASA Astrophysics Data System (ADS)

    Petri, Setembrino; Campanha, Vilma A.

    1981-04-01

    Cretaceous deposits in Brazil are very well developed, chiefly in continental facies and in thick sequences. Sedimentation occurred essentially in rift-valleys inland and along the coast. Three different sequences can be distinguished: (1) a lower clastic non-marine section, (2) a middle evaporitic section, (3) an upper marine section with non-marine regressive lithosomes. Continental deposits have been laid down chiefly between the latest Jurassic and Albian. The lower lithostratigraphic unit is represented by red shales with occasional evaporites and fresh-water limestones, dated by ostracods. A series of thick sandstone lithosomes accumulated in the inland rift-valleys. In the coastal basins these sequences are often incompletely preserved. Uplift in the beginning of the Aptian produced a widespread unconformity. In many of the inland rift-valleys sedimentation ceased at that time. A later transgression penetrated far into northeastern Brazil, but shortly after continental sedimentation continued, with the deposition of fluvial sandstones which once covered large areas of the country and which have been preserved in many places. The continental Cretaceous sediments have been laid down in fluvial and lacustrine environments, under warm climatic conditions which were dry from time to time. The fossil record is fairly rich, including besides plants and invertebrates, also reptiles and fishes. As faulting tectonism was rather strong, chiefly during the beginning of the Cretaceous, intercalations of igneous rocks are frequent in some places. Irregular uplift and erosion caused sediments belonging to the remainder of this period to be preserved only in tectonic basins scattered across the country.

  11. Impact of moisture source regions on the isotopic composition of precipitation events at high-mountain continental site Kasprowy Wierch, southern Poland

    NASA Astrophysics Data System (ADS)

    Rozanski, Kazimierz; Chmura, Lukasz; Dulinski, Marek

    2016-04-01

    Five-year record of deuterium and oxygen-18 isotope composition of precipitation events collected on top of the Kasprowy Wierch mountain (49° 14'N, 19° 59'E, 1989 m a.s.l.) located in north-western High Tatra mountain ridge, southern Poland, is presented and discussed. In total 670 precipitation samples have been collected and analysed. Stable isotope composition of the analysed precipitation events varied in a wide range, from -2.9 to -26.6‰ for δ18O and from -7 to -195 ‰ for δ2H. The local meteoric water line (LMWL) defined by single events data (δ2H=(7.86±0.05)δ18O+(12.9±0.6) deviate significantly from the analogous line defined by monthly composite precipitation data available for IAEA/GNIP station Krakow-Balice (50o04'N, 19o55'E, 220 m a.s.l.), located ca. 100 km north of Kasprowy Wierch ((δ2H=(7.82±0.11)δ18O+(6.9±1.1). While slopes of those two LMWLs are statistically indistinguishable, the intercept of Kasprowy Wierch line is almost two times higher that that characterizing Krakow monthly precipitation. This is well-documented effect associated with much higher elevation of Kasprowy Wierch sampling site when compared to Krakow. The isotope data for Kasprowy Wierch correlate significantly with air temperature, with the slope of the regression line being equal 0.35±0.02 ‰oC for δ18O, whereas no significant correlation with precipitation amount could be established. The impact of moisture source regions on the isotopic composition of precipitation events collected at Kasprowy Wierch site was analysed using HYSPLITE back trajectory model. Five-days back trajectories were calculated for all analysed precipitation events and seasonal maps of trajectory distribution were produced. They illustrate changes in the prevailing transport patterns of air masses bringing precipitation to the sampling site. Back trajectories for the events yielding extreme isotopic composition of precipitation collected at Kasprowy Wierch were analyzed in detail

  12. Seasonal dynamics of circulation in Hooghly Estuary and its adjacent coastal oceans

    NASA Astrophysics Data System (ADS)

    Mishra, Shashank Kr.; Nayak, Gourav; Nayak, R. K.; Dadhwal, V. K.

    2016-05-01

    Hooghly is one of the major estuaries in Ganges, the largest and longest river in the Indian subcontinent. The Hooghly estuary is a coastal plain estuary lying approximately between 21°-23° N and 87°-89° E. We used a terrain following ocean model to study tide driven residual circulations, seasonal mean flow patterns and its energetics in the Hooghly estuary and adjacent coastal oceans on the north eastern continental shelf of India. The model is driven by tidal levels at open ocean end and winds at the air-sea interface. The sources of forcing fields for tides were from FES2012, winds from ECMWF. Harmonic analysis is carried out to compute the tidal and non-tidal components of currents and sea level from the model solutions. The de-tidal components were averaged for the entire period of simulation to describe residual and mean-seasonal circulations in the regions. We used tide-gauge, SARAL-ALTIKA along track sea level measurements to evaluate model solutions. Satellite measure Chla were used along with simulated currents to describe important features of the circulations in the region.

  13. Effects of Isolation by Continental Islands in the Seto Inland Sea, Japan, on Genetic Diversity of the Large Japanese Field Mouse, Apodemus speciosus (Rodentia: Muridae), Inferred from the Mitochondrial Dloop Region.

    PubMed

    Sato, Jun J; Tasaka, Yurina; Tasaka, Ryoya; Gunji, Kentaro; Yamamoto, Yuya; Takada, Yasushi; Uematsu, Yasushi; Sakai, Eiichi; Tateishi, Takashi; Yamaguchi, Yasunori

    2017-04-01

    To study the effects of post-glacial isolation by islands on population genetic diversity and differentiation of the large Japanese field mouse, Apodemus speciosus, we examined partial nucleotide sequences of the mitochondrial Dloop region (ca. 300 bp) in 231 individuals collected from islands in the Seto Inland Sea and adjacent regions on Honshu and Shikoku Islands in the western part of the Japanese archipelago. Molecular phylogenetic and network analyses showed that haplotypes in each island tended to form monophyletic groups, while those in Honshu and Shikoku (the major Japanese islands) showed scattered relationships and were connected with island haplotypes. These observations suggest that a set of Honshu and Shikoku haplotypes became the ancestral lineages of the island population. No gene flow was detected among island populations, indicating that independent evolution occurred on each island, without the influence of human activities, since the establishment of the islands in the Holocene. Population genetic diversities on each island were lower than those on Honshu and Shikoku. Comparison between genetic diversity and island area size showed positive correlations and supported the suggestion that genetic drift is a major factor that shaped the current haplotype constitution of the islands in the Seto Inland Sea.

  14. A seismic-reflection investigation of gas hydrates and sea-floor features of the upper continental slope of the Garden Banks and Green Canyon regions, northern Gulf of Mexico: report for cruise G1-99-GM (99002)

    USGS Publications Warehouse

    Cooper, Alan; Twichell, David; Hart, Patrick

    1999-01-01

    During April 1999, the U.S. Geological Survey (USGS) conducted a 13-day cruise in the Garden Banks and Green Canyon regions of the Gulf of Mexico. The R/V Gyre, owned by Texas A&M University, was chartered for the cruise. The general objectives were (1) to acquire very high resolution seismic-reflection data and side-scan sonar images of the upper and middle continental slope (200-1200-m water depths), (2) to study the acoustic character and features of the sea floor for evidence of sea-floor hazards, and (3) to look for evidence of subsurface gas hydrates and their effects. The Gulf of Mexico is well known for hydrocarbon resources, with emphasis now on frontier deep-water areas. For water depths greater than about 250 m, the pressure-termperature conditions are correct for the development of shallow-subsurface gas hydrate formation (Anderson et al., 1992). Gas hydrates are ice-like mixtures of gas and water (Kvenvolden, 1993). They are known to be present from extensive previous sampling in sea-floor cores and from mound-like features observed on the sea floor in many parts of the northern Gulf, including the Green Canyon and Garden Banks areas (e.g., Roberts, 1995). Seismic-reflection data are extensive in the Gulf of Mexico, but few very-high-resolution data like those needed for gas-hydrate studies exist in the public domain. The occurrence and mechanisms of gas hydrate formation and dissociation are important to understand, because of their perceived economic potential for methane gas, their potential controls on local and regional sea-floor stability, and their possible effects on earth climates due to massive release of methane greenhouse gas into the atmosphere. Three high-resolution seismic-reflection systems and one side-scan sonar system were used on the cruise to map the surface reflectance and features of the sea floor and the acoustic geometries and character of the shallow sub-surface. The cruise was designed to acquire regional and detailed local

  15. Gas hydrates of outer continental margins

    SciTech Connect

    Kvenvolden, K.A. )

    1990-05-01

    Gas hydrates are crystalline substances in which a rigid framework of water molecules traps molecules of gas, mainly methane. Gas-hydrate deposits are common in continental margin sediment in all major oceans at water depths greater than about 300 m. Thirty-three localities with evidence for gas-hydrate occurrence have been described worldwide. The presence of these gas hydrates has been inferred mainly from anomalous lacoustic reflectors seen on marine seismic records. Naturally occurring marine gas hydrates have been sampled and analyzed at about tensites in several regions including continental slope and rise sediment of the eastern Pacific Ocean and the Gulf of Mexico. Except for some Gulf of Mexico gas hydrate occurrences, the analyzed gas hydrates are composed almost exclusively of microbial methane. Evidence for the microbial origin of methane in gas hydrates includes (1) the inverse relation between methane occurence and sulfate concentration in the sediment, (2) the subparallel depth trends in carbon isotopic compositions of methane and bicarbonate in the interstitial water, and (3) the general range of {sup 13}C depletion ({delta}{sub PDB}{sup 13}C = {minus}90 to {minus}60 {per thousand}) in the methane. Analyses of gas hydrates from the Peruvian outer continental margin in particular illustrate this evidence for microbially generated methane. The total amount of methane in gas hydrates of continental margins is not known, but estimates of about 10{sup 16} m{sup 3} seem reasonable. Although this amount of methane is large, it is not yet clear whether methane hydrates of outer continental margins will ever be a significant energy resource; however, these gas hydrates will probably constitute a drilling hazard when outer continental margins are explored in the future.

  16. Rheological Stratification of the Continental Lithosphere: Constraints from Space Geodesy

    NASA Astrophysics Data System (ADS)

    Thatcher, W.

    2003-12-01

    Postseismic transient deformation, isostatic rebound from removal of pluvial lake loads, and lithospheric deflection due to reservoir impoundment are each converging on consistent rheological models for the crust and upper mantle of actively deforming continental regions. These results imply a strong elastic crust 25-40 km thick overlain by a viscoelastic substrate with an effective viscosity of ~10**18 to 10**19 Pa-s. The most surprising result of these studies is that the upper mantle is weaker than the lower crust. However, the lower crust in these regions may deform by ductile flow on longer time scales, and the data provide a lower bound of ~10**20 Pa-s for its effective viscosity. This bound on lower crustal viscosity is consistent with spectral admittance studies of the gravity field and its relation to topography in the western U. S. (Lowry et al., 2000). These results indicate effective elastic lithospheric thickness is 5-15 km in the same regions where the post-loading results indicate the entire crust is strong over about 10 to 10,000 years. Recent (and not so recent) relevant results include: (1) Deformation imaged by InSAR and GPS following the 1992 Landers and 1999 Hector Mine, California earthquakes; (2) Leveling surveys following the 1959 M=7.3 Hegben Lake, Montana earthquake; (3) Isostatic rebound of Lake Bonneville, Utah; (4) Leveling surveys following filling of Lake Mead, Arizona in 1935. Postseismic transient deformation observed following several other recent large earthquakes provides potential constraints on bulk rheology of the lithosphere. However, deformation following events at major plate boundaries, including the 1993 Hokkaido-oki (M=7.8), 1999 Taiwan (M=7.6) and 1999 Izmet (M=7.5) earthquakes is dominated by the effects of buried aseismic afterslip, making it difficult to extract any signals that may be due to bulk relaxation of the lower crust and upper mantle. This suggests that large intraplate earthquakes on faults adjacent to

  17. Tectonic evolution of a continental subduction-exhumation channel: Variscan structure of the basal allochthonous units in NW Spain

    NASA Astrophysics Data System (ADS)

    DíEz FernáNdez, RubéN.; MartíNez CataláN, José Ramón; Arenas MartíN, Ricardo; Abati Gómez, Jacobo

    2011-06-01

    A regional study starting from detailed geological mapping has been carried out in the Malpica-Tui Complex of Galicia in NW Spain. The complex is formed by two units representing pieces of the external edge of Gondwana, subducted and exhumed during the Variscan collision. The study shows that synsubduction and early synexhumation structures in continental subduction channels tends to be obscured and even erased once exhumation is complete. Detailed structural analysis, matched with the knowledge of the history, and available data for other Galician basal units have elucidated the major structures developed during the subduction-exhumation process. The results include evidence of the plate convergence causing early Variscan continental subduction of the Gondwana margin. Subduction was followed by exhumation driven by ductile thrusting within the subduction channel, which, in turn, provoked crustal duplication in the subducted slab and modified the initial tectonometamorphic architecture of the subduction wedge. The next step was accretion to the adjacent continental domains, placing the subduction wedge on top of unsubducted parts of the Gondwana margin via ductile thrusting. Thrusting was preceded by progressive propagation of a train of recumbent folds toward the foreland that affected the previous structural stack. Subsequent transference of oceanic (Rheic) and peri-Gondwanan terranes to the Gondwana margin took place by out-of-sequence thrusting followed by crustal extensional collapse and strike-slip tectonics.

  18. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  19. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  20. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  1. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  2. Regional Phases: Oceanic and Continental Propagation

    DTIC Science & Technology

    1989-03-04

    the single frequency microseism peak is fundamentally different. Early observations of this peak were made by Wiechert (1904), Oliver and Ewing (1957...A., 243, 1-35. Oliver , J., Ewing, M., 1957, Microseisms in the 11 to 18 second period range, Bull. Seism. Soc. Am., 47, 111-127. Orcutt, J.A...The "shah" function is tapered exponentially to simulate the effect of attenuation and is multiplied by the Heaviside step function to exclude any

  3. Cry1A toxins of Bacillus thuringiensis bind specifically to a region adjacent to the membrane-proximal extracellular domain of BT-R(1) in Manduca sexta: involvement of a cadherin in the entomopathogenicity of Bacillus thuringiensis.

    PubMed

    Dorsch, J A; Candas, M; Griko, N B; Maaty, W S A; Midboe, E G; Vadlamudi, R K; Bulla, L A

    2002-09-01

    Many subspecies of the soil bacterium Bacillus thuringiensis produce various parasporal crystal proteins, also known as Cry toxins, that exhibit insecticidal activity upon binding to specific receptors in the midgut of susceptible insects. One such receptor, BT-R(1) (210 kDa), is a cadherin located in the midgut epithelium of the tobacco hornworm, Manduca sexta. It has a high binding affinity (K(d) approximately 1nM) for the Cry1A toxins of B. thuringiensis. Truncation analysis of BT-R(1) revealed that the only fragment capable of binding the Cry1A toxins of B. thuringiensis was a contiguous 169-amino acid sequence adjacent to the membrane-proximal extracellular domain. The purified toxin-binding fragment acted as an antagonist to Cry1Ab toxin by blocking the binding of toxin to the tobacco hornworm midgut and inhibiting insecticidal action. Exogenous Cry1Ab toxin bound to intact COS-7 cells expressing BT-R(1) cDNA, subsequently killing the cells. Recruitment of BT-R(1) by B. thuringiensis indicates that the bacterium interacts with a specific cell adhesion molecule during its pathogenesis. Apparently, Cry toxins, like other bacterial toxins, attack epithelial barriers by targeting cell adhesion molecules within susceptible insect hosts.

  4. Coordination: southeast continental shelf studies. Progress report

    SciTech Connect

    Menzel, D.W.

    1980-03-01

    The GABEX I experiment is designed to provide synoptic coverage of a series of Gulf Stream wave-like disturbances, the effect of these on the circulation of the entire shelf, and on biological and chemical processes. This study was initiated in February 1980 when current meter arrays were deployed. These meters will be removed in July 1980. In April three ships will simultaneously study the effects of Gulf Stream disturbances on the hydrography, chemistry, and biology of the shelf. One vessel will track a specific wave-like disturbance and provide synoptic coverage of the shelf area. The second vessel will determine the effect of shelf break processes on adjacent shelf water; and the third will study trace metal distributions in and outside of disturbances. Research progress is reported in continental shelf studies, nearshore and estuarine studies (diffusion of freshwater out of nearshore zone), tidal currents and material transport, and mixing of inlet plumes.

  5. Iceberg scouring on the Norwegian continental shelf

    SciTech Connect

    Lien, R.

    1983-05-01

    This paper is a condensed version of parts of a Dr. ing. thesis to be presented during 1983. The first part of the paper deals with the regional distribution of iceberg scouring on the Norwegian continental shelf, and some general aspects related to it. The second part deals with iceberg scouring as a local phenomenon and its relation to the sea floor topography, sediment distribution, and geological and geotechnical properties of the sediments.

  6. Geohistory analysis of the Santa Maria basin, California, and its relationship to tectonic evolution of the continental margin

    SciTech Connect

    McCrory, P.A.; Arends, R.G. ); Ingle, J.C. Jr. ); Isaacs, C.M.; Stanley, R.G. ); Thornton, M.L.C. )

    1991-02-01

    The Santa Maria basin of central California is a geologically complex area located along the tectonically active California continental margin. The record of Cenozoic tectonism preserved in Santa Maria strata provides an opportunity to compare the evolution of the region with plate tectonic models for Cenozoic interactions along the margin. Geohistory analysis of Neogene Santa Maria basin strata provides important constraints for hypotheses of the tectonic evolution of the central California margin during its transition from a convergent to a transform plate boundary. Preliminary analyses suggest that the tectonic evolution of the Santa Maria area was dominated by coupling between adjacent oceanic plates and the continental margin. This coupling is reflected in the timing of major hiatuses within the basin sedimentary sequence and margin subsidence and uplift which occurred during periods of tectonic plate adjustment. Stratigraphic evidence indicates that the Santa Maria basin originated on the continental shelf in early Miocene time. A component of margin subsidence is postulated to have been caused by cessation of spreading on adjacent offshore microplates approximately 19-18 ma. A sharp reduction in rate of tectonic subsidence in middle Miocene time, observed in the Santa Maria basin both onshore and offshore, was coeval with rotation of crustal blocks as major shearing shifts shoreward. Tectonic uplift of two eastern sites, offshore Point Arguello and near Point Sal, in the late Miocene may have been related to a change to transpressional motion between the Pacific and North American plates, as well as to rotation of the western Transverse Ranges in a restraining geometry.

  7. The impact of ocean deoxygenation on iron release from continental margin sediments

    NASA Astrophysics Data System (ADS)

    Scholz, Florian; McManus, James; Mix, Alan C.; Hensen, Christian; Schneider, Ralph R.

    2014-06-01

    In the oceans' high-nitrate-low-chlorophyll regions, such as the Peru/Humboldt Current system and the adjacent eastern equatorial Pacific, primary productivity is limited by the micronutrient iron. Within the Peruvian upwelling area, bioavailable iron is released from the reducing continental margin sediments. The magnitude of this seafloor source could change with fluctuations in the extension or intensity of the oxygen minimum zones. Here we show that measurements of molybdenum, uranium and iron concentrations can be used as a proxy for sedimentary iron release, and use this proxy to assess iron release from the sea floor beneath the Peru upwelling system during the past 140,000 years. We observe a coupling between levels of denitrification, as indicated by nitrogen isotopes, trace metal proxies for oxygenation, and sedimentary iron concentrations. Specifically, periods with poor upper ocean oxygenation are characterized by more efficient iron retention in the sediment and a diminished iron supply to the water column. We attribute efficient iron retention under more reducing conditions to widespread sulphidic conditions in the surface sediment and concomitant precipitation of iron sulphides. We argue that iron release from continental margin sediments is most effective in a narrow redox window where neither oxygen nor sulphide is present. We therefore suggest that future deoxygenation in the Peru upwelling area would be unlikely to result in increased iron availability, whereas in weaker oxygen minimum zones partial deoxygenation may enhance the iron supply.

  8. The footprint of continental-scale ocean currents on the biogeography of seaweeds.

    PubMed

    Wernberg, Thomas; Thomsen, Mads S; Connell, Sean D; Russell, Bayden D; Waters, Jonathan M; Zuccarello, Giuseppe C; Kraft, Gerald T; Sanderson, Craig; West, John A; Gurgel, Carlos F D

    2013-01-01

    Explaining spatial patterns of biological organisation remains a central challenge for biogeographic studies. In marine systems, large-scale ocean currents can modify broad-scale biological patterns by simultaneously connecting environmental (e.g. temperature, salinity and nutrients) and biological (e.g. amounts and types of dispersed propagules) properties of adjacent and distant regions. For example, steep environmental gradients and highly variable, disrupted flow should lead to heterogeneity in regional communities and high species turnover. In this study, we investigated the possible imprint of the Leeuwin (LC) and East Australia (EAC) Currents on seaweed communities across ~7,000 km of coastline in temperate Australia. These currents flow poleward along the west and east coasts of Australia, respectively, but have markedly different characteristics. We tested the hypothesis that, regional seaweed communities show serial change in the direction of current flow and that, because the LC is characterised by a weaker temperature gradient and more un-interrupted along-shore flow compared to the EAC, then coasts influenced by the LC have less variable seaweed communities and lower species turnover across regions than the EAC. This hypothesis was supported. We suggest that this pattern is likely caused by a combination of seaweed temperature tolerances and current-driven dispersal. In conclusion, our findings support the idea that the characteristics of continental-scale currents can influence regional community organisation, and that the coupling of ocean currents and marine biological structure is a general feature that transcends taxa and spatial scales.

  9. A sequence-specific DNA-binding factor (VF1) from Anabaena sp. strain PCC 7120 vegetative cells binds to three adjacent sites in the xisA upstream region.

    PubMed Central

    Chastain, C J; Brusca, J S; Ramasubramanian, T S; Wei, T F; Golden, J W

    1990-01-01

    A DNA-binding factor (VF1) partially purified from Anabaena sp. strain PCC 7120 vegetative cell extracts by heparin-Sepharose chromatography was found to have affinity for the xisA upstream region. The xisA gene is required for excision of an 11-kilobase element from the nifD gene during heterocyst differentiation. Previous studies of the xisA upstream sequences demonstrated that deletion of this region is required for the expression of xisA from heterologous promoters in vegetative cells. Mobility shift assays with a labeled 250-base-pair fragment containing the binding sites revealed three distinct DNA-protein complexes. Competition experiments showed that VF1 also bound to the upstream sequences of the rbcL and glnA genes, but the rbcL and glnA fragments showed only single complexes in mobility shift assays. The upstream region of the nifH gene formed a weak complex with VF1. DNase footprinting and deletion analysis of the xisA binding site mapped the binding to a 66-base-pair region containing three repeats of the consensus recognition sequence ACATT. Images PMID:2118506

  10. Benthic polychaete diversity patterns and community structure in the Whittard Canyon system and adjacent slope (NE Atlantic)

    NASA Astrophysics Data System (ADS)

    Gunton, Laetitia M.; Neal, Lenka; Gooday, Andrew J.; Bett, Brian J.; Glover, Adrian G.

