Science.gov

Sample records for adjacent ocean basins

  1. Gulf of California analogue for origin of Late Paleozoic ocean basins adjacent to western North America

    SciTech Connect

    Murchey, B.L. )

    1993-04-01

    Ocean crust accreted to the western margin of North America following the Late Devonian to earliest Missippian Antler orogeny is not older than Devonian. Therefore, ocean crust all along the margin of western North America may have been very young following the Antler event. This situation can be compared to the present-day margin of North America which lies adjacent to young ocean crust as a result of the subduction of the Farallon plate and arrival of the East Pacific spreading ridge. Syn- and post-Antler rifting that occurred along the North American margin may well be analogous to the formation of the Gulf of California by the propagation of the East Pacific spreading ridge. Black-arc rifting associated with the subduction of very old ocean crust seems a less likely mechanism for the early stages of ocean basin formation along the late Paleozoic margin of western North America because of the apparent absence of old ocean crust to the west of the arc terranes. The eastern Pacific basins were as long-lived as any truly oceanic basins and may have constituted, by the earliest Permian, a single wedge-shaped basin separated from the western Pacific by rifted fragments of North American arc-terranes. In the Permian, the rifted arcs were once again sites of active magmatism and the eastern Pacific basins began to close, from south (Golconda terrane) to north. Final closure of the northernmost eastern Pacific basin (Angayucham in Alaska) did not occur until the Jurassic.

  2. A modern analog for carbonate source-to-sink sedimentary systems: the Glorieuses archipelago and adjacent basin (SW Indian Ocean)

    NASA Astrophysics Data System (ADS)

    Jorry, S.; Jouet, G.; Prat, S.; Courgeon, S.; Le Roy, P.; Camoin, G.; Caline, B.

    2014-12-01

    This study presents the geomorphological and sedimentological analysis of a modern carbonate source-to-sink system located north of Madagascar (SW Indian Ocean). The sedimentary system is composed of an isolated carbonate platform sited on top of a seamount rising steeply from the seabed located at 3000 m water depth. The slope of the seamount is incised by canyons, and meandering channels occur above lobbed sedimentary bodies at the foot of the slope. The dataset consists of dredges, sediment piston cores, swath bathymetry and seismic (sparker and 2D high-resolution) lines collected from inner platform (less than 5 m deep) to the adjacent deep sedimentary basin. Particle size analysis and composition of carbonate grains are used to characterize the distribution and heterogeneity of sands accumulated on the archipelago. Main results show that composition of carbonate sediments is dominated by segments of Halimeda, large benthic foraminifera, coral debris, molluscs, echinoderms, bryozoans and sponges. According to the shape and the position of sandwaves and intertidal sandbars developed in the back-barrier reef, the present organization of these well-sorted fine-sand accumulations appears to be strongly influenced by flood tidal currents. Seismic lines acquired from semi-enclosed to open lagoon demonstrate that most of the sediment is exported and accumulated along the leeward margin of the platform, which is connected to a canyon network incising the outer slope. Following the concept of highstand shedding of carbonate platforms (Schlager et al., 1994), excess sediment is exported by plumes and gravity flows to the adjacent deep sea where it feeds a carbonate deep-sea fan. Combined observations from platform to basin allow to explain how the Glorieuses carbonate source to sink system has evolved under the influence of climate and of relative sea-level changes since the last interglacial.

  3. Seismic structure of the crust and uppermost mantle of north America and adjacent oceanic basins: A synthesis

    USGS Publications Warehouse

    Chulick, G.S.; Mooney, W.D.

    2002-01-01

    We present a new set of contour maps of the seismic structure of North America and the surrounding ocean basins. These maps include the crustal thickness, whole-crustal average P-wave and S-wave velocity, and seismic velocity of the uppermost mantle, that is, Pn and Sn. We found the following: (1) The average thickness of the crust under North America is 36.7 km (standard deviation [s.d.] ??8.4 km), which is 2.5 km thinner than the world average of 39.2 km (s.d. ?? 8.5) for continental crust; (2) Histograms of whole-crustal P- and S-wave velocities for the North American crust are bimodal, with the lower peak occurring for crust without a high-velocity (6.9-7.3 km/sec) lower crustal layer; (3) Regions with anomalously high average crustal P-wave velocities correlate with Precambrian and Paleozoic orogens; low average crustal velocities are correlated with modern extensional regimes; (4) The average Pn velocity beneath North America is 8.03 km/sec (s.d. ?? 0.19 km/sec); (5) the well-known thin crust beneath the western United States extends into northwest Canada; (6) the average P-wave velocity of layer 3 of oceanic crust is 6.61 km/ sec (s.d. ?? 0.47 km/sec). However, the average crustal P-wave velocity under the eastern Pacific seafloor is higher than the western Atlantic seafloor due to the thicker sediment layer on the older Atlantic seafloor.

  4. Petroleum basins of Sakhalin and adjacent shelf

    SciTech Connect

    Mavrinski, Y.; Koblov, E. )

    1993-09-01

    Sixty-seven oil and gas fields have been discovered on Sakhalin and the adjacent shelf but the distribution of fields is uneven in north Sakhalin, south Sakhalin, and the Tatar basins. The sedimentary cover is composed of sandy, clayey, and siliceous rocks, with volcanogenic and coal-bearing deposits of Upper Cretaceous, Paleogene, and Neogene 8-12 km thick. Marine clayey and siliceous oil source rocks are regionally developed in the section at different stratigraphic levels; the organic matter is of mixed type and the content varies from 0.5 to 1.5%. The upper Oligocene and middle-upper Miocene source rocks in the north Sakhalin basin are typical, and the organic carbon content ranges from 1 to 5%. The level of organic matter catagenesis and conversion into hydrocarbons is high because of the high differential geothermal gradient in the basins, 30-50[degrees]C per km. Porous sandstones in the Miocene form the reservoirs in all fields with the exception of Okruzhnoye, where the pay zone is a siliceous claystone. Growth-fault rollovers and anticlines form the main traps ranging in area from 5 to 300 km[sup 2], with amplitudes between 100 and 600 m. both stratigraphic and structural traps have been identified. Considerable volumes of reserves are associated with the Miocene deposits of north Sakhalin, which are characterized by an optimum combination of oil source rocks, focused migration paths, and thick sequences of reservoirs and cap rocks. Six large fields have been discovered in the past 15 yr. Oil and condensate reserves stand at over 300 million MT, and gas reserves are about 900 billion m[sup 3].

  5. Aleutian basin oceanic crust

    USGS Publications Warehouse

    Christeson, Gail L.; Barth, Ginger A.

    2015-01-01

    We present two-dimensional P-wave velocity structure along two wide-angle ocean bottom seismometer profiles from the Aleutian basin in the Bering Sea. The basement here is commonly considered to be trapped oceanic crust, yet there is a change in orientation of magnetic lineations and gravity features within the basin that might reflect later processes. Line 1 extends ∼225 km from southwest to northeast, while Line 2 extends ∼225 km from northwest to southeast and crosses the observed change in magnetic lineation orientation. Velocities of the sediment layer increase from 2.0 km/s at the seafloor to 3.0–3.4 km/s just above basement, crustal velocities increase from 5.1–5.6 km/s at the top of basement to 7.0–7.1 km/s at the base of the crust, and upper mantle velocities are 8.1–8.2 km/s. Average sediment thickness is 3.8–3.9 km for both profiles. Crustal thickness varies from 6.2 to 9.6 km, with average thickness of 7.2 km on Line 1 and 8.8 km on Line 2. There is no clear change in crustal structure associated with a change in orientation of magnetic lineations and gravity features. The velocity structure is consistent with that of normal or thickened oceanic crust. The observed increase in crustal thickness from west to east is interpreted as reflecting an increase in melt supply during crustal formation.

  6. Mesozoic tectonics and paleogeography of the western U. S. and the adjacent Pacific basin

    SciTech Connect

    Dilek, Y. )

    1990-06-01

    Recent geological, geochemical, and geochronological information from Jurassic and older ophiolite complexes and arc rocks in northern California provides new interpretations for Mesozoic tectonics of the western US and the adjacent Pacific basin. This information is discussed in conjunction with the Mesozoic tectonics and paleogeography of the western United States and the Pacific Ocean.

  7. Crustal architecture and deep structure of the Namibian continental shelf and adjacent oceanic basins around the landfall of Walvis Ridge from wide-angle seismic and marine magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Planert, L.; Behrmann, J.; Jegen, M.; Heincke, B.; Jokat, W.; Bialas, J.; Marti, A.

    2012-12-01

    results for a marine magnetotelluric profile. Tomographic analysis of the seismic data reveals the velocity structure of the crust down into the uppermost mantle. The probably most striking feature of our models is the sharp lateral transition in crustal structure and thickness associated with the northern boundary zone of Walvis Ridge towards the Angola Basin. Here, the rather thin oceanic crust in the basin lies opposite to the ~35 km thick igneous crustal root founding the highest elevated northern portions of Walvis Ridge. In contrast, the southern termination of Walvis Ridge and the corresponding transition towards the adjacent 25-30 km thick crustal portions further south is much more subdued. Due to the presence of a high-velocity (6.5-7.2 km/s) lower crust we argue that the Namibian shelf south of Walvis Ridge comprises a transitional igneous origin. We suggest that the northern boundary zone close to the landfall of Walvis Ridge represents an important transtensional tectonic feature which may have provoked the preferential extraction of melts into the footwall of this structure.

  8. Origin of the earth's ocean basins

    NASA Technical Reports Server (NTRS)

    Frey, H.

    1977-01-01

    The earth's original ocean basins are proposed to be mare-type basins produced 4 billion y.a. by the flux of asteroid-sized objects responsible for the lunar mare basins. Scaling upward from the observed number of lunar basins for the greater capture cross-section and impact velocity of the earth indicates that at least 50% of an original global crust would have been converted to basin topography. These basins were flooded by basaltic liquids in times short compared to the isostatic adjustment time for the basin. The modern crustal dichotomy (60% oceanic, 40% continental crust) was established early in the history of the earth, making possible the later onset of plate tectonic processes. These later processes have subsequently reworked, in several cycles, principally the oceanic parts of the earth's crust, changing the configuration of the continents in the process. Ocean basins (and oceans themselves) may be rare occurrences on planets in other star systems.

  9. Origin of the earth's ocean basins

    NASA Technical Reports Server (NTRS)

    Frex, H.

    1977-01-01

    The earth's original ocean basins were mare-type basins produced 4 billion years ago by the flux of asteroid-sized objects responsible for the lunar mare basins. Scaling upwards from the observed number of lunar basins for the greater capture cross-section and impact velocity of the Earth indicates that at least 50 percent of an original global crust would have been converted to basin topography. These basins were flooded by basaltic liquids in times short compared to the isostatic adjustment time for the basin. The modern crustal dichotomy (60 percent oceanic, 40 percent continental crust) was established early in the history of the earth, making possible the later onset of plate tectonic processes. These later processes have subsequently reworked, in several cycles, principally the oceanic parts of the earth's crust, changing the configuration of the continents in the process. Ocean basins (and oceans themselves) may be rare occurrences on planets in other star systems.

  10. Oceanic basins in prehistory of the evolution of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Khain, V. E.; Filatova, N. I.

    2010-06-01

    During geodynamic reconstruction of the Late Mezozoic-Cenozoic evolution of the Arctic Ocean, a problem arises: did this ocean originate as a legacy structure of ancient basins, or did it evolve independently? Solution of this problem requires finding indicators of older oceanic basins within the limits of the Arctic Region. The Arctic Region has structural-material complexes of several ancient oceans, namely, Mesoproterozoic, Late Neoproterozoic, Paleozoic (Caledonian and Hercynian), Middle Paleozoic-Late Jurassic, and those of the Arctic Ocean, including the Late Jurassic-Early Cretaceous Canadian, the Late Cretaceous-Paleocene Podvodnikov-Makarov, and the Cenozoic Eurasian basins. The appearances of all these oceans were determined by a complex of global geodynamical factors, which were principally changed in time, and, as a result of this, location and configuration of newly opened oceans, as well as ones of adjacent continents, which varied from stage to stage. By the end of the Paleozoic, fragments of the crust corresponding to Precambrian and Caledonian oceans were transported during plate-tectonic motions from southern and near equatorial latitudes to moderately high and arctic ones, and, finally, became parts of the Pangea II supercontinent. The Arctic Ocean that appeared after the Pangea II breakup (being a part of the Atlantic Ocean) has no direct either genetic or spatial relation with more ancient oceans.

  11. Evidence for a thick oceanic crust adjacent to the Norwegian Margin

    NASA Astrophysics Data System (ADS)

    Mutter, John C.; Talwani, Manik; Stoffa, Paul L.

    1984-01-01

    The oceanic crust created during this first few million years of accretion in the Norwegian-Greenland Sea lies at an unusually shallow depth for its age, has a smooth upper surface, and in many places the results of multichannel seismic reflection profiling reveal that its upper layers comprise a remarkable sequence of arcuate, seaward-dipping reflectors. These have been attributed to lava flows generated during a brief period of subaerial seafloor spreading. We describe the results of inversions of digitally recorded sonobuoy measurements and two-ship expanded spread profiles collected over the oceanic crust adjacent to the Norwegian passive margin. We find that the crust of the deep Lofoten Basin is indistinguishable from normal oceanic crust in thickness and structure. Closer to the margin we observe up to a four times expansion in thickness of layers with velocities equal to those of oceanic layer 2, while the layer 3 region retains approximately the same thickness. The area over which the seaward-dipping reflectors can be observed on reflection profiles corresponds to the region of greatest expansion in "Layer 2" thickness. In the very oldest crust immediately adjacent to an escarpment that probably marks the continent-ocean boundary, we see evidence for a low velocity zone overlying an indistinct reflector that may mark the dyke-lava interface in the thick crust. Comparing the structure of the thick crust to that of eastern Iceland, we find a strong resemblance, especially in the expansion in thickness of material with layer 2 velocities. These results support the suggestion that during the earliest stages of spreading extrusive volcanism at the ridge crest was unusually voluminous, building a thick pile of lavas erupted from a subaerial spreading center.

  12. Downscaling ocean conditions with application to the Gulf of Maine, Scotian Shelf and adjacent deep ocean

    NASA Astrophysics Data System (ADS)

    Katavouta, Anna; Thompson, Keith R.

    2016-08-01

    The overall goal is to downscale ocean conditions predicted by an existing global prediction system and evaluate the results using observations from the Gulf of Maine, Scotian Shelf and adjacent deep ocean. The first step is to develop a one-way nested regional model and evaluate its predictions using observations from multiple sources including satellite-borne sensors of surface temperature and sea level, CTDs, Argo floats and moored current meters. It is shown that the regional model predicts more realistic fields than the global system on the shelf because it has higher resolution and includes tides that are absent from the global system. However, in deep water the regional model misplaces deep ocean eddies and meanders associated with the Gulf Stream. This is not because the regional model's dynamics are flawed but rather is the result of internally generated variability in deep water that leads to decoupling of the regional model from the global system. To overcome this problem, the next step is to spectrally nudge the regional model to the large scales (length scales > 90 km) of the global system. It is shown this leads to more realistic predictions off the shelf. Wavenumber spectra show that even though spectral nudging constrains the large scales, it does not suppress the variability on small scales; on the contrary, it favours the formation of eddies with length scales below the cutoff wavelength of the spectral nudging.

  13. Numerical Simulation of Salinity and Dissolved Oxygen at Perdido Bay and Adjacent Coastal Ocean

    EPA Science Inventory

    Environmental Fluid Dynamic Code (EFDC), a numerical estuarine and coastal ocean circulation hydrodynamic model, was used to simulate the distribution of the salinity, temperature, nutrients and dissolved oxygen (DO) in Perdido Bay and adjacent Gulf of Mexico. External forcing fa...

  14. Radargrams of Buried Basin from Two Adjacent Orbits

    NASA Technical Reports Server (NTRS)

    2005-01-01

    These two radargrams from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) show echoes from an approximately 250-kilometer (155-mile) diameter circular structure below the surface of Mars. The circular structure is interpreted to be a buried impact basin.

    In two orbits spaced about 50 kilometers (31 miles) apart, MARSIS detected a series of arc-shaped reflectors that have no apparent source in the surface topography or geology. In the lower image, a linear reflector nearly parallel to the surface is seen embedded in the arcs. This reflection may be coming from the floor of the basin. The time delay to the linear reflector suggests a depth of 1.5 to 2.5 kilometers (0.9 to 1.6 miles).

    MARSIS is an instrument on the European Space Agency's Mars Express orbiter. NASA and the Italian Space Agency jointly funded the instrument.

