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  1. Lithospheric Architecture Beneath Hudson Bay

    Science.gov (United States)

    Porritt, R. W.; Miller, M. S.; Darbyshire, F. A.

    2015-12-01

    Hudson Bay overlies some of the thickest Precambrian lithosphere on Earth, whose internal structures contain important clues to the earliest workings of plate formation. The terminal collision, the Trans-Hudson Orogen, brought together the Western Churchill craton to the northwest and the Superior craton to the southeast. These two Archean cratons along with the Paleo-Proterozoic Trans-Hudson internides, form the core of the North American craton. We use S to P converted wave imaging and absolute shear velocity information from a joint inversion of P to S receiver functions, new ambient noise derived phase velocities, and teleseismic phase velocities to investigate this region and determine both the thickness of the lithosphere and the presence of internal discontinuities. The lithosphere under central Hudson Bay approaches 􏰂350 km thick but is thinner (􏰂200-250 km) around the periphery of the Bay. Furthermore, the amplitude of the lithosphere-asthenosphere boundary (LAB) conversion from the S receiver functions is unusually large for a craton, suggesting a large thermal contrast across the LAB, which we interpret as direct evidence of the thermal insulation effect of continents on the asthenosphere. Within the lithosphere, midlithospheric discontinuities, significantly shallower than the base of the lithosphere, are often imaged, suggesting the mechanisms that form these layers are common. Lacking time-history information, we infer that these discontinuities reflect reactivation of formation structures during deformation of the craton.

  2. Paleoproterozoic Collisional Structures in the Hudson Bay Lithosphere Constrained by Multi-Observable Probabilistic Inversion

    Science.gov (United States)

    Darbyshire, F. A.; Afonso, J. C.; Porritt, R. W.

    2015-12-01

    The Paleozoic Hudson Bay intracratonic basin conceals a Paleoproterozoic Himalayan-scale continental collision, the Trans-Hudson Orogen (THO), which marks an important milestone in the assembly of the Canadian Shield. The geometry of the THO is complex due to the double-indentor geometry of the collision between the Archean Superior and Western Churchill cratons. Seismic observations at regional scale show a thick, seismically fast lithospheric keel beneath the entire region; an intriguing feature of recent models is a 'curtain' of slightly lower wavespeeds trending NE-SW beneath the Bay, which may represent the remnants of more juvenile material trapped between the two Archean continental cores. The seismic models alone, however, cannot constrain the nature of this anomaly. We investigate the thermal and compositional structure of the Hudson Bay lithosphere using a multi-observable probabilistic inversion technique. This joint inversion uses Rayleigh wave phase velocity data from teleseismic earthquakes and ambient noise, geoid anomalies, surface elevation and heat flow to construct a pseudo-3D model of the crust and upper mantle. Initially a wide range of possible mantle compositions is permitted, and tests are carried out to ascertain whether the lithosphere is stratified with depth. Across the entire Hudson Bay region, low temperatures and a high degree of chemical depletion characterise the mantle lithosphere. Temperature anomalies within the lithosphere are modest, as may be expected from a tectonically-stable region. The base of the thermal lithosphere lies at depths of >250 km, reaching to ~300 km depth in the centre of the Bay. Lithospheric stratification, with a more-depleted upper layer, is best able to explain the geophysical data sets and surface observables. Some regions, where intermediate-period phase velocities are high, require stronger mid-lithospheric depletion. In addition, a narrow region of less-depleted material extends NE-SW across the Bay

  3. Surface-Wave Tomographic Studies of the Hudson Bay Lithosphere: Implications for Paleoproterozoic Tectonic Processes and the Assembly of the Canadian Shield

    Science.gov (United States)

    Darbyshire, F. A.

    2015-12-01

    Hudson Bay is a shallow intracratonic basin that partially conceals the Trans-Hudson Orogen (THO) in northern Canada. The THO is thought to be a Himalayan-scale Paleoproterozoic orogenic event that was an important component of assembly of the Canadian Shield, marking the collision of the Archean Superior and Western Churchill plates. Until recently, only global and continental-scale seismic tomographic models had imaged the upper-mantle structure of the region, giving a broad but relatively low-resolution picture of the thick lithospheric keel. The Hudson Bay Lithospheric Experiment (HuBLE) investigated the present-day seismic structure beneath Hudson Bay and its surroundings, using a distributed broadband seismograph network installed around the periphery of the Bay and complemented by existing permanent and temporary seismographs further afield. This configuration, though not optimal for body-wave studies which use subvertical arrivals, is well-suited to surface wave tomographic techniques, with many paths crossing the Bay. As there is little seismicity in the region around the Canadian Shield, two-station measurements of teleseismic Rayleigh wave phase velocity formed the principal data set for lithospheric studies. The interstation measurements were combined in a linearized tomographic inversion for maps of phase velocity and azimuthal anisotropy at periods of 20-200 s; these maps were then used to calculate a pseudo-3D anisotropic upper-mantle shear-wavespeed model of the region. The model shows thick (~180-260 km), seismically fast lithosphere across the Hudson Bay region, with a near-vertical 'curtain' of lower wavespeeds trending NE-SW across the Bay, likely associated with more juvenile material trapped between the Archean Superior and Churchill continental cores during the THO. The lithosphere is layered, suggesting a 2-stage formation process. Seismic anisotropy patterns vary with depth; a circular pattern in the uppermost mantle wrapping around the

  4. Nelson River and Hudson Bay

    Science.gov (United States)

    2002-01-01

    Rivers that empty into large bodies of water can have a significant impact on the thawing of nearshore winter ice. This true-color Moderate Resolution Imaging Spectroradiometer (MODIS) image from May 18, 2001, shows the Nelson River emptying spring runoff from the Manitoba province to the south into the southwestern corner of Canada's Hudson Bay. The warmer waters from more southern latitudes hasten melting of ice near the shore, though some still remained, perhaps because in shallow coastal waters, the ice could have been anchored to the bottom. High volumes of sediment in the runoff turned the inflow brown, and the rim of the retreating ice has taken on a dirty appearance even far to the east of the river's entrance into the Bay. The sediment would have further hastened the melting of the ice because its darker color would have absorbed more solar radiation than cleaner, whiter ice. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  5. The Hudson Bay Lithospheric Experiment

    Science.gov (United States)

    Bastow, I. D.; Kendall, J.-M.; Helffrich, G. R.; Thompson, D. A.; Wookey, J.; Brisbourne, A. M.; Hawthorn, D.; Eaton, D.; Snyder, D. B.

    2011-12-01

    I D Bastow, J-M Kendall, A M Brisbourne, D B Snyder, D Thompson, D Hawthorn, G R Helffrich, J Wookey, A Horleston and D Eaton describe the motivation for - and successful operation of - a remote seismic survey in Arctic Canada.

  6. Integrating shear velocity observations of the Hudson Bay

    Science.gov (United States)

    Porritt, R. W.; Miller, M. S.; Darbyshire, F. A.

    2013-12-01

    Hudson Bay is the core of the Laurentia craton of North America. This region contains some of the thickest lithosphere globally, reaching 250-300 km depth. Previous studies have shown that much of this region is composed of amalgamated proto-continents including the Western Churchill and Superior provinces and that much of the structure of these constituents has been retained since the Trans-Hudson Orogen at 1.8 Ga. Using the Hudson Bay Lithospheric Experiment (HuBLE) and other permanent and POLARIS broadband seismic data, we image the region with S to P receiver functions, joint inversion of P to S receiver functions with surface waves, and teleseismic S and P wave travel-times. The receiver function imaging reveals a persistent mid-lithospheric layer at ~80 km depth under all stations, but a variable lithospheric thickness. The teleseismic S delay times show a pattern of early arrivals around the center of the network, beneath Hudson Bay where the lithosphere is thickest, while the P delay times are early in the Superior province relative to the Western Churchill province. This suggests higher Vp/Vs ratios in the Superior province, which is evidence that stacked oceanic plates formed this province. The relatively flat Moho imaged by earlier receiver function studies and the lower mantle Vp/Vs of the Western Churchill province provides evidence of formation by plume head extraction. The joint inversion shows an LAB that is typically a broad discontinuity spanning ~20-30 km at ~220 km depth suggesting a primarily thermal boundary zone. The mid-lithospheric layer is composed of increasing velocity from the ~40 km depth Moho defined by H-k stacking of PRFs to a broad, constant velocity lithospheric lid spanning 80-200 km depth. We suggest this mid-lithospheric layer represents the mantle lithosphere of the proto-continents prior to collision and the lid formed due to post-collisional cooling. The integration of these seismic datasets furthers our understanding of

  7. Riverine organic matter composition and fluxes to Hudson Bay

    Science.gov (United States)

    Kuzyk, Z. Z. A.; Macdonald, R. W.; Goni, M. A.; Godin, P.; Stern, G. A.

    2016-12-01

    With warming in northern regions, many changes including permafrost degradation, vegetation alteration, and wildfire incidence will impact the carbon cycle. Organic carbon (OC) carried by river runoff to northern oceans has the potential to provide integrated evidence of these impacts. Here, concentrations of dissolved (DOC) and particulate (POC) OC are used to estimate terrestrial OC transport in 17 major rivers draining varied vegetative and permafrost conditions into Hudson Bay and compositional data (lignin and 14C) to infer OC sources. Hudson Bay lies just south of the Arctic Circle in Canada and is surrounded by a large drainage basin (3.9 × 106 km2) dominated by permafrost. Analysis of POC and DOC in the 17 rivers indicates that DOC dominates the total OC load. The southern rivers dominate. The Nelson and Churchill Rivers to the southwest are particularly important suppliers of OC partly because of large drainage basins but also perhaps because of impacts by hydroelectric development, as suggested by a 14C age of DOC in the Churchill River of 2800 years. Higher DOC and POC concentrations in the southern rivers, which have substantive areas only partially covered by permafrost, compared to northern rivers draining areas with complete permafrost cover, implies that warming - and hence permafrost thawing - will lead to progressively higher DOC and POC loads for these rivers. Lignin composition in the organic matter (S/V and C/V ratios) reveals mixed sources of OC consistent with the dominant vegetation in the river basins. This vegetation is organized by latitude with southern regions below the tree line enriched by woody gymnosperm sources (boreal forest) and northern regions enriched with organic matter from non-woody angiosperms (flowering shrubs, tundra). Acid/Aldehyde composition together with Δ14C data for selected DOC samples suggest that most of the lignin has undergone oxidative degradation, particularly the DOC component. However, high Δ14C ages

  8. Climate change and sea ice: Shipping accessibility on the marine transportation corridor through Hudson Bay and Hudson Strait (1980–2014

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    Jonathan Andrews

    2017-03-01

    Full Text Available Shipping traffic has been increasing in Hudson Strait and Hudson Bay and the shipping route through these waters to the Port of Churchill may soon become a federally-designated transportation corridor. A dataset on passive microwave-based sea ice concentration was used to characterize the timing of the ice on the shipping corridor to the Port between 1980 and 2014. Efforts were made to produce results in a readily accessible format for stakeholders of the shipping industry; for example, open water was defined using a sea ice concentration threshold of ≤ 15% and results are presented in terms of real dates instead of anomalies. Between 1980 and 2014, the average breakup date on the corridor was July 4, the average freeze-up date was November 25, and the average length of the open water season was 145 days. However, each of these three variables exhibited significant long-term trends and spatial variability over the 34-year time period. Regression analysis revealed significant linear trends towards earlier breakup (–0.66 days year–1, later freeze-up (+0.52 days year–1, and a longer open water season (+1.14 days year–1 along the shipping corridor between 1980 and 2014. Moreover, the section of the corridor passing through Hudson Strait displayed significantly stronger trends than the two sections in Hudson Bay (i.e., “Hudson Islands” and “Hudson Bay”. As a result, sea ice timing in the Hudson Strait section of the corridor has diverged from the timing in the Hudson Bay sections. For example, the 2010–2014 median length of the open water season was 177 days in Hudson Strait and 153 days in the Hudson Bay sections. Finally, significant linear relationships were observed amongst breakup, freeze-up, and the length of the open water season for all sections of the corridor; correlation analysis suggests that these relationships have greatest impact in Hudson Strait.

  9. Variability of an under-ice river plume in Hudson Bay

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    Ingram, R. Grant; Larouche, Pierre

    1987-08-01

    Observations of the Great Whale River plume in the coastal waters of Hudson Bay, Canada, during late winter and early spring during four different years showed its area to vary as a power of the discharge. The under-ice plume area was much larger than plume area in open water for comparable discharges. Differences in plume geometry were related to elapsed time since ice formation and low-frequency variability of the coastal circulation. The strength and orientation of the coastal motion was weakly correlated with the cross-Hudson Bay atmospheric pressure gradient. The passage of low-pressure systems over Hudson Bay is thought to generate a progressive edge wave in the absence of direct wind forcing. The amplitude of the low-frequency variations in coastal circulation decreased with the increasing spatial extent of the landfast ice in the study area.

  10. Estimating the Economic Value of Narwhal and Beluga Hunts in Hudson Bay, Nunavut

    NARCIS (Netherlands)

    Hoover, C.; Bailey, M.L.; Higdon, J.; Ferguson, S.H.; Sumaila, R.

    2013-01-01

    Hunting of narwhal (Monodon monoceros) and beluga (Delphinapterus leucas) in Hudson Bay is an important activity, providing food and income in northern communities, yet few studies detail the economic aspects of these hunts. We outline the uses of narwhal and beluga and estimate the revenues, costs,

  11. Demography and population status of polar bears in western Hudson Bay

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    Lunn, Nicholas J.; Regher, Eric V; Servanty, Sabrina; Converse, Sarah J.; Richardson, Evan S.; Stirling, Ian

    2013-01-01

    We evaluated the demography and population status of the Western Hudson Bay (WH) polar bear subpopulation for the period 1984-2011, using live-recapture data from research studies and management actions, and dead-recovery data from polar bears harvested for subsistence purposes or removed during human-bear conflicts.

  12. Inorganic carbon cycling and biogeochemical processes in an Arctic inland sea (Hudson Bay)

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    Burt, William J.; Thomas, Helmuth; Miller, Lisa A.; Granskog, Mats A.; Papakyriakou, Tim N.; Pengelly, Leah

    2016-08-01

    The distributions of carbonate system parameters in Hudson Bay, which not only receives nearly one-third of Canada's river discharge but is also subject to annual cycles of sea-ice formation and melt, indicate that the timing and magnitude of freshwater inputs play an important role in carbon biogeochemistry and acidification in this unique Arctic ecosystem. This study uses basin-wide measurements of dissolved inorganic carbon (DIC) and total alkalinity (TA), as well as stable isotope tracers (δ18O and δ13CDIC), to provide a detailed assessment of carbon cycling processes within the bay. Surface distributions of carbonate parameters reveal the particular importance of freshwater inputs in the southern portion of the bay. Based on TA, we surmise that the deep waters in the Hudson Bay are largely of Pacific origin. Riverine TA end-members vary significantly both regionally and with small changes in near-surface depths, highlighting the importance of careful surface water sampling in highly stratified waters. In an along-shore transect, large increases in subsurface DIC are accompanied by equivalent decreases in δ13CDIC with no discernable change in TA, indicating a respiratory DIC production on the order of 100 µmol kg-1 DIC during deep water circulation around the bay.

  13. Multiyear total and methyl mercury exports from two major sub-Arctic rivers draining into Hudson Bay, Canada.

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    Kirk, Jane L; St Louis, Vincent L

    2009-04-01

    From 2003 to 2007, concentrations of total mercury and methylmercury (THg and MeHg) were continuously measured in two Canadian sub-Arctic rivers (the Nelson and the Churchill) that drain into western Hudson Bay. THg and MeHg concentrations were low in the Nelson River (mean i standard deviation, 0.88 +/- 0.33 and 0.05 +/- 0.03 ng L(-1), respectively). The Churchill River, however, had high concentrations of Hg, particularly MeHg (1.96 +/- 0.8 and 0.18 +/- 0.09 ng L(-1), respectively) and hence may be an important source of MeHg to organisms feeding in the Churchill River estuary. A large portion of THg in the Nelson River was particulate-bound (39 +/- 23%), while in the Churchill River, most was in the dissolved form (78 +/- 15%) and is likely dissolved organic carbon (DC)-bound Hg originating in the surrounding wetlands. In fact, both the Nelson and Churchill Rivers had high DOC concentrations and were therefore large exporters of DOC to Hudson Bay (1480 +/- 723 and 392 +/- 309 x 10(3) t year(-1), respectively) compared to rivers to the south and east Despite high Churchill River Hg concentrations, due to large Nelson River flows, average THg and MeHg exports to Hudson Bay from the Churchill River (37 +/- 28 and 4 +/- 4 kg year(-1), respectively) were about one-third and half the Nelson River exports (113 +/- 52 and 9 +/- 4 kg year(-1)). Interestingly, combined Hg exports to Hudson Bay from Nelson and Churchill River discharge are comparable to THg inputs from Hudson Bay springtime snowmelt (177 +/-140 kg year(-1)) but are approximately 13 times greater than MeHg snowmelt inputs (1 +/- 1 kg year(-1)). Although Hg inputs from rivers and snowmelt together may account for a large portion of the THg pool in Hudson Bay, these inputs account for a lesser portion of the MeHg pool, thus highlighting the importance of water column Hg(ll) methylation as a source of MeHg to Hudson Bay marine food webs.

  14. Multi Year Total and Methyl Mercury Exports from Two Major Sub Arctic Rivers Draining into Hudson Bay, Canada

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    Kirk, J. L.; St. Louis, V. L.

    2009-05-01

    From 2003 to 2007, concentrations of total and methyl mercury (THg and MeHg), were continuously measured in two Canadian sub Arctic rivers (the Nelson and the Churchill) that drain into western Hudson Bay. THg and MeHg concentrations were low in the Nelson River (mean ± standard deviation; 0.88±0.33 and 0.05±0.03 ng/L, respectively). The Churchill River, however, had high concentrations of Hg, particularly MeHg (1.96±0.8 and 0.18±0.09 ng/L, respectively), and hence may be an important source of MeHg to organisms feeding in the Churchill River estuary. A large portion of THg in the Nelson River was particulate- bound (39±23%), while in the Churchill River, most was in the dissolved form (78±15%) and is likely DOC-bound Hg originating in surrounding wetlands. In fact, both the Nelson and Churchill Rivers had high DOC concentrations and were therefore large exporters of DOC to Hudson Bay (1480±723 and 392±309 x 103 tonnes/year, respectively) compared to rivers to the south and east. Despite high Churchill River Hg concentrations, due to large Nelson River flows, average THg and MeHg exports to Hudson Bay from the Churchill River (37±28 and 4±4 kg/year, respectively) were ˜ one third and half Nelson River exports (113±52 and 9±4 kg/year). Interestingly, combined Hg exports to Hudson Bay from Nelson and Churchill River discharge are comparable to THg inputs from Hudson Bay spring-time snowmelt (177±140 kg/year) but are approximately 13 times greater than MeHg snowmelt inputs (1±1 kg/year). Although Hg inputs from rivers and snowmelt together may account for a large portion of the THg pool in Hudson Bay, these inputs account for a lesser portion of the MeHg pool, thus highlighting the importance of water column Hg(II) methylation as a large source of MeHg to Hudson Bay marine foodwebs.

  15. Sea Level and Paleoenvironment Control on Late Ordovician Source Rocks, Hudson Bay Basin, Canada

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    Zhang, S.; Hefter, J.

    2009-05-01

    Hudson Bay Basin is one of the largest Paleozoic sedimentary basins in North America, with Southampton Island on its north margin. The lower part of the basin succession comprises approximately 180 to 300 m of Upper Ordovician strata including Bad Cache Rapids and Churchill River groups and Red Head Rapids Formation. These units mainly comprise carbonate rocks consisting of alternating fossiliferous limestone, evaporitic and reefal dolostone, and minor shale. Shale units containing extremely high TOC, and interpreted to have potential as petroleum source rocks, were found at three levels in the lower Red Head Rapids Formation on Southampton Island, and were also recognized in exploration wells from the Hudson Bay offshore area. A study of conodonts from 390 conodont-bearing samples from continuous cores and well cuttings from six exploration wells in the Hudson Bay Lowlands and offshore area (Comeault Province No. 1, Kaskattama Province No. 1, Pen Island No. 1, Walrus A-71, Polar Bear C-11 and Narwhal South O-58), and about 250 conodont-bearing samples collected from outcrops on Southampton Island allows recognition of three conodont zones in the Upper Ordovician sequence, namely (in ascendant sequence) Belodina confluens, Amorphognathus ordovicicus, and Rhipidognathus symmetricus zones. The three conodont zones suggest a cycle of sea level changes of rising, reaching the highest level, and then falling during the Late Ordovician. Three intervals of petroleum potential source rock are within the Rhipidognathus symmetricus Zone in Red Head Rapids Formation, and formed in a restricted anoxic and hypersaline condition during a period of sea level falling. This is supported by the following data: 1) The conodont Rhipidognathus symmetricus represents the shallowest Late Ordovician conodont biofacies and very shallow subtidal to intertidal and hypersaline condition. This species has the greatest richness within the three oil shale intervals to compare other parts of Red

  16. The changing freshwater regime of the Hudson Bay Drainage Basin: from present to 2070

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    MacDonald, M. K.; Stadnyk, T. A.; Déry, S.; Braun, M.; Koenig, K. A.

    2016-12-01

    The Hudson Bay Drainage Basin (HBDB) drains over a third of Canada's land mass and contains important hydroelectric infrastructure. Projecting future freshwater discharge in the HBDB is critical for forecasting generating potential, and for understanding potential changes to Hudson Bay sea ice coverage, contaminant, and nutrient cycling. Anticipated changes to the HBDB freshwater regime are characterized for the 2011-2040 and 2041-2070 climate normal periods relative to the baseline period (1981-2010). Existing flow regulation practices are held constant. A regional implementation of the Arctic-HYPE continental scale hydrological model is used. Historical calibration is performed over a split-sample period from 1971-2005 to span a range of climatic conditions. Gauges selected for calibration are non-biased with respect to drainage area covered by eight flow signatures. Lakes are plentiful across the HBDB, few of which are gauged directly at their outlet. A novel approach is used to parameterize lake storage-discharge relationships. K-means cluster analysis is used to group lakes based on similar physiographic characteristics, where they are given common discharge rating curve parameters. Nineteen members of the CMIP5 climate modeling experiment are used for meteorological forcing for discharge projections. Output from the climate models span the range of projected changes to precipitation and temperature over the region. Mean annual temperature is projected to increase by 1.2°C to 5.7°C from the baseline period to 2041-2070, and mean annual precipitation is projected to increase by 3% to 18%. The ensemble mean of discharge projections shows a general increase in mean annual and peak discharge across the HBDB during 2041-2070 compared to the baseline. Peak annual discharge shows the greatest increase over most northern regions of the basin, where there are the fewest hydrometric gauges. Low flows are projected to increase the least to the west of Hudson Bay, with

  17. Atmospheric forcing of sea ice in Hudson Bay during the fall period, 1980-2005

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    Hochheim, K. P.; Barber, D. G.

    2010-05-01

    The principal objective of this study is to describe the autumn sea ice regime of Hudson Bay in the context of atmospheric forcing from 1980 to 2005. Both gridded Canadian Ice Service (CIS) data and Passive Microwave (PMW) data are used to examine the freezeup period for weeks of year (WOY) 43-52. Sea ice concentration (SIC) anomalies reveal statistically significant trends, ranging from -23.3% to -26.9% per decade, during WOY 43-48 using the CIS data and trends ranging from -12.7% to -16.8% per decade during WOY 45-50 using the PMW data. Surface air temperature (SAT) anomalies are highly correlated with SIC anomalies (r2 = 0.52-0.72) and with sea ice extents (r2 = 0.53-0.72). CIS data show that mean sea ice extents based on SICs ≥80% (consolidated ice) have decreased by 1.05 × 105 to 1.17 × 105 km2 for every 1°C increase in temperature in late November; PMW data show similar results. Regression analysis between SAT and standardized climate indices over the 1951-2005 period show that the East Pacific/North Pacific index is highly predictive of interannual SATs followed by the North Atlantic Oscillation and Arctic Oscillation indices. The data show that the Hudson Bay area has recently undergone a climate regime shift, in the mid 1990s, which has resulted in a significant reduction in sea ice during the freezeup period and that these changes appear to be related to atmospheric indices.

  18. Hydrological Research in Hudson Bay,Canada%加拿大Hudson海湾地区的水文研究

    Institute of Scientific and Technical Information of China (English)

    William A.Gough

    2004-01-01

    Hudson Bay streamflow represents a major component of the streamflow in Canada, approximately 30% of all river discharge enters Hudson and James Bays. Three current hydrological research issues are examined for this region. First the relationship between streamflow and local climate change is reviewed. Second the impact of river discharge in James Bay is linked to sea level variations in Churchill, Manitoba and the implications of this on Hudson Bay recirculation are explored. Finally, the historical and projected sea level variations in the Bay are examined with particular emphasis on the Churchill, Manitoba record. The report is concluded by a discussion of future directions for hydrological research in the Hudson Bay region.%Hudson海湾的河川径流量在整个加拿大河川径流量中占有很大的比例,所有河流排泄量约30%流入了Hudson和James海湾.研究了该地区河川径流与当地气候变化之间的关系;把河川向James海湾的排泄与曼尼托巴省Churchill地区海水位的变化联系起来,讨论了其对Hudson海湾再循环的影响;根据曼尼托巴省Churchill地区海水位的观测资料重点讨论了该地区海水位在历史时期的变化及未来的预测变化等三个重要水文问题.最后指出了今后在Hudson海湾地区进行水文研究的方向.

  19. Magnitude and Seasonality of Wetland Methane Emissions from the Hudson Bay Lowlands (Canada)

    Science.gov (United States)

    Pickett-Heaps, C. A.; Jacob, D. J.; Wecht, K. J.; Kort, E. A.; Wofsy, S. C.; Diskin, G. S.; Worthy, D. E. J.; Kaplan, J. O.; Bey, I.; Drevet, J.

    2011-01-01

    The Hudson Bay Lowlands (HBL) is the second largest boreal wetland ecosystem in the world and an important natural source of global atmospheric methane. We quantify the HBL methane emissions by using the GEOS-Chem chemical transport model to simulate aircraft measurements over the HBL from the ARCTAS and pre-HIPPO campaigns in May-July 2008, together with continuous 2004-2008 surface observations at Fraserdale (southern edge of HBL) and Alert (Arctic background). The difference in methane concentrations between Fraserdale and Alert is shown to be a good indicator of HBL emissions, and implies a sharp seasonal onset of emissions in late May (consistent with the aircraft data), a peak in July-August, and a seasonal shut-off in September. The model, in which seasonal variation of emission is mainly driven by surface temperature, reproduces well the observations in summer but its seasonal shoulders are too broad. We suggest that this reflects the suppression of emissions by snow cover and greatly improve the model simulation by accounting for this effect. Our resulting best estimate for HBL methane emissions is 2.3 Tg/a, several-fold higher than previous estimates (Roulet et al., 1994; Worthy et al., 2000).

  20. Magnitude and seasonality of wetland methane emissions from the Hudson Bay Lowlands (Canada

    Directory of Open Access Journals (Sweden)

    C. A. Pickett-Heaps

    2011-04-01

    Full Text Available The Hudson Bay Lowlands (HBL is the second largest boreal wetland ecosystem in the world and an important natural source of global atmospheric methane. We quantify the HBL methane emissions by using the GEOS-Chem chemical transport model to simulate aircraft measurements over the HBL from the ARCTAS and pre-HIPPO campaigns in May–July 2008, together with continuous 2004–2008 surface observations at Fraserdale (southern edge of HBL and Alert (Arctic background. The difference in methane concentrations between Fraserdale and Alert is shown to be a good indicator of HBL emissions, and implies a sharp seasonal onset of emissions in late May (consistent with the aircraft data, a peak in July–August, and a seasonal shut-off in September. The model, in which seasonal variation of emission is mainly driven by surface temperature, reproduces well the observations in summer but its seasonal shoulders are too broad. We suggest that this reflects the suppression of emissions by snow cover and greatly improve the model simulation by accounting for this effect. Our resulting best estimate for HBL methane emissions is 2.3 Tg a−1, several-fold higher than previous estimates (Roulet et al., 1994; Worthy et al., 2000.

  1. Adenomatous hyperplasia of the thyroid gland in beluga whales (Delphinapterus leucas) from the St. Lawrence Estuary and Hudson Bay, Quebec, Canada.

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    Mikaelian, I; Labelle, P; Kopal, M; De Guise, S; Martineau, D

    2003-11-01

    We evaluated thyroid gland lesions in beluga whales (Delphinapterus leucas) from the St. Lawrence Estuary (n = 16) and Hudson Bay (n = 14). Follicular cysts and nodules of adenomatous hyperplasia of the thyroid gland were found in eight and nine adults from the St. Lawrence Estuary (n = 10), respectively, and in four and six adults from Hudson Bay (n = 14), respectively. The total volume of the lesions of thyroid adenomatous hyperplasia was positively correlated with age in both populations. Comparison between populations could not be performed because of differences in age structures of sample groups. Beluga whales from both populations have unique thyroid lesions among marine mammals.

  2. Groups of related belugas (Delphinapterus leucas) travel together during their seasonal migrations in and around Hudson Bay.

    Science.gov (United States)

    Colbeck, Gabriel J; Duchesne, Pierre; Postma, Lianne D; Lesage, Véronique; Hammill, Mike O; Turgeon, Julie

    2013-02-07

    Social structure involving long-term associations with relatives should facilitate the learning of complex behaviours such as long-distance migration. In and around Hudson Bay (Canada), three stocks of beluga whales form a panmictic unit, but have different migratory behaviours associated with different summering areas. We analysed genetic variation at 13 microsatellite loci among 1524 belugas, to test hypotheses about social structure in belugas. We found significant proportions of mother-offspring pairs throughout the migratory cycle, but average relatedness extended beyond close kinship only during migration. Average relatedness was significantly above random expectations for pairs caught at the same site but on different days or months of a year, suggesting that belugas maintain associations with a network of relatives during migration. Pairs involving a female (female-female or male-female) were on average more related than pairs of males, and males seemed to disperse from their matrilineal group to associate with other mature males. Altogether, our results indicate that relatives other than strictly parents, and especially females, play a role in maintaining a social structure that could facilitate the learning of migration routes. Cultural conservatism may limit contributions from nearby summer stocks to endangered stocks such as the Eastern Hudson Bay beluga.

  3. The role of lichen on peatland development in the Hudson Bay Lowlands, Canada

    Science.gov (United States)

    Harris, Lorna; Moore, Tim; Roulet, Nigel

    2015-04-01

    Lichen (Cladina stellaris) can be a dominant vegetation cover on bogs within the extensive peatland landscape of the Hudson Bay Lowlands (HBL), northern Ontario, Canada. The unique characteristics of lichens (growth structure and function as a symbiotic organism), their ability to form thick, dense mats across the HBL bogs, and their increased tolerance of extreme environmental conditions, points to their importance as a distinct plant functional type. However, the role of lichen within the peatland ecosystem is poorly understood, particularly ecosystem interactions (vegetation associations) and peatland development (including microtopography) and the resulting carbon sink. Many studies consider the role of different plant functional types on peatland CO2 and CH4 exchange (e.g. Bubier et al., 2003; Strack et al., 2006), and this understanding is included in peatland growth and climate change models. As far as we are aware lichens are currently omitted from these models. We suggest that lichens represent a distinct plant functional type with CO2 exchange characteristics (NEE and respiration) that are quite different to vascular plants and mosses. In this study we measured lichen CO2 exchange in both natural and modified moisture conditions at field sites in the HBL over two field seasons. Our results indicate that lichen productivity is strongly influenced by abiotic factors that affect lichen moisture content, with very dry lichen exhibiting little or no photosynthetic capacity. We suggest that the low productivity of lichen mats results in lower rates of peat accumulation compared to Sphagnum-dominated peatland areas, and that this has consequences for the development of peatland microtopography (hummocks and hollows) and feedback mechanisms. To better understand the role of lichen mats on peat accumulation and to test possible feedback mechanisms we developed a model, the parameters of which are supported by data from field sites in the HBL. This dependence of

  4. Drought as a Disturbance: Implications for Peatland Carbon Budgets in the Hudson Bay Lowland

    Science.gov (United States)

    Bello, R.; Abnizova, A.; Miller, E.

    2009-05-01

    Carbon feedbacks are of particular importance in high latitudes, both because of large circumpolar peatland carbon pools and because climate warming is occurring more rapidly at these latitudes. Longer-term net ecosystem exchange will be influenced by the capacity of plant communities to respond to changing conditions. The nature of community change and the factors inducing change are examined in this study of a disturbance generated by severe drought in 1994 causing widespread mortality in the dominant moss, Dicranum elongatum, occupying an upland tundra site within the Hudson Bay Lowland near Churchill, Manitoba. One quarter of this moss has recently died and become encrusted with the micro-lichen, Ochrolechia spp. Moss cushions affected in this manner exhibit strong allelopathic inhibition of seedling establishment progressing to complete moss decay. Chamber NEE growing-season flux measurements show an average net release of 642 mg C /m2/d from the dead moss compared to an average net uptake of 164 mg C /m2/d from completely healthy cushions. Between these two extremes, stressed living moss cushions support abundant seedling cover which increases in direct proportion with the fractional mortality. A proxy method for estimating the growth rates of cushions, based on the length of green living shoots, indicates that the moss community is uniform in age and established shortly after the most severe drought of historical record in 1966. Subsequent growth rates of cushions show a strong dependency on proximity to the water table (4.17-1.11 mm/y over 58 cm height interval). A growing-season moss water budget identifies the dominant water flow pathways and indicates capillary uptake (0.08 mm h-1) provides 64% of the storage gains, emphasizing the importance of groundwater for growth and survival. Maximum storage capacities are directly related to cushion biomass, leading to both enhanced moisture stress and increased susceptibility to mortality as cushion size

  5. Air mass distribution and the heterogeneity of the climate change signal in the Hudson Bay/Foxe Basin region, Canada

    Science.gov (United States)

    Leung, Andrew; Gough, William

    2016-08-01

    The linkage between changes in air mass distribution and temperature trends from 1971 to 2010 is explored in the Hudson Bay/Foxe Basin region. Statistically significant temperature increases were found of varying spatial and temporal magnitude. Concurrent statistically significant changes in air mass frequency at the same locations were also detected, particularly in the declining frequency of dry polar (DP) air. These two sets of changes were found to be linked, and we thus conclude that the heterogeneity of the climatic warming signal in the region is at least partially the result of a fundamental shift in the concurrent air mass frequency in addition to global and regional changes in radiative forcing due to increases in long-lived greenhouse gases.

  6. Cenozoic lithospheric evolution of the Bohai Bay Basin, eastern North China Craton: Constraint from tectono-thermal modeling

    Science.gov (United States)

    Liu, Qiongying; He, Lijuan; Huang, Fang; Zhang, Linyou

    2016-01-01

    It is well established that the lithosphere beneath the eastern North China Craton (NCC) had been thinned before the Cenozoic. A 2D multi-phase extension model, in which the initial crustal and lithospheric thicknesses are variable, is presented to reconstruct the initial thicknesses of the crust and lithosphere in the early Cenozoic and to further investigate the lithospheric evolution beneath the eastern NCC through the Cenozoic. We conduct thermal modeling along three profiles from east to west in the Bohai Bay Basin, which is the center of the lithospheric destruction and thinning of the NCC. Using multiple constraints, such as tectonic subsidence, the present-day heat flow and the Moho depth, we determine the initial crustal and lithospheric thicknesses of the Bohai Bay Basin before the Cenozoic rift to be 33-36 km and 80-105 km, respectively. The model results show that the most rapid lithospheric thinning during the Cenozoic occurred in the middle Eocene for most depressions, and the thinning activity ceased at the end of the Oligocene, reaching a minimum lithospheric thickness of 53-74 km, followed by a thermal relaxation phase. Combined with previous studies, we infer that the lithosphere beneath the eastern NCC experienced two stages of alternating thinning and thickening: notable thinning in the Early Cretaceous and Paleogene, and thickening in the Late Cretaceous and late Cenozoic. We believe that thermo-chemical erosion, together with extension, was probably the major mechanism of the significant lithospheric removal during the Mesozoic, whereas the Cenozoic lithospheric thinning was mainly dominated by tectonic extension in the eastern NCC; lithospheric thickening was generally a result of thermal cooling.

  7. Legacy and new halogenated persistent organic pollutants in polar bears from a contamination hotspot in the Arctic, Hudson Bay Canada.

    Science.gov (United States)

    Letcher, R J; Morris, A D; Dyck, M; Sverko, E; Reiner, E J; Blair, D A D; Chu, S G; Shen, L

    2017-08-10

    A large and complex suite of 295 legacy and new halogenated persistent organic pollutants (POPs) were investigated in fat or liver tissue samples of polar bears collected in 2013-2014 from Southern (SHB) and Western (WHB) subpopulations of the Canadian Arctic contaminants hotspot of Hudson Bay. A total of 210 POPs were detected and/or quantifiable with some frequency in all fat or liver samples. POP profile and concentration differences were investigated both within (e.g. age and sex) and between the two subpopulations. Two time-point comparisons were made relative to POPs reported for Hudson Bay polar bears harvested in 2007-2008. ΣPolychlorinated biphenyl (PCB) concentrations at both time points were the most concentrated of the POP groups, and were spatially uniform with no detectable influence of sex or age, as were concentrations of the dominant congener CB153. ΣChlordanes (ΣCHLs, 74-79% oxychlordane) and the Σperfluoroalkyl substances (ΣPFASs, ≈60% perfluorooctane sulfonate (PFOS)) had the second greatest POP group concentrations in SHB and WHB respectively, with ΣPFASs and ΣCHLs being significantly influenced by age and/or sex. ΣCHLs were spatially uniform but ΣPFASs were greater in the SHB bears, as were e.g. some flame retardants, due to e.g. local contamination and/or changes in bear behavior and diet. Endosulfans and hexabromocyclododecane were detectable in samples from 2007-2008 but not from 2013-2014, which is consistent with their global POP regulations. ΣPolychlorinated naphthalenes (ΣPCNs) were consistently detected at relatively high concentrations compared to other arctic wildlife, however these concentrations were low relative to legacy POPs. ΣShort-chain chlorinated paraffins (ΣSCCPs) were major contributors to the overall POPs burden with concentrations comparable to other legacy POPs, though there was no significant difference between or within subpopulations for PCNs or SCCPs. Except for octachlorostyrene, POPs concentrations

  8. Dinoflagellate cyst production in Hudson Bay, the world's largest inland sea, based on monthly sediment trap data

    Science.gov (United States)

    Heikkilä, Maija; Pospelova, Vera; Forest, Alexandre; Stern, Gary

    2014-05-01

    Phytoplankters, microscopic primary producers of oceans are capable of responding rapidly to environmental fluctuations due to their high cell replication rates. Fast phytoplankton growth maybe balanced out by equally fast consumption by herbivorous grazers. In high-latitude marine systems, seasonal fluctuations in plankton biomass are essentially linked to light regime controlled by the waxing and waning sea-ice cover. In addition, nutrient limitation in surface waters, seasonal temperature fluctuations and changes in freshwater inputs may play important roles. In cold-water seas, many planktonic organisms cope with seasonal harshness by the production of benthic dormant stages. Dinoflagellates are a diverse group of single-celled plankton, constituting major marine primary producers, as well as herbivorous grazers of the microbial loop. Many dinoflagellate species produce highly resistant, organic-walled resting cysts that are archived in sediments and have been increasingly used to reconstruct past environmental conditions, e.g., sea-surface temperature and salinity, productivity, sea-ice cover and eutrophication. Marine sediment core sequences are characterized by slow accumulation rates and high mixing rates: the top centimeter of surface sediment from an arctic shelf may correspond to several years or decades of deposition. Consequently, sedimentary archives do not give direct information on long-term changes in seasonal bloom patterns or cues of annually recurring life-cycle events. We used two particle-intercepting sediment traps moored in eastern and western Hudson Bay, respectively, to study monthly fluctuations in dinoflagellate cyst production from October 2005 to September 2006. The traps were deployed close to the seafloor and recovered during the ArcticNet annual expeditions onboard the CCGS Amundsen in 2005 and the CCGS Pierre Radisson in 2006. We document the seasonal succession of dinoflagellate cyst taxa, together with cyst species composition

  9. The influence of a river plume on the sea-ice meiofauna in south-eastern Hudson Bay

    Science.gov (United States)

    Grainger, E. H.

    1988-08-01

    Outflow from the Great Whale River produces a substantial freshwater layer (plume) beneath the winter ice cover and above water of higher salinity in south-eastern Hudson Bay. In 1983, samples of the lower-ice fauna and of zooplankton beneath the ice, were taken within, below and beyond the offshore reach of the plume. Nematodes accounted for the highest numbers (mean of 1956 1 1in the lower 3 cm of ice), and copepods, mainly Harpacticus and Halectinosoma with fewer Tisbe and Oithona, for the greatest biomass. All ice-inhabiting taxa were also found in the water below the ice, but many zooplankters occurring immediately beneath the ice did not form part of the ice fauna. No major qualitative differences were evident between the ice communities existing above the plume and offshore from it, but quantitative distinctions were readily apparent. Animals were consistently more concentrated (by 2-3 orders of magnitude) in the lower 3 cm of the ice than in the water immediately below, both over the plume and outside it. Except for the dominant rotifers in the plume, the concentration of zooplankton there was only 10% of that found in the surface water outside the plume. The river plume exerts a strong influence over the quantity of the fauna in the sea ice immediately above it. Changes in location and extent of the plume therefore may have an important effect on the food chain based in the sea ice.

  10. Mixing and photoreactivity of dissolved organic matter in the Nelson/Hayes estuarine system (Hudson Bay, Canada)

    Science.gov (United States)

    Guéguen, C.; Mokhtar, M.; Perroud, A.; McCullough, G.; Papakyriakou, T.

    2016-09-01

    This work presents the results of a 4-year study (2009-2012) investigating the mixing and photoreactivity of dissolved organic matter (DOM) in the Nelson/Hayes estuary (Hudson Bay). Dissolved organic carbon (DOC), colored DOM, and humic-like DOM decreased with increasing salinity (r2 = 0.70-0.84). Removal of DOM was noticeable at low to mid salinity range, likely due to degradation and/or adsorption to particles. DOM photobleaching rates (i.e., decrease in DOM signal resulting from exposure to solar radiation) ranged from 0.005 to 0.030 h- 1, corresponding to half-lives of 4.9-9.9 days. Dissolved organic matter from the Nelson and Hayes Rivers was more photoreactive than from the estuary where the photodegradation of terrestrial DOM decreased with increasing salinity. Coincident with the loss of CDOM absorption was an increase in spectral slope S, suggesting a decrease in DOM molecular weight. Marked differences in photoreactivity of protein- and humic-like DOM were observed with highly humidified material being the most photosensitive. Information generated by our study will provide a valuable data set for better understanding the impacts of future hydroelectric development and climate change on DOM biogeochemical dynamics in the Nelson/Hayes estuary and coastal domain. This study will constitute a reference on terrestrial DOM fate prior to building additional generating capacity on the Nelson River.

  11. Divergent hydrological responses to 20th century climate change in shallow tundra ponds, western Hudson Bay Lowlands

    Science.gov (United States)

    Wolfe, Brent B.; Light, Erin M.; Macrae, Merrin L.; Hall, Roland I.; Eichel, Kaleigh; Jasechko, Scott; White, Jerry; Fishback, LeeAnn; Edwards, Thomas W. D.

    2011-12-01

    The hydrological fate of shallow tundra lakes and ponds under conditions of continued warming remains uncertain, but has important implications for wildlife habitat and biogeochemical cycling. Observations of unprecedented pond desiccation, in particular, signify catastrophic loss of aquatic habitat in some Arctic locations. Shallow tundra ponds are a ubiquitous feature in the western Hudson Bay Lowlands (HBL), a region that has undergone intense warming over the past ˜50 years. But it remains unknown how hydrological processes in these ponds have responded. Here, we use cellulose-inferred pond water oxygen isotope records from sediment cores, informed by monitoring of modern pond water isotope compositions during the 2009 and 2010 ice-free seasons, to reconstruct hydrological conditions of four shallow tundra ponds in the western HBL over the past three centuries. Following an interval of relative hydrological stability during the early part of the records, results reveal widely differing hydrological responses to 20th century climate change among the study sites, which is largely dependent on hydrological connectivity of the basins within their respective surrounding peatlands. These findings suggest the 20th century has been characterized by an increasingly dynamic landscape that has variably influenced surface water balance - a factor that is likely to play a key role in determining the future water balance of ponds in this region.

  12. Variation of upper layer dynamics during breakup of the seasonal ice cover in Hudson Bay

    Science.gov (United States)

    Lepage, Serge; Ingram, R. Grant

    1991-07-01

    The present study describes circulation and stratification changes associated with the melt and breakup of the seasonal ice cover in the coastal waters of southeast Hudson Day. Field work was carried out at a station located 25 km north of the Great Whale River. Buoyancy fluxes and dissipation rates were calculated as well as changes in potential energy. Surface velocity data were partitioned into frequency bands and complex demodulated. Throughout the sampling period, most of the current energy was found to be in the semi-diurnal tidal band. After ice breakup, however, low frequency and inertial motions became relatively more important in response to direct wind forcing at the sea surface. Changes in amplitudes and phases of the major tidal constituents occurred and are related to the presence of the sea ice cover. Between early April and mid-June, semi-diurnal current amplitude doubled while its phase shifted by 45 to 60 degrees. In early June, the ice cover was sufficiently dispersed to allow the surface turbulence to overcome the buoyancy flux and mix the upper water column.

  13. Impact of freshwater on a subarctic coastal ecosystem under seasonal sea ice (southeastern Hudson Bay, Canada). I. Interannual variability and predicted global warming influence on river plume dynamics and sea ice

    Science.gov (United States)

    Ingram, R. G.; Wang, J.; Lin, C.; Legendre, L.; Fortier, L.

    1996-02-01

    Analysis of sea ice cover, runoff and air temperature observations in Hudson Bay shows marked interannual variability. This variability is thought to play a major role in determining overall productivity of the coastal ecosystem by changes to river plume extent, under-ice light conditions and nutrient levels during spring. Extensive field work off the Great Whale River in southeastern Hudson Bay has shown the importance of freshwater discharge, sea ice cover and meteorological forcing on the production of under-ice microalgae and the success of first feeding in fish larvae. Recent global climate model (GCM) results for a doubling of present atmospheric carbon dioxide indicate increases of both air temperature and precipitation in the Hudson Bay area. Predictions based on GCM results are used to estimate future changes to the sea ice and runoff regime. Sea ice breakup in the offshore is predicted to occur about one month earlier than presently. Estimates of the spring freshet in the Great Whale River indicate it will also advance by approximately one month. Onset of the spring freshet will occur about one month before Hudson Bay ice breakup, similar to present. A predicted reduction of about 35% in maximum sea ice thickness will lead to an increase in the ice-ocean interface irradiance and a decrease in melt water input to the Hudson Bay surface waters. These results are used in a discussion of potential effects of global climate change on northern coastal marine environments.

  14. Lithosphere structure and upper mantle characteristics below the Bay of Bengal

    Science.gov (United States)

    Rao, G. Srinivasa; Radhakrishna, M.; Sreejith, K. M.; Krishna, K. S.; Bull, J. M.

    2016-07-01

    The oceanic lithosphere in the Bay of Bengal (BOB) formed 80-120 Ma following the breakup of eastern Gondwanaland. Since its formation, it has been affected by the emplacement of two long N-S trending linear aseismic ridges (85°E and Ninetyeast) and by the loading of ca. 20-km of sediments of the Bengal Fan. Here, we present the results of a combined spatial and spectral domain analysis of residual geoid, bathymetry and gravity data constrained by seismic reflection and refraction data. Self-consistent geoid and gravity modelling defined by temperature-dependent mantle densities along a N-S transect in the BOB region revealed that the depth to the lithosphere-asthenosphere boundary (LAB) deepens steeply from 77 km in the south to 127 km in north, with the greater thickness being anomalously thick compared to the lithosphere of similar-age beneath the Pacific Ocean. The Geoid-Topography Ratio (GTR) analysis of the 85°E and Ninetyeast ridges indicate that they are compensated at shallow depths. Effective elastic thickness (Te) estimates obtained through admittance/ coherence analysis as well as the flexural modelling along these ridges led to the conclusions: (i) 85°E Ridge was emplaced in off-ridge environment (Te = 10-15 km); (ii) the higher Te values of ˜25 km over the Afanasy Nikitin Seamount (ANS) reflect the secondary emplacement of the seamount peaks in off-ridge environment, (iii) that the emplacement of the Ninetyeast Ridge north of 2°N occurred in an off-ridge environment as indicated by higher Te values (25-30 km). Furthermore, the admittance analysis of geoid and bathymetry revealed that the admittance signatures at wavelengths >800 km are compensated by processes related to upper mantle convection.

  15. Upscaling reflectance information of lichens and mosses using a singularity index: a case study of the Hudson Bay Lowlands, Canada

    Directory of Open Access Journals (Sweden)

    T. Neta

    2010-08-01

    Full Text Available Assessing moisture contents of lichens and mosses using ground-based high spectral resolution spectrometers (400–2500 nm offers immense opportunities for a comprehensive monitoring of peatland moisture status by satellite/airborne imagery. This information may be valuable for present and future carbon balance modeling. Previous studies are based upon point measurements of vegetation moisture content and water table position, and therefore a detailed moisture status of entire northern peatlands is not available. Consequently, upscaling ground and remotely sensed data to the desired spatial resolutions is inevitable. This study continues our previous investigation of the impact of various moisture conditions of common sub-Arctic lichen and moss species (i.e., Cladina stellaris, Cladina rangiferina, Dicranum elongatum, and Tomenthypnum nitens upon the spectral signatures obtained in the Hudson Bay Lowlands, Canada. Upscaling reflectance measurements of the above species were conducted in the field, and reflectance analysis using a singularity index was made, since this study serves as a basis for future aircraft/satellite research. An attempt to upscale current and new spectral reflectance indices developed in our previous studies was made as well. Our findings indicate that the spectral index C. rangiferina is to a lesser amount influenced by scale since it has a small R2 values between the log of the index and the log of the resolution, reduced slopes between the log of the index and the log of the resolution, and similar slopes between log reflectance and log resolution (α of two wavelengths employed by the index. Future study should focus on concurrent monitoring of moisture variations in lichens and mosses both in situ and from satellite and airborne images, as well as analysis of fractal models in relations to the upscaling experiments.

  16. Slip rates on San Francisco Bay area faults from anelastic deformation of the continental lithosphere

    Science.gov (United States)

    Geist, Eric L.; Andrews, D. J.

    2000-11-01

    Long-term slip rates on major faults in the San Francisco Bay area are predicted by modeling the anelastic deformation of the continental lithosphere in response to regional relative plate motion. The model developed by Bird and Kong [1994] is used to simulate lithospheric deformation according to a Coulomb frictional rheology of the upper crust and a dislocation creep rheology at depth. The focus of this study is the long-term motion of faults in a region extending from the creeping section of the San Andreas fault to the south up to the latitude of Cape Mendocino to the north. Boundary conditions are specified by the relative motion between the Pacific plate and the Sierra Nevada-Great Valley microplate [Argus and Gordon, 2000]. Rheologic-frictional parameters are specified as independent variables, and prediction errors are calculated with respect to geologic estimates of slip rates and maximum compressive stress directions. The model that best explains the region-wide observations is one in which the coefficient of friction on all of the major faults is less than 0.15, with the coefficient of friction for the San Andreas fault being approximately 0.09, consistent with previous inferences of San Andreas fault friction. Prediction error increases with lower fault friction on the San Andreas, indicating a lower bound of μSAF > 0.08. Discrepancies with respect to previous slip rate estimates include a higher than expected slip rate along the peninsula segment of the San Andreas fault and a slightly lower than expected slip rate along the San Gregorio fault.

  17. Distribution and diversity of diatom assemblages in surficial sediments of shallow lakes in Wapusk National Park (Manitoba, Canada) region of the Hudson Bay Lowlands.

    Science.gov (United States)

    Jacques, Olivier; Bouchard, Frédéric; MacDonald, Lauren A; Hall, Roland I; Wolfe, Brent B; Pienitz, Reinhard

    2016-07-01

    The hydrology of shallow lakes (and ponds) located in the western Hudson Bay Lowlands (HBL) is sensitive to climate warming and associated permafrost thaw. However, their biological characteristics are poorly known, which hampers effective aquatic ecosystem monitoring. Located in northern Manitoba along the southwestern coast of Hudson Bay, Wapusk National Park (WNP) encompasses numerous shallow lakes representative of the subarctic zone. We analyzed the distribution and diversity of diatom (microscopic algae; class Bacillariophyceae) assemblages in surficial sediments of 33 lakes located in three different ecozones spanning a vegetation gradient, from NE to SW: the Coastal Fen (CF), the Interior Peat Plateau (IPP), and the Boreal Spruce Forest (BSF). We found significant differences (P lakes, and CF and BSF lakes, but not between IPP and BSF lakes. These results are consistent with water chemistry measurements, which indicated distinct limnological conditions for CF lakes. Diatom communities in CF lakes were generally dominated by alkaliphilous taxa typical of waters with medium to high conductivity, such as Nitzschia denticula. In contrast, several IPP and BSF lakes were dominated by acidophilous and circumneutral diatom taxa with preference for low conductivity (e.g., Tabellaria flocculosa, Eunotia mucophila, E. necompacta var. vixcompacta). This exploratory survey provides a first detailed inventory of the diatom assemblages in the WNP region needed for monitoring programs to detect changes in shallow lake ecosystems and ecozonal shifts in response to climate variations.

  18. Constraining the Late Pleistocene history of the Laurentide Ice Sheet by dating the Missinaibi Formation, Hudson Bay Lowlands, Canada

    Science.gov (United States)

    Dalton, April S.; Finkelstein, Sarah A.; Barnett, Peter J.; Forman, Steven L.

    2016-08-01

    Well-dated paleorecords from periods prior to the Last Glacial Maximum (LGM) are important for validating models of ice sheet build-up and growth. However, owing to glacial erosion, most Late Pleistocene records lie outside of the previously glaciated region, which limits their ability to inform about the dynamics of paleo-ice sheets. Here, we evaluate new and previously published chronology data from the Missinaibi Formation, a Pleistocene-aged deposit in the Hudson Bay Lowlands (HBL), Canada, located near the geographic center of the Laurentide Ice Sheet (LIS). Available radiocarbon (AMS = 44, conventional = 36), amino acid (n = 13), uranium-thorium (U-Th, n = 14), thermoluminescence (TL, n = 15) and optically stimulated luminescence (OSL, n = 5) data suggest that an ice-free HBL may have been possible during parts of Marine Isotope Stage 7 (MIS 7; ca. 243,000 to ca. 190,000 yr BP), MIS 5 (ca. 130,000 to ca. 71,000 yr BP) and MIS 3 (ca. 29,000 to ca. 57,000). While MIS 7 and MIS 5 are well-documented interglacial periods, the development of peat, forest bed and fluvial deposits dating to MIS 3 (n = 20 radiocarbon dates; 4 TL dates, 3 OSL dates), suggests that the LIS retreated and remained beyond, or somewhere within, the boundaries of the HBL during this interstadial. Ice sheet models approximate the margin of the LIS to Southern Ontario during this time, which is 700 km south of the HBL. Therefore, if correct, our data help constrain a significantly different configuration and dynamicity for the LIS than previously modelled. We can find no chronological basis to discount the MIS 3 age assignments. However, since most data originate from radiocarbon dates lying close to the reliable limit of this geochronometer, future work on dating the Missinaibi Formation using other geochronological methods (e.g. U-Th, OSL) is necessary in order to confirm the age estimates and strengthen the boundaries of the LIS during this period.

  19. Organic matter compositions of rivers draining into Hudson Bay: Present-day trends and potential as recorders of future climate change

    Science.gov (United States)

    Godin, Pamela; Macdonald, Robie W.; Kuzyk, Zou Zou A.; Goñi, Miguel A.; Stern, Gary A.

    2017-07-01

    Concentrations and compositions of particulate and dissolved organic carbon (POC and DOC, respectively) and aromatic compounds including lignin were analyzed in water samples from 17 rivers flowing into Hudson Bay, northern Canada. These rivers incorporate basins to the south with no permafrost to basins in the north with continuous permafrost, and dominant vegetation systems that include Boreal Forest, the Hudson Plains, Taiga Shield, and Tundra. Major latitudinal trends in organic carbon and lignin concentrations and compositions were evident, with both DOC and dissolved lignin concentrations dominating over their particulate counterparts and exhibiting significant correlations with total dissolved and suspended solids, respectively. The composition of lignin reaction products in terms of the syringyl, cinnamyl, and vanillyl compositions indicate mixed sources of vascular land plant-derived organic carbon, with woody gymnosperms contributions dominating in the southern river basins whereas nonwoody angiosperm sources were more important in the most northerly rivers. The composition of nonlignin aromatic compounds, which provides a tracer for nonvascular plant contributions, suggests stronger contributions from Sphagnum mosses to dissolved organic matter in rivers below the tree line, including those with large peat bogs in their basins. Acid/aldehyde ratios of the lignin products together with Δ14C data for DOC in selected rivers indicate that DOC has generally undergone greater alteration than POC. Interestingly, several northern rivers exhibited relatively old DOC according to the Δ14C data suggesting that either old DOC is being released from permafrost or old DOC survives river transport in these rivers.

  20. The Competition of Tidal Mixing and Freshwater Forcing in Shaping the Outflow from Hudson Strait

    Science.gov (United States)

    2011-04-01

    Strait outflow. Journal of Marine Systems , special issue on Hudson Bay, in press. St. Laurent, P., F. Straneo, J.F. Dumais, D.G. Barber, 2011 What...is the fate of the river waters of Hudson Bay? Journal of Marine Systems , special issue on Hudson Bay, in press. Straneo, F., D. Sutherland, D

  1. The Energetic Value of Land-Based Foods in Western Hudson Bay and Their Potential to Alleviate Energy Deficits of Starving Adult Male Polar Bears.

    Directory of Open Access Journals (Sweden)

    Linda J Gormezano

    Full Text Available Climate change is predicted to expand the ice-free season in western Hudson Bay and when it grows to 180 days, 28-48% of adult male polar bears are projected to starve unless nutritional deficits can be offset by foods consumed on land. We updated a dynamic energy budget model developed by Molnar et al. to allow influx of additional energy from novel terrestrial foods (lesser snow geese, eggs, caribou that polar bears currently consume as part of a mixed diet while on land. We calculated the units of each prey, alone and in combination, needed to alleviate these lethal energy deficits under conditions of resting or limited movement (2 km d-1 prior to starvation. We further considered the total energy available from each sex and age class of each animal prey over the period they would overlap land-bound polar bears and calculated the maximum number of starving adult males that could be sustained on each food during the ice-free season. Our results suggest that the net energy from land-based food, after subtracting costs of limited movement to obtain it, could eliminate all projected nutritional deficits of starving adult male polar bears and likely other demographic groups as well. The hunting tactics employed, success rates as well as behavior and abundance of each prey will determine the realized energetic values for individual polar bears. Although climate change may cause a phenological mismatch between polar bears and their historical ice-based prey, it may simultaneously yield a new match with certain land-based foods. If polar bears can transition their foraging behavior to effectively exploit these resources, predictions for starvation-related mortality may be overestimated for western Hudson Bay. We also discuss potential complications with stable-carbon isotope studies to evaluate utilization of land-based foods by polar bears including metabolic effects of capture-related stress and consuming a mixed diet.

  2. Impact of freshwater on a subarctic coastal ecosystem under seasonal sea ice (southeastern Hudson Bay, Canada). III. Feeding success of marine fish larvae

    Science.gov (United States)

    Fortier, L.; Gilbert, M.; Ponton, D.; Ingram, R. G.; Robineau, B.; Legendre, L.

    1996-02-01

    We monitored the feeding success (percent feeding incidence at length and mean feeding ratio at length) of Arctic cod ( Boreogadus saida) and sand lance ( Ammodytes sp.) larvae in relation to prey density, light, temperature and potential predator density under the ice cover of southeastern Hudson Bay in the spring of 1988, 1989 and 1990. Both prey density and light limited larval fish feeding. The relationship between feeding success and actual food availability (nauplii density X irradiance) was adequately described by an Ivlev function which explained 64 and 76% of the variance in Arctic cod and sand lance feeding success respectively. By affecting both prey density and irradiance, the thickness of the Great Whale River plume (as defined by the depth of the 25 isohaline) was the main determinant of prey availability. Arctic cod and sand lance larvae stopped feeding when the depth of the 25 isohaline exceeded 9 m. Limitation of feeding success attributable to freshwater inputs occurred exclusively in 1988, the only time when the depth of the 25 isohaline exceeded the 9 m threshold. The close dependence of larval fish feeding success on the timing of the freshet and plume dynamics suggests a direct link between climate and survival of Arctic cod and sand lance larvae. The actual impact of climate fluctuations and/or hydro-electric developments on recruitment will depend on the fraction of the larval dispersal area of the two species that is affected by river plumes.

  3. Limnological regime shifts caused by climate warming and Lesser Snow Goose population expansion in the western Hudson Bay Lowlands (Manitoba, Canada).

    Science.gov (United States)

    MacDonald, Lauren A; Farquharson, Nicole; Merritt, Gillian; Fooks, Sam; Medeiros, Andrew S; Hall, Roland I; Wolfe, Brent B; Macrae, Merrin L; Sweetman, Jon N

    2015-02-01

    Shallow lakes are dominant features in subarctic and Arctic landscapes and are responsive to multiple stressors, which can lead to rapid changes in limnological regimes with consequences for aquatic resources. We address this theme in the coastal tundra region of Wapusk National Park, western Hudson Bay Lowlands (Canada), where climate has warmed during the past century and the Lesser Snow Goose (LSG; Chen caerulescens caerulescens) population has grown rapidly during the past ∽40 years. Integration of limnological and paleolimnological analyses documents profound responses of productivity, nutrient cycling, and aquatic habitat to warming at three ponds ("WAP 12", "WAP 20", and "WAP 21″), and to LSG disturbance at the two ponds located in an active nesting area (WAP 20, WAP 21). Based on multiparameter analysis of (210)Pb-dated sediment records from all three ponds, a regime shift occurred between 1875 and 1900 CE marked by a transition from low productivity, turbid, and nutrient-poor conditions of the Little Ice Age to conditions of higher productivity, lower nitrogen availability, and the development of benthic biofilm habitat as a result of climate warming. Beginning in the mid-1970s, sediment records from WAP 20 and WAP 21 reveal a second regime shift characterized by accelerated productivity and increased nitrogen availability. Coupled with 3 years of limnological data, results suggest that increased productivity at WAP 20 and WAP 21 led to atmospheric CO2 invasion to meet algal photosynthetic demand. This limnological regime shift is attributed to an increase in the supply of catchment-derived nutrients from the arrival of LSG and their subsequent disturbance to the landscape. Collectively, findings discriminate the consequences of warming and LSG disturbance on tundra ponds from which we identify a suite of sensitive limnological and paleolimnological measures that can be utilized to inform aquatic ecosystem monitoring.

  4. Impact of freshwater on a subarctic coastal ecosystem under seasonal sea ice (southeastern Hudson Bay, Canada) II. Production and export of microalgae

    Science.gov (United States)

    Legendre, L.; Robineau, B.; Gosselin, M.; Michel, C.; Ingram, R. G.; Fortier, L.; Therriault, J. C.; Demers, S.; Monti, D.

    1996-02-01

    In the under-ice plume of the Grande rivière de la Baleine (Great Whale River) and offshore waters of southeastern Hudson Bay (Canada), several environmental factors influence the distribution, growth, taxonomic composition and sedimentation of algae found in the sea ice, at the ice-water interface and in the underlying water column. During the spring and early summer, these factors include: salinity of bottom ice, water turbidity, nutrients and vertical stability of the water column. In the present study, relationships between three predictor variables (water salinity, river runoff and seasonal air temperature index) and biological variables are used to assess the impact of freshwater on production and export of microalgae. Relationships are derived from existing data, which were collected between 1978 and 1990. Correlations with water salinity are positive for some variables (salinity of bottom ice, phosphate, ammonium, Σ:Si, and algae in bottom ice and at the interface) and negative for others (coefficient of light attenuation, silicate, ΣN:P, ΣSi:P and water column phytoplankton). Using together salinity and the seasonal index leads to improved proportions of explained variance for nitrate, ammonium, ΣN:P and phytoplankton. The amount of sedimenting algae is positively correlated with runoff, and chemical composition (C/N) of the sedimenting material is negatively correlated with salinity. The empirical relationships are applied to the results of a model of river plume dynamics, for three runoff conditions. Seasonally averaged total Chl. a concentrations, derived from the model, are higher for maximum river runoff than for mean or minimum conditions. This is because, in the studied environment, areal concentrations of phytoplankton are higher than those of ice algae, especially under condition of maximum runoff.

  5. Limnological regime shifts caused by climate warming and Lesser Snow Goose population expansion in the western Hudson Bay Lowlands (Manitoba, Canada)

    Science.gov (United States)

    MacDonald, Lauren A; Farquharson, Nicole; Merritt, Gillian; Fooks, Sam; Medeiros, Andrew S; Hall, Roland I; Wolfe, Brent B; Macrae, Merrin L; Sweetman, Jon N

    2015-01-01

    Shallow lakes are dominant features in subarctic and Arctic landscapes and are responsive to multiple stressors, which can lead to rapid changes in limnological regimes with consequences for aquatic resources. We address this theme in the coastal tundra region of Wapusk National Park, western Hudson Bay Lowlands (Canada), where climate has warmed during the past century and the Lesser Snow Goose (LSG; Chen caerulescens caerulescens) population has grown rapidly during the past ∽40 years. Integration of limnological and paleolimnological analyses documents profound responses of productivity, nutrient cycling, and aquatic habitat to warming at three ponds (“WAP 12”, “WAP 20”, and “WAP 21″), and to LSG disturbance at the two ponds located in an active nesting area (WAP 20, WAP 21). Based on multiparameter analysis of 210Pb-dated sediment records from all three ponds, a regime shift occurred between 1875 and 1900 CE marked by a transition from low productivity, turbid, and nutrient-poor conditions of the Little Ice Age to conditions of higher productivity, lower nitrogen availability, and the development of benthic biofilm habitat as a result of climate warming. Beginning in the mid-1970s, sediment records from WAP 20 and WAP 21 reveal a second regime shift characterized by accelerated productivity and increased nitrogen availability. Coupled with 3 years of limnological data, results suggest that increased productivity at WAP 20 and WAP 21 led to atmospheric CO2 invasion to meet algal photosynthetic demand. This limnological regime shift is attributed to an increase in the supply of catchment-derived nutrients from the arrival of LSG and their subsequent disturbance to the landscape. Collectively, findings discriminate the consequences of warming and LSG disturbance on tundra ponds from which we identify a suite of sensitive limnological and paleolimnological measures that can be utilized to inform aquatic ecosystem monitoring. PMID:25750718

  6. Demography of an apex predator at the edge of its range: impacts of changing sea ice on polar bears in Hudson Bay

    Science.gov (United States)

    Lunn, Nicholas J.; Servanty, Sabrina; Regehr, Eric V.; Converse, Sarah J.; Richardson, Evan S.; Stirling, Ian

    2016-01-01

    Changes in the abundance and distribution of wildlife populations are common consequences of historic and contemporary climate change. Some Arctic marine mammals, such as the polar bear (Ursus maritimus), may be particularly vulnerable to such changes due to the loss of Arctic sea ice. We evaluated the impacts of environmental variation on demographic rates for the Western Hudson Bay (WH), polar bear subpopulation from 1984 to 2011 using live-recapture and dead-recovery data in a Bayesian implementation of multistate capture–recapture models. We found that survival of female polar bears was related to the annual timing of sea ice break-up and formation. Using estimated vital rates (e.g., survival and reproduction) in matrix projection models, we calculated the growth rate of the WH subpopulation and projected population responses under different environmental scenarios while accounting for parametric uncertainty, temporal variation, and demographic stochasticity. Our analysis suggested a long-term decline in the number of bears from 1185 (95% Bayesian credible interval [BCI] = 993–1411) in 1987 to 806 (95% BCI = 653–984) in 2011. In the last 10 yr of the study, the number of bears appeared stable due to temporary stability in sea ice conditions (mean population growth rate for the period 2001–2010 = 1.02, 95% BCI = 0.98–1.06). Looking forward, we estimated long-term growth rates for the WH subpopulation of ~1.02 (95% BCI = 1.00–1.05) and 0.97 (95% BCI = 0.92–1.01) under hypothetical high and low sea ice conditions, respectively. Our findings support previous evidence for a demographic linkage between sea ice conditions and polar bear population dynamics. Furthermore, we present a robust framework for sensitivity analysis with respect to continued climate change (e.g., to inform scenario planning) and for evaluating the combined effects of climate change and management actions on the status of wildlife populations.

  7. Demography of an apex predator at the edge of its range: impacts of changing sea ice on polar bears in Hudson Bay.

    Science.gov (United States)

    Lunn, Nicholas J; Servanty, Sabrina; Regehr, Eric V; Converse, Sarah J; Richardson, Evan; Stirling, Ian

    2016-07-01

    Changes in the abundance and distribution of wildlife populations are common consequences of historic and contemporary climate change. Some Arctic marine mammals, such as the polar bear (Ursus maritimus), may be particularly vulnerable to such changes due to the loss of Arctic sea ice. We evaluated the impacts of environmental variation on demographic rates for the Western Hudson Bay (WH), polar bear subpopulation from 1984 to 2011 using live-recapture and dead-recovery data in a Bayesian implementation of multistate capture-recapture models. We found that survival of female polar bears was related to the annual timing of sea ice break-up and formation. Using estimated vital rates (e.g., survival and reproduction) in matrix projection models, we calculated the growth rate of the WH subpopulation and projected population responses under different environmental scenarios while accounting for parametric uncertainty, temporal variation, and demographic stochasticity. Our analysis suggested a long-term decline in the number of bears from 1185 (95% Bayesian credible interval [BCI] = 993-1411) in 1987 to 806 (95% BCI = 653-984) in 2011. In the last 10 yr of the study, the number of bears appeared stable due to temporary stability in sea ice conditions (mean population growth rate for the period 2001-2010 = 1.02, 95% BCI = 0.98-1.06). Looking forward, we estimated long-term growth rates for the WH subpopulation of ~1.02 (95% BCI = 1.00-1.05) and 0.97 (95% BCI = 0.92-1.01) under hypothetical high and low sea ice conditions, respectively. Our findings support previous evidence for a demographic linkage between sea ice conditions and polar bear population dynamics. Furthermore, we present a robust framework for sensitivity analysis with respect to continued climate change (e.g., to inform scenario planning) and for evaluating the combined effects of climate change and management actions on the status of wildlife populations.