    2015-12-01

    We examined deep-sea macrofaunal polychaete species assemblage composition, diversity and turnover in the Whittard Canyon system (NE Atlantic) using replicate megacore samples from three of the canyon branches and one site on the continental slope to the west of the canyon, all at ~3500 m water depth. A total of 110 polychaete species were recorded. Paramphinome jeffreysii was the most abundant species (2326 ind. m-2) followed by Aurospio sp. B (646 ind. m-2), Opheliidae sp. A (393 ind. m-2), Prionospio sp. I (380 ind. m-2), and Ophelina abranchiata (227 ind. m-2). Species composition varied significantly across all sites. From west to east, the dominance of Paramphinome jeffreysii increased from 12.9% on the slope to 39.6% in the Eastern branch. Ordination of species composition revealed that the Central and Eastern branches were most similar, whereas the Western branch and slope sites were more distinct. High abundances of P. jeffreysii and Opheliidae sp. A characterised the Eastern branch of the canyon and may indicate an opportunistic response to a possible recent input of organic matter inside the canyon. Species richness and diversity indices were higher on the slope compared with inside the canyon, and the slope site had higher species evenness. Within the canyon, species diversity between branches was broadly similar. Despite depressed diversity within the canyon compared with the adjacent slope, the fact that 46 of the 99 polychaete species found in the Whittard Canyon were not present on the adjacent slope suggests that this feature may enhance the regional species pool. However, our sampling effort on the adjacent slope was insufficient to confirm this conclusion.

  11. Preliminary report on geology along Atlantic Continental Margin of northeastern United States

    USGS Publications Warehouse

    Minard, J.P.; Perry, W.J.; Weed, E.G.A.; Rhodehamel, E.C.; Robbins, E.I.; Mixon, R.B.

    1974-01-01

    The U.S. Geological Survey is conducting a geologic and geophysical study of the northeastern United States outer continental shelf and the adjacent slope from Georges Bank to Cape Hatteras. The study also includes the adjacent coastal plain because it is a more accessible extension of the shelf. The total study area is about 324,000 sq km, of which the shelf and slope constitute about 181,000 sq km and the coastal plain constitutes 143,000 sq km. The shelf width ranges from about 30 km at Cape Hatteras to about 195 km off Raritan Bay and on Georges Bank. Analyses of bottom samples make it possible to construct a preliminary geologic map of the shelf and slope to a water depth of 2,000 m. The oldest beds cropping out in the submarine canyons and on the slope are of early ate Cretaceous age. Beds of Early Cretaceous and Jurassic age are present in deep wells onshore and probably are present beneath the shelf in the area of this study. Such beds are reported beneath the Scotian shelf on the northeast where they include limestone, salt, and anhydrite. Preliminary conclusions suggest a considerably thicker Mesozoic sedimentary sequence than has been described previously. The region is large; the sedimentary wedge is thick; structures seem favorable; and the hydrocarbon potential may be considerable.

  12. Mechanisms of continental intraplate earthquakes

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, Abhijit Kumar

    To better understand the mechanisms of continental intraplate earthquakes, a multistep approach was used. The first step involved analysis and synthesis of multidisciplinary data from 39 intraplate earthquakes spanning 20 continental intraplate regions, to identify their characteristic and diagnostic features. This led to the following testable hypothesis: Intraplate earthquakes occur within pre-existing zones of weakness (most commonly failed rifts), in the vicinity of stress concentrators, such as, intersecting faults, buried plutons, and/or rift pillows in the presence of the ambient stress field. The next step involved testing this hypothesis---first with 2-D mechanical models and then with 3-D models. Since two-thirds of the examined intraplate regions had intersecting faults as a stress concentrator, its role was first evaluated. A Distinct Element Method was used wherein the models comprised of the structural framework of the concerned region represented by a set of rock blocks that are assigned elastic properties conforming to the known geology, and subjected to tectonic loading along the direction of maximum regional compression (S Hmax) at a rate similar to the ambient plate velocity. The 2-D modeling was performed for two major intraplate regions in eastern U.S., viz., New Madrid and Middleton Place Summerville seismic zones, using a commercially available code called UDEC. These models adequately explain the spatial distribution of current seismicity in the regions. However, the absence of the third dimension limited the observation of tectonics in the depth dimension. Thus, 3-D models were developed for these two regions using the 3-D version of UDEC, called 3DEC. The preliminary results of these models adequately demonstrate correlation of locations of current seismicity with fault intersections in 3-D space, and also duplicate vertical movements. Although, the mechanical models demonstrated a causal association of seismicity with intersecting faults

  13. Aeromagnetic and gravity investigations of the Coastal Area and Continental Shelf of Liberia, West Africa, and their relation to continental drift

    USGS Publications Warehouse

    Behrendt, John C.; Wotorson, Cletus S.

    1970-01-01

    anomalies exist over two Cretaceous basins in the coastal area; a negative Bouguer anomaly exists over one of the basins southwest of Monrovia, as shown by a marine traverse, suggesting that Cretaceous or younger sedimentary rocks fill these basins also. A 50 to 60 mgal positive Bouguer anomaly area exists along the coast from Sierra Leone to Ivory Coast. This anomaly correlates with mafic granulites in the Monrovia region, where the gradient is too steep to be entirely due to crustal thickening at the continental margin and may be related to tectonic activity associated with the basins. The only major break in this positive anomaly above basement rocks along the entire coast of Liberia is over granite gneiss adjacent to (and presumably underlying) the only onshore basins on the Liberian coast. Three seismic reflection profiles support the interpretation of a substantial section of sedimentary rock offshore. A suggested sequence of events indicates tectonic activity in the periods about 2700, about 2000, and about 550 m.y. B.P.; uplift and exposure of deep crustal rocks; deposition of Paleozoic sediments; intrusion of diabase dikes in inland zones; intrusion of 176 to 192 m.y.-old dikes and sills accompanying separation of Africa and South and North America; block faulting along coast and continental shelf, and active sea-floor spreading; filling of basins in Cretaceous and Tertiary(?) time; basaltic extrusion on spreading sea floor and sedimentation on continental shelf and slope.

  14. Lomonosov Ridge as a Natural Component of Continental Margin

    NASA Astrophysics Data System (ADS)

    Poselov, V.; Kaminsky, V. D.; Butsenko, V. V.; Grikurov, G. E.

    2010-12-01

    In geodynamic context, Lomonosov Ridge is interpreted as a rifted passive margin framing the Eurasian oceanic basin. At the same time its near-Siberian segment is intimately associated with the Russian Arctic shelf, as evidenced by morphological data and the results of “Trans-Arctic 1992” and “Arctic-2007” geotransect studies. Coring and ACEX data demonstrated the presence in the uppermost geological section of the ridge of Late Cretaceous through Cenozoic sediments and Jurassic-Cretaceous sedimentary rocks; the latter may belong to deeper levels of sedimentary cover, or may represent the Mesozoic folded basement. Coarse bottom debris contains also the fragments of Riphean-Paleozoic rocks probably derived from the local bedrock source. Structure of sedimentary cover is imaged by continuous seismic observations from the shelf of East Siberian Sea along the length of Lomonosov Ridge to 85 N. In the upper part of the section there are two sedimentary sequences separated by a regional unconformity; their seismic velocities are 2.4-3.1 km/s in the upper sequence and 3.4-4.0 km/s in the lower one, and the total thickness reaches ~ 8 km in the deepest part of New Siberian Basin. Both these sequences and the unconformity are traced from Lomonosov Ridge into Amundsen Basin on seismic reflection sections obtained by drifting ice stations North Pole 2479 and 2480. The low-velocity sediments are underlain by a metasedimetary sequence with velocities decreasing from 4.7-4.9 km/s on the shelf to 4.4-4.9 km/s beneath continental slope and 4.2-4.8 km/s on Lomonosov Ridge. The thickness of metasedimentary sequence is about 7 km on the shelf, up to 3.5 km under continental slope, and strongly variable (1-5 km) on Lomonosov Ridge. The upper layer of consolidated crust is 8-9 km thick on the shelf with velocities 6.1-6.2 km/s; on Lomonosov Ridge both its thickness and velocities increase to 10 km and 6.0-6.4 km/s, respectively. In the lower crust the velocities do not exceed 6

  15. Phytoplankton assemblages within the Chesapeake Bay plume and adjacent waters of the continental shelf

    NASA Technical Reports Server (NTRS)

    Marshall, H. G.

    1981-01-01

    The Chesapeake Bay plume was identified and plotted in relation to the presence and high concentrations of phytoplankton assemblages. Seasonal differences occurred within the plume during the collection period, with Skeletonema costatum and an ultraplankton component the dominant forms. Patchiness was found along the transects, with variations in composition and concentrations common on consecutive day sampling within the plume in its movement along the shelf. The presence of 236 species is noted, with their presence indicated for plume and shelf stations during the March, June, and October 1980 collections.

  16. Mapping of lithologic and structural units using multispectral imagery. [Afar-Triangle/Ethiopia and adjacent areas (Ethiopian Plateau, Somali Plateau, and parts of Yemen and Saudi Arabia)

    NASA Technical Reports Server (NTRS)

    Kronberg, P. (Principal Investigator)

    1974-01-01

    The author has identified the following significant results. ERTS-1 MSS imagery covering the Afar-Triangle/Ethiopia and adjacent regions (Ethiopian Plateau, Somali Plateau, and parts of Yemen and Saudi Arabi) was applied to the mapping of lithologic and structural units of the test area at a scale 1:1,000,000. Results of the geological evaluation of the ERTS-1 imagery of the Afar have proven the usefullness of this type of satellite data for regional geological mapping. Evaluation of the ERTS images also resulted in new aspects of the structural setting and tectonic development of the Afar-Triangle, where three large rift systems, the oceanic rifts of the Red Sea and Gulf of Aden and the continental East African rift system, seem to meet each other. Surface structures mapped by ERTS do not indicate that the oceanic rift of the Gulf of Aden (Sheba Ridge) continues into the area of continental crust west of the Gulf of Tadjura. ERTS data show that the Wonji fault belt of the African rift system does not enter or cut through the central Afar. The Aysha-Horst is not a Horst but an autochthonous spur of the Somali Plateau.

  17. Middle America - Regional Geological Integrity, Hydrocarbon Implications.

    NASA Astrophysics Data System (ADS)

    James, K. H.

    2008-05-01

    Dogma holds that the Caribbean Plate and its islands formed in the Pacific and comprise oceanic crust and intra- oceanic arc rocks. Middle America, between N and S America, manifests a regional, N35°E and N60°W tectonic fabric. The NE trend results from Triassic-Jurassic reactivation of Palaeozoic convergent structures as extensional faults during Pangean rifting and commencement of N America drift. The NW trend parallels major inter-continental faults and oceanic fractures along which extension and drift occurred. Triassic-Jurassic red beds accumulated in the NE trending, intra-continental rifts of N, S and Central America. Proximal extended continental margins subsided to accommodate thick Cretaceous carbonate sections (Florida - Bahamas, Campeche, Nicaragua Rise). Distal margins formed continental blocks flanked by seaward-dipping wedges. Seismic and drilling in basins along the eastern seaboard of N America (Baltimore Canyon to Blake Plateau) document Triassic-Jurassic red beds overlain by salt and carbonates. Hydrocarbons are present. In Middle America the Gulf of Mexico remained "intra-continental", surrounded by continental blocks (N America, Maya, Florida). The area further south experienced greater extension, manifest by diverging oceanic fracture patterns to the east and west. Seismic data over the Caribbean Plateau reveal deep architecture of NE trending highs flanked by dipping wedges of reflections, similar to eastern N America distal basins. DSDP drilling calibrated the overlying smooth seismic Horizon B" as recording Cenomanian basalts. Smoothness, great lateral extent and coeval exposed sections with palaeosols followed by shallow marine carbonates suggest they were sub-aerial. Adjacent, rough seismic Horizon B" probably records top of submarine, serpentinized mantle. Seismic over the plateau also reveals features identical to drilled Sigsbee salt diapirs of the Gulf of Mexico. The regional tectonic fabric demonstrates a shared geological history

  18. Map showing spatial and temporal relations of mountain and continental glaciations on the Northern Plains, primarily in northern Montana and northwestern North Dakota

    USGS Publications Warehouse

    Fullerton, David S.; Colton, Roger B.; Bush, Charles A.; Straub, Arthur W.

    2004-01-01

    This report is an overview of glacial limits and glacial history on the plains in northern Montana and northeastern North Dakota (long 102?-114?W.) and also in adjacent southern Alberta and Saskatchewan, Canada. In the Rocky Mountains and on the plains adjacent to the mountains in Montana, the map also depicts spatial relations of valley glaciers and piedmont ice lobes to continental ice sheets. Glacial limits east of 102?, in the United States and also in adjacent Canada, are depicted on published maps of the U.S. Geological Survey Quaternary Geologic Atlas of the United States (I-1420) map series. The limits shown here are from data compiled for the Lethbridge, Regina, Yellowstone, and Big Horn Mountains 4? x 6? quadrangles in the Quaternary Geologic Atlas series. This geospatial database has been prepared with a degree of detail appropriate for viewing at a scale of 1:1,000,000. Because of the degree of generalization required, the map is intended for regional analysis, rather than for detailed analysis in specific areas. It depicts the geographic positions of the limits of mountain and continental glaciations and the limits of selected glacial readvances. That information provides a foundation for reconstruction of geologic history and for reconstruction. The base map is simplified. Selected hydrographic features, selected towns and cities, selected physiographic features, and a grid of 1? x 2? topographic quadrangles are included to aid the reader in location of the glacial limits and other features that are depicted here on other maps at different scales. Most of the geologic data were compiled at 1:250,000 scale. The nominal reading scale of the digitized map data is 1:1,000,000. Enlargement will not restore resolution that was lost by simplification or generalization of data. Accompanying illustrations show regional directions of ice movement from Canada into the United States during maximum Illinoian glaciation, during maximum late Wisconsin glaciation

  19. Late Cenozoic evolution of the East China continental margin: Insights from seismic, gravity, and magnetic analyses

    NASA Astrophysics Data System (ADS)

    Shang, Lu-Ning; Zhang, Xun-Hua; Jia, Yong-Gang; Han, Bo; Yang, Chuan-Sheng; Geng, Wei; Pang, Yu-Mao

    2017-02-01

    Seismic reflection profiles reveal the structural characteristics beneath the East China Sea shelf margin and the Okinawa Trough, and provide new constraints on the Late Cenozoic evolution of the East China continental margin. The Frontal Shelf Basin between the Taiwan-Sinzi Uplift and the trough axis occupies the western half of the Northern-Middle Okinawa Trough. In this basin, the Middle-Late Miocene sediments are confined to grabens or half-grabens dominated by listric faults, whereas the overlying Pliocene-Quaternary sequence is characterized by a uniform thickness and dense planar-type faults, suggesting that rifting of the Northern-Middle Okinawa Trough initiated during the Middle Miocene but slowed down during the earliest Pliocene. Since that time, the opening of the Okinawa Trough has been dominated by diffuse rifting. The Southern Okinawa Trough is predominately filled by Quaternary sediments, indicating that its back-arc rifting began during the earliest Pleistocene. Contractional structures identified in the pre-Quaternary sequence beneath the continental slope, along with an erosional Pleistocene-pre-Pleistocene unconformity in the Southern Okinawa Trough, demonstrate the existence of pre-rifting compression and uplifting in this region. We use this evidence and previously published results, to propose an evolutionary model of the East China continental margin during the Late Cenozoic. The Northern-Middle Okinawa Trough began rifting during the Middle Miocene on a paleo-uplift. The Luzon Arc initially impinged upon the Eurasian continental margin during the Late Miocene near the southeastern end of the Miyako Fault Belt and activated the proto-Taiwan Orogeny in today's Southern Okinawa Trough and adjacent regions. During the Late Miocene-Pliocene, the orogeny quickly propagated southwestward along with the west-northwest-moving Philippine Sea Plate. Subsequently, the rifting of the Southern Okinawa Trough was initiated during the earliest Pleistocene

  20. A study of models and controls for basin formation during continental collision: (1) Australian lithosphere along Banda orogen (Indonesia) and (2) Alboran Sea basin (western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Tandon, Kush

    Mechanisms for the formation of a foreland basin at the beginning of continental collision (Pliocene-Recent Australian continental foreland along the Banda orogen) and a post-orogenic, continental, Miocene extensional basin (Alboran Sea) are studied. Such a study investigates the controls on the basin formation during the start of the Wilson cycle and later during the break up of a thickened continent in a collisional environment. Effective Elastic Thickness (EET) of the Australian continental lithosphere from Roti to the Kai Plateau ({˜}121sp°{-}137sp°E longitude) are estimated using an elastic-half beam model to match the sea floor bathymetry and the Bouguer gravity anomalies. Range of constant EET values from 27-75 km across the shelf of Australian lithosphere shows a variation of 64% with the highest value in the vicinity of central Timor where the collision is most advanced. Downdip on the Australian continental lithosphere from shelf to beneath the Banda orogen, the reduction in EET is from ˜90 km-˜30 km (66%). Variations in EET can be explained by inelastic yielding (brittle and plastic failure, crust-mantle decoupling in the lower crust and brittle-ductile decoupling in the upper-middle crust) in the Australian lithosphere. Change in EET occurred at the start of continental subduction due to change in curvature, both in map and cross-sectional view. Oroclinal bending of the continental Australian lithosphere increased the inelastic failure in the eastern end. Different mechanisms of basin formation at a site of post-orogenic collapse are studied by constraining the timing of rifting in the western, eastern, and northern parts of the Alboran Sea basin on seismic reflectors via synthetic seismograms using ODP Leg 161 and Andalucia A-1 data. Regions of adjacent coeval compression and extension are found in the Alboran Sea basin. Normal faulting continues in parts of the eastern Alboran Sea basin later than in the western Alboran Sea basin. The development

  1. Transform continental margins - part 1: Concepts and models

    NASA Astrophysics Data System (ADS)

    Basile, Christophe

    2015-10-01

    of the transform continental margin with the adjacent oceanic lithosphere.

  2. Gravity and structure of the continental margins of southwestern Mexico and northwestern Guatemala

    NASA Astrophysics Data System (ADS)

    Couch, Richard; Woodcock, Stephen

    1981-03-01

    Geophysical measurements over the eastern end of the Tehuantepec Ridge and adjacent continental margins of southern Mexico and northern Guatemala indicate that the ridge is a fracture zone and that it marks the boundary between two different subduction provinces. A positive free-air gravity anomaly which extends northwestward along the outer continental shelf of Guatemala curves abruptly landward in the Gulf of Tehuantepec. The positive shelf anomaly is on trend with the positive anomaly of the Nicoya Peninsula, Costa Rica, and suggests that rocks genetically related to Cretaceous rocks of the Nicoya Complex extend northwestward along the continental shelf to the Gulf of Tehuantepec. A crustal and subcrustal cross section of the continental margin of Guatemala, constrained by gravity, magnetic, and seismic refraction data, indicates that the rock strata causing the outer shelf gravity high dip landward, consistent with imbricate thrusting of the oceanic crust beneath and into the continental margin. A model crustal cross section of the continental margin of southern Mexico, north of the Tehuantepec Ridge, shows a markedly different margin structure with a relatively small amount of continental accretion and a continental crustal block extending to within approximately 25 km of the trench axis.

  3. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 1 2014-10-01 2014-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of...

  4. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 1 2012-10-01 2011-10-01 true Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of...

  5. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 1 2013-10-01 2013-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of...

  6. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of...

  7. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of...

  8. A pair of adjacent genes, cry5Ad and orf2-5Ad, encode the typical N- and C-terminal regions of a Cry5Adelta-endotoxin as two separate proteins in Bacillus thuringiensis strain L366.

    PubMed

    Lenane, Ian J; Bagnall, Neil H; Josh, Peter F; Pearson, Roger D; Akhurst, Ray J; Kotze, Andrew C

    2008-01-01

    A new DNA sequence cry5Ad/orf2-5Ad (GenBank accession number EF219060) was isolated from Bacillus thuringiensis strain L366. This DNA sequence contains two ORFs: cry5Ad (a previously unreported member of the cry5A gene family) and orf2-5Ad. cry5Ad is unique among cry5A genes in that it encodes only the N-terminal region of a typical Cry5Adelta-endotoxin. The cry5Ad sequence includes homology blocks 1-5, which are present in most B. thuringiensisdelta-endotoxins. The usual C-terminal region of a Cry5Adelta-endotoxin (including homology blocks 6-8) is encoded by orf2-5Ad. Both proteins encoded by cry5Ad and orf2-5Ad were found in IPTG-induced Escherichia coli, after a copy of cry5Ad/orf2-5Ad was cloned into the pQE32 expression vector and transformed into pREP4 E. coli cells. Both proteins were also found in parasporal crystal inclusions of B. thuringiensis L366. Sequencing of cDNA derived from transformed E. coli cells showed that the two ORFs are transcribed as a single mRNA. Extracts prepared from the recombinant E. coli expressing Cry5Ad and Orf2-5Ad were not toxic to nematode larvae (Haemonchus contortus), indicating that these two proteins are most likely not responsible for the nematocidal activity seen previously in the B. thuringiensis strain L366.

  9. Palaeomagnetism and the continental crust

    SciTech Connect

    Piper, J.D.A.

    1987-01-01

    This book is an introduction to palaeomagnetism offering treatment of theory and practice. It analyzes the palaeomagnetic record over the whole of geological time, from the Archaean to the Cenozoic, and goes on to examine the impact of past geometries and movements of the continental crust at each geological stage. Topics covered include theory of rock and mineral magnetism, field and laboratory methods, growth and consolidation of the continental crust in Archaean and Proterozoic times, Palaeozoic palaeomagnetism and the formation of Pangaea, the geomagnetic fields, continental movements, configurations and mantle convection.

  10. Modeling a three-dimensional river plume over continental shelf using a 3D unstructured grid model

    USGS Publications Warehouse

    Cheng, R.T.; Casulli, V.; ,

    2004-01-01

    River derived fresh water discharging into an adjacent continental shelf forms a trapped river plume that propagates in a narrow region along the coast. These river plumes are real and they have been observed in the field. Many previous investigations have reported some aspects of the river plume properties, which are sensitive to stratification, Coriolis acceleration, winds (upwelling or downwelling), coastal currents, and river discharge. Numerical modeling of the dynamics of river plumes is very challenging, because the complete problem involves a wide range of vertical and horizontal scales. Proper simulations of river plume dynamics cannot be achieved without a realistic representation of the flow and salinity structure near the river mouth that controls the initial formation and propagation of the plume in the coastal ocean. In this study, an unstructured grid model was used for simulations of river plume dynamics allowing fine grid resolution in the river and in regions near the coast with a coarse grid in the far field of the river plume in the coastal ocean, in the vertical, fine fixed levels were used near the free surface, and coarse vertical levels were used over the continental shelf. The simulations have demonstrated the uniquely important role played by Coriolis acceleration. Without Coriolis acceleration, no trapped river plume can be formed no matter how favorable the ambient conditions might be. The simulation results show properties of the river plume and the characteristics of flow and salinity within the estuary; they are completely consistent with the physics of estuaries and coastal oceans.

  11. Sediments, structural framework, petroleum potential, environmental conditions, and operational considerations of the United States South Atlantic Outer Continental Shelf

    USGS Publications Warehouse

    ,

    1975-01-01

    The area designated for possible oil and gas lease sale in Bureau of Land Management memorandum 3310 #43 (722) and referred to therein as part of the United States South Atlantic Outer Continental Shelf (OCS) contains about 98,000 square kilometres of the continental margin seaward of the 3 mile offshore limit and within the 600 metre isobath. The designated area, offshore of North Carolina, South Carolina, Georgia, and Florida, encompasses parts of three physiographic provinces: the Continental Shelf, the Florida-Hatteras Slope, and the Blake Plateau. The structural framework of the U.3. South Atlantic region is dominated by the Southeast Georgia Embayment --an east-plunging depression recessed into the Atlantic Coastal Plain and shelf between Cape Fear, North Carolina and Jacksonville, Florida. The embayment is bounded to the north by the Cape Fear Arch and to southeast by the Peninsular Arch. Refraction data indicate a minor basement(?) ridge beneath the outer shelf between 30? and 32?N at 80?W. Drill hole data also suggest a gentle fold or accretionary structure (reef?) off the east coast of Florida. Several other structural features have been identified by refraction and reflection techniques and drilling. These are the Yamacraw Uplift, Burton High, Stone Arch, and the Suwannee Channel. Gravity and magnetic anomalies within the area probably result from emplacement of magma bodies along linear features representing fundamental crustal boundaries. Of these anomalies, the most prominent, is a segment of the East Coast Magnetic Anomaly which crosses the coast at Brunswick, Georgia. This anomaly has been interpreted as representing an ancient continental boundary where two formerly separate continental plates collided and were welded together. There may be as much as 5,000 m of sedimentary rocks in the Southeast Georgia Embayment out to the 600 m isobath. Basement rocks beneath the Southeast Georgia Embayment are expected to be similar to those exposed in the

  12. Heat and Groundwater Flow through Continental Flood Basalt Provinces: Insights Gained from Alternative Models of Permeability/Depth Relationships for the Columbia Plateau, USA

    NASA Astrophysics Data System (ADS)

    Burns, E. R.; Williams, C. F.; Ingebritsen, S.; Voss, C. I.; Spane, F.; DeAngelo, J.