  15. Oceanic Crust in the Canada Basin of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Hutchinson, Deborah; Chian, Deping; Jackson, Ruth; Lebedeva-Ivanova, Nina; Shimeld, John; Li, Qingmou; Mosher, David; Saltus, Richard; Oakey, Gordon

    2015-04-01

    Crustal velocities from 85 expendable sonobuoys in the Canada Basin of the Arctic Ocean acquired between 2007 and 2011 distinguish oceanic, transitional, and extended continental crust. Crustal type was based on objective assignments of diagnostic velocities - oceanic from the presence of layer 3 velocities (6.7-7.2 km/s); transitional from the presence of a lower-most, high velocity layer (7.2-7.7 km/s), and continental for velocities typical of continental crust (≤6.6 km/s). Combined interpretations of sonobuoys, coincident multichannel seismic reflection profiles and existing maps of potential field (gravity and magnetic) are used to refine the distribution of oceanic crust. Oceanic crust forms a polygon approximately 320-350 km wide (east-west) by ~500 km (north-south). The northern segment of the Canada Basin Gravity Low (CBGL) bisects this zone of oceanic crust, as would be expected from the axis of the spreading center. The multichannel profiles also image a prominent bathymetric valley along this segment of the CBGL, similar to axial valleys found on slow and ultra-slow spreading ridges. Paired magnetic anomalies are associated only with crust that has typical oceanic velocities and are interpreted to represent possibly Mesozoic marine magnetic anomalies M0r - M4 (?), for a duration of opening of 8 million years, and a half spreading rate of ~10 mm/a. The southern segment of the CBGL, where it trends toward the Mackenzie Delta/fan, is associated with transitional velocities that are interpreted to represent serpentinized peridotite (mantle). As a result of being close to the inferred pole of rotation, this southern area may have had a spreading rate too low to support magmatism, producing amagmatic transitional crust. Further north, near Alpha Ridge and along Northwind Ridge, transitional crust is interpreted to be underplated or intruded material related to the emplacement of the High Arctic Large Igneous Province. Seismic reflection profiles across the

  16. 33 CFR 334.600 - TRIDENT Basin adjacent to Canaveral Harbor at Cape Canaveral Air Force Station, Brevard County...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false TRIDENT Basin adjacent to... DANGER ZONE AND RESTRICTED AREA REGULATIONS § 334.600 TRIDENT Basin adjacent to Canaveral Harbor at Cape... at latitude 28°24′37″, longitude 80°35′26″ and the entire basin. (b) Regulations. (1) No...

  17. 33 CFR 334.600 - TRIDENT Basin adjacent to Canaveral Harbor at Cape Canaveral Air Force Station, Brevard County...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false TRIDENT Basin adjacent to... DANGER ZONE AND RESTRICTED AREA REGULATIONS § 334.600 TRIDENT Basin adjacent to Canaveral Harbor at Cape... at latitude 28°24′37″, longitude 80°35′26″ and the entire basin. (b) Regulations. (1) No...

  18. Petroleum prospectivity of the Canada Basin, Arctic Ocean

    USGS Publications Warehouse

    Grantz, A.; Hart, P.E.

    2011-01-01

    Reconnaissance seismic reflection data indicate that Canada Basin is a remnant of the Amerasia Basin of the Arctic Ocean that lies south of the Alpha-Mendeleev Large Igneous Province, which was constructed on the northern part of the Amerasia Basin between about 127 and 89-75 Ma. Canada Basin is filled with Early Jurassic to Holocene detritus from the Mackenzie River system, which drains the northern third of interior North America, with sizable contributions from Alaska and Northwest Canada. Except for the absence of a salt- and shale-bearing mobile substrate Canada Basin is analogous to the Mississippi Delta and the western Gulf of Mexico. Canada Basin contains about 7 to >14 km of sediment beneath the Mackenzie Prodelta on the southeast, 6 to 7 km of sediment beneath the abyssal plain on the west, and roughly 5 or 6 million cubic km of sediment. About three fourths of the basin fill generates low amplitude seismic reflections, interpreted to represent hemiplegic deposits, and a fourth of the fill generates interbedded lenses to extensive layers of moderate to high amplitude reflections interpreted to represent unconfined turbidite and amalgamated channel deposits. Extrapolation from Arctic Alaska and Northwest Canada suggests that three fourths of the section in Canada Basin may contain intervals of hydrocarbon source rocks and the apparent age of the basin suggests that it contains three of the six stratigraphic intervals that together provided >90?? of the World's discovered reserves of oil and gas.. Worldwide heat flow averages suggest that about two thirds of Canada Basin lies in the oil or gas window. At least five types of structural or stratigraphic features of local to regional occurrence offer exploration targets in Canada Basin. These consist of 1) a belt of late Eocene to Miocene shale-cored detachment folds containing with at least two anticlines that are capped by beds with bright spots, 2) numerous moderate to high amplitude reflection packets

  19. A regional ocean reanalysis system for coastal waters of China and adjacent seas

    NASA Astrophysics Data System (ADS)

    Han, Guijun; Li, Wei; Zhang, Xuefeng; Li, Dong; He, Zhongjie; Wang, Xidong; Wu, Xinrong; Yu, Ting; Ma, Jirui

    2011-05-01

    A regional ocean reanalysis system for the coastal waters of China and adjacent seas has been developed by the National Marine Data and Information Service (NMDIS). It produces a dataset package called CORA (China ocean reanalysis). The regional ocean model used is based on the Princeton Ocean Model with a generalized coordinate system (POMgcs). The model is parallelized by NMDIS with the addition of the wave breaking and tidal mixing processes into model parameterizations. Data assimilation is a sequential three-dimensional variational (3D-Var) scheme implemented within a multigrid framework. Observations include satellite remote sensing sea surface temperature (SST), altimetry sea level anomaly (SLA), and temperature/salinity profiles. The reanalysis fields of sea surface height, temperature, salinity, and currents begin with January 1986 and are currently updated every year. Error statistics and error distributions of temperature, salinity and currents are presented as a primary evaluation of the reanalysis fields using sea level data from tidal gauges, temperature profiles, as well as the trajectories of Argo floats. Some case studies offer the opportunity to verify the evolution of certain local circulations. These evaluations show that the reanalysis data produced provide a good representation of the ocean processes and phenomena in the coastal waters of China and adjacent seas.

  20. Eddies and vortices in ocean basin dynamics

    NASA Astrophysics Data System (ADS)

    Siegel, A.; Weiss, Jeffrey B.; Toomre, Juri; McWilliams, James C.; Berloff, Pavel S.; Yavneh, Irad

    A wind-driven, closed-basin quasi-geostrophic ocean model is computed at very high horizontal resolution to study the effect of increasing Reynolds number (Re) on eddy variability. Five numerical simulations are performed with identical configurations, varying only in horizontal resolution and viscosity coefficient (and therefore Re). Qualitative changes in the structure of eddy variability are evident in the dramatic increase of isolated vortex structures at the highest Re. While the time-mean kinetic energy is relatively independent of Re, the vortex emergence contributes to a continual increase with Re of eddy kinetic energy and meridional vorticity flux. The rate of increase slows somewhat at the highest Re, indicating the possibility of a regime where eddy variability becomes insensitive to further increases in Re.

  1. Paleogeographic evolution of foldbelts adjacent to petroleum basins of Venezuela and Trinidad

    SciTech Connect

    Goodman, E.D.; Koch, P.S.; Summa, L.L.

    1996-08-01

    The foldbelts of Venezuela and Trinidad have shaped the history of adjacent sedimentary basins. A set of paleogeographic maps on reconstructed bases depict the role of foldbelts in the development of the sedimentary basins of Venezuela. Some of the foldbelts are inverted, pre-Tertiary graben/passive margin systems. Other foldbelts are allochthonous nappes or parautochthons that override the Mesozoic passive margin hinge without inversion. The emergence of these foldbelts changed the course of existing river systems and provided a new source for sediments and maturation in adjacent deeps. The Merida Andes area was remobilized beginning in the Early Miocene as a zone of lateral shear, along which the Bonaire Block has moved over 200 km to the northeast, dismembering the Maracaibo and Barinas basins. Late Miocene to Recent transpression and fault reactivation have driven rapid Andean uplift with thrust-related subsidence and maturation (e.g., SE Maracaibo foredeep). To the east, uplift and erosion of the Serrania del Interior (1) curtailed mid-Tertiary fluvial systems flowing northward from the igneous and sedimentary rocks of the Guyana Shield, deflecting them eastward, and (2) removed the thick early Miocene foredeep fill into a younger foredeep. Thus, the fold-thrust belts and sedimentary basins in this region are linked in their evolutionary histories.

  2. Possible Factors affecting the Thermal Contrast between Middle-Latitude Asian Continent and Adjacent Ocean

    NASA Astrophysics Data System (ADS)

    Cheng, Huaqiong; Wu, Tongwen; Dong, Wenjie

    2015-04-01

    A middle-latitude Land-Sea thermal contrast Index was used in this study which has close connection to the East Asian summer precipitation. The index has two parts which are land thermal index defined as JJA 500-hPa geopotential height anomalies at a land area (75°-90° E, 40° -55°N ) and ocean thermal index defined as that at an oceanic area (140° -150°E, 35° -42.5°N). The impact of the surface heat flux and atmospheric diabatic heating over the land and the ocean on the index was studied. The results show that the surface heat flux over Eurasian inner land has little influence to the land thermal index, while the variation of the surface latent heat flux and long-wave radiation over the Pacific adjacent to Japan has highly correlation with the ocean thermal index. The changes with height of the atmospheric diabatic heating rates over the Eurasian inner land and the Pacific adjacent to Japan have different features. The variations of the middle troposphere atmospheric long-wave and short-wave radiation heating have significantly influences on land thermal index, and that of the low troposphere atmospheric long-wave radiation, short-wave radiation and deep convective heating also have impact on the yearly variation of the land thermal index. For the ocean thermal index, the variations of the surface layer atmospheric vertical diffuse heating, large-scale latent heating and long-wave radiation heating are more important, low and middle troposphere atmospheric large-scale latent heating and shallow convective heating also have impact on the yearly variation of the ocean thermal index. And then the ocean thermal index has closely connection with the low troposphere atmospheric temperature, while the land thermal index has closely connection with the middle troposphere atmospheric temperature. The Effect of the preceding global SST anomalies on the index also was analyzed. The relations of land thermal index and ocean thermal index and the global SST anomalies

  3. Ocean tides in the northern North Atlantic and adjacent seas from ERS 1 altimetry

    NASA Astrophysics Data System (ADS)

    Andersen, Ole Baltazar

    1994-11-01

    Twenty months of ERS 1 35-day repeat altimeter data containing 18 repeat cycles have been used to estimate the major diurnal and semidiurnal ocean tide signals in the northern parts of the North Atlantic and adjacent seas. ERS 1 provides valuable information when investigating ocean tides, owing to the repeated dense spatial sampling. However, several tidal constituents are extremely difficult to resolve using conventional harmonic analysis with the chosen sun syncronous orbit. Instead, temporal analysis at each crossover location is applied using a modified form of the orthotide formulation, which simultaneously solves for the diurnal and semidiurnal species as well as for the annual signal. The use of the response formalism ensures that the sun syncronous component S2 can be resolved, although this component is "frozen" in the orbit. Maps of the M2, S2 and K1 tidal amplitudes and phases in 0.5°×0.5° grids are presented and are seen to compare favorably with measurements at 68 pelagic tide gauges provided by the International Association for Physical Sciences of the Ocean. The major tidal constituents of the ERS 1 derived model are also in close agreement with the improved Flather (1981) ocean tide model for the northwest European continental shelf area, as well as a numerical model for the Arctic and Nordic Seas by Gjevik and Straume (1989).

  4. A new version of regional ocean reanalysis for coastal waters of China and adjacent seas

    NASA Astrophysics Data System (ADS)

    Han, Guijun; Li, Wei; Zhang, Xuefeng; Wang, Xidong; Wu, Xinrong; Fu, Hongli; Zhang, Xiaoshuang; Zhang, Lianxin; Li, Dong

    2013-07-01

    A new regional ocean reanalysis over multiple decades (1958-2008) for the coastal waters of China and adjacent seas has been completed by the National Marine Data and Information Service (NMDIS) under the CORA (China Ocean ReAnalysis) project. Evaluations were performed on three aspects: (1) the improvement of general reanalysis quality; (2) eddy structures; and (3) decadal variability of sea surface height anomalies (SSHAs). Results showed that the quality of the new reanalysis has been enhanced beyond ˜40% (39% for temperature, 44% for salinity) in terms of the reduction of root mean squared errors (RMSEs) for which the reanalysis values were compared to observed values in the observational space. Compared to the trial version released to public in 2009, the new reanalysis is able to reproduce more detailed eddy structures as seen in satellite and in situ observations. EOF analysis of the reanalysis SSHAs showed that the new reanalysis reconstructs the leading modes of SSHAs much better than the old version. These evaluations suggest that the new CORA regional reanalysis represents a much more useful dataset for the community of the coastal waters of China and adjacent seas.

  5. Glacial lake drainage in Patagonia (13-8 kyr) and response of the adjacent Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Glasser, Neil F.; Jansson, Krister N.; Duller, Geoffrey A. T.; Singarayer, Joy; Holloway, Max; Harrison, Stephan

    2016-02-01

    Large freshwater lakes formed in North America and Europe during deglaciation following the Last Glacial Maximum. Rapid drainage of these lakes into the Oceans resulted in abrupt perturbations in climate, including the Younger Dryas and 8.2 kyr cooling events. In the mid-latitudes of the Southern Hemisphere major glacial lakes also formed and drained during deglaciation but little is known about the magnitude, organization and timing of these drainage events and their effect on regional climate. We use 16 new single-grain optically stimulated luminescence (OSL) dates to define three stages of rapid glacial lake drainage in the Lago General Carrera/Lago Buenos Aires and Lago Cohrane/Pueyrredón basins of Patagonia and provide the first assessment of the effects of lake drainage on the Pacific Ocean. Lake drainage occurred between 13 and 8 kyr ago and was initially gradual eastward into the Atlantic, then subsequently reorganized westward into the Pacific as new drainage routes opened up during Patagonian Ice Sheet deglaciation. Coupled ocean-atmosphere model experiments using HadCM3 with an imposed freshwater surface “hosing” to simulate glacial lake drainage suggest that a negative salinity anomaly was advected south around Cape Horn, resulting in brief but significant impacts on coastal ocean vertical mixing and regional climate.

  6. Glacial lake drainage in Patagonia (13-8 kyr) and response of the adjacent Pacific Ocean

    PubMed Central

    Glasser, Neil F.; Jansson, Krister N.; Duller, Geoffrey A. T.; Singarayer, Joy; Holloway, Max; Harrison, Stephan

    2016-01-01

    Large freshwater lakes formed in North America and Europe during deglaciation following the Last Glacial Maximum. Rapid drainage of these lakes into the Oceans resulted in abrupt perturbations in climate, including the Younger Dryas and 8.2 kyr cooling events. In the mid-latitudes of the Southern Hemisphere major glacial lakes also formed and drained during deglaciation but little is known about the magnitude, organization and timing of these drainage events and their effect on regional climate. We use 16 new single-grain optically stimulated luminescence (OSL) dates to define three stages of rapid glacial lake drainage in the Lago General Carrera/Lago Buenos Aires and Lago Cohrane/Pueyrredón basins of Patagonia and provide the first assessment of the effects of lake drainage on the Pacific Ocean. Lake drainage occurred between 13 and 8 kyr ago and was initially gradual eastward into the Atlantic, then subsequently reorganized westward into the Pacific as new drainage routes opened up during Patagonian Ice Sheet deglaciation. Coupled ocean-atmosphere model experiments using HadCM3 with an imposed freshwater surface “hosing” to simulate glacial lake drainage suggest that a negative salinity anomaly was advected south around Cape Horn, resulting in brief but significant impacts on coastal ocean vertical mixing and regional climate. PMID:26869235

  7. Glacial lake drainage in Patagonia (13-8 kyr) and response of the adjacent Pacific Ocean.

    PubMed

    Glasser, Neil F; Jansson, Krister N; Duller, Geoffrey A T; Singarayer, Joy; Holloway, Max; Harrison, Stephan

    2016-01-01

    Large freshwater lakes formed in North America and Europe during deglaciation following the Last Glacial Maximum. Rapid drainage of these lakes into the Oceans resulted in abrupt perturbations in climate, including the Younger Dryas and 8.2 kyr cooling events. In the mid-latitudes of the Southern Hemisphere major glacial lakes also formed and drained during deglaciation but little is known about the magnitude, organization and timing of these drainage events and their effect on regional climate. We use 16 new single-grain optically stimulated luminescence (OSL) dates to define three stages of rapid glacial lake drainage in the Lago General Carrera/Lago Buenos Aires and Lago Cohrane/Pueyrredón basins of Patagonia and provide the first assessment of the effects of lake drainage on the Pacific Ocean. Lake drainage occurred between 13 and 8 kyr ago and was initially gradual eastward into the Atlantic, then subsequently reorganized westward into the Pacific as new drainage routes opened up during Patagonian Ice Sheet deglaciation. Coupled ocean-atmosphere model experiments using HadCM3 with an imposed freshwater surface "hosing" to simulate glacial lake drainage suggest that a negative salinity anomaly was advected south around Cape Horn, resulting in brief but significant impacts on coastal ocean vertical mixing and regional climate. PMID:26869235

  8. Ocean basin volume constraints on global sea level since the Jurassic

    NASA Astrophysics Data System (ADS)

    Seton, M.; Müller, R. D.