  8. The role of diet on long-term concentration and pattern trends of brominated and chlorinated contaminants in western Hudson Bay polar bears, 1991-2007

    Energy Technology Data Exchange (ETDEWEB)

    McKinney, Melissa A., E-mail: melissaamckinney@gmail.com [Ecotoxicology and Wildlife Health Division, Science and Technology Branch, Environment Canada, Carleton University (Raven Road), Ottawa, Ontario K1A 0H3 (Canada); Department of Chemistry, Carleton University, Ottawa, Ontario K1S 5B6 (Canada); Stirling, Ian; Lunn, Nick J. [Wildlife Research Division, Science and Technology Branch, Environment Canada, 5320 122 Street, Edmonton, Alberta T6H 3S5 (Canada); Peacock, Elizabeth [Department of Environment, Government of Nunavut, Igloolik, Nunavut X0A 0L0 (Canada); Letcher, Robert J., E-mail: robert.letcher@ec.gc.ca [Ecotoxicology and Wildlife Health Division, Science and Technology Branch, Environment Canada, Carleton University (Raven Road), Ottawa, Ontario K1A 0H3 (Canada); Department of Chemistry, Carleton University, Ottawa, Ontario K1S 5B6 (Canada)

    2010-11-15

    Adipose tissue was sampled from the western Hudson Bay (WHB) subpopulation of polar bears at intervals from 1991 to 2007 to examine temporal trends of PCB and OCP levels both on an individual and sum-({Sigma}-)contaminant basis. We also determined levels and temporal trends of emerging polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), polybrominated biphenyls (PBBs) and other current-use brominated flame retardants. Over the 17-year period, {Sigma} DDT (and p,p'-DDE, p,p'-DDD, p,p'-DDT) decreased (-8.4%/year); {alpha}-hexachlorocyclohexane ({alpha}-HCH) decreased (-11%/year); {beta}-HCH increased (+ 8.3%/year); and {Sigma} PCB and {Sigma} chlordane (CHL), both contaminants at highest concentrations in all years (> 1 ppm), showed no distinct trends even when compared to previous data for this subpopulation dating back to 1968. Some of the less persistent PCB congeners decreased significantly (-1.6%/year to -6.3%/year), whereas CB153 levels tended to increase (+ 3.3%/year). Parent CHLs (c-nonachlor, t-nonachlor) declined, whereas non-monotonic trends were detected for metabolites (heptachlor epoxide, oxychlordane). {Sigma} chlorobenzene, octachlorostyrene, {Sigma} mirex, {Sigma} MeSO{sub 2}-PCB and dieldrin did not significantly change. Increasing {Sigma} PBDE levels (+ 13%/year) matched increases in the four consistently detected congeners, BDE47, BDE99, BDE100 and BDE153. Although no trend was observed, total-({alpha})-HBCD was only detected post-2000. Levels of the highest concentration brominated contaminant, BB153, showed no temporal change. As long-term ecosystem changes affecting contaminant levels may also affect contaminant patterns, we examined the influence of year (i.e., aging or 'weathering' of the contaminant pattern), dietary tracers (carbon stable isotope ratios, fatty acid patterns) and biological (age/sex) group on congener/metabolite profiles. Patterns of PCBs, CHLs and PBDEs were correlated with

  9. Researcher Interview: Tom Hudson

    Science.gov (United States)

    Tom Hudson, M.D., President and Scientific Director of the Ontario Institute for Cancer Research, describes the International Cancer Genome Consortium (ICGC), which brings together cancer genomic data and research from across the world.

  10. Utilization of high resolution satellite geoid data for estimation of lithospheric thickness in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Majumdar, T.J.; Bhattacharyya, R.; Chatterjee, S.; Krishna, K.S.

    height anomalies have been analyzed across the Ninetyeast and 85 degrees E Ridges within the Bay of Bengal. Present data sets are more accurate and detailed (off-track resolution: about 3.33 km and grid size: about 3.5 km). Observed geoid height - age...

  11. Hudson 3 essentials

    CERN Document Server

    Meinholz, Lloyd

    2013-01-01

    A practical guide, packed with illustrations, that will help you become proficient with Hudson and able to utilize it how you want.If you are a Java developer or administrator who would to like automate some of the mundane work required to build and test software and improve software quality, this is the book for you. If you are a development manager or tester, you can also benefit from learning how Hudson works by gaining some insight into test results and historical trends.

  12. Lithosphere Anisotropy of Prydz Bay,Antarctica:From Ocean Bottom Seismometer Long Term Observation%南极洲普里兹湾岩石圈各向异性:海底地震仪观测

    Institute of Scientific and Technical Information of China (English)

    牛雄伟; 高金耀; 吴招才; 阮爱国; 卫小冬; 刘晨光; 李天光; 沈中延; 潘少军

    2016-01-01

    In order to understand better the stress field and dynamics characteristic of the lithosphere at Prydz bay in the Ant-arctica,rotation-correlation shear wave splitting method is used to study 5 earthquakes recorded by three ocean bottom seis-mometers recovered at Prydz bay during the 31th Chinese Antarctic Research Expedition to obtain the anisotropy characteristics of the continent and ocean transition of Prydz bay in this paper.Our inversion results show strong anisotropy in the lithosphere of Prydz bay with spatial differences in small scale.The fast shear wave polarization directions are from N40°E to N60°E,fast and slow shear wave times delay are from 0.2 s to 1.3 s.We think that the anisotropy at the oceanic part is dominated by the mantle flow of mid-ocean ridge spreading,while the continental part is dominated by the relic structural fabric of the ancient lithosphere at the top of the upper mantle,and the middle zone with shallower and thinner anisotropy layer may be influenced by the both reasons above.%为了研究南极普里兹湾岩石圈深部应力场及其动力学,采用S波分裂旋转相关法,对中国第31次南极科学考察成功回收的3个站位海底地震仪数据(5个远震记录)进行了反演,获得了普里兹湾洋陆过渡带岩石圈各向异性特征.结果表明,台站所在区域各向异性显著,在较小的范围内存在明显的空间差异,快S波偏振方向变化范围是N40°E~N60°E,快慢波时间延迟变化范围为0.2~1.3 s.洋盆的各向异性主要取决于海底扩张地幔流作用,大陆及附近的各向异性主要受上地幔顶部残留构造的影响,而中间过渡带各向异性层厚度较小集中在地壳内,它可能受海底扩张地幔流和残留构造共同作用.

  13. Methylsulfone polychlorinated biphenyl and 2,2-bis(chlorophenyl)-1,1-dichloroethylene metabolites in beluga whale (Delphinapterus leucas) from the St. Lawrence River estuary and western Hudson Bay, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Letcher, R.J.; Norstrom, R.J.; Muir, D.C.G.; Sandau, C.D.; Koczanski, K.; Michaud, R.; De Guise, S.; Beland, P.

    2000-05-01

    Knowledge is limited regarding methylsulfone (MeSO{sub 2})-polychlorinated biphenyl (PCB), and especially MeSo{sub 2}-2,2-bis(chlorophenyl)-1,1-dichloroethylene (DDE), metabolites in cetacean species. The authors hypothesized that the ability of beluga whale (Delphinapterus leucas) to biotransform PCB and DDE compounds, and to form and degrade their MeSO{sub 2}-PCB and -DDE metabolites, is related to the capacity for xenobiotic metabolism. Adipose biopsies were collected from male and female beluga whale from distinct populations in the St. Lawrence River estuary (STL) and western Hudson Bay (WHB), Canada, which are contrasted by the exposure to different levels of cytochrome P450 enzyme-inducing, chlorinated hydrocarbon contaminants. The PCBs, DDTs, DDEs, 28 MeSO{sub 2} metabolites of 14 meta-para chlorine-unsubstituted PCBs, and four MeSO{sub 2} metabolites of 4,4{prime}- and 2,4{prime}-DDE were determined. The mean concentrations of total ({Sigma}-) MeSO{sub 2}-PCB in male STL beluga (230 ng/g), and ratios of {Sigma}-MeSO{sub 2}-PCB to {Sigma}-PCB (0.05) and {Sigma}-precursor-PCB (0.17) were approximately twofold higher, whereas the {Sigma}-precursor-PCB to {Sigma}-PCB ratio was approximately twofold lower, than in male WHB beluga. Both populations had a low formation capacity for MeSO{sub 2}-PCBs with {le} six chlorines (<4% of {Sigma}-MeSO{sub 2}-PCBs). The congener patterns were dominated by trichloro- and tetrachloro-MeSO{sub 2}-PCBs, and tetrachloro- and pentachloro-MeSO{sub 2}-PCBs in WHB and STL animals, respectively. In addition to 2- and 3-MeSO{sub 2}-4,4{prime}-DDE, two unknown MeSO{sub 2}-2,4{prime}-DDEs were detected. The mean 3-MeSO{sub 2}-4,4{prime}-DDE concentration in STL beluga (1.2 ng/g) was much greater than in WHB animals. The concentrations of 4,4{prime}-DDE, and not 3-MeSO{sub 2}-4,4{prime}-DDE, increased with age in male STL animals. The authors demonstrated that sulfone formation and clearance is related to metabolic capacity, and thus

  14. Seismological Structure of the 1.8Ga Trans-Hudson Orogen of North America and its affinity to present-day Tibet

    Science.gov (United States)

    Gilligan, A.; Bastow, I. D.; Darbyshire, F. A.

    2015-12-01

    How tectonic processes operated and changed through the Precambrian is debated: what was the nature and scale of orogenic events and were they different on the younger, hotter, more ductile Earth? The geology of northern Hudson Bay records the Paleoproterozoic collision between the Western Churchill and Superior plates: the 1.8Ga Trans-Hudson Orogeny (THO) and is thus an ideal study locale to address this issue. It has been suggested, primarily on the strength of traditional field geology, that the THO was comparable in scale and style to the present-day Himalayan-Karakoram-Tibet Orogen (HKTO). However, understanding of the deep crustal architecture of the THO, and how it compares to the evolving HKTO is presently lacking. Through joint inversion of teleseismic receiver functions and surface wave data, we obtain new Moho depth estimates and shear velocity models for the crust and upper mantle. Archean crust in the Rae, Hearne and Churchill domains is thin and structurally simple, with a sharp Moho; upper crustal wavespeed variations are readily attributed to post-formation events. However, the Paleoproterozoic Quebec-Baffin segment of the THO has a deeper Moho and more complex crustal structure. Our observations are strikingly similar to recent models, computed using the same methods, of the HKTO lithosphere, where deformation also extends >400km beyond the collision front. On the strength of Moho character, present-day crustal thickness, and metamorphic grade, we thus propose that southern Baffin experienced uplift of a similar magnitude and spatial extent to the Himalayas during the Paleoproterozoic Trans-Hudson Orogeny.

  15. Lithospheric processes

    Energy Technology Data Exchange (ETDEWEB)

    Baldridge, W. [and others

    2000-12-01

    The authors used geophysical, geochemical, and numerical modeling to study selected problems related to Earth's lithosphere. We interpreted seismic waves to better characterize the thickness and properties of the crust and lithosphere. In the southwestern US and Tien Shari, crust of high elevation is dynamically supported above buoyant mantle. In California, mineral fabric in the mantle correlate with regional strain history. Although plumes of buoyant mantle may explain surface deformation and magmatism, our geochemical work does not support this mechanism for Iberia. Generation and ascent of magmas remains puzzling. Our work in Hawaii constrains the residence of magma beneath Hualalai to be a few hundred to about 1000 years. In the crust, heat drives fluid and mass transport. Numerical modeling yielded robust and accurate predictions of these processes. This work is important fundamental science, and applies to mitigation of volcanic and earthquake hazards, Test Ban Treaties, nuclear waste storage, environmental remediation, and hydrothermal energy.

  16. 2010 Hudson River Shallow Water Sediment Cores

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Hudson River Shallow Water Mapping project characterizes the bottom of the Hudson River Estuary in shallow water (<3 m). The characterization includes...

  17. 2010 Hudson River Shallow Water Sediment Grabs

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Hudson River Shallow Water Mapping project characterizes the bottom of the Hudson River Estuary in shallow water (<3 m). The characterization includes...

  18. Seismic structure of the North American lithosphere and upper mantle imaged using Surface and S waveform tomography

    Science.gov (United States)

    Schaeffer, A. J.; Lebedev, S.

    2010-12-01

    The evolution, stability, and dynamics of continental lithosphere remain a central focus of Earth Science research. The continued deployment of the US Array is producing a massive new dataset that samples North America at scales from tectonic units to continent-wide domains and enables resolution of structure and deformation of the lithosphere previously possible only at regional scales. With this resolving power come new challenges relating to efficient management and processing of such large data volumes. In this study, we have assembled a dataset comprising over 3.5 million three-component broadband seismic waveforms from more than 3000 stations. We augment available US Array stations with ~600 additional North American stations of the GSN and affiliates, Canadian National Seismograph Network, regional arrays, past PASSCAL experiments, and other stations from Iceland, Greenland, Central and South America, the Caribbean, and several Mid-Atlantic Islands. We exploit the resolving power of this unprecedentedly large dataset using the Automated Multimode Inversion of surface- and S-wave forms. The waveforms are inverted for path-averaged linear constraints on elastic structure along the source-receiver paths. The linear equations are then simultaneously solved for a high-resolution 3D upper mantle shear velocity model of the continent. We present a model of the North American continent's and the surrounding Ocean's (Pacific, Atlantic, Gulf of Mexico) upper mantle structure down to the 660 km discontinuity. Clearly identifiable boundaries between different tectonic features such as basins and relic mountain ranges are readily observable. For example, a strong correlation between the Hudson Bay geoid anomaly can be identified with an underlying domain of particularily cold cratonic lithosphere. Our model also includes the 3D distribution of azimuthal anisotropy within these structures, which provides new insight into past and present dynamics of the lithosphere and

  19. Lithospheric stretching and the long wavelength free-air gravity anomaly of the Eastern Continental margin of India and the 85 degree E Ridge, Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Rajesh, S.; Majumdar, T.J.; Krishna, K.S.

    Among the submarine ridge systems in the northern Indian Ocean, the 85 degree E Ridge in the Bay of Bengal is more enigmatic owing to its peculiar anomalous negative free-air gravity. In general, this has been attributed to the isostatic...

  20. 77 FR 41048 - Safety Zone; Hudson Valley Triathlon, Ulster Landing, Hudson River, NY

    Science.gov (United States)

    2012-07-12

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Hudson Valley Triathlon, Ulster Landing... Landing, NY for the 16th Annual Hudson Valley Triathlon swim event. This temporary safety zone is.... Regulatory History and Information The Hudson Valley Triathlon swim is an annual recurring event that has...

  1. 77 FR 40518 - Swim Events in the Captain of the Port New York Zone; Hudson River, East River, Upper New York...

    Science.gov (United States)

    2012-07-10

    ... Upper New York Bay, Hudson River 5.1 Brooklyn Bridge Swim Date: July 15, 2012. Rain Date: NA... Water Swim Clinics, Verrazano Bridge Swim, Rose Pitonof Swim, and Liberty to Freedom Swim. The sponsors... York Bay 2.1 Verrazano Bridge Swim Date: July 21, 2012. Rain Date: July 22, 2012. Enforcement Period...

  2. Hudson River Sub-Bottom Profile Points

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Hudson River Estuary Shallow Water Surveys. Subbottom Profile Points. Subbottom data was collected November 5 to December 15, 2009, in the estuary north from...

  3. Defining the Pen Islands Caribou Herd of southern Hudson Bay

    Directory of Open Access Journals (Sweden)

    Kenneth F. Abraham

    1998-03-01

    Full Text Available In this paper, we describe the Pen Islands Herd of caribou, the largest aggregation of caribou in Ontario (it also occupies a portion of northeastern Manitoba. Photographic counts showed the herd had a minimum population of 2300 in 1979, 4660 in 1986, 7424 in 1987 and 10 798 in 1994. Throughout the 1980s, the Pen Islands caribou exhibited population behaviour similar to migratory barren-ground caribou herds, although morphology suggests they are woodland caribou or possibly a mixture of subspecies. The herd had well-defined traditional tundra calving grounds, formed nursery groups and large mobile post-calving aggregations, and migrated over 400 km between tundra summer habitats and boreal forest winter habitats. Its migration took it into three Canadian jurisdictions (Ontario, Manitoba, Northwest Territories and it was important to residents of both Manitoba and Ontario. It is clear that the herd should be managed as a migratory herd and the critical importance of both the coastal and variable large winter ranges should be noted in ensuring the herd's habitat needs are secure.

  4. Babesiosis in Lower Hudson Valley, New York

    Centers for Disease Control (CDC) Podcasts

    2011-05-12

    This podcast discusses a study about an increase in babesiosis in the Lower Hudson Valley of New York state. Dr. Julie Joseph, Assistant Professor of Medicine at New York Medical College, shares details of this study.  Created: 5/12/2011 by National Center for Emerging Zoonotic and Infectious Diseases (NCEZID).   Date Released: 5/23/2011.

  5. The continental lithosphere

    DEFF Research Database (Denmark)

    Artemieva, Irina

    2009-01-01

    The goal of the present study is to extract non-thermal signal from seismic tomography models in order to distinguish compositional variations in the continental lithosphere and to examine if geochemical and petrologic constraints on global-scale compositional variations in the mantle are consist......The goal of the present study is to extract non-thermal signal from seismic tomography models in order to distinguish compositional variations in the continental lithosphere and to examine if geochemical and petrologic constraints on global-scale compositional variations in the mantle...... are consistent with modern geophysical data. In the lithospheric mantle of the continents, seismic velocity variations of a non-thermal origin (calculated from global Vs seismic tomography data [Grand S.P., 2002. Mantle shear-wave tomography and the fate of subducted slabs. Philosophical Transactions...... of the Royal Society of London. Series A, 360, 2475–2491.; Shapiro N.M., Ritzwoller M.H. 2002. Monte-Carlo inversion for a global shear velocity model of the crust and upper mantle. Geophysical Journal International 151, 1–18.] and lithospheric temperatures [Artemieva I.M., Mooney W.D., 2001. Thermal structure...

  6. Sea-level Rise Impacts on Hudson River Marshes and their Vegetation Zonation

    Science.gov (United States)

    Hooks, A.; Nitsche, F. O.

    2016-12-01

    Rising sea levels may cause tidal marshes to be vulnerable to submergence and affect their ability to perform ecosystem services. However, tidal marshes are dynamic ecosystems that can adapt to sea-level rise through inland migration and vertical growth. This study examines how four tidal marshes on the Hudson River (Piermont Marsh, Iona Island Marsh, Tivoli Bays, and Stockport Flats) would be affected by 0.5m, 1m, and 1.5m of sea-level rise by 2100. Using high-resolution LiDAR elevation data and vegetation data, we mapped sea-level rise projections in GIS, accounting for current accretion rates unique to each marsh. We calculated the submerged area of each marsh and analyzed how vegetation zonation in each marsh is expected to change due to rising sea levels. We found that the steep topography of the Hudson River banks limits the marshes' ability to migrate inland, emphasizing the role of elevation-building processes in adaptation. The marshes studied would experience minimal to no inundation under lower rates of sea-level rise such as 0.5m by 2100. At higher projected rates of sea-level rise (1.5m by 2100), Piermont Marsh and Tivoli Bays would experience significant inundation while Iona Island marsh and Stockport Flats would be less affected. Overall, Stockport Flats is projected to be the marsh most resilient to sea-level rise due to its higher accretion rate and its topography. Rising sea levels are also expected to change the areas of vegetation zones, with upland, high marsh, and mid marsh zones generally declining in area and with subtidal and low marsh vegetation zones generally expanding under high rates of sea-level rise. Understanding the impacts of sea-level rise on Hudson River marshes enables long-term planning to adapt to potential changes in marsh ecosystem services and could motivate and inform conservation efforts.

  7. SOLAR PANELS ON HUDSON COUNTY FACILITIES

    Energy Technology Data Exchange (ETDEWEB)

    BARRY, KEVIN

    2014-06-06

    This project involved the installation of an 83 kW grid-connected photovoltaic system tied into the energy management system of Hudson County's new 60,000 square foot Emergency Operations and Command Center and staff offices. Other renewable energy features of the building include a 15 kW wind turbine, geothermal heating and cooling, natural daylighting, natural ventilation, gray water plumbing system and a green roof. The County intends to seek Silver LEED certification for the facility.

  8. Budování značky Hudson Global Resources

    OpenAIRE

    Šamšulová, Kristýna

    2014-01-01

    The main topic of this bachelor thesis is Hudson brand building of the recruitment company Hudson Global Resources s.r.o. in Czech market. The aim of the thesis is to define according my own research the Hudson brand perception by clients of the company and propose a Hudson brand strategy and also to evalute which brand management tool the company should use.

  9. NSF Continental Lithosphere Program

    Science.gov (United States)

    Mayhew, Michael; MacGregor, Ian

    For several months the Continental Lithosphere Program (CL) of the National Science Foundation has been subject to a major review. The process was stimulated by a series of budget setbacks over the past few years. Although Presidential budget requests have been very favorable for the Division of Earth Sciences (EAR), and there has been strong support within the National Science Foundation and Congress, actual appropriations by Congress have been disappointing.In each year the final allocation to EAR has been affected by external factors beyond the control of the Foundation. In the four fiscal years from 1986 through 1989 the factors include reductions tied to the Gramm-Rudman deficit reduction measures, congressional reaction to the October 1987 stock market crash, and two years of protection for the Ocean Sciences part of the NSF budget that was paid for from the budgets of the Atmospheric and Earth Sciences divisions.

  10. Distribution and relative abundance of caribou in the Hudson Plains Ecozone of Ontario

    Directory of Open Access Journals (Sweden)

    Audrey J. Magoun

    2005-05-01

    Full Text Available To determine past distribution and relative abundance of caribou (Rangifer tarandus caribou in the Hudson Plains Ecozone (HPE of Ontario, we reviewed past HPE-wide winter systematic aerial surveys, partial winter systematic surveys, summer photographic surveys, incidental observations of caribou, and other sources of information from the period 1950—2003. We conducted new HPE-wide aerial surveys in February 2003 and 2004 to evaluate current distribution patterns. From this information, we defined 9 core wintering areas in the HPE and differentiated between 3 catego¬ries of relative abundance. Wintering areas for the January—March period have changed relatively little over the past 45 years. Summer distribution of caribou along the Hudson Bay coast apparently shifted or expanded from the area west of the Severn River to the central and eastern portions of the coast since the 1980s, and caribou observations have become much more common in the area east of the Winisk River since 1998. Because major resource development activities in the HPE are proposed and some are imminent, we recommend additional caribou surveys to document current caribou population identity, size, and distribution, and research projects to better define caribou wintering areas, calving areas, and movement patterns in the HPE.

  11. Impact of impingement on the Hudson River white perch population. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Barnthouse, L.W.; Van Winkle, W.; Kirk, B.L.; Vaughan, D.S.

    1982-02-01

    This report summarizes a series of analyses of the magnitude and biological significance of the impingement of white perch at the Indian Point Nuclear Generating Station and other Hudson River power plants. Included in these analyses were evaluations of: (1) two independent lines of evidence relating to the magnitude of impingement impacts on the Hudson River white perch population; (2) the additional impact caused by entrainment of white perch; (3) data relating to density-dependent growth among young-of-the-year white perch; (4) the feasibility of performing population-level analyses of impingement impacts on the white perch populations of Chesapeake Bay and the Delaware River; and (5) the feasibility of using simple food chain and food web models to evaluate community-level effects of impingement and entrainment. Estimated reductions in the abundances of the 1974 and 1975 white perch year classes, caused by impingement and entrainment, were high enough that the possibility of adverse long-term effects cannot be excluded.

  12. Habitat Mapping Cruise - Hudson Canyon (HB0904, EK60)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Objectives are to: 1) perform multibeam mapping of transitional and deepwater habitats in Hudson Canyon (off New Jersey) with the National Institute of Undersea...

  13. Distributions of polyhalogenated compounds in Hudson River (New York, USA) fish in relation to human uses along the river

    Energy Technology Data Exchange (ETDEWEB)

    Skinner, Lawrence C., E-mail: lxskinne@gw.dec.state.ny.us [New York State Department of Environmental Conservation, 625 Broadway, Albany, NY 12233 (United States)

    2011-10-15

    PCBs (as Aroclor concentrations) have been extensively examined in fish along the Hudson River, but other xenobiotic chemicals in fish have had limited assessment. This study determined concentrations and congener distributions of polybrominated diphenyl ethers (PBDEs), polybrominated and polychlorinated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs and PCDD/Fs), and polychlorinated biphenyls (PCBs) in smallmouth bass and striped bass taken from a 385 km reach of the Hudson River. Concentrations of PBDEs and PCBs in smallmouth bass, and PCBs in striped bass, were positively related to human uses of the compounds in the basin. Generally low levels of PCDD/Fs were found. One striped bass, however, contained elevated 2,3,7,8-TCDD, indicating exposure to a known source in the adjacent Newark Bay-Passaic River basin. PBDDs were generally below detection. PBDFs were present in four of 18 smallmouth bass, but were not detected in striped bass. Dioxin-like PCBs contribute most to 2,3,7,8-TCDD toxic equivalents in 29 of 30 samples. - Highlights: > In the Hudson River, > PBDEs in smallmouth bass follow human population patterns, but do not for striped bass. > Proximity to known PCB sources govern PCB levels and patterns in fish. > PBDFs were in smallmouth bass but not striped bass. PBDDs were present in one fish. > PCDD/Fs were low in 29 of 30 fish. A 2,3,7,8-TCDD source affected one striped bass. > PCBs contribute most to 2,3,7,8-TCDD toxic equivalents in 29 of 30 samples. - Residues of polyhalogenated compounds in resident and migratory fish from the Hudson River are compared with human uses of the compounds in the river basin.

  14. How thick is the lithosphere?

    Science.gov (United States)

    Kanamori, H; Press, F

    1970-04-25

    A rapid decrease in shear velocity in the suboceanic mantle is used to infer the thickness of the lithosphere. It is proposed that new and highly precise group velocity data constrain the solutions and imply a thickness near 70 km.

  15. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from the LOUIS S. ST. LAURENT in the Baffin Bay, Davis Strait and others from 1997-08-03 to 1997-08-18 (NODC Accession 0114432)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NODC Accession 0114432 includes chemical, discrete sample, physical and profile data collected from LOUIS S. ST. LAURENT in the Baffin Bay, Davis Strait, Hudson...

  16. Mechanical heterogeneities and lithospheric extension

    Science.gov (United States)

    Duretz, Thibault; Petri, Benoit; Mohn, Geoffroy; Schenker, Filippo L.; Schmalholz, Stefan

    2016-04-01

    Detailed geological and geophysical studies of passive margins have highlighted the multi-stage and depth-dependent aspect of lithospheric thinning. Lithospheric thinning involves a variety of structures (normal faults, low angle detachments, extensional shear zones, extraction faults) and leads to a complex architecture of passive margins (with e.g. necking zone, mantle exhumation, continental allochthons). The processes controlling the generation and evolution of these structures as well as the impact of pre-rift inheritance are so far incompletely understood. In this study, we investigate the impact of pre-rift inheritance on the development of rifted margins using two-dimensional thermo-mechanical models of lithospheric thinning. To first order, we represent the pre-rift mechanical heterogeneities with lithological layering. The rheologies are kept simple (visco-plastic) and do not involve any strain softening mechanism. Our models show that mechanical layering causes multi-stage and depth-dependent extension. In the initial rifting phase, lithospheric extension is decoupled: as the crust undergoes thinning by brittle (frictional-plastic) faults, the lithospheric mantle accommodates extension by symmetric ductile necking. In a second rifting phase, deformation in the crust and lithospheric mantle is coupled and marks the beginning of an asymmetric extension stage. Low angle extensional shear zones develop across the lithosphere and exhume subcontinental mantle. Furthemore, crustal allochthons and adjacent basins develop coevally. We describe as well the thermal evolution predicted by the numerical models and discuss the first-order implications of our results in the context of the Alpine geological history.

  17. 78 FR 76140 - Extension of Public Comment Period for the Champlain Hudson Power Express Transmission Line...

    Science.gov (United States)

    2013-12-16

    ... Extension of Public Comment Period for the Champlain Hudson Power Express Transmission Line Project Draft... Hudson Power Express Transmission Line Project Draft Environmental Impact Statement (DOE/EIS-0447). The... permit to the Applicant, Champlain Hudson Power Express, Inc. (CHPEI), to construct, operate,...

  18. 40 CFR 81.129 - Hudson Valley Intrastate Air Quality Control Region.

    Science.gov (United States)

    2010-07-01

    ... Quality Control Regions § 81.129 Hudson Valley Intrastate Air Quality Control Region. The Hudson Valley Intrastate Air Quality Control Region (New York) consists of the territorial area encompassed by the... 40 Protection of Environment 17 2010-07-01 2010-07-01 false Hudson Valley Intrastate Air...

  19. 77 FR 32984 - Notice of Inventory Completion: University of Maine, Hudson Museum, Orono, ME

    Science.gov (United States)

    2012-06-04

    ... National Park Service Notice of Inventory Completion: University of Maine, Hudson Museum, Orono, ME AGENCY: National Park Service, Interior. ACTION: Notice. SUMMARY: The University of Maine, Hudson Museum has... contact the University of Maine, Hudson Museum. Repatriation of the human remains to the Indian...

  20. 76 FR 63342 - Environmental Impact Statement, Tappan Zee Hudson River Crossing Project (Rockland and...

    Science.gov (United States)

    2011-10-12

    ... Impact Statement, Tappan Zee Hudson River Crossing Project (Rockland and Westchester Counties, NY) AGENCY... Tappan Zee Hudson River crossing in Rockland and Westchester Counties, New York. The purpose of this... infrastructure of the Tappan Zee Hudson River crossing. 1. Description of the Project Area The Tappan Zee...

  1. Transport of Cerro Hudson SO2 clouds

    Science.gov (United States)

    Doiron, Scott D.; Bluth, Gregg J. S.; Schnetzler, Charles C.; Krueger, Arlin J.; Walter, Louis S.

    The Cerro Hudson volcano in southern Chile (45.92°S, 73.0°W) emitted large ash and sulfur dioxide clouds on August 12-15, following several days of minor activity [Global Volcanism Network Bulletin, 1991]. The SO2 clouds were observed using (preliminary) near real-time data from the Total Ozone Mapping Spectrometer (TOMS) as they encircled the south polar region. The injection of SO2 into the stratosphere has essentially created a gigantic chemical tracer that could provide new insights into the wind patterns and seasonal circulation around the Antarctic region.around the Antarctic region. The TOMS instrument, on board the National Aeronautic and Space Administration's Nimbus 7 satellite, measures the ratio of backscattered Earth radiance to incoming solar irradiance in the ultraviolet spectrum. Although originally designed to measure ozone, it was later discovered that the TOMS instrument could also detect and quantify SO2 [Krueger, 1985]. After this discovery, measurements from TOMS were examined for SO2 emissions for all recorded volcanic eruptions since Nimbus-7 was launched in October 1978, and current data are analyzed as new eruptions occur. The satellite is in a polar, Sun-synchronous orbit so that it crosses the equator at local noon and observes the whole sunlit Earth in approximately 14 orbits each day. Total column amounts of SO2 are determined that represent the amount of gas affecting the reflection of ultraviolet light through a column of the atmosphere from the satellite to the reflecting surface, Earth, given in terms of milli atmospheres centimeter (1000 milli atm cm = a gas layer 1-cm thick at STP). The mass of SO2 is calculated by integrating over the cloud area to obtain a volume, then converting to tons.

  2. Lithospheric thermal structure of the North China Craton and its geodynamic implications

    Science.gov (United States)

    Liu, Qiongying; Zhang, Linyou; Zhang, Chao; He, Lijuan

    2016-12-01

    We conduct 2-D numerical modeling of the lithospheric thermal structure of the North China Craton (NCC) on basis of twenty-four crustal velocity structure profiles. About five hundred heat flow data constitute the principal constraints for our modeling. The modeling results demonstrate marked lateral variations in thermal regime of the crust-lithosphere system in the NCC. The average mantle heat flow decreases from 38 ± 5 mW m-2 under the Bohai Bay Basin in the eastern NCC to 27 ± 4 mW m-2 under the Ordos Basin in the western NCC, characterized by a 'cold crust but hot mantle' structure and a 'hot crust but cold mantle' structure, respectively. Thermal lithospheric thickness varies from ∼65 km beneath the Tan-Lu Fault zone to ∼160 km beneath the western and northern Ordos Basin, with similar trend to the seismic lithosphere. However, the disparities in thickness between the thermal and seismic lithosphere are within 20 km beneath the Bohai Bay Basin, but 30-90 km beneath the Shanxi-Weihe Graben and 50-120 km beneath the Ordos Basin. This may imply a westward thickening trend of the rheological boundary layer, which might be attributed to the reducing of asthenosphere viscosity due to hydrous fluid released by dehydration of the subducting Pacific Plate under the eastern NCC. Combined with other pieces of evidence, we suggest that vigorous mantle processes may occur beneath the eastern NCC, whereas the western NCC is relatively stable.

  3. Lithospheric structure and continental geodynamics

    Institute of Scientific and Technical Information of China (English)

    许忠淮; 石耀霖

    2003-01-01

    This paper briefly reviews main progress in the research on lithospheric structure and continental geodynamics made by Chinese geophysicists during last 4 years since 22nd IUGG general assembly in July 1999. The research mainly covers the following fields: investigations on regional lithospheric structure, DSS survey of crust and upper mantle velocity structure, study on present-day inner movement and deformation of Chinese mainland by analyzing GPS observations, geodynamics of Qingzang plateau, geophysical survey of the Dabie-Sulu ultra-high pressure metamorphic belt and probing into its formation mechanism, geophysical observations in sedimentary basins and study on their evolution process, and plate dynamics, etc.

  4. Deflection rheoevolution of lithosphere under subduction

    Institute of Scientific and Technical Information of China (English)

    韩玉英; 王维襄

    1997-01-01

    Along the continental margin, the tectonic system consisting of trench, island arc, back arc basin and outer rise is often known as a convergent transitional belt between the oceanic lithosphere and the continental litho-sphere. The occurrence, development and activity of trench and outer rise bear closely on the underthrusting process of the oceanic lithosphere. A generalized analytical theory of deflection rheoevolution of lithosphere under subduction is established, and solutions with universal significance have been obtained.

  5. Satellite-derived geoid for the estimation of lithospheric cooling and basal heat flux anomalies over the northern Indian Ocean lithosphere

    Indian Academy of Sciences (India)

    S Rajesh; T J Majumdar

    2015-12-01

    The northern Indian Ocean consists of older Bay of Bengal (BOB) oceanic lithosphere with numerous intra-plate loads; whereas, contrasting elements like active Mid-Ocean ridge divergence and slow spreading ridges are present in the relatively younger (<60 Ma) Arabian Sea oceanic lithosphere. The mechanism of lithospheric cooling of young age oceanic lithosphere from the moderately active and slow spreading Carlsberg Ridge is analysed by considering the hypothesis of near lithospheric convective action or whole upper mantle convection. We addressed these issues by studying the marine geoid at different spatial wavelengths and retrieved and compared their lithospheric cooling signatures, plate spreading and distribution of mass and heat anomalies along with seismicity, bathymetry, gravity and isochron age data. Results show that progressive cooling of young-aged oceanic lithosphere from the Mid-Ocean Carlsberg Ridge is because of conductive cooling and those signals are retrieved in the shorter wavelength band (111 < < 1900 km) of constrained residual geoid with mass anomaly sources near to sublithospheric. This shows steadiness in the geoid anomaly decay rate (∼–0.1 m/Ma), consistency in the growth of thermal boundary layer and progressive fall of basal temperature and heat flux (900–300 K and 100–18 mW m−2) with increase of lithospheric age. The above observations are attributed to the fact that the advective–convective action beneath the Mid-Ocean Carlsberg Ridge is driven by the basal temperature gradient between the lithosphere and the near lithospheric low viscose thin layer. But, for the case of old-aged oceanic lithosphere in the BOB, the residual geoid anomaly cooling signals are not prominently seen in the same band as that of the Arabian Sea because of the Ninetyeast Ridge magmatism. However, its cooling anomaly signatures are retrieved at relatively higher band (1335 ≤ ≤ 3081 km) having erratic geoid decay rates (–0.3 to 0.2 m/Ma) owing

  6. Seismological structure of the 1.8 Ga Trans-Hudson Orogen of North America

    Science.gov (United States)

    Gilligan, Amy; Bastow, Ian D.; Darbyshire, Fiona A.

    2016-06-01

    Precambrian tectonic processes are debated: what was the nature and scale of orogenic events on the younger, hotter, and more ductile Earth? Northern Hudson Bay records the Paleoproterozoic collision between the Western Churchill and Superior plates—the ˜1.8 Ga Trans-Hudson Orogeny (THO)—and is an ideal locality to study Precambrian tectonic structure. Integrated field, geochronological, and thermobarometric studies suggest that the THO was comparable to the present-day Himalayan-Karakoram-Tibet Orogen (HKTO). However, detailed understanding of the deep crustal architecture of the THO, and how it compares to that of the evolving HKTO, is lacking. The joint inversion of receiver functions and surface wave data provides new Moho depth estimates and shear velocity models for the crust and uppermost mantle of the THO. Most of the Archean crust is relatively thin (˜39 km) and structurally simple, with a sharp Moho; upper-crustal wave speed variations are attributed to postformation events. However, the Quebec-Baffin segment of the THO has a deeper Moho (˜45 km) and a more complex crustal structure. Observations show some similarity to recent models, computed using the same methods, of the HKTO crust. Based on Moho character, present-day crustal thickness, and metamorphic grade, we support the view that southern Baffin Island experienced thickening during the THO of a similar magnitude and width to present-day Tibet. Fast seismic velocities at >10 km below southern Baffin Island may be the result of partial eclogitization of the lower crust during the THO, as is currently thought to be happening in Tibet.

  7. Impact of entrainment and impingement on fish populations in the Hudson River estuary. Volume I. Entrainment-impact estimates for six fish populations inhabiting the Hudson River estuary

    Energy Technology Data Exchange (ETDEWEB)

    Boreman, J.; Barnthouse, L.W.; Vaughn, D.S.; Goodyear, C.P.; Christensen, S.W.; Kumar, K.D.; Kirk, B.L.; Van Winkle, W.

    1982-01-01

    This volume is concerned with the estimation of the direct (or annual) entrainment impact of power plants on populations of striped bass, white perch, Alosa spp. (blueback herring and alewife), American shad, Atlantic tomcod, and bay anchovy in the Hudson River estuary. Entrainment impact results from the killing of fish eggs, larvae, and young juveniles that are contained in the cooling water cycled through a power plant. An Empirical Transport Model (ETM) is presented as the means of estimating a conditional entrainment mortality rate (defined as the fraction of a year class which would be killed due to entrainment in the absence of any other source of mortality). Most of this volume is concerned with the estimation of several parameters required by the ETM: physical input parameters (e.g., power-plant withdrawal flow rates); the longitudinal distribution of ichthyoplankton in time and space; the duration of susceptibility of the vulnerable organisms; the W-factors, which express the ratios of densities of organisms in power plant intakes to densities of organisms in the river; and the entrainment mortality factors (f-factors), which express the probability that an organism will be killed if it is entrained. Once these values are obtained, the ETM is used to estimate entrainment impact for both historical and projected conditions.

  8. Babesiosis in Lower Hudson Valley, New York, USA

    Science.gov (United States)

    Roy, Sumith S.; Shams, Navid; Visintainer, Paul; Nadelman, Robert B.; Hosur, Srilatha; Nelson, John; Wormser, Gary P.

    2011-01-01

    Although Lyme disease has been endemic to parts of the Lower Hudson Valley of New York, United States, for >2 decades, babesiosis has emerged there only since 2001. The number of Lower Hudson Valley residents in whom babesiosis was diagnosed increased 20-fold, from 6 to 119 cases per year during 2001–2008, compared with an ≈1.6-fold increase for the rest of New York. During 2002–2009, a total of 19 patients with babesiosis were hospitalized on 22 occasions at the regional tertiary care center. Concurrent conditions included advanced age, malignancies, splenectomy, and AIDS. Two patients acquired the infection from blood transfusions and 1 from perinatal exposure, rather than from a tick bite. One patient died. Clinicians should consider babesiosis in persons with fever and hemolytic anemia who have had tick exposure or have received blood products. PMID:21529393

  9. Utility company installs first Hudson River drilled crossing

    Energy Technology Data Exchange (ETDEWEB)

    1993-12-01

    Directionally drilling a natural gas pipe line under the Hudson River called for innovative installation techniques including an elevated pullback over a heavily traveled commuter railroad. The 3,700-ft crossing was installed for Central Hudson Gas and Electric Corp. as part of an 11-mi system to supply natural gas from the Iroquois Gas Transmission System to the utility company's Roseton Generating Station. It represents the first horizontal drilled pipe line installation of the Hudson River and the longest drilled crossing in the US Northeast. At the point of installation, the line was designed to contend with an existing glacial till geology, the river crossing, eight electric cables near the right-of-way and the high-speed Metro North Railroad on the east side of the river. Through the interconnection with Iroquois, the utility receives up to 100 MMcfd of natural gas at 750 psig. Total cost of the new system was about $13.1 million with nearly $3.2 million dedicated to the crossing. This paper describes the installation procedures used in this project.

  10. Crustal response to lithosphere evolution

    DEFF Research Database (Denmark)

    Artemieva, Irina; Thybo, Hans; Cherepanova, Yulia;

    2012-01-01

    We present a new model for the structure of the crust in an area which stretches from the North Atlantic region in the west to the Verkhoyansk Ridge in the east and encompasses Greenland, Iceland, most of Europe, West Siberian basin, and the Siberian cratons. The model is based on critically...... such as lower crust/lithospheric mantle delamination in the Variscan Europe and large-scale rifting across the entire West Siberian basin. The results are summarized in a series of maps of lateral variations in crustal properties, including the depth to the basement and to the Moho, average crustal velocity......, thicknesses of different crustal layers, and Pn seismic velocities....

  11. Anatomy of lithosphere necking during orthogonal rifting

    Science.gov (United States)

    Nestola, Yago; Cavozzi, Cristian; Storti, Fabrizio

    2013-04-01

    The evolution of lithosphere necking is a fundamental parameter controlling the structural architecture and thermal-state of rifted margin. The necking shape depends on several parameters, including the extensional strain-rate and thermal layering of the lithosphere. Despite a large number of analogue and numerical modelling studies on lithosphere extension, a quantitative description of the evolution of necking through time is still lacking. We used analogue modelling to simulate in three-dimension the progression of lithosphere thinning and necking during orthogonal rifting. In our models we simulated a typical "cold and young" 4-layer lithosphere stratigraphy: brittle upper crust (loose quartz sand), ductile lower crust (silicon-barite mixture), brittle upper mantle (loose quartz sand), and ductile lower mantle (silicon-barite mixture). The experimental lithosphere rested on a glucose syrup asthenosphere. We monitored model evolution by periodic and coeval laser scanning of both the surface topography and the lithosphere base. After model completion, each of the four layers was removed and the top of the underlying layer was scanned. This technical approach allowed us to quantify the evolution in space and time of the thinning factors for both the whole lithosphere (βz) and the crust (γ). The area of incremental effective stretching (βy) parallel to the extensional direction was obtained from the βz maps.

  12. Thermal-rheological structure of the lithosphere beneath Jiyang Depression: Its implications for geodynamics

    Institute of Scientific and Technical Information of China (English)

    LIU Shaowen; WANG Liangshu; GONG Yuling; LI Cheng; LI Hua; HAN Yongbing

    2005-01-01

    Jiyang Depression, located in the southeast Bohai Bay Basin, has the geomorphologic framework of multiple uplifts intervening with sags. Combined the abundant geo-temperature data and thermo-physical parameters of rock samples derived from oil and gas exploration during the past years, with geothermal approaches, here we investigate the lithospheric thermal regime of this depression. Consequently, based on the obtained thermal structure of the lithosphere, along with rheological modeling, the lithospheric rheological profiles of Jiyang Depression are then determined. Our results show that the temperature at the bottom of sedimentary cover within depression varies from 129℃ to 298℃, accompanied with the basement heat flow ranging between 54.3 and 60.5 mW/m2; and 406℃-436℃ for temperature at the bottom of the upper crust, along with heat flow varying from 47.7 to 52.6 mW/m2; while the temperature at the bottom of the middle crust is between 537℃ and 572℃, as well as heat flow ranging from 41.3 to 56.3 mW/m2. The temperature at Moho ranges from 669℃ to 721℃, the heat flow derived from mantle is between 38.1 and 43.1 mW/m2, and calculated thickness of the thermal lithosphere beneath depression varies from 71 to 90 km. Lithospheric thermal regime is a close correlation with such factors as crustal thickness and surface heat flow, etc. Usually, the larger the surface heat flow, the larger the deep temperature and heat flow within lithosphere, and the thinner the thermal lithospheric thickness. This high thermal regime of the lithosphere in Jiyang Depression is thought to be related to Cenozoic back-arc spreading during the western Pacific plate subduction into Eurasian continent. Lithospheric rheological modeling shows that the lithosphere in Jiyang Depression is characterized by its distinct rheological stratification as follows: The upper and most part of the middle crust are of brittle, while the lower crust and the lower part of middle crust are all

  13. Detrital carbonate peaks on the Labrador shelf, a 13-7 ka template for freshwater forcing from the Hudson Strait outlet of the Laurentide Ice Sheet into the subpolar gyre

    Science.gov (United States)

    Jennings, Anne; Andrews, John; Pearce, Christof; Wilson, Lindsay; Ólfasdótttir, Sædís

    2015-01-01

    The Laurentide Ice Sheet (LIS) was a large, dynamic ice sheet in the early Holocene. The glacial events through Hudson Strait leading to its eventual demise are recorded in the well-dated Labrador shelf core, MD99-2236 from the Cartwright Saddle. We develop a detailed history of the timing of ice-sheet discharge events from the Hudson Strait outlet of the LIS during the Holocene using high-resolution detrital carbonate, ice rafted detritus (IRD), δ18O, and sediment color data. Eight detrital carbonate peaks (DCPs) associated with IRD peaks and light oxygen isotope events punctuate the MD99-2236 record between 11.5 and 8.0 ka. We use the stratigraphy of the DCPs developed from MD99-2236 to select the appropriate ΔR to calibrate the ages of recorded glacial events in Hudson Bay and Hudson Strait such that they match the DCPs in MD99-2236. We associate the eight DCPs with H0, Gold Cove advance, Noble Inlet advance, initial retreat of the Hudson Strait ice stream (HSIS) from Hudson Strait, opening of the Tyrrell Sea, and drainage of glacial lakes Agassiz and Ojibway. The opening of Foxe Channel and retreat of glacial ice from Foxe Basin are represented by a shoulder in the carbonate data. ΔR of 350 years applied to the radiocarbon ages constraining glacial events H0 through the opening of the Tyrell Sea provided the best match with the MD99-2236 DCPs; ΔR values and ages from the literature are used for the younger events. A very close age match was achieved between the 8.2 ka cold event in the Greenland ice cores, DCP7 (8.15 ka BP), and the drainage of glacial lakes Agassiz and Ojibway. Our stratigraphic comparison between the DCPs in MD99-2236 and the calibrated ages of Hudson Strait/Bay deglacial events shows that the retreat of the HSIS, the opening of the Tyrell Sea, and the catastrophic drainage of glacial lakes Agassiz and Ojibway at 8.2 ka are separate events that have been combined in previous estimates of the timing of the 8.2 ka event from marine records

  14. Tracklines of a multibeam survey of the Hudson Shelf Valley carried out in 1998 (polyline shapefile, geographic, WGS 84)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The Hudson Shelf Valley is the submerged seaward extension of the ancestral Hudson River drainage system and is the largest physiographic feature on the Middle...

  15. The Lithospheric Structure of Madagascar

    Science.gov (United States)

    Wysession, M. E.; Pratt, M. J.; Andriampenomanana Ny Ony, F. S. T.; Tsiriandrimanana, R.; Nyblade, A.; Aleqabi, G. I.; Shore, P.; Tucker, R.; Wiens, D. A.; Rambolamanana, G.

    2016-12-01

    The lithosphere of Madagascar is revealed for the first time from a combination of studies using data from the 2011-2013 MACOMO (Madagascar, the Comoros, and Mozambique) broadband seismic array from the IRIS PASSCAL program (funded by NSF, with additional data from the RHUM-RUM and Madagascar Seismic Profile projects). Methods include seismicity locations, body-wave receiver functions, Pn tomography, body-wave tomography, and ambient-noise and two-plane-wave earthquake surface-wave analyses. Madagascar's crustal thickness varies greatly, from 20 to 45 km, in good agreement with its past tectonic history of rifting from the mainland and having India break away to the north. The crust is thickest along the central spine of the island, along a ridge of mountains, but unusually high elevations suggest some amount f thermal buoyancy in the mantle. Crust is also thick along the east coast, where archean terranes were severed from India. Crust is thinnest along the west coast, where thick sedimentary basins up to 8 km thick are found on top of unusually thinned basement crust (about 12 km thick), a remnant of rifting away from Africa 130-160 Ma ago. Madagascar has an unusually high level of intraplate seismicity, with 918 earthquakes located during the 2-year period. Seismicity shows interesting correlations with paleotectonic features, but much is located in the central regions of the island, associated with normal faulting along several graben structures. This region also corresponds to the central of three regions within Madagascar (north, central, and southwest) that display strong lithospheric seismic low-velocity anomalies that underlie regions of current or recent volcanic activity. Surface waves show that these low-velocity zones (LVZs) extending down into the asthenosphere, and body-wave tomography shows them extending even deeper. Pn tomography shows that the width of the central LVZ is only about 100-200 km in diameter at the top of the mantle, indicative of

  16. The Riso-Hudson Enneagram Type Indicator: Estimates of Reliability and Validity

    Science.gov (United States)

    Newgent, Rebecca A.; Parr, Patricia E.; Newman, Isadore; Higgins, Kristin K.

    2004-01-01

    This investigation was conducted to estimate the reliability and validity of scores on the Riso-Hudson Enneagram Type Indicator (D. R. Riso & R. Hudson, 1999a). Results of 287 participants were analyzed. Alpha suggests an adequate degree of internal consistency. Evidence provides mixed support for construct validity using correlational and…

  17. 78 FR 20169 - Notice of Availability of an Environmental Assessment for the Proposed Hudson Yards Concrete...

    Science.gov (United States)

    2013-04-03

    ... Hudson Yards Concrete Casing Project in New York, New York AGENCY: Federal Railroad Administration (FRA... Assessment for the Hudson Yards Concrete Casing Construction. SUMMARY: This notice advises the public that... coordination with Federal Railroad Administration (FRA) for the construction of an underground concrete casing...

  18. 75 FR 39839 - Regulated Navigation Area; Hudson River and Port of NY/NJ

    Science.gov (United States)

    2010-07-13

    ... restrictions with the Kiewit and Weeks Marine contractors, and with Hudson River and Sandy Hook Pilots... transfer of the bridge span from shore to the barges has been scheduled on a weekday when it is expected to... Overtaking zones are established in areas identified by Weeks Marine, Hudson River and Sandy Hook Pilots as...

  19. Comments on James D. Brown and Thom Hudson's "The Alternatives in Language Assessment."

    Science.gov (United States)

    Bruton, Anthony; Brown, James Dean; Hudson, Thom

    1999-01-01

    Anthony Bruton comments on Brown and Hudson's article "The Alternatives in Language Assessment," (v32 n4 Win 1998). Raises questions about some of their definitions and categories and suggests additional items that need to be considered by test takers. Brown and Hudson reply with clarifications of terms and definition of the scope of their paper.…

  20. 33 CFR 165.170 - Safety Zone: Triathlon, Ulster Landing, Hudson River, NY.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Safety Zone: Triathlon, Ulster Landing, Hudson River, NY. 165.170 Section 165.170 Navigation and Navigable Waters COAST GUARD, DEPARTMENT... § 165.170 Safety Zone: Triathlon, Ulster Landing, Hudson River, NY. (a) Regulated area. The...

  1. 77 FR 65929 - Notice of Final Federal Agency Actions on the Tappan Zee Hudson River Crossing Project in New York

    Science.gov (United States)

    2012-10-31

    ... Federal Highway Administration Notice of Final Federal Agency Actions on the Tappan Zee Hudson River.... Sec. 139(l)(1). The actions relate to the Tappan Zee Hudson River Crossing Project located in Rockland... the following highway project in the State of New York: Tappan Zee Hudson River Crossing...

  2. 78 FR 27473 - Notice of Final Federal Agency Actions on the Tappan Zee Hudson River Crossing Project in New York

    Science.gov (United States)

    2013-05-10

    ... Federal Highway Administration Notice of Final Federal Agency Actions on the Tappan Zee Hudson River... within the meaning of 23 U.S.C. 139(l)(1). The actions relate to the Tappan Zee Hudson River Crossing... FHWA published a ``Notice of Final Federal Agency Actions'' on the Tappan Zee Hudson River...

  3. Deformation in the continental lithosphere

    Science.gov (United States)

    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.

  4. Analyzing a Mid-Air Collision Over the Hudson River

    Science.gov (United States)

    Brown, Sean; Holloway, C. Michael

    2012-01-01

    On August 8, 2009, a private airplane collided with a sightseeing helicopter over the Hudson River near Hoboken, New Jersey. All three people aboard the airplane, the pilot and two passengers, and all six people aboard the helicopter, the pilot and five passengers, were killed. The National Transportation Safety Board report on the accident identified inherent limitations of the see-and-avoid concept, inadequate regulations, and errors by the pilots and an air traffic controller as causing or contributing to the accident. This paper presents the results of analyzing the accident using the Systems-Theoretic Accident Model and Processes (STAMP) approach to determining accident causation.

  5. The lithosphere-asthenosphere Italy and surroundings

    CERN Document Server

    Panza, G F; Chimera, G; Pontevivo, A; Raykova, R

    2003-01-01

    The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by surface wave velocity tomography and non-linear inversion. Maps of the Moho depth, of the thickness of the lithosphere and of the shear-wave velocities, down to depths of 200 km and more, are constructed. A mantle wedge, identified in the uppermost mantle along the Apennines and the Calabrian Arc, underlies the principal recent volcanoes, and partial melting can be relevant in this part of the uppermost mantle. In Calabria a lithospheric doubling is seen, in connection with the subduction of the Ionian lithosphere. The asthenosphere is shallow in the Southern Tyrrhenian Sea. High velocity bodies, cutting the asthenosphere, outline the Adria-lonian subduction in the Tyrrhenian Sea and the deep-reaching lithospheric root in the Western Alps. Less deep lithospheric roots are seen in the Central Apennines. The lithosphere-asthenosphere properties delineat...

  6. Magnetotelluric investigations of the lithosphere beneath the central Rae craton, mainland Nunavut, Canada

    Science.gov (United States)

    Spratt, Jessica E.; Skulski, Thomas; Craven, James A.; Jones, Alan G.; Snyder, David B.; Kiyan, Duygu

    2014-03-01

    New magnetotelluric soundings at 64 locations throughout the central Rae craton on mainland Nunavut constrain 2-D resistivity models of the crust and lithospheric mantle beneath three regional transects. Responses determined from colocated broadband and long-period magnetotelluric recording instruments enabled resistivity imaging to depths of > 300 km. Strike analysis and distortion decomposition on all data reveal a regional trend of 45-53°, but locally the geoelectric strike angle varies laterally and with depth. The 2-D models reveal a resistive upper crust to depths of 15-35 km that is underlain by a conductive layer that appears to be discontinuous at or near major mapped geological boundaries. Surface projections of the conductive layer coincide with areas of high grade, Archean metasedimentary rocks. Tectonic burial of these rocks and thickening of the crust occurred during the Paleoproterozoic Arrowsmith (2.3 Ga) and Trans-Hudson orogenies (1.85 Ga). Overall, the uppermost mantle of the Rae craton shows resistivity values that range from 3000 Ω m in the northeast (beneath Baffin Island and the Melville Peninsula) to 10,000 Ω m beneath the central Rae craton, to >50,000 Ω m in the south near the Hearne Domain. Near-vertical zones of reduced resistivity are identified within the uppermost mantle lithosphere that may be related to areas affected by mantle melt or metasomatism associated with emplacement of Hudsonian granites. A regional decrease in resistivities to values of 500 Ω m at depths of 180-220 km, increasing to 300 km near the southern margin of the Rae craton, is interpreted as the lithosphere-asthenosphere boundary.

  7. Rheology of the lithosphere: selected topics.

    Science.gov (United States)

    Kirby, S.H.; Kronenberg, A.K.

    1987-01-01

    Reviews recent results concerning the rheology of the lithosphere with special attention to the following topics: 1) the flexure of the oceanic lithosphere, 2) deformation of the continental lithosphere resulting from vertical surface loads and forces applied at plate margins, 3) the rheological stratification of the continents, 4) strain localization and shear zone development, and 5) strain-induced crystallographic preferred orientations and anisotropies in body-wave velocities. We conclude with a section citing the 1983-1986 rock mechanics literature by category.-Authors

  8. Rifting Thick Lithosphere - Canning Basin, Western Australia

    Science.gov (United States)

    Czarnota, Karol; White, Nicky

    2016-04-01

    The subsidence histories and architecture of most, but not all, rift basins are elegantly explained by extension of ~120 km thick lithosphere followed by thermal re-thickening of the lithospheric mantle to its pre-rift thickness. Although this well-established model underpins most basin analysis, it is unclear whether the model explains the subsidence of rift basins developed over substantially thick lithosphere (as imaged by seismic tomography beneath substantial portions of the continents). The Canning Basin of Western Australia is an example where a rift basin putatively overlies lithosphere ≥180 km thick, imaged using shear wave tomography. Subsidence modelling in this study shows that the entire subsidence history of the Canning Basin is adequately explained by mild Ordovician extension (β≈1.2) of ~120 km thick lithosphere followed by post-rift thermal subsidence. This is consistent with the established model, described above, albeit with perturbations due to transient dynamic topography support which are expressed as basin-wide unconformities. In contrast the Canning Basin reveals an almost continuous period of normal faulting between the Ordovician and Carboniferous (βCanning Basin to rifting of thick lithosphere beneath the eastern part, verified by the presence of ~20 Ma diamond-bearing lamproites intruded into the basin depocentre. In order to account for the observed subsidence, at standard crustal densities, the lithospheric mantle is required to be depleted in density by 50-70 kg m-3, which is in line with estimates derived from modelling rare-earth element concentrations of the ~20 Ma lamproites and global isostatic considerations. Together, these results suggest that thick lithosphere thinned to > 120 km is thermally stable and is not accompanied by post-rift thermal subsidence driven by thermal re-thickening of the lithospheric mantle. Our results show that variations in lithospheric thickness place a fundamental control on basin architecture

  9. The Arctic lithosphere: an overview

    Science.gov (United States)

    Drachev, S.; Pease, V.; Stephenson, R.

    2012-04-01

    The Arctic is comprised of three deepwater oceanic basins, the Norwegian-Greenland, Eurasia, and Amerasia basins, surrounded by continental masses of the Achaean to Early Proterozoic North American, Baltica and Siberian cratons and intervening Neoproterozoic and Phanerozoic fold belts. Though the tectonic history of the Arctic continental realm spans almost three billions of years, the formation of the Arctic began with the creation of Pangaea-II supercontinent at end of Permian epoch. Between 250 and 150 Ma the Proto-Arctic was represented by the Anyui Ocean, or Angayuchum Sea - a Paleo-Pacific embayment into Pangaea II. During the Mesozoic Pangaea II was destroyed and the Anyi Ocean was isolated from the Paleo-Pacific, finally leading to the separation of Arctic Alaska-Chukchi Microcontinent from the North American side of Laurasia; the collision of this microplate with the Siberian margin occurred at ca. 125 Ma in association with the opening of the Canada Basin. The final stage of the Arctic formation took place in the Cenozoic, and was related to the propagation of the divergent Atlantic lithospheric plate boundary between North America and Baltica with the separation of the Lomonosov continental sliver from the Eurasian margin and opening of the Eurasia oceanic basin between 56 and 0 Ma. The present-day Arctic, especially its shelves and oceanic basins, is one of the least studied places on the Earth. Though we know the geology of the surrounding continental masses, there are still many questions remaining about major lithospheric divides beneath the Arctic seas, such as: • Where are the plate boundaries associated with the Amerasia Basin? • How and when did the Canada Basin open? • What was the pre-drift setting of the Chukchi Borderland? • Which tectonic processes formed the East Siberian shelves? • How and when did the major ridges in the Amerasia Basin form? • Where are the Early Tertiary plate boundaries in the Arctic? • What is the

  10. Sea Level, Land Motion, and the Anomalous Tide at Churchill, Hudson Bay

    Science.gov (United States)

    Ray, R. D.

    2015-12-01

    The importance of the tide gauge at Churchill, Manitoba, cannot be overstated. It is the only permanently operating tide gauge in the central Canadian Arctic, and it sits on a prime spot for monitoring the mantle's rebound from the Laurentide ice loss. Yet interpretation of the sea-level time series at Churchill has long been problematic, going back even to early work by Gutenberg in the 1940s. The long-term relative sea-level rates are inconsistent: approximately -4, -19, -5 ± 1 mm/y for the periods 1940-1970, 1970-1990, 1990-2014 respectively. Annual mean high water (MHW) and mean low water (MLW) reflect these trends until around 1990, after which MLW leveled off and is now nearly unchanging. Slightly later, around 2000, the semidiurnal tides became very anomalous, with falling amplitudes and slightly increasing phase lags. The amplitude of M2 was approximately 154 cm before 2000; it dropped to about 146 cm by 2010 and reached an all-time low of 142 cm in 2014. Satellite altimeter estimates of the tide in this region, although challenging because of seasonal ice cover, show no comparable M2 changes, so the tidal changes must be localized to the near vicinity of the gauge (or to the gauge itself if caused by a malfunction). On the other hand, altimetry confirms the post-1992 Churchill measurements of mean sea level, thanks to the long time series of land motion measurements obtained at GPS station CHUR, which gives a vertical uplift of 10.1 mm/y. Combining satellite altimeter data with the Churchill tide-gauge data gives an implied vertical crustal rate of about 9.0 ± 0.8 mm/y, in reasonable agreement with the GPS. In summary, we have still anomalous MSL measurements at the Churchill gauge for the intermediate 1970-1990 era, and very anomalous tidal measurements since 2000, but we have apparently quite reliable MSL rates since 1990.

  11. Seasonal dynamics of methane emissions from a subarctic fen in the Hudson Bay Lowlands

    Directory of Open Access Journals (Sweden)

    K. L. Hanis

    2013-03-01

    Full Text Available Ecosystem-scale methane (CH4 flux (FCH4 over a subarctic fen at Churchill, Manitoba, Canada was measured to understand the magnitude of emissions during spring and fall shoulder seasons, and the growing season in relation to physical and biological conditions. FCH4 was measured using eddy covariance with a closed-path analyzer in four years (2008–2011. Cumulative measured annual FCH4 (shoulder plus growing seasons ranged from 3.0 to 9.6 g CH4 m−2 yr−1 among the four study years, with a mean of 6.5 to 7.1 g CH4 m−2 yr−1 depending upon gap-filling method. Soil temperatures to depths of 50 cm and air temperature were highly correlated with FCH4, with near surface soil temperature at 5 cm most correlated across spring, fall, and the whole season. The response of FCH4 to soil temperature at the 5 cm depth and air temperature was more than double in spring to that of fall. Emission episodes were generally not observed during spring thaw. Growing season emissions also depended upon soil and air temperatures but water table also exerted influence with FCH4 highest when water was 2–13 cm below and least when it was at or above the mean peat surface.

  12. Estimation of arboreal lichen biomass available to woodland caribou in Hudson Bay lowland black spruce sites

    Directory of Open Access Journals (Sweden)

    Sarah K. Proceviat

    2003-04-01

    Full Text Available An arboreal lichen index to be utilized in assessing woodland caribou habitat throughout northeastern Ontario was developed. The "index" was comprised of 5 classes, which differentiated arboreal lichen biomass on black spruce trees, ranging from maximal quantities of arboreal lichen (class 5 to minimal amounts of arboreal lichen (class 1. This arboreal lichen index was subsequently used to estimate the biomass of arboreal lichen available to woodland caribou on lowland black spruce sites ranging in age from 1 year to 150 years post-harvest. A total of 39 sites were assessed and significant differences in arboreal lichen biomass were found, with a positive linear relationship between arboreal lichen biomass and forest age. It is proposed that the index be utilized by government and industry as a means of assessing the suitability of lowland black spruce habitat for woodland caribou in this region.

  13. Lithospheric deformation in the Canadian Appalachians: evidence from shear wave splitting

    Science.gov (United States)

    Gilligan, Amy; Bastow, Ian D.; Watson, Emma; Darbyshire, Fiona A.; Levin, Vadim; Menke, William; Lane, Victoria; Hawthorn, David; Boyce, Alistair; Liddell, Mitchell V.; Petrescu, Laura

    2016-08-01

    Plate-scale deformation is expected to impart seismic anisotropic fabrics on the lithosphere. Determination of the fast shear wave orientation (φ) and the delay time between the fast and slow split shear waves (δt) via SKS splitting can help place spatial and temporal constraints on lithospheric deformation. The Canadian Appalachians experienced multiple episodes of deformation during the Phanerozoic: accretionary collisions during the Palaeozoic prior to the collision between Laurentia and Gondwana, and rifting related to the Mesozoic opening of the North Atlantic. However, the extent to which extensional events have overprinted older orogenic trends is uncertain. We address this issue through measurements of seismic anisotropy beneath the Canadian Appalachians, computing shear wave splitting parameters (φ, δt) for new and existing seismic stations in Nova Scotia and New Brunswick. Average δt values of 1.2 s, relatively short length scale (≥100 km) splitting parameter variations, and a lack of correlation with absolute plate motion direction and mantle flow models, demonstrate that fossil lithospheric anisotropic fabrics dominate our results. Most fast directions parallel Appalachian orogenic trends observed at the surface, while δt values point towards coherent deformation of the crust and mantle lithosphere. Mesozoic rifting had minimal impact on our study area, except locally within the Bay of Fundy and in southern Nova Scotia, where fast directions are subparallel to the opening direction of Mesozoic rifting; associated δt values of >1 s require an anisotropic layer that spans both the crust and mantle, meaning the formation of the Bay of Fundy was not merely a thin-skinned tectonic event.

  14. Water in the Cratonic Mantle Lithosphere

    Science.gov (United States)

    Peslier, A. H.

    2016-01-01

    The fact that Archean and Proterozoic cratons are underlain by the thickest (>200 km) lithosphere on Earth has always puzzled scientists because the dynamic convection of the surrounding asthenosphere would be expected to delaminate and erode these mantle lithospheric "keels" over time. Although density and temperature of the cratonic lithosphere certainly play a role in its strength and longevity, the role of water has only been recently addressed with data on actual mantle samples. Water in mantle lithologies (primarily peridotites and pyroxenites) is mainly stored in nominally anhydrous minerals (olivine, pyroxene, garnet) where it is incorporated as hydrogen bonded to structural oxygen in lattice defects. The property of hydrolytic weakening of olivine [4] has generated the hypothesis that olivine, the main mineral of the upper mantle, may be dehydrated in cratonic mantle lithospheres, contributing to its strength. This presentation will review the distribution of water concentrations in four cratonic lithospheres. The distribution of water contents in olivine from peridotite xenoliths found in kimberlites is different in each craton (Figure 1). The range of water contents of olivine, pyroxene and garnet at each xenolith location appears linked to local metasomatic events, some of which occurred later then the Archean and Proterozoic when these peridotites initially formed via melting. Although the low olivine water contents ( 6 GPa at the base of the Kaapvaal cratonic lithosphere may contribute to its strength, and prevent its delamination, the wide range of those from Siberian xenoliths is not compatible with providing a high enough viscosity contrast with the asthenophere. The water content in olivine inclusions from Siberian diamonds, on the other hand, have systematically low water contents (water contents. The olivine inclusions, however, may have been protected from metasomatism by their host diamond and record the overall low olivine water content of

  15. Rock Engineering Design by Xiating Feng and John A Hudson

    Institute of Scientific and Technical Information of China (English)

    E.T.Brown

    2012-01-01

    This highly original and innovative book is the outcome of the work of the Commission on Rock Engineering Design Methodology of the International Society for Rock Mechanics (ISRM) in the period 2007-2011.The work of the Commission was managed by the authors,Professor John A Hudson,ISRM President for 2007-2011,and Professor Xiating Feng,ISRM President for 2011-2015,in association with the Chinese Society for Rock Mechanics and Engineering.Recently,this reviewer (2011) has argued that the work of its Commissions has been among the major achievements of the ISRM in the 50 years since its foundation in 1962.This book adds to that impressive record of achievement.

  16. Intraplate orogenesis within accreted and scarred lithosphere: Example of the Eurekan Orogeny, Ellesmere Island

    Science.gov (United States)

    Heron, Philip J.; Pysklywec, Russell N.; Stephenson, Randell

    2015-11-01

    The Eurekan Orogeny, which created much of the high topography of Ellesmere Island and adjacent Greenland, exhibits a crustal architecture linked to intraplate orogenesis in the Cenozoic. It is generally considered that the rotation of Greenland in the Eocene (related to sedimentary basin formation in Baffin Bay) produced compressional intraplate tectonics. Deformation in the region is notably localized to the Central Ellesmere Domain and the Northern Ellesmere Domain. However, an important tectonic feature of Ellesmere Island is the Hazen Stable Block, which shows horizontal Paleogene Eureka Sound group strata overlying Palaeozoic-age steeply dipping beds. The intense deformation in the Hazen Stable Block is related to continental orogenesis in the Late Silurian-Devonian. Therefore, the Hazen Stable Block is thought to have undergone only minor Eurekan-age (55-35 Ma) deformation, while surrounding (highly deformed) units may have re-activated faults from Paleocene continental amalgamation. Here, high-resolution thermal-mechanical numerical experiments are implemented to explore lithospheric deformation (related to continental shortening) for a range of tectonic scenarios, namely, the presence of inherent deformational "scars" and rheologically strengthened crust/mantle lithosphere (both due to ancient continental accretion). This study marks the first geodynamic excursion to this high Arctic region, and we present some of the first interpretations of the development of Eurekan-age lithospheric evolution. Our results show that a rheologically strong Hazen Stable Block crust produces tectonics similar to the Eurekan Orogeny. Furthermore, lithospheric scars can generate more localized deformation and topography than rheological changes to the lithosphere and may offer a new interpretation on enigmatic intraplate tectonics.

  17. 2012 FEMA Topographic Lidar: Hudson-Hoosic and Deerfield Watersheds, Massachusetts

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Light Detection and Ranging (LiDAR) dataset is a survey of the Hudson-Hoosic and Deerfield project area. The entire survey area for Massachusetts is...

  18. Sensitivity of Coastal Environments and Wildlife to Spilled Oil: Hudson River: INVERT (Invertebrate Polygons)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive biological resource data for marine and estuarine invertebrate species for the Hudson River. Vector polygons in this data set...