    2014-12-01

    Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (~3.5 orders of magnitude) at 600-900 m depth and ~40oC. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at ~600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Abrupt k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration. Because pore filling hydrothermal minerals are largely controlled by the major mineral assemblages of the volcanic rocks, other continental flood basalt provinces may also have large permeability changes at depths corresponding to ~40oC.

  13. Geodynamic settings of microcontinents, non-volcanic islands and submerged continental marginal plateau formation

    NASA Astrophysics Data System (ADS)

    Dubinin, Evgeny; Grokholsky, Andrey; Makushkina, Anna

    2016-04-01

    Complex process of continental lithosphere breakup is often accompanied by full or semi isolation of small continental blocks from the parent continent such as microcontinents or submerged marginal plateaus. We present different types of continental blocks formed in various geodynamic settings. The process depends on thermo-mechanical properties of rifting. 1) The continental blocks fully isolated from the parent continent. This kind of blocks exist in submerged form (Elan Bank, the Jan-Mayen Ridge, Zenith Plateau, Gulden Draak Knoll, Batavia Knoll) and in non-submerged form in case of large block size. Most of listed submerged blocks are formed in proximity of hot-spot or plume. 2) The continental blocks semi-isolated from the parent continent. Exmouth Plateau, Vøring, Agulhas, Naturaliste are submerged continental plateaus of the indicated category; Sri Lanka, Tasmania, Socotra are islands adjacent to continent here. Nowadays illustration of this setting is the Sinai block located between the two continental rifts. 3) The submerged linear continental blocks formed by the continental rifting along margin (the Lomonosov Ridge). Suggested evolution of this paragraph is the rift propagation along existing transtensional (or another type) transform fault. Future example of this type might be the California Peninsula block, detached from the North American plate by the rifting within San-Andreas fault. 4) The submerged continental blocks formed by extensional processes as the result of asthenosphere flow and shear deformations. Examples are submerged blocks in the central and southern Scotia Sea (Terror Bank, Protector Basin, Discovery Bank, Bruce Bank etc.). 5) The continental blocks formed in the transform fault systems originated in setting of contradict rifts propagation in presence of structure barriers, rifts are shifted by several hundreds kilometers from each other. Examples of this geodynamic setting are Equatorial Atlantic at the initial development stage

  14. Novel use of polymerase chain reaction to amplify cellular DNA adjacent to an integrated provirus.

    PubMed Central

    Silver, J; Keerikatte, V

    1989-01-01

    We describe a modification of the polymerase chain reaction technique which allows amplification of cellular DNA adjacent to an integrated provirus given sequence information for the provirus only. The modified technique should be generally useful for studies of insertional mutagenesis and other situations in which one wishes to isolate DNA adjacent to a region of known sequence. Images PMID:2704070

  15. Coordination: Southeast continental shelf studies

    SciTech Connect

    Menzel, D.W.

    1989-01-26

    The objective of this investigation is to obtain model descriptions of the flow modifications in the Southeast Atlantic continental shelf due to Gulf Stream fluctuations and topographic effects. 2 refs., 4 figs.

  16. Isotopic characterisation of the sub-continental lithospheric mantle beneath Zealandia, a rifted fragment of Gondwana

    NASA Astrophysics Data System (ADS)

    Waight, Tod E.; Scott, James M.; van der Meer, Quinten H. A.

    2013-04-01

    The greater New Zealand region, known as Zealandia, represents an amalgamation of crustal fragments accreted to the paleo-Pacific Gondwana margin and which underwent significant thinning during the subsequent split from Australia and Antarctica in the mid-Cretaceous following opening of the Tasman Sea and the Southern Ocean. We present Sr, Nd and Pb isotopes and laser ablation trace element data for a comprehensive suite of clinopyroxene separates from spinel peridotite xenoliths (lherzolite to harzburgite) from the sub-continental lithospheric mantle across southern New Zealand. These xenoliths were transported to the surface in intra-plate alkaline volcanics that erupted across the region in the Eocene and Miocene (33-10 m.y.a.). Most of the volcanic suites have similar geochemical and isotopic properties that indicate melting of an OIB-like mantle source in the garnet stability zone and that contained a HIMU component. The volcanics have tapped two adjacent but chemically contrasting upper mantle domains: a fertile eastern domain and an extremely depleted western domain. Both domains underlie Mesozoic metasedimentary crust. Radiogenic isotope compositions of the clinopyroxene have 87Sr/86Sr between 0.7023 to 0.7035, 143Nd/144Nd between 0.5128 and 0.5132 (corresponding to ?Nd between +3 and +13) with a few samples extending to even more depleted compositions, 206Pb/204 Pb between ca. 19.5 to 21.5 and 208Pb/204 Pb between ca. 38.5 to 40.5. No correlations are observed between isotopic composition, age or geographical separation. These isotopic compositions indicate that the sub-continental lithospheric mantle under southern New Zealand has a regionally distinct and pervasive FOZO to HIMU - like signature. The isotopic signatures are also similar to those of the alkaline magmas that transported the xenoliths and suggest that most of the HIMU signature observed in the volcanics could be derived from a major source component in the sub-continental lithospheric mantle

  17. Ocean processes at the Antarctic continental slope

    PubMed Central

    Heywood, Karen J.; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D.; Queste, Bastien Y.; Stevens, David P.; Wadley, Martin; Thompson, Andrew F.; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K.; Smith, Walker

    2014-01-01

    The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean–atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system. PMID:24891389

  18. Ocean processes at the Antarctic continental slope.

    PubMed

    Heywood, Karen J; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D; Queste, Bastien Y; Stevens, David P; Wadley, Martin; Thompson, Andrew F; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K; Smith, Walker

    2014-07-13

    The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean-atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system.

  19. Stages of early mesozoic continental sedimentation in central asia

    SciTech Connect

    Polyanskii, B.V.

    1985-11-01

    On the basis of lithologic-facies and cycle analysis, the genesis of continental sediments in the intramontane sedimentary basins is investigated with special reference to the Triassic-Jurassic coal-bearing formation of the Zeravshan-Ghissar mountain region. The subdivision of continental formations into suites for their separation and correlation is shown to be inconsistent. A correlation of sedimentation in the region based on sedimentary macrocycles is proposed. The widespread presence of Late Triassic coarse-clastic graywacke rocks, unconformably overlain by the mainly quartzose Jurassic, is confirmed.

  20. Exhumation and continental strike-slip fault systems: Introduction

    USGS Publications Warehouse

    Roeske, S.M.; Till, A.B.; Foster, D.A.; Sample, J.C.

    2007-01-01

    Metamorphic rocks adjacent to and within strike-slip faultsystems occur in a wide range of tectonic settings. Detailed studies show that for a number of these locales a significant part of the exhumation occurred during strike-slip fault motion, but the specific processes involved are often cryptic. Although some sites share characteristic features, such as metamorphic rocks exhumed in extensional step-overs within overall transtensional systems, no one common theme emerges from all of the studies. Our understanding of the variables that control continental strike-slip faults' interaction with mid- to lower-crustal structures is still primitive.

  1. Survival Of Magnetic Paleoclimatic Signals From Shallow To Deep Water Marine Redoxomorphic Sediments Across The Northwest Iberian Continental Margin

    NASA Astrophysics Data System (ADS)

    Mohamed Falcon, K. J.; Rey, D.; Rubio, B.

    2013-05-01

    The magnetic properties of marine sediments on the North Atlantic Iberian continental Margin are strongly dependent on the organic matter input to the sediments and the onset of reductive diagenesis. An onshore-offshore gradient in the intensity of early diagenesis was recently described for the Ría de Vigo, matched by similar patterns in the adjacent rias of Pontevedra and Muros. In the ria environments of NW Iberia, early diagenetic dissolution of magnetic minerals can lead to magnetite half-lives of a few decades, and virtually obliterates any paleoenvironmental signal carried by magnetic minerals, rendering magnetic properties especially useful for the study of early diagenesis dynamics. Early diagenesis has also been identified in sediments of the adjacent continental shelf and deeper environments of the Galician Bank and Iberian Abyssal Plain. However, in these settings, slower dissolution of magnetic minerals allows the preservation of paleoclimatic signatures on different temporal scales. For instance, magnetic properties of continental shelf sediments reveal periods of enhanced rainfall and continental sediment input to the shelf, coincident with the Roman Warm Period and Medieval Climatic Optimum. On the contrary, cold periods are associated with less detrital input. Furthermore, levels of intensified diagenesis are also recorded during cold periods, which have been interpreted as periods of intensified coastal upwelling probably related to long-term North Atlantic Oscillation positive state. At the Galician Bank and Iberian Abyssal Plain sediments early diagenesis is also pervasive, although a paleoceanographic record of changes in the concentration of magnetic minerals transported by water masses flowing from the Portuguese Margin can still be identified. In addition to the progressive dissolution of magnetic minerals with depth, bulk magnetic properties in these deep marine settings show strong dependence on the pelagic carbonate sedimentation and low

  2. Thermal history and evolution of the Rio de Janeiro - Barbacena section of the southeastern Brazilian continental margin

    NASA Astrophysics Data System (ADS)

    Neri Gezatt, Julia; Stephenson, Randell; Macdonald, David

    2015-04-01

    formation of the Atlantic Ocean. The preliminary results add to the growing thermochronological data base for the southeastern Brazilian continental margin and to deciphering the complex evolution of the region, as well as to the knowledge about the development and evolution of divergent continental margins in general. In a regional setting, AFT ages from this study, though not broadly variant locally, are distinct from basement rock AFT ages for adjacent areas produced by other authors along the southeastern continental margin. Similar ages are found at the southern Bocaina Plateau, for example, where structural control of age distribution is evident. Such regional thermal age difference has been previously attributed to continental scale structural compartmentalization throughout the continental passive margin, related to Late Cretaceous and Cenozoic reactivation of the E-W fracture zones linked to rifting of the South Atlantic. The present AFT results are compatible with Late Cretaceous reactivation but show no relation with younger events.

  3. The geology and petroleum potential of the North Afghan platform and adjacent areas (northern Afghanistan, with parts of southern Turkmenistan, Uzbekistan and Tajikistan)

    NASA Astrophysics Data System (ADS)

    Brookfield, Michael E.; Hashmat, Ajruddin

    2001-10-01

    The North Afghan platform has a pre-Jurassic basement unconformably overlain by a Jurassic to Paleogene oil- and gas-bearing sedimentary rock platform cover, unconformably overlain by Neogene syn- and post-orogenic continental clastics. The pre-Jurassic basement has four units: (1) An ?Ordovician to Lower Devonian passive margin succession developed on oceanic crust. (2) An Upper Devonian to Lower Carboniferous (Tournaisian) magmatic arc succession developed on the passive margin. (3) A Lower Carboniferous (?Visean) to Permian rift-passive margin succession. (4) A Triassic continental magmatic arc succession. The Mesozoic-Palaeogene cover has three units: (1) A ?Late Triassic to Middle Jurassic rift succession is dominated by variable continental clastics. Thick, coarse, lenticular coal-bearing clastics were deposited by braided and meandering streams in linear grabens, while bauxites formed on the adjacent horsts. (2) A Middle to Upper Jurassic transgressive-regressive succession consists of mixed continental and marine Bathonian to Lower Kimmeridgian clastics and carbonates overlain by regressive Upper Kimmeridgian-Tithonian evaporite-bearing clastics. (3) A Cretaceous succession consists of Lower Cretaceous red beds with evaporites, resting unconformably on Jurassic and older deposits, overlain (usually unconformably) by Cenomanian to Maastrichtian shallow marine limestones, which form a fairly uniform transgressive succession across most of Afghanistan. (4) A Palaeogene succession rests on the Upper Cretaceous limestones, with a minor break marked by bauxite in places. Thin Palaeocene to Upper Eocene limestones with gypsum are overlain by thin conglomerates, which pass up into shales with a restricted brackish-water ?Upper Oligocene-?Lower Miocene marine fauna. The Neogene succession consists of a variable thickness of coarse continental sediments derived from the rising Pamir mountains and adjacent ranges. Almost all the deformation of the North Afghan

  4. How subaerial salt extrusions influence water quality in adjacent aquifers

    NASA Astrophysics Data System (ADS)

    Mehdizadeh, Razieh; Zarei, Mehdi; Raeisi, Ezzat

    2015-12-01

    Brines supplied from salt extrusions cause significant groundwater salinization in arid and semi-arid regions where salt rock is exposed to dissolution by episodic rainfalls. Here we focus on 62 of the 122 diapirs of Hormuz salt emergent in the southern Iran. To consider managing the degradation effect that salt extrusions have on the quality of adjoining aquifers, it is first necessary to understand how they influence adjacent water resources. We evaluate here the impacts that these diapirs have on adjacent aquifers based on investigating their geomorphologies, geologies, hydrologies and hydrogeologies. The results indicate that 28/62 (45%) of our sample of salt diapirs have no significant impact on the quality of groundwater in adjoining aquifers (namely Type N), while the remaining 34/62 (55%) degrade nearby groundwater quality. We offer simple conceptual models that account for how brines flowing from each of these types of salt extrusions contaminate adjacent aquifers. We identify three main mechanisms that lead to contamination: surface impact (Type A), subsurface intrusion (Type B) and indirect infiltration (Type C). A combination of all these mechanisms degrades the water quality in nearby aquifers in 19/62 (31%) of the salt diapirs studied. Having characterized the mechanism(s) by which each diapir affects the adjacent aquifer, we suggest a few possible remediation strategies to be considered. For instance, engineering the surface runoff of diapirs Types A and C into nearby evaporation basins would improve groundwater quality.

  5. Regionalization of the Arctic Region, Siberia and Eurasian Continental Area

    DTIC Science & Technology

    1976-05-31

    the model wherein the 1ithosphere-asthenosphere interface is at the solidus for wet peridotite . The results of the Kausel and the Leeds Ph.D...provinces. " and by constraining the bottom of the lid to fit the melt- ing curve for peridotite . 5) To acquire Love wave data plus SRO and high-gain data

  6. Regionalization of the Arctic Region, Siberia and Eurasian Continental Area

    DTIC Science & Technology

    1977-10-01

    Research Projects Agency (DOD) ARPA Order No. 3291 Monitored by AFOSR Under Contract #F49620-76-C-0038 lIstitute di Geodesia e Geofisica, Universit...Istituto di Geodesia e Geofisica, UniversitA di Bari; we are grateful to these institutions for supporting our computations. We also wish to express our

  7. Closing the North American Carbon Budget: Continental Margin Fluxes Matter!

    NASA Astrophysics Data System (ADS)

    Najjar, R.; Benway, H. M.; Siedlecki, S. A.; Boyer, E. W.; Cai, W. J.; Coble, P. G.; Cross, J. N.; Friedrichs, M. A.; Goni, M. A.; Griffith, P. C.; Herrmann, M.; Lohrenz, S. E.; Mathis, J. T.; McKinley, G. A.; Pilskaln, C. H.; Smith, R. A.; Alin, S. R.

    2015-12-01

    Despite their relatively small surface area, continental margins are regions of intense carbon and nutrient processing, export and exchange, and thus have a significant impact on global biogeochemical cycles. In response to recommendations for regional synthesis and carbon budget estimation for North America put forth in the North American Continental Margins workshop report (Hales et al., 2008), the Ocean Carbon and Biogeochemistry (OCB) Program and North American Carbon Program (NACP) began coordinating a series of collaborative, interdisciplinary Coastal CARbon Synthesis (CCARS) research activities in five coastal regions of North America (Atlantic Coast, Pacific Coast, Gulf of Mexico, Arctic, Laurentian Great Lakes) to improve quantitative assessments of the North American carbon budget. CCARS workshops and collaborative research activities have resulted in the development of regional coastal carbon budgets based on recent literature- and model-based estimates of major carbon fluxes with estimated uncertainties. Numerous peer-reviewed papers and presentations by involved researchers have highlighted these findings and provided more in-depth analyses of processes underlying key carbon fluxes in continental margin systems. As a culminating outcome of these synthesis efforts, a comprehensive science plan highlights key knowledge gaps identified during this synthesis and provides explicit guidance on future research and observing priorities in continental margin systems to help inform future agency investments in continental margins research. This presentation will provide an overview of regional and flux-based (terrestrial inputs, biological transformations, sedimentary processes, atmospheric exchanges, lateral carbon transport) synthesis findings and key recommendations in the science plan, as well as a set of overarching priorities and recommendations on observations and modeling approaches for continental margin systems.

  8. Anomalous Subsidence of the Ocean Continent Transition at Rifted Continental Margins: Observations from the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Cowie, L.; Kusznir, N. J.

    2011-12-01

    It has been proposed that some continental rifted margins have anomalous early subsidence histories and that at break-up they were elevated at shallower bathymetries than the isostatic response of classical rift models (McKenzie 1978) would predict. The existence of anomalous syn- or early post-breakup subsidence, of this form, would have important implications for our understanding of the geodynamics of continental breakup and sea-floor spreading initiation and important consequences for syn- and post-breakup depositional systems. Possible explanations for anomalous subsidence during continental breakup could include transient effects as the continental geotherm evolves towards an oceanic form, or small scale convection. Lucazeau et al. (2008) have reported anomalously high heat-flows in the ocean continent transition (OCT) of the young rifted margin of the Eastern Gulf of Aden which would have implications for its subsidence history. In order to verify (or otherwise) the proposition of an anomalous early post-breakup subsidence history in the Eastern Gulf of Aden, we have determined anomalous oceanic subsidence using residual depth anomaly (RDA) analysis and have compared lithosphere thinning across the OCT measured using subsidence analysis with continental crustal basement thinning from gravity inversion. Both 3D regional and localised 2D analyses have been carried out. The localised studies focus on published seismic reflection lines (Autin et al, 2010; D'Acremont et al, 2005; Fournier et al, 2007; Leroy et al, 2004; Leroy et al, 2010; Lucazeau et al 2008; Lucazeau et al 2010). RDAs have been calculated by comparing observed and predicted oceanic bathymetries. Regional 3D RDAs for the Gulf of Aden, without a sediment correction, show positive RDAs between 3km and 4km at the rifted margins decreasing to 0.5km at the ocean ridge axis. Localised 2D sediment corrected RDA profiles determined within and adjacent to the OCT of the Eastern Gulf of Aden are also

  9. Dependency of continental crustal rupture, decompression melt initiation and OCT architecture on lithosphere deformation modes during continental breakup: Numerical experiments

    NASA Astrophysics Data System (ADS)

    Jeanniot, L.; Kusznir, N. J.; Manatschal, G.

    2012-12-01

    -floor spreading initiation and rifted margin formation, starting (1) with a wide region of lithosphere thinning and stretching inducing a passive upwelling, followed by (2) the onset of additional buoyancy driven small-scale convection, and (3) a focusing of pure-shear deformation width to a narrower region at the initiation of decompression melting and its extraction. The lateral migration of the deformation flow axis is shown to have an important effect on the rupture of continental crust and lithosphere, and melt initiation. Rapid lateral migration of deformation relative to the half-spreading rate Vx generates a broad region of thinned continental crust, with no melt initiation or rupture of the continental lithosphere.

  10. Seals map bathymetry of the Antarctic continental shelf

    NASA Astrophysics Data System (ADS)

    Padman, Laurie; Costa, Daniel P.; Bolmer, S. Thompson; Goebel, Michael E.; Huckstadt, Luis A.; Jenkins, Adrian; McDonald, Birgitte I.; Shoosmith, Deborah R.

    2010-11-01

    We demonstrate the first use of marine mammal dive-depth data to improve maps of bathymetry in poorly sampled regions of the continental shelf. A group of 57 instrumented elephant seals made on the order of 2 × 105 dives over and near the continental shelf on the western side of the Antarctic Peninsula during five seasons, 2005-2009. Maximum dive depth exceeded 2000 m. For dives made near existing ship tracks with measured water depths H<700 m, ˜30% of dive depths were to the seabed, consistent with expected benthic foraging behavior. By identifying the deepest of multiple dives within small areas as a dive to the seabed, we have developed a map of seal-derived bathymetry. Our map fills in several regions for which trackline data are sparse, significantly improving delineation of troughs crossing the continental shelf of the southern Bellingshausen Sea.

  11. Bioenergetics of Continental Serpentinites

    NASA Astrophysics Data System (ADS)

    Cardace, D.; Meyer-Dombard, D. R.

    2011-12-01

    Serpentinization is the aqueous alteration of ultramafic (Fe- and Mg-rich) rocks, resulting in secondary mineral assemblages of serpentine, brucite, iron oxyhydroxides and magnetite, talc, and possibly carbonate and silica-rich veins and other minor phases-all depending on the evolving pressure-temperature-composition of the system. The abiotic evolution of hydrogen and possibly organic compounds via serpentinization (McCollom and Bach, 2009) highlights the relevance of this geologic process to carbon and energy sources for the deep biosphere. Serpentinization may fuel life over long stretches of geologic time, throughout the global seabed and in exposed, faulted peridotite blocks (as at Lost City Hydrothermal Field, Kelley et al., 2005), and in obducted oceanic mantle units in ophiolites (e.g., Tiago et al., 2004). Relatively little work has been published on life in continental serpentinite settings, though they likely host a unique resident microbiota. In this work, we systematically model the serpentinizing fluid as an environmental niche. Reported field data for high and moderate pH serpentinizing fluids were modeled from Cyprus, the Philippines, Oman, Northern California, New Caledonia, Yugoslavia, Portugal, Italy, Newfoundland Canada, New Zealand, and Turkey. Values for Gibbs Energy of reaction (ΔGr), kJ per mole of electrons transferred for a given metabolism, are calculated for each field site. Cases are considered both for (1) modest assumptions of 1 nanomolar hydrogen and 1 micromolar methane, based on unpublished data for a similar northern California field site (Cardace and Hoehler, in prep.) and (2) an upper estimate of 10 nanomolar hydrogen and 500 micromolar methane. We survey the feasibility of microbial metabolisms for key steps in the nitrogen cycle, oxidation of sulfur in pyrite, iron oxidation or reduction reactions, sulfate reduction coupled to hydrogen or methane oxidation, methane oxidation coupled to the reduction of oxygen, and

  12. 76 FR 2919 - Outer Continental Shelf Official Protraction Diagram and Supplemental Official Outer Continental...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-18

    ... Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf Official Protraction Diagram and Supplemental Official Outer Continental Shelf Block Diagrams AGENCY: Bureau of Ocean... American Datum of 1983 (NAD 83) Outer Continental Shelf Official Protraction Diagram and...