    2011-12-01

    Changes in the volume of the ocean basins, predominately via changes in the age-area distribution of oceanic lithosphere, have been suggested as the main driver for long-term eustatic sea-level change. As ocean lithosphere cools and thickens, ocean depth increases. The balance between the abundance of hot and buoyant crust along mid ocean ridges relative to abyssal plains is the primary driving force of long-term sea level changes. The emplacement of volcanic plateaus and chains as well as sedimentation contribute to raising eustatic sea level. Quantifying the average ocean basin depth through time primarily relies on the present day preserved seafloor spreading record, an analysis of the spatio-temporal record of plate boundary processes recorded on the continental margins adjacent to ocean basins as well as a consideration of the rules of plate tectonics, to reconstruct the history of seafloor spreading in the oceanic basins through time. This approach has been successfully applied to predict the magnitude and pattern of eustatic sea-level change since the Cretaceous (Müller et. al. 2008) but uncertainties in reconstructing mid ocean ridges and flanks increase back through time, given that we mainly depend on information preserved in preserved ocean crust. We have reconstructed the age-area distribution of oceanic lithosphere and the plate boundary configurations back to the Jurassic (200 Ma) in order to assess long-term sea-level change from amalgamation to dispersal of Pangaea. We follow the methodology presented in Müller et. al. (2008) but incorporate a new absolute plate motion model derived from Steinberger and Torsvik (2008) prior to 100 Ma, a merged Wessel et. al. (2006) and Wessel and Kroenke (2008) fixed Pacific hotspot reference frame, and a revised model for the formation of Panthalassa and the Cretaceous Pacific. Importantly, we incorporate a model for the break-up of the Ontong Java-Manihiki-Hikurangi plateaus between 120-86 Ma. We extend a

  9. Correlation of sea level falls interpreted from atoll stratigraphy with turbidites in adjacent basins

    SciTech Connect

    Lincoln, J.M. )

    1990-05-01

    Past sea levels can be derived from any atoll subsurface sediments deposited at or near sea level by determining the ages of deposition and correcting the present depths to the sediments for subsidence of the underlying edifice since the times of deposition. A sea level curve constructed by this method consists of discontinuous segments, each corresponding to a period of rising relative sea level and deposition of a discrete sedimentary package. Discontinuities in the sea level curve derived by this method correspond to relative sea level falls and stratigraphic hiatuses in the atoll subsurface. During intervals of relative sea level fall an atoll emerges to become a high limestone island. Sea level may fluctuate several times during a period of atoll emergence to become a high limestone island. Sea level may fluctuate several times during a period of atoll emergence without depositing sediments on top of the atoll. Furthermore, subaerial erosion may remove a substantial part of the depositional record of previous sea level fluctuations. For these reasons the authors must look to the adjacent basins to complement the incomplete record of sea level change recorded beneath atolls. During lowstands of sea level, faunas originally deposited near sea level on an atoll may be eroded and redeposited as turbidites in deep adjacent basins. Three such turbidites penetrated during deep-sea drilling at Sites 462 and 315 in the central Pacific correlate well with a late Tertiary sea level curve based on biostratigraphic ages and {sup 87}Sr/{sup 86}Sr chronostratigraphy for core from Enewetak Atoll in the northern Marshall Islands. Further drilling of the archipelagic aprons adjacent to atolls will improve the sea level history that may be inferred from atoll stratigraphy.

  10. Hydrogeochemical studies of historical mining areas in the Humboldt River basin and adjacent areas, northern Nevada

    USGS Publications Warehouse

    Nash, J. Thomas

    2005-01-01

    The study area comprises the Humboldt River Basin and adjacent areas, with emphasis on mining areas relatively close to the Humboldt River. The basin comprises about 16,840 mi2 or 10,800,000 acres. The mineral resources of the Humboldt Basin have been investigated by many scientists over the past 100 years, but only recently has our knowledge of regional geology and mine geology been applied to the understanding and evaluation of mining effects on water and environmental quality. The investigations reported here apply some of the techniques and perspectives developed in the Abandoned Mine Lands Initiative (AMLI) of the U.S. Geological Survey (USGS), a program of integrated geological-hydrological-biological-chemical studies underway in the Upper Animas River watershed in Colorado and the Boulder River watershed in, Montana. The goal of my studies of sites and districts is to determine the character of mining-related contamination that is actively or potentially a threat to water quality and to estimate the potential for natural attenuation of that contamination. These geology-based studies and recommendations differ in matters of emphasis and data collection from the biology-based assessments that are the cornerstone of environmental regulations.

  11. Relative motions between oceanic plates of the Pacific Basin

    NASA Astrophysics Data System (ADS)

    Engebretson, David C.; Cox, Allan; Gordon, Richard G.

    1984-11-01

    Appendix tables are available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C., 20009. Document B84-012; $2.50. Payment must accompany order. Relative motion poles describing the displacement histories between the Pacific plate and once adjacent oceanic plates (Farallon, Kula, Izanagi I, Izanagi II, and Phoenix) were derived for the late Mesozoic and Cenozoic eras. Because fracture zone and magnetic anomaly data are generally available from the Pacific plate but not from adjacent plates, a new method of analysis for onesided data was required. This analysis produced stage poles and rates of relative plate motion and estimates of their confidence regions. The following are the main conclusions drawn from our analysis: (1) For time intervals of the order of 107 years, termed stages, relative motion poles for plate pairs remained nearly fixed. Between stages, shifts in poles were commonly both large and abrupt. Within stages, rates of plate motion were commonly observed to change markedly, indicating that plates changed speed more frequently than they changed direction. (2) The relative motions of all of the plates analyzed changed at about chron M11 (135 Ma), chron 34 (85 Ma), and chron 25 (56 Ma). (3) During the Early Cretaceous there were five oceanic plates in the Pacific basin rather than the four recognized by previous workers. (4) To determine the number of Farallon plates that existed to the east of the Pacific plate during the time interval from chron 34 (85 Ma) to chron 25 (56 Ma), fracture zones and magnetic anomalies that record Pacific-Farallon spreading from the northern, central, and southern Pacific plate were analyzed separately and collectively. The analysis shows that a single Pacific-Farallon relative motion pole and a single rate are consistent with all of the data. (5) Spreading rates along the Pacific-Kula ridge decreased markedly between chrons 32b and 25 (72-56 Ma), probably

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  13. Particle release transport in Danshuei River estuarine system and adjacent coastal ocean: a modeling assessment.

    PubMed

    Chen, Wei-Bo; Liu, Wen-Cheng; Kimura, Nobuaki; Hsu, Ming-Hsi

    2010-09-01

    A three-dimensional hydrodynamic model was created to study the Danshuei River estuarine system and adjacent coastal ocean in Taiwan. The model was verified using measurements of the time-series water surface elevation, tidal current, and salinity from 1999. We conclude that our model is consistent with these observations. Our particle-tracking model was also used to explore the transport of particles released from the Hsin-Hai Bridge, an area that is heavily polluted. The results suggest that it takes a much longer time for the estuary to be flushed out under low freshwater discharge conditions than with high freshwater discharge. We conclude that the northeast and southwest winds minimally impact particle dispersion in the estuary. The particles fail to settle to the bottom in the absence of density-induced circulation. Our model was also used to simulate the ocean outfall at the Bali. Our experimental results suggest that the tidal current dominates the particle trajectories and influences the transport properties in the absence of a wind stress condition. The particles tend to move northeast or southwest along the coast when northeast or southwest winds prevail. Our data suggest that wind-driven currents and tidal currents play important roles in water movement as linked with ocean outfall in the context of the Danshuei River. PMID:19680754

  14. Basin-Wavelength Equatorial Deep Jet Signals Across Three Oceans

    NASA Astrophysics Data System (ADS)

    Youngs, M. K.; Johnson, G. C.

    2015-12-01

    Equatorial Deep Jets (EDJs) are equatorially trapped, stacked, zonal currents that reverse direction every few hundred meters in depth throughout much of the water column. This study evaluates their structure observationally in all three oceans using new high vertical resolution Argo float conductivity-temperature-depth (CTD) instrument profiles from 2010--2014 augmented with historical shipboard CTD from 1972--2014 and lower vertical resolution Argo float profiles from 2007--2014. Vertical strain of density is calculated from the profiles and analyzed in a stretched vertical coordinate system determined from the mean vertical density structure. The power spectra of vertical strain in each basin are analyzed using a wavelet decomposition. In the Indian and Pacific oceans, there are two distinct peaks in the power spectra, one Kelvin-wave-like and the other entirely consistent with the dispersion relation of a linear first-meridional-mode equatorial Rossby wave. In the Atlantic Ocean, the first-meridional-mode Rossby wave signature is very strong, and dominates. In all three ocean basins Rossby-wave-like signatures are coherent across the basin width, and appear to have wavelengths the scale of the basin width, with periods of about 5 years in the Indian and Atlantic oceans and about 12 years in the Pacific Ocean. Their observed meridional scales are about 1.5 times the linear theoretical values. Their phase propagation is downward with time, implying upward energy propagation if linear wave dynamics hold.

  15. A numerical study of the plume in Cape Fear River Estuary and adjacent coastal ocean

    NASA Astrophysics Data System (ADS)

    Xia, M.; Xia, L.; Pietrafesa, L. J.

    2006-12-01

    Cape Fear River Estuary (CFRE), located in southeast North Carolina, is the only river estuary system in the state which is directly connected to the Atlantic Ocean. It is also an important nursery for economically and ecologically important juvenile fish, crabs, shrimp, and other species because of the tidal influence and saline waters. In this study, Environmental Fluid Dynamic Code (EFDC) is used to simulate the salinity plume and trajectory distribution at the mouth of the CFRE and adjacent coastal ocean. Prescribed with the climatological freshwater discharge rates in the rivers, the modeling system was used to simulate the salinity plume and trajectory distribution distribution in the mouth of the CFRE under the influence of climatological wind conditions and tidal effect. We analyzed the plume formation processes and the strong relationship between the various plume distributions with respect to the wind and river discharge in the region. The simulations also indicate that strong winds tend to reduce the surface CFRE plume size and distorting the bulge region near the estuary mouth due to enhanced wind induced surface mixing. Even moderate wind speeds could fully reverse the buoyancy-driven plume structure in CFRE under normal river discharge conditions. Tide and the river discharge also are important factors to influence the plume structure. The comparions between the distribution of salinity plume and trajectory also are discussed in the study.

  16. Melting barriers to faunal exchange across ocean basins.

    PubMed

    McKeon, C Seabird; Weber, Michele X; Alter, S Elizabeth; Seavy, Nathaniel E; Crandall, Eric D; Barshis, Daniel J; Fechter-Leggett, Ethan D; Oleson, Kirsten L L

    2016-02-01

    Accelerated loss of sea ice in the Arctic is opening routes connecting the Atlantic and Pacific Oceans for longer periods each year. These changes may increase the ease and frequency with which marine birds and mammals move between the Pacific and Atlantic Ocean basins. Indeed, recent observations of birds and mammals suggest these movements have intensified in recent decades. Reconnection of the Pacific and Atlantic Ocean basins will present both challenges to marine ecosystem conservation and an unprecedented opportunity to examine the ecological and evolutionary consequences of interoceanic faunal exchange in real time. To understand these changes and implement effective conservation of marine ecosystems, we need to further develop modeling efforts to predict the rate of dispersal and consequences of faunal exchange. These predictions can be tested by closely monitoring wildlife dispersal through the Arctic Ocean and using modern methods to explore the ecological and evolutionary consequences of these movements. PMID:26618788

  17. Geophysical observations on northern part of Georges Bank and adjacent basins of Gulf of Maine

    USGS Publications Warehouse

    Oldale, R.N.; Hathaway, J.C.; Dillon, William P.; Hendricks, J.D.; Robb, James M.

    1974-01-01

    Continuous-seismic-reflection and magnetic-intensity profiles provide data for inferences about the geology of the northern part of Georges Bank and the basins of the Gulf of Maine adjacent to the bank. Basement is inferred to be mostly sedimentary and volcanic rocks of Paleozoic age that were metamorphosed and intruded locally by felsic and mafic plutons near the end of the Paleozoic Era. During Late Triassic time, large fault basins formed within the Gulf of Maine and probably beneath Georges Bank. The fault basins and a possible major northeast-trending fault zone beneath the northern part of the bank probably formed as a result of the opening Atlantic during the Mesozoic. Nonmarine sediments, associated with mafic flows and intrusive rocks, were deposited in the fault basins as they formed. The upper surface of the Triassic and pre-Triassic rocks that comprise basement is an unconformity that makes up much of the bottom of the Gulf of Maine. Depth to the basement surface beneath the gulf differ greatly because of fluvial erosion in Tertiary time and glacial erosion in Pleistocene time. Beneath the northern part of Georges Bank the basement surface is smoother and slopes southward. Prominent valleys, cut before Late Cretaceous time, are present beneath this part of the bank. Cretaceous, Tertiary, and possibly Jurassic times were characterized by episodes of coastal-plain deposition and fluvial erosion. During this time a very thick wedge of sediment, mostly of Jurassic(?) and Cretaceous ages, was deposited on the shelf. Major periods of erosion took place at the close of the Cretaceous and during the Pliocene. Fluvial erosion during the Pliocene removed much of the coastal-plain sedimentary wedge and formed the Gulf of Maine. Pleistocene glaciers eroded all but a few remnants of the coastal-plain sediments within the gulf and deposited a thick section of drift against the north slope of Georges Bank and a thin veneer of outwash on the bank. Marine sediments were

  18. Cleanup Verification Package for the 118-F-8:4 Fuel Storage Basin West Side Adjacent and Side Slope Soils

    SciTech Connect

    L. D. Habel

    2008-03-18

    This cleanup verification package documents completion of remedial action, sampling activities, and compliance with cleanup criteria for the 118-F-8:4 Fuel Storage Basin West Side Adjacent and Side Slope Soils. The rectangular-shaped concrete basin on the south side of the 105-F Reactor building served as an underwater collection, storage, and transfer facility for irradiated fuel elements discharged from the reactor.

  19. A database for the monitoring of thermal anomalies over the Amazon forest and adjacent intertropical oceans.

    PubMed

    Jiménez-Muñoz, Juan C; Mattar, Cristian; Sobrino, José A; Malhi, Yadvinder

    2015-01-01

    Advances in information technologies and accessibility to climate and satellite data in recent years have favored the development of web-based tools with user-friendly interfaces in order to facilitate the dissemination of geo/biophysical products. These products are useful for the analysis of the impact of global warming over different biomes. In particular, the study of the Amazon forest responses to drought have recently received attention by the scientific community due to the occurrence of two extreme droughts and sustained warming over the last decade. Thermal Amazoni@ is a web-based platform for the visualization and download of surface thermal anomalies products over the Amazon forest and adjacent intertropical oceans using Google Earth as a baseline graphical interface (http://ipl.uv.es/thamazon/web). This platform is currently operational at the servers of the University of Valencia (Spain), and it includes both satellite (MODIS) and climatic (ERA-Interim) datasets. Thermal Amazoni@ is composed of the viewer system and the web and ftp sites with ancillary information and access to product download. PMID:26029379

  20. A database for the monitoring of thermal anomalies over the Amazon forest and adjacent intertropical oceans

    PubMed Central

    Jiménez-Muñoz, Juan C.; Mattar, Cristian; Sobrino, José A.; Malhi, Yadvinder

    2015-01-01

    Advances in information technologies and accessibility to climate and satellite data in recent years have favored the development of web-based tools with user-friendly interfaces in order to facilitate the dissemination of geo/biophysical products. These products are useful for the analysis of the impact of global warming over different biomes. In particular, the study of the Amazon forest responses to drought have recently received attention by the scientific community due to the occurrence of two extreme droughts and sustained warming over the last decade. Thermal Amazoni@ is a web-based platform for the visualization and download of surface thermal anomalies products over the Amazon forest and adjacent intertropical oceans using Google Earth as a baseline graphical interface (http://ipl.uv.es/thamazon/web). This platform is currently operational at the servers of the University of Valencia (Spain), and it includes both satellite (MODIS) and climatic (ERA-Interim) datasets. Thermal Amazoni@ is composed of the viewer system and the web and ftp sites with ancillary information and access to product download. PMID:26029379

  1. (Inorganic carbon surveys of oceanic basins)

    SciTech Connect

    Wilke, R.J.

    1991-04-25

    Measurements were made aboard the F. S. Meteor, along the 19 degree South cruise track of the following chemical parameters: total dissolved inorganic carbon, pH, pCO2, CFC-12, CFC-11, CFC-113, CC14. This was the first cruise of OASD's newly formed CO2 group. The purpose was to survey World Ocean Circulation Experiment (WOCE) line A9 for inorganic carbon for the Department of Energy's Office of CO2 Research. 1 fig.

  2. Hydrogeologic framework of the Great Basin region of Nevada, Utah, and adjacent states

    USGS Publications Warehouse

    Plume, R.W.

    1996-01-01

    Regional aquifer systems in the Great Basin consist of carbonate-rock aquifers in the eastern Great Basin and basin-fill aquifers throughout the region. In the carbonate-rock aquifers, barriers to regional flow include Precambrian crystalline basement, upper Precambrian and Lower Cambrian clastic sedimentary rocks, and Jurassic to Tertiary granitic rocks. Basin-fill aquifers are connected to carbonate-rock aquifers in the eastern Great Basin and can be hydraulically connected with each other throughout the Great Basin.

  3. Probable rift origin of Canada Basin, Arctic Ocean

    USGS Publications Warehouse

    Tailleur, Irvin L.

    1973-01-01

    Formation of the Canada basin by post-Triassic rifting seems the most workable and logical hypothesis on the basis of available information. Speculated counterclockwise rotation of the Alaska-Chukchi continental edge best rationalizes the complex geology of northern Alaska, whereas the assumption that a single continental block was present before the Jurassic makes the best palinspastic fit for Arctic America. The Arctic Ocean is the focus of present-day spreading and probably was the focus of earlier stages of spreading in which spread of the Canada basin would have been an initial stage. Spread of the Canada basin is probable if the Atlantic formed by sea-floor spreading, because analogies between the Arctic and Atlantic edges indicate a common origin for the ocean basins. Late Cretaceous and younger deflections of the Cordillera in the Arctic and diabasic emplacements in the northern Arctic Islands may reflect later stages of spreading. Pre-Mesozoic plate tectonism may be represented by the widespread Proterozoic diabasic emplacements in the Canadian Arctic and by the Franklinian-lnnuitian tract, where the volcanogenic rocks and deformation resulted not from a classical eugeosyncline-miogeosyncline couple, but from the junction of a mid-Paleozoic continental edge and another plate on closure of a pre-Arctic Ocean.

  4. Modern benthic foraminifer distribution in the Amerasian Basin, Arctic Ocean

    USGS Publications Warehouse

    Ishman, S.E.; Foley, K.M.