  19. Environmental Sensitivity Index (ESI) Atlas: Hudson River, maps and geographic information systems data (NODC Accession 0014791)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set comprises the Environmental Sensitivity Index (ESI) data for the Hudson River from 1942 to 2005. ESI data characterize estuarine environments and...

  20. Hudson River Sub_Bottom Profile Data - Raw SEG-Y Files (*.sgy)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Hudson River Estuary Shallow Water Surveys. Subbottom data was collected November 5 to December 15, 2009, in the estuary north from Saugerties to Troy. Data...

  1. Sensitivity of Coastal Environments and Wildlife to Spilled Oil: Hudson River: MGT (Management Area Polygons)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive human-use data for regional and state parks, historic sites, marine sanctuaries, and other managed areas for the Hudson River....

  2. 2012 FEMA Topographic Lidar: Hudson-Hoosic and Deerfield Watersheds, Massachusetts

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Light Detection and Ranging (LiDAR) dataset is a survey of the Hudson-Hoosic and Deerfield project area. The entire survey area for Massachusetts is...

  3. Sensitivity of Coastal Environments and Wildlife to Spilled Oil: Hudson River: SENSITIV (Sensitive Area Points)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains human-use resource data for sensitive areas along the Hudson River. Vector points in this data set represent sensitive areas. This data set...

  4. Sensitivity of Coastal Environments and Wildlife to Spilled Oil: Hudson River: FISH (Fish Polygons)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive biological resource data for marine, estuarine, anadromous, and freshwater fish species in the Hudson River. Vector polygons in this...

  5. Sensitivity of Coastal Environments and Wildlife to Spilled Oil: Hudson River: HYDRO (Hydrography Lines and Polygons)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains vector lines and polygons representing coastal hydrography used in the creation of the Environmental Sensitivity Index (ESI) for the Hudson...

  6. Magnetic mineralogy of the Mercurian lithosphere

    Science.gov (United States)

    Strauss, B. E.; Feinberg, J. M.; Johnson, C. L.

    2016-11-01

    Mercury and Earth are the only inner solar system planets with active, internally generated dynamo magnetic fields. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission recently detected magnetic fields on Mercury that are consistent with lithospheric magnetization. We investigate the physical and chemical environment of Mercury's lithosphere, past and present, to establish the conditions under which magnetization may have been acquired and modified. Three factors are particularly crucial to the determination of crustal composition and iron mineralogy: redox conditions in the planet's crust and mantle, the iron content of the lithosphere, and, for any remanent magnetization, the temperature profile of the lithosphere and its evolution over time. We explore potential mechanisms for remanence acquisition and alteration on Mercury, whose surface environment is both hot and highly reducing. The long-term thermal history of Mercury's crust plays an important role in the longevity of any remanent crustal magnetization, which may be subject to remagnetization through thermal, viscous, and shock mechanisms. This thermal and compositional framework is used both to constrain plausible candidate minerals that could carry magnetic remanence on Mercury and to evaluate their capacity to acquire and retain sufficient magnetization to be detectable from satellite orbit. We propose that iron metal and its alloys are likely to be the dominant contributors to induced and remanent magnetization in Mercury's lithosphere, with additional contributions from iron silicides, sulfides, and carbides.

  7. Three-Dimensional Scale-Model Tank Experiment of the Hudson Canyon Region

    Science.gov (United States)

    2014-09-30

    Three-Dimensional Scale-Model Tank Experiment of the Hudson Canyon Region Jason D. Sagers Applied Research Laboratories at The University of...planning for future experiments in ocean environments with slopes and canyons . APPROACH The development of fully 3D numerical acoustic propagation models...Experiment of the Hudson Canyon Region 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER

  8. Evaluation of dredged material proposed for ocean disposal from Hudson River, New York

    Energy Technology Data Exchange (ETDEWEB)

    Gardiner, W.W.; Barrows, E.S.; Antrim, L.D.; Gruendell, B.D.; Word, J.Q.; Tokos, J.J.S. [Battelle/Marine Sciences Lab., Sequim, WA (United States)

    1996-09-01

    The Hudson River (Federal Project No. 41) was one of seven waterways that the U.S. Army Corps of Engineers-New York District (USACE-NYD) requested the Battelle Marine Sciences Laboratory (MSL) to sample and evaluate for dredging and disposal in March 1994. Sediment samples were collected from the Hudson River. Tests and analyses were conducted on Hudson River sediment core samples. The evaluation of proposed dredged material from the Hudson River included bulk sediment chemical analyses, chemical analyses of site water and elutriate, water-column and benthic acute toxicity tests, and bioaccumulation studies. Individual sediment core samples collected from Hudson River were analyzed for grain size, moisture content, and total organic carbon (TOC). A composite sediment sample, representing the entire area proposed for dredging, was analyzed for bulk density, specific gravity, metals, chlorinated pesticides, polychlorinated biphenyl (PCB) congeners, polynuclear aromatic hydrocarbons (PAH), and 1,4-dichlorobenzene. Site water and elutriate water, prepared from the suspended-particulate phase (SPP) of Hudson River sediment, were analyzed for metals, pesticides, and PCBS. Water-column or SPP toxicity tests were performed with three species. Benthic acute toxicity tests were performed. Bioaccumulation tests were also conducted.

  9. Lithospheric stress patterns: A global view

    Science.gov (United States)

    Zoback, Mary Lou; Burke, Kevin

    The present-day lithospheric stress state is the result of a variety of forces that act on and within the tectonic plates forming the Iithosphere. Knowledge of this stress state provides important constraints on forces acting at a variety of scales and, hence, helps to solve scientific problems of interest to a wide spectrum of scientists and engineers.Six years of effort by scientists from all over the world (listed at end of article) brought together under the International Lithosphere Program (ILP) of the joint International Union of Geodesy and Geophysics/International Union of Geological Sciences (IUGG/IUGS) Interunion Commission on the Lithosphere culminated in the July 1992 publication of the World Stress Map and nineteen accompanying research papers in a special issue of the Journal of Geophysical Research-Solid Earth (volume 87, number B8). Figure 1 shows a reduced version of the published 1:40,000,000 color map.

  10. Lithospheric structure in the Pacific geoid

    Science.gov (United States)

    Marsh, B. D.; Hinojosa, J. H.

    1985-01-01

    The high degree and order SEASAT geoid in the central Pacific correlates closely with the structure of the cooling lithosphere. Relative changes in plate age across major fracture zones in relatively young seafloor frame the east-west trending pattern formed by the geoid anomalies. The field removal in bathymetry corresponds to removal of some of the low degree and order geoidal components, the step like structure across fracture zones is also removed. The regional thermal subsidence was removed from the bathymetry by subtracting a mean subsidence surface from the observed bathymetry. This produces a residual bathymetry map analogous to the usual residual depth anomaly maps. The residual bathymetry obtained in this way contains shallow depths for young seafloor, and larger depths for older seafloor, thus retaining the structure of the lithosphere while removing the subsidence of the lithosphere.

  11. BASE Flexible Array Preliminary Lithospheric Structure Analysis

    Science.gov (United States)

    Yeck, W. L.; Sheehan, A. F.; Anderson, M. L.; Siddoway, C. S.; Erslev, E.; Harder, S. H.; Miller, K. C.

    2009-12-01

    The Bighorns Arch Seismic Experiment (BASE) is a Flexible Array experiment integrated with EarthScope. The goal of BASE is to develop a better understanding of how basement-involved foreland arches form and what their link is to plate tectonic processes. To achieve this goal, the crustal structure under the Bighorn Mountain range, Bighorn Basin, and Powder River Basin of northern Wyoming and southern Montana are investigated through the deployment of 35 broadband seismometers, 200 short period seismometers, 1600 “Texan” instruments using active sources and 800 “Texan” instruments monitoring passive sources, together with field structural analysis of brittle structures. The novel combination of these approaches and anticipated simultaneous data inversion will give a detailed structural crustal image of the Bighorn region at all levels of the crust. Four models have been proposed for the formation of the Bighorn foreland arch: subhorizontal detachment within the crust, lithospheric buckling, pure shear lithospheric thickening, and fault blocks defined by lithosphere-penetrating thrust faults. During the summer of 2009, we deployed 35 broadband instruments, which have already recorded several magnitude 7+ teleseismic events. Through P wave receiver function analysis of these 35 stations folded in with many EarthScope Transportable Array stations in the region, we present a preliminary map of the Mohorovicic discontinuity. This crustal map is our first test of how the unique Moho geometries predicted by the four hypothesized models of basement involved arches fit seismic observations for the Bighorn Mountains. In addition, shear-wave splitting analysis for our first few recorded teleseisms helps us determine if strong lithospheric deformation is preserved under the range. These analyses help lead us to our final goal, a complete 4D (3D spatial plus temporal) lithospheric-scale model of arch formation which will advance our understanding of the mechanisms

  12. The lithosphere thermal structure of the Southeast Asia: constrained by Vs data

    Science.gov (United States)

    Chuanhai, Yu; Xiaobin, Shi; Qunshu, Tang; Xiaoqiu, Yang

    2016-04-01

    The Southeast Asia, located in the southeastern part of the Eurasian Plate, comprises a complex collage of continental fragments, volcanic arcs, suture zones and marginal oceanic basins, and is surrounded by tectonically active margins which exhibit intense seismicity and volcanism. As we all know, the tectonic evolution is closely related to the deep thermal structure state. Therefore, an accurate estimation of lithosphere thermal structure and lithosphere thickness is important in extracting information on tectonics and geodynamics. Though the thermal regime could be calculated with the observed surface heat flow, there are many uncertainties in the calculated deep thermal state. In this study, we calculated the deep lithosphere thermal structure of Southeast Asia regions by employing an empirical relationship between Vs and temperature, from the calculated temperature-depth profiles, we can identify the base of the thermal lithosphere. The results show that the temperature contours at 80km depth is about 200-300°C higher in the rifted basins and oceanic basins such as Andaman Sea, Thailand Bay, Thailand Rift Basin, South China Sea than in the plateaus and subduction zones such as Khorat Plateau, Sumatra Island and Philippine Trench regions. Generally, the thermal state indicated by the temperature contours at 80 km depth is in agreement with those suggested by the observed surface heat flow. The temperature at 100 km and 200 km depth in Southeast Asia regions is 1450-1500°C and 1650-1780°C which suggest that the study regions might have a higher thermal state than other regions. Our results also show that the estimated thickness of the lithosphere are 85-95 km in the regions of Subduction and collision regions surrounding the study area such as Java trench system, Sumatra trench system, Indo-Asian collision suture zone, Taiwan orogenic belt, Luzon Island, Celebes Island and Northeast of Borneo and becomes smaller toward the South China Sea. In the South China

  13. Lithospheric thinning beneath rifted regions of Southern California.

    Science.gov (United States)

    Lekic, Vedran; French, Scott W; Fischer, Karen M

    2011-11-11

    The stretching and break-up of tectonic plates by rifting control the evolution of continents and oceans, but the processes by which lithosphere deforms and accommodates strain during rifting remain enigmatic. Using scattering of teleseismic shear waves beneath rifted zones and adjacent areas in Southern California, we resolve the lithosphere-asthenosphere boundary and lithospheric thickness variations to directly constrain this deformation. Substantial and laterally abrupt lithospheric thinning beneath rifted regions suggests efficient strain localization. In the Salton Trough, either the mantle lithosphere has experienced more thinning than the crust, or large volumes of new lithosphere have been created. Lack of a systematic offset between surface and deep lithospheric deformation rules out simple shear along throughgoing unidirectional shallow-dipping shear zones, but is consistent with symmetric extension of the lithosphere.

  14. Sea-Level Rise Impacts on Hudson River Marshes

    Science.gov (United States)

    Hooks, A.; Nitsche, F. O.

    2015-12-01

    The response of tidal marshes to increasing sea-level rise is uncertain. Tidal marshes can adapt to rising sea levels through vertical accretion and inland migration. Yet tidal marshes are vulnerable to submergence if the rate of sea-level rise exceeds the rate of accretion and if inland migration is limited by natural features or development. We studied how Piermont and Iona Island Marsh, two tidal marshes on the Hudson River, New York, would be affected by sea-level rise of 0.5m, 1m, and 1.5m by 2100. This study was based on the 2011-2012 Coastal New York LiDAR survey. Using GIS we mapped sea-level rise projections accounting for accretion rates and calculated the submerged area of the marsh. Based on the Hudson River National Estuarine Research Reserve Vegetation 2005 dataset, we studied how elevation zones based on vegetation distributions would change. To evaluate the potential for inland migration, we assessed land cover around each marsh using the National Land Cover Database 2011 Land Cover dataset and examined the slope beyond the marsh boundaries. With an accretion rate of 0.29cm/year and 0.5m of sea-level rise by 2100, Piermont Marsh would be mostly unchanged. With 1.5m of sea-level rise, 86% of Piermont Marsh would be flooded. For Iona Island Marsh with an accretion rate of 0.78cm/year, sea-level rise of 0.5m by 2100 would result in a 4% expansion while 1.5m sea-level rise would cause inundation of 17% of the marsh. The results indicate that Piermont and Iona Island Marsh may be able to survive rates of sea-level rise such as 0.5m by 2100 through vertical accretion. At rates of sea-level rise like 1.5m by 2100, vertical accretion cannot match sea-level rise, submerging parts of the marshes. High elevations and steep slopes limit Piermont and Iona Island Marsh's ability to migrate inland. Understanding the impacts of sea-level rise on Piermont and Iona Island Marsh allows for long-term planning and could motivate marsh conservation programs.

  15. Lithosphere Response to Intracratonic Rifting: Examples from Europe and Siberia

    DEFF Research Database (Denmark)

    Artemieva, I. M.; Thybo, H.; Herceg, M.;

    2012-01-01

    . The pattern of is controlled by the pre-existing tectonic setting and the intensity of lithosphere-mantle interaction. The results are summarized in a series of maps of lateral variations in lithosphere structure, including the depth to the LAB and compositional heterogeneity of the lithosphere as reflected...

  16. Volcanism, Earth Degassing and Replenished Lithosphere Mantle

    Science.gov (United States)

    Bailey, D. K.

    1980-07-01

    Volcanism that pierces plate interiors is characteristically rich in alkalis and volatiles, and its cause and persistence are essentially expressions of the Earth's outgassing. The general balance of mobile elements (such as H, C, F and Cl) rules out recycling of sea floor, hydrosphere, sediments or atmosphere: furthermore, it is not in accord with accepted planet degassing budgets. The typical eruptive mode of volatile-rich magmatism means that the observed regional chemical variations, and even differences between adjacent volcanoes, must largely reflect source heterogeneity. In a broader context, this magmatism is also at odds with a concept of continental crust underlain by strongly depleted (refractory) mantle. Repetition of activity along crustal zones of weakness shows that the lithosphere mantle (a) is structurally complex and (b) still holds continuing (or continual) rich reserves of mobile elements. Unbroken lithosphere muffles the evolutionary escape of volatiles from the deep mantle: any lesion that appears then offers easy escape channels, whereby volatiles are drained from a large mantle region and funnelled through the plate. Horizontal movement of thick continental lithosphere releases volatiles from deep sources, imparting some of the special chemical characteristics of the stable continental magmatism. Present evidence requires consideration of the continental lithosphere as a site of primordial heterogeneity that has been accentuated rather than diminished by geological processes.

  17. The lithospheric mantle below southern West Greenland

    DEFF Research Database (Denmark)

    Sand, Karina Krarup; Waight, Tod Earle; Pearson, D. Graham

    2009-01-01

    Geothermobarometry of primarily garnet lherzolitic xenoliths from several localities in southern West Greenland is applied to address the diamond potential, pressure and temperature distribution and the stratigraphy of the subcontinental lithospheric mantle ~600 Ma ago. The samples are from kimbe...... into the reworked Archean North of the Naqssugtoqidian deformation front....

  18. The lithosphere structure of Northeast China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xingzhou; YANG Baojun; WU Fuyuan; LIU Guoxing

    2007-01-01

    The lithosphere of northeastern China is composed of the Erguna, Xingan, Songnen, Jiamusi blocks and Mesozoic Wandashan accretionary complex from west to east. Nd isotope model ages indicate that the Xingan and Songnen blocks have the same Nd model ages ranging from 500 to 1 000 Ma. These are obviously younger than those of the Jiamusi block (1 500-2 000 Ma) and the Erguna block (1 500-1 700 Ma), reflecting the different evolutions of indi- vidual blocks in the early times. Geochemical tracing analysis shows that the Nd model ages of Paleozoic supercrustal rocks in the four blocks are dominantly Mesoproterozoic, while those of Mesozoic granites are mainly Neoproterozoic. It is shown that the crust ages of the region are characterized by being younger in the lower part and older in the upper part. The Os isotope analysis also indicates that the lithosphere mantle of the region is characteristic of a younger age. The P-wave velocities of the region show more complicated struc- tures in lithosphere and asthenosphere. First of all, notably different from traditional concept of the seismic lithosphere, the low velocity zone of the lithosphere beneath the region has no persistent and continuous top interface which is highly varied in depth and intersected with the high velocity layers, forming sharp velocity discontinuities beneath major tectonic belts, even up to the Moho beneath some tectonic units. But the bottom interface of the low velocity zone is relatively per- sistent, occurring at a depth of 230-240 km. Another feature is that the lithosphere is characterized by an "overpass type" velocity structure vertically, in which the contoured velocity is distributed in the NE trending within the crust, in a nearly NS trending in the lithosphere mantle from a depth of 45 to 90 km, in a nearly EW trending in the upper part of the asthe- nosphere from 90 to 170 km and in a ring-like distribution with a diameter of about 300 km in the lower part of the asthenosphere from

  19. Galveston Bay

    Science.gov (United States)

    Handley, Lawrence R.; Spear, Kathryn A.; Eleonor Taylor,; Thatcher, Cindy

    2011-01-01

    The Galveston Bay estuary is located on the upper Texas Gulf coast (Lester and Gonzalez, 2002). It is composed of four major sub-bays—Galveston, Trinity, East, and West Bays. It is Texas’ largest estuary on the Gulf Coast with a total area of 155,399 hectares (384,000 acres) and 1,885 km (1,171 miles) of shoreline (Burgan and Engle, 2006). The volume of the bay has increased over the past 50 years due to subsidence, dredging, and sea level rise. Outside of ship channels, the maximum depth is only 3.7 m (12 ft), with the average depth ranging from 1.2 m (4 ft) to 2.4 m (8 ft)— even shallower in areas with widespread oyster reefs (Lester and Gonzalez, 2002). The tidal range is less than 0.9 m (3 ft), but water levels and circulation are highly influenced by wind. The estuary was formed in a drowned river delta, and its bayous were once channels of the Brazos and Trinity Rivers. Today, the watersheds surrounding the Trinity and San Jacinto Rivers, along with many other smaller bayous, feed into the bay. The entire Galveston Bay watershed is 85,470 km2 (33,000 miles2 ) large (Figure 1). Galveston Island, a 5,000 year old sand bar that lies at the western edge of the bay’s opening into the Gulf of Mexico, impedes the freshwater flow of the Trinity and San Jacinto Rivers into the Gulf, the majority of which comes from the Trinity. The Bolivar Peninsula lies at the eastern edge of the bay’s opening into the Gulf. Water flows into the Gulf at Bolivar Roads, 1 U.S. Geological Survey National Wetlands Research Center, 700 Cajundome Blvd., Lafayette, LA 70506 2 Harte Research Institute for Gulf of Mexico Studies, Texas A&M University - Corpus Christi, 6300 Ocean Drive, Unit 5869, Corpus Christi, Texas 78412 2 Galveston Pass, between Galveston Island and Bolivar Peninsula, and at San Luis Pass, between the western side of Galveston Island and Follets Island.

  20. Geochemical evidence for formation of the Bay of Islands ophiolite above a subduction zone

    Science.gov (United States)

    Elthon, Don

    1991-11-01

    The existence of a substantial tantalum depletion in Bay of Islands (BOI) magmas is reported. These depletions, together with that of niobium shown by Jenner et al., is characteristic of magmas erupted above subduction zones but not at midocean ridges. This indicates that the BOI is not a good analog for lithosphere formed at midocean ridges.

  1. Electrical conductivity in the precambrian lithosphere of western canada

    Science.gov (United States)

    Boerner; Kurtz; Craven; Ross; Jones; Davis

    1999-01-29

    The subcrustal lithosphere underlying the southern Archean Churchill Province (ACP) in western Canada is at least one order of magnitude more electrically conductive than the lithosphere beneath adjacent Paleoproterozoic crust. The measured electrical properties of the lithosphere underlying most of the Paleoproterozoic crust can be explained by the conductivity of olivine. Mantle xenolith and geological mapping evidence indicate that the lithosphere beneath the southern ACP was substantially modified as a result of being trapped between two nearly synchronous Paleoproterozoic subduction zones. Tectonically induced metasomatism thus may have enhanced the subcrustal lithosphere conductivity of the southern ACP.

  2. Bathymetry of the Hudson Shelf Valley (12-m resolution Esri binary grid and 32-bit GeoTIFF, Mercator, WGS 84)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The Hudson Shelf Valley is the submerged seaward extension of the ancestral Hudson River drainage system and is the largest physiographic feature on the Middle...

  3. Tsunami hazard assessment in the Hudson River Estuary based on dynamic tsunami-tide simulations

    Science.gov (United States)

    Shelby, Michael; Grilli, Stéphan T.; Grilli, Annette R.

    2016-12-01

    This work is part of a tsunami inundation mapping activity carried out along the US East Coast since 2010, under the auspice of the National Tsunami Hazard Mitigation program (NTHMP). The US East Coast features two main estuaries with significant tidal forcing, which are bordered by numerous critical facilities (power plants, major harbors,...) as well as densely built low-level areas: Chesapeake Bay and the Hudson River Estuary (HRE). HRE is the object of this work, with specific focus on assessing tsunami hazard in Manhattan, the Hudson and East River areas. In the NTHMP work, inundation maps are computed as envelopes of maximum surface elevation along the coast and inland, by simulating the impact of selected probable maximum tsunamis (PMT) in the Atlantic ocean margin and basin. At present, such simulations assume a static reference level near shore equal to the local mean high water (MHW) level. Here, instead we simulate maximum inundation in the HRE resulting from dynamic interactions between the incident PMTs and a tide, which is calibrated to achieve MHW at its maximum level. To identify conditions leading to maximum tsunami inundation, each PMT is simulated for four different phases of the tide and results are compared to those obtained for a static reference level. We first separately simulate the tide and the three PMTs that were found to be most significant for the HRE. These are caused by: (1) a flank collapse of the Cumbre Vieja Volcano (CVV) in the Canary Islands (with a 80 km3 volume representing the most likely extreme scenario); (2) an M9 coseismic source in the Puerto Rico Trench (PRT); and (3) a large submarine mass failure (SMF) in the Hudson River canyon of parameters similar to the 165 km3 historical Currituck slide, which is used as a local proxy for the maximum possible SMF. Simulations are performed with the nonlinear and dispersive long wave model FUNWAVE-TVD, in a series of nested grids of increasing resolution towards the coast, by one

  4. The Bible and mission in faith perspective: J.Hudson Taylor and the early China Inland Mission

    NARCIS (Netherlands)

    Wigram, C.E.M.

    2007-01-01

    The thesis 'The Bible and Mission in Faith Perspective: J.Hudson Taylor and the Early China Inland Mission' by Christopher E.M. Wigram analysis the hermeneutical assumptions that underlay Hudson Taylor's approach to biblical interpretation, and the significance of his approach for the mission which

  5. Flexure and rheology of Pacific oceanic lithosphere

    Science.gov (United States)

    Hunter, Johnny; Watts, Tony

    2016-04-01

    The idea of a rigid lithosphere that supports loads through flexural isostasy was first postulated in the late 19th century. Since then, there has been much effort to investigate the spatial and temporal variation of the lithosphere's flexural rigidity, and to understand how these variations are linked to its rheology. We have used flexural modelling to first re-assess the variation in the rigidity of oceanic lithosphere with its age at the time of loading, and then to constrain mantle rheology by testing the predictions of laboratory-derived flow laws. A broken elastic plate model was used to model trench-normal, ensemble-averaged profiles of satellite-derived gravity at the trench-outer rise system of circum-Pacific subduction zones, where an inverse procedure was used to find the best-fit Te and loading conditions. The results show a first-order increase in Te with plate age, which is best fit by the depth to the 400 ± 35°C plate-cooling isotherm. Fits to the observed gravity are significantly improved by an elastic plate that weakens landward of the outer rise, which suggests that bending-induced plate weakening is a ubiquitous feature of circum-Pacific subduction zones. Two methods were used to constrain mantle rheology. In the first, the Te derived by modelling flexural observations was compared to the Te predicted by laboratory-derived yield strength envelopes. In the second, flexural observations were modelled using elastic-plastic plates with laboratory-derived, depth-dependent yield strength. The results show that flow laws for low-temperature plasticity of dry olivine provide a good fit to the observations at circum-Pacific subduction zones, but are much too strong to fit observations of flexure in the Hawaiian Islands region. We suggest that this discrepancy can be explained by differences in the timescale of loading combined with moderate thermal rejuvenation of the Hawaiian lithosphere.

  6. Pn Anisotropy in Old Pacific Lithosphere

    Science.gov (United States)

    Shintaku, N.; Forsyth, D. W.; Weeraratne, D. S.

    2012-12-01

    Pn is the high frequency, scattered P phase guided for great distances within old oceanic lithosphere, which is also known as Po. Two arrays of ocean bottom seismometers were deployed on old (~150-160Ma) seafloor in the northwestern Pacific south of Shatsky Rise for the PLATE experiment (Pacific Lithosphere Anisotropy and Thickness Experiment). More than 5 or 6 Pn phases per day are recorded on these ocean bottom seismometers generated by earthquakes in western Pacific subduction zones during one year of deployment; we used 512 Pn phases from earthquakes with locations reported in routine bulletins. Each array was deployed on a separate limb of a magnetic bight, formed at a ridge-ridge-ridge triple junction. The spreading rates on both limbs were ~ 70mm/yr, and the current plate motion direction in the hotspot coordinate frame is WNW. Our overall goal is to identify the pattern of fossil anisotropy in the old oceanic lithosphere, and dynamically generated anisotropy in underlying asthenosphere using both body waves and surface waves. Using high frequency waves (3-10 Hz), we look at variations of Pn velocities as a function of backazimuth. In the western array, where the spreading direction is parallel to the absolute plate motion direction, we find clear Pn anisotropy with velocities varying from ~8.5 km/s in the spreading direction to ~ 8.0 km/s perpendicular to the spreading direction. However, in the eastern array where the fossil spreading direction is perpendicular to the current plate motion, the velocity variations as a function of backazimuth are much less obvious. This may be due to heterogeneity of anisotropy in the oceanic lithosphere, with the fast direction changing from the fossil direction at shallow levels to the absolute direction at greater depth.

  7. Gravity, geoid and the oceanic lithosphere

    Science.gov (United States)

    Watts, A. B.

    1985-01-01

    Plate tectonics and its contribution to progress in studies of the Earth's gravitational field is discussed. In acquisition, the development of forced feedback accelerometers, satellite navigation, and satellite radar altimetry significantly improved the accuracy and coverage of gravity data over the oceans. In interpretation, gravity and geoid anomalies are used to determine information on the thermal and mechanical properties of the oceanic lithosphere and the forces that drive plate motions.

  8. A statistical forecast model for Tropical Cyclone Rainfall and flood events for the Hudson River

    Science.gov (United States)

    Cioffi, Francesco; Conticello, Federico; Hall, Thimoty; Lall, Upmanu; Orton, Philip

    2014-05-01

    Tropical Cyclones (TCs) lead to potentially severe coastal flooding through wind surge and also through rainfall-runoff processes. There is growing interest in modeling these processes simultaneously. Here, a statistical approach that can facilitate this process is presented with an application to the Hudson River Basin that is associated with the New York City metropolitan area. Three submodels are used in sequence. The first submodel is a stochastic model of the complete life cycle of North Atlantic (NA) tropical cyclones developed by Hall and Yonekura (2011). It uses archived data of TCs throughout the North Atlantic to estimate landfall rates at high geographic resolution as a function of the ENSO state and of sea surface temperature (SST). The second submodel translates the attributes of a tropical cyclone simulated by the first model to rainfall intensity at selected stations within the watershed of Hudson River. Two different approaches are used and compared: artificial neural network (ANN) and k-nearest neighbor (KNN). Finally, the third submodel transforms, once again, by using an ANN approach and KNN, the rainfall intensities, calculated for the ensemble of the stations, to the streamflows at specific points of the tributaries of the Hudson River. These streamflows are to be used as inputs in a hydrodynamic model that includes storm surge surge dynamics for the simulation of coastal flooding along the Hudson River. Calibration and validation of the model is carried out by using, selected tropical cyclone data since 1950, and hourly station rainfall and streamflow recorded for such extreme events. Four stream gauges (Troy dam, Mohawk River at Cohoes, Mohawk River diversion at Crescent Dam, Hudson River above lock one nr Waterford), a gauge from a tributary in the lower Hudson River, and over 20 rain gauges are used. The performance of the proposed model as tool for storm events is then analyzed and discussed.

  9. Arctic and N Atlantic Crustal Thickness and Oceanic Lithosphere Distribution from Gravity Inversion

    Science.gov (United States)

    Kusznir, Nick; Alvey, Andy

    2014-05-01

    consistent with these basins being oceanic. Larger crustal thicknesses, in the range 20 - 30 km, are predicted for the Lomonosov, Alpha and Mendeleev Ridges. Crustal basement thicknesses of 10-15 km are predicted under the Laptev Sea which is interpreted as highly thinned continental crust formed at the eastward continuation of Eurasia Basin sea-floor spreading. Thin continental or oceanic crust of thickness 7 km or less is predicted under the North Chukchi Basin and has major implications for understanding the Mesozoic and Cenozoic plate tectonic history of the Siberian and Chukchi Amerasia Basin margins. Restoration of crustal thickness and continent-ocean boundary location from gravity inversion may be used to test and refine plate tectonic reconstructions. Using crustal thickness and continental lithosphere thinning factor maps with superimposed shaded-relief free-air gravity anomaly, we improve the determination of pre-breakup rifted margin conjugacy and sea-floor spreading trajectory within the Arctic and N Atlantic basins. By restoring crustal thickness & continental lithosphere thinning maps of the Eurasia Basin & NE Atlantic to their initial post-breakup configuration we show the geometry and segmentation of the rifted continental margins at their time of breakup, together with the location of highly-stretched failed breakup basins and rifted micro-continents. We interpret gravity inversion crustal thicknesses underneath Morris Jessop Rise & Yermak Plateau as continental crust which provided a barrier to the tectonic and palaeo-oceanic linkage between the Arctic & North Atlantic until the Oligocene. Before this time, we link the seafloor spreading within the Eurasia Basin to that in Baffin Bay.

  10. Adakites from collision-modified lithosphere

    Science.gov (United States)

    Haschke, M.; Ben-Avraham, Z.

    2005-08-01

    Adakitic melts from Papua New Guinea (PNG) show adakitic geochemical characteristics, yet their geodynamic context is unclear. Modern adakites are associated with hot-slab melting and/or remelting of orogenic mafic underplate at convergent margins. Rift-propagation over collision-modified lithosphere may explain the PNG adakite enigma, as PNG was influenced by rapid creation and subduction of oceanic microplates since Mesozoic times. In a new (rift) tectonic regime, decompressional rift melts encountered and melted remnant mafic eclogite and/or garnet-amphibolite slab fragments in arc collisional-modified mantle, and partially equilibrated with metasomatized mantle. Alternatively, hot-slab melting in a proposed newborn subduction zone along the Trobriand Trough could generate adakitic melts, but recent seismic P-wave tomographic models lack evidence for subducting oceanic lithosphere in the adakite melt region; however they do show deep subduction zone remnants as a number of high P-wave anomalies at lithospheric depths, which supports our proposed scenario.

  11. Structure, seismicity, and instrumentation of stable North American lithosphere

    Science.gov (United States)

    Wolin, Emily Lynne Gregonis

    The work in this thesis covers a number of different fields in seismology. These can be divided into three parts. In the first, I discuss earthquakes that occur along the North American passive margin. In the second, I investigate the noise characteristics of Superior Rifting Earthscope Experiment (SPREE) seismic stations. In the third, I evaluate the predictions of pre-existing tomographic models, expand raypath coverage in eastern North America by fitting waveforms, and produce an updated tomographic model focusing on the structure of stable North American lithosphere. First, I explore the rare, but moderate-to-large earthquakes that occur along the passive margin of North America, such as the August 2011 Mineral, Virginia earthquake. I discuss the tectonic setting, possible causes, and challenges of studying such earthquakes and propose directions for their future study. Examining the seismicity of the regions surrounding the 1929 Grand Banks and 1933 Baffin Bay earthquakes, I conclude that the aftershocks of these events continue today due to low strain rates along the margin. Second, I characterize the long-period noise characteristics of SPREE stations. At periods greater than 20 seconds, horizontal noise levels at SPREE stations vary seasonally and diurnally. I find that SPREE stations in sandy soil have the most consistent noise levels. Stations in fine-grained soil become extremely noisy during summer days, but very quiet when the surrounding soil freezes solid in winter. Finally, I evaluate previous generations of tomographic models and develop my own. I calculate synthetic seismograms for three tomographic models and compare them to new observed seismograms from earthquakes in stable North America. I find that adding data to a tomographic model does not necessarily improve predictions of regional S and Rayleigh waveforms. With this in mind, I apply the method of partitioned waveform inversion to derive constraints on S-velocity structure. I add these

  12. Lithospheric Thickness Modeled from Long Period Surface Wave Dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Pasyanos, M E

    2008-05-15

    The behavior of surface waves at long periods is indicative of subcrustal velocity structure. Using recently published dispersion models, we invert surface wave group velocities for lithospheric structure, including lithospheric thickness, over much of the Eastern Hemisphere, encompassing Eurasia, Africa, and the Indian Ocean. Thicker lithosphere under Precambrian shields and platforms are clearly observed, not only under the large cratons (West Africa, Congo, Baltic, Russia, Siberia, India), but also under smaller blocks like the Tarim Basin and Yangtze craton. In contrast, it is found that remobilized Precambrian structures like the Saharan Shield and Sino-Korean Paraplatform do not have well-established lithospheric keels. The thinnest lithospheric thickness is found under oceanic and continental rifts, as well as along convergence zones. We compare our results to thermal models of continental lithosphere, lithospheric cooling models of oceanic lithosphere, lithosphere-asthenosphere boundary (LAB) estimates from S-wave receiver functions, and velocity variations of global tomography models. In addition to comparing results for the broad region, we examine in detail the regions of Central Africa, Siberia, and Tibet. While there are clear differences in the various estimates, overall the results are generally consistent. Inconsistencies between the estimates may be due to a variety of reasons including lateral and depth resolution differences and the comparison of what may be different lithospheric features.

  13. Quantum Random Walks and their Convergence to Evans-Hudson Flows

    Indian Academy of Sciences (India)

    Lingaraj Sahu

    2008-08-01

    Using coordinate-free basic operators on toy Fock spaces, quantum random walks are defined following the ideas of Attal and Pautrat. Extending the result for one dimensional noise, strong convergence of quantum random walks associated with bounded structure maps to Evans–Hudson flow is proved under suitable assumptions. Starting from the bounded generator of a given uniformly continuous quantum dynamical semigroup on a von Neumann algebra, we have constructed quantum random walks which converges strongly and the strong limit gives an Evans–Hudson dilation for the semigroup.

  14. Analog Modeling of Continental Lithosphere Subduction

    Science.gov (United States)

    Willingshofer, E.; Sokoutis, D.; Luth, S.; Beekman, F.; Cloetingh, S.

    2012-12-01

    Lithospheric-scale analog modeling sheds light on the consequences of decoupling within the continental lithosphere and along plate interfaces during continental collision. The model results provide valuable information in terms of strain localization, deformation of the subducting slab and the evolution and architecture of the overlying mountain belt and its topography. A weak layer has been implemented in three-layer models to simulate decoupling along the plate interface and at different levels of the lithosphere (brittle-ductile transition, entire lower crust, crust-mantle boundary). Additionally, varying the strength of the mantle lithosphere of both the upper as well as the lower plate regulated the degree of plate coupling. Plate boundaries were orthogonal to the convergence direction. All models emphasize that strong decoupling at the plate interface is a pre-requisite for the subduction of continental lithosphere. In addition, deformation of the subducting slab was found to be sensitive to the strength contrast between the subduction zone and the mantle lithosphere of the downgoing as well as the upper plate. As such, a low strength contrast between the plate interface and the lower plate leads to deformation of the subducting slab by thickening and the development of a shallow slab. Conversely, when the strength contrast is high, deep slabs evolve which undergo relatively less deformation. Furthermore, the level of decoupling in the downgoing plate governs how much continental crust is subducted together with the mantle lithosphere. Shallow decoupling, at the brittle-ductile transition, results in subduction of the lower crust whereas small amounts of lower crust are subducted when decoupling occurs at the level of the Moho. Weak plate coupling and a weak lower crust of the lower plate steer the evolution of mountain belts such that deformation propagates outward, in the direction of the incoming plate, by successive imbrication of upper crustal thrust

  15. U. S. groups fight James Bay II

    Energy Technology Data Exchange (ETDEWEB)

    This article reviews the opposition program to the James Bay II hydroelectric project. The environmental costs of the first phase of James Bay, the La Grande project, have been huge, resulting in massive alterations of the environment and causing widespread mercury poisoning of fish, loss of wetlands and disruption of caribou calving grounds. Start-up of the Great Whale project is imminent, and will result in the flooding of ca 5,000 square kilometers of wilderness. The environmental costs of phases 2 and 3 will be even larger than for the first phase, with potential for significant disruption of fresh-water input into James and Hudson Bays. Drastic changes in the volume and salinity of the water will jeopardize the life patterns of many migratory birds, polar bears, beluga wales, seals and other wildlife. These, along with other social costs, are prohibitive for the Cree. The Cree have been actively opposing the project in the United States, and a groundswell of American opposition has been building. The Cree have been successful in persuading Bangor, Maine, to cancel a proposed contract with Hydro Quebec, on economic grounds. Opposition is building in Burlington, Vermont, to a contract with Hydro Quebec for the planned purchase of 15 MW of power from Hydro Quebec. Secret contracts between Hydro Quebec and thirteen multinational aluminum corporations, to supply power at below cost, have been publicized. The signing of an energy contract between New York and Quebec has been delayed for one year due to the inability of Hydro Quebec to make progress on the project in the face of opposition at home.

  16. Abrupt Atmospheric Methane Increases Associated With Hudson Strait Heinrich Events

    Science.gov (United States)

    Rhodes, R.; Brook, E.; Chiang, J. C. H.; Blunier, T.; Maselli, O. J.; McConnell, J. R.; Romanini, D.; Severinghaus, J. P.

    2015-12-01

    The drivers of abrupt climate change during the Last Glacial Period are not well understood. While Dansgaard-Oeschger (DO) cycles are thought to be linked to variations in the strength of the Atlantic Meridional Ocean Circulation (AMOC), it is not clear how or if Heinrich Events—extensive influxes of icebergs into the North Atlantic Ocean that impacted global climate and biogeochemistry—are related. An enduring problem is the difficultly in dating iceberg rafted debris deposits that typically lack foraminifera. Here we present an ultra-high resolution record of methane from the West Antarctic Ice Sheet Divide ice core at unprecedented, continuous temporal resolution from 67.2-9.8 ka BP, which we propose constrains the timing of Heinrich events. Our methane record essentially mirrors Greenland ice core stable isotope variability across D-O events, except during Heinrich stadials 1, 2, 4 and 5. Partway through these stadials only, methane increases abruptly and rapidly, as at the onset of a D-O event but Greenland temperature exhibits no equivalent response. Speleothem records exhibit signatures of drought in the Northern extra-tropics and intensified monsoonal activity over South America at these times. We use a simple heuristic model to propose that cold air temperatures and extensive sea ice in the North, resulting from Heinrich events, caused extreme reorganization of tropical hydroclimate. This involved curtailment of the seasonal northerly migration of tropical rain belts, leading to intensification of rainfall over Southern Hemisphere tropical wetlands, thus allowing production of excess methane relative to a 'normal' Greenland stadial. We note that this mechanism can operate if AMOC is already in a slowed state when a Heinrich event occurs, as paleo-evidence suggests it was. Heinrich events and associated sea ice cover would therefore act to prolong the duration of this AMOC state. Our findings place the big four Heinrich events of Hudson Strait origin

  17. Foundering lithosphere imaged beneath the southern Sierra Nevada, California, USA.

    Science.gov (United States)

    Boyd, Oliver S; Jones, Craig H; Sheehan, Anne F

    2004-07-30

    Seismic tomography reveals garnet-rich crust and mantle lithosphere descending into the upper mantle beneath the southeastern Sierra Nevada. The descending lithosphere consists of two layers: an iron-rich eclogite above a magnesium-rich garnet peridotite. These results place descending eclogite above and east of high P wave speed material previously imaged beneath the southern Great Valley, suggesting a previously unsuspected coherence in the lithospheric removal process.

  18. Inherent and apparent optical measurements in the Hudson/Raritan estuary

    NARCIS (Netherlands)

    Bagheri, S.; Rijkeboer, M.; Gons, H.J.

    2002-01-01

    During an August, 1999 field campaign, measurements were made to establish hydrologic optical properties of the Hudson/Raritan Estuary (New York-New Jersey): 1) concurrent above-and below-surface spectral irradiance; 2) sampling for laboratory determination of inherent optical properties; and 3) con

  19. Library Resources in the Mid-Hudson Valley: Columbia, Dutchess, Greene, Orange, Putnam, Rockland, Sullivan, Ulster.

    Science.gov (United States)

    Reichmann, Felix; And Others

    The purpose of this study was to "survey the library resources in the eight Mid-Hudson Counties of Columbia, Dutchess, Greene, Orange, Putnam, Rockland, Sullivan, and Ulster in order to develop a plan of service in which assets would be shared, resources developed, and services extended." Survey data were collected by six questionnaires;…

  20. Science, law, and Hudson River power plants: A case study in environmental impact assessment

    Energy Technology Data Exchange (ETDEWEB)

    Barnthouse, L.W.; Klauda, R.J.; Vaughan, D.S.; Kendall, R.L. (eds.)

    1988-01-01

    Between 1963 and 1980, the Hudson River estuary was the focus of one of the most ambitious environmental research and assessment programs ever performed. The studies supported a series of US federal proceedings involving licenses and discharge permits for two controversial electric power generating facilities: the Cornwall pumped storage facility, and units 2 and 3 of the Indian Point nuclear generating station. Both facilities were to draw large volumes of water from a region of the Hudson used as spawning and nursery habitat by several fish species, including the striped bass. Fishermen and conservationists feared that a major fraction of the striped bass eggs and larvae in the Hudson would be entrained with the pumped water and killed. Additional fish would be killed on trash screens at the intakes. Scientists were asked to aid the utility companies and regulatory agencies in determining the biological importance of entrainment and impingement. This monograph contains both technical papers that present research results and synthesis papers that summarize and interpret the results. The intent was to: (1) summarize the scientific issues and approaches; (2) present the significant results of the Hudson River biological studies; (3) describe the role of the studies in the decision-making process; (4) evaluate the successes and failures of the studies; and (5) present recommendations for future estuarine impact assessments. Separate abstracts are processed for 22 papers for inclusion in the appropriate data bases.

  1. 77 FR 46613 - Safety Zone; 2012 Ironman US Championship Swim, Hudson River, Fort Lee, NJ

    Science.gov (United States)

    2012-08-06

    ...) entitled 2012 Ironman US Championship Swim, Hudson River, Fort Lee, NJ in the Federal Register (77 FR 34285...) 366-9826. SUPPLEMENTARY INFORMATION: Table of Acronyms DHS Department of Homeland Security FR Federal... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; 2012 Ironman US Championship Swim,...

  2. 77 FR 41271 - Safety Zone; Newburgh to Beacon Swim, Newburgh, Hudson River, NY

    Science.gov (United States)

    2012-07-13

    ... Acronyms DHS Department of Homeland Security FR Federal Register CFR Code of Federal Regulations NPRM... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Newburgh to Beacon Swim, Newburgh, Hudson... Newburgh, NY for the annual Newburgh Beacon Swim event. This temporary safety zone is necessary to...

  3. 75 FR 10229 - Application for Presidential Permit; Champlain Hudson Power Express, Inc.

    Science.gov (United States)

    2010-03-05

    ... Connecticut. CHPEI proposes to construct and operate a primarily underground and submarine high-voltage direct... underground cables connected as a bipole pair. Each bipole will at all times utilize its partner in the bipole... railroad ROW for a distance of approximately 69.9 miles (107.7 km). The cables would re-enter the Hudson...

  4. 3D lithospheric mapping of the Iberian Peninsula and surrounding Atlantic and Mediterranean margins from 3D joint inversion of potential field and elevation data.

    Science.gov (United States)

    Torne, Montserrat; Zeyen, Hermann; Jimenez-Munt, Ivone; Fernandez, Manel; Vergés, Jaume

    2017-04-01

    We investigate the lithospheric density structure of the Iberian Peninsula and the surrounding Atlantic and Mediterranean margins from a 3D joint inversion of free-air, geoid and elevation data, based on a Bayesian approach. In addition, the crustal structure has been further constrained by incorporating about 750 Moho values from DSS investigations and RF analysis covering the entire region. Our preliminary results shows a significant lithospheric deformation along the plate boundaries, the Bay of Biscay-Pyrenees to the North and the Azores-Gibraltar to the south, where the CMB and LAB are located at depths more than 45 and 150 km, respectively. Noteworthy is the arcuate lithospheric thickening located at the westernmost end of the Gibraltar Arc system showing the presence of the NW-to-Westward retreated Gibraltar Arc slab that has given rise to the formation of the Betics-Rif Alpine belt system and the back arc Alboran basin. To the west, the stable-slightly deformed Iberian massif shows a quasi-flat CMB and LAB topography (30 to 32 km and about 110 km, respectively). The crust and mantle lithosphere thin towards the Mediterranean and Atlantic margins, with the exception of its northern margin where lithospheric thickening extends offshore to the Gulf of Biscay. In the western Mediterranean the SE-Neogene slab retreat has resulted in a significant thinning of the crust and mantle lithosphere. Thin lithosphere is also observed in the Tagus-Horseshoe abyssal plain region where the LAB shallows to less than 90 km. This work has been funded by the Spanish projects MITE (CGL2014-59516-P) and WEME-CSIC project 201330E11.

  5. Pn anisotropy in Mesozoic western Pacific lithosphere

    Science.gov (United States)

    Shintaku, Natsumi; Forsyth, Donald W.; Hajewski, Christina J.; Weeraratne, Dayanthie S.

    2014-04-01

    Pn is the high-frequency, scattered P phase guided for great distances within the old oceanic lithosphere. Two arrays of ocean bottom seismometers were deployed on old (150-160 Ma) seafloor in the northwestern Pacific south of Shatsky Rise for the Pacific Lithosphere Anisotropy and Thickness Experiment. We use Pn phases from 403 earthquakes during the 1 year of deployment to measure apparent velocities across the arrays. Each array was deployed on a separate limb of a magnetic bight, formed near a fast-spreading, ridge-ridge-ridge triple junction. Using high-frequency waves (5-10 Hz), we look at variations of Pn velocities as a function of azimuth. In the western array, we find Pn anisotropy with velocities ranging from ~8.7 km/s in the back azimuth (θ) direction of 310° to ~7.7 km/s at ~350°. In the eastern array, the velocity ranges from ~8.5 km/s in back azimuth direction of ~210° to ~7.7 km/s at 260° and ~310°. We observe rapid velocity changes with azimuth in the both arrays requiring sinusoidal variations of roughly equal amplitude as a function of both 2θ and 4θ, which is not expected for the orthorhombic symmetry of olivine or orthopyroxene. The fastest directions on the two limbs are roughly orthogonal to each other suggesting the dominance of fossil anisotropy, but the fast directions of the 2θ components are skewed counterclockwise from the spreading directions. We speculate that the rapid azimuthal variations may be caused by vertical stratification with changing anisotropy with depth in the oceanic lithosphere.

  6. Cratonic lithospheric mantle: Is anything subducted?

    Institute of Scientific and Technical Information of China (English)

    William L. Griffin; Suzanne Y. O'ReiUy

    2007-01-01

    @@ If the subcontinental lithospheric mantle (SCLM) formed through the repeated underthrusting of oceanic slabs, peridotitic SCLM should resemble oceanic peridotites, and mafic rocks (eclogites, s.l.) should be distributed throughout the SCLM. However, cratonic peridotites (both exposed massifs and xenoliths) differ markedly from oceanic and ophiolitic peridotites in their Fe-Cr-Al relationships and abundances of trace elements (Li and B) diagnostic of subduction. "Typical"cratonic peridotites have experienced extensive metaso matism; modelling of their refractory protoliths indicates high-degree melting at high P, perhaps a uniquely Archean process.

  7. Bayes and empirical Bayes: do they merge?

    CERN Document Server

    Petrone, Sonia; Scricciolo, Catia

    2012-01-01

    Bayesian inference is attractive for its coherence and good frequentist properties. However, it is a common experience that eliciting a honest prior may be difficult and, in practice, people often take an {\\em empirical Bayes} approach, plugging empirical estimates of the prior hyperparameters into the posterior distribution. Even if not rigorously justified, the underlying idea is that, when the sample size is large, empirical Bayes leads to "similar" inferential answers. Yet, precise mathematical results seem to be missing. In this work, we give a more rigorous justification in terms of merging of Bayes and empirical Bayes posterior distributions. We consider two notions of merging: Bayesian weak merging and frequentist merging in total variation. Since weak merging is related to consistency, we provide sufficient conditions for consistency of empirical Bayes posteriors. Also, we show that, under regularity conditions, the empirical Bayes procedure asymptotically selects the value of the hyperparameter for ...

  8. Meso-Cenozoic thermal-rheological evolution in Jiyang sub-basin, Bohai Bay Basin and its implication for basin extension revealed by numerical modelling

    Science.gov (United States)

    Li, Lu; Qiu, Nansheng; Xu, Wei

    2016-04-01

    Jiyang sub-basin is an oil-rich depression located in the southeast of Bohai Bay Basin, which is one of the most important hydrocarbon area in east of China. The thermal-rheological structure of the lithosphere can explain the dynamics evolution processes of basins, continental margins and orogenic belts, which directly reflects the characteristics of the lithosphere geodynamics. Nevertheless it is poorly to understand the evolution of lithospheric thermal-rheological structure in Jiyang sub-basin and its implication for basin extension. In this study, two dimensional numerical modelling is applied to calculate the paleo-temperature field and the thermo-lithospheric structure, which are used to estimate the evolution of lithospheric thermal-rheological structure. The results of study show that in Mesozoic the lithosphere was of relative rigidity and stable, as featured by large thickness and strength whereas after late Cretaceous the lithospheric strength decreased rapidly. The analysis of thermal-rheological properties shows that the lithospheric thermo-lithospheric structure is sandwiched-like with two ductile layers and two brittle layers. The upper crust is usually brittle. The brittle layers appear at outer 20km of the crust, below 20km ductile deformation predominates. There is also a 10km brittle layer on the top of the upper mantle. The integrated lithospheric yield strength is about 1.3-4.5×1012N/m, showing a weak lithosphere which may support the idea that the extension achieved by the ductile flow below the brittle layers. Keywords: lithospheric thermal-rheological structure; Jiyang sub-basin; Numerical modeling

  9. The correct mechanism of lithospheric plates movement

    Science.gov (United States)

    Ostrihansky, L.

    2016-12-01

    Imagination that lithospheric plates move above low-viscous seismic low-velocity zone contradicts to reality but alternating movement of variations of the Earth's rotation deform plastic mantle. Because these deformations never return to original position and solidified ascending magma in mid-ocean ridge prevents return, the lithospheric plates move plunging to mantle by their own weight and move westward pushed by force of tidal friction enlarged by alternating movement of heavy and large-volume mantle. This imagination has been proven by calculating azimuths of Moon and opposite tidal bulging in a moment of earthquake. They resulted occurring on local eastern horizon when earthquake was triggered and also calculated tidal torques in their maximums coincided with earthquakes. To distinguish these tidal properties the earthquakes in Hindu Kush in westward moving Eurasian plate were examined and also in northward moving Indian plate. LOD graph has shown that in Hindu Kush tidal friction triggers earthquake almost every day and large earthquakes are triggered in large positive LOD anomalies corresponding to deceleration. In the Indian plate the calculated maximum tidal torques corresponding to accelerations (LOD minimums) coincided with the greatest earthquakes: with the Great Sumatra 2004, largest Nepal earthquake 1934, large earthquake Nepal 2015 evoked by resonance effect and others.

  10. Watershed nutrient inputs, phytoplankton accumulation, and C stocks in Chesapeake Bay

    Science.gov (United States)

    Fisher, T. R.; Boynton, W. R.; Hagy, J. D.

    2002-12-01

    Inputs of N and P to Chesapeake Bay have been enhanced by anthropogenic activities. Fertilizers, urbanization, N emissions, and industrial effluents contribute to point and diffuse sources currently 2-7X higher for P and 5-20X higher for N than those from undisturbed watersheds. Enhanced nutrient inputs cause phytoplankton blooms which obscure visibility, eliminate submerged grasses, and influence the distribution of C within the Bay. Accumulations of dissolved organic and particulate organic C lead to enhanced microbial respiration in isolated bottom waters, and dissolved oxygen is seasonally reduced to trace levels during summer. Cultural eutrophication is not unique to Chesapeake Bay. Although some estuaries such as the Delaware, Hudson, and San Francisco Bay also have high anthropogenic inputs, these estuaries have much shorter residence times, and much of the N and P may be exported to the coastal ocean. However, in Chesapeake Bay, with residence times >2 months, internal processing of watershed inputs results in local algal blooms within the estuary. Watershed restoration strategies for Chesapeake watersheds have had limited success to date. Groundwaters are enriched with nitrate, and the long residence times of groundwaters mean slow responses to watershed improvements. The few successes in the Chesapeake have been associated with point source reductions, although continued human population growth can easily override restoration efforts. Widespread improvement in water quality has yet to occur, but the limited successes show that the Bay responds to load changes.

  11. Selective analysis of power plant operation on the Hudson River with emphasis on the Bowline Point Generating Station. Volume 2. [Multiple impact of power plant once-through cooling systems on fish populations

    Energy Technology Data Exchange (ETDEWEB)

    Barnthouse, L. W.; Cannon, J. B.; Christensen, S. G.

    1977-07-01

    Because of the location of the Bowline, Roseton, and Indian Point power generating facilities in the low-salinity zone of the Hudson estuary, operation of these plants with the present once-through cooling systems will adversely influence the fish populations that use the area for spawning and initial periods of growth and development. Recruitment rates and standing crops of several fish species may be lowered in response to the increased mortality caused by entrainment of nonscreenable eggs and larvae and by impingement of screenable young of the year. Entrainment and impingement data are particularly relevant for assessing which fish species have the greatest potential for being adversely affected by operation of Bowline, Roseton, and Indian Point with once-through cooling. These data from each of these three plants suggest that the six species that merit the greatest consideration are striped bass, white perch, tomcod, alewife, blueback herring, and bay anchovy. Two points of view are available for assessing the relative importance of the fish species in the Hudson River. From the fisheries point of view, the only two species of major importance are striped bass and shad. From the fish-community and ecosystem point of view, the dominant species, as determined by seasonal and regional standing crops (in numbers and biomass per hectare), are the six species most commonly entrained and impinged, namely, striped bass, white perch, tomcod, alewife, blueback herring, and anchovy.

  12. Sensitivity of Coastal Environments and Wildlife to Spilled Oil: Hudson River: T_MAMMAL (Terrestrial Mammal Polygons)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive biological resource data for small terrestrial mammals (woodrats, myotis, muskrat, mink) for the Hudson River. Vector polygons in...

  13. 77 FR 22525 - Safety Zone; Swim Events in the Captain of the Port New York Zone; Hudson River, East River...

    Science.gov (United States)

    2012-04-16

    ...) Ederle Swim: Within the waters of the Hudson River between North Cove Marina, New York, NY and Sandy Hook... patrol vessel or may be on shore and will communicate with vessels via VHF-FM radio or loudhailer. In...

  14. Sensitivity of Coastal Environments and Wildlife to Spilled Oil: Hudson River: WETLANDS (Environmental Sensitivity Index Wetland Types - Polygons)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains vector polygons representing coastal wetland habitats for the Hudson River classified according to the Environmental Sensitivity Index (ESI)...

  15. National Status and Trends: Bioeffects Program - Magnitude and Extent of Sediment Toxicity in the Hudson-Raritan Estuary

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A survey of the toxicity of sediments was performed by NOAA's National Status and Trends (NSandT) Program throughout the Hudson-Raritan Estuary. The objectives of...

  16. Sensitivity of Coastal Environments and Wildlife to Spilled Oil: Hudson River: M_MAMMAL (Marine Mammal Polygons)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive biological resource data for marine mammals (seals) in the Hudson River. Vector polygons in this data set represent marine mammal...

  17. Subduction-driven recycling of continental margin lithosphere.

    Science.gov (United States)

    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.

  18. Lithospheric cooling as a basin forming mechanism within accretionary crust.

    Science.gov (United States)

    Holt, P. J.; Allen, M.; van Hunen, J.; Björnseth, H. M.

    2009-04-01

    Widely accepted basin forming mechanisms are limited to flexure of the lithosphere, lithospheric stretching, lithospheric cooling following rifting and, possibly, dynamic topography. In this work forward models have been used to investigate lithospheric growth due to cooling beneath accretionary crust, as a new basin forming mechanism. Accretionary crust is formed from collision of island arcs, accretionary complexes and fragments of reworked older crust at subduction zones, and therefore has thin lithosphere due to melting and increased convection. This is modeled using a 1D infinite half space cooling model similar to lithospheric cooling models for the oceans. The crustal composition and structure used in the models has been varied around average values of accretionary crust to represent the heterogeneity of accretionary crust. The initial mantle lithosphere thickness used in the model was 20 km. The model then allows the lithosphere to thicken as it cools and calculates the subsidence isostatically. The model produces sediment loaded basins of 2-7 km for the various crustal structures over 250 Myrs. Water-loaded tectonic subsidence curves from the forward models were compared to tectonic subsidence curves produced from backstripping wells from the Kufrah and Ghadames basins, located on the accretionary crust of North Africa. A good match between the subsidence curves for the forward model and backstripping is produced when the best estimates for the crustal structure, composition and the present day thickness of the lithosphere for North Africa are used as inputs for the forward model. This shows that lithospheric cooling provides a good method for producing large basins with prolonged subsidence in accretionary crust without the need for initial extension.

  19. Folded Lithospheric Basins in Central Asia: Altai-Sayan and Tien Shan basins in a folding lithosphere

    Science.gov (United States)

    Delvaux, Damien; Cloetingh, Sierd; Beekman, Fred; Sokoutis, Dimitrios; Burov, Evguenii; Buslov, Misha; Abdrakhmatov, Kanatbeck

    2014-05-01

    Central Asia is a classic example for continental lithospheric folding. In particular, the Altay-Sayan belt in South-Siberia and the Kyrgyz Tien Shan display a special mode of lithospheric deformation, involving decoupled lithospheric mantle folding and upper crustal folding and faulting. A review of the paleostress data and tectono-stratigraphic evolution of the Kurai-Chuya basin in Siberian Altai, Zaisan basin in Kazakh South Altai and Issyk-Kul basin in Kyrgyz Tien Shan suggests that these basins were initiated in an extensional context and later inverted by a combination of fault-controlled deformation and flexural folding. They deformed by a combination of lithospheric buckling inducing surface tilting, uplift and subsidence, together with upper crustal fault-controlled deformation. They are good examples of Folded Lithospheric Basins (FLB) which typically form in a buckling lithosphere. Their characteristic basin fill and symmetry, inner structure, folding wavelength and amplitude, thermal regime and time frame are examined in relation to basement structure, stress field, strain rate, timing of deformation, and compared to existing modelling results. Both regions of active lithospheric folding have a heterogeneous crust with a long history of accretion-collision, subsequently reactivated as a far-field effect of the Indian-Eurasian collision. Thanks to the youthfulness of the tectonic deformation in this region (peak deformation in late Pliocene - early Pleistocene), the surface expression of lithospheric deformation is well documented by the surface topography and superficial tectonic structures.

  20. Recovering lateral variations in lithospheric strength from bedrock motion data using a coupled ice sheet-lithosphere model

    NARCIS (Netherlands)

    Berg, J. van den; Wal, R.S.W. van de; Oerlemans, J.

    2006-01-01

    A vertically integrated two-dimensional ice flow model was coupled to an elastic lithosphere-Earth model to study the effects of lateral variations in lithospheric strength on local bedrock adjustment. We used a synthetic bedrock profile and a synthetic climate to model a characteristic ice sheet

  1. Recovering lateral variationin lithospheric strength from bedrock motion data using a coupled ice sheet-lithosphere model

    NARCIS (Netherlands)

    van de Berg, W.J.; van de Wal, R.S.W.; Oerlemans, J.

    2006-01-01

    A vertically integrated two-dimensional ice flow model was coupled to an elastic lithosphere-Earth model to study the effects of lateral variations in lithospheric strength on local bedrock adjustment. We used a synthetic bedrock profile and a synthetic climate to model a characteristic ice sheet

  2. 'Celebrities of the future’:fame and notability in Henry James’s Roderick Hudson and the American

    OpenAIRE

    2015-01-01

    Focusing on two of Henry James’s earliest novels, Roderick Hudson (1875) and The American (1877), this essay explores the ways in which James’s initial formulation of his signature ‘international theme’ intersects with nineteenth-century discourses on fame. Roderick Hudson positions the eponymous American sculptor as a lion and notable in Europe, and then shows his fatal attempts to transcend the objectification and commodification that accompany fame. In The American the protagonist, Christo...

  3. Density heterogeneity of the cratonic lithosphere

    DEFF Research Database (Denmark)

    Cherepanova, Yulia; Artemieva, Irina

    2015-01-01

    Using free-board modeling, we examine a vertically-averaged mantle density beneath the Archean-Proterozoic Siberian craton in the layer from the Moho down to base of the chemical boundary layer (CBL). Two models are tested: in Model 1 the base of the CBL coincides with the LAB, whereas in Model 2...... the base of the CBL is at a 180 km depth. The uncertainty of density model is density structure of the Siberian lithospheric mantle with a strong...... correlation between mantle density variations and the tectonic setting. Three types of cratonic mantle are recognized from mantle density anomalies. 'Pristine' cratonic regions not sampled by kimberlites have the strongest depletion with density deficit of 1.8-3.0% (and SPT density of 3.29-3.33 t/m3...

  4. Rejuvenation of the lithosphere by the Hawaiian plume.

    Science.gov (United States)

    Li, Xueqing; Kind, Rainer; Yuan, Xiaohui; Wölbern, Ingo; Hanka, Winfried

    2004-02-26

    The volcanism responsible for creating the chain of the Hawaiian islands and seamounts is believed to mark the passage of the oceanic lithosphere over a mantle plume. In this picture hot material rises from great depth within a fixed narrow conduit to the surface, penetrating the moving lithosphere. Although a number of models describe possible plume-lithosphere interactions, seismic imaging techniques have not had sufficient resolution to distinguish between them. Here we apply the S-wave 'receiver function' technique to data of three permanent seismic broadband stations on the Hawaiian islands, to map the thickness of the underlying lithosphere. We find that under Big Island the lithosphere is 100-110 km thick, as expected for an oceanic plate 90-100 million years old that is not modified by a plume. But the lithosphere thins gradually along the island chain to about 50-60 km below Kauai. The width of the thinning is about 300 km. In this zone, well within the larger-scale topographic swell, we infer that the rejuvenation model (where the plume thins the lithosphere) is operative; however, the larger-scale topographic swell is probably supported dynamically.

  5. Lithospheric cooling and thickening as a basin forming mechanism

    Science.gov (United States)

    Holt, Peter J.; Allen, Mark B.; van Hunen, Jeroen; Bjørnseth, Hans Morten

    2010-12-01

    Widely accepted basin forming mechanisms are limited to flexure of the lithosphere, and lithospheric stretching followed by cooling and thermal subsidence. Neither of these mechanisms works for a group of large basins, sometimes known as "intracontinental sags". In this paper we investigate cooling and thickening of initially thin lithosphere as a basin forming mechanism, by a combination of forward modelling and a backstripping study of two Palaeozoic North African basins: Ghadames and Al Kufrah. These are two of a family of basins, once unified, which lie over the largely accretionary crust of North Africa and Arabia. Such accretionary crust tends to be juvenile, consisting of amalgamated island arcs, accretionary prisms and melanges, and typically has near-normal crustal thicknesses but initially thin mantle lithosphere. Post-accretion subsidence is modelled using a plate cooling model similar to cooling models for oceanic lithosphere. The crustal composition and thickness used in the models are varied around average values of accretionary crust to represent likely heterogeneity. The model allows the lithosphere to thicken as it cools and calculates the resulting isostatic subsidence. Water-loaded tectonic subsidence curves from these forward models are compared to tectonic subsidence curves produced from backstripped wells from Al Kufrah and Ghadames Basins. A good match between the subsidence curves for the forward model and backstripping is produced when the best estimates for the crustal structure, composition and the present day thickness of the lithosphere for North Africa are used as inputs for the forward model. The model produces sediment loaded basins of 2-7 km thickness for the various crustal assemblies over ~ 250 Myr. This shows that lithospheric cooling provides a viable method for producing large basins with prolonged subsidence, without the need for initial extension, provided the condition of initially thin mantle lithosphere is met.

  6. Measurement Error Affects Risk Estimates for Recruitment to the Hudson River Stock of Striped Bass

    OpenAIRE

    Dennis J. Dunning; Ross, Quentin E.; Munch, Stephan B.; Ginzburg, Lev R.

    2002-01-01

    We examined the consequences of ignoring the distinction between measurement error and natural variability in an assessment of risk to the Hudson River stock of striped bass posed by entrainment at the Bowline Point, Indian Point, and Roseton power plants. Risk was defined as the probability that recruitment of age-1+ striped bass would decline by 80% or more, relative to the equilibrium value, at least once during the time periods examined (1, 5, 10, and 15 years). Measurement error, estimat...

  7. Public support for ecosystem restoration in the Hudson River Valley, USA.

    Science.gov (United States)

    Connelly, Nancy A; Knuth, Barbara A; Kay, David L

    2002-04-01

    We applied the Theory of Planned Behavior to help understand the relationships between environmental beliefs, support for ecosystem restoration actions, and willingness to pay (WTP) for restoration and protection goals in the Hudson River estuary, New York State, USA. We conducted a mail survey with 3,000 randomly-chosen local residents of the Hudson River estuary in the fall of 1999. As hypothesized, the broad ecosystem restoration goals of the Hudson River Estuary Action Plan were more strongly supported than the corresponding specific implementation actions. We found that beliefs and past behavior were better explanatory variables than sociodemographic characteristics for explaining people's support for ecosystem restoration actions and WTP for restoration and protection goals. Because ecosystem restoration goals appear to be more generally acceptable than specific restoration actions, proponents of restoration programs should not become complacent about the need for active public outreach and involvement even if initial restoration program discussions have been low in controversy. Efforts to assess and foster support for ecosystem restoration should be targeted toward audiences identified on the basis of beliefs and past behaviors rather than on sociodemographic characteristics.

  8. Linking habitat use of Hudson River striped bass to accumulation of polychlorinated biphenyl congeners

    Energy Technology Data Exchange (ETDEWEB)

    Ashley, J.T.F.; Secor, D.H.; Zlokovitz, E.; Wales, S.Q.; Baker, J.E.

    2000-03-15

    Since 1976, the commercial striped bass fishery in the Hudson River (NY) has been closed due to total polychlorinated biphenyl (t-PCB) concentrations that exceed the US Food and Drug Administration's advisory level of 2 {micro}g/g-wet weight. Extensive monitoring of Hudson River striped bass demonstrated much more variability in t-PCB levels among individual striped bass than could be explained by their age, sex, or lipid contents. To investigate the possible role of differential habitat use among subpopulations of striped bass in controlling their PCB exposures, 70 fish collected throughout the Hudson River estuary and Long Island Sound in 1994--1995 were analyzed for PCB congeners, and their lifetime migration behaviors were estimated by otolith microchemistry. The mean salinity encountered during the fish's last growth season prior to capture was inversely correlated with the t-PCB body burden. Striped bass permanently residing in fresh and oligohaline portions of the estuary adjacent to known PCB sources had elevated t-PCB levels and congeneric patterns with higher proportions of di-, tri-, and tetrachlorobiphenyls. Conversely, fish spending the majority of their life in more saline waters of the estuary or migrating frequently throughout the salinity gradient contained lower PCB levels composed of more highly chlorinated congeners. The approach used in this study allows habitat use to be incorporated into exposure assessments for anadromous fish species such as striped bass.

  9. Lithosphere types in North China: Evidence from geology and geophysics

    Institute of Scientific and Technical Information of China (English)

    QIU; Ruizhao; DENG; Jinfu; ZHOU; Su; LI; Jinfa; XIAO; Qingh

    2005-01-01

    On the basis of the characteristics of geology and geophysics in North China, three types of lithosphere, namely, the cratonic, the orogenic and the rift lithospheres can be classified. In terms of petrological method (based on the information from Precambrian rock assemblages, igneous activities, deep-seated enclaves, etc.) and the relationship between seismic velocity and rock compositions, the crust-mantle petrological and chemical structure models can be set up. Researching results indicate that the geology and geophysics of North China platform bears the similar characteristics in comparison with those of the global typical cratons. The Eerduosi(Ordos) block located in the west of the North China Platform is a remnant of cratonic lithosphere after the North China platform had undergone "activation" in Mesozoic and "reconstruction" in Cenozoic times. The continental crust consists mainly of TTG rock assemblage while the subcontinental lithosphere mantle mainly consists of strongly depleted harzburgite. The craton was finally formed in late Archaean and early Proterozoic, and has been kept in stability up to present; its crustal-mantle petrological structures of lithosphere can be set up as a reference for the study of North China craton and even Sino-Korean craton. In the Mesozoic period, the middle and east areas of North China platform were activated in the Yanshanian orogenic process, the continental crust was reformed by material and heat-transfer of convective mantle and the original crustal TTG component was reconstructed to be granitic crust, and the subcontinental lithosphere mantle was replaced by the Yanshanian harzburgite-lherzolite. The Yanshan-Taihang Mountains were the remnants of orogenic lithosphere after the rifting in eastern North China in Cenozoic. The present thickness of continental crust and lithosphere in the Yanshan-Taihang Mountains is not equal to their thickness during the Yanshanian orogenic movement because they had undergone the

  10. Contribution of remote sensing to understand the Bay as a system

    Science.gov (United States)

    Park, A. B.; Anderson, D.; Bohn, C. G.; Chen, W. T.; Johnson, R. W.