  13. Weighing the deep continental biosphere.

    PubMed

    McMahon, Sean; Parnell, John

    2014-01-01

    There is abundant evidence for widespread microbial activity in deep continental fractures and aquifers, with important implications for biogeochemical cycling on Earth and the habitability of other planetary bodies. Whitman et al. (P Natl Acad Sci USA, 95, 1998, 6578) estimated a continental subsurface biomass on the order of 10(16) -10(17) g C. We reassess this value in the light of more recent data including over 100 microbial population density measurements from groundwater around the world. Making conservative assumptions about cell carbon content and the ratio of attached and free-living microorganisms, we find that the evidence continues to support a deep continental biomass estimate of 10(16) -10(17) g C, or 2-19% of Earth's total biomass.

  14. Continental crust: a geophysical approach

    SciTech Connect

    Meissner, R.

    1986-01-01

    This book develops an integrated and balanced picture of present knowledge of the continental crust. Crust and lithosphere are first defined, and the formation of crusts as a general planetary phenomenon is described. The background and methods of geophysical studies of the earth's crust and the collection of related geophysical parameters are examined. Creep and friction experiments and the various methods of radiometric age dating are addressed, and geophysical and geological investigations of the crustal structure in various age provinces of the continents are studied. Specific tectonic structures such as rifts, continental margins, and geothermal areas are discussed. Finally, an attempt is made to give a comprehensive view of the evolution of the continental crust and to collect and develop arguments for crustal accretion and recycling. 647 references.

  15. Continental rifts and mineral resources

    SciTech Connect

    Burke, K. . Geosciences Dept.)

    1992-01-01

    Continental rifts are widespread and range in age from the present to 3 b.y. Individual rifts may form parts of complex systems as in E. Africa and the Basin and Range. Rifts have originated in diverse environments such as arc-crests, sites of continental collision, collapsing mountain belts and on continents at rest over the mantle circulation pattern. Continental rift resources can be classified by depth of origin: For example, in the Great Dike, Norilsk and Mwadui magma from the mantle is the host. At shallower depths continental crust partly melted above mafic magma hosts ore (Climax, Henderson). Rift volcanics are linked to local hydrothermal systems and to extensive zeolite deposits (Basin and Range, East Africa). Copper (Zambia, Belt), zinc (Red Dog) and lead ores (Benue) are related to hydrothermal systems which involve hot rock and water flow through both pre-rift basement and sedimentary and volcanic rift fill. Economically significant sediments in rifts include coals (the Gondwana of Inida), marine evaporites (Lou Ann of the Gulf of Mexico) and non-marine evaporites (East Africa). Oil and gas in rifts relate to a variety of source, reservoir and trap relations (North Sea, Libya), but rift-lake sediment sources are important (Sung Liao, Bo Hai, Mina, Cabinda). Some ancient iron ores (Hammersley) may have formed in rift lakes but Algoman ores and greenstone belt mineral deposits in general are linked to oceanic and island arc environments. To the extent that continental environments are represented in such areas as the Archean of the Superior and Slave they are Andean Arc environments which today have locally rifted crests (Ecuador, N. Peru). The Pongola, on Kaapvaal craton may, on the other hand represent the world's oldest preserved, little deformed, continental rift.

  16. Seasonal variability of the M2 tide in the seas adjacent to Korea

    NASA Astrophysics Data System (ADS)

    Kang, Sok Kuh; Chung, Jong-yul; Lee, Sang-Ryong; Yum, Ki-Dat

    1995-08-01

    Seasonal variability of the M2 tidal harmonic constants is revealed through analyses of monthly tidal data at 12 representative tidal stations in the seas adjacent to the Korean peninsula. The variability remain systematic over the 9 years (1965-1973) of data analysis with a range comparable to that of the 18.6 year nodal modulation. Spatial inhomogeneity of the seasonal variability in the observed harmonic constants is found to exist. The largest seasonal variability in M2 appears in the stations located along the Korea Strait. This variability is not explained by the equilibrium theory of tides, and such a variability or irregularities in the harmonic constants are considered as either a noise as done by Cartwright and Amin (1986), Deutsch Hydrography Zeitschrift, 39, 235-253, or a manifestation of frictional interaction as done by Godin and Gutierrez (1986) Continental Shelf Research, 5, 379-402 for the Bay of Fundy. Considering the opposite relation between monthly mean sea level differences in Izuhara-Pusan section and tidal characteristics in the Korea Strait, it is hypothesized that the interaction between the predominant tidal currents and oceanic currents varying with the seasons might be the main cause of the observed temporal variability in the M2 tide. The nonlinear effect of the Kuroshio is investigated along the shelf break region through scale analyses, which show that the presence of a mean current increases the non-linear terms in the momentum balance by about one order of magnitude. The seasonally different damping effect of the Tsushima Current to the M2 tide is also discussed to explain the process of dominant seasonal variability along the Korea Strait based on the actual current data, but further thorough investigation, considering the advection effect of the mean current, is required to investigate the associated dynamics more completely.

  17. On the time-course of adjacent and non-adjacent transposed-letter priming

    PubMed Central

    Ktori, Maria; Kingma, Brechtsje; Hannagan, Thomas; Holcomb, Phillip J.; Grainger, Jonathan

    2014-01-01

    We compared effects of adjacent (e.g., atricle-ARTICLE) and non-adjacent (e.g., actirle-ARTICLE) transposed-letter (TL) primes in an ERP study using the sandwich priming technique. TL priming was measured relative to the standard double-substitution condition. We found significantly stronger priming effects for adjacent transpositions than non-adjacent transpositions (with 2 intervening letters) in behavioral responses (lexical decision latencies), and the adjacent priming effects emerged earlier in the ERP signal, at around 200 ms post-target onset. Non-adjacent priming effects emerged about 50 ms later and were short-lived, being significant only in the 250-300 ms time-window. Adjacent transpositions on the other hand continued to produce priming in the N400 time-window (300-500 ms post-target onset). This qualitatively different pattern of priming effects for adjacent and non-adjacent transpositions is discussed in the light of different accounts of letter transposition effects, and the utility of drawing a distinction between positional flexibility and positional noise. PMID:25364497

  18. Sediment metabolism on the Louisiana continental shelf - Eldridge

    EPA Science Inventory

    Rates of aerobic and anaerobic sediment metabolism were measured on the Louisiana Continental Shelf during 5 cruises in 2006 and 2007. On each cruise, 3-4 stations were occupied in regions of the shelf that experience summer bottom-water hypoxia. Net DIC, O2, N2, and nutrient f...

  19. Outer Continental Shelf Environmental Assessment Program: comprehensive bibliography, January 1988

    SciTech Connect

    Not Available

    1988-01-01

    The bibliography lists reports from investigators of the Alaska Outer Continental Shelf Environmental Assessment Program. Some non-program documents are also included. More than 3600 entries are sorted by author and citation number. Cross-references are available by Alaska region, discipline and research unit number.

  20. The Late Paleozoic Southern Margin of the Siberian paleocontinent: transformation from an active continental margin to intracontinental rifting

    NASA Astrophysics Data System (ADS)

    Kozlovsky, A. M.; Yarmolyuk, V. V.; Sal'Nikova, E. B.

    2009-04-01

    The large volcanoplutonic belt was formed on the southern margin of Siberian paleocontinent in the Early Carboniferous-Early Permian. Now it's stretched through whole Mongolia and the adjacent region of China. In the belt structure there are defined the successive rock complexes: the older one represented by differentiated basalt-andesite-rhyodacite series and younger bimodal complex of basalt-comendite-trachyrhyolite composition. The granodiorite-plagiogranite and diorite-monzonite-granodiorite plutonic massifs are associated with the former, while peralkaline granite massifs are characteristic of the latter. Geochronological results and geological relations between rocks of the bimodal and differentiated complexes showed first that rocks of the differentiated complex originated 350 to 330 Ma ago at the initial stage of forming of the marginal continental belt, linked with development active continental margin. This is evident from geochronological dates obtained for the Adzh-Bogd and Edrengiyn-Nuruu massifs and for volcanic associations of the complex. The dates are consistent with paleontological data. The bimodal association was formed later, 320 to 290 Ma ago. The time span separating formation of two igneous complexes ranges from several to 20-30 m.y. in different areas of the marginal belt. The bimodal magmatism was interrelated with rifting responsible for development of the Gobi-Tien Shan rift zone in the belt axial part and the Main Mongolian lineament along the belt northern boundary. Loci of bimodal rift magmatism likely migrated with time: the respective magmatic activity first initiated on the west of the rift system and then advanced gradually eastward with development of rift structures. Normal granitoids untypical but occurring nevertheless among the products of rift magmatism in addition to peralkaline massifs are assumed to have been formed, when the basic magmatism associated with rifting stimulated crustal anatexis and generation of crustal

  1. Temperature Control of Continental Lithosphere Elastic Thickness: Effective Elastic Thickness Te vs Upper Mantle Velocity Vs

    NASA Astrophysics Data System (ADS)

    Hyndman, R. D.; Currie, C. A.; Mazzotti, S.; Frederiksen, A.

    2006-12-01

    The elastic thickness of continental lithosphere is closely related to its total strength and therefore to its susceptibility to tectonic deformation and earthquakes. Recently it has been questioned whether the elastic thickness and strength are dependent on crust and upper mantle temperatures and compositions in the way predicted by laboratory data. We test this dependence in western North America by a regional comparison of the effective elastic thickness (Te) from topography-gravity coherence, and upper mantle temperatures mapped by tomography shear wave velocities (Vs). We find a good correlation between Te and Vs of the form expected based on the thermal and laboratory data. The Te distribution is strongly bimodal as previously found globally, less than 20 km for the high temperature Cordillera and over 100 km for the adjacent cold stable Canadian Shield. Only intermediate thermal regimes have intermediate Te that suggests a weak layer in the lower crust over a stronger upper mantle. Strength envelopes based on laboratory data correspond to the observed Te for thermal regimes with temperatures at the Moho of 800-900C for the Cordillera and 400-500C for the Shield, in agreement with temperatures from Vs and other estimators. Our study supports the conclusion that lithosphere elastic thickness and strength are controlled primarily by temperature and that laboratory- based rheology provides a good first order estimate of the deformation behaviour of the crust and upper mantle. The Cordillera and other continental backarcs are weak enough to be deformed by plate boundary forces, whereas cratons are generally much too strong. In the Cordillera, the upper mantle is too hot for brittle failure and earthquakes occur only in the upper 10-15 km of the crust. In the cool craton, earthquakes occur rarely in the upper mantle because the total lithosphere strength is too great for significant deformation by plate tectonic forces.

  2. GEWEX Continental-scale International Project (GCIP)

    NASA Technical Reports Server (NTRS)

    Try, Paul

    1993-01-01

    The Global Energy and Water Cycle Experiment (GEWEX) represents the World Climate Research Program activities on clouds, radiation, and land-surface processes. The goal of the program is to reproduce and predict, by means of suitable models, the variations of the global hydrological regime and its impact on atmospheric and oceanic dynamics. However, GEWEX is also concerned with variations in regional hydrological processes and water resources and their response to changes in the environment such as increasing greenhouse gases. In fact, GEWEX contains a major new international project called the GEWEX Continental-scale International Project (GCIP), which is designed to bridge the gap between the small scales represented by hydrological models and those scales that are practical for predicting the regional impacts of climate change. The development and use of coupled mesoscale-hydrological models for this purpose is a high priority in GCIP. The objectives of GCIP are presented.

  3. Resonant generation of internal waves on a model continental slope.

    PubMed

    Zhang, H P; King, B; Swinney, Harry L

    2008-06-20

    We study internal wave generation in a laboratory model of oscillating tidal flow on a continental margin. Waves are found to be generated only in a near-critical region where the slope of the bottom topography matches that of internal waves. Fluid motion with a velocity an order of magnitude larger than that of the forcing occurs within a thin boundary layer above the bottom surface. The resonant wave is unstable because of strong shear; Kelvin-Helmholtz billows precede wave breaking. This work provides a new explanation for the intense boundary flows on continental slopes.

  4. Paleostress adjacent to the Alpine Fault of New Zealand - Fault, vein, and styolite data from the Doctors Dome area

    NASA Astrophysics Data System (ADS)

    Nicol, Andrew; Wise, Donald U.

    1992-11-01

    Doctors Dome, 75 km north of Christchurch, New Zealand, is an early Pleistocene to Recent structure being deformed along the southeast edge of the Pacific-Australian plate boundary. Paleostress in the area has been determined in basement rocks of the Mesozoic meta-graywacke Torlesse Supergroup which lies unconformably beneath Cretaceous and younger cover rocks. Inversion of basement fault data for the area indicates a general northwest compression with two peaks, one WNW-ESE parallel to the shortening suggested by the older vein system and the other parallel to southeast-northwest stylolite columns in the cover rocks. This direction is approximately parallel to regional indicators of contemporary deformation in and adjacent to the Alpine Fault Zone and suggests that the stress field affecting these rocks has not changed significantly since the late Pliocene-early Pleistocene. Like the San Andreas system, this compression is at a high angle to the strike of the zone as a whole, but is compatible with the direction of plate convergence and motion of the major faults. Between the overlappig ends of the Alpine Fault and the Hikurangi Subduction Zone the Alpine Fault may become subhorizontal at middle-lower crustal levels, partially decoupling the crust from underlying structures, and thus allowing oblique motion to be transferred directly onto the fault from the subduction complex, while aiding the change from subduction to continental collision.

  5. Fractal behavior in continental crustal heat production

    NASA Astrophysics Data System (ADS)

    Vedanti, N.; Srivastava, R. P.; Pandey, O. P.; Dimri, V. P.

    2011-02-01

    The distribution of crustal heat production, which is the most important component in the elucidation of continental thermal structure, still remains a theoretical assumption. In general the heat production values must decrease with depth, but the form of decrease of heat production in the crust is not well understood. The commonly used heat production models are: "block model", in which heat production is constant from the surface to a given depth and the "exponential model", in which heat production diminishes as an exponential function of depth. The exponential model is more widely used wherein sources of the errors are heterogeneity of rock and long wavelength changes due to changes in lithology and tectonic elements, and as such exponential distribution does not work satisfactorily for the entire crust. In the present study, we analyze for the first time, deep crustal heat production data of six global areas namely Dharwar craton (India), Kaapvaal craton (South Africa), Baltic shield (Kola, Russia), Hidaka metamorphic belt (Japan), Nissho pluton (Japan) and Continental Deep Drilling site (KTB, Germany). The power spectrum of all the studied data sets exhibits power law behaviour. This would mean slower decay of heat production with depth, which conforms to the known geologic composition of the crust. Minimum value of the scaling exponent has been found for the KTB borehole, which is apparently related to higher heat production of gneisses, however for other study areas, scaling exponent is almost similar. We also found that the lower values of scaling exponents are related to higher heat production in the crust as is the case in KTB. Present finding has a direct relevance in computation of temperature-depth profiles in continental regions.

  6. Transport of particles across continental shelves

    SciTech Connect

    Nittrouer, C.A. ); Wright, L.D. College of William and Mary, Gloucester Point, VA )

    1994-02-01

    Transport of particulate material across continental shelves is well demonstrated by the distributions on the seabed and in the water column of geological, chemical, or biological components, whose sources are found farther landward or farther seaward. This paper addresses passive (incapable of swimming) particles and their transport across (not necessarily off) continental shelves during high stands of sea level. Among the general factors that influence across-shelf transport are shelf geometry, latitudinal constraints, and the timescale of interest. Research studies have investigated the physical mechanisms of transport and have made quantitative estimates of mass flux across continental shelves. Important mechanisms include wind-driven flows, internal wave, wave-orbital flows, infragravity phenomena, buoyant plumes, and surf zone processes. Most particulate transport occurs in the portion of the water column closest to the seabed. Therefore physical processes are effective where and when they influence the bottom boundary layer, causing shear stresses sufficient to erode and transport particulate material. Biological and geological processes at the seabed play important roles within the boundary layer. The coupling of hydrodynamic forces from currents and surface gravity waves has a particularly strong influence on across-shelf transport; during storm events, the combined effect can transport particles tens of kilometers seaward. Several important mechanisms can cause bidirectional (seaward and landward) transport, and estimates of the net flux are difficult to obtain. Also, measurements of across-shelf transport are made difficult by the dominance of along-shelf transport. Geological parameters are often the best indicators of net across-shelf transport integrated over time scales longer than a month. For example, fluvially discharged particles with distinct composition commonly accumulate in the midshelf region. 47 refs., 16 figs.

  7. Continental Lower Crust: Wavespeeds, Composition, and Relamination

    NASA Astrophysics Data System (ADS)

    Hacker, B. R.; Kelemen, P. B.; Behn, M. D.

    2015-12-01

    The composition of much of Earth's lower continental crust is enigmatic. The available heat-flow and wavespeed constraints can be satisfied if lower continental crust elsewhere contains anywhere from 49 to 62 wt% SiO2 (similar to andesite and dacite), with high to moderate concentrations of K, Th and U. Beneath shields and platforms, Vp suggests that 20-30% of lower crust is mafic. A large fraction of this material could be denser than peridotite. In these settings the underlying upper mantle is too cold to permit development of a convective instability. High Vp lithologies in these settings may be the result of mafic underplating, or slow metamorphic growth of large proportions of garnet. Vp from lower crust of Paleozoic-Mesozoic orogens indicates a smaller amount of mafic rock and little or no material that is denser than peridotite. Beneath rifts, arcs, and volcanic plateaux and beneath continent-collision zones, ~10-20% of lower crust is mafic, and about half that is denser than peridotite. The inferred gravitational instability and high Moho temperatures suggest that the mafic lower crust in these regions may be temporary. During sediment subduction, subduction erosion, arc subduction, and continent subduction, mafic rocks become eclogite and may continue to descend into the mantle, whereas more silica-rich rocks are transformed into felsic gneisses that are less dense than peridotite but more dense than continental upper crust. These more-felsic rocks may rise buoyantly, undergo decompression melting and melt extraction, and may be relaminated to the base of the crust. As a result of this refining/differentiation process, such relatively felsic rocks could form much of lower crust.

  8. Drift of continental rafts with asymmetric heating.

    PubMed

    Knopoff, L; Poehls, K A; Smith, R C

    1972-06-02

    A laboratory model of a lithospheric raft is propelled through a viscous asthenospheric layer with constant velocity of scaled magnitude appropriate to continental drift. The propulsion is due to differential heat concentration in the model oceanic and continental crusts.

  9. Formation of Continental Fragments: The Tamayo Bank, Gulf of California

    NASA Astrophysics Data System (ADS)

    van Wijk, J.; Abera, R.; Axen, G. J.

    2015-12-01

    Potential field data are used to construct a two-dimensional crustal model along a profile through the Tamayo Trough and Bank in the Gulf of California. The model is constrained by seismic reflection and refraction data, and field observations. The potential field data do not fit a model where the crust of the Tamayo trough is continental, but they fit well with a model where the Tamayo trough crust is oceanic. This implies that the Tamayo Bank is entirely bounded by oceanic crust and is a microcontinent. The oceanic crust of the Tamayo trough that separates the Tamayo Bank from the mainland of Mexico is thin (~4 km), so oceanic spreading was probably magma-starved before it ceased. This led us to come up with a model that explains the formation of microcontinents that are smaller in size and are not found in the proximity of hotspots. At first, seafloor spreading commences following continental breakup. When the magma supply to the ridge slows down, the plate boundary strengthens. Hence, the ridge may be abandoned while tectonic extension begins elsewhere, or slow spreading may continue while a new ridge starts to develop. The old spreading ridge becomes extinct. An asymmetric ocean basin forms if the ridge jumps within oceanic lithosphere; a microcontinent forms if the ridge jumps into a continental margin. This model for formation of continental fragments is applicable to other regions as well, eliminating the need of mantle plume impingement to facilitate rifting of a young continental margin and microcontinent formation.

  10. Variable length adjacent partitioning for PTS based PAPR reduction of OFDM signal

    SciTech Connect

    Ibraheem, Zeyid T.; Rahman, Md. Mijanur; Yaakob, S. N.; Razalli, Mohammad Shahrazel; Kadhim, Rasim A.

    2015-05-15

    Peak-to-Average power ratio (PAPR) is a major drawback in OFDM communication. It leads the power amplifier into nonlinear region operation resulting into loss of data integrity. As such, there is a strong motivation to find techniques to reduce PAPR. Partial Transmit Sequence (PTS) is an attractive scheme for this purpose. Judicious partitioning the OFDM data frame into disjoint subsets is a pivotal component of any PTS scheme. Out of the existing partitioning techniques, adjacent partitioning is characterized by an attractive trade-off between cost and performance. With an aim of determining effects of length variability of adjacent partitions, we performed an investigation into the performances of a variable length adjacent partitioning (VL-AP) and fixed length adjacent partitioning in comparison with other partitioning schemes such as pseudorandom partitioning. Simulation results with different modulation and partitioning scenarios showed that fixed length adjacent partition had better performance compared to variable length adjacent partitioning. As expected, simulation results showed a slightly better performance of pseudorandom partitioning technique compared to fixed and variable adjacent partitioning schemes. However, as the pseudorandom technique incurs high computational complexities, adjacent partitioning schemes were still seen as favorable candidates for PAPR reduction.

  11. Oceanic and terrestrial sources of continental precipitation

    NASA Astrophysics Data System (ADS)

    Gimeno, Luis; Stohl, Andreas; Trigo, Ricardo M.; Dominguez, Francina; Yoshimura, Kei; Yu, Lisan; Drumond, Anita; DuráN-Quesada, Ana MaríA.; Nieto, Raquel

    2012-12-01

    The most important sources of atmospheric moisture at the global scale are herein identified, both oceanic and terrestrial, and a characterization is made of how continental regions are influenced by water from different moisture source regions. The methods used to establish source-sink relationships of atmospheric water vapor are reviewed, and the advantages and caveats associated with each technique are discussed. The methods described include analytical and box models, numerical water vapor tracers, and physical water vapor tracers (isotopes). In particular, consideration is given to the wide range of recently developed Lagrangian techniques suitable both for evaluating the origin of water that falls during extreme precipitation events and for establishing climatologies of moisture source-sink relationships. As far as oceanic sources are concerned, the important role of the subtropical northern Atlantic Ocean provides moisture for precipitation to the largest continental area, extending from Mexico to parts of Eurasia, and even to the South American continent during the Northern Hemisphere winter. In contrast, the influence of the southern Indian Ocean and North Pacific Ocean sources extends only over smaller continental areas. The South Pacific and the Indian Ocean represent the principal source of moisture for both Australia and Indonesia. Some landmasses only receive moisture from the evaporation that occurs in the same hemisphere (e.g., northern Europe and eastern North America), while others receive moisture from both hemispheres with large seasonal variations (e.g., northern South America). The monsoonal regimes in India, tropical Africa, and North America are provided with moisture from a large number of regions, highlighting the complexities of the global patterns of precipitation. Some very important contributions are also seen from relatively small areas of ocean, such as the Mediterranean Basin (important for Europe and North Africa) and the Red Sea

  12. Barrier Displacement on a Neutral Landscape: Toward a Theory of Continental Biogeography.

    PubMed

    Albert, James S; Schoolmaster, Donald R; Tagliacollo, Victor; Duke-Sylvester, Scott M

    2017-03-01

    Macroevolutionary theory posits three processes leading to lineage diversification and the formation of regional biotas: dispersal (species geographic range expansion), speciation (species lineage splitting), and extinction (species lineage termination). The Theory of Island Biogeography (TIB) predicts species richness values using just two of these processes; dispersal and extinction. Yet most species on Earth live on continents or continental shelves, and the dynamics of evolutionary diversification at regional and continental scales are qualitatively different from those that govern the formation of species richness on biogeographic islands. Certain geomorphological processes operating perennially on continental platforms displace barriers to gene flow and organismal dispersal, and affect all three terms of macroevolutionary diversification. For example, uplift of a dissected landscape and river capture both merge and separate portions of adjacent areas, allowing dispersal and larger geographic ranges, vicariant speciation and smaller geographic ranges, and extinction when range sizes are subdivided below a minimum persistence threshold. The TIB also does not predict many biogeographic and phylogenetic patterns widely observed in continentally distributed taxa, including: (i) power function-like species-area relationships; (ii) log-normal distribution of species geographic range sizes, in which most species have restricted ranges (are endemic) and few species have broad ranges (are cosmopolitan); (iii) mid-domain effects with more species toward the geographic center, and more early-branching, species-poor clades toward the geographic periphery; (iv) exponential rates of net diversification with log-linear accumulation of lineages through geological time; and (v) power function-like relationships between species-richness and clade diversity, in which most clades are species-poor and few clades are species-rich. Current theory does not provide a robust

  13. Yellowstone hotspot-continental lithosphere interaction

    NASA Astrophysics Data System (ADS)

    Jean, Marlon M.; Hanan, Barry B.; Shervais, John W.