    1996-01-01

    A total of 38 box cores were collected from the Amerasian Basin, Arctic Ocean during the U.S. Geological Survey 1992 (PI92-AR) and 1993 (PI93-AR) Arctic Cruises aboard the U.S. Coast Guard Icebreaker Polar Star. In addition, the cruises collected geophysical data, piston cores and hydrographic data to address the geologic and oceanographic history of the western Arctic Ocean. This paper reports the results of the quantitative analyses of benthic foraminifer distribution data of the total (live + dead) assemblages derived from 22 box core-top samples. The results show that a distinct depth distribution of three dominant benthic foraminifer assemblages, the Textularia spp. - Spiroplectammina biformis, Cassidulina teretis and Oridorsalis tener - Eponides tumidulus Biofacies are strongly controlled by the dominant water masses within the Canada Basin: the Arctic Surface Water, Arctic Intermediate Water and Canada Basin Deep Water. The faunal distributions and their oceanographic associations in the Canada Basin are consistent with observations of benthic foraminifer distributions from other regions within the Arctic Ocean.

  5. Probable rift origin of the Canada basin, Arctic Ocean

    USGS Publications Warehouse

    Tailleur, Irvin L.

    1973-01-01

    Formation of the Canada basin by post-Triassic rifting seems the most workable and logical hypothesis with information available. Speculated counterclockwise rotation of the Alaska-Chukchi continental edge best rationalizes the complex geology of northern Alaska, whereas a single continental block before the Jurassic makes the best palinspastic fit for Arctic America. The Arctic Ocean is the focus of present-day spreading and probably was the focus of earlier stages of spreading in which spread of the Canada basin would be an initial stage. If the Atlantic formed by seafloor spreading, spread of the Canada basin is probable because analogies between the Arctic and Atlantic edges indicate a common origin for the ocean basins. Late Cretaceous and younger deflections of the Cordillera in the Arctic and diabasic emplacements in the northern Arctic Islands may reflect later stages of spreading. Pre-Mesozoic plate tectonism may be represented by the widespread Proterozoic diabasic emplacements in the Canadian Arctic and by the Franklinian-Innuitian tract where the volcanogenic rocks and deformation resulted not from a classical eugeosyncline-miogeosyncline couple but from the junction of a mid-Paleozoic continental edge and another plate on closure of a pre-Arctic Ocean.

  6. Rift basins of ocean-continent convergent margins

    SciTech Connect

    Forsythe, R.D.; Newcomb, K.R.

    1986-05-01

    Modern and ancient circum-Pacific convergent margins contain many examples of forearc basins where subsidence, occurring simultaneously with subduction of oceanic lithosphere, is controlled by rifting transverse to the margin. The elongate axes of these deep and narrow basins jut obliquely from the plate margin into the interior of the forearc. Similar to aulacogens, faulting and related subsidence appear greatest at their seaward limits and decreases inland. Examples from eastern Pacific forearcs suggest that localized rifting accommodates margin-parallel extension of forearc blocks that are kinetically linked to motions along major margin-parallel strike-slip fault systems. The most prominent examples of modern forearc rift basins are the Sanak and East Sanak basins of the western Alaska Peninsula subduction zone. In this region, the continental shelf is being rifted apart by a series of northwest- and northeast-trending faults. Basement-activated normal faults bounding the basins have listric geometries. Seismostratigraphic relationships within the basins indicate the protracted, synsedimentary, and active nature of faulting and basin subsidence. Along the Peru-Chile trench, two prominent rifted basins also occur: the Gulf of Guayaquil and the Gulf of Penas-Taitao basin of southern Chile. There, margin-parallel rifting controls subsidence in localized basins at the southern terminus to margin-parallel dextral fault systems. These and other examples suggest that strike-slip motion and transverse rifting of forearcs is a common phenomenon inadequately described by existing two-dimensional models of forearcs. Margin-parallel motions of forearc blocks can be related not only to oblique plate convergence, but also to the geometric and compositional nature of the overriding and subducted plates.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  8. Acquiring Marine Data in the Canada Basin, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Hutchinson, Deborah R.; Jackson, H. Ruth; Shimeld, John W.; Chapman, C. Borden; Childs, Jonathan R.; Funck, Thomas; Rowland, Robert W.

    2009-06-01

    Despite the record minimum ice extent in the Arctic Ocean for the past 2 years, collecting geophysical data with towed sensors in ice-covered regions continues to pose enormous challenges. Significant parts of the Canada Basin in the western Arctic Ocean have remained largely unmapped because thick multiyear ice has limited access even by research vessels strengthened against ice [Jackson et al., 1990]. Because of the resulting paucity of data, the western Arctic Ocean is one of the few areas of ocean in the world where major controversies still exist with respect to its origin and tectonic evolution [Grantz et al., 1990; Lawver and Scotese, 1990; Lane, 1997; Miller et al., 2006]. This article describes the logistical challenges and initial data sets from geophysical seismic reflection, seismic refraction, and hydrographic surveys in the Canada Basin conducted by scientists with U.S. and Canadian government agencies (Figure 1a) to fulfill the requirements of the United Nations Convention on the Law of the Sea to determine sediment thickness, geological origin, and basin evolution in this unexplored part of the world. Some of these data were collected using a single ship, but the heaviest ice conditions necessitated using two icebreakers, similar to other recent Arctic surveys [e.g., Jokat, 2003].

  9. Phanerozoic stratigraphy of Northwind Ridge, magnetic anomalies in the Canada Basin, and the geometry and timing of rifting in the Amerasia Basin, Arctic Ocean

    USGS Publications Warehouse

    Grantz, A.; Clark, D.L.; Phillips, R.L.; Srivastava, S.P.; Blome, C.D.; Gray, L.-B.; Haga, H.; Mamet, B.L.; McIntyre, D.J.; McNeil, D.H.; Mickey, M.B.; Mullen, M.W.; Murchey, B.I.; Ross, C.A.; Stevens, C.H.; Silberling, Norman J.; Wall, J.H.; Willard, D.A.

    1998-01-01

    Cores from Northwind Ridge, a high-standing continental fragment in the Chukchi borderland of the oceanic Amerasia basin, Arctic Ocean, contain representatives of every Phanerozoic system except the Silurian and Devonian systems. Cambrian and Ordovician shallow-water marine carbonates in Northwind Ridge are similar to basement rocks beneath the Sverdrup basin of the Canadian Arctic Archipelago. Upper Mississippian(?) to Permian shelf carbonate and spicularite and Triassic turbidite and shelf lutite resemble coeval strata in the Sverdrup basin and the western Arctic Alaska basin (Hanna trough). These resemblances indicate that Triassic and older strata in southern Northwind Ridge were attached to both Arctic Canada and Arctic Alaska prior to the rifting that created the Amerasia basin. Late Jurassic marine lutite in Northwind Ridge was structurally isolated from coeval strata in the Sverdrup and Arctic Alaska basins by rift shoulder and grabens, and is interpreted to be a riftogenic deposit. This lutite may be the oldest deposit in the Canada basin. A cape of late Cenomanian or Turonian rhyodacite air-fall ash that lacks terrigenous material shows that Northwind Ridge was structurally isolated from the adjacent continental margins by earliest Late Cretaceous time. Closing Amerasia basin by conjoining seafloor magnetic anomalies beneath the Canada basin or by uniting the pre-Jurassic strata of Northwind Ridge with kindred sections in the Sverdrup basin and Hanna trough yield simular tectonic reconstructions. Together with the orientation and age of rift-marine structures, these data suggest that: 1) prior to opening of the Amerasia basin, both northern Alaska and continental ridges of the Chukchi borderland were part of North America, 2) the extension that created the Amerasia basin formed rift-margin graben beginning in Early Jurassic time and new oceanic crust probably beginning in Late Jurassic or early Neocomian time. Reconstruction of the Amerasia basin on the

  10. Petroleum prospectivity of the Canada Basin, Arctic Ocean

    USGS Publications Warehouse

    Grantz, A.; Hart, P.E.

    2012-01-01

    Reconnaissance seismic reflection data indicate that Canada Basin is a >700,000 sq. km. remnant of the Amerasia Basin of the Arctic Ocean that lies south of the Alpha-Mendeleev Large Igneous Province, which was constructed across the northern part of the Amerasia Basin between about 127 and 89-83.5 Ma. Canada Basin was filled by Early Jurassic to Holocene detritus from the Beaufort-Mackenzie Deltaic System, which drains the northern third of interior North America, with sizable contributions from Alaska and Northwest Canada. The basin contains roughly 5 or 6 million cubic km of sediment. Three fourths or more of this volume generates low amplitude seismic reflections, interpreted to represent hemipelagic deposits, which contain lenses to extensive interbeds of moderate amplitude reflections interpreted to represent unconfined turbidite and amalgamated channel deposits.Extrapolation from Arctic Alaska and Northwest Canada suggests that three fourths of the section in Canada Basin is correlative with stratigraphic sequences in these areas that contain intervals of hydrocarbon source rocks. In addition, worldwide heat flow averages suggest that about two thirds of Canada Basin lies in the oil or gas windows. Structural, stratigraphic and combined structural and stratigraphic features of local to regional occurrence offer exploration targets in Canada Basin, and at least one of these contains bright spots. However, deep water (to almost 4000 m), remoteness from harbors and markets, and thick accumulations of seasonal to permanent sea ice (until its possible removal by global warming later this century) will require the discovery of very large deposits for commercial success in most parts of Canada Basin. ?? 2011 Elsevier Ltd.

  11. Late Miocene - Pliocene exhumation of the Qinghai Nan Shan (Northeastern Tibetan Plateau) constrained by adjacent Chaka basin magnetostratigraphic architecture

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Yuan, D.; Craddock, W.; Zhang, P.; Zheng, D.; Zheng, W.; Molnar, P.; Lease, R.

    2008-12-01

    Magnetostratigraphy from the Chaka basin in northeastern Tibet suggests that sedimentation began near 10 Ma, and sedimentary facies suggest that the adjacent Qinghai Nan Shan immediately north developed at that time, tens of millions of years after India and Eurasia collided. A fining-upward sequence and provenance analysis indicate a growing transport distance for southeastward flowing paleo-drainages from ~10 Ma to 6.4 Ma. The disappearance of granite gravel at 7.4 Ma, eroded from the southern Qinghai Nan Shan to the north, indicates that the paleo-Qinghai Nan Shan temporarily became isolated from the Chaka basin, potentially by burial or partial burial of the lacustrine sediment. A change in paleocurrent direction, from south-southeastward to southwestward flow, along the mapped section at 6.4 Ma agrees with the reappearance of granite clasts provided by the southern Qinghai Nan Shan. Following this re-exhumation signal within the basin deposits, a coarsening-upward architecture, together with enhanced granite gravel input into the Chaka basin, indicates the decrease in transport distance from 6.4 Ma to ~3.0 Ma, which might represent increased relief and/or horizontal shortening during that period, even until present. Finally, by preliminary comparison of landscape characteristics for four nearby basin sections in northeastern Tibet, we suggest that the temporal variations of conglomerate deposition might reflect slightly different responses to regional climate change due to differences of transport distances and/or in relief. The onsets of conglomerate deposition at 4.2 Ma in Chaka basin, 3.6 Ma in Guide basin, and at 3.6 - 4.5 Ma in Linxia basin precede that at 2.5 Ma in Qaidam basin perhaps due to shorter transportation distances between ranges and the first three basins and higher local relief than those for the much wider Qaidam basin.

  12. A tale of two basins: An integrated physical and biological perspective of the deep Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Bluhm, B. A.; Kosobokova, K. N.; Carmack, E. C.

    2015-12-01

    domains have vertical stratification that constrains the transfer of nutrients to the surface layer (euphotic zone), thus leading to their oligotrophic state, particularly in the more strongly stratified Pacific Arctic where, despite high nutrient values in the inflow, convective reset of surface layer nutrients by haline convection in winter is virtually absent. First and multi-year sea ice drastically alters albedo and insulates the underlying water column from extreme winter heat loss while its mechanical properties (thickness, concentration, roughness, etc.) greatly affect the efficiency of momentum transfer from the wind to the underlying water. Biologically, sea ice algal growth in the basins is proportionally almost equal to or exceeding phytoplankton production, and is a habitat and transport platform for sympagic (ice-associated) fauna. Owing to nutrient limitation due to strong stratification and light limitation due to snow and ice cover and extreme sun angle, primary production in the two basin domains is very low compared to the adjacent shelves. Severe nutrient limitation and complete euphotic zone drawdown in the AB favors small phytoplankton, a ubiquitous deep chlorophyll maximum layer, a low f-ratio of new to recycled carbon fixation, and a low energy food web. In contrast, nutrients persist -albeit in low levels- in the western EB, even in summer, suggesting light limitation, heavy grazing or both. The higher stocks of nutrients in the EB are more conducive to marginal ice blooms than in the AB. The large-scale ocean currents (NHTC and ACBC) import substantial expatriate, not locally reproducing zooplankton biomass especially from the adjoining subarctic Atlantic (primarily Calanus finmarchicus), but also from the Pacific (e.g., Pseudocalanus spp., Neocalanus spp. and Metridia pacifica). These advective inputs serve both as source of food to resident pelagic and benthic biota within the basins, and as potential grazers exerting top down control on

  13. Methods for delineating flood-prone areas in the Great Basin of Nevada and adjacent states

    USGS Publications Warehouse

    Burkham, D.E.

    1988-01-01

    The Great Basin is a region of about 210,000 square miles having no surface drainage to the ocean; it includes most of Nevada and parts of Utah, California, Oregon, Idaho, and Wyoming. The area is characterized by many parallel mountain ranges and valleys trending north-south. Stream channels usually are well defined and steep within the mountains, but on reaching the alluvial fan at the canyon mouth, they may diverge into numerous distributary channels, be discontinuous near the apex of the fan, or be deeply entrenched in the alluvial deposits. Larger rivers normally have well-defined channels to or across the valley floors, but all terminate at lakes or playas. Major floods occur in most parts of the Great Basin and result from snowmelt, frontal-storm rainfall, and localized convective rainfall. Snowmelt floods typically occur during April-June. Floods resulting from frontal rain and frontal rain on snow generally occur during November-March. Floods resulting from convective-type rainfall during localized thunderstorms occur most commonly during the summer months. Methods for delineating flood-prone areas are grouped into five general categories: Detailed, historical, analytical, physiographic, and reconnaissance. The detailed and historical methods are comprehensive methods; the analytical and physiographic are intermediate; and the reconnaissance method is only approximate. Other than the reconnaissance method, each method requires determination of a T-year discharge (the peak rate of flow during a flood with long-term average recurrence interval of T years) and T-year profile and the development of a flood-boundary map. The procedure is different, however, for each method. Appraisal of the applicability of each method included consideration of its technical soundness, limitations and uncertainties, ease of use, and costs in time and money. Of the five methods, the detailed method is probably the most accurate, though most expensive. It is applicable to

  14. Evidence for oceanic crust in the Herodotus Basin

    NASA Astrophysics Data System (ADS)

    Granot, Roi

    2016-04-01

    Some of the fundamental tectonic problems of the Eastern Mediterranean remain unresolved due to the extremely thick sedimentary cover (10 to 15 km) and the lack of accurate magnetic anomaly data. I have collected 7,000 km of marine magnetic profiles (2012-2014) across the Herodotus and Levant Basins, Eastern Mediterranean, to study the nature and age of the underlying igneous crust. The towed magnetometer array consisted of two Overhauser sensors recording the total magnetic anomaly field in a longitudinal gradiometer mode, and a fully oriented vector magnetometer. The total field data from the Herodotus Basin reveal a newly detected short sequence of long-wavelength NE-SW lineated anomalies that straddle the entire basin suggesting a deep two-dimensional magnetic source layer. The three components of the magnetic vector data indicate that an abrupt transition from a 2D to 3D magnetic structure occurs east of the Herodotus Basin, along where a prominent NE-SW gravity feature is found. Altogether, these new findings confirm that the Herodotus Basin preserves remnants of oceanic crust that formed along the Neotethyan mid-ocean ridge system. The continuous northward and counterclockwise motion of the African Plate during the Paleozoic and Mesozoic allow predicting the evolution of remanent magnetization directions, which in-turn dictate that shape of the anomalies. The shape of the Herodotus anomalies best fit Late Carboniferous to Early Permian (300±20 Myr old) magnetization directions. Finally, I will discuss the implications of these results on the tectonic architecture of the region as well as on various geodynamic processes.

  15. Arctic Ocean basin liquid freshwater storage trend 1992-2012

    NASA Astrophysics Data System (ADS)

    Rabe, B.; Karcher, M.; Kauker, F.; Schauer, U.; Toole, J. M.; Krishfield, R. A.; Pisarev, S.; Kikuchi, T.; Su, J.

    2014-02-01

    Freshwater in the Arctic Ocean plays an important role in the regional ocean circulation, sea ice, and global climate. From salinity observed by a variety of platforms, we are able, for the first time, to estimate a statistically reliable liquid freshwater trend from monthly gridded fields over all upper Arctic Ocean basins. From 1992 to 2012 this trend was 600±300 km3 yr-1. A numerical model agrees very well with the observed freshwater changes. A decrease in salinity made up about two thirds of the freshwater trend and a thickening of the upper layer up to one third. The Arctic Ocean Oscillation index, a measure for the regional wind stress curl, correlated well with our freshwater time series. No clear relation to Arctic Oscillation or Arctic Dipole indices could be found. Following other observational studies, an increased Bering Strait freshwater import to the Arctic Ocean, a decreased Davis Strait export, and enhanced net sea ice melt could have played an important role in the freshwater trend we observed.