    1978-01-01

    The natural resource management information system concept designed specifically for use with remote sensing is discussed in terms of understanding and studying the Chesapeake Bay as a total system. The Bay is defined as a system comprising the lithosphere, the hydrosphere, and the biosphere, that is the vertical profile encompassed by the systems and a two dimensional plane defining the total watershed of the Bay from the headwaters of its tributaries to a distance in the ocean defined by ten tidal cycles. The Chesapeake Bay system is assumed to be the ecosystem in the largest sense. Ecological partitioning, a methodology resulting from studies of land systems for partitioning the land into geobotanical landscape units, is included along with a breakdown of LANDSAT investigations according to subject area.

  11. Polychlorinated biphenyls, dioxins, furans, and organochlorine pesticides in spotted sandpiper eggs from the upper Hudson River basin, New York

    Science.gov (United States)

    Custer, T.W.; Custer, Christine M.; Gray, B.R.

    2010-01-01

    In 2004, spotted sandpipers (Actitis macularia) were studied on the Hudson River near Fort Edward south to New Baltimore, NY and on two river drainages that flow into the Hudson River. Concentrations of 28 organochlorine pesticides, 160 polychlorinated biphenyl (PCB) congeners, and 17 dioxin and furan (PCDD-F) congeners were quantified in eggs collected on and off the Hudson River. The pattern of organochlorine pesticides and PCDD-F congeners did not differ significantly between eggs collected on and off the Hudson River. In contrast, the pattern of PCB congeners differed significantly between the Hudson River and other rivers. Total PCBs were significantly greater in eggs from the Hudson River (geometric mean = 9.1 ??g PCBs/g wet weight) than from the other two rivers (0.6 and 0.6 ??g PCBs/g wet weight). Seven of 35 (20%) eggs exceeded 20 ??g PCBs/g wet weight, the estimated threshold for reduced hatching in tree swallows (Tachycineta bicolor) and some raptor species; the maximum concentration was 72.3 ??g PCBs/g wet weight. Models that predicted nest survival and egg success (the proportion of eggs hatching in a clutch if at least one egg hatched) as functions of contaminant levels were poorly distinguished from models that presumed no such associations. While small sample size could have contributed to the inability to distinguish among contaminant and no toxicant models, we cannot rule out the possibility that contaminant concentrations on the Hudson River were not sufficiently high to demonstrate a relationship between contaminant concentrations and reproductive success. ?? 2009 Springer Science+Business Media, LLC.

  12. 75 FR 25794 - Regulated Navigation Area: Red Bull Air Race World Championship, Upper New York Bay, Lower Hudson...

    Science.gov (United States)

    2010-05-10

    ... Gates'' that will be strategically placed in the water to form the race course. The event organizer will... will issue maritime advisories widely available to users of the waterway. If you think that your... think it qualifies and how and to what degree this rule would economically affect it. Assistance...

  13. Global strength and elastic thickness of the lithosphere

    NARCIS (Netherlands)

    Tesauro, M.; Kaban, M.K.; Cloetingh, S.A.P.L.

    2012-01-01

    Thestrengthand effective elasticthickness (Te) ofthelithosphere control its response to tectonic and surface processes. Here, we present the first globalstrengthand effective elasticthickness maps, which are determined using physical properties from recent crustal and lithospheric models. Pronounced

  14. Lithospheric instability beneath the Transverse Ranges of California

    OpenAIRE

    Houseman, Gregory A.; Neil, Emily A.; Kohler, Monica D.

    2000-01-01

    Recent high-resolution seismic experiments reveal that the crust beneath the San Gabriel Mountains portion of the Transverse Ranges thickens by 10–15 km (contrary to earlier studies). Associated with the Transverse Ranges, there is an anomalous ridge of seismically fast upper mantle material extending at least 200 km into the mantle. This high-velocity anomaly has previously been interpreted as a lithospheric downwelling. Both lithospheric downwelling and crustal thickening are associated wit...

  15. The effects of strain heating in lithospheric stretching models

    Science.gov (United States)

    Stanton, M.; Hodge, D.; Cozzarelli, F.

    1985-01-01

    The deformation by stretching of a continental type lithosphere has been formulated so that the problem can be solved by a continuum mechanical approach. The deformation, stress state, and temperature distribution are constrained to satisfy the physical laws of conservation of mass, energy, momentum, and an experimentally defined rheological response. The conservation of energy equation including a term of strain energy dissipation is given. The continental lithosphere is assumed to have the rheology of an isotropic, incompressible, nonlinear viscous, two layered solid.

  16. The elastic properties of the lithosphere beneath Scotian basin

    Science.gov (United States)

    Zheng, Ying; Arkani-Hamed, Jafar

    2002-02-01

    To assess the possibility that the North Atlantic Ocean may subduct at Scotian basin east of Canada, we investigate the present compensation state of this deep basin. A Fourier domain analysis of the bathymetry, depth to basement and observed gravity anomalies over the oceanic area east of Nova Scotia indicates that the basin is not isostatically compensated. Moreover, the analysis emphasizes that in addition to the sediments, density perturbations exist beneath the basin. The load produced by the sediments and these density perturbations must have been supported by the lithosphere. We simulate the flexure of the lithosphere under this load by that of a thin elastic plate overlying an inviscid interior. It is shown that a plate with a uniform rigidity does not adequately represent the lithosphere beneath the basin as well as the oceanic lithosphere far from the basin, rather the rigidity of the lithosphere directly beneath the basin is about one to two orders of magnitude smaller than elsewhere. We relate this weakening to the thermal blanketing effects of the thick sediments and the fact that the lithosphere has a temperature-dependent rheology. We suggest that this weak zone would have a controlling effect on the reactivation of normal faults at the hinge zone of the basin, that were formed during the break-up of Africa and North America and were locked in the early stages after the break-up. The weak zone would facilitate reactivation of the faults if tensional stresses were produced by possible reorientation of the spreading direction of the North Atlantic Ocean in the future. The reactivation of the faults would create a free boundary condition at the hinge zone, allowing further bending of the lithosphere beneath the basin and juxtaposition of this lithosphere to the mantle beneath the continent. This may provide a favorable situation for initiation of slow subduction due to subsequent compressional forces.

  17. Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (Mid-Atlantic). Bay Anchovy

    Science.gov (United States)

    1989-02-01

    Laguna Madre of Pearcy, W., and S.W. Richards. 1962. Texas . Publ. Inst. Mar. Sc. Univ. Distribution and ecology of fishes Tex. 4(2):156-200. of the Mystic...ppt) in striped bass (Morone saxatilis) in the Upper Laguna Madre , Texas (Simmons Hudson River estuary were almost 1957). In the Mid-Atlantic Region...Seasonal abundance and distribution of marine fishes at a hot-water Fish . Serv. Fish . Bull. discharge in Galveston Bay, Texas . 76(2):438-487. Contrib. Mar

  18. Effect of Upper Mantle Heterogeneities on Lithosphere Stresses and Topography

    Science.gov (United States)

    Osei Tutu, A.; Steinberger, B.; Rogozhina, I.; Sobolev, S. V.

    2016-12-01

    The orientation and magnitude of lithosphere stresses give us knowledge about most of the processes within the Earth that are not easy to observe. It has been established (Steinberger, Schmeling, and Marquart 2001) that large contribution of the forces producing lithosphere stresses have their source origination from the buoyancies of both the upper and lower mantle acting beneath the lithosphere. The contribution of the crustal thickness to the stresses has been estimated to be less than 10% (Steinberger et al. 2001) in most region and increases in areas with high gravitational potential energy like the Himalayas. In most of these studies, the effect of the crust was determined separately by computing the gravitational potential energy from the crust (Ghosh et al. 2013) and applied as correction. (Artyushkov 1973) showed that the inhomogeneous nature of the crust contribute to the stresses observed as against using constant lithosphere thickness in most studies, due to the complexities for implementing a variable lithosphere. We seek extend the approach of Ghosh et al. (2013) by coupling the Crust 1.0 (Laske et al. 2013) to a varaible lithosphere thickness in our numerical method. Using a 3D global lithosphere-asthenosphere model (Popov and Sobolev 2008) with visco-elasto-plastic rheology, coupled at 300 km depth to a mantle modeled with a spectral technique (Hager and O'Connell, 1981), we compute lithosphere stresses and topography. we compare our model with observations; the World Stress Map, Global Strain Rate Map and the observed topgraphy. We use S40RTS seismic tomography below 300 km depth, with radial viscosity distribution (Steinberger et al 2006). To account for all the heterogeneities in the upper mantle (300 km) we used different 3D temperatures models setups. The first model is the thermal lithosphere model (Artemieva and Mooney, 2001) in continental regions and assumes half-space cooling of sea floor with age (Müller et al. 2008) for oceans. For the

  19. Geodynamic inversion to constrain the nonlinear rheology of the lithosphere

    Science.gov (United States)

    Baumann, Tobias; Kaus, Boris

    2015-04-01

    A common method to determine the strength of the lithosphere is through estimating its effective elastic thickness from the coherence between gravity and topography. This method assumes a priori that the lithosphere is a thin elastic plate floating on a viscous mantle. Whereas this seems to work well with oceanic plates, it has given controversial results in continental collision zones. Usually, continental collisions zones are well-studied areas for which additional geophysical datasets such as receiver functions and seismic tomography exist that constrain the geometry of the lithosphere and often show that it is rather complex. Yet, lithospheric geometry by itself is insufficient to understand the dynamics of the lithosphere, as this also requires knowledge of the rheology of the lithosphere. Experimental results show significant variability between various rock types and there are large uncertainties in extrapolating laboratory values to nature, which leaves room for speculation. An independent approach is thus required to better understand the rheology and dynamics of the lithosphere in collision zones. Our method combines numerical thermo-mechanical forward models of the present-day lithosphere with a massively parallel Bayesian inversion approach. The geometry of the forward models is part of the a priori knowledge and is constructed from seismological data. We jointly invert topography, gravity, horizontal and vertical surface velocities to constrain the unknown rheological material parameters of the forward models in a probabilistic sense. The model rheology is described with experimentally determined viscous creep laws and other parameters describing the plastic behaviour. As viscosity is temperature dependent, the temperature structure of the forward models is parameterised as well. We apply the method to cross-sections of the India-Asia collision system. In this case, we deal with 17 to 20 model parameters, which requires solving up to 2 × 106 forward

  20. Lithosphere structure and upper mantle characteristics below the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, G.S.; Radhakrishna, M.; Sreejith, K.M.; Krishna, K.S.; Bull, J.M.

    ) and by the loading of ca. 20-km of sediments of the Bengal Fan. Here, we present the results of a combined spatial and spectral domain analysis of residual geoid, bathymetry and gravity data constrained by seismic reflection and refraction data. Self-consistent geoid...

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

    Science.gov (United States)

    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

  2. Real-time Monitoring Network to Characterize Anthropogenic and Natural Events Affecting the Hudson River, NY

    Science.gov (United States)

    Islam, M. S.; Bonner, J. S.; Fuller, C.; Kirkey, W.; Ojo, T.

    2011-12-01

    The Hudson River watershed spans 34,700 km2 predominantly in New York State, including agricultural, wilderness, and urban areas. The Hudson River supports many activities including shipping, supplies water for municipal, commercial, and agricultural uses, and is an important recreational resource. As the population increases within this watershed, so does the anthropogenic impact on this natural system. To address the impacts of anthropogenic and natural activities on this ecosystem, the River and Estuary Observatory Network (REON) is being developed through a joint venture between the Beacon Institute, Clarkson University, General Electric Inc. and IBM Inc. to monitor New York's Hudson and Mohawk Rivers in real-time. REON uses four sensor platform types with multiple nodes within the network to capture environmentally relevant episodic events. Sensor platform types include: 1) fixed robotic vertical profiler (FRVP); 2) mobile robotic undulating platform (MRUP); 3) fixed acoustic Doppler current profiler (FADCP) and 4) Autonomous Underwater Vehicle (AUV). The FRVP periodically generates a vertical profile with respect to water temperature, salinity, dissolved oxygen, particle concentration and size distribution, and fluorescence. The MRUP utilizes an undulating tow-body tethered behind a research vessel to measure the same set of water parameters as the FRVP, but does so 'synchronically' over a highly-resolved spatial regime. The fixed ADCP provides continuous water current profiles. The AUV maps four-dimensional (time, latitude, longitude, depth) variation of water quality, water currents and bathymetry along a pre-determined transect route. REON data can be used to identify episodic events, both anthropogenic and natural, that impact the Hudson River. For example, a strong heat signature associated with cooling water discharge from the Indian Point nuclear power plant was detected with the MRUP. The FRVP monitoring platform at Beacon, NY, located in the

  3. CASCO BAY PLAN

    Science.gov (United States)

    Casco Bay lies at the heart of Maine's most populated area. The health of its waters, wetlands, and wildlife depend in large part on the activities of the quarter-million residents who live in its watershed. Less than 30 years ago, portions of Casco Bay were off-limits to recr...

  4. eBay.com

    DEFF Research Database (Denmark)

    Engholm, Ida

    2014-01-01

    Celebrated as one of the leading and most valuable brands in the world, eBay has acquired iconic status on par with century-old brands such as Coca-Cola and Disney. The eBay logo is now synonymous with the world’s leading online auction website, and its design is associated with the company...

  5. Measurement error affects risk estimates for recruitment to the Hudson River stock of striped bass.

    Science.gov (United States)

    Dunning, Dennis J; Ross, Quentin E; Munch, Stephan B; Ginzburg, Lev R

    2002-06-07

    We examined the consequences of ignoring the distinction between measurement error and natural variability in an assessment of risk to the Hudson River stock of striped bass posed by entrainment at the Bowline Point, Indian Point, and Roseton power plants. Risk was defined as the probability that recruitment of age-1+ striped bass would decline by 80% or more, relative to the equilibrium value, at least once during the time periods examined (1, 5, 10, and 15 years). Measurement error, estimated using two abundance indices from independent beach seine surveys conducted on the Hudson River, accounted for 50% of the variability in one index and 56% of the variability in the other. If a measurement error of 50% was ignored and all of the variability in abundance was attributed to natural causes, the risk that recruitment of age-1+ striped bass would decline by 80% or more after 15 years was 0.308 at the current level of entrainment mortality (11%). However, the risk decreased almost tenfold (0.032) if a measurement error of 50% was considered. The change in risk attributable to decreasing the entrainment mortality rate from 11 to 0% was very small (0.009) and similar in magnitude to the change in risk associated with an action proposed in Amendment #5 to the Interstate Fishery Management Plan for Atlantic striped bass (0.006)--an increase in the instantaneous fishing mortality rate from 0.33 to 0.4. The proposed increase in fishing mortality was not considered an adverse environmental impact, which suggests that potentially costly efforts to reduce entrainment mortality on the Hudson River stock of striped bass are not warranted.

  6. Measurement Error Affects Risk Estimates for Recruitment to the Hudson River Stock of Striped Bass

    Directory of Open Access Journals (Sweden)

    Dennis J. Dunning

    2002-01-01

    Full Text Available We examined the consequences of ignoring the distinction between measurement error and natural variability in an assessment of risk to the Hudson River stock of striped bass posed by entrainment at the Bowline Point, Indian Point, and Roseton power plants. Risk was defined as the probability that recruitment of age-1+ striped bass would decline by 80% or more, relative to the equilibrium value, at least once during the time periods examined (1, 5, 10, and 15 years. Measurement error, estimated using two abundance indices from independent beach seine surveys conducted on the Hudson River, accounted for 50% of the variability in one index and 56% of the variability in the other. If a measurement error of 50% was ignored and all of the variability in abundance was attributed to natural causes, the risk that recruitment of age-1+ striped bass would decline by 80% or more after 15 years was 0.308 at the current level of entrainment mortality (11%. However, the risk decreased almost tenfold (0.032 if a measurement error of 50% was considered. The change in risk attributable to decreasing the entrainment mortality rate from 11 to 0% was very small (0.009 and similar in magnitude to the change in risk associated with an action proposed in Amendment #5 to the Interstate Fishery Management Plan for Atlantic striped bass (0.006— an increase in the instantaneous fishing mortality rate from 0.33 to 0.4. The proposed increase in fishing mortality was not considered an adverse environmental impact, which suggests that potentially costly efforts to reduce entrainment mortality on the Hudson River stock of striped bass are not warranted.

  7. Diatoms as Proxies for Abrupt Events in the Hudson River Estuary

    Science.gov (United States)

    Skorski, W.; Abbott, D. H.; Recasens, C.; Breger, D. L.

    2014-12-01

    The Hudson River estuary has been subject to many abrupt events throughout its history including hurricanes, droughts and pluvials. Hurricanes in particular are rare, discrete events that if fingerprinted can be used to develop better age models for Hudson River sediments. Proxies use observed physical characteristics or biological assemblages (e.g. diatom and foraminiferal assemblages) as tools to reconstruct past conditions prior to the modern instrumental record. Using a sediment core taken from the Hudson River (CDO2-29A), in New York City, drought and pluvial layers were selected based on Cs-137 dating while hurricane layers were determined from occurrences of tropical to subtropical foraminifera. Contrary to previous studies (Weaver, 1970, Weiss et al, 1978), more than sixty different diatom species have been identified using a scanning electron microscope (SEM). Cosmopolitan, hurricane and drought assemblages have begun to be identified after observing multiple layers (Table 1). Tropical foraminifera dominated by Globigerinoides ruber pink were also found in a hurricane layer that we infer was deposited during Hurricane Belle in 1976. More diatom abundance analyses and cataloged SEM pictures will provide further insight into these proxies. Table 1 Diatom Genera and Species Environment Clarification Cyclotella caspia Planktonic, marine-brackish Cosmopolitan Karayevia clevei Freshwater Cosmopolitan Melosira sp Planktonic, marine Cosmopolitan Thalassiosira sp Marine, brackish Cosmopolitan Staurosirella leptostauron Benthic, freshwater Cosmopolitan Actinoptychus senarius Planktonic or benthic, freshwater to brackish Hurricane and pluvial layers Amphora aff. sp Benthic, marine or freshwater Hurricane layers only Nitzschia sp Benthic, marine or freshwater Hurricane layers only Gomphonema sp Freshwater Hurricane layers only Surirella sp Marine-brackish Drought layer only Triceratium sp Marine Drought layer only Other Genera and species Environment Clarification

  8. Suspended sediment transport in the freshwater reach of the Hudson river estuary in eastern New York

    Science.gov (United States)

    Wall, G.R.; Nystrom, E.A.; Litten, S.

    2008-01-01

    Deposition of Hudson River sediment into New York Harbor interferes with navigation lanes and requires continuous dredging. Sediment dynamics at the Hudson estuary turbidity maximum (ETM) have received considerable study, but delivery of sediment to the ETM through the freshwater reach of the estuary has received relatively little attention and few direct measurements. An acoustic Doppler current profiler was positioned at the approximate limit of continuous freshwater to develop a 4-year time series of water velocity, discharge, suspended sediment concentration, and suspended sediment discharge. This data set was compared with suspended sediment discharge data collected during the same period at two sites just above the Hudson head-of-tide (the Federal Dam at Troy) that together represent the single largest source of sediment entering the estuary. The mean annual suspended sediment-discharge from the freshwater reach of the estuary was 737,000 metric tons. Unexpectedly, the total suspended sediment discharge at the study site in November and December slightly exceeded that observed during March and April, the months during which rain and snowmelt typically result in the largest sediment discharge to the estuary. Suspended sediment discharge at the study site exceeded that from the Federal Dam, even though the intervening reach appears to store significant amounts of sediment, suggesting that 30-40% of sediment discharge observed at the study site is derived from tributaries to the estuary between the Federal Dam and study site. A simple model of sediment entering and passing through the freshwater reach on a timescale of weeks appears reasonable during normal hydrologic conditions in adjoining watersheds; however, this simple model may dramatically overestimate sediment delivery during extreme tributary high flows, especially those at the end of, or after, the "flushing season" (October through April). Previous estimates of annual or seasonal sediment delivery

  9. Formation of Oceanic Lithosphere by Basal Magma Accretion

    Science.gov (United States)

    Hamza, V. M.; Cardoso, R. R.; Alexandrino, C. H.

    2009-12-01

    The thermal models of the lithosphere proposed to date have failed to provide satisfactory accounts of some of the important features in large-scale variations of ocean floor bathymetry and heat flow. The systematic difference between model calculations and observational data have given rise to the so-called “oceanic heat flow paradox”, for which no satisfactory solution has been found for over the last forty years. In the present work, we point out that this paradox is a consequence of the assumption that lateral temperature variations are absent in the sub-lithospheric mantle. In the present work we propose a simple magma accretion model and examine its implications for understanding the thermal field of oceanic lithosphere. The new model (designated VBA) assumes existence of lateral variations in magma accretion rates and temperatures at the boundary zone between the lithosphere and the asthenosphere, similar in character to those observed in magma solidification processes in the upper crust. However, unlike the previous thermal models of the lithosphere, the ratio of advection to conduction heat transfer (the Peclet number) is considered a space dependent variable. The solution to the problem of variable basal heat input has been obtained by the method of integral transform. The results of VBA model simulations reveal that the thickness of the young lithosphere increases with distance from the ridge axis, at rates faster than those predicted by Half-Space Cooling and Plate models. Another noteworthy feature of the new model is its ability to account for the main observational features in the thermal behavior of both young and old oceanic lithosphere. Thus, heat flow and bathymetry variations calculated on the basis of the VBA model provide vastly improved fits to respective observational datasets. More importantly, the improved fits to bathymetry and heat flow have been achieved for the entire age range of oceanic lithosphere and without the need to invoke

  10. The structural evolution of the deep continental lithosphere

    Science.gov (United States)

    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 ( 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 formation

  11. Descending lithosphere slab beneath the Northwest Dinarides from teleseismic tomography

    Science.gov (United States)

    Šumanovac, Franjo; Dudjak, Darko

    2016-12-01

    The area of study covers the marginal zone between the Adriatic microplate (African plate) and the Pannonian segment (Eurasian plate). We present a tomography model for this area, with special emphasis on the northwest Dinarides. A dense distribution of temporary seismic stations in the area of the Northern Dinarides along with permanent seismic stations located in the area, allowed us to construct this P-wave tomographic model. We assembled our travel-time dataset based on 26 seismic stations were used to collect the dataset. Teleseismic events were recorded for a period of 18 months and a set of 76 distant earthquakes were used to calculate the P-wave travel-time residuals. We calculated relative rather than absolute arrival-time residuals in the inversion to obtain depths of 0-400 km. We imaged a pronounced fast velocity anomaly below the NW Dinarides which directly indicates a lithosphere slab downgoing beneath the Dinarides. This fast anomaly extends towards the NW direction to at least 250 km depth, and we interpreted it as a descending lithosphere slab. The thrusting of the Adriatic microplate may be brought about by sub-lithosphere rising movement beneath the Pannonian region, along with a push from African plate. In our interpretation, the Adriatic lower lithosphere has been detached from the crust, and steeply sinks beneath the Dinarides. A lithosphere model of the contact between the Adriatic microplate and Pannonian tectonic segment was constructed based on the tomographic velocity model and results of previous crustal studies.

  12. Post-processing scheme for modelling the lithospheric magnetic field

    Directory of Open Access Journals (Sweden)

    V. Lesur

    2013-03-01

    Full Text Available We investigated how the noise in satellite magnetic data affects magnetic lithospheric field models derived from these data in the special case where this noise is correlated along satellite orbit tracks. For this we describe the satellite data noise as a perturbation magnetic field scaled independently for each orbit, where the scaling factor is a random variable, normally distributed with zero mean. Under this assumption, we have been able to derive a model for errors in lithospheric models generated by the correlated satellite data noise. Unless the perturbation field is known, estimating the noise in the lithospheric field model is a non-linear inverse problem. We therefore proposed an iterative post-processing technique to estimate both the lithospheric field model and its associated noise model. The technique has been successfully applied to derive a lithospheric field model from CHAMP satellite data up to spherical harmonic degree 120. The model is in agreement with other existing models. The technique can, in principle, be extended to all sorts of potential field data with "along-track" correlated errors.

  13. Lithospheric structure models applied for locating the Romanian seismic events

    Directory of Open Access Journals (Sweden)

    V. Oancea

    1994-06-01

    Full Text Available The paper presents our attempts made for improving the locations obtained for local seismic events, using refined lithospheric structure models. The location program (based on Geiger method supposes a known model. The program is run for some seismic sequences which occurred in different regions, on the Romanian territory, using for each of the sequences three velocity models: 1 7 layers of constant velocity of seismic waves, as an average structure of the lithosphere for the whole territory; 2 site dependent structure (below each station, based on geophysical and geological information on the crust; 3 curves deseribing the dependence of propagation velocities with depth in the lithosphere, characterizing the 7 structural units delineated on the Romanian territory. The results obtained using the different velocity models are compared. Station corrections are computed for each data set. Finally, the locations determined for some quarry blasts are compared with the real ones.

  14. A global view of the lithosphere-asthenosphere boundary.

    Science.gov (United States)

    Rychert, Catherine A; Shearer, Peter M

    2009-04-24

    The lithosphere-asthenosphere boundary divides the rigid lid from the weaker mantle and is fundamental in plate tectonics. However, its depth and defining mechanism are not well known. We analyzed 15 years of global seismic data using P-to-S (Ps) converted phases and imaged an interface that correlates with tectonic environment, varying from 95 +/- 4 kilometers beneath Precambrian shields and platforms to 81 +/- 2 kilometers beneath tectonically altered regions and 70 +/- 4 kilometers at oceanic island stations. High-frequency Ps observations require a sharp discontinuity; therefore, this interface likely represents a boundary in composition, melting, or anisotropy, not temperature alone. It likely represents the lithosphere-asthenosphere boundary under oceans and tectonically altered regions, but it may constitute another boundary in cratonic regions where the lithosphere-asthenosphere boundary is thought to be much deeper.

  15. Properties of the lithosphere and asthenosphere deduced from geoid observations

    Science.gov (United States)

    Turcotte, D. L.

    1985-01-01

    Data from the GEOS-3 and SEASAT Satellites provided a very accurate geoid map over the oceans. Broad bathymetric features in the oceans such as oceanic swells and plateaus are fully compensated. It is shown that the geoid anomalies due to the density structures of the lithosphere are proportional to the first moment of the density distribution. The deepening of the ocean basins is attributed to thermal isostasy. The thickness of the oceanic lithosphere increases with age due to the loss of heat to the sea floor. Bathymetry and the geoid provide constraints on the extent of this heat loss. Offsets in the geoid across major fracture zones can also be used to constrain this problem. Geoid bathymetry correlations show that the Hawaiian and Bermuda swells and the Cape Verde Rise are probably due to lithospheric thinning.

  16. Lithospheric strength and elastic thickness of the Barents Sea and Kara Sea region

    Science.gov (United States)

    Gac, Sébastien; Klitzke, Peter; Minakov, Alexander; Faleide, Jan Inge; Scheck-Wenderoth, Magdalena

    2016-11-01

    Interpretation of tomography data indicates that the Barents Sea region has an asymmetric lithospheric structure characterized by a thin and hot lithosphere in the west and a thick and cold lithosphere in the east. This suggests that the lithosphere is stronger in the east than in the west. This asymmetric lithosphere strength structure may have a strong control on the lithosphere response to tectonic and surface processes. In this paper, we present computed strength and effective elastic thickness maps of the lithosphere of the Barents Sea and Kara Sea region. Those are estimated using physical parameters from a 3D lithospheric model of the Barents Sea and Kara Sea region. The lithospheric strength is computed assuming a temperature-dependent ductile and brittle rheology for sediments, crust and mantle lithosphere. Results show that lithospheric strength and elastic thickness are mostly controlled by the lithosphere thickness. The model generally predicts much larger lithospheric strength and elastic thickness for the Proterozoic parts of the East Barents Sea and Kara Sea. Locally, the thickness and lithology of the continental crust disturb this general trend. At last, the gravitational potential energy (GPE) is computed. Our results show that the difference in GPE between the Barents Sea and the Mid-Atlantic Ridge provides a net horizontal force large enough to cause contraction in the western and central Barents Sea.

  17. Carbonate Chemistry Dynamics in an Area of Active Gas Seepage: the Hudson Canyon, US Atlantic Margin

    Science.gov (United States)

    Garcia-Tigreros Kodovska, F.; Kessler, J. D.; Leonte, M.; Chepigin, A.; Kellermann, M. Y.; Arrington, E. C.; Valentine, D. L.

    2015-12-01

    The fate of oceanic methane and its impact on the global climate has been of particular interest to the global community. The potential for vast amounts of methane to be emitted from the seafloor into the atmosphere due to gas hydrate decomposition has been under scientific evaluation. However, despite the great extent of these geological reservoirs, much of the methane released from the seafloor in deep ocean environments does not reach the atmosphere. Once dissolved in ocean water, the emitted methane can be microbially converted to either carbon dioxide or assimilated to biomass. Here, we will present results from a research cruise to the Hudson Canyon, northern US Atlantic Margin, where we investigated changes in ocean water carbonate chemistry induced by the oxidation of methane released from gas seeps. We will be presenting high precision pH data as well as methane and DIC concentrations, natural stable isotopes, and methane oxidation rates collected inside and adjacent to the Hudson Canyon in the summer of 2014.

  18. Low PCB concentrations observed in American eel (Anguilla rostrata) in six Hudson River tributaries

    Science.gov (United States)

    Limburg, K.E.; Machut, L.S.; Jeffers, P.; Schmidt, R.E.

    2008-01-01

    We analyzed 73 eels, collected in 2004 and 2005 above the head of tide in six Hudson River tributaries, for total PCBs, length, weight, age, and nitrogen stable isotope ratios (??15N). Mean total PCB concentration (wet weight basis) was 0.23 ppm ?? 0.08 (standard error), with a range of 0.008 to 5.4 ppm. A majority of eels (84) had concentrations below 0.25 ppm, and only seven eels (10%) had concentrations exceeding 0.5 ppm. Those eels with higher PCB concentrations were ???12 yr; there was a weak correlation of PCB concentration with ??15N and also with weight. Compared to recent (2003) data from the mainstem of the Hudson River estuary, these results indicate that tributaries are generally much less contaminated with PCBs. We hypothesize that those tributary eels with high PCB concentrations were relatively recent immigrants from the mainstem. Given concern over the possible adverse effects of PCBs on eel reproduction, these tributaries may serve as refugia. Therefore, providing improved access to upland tributaries may be critically important to this species. ?? 2008 Northeastern Naturalist.

  19. Hudson River Paleoclimate, Sea Level, and Human Impact: A Record From Piermont Marsh, NY

    Science.gov (United States)

    Kurdyla; Peteet, Dorothy; Liberman, Louisa; Sugar; Wong; Hansen, James E. (Technical Monitor)

    2001-01-01

    A 13.77 meter sediment core from Piermont Marsh, NY (40 00 N, 73 55W) records the local and regional vegetational and foraminiferal history of the Hudson Estuary. The sediments were sampled every 4 cm, which represents a decadal to centuryscale resolution. Basal sediment dating is in progress, and the 11-m depth represents about 4000 years. Changes in plant macrofossils and charcoal appear to indicate differences in salinIty and drought, suggesting changes in climate. Scirpus, Salicornia, and high levels of charcoal seem to indicate drier/more saline conditions, while lack of these macrofossils and increases in Chara/Nitella, aquatic leaves, and very little charcoal suggests wetter conditions. Other macrofossils include Carex, Juncus, Polygonum, Zanichellia, Ruppia. High resolution AMS dating of plant macrofossils is in progress, and will be compared with changes in Hudson River sediment cores offshore. Foraminiferal assemblages from key intervals of the core will be presented. Human impact in the upper sediments is visible from the influx of grass seeds, primarily Phragmites, and the ragweed pollen rise.

  20. Heterogeneity of Water Concentrations in the Mantle Lithosphere Beneath Hawaii

    Science.gov (United States)

    Bizimis, M.; Peslier, A. H.; Clague, D.

    2017-01-01

    The amount and distribution of water in the oceanic mantle lithosphere has implications on its strength and of the role of volatiles during plume/lithosphere interaction. The latter plays a role in the Earth's deep water cycle as water-rich plume lavas could re-enrich an oceanic lithosphere depleted in water at the ridge, and when this heterogeneous lithosphere gets recycled back into the deep mantle. The main host of water in mantle lithologies are nominally anhydrous minerals like olivine, pyroxene and garnet, where hydrogen (H) is incorporated in mineral defects by bonding to structural oxygen. Here, we report water concentrations by Fourier transform infrared spectrometry (FTIR) on olivine, clino- and orthopyroxenes (Cpx & Opx) from spinel peridotites from the Pali vent and garnet pyroxenite xenoliths from Aliamanu vent, both part of the rejuvenated volcanism at Oahu (Hawaii). Pyroxenes from the Aliamanu pyroxenites have high water concentrations, similar to the adjacent Salt Lake Crater (SLC) pyroxenites (Cpx 400-500 ppm H2O, Opx 200 ppm H2O). This confirms that pyroxenite cumulates form water-rich lithologies within the oceanic lithosphere. In contrast, the Pali peridotites have much lower water concentrations than the SLC ones (10% modal Cpx and low spinel Cr# (0.09-0.10). The contrast between the two peridotite suites is also evident in their trace elements and radiogenic isotopes. The Pali Cpx are depleted in light REE, consistent with minimal metasomatism. Those of SLC have enriched light REE patterns and Nd and Hf isotopes consistent with metasomatism by alkaline melts. These observations are consistent with heterogeneous water distribution in the oceanic lithosphere that may be related to metasomatism, as well as relatively dry peridotites cross-cut by narrow (?) water-rich melt reaction zones.

  1. Understanding lithospheric stresses in Arctic: constraints and models

    Science.gov (United States)

    Medvedev, Sergei; Minakov, Alexander; Lebedeva-Ivanova, Nina; Gaina, Carmen

    2016-04-01

    This pilot project aims to model stress patterns and analyze factors controlling lithospheric stresses in Arctic. The project aims to understand the modern stresses in Arctic as well as to define the ways to test recent hypotheses about Cenozoic evolution of the region. The regions around Lomonosov Ridge and Barents Sea are of particular interest driven by recent acquisition of high-resolution potential field and seismic data. Naturally, the major contributor to the lithospheric stress distribution is the gravitational potential energy (GPE). The study tries to incorporate available geological and geophysical data to build reliable GPE. In particular, we use the recently developed integrated gravity inversion for crustal thickness which incorporates up-to-date compilations of gravity anomalies, bathymetry, and sedimentary thickness. The modelled lithosphere thermal structure assumes a pure shear extension and the ocean age model constrained by global plate kinematics for the last ca. 120 Ma. The results of this approach are juxtaposed with estimates of the density variation inferred from the upper mantle S-wave velocity models based on previous surface wave tomography studies. Although new data and interpretations of the Arctic lithosphere structure become available now, there are areas of low accuracy or even lack of data. To compensate for this, we compare two approaches to constrain GPE: (1) one that directly integrates density of modelled lithosphere and (2) one that uses geoid anomalies which are filtered to account for density variations down to the base of the lithosphere only. The two versions of GPE compared to each other and the stresses calculated numerically are compared with observations. That allows us to optimize GPE and understand density structure, stress pattern, and factors controlling the stresses in Arctic.

  2. Effect Of Oceanic Lithosphere Age Errors On Model Discrimination

    Science.gov (United States)

    DeLaughter, J. E.

    2016-12-01

    The thermal structure of the oceanic lithosphere is the subject of a long-standing controversy. Because the thermal structure varies with age, it governs properties such as heat flow, density, and bathymetry with important implications for plate tectonics. Though bathymetry, geoid, and heat flow for young (geoid, and heat flow data to an inverse model to determine lithospheric structure details. Though inverse models usually include the effect of errors in bathymetry, heat flow, and geoid, they rarely examine the effects of errors in age. This may have the effect of introducing subtle biases into inverse models of the oceanic lithosphere. Because the inverse problem for thermal structure is both ill-posed and ill-conditioned, these overlooked errors may have a greater effect than expected. The problem is further complicated by the non-uniform distribution of age and errors in age estimates; for example, only 30% of the oceanic lithosphere is older than 80 MY and less than 3% is older than 150 MY. To determine the potential strength of such biases, I have used the age and error maps of Mueller et al (2008) to forward model the bathymetry for half space and GDH1 plate models. For ages less than 20 MY, both models give similar results. The errors induced by uncertainty in age are relatively large and suggest that when possible young lithosphere should be excluded when examining the lithospheric thermal model. As expected, GDH1 bathymetry converges asymptotically on the theoretical result for error-free data for older data. The resulting uncertainty is nearly as large as that introduced by errors in the other parameters; in the absence of other errors, the models can only be distinguished for ages greater than 80 MY. These results suggest that the problem should be approached with the minimum possible number of variables. For example, examining the direct relationship of geoid to bathymetry or heat flow instead of their relationship to age should reduce uncertainties

  3. The principal characteristics of the lithosphere of China

    Institute of Scientific and Technical Information of China (English)

    Tingdong Li

    2010-01-01

    The lithospheric structure of China and its adjacent area is very complex and is marked by several prominent characteristics. Firstly, China's continental crust is thick in the west but thins to the east, and thick in the south but thins to the north. Secondly, the continental crust of the Qinghai-Tibet Plateau has an average thickness of 60-65 km with a maximum thickness of 80 km, whereas in eastern China the average thickness is 30-35 kin, with a minimum thickness of only 5 km in the center of the South China Sea. The average thickness of continental crust in China is 47.6 km, which greatly exceeds the global average thickness of 39.2 km. Thirdly, as with the crust, the lithosphere of China and its adjacent areas shows a general pattern of thicker in the west and south, and thinner in the east and north. The lithosphere of the Qinghai-Tibet Plateau and northwestern China has an average thickness of 165 kin,with a maximum thickness of 180-200 km in the central and eastern parts of the Tarim Basin, Pamir,and Changdu areas. In contrast, the vast areas to the east of the Da Hinggan Ling-Taihang-Wuling Mountains, including the marginal seas, are characterized by lithospheric thicknesses of only 50-85 km. Fourthly, in western China the lithosphere and asthenosphere behave as a "layered structure",reflecting their dynamic background of plate collision and convergence. The lithosphere and asthenosphere in eastern China display a "block mosaic structure", where the lithosphere is thin and the asthenosphere is very thick, a pattern reflecting the consequences of crustal extension and an upsurge of asthenospheric materials. The latter is responsible for a huge low velocity anomaly at a depth of 85-250 km beneath East Asia and the western Pacific Ocean. Finally, in China there is an age structure of "older in the upper layers and younger in the lower layers" between both the upper and lower crusts and between the crust and the lithospheric mantle.

  4. Satellite tidal magnetic signals constrain oceanic lithosphere-asthenosphere boundary

    DEFF Research Database (Denmark)

    Grayver, Alexander V.; Schnepf, Neesha R.; Kuvshinov, Alexey V.

    2016-01-01

    , there are no reports that these signals have been used to infer subsurface structure. We use satellite-detected tidal magnetic fields to image the global electrical structure of the oceanic lithosphere and upper mantle down to a depth of about 250 km. Themodel derived from more than 12 years of satellite data reveals...... a ≈72-km-thick upper resistive layer followed by a sharp increase in electrical conductivity likely associated with the lithosphere-asthenosphere boundary, which separates colder rigid oceanic plates from the ductile and hotter asthenosphere....

  5. Seismic imaging of the downwelling Indian lithosphere beneath central Tibet.

    Science.gov (United States)

    Tilmann, Frederik; Ni, James

    2003-05-30

    A tomographic image of the upper mantle beneath central Tibet from INDEPTH data has revealed a subvertical high-velocity zone from approximately 100- to approximately 400-kilometers depth, located approximately south of the Bangong-Nujiang Suture. We interpret this zone to be downwelling Indian mantle lithosphere. This additional lithosphere would account for the total amount of shortening in the Himalayas and Tibet. A consequence of this downwelling would be a deficit of asthenosphere, which should be balanced by an upwelling counterflow, and thus could explain the presence of warm mantle beneath north-central Tibet.

  6. Remobilization in the cratonic lithosphere recorded in polycrystalline diamond

    Science.gov (United States)

    Jacob; Viljoen; Grassineau; Jagoutz

    2000-08-18

    Polycrystalline diamonds (framesites) from the Venetia kimberlite in South Africa contain silicate minerals whose isotopic and trace element characteristics document remobilization of older carbon and silicate components to form the framesites shortly before kimberlite eruption. Chemical variations within the garnets correlate with carbon isotopes in the diamonds, indicating contemporaneous formation. Trace element, radiogenic, and stable isotope variations can be explained by the interaction of eclogites with a carbonatitic melt, derived by remobilization of material that had been stored for a considerable time in the lithosphere. These results indicate more recent formation of diamonds from older materials within the cratonic lithosphere.

  7. Groundwater quality in the Upper Hudson River Basin, New York, 2012

    Science.gov (United States)

    Scott, Tia-Marie; Nystrom, Elizabeth A.

    2014-01-01

    Water samples were collected from 20 production and domestic wells in the Upper Hudson River Basin (north of the Federal Dam at Troy, New York) in New York in August 2012 to characterize groundwater quality in the basin. The samples were collected and processed using standard U.S. Geological Survey procedures and were analyzed for 148 physiochemical properties and constituents, including dissolved gases, major ions, nutrients, trace elements, pesticides, volatile organic compounds (VOCs), radionuclides, and indicator bacteria. The Upper Hudson River Basin covers 4,600 square miles in upstate New York, Vermont, and Massachusetts; the study area encompasses the 4,000 square miles that lie within New York. The basin is underlain by crystalline and sedimentary bedrock, including gneiss, shale, and slate; some sandstone and carbonate rocks are present locally. The bedrock in some areas is overlain by surficial deposits of saturated sand and gravel. Eleven of the wells sampled in the Upper Hudson River Basin are completed in sand and gravel deposits, and nine are completed in bedrock. Groundwater in the Upper Hudson River Basin was typically neutral or slightly basic; the water typically was moderately hard. Bicarbonate, chloride, calcium, and sodium were the major ions with the greatest median concentrations; the dominant nutrient was nitrate. Methane was detected in 7 samples. Strontium, iron, barium, boron, and manganese were the trace elements with the highest median concentrations. Two pesticides, an herbicide degradate and an insecticide degredate, were detected in two samples at trace levels; seven VOCs, including chloroform, four solvents, and the gasoline additive methyl tert-butyl ether (MTBE) were detected in four samples. The greatest radon-222 activity, 2,900 picocuries per liter, was measured in a sample from a bedrock well; the median radon activity was higher in samples from bedrock wells than in samples from sand and gravel wells. Coliform bacteria were

  8. Deformation of the Pannonian lithosphere and related tectonic topography: a depth-to-surface analysis

    NARCIS (Netherlands)

    Dombrádi, E.

    2012-01-01

    Fingerprints of deep-seated, lithospheric deformation are often recognised on the surface, contributing to topographic evolution, drainage organisation and mass transport. Interactions between deep and surface processes were investigated in the Carpathian-Pannonian region. The lithosphere beneath th

  9. Deformation of the Pannonian lithosphere and related tectonic topography: a depth-to-surface analysis

    NARCIS (Netherlands)

    Dombrádi, E.

    2012-01-01

    Fingerprints of deep-seated, lithospheric deformation are often recognised on the surface, contributing to topographic evolution, drainage organisation and mass transport. Interactions between deep and surface processes were investigated in the Carpathian-Pannonian region. The lithosphere beneath th

  10. Biscayne Bay Alongshore Epifauna

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Field studies to characterize the alongshore epifauna (shrimp, crabs, echinoderms, and small fishes) along the western shore of southern Biscayne Bay were started in...

  11. Bathymetry in Jobos Bay

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a 4x4 meter resolution bathymetric surface for Jobos Bay, Puerto Rico (in NAD83 UTM 19 North). The depth values are in meters referenced to the...

  12. Hammond Bay Biological Station

    Data.gov (United States)

    Federal Laboratory Consortium — Hammond Bay Biological Station (HBBS), located near Millersburg, Michigan, is a field station of the USGS Great Lakes Science Center (GLSC). HBBS was established by...

  13. Chesapeake Bay Tributary Strategies

    Science.gov (United States)

    Chesapeake Bay Tributary Strategies were developed by the seven watershed jurisdictions and outlined the river basin-specific implementation activities to reduce nutrient and sediment pollutant loads from point and nonpoint sources.

  14. Humboldt Bay Orthoimages

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set consists of 0.5-meter pixel resolution, four band orthoimages covering the Humboldt Bay area. An orthoimage is remotely sensed image data in which...

  15. De vluchtige olie van enkele chemotypen van mentha suaveolens EHRH. en van hybriden met mentha longifolia (L.) HUDSON

    NARCIS (Netherlands)

    Hendriks, Hindrik

    1974-01-01

    De opvatting dat Mentha x piperita L. een bastaard zou zijn van Mentha spicata L. en Mentha aquatica L. werd nader besproken. Hierbij werd Mentha spicata beschouwd als een bastaard van Mentha longifolia (L.) HUDSON en Mentha suaveolens EHRH. ... Zie: Samenvatting.

  16. De vluchtige olie van enkele chemotypen van mentha suaveolens EHRH. en van hybriden met mentha longifolia (L.) HUDSON

    NARCIS (Netherlands)

    Hendriks, Hindrik

    1974-01-01

    De opvatting dat Mentha x piperita L. een bastaard zou zijn van Mentha spicata L. en Mentha aquatica L. werd nader besproken. Hierbij werd Mentha spicata beschouwd als een bastaard van Mentha longifolia (L.) HUDSON en Mentha suaveolens EHRH. ... Zie: Samenvatting.

  17. Declining metal levels at Foundry Cove (Hudson River, New York): Response to localized dredging of contaminated sediments

    Energy Technology Data Exchange (ETDEWEB)

    Mackie, Joshua A. [Moss Landing Marine Laboratories, Invertebrate Zoology, 8272 Moss Landing Road, CA 95039-9647 (United States)], E-mail: jmackie@mlml.calstate.edu; Natali, Susan M.; Levinton, Jeffrey S. [Stony Brook University, Department of Ecology and Evolution, Stony Brook, NY 11794-5245 (United States); Sanudo-Wilhelmy, Sergio A. [Stony Brook University, Department of Ecology and Evolution, Stony Brook, NY 11794-5245 (United States); University of Southern California, Marine and Environmental Biology, Los Angeles, CA 90089-0371 (United States)

    2007-09-15

    This study examines the effectiveness of remediating a well-recognized case of heavy metal pollution at Foundry Cove (FC), Hudson River, New York. This tidal freshwater marsh was polluted with battery-factory wastes (1953-1979) and dredged in 1994-1995. Eight years after remediation, dissolved and particulate metals (Cd, Co, Cu, Pb, Ni, and Ag) were found to be lower than levels in the lower Hudson near New York City. Levels of metals (Co, Ni, Cd) on suspended particles were comparatively high. Concentrations of surface sediment Cd throughout the marsh system remain high, but have decreased both in the dredged and undredged areas: Cd was 2.4-230 mg/kg dw of sediment in 2005 vs. 109-1500 mg/kg in the same area in 1983. The rate of tidal export of Cd from FC has decreased by >300-fold, suggesting that dredging successfully stemmed a major source of Cd to the Hudson River. - Dredging of a hotspot of metal-contaminated sediment is associated with a recognizable local and river-wide decline in cadmium in the Hudson River, New York.

  18. 77 FR 34285 - Safety Zone; 2012 Ironman U.S. Championship Swim, Hudson River, Fort Lee, NJ

    Science.gov (United States)

    2012-06-11

    ... the January 17, 2008, issue of the Federal Register (73 FR 3316). Public Meeting We do not plan now to... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; 2012 Ironman U.S. Championship Swim, Hudson... vicinity of Englewood Cliffs and Fort Lee, NJ for the 2012 Ironman U.S. Championship swim event....

  19. 77 FR 66215 - Notice of Final Federal Agency Actions on the Tappan Zee Hudson River Crossing Project in New York

    Science.gov (United States)

    2012-11-02

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF TRANSPORTATION Federal Highway Administration Notice of Final Federal Agency Actions on the Tappan Zee Hudson River Crossing Project in New York Correction In notice document 2012-26799, appearing on page 65929 in the...

  20. 78 FR 59231 - Regulated Navigation Area-Tappan Zee Bridge Construction Project, Hudson River; South Nyack and...

    Science.gov (United States)

    2013-09-26

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA11 Regulated Navigation Area--Tappan Zee Bridge... area (RNA) on the navigable waters of the Hudson River surrounding the Tappan Zee Bridge. This... situation created by the construction of the Tappan Zee Bridge. The Coast Guard has discussed this...

  1. eBay.com

    DEFF Research Database (Denmark)

    Engholm, Ida

    2014-01-01

    Celebrated as one of the leading and most valuable brands in the world, eBay has acquired iconic status on par with century-old brands such as Coca-Cola and Disney. The eBay logo is now synonymous with the world’s leading online auction website, and its design is associated with the company......’s purpose: selling millions of goods, some of which are ‘designer’ items and some of which are considered design icons....

  2. Lateral heterogeneity and vertical stratification of cratonic lithospheric keels: examples from Europe, Siberia, and North America

    DEFF Research Database (Denmark)

    Artemieva, Irina; Cherepanova, Yulia; Herceg, Matija;

    The presentation summarizes geophysical models for Precambrian cratons, including the structure of the crust and the lithospheric mantle. A particular focus is on thermo-compositional heterogeneity of the lithospheric mantle as constrained by different geophysical data sets: (i) thermal structure...... by an increase in mantle density as compared to light and strongly depleted lithospheric mantle of the Archean nuclei....

  3. Basin evolution in a folding lithosphere: Altai-Sayan and Tien Shan belts in Central Asia

    NARCIS (Netherlands)

    Delvaux, D.; Cloetingh, S.; Beekman, F.; Sokoutis, D.; Burov, E.; Buslov, M.M.; Abdrakhmatov, K.E.

    2013-01-01

    Central Asia is a classical example for continental lithospheric folding. In particular, the Altay–Sayan belt in South-Siberia and the Kyrgyz Tien Shan display a special mode of lithospheric deformation, involving decoupled lithospheric mantle folding and upper crustal folding and faulting. Both are

  4. The crust and lithosphere thicknesses in South America: trying to find the lithosphere- asthenosphere boundary

    Science.gov (United States)

    Heit, B.; Sodoudi, F.; Yuan, X.; Bianchi, M.; Kind, R.

    2007-05-01

    During the past years, a series of seismological investigations have been carried out to study the crustal and mantle structures all over the world. In South America, this investigation has not been an easy task as there are different regions where the geodynamics involves the subduction of an oceanic plate, the building of a mountain range as the Andes, the interaction with older lithosphere as the Brazilian Shield and the presence of active deformation fronts between the last two regions. In order to investigate the thickness of the lithosphere in such a complex context we have performed S-wave receiver function analysis (Vinnik and Farra, 2000; Li et al., 2004). The S receiver function technique looks for the S-to-P converted waves at seismic discontinuities beneath a station in the same way as the conventional P receiver function method that deals with P-to-S conversions. The S receiver function technique have proved to be useful to map the Moho and the LAB in many regions where other methods (i.e. surface waves) failed to provide reliable information (e.g. Li et al., 2004; Kumar et al., 2004a, 2004b; Sodoudi et al., 2006). We present here the results of S receiver function technique that has been applied to all the available temporary seismic experiments (e.g. BANJO, SEDA, REFUCA, BLSP) and the permanent stations from the IRIS network. We have been able to investigate the upper mantle discontinuities at all the depths beneath the stations and obtained coherent Moho depths along the entire Andes and in other South American continental regions. The LAB has been clearly detected below some stations, particularly those that are located far away from the subduction zone. By comparing our results with those from the P receiver functions, we have been able to further constrain the thicknesses of the crust and LAB in different regions including shields, mobile belts, basins and mountain ranges. At many stations we have also been able to map the upper mantle

  5. Petrological imaging of the Cordilleran lithosphere beneath Craven Lake, NCVP, BC, Canada: local evidence for a texturally diverse, hydrous lithosphere

    Science.gov (United States)

    Miller, Christine; Edwards, Benjamin R.; Russell, James K.; Peterson, Nils

    2010-05-01

    Peridotite and pyroxenite xenoliths from the glaciovolcanic Craven Lake center (Edwards et al., 2006) provide local evidence for a texturally diverse, hydrous lithosphere beneath the Stikine terrane, in the Canadian Cordilleran lithosphere. Although the xenolith suite is dominated by spinel lherzolite, websterite and Ol websterite xenoliths also occur. Veins of amphibole, with local apatite, have so far been found in one spinel lherzolite and one websterite xenolith. Although interstitial amphibole has been reported from at least two localities in the northern Cordillera, we believe that this is the first documented occurrence of an amphibole vein in lithospheric peridotite and pyroxenite. Textural analysis shows that the xenoliths from Craven Lake are on average finer grained (~2.0 mm) and less equigranular than xenolith suites from localities to the north (e.g. Harder and Russell, 2005) or to the south (e.g. Peslier et al., 2002). Clinopyroxene-orthopyroxene geothermometry of a peridotite sample indicates that the temperatures of equilibration (964-1022C at 0.1 GPa) are well within the established stability limits of amphibole at lithospheric pressures. Observations on the Craven Lake suite have important implications for the petrology of the Cordilleran lithosphere. Textural observations confirm that the lithosphere beneath the accreted terranes in British Columbia is distinctly heterogeneous, which is consistent with at least local lithospheric variation that could be due in part to tectonism during Mesozoic terrane accretion. Documentation of veins of amphibole plus apatite in the Cordilleran lithosphere is consistent with the Francis and Ludden (1995) hypothesis that the veins could be lithospheric sources for volumetrically minor but spatially wide-spread nephelinite throughout the Canadian Cordilleran, which were remelted during Neogene to Recent, extension-related magmatism. The formation of the veins may be linked to Mesozoic subduction zone metasomatism

  6. A lithospheric perspective on structure and evolution of Precambrian cratons

    DEFF Research Database (Denmark)

    Artemieva, Irina

    2012-01-01

    the roots of the continents, and moves together with continental plates. Depending on geophysical techniques (and physical properties measured), the lithosphere has different practical definitions. Most of them (i.e., seismic, electrical) are on the basis of a sharp change in temperature-dependent physical...

  7. Seismicity in Romania--evidence for the sinking lithosphere.

    Science.gov (United States)

    Roman, C

    1970-12-19

    The revision of Romanian earthquakes shows a distribution suggesting a sinking lithosphere under the Carpathian arc. Thermal and gravitational anomalies, as well as petrological and tectonic features, provide further evidence on the cause and character of intermediate earthquakes of Romania. This is consistent with the theory of plate tectonics in south-east Europe.

  8. Upper mantle viscosity and lithospheric thickness under Iceland

    NARCIS (Netherlands)

    Barnhoorn, A.; Wal, W. van der; Drury, M.R.

    2011-01-01

    Deglaciation during the Holocene on Iceland caused uplift due to glacial isostatic adjustment. Relatively low estimates for the upper mantle viscosity and lithospheric thickness result in rapid uplift responses to the deglaciation cycles on Iceland. The relatively high temperatures of the upper mant

  9. European Lithospheric Mantle; geochemical, petrological and geophysical processes

    Science.gov (United States)

    Ntaflos, Th.; Puziewicz, J.; Downes, H.; Matusiak-Małek, M.

    2017-04-01

    The second European Mantle Workshop occurred at the end of August 2015, in Wroclaw, Poland, attended by leading scientists in the study the lithospheric mantle from around the world. It built upon the results of the first European Mantle Workshop (held in 2007, in Ferrara, Italy) published in the Geological Society of London Special Publication 293 (Coltorti & Gregoire, 2008).

  10. A lithospheric perspective on structure and evolution of Precambrian cratons

    DEFF Research Database (Denmark)

    Artemieva, Irina

    2012-01-01

    the roots of the continents, and moves together with continental plates. Depending on geophysical techniques (and physical properties measured), the lithosphere has different practical definitions. Most of them (i.e., seismic, electrical) are on the basis of a sharp change in temperature-dependent physical...

  11. Lithospheric Architecture, Heterogenities, Instabilities, Melting - insight form numerical modelling

    Science.gov (United States)

    Gorczyk, Weronika; Hobbs, Bruce; Ord, Alison; Gessner, Klaus; Gerya, Taras V.

    2010-05-01

    The seismological structure of the Earth's lithosphere is identified to be strongly heterogeneous in terms of thermal and rheological structures. Lithospheric discontinuities (sharp changes in the thermal and/or compositional structure) are thought to be long lived and are mostly correlated with major tectonic boundaries that commonly have been reactivated and which subsequently are the foci of magma intrusion and major mineralization. Resent studies have shown that mantle metasomatism is also controlled by such boundaries. This paper explores the control that lithospheric heterogeneity exerts on the thermal and chemical evolution during deformation subsequent to the development of the heterogeneity. We explore the behaviour of the rheological heterogeneous lithosphere in a compressional regime. The occurrence of such variations may be caused for instance by amalgamation of micro-continents such as is thought to be characteristic of the Yilgarn, Western Australia or South Africa. Theses micro-continents, due to diverse histories may be characterised by various thermal and rheological structures. The models are simplistic but illustrate the basic principles. The code used in this study is based on a conservative finite-difference, multi-grid, marker in cell method. Devolatilisation reactions and melting can affect the physical properties of rocks and are incorporated in a self-consistent manner. We use a petrological-thermomechanical modelling approach with all rock properties including mechanical properties calculated in the Lagrangian scheme for rock markers at every time step based on Gibbs free energy minimization as a function of the local pressure, temperature and rock composition. The results illustrate that initial structural complexity is necessary for and has a dramatic effect on fault and development, the growth of deep basins, core complex formation, melting and devolatilisation within the lithosphere. The horizontal and vertical variation in plastic

  12. Lithospheric Convergence Preceded Extension in the Pannonian-Carpathian System

    Science.gov (United States)

    Houseman, Gregory; Stuart, Graham; Dando, Ben; Hetenyi, Gyorgy; Lorinczi, Piroska; Hegedus, Endre; Brueckl, Ewald

    2010-05-01

    The continuing collision of the Adriatic block with European continental lithosphere has its clearest expression now in the Alpine collision zone. Recent tomographic images of the upper mantle beneath the eastern Alps and western Pannonian Basin support the interpretation that in the Early Miocene the collision zone extended further east: a steeply dipping seismically fast structure stretches downward beneath the Eastern Alps reaching to the base of the transition zone, consistent with the long history of convergence in this region. This high velocity structure also extends eastward beneath the extensional Pannonian Basin. The high velocity anomaly beneath the Basin is strongly developed in transition zone depths (410 to 660 km) but the anomaly weakens upward. High velocities beneath the center of the extensional basin are unexpected because there is substantive evidence that the onset of extension in the Pannonian domain at around 17 Ma produced rapid extension of the lithosphere and replacement of the lower part of the lithosphere by hot asthenosphere. These deeper structures, however, must be explained by the long history of convergence that preceded the extension of the basin. Further evidence of a history of sustained convergence in the present Pannonian region is found in the depression of the 660 km seismic discontinuity beneath the Alps (Lombardi et al., EPSL, 2009) and also beneath the Pannonian Basin (Hetenyi et al., GRL, 2009). The 660 km discontinuity in both places is depressed by as much as 40 km, whereas the 410 km discontinuity is at approximately nominal depths. Evidently in both regions relatively dense material derived from the mid-Miocene collision sits stagnant on top of the 660 km discontinuity, where further descent is obstructed by the negative Clapeyron slope of the spinel-to-perovskite phase transition and/or the high viscosity of the lower mantle. The rapid extension of the Intra-Carpathian Basins in the Mid-Miocene (between about 17 and

  13. Winter-time circulation and sediment transport in the Hudson Shelf Valley

    Science.gov (United States)

    Harris, C.K.; Butman, B.; Traykovski, P.

    2003-01-01

    The Hudson Shelf Valley is a bathymetric low that extends across the continental shelf offshore of New York and New Jersey. From December 1999 to April 2000 a field experiment was carried out to investigate the transport of sediment in the shelf and valley system. Near-bed tripods and water-column moorings were deployed at water depths from 38 to 75 m in the axis of the shelf valley and at about 26 m on the adjacent shelves offshore of New Jersey and Long Island, New York. These measured suspended sediment concentrations, current velocities, waves, and water column properties. This paper analyzes observations made during December 1999 and January 2000, and presents the first direct near-bed measurements of suspended sediment concentration and sediment flux from the region. Sediment transport within the Hudson Shelf Valley was coherent over tens of kilometers, and usually aligned with the axis of the shelf valley. Down-valley (off-shore) transport was associated with energetic waves, winds from the east, moderate current velocities (5-10 cm/s), and sea level setup at Sandy Hook, NJ. Up-valley (shoreward) transport occurred frequently, and was associated with winds from the west, low wave energy, high current velocities (20-40 cm/s), and sea level set-down at the coast. Within the shelf valley, net sediment flux (the product of near-bed concentration and velocity) was directed shoreward, up the axis of the valley. Current velocities and suspended sediment fluxes on the New York and New Jersey continental shelves were lower than within the shelf valley, and exhibited greater variability in alignment. Longer term meteorological data indicate that wind, setup, and wave conditions during the study period were more conducive to up-valley transport than seasonal data suggest as average. To relate the observed up-valley sediment flux to observed accumulation of contaminants within the Hudson Shelf Valley requires consideration of transport over longer timescales than those

  14. Seismic constraints on the lithosphere-asthenosphere boundary

    Science.gov (United States)

    Rychert, Catherine A.

    2014-05-01

    The basic tenet of plate tectonics is that a rigid plate, or lithosphere, moves over a weaker asthenospheric layer. However, the exact location and defining mechanism of the boundary at the base of the plate, the lithosphere-asthenosphere boundary (LAB) is debated. The oceans should represent a simple scenario since the lithosphere is predicted to thicken with seafloor age if it thermally defined, whereas a constant plate thickness might indicate a compositional definition. However, the oceans are remote and difficult to constrain, and studies with different sensitivities and resolutions have come to different conclusions. Hotspot regions lend additional insight, since they are relatively well instrumented with seismic stations, and also since the effect of a thermal plume on the LAB should depend on the defining mechanism of the plate. Here I present new results using S-to-P receiver functions to image upper mantle discontinuity structure beneath volcanically active regions including Hawaii, Iceland, Galapagos, and Afar. In particular I focus on the lithosphere-asthenosphere boundary and discontinuities related to the base of melting, which can be used to highlight plume locations. I image a lithosphere-asthenosphere boundary in the 50 - 95 km depth range beneath Hawaii, Galapagos, and Iceland. Although LAB depth variations exist within these regions, significant thinning is not observed in the locations of hypothesized plume impingement from receiver functions (see below). Since a purely thermally defined lithosphere is expected to thin significantly in the presence of a thermal plume anomaly, a compositional component in the definition of the LAB is implied. Beneath Afar, an LAB is imaged at 75 km depth on the flank of the rift, but no LAB is imaged beneath the rift itself. The transition from flank of rift is relatively abrupt, again suggesting something other than a purely thermally defined lithosphere. Melt may also exist in the asthenosphere in these regions

  15. Module bay with directed flow

    Science.gov (United States)

    Torczynski, John R.

    2001-02-27

    A module bay requires less cleanroom airflow. A shaped gas inlet passage can allow cleanroom air into the module bay with flow velocity preferentially directed toward contaminant rich portions of a processing module in the module bay. Preferential gas flow direction can more efficiently purge contaminants from appropriate portions of the module bay, allowing a reduced cleanroom air flow rate for contaminant removal. A shelf extending from an air inlet slit in one wall of a module bay can direct air flowing therethrough toward contaminant-rich portions of the module bay, such as a junction between a lid and base of a processing module.

  16. Preseismic Lithosphere-Atmosphere-Ionosphere Coupling

    Science.gov (United States)

    Kamogawa, Masashi

    hardly verified so far, a statistical approach has been unique way to promote the research. After the 2000s, several papers showing robust statistical results have arisen. In this paper, we focus on publications satisfying the following identification criteria: 1) A candidate of precursor, namely anomaly, is quantitatively defied. 2) Two time-series of anomalies and earthquake are constructed within the fixed thresholds such as a minimum magnitude, a region, and a lead-time. 3) To obtain a statistical correlation, a statistical process which includes four relations considering all combination among earthquake - no earthquake versus anomaly and no anomalies is applied, e. g., phi correlation. 4) For correlations under various thresholds the results keep consistency. 5) Large anomalies appear before large earthquakes. One of papers based on the identification criteria, which concerns preseismic geoelectrically anomalies, is introduced as an educative example. VAN method in Greece, i. e., Geo-electric potential difference measurement for precursor study in Greece, has been often discussed in the point of view of success and failure performance for practical prediction [Varotsos et al, Springer, 2011] to show a correlation and then less number of papers shows the statistical correlation with satisfying the identification criteria [Geller (ed.), GRL, 1996], so that the phenomena had been controversial. However, recent related study in Kozu-Island, Japan which satisfied the criteria showed the robust correlation [Orihara and Kamogawa et al., PNAS, 2012]. Therefore, the preseismic geoelectric anomalies are expected to be a precursor. Preseismic lithosphere-atmosphere-ionosphere coupling has been intensively discussed [Kamogawa, Eos, 2006]. According to review based on the identification criteria with considering recent publications, plausible precursors have been found, which are tropospheric anomaly [Fujiwara and Kamogawa, GRL, 2004], daytime electron depletion in F region

  17. 33 CFR 100.124 - Maggie Fischer Memorial Great South Bay Cross Bay Swim, Great South Bay, New York.

    Science.gov (United States)

    2010-07-01

    ... South Bay Cross Bay Swim, Great South Bay, New York. 100.124 Section 100.124 Navigation and Navigable... NAVIGABLE WATERS § 100.124 Maggie Fischer Memorial Great South Bay Cross Bay Swim, Great South Bay, New York... swimmer or safety craft on the swim event race course bounded by the following points: Starting Point...

  18. Transitions in the Colonial Hudson Valley: Capitalist, Bulk Goods, and Braudelian

    Directory of Open Access Journals (Sweden)

    Jonathan Leitner

    2016-03-01

    Full Text Available A long debate about the American “transition to capitalism” was apparently settled via a rough consensus on the gradual prevalence of rural capitalism in the north; and that even small, subsistence-oriented farm households engaged in some market exchange, while market-oriented farm households engaged in some subsistence activities. Yet certain Marxist scholars argue that even prevalent market exchange did not necessarily signify a capitalist economy.  Similarly, certain world-systems scholars see the debates as somewhat pointless, inasmuch as capitalism is a systemic characteristic that exists regardless of any individual identification. These latter notions derive in part from Braudel’s tripartite structure of early modern economic life, which sees self-sufficiency and basic daily survival existing alongside market economies and everyday forms of exchange, with the capitalist world-economy in turn overarching, yet not necessarily affecting, the other two levels.  This paper posits that colonial America’s “transition” to capitalism was effectively the gradual, often contested, and geographically uneven addition of Braudel’s second layer of economic life – the market economy – onto the first layer of self-sufficiency and basic material life; with this process arguably driven by the third layer of the larger capitalist economy, as other recent studies of the colonial Hudson Valley have focused on, albeit while ignoring the region’s diverse and uneven economic geography  It explores the notion of geographically-uneven Braudelian economic structures and transitions within the late 17th and 18th century colonial Hudson Valley, a region of four rather distinct subregions demonstrating that even within relatively small geographical spaces, at least at certain times, one can find different means of Braudelian economic life, and by extension, varying articulations with the world-economy and possible paths to eventual core emergence.

  19. La foresta tropicale come paradiso perduto: Green Mansions di W.H. Hudson

    Directory of Open Access Journals (Sweden)

    Nicoletta Brazzelli

    2012-05-01

    Full Text Available In W.H. Hudson’s Green Mansions (1904 the mysterious and enchanting quality of the natural world is represented through the writer’s powerful imagination, and the exotic landscape of the South American rainforest is related to British territorial expansion: according to a long-standing literary tradition, the European colonial desire is projected onto remote, unknown places. On the one hand, the pristine forest appears a pure space, a site unspoiled by colonial expansion, the primitive and sacred world nourishing Western exotic dreams. On the other hand, by revisiting the myth of the lost paradise, Hudson conveys the late nineteenth-early twentieth century European perception of the tropical world, a patchwork of Charles Darwin’s theories, Biblical echoes and colonial ideology. Abel surrenders to the influence of the wild, ventures into the weird and entangled forest, seemingly refusing male invasion and domination. Rima’s subsequent death symbolizes the ecological catastrophe brought about by the Europeans in the primitive world of South America: the feathered bird-girl is assimilated to an Edenic being at the mercy of destructive forces. At the same time, Abel’s wish to possess the land reinforces the colonial viewpoint of the narration, while the movement from civilization to the wilderness implies the representation of a Darwinian struggle. Hudson frames the tropical space as substantially ambiguous, attractive and destructive for both colonizers and colonized, and through his narrative he introduces the fear of natural loss in the extreme form of the extinction of the green world.

  20. The Fermi's Bayes Theorem

    CERN Document Server

    D'Agostini, G

    2005-01-01

    It is curious to learn that Enrico Fermi knew how to base probabilistic inference on Bayes theorem, and that some influential notes on statistics for physicists stem from what the author calls elsewhere, but never in these notes, {\\it the Bayes Theorem of Fermi}. The fact is curious because the large majority of living physicists, educated in the second half of last century -- a kind of middle age in the statistical reasoning -- never heard of Bayes theorem during their studies, though they have been constantly using an intuitive reasoning quite Bayesian in spirit. This paper is based on recollections and notes by Jay Orear and on Gauss' ``Theoria motus corporum coelestium'', being the {\\it Princeps mathematicorum} remembered by Orear as source of Fermi's Bayesian reasoning.

  1. Matching Lithosphere velocity changes to the GOCE gravity signal

    Science.gov (United States)

    Braitenberg, Carla

    2016-07-01

    Authors: Carla Braitenberg, Patrizia Mariani, Alberto Pastorutti Department of Mathematics and Geosciences, University of Trieste Via Weiss 1, 34100 Trieste Seismic tomography models result in 3D velocity models of lithosphere and sublithospheric mantle, which are due to mineralogic compositional changes and variations in the thermal gradient. The assignment of density is non-univocal and can lead to inverted density changes with respect to velocity changes, depending on composition and temperature. Velocity changes due to temperature result in a proportional density change, whereas changes due to compositional changes and age of the lithosphere can lead to density changes of inverted sign. The relation between velocity and density implies changes in the lithosphere rigidity. We analyze the GOCE gradient fields and the velocity models jointly, making simulations on thermal and compositional density changes, using the velocity models as constraint on lithosphere geometry. The correlations are enhanced by applying geodynamic plate reconstructions to the GOCE gravity field and the tomography models which places today's observed fields at the Gondwana pre-breakup position. We find that the lithosphere geometry is a controlling factor on the overlying geologic elements, defining the regions where rifting and collision alternate and repeat through time. The study is carried out globally, with focus on the conjugate margins of the African and South American continents. The background for the study can be found in the following publications where the techniques which have been used are described: Braitenberg, C., Mariani, P. and De Min, A. (2013). The European Alps and nearby orogenic belts sensed by GOCE, Boll. Bollettino di Geofisica Teorica ed Applicata, 54(4), 321-334. doi:10.4430/bgta0105---- Braitenberg, C. and Mariani, P. (2015). Geological implications from complete Gondwana GOCE-products reconstructions and link to lithospheric roots. Proceedings of 5th

  2. New isostatic model of the lithosphere and gravity field

    Science.gov (United States)

    Kaban, M. K.; Schwintzer, P.; Reigber, Ch.