    2014-03-01

    The Snake River Plain represents 17 m.y. of volcanic activity that took place as the North American continent migrated over a relatively fixed magma source, or hotspot. We present new Pb, Sr, and Nd data for a suite of 25 basalts collected from Western and Central Snake River Plain (SRP). The new isotope data, combined with previously published data from the SRP, provide a traverse of the Wyoming craton margin, from the 87Sr/86Sr = 0.706 line boundary of western SRP with Phanerozoic accreted terranes, east through the central and eastern SRP, to the Yellowstone Plateau. Low-K basalts from the western SRP, overlain by high-K basalts, provide a temporal record of regional source variation from ∼16.8 to 0.2 Ma. Principal Component Analysis (PCA) of the new and previously published SRP basalt Pb isotopes reveals that >97% of the total variability is accounted for by mixing between three end-members and is consistent with a sublithospheric Yellowstone hotspot mantle source with a radiogenic isotope composition similar to the mantle source of the early Columbia River Basalt Group (CRBG) and two continental lithosphere end-members, heterogeneous in age and composition. We use the SRP Pb, Sr, and Nd isotope data to model the Yellowstone Hotspot-continental lithosphere interaction by three component mixing between two continental lithospheric components, Archean lithosphere (CL1) that represents older lithosphere underlying the Yellowstone Plateau in the east, and Paleoproterozoic lithosphere (CL2) representing the younger lithosphere underlying the SRP in the west near the craton margin, and a sublithospheric end-member, representing the Yellowstone hotspot (PL). The results suggest a continuous flow of PL material westward as the NA continental lithosphere migrated over the upwelling hotspot along a shoaling gradient in the sub-continental mantle lithosphere. The model shows a decrease in Total Lithosphere end-members (CL1 + CL2) and the Lithosphere Ratio (CL1/CL2

  14. Large-scale subduction of continental crust implied by India-Asia mass-balance calculation

    NASA Astrophysics Data System (ADS)

    Ingalls, Miquela; Rowley, David B.; Currie, Brian; Colman, Albert S.

    2016-11-01

    Continental crust is buoyant compared with its oceanic counterpart and resists subduction into the mantle. When two continents collide, the mass balance for the continental crust is therefore assumed to be maintained. Here we use estimates of pre-collisional crustal thickness and convergence history derived from plate kinematic models to calculate the crustal mass balance in the India-Asia collisional system. Using the current best estimates for the timing of the diachronous onset of collision between India and Eurasia, we find that about 50% of the pre-collisional continental crustal mass cannot be accounted for in the crustal reservoir preserved at Earth's surface today--represented by the mass preserved in the thickened crust that makes up the Himalaya, Tibet and much of adjacent Asia, as well as southeast Asian tectonic escape and exported eroded sediments. This implies large-scale subduction of continental crust during the collision, with a mass equivalent to about 15% of the total oceanic crustal subduction flux since 56 million years ago. We suggest that similar contamination of the mantle by direct input of radiogenic continental crustal materials during past continent-continent collisions is reflected in some ocean crust and ocean island basalt geochemistry. The subduction of continental crust may therefore contribute significantly to the evolution of mantle geochemistry.

  15. Illustrations of the importance of mass wasting in the evolution of continental margins

    SciTech Connect

    Pratson, L.; Ryan, W. ); Twichell, D. )

    1990-05-01

    Side-looking sonar imagery and swath bathymetry from a variety of contemporary continental slopes all display erosional scars and debris aprons, illustrating the importance of mass wasting in the evolution of continental margins. The continental slopes examined include slopes fed directly from the fronts of ice sheets, slopes adjacent to continental shelves that were the sites of glacial outwash, slopes supplied exclusively by fluvial drainage, slopes at carbonate platforms, and slopes on accretionary prisms. Examples are drawn from the Atlantic Ocean, the Gulf of Mexico, and the Mediterranean Sea in both passive and active continental margin settings. The sonar imagery and bathymetry used in this study indicate that continental slopes in different tectonic and climatic environments show similar forms of mass wasting. However, in some cases the dominant mode of erosion and/or the overall degree of mass wasting appears to be distinct to particular sedimentary environments. Timing of both recent and older exhumed erosional surfaces identified in the imagery and in seismic reflection profiles is obtained by ground truth observations using submersibles, towed camera sleds, drilling, and coring. These observations suggest that eustatic fluctuations common to all the margins examined do not explain the range in magnitude and areal density of the observed mass wasting. More localized factors such as lithology, diagenesis, pore fluid conditions, sediment supply rates, and seismic ground motion appear to have a major influence in the evolution of erosional scars and their corresponding unconformities.

  16. Map of Distribution of Bottom Sediments on the Continental Shelf, Gulf of Alaska

    USGS Publications Warehouse

    Evans, Kevin R.; Carlson, Paul R.; Hampton, Monty A.; Marlow, Michael S.; Barnes, Peter W.

    2000-01-01

    Introduction The U.S. Geological Survey has a long history of exploring marine geology in the Gulf of Alaska. As part of a cooperative program with other federal and state agencies, the USGS is investigating the relations between ocean-floor geology and benthic marine biohabitats. This bottom sediment map, compiled from published literature will help marine biologists develop an understanding of sea-floor geology in relation to various biological habitats. The pattern of sea-floor sedimentation and bottom morphology in the Gulf of Alaska reflects a complex interplay of regional tectonism, glacial advances and retreats, oceanic and tidal currents, waves, storms, eustatic change, and gravity-driven processes. This map, based on numerous cruises during the period of 1970-1996, shows distribution of bottom sediments in areas of study on the continental shelf. The samples were collected with piston, box, and gravity corers, and grab samplers. The interpretations of sediment distribution are the products of sediment size analyses combined with interpretations of high-resolution seismic reflection profiles. The sea floor was separated into several areas as follows: Cook Inlet -- Hazards studies in this embayment emphasized sediment distribution, sediment dynamics, bedforms, shallow faults, and seafloor stability. Migrating mega-sandwaves, driven by strong tidal currents, influence seabed habitats and stability of the seafloor, especially near pipelines and drilling platforms. The coarseness of the bottom sediment reinforces the influence of the strong tidal currents on the seafloor habitats. Kodiak Shelf -- Tectonic framework studies demonstrate the development of an accretionary wedge as the Pacific Plate underthrusts the Alaskan landmass. Seismic data across the accretionary wedge reveal anomalies indicative of fluid/gas vent sites in this segment of the continental margin. Geologic hazards research shows that movement along numerous shallow faults poses a risk to sea

  17. Hydrocarbon prospectivity of the Argentine Continental Slope

    SciTech Connect

    Light, M.P.R.; Keeley M.L.; Maslanyj, M.P.; Urien, C.M.; Hoggs, S.L.

    1993-02-01

    A rift basin containing stratigraphic and structural closures is developed along the Argentine slope over a distance of some 1000 km and area of 50,000 km[sup 2] in potentially exploitable water depths of 200 to 1500 m. No wells exist on this part of the continental margin. Rifting began during the Late Triassic/Jurassic and ended in Early Cretaceous. The first marine seaways flooded the Rift alluvial plains and lake. In Hauterian-Barrenian time, low circulation marine conditions with oxygen deficiency prevailed up to Rio Grande/Walvis Ridge flooding in part the coastal pull-apart basins. A major marine transgression in the Maastrichtian formed a widespread seal over the entire shelf and slope area. Four play types were identified: (1) a major north-east trending elongate delta system sourced inland from the San Julien (N. Malvinas) Basin and deposited on the southern Patagonian shelf and rise, (2) reworked deltaic barrier sands accumulated along the crest of the Outer Basement Ridge, (3) The Outer Basement Ridge, a major structural closure 400 km long, and (4) a series of margin-parallel rift systems in the offshore region between the 200 m and 1500 m isobaths. Regional seismic data and geological correlations suggest that oil prone source rocks are likely in the Middle and Upper Jurassic and Cretaceous formations. Source rocks are probably mature east and west of the Outer Basement Ridge and in the easterndepocenter of the Colorado Basin. Eastward migration from Jurassic age lacustrine source rocks in the Colorado Basin may have charged traps along the crest of the Outer Basement Ridge. Westward directed migration from deeply buried Aptian age marine source rocks in the Atlantic basins has probably charged prospective stratigraphic and structural traps in a suite of coast-parallel grabens developed on the Argentine continental shelf and slope. The Argentine offshore region, therefore, offers significant encouragement as a productive hydrocarbon province.

  18. The Role of Plumes in Breakup Processes - Traces Found in the Deep Crustal Structure at the Intersection of Walvis Ridge with the African Continental Margin

    NASA Astrophysics Data System (ADS)

    Fromm, T.; Jokat, W.; Behrmann, J. H.; Ryberg, T.; Weber, M. H.

    2014-12-01

    Large igneous provinces (LIP) are often found in close temporal and spatial proximity with continental breakups, supporting the model, that an arriving mantle plume produces large amounts of melt and has a massive influence on the breakup process. The South Atlantic is a classical example, with flood basalts on both adjacent continents and a paired age progressing ridge system connecting them with the current hotspot location at Tristan da Cunha. To estimate the influence of the plume on the preexisting continental crust, a large-scale geophysical experiment was conducted in 2011 at the intersection of Walvis Ridge with the African continent. We present four P-wave velocity models derived from seismic refraction data. One extends 430 km along the ridge crest and continues onshore to a total length of 730 km, while the other three crossing the ridge perpendicular: one (480 km long) far offshore in the oceanic regime, one (600 km) close to shelf break and the last one (400 km) onshore. Crustal velocities beneath Walvis Ridge range between 5.5 km/s and 7.0 km/s, which are typical velocities for oceanic crust. The crustal thickness, however, is approximately three times larger than of normal oceanic crust: 17 km in the western part increasing to 22 km towards the continent. The continent ocean transition is characterized by 30 km thick crust with a high velocity body (HVB) in the lower crust and seismic velocities up to 7.5 km/s. The western extend of the HVB is to a similar distance from shore as for HVBs observed south of Walvis Ridge. In contrast, the eastern boundary lies well within the continental domain, at the 40 km thick crust of the Kaoko fold belt. Here, the variation of seismic velocities indicates that hot material intruded the continental crust during the initial rifting stage. However, beyond this relatively sharp boundary (40 km wide), the remaining continental crust seems unaffected by intrusions and the root of the Kaoko belt is no eroded. The cross

  19. Continental collisions and seismic signature

    NASA Astrophysics Data System (ADS)

    Meissner, R.; Wever, Th.; Sadowiak, P.

    1991-04-01

    Reflection seismics in compressional belts has revealed the structure of crustal shortening and thickening processes, showing complex patterns of indentation and interfingering of colliding crusts and subcrustal lithospheres. Generally, in the upper crust large zones of detachments develop, often showing duplexes and 'crocodile' structures. The lower crust from zones of active collision (e.g. Alps, Pyrenees) is characterized by strongly dipping reflections. The base of the crust with the Moho must be continuously equilibrating after orogenic collapse as areas of former continental collision exhibit flat Mohos and subhorizontal reflections. The depth to the Moho increases during collision and decreases after the onset of post-orogenic extension, until finally the crustal root disappears completely together with the erosion of the mountains. Processes, active during continental collisions and orogenic collapse, create distinct structures which are imaged by reflection seismic profiling. Examples are shown and discussed.

  20. Collision zone magmatism aids continental crustal growth

    NASA Astrophysics Data System (ADS)

    Savov, Ivan; Meliksetian, Khachatur; Ralf, Halama; Gevorg, Navasardian; Chuck, Connor; Massimo, D'Antonio; Samuele, Agostini; Osamu, Ishizuka; Sergei, Karapetian; Arkadi, Karakhanian

    2014-05-01

    The continental crust has a broadly andesitic bulk composition and is predominantly generated at convergent margins. However, estimates of the bulk composition of oceanic arcs indicate a bulk composition closer to basalt than to andesite. Hence, reworking processes that transform basaltic island arc crust into andesitic continental crust are essential[1] and explaining growth of andesitic continental crust via accretion of arc crustal fragments remains problematic. Recent studies of magmatism in the Great Tibetan Plateau[2], as site of multiple and still active continent-continent collisions, have proposed that andesitic CC is generated via amalgamation of large volumes of collision-related felsic magmas generated by melting of hydrated oceanic crust with mantle geochemical signatures. We aim to test this hypothesis by evaluating geochemical data from the volcanically and tectonically active Lesser Caucasus region (Armenia, Azerbaijan, Georgia and E. Turkey), as the only other region where active continent-continent collision takes place. We will benefit from the newly compiled volcano-tectonic database of collision-related volcanic and plutonic rocks of Armenia that is comparable in quality and detail to the one available on Tibet. Our dataset combines several detailed studies from the large Aragats shield volcano[3] and associated monogenetic volcanic fields (near the capital city of Yerevan), as well as > 500 Quaternary to Holocene volcanoes from Gegham, Vardenis and Syunik volcanic highlands (toward Armenia-Nagorno-Karabakh-Azerbaijan-Iran border). The Armenian collision-related magmatism is diverse in volume, composition, eruption style and volatile contents. Interestingly, the majority of exposed volcanics are andesitic in composition. Nearly all collision-related volcanic rocks, even the highly differentiated dacite and rhyolite ignimbrites, have elevated Sr concentrations and 87Sr/86Sr and 143Nd/144Nd ratios varying only little (average ~ 0.7043 and ~ 0

  1. New constraints of subducted mantle lithosphere on plate-tectonic reconstructions of deformed continental blocks

    NASA Astrophysics Data System (ADS)

    Suppe, J.; Wu, J.; Kanda, R. V. S.; Lu, R.; Lin, C. D. J.

    2012-04-01

    Global seismic tomography and earthquake locations are now sufficiently good that many subducted slabs can be mapped in 3D, unfolded and restored to the surface of the Earth, thereby providing important new quantitative constraints on plate-tectonic reconstructions. The size, shape, present horizontal and vertical positions and seismic velocities of subducted slabs provide rich data constraints on plate-tectonic reconstructions of past plate networks into which the deformed continental regions such as Eurasia and SE Asia must fit. Commonly, we find that well-imaged and restored slabs of mantle lithosphere fit together along their edges in approximate "picture-puzzle" fashion, within seismic resolution. The slab edges correspond to plate transforms, slab tears, initial positions of trenches and edges of slab windows. This use of subducted slabs provides for more data-rich reconstructions of lost ocean basins such as those consumed between India and Eurasia and between Southeast Asia and Australia, and thereby constrains deformation of the adjacent continents. We describe our methodologies for mapping and unfolding slabs in Gocad, and using these restored slabs in GPlates. Examples are shown from Taiwan, the India-Asia collision, Southeast Asia, and Greater northeast Australia.

  2. Pore networks in continental and marine mudstones: Characteristics and controls on sealing behavior

    USGS Publications Warehouse

    Heath, J.E.; Dewers, T.A.; McPherson, B.J.O.L.; Petrusak, R.; Chidsey, T.C.; Rinehart, A.J.; Mozley, P.S.

    2011-01-01

    Mudstone pore networks are strong modifiers of sedimentary basin fluid dynamics and have a critical role in the distribution of hydrocarbons and containment of injected fluids. Using core samples from continental and marine mudstones, we investigate properties of pore types and networks from a variety of geologic environments, together with estimates of capillary beam- scanning electron microscopy, suggest seven dominant mudstone pore types distinguished by geometry and connectivity. A dominant planar pore type occurs in all investigated mudstones and generally has high coordination numbers (i.e., number of neighboring connected pores). Connected networks of pores of this type contribute to high mercury capillary pressures due to small pore throats at the junctions of connected pores and likely control most matrix transport in these mudstones. Other pore types are related to authigenic (e.g., replacement or pore-lining precipitation) clay minerals and pyrite nodules; pores in clay packets adjacent to larger, more competent clastic grains; pores in organic phases; and stylolitic and microfracture-related pores. Pores within regions of authigenic clay minerals often form small isolated networks (<3 ??m). Pores in stringers of organic phases occur as tubular pores or slit- and/or sheet-like pores. These form short, connected lengths in 3D reconstructions, but appear to form networks no larger than a few microns in size. Sealing efficiency of the studied mudstones increases with greater distal depositional environments and greater maximum depth of burial. ?? 2011 Geological Society of America.

  3. The geology and petroleum potential of the Queen Charlotte Basin, Pacific Continental Margin, Canada

    SciTech Connect

    Dietrich, J.R.; Higgs, R.; Rohr, K. )

    1990-05-01

    The Queen Charlotte basin is a 40,000 km{sup 2} late Paleogene-Neogene basin underlying the Queen Charlotte Islands, Hecate Strait, and Queen Charlotte Sound region of the Canadian Pacific continental margin. The basin formed during Eocene to Pliocene extension along and adjacent to a transform segment of the Pacific-North American plate boundary. Oblique subduction along the plate boundary in the late Cenozoic resulted in uplift and folding of portions of the northern half of the basin. In detail, the basin consists of numerous, variably oriented half-grabens and subbasins separated and underlain by complexly structured Mesozoic rocks of the Wranellia terrane. Most of the offshore subbasins contain clastic sediments in excess of 3,000 m thick and strata as thick as 6,000 m are known to occur in the deepest depocenters. The older (pre-Pliocene) portions of the basin locally contain volcanics, often interbedded with clastics. Potential hydrocarbon reservoirs within the basin include alluvial-fan fan-delta and tidal-shelf sandstones. Potential hydrocarbon source rocks include Upper Triassic-Lower Jurassic shales and limestones locally preserved below the basin and Tertiary shales within the deeper portions of the basin fill. Possible hydrocarbon traps include folds, rollover anticlines, basement fault blocks, and a variety of combined structural-stratigraphic traps. The Queen Charlotte basin is considered to be one of the most prospective areas for significant hydrocarbon resources along the northeast Pacific margin.

  4. Why does continental convergence stop

    SciTech Connect

    Hynes, A.

    1985-01-01

    Convergence between India and Asia slowed at 45 Ma when they collided, but continues today. This requires that substantial proportions of the Indian and/or Asian lithospheric mantle are still being subducted. The resulting slab-pull is probably comparable with that from complete lithospheric slabs and may promote continued continental convergence even after collision. Since descending lithospheric slabs are present at all collision zones at the time of collision such continued convergence may be general after continental collisions. It may cease only when there is a major (global) plate reorganization which results in new forces on the convergent continents that may counteract the slab-pull. These inferences may be tested on the late Paleozoic collision between Gondwanaland and Laurasia. This is generally considered to have been complete by mid-Permian time (250 Ma). However, this may be only the time of docking of Gondwanaland with North America, not that of the cessation of convergence. Paleomagnetic polar-wander paths for the Gondwanide continents exhibit consistently greater latitudinal shifts from 250 Ma to 200 Ma than those of Laurasia when corrected for post-Triassic drift, suggesting that convergence continued through late Permian well into the Triassic. It may have been accommodated by crustal thickening under what is now the US Coastal Plain, or by strike-slip faulting. Convergence may have ceased only when Pangea began to fragment again, in which case the cause for its cessation may be related to the cause of continental fragmentation.

  5. Continental Margins of the Arctic Ocean: Implications for Law of the Sea

    NASA Astrophysics Data System (ADS)

    Mosher, David

    2016-04-01

    A coastal State must define the outer edge of its continental margin in order to be entitled to extend the outer limits of its continental shelf beyond 200 M, according to article 76 of the UN Convention on the Law of the Sea. The article prescribes the methods with which to make this definition and includes such metrics as water depth, seafloor gradient and thickness of sediment. Note the distinction between the "outer edge of the continental margin", which is the extent of the margin after application of the formula of article 76, and the "outer limit of the continental shelf", which is the limit after constraint criteria of article 76 are applied. For a relatively small ocean basin, the Arctic Ocean reveals a plethora of continental margin types reflecting both its complex tectonic origins and its diverse sedimentation history. These factors play important roles in determining the extended continental shelves of Arctic coastal States. This study highlights the critical factors that might determine the outer edge of continental margins in the Arctic Ocean as prescribed by article 76. Norway is the only Arctic coastal State that has had recommendations rendered by the Commission on the Limits of the Continental Shelf (CLCS). Russia and Denmark (Greenland) have made submissions to the CLCS to support their extended continental shelves in the Arctic and are awaiting recommendations. Canada has yet to make its submission and the US has not yet ratified the Convention. The various criteria that each coastal State has utilized or potentially can utilize to determine the outer edge of the continental margin are considered. Important criteria in the Arctic include, 1) morphological continuity of undersea features, such as the various ridges and spurs, with the landmass, 2) the tectonic origins and geologic affinities with the adjacent land masses of the margins and various ridges, 3) sedimentary processes, particularly along continental slopes, and 4) thickness and

  6. Understanding Continental Margin Biodiversity: A New Imperative

    NASA Astrophysics Data System (ADS)

    Levin, Lisa A.; Sibuet, Myriam

    2012-01-01

    Until recently, the deep continental margins (200-4,000 m) were perceived as monotonous mud slopes of limited ecological or environmental concern. Progress in seafloor mapping and direct observation now reveals unexpected heterogeneity, with a mosaic of habitats and ecosystems linked to geomorphological, geochemical, and hydrographic features that influence biotic diversity. Interactions among water masses, terrestrial inputs, sediment diagenesis, and tectonic activity create a multitude of ecological settings supporting distinct communities that populate canyons and seamounts, high-stress oxygen minimum zones, and methane seeps, as well as vast reefs of cold corals and sponges. This high regional biodiversity is fundamental to the production of valuable fisheries, energy, and mineral resources, and performs critical ecological services (nutrient cycling, carbon sequestration, nursery and habitat support). It is under significant threat from climate change and human resource extraction activities. Serious actions are required to preserve the functions and services provided by the deep-sea settings we are just now getting to know.

  7. Understanding continental margin biodiversity: a new imperative.

    PubMed

    Levin, Lisa A; Sibuet, Myriam

    2012-01-01

    Until recently, the deep continental margins (200-4,000 m) were perceived as monotonous mud slopes of limited ecological or environmental concern. Progress in seafloor mapping and direct observation now reveals unexpected heterogeneity, with a mosaic of habitats and ecosystems linked to geomorphological, geochemical, and hydrographic features that influence biotic diversity. Interactions among water masses, terrestrial inputs, sediment diagenesis, and tectonic activity create a multitude of ecological settings supporting distinct communities that populate canyons and seamounts, high-stress oxygen minimum zones, and methane seeps, as well as vast reefs of cold corals and sponges. This high regional biodiversity is fundamental to the production of valuable fisheries, energy, and mineral resources, and performs critical ecological services (nutrient cycling, carbon sequestration, nursery and habitat support). It is under significant threat from climate change and human resource extraction activities. Serious actions are required to preserve the functions and services provided by the deep-sea settings we are just now getting to know.

  8. Composition of the Continental Crust

    NASA Astrophysics Data System (ADS)

    Rudnick, R. L.; Gao, S.