  16. Weekly Cycle of Lightning and Associated Patterns of Rainfall, Cloud, and Aerosols over Korea and Adjacent Oceans during Boreal Summer

    NASA Technical Reports Server (NTRS)

    Kim, Ji-In; Kim, Kyu-Myong

    2011-01-01

    In this study, we analyze the weekly cycle of lightning over Korea and adjacent oceans and associated variations of aerosols, clouds, precipitation, and atmospheric circulations, using aerosol optical depth (AOD) from the NASA Moderate resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging SpectroRadiometer (MISR), cloud properties from MODIS, precipitation and storm height from Tropical Rainfall Measuring Mission (TRMM) satellite, and lightning data from the Korean Lightning Detection Network (KLDN) during 9-year from 2002 to 2010. Lightning data was divided into three approximately equal areas, land area of Korea, and two adjacent oceans, Yellow Sea and South Sea. Preliminary results show that the number of lightning increases during the middle of the week over Yellow Sea. AOD data also shows moderately significant midweek increase at about the same time as lightning peaks. These results are consistent with the recent studies showing the invigoration of storms with more ice hydrometeors by aerosols, and subsequently wash out of aerosols by rainfall. Frequency of lightning strokes tend to peak at weekend in land area and over South Sea, indicating local weekly anomalous circulation between land and adjacent ocean. On the other hand, lightning frequency over Yellow Sea appears to have very strong weekly cycle with midweek peak on around Wednesday. It is speculated that the midweek peak of lightning over Yellow Sea was related with aerosol transport from adjacent land area. AOD data also suggests midweek peak over Yellow Sea, however, the weekly cycle of AOD was not statistically significant. Changes in weekly cycle of lightning from pre-monsoon to monsoon season, as well as associated clouds and circulation patterns are also discussed.

  17. Controls on bacterial gas accumulations in thick Tertiary coal beds and adjacent channel sandstones, Powder River basin, Wyoming and Montana

    SciTech Connect

    Rice, D.D.; Flores, R.M. )

    1991-03-01

    Coal beds, as much as 250 ft thick, and adjacent sandstones in the Paleocene Tongue River Member of the Fort Union Formation are reservoirs for coal-derived natural gas in the Powder River basin. The discontinuous coal beds were deposited in raised, ombrotrophic peat bogs about 3 mi{sup 2} in size, adjoining networks of fluvial channels infilled by sand. Coal-bed thickness was controlled by basin subsidence and depositional environments. The average maceral composition of the coals is 88% huminite (vitrinite), 5% liptinite, and 7% inertinite. The coals vary in rank from subbituminous C to A (R{sub o} values of 0.4 to 0.5%). Although the coals are relatively low rank, they display fracture systems. Natural gas desorbed and produced from the coal beds and adjacent sandstones is composed mainly of methane with lesser amount of Co{sub 2} ({lt}10%). The methane is isotopically light and enriched in deuterium. The gases are interpreted to be generated by bacterial processes and the fermentation pathway, prior to the main phase of thermogenic methane generation by devolatilization. Large amounts of bicarbonate water generated during early stages of coalification will have to be removed from the fracture porosity in the coal beds before desorption and commercial gas production can take place. Desorbed amounts of methane-rich, bacterial gas in the Powder River basin are relatively low ({lt}60 Scf/ton) compared to amounts of thermogenic coal-bed gases (hundreds of Scf/ton) from other Rocky Mountain basins. However, the total coal-bed gas resource in both the coal beds and the adjacent sandstones is considered to be large (as much as 40 Tcf) because of the vast coal resources (as much as 1.3 trillion tons).

  18. Searching for the Lost Jurassic and Cretaceous Ocean Basins of the Circum-Arctic Linking Plate Models and Seismic Tomography

    NASA Astrophysics Data System (ADS)

    Shephard, G. E.; Müller, R.

    2012-12-01

    The tectonic evolution of the circum-Arctic since the breakup of Pangea involves the opening and closing of ocean basins including the Oimyakon, Angayucham, South Anuyi, Amerasia and Eurasia basins. The time-dependent configurations and kinematic history of the basins, adjacent continental terranes, and subduction zones involved are not well understood, and many published tectonic models for particular regions are inconsistent with models for adjacent areas. The age, location, geometry and convergence rates of the subduction zones associated with these ancient ocean basins since at least the Late Jurassic have implications for mantle structure, which can be used as an additional constraint for building plate and plate boundary models. Here we integrate an analysis of both surface and deep mantle observations back to 200 Ma. Based on a digitized set of tectonic features with time-dependent rotational histories we present a refined plate model with topologically closed plate polygons for the circum-Arctic with particular focus on the northern Pacific, Siberian and Alaskan margins (Fig 1). We correlate the location, geometry and timing of subduction zones with associated seismic velocities anomalies from global P and S wave tomography models across different depths. We design a plate model that best matches slabs imaged in seismic tomography in an iterative fashion. This match depends on a combination of relative and absolute plate motions. Therefore we test two end-member absolute plate motion models, evaluating a paleomagnetic model and a model based on hotspot tracks and large igneous provinces. This method provides a novel approach to deciphering the Arctic tectonic history in a global context. Fig 1:Plate reconstruction at 200Ma and 140Ma, visualized using GPlates software. Present-day topography raster (ETOPO2) segmented into major tectonic elements of the circum-Arctic. Plate boundaries delineated in black and selected subduction and arc features labeled in

  19. Mercury profiles in sediments of the Arctic Ocean basins

    SciTech Connect

    Gobeil, C.; MacDonald, R.W.; Smith, J.N.

    1999-12-01

    Total Hg distribution shave been measured for seven sediment cores collected from the major basins of the Arctic Ocean during the Arctic Ocean Section in 1994. Hg determinations were performed on the top 10 cm of the sectioned cores using gold amalgamation atomic fluorescence spectroscopy. In five cores, Jg concentrations decrease downward from 34 to 116 ng g{sup {minus}1} at the sediment surface to 10--65 ng g{sup {minus}1} at 5 cm depth and then remain almost constant with increasing depth. In the other two cores, the Hg decrease with depth is interrupted by a maximum (96--107 ng g{sup {minus}1}) at 7--8 cm. The obvious inference--pervasive Hg contamination from anthropogenic sources even at the North Pole--is discounted after a careful evaluation of sediment geochemistry. The evidence suggests that these Hg profiles have been produced by Hg redistribution during diagenesis. In all seven cores, strong similarities are observed between the Hg and the reactive Fe profiles, implying that a portion of the total Hg deposited is recycled along with Fe during redox changes. Intense redox processing in these cores is demonstrated by sharp decreases in organic content with depth and by vertical profiles showing surface enrichments for Mn and Fe. The crucial factors governing surface Hg enrichments in Arctic basin sediments are the low sedimentation rates and sediment mixing rates that permit even minor Hg fluxes to have a significant cumulative effect.

  20. The concentration of radionuclides and metals in vegetation adjacent to and in the SRL Seepage Basins

    SciTech Connect

    Murphy, C. E. Jr.

    1992-12-14

    In 1991 the trees on the dikes surrounding the SRL Seepage Basins were sampled and analyzed to inventory the contaminants transported from the basins into the vegetation. Tree leaves and wood were collected and analyzed for [sup 90]Sr, [sup 60]Co, [sup 137]Cs, [sup 238]Pu, [sup 239,240]Pu, [sup 242,244]Cm, [sup 241]Am, Ba, Cr, Hg, Mg, Mn, Ni, and Pb. The concentrations of contaminants were influenced by sample type (leaves versus wood), species type (pines versus hardwoods), and location relative to distance from the basin. The total inventory of each contaminant in the trees was estimated. The relationships between leaf and wood, pines and hardwood, location, and mass of the material in each of these classes were used to weight the total inventory estimate. The radionuclide with the largest inventory was 0.7 mCi for [sup 90]Sr. The metallic contaminant with the largest inventory was Mn at 200 gm.

  1. The concentration of radionuclides and metals in vegetation adjacent to and in the SRL Seepage Basins

    SciTech Connect

    Murphy, C. E. Jr.

    1992-12-14

    In 1991 the trees on the dikes surrounding the SRL Seepage Basins were sampled and analyzed to inventory the contaminants transported from the basins into the vegetation. Tree leaves and wood were collected and analyzed for {sup 90}Sr, {sup 60}Co, {sup 137}Cs, {sup 238}Pu, {sup 239,240}Pu, {sup 242,244}Cm, {sup 241}Am, Ba, Cr, Hg, Mg, Mn, Ni, and Pb. The concentrations of contaminants were influenced by sample type (leaves versus wood), species type (pines versus hardwoods), and location relative to distance from the basin. The total inventory of each contaminant in the trees was estimated. The relationships between leaf and wood, pines and hardwood, location, and mass of the material in each of these classes were used to weight the total inventory estimate. The radionuclide with the largest inventory was 0.7 mCi for {sup 90}Sr. The metallic contaminant with the largest inventory was Mn at 200 gm.

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

    SciTech Connect

    Marzolf, J.E. )

    1990-05-01

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

  3. Near-island biological hotspots in barren ocean basins.

    PubMed

    Gove, Jamison M; McManus, Margaret A; Neuheimer, Anna B; Polovina, Jeffrey J; Drazen, Jeffrey C; Smith, Craig R; Merrifield, Mark A; Friedlander, Alan M; Ehses, Julia S; Young, Charles W; Dillon, Amanda K; Williams, Gareth J

    2016-01-01

    Phytoplankton production drives marine ecosystem trophic-structure and global fisheries yields. Phytoplankton biomass is particularly influential near coral reef islands and atolls that span the oligotrophic tropical oceans. The paradoxical enhancement in phytoplankton near an island-reef ecosystem--Island Mass Effect (IME)--was first documented 60 years ago, yet much remains unknown about the prevalence and drivers of this ecologically important phenomenon. Here we provide the first basin-scale investigation of IME. We show that IME is a near-ubiquitous feature among a majority (91%) of coral reef ecosystems surveyed, creating near-island 'hotspots' of phytoplankton biomass throughout the upper water column. Variations in IME strength are governed by geomorphic type (atoll vs island), bathymetric slope, reef area and local human impacts (for example, human-derived nutrient input). These ocean oases increase nearshore phytoplankton biomass by up to 86% over oceanic conditions, providing basal energetic resources to higher trophic levels that support subsistence-based human populations. PMID:26881874

  4. Near-island biological hotspots in barren ocean basins

    PubMed Central

    Gove, Jamison M.; McManus, Margaret A.; Neuheimer, Anna B.; Polovina, Jeffrey J.; Drazen, Jeffrey C.; Smith, Craig R.; Merrifield, Mark A.; Friedlander, Alan M.; Ehses, Julia S.; Young, Charles W.; Dillon, Amanda K.; Williams, Gareth J.

    2016-01-01

    Phytoplankton production drives marine ecosystem trophic-structure and global fisheries yields. Phytoplankton biomass is particularly influential near coral reef islands and atolls that span the oligotrophic tropical oceans. The paradoxical enhancement in phytoplankton near an island-reef ecosystem—Island Mass Effect (IME)—was first documented 60 years ago, yet much remains unknown about the prevalence and drivers of this ecologically important phenomenon. Here we provide the first basin-scale investigation of IME. We show that IME is a near-ubiquitous feature among a majority (91%) of coral reef ecosystems surveyed, creating near-island ‘hotspots' of phytoplankton biomass throughout the upper water column. Variations in IME strength are governed by geomorphic type (atoll vs island), bathymetric slope, reef area and local human impacts (for example, human-derived nutrient input). These ocean oases increase nearshore phytoplankton biomass by up to 86% over oceanic conditions, providing basal energetic resources to higher trophic levels that support subsistence-based human populations. PMID:26881874

  5. New view on tectonic structure of Siberian Sector of the Amerasian Basin (Arctic Ocean)

    NASA Astrophysics Data System (ADS)

    Vinokurov, Yu. I.

    2014-05-01

    In 2012, JSC Sevmorgeo with assistance of several research institutions of Federal Agency of Mineral Resources (Rosnedra) and Ministry of Defense carried out a unique set of offshore seismic and geological studies in the Mendeleev Rise area and adjacent areas of the Amerasia Basin. Two specially re-equipped icebreakers ("Kapitan Dranitsin" and "Dixon") were used in this campaign. The main results of the expedition were 5315 km of multichannel seismic profiles both with long and short streamers (4500 m and 600 m, respectively), 480 km long refraction profile crossing Mendeleev Rise. Seismic acquisition with short streamers was accompanied by deployment of sonobuoys. Geological studies included deep-water drilling and sea-bottom sampling by dredge, gravity corer, grab and by specially equipped research submarine. The newly acquired geological and geophysical data allowed for the following conclusions: 1. The Mendeleev Rise, the adjacent Lomonosov Ridge and Chukchi Plateau are the direct continuations of the East Siberian Sea tectonic structures. It is confirmed by direct tracking of some morphostructures, faults, gravity and magnetic anomalies from the shelf to deep-water highs. 2. The East Arctic Shelf and the adjacent Arctic Ocean represent offshore extent of the Verkhoyansk-Kolyma crustal domain constituted by a mosaic of separate blocks of the Pre-Cambrian basement (Okhotsk, Omulevka, Omolon, Wrangel-Gerald and Central Arctic) and Late Mesozoic orogens. This area differs significantly from the Ellesmerian crustal domain located to the east (including the Northwind Ridge, which coincides with inferred eastern boundary of the Mesozoides). The Central Arctic domain includes structures of the Mendeleev Ridge and the Chukchi Plateau. Western boundary of this block is inferred along the Spur of Geophysicists, which separates the Podvodnikov Basin into two unequal parts with different basement structure. From the south, southwest and west, the Central Arctic domain is

  6. Hydrogeochemistry and stable isotopes of ground and surface waters from two adjacent closed basins, Atacama Desert, northern Chile

    USGS Publications Warehouse

    Alpers, C.N.; Whittemore, D.O.

    1990-01-01

    The geochemistry and stable isotopes of groundwaters, surface waters, and precipitation indicate different sources of some dissolved constituents, but a common source of recharge and other constituents in two adjacent closed basins in the Atacama Desert region of northern Chile (24??15???-24??45???S). Waters from artesian wells, trenches, and ephemeral streams in the Punta Negra Basin are characterized by concentrations of Na>Ca>Mg and Cl ???SO4, with TDS Mg ??? Ca and SO4 > Cl, with TDS also Mg ??? Ca and SO4 > Cl, but with TDS up to 40 g/l. The deep mine waters have pH between 3.2 and 3.9, and are high in dissolved CO2 (??13 C = -4.8%PDB), indicating probable interaction with oxidizing sulfides. The deep mine waters have ??18O values of ???-1.8%.compared with values < -3.5??? for other Hamburgo Basin waters; thus the mine waters may represent a mixture of meteoric waters with deeper "metamorphic" waters, which had interacted with rocks and exchanged oxygen isotopes at elevated temperatures. Alternatively, the deep mine waters may represent fossil meteoric waters which evolved isotopically along an evaporative trend starting from values quite depleted in ??18O and ??Dd relative to either precipitation or shallow groundwaters. High I/Br ratios in the Hamburgo Basin waters and La Escondida mine waters are consistent with regionally high I in surficial deposits in the Atacama Desert region and may represent dissolution of a wind-blown evaporite component. Rain and snow collected during June 1984, indicate systematic ??18O and ??D fractionation with increasing elevation between 3150 and 4180 m a.s.l. (-0.21??.??18O and -1.7??.??D per 100 m). Excluding the deep mine waters from La Escondida, the waters from the Hamburgo and Punta Negra Basins have similar ??D and ??18O values and together show a distinct evaporative trend (??D = 5.0 ??18O - 20.2). Snowmelt from the central Andes Cordillera to the east is the most likely source of recharge to both basins. Some of the

  7. Ocean basin structure offshore the Southeastern United States: Is it the rift's fault?

    NASA Astrophysics Data System (ADS)

    Heffner, D. M.; Knapp, J. H.

    2012-12-01

    Continental rifts typically exhibit an asymmetrical geometry where major normal faults bound one side of a rotated block, and the rift basins thin toward the opposite hinge side. Differential extension on major faults is accommodated by transverse structures referred to as transfer zones, across which the asymmetric geometry may reverse polarity. It was proposed several decades ago that oceanic transforms between mid-ocean ridge spreading centers are inherited features of these rift-related transfer zones, and that these intra-plate structures are tectonically active. However, preserved evidence of onshore transfer zones is often lacking, particularly along the rifted margin of Eastern North America, and recent studies have suggested that oceanic transforms are not inherited structures. Observations of seismic reflection data integrated with well data show that adjacent basin bounding faults of the South Georgia Rift, a Triassic rift in the southeastern United States, occur on opposite sides of the rift flanks. The Walterboro and Warner Robins Transfer Zones identified in this study project along the small circles of Schettino and Turco (2009) into the Jacksonville and Bahamas Fracture Zones respectively. This projection is particularly interesting as it suggests the correlation of continental to oceanic features is one step south compared to previous studies which projected the Blake Spur Fracture Zone through the Charleston, SC region, and the Jacksonville Fracture Zone through Georgia. Using the same small circle solution, the Blake Spur Fracture Zone projects through the Blake Outer Ridge, a sedimentary drift which shows up prominently as a gravity anomaly the core of which has been identified as a tectonic feature reminiscent of a fracture zone on the basis of gravity modeling (Dove et al., 2007). Although no transfer zone has been identified where this small circle project onshore, it is approximately coincident with axis of the Cape Fear Arch which has been

  8. Is the Ordos Basin floored by a trapped oceanic plateau?

    NASA Astrophysics Data System (ADS)

    Kusky, Tim; Mooney, Walter

    2015-11-01

    The Ordos Basin in China has about 10 km of Neoarchean to Quaternary sediments covering an enigmatic basement of uncertain origin. The basement is tectonically stable, has a thick mantle root, low heat flow, few earthquakes, and has been slowly subsiding for billions of years. The basement has geophysical signatures that indicate it is dominantly intermediate to mafic in composition, and is similar to some other cratons world-wide, and also to several major oceanic plateaus. It was accreted to the amalgamated Eastern Block and Central Orogenic belt of the North China Craton (NCC) in the Paleoproterozoic, then involved in several Proterozoic tectonic events including being over-thrust by an accretionary orogen, and intruded by Andean arc-related magmas, and then involved in a continent-continent collision during amalgamation with the Columbia Supercontinent. Thus, the basement rocks are deformed, metamorphosed to granulite facies, and determining their initial origin is difficult. We suggest that the data is consistent with an origin as an oceanic plateau that accreted to the NCC and, later experienced different episodes of differentiation associated with later subduction and collisions. Formation of cratonic lithosphere by accretion of oceanic plateaus may be one mechanism to create stable cratons. Other cratons that apparently formed by partial melting of underplated and imbricated oceanic slabs are stable in some cases, but also re-activated and "de-cratonized" in some cases in Asia, where they have been affected by younger subduction, hydration, slab roll-back, and melt-peridotite reactions. This suggests that the initial mode of craton formation may be a factor in the preservation of stable cratons, and de-cratonization is not only influenced by younger tectonic activity.