    2003-04-01

    A new global model of the isostatic gravity field based on the up-to-date data sets is computed in terms of gravity and geoid. The initial gravity field model is improved using the new CHAMP data. For a construction of the isostatic model of the lithosphere we use the latest compilation of crustal data. Globally this is the CRUST2.0 model, which is supplemented by detailed original data for large parts of North America and North Eurasia. The long-wavelengths of the computed isostatic anomalies up to spherical harmonic degree 20 reflect deep density heterogeneities and the influence of mantle convection through the dynamic topography. The signal contribution of the isostatically balanced lithosphere to the observed gravity or geoid is still significant also for the long-wavelengths: -30- +60 mGal and -15- +40 m peak-to-peak, respectively. Generally the long-wavelength isostaticaly reduced gravity field has much less correlation with the lithosphere patterns than the observed field. This demonstrates that the long-wavelength isostatic gravity field is more appropriate for a modelling of mantle convection than the observed one. The smaller scale isostatic anomalies (wavelengths less than 2000 km) on the other hand are highly sensitive to the quality of the input data used for their computation. To a large extent they reflect internal crustal density inhomogeneities, not included in the isostatic compensation scheme, and uncertainties in the initial crustal data. Thus, small-scale isostatic anomalies may not be always interpreted as a measure of the disturbances of isostatic balance of the lithosphere. Instead we suggest to compute for the smaller scale spectral part the non-isostatic residual topography. The initial crust - upper mantle density model is corrected by gravity inversion in a least squares adjustment. Then, the residual (unbalanced) topography computed with the corrected density distribution represents the isostatic state of the lithosphere. The maximum

  3. South China Sea crustal thickness and lithosphere thinning from satellite gravity inversion incorporating a lithospheric thermal gravity anomaly correction

    Science.gov (United States)

    Kusznir, Nick; Gozzard, Simon; Alvey, Andy

    2016-04-01

    The distribution of ocean crust and lithosphere within the South China Sea (SCS) are controversial. Sea-floor spreading re-orientation and ridge jumps during the Oligocene-Miocene formation of the South China Sea led to the present complex distribution of oceanic crust, thinned continental crust, micro-continents and volcanic ridges. We determine Moho depth, crustal thickness and continental lithosphere thinning (1- 1/beta) for the South China Sea using a gravity inversion method which incorporates a lithosphere thermal gravity anomaly correction (Chappell & Kusznir, 2008). The gravity inversion method provides a prediction of ocean-continent transition structure and continent-ocean boundary location which is independent of ocean isochron information. A correction is required for the lithosphere thermal gravity anomaly in order to determine Moho depth accurately from gravity inversion; the elevated lithosphere geotherm of the young oceanic and rifted continental margin lithosphere of the South China Sea produces a large lithosphere thermal gravity anomaly which in places exceeds -150 mGal. The gravity anomaly inversion is carried out in the 3D spectral domain (using Parker 1972) to determine 3D Moho geometry and invokes Smith's uniqueness theorem. The gravity anomaly contribution from sediments assumes a compaction controlled sediment density increase with depth. The gravity inversion includes a parameterization of the decompression melting model of White & McKenzie (1999) to predict volcanic addition generated during continental breakup lithosphere thinning and seafloor spreading. Public domain free air gravity anomaly, bathymetry and sediment thickness data are used in this gravity inversion. Using crustal thickness and continental lithosphere thinning factor maps with superimposed shaded-relief free-air gravity anomaly, we improve the determination of pre-breakup rifted margin conjugacy, rift orientation and sea-floor spreading trajectory. SCS conjugate margins

  4. Metasomatized lithosphere and the origin of alkaline lavas.

    Science.gov (United States)

    Pilet, Sébastien; Baker, Michael B; Stolper, Edward M

    2008-05-16

    Recycled oceanic crust, with or without sediment, is often invoked as a source component of continental and oceanic alkaline magmas to account for their trace-element and isotopic characteristics. Alternatively, these features have been attributed to sources containing veined, metasomatized lithosphere. In melting experiments on natural amphibole-rich veins at 1.5 gigapascals, we found that partial melts of metasomatic veins can reproduce key major- and trace-element features of oceanic and continental alkaline magmas. Moreover, experiments with hornblendite plus lherzolite showed that reaction of melts of amphibole-rich veins with surrounding lherzolite can explain observed compositional trends from nephelinites to alkali olivine basalts. We conclude that melting of metasomatized lithosphere is a viable alternative to models of alkaline basalt formation by melting of recycled oceanic crust with or without sediment.

  5. The Gutenberg discontinuity: melt at the lithosphere-asthenosphere boundary.

    Science.gov (United States)

    Schmerr, Nicholas

    2012-03-23

    The lithosphere-asthenosphere boundary (LAB) beneath ocean basins separates the upper thermal boundary layer of rigid, conductively cooling plates from the underlying ductile, convecting mantle. The origin of a seismic discontinuity associated with this interface, known as the Gutenberg discontinuity (G), remains enigmatic. High-frequency SS precursors sampling below the Pacific plate intermittently detect the G as a sharp, negative velocity contrast at 40- to 75-kilometer depth. These observations lie near the depth of the LAB in regions associated with recent surface volcanism and mantle melt production and are consistent with an intermittent layer of asthenospheric partial melt residing at the lithospheric base. I propose that the G reflectivity is regionally enhanced by dynamical processes that produce melt, including hot mantle upwellings, small-scale convection, and fluid release during subduction.

  6. Swarm magnetic and GOCE gravity gradient grids for lithospheric modelling

    DEFF Research Database (Denmark)

    Bouman, Johannes; Ebbing, Jörg; Kotsiaros, Stavros

    We explore how Swarm magnetic gradient and GOCE gravity gradient data can improve modelling of the Earth’s lithosphere and thereby contribute to a better understanding of Earth’s dynamic processes. We study the use of gradient grids to provide improved information about the lithosphere and upper...... mantle in the well-surveyed North-East Atlantic Margin. In particular, we present the computation of magnetic and gravity gradient grids at satellite altitude (roughly 450 km and 250 km above the Earth for Swarm and GOCE respectively). It is shown that regional solutions based on a tesseroid approach may...... contain more signal content than global models do. The patchwork of regional grids is presented as well as the subsequent error reduction through iterative downward and upward continuation using the Poisson integral equation. The promises and pitfalls are discussed of using grids at mean satellite...

  7. Physico-chemical constraints on cratonic lithosphere discontinuities

    Science.gov (United States)

    Aulbach, Sonja; Rondenay, Stéphane; Huismans, Ritske

    2014-05-01

    The origins of the mid-lithospheric discontinuity (MLD) and lithosphere-asthenosphere boundary (LAB) have received much attention over the recent years. Peculiarities of cratonic lithosphere construction - compositional and rheological stratification due to thickening in collisional settings or by plume subcretion, multiple metasomatic overprints due to longevity - offer a variety of possibilities for the generation of discontinuities. Interconnected small degrees of conductive partial melt (carbonate-rich melts, such as carbonatites and kimberlites, or highly alkaline melts) at the cratonic LAB, which produce seismic discontinuities, may be generated in the presence of volatiles. These depress the peridotite solidus sufficiently to intersect the mantle adiabat at depths near the cratonic LAB at ~160-220 km, i.e. above the depth of metal saturation where carbonatite becomes unstable. The absence of agreement between the different seismic and magnetotelluric estimates for the depth of the LAB beneath Kaapvaal may be due to impingement of a plume, leading to a pervasively, but heterogeneously metasomatised ('asthenospherised') hot and deep root. Such a root and hot sublithosphere may yield conflicting seismic-thermal-geochemical depths for the LAB. The question arises whether the chemical boundary layer should be defined as above or below the asthenospherised part of the SCLM, which has preserved isotopic, compositional (non-primitive olivine forsterite content) and physical evidence (e.g. from teleseismic tomography and receiver functions) for a cratonic heritage and which therefore is still distinguishable from the asthenospheric mantle. If cratonic lithosphere overlies anomalously hot mantle for extended periods of time, the LAB may be significantly thinned, aided by penetration of relatively high-degree Fe-rich partial melts, as has occurred beneath the Tanzanian craton. Xenoliths from the deep Slave craton show little evidence for 'asthenospherisation'. Its root

  8. Fifth generation lithospheric magnetic field model from CHAMP satellite measurements

    OpenAIRE

    Maus, S.; Hermann Lühr; Martin Rother; Hemant, K.; Balasis, G.; Patricia Ritter; Claudia Stolle

    2007-01-01

    Six years of low-orbit CHAMP satellite magnetic measurements have provided an exceptionally high-quality data resource for lithospheric magnetic field modeling and interpretation. Here we describe the fifth-generation satellite-only magnetic field model MF5. The model extends to spherical harmonic degree 100. As a result of careful data selection, extensive corrections, filtering, and line leveling, the model has low noise levels, even if evaluated at the Earth's surface. The model is particu...

  9. Alpine Lithosphere and Upper Mantle Passive Seismic Monitoring

    OpenAIRE

    Brückl, Ewald; Hausmann, Helmut; Behm, Michael; Lippitsch, Regina; Mitterbauer, Ulrike; Institute of Geodesy and Geophysics Vienna University of Technology (Hrsg.)

    2008-01-01

    The project ALPASS is a passive seismic monitoring project aiming to reveal upper mantle, lower lithosphere, and asthenosphere beneath the wider Eastern Alpine region, including the Bohemian Massive, the Carpathians, the Pannonian Basin, and the Dinarides. A 3D seismic model which will provide crustal corrections to the seismic travel times has been generated in this area down to the Moho and the uppermost mantle from data of former projects CELEBRATION 2000 and ALP 2002. ALPASS will yield in...

  10. The effects of lithospheric thickness and density structure on Earth's stress field

    Science.gov (United States)

    Naliboff, J. B.; Lithgow-Bertelloni, C.; Ruff, L. J.; de Koker, N.

    2012-01-01

    Lithospheric density and thickness variations are important contributors to the state of stress of the plates. The relationship between the lithosphere's isostatic state, subcrustal structure and stress field, however, remains unresolved due to the uncertainties on its thickness, composition and rheology. To study the influence of lithospheric structure on intraplate stresses, we use a new model of global lithospheric structure (TDL) that accounts for the presence of depleted mantle to explore the effects of isostatic compensation, mantle density structure, lithospheric thickness (base depth) and mechanical coupling within the lithosphere on wavelengths >200 km. We compute the mean lithostatic stress (Ω) of 2°× 2° lithospheric columns and then solve for the resulting global 'tectonic' stress field for a homogeneous elastic lithosphere with the finite element package ABAQUS. For a 100 km base depth, a historically common value for lithospheric thickness, tectonic stress patterns are largely insensitive to mantle density structure and match patterns in the world stress map, for both isostatically compensanted and non-compensated lithospheric structure. Increasing the base depth up to 250 km to account for thick continental roots, however, leads to sharp variations in the stress field between isostatic lithospheric structure models and TDL as the mantle portion of the lithosphere dominates Ω. Decreasing the model base depths up to 25 km as a proxy for vertical strength variations due to low viscosity channels within the crust or lithosphere as a whole, strongly alters stresses in magnitude, azimuth and regime, as the influence of topography and shallow crustal structure increases. We find that restricting spatial changes in Ω to a specified region to mimic lateral variations in strength also has a large effect on the resulting stresses, which leads us to conclude that regional models may not always be adequate for modelling the stress field. Strong deviations

  11. The State of Lithospheric Stress in Greater Thailand

    Science.gov (United States)

    Meyers, B.; Furlong, K. P.; Pananont, P.; Pornsopin, P.

    2013-12-01

    Thailand and its surrounding regions occupy an important, but often overlooked, location in terms of plate tectonics and lithospheric deformation. The lateral extrusion of Tibet southeastward and eastward along deep strike slip faults to the north and the Sumatra-Andaman subduction zone to the south and west bound the region of greater Thailand. While it is adjacent to some of the most seismically active plate boundaries and intra-plate regions on Earth, this region has experienced only a low level of background seismicity. Thus, the long-term seismic potential of greater Thailand remains highly uncertain. Although historic seismicity is one indicator for future seismicity it is not the only tool we have for determining seismic hazard; we can assess the state of lithospheric stress. The stress conditions in this apparent aseismic region will be controlled by the forces acting on it boundaries. We can analyze those conditions through a study of fault structure, earthquake activity, and kinematics in the boundary area. Using Global Seismic Network (GSN) data augmented with Thai seismic network data to constrain the kinematics, and numerical finite element modeling of crustal and lithospheric deformation of the region, we are able to determine to overall stress conditions. This stress model can be compared to the known fault states in Thailand to assess the potential for earthquake activity.

  12. A Top to Bottom Lithospheric Study of Africa and Arabia

    Energy Technology Data Exchange (ETDEWEB)

    Pasyanos, M

    2006-10-31

    We study the lithospheric structure of Africa, Arabia and adjacent oceanic regions with fundamental-mode surface waves over a wide period range. Including short period group velocities allows us to examine shallower features than previous studies of the whole continent. In the process, we have developed a crustal thickness map of Africa. Main features include crustal thickness increases under the West African, Congo, and Kalahari cratons. We find crustal thinning under Mesozoic and Cenozoic rifts, including the Benue Trough, Red Sea, and East, Central, and West African rift systems. Crustal shear wave velocities are generally faster in oceanic regions and cratons, and slower in more recent crust and in active and formerly active orogenic regions. Deeper structure, related to the thickness of cratons and modern rifting, is generally consistent with previous work. Under cratons we find thick lithosphere and fast upper mantle velocities, while under rifts we find thinned lithosphere and slower upper mantle velocities. There are no consistent effects in areas classified as hotspots, indicating that there seem to be numerous origins for these features. Finally, it appears that the African Superswell has had a significantly different impact in the north and the south, indicating specifics of the feature (temperature, time of influence, etc.) to be dissimilar between the two regions. Factoring in other information, it is likely that the southern portion has been active in the past, but that shallow activity is currently limited to the northern portion of the superswell.

  13. Mechanisms Responsible for the Observed Thermodynamic Structure in a Convective Boundary Layer Over the Hudson Valley of New York State

    Science.gov (United States)

    Freedman, Jeffrey M.; Fitzjarrald, David R.

    2017-02-01

    We examine cases of a regional elevated mixed layer (EML) observed during the Hudson Valley Ambient Meteorology Study (HVAMS) conducted in New York State, USA in 2003. Previously observed EMLs referred to topographic domains on scales of 105 -106 km2 . Here, we present observational evidence of the mechanisms responsible for the development and maintenance of regional EMLs overlying a valley-based convective boundary layer (CBL) on much smaller spatial scales (deployed during the HVAMS, we show that cross-valley horizontal advection, along-valley channelling, and fog-induced cold-air pooling are responsible for the formation and maintenance of the EML and valley-CBL coupling over New York State's Hudson Valley. The upper layer stability of the overlying EML constrains growth of the valley CBL, and this has important implications for air dispersion, aviation interests, and fog forecasting.

  14. OTOLITH MICROCHEMISTRY INDICATES UNEXPECTED PATTERNS OF RESIDENCY AND ANADROMY IN BLUEBACK HERRING, ALOSA AESTIVALIS, IN THE HUDSON AND MOHAWK RIVERS.

    Directory of Open Access Journals (Sweden)

    LIMBURG K. E.

    2001-07-01

    PIXE, providing a detailed time series of data on the Sr:Ca, and thus habitat use history, of the fish. We also analyzed otoliths of Mohawk and Hudson River young-of-year (YOY. The Sr:Ca ratios of Mohawk YOY are slightly but significantly higher than those of Hudson YOY. Life history transects for 51 adults show complex patterns of Sr:Ca, indicating that many of the fish move into salt water at least for brief periods. However, many fish appear to spend extended parts of their post-YOY lives in fresh water, and at least two adults (caught in the Mohawk near Rome, NY appear never to have changed habitats at all. This is thus the first demonstration of residency in Mohawk River herring.

  15. Richards Bay effluent pipeline

    CSIR Research Space (South Africa)

    Lord, DA

    1986-07-01

    Full Text Available This report discusses the adequate provision for waste disposal is an essential part of the infrastructure needed in the development of Richards Bay as a deepwater harbour and industrial/metropolitan area. Having considered various options for waste...

  16. Polychlorinated biphenyls (PCBs) in adult and juvenile mallards (Anas platyrhynchos) from the Hudson River, New York, USA.

    Science.gov (United States)

    Madden, Sean S; Skinner, Lawrence C

    2016-09-01

    The Hudson River, NY, USA is contaminated for over 300 km with polychlorinated biphenyls (PCBs) released from two General Electric (GE) capacitor plants. We collected adult and juvenile mallards (Anas platyrhynchos) from four different areas of the river; an area upstream of the GE plants (n = 38), two areas directly downstream of the GE plants (n = 41, n = 38), and an area more than 100 km downstream in the freshwater tidal river (n = 20). Collections occurred during July and August (2008) when ducks were flightless to ensure ducks were "resident" and exposures were local. Fat and muscle tissue were analyzed for PCBs. PCBs were detected in all samples, and mallards below the GE plant sites on the Hudson River had orders of magnitude higher concentrations of PCBs than those above the plants. Juvenile mallards from areas directly downstream of the GE plant sites tended to have higher PCB concentrations in fat than adults. The patterns of PCB congeners and homolog groups varied across the study areas, with areas directly downstream of the GE plants dominated by tetra-chloro biphenyls whereas samples from upstream and the freshwater tidal river tended towards higher chlorinated congeners. Congener patterns between male and female and juvenile and adult mallards were generally similar within study areas, with the exception of one area downstream of the GE plants where adult birds exhibited different patterns than juveniles. Evidence of PCBs from the GE plant sites was detected in the tidal Hudson River, more than 100 km downstream of the plant sites. More than 90% of the ducks collected in areas downstream of the GE plants but above the tidally influenced river exceed the USFDA tolerance level for PCBs in poultry, which should be a concern for consumers of waterfowl taken in proximity to the upper Hudson River.

  17. Catastrophic meltwater discharge down the Hudson Valley: a potential trigger for the Intra-Allerød cold period

    Science.gov (United States)

    Donnelly, Jeffrey P.; Driscoll, Neal W.; Uchupi, Elazar; Keigwin, Loyd D.; Schwab, William C.; Thieler, E. Robert; Swift, Stephen A.

    2005-01-01

    Glacial freshwater discharge to the Atlantic Ocean during deglaciation may have inhibited oceanic thermohaline circulation, and is often postulated to have driven climatic fluctuations. Yet attributing meltwater-discharge events to particular climate oscillations is problematic, because the location, timing, and amount of meltwater discharge are often poorly constrained. We present evidence from the Hudson Valley and the northeastern U.S. continental margin that establishes the timing of the catastrophic draining of Glacial Lake Iroquois, which breached the moraine dam at the Narrows in New York City, eroded glacial lake sediments in the Hudson Valley, and deposited large sediment lobes on the New York and New Jersey continental shelf ca. 13,350 yr B.P. Excess 14C in Cariaco Basin sediments indicates a slowing in thermohaline circulation and heat transport to the North Atlantic at that time, and both marine and terrestrial paleoclimate proxy records around the North Atlantic show a short-lived (<400 yr) cold event (Intra-Aller??d cold period) that began ca. 13,350 yr B.P. The meltwater discharge out the Hudson Valley may have played an important role in triggering the Intra-Aller??d cold period by diminishing thermohaline circulation. ?? 2005 Geological Society of America.

  18. Lithospheric Stress and Geodynamics: History, Accomplishments and Challenges

    Science.gov (United States)

    Richardson, R. M.

    2016-12-01

    The kinematics of plate tectonics was established in the 1960s, and shortly thereafter the Earth's stress field was recognized as an important constraint on the dynamics of plate tectonics. Forty years ago the 1976 Chapman Conference on the Stress in the Lithosphere, which I was fortunate to attend as a graduate student, and the ensuing 1977 PAGEOPH Stress in the Earth publication's 28 articles highlighted a range of datasets and approaches that established fertile ground for geodynamic research ever since. What are the most useful indicators of stress? Do they measure residual or tectonic stresses? Local or far field sources? What role does rheology play in concentrating deformation? Great progress was made with the first World Stress Map in 1991 by Zoback and Zoback, and the current version (2016 release with 42,348 indicators) remains a tremendous resource for geodynamic research. Modeling sophistication has seen significant progress over the past 40 years. Early applications of stress to dynamics involved simple lithospheric flexure, particularly at subduction zones, Hawaii, and continental foreland basin systems. We have progressed to full 3-D finite element models for calculating the flexure and stress associated with loads on a crust and mantle with realistic non-linear viscoelastic rheology, including frictional sliding, low-temperature plasticity, and high-temperature creep. Initial efforts to use lithospheric stresses to constrain plate driving forces focused on a "top-down" view of the lithosphere. Such efforts have evolved to better include asthenosphere-lithosphere interactions, have gone from simple to complicated rheologies, from 2-D to 3-D, and seek to obtain a fully thermo-mechanical model that avoids relying on artificial boundary conditions to model plate dynamics. Still, there are a number of important issues in geodynamics, from philosophy (when are more complicated models necessary? can one hope to identify "the" answer with modeling, or only

  19. Structure of the Lithosphere in Central Europe: Integrated Density Modelling

    Science.gov (United States)

    Bielik, M.; Grinč, M.; Zeyen, H. J.; Plašienka, D.; Pasteka, R.; Krajňák, M.; Bošanský, M.; Mikuška, J.

    2014-12-01

    Firstly, we present new results related to the lithospheric structure and tectonics of the Central Europe and the Western Carpathians. For geophysical study of the lithosphere in Central Europe we calculated four original 2D lithosphere-scales transects crossing this area from the West European Platform in the North to the Aegean Sea in the South and from the Adriatic Sea in the West to the East European Platform in the East. Modelling is based on the joint interpretation of gravity, geoid, topography and surface heat flow data with temperature-dependent density. Wherever possible, crustal structure is constrained by seismic data. The thickness of the lithosphere decreases from the older and colder platforms to the younger and hotter Pannonian Basin with a maximum thickness under the Eastern and Southern Carpathians. The thickness of the Carpathian arc lithosphere varies between 150 km in the North (the Western Carpathians) and about 300 km in the Vrancea zone (the Eastern and Southern Carpathian junction). In the Platform areas it is between 120 and 150 km and in the Pannonian Basin it is about 70 km. The models show that the Moesian Platform is overthrust from the North by the Southern Carpathians and from the South by the Balkanides and characterized by bending of this platform. In all transects, the thickest crust is found underneath the Carpathian Mountains or, as in the case of the Vrancea area, under their immediate foreland. The thickest crust outside the orogens is modelled for the Moesian Platform with Moho depths of up to 45 km. The thinnest crust is located under the Pannonian Basin with about 26-27 km. Secondly, our presentation deals with construction of the stripped gravity map in the Turiec Basin, which represents typical intramontane Neogene depression of the Western Carpathians. Based on this new and original gravity map corrected by regional gravity effect we were able to interpret the geological structure and tectonics of this sedimentary basin

  20. Latest Holocene evolution and human disturbance of a channel segment in the Hudson River Estuary

    Science.gov (United States)

    Klingbeil, A.D.; Sommerfield, C.K.

    2005-01-01

    The latest Holocene sedimentary record of a cohesive channel and subtidal shoal in the lower Hudson River Estuary was examined to elucidate natural (sea-level rise, sediment transport) and anthropogenic (bulkheading, dredging) influences on the recent morphodynamic evolution of the system. To characterize the seafloor and shallow subbottom, ??? 100 km of high-resolution seismic reflection profiles (chirp) were collected within a 20-km reach of the estuary and correlated with sediment lithologies provided by eight vibracores recovered along seismic lines. Sediment geochronology with 137Cs and 14C was used to estimate intermediate and long-term sedimentation rates, respectively, and historical bathymetric data were analyzed to identify regional patterns of accretion and erosion, and to quantify changes in channel geometry and sediment volume. The shoal lithosome originated around 4 ka presumably with decelerating eustatic sea level rise during the latest Holocene. Long-term sedimentation rates on the shoal (2.3-2.6 mm/yr) are higher than in the channel (2 mm/yr) owing to hydrodynamic conditions that preferentially sequester suspended sediment on the western side of the estuary. As a result, the shoal accretes oblique to the principal axis of tidal transport, and more rapidly than the channel to produce an asymmetric cross-section. Shoal deposits consist of tidally bedded muds and are stratified by minor erosion surfaces that seismic profiles reveal to extend for 10s of meters to kilometers. The frequency and continuity of these surfaces suggest that the surficial shoal is catastrophically stripped on decadal-centennial time scales by elevated tidal flows; tidal erosion maintains the shoal at a uniform depth below sea level and prevents it from transitioning to an intertidal environment. Consequently, the long-term sedimentation rate approximates the rate of sea-level rise in the lower estuary (1-3 mm/yr). After the mid 1800s, the natural geometry of the lower Hudson

  1. Hudson Canyon benthic habitats characterization and mapping by integrated analysis of multidisciplinary data

    Science.gov (United States)

    Pierdomenico, Martina; Guida, Vincent G.; Rona, Peter A.; Macelloni, Leonardo; Scranton, Mary I.; Asper, Vernon; Diercks, Arne

    2013-04-01

    Hudson Canyon, about 180 km SE of New York City, is the largest eastern U.S. submarine canyon and is under consideration for HAPC (Habitat Area of Particular Concern) status, representing a fisheries and biodiversity hot spot. Interest in the area, within the perspective of ecosystem based management, marine spatial planning, habitat and species conservation, led to a joint project between NOAA Northeast Fisheries, U.S. Geological Survey (USGS), Mississippi Mineral Research Institute (MMRI), National Institute for Undersea Science and Technology (NIUST), Stony Brook and Rutgers Universities for the study of benthic habitats, that includes the assembly of existing data with newly collected ones: acoustic mapping, visual ground-truthing, hydrographic, sedimentological, and trawl data collections. Acoustic mapping, performed using AUV-mounted multibeam sonar, provided ultra-high resolution bathymetric and backscatter imagery (3m and 1m respectively) at all water depths for identification of geomorphological features and for the characterization of surficial sediments along the two thirds of the shelf portion of the canyon. Identification of benthic and demersal communities was accomplished by visual ground thruthing with underwater vehicle video and still cameras, and from trawl catch data. A CTD-rosette sampler provided water column salinity-temperature profiles and water samples for dissolved methane analysis in the vicinity of suspected bottom sources. Analysis of data revealed a complex of topographic structures and hydrological patterns that provide a wide range of physical habitats in a relatively small area. A mosaic of sandy and muddy substrates, gravel beds, rock outcrops, and semilithified clay outcrops host rich and varied faunal assemblages, including deepwater corals and sponge communities. Pockmark fields, occurring below 300 m depth, suggest that methane-based chemosynthetic carbonate deposition contributes to creation of specific hard bottom habitats

  2. Preface to "Insights into the Earth's Deep Lithosphere"

    Energy Technology Data Exchange (ETDEWEB)

    Pasyanos, M E

    2009-11-19

    Dear Readers: I am pleased to present a special issue of Tectonophysics entitled 'Insights into the Earth's Deep Lithosphere.' This compilation sought to capture the flavor of the increasing number of studies that are emerging to investigate the complex lithospheric structure of the earth. This issue evolved out of a Fall 2007 AGU special session entitled 'Understanding the Earth's Deep Lithosphere' that I organized with Irina Artemieva from the University of Copenhagen. For that session, we solicited talks that discussed the increasing number of methods that have surfaced to study various aspects of the earth's deep lithosphere. These methods include seismic, gravity, thermal, geochemical, and various combinations of these methods. The quality of the presentations (2 oral sessions with 16 talks and 23 associated poster presentations) was such that we felt that the emerging topic deserved a dedicated forum to address these questions in greater detail. The availability of new data sets has also improved the number and quality of lithospheric studies. With many new studies and methodologies, a better understanding of both continental and oceanic lithospheres is starting to emerge. Questions remain about the thickness and evolution of the lithosphere, the presence of lithospheric keels, the density and anisotropy of lithospheric roots, mechanisms of lithospheric thinning, and differences between mechanical, thermal and chemical boundary layers. While we did not get contributions on the full gamut of methods and regions, a lot of ground was covered in this issue's manuscripts. Like any collection of papers on the deep lithosphere, the topics are quite varied in methodology, geographic location, and what aspect of the lithosphere being studied. Still, the results highlight the rewarding aspects of earth structure, history, and evolution that can be gleaned. A brief synopsis of the papers contained in this issue is given.

  3. Global map of lithosphere thermal thickness on a 1 deg x 1 deg grid - digitally available

    DEFF Research Database (Denmark)

    Artemieva, Irina

    2014-01-01

    than 250 km) lithosphere is restrictedsolely to young Archean terranes (3.0–2.6 Ga), while in old Archean cratons (3.6–3.0 Ga) lithospheric roots donot extend deeper than 200–220 km.The TC1 model is presented by a set of maps, which show significant thermal heterogeneity within continentalupper mantle......This presentation reports a 1 deg 1 deg global thermal model for the continental lithosphere (TC1). The modelis digitally available from the author’s web-site: www.lithosphere.info.Geotherms for continental terranes of different ages (early Archean to present) are constrained by reliabledata...

  4. Bathymetric controls on sediment transport in the Hudson River estuary: Lateral asymmetry and frontal trapping

    Science.gov (United States)

    Ralston, David K.; Geyer, W. Rockwell; Warner, John C.

    2012-01-01

    Analyses of field observations and numerical model results have identified that sediment transport in the Hudson River estuary is laterally segregated between channel and shoals, features frontal trapping at multiple locations along the estuary, and varies significantly over the spring-neap tidal cycle. Lateral gradients in depth, and therefore baroclinic pressure gradient and stratification, control the lateral distribution of sediment transport. Within the saline estuary, sediment fluxes are strongly landward in the channel and seaward on the shoals. At multiple locations, bottom salinity fronts form at bathymetric transitions in width or depth. Sediment convergences near the fronts create local maxima in suspended-sediment concentration and deposition, providing a general mechanism for creation of secondary estuarine turbidity maxima at bathymetric transitions. The lateral bathymetry also affects the spring-neap cycle of sediment suspension and deposition. In regions with broad, shallow shoals, the shoals are erosional and the channel is depositional during neap tides, with the opposite pattern during spring tides. Narrower, deeper shoals are depositional during neaps and erosional during springs. In each case, the lateral transfer is from regions of higher to lower bed stress, and depends on the elevation of the pycnocline relative to the bed. Collectively, the results indicate that lateral and along-channel gradients in bathymetry and thus stratification, bed stress, and sediment flux lead to an unsteady, heterogeneous distribution of sediment transport and trapping along the estuary rather than trapping solely at a turbidity maximum at the limit of the salinity intrusion.

  5. Accumulation of polychlorinated biphenyls in american shad during their migration in the Hudson River, spring 1977.

    Science.gov (United States)

    Pastel, M; Bush, B; Kim, J S

    1980-06-01

    Fifty-two female American shad (Alosa sapidissima) were collected during the spring of 1977 at two sites on the lower Hudson River, 27 miles and 75 miles from the river mouth. The fish were extracted with hexane, and the extracts were analyzed by electron-capture gas chromatography (EC-GC) and by GC/mass spectrometry (MS), PCBs were quantitated by EC-GC, and the concentrations were compared by fish length and by site. Fish collected from the downstream site contained a mean PCB concentration of 2.0 +/- 1.0 microgram/g, wet weight; fish from the upstream site contained a mean PCB concentration of 6.1 +/- 2.6 microgram/g, wet weight. Aliquots of the hexane extracts were fractionated before analysis by GC/MS. The presence of PCBs was confirmed, and DDE and the alkane series from C22 through C26 were detected. American shad are saltwater fish that only enter fresh water to spawn. Because they do not feed in fresh water before spawning, they may be used as an indicator of water contamination.

  6. A simulation of the Cerro Hudson SO[sub 2] cloud

    Energy Technology Data Exchange (ETDEWEB)

    Schoeberl, M.R.; Lait, L.R.; Newman, P.A.; Krueger, A.J. (NASA Goddard Space Flight Center, Greenbelt, MD (United States)); Doiron, S.D. (Hughes STX Corp., Lanham, MD (United States))

    1993-02-20

    An isentropic trajectory model is used to simulate the evolution of the southern hemisphere SO[sub 2] cloud associated with the eruption of Cerro Hudson. By matching the parcel trajectories with total ozone mapping spectrometer SO[sub 2] retrievals, the principal stratospheric injection region is determined to be between 11 and 16 km in altitude. This region is characterized by weak wind shears and is located just poleward of the subtropical jet in the outer fringe of the stratospheric polar vortex. The lack of wind shear in the injection region explains the slow zonal dispersal of the SO[sub 2] cloud which was still clearly observed 19 days after the eruption. The trajectory model simulation of the SO[sub 2] cloud shows good agreement with observations for 7 days after the eruption. Using the potential vorticity and potential temperature estimates of the initial eruption cloud, the cloud position relative to the polar night jet is shown to be nearly fixed up to September 2, 1991, which was as long as the cloud was observed. This result suggests that the lower stratopsheric polar and mid-latitude regions are nearly isolated from each other during the late August period. 9 refs., 5 figs.

  7. The lithosphere of the Appalachian orogen and Atlantic passive margin

    Science.gov (United States)

    Fischer, K. M.; MacDougall, J. G.; Hawman, R. B.; Parker, E. H.; Wagner, L. S.

    2012-12-01

    The lithosphere of the Appalachian orogen and Atlantic passive margin has recorded repeated episodes of continental collision and break-up. Improved resolution of crust and mantle structure in this region holds promise for better understanding of orogenesis, rifting and passive margin development. At a broad scale, tomographic models manifest a decrease in lithospheric thickness from the central U.S. craton into the Appalachian orogen. Migration of Sp scattered waves indicates that a significant drop in shear-wave velocity typically occurs at depths of 80-120 km in the eastern U.S., and where these phases fall within the transition from high velocity lid to lower velocity mantle obtained from tomography, they are interpretable as the seismological lithosphere-asthenosphere boundary. Beneath the Appalachians and coastal plain, Sp-derived lithospheric thicknesses are larger than those found in the tectonically active western U.S. where values range from 40-90 km. The vertical shear velocity gradients required to produce the observed Sp phases are sharp (drops of 4-10% over governed solely by temperature, but they may be explained by small amounts of partial melt or enhanced volatile content in the asthenosphere. While an asthenospheric low velocity zone appears to be ubiquitous beneath the continent, minimum velocities (and likely viscosities) within the eastern U.S. asthenosphere are not as low as those in the western U.S. At smaller scales, Sp imaging hints at lithospheric thickness variations that are correlated with tectonic features (e.g. orogenic boundaries, failed rifts) but resolution will be vastly improved with analysis of data from USArray Transportable and Flexible Arrays. The goal of the Southeastern Suture of the Appalachian Margin Experiment (SESAME) is to better understand lithospheric structures produced by accretion and rifting processes, with a particular focus on the Laurentia-Gondwana suture proposed in southern Georgia, adjacent regions of

  8. Interactions of multi-scale heterogeneity in the lithosphere: Australia

    Science.gov (United States)

    Kennett, B. L. N.; Yoshizawa, K.; Furumura, T.

    2017-10-01

    Understanding the complex heterogeneity of the continental lithosphere involves a wide variety of spatial scales and the synthesis of multiple classes of information. Seismic surface waves and multiply reflected body waves provide the main constraints on broad-scale structure, and bounds on the extent of the lithosphere-asthenosphere transition (LAT) can be found from the vertical gradients of S wavespeed. Information on finer-scale structures comes through body wave studies, including detailed seismic tomography and P-wave reflectivity extracted from stacked autocorrelograms of continuous component records. With the inclusion of deterministic large-scale structure and realistic medium-scale stochastic features fine-scale variations are subdued. The resulting multi-scale heterogeneity model for the Australian region gives a good representation of the character of observed seismograms and their geographic variations and matches the observations of P-wave reflectivity. P reflections in the 0.5-3.0 Hz band in the uppermost mantle suggest variations on vertical scales of a few hundred metres with amplitudes of the order of 1%. Interference of waves reflected or converted at sequences of such modest variations in physical properties produce relatively simple behaviour for lower frequencies, which can suggest simpler structures than are actually present. Vertical changes in the character of fine-scale heterogeneity can produce apparent discontinuities. In Central Australia a 'mid-lithospheric discontinuity' can be tracked via changes in frequency content of station reflectivity, with links to the broad-scale pattern of wavespeed gradients and, in particular, the gradients of radial anisotropy. Comparisons with xenolith results from southeastern Australia indicate a strong tie between geochemical stratification and P-wave reflectivity.

  9. Lithospheric scale model of Merida Andes, Venezuela (GIAME Project)

    Science.gov (United States)

    Schmitz, M.; Orihuela, N. D.; Klarica, S.; Gil, E.; Levander, A.; Audemard, F. A.; Mazuera, F.; Avila, J.

    2013-05-01

    Merida Andes (MA) is one of the most important orogenic belt in Venezuela and represents the northern culmination of South America Andes. During the last 60 years, several models have been proposed to explain the shallow and deep structure, using different geological, geophysical, seismological, geochemical and petrologic concepts; nevertheless, most of them have applied local observation windows, and do not represent the major structure of MA. Therefore, a multidisciplinary research group, coordinated by FUNVISIS, in close cooperation with UCV, ULA and PDVSA, is proposed in order to get the outlined goals in the project entitled GIAME ("Geociencia Integral de los Andes de MErida") was established, which aims to generate a lithospheric scale model and the development of a temporal dynamic model for the MA. As a base for lithospheric investigations of the Merida Andes, we are proposing three wide angle seismic profiles across the orogen on three representative sites, in order to determine the inner structure and its relation with the orogen's gravimetric root. To the date, there are no seismic studies at lithospheric scale which cross MA. The wide angle seismic will be complemented with the re-processing and re-interpretation of existing reflection seismic data, which will allow to establish a relationship between MA and its associated flexural basins (Maracaibo and Barinas-Apure basins). Depending on the results of the VENCORP Project (VENezuelan COntinental Reflection Profiling), which might show some reliable results about crustal features and Moho reflectors along three long seismic profiles at Caribbean Moutain system, a reflection seismic profile across the central portion of MA is proposed. Additional tasks, consisting in MA quaternary deformation studies, using research methods like neotectonics and paleoseismology, georadar, numerical modeling, cinematic GPS, SAR interferometry, thermocronology, detailed studies on regional geology, flexural modeling

  10. Remarks on kernel Bayes' rule

    OpenAIRE

    Johno, Hisashi; Nakamoto, Kazunori; Saigo, Tatsuhiko

    2015-01-01

    Kernel Bayes' rule has been proposed as a nonparametric kernel-based method to realize Bayesian inference in reproducing kernel Hilbert spaces. However, we demonstrate both theoretically and experimentally that the prediction result by kernel Bayes' rule is in some cases unnatural. We consider that this phenomenon is in part due to the fact that the assumptions in kernel Bayes' rule do not hold in general.

  11. Lithosphere Response to Intracratonic Rifting: Examples from Europe and Siberia

    DEFF Research Database (Denmark)

    Artemieva, I. M.; Thybo, H.; Herceg, M.

    2012-01-01

    is based on critically assessed results from various seismic studies, including reflection and refraction profiles and receiver function studies. We also use global shear-wave tomography models, gravity constraints based on GOCE data, and thermal models for the lithosphere to speculate on thermo...... of basaltic magmas and consequently in a change in mantle density and seismic velocities. Although kimberlite magmatism is commonly not considered as a rifting events, its deep causes may be similar to the mantle-driven rifting and, as a consequence, modification of mantle density and velocity structure may...... in it seismic wave velocity and density structure....

  12. On searching applicants for mechanism of solar-lithosphere relations

    Science.gov (United States)

    Kairatkyzy, Dina; Andreyev, Alexey; Zhumabayeva, Saltanat; Seraliyev, Alibek

    2016-04-01

    It is actively discussed at present a question on possible influence of solar activity (high-speed solar wind streams bearing the "frozen" magnetic field lines of the Sun) on the stress status of the lithosphere and, consequently, on the Earth's seismic activity (e.g. Zhang, 1998, Acta Seismologica Sinica; Khachikyan et al., EGU2016-2754-1; IUGG2015-3132). There are at least two ideas on possible applicants for physical mechanism of solar-lithosphere relations: (i) - the muons of cosmic rays, which can penetrate the Earth's crust to a depth of at least the first ten kilometers and in tense seismic environment generate nuclear-electromagnetic cascade which energy can be a trigger of earthquake (Tsarev and Chechin, 1988, Preprint № 179, Physical Institute after Lebedev, Moscow); (ii) - the geomagnetic storms (Sobolev et al., 1998, Physics of the Earth #7) when the high-frequency oscillations of the geomagnetic field during the main phase of the storm generate significant induction currents which electric energy entering into the crust can be converted into mechanical energy increasing the stress status of the lithosphere (Sobolev and Demin, Mechano-electric phenomena into the Earth. M . Nauka. 1980). Besides this, among the possible cosmogenic factors changing the stress state of the lithosphere, could be the variation of the angular velocity of rotation of the Earth (e.g. Bostrom, 2000. Tectonic consequence of the Earth's Rotation), if it depends on solar activity variations. More of 50 years ago, Munk and Donald (The Rotation of the Earth, Cambrige University Press, 1960) suggested that the interaction between solar wind and geomagnetic field would probably influence the short period variation of angular velocity of the Earth. In this work, we check up this suggestion on the base of very precise data on the length of day (LOD) from 1986 to the present, which are presented by the International Earth Rotation and Reference Systems Service (IERS). Using the methods

  13. BCDC Bay Trail Alignment 2009

    Data.gov (United States)

    California Department of Resources — The Bay Trail provides easily accessible recreational opportunities for outdoor enthusiasts, including hikers, joggers, bicyclists and skaters. It also offers a...

  14. BCDC Bay Trail Alignment 2009

    Data.gov (United States)

    California Department of Resources — The Bay Trail provides easily accessible recreational opportunities for outdoor enthusiasts, including hikers, joggers, bicyclists and skaters. It also offers a...

  15. Continental collision with a sandwiched accreted terrane: Insights into Himalayan-Tibetan lithospheric mantle tectonics?

    Science.gov (United States)

    Kelly, Sean; Butler, Jared P.; Beaumont, Christopher

    2016-12-01

    Many collisional orogens contain exotic terranes that were accreted to either the subducting or overriding plate prior to terminal continent-continent collision. The ways in which the physical properties of these terranes influence collision remain poorly understood. We use 2D thermomechanical finite element models to examine the effects of prior 'soft' terrane accretion to a continental upper plate (retro-lithosphere) on the ensuing continent-continent collision. The experiments explore how the style of collision changes in response to variations in the density and viscosity of the accreted terrane lithospheric mantle, as well as the density of the pro-lithospheric mantle, which determines its propensity to subduct or compress the accreted terrane and retro-lithosphere. The models evolve self-consistently through several emergent phases: breakoff of subducted oceanic lithosphere; pro-continent subduction; shortening of the retro-lithosphere accreted terrane, sometimes accompanied by lithospheric delamination; and, terminal underthrusting of pro-lithospheric mantle beneath the accreted terrane crust or mantle. The modeled variations in the properties of the accreted terrane lithospheric mantle can be interpreted to reflect metasomatism during earlier oceanic subduction beneath the terrane. Strongly metasomatized (i.e., dense and weak) mantle is easily removed by delamination or entrainment by the subducting pro-lithosphere, and facilitates later flat-slab underthrusting. The models are a prototype representation of the Himalayan-Tibetan orogeny in which there is only one accreted terrane, representing the Lhasa terrane, but they nonetheless exhibit processes like those inferred for the more complex Himalayan-Tibetan system. Present-day underthrusting of the Tibetan Plateau crust by Indian mantle lithosphere requires that the Lhasa terrane lithospheric mantle has been removed. Some of the model results support previous conceptual interpretations that Tibetan

  16. Fossilized Dipping Fabrics in Continental Mantle Lithosphere as Possible Remnants of Stacked Oceanic Paleosubductions

    Science.gov (United States)

    Babuska, V.; Plomerova, J.; Vecsey, L.; Munzarova, H.

    2015-12-01

    We have examined seismic anisotropy within the mantle lithosphere of Archean, Proterozoic and Phanerozoic provinces of Europe by means of shear-wave splitting and P-wave travel-time deviations of teleseismic waves observed at dense arrays of seismic stations (e.g., Vecsey et al., Tectonophys. 2007). Lateral variations of seismic-wave anisotropy delimit domains of the mantle lithosphere, each of them having a consistent fabric. The domains, modeled in 3D by olivine aggregates with dipping lineation a, or foliation (a,c), represent microplates or their fragments that preserved their pre-assembly fossil fabrics in the mantle lithosphere. Evaluating seismic anisotropy in 3D, as well as mapping boundaries of the domains helps to decipher processes of the lithosphere formation. Systematically dipping mantle fabrics and other seismological findings seem to support a model of continental lithosphere built from systems of paleosubductions of plates of ancient oceanic lithosphere (Babuska and Plomerova, AGU Geoph. Monograph 1989), or by stacking of the plates (Helmstaedt and Schulze, Geol. Soc. Spec. Publ. 1989). Seismic anisotropy in the oceanic mantle lithosphere, explained mainly by the olivine A- or D-type fabric (Karato et al., Annu. Rev. Earth Planet. Sci. 2008), was discovered a half century ago (Hess, Nature 1964). Field observations and laboratory experiments indicate the oceanic olivine fabric might be preserved in the subducting lithosphere to a depth of at least 200-300 km. We thus interpret the dipping anisotropic fabrics in domains of the European mantle lithosphere as systems of "frozen" paleosubductions (Babuska and Plomerova, PEPI 2006), and the lithosphere base as a boundary between a fossil anisotropy in the lithospheric mantle and an underlying seismic anisotropy related to present-day flow in the asthenosphere (Plomerova and Babuska, Lithos 2010).

  17. Reflection Character of the Continental Lithosphere and Crustal Evolution

    Science.gov (United States)

    Brown, L. D.

    2015-12-01

    Reflection images represent the high-frequency end member of the suite of seismological tools commonly used to probe the lithosphere. The global inventory of deep reflection profiles has documented reflection characters as varied as the surface geology that provides the primary boundary condition for the interpretation of reflection images. Past reviews of reflection results have stressed similarities in reflection patterns between various geographic regions and attempted to associate these patterns with specific tectonic processes. Examples include: laminated sequences (shear fabrics formed during extension or collision), reflective Mohos (mafic underplating), bright spots (contemporary and fossil magma bodies), dipping mantle reflections rooted in the lower crust (fossil subduction zones) and subhorizontal mantle reflections (phase changes in the lower lithosphere). Here I focus on relating reflection character to the inversion and/or interpretation of results from broadband techniques such as receiver functions, body wave and surface wave tomography. Among the underappreciated aspects of reflectivity are its dependence upon density as well as velocity, and the limitations of 2D images in a 3D world. A core consideration is the need to meaningfully relate integrated physical properties (e.g. velocity inferred from refraction and surface wave measurements) with the differential physical properties (e.g. reflection coefficients) to which reflection images are primarily sensitive. Examples from Tibet and Eurasia are used to illustrate examples of successful integration of controlled (active) and natural (passive) source observations to constrain models of crustal evolution.

  18. Lithospheric radial anisotropy beneath the Gulf of Mexico

    Science.gov (United States)

    Chu, Risheng; Ko, Justin Yen-Ting; Wei, Shengji; Zhan, Zhongwen; Helmberger, Don

    2017-05-01

    The Lithosphere-Asthenosphere Boundary (LAB), where a layer of low viscosity asthenosphere decouples with the upper plate motion, plays an essential role in plate tectonics. Most dynamic modeling assumes that the shear velocity can be used as a surrogate for viscosity which provides key information about mantle flow. Here, we derive a shear velocity model for the LAB structure beneath the Gulf of Mexico allowing a detailed comparison with that beneath the Pacific (PAC) and Atlantic (ATL). Our study takes advantage of the USArray data from the March 25th, 2013 Guatemala earthquake at a depth of 200 km. Such data is unique in that we can observe a direct upward traveling lid arrival which remains the first arrival ahead of the triplications beyond 18°. This extra feature in conjunction with upper-mantle triplication sampling allows good depth control of the LAB and a new upper-mantle seismic model ATM, a modification of ATL, to be developed. ATM has a prominent low velocity zone similar to the structure beneath the western Atlantic. The model contains strong radial anisotropy in the lid where VSH is about 6% faster than VSV. This anisotropic feature ends at the bottom of the lithosphere at about the depth of 175 km in contrast to the Pacific where it extends to over 300 km. Another important feature of ATM is the weaker velocity gradient from the depth of 175 to 350 km compared to Pacific models, which may be related to differences in mantle flow.

  19. Chapman Conference on Generation of the Oceanic Lithosphere

    Science.gov (United States)

    Presnall, D. C.; Hales, A. L.; Frey, F. A.

    On April 6-10, 1981, the Chapman conference on Generation of the Oceanic Lithosphere was held at Airlie House, Warrenton, Virginia. It was convened by D.C. Presnall, A.L. Hales (both at the University of Texas at Dallas), and F.A. Frey (Massachusetts Institute of Technology). The purpose of the conference was to bring together scientists with diverse specialties to develop a better understanding of the constraints imposed by geophysics, geochemistry, petrology, and tectonics on processes of oceanic lithosphere generation. Sessions were held on the nature of the crust and upper mantle at spreading centers; trace elements and isotopes; experimental petrology; magma chamber dynamics, melt migration, and mantle flow; slow versus fast spreading ridges; Atlantic spreading centers; Pacific spreading centers; and hydrothermal activity, metasomatism, and metamorphism. Fifty-four oral papers and 47 poster papers were presented. One hundred twenty-eight scientists attended from Australia, Canada, Cyprus, Denmark, France, Iceland, Japan, Mexico, United Kingdom, United States, and the USSR.

  20. Continents as lithological icebergs: The importance of buoyant lithospheric roots

    Science.gov (United States)

    Abbott, D.H.; Drury, R.; Mooney, W.D.

    1997-01-01

    An understanding of the formation of new continental crust provides an important guide to locating the oldest terrestrial rocks and minerals. We evaluated the crustal thicknesses of the thinnest stable continental crust and of an unsubductable oceanic plateau and used the resulting data to estimate the amount of mantle melting which produces permanent continental crust. The lithospheric mantle is sufficiently depleted to produce permanent buoyancy (i.e., the crust is unsubductable) at crustal thicknesses greater than 25-27 km. These unsubductable oceanic plateaus and hotspot island chains are important sources of new continental crust. The newest continental crust (e.g., the Ontong Java plateau) has a basaltic composition, not a granitic one. The observed structure and geochemistry of continents are the result of convergent margin magmatism and metamorphism which modify the nascent basaltic crust into a lowermost basaltic layer overlain by a more silicic upper crust. The definition of a continent should imply only that the lithosphere is unsubductable over ??? 0.25 Ga time periods. Therefore, the search for the oldest crustal rocks should include rocks from lower to mid-crustal levels.

  1. GAS BUBBLE-FACILITATED TRANSPORT OF METALS IN LITHOSPHERE

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    A physicochemical model for transport of mobile forms of occurrence of elements by gas bubbles in porous medium-gas bubble-facilitated transport of metals in the lithosphere is proposed and its corresponding mathematical model is discussed. The physico-chemical model consists of three phases: water with dissolved metallic elements, gas bubbles and solid matrix of the porous medium. In the model the gas bubbles act as carriers to transport the elements in the pore water from the depth in the lithosphere to the Earth's surface. In the process of transportation the elements dissipate in porous rocks and consequently a new kind of geochemical halo-jet halo of dispersion is formed in the rocks. In order to describe the transport and fate of the elements in the porous rocks a nonlinear quasiconvection mathematical model is developed, in which the transport of elements is modeled by a quasiconvection of gas bubbles with the elements and the interaction of elements with the porous medium is represented by a second-order chemical kinetics. A finite difference scheme is provided to solve the nonlinear quasiconvection model. From the numerical solutions a stabilization effect of concentration front in the transportation of elements in the porous medium is discovered. The sensitivities of the stabilization effect to model parameters are analyzed. To verify the reality of the mathematical model, physicochemical modeling experiments are conducted. The obtained experimental data support the proposed model in this work.

  2. Colorado Plateau magmatism and uplift by warming of heterogeneous lithosphere.

    Science.gov (United States)

    Roy, Mousumi; Jordan, Thomas H; Pederson, Joel

    2009-06-18

    The forces that drove rock uplift of the low-relief, high-elevation, tectonically stable Colorado Plateau are the subject of long-standing debate. While the adjacent Basin and Range province and Rio Grande rift province underwent Cenozoic shortening followed by extension, the plateau experienced approximately 2 km of rock uplift without significant internal deformation. Here we propose that warming of the thicker, more iron-depleted Colorado Plateau lithosphere over 35-40 Myr following mid-Cenozoic removal of the Farallon plate from beneath North America is the primary mechanism driving rock uplift. In our model, conductive re-equilibration not only explains the rock uplift of the plateau, but also provides a robust geodynamic interpretation of observed contrasts between the Colorado Plateau margins and the plateau interior. In particular, the model matches the encroachment of Cenozoic magmatism from the margins towards the plateau interior at rates of 3-6 km Myr(-1) and is consistent with lower seismic velocities and more negative Bouguer gravity at the margins than in the plateau interior. We suggest that warming of heterogeneous lithosphere is a powerful mechanism for driving epeirogenic rock uplift of the Colorado Plateau and may be of general importance in plate-interior settings.

  3. Thermal structure of the lithosphere: a petrologic model.

    Science.gov (United States)

    Macgregor, I D; Basu, A R

    1974-09-20

    A preliminary evaluation of the thermal history of the upper mantle as determined by petrologic techniques indicates a general correspondence with theoretically derived models. The petrologic data supply direct information which may be used as an independent calibration of calculated models, serve as a base for evaluating the assumptions of the theoretical approach, and allow more careful selection of the variables describing mantle thermal properties and processes. Like the theoretical counterpart, the petrological approach indicates that the lithosphere is dominated by two thermal regimes: first, there is a continental regime which cools at rates of the order of 10(9) years and represents the longterm cooling of the earth. Secondly, superimposed on the continental evolution is the thermal event associated with the formation of an oceanic basin, and which may be thought of as a 10(8) year convective perturbation on the continental cycle. Of special interest is petrologic evidence for a sudden steepening of the thermal gradients across the lithosphere-asthenosphere boundary not seen in the theoretical models. The unexpected change of slope points to the need for a critical reevaluation of the thermal processes and properties extant in the asthenosphere. The potential of the petrologic contribution has yet to be fully realized. For a start, this article points to an important body of independent evidence critical to our understanding of the earth's thermal history.

  4. Anisotropic Lithospheric Structure of Southern Madagascar from Ambient Seismic Noise

    Science.gov (United States)

    Dreiling, J.; Tilmann, F. J.; Yuan, X.; Rumpker, G.

    2016-12-01

    The island of Madagascar occupied a key region in both the assembly and the multi-stage breakup of Gondwana. Madagascar consists of amalgamated continental material comprising several distinct tectonic units. Because of its key role in the assembly of Gondwana, numerous geological and geophysical investigations have been carried out in Madagascar to understand the evolution of Gondwana.The aim of this study is to characterize the lithospheric structure of Southern Madagascar using ambient seismic noise correlation. Radial anisotropy is determined to learn about the crust/mantle deformation around the central Southern Madagascan shear zones (i.e. the Ampanihy, Beraketa and Ranotsara shear zones) and to shed light on the geological development of Madagascar and its role during the breakup of Gondwana. In the analysis we included seismic data from the SELASOMA project in Southern Madagascar, which is a passive seismic experiment carried out by the GFZ German Research Centre for Geosciences from May 2012 to May 2014. Seismic data recorded by 61 three-component seismometers were pre-processed and cross-correlated. Group velocity dispersion curves were picked manually for the vertical-vertical and transverse-transverse component correlations, which represent the Rayleigh (ZZ) and Love (TT) surface waves, respectively. Velocities from periods between 0.7 and 20 seconds are used for tomography and computation of radial anisotropy of the lithosphere.

  5. Lithospheric structure of the Western Iberian Atlantic Margin

    Science.gov (United States)

    Tunini, Lavinia; Vergés, Jaume; Fernandez, Manel; Jiménez-Munt, Ivone; Torne, Montserrat

    2017-04-01

    The Western Iberia Atlantic margin has been the object of multiple geophysical surveys in the last two decades, which highlight the crustal architecture of a hyperextended, magma-poor passive margin with a wide transition zone of exhumed mantle peridotites and anomalously small magma fractions. However, studies dealing with its lithospheric structure are lacking. We present a 2D model of the present-day lithospheric structure along a 530-km transect of the Western Iberian Margin, from the Southern Iberian Abyssal Plain to the Lusitanian Basin. The model combines seismic and geological data, mantle petrology, mineral physics and geophysical observables (gravity, geoid, topography, mantle seismic velocities and heat flow) within a self-consistent thermodynamic framework. Results show that the crustal thickness decreases gradually from 30 km below the Lusitanian Basin onshore to 11 km in the Abyssal Plain, 250 km further oceanwards, while the LAB rises from 140 km to 110 km, respectively. Furthermore, our results favour a 22% degree of serpentinization of the exhumed mantle which represents a 4.4% of water content. The study is supported by project ALPIMED (PIE-CSIC-201530E082)

  6. Thermal cooling of the oceanic lithosphere from geoid height data

    Science.gov (United States)

    Cazenae, A.

    1985-01-01

    Another type of geophysical observation has proved to be very useful in the study of thermal cooling of the oceanic lithosphere. It is the geoid height derivative with respect to plate age, a quantity computed from the short wavelength geoid step across fracture zones measured by altimeter satellites. Two categories of simples models are proposed to describe cooling and contraction of the oceanic lithosphere with age. Both plate model and half space model, give almost similar results up to ages of 50 to 70 ma, but predict quite distinct behavior of seafloor depth, heat flow and other parameters in old basins. Tests of thermal models are based on heat flow and topography data. However, heat flow is not very sensitive to the form of the thermal model. Large areas of the ocean floor are particularly shallow, and as a result topography data may not be very appropriate to discriminate between plate and half space models, and no clear concensus on a preferred model yet exists.

  7. The Cascadia Subduction Zone: two contrasting models of lithospheric structure

    Science.gov (United States)

    Romanyuk, T.V.; Blakely, R.; Mooney, W.D.

    1998-01-01

    The Pacific margin of North America is one of the most complicated regions in the world in terms of its structure and present day geodynamic regime. The aim of this work is to develop a better understanding of lithospheric structure of the Pacific Northwest, in particular the Cascadia subduction zone of Southwest Canada and Northwest USA. The goal is to compare and contrast the lithospheric density structure along two profiles across the subduction zone and to interpet the differences in terms of active processes. The subduction of the Juan de Fuca plate beneath North America changes markedly along the length of the subduction zone, notably in the angle of subduction, distribution of earthquakes and volcanism, goelogic and seismic structure of the upper plate, and regional horizontal stress. To investigate these characteristics, we conducted detailed density modeling of the crust and mantle along two transects across the Cascadia subduction zone. One crosses Vancouver Island and the Canadian margin, the other crosses the margin of central Oregon.

  8. Ground-Water Quality in the Upper Hudson River Basin, New York, 2007

    Science.gov (United States)

    Nystrom, Elizabeth A.

    2009-01-01

    Water samples were collected from 25 production and domestic wells in the Upper Hudson River Basin (north of the Federal Dam at Troy, N.Y.) from August through November 2007 to characterize the ground-water quality. The Upper Hudson River Basin covers 4,600 square miles in upstate New York, Vermont, and Massachusetts; the study area encompasses the 4,000 square miles that lie within New York. The basin is underlain by crystalline and sedimentary bedrock, including gneiss, shale, and slate; some sandstone and carbonate rocks are present locally. The bedrock in some areas is overlain by surficial deposits of saturated sand and gravel. Of the 25 wells sampled, 13 were finished in sand and gravel deposits, and 12 were finished in bedrock. The samples were collected and processed by standard U.S. Geological Survey procedures and were analyzed for 225 physical properties and constituents, including major ions, nutrients, trace elements, radon-222, pesticides, volatile organic compounds (VOCs), and indicator bacteria. Water quality in the study area is generally good, but concentrations of some constituents exceeded current or proposed Federal or New York State drinking-water standards; these were: color (1 sample), pH (2 samples), sodium (5 samples), nitrate plus nitrite (2 samples), aluminum (3 samples), iron (1 sample), manganese (7 samples), radon-222 (11 samples), and bacteria (1 sample). Dissolved-oxygen concentrations in samples from wells finished in sand and gravel [median 5.4 milligrams per liter (mg/L)] were greater than those from wells finished in bedrock (median 0.4 mg/L). The pH of all samples was typically neutral or slightly basic (median 7.6); the median water temperature was 9.7 deg C. The ions with the highest concentrations were bicarbonate (median 123 mg/L) and calcium (median 33.9 mg/L). Ground water in the basin is generally soft to moderately hard (less than or equal to 120 mg/L as CaCO3) (median hardness 110 mg/L as CaCO3). Concentrations of

  9. An Equivalent Source Method for Modelling the Global Lithospheric Magnetic Field

    DEFF Research Database (Denmark)

    Kother, Livia Kathleen; Hammer, Magnus Danel; Finlay, Chris;

    We produce a new model of the global lithospheric magnetic field based on 3-component vector field observations at all latitudes from the CHAMP satellite using an equivalent source technique.......We produce a new model of the global lithospheric magnetic field based on 3-component vector field observations at all latitudes from the CHAMP satellite using an equivalent source technique....

  10. Lithospheric Thickness Variations from Gravity and Topography in Areas of High Crustal Remanent Magnetization on Mars

    Science.gov (United States)

    Smrekar, S. E.; Raymond, C. A.

    2001-01-01

    Large regions of intense crustal re- manent magnetization were fortuitously discovered on Mars by the Mars Global Surveyor (MGS) spacecraft. Gravity and topography admittance studies are used to examine lithospheric structure in the areas of intense magnetization. Areas with positively magnetized crust appear to have thinner crust and elastic lithosphere than negatively magnetized crust. Additional information is contained in the original extended abstract.

  11. Mid-ocean-ridge seismicity reveals extreme types of ocean lithosphere.

    Science.gov (United States)

    Schlindwein, Vera; Schmid, Florian

    2016-07-14

    Along ultraslow-spreading ridges, where oceanic tectonic plates drift very slowly apart, conductive cooling is thought to limit mantle melting and melt production has been inferred to be highly discontinuous. Along such spreading centres, long ridge sections without any igneous crust alternate with magmatic sections that host massive volcanoes capable of strong earthquakes. Hence melt supply, lithospheric composition and tectonic structure seem to vary considerably along the axis of the slowest-spreading ridges. However, owing to the lack of seismic data, the lithospheric structure of ultraslow ridges is poorly constrained. Here we describe the structure and accretion modes of two end-member types of oceanic lithosphere using a detailed seismicity survey along 390 kilometres of ultraslow-spreading ridge axis. We observe that amagmatic sections lack shallow seismicity in the upper 15 kilometres of the lithosphere, but unusually contain earthquakes down to depths of 35 kilometres. This observation implies a cold, thick lithosphere, with an upper aseismic zone that probably reflects substantial serpentinization. We find that regions of magmatic lithosphere thin dramatically under volcanic centres, and infer that the resulting topography of the lithosphere-asthenosphere boundary could allow along-axis melt flow, explaining the uneven crustal production at ultraslow-spreading ridges. The seismicity data indicate that alteration in ocean lithosphere may reach far deeper than previously thought, with important implications towards seafloor deformation and fluid circulation.

  12. Lithosphere-mantle coupling and the dynamics of the Eurasian Plate

    NARCIS (Netherlands)

    Warners-Ruckstuhl, K.N.; Govers, R.; Wortel, R.

    2012-01-01

    Mechanical equilibrium of tectonic plates implies that lithospheric edge and body forces are balanced by forces arising from interaction with the underlying mantle. We use this quantitative physical relation to integrate existing modelling approaches of lithosphere dynamics and mantle flow into a ne

  13. The Bayes Inference Engine

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, K.M.; Cunningham, G.S.

    1996-04-01

    The authors are developing a computer application, called the Bayes Inference Engine, to provide the means to make inferences about models of physical reality within a Bayesian framework. The construction of complex nonlinear models is achieved by a fully object-oriented design. The models are represented by a data-flow diagram that may be manipulated by the analyst through a graphical programming environment. Maximum a posteriori solutions are achieved using a general, gradient-based optimization algorithm. The application incorporates a new technique of estimating and visualizing the uncertainties in specific aspects of the model.

  14. Sedimentary facies, geomorphic features and habitat distribution at the Hudson Canyon head from AUV multibeam data

    Science.gov (United States)

    Pierdomenico, Martina; Guida, Vincent G.; Macelloni, Leonardo; Chiocci, Francesco L.; Rona, Peter A.; Scranton, Mary I.; Asper, Vernon; Diercks, Arne

    2015-11-01

    Mapping of physical benthic habitats at the head of Hudson Canyon was performed by means of integrated analysis of acoustic data, video surveys and seafloor sampling. Acoustic mapping, performed using AUV-mounted multibeam sonar, provided ultra-high resolution bathymetric and backscatter imagery for the identification of geomorphological features and the characterization of surficial sediments. Habitat characterization in terms of seafloor texture and identification of benthic and demersal communities was accomplished by visual analysis of still photographs from underwater vehicles. Habitat classes were defined on the basis of the seafloor texture observed on photos and then compared with the geophysical data in order to associate habitats to acoustic classes and/or geomorphological features. This enabled us to infer habitat distribution on the basis of morpho-acoustic classes and extrapolate results over larger areas. Results from bottom trawling were used to determine the overall biodiversity within the identified habitats. Our analysis revealed a variety of topographic and sedimentological structures that provide a wide range of physical habitats. A variety of sandy and muddy substrates, gravel patches and mudstone outcrops host rich and varied faunal assemblages, including cold-water corals and sponge communities. Pockmark fields below 300 m depth suggest that methane-based chemosynthetic carbonate deposition may contributes to creation of specific benthic habitats. Hummocky terrain has been delineated along the canyon rims and associated with extensive, long-term burrowing activity by golden tilefish (Lopholatilus chamaeleonticeps). These results show the relationships of physical features to benthic habitat variation, support the notion of the area as a biodiversity hotspot and define essential habitats for planning of sustainable regional fisheries.

  15. The vertical structure of the circulation and dynamics in Hudson Shelf Valley

    Science.gov (United States)

    Lentz, Steven J.; Butman, Bradford; Harris, Courtney K.

    2014-01-01

    Hudson Shelf Valley is a 20–30 m deep, 5–10 km wide v-shaped submarine valley that extends across the Middle Atlantic Bight continental shelf. The valley provides a conduit for cross-shelf exchange via along-valley currents of 0.5 m s−1 or more. Current profile, pressure, and density observations collected during the winter of 1999–2000 are used to examine the vertical structure and dynamics of the flow. Near-bottom along-valley currents having times scales of a few days are driven by cross-shelf pressure gradients setup by wind stresses, with eastward (westward) winds driving onshore (offshore) flow within the valley. The along-valley momentum balance in the bottom boundary layer is predominantly between the pressure gradient and bottom stress because the valley bathymetry limits current veering. Above the bottom boundary layer, the flow veers toward an along-shelf (cross-valley) orientation and a geostrophic balance with some contribution from the wind stress (surface Ekman layer). The vertical structure and strength of the along-valley current depends on the magnitude and direction of the wind stress. During offshore flows driven by westward winds, the near-bottom stratification within the valley increases resulting in a thinner bottom boundary layer and weaker offshore currents. Conversely, during onshore flows driven by eastward winds the near-bottom stratification decreases resulting in a thicker bottom boundary layer and stronger onshore currents. Consequently, for wind stress magnitudes exceeding 0.1 N m−2, onshore along-valley transport associated with eastward wind stress exceeds the offshore transport associated with westward wind stress of the same magnitude.

  16. Numerical validation of the 'Pop-Down tectonics' as a structural frame for hot lithospheres with particular reference to the Hearne craton (Canadian Shield)

    Science.gov (United States)

    Poh, Jonathan; Yamato, Philippe; Gapais, Denis; Duretz, Thibault; Ledru, Patrick

    2017-04-01

    The formation of the architecture of the main cratons of the Canadian Shield has been debated over the past three decades. Understanding the role of tangential Vs. vertical tectonics in the Rae craton is of great interest as the role of inherited structure is fundamental for the subsequent drainage of fluids and the formation of high to ultra-high grade unconformity-type uranium deposits. These deposits are located in the vicinity of the intersection between the unconformity at the base of the Paleoproterozoic Athabasca sedimentary basin (1.75-1.5 Ga) and the graphite-rich metasediments of the Wollaston-Mudjatik transition zone, one of the main fault system of the Rae Craton related to the Trans-Hudson orogeny (1.82-1.78 Ga). A new tectonic model, Pop-down tectonics, was proposed as the primary driving process to concentrate supracrustal materials, strains, fluid transfers and metal transport in permeability enhanced deformation zones. The sub-vertical structural patterns with regional horizontal shortening seen in the tectonic model appear to be consistent with field evidences and has the potential for sustaining strong fluid-rock interactions. In the light of previous analogue modelling studies, we test the viability of the Pop-down tectonics model in a thermo-mechanical framework. The numerical experiments are based on a series of 2D visco-elasto-plastic thermo-mechanical models. We employ various thermal and rheological parameters derived from laboratory experiments. The geometry, thermicity and kinematics of the models are further constrained by applying existing geophysical and geological data. We impose a fixed upper mantle temperature of 1330 °C and a thin crust ranging from 30 - 40 km. The outcome of the models will provide insights into the mechanical processes controlling the deformation of hot lithospheres in convergent settings.

  17. Thin elastic shells with variable thickness for lithospheric flexure of one-plate planets

    CERN Document Server

    Beuthe, Mikael

    2007-01-01

    Planetary topography can either be modeled as a load supported by the lithosphere, or as a dynamical effect due to lithospheric flexure caused by mantle convection. In both cases the response of the lithosphere to external forces can be calculated with the theory of thin elastic plates or shells. On one-plate planets the spherical geometry of the lithospheric shell plays an important role in the flexure mechanism. So far the equations governing the deformations and stresses of a spherical shell have only been derived under the assumption of a shell of constant thickness. However local studies of gravity and topography data suggest large variations in the thickness of the lithosphere. In this article we obtain the scalar flexure equations governing the deformations of a thin spherical shell with variable thickness or variable Young's modulus. The resulting equations can be solved in succession, except for a system of two simultaneous equations, the solutions of which are the transverse deflection and an associ...