    2003-12-01

    The Earth is an unusual planet in our solar system in having a bimodal topography that reflects the two distinct types of crust found on our planet. The low-lying oceanic crust is thin (˜7 km on average), composed of relatively dense rock types such as basalt and is young (≤200 Ma old) (see Chapter 3.13). In contrast, the high-standing continental crust is thick (˜40 km on average), is composed of highly diverse lithologies (virtually every rock type known on Earth) that yield an average intermediate or "andesitic" bulk composition (Taylor and McLennan (1985) and references therein), and contains the oldest rocks and minerals yet observed on Earth (currently the 4.0 Ga Acasta gneisses (Bowring and Williams, 1999) and 4.4 Ga detrital zircons from the Yilgarn Block, Western Australia (Wilde et al., 2001)), respectively. Thus, the continents preserve a rich geological history of our planet's evolution and understanding their origin is critical for understanding the origin and differentiation of the Earth.The origin of the continents has received wide attention within the geological community, with hundreds of papers and several books devoted to the topic (the reader is referred to the following general references for further reading: Taylor and McLennan (1985), Windley (1995), and Condie (1997). Knowledge of the age and composition of the continental crust is essential for understanding its origin. Patchett and Samson (Chapter 3.10) review the present-day age distribution of the continental crust and Kemp and Hawkesworth (Chapter 3.11) review secular evolution of crust composition. Moreover, to understand fully the origin and evolution of continents requires an understanding of not only the crust, but also the mantle lithosphere that formed more-or-less contemporaneously with the crust and translates with it as the continents move across the Earth's surface. The latter topic is reviewed in Chapter 2.05.This chapter reviews the present-day composition of the

  9. Adjacent Segment Pathology after Anterior Cervical Fusion

    PubMed Central

    Chung, Jae Yoon; Park, Jong-Beom; Seo, Hyoung-Yeon

    2016-01-01

    Anterior cervical fusion has become a standard of care for numerous pathologic conditions of the cervical spine. However, subsequent development of clinically significant disc disease at levels adjacent to fused discs is a serious long-term complication of this procedure. As more patients live longer after surgery, it is foreseeable that adjacent segment pathology (ASP) will develop in increasing numbers of patients. Also, ASP has been studied more intensively with the recent popularity of motion preservation technologies like total disc arthroplasty. The true nature and scope of ASP remains poorly understood. The etiology of ASP is most likely multifactorial. Various factors including altered biomechanical stresses, surgical disruption of soft tissue and the natural history of cervical disc disease contribute to the development of ASP. General factors associated with disc degeneration including gender, age, smoking and sports may play a role in the development of ASP. Postoperative sagittal alignment and type of surgery are also considered potential causes of ASP. Therefore, a spine surgeon must be particularly careful to avoid unnecessary disruption of the musculoligamentous structures, reduced risk of direct injury to the disc during dissection and maintain a safe margin between the plate edge and adjacent vertebrae during anterior cervical fusion. PMID:27340541

  10. Lithospheric mantle heterogeneity across the continental-oceanic transition, northwest Ross Sea, Antarctica: new evidence from oxygen isotopes

    NASA Astrophysics Data System (ADS)

    Krans, S. R.; Panter, K. S.; Castillo, P.; Deering, C. D.; Kitajima, K.; Valley, J. W.; Hart, S. R.; Kyle, P. R.

    2013-12-01

    . Based on this evidence we propose three different mantle source domains in this region: 1) lower δ18O metasomatic veins in the continental and oceanic lithospheric mantle, 2) ambient continental lithospheric mantle with lower Sr and higher δ18O (for alkali basalt), and 3) ambient oceanic lithospheric mantle with higher Sr and δ18O akin to continental lithosphere (for basanite). Low degree melts will preferentially tap the more easily fusible veins while higher degree melts incorporate greater proportions of the adjacent ambient mantle. [1] Eiler (2001) RiMG, 43(1), 319-364. [2] Gamble and Kyle (1987) J. Petrol., 28(5), 755-779. [3] Coltorti et al. (2004) Lithos, 75(1), 115-139. [4] Perinelli et al. (2006) CMP, 151(3), 245-266. [5] Castillo et al. (2011) AGU Fall meeting.

  11. Tectonics of China: Continental scale cataclastic flow

    NASA Astrophysics Data System (ADS)

    Gallagher, John J., Jr.

    Stratigraphic, structural, and earthquake evidence indicates that cataclastic flow, that is, flow by brittle mechanisms (e.g., fracture and slip), was dominant in China from late Paleozoic. This process has operated over a range of scales including the continental scale. China is made up of large brittle basement elements immersed in ductile zones which are analogous to porphyroclasts (large, often brittle fragments) surrounded by fluxion (foliation or flow) structures in cataclastic rocks, respectively. This basement fabric for China is seen on Landsat imagery and on tectonic maps and is comparable to cataclastic rock fabrics seen in fault zones, on outcrops, and in thin sections. Brittle basement elements are broken into two or more large rigid blocks, and the dimensions of elements and blocks are within 1 order of magnitude of each other. Ductile zones are made up of fragments which are many orders of magnitude smaller than the ductile zones. Rigid blocks and fragments are identified, and their dimensions are measured through earthquake, fault, and fracture patterns. Rigid basement blocks are surrounded by earthquakes. The sedimentary rocks over the basement faults at the block boundaries seem to be affected by fault movements because they are characterized by facies changes, thickness changes, high-angle faults, and forced folds. Ductile basement zones are earthquake prone, and deformation of the ductile basement affects the overlying sedimentary rocks, as is demonstrated by unconformities and by a wide variety of structures. Thrust faults, buckle folds, and strike slip faults are common in and adjacent to western ductile zones. Structures are most intensely developed where ductile zones abut brittle elements. Both brittle elements and ductile zones are rifted and cut by strike slip faults in eastern China. The mechanical fabric of China and the boundary conditions acting on China are now and always have been determined by its plate tectonic history. This

  12. Understanding heat and groundwater flow through continental flood basalt provinces: insights gained from alternative models of permeability/depth relationships for the Columbia Plateau, USA

    SciTech Connect

    Burns, Erick R.; Williams, Colin F.; Ingebritsen, Steven E.; Voss, Clifford I.; Spane, Frank A.; DeAngelo, Jacob

    2015-02-01

    Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600–900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration.

  13. Understanding heat and groundwater flow through continental flood basalt provinces: insights gained from alternative models of permeability/depth relationships for the Columbia Plateau, USA

    USGS Publications Warehouse

    Burns, Erick R.; Williams, Colin F.; Ingebritsen, Steven E.; Voss, Clifford I.; Spane, Frank A.; DeAngelo, Jacob

    2015-01-01

    Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600–900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration.

  14. Continuous Mantle Exhumation at the Outer Continental Margin of the Santos, Campos and Espírito Santo Basins, Brazil

    NASA Astrophysics Data System (ADS)

    Zalan, P. V.; Severino, M. G.; Rigoti, C. A.; Magnavita, L. P.; Oliveira, J. B.; Viana, A. R.

    2011-12-01

    The interpretation of 12,000 km of very deep (PSTM to 16 sec., PSDM to 25 km) 2D seismic sections, coupled with gravimetric and magnetometric modeling line-by-line, and the integration of the results with the regional data bank of Petrobras, all together viewed in terms of the recent tectonic models developed for the rupturing and separation of mega-plates, led to a regional (500,000 km2), first-time ever, 3D-view of the deep structure underlying the prolific sedimentary basins of Santos, Campos and Espírito Santo in southeastern Brazil. The three basins are situated onto a continental margin that narrows gradually, from south to north, from a very wide (Santos), through an intermediate (Campos), and then to a narrow (Espírito Santo) passive margin. The seismic sections shows very well the dual rheological behavior of the continental crust, consisting of a deeper and plastic lower crust (with numerous short and strong reflections that display sub-horizontal ductile flow) and a shallower and brittle upper crust (represented by a mostly transparent and faulted seismic facies topped by the sedimentary sections of the rift and thermal subsidence phases). The crustal structure of the Santos Basin shows a zonation from west to east of alternating bands of NE-SW-trending thin (plastic basement terrains) and thick (resistant basement terrains) stretched continental crust. In vertical section this zonation is displayed as a series of necking zones, leading to a highly irregular, low to moderate crustal taper. Such zonation is less developed in the Campos Basin, where the crustal taper is moderate and regular, and practically non-existent in the Espírito Santo Basin, where the crustal taper is high. The most outstanding crustal feature shared in common by the three basins is the exhumation of mantle between the tip of the hyper-extended continental crust and the tabular-shaped oceanic crust. Although the crustal taper varies significantly from basin to basin their

  15. Adjacent-level arthroplasty following cervical fusion.

    PubMed

    Rajakumar, Deshpande V; Hari, Akshay; Krishna, Murali; Konar, Subhas; Sharma, Ankit

    2017-02-01

    OBJECTIVE Adjacent-level disc degeneration following cervical fusion has been well reported. This condition poses a major treatment dilemma when it becomes symptomatic. The potential application of cervical arthroplasty to preserve motion in the affected segment is not well documented, with few studies in the literature. The authors present their initial experience of analyzing clinical and radiological results in such patients who were treated with arthroplasty for new or persistent arm and/or neck symptoms related to neural compression due to adjacent-segment disease after anterior cervical discectomy and fusion (ACDF). METHODS During a 5-year period, 11 patients who had undergone ACDF anterior cervical discectomy and fusion (ACDF) and subsequently developed recurrent neck or arm pain related to adjacent-level cervical disc disease were treated with cervical arthroplasty at the authors' institution. A total of 15 devices were implanted (range of treated levels per patient: 1-3). Clinical evaluation was performed both before and after surgery, using a visual analog scale (VAS) for pain and the Neck Disability Index (NDI). Radiological outcomes were analyzed using pre- and postoperative flexion/extension lateral radiographs measuring Cobb angle (overall C2-7 sagittal alignment), functional spinal unit (FSU) angle, and range of motion (ROM). RESULTS There were no major perioperative complications or device-related failures. Statistically significant results, obtained in all cases, were reflected by an improvement in VAS scores for neck/arm pain and NDI scores for neck pain. Radiologically, statistically significant increases in the overall lordosis (as measured by Cobb angle) and ROM at the treated disc level were observed. Three patients were lost to follow-up within the first year after arthroplasty. In the remaining 8 cases, the duration of follow-up ranged from 1 to 3 years. None of these 8 patients required surgery for the same vertebral level during the follow

  16. The structural evolution of the deep continental lithosphere

    NASA Astrophysics Data System (ADS)

    Cooper, C. M.; Miller, Meghan S.; Moresi, Louis

    2017-01-01

    Continental lithosphere houses the oldest and thickest regions of the Earth's surface. Locked within this deep and ancient rock record lies invaluable information about the dynamics that has shaped and continue to shape the planet. Much of that history has been dominated by the forces of plate tectonics which has repeatedly assembled super continents together and torn them apart - the Wilson Cycle. While the younger regions of continental lithosphere have been subject to deformation driven by plate tectonics, it is less clear whether the ancient, stable cores formed and evolved from similar processes. New insight into continental formation and evolution has come from remarkable views of deeper lithospheric structure using enhanced seismic imaging techniques and the increase in large volumes of broadband data. Some of the most compelling observations are that the continental lithosphere has a broad range in thicknesses (< 100 to > 300 km), has complex internal structure, and that the thickest portion appears to be riddled with seismic discontinuities at depths between 80 and 130 km. These internal structural features have been interpreted as remnants of lithospheric formation during Earth's early history. If they are remnants, then we can attempt to investigate the structure present in the deep lithosphere to piece together information about early Earth dynamics much as is done closer to the surface. This would help delineate between the differing models describing the dynamics of craton formation, particularly whether they formed in the era of modern plate tectonics, a transitional mobile-lid tectonic regime, or are the last fragments of an early, stagnant-lid planet. Our review paper (re)introduces readers to the conceptual definitions of the lithosphere and the complex nature of the upper boundary layer, then moves on to discuss techniques and recent seismological observations of the continental lithosphere. We then review geodynamic models and hypotheses for the

  17. Thermal models pertaining to continental growth

    NASA Technical Reports Server (NTRS)

    Morgan, Paul; Ashwal, Lew

    1988-01-01

    Thermal models are important to understanding continental growth as the genesis, stabilization, and possible recycling of continental crust are closely related to the tectonic processes of the earth which are driven primarily by heat. The thermal energy budget of the earth was slowly decreasing since core formation, and thus the energy driving the terrestrial tectonic engine was decreasing. This fundamental observation was used to develop a logic tree defining the options for continental growth throughout earth history.

  18. Postcollisional mafic igneous rocks record crust-mantle interaction during continental deep subduction.

    PubMed

    Zhao, Zi-Fu; Dai, Li-Qun; Zheng, Yong-Fei

    2013-12-04

    Findings of coesite and microdiamond in metamorphic rocks of supracrustal protolith led to the recognition of continental subduction to mantle depths. The crust-mantle interaction is expected to take place during subduction of the continental crust beneath the subcontinental lithospheric mantle wedge. This is recorded by postcollisional mafic igneous rocks in the Dabie-Sulu orogenic belt and its adjacent continental margin in the North China Block. These rocks exhibit the geochemical inheritance of whole-rock trace elements and Sr-Nd-Pb isotopes as well as zircon U-Pb ages and Hf-O isotopes from felsic melts derived from the subducted continental crust. Reaction of such melts with the overlying wedge peridotite would transfer the crustal signatures to the mantle sources for postcollisional mafic magmatism. Therefore, postcollisonal mafic igneous rocks above continental subduction zones are an analog to arc volcanics above oceanic subduction zones, providing an additional laboratory for the study of crust-mantle interaction at convergent plate margins.

  19. Postcollisional mafic igneous rocks record crust-mantle interaction during continental deep subduction

    PubMed Central

    Zhao, Zi-Fu; Dai, Li-Qun; Zheng, Yong-Fei

    2013-01-01

    Findings of coesite and microdiamond in metamorphic rocks of supracrustal protolith led to the recognition of continental subduction to mantle depths. The crust-mantle interaction is expected to take place during subduction of the continental crust beneath the subcontinental lithospheric mantle wedge. This is recorded by postcollisional mafic igneous rocks in the Dabie-Sulu orogenic belt and its adjacent continental margin in the North China Block. These rocks exhibit the geochemical inheritance of whole-rock trace elements and Sr-Nd-Pb isotopes as well as zircon U-Pb ages and Hf-O isotopes from felsic melts derived from the subducted continental crust. Reaction of such melts with the overlying wedge peridotite would transfer the crustal signatures to the mantle sources for postcollisional mafic magmatism. Therefore, postcollisonal mafic igneous rocks above continental subduction zones are an analog to arc volcanics above oceanic subduction zones, providing an additional laboratory for the study of crust-mantle interaction at convergent plate margins. PMID:24301173

  20. Tissue microenvironments within functional cortical subdivisions adjacent to focal stroke.

    PubMed

    Katsman, Diana; Zheng, Jian; Spinelli, Kateri; Carmichael, S Thomas

    2003-09-01

    Stroke produces a region of complete cell death and areas of partial damage, injury, and gliosis. The spatial relationship of these regions of damage to the infarct core and within spared neuronal circuits has not been identified. A model of cortical stroke was developed within functional subsets of the somatosensory cortex. Infarct size, regions of apoptosis, oxidative DNA damage, heat shock protein induction, and subtypes of reactive gliosis were precisely mapped with the somatosensory body map, quantified, and interrelated. Three tissue microenvironments were recognized: zones of partial ischemic damage, heat shock protein induction, and distributed gliosis. These three zones involved progressively more distant cortical regions, each larger than the infarct core. The zone of partial ischemic damage represents an overlap region of apoptotic cell death, oxidative DNA damage, loss of synaptic connections, and local reactive gliosis. The zone of distributed gliosis occupies distinct functional areas of the somatosensory cortex. The tissue reorganization induced by stroke is much larger than the stroke site itself. Adjacent tissue microenvironments are sites of distinct reactive cellular signaling and may serve as a link between the processes of acute cell death and delayed neuronal plasticity after focal stroke.

  1. Habitat Specialization in Tropical Continental Shelf Demersal Fish Assemblages

    PubMed Central

    Fitzpatrick, Ben M.; Harvey, Euan S.; Heyward, Andrew J.; Twiggs, Emily J.; Colquhoun, Jamie

    2012-01-01

    The implications of shallow water impacts such as fishing and climate change on fish assemblages are generally considered in isolation from the distribution and abundance of these fish assemblages in adjacent deeper waters. We investigate the abundance and length of demersal fish assemblages across a section of tropical continental shelf at Ningaloo Reef, Western Australia, to identify fish and fish habitat relationships across steep gradients in depth and in different benthic habitat types. The assemblage composition of demersal fish were assessed from baited remote underwater stereo-video samples (n = 304) collected from 16 depth and habitat combinations. Samples were collected across a depth range poorly represented in the literature from the fringing reef lagoon (1–10 m depth), down the fore reef slope to the reef base (10–30 m depth) then across the adjacent continental shelf (30–110 m depth). Multivariate analyses showed that there were distinctive fish assemblages and different sized fish were associated with each habitat/depth category. Species richness, MaxN and diversity declined with depth, while average length and trophic level increased. The assemblage structure, diversity, size and trophic structure of demersal fishes changes from shallow inshore habitats to deeper water habitats. More habitat specialists (unique species per habitat/depth category) were associated with the reef slope and reef base than other habitats, but offshore sponge-dominated habitats and inshore coral-dominated reef also supported unique species. This suggests that marine protected areas in shallow coral-dominated reef habitats may not adequately protect those species whose depth distribution extends beyond shallow habitats, or other significant elements of demersal fish biodiversity. The ontogenetic habitat partitioning which is characteristic of many species, suggests that to maintain entire species life histories it is necessary to protect corridors of connected

  2. Habitat specialization in tropical continental shelf demersal fish assemblages.

    PubMed

    Fitzpatrick, Ben M; Harvey, Euan S; Heyward, Andrew J; Twiggs, Emily J; Colquhoun, Jamie

    2012-01-01

    The implications of shallow water impacts such as fishing and climate change on fish assemblages are generally considered in isolation from the distribution and abundance of these fish assemblages in adjacent deeper waters. We investigate the abundance and length of demersal fish assemblages across a section of tropical continental shelf at Ningaloo Reef, Western Australia, to identify fish and fish habitat relationships across steep gradients in depth and in different benthic habitat types. The assemblage composition of demersal fish were assessed from baited remote underwater stereo-video samples (n = 304) collected from 16 depth and habitat combinations. Samples were collected across a depth range poorly represented in the literature from the fringing reef lagoon (1-10 m depth), down the fore reef slope to the reef base (10-30 m depth) then across the adjacent continental shelf (30-110 m depth). Multivariate analyses showed that there were distinctive fish assemblages and different sized fish were associated with each habitat/depth category. Species richness, MaxN and diversity declined with depth, while average length and trophic level increased. The assemblage structure, diversity, size and trophic structure of demersal fishes changes from shallow inshore habitats to deeper water habitats. More habitat specialists (unique species per habitat/depth category) were associated with the reef slope and reef base than other habitats, but offshore sponge-dominated habitats and inshore coral-dominated reef also supported unique species. This suggests that marine protected areas in shallow coral-dominated reef habitats may not adequately protect those species whose depth distribution extends beyond shallow habitats, or other significant elements of demersal fish biodiversity. The ontogenetic habitat partitioning which is characteristic of many species, suggests that to maintain entire species life histories it is necessary to protect corridors of connected habitats

  3. Atmospheric water vapor transport: Estimation of continental precipitation recycling and parameterization of a simple climate model. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Brubaker, Kaye L.; Entekhabi, Dara; Eagleson, Peter S.

    1991-01-01

    The advective transport of atmospheric water vapor and its role in global hydrology and the water balance of continental regions are discussed and explored. The data set consists of ten years of global wind and humidity observations interpolated onto a regular grid by objective analysis. Atmospheric water vapor fluxes across the boundaries of selected continental regions are displayed graphically. The water vapor flux data are used to investigate the sources of continental precipitation. The total amount of water that precipitates on large continental regions is supplied by two mechanisms: (1) advection from surrounding areas external to the region; and (2) evaporation and transpiration from the land surface recycling of precipitation over the continental area. The degree to which regional precipitation is supplied by recycled moisture is a potentially significant climate feedback mechanism and land surface-atmosphere interaction, which may contribute to the persistence and intensification of droughts. A simplified model of the atmospheric moisture over continents and simultaneous estimates of regional precipitation are employed to estimate, for several large continental regions, the fraction of precipitation that is locally derived. In a separate, but related, study estimates of ocean to land water vapor transport are used to parameterize an existing simple climate model, containing both land and ocean surfaces, that is intended to mimic the dynamics of continental climates.

  4. Heat flow and continental breakup: The Gulf of Elat (Aqaba)

    NASA Technical Reports Server (NTRS)

    Ben-Avraham, Z.; Vonherzen, R. P.

    1985-01-01

    Heat flow measurements were made in the major basins of the Gulf of Elat (Aqaba), northern Red Sea. The gulf is located at the southern portion of the Dead Sea rift which is a transform plate boundary. Gradient measurements at each site were made with a probe which allows multiple penetration of the bottom during a single deployment of the instrument. Thermal conductivity was determined by needle probe measurements on sedimentary cores. The mean heat flux, about 80 mWm(-2), is significantly above the continental mean, and probably also above that from the adjacent Sinai and Arabian continental blocks. The heat flow appears to increase from north to south. Such an increase may be related to the more advanced rifting stage of the Red Sea immediately to the south, which presently includes creation of an oceanic crust. This trend also corresponds to the general trend of the deep crustal structure in the gulf. Evidence from various geophysical fields suggest a gradual thinning of the crust towards the direction of the Red Sea where a normal oceanic crust exists. The heat flow data, together with other geophysical data, indicate a propagation of mature rifting activity from the Red Sea into the Gulf of Elat. This process is acting simultaneously with the transform motion along the Dead Sea rift.

  5. Structure and development of the southern Moroccan continental shelf

    USGS Publications Warehouse

    Dillon, William P.

    1974-01-01

    The structure of the continental shelf off southern Morocco was studied by means of 2,100 km of seismic reflection profiles, magnetic and bathymetric surveys, and dredge samples. The research area lies off four geologic divisions adjacent to the coast: the Atlas Mountains; the Souss Trough; the Anti-Atlas Mountains; and the Aaiun Basin. The continental shelf, along with the western Atlas Mountains, the western Souss Trough, and the entire Aaiun Basin, has subsided along a normal fault-flexure system. This system runs along the shore at the Anti-Atlas Mountains, and cuts off this cratonic block from the shelf subsidence. The shelf is narrow and characterized by out-building off the Anti-Atlas range, whereas it is broader and characterized by upbuilding to the north and south. Deposition was essentially continuous at least from Early Cretaceous through Eocene time. Published work suggests that the last cycle of sedimentation began during Permian rifting. After Eocene time, most sediments carried to the shelf must have bypassed it and gone to construct the slope and rise or to the deep sea. Tertiary orogenies caused extensive folding of Mesozoic and early Tertiary deposits off the Atlas Mountains. ?? 1974.

  6. 77 FR 7148 - Notice of Approval of Clean Air Act Outer Continental Shelf Permits Issued to Shell Gulf of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-10

    ... AGENCY Notice of Approval of Clean Air Act Outer Continental Shelf Permits Issued to Shell Gulf of Mexico... Region 10 has issued two final permit decisions granting Clean Air Act Outer Continental Shelf (OCS... entities: (1) The Inupiat Community of the Arctic Slope (ICAS); \\1\\ (2) The Native Village of Point...

  7. Geology of the Cape Mendocino, Eureka, Garberville, and Southwestern Part of the Hayfork 30 x 60 Minute Quadrangles and Adjacent Offshore Area, Northern California

    USGS Publications Warehouse

    McLaughlin, Robert J.; Ellen, S.D.; Blake, M.C.; Jayko, Angela S.; Irwin, W.P.; Aalto, K.R.; Carver, G.A.; Clarke, S.H.; Barnes, J.B.; Cecil, J.D.; Cyr, K.A.