  9. Timing the structural events in the Palaeoproterozoic Bolé-Nangodi belt terrane and adjacent Maluwe basin, West African craton, in central-west Ghana

    NASA Astrophysics Data System (ADS)

    de Kock, G. S.; Théveniaut, H.; Botha, P. M. W.; Gyapong, W.

    2012-04-01

    The Maluwe basin, north-adjacent to the Sunyani basin, is the northernmost of the northeast-trending Eburnean volcaniclastic depositories in Ghana. These basins are separated from one another by remnants of Eoeburnean crust, all formed during the evolution of an arc-backarc basins complex in a Palaeoproterozoic intraoceanic environment. The Bolé-Nangodi belt terrane to the northwest, of mostly Eoeburnean crust is fault bounded with the Maluwe basin along the northeast-trending Bolé-Navrongo fault zone. The stratigraphic sequence, which was the key to unravelling the structural evolution of the study area, was established by means of field observations aided by precision SHRIMP geochronology. The quartzitic, pelitic, quartzofeldspathic and granitic gneisses of the Eoeburnean crust (>2150 Ma) experienced complex metamorphic mineral growth and migmatitization, mostly under static crustal conditions and were subjected to several deformation episodes. The foliated mafic and metasedimentary enclaves within the Ifanteyire granite establish deformation to have taken place prior to ˜2195 Ma, while the tectonically emplaced Kuri amphibolites within the 2187-Ma gneissic Gondo granite indicate a stage of rifting followed by collision. Deformation of granite dykes in the Gondo granites at ˜2150 Ma concluded the development of the Eoeburnean orogenic cycle (DEE). The Sawla Suite, contemporaneous with the deposition of the Maluwe Group, intruded the tectonic exhumed Bolé-Nangodi terrane during extension between ˜2137 and 2125 Ma. The rifting separated the Abulembire fragment from the Bolé-Nangodi terrane. During subsequent northwestward subduction of young back-arc basin oceanic crust the volcaniclastic strata of the Maluwe Group and Sawla granitoids were deformed (DE1) under chlorite/sericite greenschist-grade conditions. The NE-trending folds had subhorizontal axes and subvertical axial planes. Simultaneous to the DE1 orogenesis the molasses of the Banda Group was

  10. An ecological study of the KSC Turning Basin and adjacent waters

    NASA Technical Reports Server (NTRS)

    Nevin, T. A.; Lasater, J. A.; Clark, K. B.; Kalajian, E. H.

    1974-01-01

    The conditions existing in the waters and bottoms of the Turning Basin, the borrow pit near Pad 39A, and the Barge Canal connecting them were investigated to determine the ecological significance of the chemical, biological, and microbiological parameters. The water quality, biological, microbiological findings are discussed. It is recommended that future dredging activities be limited in depth, and that fill materials should not be removed down to the clay strata.

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

    USGS Publications Warehouse

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

    1983-01-01

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

  12. A tectogenetic mechanism controlling the evolution of the Texel-IJsselmeer High (northern Netherlands) and adjacent basins

    SciTech Connect

    Rijkers, R.; Geluk, M. )

    1993-09-01

    Geological studies around the Texel-IJsselmeer High have been carried out for the regional subsurface mapping project of the Geological Survey of The Netherlands. The Texel-IJsselmeer High, in the northern part of the Netherlands, is a northwest-southeast-trending structural unit, slightly tilted to the northeast. The geological evolution of the Texel-IJsselmeer High and the adjacent areas can be linked to an extensional tectonic regime during which several Jurassic basins in the Netherlands originated. During the Late Jurassic, the southern border of the Texel-IJsselmeer High was characterized by normal faulting. Main faults are dipping southwest and are generally part of a half-graben structure. Faulting is accompanied by subsidence of the hanging wall (Jurassic basin area), while the footwall (the Texel-IJsselmeer High) is isostatically uplifted and eroded. The proposed model is based on thinning of the lower crust beneath the basins during Jurassic extension by pure shear. This mechanism is coupled locally with shear zones (simple shear) as a result of lower crustal failure. The model is supported by observations on deep regional seismics at the southern margin of the basin area. During the Late Cretaceous/early Tertiary, transpressional intraplate stresses reactivated the structural weakness zones in the lower and upper crust in a reversed way (inversion). During this tectonic inversion the northwest-southeast-trending Texel-IJsselmeer High acted as a buffer zone perpendicular to the direction of maximum principal stress. Paleogeographical studies and geohistory analysis support the proposed tectogenetic model of the Texel-IJsselmeer High.

  13. A tale of two basins: An integrated physical and biological perspective of the deep Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Bluhm, B. A.; Kosobokova, K. N.; Carmack, E. C.

    2015-12-01

    domains have vertical stratification that constrains the transfer of nutrients to the surface layer (euphotic zone), thus leading to their oligotrophic state, particularly in the more strongly stratified Pacific Arctic where, despite high nutrient values in the inflow, convective reset of surface layer nutrients by haline convection in winter is virtually absent. First and multi-year sea ice drastically alters albedo and insulates the underlying water column from extreme winter heat loss while its mechanical properties (thickness, concentration, roughness, etc.) greatly affect the efficiency of momentum transfer from the wind to the underlying water. Biologically, sea ice algal growth in the basins is proportionally almost equal to or exceeding phytoplankton production, and is a habitat and transport platform for sympagic (ice-associated) fauna. Owing to nutrient limitation due to strong stratification and light limitation due to snow and ice cover and extreme sun angle, primary production in the two basin domains is very low compared to the adjacent shelves. Severe nutrient limitation and complete euphotic zone drawdown in the AB favors small phytoplankton, a ubiquitous deep chlorophyll maximum layer, a low f-ratio of new to recycled carbon fixation, and a low energy food web. In contrast, nutrients persist -albeit in low levels- in the western EB, even in summer, suggesting light limitation, heavy grazing or both. The higher stocks of nutrients in the EB are more conducive to marginal ice blooms than in the AB. The large-scale ocean currents (NHTC and ACBC) import substantial expatriate, not locally reproducing zooplankton biomass especially from the adjoining subarctic Atlantic (primarily Calanus finmarchicus), but also from the Pacific (e.g., Pseudocalanus spp., Neocalanus spp. and Metridia pacifica). These advective inputs serve both as source of food to resident pelagic and benthic biota within the basins, and as potential grazers exerting top down control on

  14. Climatic and hydrologic oscillations in the Owens Lake basin and adjacent Sierra Nevada, California

    USGS Publications Warehouse

    Benson, L.V.; Burdett, J.W.; Kashgarian, Michaele; Lund, S.P.; Phillips, F.M.; Rye, R.O.

    1996-01-01

    Oxygen isotope and total inorganic carbon values of cored sediments from the Owens Lake basin, California, indicate that Owens Lake overflowed most of the time between 52,500 and 12,509 carbon-14 (14C) years before present (B.P.). Owens Lake desiccated during or after Heinrich event H1 and was hydrologically closed during Heinrich event H2. The magnetic susceptibility and organic carbon content of cored sediments indicate that about 19 Sierra Nevada glaciations occurred between 52,500 and 23,500 14C years B.P. Most of the glacial advances were accompanied by decreases in the amount of discharge reaching Owens Lake. Comparison of the timing of glaciation with the lithic record of North Atlantic core V23-81 indicates that the number of mountain glacial cycles and the number of North Atlantic lithic events were about equal between 39,000 and 23,500 14C years B.P.

  15. Dredged bedrock samples from the Amerasia Basin, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Brumley, K. J.; Mukasa, S. B.; O'Brien, T. M.; Mayer, L. A.; Chayes, D. N.

    2013-12-01

    Between 2008-2012, as part of the U.S. Extended Continental Shelf project in the Amerasia Basin, Arctic Ocean, 17 dredges were successfully collected sampling the first rock outcrops in the Chukchi Borderland and surrounding regions for the purpose of describing the geologic nature of the bathymetric features in this area. Multiple lines of evidence indicate that the specimens were collected from submarine rock exposures and were not samples of ice rafted debris, common in the ice covered waters of the Arctic Ocean. Using the USCGC Healy, each dredge was collected along very steep slopes (>35 degrees) measured with high resolution multibeam swath bathymety data. Each haul yielded samples of similar lithologies and identical metamorphic grade with manganese crusts on the surfaces exposed to seawater and fresh surfaces where the rocks were broken from outcrop. High tension pulls on the dredge line also indicated sampling of bedrock exposures. Dredged samples from a normal fault scarp in the central Chukchi Borderland consisted of Silurian (c. 430 Ma) orthogneisses that intruded older (c. 487-500 Ma) gabbros and luecogranties that were all metamorphosed to amphibolite grade (Brumley et al., 2011). Samples from the northern Northwind Ridge consisted of metasediments (greenschist facies) interpreted to have been deposited in a proximal arc setting with detrital zircon U-Pb age peaks at 434, 980 Ma with lesser peaks between 500-600, 1100-2000 Ma, and rare 2800 Ma grains (Brumley et al, 2010). Other dredges in the region of the Northwind Ridge yielded deformed and metamorphosed calcareous sandstones and low-grade phyllites (O'Brien et al., 2013). Taken together these rocks indicate a relationship to the Pearya Terrane of northern Ellesmere Island and S.W. Svalbard that were thought to represent a Cambro-Ordovician volcanic arc terrane that was involved in Caledonian orogenesis (Brumley et al., 2011). These findings constrain plate tectonic reconstruction models and bring

  16. Composition and distribution of bivalves of the abyssal plain adjacent to the Kuril-Kamchatka Trench (Pacific Ocean)

    NASA Astrophysics Data System (ADS)

    Kamenev, Gennady M.

    2015-01-01

    The KuramBio German-Russian deep-sea expedition ("Sonne", 2012) revealed a rich fauna of bivalves (55 species belonging to 21 families) on the abyssal plain (4861-5787 m) adjacent to the Kuril-Kamchatka Trench. Per station species richness varied from 18 to 33 species. The richest families were Cuspidariidae (7 species), Tindariidae (6 species), Thyasiridae (6 species), and Xylophagidae (5 species). The families Nuculidae, Malletidae, Yoldiidae, Mytilidae, Protocuspidariidae, and Verticordiidae were represented by a single species. Representatives of the family Siliculidae were recorded in the northwestern Pacific for the first time. Thirteen species (23.6%) were most common in the investigated northwestern Pacific region. Nine species (16.4%) were only found at one of the stations. Eight species (14.5%) are first records for the northwestern Pacific, of which Yoldiella cf. jeffreysi (Hidalgo, 1877), Pristigloma cf. albaSanders and Allen, 1973, and Syssitomya cf. pourtalesianaOliver, 2012 were previously known only for the Atlantic Ocean. The high diversity and richness of the bivalve fauna on the abyssal plain in the Kuril-Kamchatka Trench area may be connected to the favorable feeding conditions in this, one of the most highly productive areas of the Pacific Ocean.

  17. Comparison of phylogeographic structure and population history of two Phrynocephalus species in the Tarim Basin and adjacent areas.

    PubMed

    Zhang, Qian; Xia, Lin; He, Jingbo; Wu, Yonghua; Fu, Jinzhong; Yang, Qisen

    2010-12-01

    An aridification of the Tarim Basin and adjacent areas since middle Pleistocene has produced significant genetic structuring of the local fauna. We examined the phylogeographic patterns, population structure and history of Phrynocephalus axillaris and Phrynocephalus forsythii using a mitochondrial fragment ND4-tRNA(LEU). Phylogenetic hypotheses were constructed using maximum parsimony and Bayesian inference, and the divergence times of major lineages were estimated by BEAST. Population structure and history were inferred by nested clade analysis, neutrality tests, mismatch distribution, and isolation by distance analysis. The two species might have experienced different evolutionary history throughout their current distribution. For P. forsythii, a vicariant event, as a consequence of geological isolation and desert expansion, might have produced the significant divergence between the Tarim and the Yanqi populations. For P. axillaris, populations of the Yanqi, Turpan and Hami Basins might have been established through dispersal during demographic expansion. Climatic fluctuations caused alternate expansion and shrinkage of rivers and oases several times, which likely led to habitat fragmentation for both species. Interaction between vicariance, dispersal and habitat fragmentation produced the current distribution and genetic diversity. The observed difference between the two species may be due partially to their different reproductive modes (ovoviviparous vs. oviparous). PMID:20955804

  18. Sulfonylurea herbicides in an agricultural catchment basin and its adjacent wetland in the St. Lawrence River basin.

    PubMed

    de Lafontaine, Yves; Beauvais, Conrad; Cessna, Allan J; Gagnon, Pierre; Hudon, Christiane; Poissant, Laurier

    2014-05-01

    The use of sulfonylurea herbicides (SU) has increased greater than 100 times over the past 30 years in both Europe and North America. Applied at low rates, their presence, persistence and potential impacts on aquatic ecosystems remain poorly studied. During late-spring to early fall in 2009-2011, concentrations of 9 SU were assessed in two agricultural streams and their receiving wetland, an enlargement of the St. Lawrence River (Canada). Six SU in concentrations >LOQ (10 ng L(-1)) were detected in 10% or less of surface water samples. Rimsulfuron was detected each year, sulfosulfuron and nicosulfuron in two years and the others in one year only, suggesting that application of specific herbicides varied locally between years. Detection frequency and concentrations of SU were not significantly associated with total precipitation which occurred 1 to 5d before sampling. Concentrations and fate of SU differed among sites due to differences in stream dynamics and water quality characteristics. The persistence of SU in catchment basin streams reflected the dissipation effects associated with stream discharge. Maximum concentrations of some SU (223 and 148 ng L(-1)) were occasionally above the baseline level (100 ng L(-1)) for aquatic plant toxicity, implying potential toxic stress to flora in the streams. Substantially lower concentrations (max 55 ng L(-1)) of SU were noted at the downstream wetland site, likely as a result from dilution and mixing with St. Lawrence River water, and represent less toxicological risk to the wetland flora. Sporadic occurrence of SU at low concentrations in air and rain samples indicated that atmospheric deposition was not an important source of herbicides to the study area. PMID:24534695

  19. Integrated geophysical data processing and interpretation of crustal structure in Ethiopia with emphasis on the Ogaden Basin and adjacent areas

    NASA Astrophysics Data System (ADS)

    Tadesse, Ketsela

    ties these results together to form a complete picture of the axial structure of the rift. The cross profiles, which are interlocked with the axial rift profile, indicate that thick (˜45km) crust is present beneath a broad region of the western plateau. The EAGLE seismic results indicate that the part of the western plateau adjacent to the rift is thickened via underplating. The Bale Mountain region on the eastern rift flank has relatively thick (˜40 km) crust, which is in agreement with receiver function results. In general, asthenospheric upwelling affects a wide zone near Afar and the southern Ethiopian rift, whereas the area of upwelling is narrower around the MER. The Abbay or Blue Nile basin was another target of my study. Integrated geophysical (seismic, remote sensing, and gravity) and geological data suggest that the sedimentary section of Abbay basin extends well to the east of the known extent of its sedimentary fill. Gravity modeling results suggest approximately 3 km of sub-volcanic sedimentary strata exist over a wide area. I also undertook an integrated analysis of the Ogaden basin that lies east of the rift valley and is associated with the break-up of Gondwanaland by Karroo rifting. Seismic reflection data were processed and interpreted and combined with gravity and magnetic data to study the evolution of the basin and its geometry. The existence of a tri-radial rift that connects to the Abbay basin is suggested by the isostatic residual gravity anomaly map produced in this study. This result provides new evidence for the relationship of the Ogaden and Abbay basins via a northwest-southeast trending Permo-Triassic rift system. The northeastern part of the Ogaden basin shows distinct gravity anomalies trending in a northeast-southwest direction that appear to be due to a series of grabens and horsts. 3D Euler deconvolution of gravity data and modeling results suggest a sedimentary thickness of about 5 km sedimentary strata in some of the grabens

  20. Geohydrology of the Aucilla-Suwannee-Ochlockonee River Basin, south-central Georgia and adjacent parts of Florida

    USGS Publications Warehouse

    Torak, Lynn J.; Painter, Jaime A.; Peck, Michael F.