  18. Dipping fossil fabrics of continental mantle lithosphere as tectonic heritage of oceanic paleosubductions

    Science.gov (United States)

    Babuska, Vladislav; Plomerova, Jaroslava; Vecsey, Ludek; Munzarova, Helena

    2016-04-01

    Subduction and orogenesis require a strong mantle layer (Burov, Tectonophys. 2010) and our findings confirm the leading role of the mantle lithosphere. We have examined seismic anisotropy of Archean, Proterozoic and Phanerozoic provinces of Europe by means of shear-wave splitting and P-wave travel-time deviations of teleseismic waves observed at dense arrays of seismic stations (e.g., Vecsey et al., Tectonophys. 2007). Lateral variations of seismic-velocity anisotropy delimit domains of the mantle lithosphere, each of them having its own consistent fabric. The domains, modeled in 3D by olivine aggregates with dipping lineation a, or foliation (a,c), represent microplates or their fragments that preserved their pre-assembly fossil fabrics. Evaluating seismic anisotropy in 3D, as well as mapping boundaries of the domains helps to decipher processes of the lithosphere formation. Systematically dipping mantle fabrics and other seismological findings seem to support a model of continental lithosphere built from systems of paleosubductions of plates of ancient oceanic lithosphere (Babuska and Plomerova, AGU Geoph. Monograph 1989), or from stacking of the plates (Helmstaedt and Schulze, Geol. Soc. Spec. Publ. 1989). Seismic anisotropy in the oceanic mantle lithosphere, explained mainly by the olivine A- or D-type fabric (Karato et al., Annu. Rev. Earth Planet. Sci. 2008), was discovered a half century ago (Hess, Nature 1964). Field observations and laboratory experiments indicate the oceanic olivine fabric might be preserved in the subducting lithosphere to a depth of at least 200-300 km. We thus interpret the dipping anisotropic fabrics in domains of the European mantle lithosphere as systems of "frozen" paleosubductions (Babuska and Plomerova, PEPI 2006) and the lithosphere base as a boundary between the fossil anisotropy in the lithospheric mantle and an underlying seismic anisotropy related to present-day flow in the asthenosphere (Plomerova and Babuska, Lithos 2010).

  19. Asymmetric vs. symmetric deep lithospheric architecture of intra-plate continental orogens

    Science.gov (United States)

    Calignano, Elisa; Sokoutis, Dimitrios; Willingshofer, Ernst; Gueydan, Frédéric; Cloetingh, Sierd

    2015-08-01

    The initiation and subsequent evolution of intra-plate orogens, resulting from continental plate interior deformation due to transmission of stresses over large distances from the active plate boundaries, is controlled by lateral and vertical strength contrasts in the lithosphere. We present lithospheric-scale analogue models combining 1) lateral strength variations in the continental lithosphere, and 2) different vertical rheological stratifications. The experimental continental lithosphere has a four-layer brittle-ductile rheological stratification. Lateral heterogeneity is implemented in all models by increased crustal strength in a central narrow block. The main investigated parameters are strain rate and strength of the lithospheric mantle, both playing an important role in crust-mantle coupling. The experiments show that the presence of a strong crustal domain is effective in localizing deformation along its boundaries. After deformation is localized, the evolution of the orogenic system is governed by the mechanical properties of the lithosphere such that the final geometry of the intra-plate mountain depends on the interplay between crust-mantle coupling and folding versus fracturing of the lithospheric mantle. Underthrusting is the main deformation mode in case of high convergence velocity and/or thick brittle mantle with a final asymmetric architecture of the deep lithosphere. In contrast, lithospheric folding is dominant in case of low convergence velocity and low strength brittle mantle, leading to the development of a symmetric lithospheric root. The presented analogue modelling results provide novel insights for 1) strain localization and 2) the development of the asymmetric architecture of the Pyrenees.

  20. Interpretación de algunas cárices (Carex L.) de la Flora Anglica de W. Hudson y tipificación de tres nombres relacionados

    OpenAIRE

    Molina González, Ana María; Acedo, Carmen; Llamas García, Félix

    2007-01-01

    Se discute la identidad de once especies y seis taxones infraespecíficos del género Carex tratados por Hudson en la Flora Anglica. Se estudia la obra de este autor, comparándola con los protólogos de Linneo y otros botánicos contemporáneos y se indica en cada caso el nombre en uso actual. Cinco especies, que Hudson llamó Carex acuta, C. brizoides, C. inflata en el sentido de la segunda edición , C. muricata y C. saxatilis, corresponden a taxones sin describir en aquel momento y actualmente s...

  1. Bayes Multiple Decision Functions

    CERN Document Server

    Wu, Wensong

    2011-01-01

    This paper deals with the problem of simultaneously making many (M) binary decisions based on one realization of a random data matrix X. M is typically large and X will usually have M rows associated with each of the M decisions to make, but for each row the data may be low dimensional. A Bayesian decision-theoretic approach for this problem is implemented with the overall loss function being a cost-weighted linear combination of Type I and Type II loss functions. The class of loss functions considered allows for the use of the false discovery rate (FDR), false nondiscovery rate (FNR), and missed discovery rate (MDR) in assessing the decision. Through this Bayesian paradigm, the Bayes multiple decision function (BMDF) is derived and an efficient algorithm to obtain the optimal Bayes action is described. In contrast to many works in the literature where the rows of the matrix X are assumed to be stochastically independent, we allow in this paper a dependent data structure with the associations obtained through...

  2. 75 FR 29891 - Special Local Regulation; Maggie Fischer Memorial Great South Bay Cross Bay Swim, Great South Bay...

    Science.gov (United States)

    2010-05-28

    ... Swim, Great South Bay, NY, in the Federal Register (74 FR 32428). We did not receive any comments or... published at 74 FR 32428 on July 8, 2009, is adopted as a final rule with the following changes: PART 100... South Bay Cross Bay Swim, Great South Bay, NY AGENCY: Coast Guard, DHS. ACTION: Final rule. SUMMARY:...

  3. Subduction Stability: Lithospheric Strength and Roll-back

    Science.gov (United States)

    Patel, P. I.; Lavier, L.; Grand, S.

    2007-12-01

    In exploring the issue of subduction zone stability, we ran a series of simulations representing subduction systems consisting of simple 2D representations of oceanic lithosphere subducting beneath continental lithosphere. Our modelling software utilizes temperature dependent visco-elasto-plastic rheologies as well as a few proxies for significant chemical processes such as ecologitization and hydration. With externally imposed convergence rates, these models evolve from a contrived subduction initiation state to "normal-looking" subduction within approximately 10 million years. The simulations are then allowed to continue to evolve for up to 30 million more years. From our early results, we note that while most systems start with similar subduction geometries, they may deviate from each other over time. Notably, subduction initiated at "cooler" (and therefore stronger) junctures tend to form very stable subduction zones which maintain normal-looking geometries throughout the life of the simulation. However, subduction initiated at warmer margins tend to result in slab rollback relatively quickly. Systems with junctures of intermediate temperature also tend to subduct stably for a substantial amount of time, yet they too eventually result in rollback as the subducting slab entrains and removes some of the cooler lithosphere near the juncture, allowing hotter asthenospheric material into the contact region between the plates. The hot, low-viscosity material sharply reduces the fluid-dynamically derived suction force that partially supports the stable subduction geometry, facilitating the retreat of the subducting slab as well as the rifting of the over-riding slab. These simulations incorporate a variety of approximations and assumptions which may not reflect the actual conditions within the Earth. However, they do offer a chance to observe how a system that at least appears geometrically similar to observed Earth systems may behave when subjected to varying

  4. Water and its influence on the lithosphere-asthenosphere boundary.

    Science.gov (United States)

    Green, David H; Hibberson, William O; Kovács, István; Rosenthal, Anja

    2010-09-23

    The Earth has distinctive convective behaviour, described by the plate tectonics model, in which lateral motion of the oceanic lithosphere of basaltic crust and peridotitic uppermost mantle is decoupled from the underlying mechanically weaker upper mantle (asthenosphere). The reason for differentiation at the lithosphere-asthenosphere boundary is currently being debated with relevant observations from geophysics (including seismology) and geochemistry (including experimental petrology). Water is thought to have an important effect on mantle rheology, either by weakening the crystal structure of olivine and pyroxenes by dilute solid solution, or by causing low-temperature partial melting. Here we present a novel experimental approach to clarify the role of water in the uppermost mantle at pressures up to 6 GPa, equivalent to a depth of 190 km. We found that for lherzolite in which a water-rich vapour is present, the temperature at which a silicate melt first appears (the vapour-saturated solidus) increases from a minimum of 970 °C at 1.5 GPa to 1,350 °C at 6 GPa. We have measured the water content in lherzolite to be approximately 180 parts per million, retained in nominally anhydrous minerals at 2.5 and 4 GPa at temperatures above and below the vapour-saturated solidus. The hydrous mineral pargasite is the main water-storage site in the uppermost mantle, and the instability of pargasite at pressures greater than 3 GPa (equivalent to more than about 90 km depth) causes a sharp drop in both the water-storage capacity and the solidus temperature of fertile upper-mantle lherzolite. The presence of interstitial melt in mantle with more than 180 parts per million of water at pressures greater than 3 GPa alters mantle rheology and defines the lithosphere-asthenosphere boundary. Modern asthenospheric mantle acting as the source for mid-oceanic ridge basalts has a water content of 50-200 parts per million (refs 3-5). We show that this matches the

  5. Continental Rifts: Lithospheric Weakness and Strength Contrasts as Triggers for Necking Instabilities

    Science.gov (United States)

    Wenker, S.; Beaumont, C.

    2014-12-01

    Rifted margin geometry is too complex and diverse to be explained by simple kinematic models. Instead, we consider the effects of strain localization and the growth of necking instabilities as they apply to rifted margins. The intrinsic layering of the lithosphere will affect the growth rate of necking instabilities, leading to depth-dependent extension. In addition, continents are far from homogeneous after multiple cycles of collision, strike-slip motion and rifting. The resulting inherited heterogeneities may serve to localize strain and initiate necking instabilities. We use 2D finite element models containing embedded finite weak zones in the crust and/or mantle as well as a vertical lithospheric boundary across which lithospheric layering changes resulting in an overall strength contrast. We show that there are two controls on the style of rifting: Control 1, the stiff/pliable nature of the lithospheric layers and; Control 2, the distribution of the background strain rate in the lithosphere. Control 1 depends on the lithospheric rheology, such that necking instabilities grow faster in a stiff, dominantly plastic, layer than in equivalent layers with a pliable, mostly viscous, rheology. Control 2 is important where a strength contrast at a lithospheric boundary influences the distribution of the background strain rate. Necking is a mechanism that amplifies the background strain rate, which implies faster necking in parts of the lithosphere where background strain rates are highest. In a laterally homogeneous lithosphere, the background strain rate will be uniform in each layer and Control 1 will dominate giving necking in stiff layers. However, juxtaposed lithospheres with different strengths will distribute strain giving the weaker lithosphere the higher strain rate, implying the fastest necking may occur under Control 2 in pliable layers with the higher strain rate. An end-member case is where strong lithosphere acts as a rigid block. Here, no necking

  6. Global distribution of the lithosphere-asthenosphere boundary: a new look

    Directory of Open Access Journals (Sweden)

    V. M. Hamza

    2012-02-01

    Full Text Available New global maps of the depth to the boundary between the lithosphere and the asthenosphere are presented. The maps are based on updated global databases for heat flow and crustal structure. For continental regions the estimates of lithospheric thickness are based on determinations of subcrustal heat flow, after corrections for contributions of radiogenic heat in crustal layers. For oceanic regions the estimates of lithospheric thickness are based on the newly proposed finite half-space (FHS model. Unlike the half-space cooling (HSC and the Plate models the FHS model takes into account effects of buffered solidification at the lower boundary of the lithosphere and assumes that vertical domain for downward growth of boundary layer have an asymptotic limit. Results of numerical simulations reveal that theoretical values derived from FHS model provide vastly improved fits to observational data for heat flow and bathymetry than can be achieved with HSC and Plate models. Also, the data fits are valid for the entire age range of the oceanic lithosphere. Hence estimates of depths to lithosphere – asthenosphere boundary (LAB based on FHS model, are believed to provide more reliable estimates than those reported in previous thermal models. The global maps of depths to LAB derived in the present work reveal several features in regional variations of lithosphere thicknesses that have not been identified in earlier studies. For example, regions of ocean floor with ages less than 55 Ma are characterized by relatively rapid thickening of the lithosphere. Also there is better resolution in mapping the transition from oceanic to continental lithosphere, as most of the latter ones are characterized by lithospheric thickness greater than 150 km. As expected the plate spreading centers in oceanic regions as well as areas of recent magmatic activity in continental regions are characterized by relatively thin lithosphere, with LAB depths of less than 50 km. On the

  7. Three-dimensional density structure of the lunar upper lithosphere

    Science.gov (United States)

    Liang, Q.; Du, J.; Chen, C.; Li, Y.

    2011-12-01

    The lithosphere of the Moon has a thickness over 1200 km according to the seismology studies. It records the giant impact events during the processes of solidification. The upper lithosphere including the crust and the upper mantle was thought to be a nonuniform layer in thickness and seismic velocity, yet the lateral density structure remains poorly understood. The global gravity data thus provides a significant constraint on the three-dimensional (3-D) density structure of the Moon. Previous studies assumed that the crust and the mantle have constant density the gravity anomalies are only produced by the variations of interface between the crust and the mantle. Therefore, the constant density may give overestimation or underestimation of the Moho depth. In contrast, we apply a 3-D inverse method in spherical coordinate to the lunar gravity anomaly. It is a direct way in recovering the density structures beneath mascon basins or the lateral density heterogeneities in the upper lithosphere. The gravity anomaly we use in this study is the Bouguer gravity anomaly calculated at 1750 km radius relative to the reference radius, 1737.153 km[1], from the newly gravity field model SGM100i[2] and the topography model LRO_LTM02[1]. In order to understand the global feature of density variation, we truncate the long wavelength anomaly up to the order of 30 to reconstruct the density distribution above the depth of 100 km in the Moon. With the inverse technique, we obtain a global 3-D density structure of the lunar lithosphere down to 100 km depth. The major features are dominated by the mascons with dense materials and the broad region of the farside highland with relative low density mass. From this structure, the huge mass concentrations are found beneath the South Pole-Aitken (SPA) basin, meaning that the oblique impact not only excavated the SPA basin into deep but also made the mantle uplifted close to a depth of 30 km (relative to a 1738 km radius). We suggest here that

  8. Seismic structure of the oceanic lithosphere inferred from guided wave

    Science.gov (United States)

    Shito, A.; Suetsugu, D.; Furumura, T.; Sugioka, H.; Ito, A.

    2012-12-01

    Characteristic seismic waves are observed by seismological experiment using Broad-Band Ocean Bottom Seismometers (BBOBSs) conducted in the northwestern Pacific from 2007 to 2008 and from 2010 to 2011. The seismic waves have low frequency onset (phases (2.5-10 Hz). The high frequency later phases have large amplitude and long duration for both P and S waves. The seismic waves are observed commonly at the BBOBS array from events in the subducting Pacific plate. To investigate generation and propagation mechanisms of the seismic wave will help us to understand the seismic structure and the origin of the oceanic lithosphere. High frequency phases travelling efficiently through the oceanic lithosphere more than 3000 km are well known phenomenon. These phases were previously called as Po/So waves. Po/So waves were observed as early as 1935, and were studied actively from the 1970s to 1990s. However, the mechanism of generation and propagation of the phases are still controversial. The guided waves propagating in subducting plate are also common phenomenon in the subduction zone. The waves are generally characterized by separation of low frequency and high frequency components. In order to explain the separation, Martin and Rietbrock [2003] considered the trapping of waves in the waveguide formed by thin low velocity former oceanic crust at the top of the plate. However, large amplitude and long duration of the high frequency component cannot be achieved by the model. From the analysis of waveform observed at the eastern seaboard of northern Japan and numerical simulation of seismic wave propagation, Furumura and Kennet [2005] demonstrate that the guided wave travelling in the subducting plate is produced by multiple forward scattering of high-frequency seismic waves due to small-scale random heterogeneity in the plate structure. We apply the method proposed by Furumura and Kennett [2005] to reproduce the seismograms recorded by the BBOBS array. We conduct 2D numerical

  9. Electromagnetic induction studies. [of earth lithosphere and asthenosphere

    Science.gov (United States)

    Hermance, J. F.

    1983-01-01

    Recent developments in electromagnetic induction studies of the lithosphere and the asthenosphere are reviewed. Attention is given to geoelectrical studies of active tectonic areas in terms of the major zones of crustal extension, the basin and range province along western regions of North America, and the Rio Grande rift. Studies have also been performed of tectonic activity around Iceland, the Salton Trough and Cerro Prieto, and the subduction zones of the Cascade Mountains volcanic belt, where magnetotelluric and geomagnetic variation studies have been done. Geomagnetic variations experiments have been reported in the Central Appalachians, and submarine electromagnetic studies along the Juan de Fuca ridge. Controlled source electromagnetic and dc resistivity investigations have been carried out in Nevada, Hawaii, and in the Adirondacks Mountains. Laboratory examinations on the conductivity of representative materials over a broad range of temperature, pressure, and chemistry are described.

  10. Rheology, tectonics, and the structure of the Venus lithosphere

    Science.gov (United States)

    Zuber, M. T.

    1994-01-01

    Given the absence of ground truth information on seismic structure, heat flow, and rock strength, or short wavelength gravity or magnetic data for Venus, information on the thermal, mechanical and compositional nature of the shallow interior must be obtained by indirect methods. Using pre-Magellan data, theoretical models constrained by the depths of impact craters and the length scales of tectonic features yielded estimates on the thickness of Venus' brittle-elastic lithosphere and the allowable range of crustal thickness and surface thermal gradient. The purpose of this study is to revisit the question of the shallow structure of Venus based on Magellan observations of the surface and recent experiments that address Venus' crustal rheology.

  11. Chesapeake Bay: Introduction to an Ecosystem.

    Science.gov (United States)

    Environmental Protection Agency, Washington, DC.

    The Chesapeake Bay is the largest estuary in the contiguous United States. The Bay and its tidal tributaries make up the Chesapeake Bay ecosystem. This document, which focuses of various aspects of this ecosystem, is divided into four major parts. The first part traces the geologic history of the Bay, describes the overall physical structure of…

  12. Constraints on Lithospheric Rheology from Observations of Coronae on Venus

    Science.gov (United States)

    O'Rourke, Joseph G.; Smrekar, Suzanne; Moresi, Louis N.

    2016-10-01

    Coronae are enigmatic, quasi-circular features found in myriad geological environments. They are primarily distinguished as rings of concentric fractures superimposed on various topographic profiles with at least small-scale volcanism. Mantle plumes may produce coronae with interior rises, whereas coronae with central depressions are often attributed to downwellings like Rayleigh-Taylor instabilities. For almost three decades, modelers have attempted to reproduce the topographic and gravity profiles measured at coronae. Until recently, few studies also considered tectonic deformation and melt production. In particular, "Type 2" coronae have complete topographic rims but arcs of fractures extending less than 180°, signifying both brittle and ductile deformation. Only a narrow range of rheological parameters like temperature and volatile content may be compatible with these observations. Ultimately, identifying how lithospheric properties differ between Earth and Venus is critical to understanding what factors permit plate tectonics on rocky, Earth-sized planets.Here we present a hierarchical approach to study the formation of coronae. First, we discuss an observational survey enabled by a new digital elevation model derived from stereo topography for ~20% of the surface of Venus, which offers an order-of-magnitude improvement over the horizontal resolution (10 to 20 kilometers) of altimetry data from NASA's Magellan mission. Next, we search this new dataset for signs of lithospheric flexure around small coronae. Simple, thin-elastic plate models were fit to topographic profiles of larger coronae in previous studies, but data resolution impeded efforts to apply this method to the entire coronae population. Finally, we show simulations of the formation of coronae using Underworld II, an open-source code adaptable to a variety of geodynamical problems. We benchmark our code using models of pure Rayleigh-Taylor instabilities and then investigate the influence of

  13. Imaging the Italian Lithosphere based on Adjoint Tomography

    Science.gov (United States)

    Magnoni, F.; Casarotti, E.; Komatitsch, D.; Melini, D.; Michelini, A.; Piersanti, A.; Tape, C.; Tromp, J.

    2016-12-01

    We exploit the powerful European computational resources awarded to our PRACE project IMAGINE_IT ("3D full-wave tomographic IMAGINg of the Entire ITalian lithosphere") to develop a reference, high-resolution 3D seismic wavespeed model for the Italian lithosphere. The inversion procedure consists of iterative improvements of an initial 3D traveltime tomographic model of the region constrained by a large number of full, high-quality observed seismic waveforms. The final model images the regional structure at unprecedented resolution ( 10 s) minimizing the misfit between recorded and synthetic data. Numerical wavefield simulations at high frequency are performed using a spectral-element method (code SPECFEM3D) that allows us to implement all complexities that characterize the studied region (lateral heterogeneity, topography, attenuation). This method is then efficiently combined with an adjoint technique to perform the 3D full-wave tomographic inversion. The Italian peninsula is characterized by very heterogeneous features resulting from complex tectonic evolution of the region mainly dominated by the interaction of Tyrrhenian, Adria and European plates. Our inversion includes 163 earthquakes that occurred in Italy and neighboring areas between 2005 and 2014, and a dense seismological network of 400 seismic recording stations. We perform 25 iterations of our iterative tomographic inversion process, as well as moment tensor inversions for the considered events. The resolution capabilities of our model are also explored based on point spread function analyses and calculation of the approximate Hessian. Thanks to our project IMAGINE_IT, at present the first application of adjoint tomography for the whole Italian region, we are able to constrain Vp as well as Vs at unprecedented resolution; the complex plate relationships start to be accurately modeled, and other inferences on the Italian geodynamical evolution or on fluid (such as CO2) distribution become possible.

  14. Trench curvature and deformation of the subducting lithosphere

    Science.gov (United States)

    Schettino, Antonio; Tassi, Luca

    2012-01-01

    The subduction of oceanic lithosphere is generally accompanied by downdip and lateral deformation. The downdip component of strain is associated with external forces that are applied to the slab during its sinking, namely the gravitational force and the mantle resistance to penetration. Here, we present theoretical arguments showing that a tectonic plate is also subject to a predictable amount of lateral deformation as a consequence of its bending along an arcuate trench zone, independently from the long-term physical processes that have determined the actual curvature of the subduction zone. In particular, we show that the state of lateral strain and the lateral strain rate of a subducting slab depend from geometric and kinematic parameters, such as trench curvature, dip function and subduction velocity. We also demonstrate that the relationship between the state of lateral strain in a subducting slab and the geometry of bending at the corresponding active margin implies a small component of lateral shortening at shallow depths, and may include large extensional lateral deformation at intermediate depths, whereas a state of lateral mechanical equilibrium can only represent a localized exception. Our formulation overcomes the flaws of the classic 'ping-pong ball' model for the bending of the lithosphere at subduction zones, which lead to severe discrepancies with the observed geometry and style of deformation of the modern subducting slabs. A study of the geometry and seismicity of eight modern subduction zones is performed, to assess the validity of the theoretical relationship between trench curvature, slab dip function, and lateral strain rate. The strain pattern within the eight present-day slabs, which is reconstructed through an analysis of Harvard CMT solutions, shows that tectonic plates cannot be considered as flexible-inextensible spherical caps, whereas the lateral intraslab deformation which is accommodated through seismic slip can be explained in terms

  15. Power law olivine crystal size distributions in lithospheric mantle xenoliths

    Science.gov (United States)

    Armienti, P.; Tarquini, S.

    2002-12-01

    Olivine crystal size distributions (CSDs) have been measured in three suites of spinel- and garnet-bearing harzburgites and lherzolites found as xenoliths in alkaline basalts from Canary Islands, Africa; Victoria Land, Antarctica; and Pali Aike, South America. The xenoliths derive from lithospheric mantle, from depths ranging from 80 to 20 km. Their textures vary from coarse to porphyroclastic and mosaic-porphyroclastic up to cataclastic. Data have been collected by processing digital images acquired optically from standard petrographic thin sections. The acquisition method is based on a high-resolution colour scanner that allows image capturing of a whole thin section. Image processing was performed using the VISILOG 5.2 package, resolving crystals larger than about 150 μm and applying stereological corrections based on the Schwartz-Saltykov algorithm. Taking account of truncation effects due to resolution limits and thin section size, all samples show scale invariance of crystal size distributions over almost three orders of magnitude (0.2-25 mm). Power law relations show fractal dimensions varying between 2.4 and 3.8, a range of values observed for distributions of fragment sizes in a variety of other geological contexts. A fragmentation model can reproduce the fractal dimensions around 2.6, which correspond to well-equilibrated granoblastic textures. Fractal dimensions >3 are typical of porphyroclastic and cataclastic samples. Slight bends in some linear arrays suggest selective tectonic crushing of crystals with size larger than 1 mm. The scale invariance shown by lithospheric mantle xenoliths in a variety of tectonic settings forms distant geographic regions, which indicate that this is a common characteristic of the upper mantle and should be taken into account in rheological models and evaluation of metasomatic models.

  16. Bayes multiple decision functions.

    Science.gov (United States)

    Wu, Wensong; Peña, Edsel A

    2013-01-01

    This paper deals with the problem of simultaneously making many (M) binary decisions based on one realization of a random data matrix X. M is typically large and X will usually have M rows associated with each of the M decisions to make, but for each row the data may be low dimensional. Such problems arise in many practical areas such as the biological and medical sciences, where the available dataset is from microarrays or other high-throughput technology and with the goal being to decide which among of many genes are relevant with respect to some phenotype of interest; in the engineering and reliability sciences; in astronomy; in education; and in business. A Bayesian decision-theoretic approach to this problem is implemented with the overall loss function being a cost-weighted linear combination of Type I and Type II loss functions. The class of loss functions considered allows for use of the false discovery rate (FDR), false nondiscovery rate (FNR), and missed discovery rate (MDR) in assessing the quality of decision. Through this Bayesian paradigm, the Bayes multiple decision function (BMDF) is derived and an efficient algorithm to obtain the optimal Bayes action is described. In contrast to many works in the literature where the rows of the matrix X are assumed to be stochastically independent, we allow a dependent data structure with the associations obtained through a class of frailty-induced Archimedean copulas. In particular, non-Gaussian dependent data structure, which is typical with failure-time data, can be entertained. The numerical implementation of the determination of the Bayes optimal action is facilitated through sequential Monte Carlo techniques. The theory developed could also be extended to the problem of multiple hypotheses testing, multiple classification and prediction, and high-dimensional variable selection. The proposed procedure is illustrated for the simple versus simple hypotheses setting and for the composite hypotheses setting

  17. USGS Tampa Bay Pilot Study

    Science.gov (United States)

    Yates, K.K.; Cronin, T. M.; Crane, M.; Hansen, M.; Nayeghandi, A.; Swarzenski, P.; Edgar, T.; Brooks, G.R.; Suthard, B.; Hine, A.; Locker, S.; Willard, D.A.; Hastings, D.; Flower, B.; Hollander, D.; Larson, R.A.; Smith, K.

    2007-01-01

    Many of the nation's estuaries have been environmentally stressed since the turn of the 20th century and will continue to be impacted in the future. Tampa Bay, one the Gulf of Mexico's largest estuaries, exemplifies the threats that our estuaries face (EPA Report 2001, Tampa Bay Estuary Program-Comprehensive Conservation and Management Plan (TBEP-CCMP)). More than 2 million people live in the Tampa Bay watershed, and the population constitutes to grow. Demand for freshwater resources, conversion of undeveloped areas to resident and industrial uses, increases in storm-water runoff, and increased air pollution from urban and industrial sources are some of the known human activities that impact Tampa Bay. Beginning on 2001, additional anthropogenic modifications began in Tampa Bat including construction of an underwater gas pipeline and a desalinization plant, expansion of existing ports, and increased freshwater withdrawal from three major tributaries to the bay. In January of 2001, the Tampa Bay Estuary Program (TBEP) and its partners identifies a critical need for participation from the U.S. Geological Survey (USGS) in providing multidisciplinary expertise and a regional-scale, integrated science approach to address complex scientific research issue and critical scientific information gaps that are necessary for continued restoration and preservation of Tampa Bay. Tampa Bay stakeholders identified several critical science gaps for which USGS expertise was needed (Yates et al. 2001). These critical science gaps fall under four topical categories (or system components): 1) water and sediment quality, 2) hydrodynamics, 3) geology and geomorphology, and 4) ecosystem structure and function. Scientists and resource managers participating in Tampa Bay studies recognize that it is no longer sufficient to simply examine each of these estuarine system components individually, Rather, the interrelation among system components must be understood to develop conceptual and

  18. Island Bay Wilderness study area : Island Bay National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document is a brief report on a wilderness study area located in the Island Bay National Wildlife Refuge. It discusses the history of the study area, its...

  19. Challenges (and Promise) of In-Situ Lithospheric Rheology from Isostatic Strength Analyses

    Science.gov (United States)

    Lowry, Anthony R.; Becker, Thorsten W.; Buehler, Janine S.; Miller, Meghan S.; Pérez-Gussinyé, Marta; Schutt, Derek L.; Seunarine, Lisa L.

    2013-04-01

    Measurements of effective elastic thickness, Te, from flexural isostatic modeling are sensitive to flow rheology of the lithosphere. Nevertheless Te has not been widely used to estimate in-situ rheology, partly owing to methodological questions regarding the measurement of Te and partly because of uncertainties in other in-situ properties of temperature, composition, water content and state-of-stress of the lithosphere. Dense seismic and other geophysical arrays such as EarthScope's USArray are providing a wealth of new information about physical state of the lithosphere, however, and the relationships of these data to Te promises new insights into lithospheric rheology and deformation processes. For example, new estimates of subsurface mass distributions derived from seismic data enable us to examine various controversial assumptions about the nature of lithospheric loads. Variations in crustal composition evident in bulk crustal velocity ratio, vP-vS, contribute a surprisingly large fraction of total loading, and elevation models better match observations if Moho flexure is not forced to match surface flexure, indicating that lower crustal flow and other crustal mass transfer processes are significant. Perhaps the most interesting new information on physical state derives from imaging of uppermost mantle velocities using refracted mantle phases, Pn and Sn, and depths to negative velocity gradients imaged as converted phases in receiver functions (seismic lithosphere-asthenosphere boundary, "LAB"). We will compare Te measurements to thermal models derived from these seismic fields, and discuss their implications for lithospheric rheological controls and thermal processes.

  20. Time-dependent rotational stability of dynamic planets with viscoelastic lithospheres

    Science.gov (United States)

    Moore, K. M.; Chan, N.-H.; Daradich, A.; Mitrovica, J. X.

    2017-06-01

    We extend previous work to derive a non-linear rotational stability theory governing true polar wander (TPW) of terrestrial planets with viscoelastic lithospheres. We demonstrate, analytically and using numerical examples, that our expressions are consistent with previous results in the limiting cases of low and infinite (i.e., purely elastic) viscosity lithospheres. To illustrate the stability theory, we compute TPW on Mars driven by a simple, prescribed mass loading. Our calculations demonstrate that on short time scales relative to the relaxation time of the viscoelastic lithosphere, the rotation axis follows a constrained path that reflects stabilization by remnant strength in the lithosphere, but that on long times scales this stabilization disappears and the load ultimately reaches the equator. Earlier work based on the assumption of a permanent remnant bulge in the case of a purely elastic lithosphere has suggested that Martian TPW would not persist for any significant time after a load is emplaced, and thus an equilibrium stability theory is sufficient to model long-term (order 1 Myr or longer) polar motion of the planet. Our results suggest, in contrast, that TPW on Mars can continue over time scales on the order of the relaxation time of the lithosphere after load emplacement; for sufficiently high lithospheric viscosities, this time scale may be comparable to the age of the planet.

  1. Utilizing thermal isostasy to estimate sub-lithospheric heat flow and anomalous crustal radioactivity

    Science.gov (United States)

    Hasterok, D.; Gard, M.

    2016-09-01

    While surface heat flow relates to the heat loss through the lithosphere, it can be difficult to quantify and separate the heat produced internally through radiogenic decay from the heat transferred across the base of the lithosphere by mantle convection. In this study, we apply a thermo-isostatic analysis to Australia and estimate the sub-lithospheric and radiogenic heat flow components by employing a simple 1-D conservation of energy model. We estimate an anomalous radiogenic heat production across much of eastern Australia generally accounting for >50 mW m-2, while western Australia appears to have high crustal compositionally corrected elevation, possibly related to chemical buoyancy of the mantle lithosphere. A moderately high sub-lithospheric heat flow (∼40 mW m-2) along the eastern and southeastern coast, including Tasmania, is coincident with locations of Cenozoic volcanism and supports an edge-driven convection hypothesis. However, the pattern of sub-lithospheric heat flow along the margin does not support the existence of hotspot tracks. Thermo-isostatic models such as these improve our ability to identify and quantify crustal from mantle sources of heat loss and add valuable constraints on tectonic and geodynamic models of the continental lithosphere's physical state and evolution.

  2. Intra-cratonic melting as a result of delamination of mantle lithosphere - insight from numerical modelling

    Science.gov (United States)

    Gorczyk, W.; Vogt, K.; Gerya, T.; Hobbs, B. E.

    2012-12-01

    It is becoming increasingly apparent that intense deformation, metamorphism and metasomatism occur within continental cratonic blocks far removed form subducting margins Such changes may occur intra-cratonically arising from lithospheric thickening and the development of gravitational instabilities, but mostly occur at the boundary of cratonic blocks. The contact of two cratons is characterized by rheological lateral variations within mantle-lithosphere and overlying crust. Tectonic stresses acting on craton/craton boundaries may lead to thinning or thickening due to delamination of the mantle lithosphere. This is reflected in tectonic deformation, topography evolution, melting and crustal metamorphism. To understand the controls on these processes a number of 2D, coupled petrological thermo-mechanical numerical experiments has been performed to test the response of a laterally weakened zone to a compressional regime. The results indicate that the presence of water-bearing minerals in the lithosphere and lower crust is essential to initiate melting, which in the later stages may expand to dry melting of crust and mantle. In the case of anhydrous crust and lithosphere, no melting occurs. Thus a variety of instabilities, melting behaviour and topographic responses occurs at the base of the lithosphere as well as intensive faulting and buckling in the crust dependent on the strength and "water" content of the lithosphere.

  3. A preliminary study on the lithospheric thermal-rheological structure of the East Qinling orogenic belt

    Institute of Scientific and Technical Information of China (English)

    CHENG Shunyou; ZHANG Guowei; DIAO Bo; GUO Anlin; YU Xiangni

    2007-01-01

    This paper considers the lithospheric rheological structure of the East Qinling orogenic belt to explore its geodynamics. The lithospheric rheological structure was calculated by the constraints of the lithospheric temperature structure. The thermal-rheological stratification structures of the lithosphere in the East Qinling orogenic belt present different features from each other within different tectonic units. The hinterland fault-bounded fold zone (HLZ) and the North Qinling thick-skinned imbricated thrust zone (NQL) in the northern half part of the Qinling orogen, with a tempera-ture of 305℃ for the Moho boundary, are characterized by "cold" geotherm, thickened lithosphere and the model C for rheological stratification structure. The South Qinling tectonic zone (SQL), with a mean temperature of 642℃ and a high temperature of 826℃ for the Moho boundary, has obvious features with the model H of"hot" geotherm, thinned lithosphere and intensive rheological behavior within moderate-lower crust and top of the upper mantle. During post-orogenesis, the NQL, being the convergent frontal region of continental subduction beneath the Qinling orogen by both the North China craton (NC) and Yangtze craton (YZ), is in a coexistence period of a dominantly thickened lithosphere and an initial delamination, and the SQL, proba-bly under pluming, has been developing new delamination and underplating and partial melting within the crust in its axel area and recycling for mass and energy (in the forms of heat transfer and convection) between the crust and mantle.

  4. Circulation in the Hudson Shelf Valley: MESA Physical Oceanographic Studies in New York Bight, 1

    Science.gov (United States)

    Mayer, Dennis A.; Han, Gregory C.; Hansen, Donald V.

    1982-11-01

    Over 900 days of current velocity data were obtained at mainly two locations in the inner and outer Hudson Shelf Valley (HSV). The large cross-axis depth gradients in the HSV, together with the strong winter cyclones and the baroclinic density distribution over the shelf, are primarily responsible for the major circulation features observed in the valley. CSTD data from 12 cruises and meteorological data from JFK International Airport and an environmental buoy were collected concurrently with the current meter data. Although the mean cross-shelf pressure gradient is generally seaward in the Middle Atlantic Bight, it is shoreward in the HSV below the level of the adjacent continental shelf (shelf horizon), thus imposing a bias toward upvalley flow. The average velocity below the surrounding shelf horizon in the HSV is upvalley or shoreward (west-northwestward ≈ 290° T) in the range of 2-5 cm/s. The circulation in the HSV is seasonal and individual events can drastically alter the mean picture. The several day average upvalley flow can sometimes approach 20 cm/s when intense winter cyclones pass over the bight and can sometimes also be directed downvalley depending upon the path of the winter cyclone. A topographically controlled barotropic flow commonly opposes the dominant (southeast-ward) wind direction even near the surface in the winter. In the context of circulation on the open shelf, upvalley (downvalley) flow events generated by winter cyclones are associated with reduced (enhanced) southwestward flow or flow reversals that are northeastward in the lower half of the water column at LTM, a typical mid/shelf site (Mayer et al., 1979). Current meter data suggest that whether or not reversals occur on the open shelf depends upon the interannual variability of the winter wind regime. Upvalley flow events are not confined only to the winter (unstratified) season but are stronger in the winter and can last for several days and longer. During the summer

  5. Imaging Canary Island hotspot material beneath the lithosphere of Morocco and southern Spain

    Science.gov (United States)

    Miller, Meghan S.; O'Driscoll, Leland J.; Butcher, Amber J.; Thomas, Christine

    2015-12-01

    The westernmost Mediterranean has developed into its present day tectonic configuration as a result of complex interactions between late stage subduction of the Neo-Tethys Ocean, continental collision of Africa and Eurasia, and the Canary Island mantle plume. This study utilizes S receiver functions (SRFs) from over 360 broadband seismic stations to seismically image the lithosphere and uppermost mantle from southern Spain through Morocco and the Canary Islands. The lithospheric thickness ranges from ∼65 km beneath the Atlas Mountains and the active volcanic islands to over ∼210 km beneath the cratonic lithosphere in southern Morocco. The common conversion point (CCP) volume of the SRFs indicates that thinned lithosphere extends from beneath the Canary Islands offshore southwestern Morocco, to beneath the continental lithosphere of the Atlas Mountains, and then thickens abruptly at the West African craton. Beneath thin lithosphere between the Canary hot spot and southern Spain, including below the Atlas Mountains and the Alboran Sea, there are distinct pockets of low velocity material, as inferred from high amplitude positive, sub-lithospheric conversions in the SRFs. These regions of low seismic velocity at the base of the lithosphere extend beneath the areas of Pliocene-Quaternary magmatism, which has been linked to a Canary hotspot source via geochemical signatures. However, we find that this volume of low velocity material is discontinuous along strike and occurs only in areas of recent volcanism and where asthenospheric mantle flow is identified with shear wave splitting analyses. We propose that the low velocity structure beneath the lithosphere is material flowing sub-horizontally northeastwards beneath Morocco from the tilted Canary Island plume, and the small, localized volcanoes are the result of small-scale upwellings from this material.

  6. Dynamic topography as constraints on stress and viscosity in the mantle and lithosphere

    Science.gov (United States)

    Zhong, S.

    2015-12-01

    Mantle convection generates stress in the mantle and lithosphere. The lithosphere stress is responsible for localized deformation including seismic deformation at plate boundaries, and localized stress highs in lithosphere are also suggested to cause dynamically self-consistent generation of plate tectonics and continental lithosphere instability, as the stress exceeds a threshold or yield stress. Modeling load-induced deformation at oceanic islands (e.g., Hawaii) constrains lithospheric stress at 100-200 MPa in the plate interiors, leading to a lower limit on lithospheric yield stress (Zhong and Watts, 2013). However, convection-induced lithospheric stress is poorly understood, ranging from 500 MPa to tens of MPa as reported in mantle convection studies. The magnitude and distribution of lithospheric and mantle stress depend critically on buoyancy and viscosity, particularly the latter. Unfortunately, lithospheric and mantle viscosity is also poorly constrained. For example, the inferred lower mantle viscosity from post-glacial rebound and geoid modeling studies ranges from 1023 Pas to 1022 Pas (e.g., Mitrovica and Forte, 2004; Simons and Hager, 1996; Paulson et al., 2007). In addition to the stress, the lower mantle viscosity may also affect the time evolution of mantle structure including sinking rate of slabs and formation of the degree-2 mantle seismic structure. Therefore, it is important to develop independent constraints on mantle viscosity and convection-induced stress. In this study, I demonstrate that dynamic topography can be used to place first-order constraints on both lithospheric stress and mantle viscosity. For a given superadiabatic temperature difference across the mantle (e.g., 2500 K), a larger mantle viscosity (or a smaller Rayleigh number) leads to a larger lithospheric stress and a larger dynamic topography. To be consistent with the inferred dynamic topography, the lower mantle viscosity is constrained to be significantly smaller than 1023

  7. Continuous deformation versus faulting through the continental lithosphere of new zealand

    Science.gov (United States)

    Molnar; Anderson; Audoine; Eberhart-Phillips; Gledhill; Klosko; McEvilly; Okaya; Savage; Stern; Wu

    1999-10-15

    Seismic anisotropy and P-wave delays in New Zealand imply widespread deformation in the underlying mantle, not slip on a narrow fault zone, which is characteristic of plate boundaries in oceanic regions. Large magnitudes of shear-wave splitting and orientations of fast polarization parallel to the Alpine fault show that pervasive simple shear of the mantle lithosphere has accommodated the cumulative strike-slip plate motion. Variations in P-wave residuals across the Southern Alps rule out underthrusting of one slab of mantle lithosphere beneath another but permit continuous deformation of lithosphere shortened by about 100 kilometers since 6 to 7 million years ago.

  8. Variations in timing of lithospheric failure on terrestrial planets due to chaotic nature of mantle convection

    Science.gov (United States)

    Wong, Teresa; Solomatov, Viatcheslav S.

    2016-05-01

    We perform numerical simulations of lithospheric failure in the stagnant lid regime of temperature-dependent viscosity convection, using the yield stress approach. We find that the time of failure can vary significantly for the same values of the controlling parameters due to the chaotic nature of the convective system. The general trend of the dependence of the time of lithospheric failure on the yield stress can be explained by treating lithospheric failure as a type of Rayleigh-Taylor instability. This study suggests that it is important to address not only the question of whether plate tectonics can occur on a planet but also when it would occur if conditions are favorable.

  9. Global map of lithosphere thermal thickness on a 1 deg x 1 deg grid - digitally available

    Science.gov (United States)

    Artemieva, Irina

    2014-05-01

    This presentation reports a 1 deg ×1 deg global thermal model for the continental lithosphere (TC1). The model is digitally available from the author's web-site: www.lithosphere.info. Geotherms for continental terranes of different ages (early Archean to present) are constrained by reliable data on borehole heat flow measurements (Artemieva and Mooney, 2001), checked with the original publications for data quality, and corrected for paleo-temperature effects where needed. These data are supplemented by cratonic geotherms based on xenolith data. Since heat flow measurements cover not more than half of the continents, the remaining areas (ca. 60% of the continents) are filled by the statistical numbers derived from the thermal model constrained by borehole data. Continental geotherms are statistically analyzed as a function of age and are used to estimate lithospheric temperatures in continental regions with no or low quality heat flow data. This analysis requires knowledge of lithosphere age globally. A compilation of tectono-thermal ages of lithospheric terranes on a 1 deg × 1 deg grid forms the basis for the statistical analysis. It shows that, statistically, lithospheric thermal thickness z (in km) depends on tectono-thermal age t (in Ma) as: z=0.04t+93.6. This relationship formed the basis for a global thermal model of the continental lithosphere (TC1). Statistical analysis of continental geotherms also reveals that this relationship holds for the Archean cratons in general, but not in detail. Particularly, thick (more than 250 km) lithosphere is restricted solely to young Archean terranes (3.0-2.6 Ga), while in old Archean cratons (3.6-3.0 Ga) lithospheric roots do not extend deeper than 200-220 km. The TC1 model is presented by a set of maps, which show significant thermal heterogeneity within continental upper mantle. The strongest lateral temperature variations (as large as 800 deg C) are typical of the shallow mantle (depth less than 100 km). A map of the

  10. Building sustainable communities using sense of place indicators in three Hudson River Valley, NY, tourism destinations: An application of the limits of acceptable change process

    Science.gov (United States)

    Laura E. Sullivan; Rudy M. Schuster; Diane M. Kuehn; Cheryl S. Doble; Duarte. Morais

    2010-01-01

    This study explores whether measures of residents' sense of place can act as indicators in the Limits of Acceptable Change (LAC) process to facilitate tourism planning and management. Data on community attributes valued by residents and the associated values and meanings were collected through focus groups with 27 residents in three Hudson River Valley, New York,...

  11. Computer simulation model for the striped bass young-of-the-year population in the Hudson River. [Effects of entrainment and impingement at power plants on population dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Eraslan, A.H.; Van Winkle, W.; Sharp, R.D.; Christensen, S.W.; Goodyear, C.P.; Rush, R.M.; Fulkerson, W.

    1975-09-01

    This report presents a daily transient (tidal-averaged), longitudinally one-dimensional (cross-section-averaged) computer simulation model for the assessment of the entrainment and impingement impacts of power plant operations on young-of-the-year populations of the striped bass, Morone saxatilis, in the Hudson River.

  12. Hydrocarbons in the Bay of Bengal and Central Indian Basin bottom sediments: Indicators of geochemical processes in the lithosphere

    Digital Repository Service at National Institute of Oceanography (India)

    Chernova, T.G.; Paropkari, A.L.; Pikovskii, Yu.I.; Alekseeva, T.A.

    that the hydrocarbons are mostly derived from marine sources. Sharp increases fo hydrocarbons are found in the vicinity of the tectonically active region of the Central Indian Basin, particularly in the sediments collected from the fracture zone. The total concentration...

  13. Vapor Intrusion Facilities - South Bay

    Data.gov (United States)

    U.S. Environmental Protection Agency — POINT locations for the South Bay Vapor Instrusion Sites were derived from the NPL data for Region 9. One site, Philips Semiconductor, was extracted from the...

  14. Lavaca Bay 1985-1987

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Samples were collected from October 15, 1985 through June 12, 1987 in emergent marsh and non-vegetated habitats throughout the Lavaca Bay system to characterize...

  15. Annual report, Bristol Bay, 1958

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Commercial fishery management activities for Bristol Bay for 1958, including lists of operators, extensive statistics, and descriptions of enforcement activities.

  16. FL BAY SPECTROUT-DIET

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Juvenile spotted seatrout and other sportfish are being monitored annually over a 6-mo period in Florida Bay to assess their abundance over time relative to...

  17. CHWAKA BAY MANGROVE SEDIMENTS, ZANZIBAR

    African Journals Online (AJOL)

    Mohammed-Studies on Benthic denitrification in the Chwaka bay mangrove. Extensive mangrove ... In this case, six sediment cores were taken randomly from the three study sites as above and a ..... Academic Press. Orlando. pp. 277-293.

  18. Annual report, Bristol Bay, 1955

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Commercial fishery management activities for Bristol Bay for 1955, including lists of operators, extensive statistics, descriptions of enforcement activities, and...

  19. Back Bay Wilderness area description

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document is a description of the lands located within the Back Bay National Wildlife Refuge. Within these lands, it designates which area is suitable for...

  20. Geodynamic inversion to constrain the rheology of the lithosphere: What is the effect of elasticity?

    Science.gov (United States)

    Baumann, Tobias; Kaus, Boris; Thielmann, Marcel

    2016-04-01

    The concept of elastic thickness (T_e) is one of the main methods to describe the integrated strength of oceanic lithosphere (e.g. Watts, 2001). Observations of the Te are in general agreement with yield strength envelopes estimated from laboratory experiments (Burov, 2007, Goetze & Evans 1979). Yet, applying the same concept to the continental lithosphere has proven to be more difficult (Burov & Diament, 1995), which resulted in an ongoing discussion on the rheological structure of the lithosphere (e.g. Burov & Watts, 2006, Jackson, 2002; Maggi et al., 2000). Recently, we proposed a new approach, which constrains rheological properties of the lithosphere directly from geophysical observations such as GPS-velocity, topography and gravity (Baumann & Kaus, 2015). This approach has the advantage that available data sets (such as Moho depth) can be directly taken into account without making the a-priori assumption that the lithosphere is thin elastic plate floating on the mantle. Our results show that a Bayesian inversion method combined with numerical thermo-mechanical models can be used as independent tool to constrain non-linear viscous and plastic parameters of the lithosphere. As the rheology of the lithosphere is strongly temperature dependent, it is even possible to add a temperature parameterisation to the inversion method and constrain the thermal structure of the lithosphere in this manner. Results for the India-Asia collision zone show that existing geophysical data require India to have a quite high effective viscosity. Yet, the rheological structure of Tibet less well constrained and a number of scenarios give a nearly equally good fit to the data. Yet, one of the assumptions that we make while doing this geodynamic inversion is that the rheology is viscoplastic, and that elastic effects do not significantly alter the large-scale dynamics of the lithosphere. Here, we test the validity of this assumption by performing synthetic forward models and retrieving

  1. Past and Future Climatic Conditions in the Hudson Bay Lowland near Churchill, Manitoba and Implications for the Fate of Shallow Water Bodies

    Science.gov (United States)

    Macrae, M. L.; Duguay, C. R.; Brown, L.; Svacina, N. A.; Parrott, J. A.

    2010-12-01

    Recent ground-based and remote sensing observations have shown a general decreasing trend in arctic lake/pond surface area over the past 50 years, suggesting that small water bodies at high latitudes are drying. This study aims to answer three key questions regarding the water balance of subarctic ponds to climate change from the second half of the 20th century to the end of the 21st century: 1) Have there been changes in precipitation quantity and distribution, annual and seasonal air temperature, and the duration of the ice-free season in the 1943-2008 observational period?; 2) Are these trends expected to continue until the end of the 21st century based on regional climate model (RCM) scenarios?; and 3) What are the implications of climate change for pond sustainability in the Churchill region? Climatic change and changes to pond hydrologic storage over the past 65 years were examined using a combination of field methods/instrumental records and modelling. Results show that annual precipitation has increased by 25% over the past 65 years. Annual rainfall during the period has increased by 50%, while annual snowfall has decreased by 17%, suggesting that snowfall is being replaced by rainfall in this region. Much of the increased annual rainfall has been observed in the months of August and September, where rainfall has increased by 60% and 88%, respectively. Mean annual air temperature has increased by approximately 1C between 1943-2008. Significant (p0.05). A comparison of modelled and observed precipitation and air temperature between 1961-2008 produced similar trends. The Canadian RCM projections indicate that both precipitation and air temperature will continue to increase for the remainder of the 21st century. Trends observed over the past 65 years and simulations of future scenarios show that rainfall is increasing at a faster rate than evaporation, causing a lessening of the summer moisture deficit that persists in this region. Consequently, conditions are becoming more wet and ponds do not appear to be at increased risk for drying. This has strong implications for pond hydrologic storage, growth and connectivity in this region.

  2. Dating Metasomatism in the Lithosphere Beneath North China Craton

    Science.gov (United States)

    Chen, L.; Zhou, X.

    2005-12-01

    Dating of mantle metasomatism had been carried out using zircons in metasomatized mantle xenoliths entrained in kimberlites (Kinny and Dawson, 1992; Rudnick et al., 1999; Konzett et al., 1998, 2000; Liati et al., 2004), because the U-Pb system in zircon can remain closed at high temperature (>900-)(Lee et al., 1997). Here we report a SHRIMP U-Pb dating analysis of zircons from a unique dunite-orthopyroxenite xenolith entrained in Cretaceous high-Mg diorite of Shandong province, which provides a timing constraint for the multi-stage metasomatism in the lithosphere beneath North China craton (NCC). Abundant ultramafic xenoliths had been found in the Tietonggou intrusion, one of the Cretaceous high-Mg diorite-dominated plutons in North China (Chen and Zhou, 2004). The lithology, mineral chemistry, equilibrium temperature (690-790A), and metasomatic characteristics of the ultramafic xenoliths indicate that they might be derived from the shallow lithosphere (the crust-mantle transitional zone or the uppermost lithospheric mantle) and had suffered multi-stage metasomatism (Chen and Zhou, 2004, 2005). Xenolith LW0006 is the most extremely metasomatized sample found so far in the xenolith suite of the Tietonggou pluton. The petrography, mineral chemistry, and major element compositions provide a clear metasomatic record of the composite xenolith: K (and/or Ca) metasomatism, and Si (Na) metasomatism (Chen and Zhou). We found seven zircons range from 100-170 Im in longest dimension, which is reflected in the unusually high Zr content of the bulk rock (49 ppm) of this sample. SHRIMP U-Pb dating reveals that these zircons might be grouped three kinds: Mesozoic (concordia age of 127-A3 Ma, 5 zircons), Paleozoic (430-470 Ma, 1 zircon only) and Mesoproterozoic (1310-1540 Ma, 1 zircon only). Cathodoluminescence (CL) images reveal that a few Mesozoic zircons and the Paleozoic zircons retain oscillatory zoning. The Mesozoic zircons are characterized with high Th, U contents and high

  3. Relict Oceanic Lithosphere in Cuba: Types and Emplacement Ages

    Science.gov (United States)

    CobiellaReguera, J. L.

    2001-12-01

    According to their composition and tectonic position, three different types of relict oceanic lithosphere are present in Cuba: (1) the northern ophiolitic belt, a complex melange that extents more than 1000 km along the island, (2) the basement of the Cretaceous volcanic arc terrane: high temperature/low pressure amphibolites with some serpentinites and, (3) tectonic slices of serpentinite melanges (with eclogites and blueschists) and high pressure amphibolites, in the metamorphic Escambray massif (tectonostratigraphic terrane, microcontinent?) of southcentral Cuba. Available age constrains (paleontological and geochronological) indicate that relicts of oceanic lithosphere in Cuba are upper Mesozoic in age. Geochemical, petrological, and regional geology data suggest that such oceanic relicts probably originated in two different tectonic environments in the Proto-Caribbean basin; (1) a small oceanic basin of Upper Jurassic- Neocomian age, related to drift between North America and a southern continental mass and (2) a suprasubduction marginal basin, between the southeastern North American passive margin and an Aptian-Albian volcanic arc. Tectonic emplacement of the Cuban relict oceanic Proto-Caribbean lithosphere was likely related to several tectonic events and processes. Serpentinite melange slices and the high pressure amphibolites in the Jurassic and Cretaceous passive margin sequences of Escambray massif, characterized by low to moderate temperature and high pressure metamorphism, probably were emplaced from subduction and closure of the small oceanic depression located to the south (present geographic coordinates) of the volcanic arc in the Albian. The basement amphibolites of the volcanic arc terrane were derived from the Upper Jurassic-Neocomian oceanic crust, metamorphosed by the high temperatures and hot solutions related to the development on this crust of an Aptian-Albian volcanic arc with a north dipping subduction zone. These amphibolites were

  4. Lithospheric seismic fabrics of Sulu ultrahigh-pressure metamorphic belt

    Institute of Scientific and Technical Information of China (English)

    YANG; Wencai; YANG; Wuyang; JIN; Zhenmin; CHENG; Zhenyan

    2005-01-01

    Calibration of seismic reflectors appearing in the crust of the Chinese continent scientific drilling site can be completed through the correlation studies between direct evidences, such as the drill cores, and geophysical signatures; therefore the interpretation of geophysical data could produce reliable results of crustal structure and composition. On the other hand, there are two Cenozoic volcanoes close to the scientific drilling site; analyzing composition of xenoliths existent in the volcanoes and evaluating their seismic velocities can also offer information about the mantle and lower crust. After the calibration via cores and well-logging data, the seismic reflectors appearing in the UHP belt can be caused by lithological changes within the UHP rock slice, ductile shearing rock-suites, and later fracture zones. Among these sources, ductile shearing resulted in displacement and detachment of original rock-sheets, producing some rock-interbeds of several hundred meters thick that are named the ductile shearing rock-suites. A suite consists of mylonized gneiss and eclogite slices that underwent shearing, becoming the major mechanism responsible to generate regional strong reflections. The UHP rock-slice is characterized by complicated structures and high density, high seismic velocity and high electrical resistivity, its thickness is usually less than 11 km. Velocity and density of the gneiss-layer beneath gradually tend to normal with increasing depth. Based on the xenoliths we can infer that the middle crust contains a lot of gneisses, and the lower crust consists of different granulites. The lithospheric mantle has multi-layer structures and consists mainly of spinal lherzolite and harzburgite, implying late Mesozoic lithospheric thinning. The seismic fabrics with different origins were possible products of different geodynamic processes. For instance, the UHP rock-slice was produced by the UHP metamorphic process and the exhumation of subducted

  5. Lithospheric analysis of satellite geopotential anomalies of East Asia

    Science.gov (United States)

    Tan, Li

    Satellite gravity and magnetic anomalies are used to study the lithosphere of East Asia. Free-air gravity anomalies are decomposed into terrain-correlated, mantle/core and intracrustal components by spectral correlation analysis of the free-air gravity anomalies and terrain gravity effects. Compensated terrain gravity anomalies are obtained by removing the terrain-correlated free-air gravity anomalies. They are used to estimate the Moho undulation and crustal thickness by Gauss-Legendre quadrature (GLQ) inversion techniques assuming a Airy-Heiskanen model of crustal compensation. These results are used to develop enhanced reduction procedures to generate an improved Magsat magnetic anomaly map for East Asia. A degree 12 core field is removed from the data that are updated for the crustal components in the core field differences between degree 14 and 12. These components are estimated by using spectral correlation analysis to compare the Magsat anomalies to the magnetic effect of the crust that is available from the first vertical derivative of the terrain-correlated free-air gravity anomalies via Poisson's theorem. External field effects are separated using pass-by-pass correlation analysis of the dusk and dawn data sets and their spectral reconstruction. Coherent components in the dusk and dawn maps are combined to estimate the magnetic anomalies of the lithosphere. Long wavelength magnetic features related to lower crustal thickness variations are converted into effective magnetization contrasts by a new GLQ inversion technique. Effective magnetization contrasts of the lower crust range over ±4 A/m in accordance petrological studies. Finally, a new GLQ integration formula for triangular wedge sources is derived for modeling of satellite-altitude geopotential field anomalies from arbitrarily shaped sources. Detailed magnetization and density contrasts for central India, the Tibetan Plateau, and the Bengal Gulf region are modeled by this new formula. Positive

  6. PRESSURE GRADIENT FROM THE CONTRIBUTION OF BOTH GEOTHERMAL AND GRAVITY IN THE LITHOSPHERE

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The pressure gradient of the lithosphere is a key to explaining various geological processes, and varies also in time and space similar to the geothermal gradient. In this paper a correlation formula of geothermal gradients and pressure gradients was built with the thermocomprestion coefficients. Based on this formula, the article has studied the relation between the pressure gradients and the geothermal gradients in the lithosphere, and the results indicate that the pressure gradient in the lithosphere is nonlinear, and its minimum value is the lithostatic gradient, and that the pressure gradient of the lithosphere will increase obviously with the contribution of both geothermal and gravity, and could be twice times more than the lithostatic gradient.

  7. Elysium Region, Mars: Tests of Lithospheric Loading Models for the Formation of Tectonic Features

    Science.gov (United States)

    Hall, J. L.; Solomon, S. C.; Head, J. W.

    1985-01-01

    In an effort to constrain the tectonic history and mechanical properties of the lithosphere in the Elysium province, the stress fields predicted by different models are compared to the observed tectonic features of the region. The models are all products of volcanic loading of the Martian lithosphere, but at three different scales: global (Tharsis), regional (Elysium Planitia), and local (individual shields). Conclusions: The concentric graben surrounding Elysium Mons can be ascribed to the flexural response of an approximately 50-km-thick elastic lithosphere to loading by the volcano. No tectonic evidence for the support of larger-scale Elysium Planitia volcanic units by lithospheric flexure. The quasi-global loading of the Tharsis rise appears to have produced identifiable tectonic effects in the Elysium region.

  8. Elysium region, Mars - Tests of lithospheric loading models for the formation of tectonic features

    Science.gov (United States)

    Hall, J. Lynn; Solomon, Sean C.; Head, James W.

    1986-01-01

    The hypothesis that the tectonic features in the Elysium region are the product of stress produced by loading of the Martian lithosphere is tested. The lithospheric loading models for the formation of tectonic features in the Elysium region are evaluated under local loading, regional loading of the lithosphere from above and below, and quasi-global loading by Tharsis. The physiographic features in the Elysium region are described. The stress fields predicted by volcanic loading and uplift of the Martian lithosphere are compared with the tectonic features in the Elysium region. It is noted that the comparison suggests the succession of stress fields operating at different times in the region and supports the hypothesis.

  9. Melt-Enhanced Rejuvenation of Lithospheric Mantle: Insights from the Colorado Plateau

    CERN Document Server

    Roy, Mousumi; Holtzman, Ben; Gaherty, James

    2012-01-01

    The stability of the lithospheric mantle beneath the ancient cratonic cores of continents is primarily a function of chemical modification during the process of melt extraction. Processes by which stable continental lithosphere may be destabilized are not well-understood, although destabilization by thickening and removal of negatively-buoyant lithospheric mantle in "delamination" events has been proposed in a number of tectonic settings. In this paper we explore an alternative process for destabilizing continents, namely, thermal and chemical modification during infiltration of metasomatic fluids and melts into the lithospheric column. We consider observations pertinent to the structure and evolution of the Colorado Plateau within the western United States to argue that the physical and chemical state of the margins of the plateau have been variably modified and destabilized by interaction with melts. In the melt-infiltration process explored here, the primary mechanism for weakening and rejuvenating the pla...

  10. Complex morphology of subducted lithosphere in the mantle beneath the Tonga trench

    NARCIS (Netherlands)

    Hilst, R.D. van der

    1995-01-01

    At the Tonga trench, old Pacific sea floor subducts at a rapid rate below the Indo-Australia plate, generating most of the world's deep earthquakes and producing a deep slab of former oceanic lithosphere.

  11. Spatial patterns in the distribution of kimberlites: relationship to tectonic processes and lithosphere structure

    DEFF Research Database (Denmark)

    Chemia, Zurab; Artemieva, Irina; Thybo, Hans

    2015-01-01

    Since the discovery of diamonds in kimberlite-type rocks more than a century ago, a number of theories regarding the processes involved in kimberlite emplacement have been put forward to explain the unique properties of kimberlite magmatism. Geological data suggests that pre-existing lithosphere...... weakness zones may control the spatial patterns of kimberlites, but this hypothesis has never been tested by geophysical methods. As the first step in our analysis of tectonic and lithosphere control of kimberlite-type magmatism, we perform a detailed global analysis of the spatial patterns of kimberlites......, and present the first results. The analysis is based on the assumption that the kimberlite emplacement is a two-stage process, and the two stages are controlled by the crustal and lithospheric mantle rheologies, respectively. Stage 1 includes the first-order, lithosphere-scale process that initiate the rise...

  12. Spatial patterns in the distribution of kimberlites: relationship to tectonic processes and lithosphere structure

    DEFF Research Database (Denmark)

    Chemia, Zurab; Artemieva, Irina; Thybo, Hans

    Since the discovery of diamonds in kimberlite-type rocks more than a century ago, a number of theories regarding the processes involved in kimberlite emplacement have been put forward to explain the unique properties of kimberlite magmatism. Geological data suggests that pre-existing lithosphere...... weakness zones may control the spatial patterns of kimberlites, but this hypothesis has never been tested by geophysical methods. As the first step in our analysis of tectonic and lithosphere control of kimberlite-type magmatism, we perform a detailed global analysis of the spatial patterns of kimberlites......, and present the first results. The analysis is based on the assumption that the kimberlite emplacement is a two-stage process, and the two stages are controlled by the crustal and lithospheric mantle rheologies, respectively. Stage 1 includes the first-order, lithosphere-scale process that initiate the rise...

  13. Seismic structure of the lithosphere beneath the ocean islands near the mid-oceanic ridges

    Science.gov (United States)

    Haldar, C.; Kumar, P.; Kumar, M. Ravi

    2013-10-01

    Deciphering the seismic character of the young lithosphere near the mid-oceanic ridges (MOR) is a challenging endeavor. In this study, we determine the seismic structure of the oceanic plate near the MORs, using the P-to-s conversions isolated from good quality data recorded at 5 broadband seismological stations situated on the ocean Islands in their vicinity. Estimates of the crustal and lithospheric thickness values from waveform modeling of the P receiver function stacks reveal that the crustal thickness varies between 6 and 8 km with the corresponding depths to the lithosphere asthenosphere boundary (LAB) varying between 43 and 68 km. However, the depth to the LAB at Macquire Island is intriguing in view of the observation of a thick (~ 87 km) lithosphere beneath a relatively young crust. At three other stations i.e., Ascension Island, Sao Jorge and Easter Island, we find evidence for an additional deeper low velocity layer probably related to the presence of a hotspot.

  14. Global map of lithosphere thermal thickness on a 1 deg x 1 deg grid - digitally available

    DEFF Research Database (Denmark)

    Artemieva, Irina

    2014-01-01

    than 250 km) lithosphere is restrictedsolely to young Archean terranes (3.0–2.6 Ga), while in old Archean cratons (3.6–3.0 Ga) lithospheric roots donot extend deeper than 200–220 km.The TC1 model is presented by a set of maps, which show significant thermal heterogeneity within continentalupper mantle......This presentation reports a 1 deg 1 deg global thermal model for the continental lithosphere (TC1). The modelis digitally available from the author’s web-site: www.lithosphere.info.Geotherms for continental terranes of different ages (early Archean to present) are constrained by reliabledata...... of the continents, the remaining areas (ca. 60% ofthe continents) are filled by the statistical numbers derived from the thermal model constrained by boreholedata. Continental geotherms are statistically analyzed as a function of age and are used to estimate lithospherictemperatures in continental regions...

  15. Support for a Uniformitarian Model of Continental Mantle Lithosphere Formation from the "Near-Cratonic" Composition of Proterozoic Southern African Mantle Lithosphere

    Science.gov (United States)

    Janney, P. E.

    2014-12-01

    The transition at the end of the Archean between the generation of cratonic and mobile belt continental lithosphere is regarded as a first-order change in the mode of generation of continental lithosphere. It is widely debated whether this transition represented a fundamental change in the process by which the lithospheric mantle was generated (i.e., as melting residues of deep-seated mantle upwellings to residues of relatively shallow mantle melting at subduction zones), or whether it primarily reflected a more gradual change in the conditions (i.e., temperatures, depths and degrees of melting) of lithosphere generation in a suprasubduction zone setting. The marked contrast, in many cases, between the major element compositions of peridotite xenoliths from Archean cratons and those from adjacent post-Archean mobile belts has accentuated the significance of this transition. Peridotite xenoliths from the post-Archean mobile belt terranes surrounding the Kaapvaal craton in southern Africa are clearly Proterozoic in age from Re-Os isotope constraints, but they are unusual in that they share several key similarities in composition and mineralogy with Archean Kaapvaal peridotites (e.g., low bulk-rock Al2O3, relatively low modal olivine and high modal orthopyroxene). Although they lack the low FeO and high olivine Mg# values of the most extreme Kaapvaal samples, they show a very large degree of overlap (extending to olivine Mg# values of greater than 93 for example). These similarities support a common mode of origin for cratonic and post-cratonic lithosphere in southern Africa (although varying somewhat in the degrees and depths of melt extraction) and a similar history of post-formation modification. A comparison of the conditions of melt extraction for cratonic and post-cratonic lithosphere inferred from compatible and mildly incompatible trace elements will be presented.

  16. Evolution of the lithosphere in the area of the Rhine Rift System

    Science.gov (United States)

    Ziegler, P. A.; Dèzes, P.

    2005-09-01

    The Rhine Rift System (RRS) forms part of the European Cenozoic Rift System (ECRIS) and transects the Variscan Orogen, Permo-Carboniferous troughs and Late Permian to Mesozoic thermal sag basins. Crustal and lithospheric thicknesses range in the RRS area between 24 36 km and 50 120 km, respectively. We discuss processes controlling the transformation of the orogenically destabilised Variscan lithosphere into an end-Mesozoic stabilised cratonic lithosphere, as well as its renewed destabilisation during the Cenozoic development of ECRIS. By end-Westphalian times, the major sutures of the Variscan Orogen were associated with 45 60 km deep crustal roots. During the Stephanian-Early Permian, regional exhumation of the Variscides was controlled by their wrench deformation, detachment of subducted lithospheric slabs, asthenospheric upwelling and thermal thinning of the mantle-lithosphere. By late Early Permian times, when asthenospheric temperatures returned to ambient levels, lithospheric thicknesses ranged between 40 km and 80 km, whilst the thickness of the crust was reduced to 28 35 km in response to its regional erosional and local tectonic unroofing and the interaction of mantle-derived melts with its basal parts. Re-equilibration of the lithosphere-asthenosphere system governed the subsidence of Late Permian-Mesozoic thermal sag basins that covered much of the RRS area. By end-Cretaceous times, lithospheric thicknesses had increased to 100 120 km. Paleocene mantle plumes caused renewed thermal weakening of the lithosphere. Starting in the late Eocene, ECRIS evolved in the Pyrenean and Alpine foreland by passive rifting under a collision-related north-directed compressional stress field. Following end-Oligocene consolidation of the Pyrenees, west- and northwest-directed stresses originating in the Alps controlled further development of ECRIS. The RRS remained active until the Present, whilst the southern branch of ECRIS aborted in the early Miocene. Extensional

  17. Seismic anisotropy of Precambrian lithosphere: Insights from Rayleigh wave tomography of the eastern Superior Craton

    Science.gov (United States)

    Petrescu, Laura; Darbyshire, Fiona; Bastow, Ian; Totten, Eoghan; Gilligan, Amy

    2017-05-01

    The thick, seismically fast lithospheric keels underlying continental cores (cratons) are thought to have formed in the Precambrian and resisted subsequent tectonic destruction. A consensus is emerging from a variety of disciplines that keels are vertically stratified, but the processes that led to their development remain uncertain. Eastern Canada is a natural laboratory to study Precambrian lithospheric formation and evolution. It comprises the largest Archean craton in the world, the Superior Craton, surrounded by multiple Proterozoic orogenic belts. To investigate its lithospheric structure, we construct a frequency-dependent anisotropic seismic model of the region using Rayleigh waves from teleseismic earthquakes recorded at broadband seismic stations across eastern Canada. The joint interpretation of phase velocity heterogeneity and azimuthal anisotropy patterns reveals a seismically fast and anisotropically complex Superior Craton. The upper lithosphere records fossilized Archean tectonic deformation: anisotropic patterns align with the orientation of the main tectonic boundaries at periods ≤110 s. This implies that cratonic blocks were strong enough to sustain plate-scale deformation during collision at 2.5 Ga. Cratonic lithosphere with fossil anisotropy partially extends beneath adjacent Proterozoic belts. At periods sensitive to the lower lithosphere, we detect fast, more homogenous, and weakly anisotropic material, documenting postassembly lithospheric growth, possibly in a slow or stagnant convection regime. A heterogeneous, anisotropic transitional zone may also be present at the base of the keel. The detection of multiple lithospheric fabrics at different periods with distinct tectonic origins supports growing evidence that cratonization processes may be episodic and are not exclusively an Archean phenomenon.