    2000-01-01

    Introduction These geologic maps and accompanying structure sections depict the geology and structure of much of northwestern California and the adjacent continental margin. The map area includes the Mendocino triple junction, which is the juncture of the North American continental plate with two plates of the Pacific ocean basin. The map area also encompasses major geographic and geologic provinces of northwestern California. The maps incorporate much previously unpublished geologic mapping done between 1980 and 1995, as well as published mapping done between about 1950 and 1978. To construct structure sections to mid-crustal depths, we integrate the surface geology with interpretations of crustal structure based on seismicity, gravity and aeromagnetic data, offshore structure, and seismic reflection and refraction data. In addition to describing major geologic and structural features of northwestern California, the geologic maps have the potential to address a number of societally relevant issues, including hazards from earthquakes, landslides, and floods and problems related to timber harvest, wildlife habitat, and changing land use. All of these topics will continue to be of interest in the region, as changing land uses and population density interact with natural conditions. In these interactions, it is critical that the policies and practices affecting man and the environment integrate an adequate understanding of the geology. This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying text file (ceghmf.ps, ceghmf.pdf, ceghmf.txt), it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The

  8. Earth's continental crustal gold endowment

    NASA Astrophysics Data System (ADS)

    Frimmel, H. E.

    2008-03-01

    The analysis of the temporal distribution of gold deposits, combined with gold production data as well as reserve and resource estimates for different genetic types of gold deposit, revealed that the bulk of the gold known to be concentrated in ore bodies was added to the continental crust during a giant Mesoarchaean gold event at a time (3 Ga) when the mantle temperature reached a maximum and the dominant style of tectonic movement changed from vertical, plume-related to subhorizontal plate tectonic. A magmatic derivation of the first generation of crustal gold from a relatively hot mantle that was characterized by a high degree of partial melting is inferred from the gold chemistry, specifically high Os contents. While a large proportion of that gold is still present in only marginally modified palaeoplacer deposits of the Mesoarchaean Witwatersrand Basin in South Africa, accounting for about 40% of all known gold, the remainder has been recycled repeatedly on a lithospheric scale, predominantly by plate-tectonically induced magmatic and hydrothermal fluid circulation, to produce the current variety of gold deposit types. Post-Archaean juvenile gold addition to the continental crust has been limited, but a mantle contribution to some of the largest orogenic or intrusion-related gold deposits is indicated, notably for the Late Palaeozoic Tien Shan gold province. Magmatic fluids in active plate margins seem to be the most effective transport medium for gold mobilization, giving rise to a large proportion of volcanic-arc related gold deposits. Due to their generally shallow crustal level of formation, they have a low preservation potential. In contrast, those gold deposits that form at greater depth are more widespread also in older rocks. This explains the high proportion of orogenic (including intrusion-related) gold (32%) amongst all known gold deposits. The overall proportion of gold concentrated in known ore bodies is only 7 × 10- 7 of the estimated total

  9. Early Continental Rifting of the South China Sea

    NASA Astrophysics Data System (ADS)

    Lee, C.; Chiu, M.; Chan, C.

    2010-12-01

    Combined two years (2007 and 2008) of OBS and MCS studies in the northern slope of the South China Sea, we suggest that the early rifting, probably during 60 - 30 mabp, is an asymmetrical Atlantic-type continental rifting. The crust thin out from 35-40 km of possible continental crust to about 10-15 km of typical oceanic crust. Along the continent-ocean boundary, we observe an intrusion of the high P-wave velocity (about 7.5-8.0 km/sec). This is possible of mantle exhumation as comparable to other Atlantic-type continental margins. The OBS result is revealed by the gravity data. Along the upper layers of the continental crust as well as the oceanic crust, the MCS and multi-beam bathymetry data show that they are covered by numerous submarine seamounts. This probably relate to a volcanic origin of the Cenozoic sea-floor spreading during 30-15 mabp as mapped by previous magnetic anomalies in this region. The sea-floor spreading spread apart in the central, NW and SW sub-basins with several different episodes. Lack of the deep crustal data in the southern slope of the South China Sea, particularly around the Sprately area, the interpretation is speculative. However, several very large-size atolls (150 - 200 km in diameter), such as the Chen-Ho, Shun-Zu, Chung-Yeh and Chiu-Cheng fringing reefs, are sub-parallel located along the south margins. We interpret that these are the upper portions of the continental rifting. Combined the two tectonic stories in the northern and southern slope of the South China Sea, we believe that it is in consistent with the complicate nature of the South China Sea crust.

  10. Crustal and basin evolution of the southwestern Barents Sea: From Caledonian orogeny to continental breakup

    NASA Astrophysics Data System (ADS)

    Gernigon, L.; Brönner, M.; Roberts, D.; Olesen, O.; Nasuti, A.; Yamasaki, T.

    2014-04-01

    A new generation of aeromagnetic data documents the post-Caledonide rift evolution of the southwestern Barents Sea (SWBS) from the Norwegian mainland up to the continent-ocean transition. We propose a geological and tectonic scenario of the SWBS in which the Caledonian nappes and thrust sheets, well-constrained onshore, swing from a NE-SW trend onshore Norway to NW-SE/NNW-SSE across the SWBS platform area. On the Finnmark and Bjarmeland platforms, the dominant inherited magnetic basement pattern may also reflect the regional and post-Caledonian development of the late Paleozoic basins. Farther west, the pre-breakup rift system is characterized by the Loppa and Stappen Highs, which are interpreted as a series of rigid continental blocks (ribbons) poorly thinned as compared to the adjacent grabens and sag basins. As part of the complex western rift system, the Bjørnøya Basin is interpreted as a propagating system of highly thinned crust, which aborted in late Mesozoic time. This thick Cretaceous sag basin is underlain by a deep-seated high-density body, interpreted as exhumed high-grade metamorphic lower crust. The abortion of this propagating basin coincides with a migration and complete reorganization of the crustal extension toward a second necking zone defined at the level of the western volcanic sheared margin and proto-breakup axis. The abortion of the Bjørnøya Basin may be partly explained by its trend oblique to the regional, inherited, structural grain, revealed by the new aeromagnetic compilation, and by the onset of further weakening later sustained by the onset of magmatism to the west.

  11. 30 CFR 56.9103 - Clearance on adjacent tracks.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Clearance on adjacent tracks. 56.9103 Section..., Hauling, and Dumping Traffic Safety § 56.9103 Clearance on adjacent tracks. Railcars shall not be left on side tracks unless clearance is provided for traffic on adjacent tracks....

  12. 30 CFR 57.9103 - Clearance on adjacent tracks.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Clearance on adjacent tracks. 57.9103 Section..., Hauling, and Dumping Traffic Safety § 57.9103 Clearance on adjacent tracks. Railcars shall not be left on side tracks unless clearance is provided for traffic on adjacent tracks....

  13. 49 CFR 236.404 - Signals at adjacent control points.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ..., INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Traffic Control Systems Standards § 236.404 Signals at adjacent control points. Signals at adjacent controlled... 49 Transportation 4 2011-10-01 2011-10-01 false Signals at adjacent control points....

  14. 49 CFR 236.404 - Signals at adjacent control points.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ..., INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Traffic Control Systems Standards § 236.404 Signals at adjacent control points. Signals at adjacent controlled... 49 Transportation 4 2010-10-01 2010-10-01 false Signals at adjacent control points....

  15. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  16. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  17. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  18. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  19. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  20. Deformation in the continental lithosphere

    NASA Astrophysics Data System (ADS)

    The Physical Properties of Earth Materials Committee, a technical committee of AGU's Tectonophysics Section, is organizing a dinner/colloquium as part of the Fall Meeting in San Francisco, Calif. This event will be held Monday, December 3rd, in the Gold Rush Room of the Holiday Inn Golden Gateway Hotel at 1500 Van Ness St. There will be a no-host bar from 6:30 to 7:30 P.M., followed by dinner from 7:30 to 8:30 P.M. Paul Tapponnier will deliver the after-dinner talk, “Large-Scale Deformation Mechanisms in the Continental Lithosphere: Where Do We Stand?” It will start at 8:30 P.M. and a business meeting will follow at 9:30 P.M.

  1. Composition of the continental plates

    USGS Publications Warehouse

    Gilluly, J.

    1954-01-01

    The structures of continental plates and of oceanic basins suggested by several seismologists are utilized to estimate the relative volumes of sial and sima in the earth's crust. It seems that sial of the composition of the average igneous rock constitutes fully 26% and perhaps as much as 43% of the total crust. This ratio is far higher than seems likely if the sial had been entirely derived through fractional crystallization of a basaltic magma. The relative paucity of intermediate rocks as compared with granite and gabbro in the crust points in the same direction. The tentative conclusion is reached that the sial owes a large part of its volume to some process other than fractional crystallization of basalt-possibly to the emanation of low-melting constituents such as water, silica, potassa, soda, and alumina directly from the mantle to the crust. ?? 1954 Springer-Verlag.

  2. Earthquakes in stable continental crust

    SciTech Connect

    Johnson, A.C.; Kanter, L.R. )

    1990-03-01

    Earthquakes can strike even in stable crust, well away from the familiar earthquake zones at the edges of tectonic plates, but their mere occurrence is both a source of concern in planning critical facilities such as nuclear power plants. The authors sought answers to two major questions: Just how much seismic activity does take place within the stable parts of continents And are there specific geologic features that make some areas of stable crust particularly susceptible to earthquakes They began by studying North America alone, but it soon became clear that the fairly short record of these rare events on a single continent would not provide enough data for reliable analysis. Hence, they decided to substitute space for time--to survey earthquake frequency and distribution in stable continental areas worldwide. This paper discusses their findings.

  3. A Facies Model for Temperate Continental Glaciers.

    ERIC Educational Resources Information Center

    Ashley, Gail Mowry

    1987-01-01

    Discusses the presence and dynamics of continental glaciers in the domination of the physical processes of erosion and deposition in the mid-latitudes during the Pleistocene period. Describes the use of a sedimentary facies model as a guide to recognizing ancient temperate continental glacial deposits. (TW)

  4. Evolution of Oxidative Continental Weathering

    NASA Astrophysics Data System (ADS)

    Konhauser, Kurt; Lalonde, Stefan

    2014-05-01

    The Great Oxidation Event (GOE) is currently viewed as a protracted process during which atmospheric oxygen levels increased above 10-5 times the present atmospheric level. This value is based on the loss of sulphur isotope mass independent fractionation (S-MIF) from the rock record, beginning at 2.45 Ga and disappearing by 2.32 Ga. However, a number of recent papers have pushed back the timing for oxidative continental weathering, and by extension, the onset of atmospheric oxygenation several hundreds of million years earlier despite the presence of S-MIF (e.g., Crowe et al., 2013). This apparent discrepancy can, in part, be resolved by the suggestion that recycling of older sedimentary sulphur bearing S-MIF might have led to this signal's persistence in the rock record for some time after atmospheric oxygenation (Reinhard et al., 2013). Here we suggest another possibility, that the earliest oxidative weathering reactions occurred in environments at profound redox disequilibrium with the atmosphere, such as biological soil crusts, riverbed and estuarine sediments, and lacustrine microbial mats. We calculate that the rate of O2 production via oxygenic photosynthesis in these terrestrial microbial ecosystems provides largely sufficient oxidizing potential to mobilise sulphate and a number of redox-sensitive trace metals from land to the oceans while the atmosphere itself remained anoxic with its attendant S-MIF signature. These findings reconcile geochemical signatures in the rock record for the earliest oxidative continental weathering with the history of atmospheric sulphur chemistry, and demonstrate the plausible antiquity of a terrestrial biosphere populated by cyanobacteria. Crowe, S.A., Dossing, L.N., Beukes, N.J., Bau, M., Kruger, S.J., Frei, R. & Canfield, D.E. Atmospheric oxygenation three billion years ago. Nature 501, 535-539 (2013). Reinhard, C.T., Planavsky, N.J. & Lyons, T.W. Long-term sedimentary recycling of rare sulphur isotope anomalies. Nature 497

  5. Scolopendromorpha of New Guinea and adjacent islands (Myriapoda, Chilopoda).

    PubMed

    Schileyko, Arkady A; Stoev, Pavel E

    2016-08-04

    The centipede fauna of the second largest island in the world, New Guinea, and its adjacent islands, is poorly known, with most information deriving from the first half of the 20th century. Here we present new data on the order Scolopendromorpha based on material collected in the area in the last 40 years, mainly by Bulgarian and Latvian zoologists. The collections comprise eleven species of six genera and three families. The diagnosis of Cryptops (Trigonocryptops) is emended in the light of the recent findings. The old and doubtful record of Scolopendra multidens Newport, 1844 from New Guinea is referred to S. subspinipes Leach, 1815 and the species is here excluded from the present day list of New Guinean scolopendromorphs. Cryptops nepalensis Lewis, 1999 is here recorded from New Guinea for the first time. An annotated list and an identification key to the scolopendromorphs of the studied region are presented.

  6. Reconnaissance geologic map of Kodiak Island and adjacent islands, Alaska

    USGS Publications Warehouse

    Wilson, Frederic H.

    2013-01-01

    Kodiak Island and its adjacent islands, located on the west side of the Gulf of Alaska, contain one of the largest areas of exposure of the flysch and melange of the Chugach terrane of southern Alaska. However, in the past 25 years, only detailed mapping covering small areas in the archipelago has been done. This map and its associated digital files (Wilson and others, 2005) present the best available mapping compiled in an integrated fashion. The map and associated digital files represent part of a systematic effort to release geologic map data for the United States in a uniform manner. The geologic data have been compiled from a wide variety of sources, ranging from state and regional geologic maps to large-scale field mapping. The map data are presented for use at a nominal scale of 1:500,000, although individual datasets (see Wilson and others, 2005) may contain data suitable for use at larger scales.

  7. Chemical Characteristics of Continental Outflow Over the Tropical South Atlantic Ocean from Brazil and Africa

    NASA Technical Reports Server (NTRS)

    Talbot, R. W.; Bradshaw, J. D.; Sandholm, S. T.; Smyth, S.; Blake, D. R.; Blake, N. R.; Sachse, G. W.; Collins, J. E.; Heikes, B. G.; Anderson, B. E.; Gregory, G. L.; Singh, H. B.; Lefer, B. L.; Bachmeier, A. S.

    1996-01-01

    The chemical characteristics of air parcels over the tropical South Atlantic during September - October 1992 are summarized by analysis of aged marine and continental outflow classifications. Positive correlations between CO and CH3CL and minimal enhancements of C2CL40, and various ChloroFluoroCarbon (CFC) species in air parcels recently advected over the South Atlantic basin strongly suggest an impact on tropospheric chemistry from biomass burning on adjacent continental areas of Brazil and Africa. Comparison of the composition of aged Pacific air with aged marine air over the South Atlantic basin from 0.3 to 12.5 km altitude indicates potential accumulation of long-lived species during the local dry season. This may amount to enhancements of up to two-fold for C2H6, 30% for CO, and 10% for CH3Cl. Nitric oxide and NO(x) were significantly enhanced (up to approx. 1 part per billion by volume (ppbv)) above 10 km altitude and poorly correlated with CO and CH3Cl. In addition, median mixing ratios of NO and NO(x) were essentially identical in aged marine and continental outflow air masses. It appears that in addition to biomass burning, lightning or recycled reactive nitrogen may be an important source of NO(x) to the upper troposphere. Methane exhibited a monotonic increase with altitude from approx. 1690 to 1720 ppbv in both aged marine and continental outflow air masses. The largest mixing ratios in the upper troposphere were often anticorrelated with CO, CH3Cl, and CO2, suggesting CH, contributions from natural sources. We also argue, based on CH4/CO ratios and relationships with various hydrocarbon and CFC species, that inputs from biomass burning and the northern hemisphere are unlikely to be the dominant sources of CO, CH4 and C2H6 in aged marine air. Emissions from urban areas would seem to be necessary to account for the distribution of at least CH4 and C2H6. Over the African and South American continents an efficient mechanism of convective vertical transport

  8. Continental Growth and the Sedimentary Record

    NASA Astrophysics Data System (ADS)

    Dhuime, B.; Hawkesworth, C. J.; Robinson, R. A. J.; Cawood, P. A.

    2014-12-01

    Detrital sedimentary rocks provide average samples of the continental crust formed at different times and in different places. Some materials are more susceptible to erosion and/or to preservation bias than others, and one issue is to understand how the compositions of a range of source rocks are then recorded in the sediments. Here we considered two different approaches to model the growth of the continental crust: (i) The variation of Nd isotopes in continental shales with different deposition ages, which requires a correction of the bias induced by preferential erosion of younger rocks through an erosion parameter usually referred to as 'K'. The determination of K, and the extent to which it varies in different erosion systems, thus have fundamental implications for the models of continental growth based on radiogenic isotopes in continental sediments. (ii) The variations in U-Pb, Hf and O isotopes in detrital zircons, from 'modern' sediments sampled worldwide. In this approach, O isotopes are used to screen 'hybrid' Hf model ages (i.e. ages resulting from mixing processes of crustal material from different ages) from Hf model ages that represent actual crust formation ages. These two approaches independently suggest that the continental crust has been generated continuously, but with a marked decrease in the continental growth rate at ~3 Ga. The >4 Ga to ~3 Ga period is characterised by relatively high net rates of continental growth (~3.0 km3.a-1), which are similar to the rates at which new crust is generated, and destroyed, at the present time. Net growth rates are much lower since 3 Ga (~0.8 km3.a-1), which may be attributed to higher rates of destruction of continental crust. The inflexion in the continental growth curve at ~3 Ga indicates a change in the way the crust was generated and preserved. This change may be linked to onset of subduction-driven plate tectonics and discrete subduction zones.

  9. Density Sorting During the Evolution of Continental Crust

    NASA Astrophysics Data System (ADS)

    Kelemen, P. B.; Behn, M. D.; Hacker, B. R.

    2015-12-01

    We consider two settings - in addition to "delamination" of arc lower crust - in which dense, mafic eclogites founder into the convecting mantle while buoyant, felsic lithologies accumulate at the base of evolving continental crust. Arc processes play a central role in generating continental crust, but it remains uncertain how basaltic arc crust is transformed to andesitic continental crust. Dense, SiO2-poor products of fractionation may founder from the base of arc crust by "delamination", but lower arc crust after delamination has significantly different trace elements compared to lower continental crust (LCC). In an alternative model, buoyant magmatic rocks generated at arcs are first subducted, mainly via subduction erosion. Upon heating, these buoyant lithologies ascend through the mantle wedge or along a subduction channel, and are "relaminated" at
the base of overlying crust (e.g., Hacker et al EPSL 11, AREPS 15). Average buoyant lavas and plutons
for the Aleutians, Izu-Bonin-Marianas, Kohistan and Talkeetna arcs fall within the range of estimated LCC major and trace elements. Relamination is more efficient in generating continental crust than delamination. Himalayan cross-sections show Indian crust thrust beneath Tibetan crust, with no intervening mantle. There is a horizontal Moho at ca 80 km depth, extending from thickened Indian crust, across the region where Tibetan crust overlies Indian crust, into thickened Tibetan crust. About half the subducted Indian crust is present, whereas the other half is missing. Data (Vp/Vs; Miocene lavas formed by interaction of continental crust with mantle; xenolith thermometry) indicate 1000°C or more from ca 50 km depth to the Moho since the Miocene. We build on earlier studies (LePichon et al Tectonics 92, T'phys 97; Schulte-Pelkum et al Nature 05; Monsalve et al JGR 08) to advance the hypothesis that rapid growth of garnet occurs at 70-80 km and 1000°C within subducting Indian crust. Dense eclogites founder

  10. Signs of continental rifting in the southwestern Japanese Island Arc

    NASA Astrophysics Data System (ADS)

    Chernysheva, E. A.; Eroshenko, D. V.

    2016-03-01

    The southwestern margin of the Japan Arc evolved in the geodynamic regime of continental rifting during the Miocene-Pleistocene. This has been verified by broad manifestations of metasomatosis of mantle peridotites that underlie the lithosphere of the Japan Islands and by episodes of deep magmatism (kimberlites and melilitites) in the region. The high enrichment of deep melts in incompatible rare and rare earth elements is partially preserved in melts of regional basalts from smaller depths. In contrast, spreading basalts of the Sea of Japan and subduction basalts from the Nankai trench at the boundary with the Philippine Plate are extremely depleted in rare elements.

  11. Tectonic framework of the Northern California continental margin

    USGS Publications Warehouse

    Clarke, S.H.

    1992-01-01

    The northern coast of California is one of the most seismically active regions in the continental United States. This activity is largely due to tectonic forces resulting from differing relative motions between three extensive lithospheric plates that meet in this region. These crustal plates are bounded by long fault systems-the Cascadia subduction zone, the San Andreas fault system, and the Mendocino fault- that accommodate these differences in plate motion and that are capable of periodically producing damaging earthquakes. Historic earthquake locations are concentrated in the victinity of the tectonically unstable intersection of these tthree plates and their bounding fault systems. 

  12. Characterization and organization of DNA sequences adjacent to the human telomere associated repeat (TTAGGG)n.

    PubMed Central

    Weber, B; Collins, C; Robbins, C; Magenis, R E; Delaney, A D; Gray, J W; Hayden, M R

    1990-01-01

    We present a strategy for the cloning of DNA sequences adjacent to the tandemly repeated DNA sequence (TTAGGG)n. Sequence analysis of 14 independently isolated clones revealed the presence of non-repetitive sequences immediately adjacent to or flanked by blocks of the simple repeat (TTAGGG)n. In addition, we provide sequence information on two previously undescribed tandemly repeated sequences, including a 9 bp repeat and a modification of the (TTAGGG)n repeat. Using different mapping approaches six sub-clones, free of the TTAGGG repeat, were assigned to a single human chromosome. Moreover, in situ hybridization mapped one of these subclones, G2 - 1H, definitively to the telomeric band on chromosome 4q. However, Bal 31 insensitivity suggests a location in a more subterminal region. All the (TTAGGG)n-adjacent unique sequences tested are highly conserved among primates but are not present in other mammalian species. Identification and mapping of TTAGGG-adjacent sequences will provide a refined insight into the genomic organization of the (TTAGGG)n repeat. The isolation of chromosome specific TTAGGG-adjacent sequences from subtelomeric regions of all human chromosomes will serve as important end points for the genetic maps and will be useful for the molecular characterization of chromosomal rearrangements involving telomeres. Images PMID:2356126

  13. Atrophy of hippocampal subfields and adjacent extrahippocampal structures in dementia with Lewy bodies and Alzheimer's disease.

    PubMed

    Delli Pizzi, Stefano; Franciotti, Raffaella; Bubbico, Giovanna; Thomas, Astrid; Onofrj, Marco; Bonanni, Laura

    2016-04-01

    The hippocampus and adjacent extrahippocampal structures are organized in distinct and specialized regions which process heterogeneous functions, including memory, and visuospatial functions. Specific alterations of the different hippocampal subfields and adjacent extrahippocampal structures could differently contribute to the pathophysiology of Alzheimer's disease (AD) and dementia with Lewy bodies (DLB). Based on visual symptoms which characterize DLB patients, the hippocampal subfields and the adjacent extrahippocampal structures which are mainly involved in the visual functions could be impaired in DLB and preserved in AD. To test this hypothesis, we performed structural magnetic resonance imaging on 19 DLB, 15 AD, and 19 age-matched healthy controls. FreeSurfer's pipelines were used to perform parcellation of hippocampus and adjacent extrahippocampal structures and to assess the structural changes within each region. The cornu ammonis and subiculum were bilaterally damaged in AD and preserved in DLB. The perirhinal cortex and parahippocampus were damaged in DLB but not in AD. Our findings demonstrate that the hippocampal subfields and adjacent extrahippocampal structures were differently altered in AD and DLB. Particularly, DLB patients showed a more focused alteration of the extrahippocampal structures linked to visual functions.