    2010-01-01

    Major streams and tributaries located in the Aucilla-Suwannee-Ochlockonee (ASO) River Basin of south-central Georgia and adjacent parts of Florida drain about 8,000 square miles of a layered sequence of clastic and carbonate sediments and carbonate Coastal Plain sediments consisting of the surficial aquifer system, upper semiconfining unit, Upper Floridan aquifer, and lower confining unit. Streams either flow directly on late-middle Eocene to Oligocene karst limestone or carve a dendritic drainage pattern into overlying Miocene to Holocene sand, silt, and clay, facilitating water exchange and hydraulic connection with geohydrologic units. Geologic structures operating in the ASO River Basin through time control sedimentation and influence geohydrology and water exchange between geohydrologic units and surface water. More than 300 feet (ft) of clastic sediments overlie the Upper Floridan aquifer in the Gulf Trough-Apalachicola Embayment, a broad area extending from the southwest to the northeast through the center of the basin. These clastic sediments limit hydraulic connection and water exchange between the Upper Floridan aquifer, the surficial aquifer system, and surface water. Accumulation of more than 350 ft of low-permeability sediments in the Southeast Georgia Embayment and Suwannee Strait hydraulically isolates the Upper Floridan aquifer from land-surface hydrologic processes in the Okefenokee Basin physiographic district. Burial of limestone beneath thick clastic overburden in these areas virtually eliminates karst processes, resulting in low aquifer hydraulic conductivity and storage coefficient despite an aquifer thickness of more than 900 ft. Conversely, uplift and faulting associated with regional tectonics and the northern extension of the Peninsular Arch caused thinning and erosion of clastic sediments overlying the Upper Floridan aquifer southeast of the Gulf Trough-Apalachicola Embayment near the Florida-Georgia State line. Limestone dissolution in

  1. New Perspectives from Satellite and Profile Observations on Tropospheric Ozone over Africa and the Adjacent Oceans: An Indian-Atlantic Ocean Link to tbe "Ozone Paradox"

    NASA Technical Reports Server (NTRS)

    Thompson, Anne M.; Witte, Jacquelyn C.; Diab, Roseanne D.; Thouret, Valerie; Sauvage, Bastien; Chatfield, B.; Guan, Hong

    2004-01-01

    In the past few years, tropospheric ozone observations of Africa and its adjacent ocenas have been greatly enhanced by high resolution (spatial and temporal) satellite measurements and profile data from aircraft (MOZAIC) and balloon-borne (SHADOZ) soundings. These views have demonstrated for the first time the complexity of chemical-dynamical interactions over the African continent and the Indian and Atlantic Oceans. The tropical Atlantic "ozone paradax" refers to the observation that during the season of maximum biomass burning in west Africa north of the Intertropical Convergence Zone (ITCZ), the highest tropospheric ozone total column occurs south of the ITCZ over the tropical Atlantic. The longitudinal view of tropospheric ozone in the southern tropics from SHADOZ (Southern Hemisphere Additional Ozonesondes) soundings shown the persistence of a "zonal-wave one" pattern that reinforces the "ozone paradox". These ozone features interact with dynamics over southern and northern Africa where anthropogenic sources include the industrial regions of the South African Highveld and Mideastern-Mediterranean influences, respectively. Our newest studies with satellites and soundings show that up to half the ozone pollution over the Atlantic in the January-March "paradox" period may originate from south Asian pollution. Individual patches of pollurion over the Indian Ocean are transported upward by convective mixing and are enriched by pyrogenic, biogenic sources and lightning as they cross Africa and descend over the Atlantic. In summary, local sources, intercontinental import and export and unique regional transport patterns put Africa at a crossroads of troposheric ozone influences.

  2. A near-uniform fluctuation of ocean bottom pressure and sea level across the deep ocean basins of the Arctic Ocean and the Nordic Seas

    NASA Astrophysics Data System (ADS)

    Fukumori, Ichiro; Wang, Ou; Llovel, William; Fenty, Ian; Forget, Gael

    2015-05-01

    Across the Arctic Ocean and the Nordic Seas, a basin-wide mode of ocean bottom pressure and sea level fluctuation is identified using satellite and in situ observations in conjunction with a global ocean circulation model and its adjoint. The variation extends across the interconnected deep ocean basins of these semi-enclosed Arctic seas, collectively called the Arctic Mediterranean, with spatially near-uniform amplitude and phase. The basin-wide fluctuation is barotropic and dominates the region's large-scale variability from sub-monthly to interannual timescales. The fluctuation results from bifurcating coastally trapped waves generated by winds along the continental slopes of the Arctic Mediterranean and its neighboring seas, including the North Atlantic Ocean. The winds drive Ekman transport across the large bathymetric gradients, forcing mass divergence between the shallow coastal area and the deep ocean basins and creating ocean bottom pressure anomalies of opposite signs in the two regions. The anomalies rapidly propagate away as barotropic coastally trapped waves with the coast and continental slope as respective boundaries. The waves subsequently bifurcate at the shallow straits connecting the Arctic Mediterranean with the rest of the globe. The straits transmit the shallow anomalies but not the deep variations, thereby inhibiting the anomalies' mutual cancelation by geographically separating the two. Anomalies that enter the deep Arctic basins equilibrate uniformly across the domain characterized by a homogeneous depth-integrated planetary potential vorticity distribution. The potential vorticity's steep gradient that borders the basins shields the region from neighboring shallow variations, giving rise to the observed spatially confined fluctuation. Compensating anomalies outside the Arctic adjust similarly across the rest of the globe but are comparatively negligible in amplitude because of the global ocean's larger area relative to that of the deep

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

    NASA Astrophysics Data System (ADS)

    Glasmacher, Ulrich Anton; Hackspacher, Peter C.

    2013-04-01

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

  4. Hydrology of the coastal springs ground-water basin and adjacent parts of Pasco, Hernando, and Citrus Counties, Florida

    USGS Publications Warehouse

    Knochenmus, Lari A.; Yobbi, Dann K.

    2001-01-01

    The coastal springs in Pasco, Hernando, and Citrus Counties, Florida consist of three first-order magnitude springs and numerous smaller springs, which are points of substantial ground-water discharge from the Upper Floridan aquifer. Spring flow is proportional to the water-level altitude in the aquifer and is affected primarily by the magnitude and timing of rainfall. Ground-water levels in 206 Upper Floridan aquifer wells, and surface-water stage, flow, and specific conductance of water from springs at 10 gaging stations were measured to define the hydrologic variability (temporally and spatially) in the Coastal Springs Ground-Water Basin and adjacent parts of Pasco, Hernando, and Citrus Counties. Rainfall at 46 stations and ground-water withdrawals for three counties, were used to calculate water budgets, to evaluate long-term changes in hydrologic conditions, and to evaluate relations among the hydrologic components. Predictive equations to estimate daily spring flow were developed for eight gaging stations using regression techniques. Regression techniques included ordinary least squares and multiple linear regression techniques. The predictive equations indicate that ground-water levels in the Upper Floridan aquifer are directly related to spring flow. At tidally affected gaging stations, spring flow is inversely related to spring-pool altitude. The springs have similar seasonal flow patterns throughout the area. Water-budget analysis provided insight into the relative importance of the hydrologic components expected to influence spring flow. Four water budgets were constructed for small ground-water basins that form the Coastal Springs Ground-Water Basin. Rainfall averaged 55 inches per year and was the only source of inflow to the Basin. The pathways for outflow were evapotranspiration (34 inches per year), runoff by spring flow (8 inches per year), ground-water outflow from upward leakage (11 inches per year), and ground-water withdrawal (2 inches per year

  5. The North Slope of Alaska and Adjacent Arctic Ocean (NSA/AAO) cart site begins operation: Collaboration with SHEBA and FIRE

    SciTech Connect

    Zak, D. B.; Church, H.; Ivey, M.; Yellowhorse, L.; Zirzow, J.; Widener, K. B.; Rhodes, P.; Turney, C.; Koontz, A.; Stamnes, K.; Storvold, R.; Eide, H. A.; Utley, P.; Eagan, R.; Cook, D.; Hart, D.; Wesely, M.

    2000-04-04

    Since the 1997 Atmospheric Radiation Measurement (ARM) Science Team Meeting, the North Slope of Alaska and Adjacent Arctic Ocean (NSA/AAO) Cloud and Radiation Testbed (CART) site has come into being. Much has happened even since the 1998 Science Team Meeting at which this paper was presented. To maximize its usefulness, this paper has been updated to include developments through July 1998.

  6. Chapter 50: Geology and tectonic development of the Amerasia and Canada Basins, Arctic Ocean

    USGS Publications Warehouse

    Grantz, A.; Hart, P.E.; Childers, V.A.

    2011-01-01

    Amerasia Basin is the product of two phases of counterclockwise rotational opening about a pole in the lower Mackenzie Valley of NW Canada. Phase 1 opening brought ocean-continent transition crust (serpentinized peridotite?) to near the seafloor of the proto-Amerasia Basin, created detachment on the Eskimo Lakes Fault Zone of the Canadian Arctic margin and thinned the continental crust between the fault zone and the proto-Amerasia Basin to the west, beginning about 195 Ma and ending prior to perhaps about 160 Ma. The symmetry of the proto-Amerasia Basin was disrupted by clockwise rotation of the Chukchi Microcontinent into the basin from an original position along the Eurasia margin about a pole near 72??N, 165 Wabout 145.5-140 Ma. Phase 2 opening enlarged the proto-Amerasia Basin by intrusion of mid-ocean ridge basalt along its axis between about 131 and 127.5 Ma. Following intrusion of the Phase 2 crust an oceanic volcanic plateau, the Alpha-Mendeleev Ridge LIP (large igneous province), was extruded over the northern Amerasia Basin from about 127 to 89-75 Ma. Emplacement of the LIP halved the area of the Amerasia Basin, and the area lying south of the LIP became the Canada Basin. ?? 2011 The Geological Society of London.

  7. Large-Scale Distribution and Activity of Prokaryotes in Deep-Sea Surface Sediments of the Mediterranean Sea and the Adjacent Atlantic Ocean

    PubMed Central

    Giovannelli, Donato; Molari, Massimiliano; d’Errico, Giuseppe; Baldrighi, Elisa; Pala, Claudia; Manini, Elena

    2013-01-01

    The deep-sea represents a substantial portion of the biosphere and has a major influence on carbon cycling and global biogeochemistry. Benthic deep-sea prokaryotes have crucial roles in this ecosystem, with their recycling of organic matter from the photic zone. Despite this, little is known about the large-scale distribution of prokaryotes in the surface deep-sea sediments. To assess the influence of environmental and trophic variables on the large-scale distribution of prokaryotes, we investigated the prokaryotic assemblage composition (Bacteria to Archaea and Euryarchaeota to Crenarchaeota ratio) and activity in the surface deep-sea sediments of the Mediterranean Sea and the adjacent North Atlantic Ocean. Prokaryotic abundance and biomass did not vary significantly across the Mediterranean Sea; however, there were depth-related trends in all areas. The abundance of prokaryotes was positively correlated with the sedimentary concentration of protein, an indicator of the quality and bioavailability of organic matter. Moving eastwards, the Bacteria contribution to the total prokaryotes decreased, which appears to be linked to the more oligotrophic conditions of the Eastern Mediterranean basins. Despite the increased importance of Archaea, the contributions of Crenarchaeota Marine Group I to the total pool was relatively constant across the investigated stations, with the exception of Matapan-Vavilov Deep, in which Euryarchaeota Marine Group II dominated. Overall, our data suggest that deeper areas of the Mediterranean Sea share more similar communities with each other than with shallower sites. Freshness and quality of sedimentary organic matter were identified through Generalized Additive Model analysis as the major factors for describing the variation in the prokaryotic community structure and activity in the surface deep-sea sediments. Longitude was also important in explaining the observed variability, which suggests that the overlying water masses might have a

  8. Propagation of signals in basin-scale ocean bottom pressure from a barotropic model

    NASA Astrophysics Data System (ADS)

    Stepanov, Vladimir N.; Hughes, Chris W.

    2006-12-01

    The exchange of atmospheric plus oceanic mass between ocean basins is investigated using a global barotropic ocean model. We find two particular cases of exchange between two basins. At periods of 4-6 days, the exchange is between the Atlantic and Pacific basins, and represents a known oscillation forced by atmospheric pressure. This mode represents a failure of the inverse-barometer relationship due to the large scale and high frequency of atmospheric forcing, and the presence of continents. Significant exchange between Atlantic and Pacific also occurs at longer periods. The second case is most prominent at periods longer than 30 days (strongest at periods longer than 100 days), and represents a mass exchange between the Southern Ocean and the Pacific. The Southern Ocean part of this exchange is clearly related to the Southern Mode of fluctuations in Antarctic circumpolar transport, forced by Southern Ocean wind stress. The reason for the exchange being with the Pacific rather than other basins is explored, and is found to be related to the balance of wind stress by form stress in Drake Passage: exchange with the Atlantic and Indian oceans becomes dominant if Drake Passage topography is removed. While recognizing the limitations of a barotropic model, we contend that it is necessary to understand the barotropic adjustment process in order to make sense of longer timescale processes. Accordingly, we end with speculation on the possible importance of the barotropic results for global sea level and tropical dynamics.

  9. Modeling the Physical and Biochemical Influence of Ocean Thermal Energy Conversion Plant Discharges into their Adjacent Waters

    SciTech Connect

    PAT GRANDELLI, P.E.; GREG ROCHELEAU; JOHN HAMRICK, Ph.D.; MATT CHURCH, Ph.D.; BRIAN POWELL, Ph.D.

    2012-09-29

    This paper describes the modeling work by Makai Ocean Engineering, Inc. to simulate the biochemical effects of of the nutrient-enhanced seawater plumes that are discharged by one or several 100 megawatt OTEC plants. The modeling is needed to properly design OTEC plants that can operate sustainably with acceptably low biological impact. In order to quantify the effect of discharge configuration and phytoplankton response, Makai Ocean Engineering implemented a biological and physical model for the waters surrounding O`ahu, Hawai`i, using the EPA-approved Environmental Fluid Dynamics Code (EFDC). Each EFDC grid cell was approximately 1 square kilometer by 20 meters deep, and used a time step of three hours. The biological model was set up to simulate the biochemical response for three classes of organisms: Picoplankton (< 2 um) such as prochlorococccus, nanoplankton (2-20 um), and microplankton (> 20 um) e.g., diatoms. The dynamic biological phytoplankton model was calibrated using chemical and biological data collected for the Hawaii Ocean Time Series (HOTS) project. Peer review of the biological modeling was performed. The physical oceanography model uses boundary conditions from a surrounding Hawai'i Regional Ocean Model, (ROM) operated by the University of Hawai`i and the National Atmospheric and Oceanic Administration. The ROM provided tides, basin scale circulation, mesoscale variability, and atmospheric forcing into the edges of the EFDC computational domain. This model is the most accurate and sophisticated Hawai'ian Regional Ocean Model presently available, assimilating real-time oceanographic observations, as well as model calibration based upon temperature, current and salinity data collected during 2010 near the simulated OTEC site. The ROM program manager peer-reviewed Makai's implementation of the ROM output into our EFDC model. The supporting oceanographic data was collected for a Naval Facilities Engineering Command / Makai project. Results: The model

  10. Chapter 50 Geology and tectonic development of the Amerasia and Canada Basins, Arctic Ocean

    USGS Publications Warehouse

    Grantz, Arthur; Hart, Patrick E.; Childers, Vicki A

    2011-01-01

    Amerasia Basin is the product of two phases of counterclockwise rotational opening about a pole in the lower Mackenzie Valley of NW Canada. Phase 1 opening brought ocean–continent transition crust (serpentinized peridotite?) to near the seafloor of the proto-Amerasia Basin, created detachment on the Eskimo Lakes Fault Zone of the Canadian Arctic margin and thinned the continental crust between the fault zone and the proto-Amerasia Basin to the west, beginning about 195 Ma and ending prior to perhaps about 160 Ma. The symmetry of the proto-Amerasia Basin was disrupted by clockwise rotation of the Chukchi Microcontinent into the basin from an original position along the Eurasia margin about a pole near 72°N, 165 W about 145.5–140 Ma. Phase 2 opening enlarged the proto-Amerasia Basin by intrusion of mid-ocean ridge basalt along its axis between about 131 and 127.5 Ma. Following intrusion of the Phase 2 crust an oceanic volcanic plateau, the Alpha–Mendeleev Ridge LIP (large igneous province), was extruded over the northern Amerasia Basin from about 127 to 89–75 Ma. Emplacement of the LIP halved the area of the Amerasia Basin, and the area lying south of the LIP became the Canada Basin.

  11. Environmental forcing on life history strategies: Evidence for multi-trophic level responses at ocean basin scales

    USGS Publications Warehouse

    Suryan, R.M.; Saba, V.S.; Wallace, B.P.; Hatch, Shyla A.; Frederiksen, M.; Wanless, S.

    2009-01-01

    Variation in life history traits of organisms is thought to reflect adaptations to environmental forcing occurring from bottom-up and top-down processes. Such variation occurs not only among, but also within species, indicating demographic plasticity in response to environmental conditions. From a broad literature review, we present evidence for ocean basin- and large marine ecosystem-scale variation in intra-specific life history traits, with similar responses occurring among trophic levels from relatively short-lived secondary producers to very long-lived apex predators. Between North Atlantic and North Pacific Ocean basins, for example, species in the Eastern Pacific exhibited either later maturation, lower fecundity, and/or greater annual survival than conspecifics in the Western Atlantic. Parallel variations in life histories among trophic levels also occur in adjacent seas and between eastern vs. western ocean boundaries. For example, zooplankton and seabird species in cooler Barents Sea waters exhibit lower fecundity or greater annual survival than conspecifics in the Northeast Atlantic. Sea turtles exhibit a larger size and a greater reproductive output in the Western Pacific vs. Eastern Pacific. These examples provide evidence for food-web-wide modifications in life history strategies in response to environmental forcing. We hypothesize that such dichotomies result from frequency and amplitude shifts in resource availability over varying temporal and spatial scales. We review data that supports three primary mechanisms by which environmental forcing affects life history strategies: (1) food-web structure; (2) climate variability affecting the quantity and seasonality of primary productivity; (3) bottom-up vs. top-down forcing. These proposed mechanisms provide a framework for comparisons of ecosystem function among oceanic regions (or regimes) and are essential in modeling ecosystem response to climate change, as well as for creating dynamic ecosystem

  12. Occurrence and source apportionment of sulfonamides and their metabolites in Liaodong Bay and the adjacent Liao River basin, North China.