  18. Peridotite-melt interaction: A key point for the destruction of cratonic lithospheric mantle

    Institute of Scientific and Technical Information of China (English)

    ZHANG HongFu

    2009-01-01

    This paper presents an overview of recent studies dealing with different ages of mantle peridotitic xenoliths and xenocrysts from the North China Craton, with aim to provide new ideas for further study on the destruction of the North China Craton. Re-Os isotopic studies suggest that the lithospheric mantle of the North China Craton is of Archean age prior to its thinning. The key reason why such a low density and highly refractory Archean lithospheric mantle would be thinned is changes in composition, thermal regime, and physical properties of the lithospheric mantle due to interaction of peridotites with melts of different origins. Inward subducUon of circum craton plates and collision with the North China Craton provided not only the driving force for the destruction of the craton, but also continuous melts derived from partial melting of subducted continental or oceanic crustal materials that resulted in the compositional change of the lithospheric mantle. Regional thermal anomaly at ca. 120 Ma led to the melting of highly modified iithospheric mantle. At the same time or subsequently lithospheric extension and asthenospheric upwelling further reinforced the melting and thinning of the lithospheric mantle. Therefore, the destruction and thinning of the North China Craton is a combined result of peridotite-melt interaction (addition of volatile), enhanced regional thermal anomaly (temperature increase) and lithospheric extension (decompression). Such a complex geological process finally produced a "mixed" lithospheric mantle of highly chemical heterogeneity during the Mesozoic and Cenozoic. It also resulted in significant difference in the composition of mantle peridotitic xenoliths between different regions and times.

  19. Possible link between numerical modeling of the lithospheric deformation and MT research fields

    OpenAIRE

    Stephan V. Sobolev; [Child, Sir Josiah, bart.] 

    2004-01-01

    There is almost no connection established yet between two rapidly developing fields of the lithospheric research, namely between numerical simulation of the thermo-mechanical processes and MT studies. To compensate for this gap I focus here on the numerical modeling of the strain localization processes at the lithosphere-scale continental transform faults and on prediction of the possible electrical conductivity structures associated with these processes. First, I use a finite-element thermo-...

  20. Groundwater quality in the Lower Hudson River Basin, New York, 2008

    Science.gov (United States)

    Nystrom, Elizabeth A.

    2010-01-01

    Water samples were collected from 32 production and domestic wells in the study area from August through November 2008 to characterize the groundwater quality. The study area, which covers 5,607 square miles, encompasses the part of the Lower Hudson River Basin that lies within New York plus the parts of the Housatonic, Hackensack, Bronx, and Saugatuck River Basins that are in New York. The study area is underlain by mainly clastic bedrock, predominantly shale, with carbonate and crystalline rock present locally. The bedrock is generally overlain by till, but surficial deposits of saturated sand and gravel are present in some areas. Of the 32 wells sampled, 16 were finished in sand and gravel deposits and 16 were finished in bedrock. The samples were collected and processed by standard U.S. Geological Survey procedures and were analyzed for 225 physiochemical properties and constituents, including major ions, nutrients, trace elements, radon-222, pesticides, and volatile organic compounds (VOCs); indicator bacteria were collected and analyzed by New York State Department of Health procedures. Water quality in the study area is generally good, but concentrations of some constituents exceeded current or proposed Federal or New York State primary or secondary drinking-water standards; the standards exceeded were color (2 samples), pH (6 samples), sodium (8 samples), fluoride (1 sample), aluminum (3 samples), arsenic (1 sample), iron (7 samples), manganese (14 samples), radon-222 (17 samples), tetrachloroethene (1 sample), and bacteria (7 samples). The pH of all samples was typically neutral or slightly basic (median 7.2); the median water temperature was 11.8 degrees C. The ions with the highest concentrations were bicarbonate [median 167 milligrams per liter (mg/L)] and calcium (median 38.2 mg/L). Groundwater in the study area ranged from very soft to very hard, but more samples were classified as very hard (181 mg/L as CaCO3 or more) than soft (60 mg/L as CaCO3 or

  1. Microearthquake activity, lithospheric structure, and deformation modes at an amagmatic ultraslow spreading Southwest Indian Ridge segment

    Science.gov (United States)

    Schmid, Florian; Schlindwein, Vera

    2016-07-01

    While nascent oceanic lithosphere at slow to fast spreading mid-ocean ridges (MOR) is relatively well studied, much less is known about the lithospheric structure and properties at ultraslow MORs. Here we present microearthquake data from a 1 year ocean bottom seismometer deployment at the amagmatic, oblique supersegment of the ultraslow spreading Southwest Indian Ridge. A refraction seismic experiment was performed to constrain upper lithosphere P-velocities and results were used to construct a 1D velocity model for earthquake location. Earthquake foci were located individually and subsequently relocated relative to each other to sharpen the image of seismically active structures. Frequent earthquake activity extends to 31 km beneath the seafloor, indicating an exceptionally thick brittle lithosphere and an undulating brittle-ductile transition that implies significant variations in the along-axis thermal structure of the lithosphere. We observe a strong relation between petrology, microseismicity distribution, and topography along the ridge axis: Peridotite-dominated areas associate with deepest hypocenters, vast volumes of lithosphere that deforms aseismically as a consequence of alteration, and the deepest axial rift valley. Areas of basalt exposure correspond to shallower hypocenters, shallower and more rugged axial seafloor. Focal mechanisms deviate from pure extension and are spatially variable. Earthquakes form an undulating band of background seismicity and do not delineate discrete detachment faults as common on slow spreading ridges. Instead, the seismicity band sharply terminates to the south, immediately beneath the rift boundary. Considering the deep alteration, large steep boundary faults might be present but are entirely aseismic.

  2. Depth-dependent extension, two-stage breakup and depleted lithospheric counterflow at rifted margins

    Science.gov (United States)

    Huismans, Ritske S.; Beaumont, Christopher

    2014-05-01

    Uniform lithospheric extension predicts basic properties of non-volcanic rifted margins but fails to explain other important characteristics. Significant discrepancies are observed at 'type I' margins (such as the Iberia-Newfoundland conjugates), where large tracts of continental mantle lithosphere are exposed at the sea floor, and 'type II' margins (such as some ultrawide central South Atlantic margins), where thin continental crust spans wide regions below which continental lower crust and mantle lithosphere have apparently been removed. Neither corresponds to uniform extension. Instead, either crust or mantle lithosphere has been preferentially removed. Using dynamical models, we demonstrate that these margins are opposite end members: in type I, depth-dependent extension results in crustal-necking breakup before mantle-lithosphere breakup and in type II, the converse is true. These two-layer, two-stage breakup behaviours explain the discrepancies and have implications for the styles of the associated sedimentary basins. Laterally flowing lower-mantle lithosphere may underplate both type I and type II margins, thereby contributing to their anomalous characteristics.

  3. A sharp lithosphere-asthenosphere boundary imaged beneath eastern North America.

    Science.gov (United States)

    Rychert, Catherine A; Fischer, Karen M; Rondenay, Stéphane

    2005-07-28

    Plate tectonic theory hinges on the concept of a relatively rigid lithosphere moving over a weaker asthenosphere, yet the nature of the lithosphere-asthenosphere boundary remains poorly understood. The gradient in seismic velocity that occurs at this boundary is central to constraining the physical and chemical properties that create differences in mechanical strength between the two layers. For example, if the lithosphere is simply a thermal boundary layer that is more rigid owing to colder temperatures, mantle flow models indicate that the velocity gradient at its base would occur over tens of kilometres. In contrast, if the asthenosphere is weak owing to volatile enrichment or the presence of partial melt, the lithosphere-asthenosphere boundary could occur over a much smaller depth range. Here we use converted seismic phases in eastern North America to image a very sharp seismic velocity gradient at the base of the lithosphere-a 3-11 per cent drop in shear-wave velocity over a depth range of 11 km or less at 90-110 km depth. Such a strong, sharp boundary cannot be reconciled with a purely thermal gradient, but could be explained by an asthenosphere that contains a few per cent partial melt or that is enriched in volatiles relative to the lithosphere.

  4. The rheological structure of the lithosphere in the Eastern Marmara region, Turkey

    Science.gov (United States)

    Oruç, Bülent; Sönmez, Tuba

    2017-05-01

    The aim of this work is to propose the geometries of the crustal-lithospheric mantle boundary (Moho) and lithosphere-asthenosphere boundary (LAB) and the 1D thermal structure of the lithosphere, in order to establish a rheological model of the Eastern Marmara region. The average depths of Moho and LAB are respectively 35 km and 51 km from radially averaged amplitude spectra of EGM08 Bouguer anomalies. The geometries of Moho and LAB interfaces are estimated from the Parker-Oldenburg gravity inversion algorithm. Our results show the Moho depth varies from 31 km at the northern part of North Anatolian Fault Zone (NAFZ) to 39 km below the mountain belt in the southern part of the NAFZ. The depth to the LAB beneath the same parts of the region ranges from 45 km to 55 km. Having lithospheric strength and thermal boundary layer structure, we analyzed the conditions of development of lithosphere thinning. A two-dimensional strength profile has been estimated for rheology model of the study area. Thus we suggest that the rheological structure consists of a strong upper crust, a weak lower crust, and a partly molten upper lithospheric mantle.

  5. A Magma Accretion Model for the Formation of Oceanic Lithosphere: Implications for Global Heat Loss

    Directory of Open Access Journals (Sweden)

    Valiya M. Hamza

    2010-01-01

    Full Text Available A magma accretion model of oceanic lithosphere is proposed and its implications for understanding its thermal field examined. The new model (designated Variable Basal Accretion—VBA assumes existence of lateral variations in magma accretion rates and temperatures at the boundary zone between the lithosphere and the asthenosphere. However, unlike the previous thermal models of the lithosphere, the ratio of advection to conduction heat transfer is considered a space dependent variable. The results of VBA model simulations reveal that the thickness of the young lithosphere increases with distance from the ridge axis, at rates faster than those predicted by Half-Space Cooling models. Another noteworthy feature of the new model is its ability to account for the main features in the thermal behavior of oceanic lithosphere. The improved fits to bathymetry have been achieved for the entire age range and without the need to invoke the ad-hoc hypothesis of large-scale hydrothermal circulation. Also, use of VBA model does not lead to artificial discontinuities in the temperature field of the lithosphere, as is the case with GDH (Global Depth Heat Flow reference models. The results suggest that estimates of global heat loss need to be downsized by at least 25%.

  6. Pre-subduction metasomatic enrichment of the oceanic lithosphere induced by plate flexure

    Science.gov (United States)

    Pilet, S.; Abe, N.; Rochat, L.; Kaczmarek, M.-A.; Hirano, N.; Machida, S.; Buchs, D. M.; Baumgartner, P. O.; Müntener, O.

    2016-12-01

    Oceanic lithospheric mantle is generally interpreted as depleted mantle residue after mid-ocean ridge basalt extraction. Several models have suggested that metasomatic processes can refertilize portions of the lithospheric mantle before subduction. Here, we report mantle xenocrysts and xenoliths in petit-spot lavas that provide direct evidence that the lower oceanic lithosphere is affected by metasomatic processes. We find a chemical similarity between clinopyroxene observed in petit-spot mantle xenoliths and clinopyroxene from melt-metasomatized garnet or spinel peridotites, which are sampled by kimberlites and intracontinental basalts respectively. We suggest that extensional stresses in oceanic lithosphere, such as plate bending in front of subduction zones, allow low-degree melts from the seismic low-velocity zone to percolate, interact and weaken the oceanic lithospheric mantle. Thus, metasomatism is not limited to mantle upwelling zones such as mid-ocean ridges or mantle plumes, but could be initiated by tectonic processes. Since plate flexure is a global mechanism in subduction zones, a significant portion of oceanic lithospheric mantle is likely to be metasomatized. Recycling of metasomatic domains into the convecting mantle is fundamental to understanding the generation of small-scale mantle isotopic and volatile heterogeneities sampled by oceanic island and mid-ocean ridge basalts.

  7. Constitutive models of faults in the viscoelastic lithosphere

    Science.gov (United States)

    Moresi, Louis; Muhlhaus, Hans; Mansour, John; Miller, Meghan

    2013-04-01

    Moresi and Muhlhaus (2006) presented an algorithm for describing shear band formation and evolution as a coallescence of small, planar, fricition-failure surfaces. This algorithm assumed that sliding initially occurs at the angle to the maximum compressive stress dictated by Anderson faulting theory and demonstrated that shear bands form with the same angle as the microscopic angle of initial failure. Here we utilize the same microscopic model to generate frictional slip on prescribed surfaces which represent faults of arbitrary geometry in the viscoelastic lithosphere. The faults are actually represented by anisotropic weak zones of finite width, but they are instantiated from a 2D manifold represented by a cloud of points with associated normals and mechanical/history properties. Within the hybrid particle / finite-element code, Underworld, this approach gives a very flexible mechanism for describing complex 3D geometrical patterns of faults with no need to mirror this complexity in the thermal/mechanical solver. We explore a number of examples to demonstrate the strengths and weaknesses of this particular approach including a 3D model of the deformation of Southern California which accounts for the major fault systems. L. Moresi and H.-B. Mühlhaus, Anisotropic viscous models of large-deformation Mohr-Coulomb failure. Philosophical Magazine, 86:3287-3305, 2006.

  8. Risk and Geodynamically active areas of Carpathian lithosphere

    Directory of Open Access Journals (Sweden)

    Lubomil Pospíšil

    2007-01-01

    Full Text Available This paper illustrates an application of multidisciplinary data analysis to the Carpathian–Pannonian region and presents a verification of a Complex model of the Carpathian - Pannonian lithosphere by recent data sets and geophysical data analyses and its utilization for the determination of risk and active geodynamic and tectonic zones of Ist order . This model can be used for the analysing any Carpathian area from the point of view of the seismic risk, hazards and geodynamic activity, which is important to know for the building of a repository for the radioactive wasted material. Besides the traditionally used geological (sedimentological and volcanological data and geomorphological data (Remote Sensing, an emphasis was laid on geodetic, grav/mag data, seismic, seismological and other geophysical data (magnetotelluric, heat flow, paleomagnetic etc.. All available geonomic (geologic, geodetic, geophysical, geomorphological data were verified and unified on the basis of the same scale and in the Western Carpathians on the Remote Sensing data. The paper concentrates on two problematic areas – the so call “rebounding area” in the Eastern Carpathians and the Raba – Muran - Malcov tectonic systems.

  9. Seismic Receiver Functions and the Lithosphere-Asthenosphere Boundary

    Science.gov (United States)

    Kind, R.; Yuan, X.; Kumar, P.

    2012-12-01

    The lower boundary of the lithospheric plates has remained as an enigmatic boundary for seismologists, since it is relatively poorly observed by seismic means. There is traditionally a broad consensus that the asthenosphere is observable as a low velocity zone by seismic surface waves. Seismic techniques which use shorter period P-to-S or S-to-P converted body waves are now far enough developed to be successful in observing such a low velocity zone with a higher resolution. The principle of this technique (the so-called receiver function technique) is that a strong teleseismic mother phase (e.g. P, S, PP or SKS) incident from below on any seismic discontinuity beneath a station produces a converted phase (Ps or Sp) which indicates its depth and properties. We discuss details of this technique. A sufficient number of such observations exist already to indicate that the top of the low velocity zone is a globally observable discontinuity and it is sharper than previously thought. An intriguing observation is that in some cratons the new seismic data indicate that the low velocity zone exists already at shallower depths than obtained from surface waves. This confirms earlier results from controlled source observations (Thybo and Perchuc 1997). We discuss possible interpretations of this shallow low velocity zone in cratonic regions.

  10. Post glacial rebounds measure the viscosity of the lithosphere

    CERN Document Server

    Garai, J

    2003-01-01

    The observed higher uplift rates before the end of deglaciation requires the existence of a low viscosity channel or layer. The uplifts observed after the end of deglaciation does not show any contribution from this low viscosity channel and a homogeneous viscosity model fits very well to the observed uplift. Most of the researchers therefore prefer the homogeneous model and suggest that the higher uplift rate before the end of deglaciation is the result of elastic contamination. It has been shown that the elastic deformation of the lithosphere is far too small to be responsible for the observed extra uplift; therefore, the homogeneous viscosity model should be discredited. The homogeneous viscosity of the postglacial period and the high uplift rate of the late glacial period can be explained with a model which has an upper layer determining the homogeneous viscosity and the layer below it which has a low viscosity. The contribution to the uplift of this low viscosity layer is indistinguishable from an instan...

  11. Dreamers in dialogue: evolution, sex and gender in the utopian visions of William Morris and William Henry Hudson

    Directory of Open Access Journals (Sweden)

    Caterina Novák

    2013-12-01

    Full Text Available The aim of this article is to explore the parallels between two late-nineteenth-century utopias,William Henry Hudsons A Crystal Age (1882 and William Morriss News from Nowhere (1891. Itaims to explore how these two works respond to the transition from a kinetic to a static conception ofutopia that under pressure from evolutionary and feminist discourses took place during the period.Particular focus lies on the way in which this is negotiated through the depiction of evolution, sexuality,and gender roles in the respective novels, and how the depiction of these disruptive elements may workas a means of ensuring the readers active engagement in political, intellectual and emotional terms.

  12. Groundwater quality in the Chemung River, Eastern Lake Ontario, and Lower Hudson River Basins, New York, 2013

    Science.gov (United States)

    Scott, Tia-Marie; Nystrom, Elizabeth A.; Reddy, James E.

    2015-11-10

    In a study conducted by the U.S. Geological Survey (USGS) in cooperation with the New York State Department of Environmental Conservation, water samples were collected from 4 production wells and 4 domestic wells in the Chemung River Basin, 8 production wells and 7 domestic wells in the Eastern Lake Ontario Basin, and 12 production wells and 13 domestic wells in the Lower Hudson River Basin (south of the Federal Lock and Dam at Troy) in New York. All samples were collected in June, July, and August 2013 to characterize groundwater quality in these basins. The samples were collected and processed using standard USGS procedures and were analyzed for 148 physiochemical properties and constituents, including dissolved gases, major ions, nutrients, trace elements, pesticides, volatile organic compounds, radionuclides, and indicator bacteria.

  13. Continental growth by successive accretion of oceanic lithosphere: Evidence from tilted seismic anisotropy

    Science.gov (United States)

    Babuska, V.; Plomerova, J.; Karato, S. I.

    2012-04-01

    Although many studies indicate that subduction-related accretion, subduction-driven magmatism and tectonic stacking are major crustal-growth mechanisms, how the mantle lithosphere forms remains enigmatic. Cook (AGU Geod. Series 1986) published a model of continental 'shingling' based on seismic reflection data indicating dipping structures in the deep crust of accreted terranes. Helmstaedt and Gurney (J. Geoch. Explor. 1995) and Hart et al. (Geology 1997) suggest that the Archean continental lithosphere consists of alternating layers of basalt and peridotite derived from subducted and obducted Archean oceanic lithosphere. Peridotite xenoliths from the Mojavian mantle lithosphere (Luffi et al., JGR 2009), as well as xenoliths of eclogites underlying the Sierra Nevada batholith in California (Horodynskij et al., EPSL 2007), are representative for oceanic slab fragments successively attached to the continent. Recent seismological findings also seem to support a model of continental lithosphere built from systems of paleosubductions of plates of ancient oceanic lithosphere (Babuska and Plomerova, AGU Geoph. Monograph 1989), or by stacking of the plates (Helmstaedt and Schulze, Geol. Soc. Aust. Spec. Publ. 1989). Seismic anisotropy in the oceanic mantle lithosphere, explained mainly by the olivine A- (or D-) type fabric (Karato et al., Annu. Rev. Earth Planet. Sci. 2008), was discovered almost a half century ago (Hess, Nature 1964). Though it is difficult to determine seismic anisotropy within an active subducting slab (e.g., Healy et al., EPSL 2009; Eberhart-Phillips and Reyners, JGR 2009), field observations and laboratory experiments indicate the oceanic olivine fabric might be preserved there to a depth of at least 200-300 km. Dipping anisotropic fabrics in domains of the European mantle lithosphere were interpreted as systems of 'frozen' paleosubductions (Babuska and Plomerova, PEPI 2006), and the lithosphere base as a boundary between a fossil anisotropy in the

  14. Immersion in a Hudson Valley Tidal Marsh and Climate Research Community - Lamont-Doherty's Secondary School Field Research Program

    Science.gov (United States)

    Peteet, D. M.; Newton, R.; Vincent, S.; Sambrotto, R.; Bostick, B. C.; Schlosser, P.; Corbett, J. E.

    2015-12-01

    A primary advantage of place-based research is the multidisciplinary and interdisciplinary research that can be applied to a single locale, with a depth of continued study through time. Through the last decade, Lamont-Doherty's Secondary School Field Research Program (SSFRP) has promoted scientific inquiry, mostly among groups under-represented in STEM fields, in Piermont Marsh, a federally protected marsh in the Hudson estuary. At the same time, Lamont Doherty Earth Observatory (LDEO) scientists have become more involved, through mentoring by researchers, postdocs and graduate students, often paired with high school teachers. The sustained engagement of high school students in a natural environment, experiencing the Hudson River and its tidal cycles, protection of coastline, water quality improvement, native and invasive plant communities, is fundamental to their understanding of the importance of wetlands with their many ecosystem services. In addition, the Program has come to see "place" as inclusive of the Observatory itself. The students' work at Lamont expands their understanding of educational opportunities and career possibilities. Immersing students in a research atmosphere brings a level of serious inquiry and study to their lives and provides them with concrete contributions that they make to team efforts. Students select existing projects ranging from water quality to Phragmites removal, read papers weekly, take field measurements, produce lab results, and present their research at the end of six weeks. Ongoing results build from year to year in studies of fish populations, nutrients, and carbon sequestration, and the students have presented at professional scientific meetings. Through the Program students gain a sense of ownership over both their natural and the academic environments. Challenges include sustained funding of the program; segmenting the research for reproducible, robust results; fitting the projects to PIs' research goals, time

  15. Simulating the Effects of Sea Level Rise on the Resilience and Migration of Tidal Wetlands along the Hudson River.

    Science.gov (United States)

    Tabak, Nava M; Laba, Magdeline; Spector, Sacha

    2016-01-01

    Sea Level Rise (SLR) caused by climate change is impacting coastal wetlands around the globe. Due to their distinctive biophysical characteristics and unique plant communities, freshwater tidal wetlands are expected to exhibit a different response to SLR as compared with the better studied salt marshes. In this study we employed the Sea Level Affecting Marshes Model (SLAMM), which simulates regional- or local-scale changes in tidal wetland habitats in response to SLR, and adapted it for application in a freshwater-dominated tidal river system, the Hudson River Estuary. Using regionally-specific estimated ranges of SLR and accretion rates, we produced simulations for a spectrum of possible future wetland distributions and quantified the projected wetland resilience, migration or loss in the HRE through the end of the 21st century. Projections of total wetland extent and migration were more strongly determined by the rate of SLR than the rate of accretion. Surprisingly, an increase in net tidal wetland area was projected under all scenarios, with newly-formed tidal wetlands expected to comprise at least 33% of the HRE's wetland area by year 2100. Model simulations with high rates of SLR and/or low rates of accretion resulted in broad shifts in wetland composition with widespread conversion of high marsh habitat to low marsh, tidal flat or permanent inundation. Wetland expansion and resilience were not equally distributed through the estuary, with just three of 48 primary wetland areas encompassing >50% of projected new wetland by the year 2100. Our results open an avenue for improving predictive models of the response of freshwater tidal wetlands to sea level rise, and broadly inform the planning of conservation measures of this critical resource in the Hudson River Estuary.

  16. Simulating the Effects of Sea Level Rise on the Resilience and Migration of Tidal Wetlands along the Hudson River.

    Directory of Open Access Journals (Sweden)

    Nava M Tabak

    Full Text Available Sea Level Rise (SLR caused by climate change is impacting coastal wetlands around the globe. Due to their distinctive biophysical characteristics and unique plant communities, freshwater tidal wetlands are expected to exhibit a different response to SLR as compared with the better studied salt marshes. In this study we employed the Sea Level Affecting Marshes Model (SLAMM, which simulates regional- or local-scale changes in tidal wetland habitats in response to SLR, and adapted it for application in a freshwater-dominated tidal river system, the Hudson River Estuary. Using regionally-specific estimated ranges of SLR and accretion rates, we produced simulations for a spectrum of possible future wetland distributions and quantified the projected wetland resilience, migration or loss in the HRE through the end of the 21st century. Projections of total wetland extent and migration were more strongly determined by the rate of SLR than the rate of accretion. Surprisingly, an increase in net tidal wetland area was projected under all scenarios, with newly-formed tidal wetlands expected to comprise at least 33% of the HRE's wetland area by year 2100. Model simulations with high rates of SLR and/or low rates of accretion resulted in broad shifts in wetland composition with widespread conversion of high marsh habitat to low marsh, tidal flat or permanent inundation. Wetland expansion and resilience were not equally distributed through the estuary, with just three of 48 primary wetland areas encompassing >50% of projected new wetland by the year 2100. Our results open an avenue for improving predictive models of the response of freshwater tidal wetlands to sea level rise, and broadly inform the planning of conservation measures of this critical resource in the Hudson River Estuary.

  17. Oceanographic Data from Winter and Spring Circulation and Sediment Transport Studies in the Hudson Shelf Valley collected in December-April (1999/2000) and April-June 2006

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The U.S. Geological Survey (USGS) conducted field experiments to understand the transport of sediments and associated contaminants in the Hudson Shelf Valley,...

  18. Temperature, salinity, and C14 profiles from bottle casts in the North Atlantic, Arctic, and other locations from the HUDSON, YMER (1980), and other platforms from 22 February 1973 to 19 September 1991 (NODC Accession 0000446)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Bottle and other data were collected in the the North Atlantic, Arctic, and other locations from the HUDSON, YMER (1980), and other platforms from 22 February 1973...

  19. Microstructure, CTD and ADCP data collected from R/V ONRUST in Hudson River Estuary during 6 short cruises from 1994-05-19 to 2001-05-01 (NCEI Accession 0146260)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Observations of turbulent mixing, stratification and currents in the Hudson River Estuary made in 6 short cruises in 1994/1995 and 2001 were assembled. The lower...

  20. Oceanographic Data from Winter and Spring Circulation and Sediment Transport Studies in the Hudson Shelf Valley collected in December-April (1999/2000) and April-June 2006

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The U.S. Geological Survey (USGS) conducted field experiments to understand the transport of sediments and associated contaminants in the Hudson Shelf Valley,...

  1. Oceanographic profile data collected from sound velocimeter casts aboard NAVIGATION RESPONSE TEAM 5 as part of project S-B916-NRT5-10 in the Hudson River on 2010-11-26 (NCEI Accession 0130785)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0130785 includes physical and profile data collected aboard the NAVIGATION RESPONSE TEAM 5 during project S-B916-NRT5-10 in the Hudson River near...

  2. The Residue of Lithospheric Convergence in the Alpine-Pannonian-Carpathian system

    Science.gov (United States)

    Houseman, G. A.; Stuart, G. W.; Hetenyi, G.; Lorinczi, P.; Dando, B. D.

    2009-12-01

    The continuing collision of the Adriatic block with European continental lithosphere has its clearest expression now in the Alpine collision zone. In the Early Miocene the collision zone extended further east and included probably all of the regions within the Carpathian Mountain Range. In the Mid-Miocene between about 17 and 12 Ma, however, the Pannonian lithosphere extended rapidly and subsequently subsided, while convergence persisted in the Alps and the Carpathian arc. The change from convergence to extension in the Pannonian domain is associated with either rapid subduction roll-back or gravitational instability in which the lower part of the lithosphere was removed and replaced by hot asthenosphere. Throughout this time however, convergence has continued in the Alpine orogeny further west. It is surprising therefore to see similarities in the mantle transition zone beneath these two neighbouring regions whose lithospheres have, in the last 17 Myr at least, evolved in such different modes. New seismic images from beneath the Pannonian Basin (Hetenyi et al., GRL, in press) and from beneath the Alps (Lombardi et al., EPSL, 2009) show that both regions have a depressed 660 km discontinuity beneath a relatively normal-depth 410 km discontinuity. An important factor in both regions evidently is that relatively dense material derived from the mid-Miocene collision sits stagnant on top of the 660 km discontinuity, where further descent is obstructed by the negative Clapeyron slope of the spinel-to-perovskite phase transition and the high viscosity of the lower mantle. While the depression of the 660 km discontinuity beneath the Alps is directly associated with ongoing convergence, that beneath the Pannonian appears to be decoupled from the upper mantle circulation that accompanied the Miocene Pannonian extension. If the cold material at the base of the Pannonian upper mantle is the residue of lithospheric subduction, delamination, or gravitational instability, the

  3. Constraining lithosphere deformation mode evolution for the Iberia-Newfoundland rifted margins

    Science.gov (United States)

    Jeanniot, Ludovic; Kusznir, Nick; Mohn, Geoffroy; Manatschal, Gianreto

    2015-04-01

    The deformation of lithosphere and asthenosphere and its evolution during continental rifting leading to breakup and seafloor spreading initiation is poorly understood. The resulting margin architecture and OCT structure is complex and diverse, and observations at magma poor margins includes hyper-extended continental crust and lithosphere, detachments faults, exhumed mantle, continental slivers and scattered embryonic oceanic crust. A coupled kinematic-dynamic model of lithosphere and asthenosphere deformation has been used to investigate the sequence of lithosphere deformation modes for 2 conjugate margin profiles for the Iberia-Newfoundland rifted margins. We use the observed water-loaded subsidence and crustal thickness, together with subsidence history and the age of melt generation, to test and constrain lithosphere and asthenosphere deformation models. A sequence of lithosphere deformation modes is represented by a succession of flow-fields, which are generated by a 2D finite element viscous flow model (FE-Margin), and is used to advect lithosphere and asthenosphere temperature and material. FE-Margin is kinematically driven by divergent deformation in the upper 15-20 km of the lithosphere inducing passive upwelling below. Buoyancy enhanced upwelling (e.g. Braun et al. 2000) is also kinematically included. The methodology of Katz et al., 2003 is used to predict melt generation by decompressional melting. The magnitude of extension used in the modelling is consistent with that proposed by Sutra et al (2013). The best fit calibrated models of lithosphere deformation evolution for the Iberia-Newfoundland conjugate margins require (i) an initial broad region of lithosphere deformation and passive upwelling, (ii) lateral migration of deformation, (iii) an increase in extension rate with time, (iv) focussing of deformation and (v) buoyancy induced upwelling. The preferred calibrated models predict faster extension rates and earlier continental crustal rupture and

  4. Lithosphere continental rifting and necking in 3D analogue experiments: role of plate divergence rate.

    Science.gov (United States)

    Nestola, Y.; Storti, F.; Cavozzi, C.

    2014-12-01

    The evolution of lithosphere necking is a fundamental parameter controlling the structural architecture and thermal state of rifted margins. Despite a large number of analogue and numerical modelling studies on lithosphere extension are available in the literature, a quantitative experimental description of lithosphere necking evolution is still lacking. Extensional strain rate and thermal layering of the lithosphere exert a fundamental control on necking shape and evolution. We focused our experimental work on the former parameter and simulated the progression of lithosphere thinning and necking during asymmetric orthogonal rifting at different plate divergence rates. Our models involve a 4-layer mechanical continental lithosphere, which rests on a glucose syrup asthenosphere. Both the topography and the base of the lithosphere were monitored by time-lapse laser scanning. This technical approach allowed us to quantify the evolution in space and time of the thinning factors for the crust, mantle, and lithosphere as a whole. Laser-scanning monitoring provided also a detailed picture of the evolving neck shape, which shows a strong dependency on the strain-rate. At low strain-rates, necking is "boxed" with steep flanks and a flat-lying roof, and few deep basins develop at surface. At high strain-rates, more distributed thinning occurs and isolates portions of less deformed mantle. More distributed deformation affects the model topography. Despite large differences in shape, the aspect ratio (amplitude/wavelength) of the cross-sectional neck shapes converges towards very similar values at the end of the experiments.The significant differences and evolutionary pathways produced by the plate divergence rate on the lithosphere necking profile, suggest that this parameter exert a fundamental control on localization vs. distribution of deformation in the crust as in the whole mechanical lithosphere. Furthermore, it can exert a fundamental control on the time and space

  5. 75 FR 36292 - Safety Zone; Bay Swim III, Presque Isle Bay, Erie, PA

    Science.gov (United States)

    2010-06-25

    ... of Presque Isle Bay, Lake Erie, near Erie, Pennsylvania between 9 a.m. to 11 a.m. on June 26, 2010.... The safety zone will encompass specified waters of Presque Isle Bay, Erie, Pennsylvania starting at... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Bay Swim III, Presque Isle Bay, Erie, PA...

  6. 77 FR 18739 - Safety Zone; Bay Swim V, Presque Isle Bay, Erie, PA

    Science.gov (United States)

    2012-03-28

    ... the January 17, 2008, issue of the Federal Register (73 FR 3316). Public Meeting We do not now plan to... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Bay Swim V, Presque Isle Bay, Erie, PA... is intended to restrict vessels from a portion of the Presque Island Bay during the Bay Swim...

  7. 77 FR 35860 - Safety Zone; Bay Swim V, Presque Isle Bay, Erie, PA

    Science.gov (United States)

    2012-06-15

    ..., Erie, PA in the Federal Register (77 FR 18739). We received no letters commenting on the proposed rule... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Bay Swim V, Presque Isle Bay, Erie, PA... restrict vessels from a portion of the Presque Island Bay during the Bay Swim V swimming event. The...

  8. 78 FR 34575 - Safety Zone; Bay Swim VI, Presque Isle Bay, Erie, PA

    Science.gov (United States)

    2013-06-10

    ... FR Federal Register NPRM Notice of Proposed Rulemaking TFR Temporary Final Rule A. Regulatory History... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Bay Swim VI, Presque Isle Bay, Erie, PA... portion of Presque Isle bay during the Bay Swim VI swimming event. This temporary safety zone is...

  9. Humboldt Bay, California Benthic Habitats 2009 Substrate

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Humboldt Bay is the largest estuary in California north of San Francisco Bay and represents a significant resource for the north coast region. Beginning in 2007 the...

  10. Humboldt Bay, California Benthic Habitats 2009 Geoform

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Humboldt Bay is the largest estuary in California north of San Francisco Bay and represents a significant resource for the north coast region. Beginning in 2007 the...

  11. Humboldt Bay, California Benthic Habitats 2009 Geodatabase

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Humboldt Bay is the largest estuary in California north of San Francisco Bay and represents a significant resource for the north coast region. Beginning in 2007 the...

  12. Humboldt Bay, California Benthic Habitats 2009 Biotic

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Humboldt Bay is the largest estuary in California north of San Francisco Bay and represents a significant resource for the north coast region. Beginning in 2007 the...

  13. SF Bay Water Quality Improvement Fund

    Science.gov (United States)

    EPAs grant program to protect and restore San Francisco Bay. The San Francisco Bay Water Quality Improvement Fund (SFBWQIF) has invested in 58 projects along with 70 partners contributing to restore wetlands, water quality, and reduce polluted runoff.,

  14. Humboldt Bay Benthic Habitats 2009 Aquatic Setting

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Humboldt Bay is the largest estuary in California north of San Francisco Bay and represents a significant resource for the north coast region. Beginning in 2007 the...

  15. Bayes linear statistics, theory & methods

    CERN Document Server

    Goldstein, Michael

    2007-01-01

    Bayesian methods combine information available from data with any prior information available from expert knowledge. The Bayes linear approach follows this path, offering a quantitative structure for expressing beliefs, and systematic methods for adjusting these beliefs, given observational data. The methodology differs from the full Bayesian methodology in that it establishes simpler approaches to belief specification and analysis based around expectation judgements. Bayes Linear Statistics presents an authoritative account of this approach, explaining the foundations, theory, methodology, and practicalities of this important field. The text provides a thorough coverage of Bayes linear analysis, from the development of the basic language to the collection of algebraic results needed for efficient implementation, with detailed practical examples. The book covers:The importance of partial prior specifications for complex problems where it is difficult to supply a meaningful full prior probability specification...

  16. 33 CFR 165.1122 - San Diego Bay, Mission Bay and their Approaches-Regulated navigation area.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false San Diego Bay, Mission Bay and... Coast Guard District § 165.1122 San Diego Bay, Mission Bay and their Approaches—Regulated navigation... waters of San Diego Bay, Mission Bay, and their approaches encompassed by a line commencing at Point La...

  17. Lithospheric Mantle heterogeneities beneath northern Santa Cruz province, Argentina

    Science.gov (United States)

    Mundl, Andrea; Ntaflos, Theodoros; Bjerg, Ernesto

    2013-04-01

    interstitial clinopyroxene appears to be of metasomatic origin. The clinopyroxene from cumulate dunites has depleted LREE abundances and low HREE indicating that they have been formed from residual melts. In contrast, clinopyroxene from mantle dunites has enriched LREE (10 x PM) and LILE suggesting that the metasomatic agent was fluid-rich silicate melt. Calculated equilibrium conditions cover a wide range, from 800 to 1100 °C. Considering the crustal thickness in the area being around 35 km, a pressure between 12 and 17 kbar can be assumed as reasonable, indicating that xenoliths were extracted from shallow depths, in the order of 40 to 60 km. Model calculations have shown that the Lithospheric Mantle beneath Don Camilo is fertile and that spinel peridotites experienced low degrees of partial melting (2-8% batch melting in the spinel peridotite field). The metasomatic agent was a fluid rich silicate melt presumably similar to that which affected the xenoliths from Cerro Clark locality, north of Don Camilo. The clinopyroxenes with the highest Sr and lowest Nd isotopic signatures suggest that the metasomatism was an old event apparently not associated to the interaction of the Lithospheric Mantle in southern Patagonia with downgoing Nazca and Antarctic plates.

  18. Metasomatism in the oceanic lithosphere beneath La Palma, Canary Islands

    Science.gov (United States)

    Janisch, Astrid; Ntaflos, Theodoros

    2016-04-01

    La Palma is the most active island within the Canary archipelago with historical eruption along the Cumbre Vieja Rift. Mantle peridotite xenoliths brought to the surface during the eruption 1677/78 at the site of San Antonio Volcano, close to Fuencaliente in the south of the island, gives us an excellent opportunity to study an old oceanic lithosphere. The collection of xenoliths comprises sp-harzburgites, sp-lherzolites, sp-dunites and pyroxenites but only the first three were used for this work. Metasomatic processes are evident in all samples. A common feature is a variable channelling of melt flow through the mantle xenoliths displayed in variations from pervasively metasomatized, through veined to dyke intruded peridotites. Orthopyroxene breakdown into olivine, clinopyroxene and glass is evidence for anhydrous melt percolation. Furthermore, fine-grained veins in various thicknesses consisting of olivine, pyroxene as well as amphibole with apatite and phlogopite reveal additional anhydrous and hydrous metasomatic processes, respectively. Peridotites mainly influenced by anhydrous metasomatism exhibit locally phlogopite and/or amphibole around spinel or in glass-veinlets. Pentlandite has been found in all veined samples. Amphiboles are mostly pargasites but kaersutites are also present in the amphibole-bearing veins. Two different types of amphibole veins have been recognized. The first type is an amphibole-apatite-glass-bearing amphibolite, forming a cross-cutting vein that propagates through the xenolith. The amphiboles in this vein are coarse-grained while the disseminated amphiboles are fine-grained. Clinopyroxene always occurs in association with amphibole and in textural equilibrium suggesting that both minerals have grown together. The glass is of tephritic/basanitic to trachy-basaltic composition. The second amphibole-vein contains phlogopite and traces of apatite. Textural evidence (cross-cutting olivine grains and the absence of hydrous minerals in the

  19. Modes of continental extension in a lithospheric wedge

    Science.gov (United States)

    Wu, G.; Lavier, L. L.; Choi, E.

    2014-12-01

    We studied extension of a lithospheric wedge as an approximation to an orogenic belt or a continental margin. We ran a series of numerical models to quantify the effects of the strength of the lower crust and a mid-crustal shear zone (MCSZ) on the extension processes. When the MCSZ is present, we found that the regional lower crustal flow plays a critical role in controlling the modes of extension. The compensation is long-wavelength when the lower crust flows from the highest to the lowest elevation in order to compensate upper crustal thinning. In response to this motion, the mantle flows towards the highest elevation in order to balance for the lower crust leaving the area under the highest topography. For weak (wet quartz regime with partial melting) or intermediate (wet quartz regime), or strong (dry quartz regime) lower crust, we recognized three predominantly decoupled modes of extension characterized by 1) significant lower crustal exhumation exemplified as a large massif, 2) formation of core complexes and detachment faults, and 3) distributive domino faulting, respectively. Without the MCSZ, however, the lower crustal flow is essentially subdued with predominantly coupled extension. For weak or intermediate, or strong lower crust, we recognized three coupled modes characterized by 1) localized generally symmetric crustal exhumation, 2) distributed grabens and narrow rifts, and 3) wide continental margins, respectively. The MCSZ controls the degree of decoupling of the lower crustal flow such that a frictionally stronger MCSZ does not change the behaviors of the models but results in a more distributed extension. Due to the long-wavelength compensation, subhorizontal Moho is achieved where intensive extension occurred for all the decoupled models with a MCSZ. Natural counterparts for each mode may be easily identified, for instance, in the Basin and Range or the Aegean.

  20. New Research initiatives for Imaging the Iberian Lithosphere

    Science.gov (United States)

    Carbonell, R.

    2006-12-01

    lithospheric processes that resulted in the present day geodynamic scenario of the Betics-Alboran-Atlas System (South Iberia Peninsula, Northern Africa).

  1. Heterogeneous structure of the lithosphere of the Taimyr Peninsula

    Science.gov (United States)

    Litvinova, Tamara; Petrova, Alevtina

    2016-04-01

    Magnetic anomalies of the lower crust is well manifested in the satellite measurements and their reductions for the heights H = 100 and 400 km. Currently, however, a great interest is the area of negative magnetic anomalies, allocated to the same heights. They are confined to a special permeable zones of the crust and lithosphere, having increased geothermal activity and are associated with a variety of minerals. In digital magnetic anomalies and gravity anomalies circumpolar map of the Arctic Ocean (Total) was built geomagnetic and density sections along latitudinal and longitudinal cross sections of negative magnetic anomalies (n = 100 km). In the Taimyr Peninsula they capture the largest Fadyukudinsko Kotuiskaya-ring structure. In the north-central Siberia Fadyukudinsko Kotuiskaya ring structure is the "hub" articulation largest geoblocks (Anabar, Kureisko-Tunguska and North Kara). It is manifested in the gravity and magnetic field is also a ring structure. With Fadyukudinsko Kotui-ring structure formation associated injectors and high-carbonate metasomatic rocks tectonites controlling uranium and thorium-uranium-fluorite-barite-rare earth mineralization (VF Proskurnin, et al. 2010). It hypabyssal front of the hot spots. Fadyukudinsko-Kotuiskaya structure is defined posletrappovoe place in the north of the Eurasian plate, responding to a hot spot or a spot lower mantle plumes Triassic [Kravchenko SM, Hain VE 1996 Sazonov AM, Zvyagin EA, Leontiev SI et al., 2010]. Latitude and longitude revealed Profile permeable zones of low magnetic properties and density, confined to a weakened layer in the middle crust. Negative satellite magnetic anomalies (n = 100 km) at depths of 20 - 25-30 km weakly magnetic lens revealed a low density. The upper crust they overlap and dense magnetic rocks. At the bottom of the crust, these lenses are underlain by layers of dense and magnetic structures.

  2. Gravity and multichannel seismic reflection constraints on the lithospheric structure of the Canary Swell

    Science.gov (United States)

    Ranero, C. R.; Torne, M.; Banda, E.

    1995-12-01

    Deep penetrating multichannel seismic reflection and gravity data have been used to study the lithospheric structure of the Canary Swell. The seismic reflection data show the transition from undisturbed Jurassic oceanic crust, away from the Canary Islands, to an area of ocean crust strongly modified by the Canary volcanism (ACV). Outside the ACV the seismic records image a well layered sedimentary cover, underlined by a bright reflection from the top of the igneous basement and also relatively continuous reflections from the base of the crust. In the ACV the definition of the boundary between sedimentary cover and igneous basement and the crust-mantle boundary remains very loose. Two-dimensional gravity modelling in the area outside the influence of the Canary volcanism, where the reflection data constrain the structure of the ocean crust, suggests a thinning of the lithosphere. The base of the lithosphere rises from 100 km, about 400 km west of the ACV, to 80 km at the outer limit of the ACV. In addition, depth conversion of the seismic reflection data and unloading of the sediments indicate the presence of a regional depth anomaly of an extension similar to the lithospheric thinning inferred from gravity modelling. The depth anomaly associated with the swell, after correction for sediment weight, is about 500 m. We interpret the lithospheric thinning as an indication of reheating of old Mesozoic lithosphere beneath the Canary Basin and along with the depth anomaly as indicating a thermal rejuvenation of the lithosphere. We suggest that the most likely origin for the Canary Islands is a hot spot.

  3. Constraining lithosphere deformation modes during continental breakup for the Iberia-Newfoundland conjugate rifted margins

    Science.gov (United States)

    Jeanniot, Ludovic; Kusznir, Nick; Mohn, Geoffroy; Manatschal, Gianreto; Cowie, Leanne

    2016-06-01

    A kinematic model of lithosphere and asthenosphere deformation has been used to investigate lithosphere stretching and thinning modes during continental rifting leading to breakup and seafloor spreading. The model has been applied to two conjugate profiles across the Iberia-Newfoundland rifted margins and quantitatively calibrated using observed present-day water loaded subsidence and crustal thickness, together with observed mantle exhumation, subsidence and melting generation histories. The kinematic model uses an evolving prescribed flow-field to deform the lithosphere and asthenosphere leading to lithospheric breakup from which continental crustal thinning, lithosphere thermal evolution, decompression melt initiation and subsidence are predicted. We explore the sensitivity of model predictions to extension rate history, deformation migration and buoyancy induced upwelling. The best fit calibrated models of lithosphere deformation evolution for the Iberia-Newfoundland conjugate margins require; (1) an initial broad region of lithosphere deformation with passive upwelling, (2) lateral migration of deformation, (3) an increase in extension rate with time, (4) focussing of the deformation and (5) buoyancy induced upwelling. The model prediction of exhumed mantle at the Iberia-Newfoundland margins, as observed, requires a critical threshold of melting to be exceeded before melt extraction. The preferred calibrated models predict faster extension rates and earlier continental crustal separation and mantle exhumation for the Iberia Abyssal Plain-Flemish Pass conjugate margin profile than for the Galicia Bank-Flemish Cap profile to the north. The predicted N-S differences in the deformation evolution give insights into the 3D evolution of Iberia-Newfoundland margin crustal separation.

  4. Evolution of the East African rift: Drip magmatism, lithospheric thinning and mafic volcanism

    Science.gov (United States)

    Furman, Tanya; Nelson, Wendy R.; Elkins-Tanton, Linda T.

    2016-07-01

    The origin of the Ethiopian-Yemeni Oligocene flood basalt province is widely interpreted as representing mafic volcanism associated with the Afar mantle plume head, with minor contributions from the lithospheric mantle. We reinterpret the geochemical compositions of primitive Oligocene basalts and picrites as requiring a far more significant contribution from the metasomatized subcontinental lithospheric mantle than has been recognized previously. This region displays the fingerprints of mantle plume and lithospheric drip magmatism as predicted from numerical models. Metasomatized mantle lithosphere is not dynamically stable, and heating above the upwelling Afar plume caused metasomatized lithosphere with a significant pyroxenite component to drip into the asthenosphere and melt. This process generated the HT2 lavas observed today in restricted portions of Ethiopia and Yemen now separated by the Red Sea, suggesting a fundamental link between drip magmatism and the onset of rifting. Coeval HT1 and LT lavas, in contrast, were not generated by drip melting but instead originated from shallower, dominantly anhydrous peridotite. Looking more broadly across the East African Rift System in time and space, geochemical data support small volume volcanic events in Turkana (N. Kenya), Chyulu Hills (S. Kenya) and the Virunga province (Western Rift) to be derived ultimately from drip melting. The removal of the gravitationally unstable, metasomatized portion of the subcontinental lithospheric mantle via dripping is correlated in each case with periods of rapid uplift. The combined influence of thermo-mechanically thinned lithosphere and the Afar plume together thus controlled the locus of continental rift initiation between Africa and Arabia and provide dynamic support for the Ethiopian plateau.

  5. Inelastic models of lithospheric stress - I. Theory and application to outer-rise plate deformation

    Science.gov (United States)

    Mueller, S.; Choy, G.L.; Spence, W.

    1996-01-01

    Outer-rise stress distributions determined in the manner that mechanical engineers evaluate inelastic stress distributions within conventional materials are contrasted with those predicted using simple elastic-plate models that are frequently encountered in studies of outer-rise seismicity. This comparison indicates that the latter are inherently inappropriate for studies of intraplate earthquakes, which are a direct manifestation of lithospheric inelasticity. We demonstrate that the common practice of truncating elastically superimposed stress profiles so that they are not permitted to exceed laboratory-based estimates of lithospheric yield strength will result in an accurate characterization of lithospheric stress only under relatively restrictive circumstances. In contrast to elastic-plate models, which predict that lithospheric stress distributions depend exclusively upon the current load, inelastic plate models predict that stress distributions are also significantly influenced by the plate-loading history, and, in many cases, this influence is the dominant factor in determining the style of potential seismicity (e.g. thrust versus normal faulting). Numerous 'intuitive' interpretations of outer-rise earthquakes have been founded upon the implicit assumption that a unique relationship exists between a specified combination of plate curvature and in-plane force, and the resulting lithospheric stress distribution. We demonstrate that the profound influence of deformation history often invalidates such interpretations. Finally, we examine the reliability of 'yield envelope' representations of lithospheric strength that are constructed on the basis of empirically determined frictional sliding relationships and silicate plastic-flow laws. Although representations of this nature underestimate the strength of some major interplate faults, such as the San Andreas, they appear to represent a reliable characterization of the strength of intraplate oceanic lithosphere.

  6. The Effect of Heterogeneous Lithospheric Structure on Surface Stress and Tectonics on Mercury

    Science.gov (United States)

    Rosenburg, M. A.; Williams, J.; Aharonson, O.

    2008-12-01

    Observations of Mercury's surface from the Mariner 10 and MESSENGER spacecraft reveal a planet-wide distribution of lobate scarps, which are interpreted to be the surface expression of thrust faults due to global contraction. Statistical analysis of scarps mapped in images from both missions suggests that the orientations of these features are not consistent with a uniform distribution, the expected outcome for a contracting lithosphere of constant thickness. One possible explanation for this observation considers Mercury's thermal state, which is driven by the insolation pattern. Mercury's 3:2 spin-orbit resonance, in concert with its substantial orbital eccentricity of e = 0.20, causes long-wavelength surface temperature variations of more than 130 K. Corresponding variations in lithospheric thickness are hence expected. If the contraction occurred while Mercury was in this dynamical state, the resulting stress distribution recorded on the surface during global cooling and inner core solidification may reflect this heterogeneity. We seek to determine whether contraction of a lithosphere with lateral thickness variations can explain the observed lobate scarp orientations on Mercury's surface. We employ the three-dimensional, viscoelastic, finite element model CitcomSVE along with a thermal evolution model to study Mercury's response to cooling, inner core formation, and lithosphere growth and to track the accumulation of stress in the lithosphere. The resulting stress pattern can then be compared to the orientations and distribution of scarps mapped on the surface of Mercury. Preliminary results indicate systematic variations between the expected orientation of faults in the "cold poles," where the lithosphere is thicker and the "hot poles," where the lithosphere is weaker. As MESSENGER returns more data, comparisons between model results and surface features will be refined.

  7. 33 CFR 117.622 - West Bay

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false West Bay 117.622 Section 117.622 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Massachusetts § 117.622 West Bay The draw of the West Bay Bridge, mile...

  8. Bayes' postulate for trinomial trials

    Science.gov (United States)

    Diniz, M. A.; Polpo, A.

    2012-10-01

    In this paper, we discuss Bayes' postulate and its interpretation. We extend the binomial trial method proposed by de Finetti [1] to trinomial trials, for which we argue that the consideration of equiprobability a priori for the possible outcomes of the trinomial trials implies that the parameter vector has Dirichlet(1,1) as prior. Based on this result, we agree with Stigler [2] in that the notion in Bayes' postulate stating "absolutely know nothing" is related to the possible outcomes of an experiment and not to "non-information" about the parameter.

  9. Implications for anomalous mantle pressure and dynamic topography from lithospheric stress patterns in the North Atlantic Realm

    DEFF Research Database (Denmark)

    Schiffer, Christian; Nielsen, Søren Bom

    2016-01-01

    -established thin sheet model in a global finite element representation. We adjust the lithospheric thickness and the sub-lithospheric pressure iteratively, comparing modelled in plane stress with the observations of the World Stress Map. We find that an anomalous mantle pressure associated with the Iceland...... of a buoyancy anomaly at the base of the North Atlantic lithosphere at or slightly before continental breakup, relatively fast dissipation of the fringes of this, and continued melt generation below Iceland....

  10. Samovar: a thermomechanical code for modeling of geodynamic processes in the lithosphere-application to basin evolution

    OpenAIRE

    Elesin, Y; Gerya, T.; Artemieva, Irina; Thybo, Hans

    2010-01-01

    We present a new 2D finite difference code, Samovar, for high-resolution numerical modeling of complex geodynamic processes. Examples are collision of lithospheric plates (including mountain building and subduction) and lithosphere extension (including formation of sedimentary basins, regions of extended crust, and rift zones). The code models deformation of the lithosphere with viscoelastoplastic rheology, including erosion/sedimentation processes and formation of shear zones in areas of hig...

  11. Benthic habitat classification in Lignumvitae Key Basin, Florida Bay, using the U.S. Geological Survey Along-Track Reef Imaging System (ATRIS)

    Science.gov (United States)

    Reich, C.D.; Zawada, D.G.; Thompson, P.R.; Reynolds, C.E.; Spear, A.H.; Umberger, D.K.; Poore, R.Z.

    2011-01-01

    The Comprehensive Everglades Restoration Plan (CERP) funded in partnership between the U.S. Army Corps of Engineers, South Florida Water Management District, and other Federal, local and Tribal members has in its mandate a guideline to protect and restore freshwater flows to coastal environments to pre-1940s conditions (CERP, 1999). Historic salinity data are sparse for Florida Bay, so it is difficult for water managers to decide what the correct quantity, quality, timing, and distribution of freshwater are to maintain a healthy and productive estuarine ecosystem. Proxy records of seasurface temperature (SST) and salinity have proven useful in south Florida. Trace-element chemistry on foraminifera and molluscan shells preserved in shallow-water sediments has provided some information on historical salinity and temperature variability in coastal settings, but little information is available for areas within the main part of Florida Bay (Brewster-Wingard and others, 1996). Geochemistry of coral skeletons can be used to develop subannually resolved proxy records for SST and salinity. Previous studies suggest corals, specifically Solenastrea bournoni, present in the lower section of Florida Bay near Lignumvitae Key, may be suitable for developing records of SST and salinity for the past century, but the distribution and species composition of the bay coral community have not been well documented (Hudson and others, 1989; Swart and others, 1999). Oddly, S. bournoni thrives in the study area because it can grow on a sandy substratum and can tolerate highly turbid water. Solenastrea bournoni coral heads in this area should be ideally located to provide a record (~100-150 years) of past temperature and salinity variations in Florida Bay. The goal of this study was to utilize the U.S. Geological Survey's (USGS) Along-Track Reef Imaging System (ATRIS) capability to further our understanding of the abundance, distribution, and size of corals in the Lignumvitae Key Basin. The

  12. Big insights from tiny peridotites: Evidence for persistence of Precambrian lithosphere beneath the eastern North China Craton

    Science.gov (United States)

    Liu, Jingao; Rudnick, Roberta L.; Walker, Richard J.; Xu, Wen-liang; Gao, Shan; Wu, Fu-yuan

    2015-05-01

    Previous studies have shown that the eastern North China Craton (NCC) lost its ancient lithospheric mantle root during the Phanerozoic. The temporal sequence, spatial extent, and cause of the lithospheric thinning, however, continue to be debated. Here we report olivine compositions, whole-rock Re-Os isotopic systematics, and platinum-group element abundances of small ( 92) lithospheric mantle is largely absent. Osmium isotopic data suggest the Wudi peridotites experienced melt depletion primarily during the Paleoproterozoic (~ 1.8 Ga), although an Archean Os model age for one xenolith indicates incorporation of a minor component of Archean lithospheric mantle. These data suggest that a previously unrecognized Paleoproterozoic orogenic event removed and replaced the original Archean lithospheric mantle beneath the sedimentary basin at the southern edge of the Bohai Sea. By contrast, the Fuxin peridotites, entrained in Cretaceous basalts that crop out along the northern edge of the eastern NCC, document the coexistence of both ancient (≥ 2.3 Ga) and modern lithospheric mantle components. Here, the original Late Archean-Early Paleoproterozoic lithospheric mantle was, at least partially, removed and replaced prior to 100 Ma. Combined with literature data, our results show that removal of the original Archean lithosphere occurred within Proterozoic collisional orogens, and that replacement of Precambrian lithosphere during the Mesozoic may have been spatially associated with the collisional boundaries and the strike-slip Tan-Lu fault, as well as the onset of Paleo-Pacific plate subduction.

  13. The role of elasticity in normal faulting and the development of axial topography in the oceanic lithosphere

    Science.gov (United States)

    Olive, J. L.; Behn, M. D.; Mittelstaedt, E. L.; Ito, G.

    2012-12-01

    In this study we compare 2D numerical simulations of lithospheric extension with and without elasticity in order to investigate its role on the development of normal faults and axial topography at oceanic spreading centers. Specifically, we use a finite difference / marker-in-cell technique to model visco-elasto-plastic (VEP) and visco-plastic (VP) deformation of the lithosphere under extension. Simulated fault zones form spontaneously as the system evolves and the associated strain localization is achieved by reducing the cohesion in proportion to the accumulated plastic strain in regions undergoing yielding. We investigate the development of different fault modes (e.g. growth of multiple faults vs. a single large-offset fault) both in a VP and a VEP lithosphere for a range of lithospheric thicknesses, spreading rates, and rates of cohesion loss. In our simulations, fault-induced bending of a VP lithosphere occurs on a larger wavelength and with less overall vertical deflection than in a VEP lithosphere. Flexural rotation of long-lived, initially steep faults does not require elasticity, but appears to have a strain-rate-dependent wavelength in a VP lithosphere. We find that thinner lithosphere and rapid weakening promote the growth of large-offset faults in both a VEP and a VP lithosphere. The effect of neglecting elasticity appears greater in thicker lithosphere, where a VP rheology favors the growth of multiple steep faults instead of a few large-offset faults. We also note that a VP lithosphere requires more total extension to achieve the same faulting pattern as a VEP lithosphere. This may be due to distributed viscous deformation taking up a portion of the extension in the VP case. To further quantify our numerical results, we develop scaling relations describing the build-up of topographic and bending stresses in a faulted VP lithosphere and compare them to those previously derived for a VEP lithosphere. These relations are then implemented in a force

  14. Geodynamic inversion to constrain the non-linear rheology of the lithosphere

    Science.gov (United States)

    Baumann, T. S.; Kaus, Boris J. P.

    2015-08-01

    One of the main methods to determine the strength of the lithosphere is by estimating it's effective elastic thickness. This method assumes that the lithosphere is a thin elastic plate that floats on the mantle and uses both topography and gravity anomalies to estimate the plate thickness. Whereas this seems to work well for oceanic plates, it has given controversial results in continental collision zones. For most of these locations, additional geophysical data sets such as receiver functions and seismic tomography exist that constrain the geometry of the lithosphere and often show that it is rather complex. Yet, lithospheric geometry by itself is insufficient to understand the dynamics of the lithosphere as this also requires knowledge of the rheology of the lithosphere. Laboratory experiments suggest that rocks deform in a viscous manner if temperatures are high and stresses low, or in a plastic/brittle manner if the yield stress is exceeded. Yet, the experimental results show significant variability between various rock types and there are large uncertainties in extrapolating laboratory values to nature, which leaves room for speculation. An independent method is thus required to better understand the rheology and dynamics of the lithosphere in collision zones. The goal of this paper is to discuss such an approach. Our method relies on performing numerical thermomechanical forward models of the present-day lithosphere with an initial geometry that is constructed from geophysical data sets. We employ experimentally determined creep-laws for the various parts of the lithosphere, but assume that the parameters of these creep-laws as well as the temperature structure of the lithosphere are uncertain. This is used as a priori information to formulate a Bayesian inverse problem that employs topography, gravity, horizontal and vertical surface velocities to invert for the unknown material parameters and temperature structure. In order to test the general methodology

  15. Thermal erosion of cratonic lithosphere as a potential trigger for mass-extinction

    Science.gov (United States)

    Pilet, Sebastien; Guex, Jean; Muntener, Othmar; Bartolini, Annachiara; Spangenberg, Jorge; Schoene, Blair; Schaltegger, Urs

    2016-04-01

    The temporal coincidence between large igneous provinces (LIPs) and mass extinctions has led many to pose a causal relationship between the two. However, there is still no consensus on a mechanistic model that explains how magmatism leads to the turnover of terrestrial and marine plants, invertebrates and vertebrates. Here, we present a synthesis of stratigraphic constraints on the Triassic-Jurassic (T-J) and Pliensbachian-Toarcian (Pl-To) boundaries combined with geochronological data in order to establish the sequence of events that initiate two of the major mass extinctions recorded in Earth's history. This synthesis demonstrates that these biotic crises are both associated with rapid change from an initial cool period to greenhouse conditions. The initial regressive events recorded at T-J and Pl-To boundaries seem difficult to reconcile either with large initial CO2 degassing associated with plume activity or by volatile-release (CO2, CH4, Cl2) from deep sedimentary reservoirs during contact metamorphism associated to dykes and sills intrusion because massive CO2 degassing is expected to produce super greenhouse conditions. We evaluate, here, an alternative suggesting that the initial cooling could be due to gas release during the initial thermal erosion of the cratonic lithosphere due to emplacement of the CAMP and Karoo-Ferrar volcanic provinces. Petrological constraints on primary magmas indicate that the mantle is hotter and melts more extensively to produce LIP lavas than for current oceanic islands basalts. However, available data suggest that the Karoo and CAMP areas were underlain by thick lithosphere (>200 km) prior to continental break up. The presence of thick lithosphere excludes significant melting of the asthenospheric mantle without initial stage of thermal erosion of the cratonic lithosphere. This initial step of thermal erosion / thermal heating of the cratonic lithosphere is critical to understand the volatile budget associated with LIPs while

  16. In-Situ Lithospheric Rheology Measurement Using Isostatic Response and Geophysical State

    Science.gov (United States)

    Lowry, A. R.; Becker, T. W.; Buehler, J. S.; ma, X.; Miller, M. S.; Perez-Gussinye, M.; Ravat, D.; Schutt, D.

    2013-12-01

    Measurements of effective elastic thickness, Te, from flexural isostatic modeling are sensitive to flow rheology of the lithosphere. Nevertheless, Te has not been widely used to estimate in-situ rheology. Past methodological controversies regarding Te measurement are partly to blame for under-utilization of isostatic response in rheology studies, but these controversies are now largely resolved. The remaining hurdles include uncertainties in properties of geophysical state such as temperature, lithology, and water content. These are ambiguous in their relative contributions to total strength, and the unknown state-of-stress adds to ambiguity in the rheology. Dense seismic and other geophysical arrays such as EarthScope's USArray are providing a wealth of new information about physical state of the lithosphere, however, and these data promise new insights into rheology and deformation processes. For example, new estimates of subsurface mass distributions derived from seismic data enable us to examine controversial assumptions about the nature of lithospheric loads. Variations in crustal lithology evident in bulk crustal velocity ratio, vP/vS, contribute a surprisingly large fraction of total loading. Perhaps the most interesting new information on physical state derives from imaging of uppermost mantle velocities using refracted mantle phases, Pn and Sn, and depths to negative velocity gradients imaged as converted phases in receiver functions (so-called seismic lithosphere-asthenosphere boundary, 'LAB', and mid-lithosphere discontinuity, 'MLD'). Imaging of the ~580°C isotherm associated with the phase transition from alpha- to beta-quartz affords another exciting new avenue for investigation, in part because the transition closely matches the Curie temperature thought to control magnetic bottom in some continental crust. Reconciling seismic estimates of temperature variations with measurements of Te and upper-mantle negative velocity gradients in the US requires

  17. Numerical models of mantle lithosphere weakening, erosion and delamination induced by melt extraction and emplacement

    Science.gov (United States)

    Wallner, Herbert; Schmeling, Harro

    2016-09-01

    Continental rifting caused by extension and heating from below affects the lithosphere or cratons in various ways. Volcanism and melt intrusions often occur along with thinning, weakening and even breaking lithosphere. Although mechanical necking models of the lithosphere are often applied, the aspects of melting and the implications due to melt transport and emplacement at shallower depths are not well understood. A two-phase flow approach employing melt extraction and shallow emplacement associated with thermal weakening is developed and compared with observations. The results of this comparison indicate the importance of partial melts and an asthenospheric magma source for increasing the rising rate of the lithosphere-asthenosphere boundary during extension. Thermo-mechanical physics of visco-plastic flow is approximated using the Finite Difference method with Eulerian formulation in 2D. The conservation of mass, momentum and energy equations are solved for a multi-component (crust-mantle) and two-phase (melt-matrix) system. Rheology is temperature- and stress-dependent. In consideration of depletion and enrichment melting and solidification are controlled by a simplified linear binary solid solution model. Melt is extracted and emplaced in predefined depth regions (emplacement zones) in the lithospheric mantle and crust. The Compaction Boussinesq Approximation was applied; its validity was tested against the Full Compaction formulation and found fully satisfactory for the case of sublithospheric melting models. A simple model guided by the geodynamic situation of the Rwenzori region typically results in updoming asthenosphere with melt-assisted erosion of the lithosphere's base. Even with a conservative approach for a temperature anomaly melting alone doubles the lithospheric erosion rate in comparison with a model without melting. With melt extraction and intrusion lithospheric erosion and upwelling of the lithosphere-asthenosphere boundary speeds up by a

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

    Science.gov (United States)

    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

  19. Evaluation of the Lithospheric Contribution to Southern Rio Grande Rift Mafic Melts

    Science.gov (United States)

    Konter, J. G.; Crocker, L.; Anaya, L. M.; Rooney, T. O.

    2011-12-01

    As continental rifting proceeds, the accommodation of lithospheric thinning by mechanical extension and magmatic intrusion represents an important but poorly constrained tectonic process. Insight into role of the magmatic component may come from the composition of volcanic products, which can record magma-lithosphere interactions. The volcanic activity in continental rift environments is frequently characterized by bimodal associations of mafic and silicic volcanism with heterogenous lithospheric contributions. We present a new integrated data set from several mafic volcanic fields in the Rio Grande Rift, consisting of major and trace element compositions, as well as isotopes. This data set provides insight into asthenospheric melting processes and interactions with the overlying lithosphere. The melting processes and the related extensional volcanism is the result of foundering of the Farallon slab. Large volume silicic eruptions such as those in the Sierra Madre Occidental originate from a large contribution of lithospheric melting, with a subordinate asthenospheric contribution. In contrast, Late Tertiary and Quaternary basaltic volcanic fields in the Rio Grande Rift were likely sourced in the asthenosphere and did not reside in the lithosphere for substantial periods. As a result the region is the ideal natural laboratory to investigate the interaction of asthenospheric melts with the lithosphere. In particular the wide array of volcanic fields contain multiple xenolith localities, such as Kilbourne Hole, providing direct samples of lithosphere and crust. Although previous studies have focused on correlations between amount of extension related to Farallon slab foundering, volcanic compositions, and their mantle sources, we present data that suggest that some compositional signatures may pre-date current tectonic processes. Radiogenic isotope data from several volcanic fields in New Mexico show a converging pattern in Pb isotope compositions, focusing on the

  20. 3D Integrated geophysical-petrological modelling of the Iranian lithosphere

    Science.gov (United States)

    Mousavi, Naeim; Ardestani, Vahid E.; Ebbing, Jörg; Fullea, Javier

    2016-04-01

    The present-day Iranian Plateau is the result of complex tectonic processes associated with the Arabia-Eurasia Plate convergence at a lithospheric scale. In spite of previous mostly 2D geophysical studies, fundamental questions regarding the deep lithospheric and sub-lithospheric structure beneath Iran remain open. A robust 3D model of the thermochemical lithospheric structure in Iran is an important step toward a better understanding of the geological history and tectonic events in the area. Here, we apply a combined geophysical-petrological methodology (LitMod3D) to investigate the present-day thermal and compositional structure in the crust and upper mantle beneath the Arabia-Eurasia collision zone using a comprehensive variety of constraining data: elevation, surface heat flow, gravity potential fields, satellite gravity gradients, xenoliths and seismic tomography. Different mantle compositions were tested in our model based on local xenolith samples and global data base averages for different tectonothermal ages. A uniform mantle composition fails to explain the observed gravity field, gravity gradients and surface topography. A tectonically regionalized lithospheric mantle compositional model is able to explain all data sets including seismic tomography models. Our preliminary thermochemical lithospheric study constrains the depth to Moho discontinuity and intra crustal geometries including depth to sediments. We also determine the depth to Curie isotherm which is known as the base of magnetized crustal/uppermost mantle bodies. Discrepancies with respect to previous studies include mantle composition and the geometry of Moho and Lithosphere-Asthenosphere Boundary (LAB). Synthetic seismic Vs and Vp velocities match existing seismic tomography models in the area. In this study, depleted mantle compositions are modelled beneath cold and thick lithosphere in Arabian and Turan platforms. A more fertile mantle composition is found in collision zones. Based on our 3

  1. Shallow and deep lithosphere slabs beneath the Dinarides from teleseismic tomography as the result of the Adriatic lithosphere downwelling

    Science.gov (United States)

    Šumanovac, Franjo; Markušić, Snježana; Engelsfeld, Tihomir; Jurković, Klaudia; Orešković, Jasna

    2017-08-01

    The study area covers the Dinarides and southwestern part of the Pannonian basin as the marginal zone between the Adriatic microplate (African plate) and the Pannonian tectonic segment (Eurasian plate). We created a three-dimensional seismic velocity model to 450 km depth using teleseismic tomography. Our travel-time dataset was collected by means of 40 seismic stations from the ORFEUS database and Croatian Seismological Survey database. A set of 90 teleseismic earthquakes were selected in the time range 2014-2015, and relative P-wave travel-time residuals were calculated. For the first time the seismic P-wave velocity model of a relatively high resolution on the entire Dinaridic mountain belt was obtained. Based on this model, a more reliable insight in the relations of the lithosphere plates has been achieved. We imaged a fast velocity anomaly extending underneath the entire Dinaridic mountain belt which indicates cold, rigid materials. The anomaly is steeply sloping towards the northeast and directly indicates the sinking of the Adriatic microplate underneath the Pannonian tectonic segment. In the Northern Dinarides the anomaly extends to the depth of 250 km, whereas in the Southern Dinarides it covers greater depths, up to 450 km. The shallow Adriatic slab extends along the External Dinarides, while the deep Adriatic slab extends beneath the Internal Dinarides and ophiolite zones in the area of central and southern Dinarides. Different slab depths are interpreted as the faster convergence of the plate in the southern Dinarides than in the northern, or the convergence of the plates had started in the southern part and systematically developed to the north.