  14. Macrofaunal production along the UK continental shelf

    NASA Astrophysics Data System (ADS)

    Bolam, S. G.; Barrio-Frojan, C. R. S.; Eggleton, J. D.

    2010-10-01

    Estimates of secondary production ( P/ B ratio and total production) by macrobenthic communities across the UK continental shelf are presented. Values for individual sampling stations varied from 0.21 to 4.1 y - 1 for community P/ B and 3.1 to 897.2 kJ m - 2 y - 1 for total production. Such data fills an important gap pertaining to our understanding of the spatial variation in production estimates for this region. Benthic production estimates varied primarily at small (inter-station) scales (24 nm), although larger-scale differences were observed. In general, the highest production estimates were exhibited by benthic communities in Cardigan Bay (Irish Sea) and East English Channel, while the lowest estimates were observed for the mid- and northern North Sea areas. The former were typified by shallow, gravelly areas of seabed which exhibit high bed tidal stress and do not thermally stratify during the summer months. On average, annelids contribute an overwhelming majority of the total production with different regions varying in the relative contributions from other phyla such as molluscs, crustaceans and echinoderms. Spatial heterogeneity of sediment granulometric variables occurred primarily between stations while those of other variables (e.g., depth, stratification, and tidal bed stress) were more regional. Although a large proportion of the spatial variation in secondary production estimates was not explained by environmental characteristics, the data indicate that such relationships are scale-dependent. Average bed temperature was a significant factor in creating some of the observed differences at large spatial scales. The possible reasons why a larger proportion of the variation in production estimates was not explained by the present study are presented.

  15. Seasonal fluctuations of deep megabenthos: Finding evidence of standing stock accumulation in a flux-rich continental slope

    NASA Astrophysics Data System (ADS)

    Tecchio, Samuele; Ramírez-Llodra, Eva; Aguzzi, Jacopo; Sanchez-Vidal, Anna; Flexas, M. Mar; Sardà, Francisco; Company, Joan B.

    2013-11-01

    Throughout the deep oceans, diversity in the benthos peaks at intermediate slope depths. In the western Mediterranean lower slope an accumulation of biomass, but not diversity, at depths of 1200-1350 m has been observed. However, the precise causes of this biomass peak are unknown. We examined the patterns of megafauna benthic biomass in the Catalan sea open slope, from 900 to 1750 m depth, expanding the results in the context of the whole continental margin. Sampling was carried out by combining an Otter-Trawl Maireta System (OTMS) and an Agassiz trawl, during four different seasons in 2008/2009. At the same time, current speed, temperature and salinity were obtained year-round by means of near-bottom deployed sensors (current meters and temperature-conductivity sensors). Total biomass followed an inverted U-shaped pattern, peaking at depths of 1050-1350 m. Range-related ecological forcings between shallower and deeper species may have caused this biomass accumulation at intermediate slope depths. We also report on the seasonal variations of biomass in the studied depth range, identifying a dynamic zone above 1000 m depth where populations of highly mobile species perform year-round migrations throughout the slope, and a more static region below 1000 m (i.e. the twilight zone end) with substantially less inter-annual variations. The arrival of new Western Mediterranean Deep Water from the deep basin to the lower slope in March-May may have driven the accumulation of biomass at 900 and 1050 m depth over the same period. In addition, an adjacent submarine canyon was sampled with the same procedures to characterize its benthic megafauna community. Analyses revealed higher diversity, but not biomass, inside the canyon than in the adjacent open slope, and a significantly different assemblage composition between the two habitats. These results strengthen the concept of submarine canyons as hotspots of biodiversity and underline the importance of their conservation as

  16. Continental drift and climate change drive instability in insect assemblages.

    PubMed

    Li, Fengqing; Tierno de Figueroa, José Manuel; Lek, Sovan; Park, Young-Seuk

    2015-06-17

    Global change has already had observable effects on ecosystems worldwide, and the accelerated rate of global change is predicted in the future. However, the impacts of global change on the stability of biodiversity have not been systematically studied in terms of both large spatial (continental drift) and temporal (from the last inter-glacial period to the next century) scales. Therefore, we analyzed the current geographical distribution pattern of Plecoptera, a thermally sensitive insect group, and evaluated its stability when coping with global change across both space and time throughout the Mediterranean region--one of the first 25 global biodiversity hotspots. Regional biodiversity of Plecoptera reflected the geography in both the historical movements of continents and the current environmental conditions in the western Mediterranean region. The similarity of Plecoptera assemblages between areas in this region indicated that the uplift of new land and continental drift were the primary determinants of the stability of regional biodiversity. Our results revealed that climate change caused the biodiversity of Plecoptera to slowly diminish in the past and will cause remarkably accelerated biodiversity loss in the future. These findings support the theory that climate change has had its greatest impact on biodiversity over a long temporal scale.

  17. Petroleum potential of northern Australian Continental Shelf

    SciTech Connect

    Smith, M.R.; Ross, J.G.

    1986-11-01

    A study of the publicly available data from the offshore northern Australian continental shelf has shown that three prospective sedimentary sequences are present. A Cenozoic basin possibly containing Miocene reefal carbonates exists in the west part of the region, a structurally distinct Mesozoic basin containing thick sandstone intervals underlies the Cenozoic, and a thick paleozoic basin, possibly containing Devonian reefs and younger Paleozoic sandstone intervals, lies southeast of the Aru Archipelago and east of a north-northeast-trending ridge located along the eastern edges of the Aru and Timor Troughs. Paleozoic sediments also underlie the Mesozoic west of this ridge. The cenozoic and Mesozoic basins and the western Paleozoic subbasin are separated by major sequence boundaries. All the basins present hydrocarbon potential to a greater or lesser extent. The Mesozoic basin will probably be the prime target for exploration over the next few years, but secondary objectives in Cenozoic and Paleozoic sediments should not be ignored. The numerous different play types identified in this study, the positive signs from exploration in the early 1970s, the recent neighboring discoveries, and improvements in seismic data quality provide an incentive for oil companies to conduct detailed exploration of the area. 7 figures.

  18. Crustal displacements due to continental water loading

    USGS Publications Warehouse

    Van Dam, T.; Wahr, J.; Milly, P.C.D.; Shmakin, A.B.; Blewitt, G.; Lavallee, D.; Larson, K.M.

    2001-01-01

    The effects of long-wavelength (> 100 km), seasonal variability in continental water storage on vertical crustal motions are assessed. The modeled vertical displacements (??rM) have root-mean-square (RMS) values for 1994-1998 as large as 8 mm, with ranges up to 30 mm, and are predominantly annual in character. Regional strains are on the order of 20 nanostrain for tilt and 5 nanostrain for horizontal deformation. We compare ??rM with observed Global Positioning System (GPS) heights (??rO) (which include adjustments to remove estimated effects of atmospheric pressure and annual tidal and non-tidal ocean loading) for 147 globally distributed sites. When the ??rO time series are adjusted by ??rM, their variances are reduced, on average, by an amount equal to the variance of the ??rM. Of the ??rO time series exhibiting a strong annual signal, more than half are found to have an annual harmonic that is in phase and of comparable amplitude with the annual harmonic in the ??rM. The ??rM time series exhibit long-period variations that could be mistaken for secular tectonic trends or post-glacial rebound when observed over a time span of a few years.

  19. Crustal Displacements Due to Continental Water Loading

    NASA Technical Reports Server (NTRS)

    vanDam, T.; Wahr, J.; Milly, P. C. D.; Shmakin, A. B.; Blewitt, G.; Lavallee, D.; Larson, K. M.

    2001-01-01

    The effects of long-wavelength (> 100 km), seasonal variability in continental water storage on vertical crustal motions are assessed. The modeled vertical displacements (delta-r(sub M)) have root-mean-square (RMS) values for 1994-1998 as large as 8 mm with ranges up to 30 mm, and are predominantly annual in character. Regional strains are on the order of 20 nanostrain for tilt and 5 nanostrain for horizontal deformation. We compare delta-r(sub M) with observed Global Positioning System (GPS) heights (delta-r(sub O)) (which include adjustments to remove estimated effects of atmospheric pressure and annual tidal and non-tidal ocean loading) for 147 globally distributed sites. When the delta-r(sub O) time series are adjusted by delta-r(sub M), their variances are reduced, on average, by an amount equal to the variance of the delta-r(sub M). Of the delta-r(sub O) time series exhibiting a strong annual signal, more than half are found to have an annual harmonic that is in phase and of comparable amplitude with the annual harmonic in the delta-r(sub M). The delta-r(sub M) time series exhibit long-period variations that could be mistaken for secular tectonic trends or post-glacial rebound when observed over a time span of a few years.

  20. Accelerating advances in continental domain hydrologic modeling

    NASA Astrophysics Data System (ADS)

    Archfield, Stacey A.; Clark, Martyn; Arheimer, Berit; Hay, Lauren E.; McMillan, Hilary; Kiang, Julie E.; Seibert, Jan; Hakala, Kirsti; Bock, Andrew; Wagener, Thorsten; Farmer, William H.; Andréassian, Vazken; Attinger, Sabine; Viglione, Alberto; Knight, Rodney; Markstrom, Steven; Over, Thomas

    2015-12-01

    In the past, hydrologic modeling of surface water resources has mainly focused on simulating the hydrologic cycle at local to regional catchment modeling domains. There now exists a level of maturity among the catchment, global water security, and land surface modeling communities such that these communities are converging toward continental domain hydrologic models. This commentary, written from a catchment hydrology community perspective, provides a review of progress in each community toward this achievement, identifies common challenges the communities face, and details immediate and specific areas in which these communities can mutually benefit one another from the convergence of their research perspectives. Those include: (1) creating new incentives and infrastructure to report and share model inputs, outputs, and parameters in data services and open access, machine-independent formats for model replication or reanalysis; (2) ensuring that hydrologic models have: sufficient complexity to represent the dominant physical processes and adequate representation of anthropogenic impacts on the terrestrial water cycle, a process-based approach to model parameter estimation, and appropriate parameterizations to represent large-scale fluxes and scaling behavior; (3) maintaining a balance between model complexity and data availability as well as uncertainties; and (4) quantifying and communicating significant advancements toward these modeling goals.

  1. Accelerating advances in continental domain hydrologic modeling

    USGS Publications Warehouse

    Archfield, Stacey A.; Clark, Martyn; Arheimer, Berit; Hay, Lauren E.; McMillan, Hilary; Kiang, Julie E.; Seibert, Jan; Hakala, Kirsti; Bock, Andrew R.; Wagener, Thorsten; Farmer, William H.; Andreassian, Vazken; Attinger, Sabine; Viglione, Alberto; Knight, Rodney; Markstrom, Steven; Over, Thomas M.

    2015-01-01

    In the past, hydrologic modeling of surface water resources has mainly focused on simulating the hydrologic cycle at local to regional catchment modeling domains. There now exists a level of maturity among the catchment, global water security, and land surface modeling communities such that these communities are converging toward continental domain hydrologic models. This commentary, written from a catchment hydrology community perspective, provides a review of progress in each community toward this achievement, identifies common challenges the communities face, and details immediate and specific areas in which these communities can mutually benefit one another from the convergence of their research perspectives. Those include: (1) creating new incentives and infrastructure to report and share model inputs, outputs, and parameters in data services and open access, machine-independent formats for model replication or reanalysis; (2) ensuring that hydrologic models have: sufficient complexity to represent the dominant physical processes and adequate representation of anthropogenic impacts on the terrestrial water cycle, a process-based approach to model parameter estimation, and appropriate parameterizations to represent large-scale fluxes and scaling behavior; (3) maintaining a balance between model complexity and data availability as well as uncertainties; and (4) quantifying and communicating significant advancements toward these modeling goals.

  2. What is the slope of the U.S. continental slope?

    SciTech Connect

    Pratson, L.F.; Haxby, W.F.

    1996-01-01

    Extensive high-resolution, multibeam bathymetry of five U. S. continental margins provides new, detailed information about the angle of continental slopes in different sedimentary and tectonic settings. The steepest continental slope examined is the passive-carbonate west Florida slope (4.4{degree} regional slope and 12.0{degree} mean local slope). The steepest of the four clastic continental slopes is the passive New Jersy-Maryland slope (2.5{degree} and 7.6{degree}). Less steep, at both regional and local scales, are the more rugged, tectonically active and probably unstable salt-tectonized louisiana slope (0.5{degree} and 2.9{degree}), strike-slip California slope (1.8{degree} and 5.2{degree}) and convergent oregon slope (2.0{degree} and 5.2{degree}). Frequency grids of local slope magnitude vs. depth and dip direction for the two passive continental slopes reflect present-day morphology predominantly being shaped by lithology (West Florida), sedimentation (New Jersey-Maryland), and downslope-directed erosion(New Jersey-Maryland, west Florida). The grids for the three tectonically acctive continental slopes reflect morphology partly (California) to predominantly (Louisiana, Oregon) being shaped by tectonics. 15 refs., 2 figs.

  3. Minimal change of thermal continentality in Slovakia within the period 1961-2013

    NASA Astrophysics Data System (ADS)

    Vilček, Jozef; Škvarenina, Jaroslav; Vido, Jaroslav; Nalevanková, Paulína; Kandrík, Radoslav; Škvareninová, Jana

    2016-08-01

    Thermal continentality plays an important role not only in the basic characterisation of the climate in particular regions but also in the phytogeographic distribution of plants and ecosystem formation. Due to ongoing climate change, questions surrounding the changes of thermal continentality are very relevant. Therefore, the aim of this study is to investigate the characteristics of thermal continentality and its temporal changes in the Slovak Republic between the years of 1961 and 2013. The study was carried out on several meteorological stations selected in respect to the geographical and geomorphological heterogeneity of Slovakia. Our results show that the continentality of Slovakia increased in the period 1961 to 2013; however, this trend is not significant. These non-significant trends are confirmed at all the stations. Nevertheless, it is necessary to be aware of this signal, especially because these changes could cause changes in ecosystem formation in future.

  4. Granitic Perspectives on the Generation and Secular Evolution of the Continental Crust

    NASA Astrophysics Data System (ADS)

    Kemp, A. I. S.; Hawkesworth, C. J.

    2003-12-01

    Every geologist is acquainted with the principle of "uniformitarianism," which holds that present-day processes are the key to those that operated in the past. But the extent this applies to the processes driving the growth and differentiation of the Earth's continental crust remains a matter of debate. Unlike its dense oceanic counterpart, which is recycled back into the mantle by subduction within 200 Ma (see Chapter 3.13), the continental crust comprises buoyant quartzofeldspathic materials and is difficult to destroy by subduction. The continental crust is, therefore, the principal record of how conditions on the Earth have changed, and how processes of crust generation have evolved through geological time. It preserves evidence of secular variation in crustal compositions, and thus the way in which the crust has formed throughout Earth's history. Exploring the nature and origin of these variations is the focus of this chapter.Continental rocks are highly differentiated, and so the crust is enriched in incompatible components compared to the primeval chondritic composition (see Chapter 3.01). Of these, water is perhaps the most relevant, both for the origin and evolution of life, and also for many models of crust generation and differentiation. Similarly, the mass of continental crust is just 0.57% of the silicate Earth, and yet it contains ˜35% of the potassium (using the crustal composition estimates in Table 1). Continental rocks comprise the buoyant shell that was once thought to float on a basaltic substratum, inferred from the wide distribution of chemically similar continental flood basalts (von Cotta, 1858). The links with the adjacent oceans were perhaps unclear, "the greatest mountains confront the widest oceans" ( Dana, 1873). Yet, it has long been argued that the rock that has the most similar composition to the average continental crust, andesite, may be generated by fractional crystallization of basalt ( Daly (1914) and Bowen (1928); but see the

  5. Red Sea Kinematics in Relation to the Regional Tectonics Setting

    NASA Astrophysics Data System (ADS)

    Alotaibi, T.; Furlong, K. P.

    2015-12-01

    The Red sSea extensional system started approximately 22+3 Ma. Although, there is evidence that lithospheric weakening and associated incipient extension may have taken place since 30 Ma. There is oceanic crust found in the southern part of the rift, while the northern-most part still involves continental stretching. Meantime magnetic anomalies have been observed for the southern rift, the northern rift is characterized by several deeps where magnetic anomalies have been observed as well as an indication of the transition from continental to oceanic rifting. GPS stations along the Red Sea are consistent with kinematics implied from the magnetic anomalies - an opening rate in the southern part of ~ 15 mm/yr relative to Eurasia fixed while the opening rate in the is ~8 mm/yr. This significant decreasing of the opening rate towards the north implies complexity within the Red Sea extensional system.Our purpose here is to place the Red Sea extensional kinematics within the regional tectonics context by combining constraints on the rate or style of extension within the Red Sea with tectonic activities on the adjacent continental regions. To accomplish this, we will model the extensional kinematics through time by comparing recent kinematics based on the geophysical observations with ones that based on geological observations. In terms of present-day geophysical observations, we have GPS and magnetic anomalies data, and crustal and lithospheric thickness. Geological observations primarily come from stratigraphic and structural data sets.Our overall target is to construct a tectonic model that links the timing of the change in the style and extensional rate with the tectonic activities in Afar, Gulf of Aden, Zagros, Dead Sea fault and Anatolian region.

  6. Continental volume and freeboard through geological time

    NASA Technical Reports Server (NTRS)

    Schubert, G.; Reymer, A. P. S.

    1985-01-01

    The consequences of approximately constant freeboard for continental growth are explored using a model that relates the volumes of isostatically compensated continents and oceans to the secular decline in terrestrial heat flow. It is found that a post-Archean increase in freeboard by 200 m requires continental growth of only 10 percent, while a decrease in freeboard by 200 m during this same period necessitates a crustal growth of 40 percent. Shrinkage of the continental crust since the end of the Archean can be ruled out. Changes of more than 10 percent in post-Archean crustal thickness are highly unlikely.

  7. Continental rifting - Progress and outlook

    NASA Technical Reports Server (NTRS)

    Baker, B. H.; Morgan, P.

    1981-01-01

    It is noted that in spite of the flood of new data on continental rifts in the last 15 years, there is little consensus about the basic mechanisms and causes of rifting. The remarkable similarities in rift cross sections (shown in a figure), are considered to suggest that the anomalous lithospheric structure of rifts is more dependent on lithosphere properties than the mode of rifting. It is thought that there is a spectrum of rifting processes for which two fundamental mechanisms can be postulated: an active mechanism, whereby thermal energy is transmitted into the lithosphere from the underlying asthenosphere, and a passive mechanism by which mechanical energy is transmitted laterally through the lithosphere as a consequence of plate interactions at a distance. In order to permit the concept of the two fundamentally different mechanisms to be tested, a tentative classification is proposed that divides rifts into two basic categories: active rifting and passive rifting. Here, the magnitude of active rifting will depend on the rate at which lithosphere moves over the thermal source, with rifts being restricted to stationary or slow-moving plates.

  8. Potential evapotranspiration and continental drying

    NASA Astrophysics Data System (ADS)

    Milly, P. C. D.; Dunne, K. A.

    2016-10-01

    By various measures (drought area and intensity, climatic aridity index, and climatic water deficits), some observational analyses have suggested that much of the Earth’s land has been drying during recent decades, but such drying seems inconsistent with observations of dryland greening and decreasing pan evaporation. `Offline’ analyses of climate-model outputs from anthropogenic climate change (ACC) experiments portend continuation of putative drying through the twenty-first century, despite an expected increase in global land precipitation. A ubiquitous increase in estimates of potential evapotranspiration (PET), driven by atmospheric warming, underlies the drying trends, but may be a methodological artefact. Here we show that the PET estimator commonly used (the Penman-Monteith PET for either an open-water surface or a reference crop) severely overpredicts the changes in non-water-stressed evapotranspiration computed in the climate models themselves in ACC experiments. This overprediction is partially due to neglect of stomatal conductance reductions commonly induced by increasing atmospheric CO2 concentrations in climate models. Our findings imply that historical and future tendencies towards continental drying, as characterized by offline-computed runoff, as well as other PET-dependent metrics, may be considerably weaker and less extensive than previously thought.

  9. Potential evapotranspiration and continental drying

    USGS Publications Warehouse

    Milly, Paul C.D.; Dunne, Krista A.

    2016-01-01

    By various measures (drought area and intensity, climatic aridity index, and climatic water deficits), some observational analyses have suggested that much of the Earth’s land has been drying during recent decades, but such drying seems inconsistent with observations of dryland greening and decreasing pan evaporation. ‘Offline’ analyses of climate-model outputs from anthropogenic climate change (ACC) experiments portend continuation of putative drying through the twenty-first century, despite an expected increase in global land precipitation. A ubiquitous increase in estimates of potential evapotranspiration (PET), driven by atmospheric warming, underlies the drying trends, but may be a methodological artefact. Here we show that the PET estimator commonly used (the Penman–Monteith PET for either an open-water surface or a reference crop) severely overpredicts the changes in non-water-stressed evapotranspiration computed in the climate models themselves in ACC experiments. This overprediction is partially due to neglect of stomatal conductance reductions commonly induced by increasing atmospheric CO2 concentrations in climate models. Our findings imply that historical and future tendencies towards continental drying, as characterized by offline-computed runoff, as well as other PET-dependent metrics, may be considerably weaker and less extensive than previously thought.

  10. Continental rifting - Progress and outlook

    SciTech Connect

    Baker, B.H.; Morgan, P.

    1981-07-21

    It is noted that in spite of the flood of new data on continental rifts in the last 15 years, there is little consensus about the basic mechanisms and causes of rifting. The remarkable similarities in rift cross sections (shown in a figure), are considered to suggest that the anomalous lithospheric structure of rifts is more dependent on lithosphere properties than the mode of rifting. It is thought that there is a spectrum of rifting processes for which two fundamental mechanisms can be postulated: an active mechanism, whereby thermal energy is transmitted into the lithosphere from the underlying asthenosphere, and a passive mechanism by which mechanical energy is transmitted laterally through the lithosphere as a consequence of plate interactions at a distance. In order to permit the concept of the two fundamentally different mechanisms to be tested, a tentative classification is proposed that divides rifts into two basic categories: active rifting and passive rifting. Here, the magnitude of active rifting will depend on the rate at which lithosphere moves over the thermal source, with rifts being restricted to stationary or slow-moving plates.

  11. Oyster Shell Dredging in Atchafalaya Bay and Adjacent Waters, Louisiana. Volume 2. Public Comments.

    DTIC Science & Technology

    1987-11-01

    Dredging in Atchafalaya Bay and Adjacent Waters, Louisiana. We appreciate the opportunity to review the DEIS. Sincerely yours, David Cottinginm Ecology ...subsequent effects on the aquatic ecosystem . General evaluation and testing procedures are outlined in the 404(b)(1) guidelines [Section 230.60 of Subpart G3...does not include zones 4-9 as integral parts of the regional ecosystem . The overall cummulative impact to the biology of the region can only be

  12. Assessment of oceanity and continentality conditions of the XX Century in the Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Andrade, Cristina; Corte-Real, João

    2016-04-01

    The oceanity and continentality conditions clearly influence the climate of a region. Seeking at understanding these influences on the Iberian Peninsula climate, the spatial distributions of air temperature, precipitation and five climatic indices are analysed in the period between 1901 and 2012 and in three sub-periods (1901-40, 1941-80 and 1981-2012). This study aims at investigating the Xerothermic index of Gaussen and the continental and oceanic characteristics of the Iberian climate by using Conrad-Pollak and Johansson Continentality Indices, as well as Kerner and Marsz Oceanity Indices. Gridded air temperature and precipitation datasets are used