  2. The Lithosphere-Asthenosphere System in the Calabrian Arc and Surrounding Seas Southern Italy

    Science.gov (United States)

    Pontevivo, Antonella; Panza, Giuliano Francesco

    2006-08-01

    A fairly detailed structural model of the lithosphere-asthenosphere system (thickness, S- and P-wave velocities of the crust and of the uppermost mantle layers) has been defined in the Calabrian Arc region (Southern Tyrrhenian Sea, Calabria and the northwestern part of the Ionian Sea) in Southern Italy using seismic data from literature as a priori constraints of the nonlinear inversion of surface-wave data. The main features identified by this study are: (1) A very shallow (less then 10 km deep) crust-mantle transition in the Southern Tyrrhenian Sea and a very low vs just below a very thin lid, in correspondence of the submarine volcanic bodies Magnaghi, Marsili and Vavilov, while the vs in the lid is quite high in the area that separates Marsili from Magnaghi-Vavilov; (2) a shallow and very low vs layer in the uppermost mantle in the areas of the Aeolian Islands, Vesuvius, Phlegraean Fields and Ischia, which represents their shallow-mantle magma source; (3) a thickened continental crust and lithospheric doubling in Calabria; (4) a crust about 25-km thick and a mantle velocity profile versus depth consistent with the presence of a continental rifted lithosphere, now thermally relaxed, in the investigated part of the Ionian Sea; (5) the subduction towards northwest of the Ionian lithosphere below the Southern Tyrrhenian Sea; (6) the subduction of the Adriatic/Ionian lithosphere underneath the Vesuvius and Phlegraean Fields.

  3. Olivine anisotropy suggests Gutenberg discontinuity is not the base of the lithosphere.

    Science.gov (United States)

    Hansen, Lars N; Qi, Chao; Warren, Jessica M

    2016-09-20

    Tectonic plates are a key feature of Earth's structure, and their behavior and dynamics are fundamental drivers in a wide range of large-scale processes. The operation of plate tectonics, in general, depends intimately on the manner in which lithospheric plates couple to the convecting interior. Current debate centers on whether the transition from rigid lithosphere to flowing asthenosphere relates to increases in temperature or to changes in composition such as the presence of a small amount of melt or an increase in water content below a specified depth. Thus, the manner in which the rigid lithosphere couples to the flowing asthenosphere is currently unclear. Here we present results from laboratory-based torsion experiments on olivine aggregates with and without melt, yielding an improved database describing the crystallographic alignment of olivine grains. We combine this database with a flow model for oceanic upper mantle to predict the structure of the seismic anisotropy beneath ocean basins. Agreement between our model and seismological observations supports the view that the base of the lithosphere is thermally controlled. This model additionally supports the idea that discontinuities in velocity and anisotropy, often assumed to be the base of the lithosphere, are, instead, intralithospheric features reflecting a compositional boundary established at midocean ridges, not a rheological boundary.

  4. Lithosphere versus asthenosphere mantle sources at the Big Pine Volcanic Field, California

    Science.gov (United States)

    Gazel, Esteban; Plank, Terry; Forsyth, Donald W.; Bendersky, Claire; Lee, Cin-Ty A.; Hauri, Erik H.

    2012-06-01

    Here we report the first measurements of the H2O content of magmas and mantle xenoliths from the Big Pine Volcanic Field (BPVF), California, in order to constrain the melting process in the mantle, and the role of asthenospheric and lithospheric sources in this westernmost region of the Basin and Range Province, western USA. Melt inclusions trapped in primitive olivines (Fo82-90) record surprisingly high H2O contents (1.5 to 3.0 wt.%), while lithospheric mantle xenoliths record low H2O concentrations (whole rock 500 ka, to cooler (˜1220°C) and shallower melting (˜1 GPa) conditions in younger magmas. The estimated depth of melting correlates strongly with some trace element ratios in the magmas (e.g., Ce/Pb, Ba/La), with deeper melts having values closer to upper mantle asthenosphere values, and shallower melts having values more typical of subduction zone magmas. This geochemical stratification is consistent with seismic observations of a shallow lithosphere-asthenosphere boundary (˜55 km depth). Combined trace element and cryoscopic melting models yield self-consistent estimates for the degree of melting (˜5%) and source H2O concentration (˜1000 ppm). We suggest two possible geodynamic models to explain small-scale convection necessary for magma generation. The first is related to the Isabella seismic anomaly, either a remnant of the Farallon Plate or foundered lithosphere. The second scenario is related to slow extension of the lithosphere.

  5. The consequences of hotspots on continental lithosphere : a thermal case study on the Arabian Plate.

    Science.gov (United States)

    Vicente De Gouveia, S.; Besse, J.; Greff-Lefftz, M.; Frizon de Lamotte, D.; Leparmentier, F.; Lescanne, M.

    2015-12-01

    Hotspots are thermal instabilities coming from various depths in the mantle. Their activity is often revealed by surface and sub-surface phenomena such as volcanic trapps or oceanic plateaus, and volcanic island tracks on the seafloor. The two first are often linked to the eruption of a hotspot head, while the third is due to the volcanic material fed by the subsequent tail. Consequences of a hotspot tail on the oceanic lithosphere are well known, while its effect on the continental lithosphere is most often masked by the thickness of the lithosphere. The aim of our study is to try and link hotspot tracks with geological events in the continental lithosphere. Hotspot tracks are first built using a modified version of the hybrid reference frame of Seton et al. (2012), and their effect on the continental lithosphere is then evaluated using geological markers issued from petroleum wells, in particular the sedimentary record, backstripping, heat flux anomaly and temperature data. A case study is performed on the Arabian Plate, potentially crossed by two hotspots (Afar and Comores). Several W-E heat flux profiles display a large thermal anomaly close to the Red Sea, while a smaller N-S elongated heat flow anomaly more to the E suggests that a hotspot track could impact the thermal history of the Arabian plate.

  6. Life in the lithosphere, kinetics and the prospects for life elsewhere.

    Science.gov (United States)

    Cockell, Charles S

    2011-02-13

    The global contiguity of life on the Earth today is a result of the high flux of carbon and oxygen from oxygenic photosynthesis over the planetary surface and its use in aerobic respiration. Life's ability to directly use redox couples from components of the planetary lithosphere in a pre-oxygenic photosynthetic world can be investigated by studying the distribution of organisms that use energy sources normally bound within rocks, such as iron. Microbiological data from Iceland and the deep oceans show the kinetic limitations of living directly off igneous rocks in the lithosphere. Using energy directly extracted from rocks the lithosphere will support about six orders of magnitude less productivity than the present-day Earth, and it would be highly localized. Paradoxically, the biologically extreme conditions of the interior of a planet and the inimical conditions of outer space, between which life is trapped, are the locations from which volcanism and impact events, respectively, originate. These processes facilitate the release of redox couples from the planetary lithosphere and might enable it to achieve planetary-scale productivity approximately one to two orders of magnitude lower than that produced by oxygenic photosynthesis. The significance of the detection of extra-terrestrial life is that it will allow us to test these observations elsewhere and establish an understanding of universal relationships between lithospheres and life. These data also show that the search for extra-terrestrial life must be accomplished by 'following the kinetics', which is different from following the water or energy.

  7. Thermal erosion of cratonic lithosphere as a potential trigger for mass-extinction.

    Science.gov (United States)

    Guex, Jean; Pilet, Sebastien; Müntener, Othmar; Bartolini, Annachiara; Spangenberg, Jorge; Schoene, Blair; Sell, Bryan; Schaltegger, Urs

    2016-03-24

    The temporal coincidence between large igneous provinces (LIPs) and mass extinctions has led many to pose a causal relationship between the two. However, there is still no consensus on a mechanistic model that explains how magmatism leads to the turnover of terrestrial and marine plants, invertebrates and vertebrates. Here we present a synthesis of ammonite biostratigraphy, isotopic data and high precision U-Pb zircon dates from the Triassic-Jurassic (T-J) and Pliensbachian-Toarcian (Pl-To) boundaries demonstrating that these biotic crises are both associated with rapid change from an initial cool period to greenhouse conditions. We explain these transitions as a result of changing gas species emitted during the progressive thermal erosion of cratonic lithosphere by plume activity or internal heating of the lithosphere. Our petrological model for LIP magmatism argues that initial gas emission was dominated by sulfur liberated from sulfide-bearing cratonic lithosphere before CO2 became the dominant gas. This model offers an explanation of why LIPs erupted through oceanic lithosphere are not associated with climatic and biotic crises comparable to LIPs emitted through cratonic lithosphere.

  8. Olivine anisotropy suggests Gutenberg discontinuity is not the base of the lithosphere

    Science.gov (United States)

    Hansen, Lars N.; Qi, Chao; Warren, Jessica M.

    2016-09-01

    Tectonic plates are a key feature of Earth’s structure, and their behavior and dynamics are fundamental drivers in a wide range of large-scale processes. The operation of plate tectonics, in general, depends intimately on the manner in which lithospheric plates couple to the convecting interior. Current debate centers on whether the transition from rigid lithosphere to flowing asthenosphere relates to increases in temperature or to changes in composition such as the presence of a small amount of melt or an increase in water content below a specified depth. Thus, the manner in which the rigid lithosphere couples to the flowing asthenosphere is currently unclear. Here we present results from laboratory-based torsion experiments on olivine aggregates with and without melt, yielding an improved database describing the crystallographic alignment of olivine grains. We combine this database with a flow model for oceanic upper mantle to predict the structure of the seismic anisotropy beneath ocean basins. Agreement between our model and seismological observations supports the view that the base of the lithosphere is thermally controlled. This model additionally supports the idea that discontinuities in velocity and anisotropy, often assumed to be the base of the lithosphere, are, instead, intralithospheric features reflecting a compositional boundary established at midocean ridges, not a rheological boundary.

  9. Electrical conductivity structure of southeastern North America: Implications for lithospheric architecture and Appalachian topographic rejuvenation

    Science.gov (United States)

    Murphy, Benjamin S.; Egbert, Gary D.

    2017-03-01

    We present the first three-dimensional view of the lithospheric electrical conductivity structure beneath southeastern North America. By inverting EarthScope long-period magnetotelluric (MT) data, we obtain an electrical conductivity image that provides new insights into both the architecture of the Appalachian Orogen and the cryptic post-rifting geodynamic history of the southeastern United States. Our inverse solutions reveal several elongate electrically conductive features that we interpret as major terrane sutures within the Appalachian Orogen. Most significantly, we resolve a highly electrically resistive layer that extends to mantle depths beneath the modern Piedmont and Coastal Plain physiographic provinces. As high resistivity values in mantle minerals require cold mantle temperatures, the MT data indicate that the sub-Piedmont thermal lithosphere must extend to greater than 200 km depth. This firm bound conflicts with conclusions from seismic results. The boundary between the anomalously thick, resistive sub-Piedmont lithosphere and the relatively thin, moderately conductive sub-Appalachian lithosphere corresponds within resolution to the modern Appalachian topographic escarpment. This newly recognized contrast in lithospheric properties likely has important implications for Appalachian topographic rejuvenation.

  10. Selective analysis of power plant operation on the Hudson River with emphasis on the Bowline Point Generating Station. Volume 1. [Effects on striped bass population

    Energy Technology Data Exchange (ETDEWEB)

    Barnthouse, L. W.; Cannon, J. B.; Christensen, S. G.

    1977-07-01

    A comprehensive study of the effects of power plant operation on the Hudson River was conducted. The study included thermal, biological, and air quality effects of existing and planned electrical generating stations. This section on thermal impacts presents a comprehensive mathematical modeling and computer simulation study of the effects of heat rejection from the plants. The overall study consisted of three major parts: near-field analysis; far-field analysis; and zone-matched near-field/far-field analysis. Near-field analyses were completed for Roseton, Danskammer, and Bowline Point Generating Stations, and near-field dilution ratios range from a low of about 2 for Bowline Point and 3 for Roseton to a maximum of 6 for both plants. The far-field analysis included a critical review of existing studies and a parametric review of operating plants. The maximum thermal load case, based on hypothetical 1974 river conditions, gives the daily maximum cross-section-averaged and 2-mile-segment-averaged water temperatures as 83.80/sup 0/F in the vicinity of the Indian Point Station and 83.25/sup 0/F in the vicinity of the Bowline Station. This maximum case will be significantly modified if cooling towers are used at certain units. A full analysis and discussion of these cases is presented. A study of the Hudson River striped bass population is divided into the following eight subsections: distribution of striped bass eggs, larvae, and juveniles in the Hudson River; entrainment mortality factor; intake factor; impingement; effects of discharges; compensation; model estimates of percent reduction; and Hudson River striped bass stock.

  11. Backscatter imagery in Jobos Bay

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a 1x1 meter resolution backscatter mosaic of Jobos Bay, Puerto Rico (in NAD83 UTM 19 North). The backscatter values are in relative 8-bit (0 –...

  12. The evolution of fault geometry and lithosphere mechanical response to faulting during lithosphere hyper-extension at magma-poor rifted margins

    Science.gov (United States)

    Gómez Romeu, Júlia; Kusznir, Nick; Manatschal, Gianreto; Roberts, Alan

    2016-04-01

    The geometry of upper lithosphere extensional faulting and the mechanical response of the lithosphere during continental breakup are controversial. The lithosphere response to extensional faulting at magma-poor rifted margins controls the distribution of thinned continental crust, exhumed mantle, continental allochthons and syn-tectonic sediments leading to the complexity of heterogeneous structure of hyper-extended domain at these margins. In order to better understand the evolving fault geometry and lithosphere mechanics during magma-poor rifted margin formation, we investigate extensional faulting for the tectonic end-members of continental rifting and slow sea-floor spreading. We presume that these end-members faulting styles both contribute to lithosphere thinning during rifted margin evolution as continental rifting evolves into sea-floor spreading. For continental rifting, large extensional faults that rupture the seismogenic brittle upper lithosphere have been shown to be planar and steeply dipping by earthquake seismology and geodesy (Stein and Barrientos 1985; Jackson 1987). These results are supported by seismic reflection imaging and structural modelling of rift basins (Kusznir et al., 1991, 1995). Individual fault heaves for continental rifting seldom exceeds approximately 10 km. The effective elastic thickness, used to parameterize lithosphere flexural strength for syn-tectonic response to extensional faulting during continental rifting, are typically between 1.5 and 3 km. For slow-spreading ocean ridges we examine extensional fault geometry and lithosphere flexural response to cumulative faulting. We focus on the TAG area (deMartin et al., 2007) and the 15°N area (Schroeder et al., 2007) of the Mid-Atlantic Ridge using a flexural isostatic extensional faulting model (Buck 1988; Kusznir et al., 1991). Modelling of fault controlled bathymetry at slow-spreading ocean ridges shows that active extensional faults at depth have a steep dip (50° - 70

  13. The elusive lithosphere-asthenosphere boundary (LAB) beneath cratons

    Science.gov (United States)

    Eaton, David W.; Darbyshire, Fiona; Evans, Rob L.; Grütter, Herman; Jones, Alan G.; Yuan, Xiaohui

    2009-04-01

    The lithosphere-asthenosphere boundary (LAB) is a first-order structural discontinuity that accommodates differential motion between tectonic plates and the underlying mantle. Although it is the most extensive type of plate boundary on the planet, its definitive detection, especially beneath cratons, is proving elusive. Different proxies are used to demarcate the LAB, depending on the nature of the measurement. Here we compare interpretations of the LAB beneath three well studied Archean regions: the Kaapvaal craton, the Slave craton and the Fennoscandian Shield. For each location, xenolith and xenocryst thermobarometry define a mantle stratigraphy, as well as a steady-state conductive geotherm that constrains the minimum pressure (depth) of the base of the thermal boundary layer (TBL) to 45-65 kbar (170-245 km). High-temperature xenoliths from northern Lesotho record Fe-, Ca- and Ti-enrichment, grain-size reduction and globally unique supra-adiabatic temperatures at 53-61 kbar (200-230 km depth), all interpreted to result from efficient advection of asthenosphere-derived melts and heat into the TBL. Using a recently compiled suite of olivine creep parameters together with published geotherms, we show that beneath cratons the probable deformation mechanism near the LAB is dislocation creep, consistent with widely observed seismic and electrical anisotropy fabrics. If the LAB is dry, it is probably diffuse (> 50 km thick) and high levels of shear stress (> 2 MPa or > 20 bar) are required to accommodate plate motion. If the LAB is wet, lower shear stress is required to accommodate plate motion and the boundary may be relatively sharp (≤ 20 km thick). The seismic LAB beneath cratons is typically regarded as the base of a high-velocity mantle lid, although some workers infer its location based on a distinct change in seismic anisotropy. Surface-wave inversion studies provide depth-constrained velocity models, but are relatively insensitive to the sharpness of the LAB

  14. Recycled dehydrated lithosphere observed in plume-influenced mid-ocean-ridge basalt.

    Science.gov (United States)

    Dixon, Jacqueline Eaby; Leist, Loretta; Langmuir, Charles; Schilling, Jean-Guy

    2002-11-28

    A substantial uncertainty in the Earth's global geochemical water cycle is the amount of water that enters the deep mantle through the subduction and recycling of hydrated oceanic lithosphere. Here we address the question of recycling of water into the deep mantle by characterizing the volatile contents of different mantle components as sampled by ocean island basalts and mid-ocean-ridge basalts. Although all mantle plume (ocean island) basalts seem to contain more water than mid-ocean-ridge basalts, we demonstrate that basalts associated with mantle plume components containing subducted lithosphere--'enriched-mantle' or 'EM-type' basalts--contain less water than those associated with a common mantle source. We interpret this depletion as indicating that water is extracted from the lithosphere during the subduction process, with greater than 92 per cent efficiency.

  15. A Magma Accretion Model for the Formation of Oceanic Lithosphere: Implications for Global Heat Loss

    CERN Document Server

    Hamza, V M; Alexandrino, C H

    2010-01-01

    A simple magma accretion model of the oceanic lithosphere is proposed and its implications for understanding the thermal field of oceanic lithosphere examined. The new model (designated VBA) assumes existence of lateral variations in magma accretion rates and temperatures at the boundary zone between the lithosphere and the asthenosphere. Heat flow and bathymetry variations calculated on the basis of the VBA model provide vastly improved fits to respective observational datasets. The improved fits have been achieved for the entire age range and without the need to invoke the ad-hoc hypothesis of large-scale hydrothermal circulation in stable ocean crust. The results suggest that estimates of global heat loss need to be downsized by at least 25%.

  16. Lithosphere-asthenosphere system in the Mediterranean region in the framework of polarized plate tectonics

    CERN Document Server

    Raykova, Reneta Blagoeva; Doglioni, Carlo

    2015-01-01

    Velocity structure of the lithosphere-asthenosphere system, to the depth of about 350 km, is obtained for almost 400 cells, sized 1 degree by 1 degree in the Mediterranean region. The models are obtained by the following sequence of methods and tools: surface-wave dispersion measurements and collection; 2D tomography of dispersion relations; non-linear inversion of cellular dispersion relations; smoothing optimization method to select a preferred model for each cell. The 3D velocity model, that satisfies Occam razor principle, is obtained as a juxtaposition of selected cellular models. The reconstructed picture of the lithosphere-asthenosphere system evidences the, globally well known, asymmetry between the W- and E-directed subduction zones, attributed to the westward drift of the lithosphere relative to the mantle. Different relationship between slabs and mantle dynamics cause strong compositional differences in the upper mantle, as shown by large variations of seismic waves velocity, consistent with Polari...

  17. Earth's lithospheric magnetic field determined to spherical harmonic degree 90 from CHAMP satellite measurements

    DEFF Research Database (Denmark)

    Maus, S.; Rother, M.; Hemant, K.;

    2006-01-01

    The CHAMP magnetic field mission is providing highly reliable measurements from which the global lithospheric magnetic field can be determined in unprecedented resolution and accuracy. Using almost 5 yr of data, we derive our fourth generation lithospheric field model termed MF4, which is expanded...... to spherical harmonic degree and order 90. After subtracting from the full magnetic field observations predicted fields from an internal field model up to degree 15, an external field model up to degree two, and the predicted magnetic field signatures for the eight dominant ocean tidal constituents, we fit...... of the lithospheric field down to an altitude of about 50 km at lower latitudes, with reduced accuracy in the polar regions. Crustal features come out significantly sharper than in previous models. In particular, bands of magnetic anomalies along subduction zones become visible by satellite for the first time....

  18. Oriented grain growth and modification of 'frozen anisotropy' in the lithospheric mantle

    Science.gov (United States)

    Boneh, Yuval; Wallis, David; Hansen, Lars N.; Krawczynski, Mike J.; Skemer, Philip

    2017-09-01

    Seismic anisotropy throughout the oceanic lithosphere is often assumed to be generated by fossilized texture formed during deformation at asthenospheric temperatures close to the ridge. Here we investigate the effect of high-temperature and high-pressure static annealing on the texture of previously deformed olivine aggregates to simulate residence of deformed peridotite in the lithosphere. Our experiments indicate that the orientation and magnitude of crystallographic preferred orientation (CPO) will evolve due to the preferential growth of grains with low dislocation densities. These observations suggest that texture and stored elastic strain energy promote a style of grain growth that modifies the CPO of a deformed aggregate. We demonstrate that these microstructural changes alter the orientation distributions and magnitudes of seismic wave velocities and anisotropy. Therefore, static annealing may complicate the inference of past deformation kinematics from seismic anisotropy in the lithosphere.

  19. Mid-lithosphere discontinuities beneath the western and central North China Craton

    Science.gov (United States)

    Sun, Weijia; Kennett, B. L. N.

    2017-02-01

    By analyzing P reflectivity extracted from stacked autocorrelograms for teleseismic events on a dense seismic profile, we obtain a detailed image of the mid-lithosphere discontinuity (MLD) beneath western and central North China Craton (NCC). This seismic daylight imaging exploits a broad high-frequency band (0.5-4 Hz) to reveal the fine-scale component of multi-scale lithospheric heterogeneity. The depth of the MLD beneath the western and central parts of the NCC ranges 80-120 km, with a good match to the transition to negative S velocity gradient with depth from Rayleigh wave tomography. The MLD inferred from seismic daylight imaging also has good correspondence with the transition from conductive to convective regimes estimated from heat flow data indicating likely thermal control within the seismological lithosphere.

  20. An Equivalent Source Method for Modelling the Lithospheric Magnetic Field Using Satellite and Airborne Magnetic Data

    DEFF Research Database (Denmark)

    Kother, Livia Kathleen; Hammer, Magnus Danel; Finlay, Chris

    for the remaining lithospheric magnetic field consists of magnetic point sources (monopoles) arranged in an icosahedron grid with an increasing grid resolution towards the airborne survey area. The corresponding source values are estimated using an iteratively reweighted least squares algorithm that includes model......We present a technique for modelling the lithospheric magnetic field based on estimation of equivalent potential field sources. As a first demonstration we present an application to magnetic field measurements made by the CHAMP satellite during the period 2009-2010. Three component vector field....... Advantages of the equivalent source method include its local nature and the ease of transforming to spherical harmonics when needed. The method can also be applied in local, high resolution, investigations of the lithospheric magnetic field, for example where suitable aeromagnetic data is available...

  1. Tectonically asymmetric Earth:From net rotation to polarized westward drift of the lithosphere

    Institute of Scientific and Technical Information of China (English)

    Carlo Doglioni; Eugenio Carminati; Mattia Crespi; Marco Cuffaro; Mattia Penati; Federica Riguzzi

    2015-01-01

    The possibility of a net rotation of the lithosphere with respect to the mantle is generally overlooked since it depends on the adopted mantle reference frames, which are arbitrary. We review the geological and geophysical signatures of plate boundaries, and show that they are markedly asym-metric worldwide. Then we compare available reference frames of plate motions relative to the mantle and discuss which is at best able to fit global tectonic data. Different assumptions about the depths of hotspot sources (below or within the asthenosphere, which decouples the lithosphere from the deep mantle) predict different rates of net rotation of the lithosphere relative to the mantle. The widely used no-net-rotation (NNR) reference frame, and low (1?/Ma) net rotation (shallow hotspots source), all plates, albeit at different velocity, move westerly along a curved trajectory, with a tectonic equator tilted about 30? relative to the geographic equator. This is consistent with the observed global tectonic asymmetries.

  2. Processes of lithosphere evolution: New evidence on the structure of the continental crust and uppermost mantle

    Science.gov (United States)

    Artemieva, I.M.; Mooney, W.D.; Perchuc, E.; Thybo, H.

    2002-01-01

    We discuss the structure of the continental lithosphere, its physical properties, and the mechanisms that formed and modified it since the early Archean. The structure of the upper mantle and the crust is derived primarily from global and regional seismic tomography studies of Eurasia and from global and regional data on seismic anisotropy. These data as documented in the papers of this special issue of Tectonophysics are used to illustrate the role of different tectonic processes in the lithospheric evolution since Archean to present. These include, but are not limited to, cratonization, terrane accretion and collision, continental rifting (both passive and active), subduction, and lithospheric basal erosion due to a relative motion of cratonic keels and the convective mantle. ?? 2002 Elsevier Science B.V. All rights reserved.

  3. Investigating Lithosphere Strength With Thin-Shell Tectonic Modeling

    Science.gov (United States)

    Moder, C.; Carena, S.

    2007-12-01

    The behavior of many major faults on Earth can only be explained if they are assumed to be much weaker than expected from Byerlee's Law alone. However, there is no agreement over what is a realistic range of friction parameters for faults, or its possible dependency on fault network geometry. Both can be studied with numerical forward modeling, but this requires knowledge of the detailed 3-D geometry of the faults. The latter is now available for most of California, thanks to the SCEC Community Fault Model (southern California) and to the USGS program "3-D Geologic Maps and Visualization" (San Francisco Bay and surrounding region). We model the behavior of the California fault network with the finite-element code SHELLS. We use as input a coarse global grid, with local high-resolution representation of actual faults based on the existing 3-D fault maps. By comparing the simulation results with data on fault-slip rates, we can determine how the faults in this network interact, the role of small faults, and we can quantify the typical fault strength in a continental transform plate boundary setting.

  4. 3-D seismic tomography of the lithosphere and its geodynamic implications beneath the northeast India region

    Science.gov (United States)

    Raoof, J.; Mukhopadhyay, S.; Koulakov, I.; Kayal, J. R.

    2017-05-01

    We have evolved 3-D seismic velocity structures in northeast India region and its adjoining areas to understand the geodynamic processes of Indian lithosphere that gently underthrusts under the Himalayas and steeply subducts below the Indo-Burma Ranges. The region is tectonically buttressed between the Himalayan arc to the north and the Indo-Burmese arc to the east. The tomographic image shows heterogeneous structure of lithosphere depicting different tectonic blocks. Though our results are limited to shallower depth (0-90 km), it matches well with the deeper continuation of lithospheric structure obtained in an earlier study. We observe low-velocity structure all along the Eastern Himalayas down to 70 km depth, which may be attributed to deeper roots/thicker crust developed by underthrusting of Indian plate. Parallel to this low-velocity zone lies a high-velocity zone in foredeep region, represents the Indian lithosphere. The underthrusting Indian lithosphere under the Himalayas as well as below the Indo-Burma Ranges is well reflected as a high-velocity dipping structure. The buckled up part of bending Indian plate in study region, the Shillong Plateau-Mikir Hills tectonic block, is marked as a high-velocity structure at shallower depth. The Eastern Himalayan Syntaxis, tectonic block where the two arcs meet, is identified as a high-velocity structure. The Bengal Basin, tectonic block to the south of Shillong Plateau, shows low velocity due to its thicker sediments. Based on the tomographic image, a schematic model is presented to elucidate the structure and geodynamics of Indian lithosphere in study region.

  5. Evolution of the Antarctic Peninsula lithosphere: Evidence from Mesozoic mafic rocks

    Science.gov (United States)

    Riley, T. R.; Curtis, M. L.; Flowerdew, M. J.; Whitehouse, M. J.

    2016-02-01

    New geochronology from a thick (> 800 m) basaltic succession along the eastern margin of the Antarctic Peninsula confirm a Middle Jurassic age (178 ± 1 Ma). This marginally postdates the adjacent Ferrar large igneous province of the Transantarctic Mountains and predates the extensive silicic volcanism of the Mapple Formation (~ 170 Ma) of the Antarctic Peninsula. The geochemistry of other rare, but broadly contemporaneous, basaltic successions of the Antarctic Peninsula, along with Cretaceous-age mafic dykes, are used to interpret the influences of lithospheric and asthenospheric mantle sources during the Mesozoic. Two significant high magmatic addition rate events occurred along the Antarctic Peninsula continental margin at 170 and 110 Ma and can be correlated to events along the South American Cordillera. These 'flare-up' events are characterised by extensive silicic (mostly ignimbrite) volcanism of the Chon Aike Province (V2 event: 170 Ma) and significant granitoid batholith emplacement of the Lassiter Coast intrusive suite (110 Ma). The 170 Ma event is exposed across large parts of the northern Antarctic Peninsula, whilst the 110 Ma event is more widespread across the southern Antarctic Peninsula. The basaltic volcanism described here precedes the 'flare-up' event at 170 Ma and has geochemical characteristics that indicate a thickened lithosphere prevailed. A major dyke swarm that followed the 170 Ma event indicates that extensive lithospheric thinning had occurred, which allowed the ascent of depleted mafic melts. The thinning was the direct result of widespread lower crustal/upper lithospheric melting associated with the silicic volcanism. In the southern Antarctic Peninsula, the lithosphere remained over thickened until the emplacement of the major batholiths of the Lassiter Coast intrusive suite at 110 Ma and was then immediately followed by the emplacement of more asthenosphere-like melts indicating extensive lithospheric thinning.

  6. Mechanical strength of extended continental lithosphere: Constraints from the Western Rift System, East Africa

    Science.gov (United States)

    Ebinger, Cynthia J.; Karner, Garry D.; Weissel, Jeffrey K.

    1991-12-01

    Although regional isostasy generally is associated with continental lithospheric compression and foreland basin formation, local isostatic compensation commonly is assumed in models of extensional basin formation. The assumption of negligible lithospheric strength during rifting often is justified on the basis of: (1) high heat flow and temperatures produced by elevating the lithosphere - asthenosphere boundary and (2) fracturing of the crust and lithosphere by normal faults. By modeling the development of rift basins within the Western rift system of East Africa and their associated free air gravity anomalies, we assess the role of basin-producing normal faults in modifying the flexural strength of extended lithosphere. Heat flow and seismicity data from the East African plateau region indicate that the Western rift system located on the western side of the plateau developed in old, cold continental lithosphere. These relatively narrow (40-70 km wide), but deep, basins are bounded along one side by high-angle border faults that penetrate to lower crustal levels, as indicated by seismicity data. Along the length of the Western rift system, depth to pre-rift basement and rift flank topography vary between basins from 1 to 8 km and from 1 to 2 km respectively, with deeper basins generally correlating with higher flanks. Comparison of model predictions with topography and free air gravity profiles reveals that the basin depth and the flank height in the majority of the Western rift basins studied can be explained simply by small heaves (3-10 km) across the border fault and with significant flexural strength of the lithosphere maintained during extension. Where both observed basin depth and flank height could not be reproduced, basins were located adjacent to eruptive volcanic centers active in Miocene-Recent times. In these areas, basin depth, rift flank elevation, and free air gravity anomaly may be modified by magmatic underplating of the crust. Estimates of

  7. Constraints on lithospheric thermal structure for the Indian Ocean from depth and heat flow data

    Science.gov (United States)

    Shoberg, Tom; Stein, Carol A.; Stein, Seth

    1993-06-01

    Models for the thermal evolution of oceanic lithosphere are primarily constrained by variations in seafloor depth and heat flow with age. These models have been largely based on data from the Pacific and Atlantic Ocean basins. We construct seafloor age relations for the Indian Ocean which we combine with bathymetric, sediment isopach and heat flow data to derive curves for depth and heat flow versus age. Comparison of these curves with predictions from three thermal models shows that they are better fit by the shallower depths and higher heat flow for the GDH1 model, which is characterized by a thinner and hotter lithosphere than previous models.

  8. Extremely depleted lithospheric mantle and diamonds beneath the southern Zimbabwe Craton

    Science.gov (United States)

    Smith, Chris B.; Pearson, D. Graham; Bulanova, Galina P.; Beard, Andrew D.; Carlson, Richard W.; Wittig, Nadine; Sims, Keith; Chimuka, Lovemore; Muchemwa, Ellah

    2009-11-01

    Inclusion-bearing diamonds, mantle xenoliths, and kimberlite concentrates from the Cambrian-aged Murowa and Sese kimberlites have been studied to characterise the nature of the lithospheric mantle beneath the southern Zimbabwe Craton. The diamonds are mostly octahedral, moderately rich in nitrogen with moderate to high aggregation, and contain mainly dunite-harzburgite mineral inclusions. Similarly, dunite xenoliths predominate over harzburgite and lherzolite and carry olivines with Mg/Mg + Fe (Mg#) values of 0.92-0.95, spanning the average signatures for Kaapvaal Craton peridotites. Eclogitic xenoliths are extremely rare, in contrast to the Kaapvaal mantle lithosphere. The Zimbabwe mantle assemblage has been only slightly affected by later silicic metasomatism and re-fertilisation with re-introduction of pyroxenes in contrast to the Kaapvaal and many cratonic lithospheric blocks elsewhere where strong metasomatism and re-fertilisation is widespread. Pyroxene, garnet and spinel thermobarometry suggests an ambient 40 mW m - 2 geotherm, with the lithosphere extending down to 210 km at the time of kimberlite eruption. Whole rock peridotite Re-Os isotope analyses yield T RD model ages of 2.7 to 2.9 Ga, providing minimum estimates of the time of melt depletion, are slightly younger in age than the basement greenstone formation. These model ages coincide with the mean T RD age of > 200 analyses of Kaapvaal Craton peridotites, whereas the average Re-Os model age for the Zimbabwe peridotites is 3.2 Ga. The Os data and low Yb n/Lu n ratios suggest a model whereby thick lithospheric mantle was stabilised during the early stages of crustal development by shallow peridotite melting required for formation of residues with sufficiently high Cr/Al to stabilise chromite which then transforms to low Ca, high Cr garnet. Sulphide inclusions in diamond produce minimum T RD model ages of 3.4 Ga indicating that parts of the lithosphere were present at the earliest stages of crust

  9. Use of along-track magnetic field differences in lithospheric field modelling

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Finlay, Chris; Olsen, Nils

    2015-01-01

    , using 2 yr of low altitude data from the CHAMP satellite, we show that use of along-track differences of vector field data results in an enhanced recovery of the small scale lithospheric field, compared to the use of the vector field data themselves. We show that the along-track technique performs....... Experiments in modelling the Earth's lithospheric magnetic field with along-track differences are presented here as a proof of concept. We anticipate that use of such along-track differences in combination with east–west field differences, as are now provided by the Swarm satellite constellation...

  10. Considerations of variations in ionospheric field effects in mapping equatorial lithospheric Magsat magnetic anomalies

    Science.gov (United States)

    Ravat, D.; Hinze, W. J.

    1993-01-01

    The longitudinal, seasonal, and altitude-dependent variability of the magnetic field in equatorial latitudes is investigated to determine the effect of these variabilities on the isolation of lithospheric Magsat magnetic anomalies. It was found that the amplitudes of the dawn dip-latitude averages were small compared to the dusk averages, and that they were of the opposite sign. The longitudinal variation in the equatorial amplitudes of the dawn dip-latitude averages was not entirely consistent with the present knowledge of the electrojet field. Based on the results, a procedure is implemented for reducing the equatorial ionospheric effects from the Magsat data on the lithospheric component.

  11. Spatial Patterns in Distribution of Kimberlites: Relationship to Tectonic Processes and Lithosphere Structure

    DEFF Research Database (Denmark)

    Chemia, Zurab; Artemieva, Irina; Thybo, Hans

    2014-01-01

    weakness zones may control the spatial patterns of kimberlites, but this hypothesis has never been tested by geophysical methods. As the first step in our analysis of tectonic and lithosphere control of kimberlite-type magmatism, we perform a detailed global analysis of the spatial patterns of kimberlites...... of kimberlite melts through the lithospheric mantle, which forms the major pipe. Stage 2 (second-order process) begins when the major pipe splits into daughter sub-pipes (tree-like pattern) at crustal depths. We apply cluster analysis to the spatial distribution of all known kimberlite fields with the goal...

  12. An Equivalent Source Method for Modelling the Global Lithospheric Magnetic Field

    DEFF Research Database (Denmark)

    Kother, Livia Kathleen; Hammer, Magnus Danel; Finlay, Chris

    2015-01-01

    are also employed to minimize the influence of the ionospheric field. The model for the remaining lithospheric magnetic field consists of magnetic equivalent potential field sources (monopoles) arranged in an icosahedron grid at a depth of 100 km belowthe surface. The corresponding model parameters......We present a new technique for modelling the global lithospheric magnetic field at Earth’s surface based on the estimation of equivalent potential field sources. As a demonstration we show an application to magnetic field measurements made by the CHAMP satellite during the period 2009–2010 when...

  13. An Equivalent Source Method for Modelling the Global Lithospheric Magnetic Field

    DEFF Research Database (Denmark)

    Kother, Livia Kathleen; Hammer, Magnus Danel; Finlay, Chris

    2014-01-01

    are also employed to minimize the influence of the ionospheric field. The model for the remaining lithospheric magnetic field consists of magnetic point sources (monopoles) arranged in an icosahedron grid. The corresponding source values are estimated using an iteratively reweighted least squares algorithm......We present a new technique for modelling the global lithospheric magnetic field at Earth's surface based on the estimation of equivalent potential field sources. As a demonstration we show an application to magnetic field measurements made by the CHAMP satellite during the period 2009-2010 when...

  14. Seismic evidence for whole lithosphere separation between Saxothuringian and Moldanubian tectonic units in central Europe

    OpenAIRE

    Heuer, B.; Horst Kämpf; Rainer Kind; W. H. Geissler

    2007-01-01

    The Bohemian Massif is part of the Variscan belt of central Europe. We carried out a high resolution mapping of lithospheric thickness beneath central Europe by investigating 264 teleseismic events recorded at 80 broad band stations in the western Bohemian Massif with the method of S receiver function analysis. A negative phase beneath the Saxothuringian and north-eastern Teplá-Barrandian units at about 9-10 s before the S onset is interpreted as caused by the lithosphere-asthenosphere bounda...

  15. Effects of recreational flow releases on natural resources of the Indian and Hudson Rivers in the Central Adirondack Mountains, New York, 2004-06

    Science.gov (United States)

    Baldigo, Barry P.; Mulvihill, C.I.; Ernst, A.G.; Boisvert, B.A.

    2011-01-01

    The U.S. Geological Survey (USGS), the New York State Department of Environmental Conservation (NYSDEC), and Cornell University carried out a cooperative 2-year study from the fall of 2004 through the fall of 2006 to characterize the potential effects of recreational-flow releases from Lake Abanakee on natural resources in the Indian and Hudson Rivers. Researchers gathered baseline information on hydrology, temperature, habitat, nearshore wetlands, and macroinvertebrate and fish communities and assessed the behavior and thermoregulation of stocked brown trout in study reaches from both rivers and from a control river. The effects of recreational-flow releases (releases) were assessed by comparing data from affected reaches with data from the same reaches during nonrelease days, control reaches in a nearby run-of-the-river system (the Cedar River), and one reach in the Hudson River upstream from the confluence with the Indian River. A streamgage downstream from Lake Abanakee transmitted data by satellite from November 2004 to November 2006; these data were used as the basis for developing a rating curve that was used to estimate discharges for the study period. River habitat at most study reaches was delineated by using Global Positioning System and ArcMap software on a handheld computer, and wetlands were mapped by ground-based measurements of length, width, and areal density. River temperature in the Indian and Hudson Rivers was monitored continuously at eight sites during June through September of 2005 and 2006; temperature was mapped in 2005 by remote imaging made possible through collaboration with the Rochester Institute of Technology. Fish communities at all study reaches were surveyed and characterized through quantitative, nearshore electrofishing surveys. Macroinvertebrate communities in all study reaches were sampled using the traveling-kick method and characterized using standard indices. Radio telemetry was used to track the movement and persistence of

  16. MID-MIOCENE SEQUENCES OF HIGH- AND MODERATE-MG VOLCANIC ROCKS IN VITIM PLATEAU, SOUTHERN SIBERIA: IMPACT OF A SUB-LITHOSPHERIC CONVECTIVE MATERIAL ON THE LITHOSPHERE

    Directory of Open Access Journals (Sweden)

    I. S. Chuvashova

    2015-09-01

    Full Text Available A comparative study of major elements, trace elements, and isotopes in high- and moderate-Mg volcanic sequences of 16–14 and 14–13 Ma, respectively, has been performed in the Bereya volcanic center. In the former (small volume sequence, contaminated by crustal material basalts and trachybasalts of K–Na series were followed by uncontaminated basanites and basalts of transitional (K–Na–K compositions and afterwards by picrobasalts and ba­salts of K series. From pressure estimates using equation [Scarrow, Cox, 1995], high-Mg magma originated at the deep range of 115–150 km. In the latter (high-volume sequence, basalts and basaltic andesites of transitional (Na–K–Na compositions and basalts of Na series were overlain by basalts and trachybasalts of K–Na series. First, there was a strong melting of its shallow garnet-free part with coeval weak melting of more deep garnet-bearing portion, then only a deep garnet-bearing portion of the lithospheric mantle melted. It is suggested that the sequential formation of high- and moderate-Mg melts reflected the mid-Miocene thermal impact of the lithosphere by hot material from the Transbaikalian low-velocity domain, which had the potential temperature Tp as high as 1510 °С. This thermal impact triggered the rifting in the lithosphere of the Baikal Rift System.

  17. Impact of the rheological layering of the lithosphere on the topography generated by sublithospheric density anomalies: Insights from analog modeling

    Science.gov (United States)

    Sembroni, A.; Globig, J.; Rozel, A.; Faccenna, C.; Funiciello, F.; Fernandez, M.

    2013-12-01

    Density anomalies located beneath the lithosphere are thought to generate dynamic topography at the surface of the Earth. Tomographic models are often used to infer the later variations of the density field in the mantle. Surface topography can then be computed using analytical solutions or numerical simulations of mantle convection. It has been shown that the viscosity profile of the upper mantle has a strong influence on the magnitude and spectral signature of surface topography and uplift rate. Here we present results from analogue modeling of the interaction between a rising ball-shaped density anomaly and the lithosphere in an isoviscous, isothermal Newtonian mantle system. Preliminary data show that surface topography is strongly influenced not only by mantle viscosity but also by density and viscosity profiles of the lithosphere. Our apparatus consists of a plexiglass square box (40x40x50 cm3) filled with glucose syrup. From the bottom a silicon ball was free to rise up until impinging a silicon plate floating on top of the syrup, mimicking the lithosphere. In order to investigate the role of lithospheric thickness and layered continental crust on stress partitioning, maximum dynamic topography, uplift rate and signal wavelength, two different configurations were tested: homogeneous lithosphere and stratified lithosphere including a low-viscosity lower crust. The topographic evolution of the surface was tracked using a laser scanning the top of the apparatus. The rise of the density anomaly was recorded by a side camera. We observe that a thick and then more resistant lithosphere makes up to 2 times lower and laterally wider topographic signatures. Layered lithospheres including a decoupling lower crust decrease the equilibrium topography and its lateral extend by ~30% to 40%. Most importantly, the uplift rate is strongly affected by the choice of lithosphere model. Both lithosphere width and the presence of a decoupling lower crust may modify the uplift

  18. Short- and long-term monitoring of underwater sound levels in the Hudson River (New York, USA).

    Science.gov (United States)

    Martin, S Bruce; Popper, Arthur N

    2016-04-01

    There is a growing body of research on natural and man-made sounds that create aquatic soundscapes. Less is known about the soundscapes of shallow waters, such as in harbors, rivers, and lakes. Knowledge of soundscapes is needed as a baseline against which to determine the changes in noise levels resulting from human activities. To provide baseline data for the Hudson River at the site of the Tappan Zee Bridge, 12 acoustic data loggers were deployed for a 24-h period at ranges of 0-3000 m from the bridge, and four of the data loggers were re-deployed for three months of continuous recording. Results demonstrate that this region of the river is relatively quiet compared to open ocean conditions and other large river systems. Moreover, the soundscape had temporal and spatial diversity. The temporal patterns of underwater noise from the bridge change with the cadence of human activity. Bridge noise (e.g., road traffic) was only detected within 300 m; farther from the bridge, boating activity increased sound levels during the day, and especially on the weekend. Results also suggest that recording near the river bottom produced lower pseudo-noise levels than previous studies that recorded in the river water column.

  19. Antimicrobial and Antioxidant Activity of the Essential Oils Obtained from Mentha longifolia L. Hudson, Dryed by Three Different Techniques

    Directory of Open Access Journals (Sweden)

    Dragana Stanisavljević

    2014-01-01

    Full Text Available The way of drying the fresh herbal material influences the chemical content and the biological activities of their essential oils. The influence of the different drying methods of the herb Mentha longifolia (L. Hudson on the antioxidant and antimicrobial activity of the extracted essential oils has been analyzed in this study. Drying has been carried out in three ways: in the natural way, in the laboratory oven (45°C and in the absorptional low-temperature condensational drier (35°C. The antioxidant activity of the essential oil has been estimated by FRAP and DPPH assays, while the antimicrobial activity has been estimated by the diffusible and micro-delusional method, testing on the nine types of bacteria and two types of fungi. The essential oil obtained from the herb dried in the natural way has shown the highest antioxidant activity and the lowest from the herb dried in the laboratory oven. Bacillus subtilis , Micrococcus luteus and Enterococcus faecalis have shown the highest sensitivity on the three samples. The oil obtained from the herb dried in the absorptional low-temperature drier has shown the strongest antimicrobial effect.

  20. Isolation of a flavonoid, apigenin 7-O-glucoside, from Mentha longifolia (L.) Hudson subspecies longifolia and its genotoxic potency.

    Science.gov (United States)

    Gulluce, Medine; Orhan, Furkan; Yanmis, Derya; Arasoglu, Tulin; Guvenalp, Zuhal; Demirezer, Lutfiye Omur

    2015-09-01

    Mentha is a medicinal and aromatic plant belonging to the Lamiaceae family, which is widely used in food, flavor, cosmetic and pharmaceutical industries. Recently, it has been found that the use of Mentha as a pharmaceutical source is based on its phytochemical constituents that have far been identified as tannins, saponins, phenolic acids and flavonoids. This study was designed to evaluate the mutagenic and antimutagenic activities of apigenin 7-O-glucoside (A7G), a flavonoid isolated from Mentha longifolia (L.) Hudson subspecies longifolia (ML). The possible antimutagenic potential of A7G was examined against mutagens ethyl methanesulfonate and acridine in an eukaryotic cell system Saccharomyces cerevisiae and sodium azide in Salmonella typhimurium TA1535 and 9-aminoacridine in S. typhimurium TA1537. According to our findings, any concentrations of the A7G used did not show mutagenic activity but exerted strong antimutagenic activities at tested concentrations. The inhibition rates for the Ames test ranged from 27.2% (S. typhimurium TA1535: 0.4 μM/plate) to 91.1% (S. typhimurium TA1537: 0.2 μM/plate) and for the yeast deletion assay from 4% to 57.7%. This genotoxicological study suggests that a flavonoid from ML owing to antimutagenic properties is of great pharmacological importance and might be beneficial to industries producing food additives, cosmetics and pharmaceuticals products.

  1. Impact of the Clean Water Act on the levels of toxic metals in urban estuaries: The Hudson River estuary revisited

    Energy Technology Data Exchange (ETDEWEB)

    Sanudo-Wilhelmy, S.A.; Gill, G.A.

    1999-10-15

    To establish the impact of the Clean Water Act on the water quality of urban estuaries, dissolved trace metals and phosphate concentrations were determined in surface waters collected along the Hudson River estuary between 1995 and 1997 and compared with samples collected in the mid-1970s by Klinkhammer and Bender. The median concentrations along the estuary have apparently declined 36--56% for Cu, 55--89% for Cd, 53--85% for Ni, and 53--90% for Zn over a period of 23 years. These reductions appear to reflect improvements in controlling discharges from municipal and industrial wastewater treatment plants since the Clean Water Act was enacted in 1972. In contrast, levels of dissolved nutrients (PO{sub 4}) have remained relatively constant during the same period of time, suggesting that wastewater treatment plant improvements in the New York/New Jersey Metropolitan area have not been as effective at reducing nutrient levels within the estuary. While more advanced wastewater treatment could potentially reduce the levels of Ag and PO{sub 4} along the estuary, these improvements would have a more limited effect on the levels of other trace metals.

  2. COMPOSITIONAL AND THERMAL DIFFERENCES BETWEEN LITHOSPHERIC AND ASTHENOSPHERIC MANTLE AND THEIR INFLUENCE ON CONTINENTAL DELAMINATION

    Directory of Open Access Journals (Sweden)

    A. I. Kiselev

    2015-09-01

    Full Text Available The lower part of lithosphere in collisional orogens may delaminate due to density inversion between the asthenosphere and the cold thickened lithospheric mantle. Generally, standard delamination models have neglected density changes within the crust and the lithospheric mantle, which occur due to phase transitions and compositional variations upon changes of P-T parameters. Our attention is focused on effects of phase and density changes that may be very important and even dominant when compared with the effect of a simple change of the thermal mantle structure. The paper presents the results of numerical modeling for eclogitization of basalts of the lower crust as well as phase composition changes and density of underlying peridotite resulted from tectonic thickening of the lithosphere and its foundering into the asthenosphere. As the thickness of the lower crust increases, the mafic granulite (basalt passes into eclogite, and density inversion occurs at the accepted crust-mantle boundary (P=20 kbar because the newly formed eclogite is heavier than the underlying peridotite by 6 % (abyssal peridotite, according to [Boyd, 1989]. The density difference is a potential energy for delamination of the eclogitic portion of the crust. According to the model, P=70 kbar and T=1300 °C correspond to conditions at the lower boundary of the lithosphere. Assuming the temperature adiabatic distribution within the asthenosphere, its value at the given parameters ranges from 1350 °C to 1400 °C. Density inversion at dry conditions occurs with the identical lithospheric and asthenospheric compositions at the expense of the temperature difference at 100 °C with the density difference of only 0.0022 %. Differences of two other asthenospheric compositions (primitive mantle, and lherzolite KH as compared to the lithosphere (abyssal peridotite are not compensated for by a higher temperature. The asthenospheric density is higher than that of the lithospheric base

  3. Constraining deformation at the lithosphere-asthenosphere boundary beneath the San Andreas fault with Sp phases

    Science.gov (United States)

    Fischer, K. M.; Ford, H. A.; Lekic, V.

    2013-12-01

    The geometry of deformation in the deep mantle lithosphere beneath strike-slip plate boundaries has been enigmatic, with models ranging from localized shear zones that are deep extensions of individual crustal faults to broad zones of diffuse, distributed shear with widths of hundreds of kilometers. Using seismic phases that convert from shear to compressional motion (Sp) at the base of the lithosphere beneath California, we find evidence for strike-slip deformation in the deepest mantle lithosphere beneath the central San Andreas fault that occurs over a horizontal width of 50 km or less. This study is based on over 135,000 Sp receiver functions from 730 seismic stations, including the Northern and Southern California Seismic Networks and the NSF EarthScope Transportable and Flexible Arrays. Individual Sp receiver functions were calculated using an extended-time multi-taper method and were migrated and stacked according to their three-dimensional conversion point locations using a model for crust (Lowry and Pérez-Gussinyé, 2011) and mantle (Obrebski et al., 2010 and 2011) velocity structure beneath each station and a spline-function representation of the Sp Fresnel zone. Sp conversion points at lithosphere-asthenosphere boundary depths are very dense on both sides of the San Andreas fault, and we interpreted the Sp common conversion point stack only at those nodes with information from more than 300 receiver functions. To the east of the plate boundary, a strong coherent Sp phase, indicative of a decrease in shear-wave velocity with depth, is present in the depth range where tomographic studies image the transition from high velocity lithosphere to low velocity asthenosphere. This phase, interpreted as the seismological lithosphere-asthenosphere boundary, has systematically lower amplitudes on the western side of the plate boundary, indicating that the drop in shear velocity from lithosphere to asthenosphere is either smaller or is distributed over a larger

  4. Constraining the rheology of the lithosphere and upper mantle with geodynamic inverse modelling

    Science.gov (United States)

    Kaus, Boris; Baumann, Tobias

    2016-04-01

    The rheology of the lithosphere is of key importance for the physics of the lithosphere. Yet, it is probably the most uncertain parameter in geodynamics as experimental rock rheologies have to be extrapolated to geological conditions and as existing geophysical methods such as EET estimations make simplifying assumptions about the structure of the lithosphere. In many geologically interesting regions, such as the Alps, Andes or Himalaya, we actually have a significant amount of data already and as a result the geometry of the lithosphere is quite well constrained. Yet, knowing the geometry is only one part of the story, as we also need to have an accurate knowledge on the rheology and temperature structure of the lithosphere. Here, we discuss a relatively new method that we developed over the last few years, which is called geodynamic inversion. The basic principle of the method is simple: we compile available geophysical data into a realistic geometric model of the lithosphere and incorporate that into a thermo-mechanical numerical model of lithospheric deformation. In order to do so, we have to know the temperature structure, the density and the (nonlinear) rheological parameters for various parts of the lithosphere (upper crust, upper mantle, etc.). Rather than fixing these parameters we assume that they are all uncertain. This is used as a priori information to formulate a Bayesian inverse problem that employs topography, gravity, horizontal and vertical surface velocities to invert for the unknown material parameters and temperature structure. In order to test the general methodology, we first perform a geodynamic inversion of a synthetic forward model of intra-oceanic subduction with known parameters. This requires solving an inverse problem with 14-16 parameters, depending on whether temperature is assumed to be known or not. With the help of a massively parallel direct-search combined with a Markov Chain Monte Carlo method, solving the inverse problem

  5. Lithospheric Rheology Constrained by Loading of the Hawaiian Islands and its Implications for the Dynamics of Plate Tectonics

    Science.gov (United States)

    Zhong, S.; Watts, A. B.

    2013-12-01

    Lithospheric rheology is important for understanding crustal and lithospheric dynamics, and the conditions for plate tectonics. For example, numerical modeling studies suggest that plate tectonics emerge from the dynamics of mantle convection when a small coefficient of friction (significantly to match the observations, together with frictional coefficient in the range from 0.1 to 0.7. However, the small coefficient of friction weakens the shallow part of the lithosphere so much that it causes the minima in strain rate and stress to occur at too large depths to be consistent with the depth distribution of seismicity at Hawaii. Our results therefore suggest that the coefficient of friction is between 0.25 and 0.7. Finally, maximum lithospheric stress under Hawaiian loads is about 100-200 MPa for models that match the observations, and this stress may be viewed as the largest lithospheric stress on the Earth.

  6. Samovar: a thermomechanical code for modeling of geodynamic processes in the lithosphere-application to basin evolution

    DEFF Research Database (Denmark)

    Elesin, Y; Gerya, T; Artemieva, Irina;

    2010-01-01

    We present a new 2D finite difference code, Samovar, for high-resolution numerical modeling of complex geodynamic processes. Examples are collision of lithospheric plates (including mountain building and subduction) and lithosphere extension (including formation of sedimentary basins, regions...... of extended crust, and rift zones). The code models deformation of the lithosphere with viscoelastoplastic rheology, including erosion/sedimentation processes and formation of shear zones in areas of high stresses. It also models steady-state and transient conductive and advective thermal processes including...... partial melting and magma transport in the lithosphere. The thermal and mechanical parts of the code are tested for a series of physical problems with analytical solutions. We apply the code to geodynamic modeling by examining numerically the processes of lithosphere extension and basin formation...

  7. Bayes reconstruction of missing teeth

    DEFF Research Database (Denmark)

    Sporring, Jon; Jensen, Katrine Hommelhoff

    2008-01-01

     We propose a method for restoring the surface of tooth crowns in a 3D model of a human denture, so that the pose and anatomical features of the tooth will work well for chewing. This is achieved by including information about the position and anatomy of the other teeth in the mouth. Our system...... contains two major parts: A statistical model of a selection of tooth shapes and a reconstruction of missing data. We use a training set consisting of 3D scans of dental cast models obtained with a laser scanner, and we have build a model of the shape variability of the teeth, their neighbors...... regularization of the log-likelihood estimate based on differential geometrical properties of teeth surfaces, and we show general conditions under which this may be considered a Bayes prior.Finally we use Bayes method to propose the reconstruction of missing data, for e.g. finding the most probable shape...

  8. Probability Theory without Bayes' Rule

    OpenAIRE

    Rodriques, Samuel G.

    2014-01-01

    Within the Kolmogorov theory of probability, Bayes' rule allows one to perform statistical inference by relating conditional probabilities to unconditional probabilities. As we show here, however, there is a continuous set of alternative inference rules that yield the same results, and that may have computational or practical advantages for certain problems. We formulate generalized axioms for probability theory, according to which the reverse conditional probability distribution P(B|A) is no...

  9. Introduction of sub-lithospheric component into melted lithospheric base by propagating crack: Case study of migrated Quaternary volcanoes in Wudalianchi, China

    Science.gov (United States)

    Chuvashova, Irina; Sun, Yi-min

    2016-04-01

    From a long-lasted discussion on origin of mantle magmatism (i.e. Foulger, 2010), it follows that magmatic sources might belong to: (1) a plume, starting from the lower thermal boundary layer of the mantle, (2) a counterflow from the lower mantle after an avalanche of slab material from the transition layer, (3) a melting anomaly of a domain that extends above the transition layer at depths of 200-410 km, (4) a melting anomaly of a domain that occurs beneath the lithosphere at depths of 50-200 km, (5) a melting anomaly of the lithospheric base, activated due to its extension, and (6) a melting anomaly of the crust-mantle boundary originated through delamination of an orogenic root in compressional conditions. In this study, we present geological and geochemical evidence on the Quaternary volcanism related to the shallow melting anomaly at the lithospheric base. Eruptions of potassic liquids at the northern terminus of the Songliao basin, subsided from the Middle Jurassic to Paleogene, are limited to the Wudalianchi zone that is exhibited by the 230-km long north-south chain of late Cenozoic volcanic fields: Erkeshan - Wudalianchi - Keluo - Xiaogulihe. Contemporaneous eruptions of potassic-sodic melts are distributed at the western and eastern flanks of this zone, in the Nuominhe and Wuyiling volcanic fields, respectively. The melting anomaly is marked by local decreasing S-wave velocities at a depth of 100 km (Rasskazov et al., 2014). Lithospheric control of the potassic volcanism is emphasized by decreasing thickness of the crust up to 33.5 km (Wang, Chen, 2005). In the Wudalianchi field, volcanism commenced at ca. 2.3 Ma and episodically rejuvenated until AD1720-1721 (Guide book ..., 2010). From comparative geochemical study of volcanic rocks from the Wudalianchi zone and Nuominhe volcanic field, the volcanism was examined to be provided by melting of the heterogeneous lithospheric base, material of which was mixed with a common sub-lithospheric component. Due to

  10. Channeling at the base of the lithosphere during the lateral flow of plume material beneath flow line hot spots

    Science.gov (United States)

    Sleep, Norman H.

    2008-08-01

    Chains of volcanic edifices lie along flow lines between plume-fed hot spots and the thin lithosphere at ridge axes. Discovery and Euterpe/Musicians Seamounts are two examples. An attractive hypothesis is that buoyant plume material flows along the base of the lithosphere perpendicular to isochrons. The plume material may conceivably flow in a broad front or flow within channels convectively eroded into the base to the lithosphere. A necessary but not sufficient condition for convective channeling is that the expected stagnant-lid heat flow for the maximum temperature of the plume material is comparable to the half-space surface heat flow of the oceanic lithosphere. Two-dimensional and three-dimensional numerical calculations confirm this inference. A second criterion for significant convective erosion is that it needs to occur before the plume material thins by lateral spreading. Scaling relationships indicate spreading and convection are closely related. Mathematically, the Nusselt number (ratio of convective to conductive heat flow in the plume material) scales with the flux (volume per time per length of flow front) of the plume material. A blob of unconfined plume material thus spreads before the lithosphere thins much and evolves to a slowly spreading and slowly convecting warm region in equilibrium with conduction into the base of the overlying lithosphere. Three-dimensional calculations illustrate this long-lasting (and hence observable) state of plume material away from its plume source. A different flow domain occurs around a stationary hot plume that continuously supplies hot material. The plume convectively erodes the overlying lithosphere, trapping the plume material near its orifice. The region of lithosphere underlain by plume material grows toward the ridge axis and laterally by convective thinning of the lithosphere at its edges. The hottest plume material channels along flow lines. Geologically, the regions of lithosphere underlain by either warm

  11. Zooplankton Biomass Data from Prince William Sound, Icy Bay and Yakutat Bay, Alaska 2010-2011

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This dataset includes zooplankton biomass from Prince William Sound, Icy Bay and Yakutat Bay, Alaska. Zooplankton were sampled with a ring net (0.6 m diameter with...

  12. Simulation of Pollutant Transport in Marmaris Bay

    Institute of Scientific and Technical Information of China (English)

    Lale BALAS

    2001-01-01

    The circulation pattern and the pollutant transport in the Marmaris Bay are simulated by the developed three-dimensional baroclinic model. The Marmaris Bay is located at the Mediterranean Sea coast of Turkey. Since the sp ring tidal range is typically 20~30 cm, the dominant forcing for the circulation and water exchange is due to the wind action. In the Marmaris Bay, there is sea outfall discharging directly into the bay, and that threats the bay water quality significantly. The current patterns in the vicinity of the outfall have been observed by tracking drogues which are moved by currents at different water depths. In the simulations of pollutant transport, the coliforms-counts is used as the tracer.The model provides realistic predictions for the circulation and pollutant transport in the Marmaris Bay. The transport model component predictions well agree with the results of a laboratory model study.

  13. Towards an improved determination of Earth’s lithospheric field from satellite observations

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Olsen, Nils; Finlay, Chris

    the lithospheric signal is contaminated by much larger and highly time-dependent contributions from sources in the ionosphere and magnetosphere. Simultaneous, high-quality measurements from different locations as well as gradient estimates provided by the three Swarm satellites open new possibilities...

  14. Shallow and buoyant lithospheric subduction : causes and implications from thermo-chemical numerical modeling

    NARCIS (Netherlands)

    Hunen, Jeroen van

    2001-01-01

    Where two lithospheric plates converge on the Earth, one of them disappears into the mantle. The dominant driving mechanism for plate motion is regarded to be `slab pull': the subducted plate, the slab, exerts a pulling force on the attached plate at the surface. However, what has been puzzling geod

  15. Abnormal lithium isotope composition from the ancient lithospheric mantle beneath the North China Craton.

    Science.gov (United States)

    Tang, Yan-Jie; Zhang, Hong-Fu; Deloule, Etienne; Su, Ben-Xun; Ying, Ji-Feng; Santosh, M; Xiao, Yan

    2014-03-04

    Lithium elemental and isotopic compositions of olivines in peridotite xenoliths from Hebi in the North China Craton provide direct evidence for the highly variable δ(7)Li in Archean lithospheric mantle. The δ(7)Li in the cores of olivines from the Hebi high-Mg# peridotites (Fo > 91) show extreme variation from -27 to +21, in marked deviation from the δ(7)Li range of fresh MORB (+1.6 to +5.6) although the Li abundances of the olivines are within the range of normal mantle (1-2 ppm). The Li abundances and δ(7)Li characteristics of the Hebi olivines could not have been produced by recent diffusive-driven isotopic fractionation of Li and therefore the δ(7)Li in the cores of these olivines record the isotopic signature of the subcontinental lithospheric mantle. Our data demonstrate that abnormal δ(7)Li may be preserved in the ancient lithospheric mantle as observed in our study from the central North China Craton, which suggest that the subcontinental lithospheric mantle has experienced modification of fluid/melt derived from recycled oceanic crust.

  16. Microcosmic analysis of ductile shearing zones of coal seams of brittle deformation domain in superficial lithosphere

    Institute of Scientific and Technical Information of China (English)

    JU; Yiwen; WANG; Guiliang; JIANG; Bo; HOU; Quanlin

    2004-01-01

    The ductile shearing zones of coal seams in a brittle deformation domain in superficial lithosphere are put forward based on the study on bedding shearing and ductile rheology of coal seams. The macrocosmic and microcosmic characteristics include wrinkle fold, mymonitized zones and ductile planar structure of coal seams, etc., while the microcosmic characteristics may also include different optic-axis fabrics and the anisotropy of vitrinite reflectance as well as the change of chemical structure and organic geochemistry components. The forming mechanism is analyzed and the strain environment of ductile shearing zones of coal seams discussed. The result indicates that, in the superficial brittle deformation domain, the coal seams are easy to be deformed, resulting in not only brittle deformation but also ductile shearing deformation under the action of force. Because of simple shearing stress, the interlayer gliding or ductile rheology may take place between coal seams and wall rocks. Therefore, many ductile shearing zones come into being in superficial lithosphere (<5 km). The research on ductile shearing zone of brittle deformation domain in superficial lithosphere is significant not only theoretically for the study of ductile shearing and ductile rheology of the lithosphere but also practically for the structural movement of coal seams, the formation and accumulation of coal-bed methane, and the prevention and harness of gas burst in coal mine.

  17. The effect of bimineralic composition on extensional processes at lithospheric scale

    Science.gov (United States)

    Jammes, Suzon; Lavier, Luc L.

    2016-08-01

    We investigate how lithospheric scale compositional heterogeneities affect kilometric scale deformation processes. To this end, we perform numerical experiments of lithospheric extension in which we vary the Moho temperature and the mineralic composition of the mantle and the crust. In both the crust and the mantle, we use an explicit bimineralic composition by randomly distributing two mineral phases in the materials. Comparison of our models to simulations using an implicit bimineralic composite (one average viscous flow laws for a two-phase aggregate) crust and mantle demonstrates that an explicit bimineralic composition assimilated to heterogeneities succeeds in explaining observations related to the formation of rifted margins such a: (1) the absence of a sharp deformation zone at the brittle ductile transition (BDT), (2) the initiation of the rifting process as a wide delocalized rift system with multiple normal faults dipping in both directions; (3) the development of anastomosing shear zones in the middle/lower crust and the upper lithospheric mantle similar to the crustal scale anastomosing patterns observed in the field or in seismic data; (4) the preservation of undeformed lenses of material leading to lithospheric scale boudinage structure and resulting in the formation of continental ribbons as observed along the Iberian-Newfoundland margin.

  18. Interplay of variable thermal conductivity and expansivity on the thermal structure of oceanic lithosphere II

    Science.gov (United States)

    Honda, S.; Yuen, D. A.

    2004-04-01

    We have extended our previous analysis of the effects of constant vs. variable, i.e., pressure and temperature dependent thermal conductivity (k) and constant thermal expansivity (a) on the thermal structure of the oceanic lithosphere. We apply our analysis to the actual data set including information on the geoid slope. The heat flow and ocean floor depth data constrain the thermal expansivity (a ≍ 3 × 10-5 1/°C). Including geoid slope data may loosely constrain both the thermal expansivity and the thermal conductivity. The probable value of thermal conductivity is ≍ 3 W/m/°C for the constant k case and ≍ 4 W/m/°C (at ambient conditions) for the variable k case. These a and k are generally consistent with laboratory data of appropriate lithospheric materials. Our analysis supports the plate model with thin lithosphere and high bottom temperature, such as GDH1 (95 km; 1450°C). Variable k case requires slightly thinner and higher temperature lithosphere (≍ 85 km and ≍ 1500°C) and gives a slightly better fit to the geoid slope data.

  19. Comparison of plate and asthenospheric flow models for the thermal evolution of oceanic lithosphere

    Science.gov (United States)

    Stein, Carol A.; Stein, Seth

    1994-04-01

    Although seafloor depth and heat flow for young oceanic lithosphere can be descibed by modeling the lithosphere as the boundary layer of a cooling halfspace, a long standing question has been why data at older ages deviate from those expected for a halfspace. Two classes of models have been proposed for these deviations. In one, heat added from below 'flattens' depth and heat flow. In the other, asthenospheric flow beneath the lithosphere perturbs the depths. We compare recent versions of the model classes: the GDH1 thin-lithosphere plate model (Stein and Stein, 1992) and an asthenospehric flow model (Phipps Morgan and Smith, 1992). The plate model fits heat flow data better than the flow model for all cases considered, and topographic data in all but one case. The flow model significantly overpredicts depths for the North Atlantic, because the assumed asthenospheric flow in the plate motion direction would yield deepening for old ages rather than the observed flattening. Overall, the GDH1 global average model does better than this flow model, whose parameters were fit to specific plates. Moreover, the plate models fit to specific plates do better than the flow model. Plate models thus appear more useful than this flow model, suggesting that deviations from a cooling halfspace are largely thermal in origin.

  20. Offshore Southern California lithospheric velocity structure from noise cross-correlation functions

    Science.gov (United States)

    Bowden, D. C.; Kohler, M. D.; Tsai, V. C.; Weeraratne, D. S.

    2016-05-01

    A new shear wave velocity model offshore Southern California is presented that images plate boundary deformation including both thickening and thinning of the crustal and mantle lithosphere at the westernmost edge of the North American continent. The Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment (ALBACORE) ocean bottom seismometer array, together with 65 stations of the onshore Southern California Seismic Network, is used to measure ambient noise correlation functions and Rayleigh wave dispersion curves which are inverted for 3-D shear wave velocities. The resulting velocity model defines the transition from continental lithosphere to oceanic, illuminating the complex history and deformation in the region. A transition to the present-day strike-slip regime between the Pacific and North American Plates resulted in broad deformation and capture of the now >200 km wide continental shelf. Our velocity model suggests the persistence of the uppermost mantle volcanic processes associated with East Pacific Rise spreading adjacent to the Patton Escarpment, which marks the former subduction of Farallon Plate underneath North America. The most prominent of these seismic structures is a low-velocity anomaly underlying the San Juan Seamount, suggesting ponding of magma at the base of the crust, resulting in thickening and ongoing adjustment of the lithosphere due to the localized loading. The velocity model also provides a robust framework for future earthquake location determinations and ground-shaking simulations for risk estimates.