    PubMed

    Jia, Ai; Hu, Jianying; Wu, Xiaoqin; Peng, Hui; Wu, Shimin; Dong, Zhaomin

    2011-06-01

    The presence of antibiotics in the environment is of great concern because of their potential for resistance selection among pathogens. In the present study we investigated the occurrence of 19 sulfonamides, five N-acetylated sulfonamide metabolites, and trimethoprim in the Liao River basin and adjacent Liaodong Bay, China, as well as 10 human/agricultural source samples. Within the 35 river samples, 12 sulfonamides, four acetylated sulfonamides, and trimethoprim were detected, with the dominant being sulfamethoxazole (66.6 ng/L), N-acetylsulfamethoxazole (63.1 ng/L), trimethoprim (29.0 ng/L), sulfadiazine (14.0 ng/L), and sulfamonomethoxine (8.4 ng/L); within the 36 marine samples, 10 chemicals were detected, with the main contributions from sulfamethoxazole (25.2 ng/L) and N-acetylsulfamethoxazole (28.6 ng/L). Sulfamethoxazole (25.9%), N-acetylsulfamethoxazole (46.6%), trimethoprim (22.9%), and sulfapyridine (1.4%) were the main chemicals from human sources, while sulfamonomethoxine, sulfamethazine, sulfaquinoxaline, sulfaguanidine, sulfadiazine, sulfanilamide, and sulfamethoxypyridazine were dominant in the animal husbandry sources, specifically, swine and poultry farms, and sulfamethoxazole (91%) was dominant in the mariculture source. A principal component analysis with multiple linear regression was performed to evaluate the source apportionment of total sulfonamides in Liaodong Bay. It was found that animal husbandry contributed 15.2% of total sulfonamides, while human sources contributed 28.5%, and combined human and mariculture sources contributed 56.3%. In addition, the mariculture contribution was 24.1% of total sulfonamides into the sea based on mass flux estimation. The present study is the first report that the environmental levels of sulfonamide metabolites were comparable to the corresponding parents; therefore, we should pay attention to their environmental occurrence. Source apportionment showed human discharge (60.7%) significantly

  13. Estimation of nutrient contributions from the ocean across a river basin using stable isotope analysis

    NASA Astrophysics Data System (ADS)

    Nakayama, K.; Maruya, Y.; Matsumoto, K.; Komata, M.; Komai, K.; Kuwae, T.

    2015-11-01

    Total nitrogen (TN), which consists of total particulate nitrogen (TPN) and total dissolved nitrogen (TDN), is transported with not only in river channels but also across the entire river basin, including via ground water and migratory animals. In general, TPN export from an entire river basin to the ocean is larger than TDN in a mountainous region. Since marine derived nutrients (MDN) are hypothesized to be mainly transported as suspended matters from the ground surface, it is necessary to investigate the contribution of MDN to the forest floor (soils) in order to quantify the true role of MDN at the river ecosystem scale. This study investigated TN export from an entire river basin, and also we estimated the contribution of pink (Oncorhynchus gorbuscha) and chum salmon (O. keta) to total oceanic nitrogen input across a river basin. The maximum potential contribution of TN entering the river basin by salmon was found to be 23.8 % relative to the total amount of TN exported from the river basin. The contribution of particulate nitrogen based on suspended sediment from the ocean to the river basin soils was 22.9 % with SD of 3.6 % by using stable isotope analysis (SIA) of nitrogen (δ15N).

  14. Multi-property modeling of ocean basin carbon fluxes

    NASA Technical Reports Server (NTRS)

    Volk, Tyler

    1988-01-01

    The objectives of this project were to elucidate the causal mechanisms in some of the most important features of the global ocean/atomsphere carbon system. These included the interaction of physical and biological processes in the seasonal cycle of surface water pCo2, and links between productivity, surface chlorophyll, and the carbon cycle that would aid global modeling efforts. In addition, several other areas of critical scientific interest involving links between the marine biosphere and the global carbon cycle were successfully pursued; specifically, a possible relation between phytoplankton emitted DMS and climate, and a relation between the location of calcium carbonate burial in the ocean and metamorphic source fluxes of CO2 to the atmosphere. Six published papers covering the following topics are summarized: (1) Mass extinctions, atmospheric sulphur and climatic warming at the K/T boundary; (2) Sensitivity of climate and atmospheric CO2 to deep-ocean and shallow-ocean carbonate burial; (3) Controls on CO2 sources and sinks in the earthscale surface ocean; (4) pre-anthropogenic, earthscale patterns of delta pCO2 between ocean and atmosphere; (5) Effect on atmospheric CO2 from seasonal variations in the high latitude ocean; and (6) Limitations or relating ocean surface chlorophyll to productivity.

  15. Decrease in the CO2 uptake capacity in an ice-free Arctic Ocean basin.

    PubMed

    Cai, Wei-Jun; Chen, Liqi; Chen, Baoshan; Gao, Zhongyong; Lee, Sang H; Chen, Jianfang; Pierrot, Denis; Sullivan, Kevin; Wang, Yongchen; Hu, Xinping; Huang, Wei-Jen; Zhang, Yuanhui; Xu, Suqing; Murata, Akihiko; Grebmeier, Jacqueline M; Jones, E Peter; Zhang, Haisheng

    2010-07-30

    It has been predicted that the Arctic Ocean will sequester much greater amounts of carbon dioxide (CO2) from the atmosphere as a result of sea ice melt and increasing primary productivity. However, this prediction was made on the basis of observations from either highly productive ocean margins or ice-covered basins before the recent major ice retreat. We report here a high-resolution survey of sea-surface CO2 concentration across the Canada Basin, showing a great increase relative to earlier observations. Rapid CO2 invasion from the atmosphere and low biological CO2 drawdown are the main causes for the higher CO2, which also acts as a barrier to further CO2 invasion. Contrary to the current view, we predict that the Arctic Ocean basin will not become a large atmospheric CO2 sink under ice-free conditions. PMID:20651119

  16. Spring Database for the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah

    USGS Publications Warehouse

    Pavelko, Michael T.

    2007-01-01

    A database containing nearly 3,400 springs was developed for the Basin and Range carbonate-rock aquifer system study area in White Pine County, Nevada, and adjacent areas in Nevada and Utah. The spring database provides a foundation for field verification of springs in the study area. Attributes in the database include location, geographic and general geologic settings, and available discharge and temperature data for each spring.

  17. Leveraging Somali Basin Magnetic Anomalies to Constrain Gondwana Breakup and Early Indian Ocean Formation

    NASA Astrophysics Data System (ADS)

    Davis, J. K.; Lawver, L. A.; Norton, I. O.; Gahagan, L.

    2015-12-01

    The Somali Basin, found between the Horn of Africa and Madagascar was formed during the rifting of East and West Gondwana. Understanding the evolution of the basin has historically been hindered by enigmatic seafloor fabric and an apparent paucity of magnetic anomaly data. Recent iterations of satellite gravity data have revealed nearly complete fracture zones as well as a distinct extinct spreading ridge within the basin. Through a thorough compilation of available Somali Basin shiptrack profiles, we have been able to successfully model and interpret magnetic anomalies with exceptional detail. This complication is unrivaled in completeness and provides unprecedented insight into basin formation. Using this high quality data, we have interpreted magnetic anomalies M0r (120.8 Ma) to M24Bn (152.43 Ma) about the extinct ridge. The interpreted Somali Basin spreading rate and spreading direction, through anomaly M15n (135.76 Ma), are similar to those observed in the neighboring coeval Mozambique Basin. This similarity suggests that East Gondwana separated from West Gondwana as a cohesive unit, and that the internal rifting of East Gondwana began later around 135 Ma. Our magnetic anomaly interpretations have been combined with additional magnetic interpretations from around the Indian Ocean to build a regionally consistent plate model of Gondwana breakup and early Indian Ocean formation. This plate model will be crucial for future efforts unraveling a precise history of East Gondwana fragmentation and constraining the formation of the Enderby Basin offshore East Antarctica and Bay of Bengal offshore East India.

  18. Lance water injection tests adjacent to the 281-3H retention basin at the Savannah River Site, Aiken, South Carolina

    SciTech Connect

    Freifeld, B.; Myer, L.; Moridis, G.; Cook, P.; James, A.; Pellerin, L.; Pruess, K.

    1996-09-01

    A pilot-scale field demonstration of waste isolation using viscous- liquid containment barriers has been planned for the 281-3H retention basin at the Savannah River Site, Aiken, SC. The 281-3H basin is a shallow retention/seepage basin contaminated mainly by radionuclides. The viscous-liquid containment barrier utilizes the permeation of liquid grout to either entomb the contaminants within a monolithic grout structure or to isolate the waste by drastically reducing the permeability, of the soils around the plume. A clear understanding of the hydrogeologic setting of the retention basin is necessary for proper design of the viscous liquid barrier. To aid in the understanding of the hydrogeology of the 281-3H retention basin, and to obtain critical parameters necessary for grout injection design, a series of tests were undertaken in a region immediately adjacent to the basin. The objectives of the LWIT were: 1. To evaluate the general performance of the Lance Injection Technique for grout emplacement at the site, including the range and upper limits of injection pressures, the flow rates applicable for site conditions, as well as the mechanical forces needed for lance penetration. 2. To obtain detailed information on the injectability of the soils immediately adjacent to the H-area retention basin. 3. To identify any high permeability zones suitable for injection and evaluate their spatial distribution. 4. To perform ground penetrating radar (GPR) to gain information on the structure of the soil column and to compare the results with LWIT data. This report will focus on results pertinent to these objectives.

  19. Double-diffusive layering in the Eurasian Basin of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Rudels, Bert; Björk, Göran; Muench, Robin D.; Schauer, Ursula

    1999-06-01

    The central basins of the Arctic Ocean, below the surface mixed layer and remote from peripheral boundary currents, comprise an extremely low energy oceanic environment. Water masses having distinctly different Θ- S characteristics are organised throughout the central basins in extensive layers, consistent with occurrence of double-diffusive convection. In the Eurasian Basin, these structures can be explained by invoking formation along the narrow frontal region associated with the confluence of Fram Strait and Barents Sea waters north of the Kara Sea, and subsequent advection by the main circulation field. The presence of features in the interior of the basins requires a combination of processes that could include self-induced migration, through double-diffusive convection, as well as advection, across the central regions having weak horizontal gradients in temperature and salinity.

  20. Structure and tectonic evolution of the Southern Eurasia Basin, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Sekretov, Sergey B.

    2002-07-01

    Multichannel seismic reflection data acquired by Marine Arctic Geological Expedition (MAGE) of Murmansk, Russia in 1990 provide the first view of the geological structure of the Arctic region between 77-80°N and 115-133°E, where the Eurasia Basin of the Arctic Ocean adjoins the passive-transform continental margin of the Laptev Sea. South of 80°N, the oceanic basement of the Eurasia Basin and continental basement of the Laptev Sea outer margin are covered by 1.5 to 8 km of sediments. Two structural sequences are distinguished in the sedimentary cover within the Laptev Sea outer margin and at the continent/ocean crust transition: the lower rift sequence, including mostly Upper Cretaceous to Lower Paleocene deposits, and the upper post-rift sequence, consisting of Cenozoic sediments. In the adjoining Eurasia Basin of the Arctic Ocean, the Cenozoic post-rift sequence consists of a few sedimentary successions deposited by several submarine fans. Based on the multichannel seismic reflection data, the structural pattern was determined and an isopach map of the sedimentary cover and tectonic zoning map were constructed. A location of the continent/ocean crust transition is tentatively defined. A buried continuation of the mid-ocean Gakkel Ridge is also detected. This study suggests that south of 78.5°N there was the cessation in the tectonic activity of the Gakkel Ridge Rift from 33-30 until 3-1 Ma and there was no sea-floor spreading in the southernmost part of the Eurasia Basin during the last 30-33 m.y. South of 78.5°N all oceanic crust of the Eurasia Basin near the continental margin of the Laptev Sea was formed from 56 to 33-30 Ma.

  1. Estimation of nutrient contributions from the ocean across a river basin using stable isotope analysis

    NASA Astrophysics Data System (ADS)

    Nakayama, K.; Maruya, Y.; Matsumoto, K.; Komata, M.; Komai, K.; Kuwae, T.

    2015-04-01

    Since marine derived nutrients (MDN) are transported not only in river channels but also across the entire river basin, including via ground water and migratory animals, it is necessary to investigate the contribution of MDN to the forest floor (soils) in order to quantify the true role of MDN at the river ecosystem scale. This study investigated the contribution of pink (Oncorhynchus gorbuscha) and chum salmon (O. keta) to total oceanic nitrogen (TN) input across a river basin using stable isotope analysis (SIA) of nitrogen (δ15N). The contribution of TN entering the river basin by salmon was 23.8 % relative to the total amount of TN exported from the river basin, providing a first estimate of MDN export for a river basin. The contribution of nitrogen from the ocean to the river basin soils was between 22.9 and 23.8 %. Furthermore, SIA showed that the transport of oceanic TN by sea eagles (Haliaeetus spp.) was greater than that by bears (Ursus arctos), which had previously been that bears are thought to be the major animal transporter of nutrients in the northern part of Japan.

  2. 33 CFR 334.910 - Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine Corps Base, Camp Pendleton, Calif...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine Corps Base, Camp Pendleton, Calif.; restricted area. 334.910 Section 334.910... AND RESTRICTED AREA REGULATIONS § 334.910 Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine...

  3. 33 CFR 334.910 - Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine Corps Base, Camp Pendleton, Calif...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine Corps Base, Camp Pendleton, Calif.; restricted area. 334.910 Section 334.910... AND RESTRICTED AREA REGULATIONS § 334.910 Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine...

  4. 33 CFR 334.910 - Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine Corps Base, Camp Pendleton, Calif...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine Corps Base, Camp Pendleton, Calif.; restricted area. 334.910 Section 334.910... AND RESTRICTED AREA REGULATIONS § 334.910 Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine...

  5. 33 CFR 334.910 - Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine Corps Base, Camp Pendleton, Calif...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine Corps Base, Camp Pendleton, Calif.; restricted area. 334.910 Section 334.910... AND RESTRICTED AREA REGULATIONS § 334.910 Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine...

  6. 33 CFR 334.910 - Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine Corps Base, Camp Pendleton, Calif...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine Corps Base, Camp Pendleton, Calif.; restricted area. 334.910 Section 334.910... AND RESTRICTED AREA REGULATIONS § 334.910 Pacific Ocean, Camp Pendleton Boat Basin, U.S. Marine...

  7. Basin-Specific Variations in the Thermal Aging of Oceanic Asthenosphere

    NASA Astrophysics Data System (ADS)

    Paulson, E.; Jordan, T. H.

    2014-12-01

    To investigate the depth extent of mantle thermal aging beneath ocean basins, we project 3D Voigt averaged S-velocity variations from an ensemble of global tomographic models onto a 1º x 1º degree age-based regionalization and average each major ocean basin (Pacific, Atlantic, and Indian) in equal increments of the square-root of crustal age. By comparing the age averaged S-wave profiles, we estimate convergence depths, the minimum depths where age variations become statistically insignificant. Following Jordan & Paulson (JGR, doi:10.1002/jgrb.50263, 2013), we estimate aleatory variability in the S-wave profiles, correct for vertical smearing bias, and estimate epistemic uncertainties over the model ensemble. We can assert with 90% confidence that the age-correlated variations in Voigt-averaged S velocities persist to depths greater than 170 km. Given the strong evidence that the G discontinuity (~70 km) approximates the lithosphere-asthenosphere boundary (LAB) beneath ocean basins, we conclude that the upper part of the oceanic asthenosphere participates in the cooling that forms the kinematic plates. Age-averaged profiles show significant differences among the ocean basins. To quantify this, we fit age-dependent vertical travel times through the uppermost mantle of the models with an idealized Earth model having a strict square-root of age velocity structure in the ocean basins, suitably filtered to mimic tomographic smoothing. Good fits can be obtained for the Atlantic and Indian ocean basins out to 170 My, although the travel-time slopes for the former are steeper than the latter, implying more rapid cooling in the Atlantic. The Pacific basin shows significant deviations from simple conductive cooling for ages greater than about 50 My, in general agreement with previously published surface-wave models, indicating perturbations associated with small-scale convective processes. We conclude that large-scale flow advects small-scale heterogeneities due to

  8. A sediment budget for the Transkei Basin, Southwest Indian Ocean

    NASA Astrophysics Data System (ADS)

    Uenzelmann-Neben, Gabriele; Clift, Peter D.

    2015-12-01

    Deep sea sediment budgets can be used to constrain erosion rates in the neighboring continents from which the material was derived. Here we construct a sediment budget for the Transkei Basin, offshore South Africa using an existing seismic reflection survey and dated by correlation of seismic attributes to dated sections in nearby basins. Backstripping of the sections reveals that sediment accumulation rates fell from 110 to 11 Ma, with a possible period of rapid accumulation from 36 to 34 Ma that may be driven by strengthening of the Antarctic Bottom Water (AABW). The long term trend is linked to erosional degradation of the onshore continental escarpment, formed as a consequence of continental break-up. No change is noted at 30 Ma, coincident with proposed uplift of southern Africa driven by plume activity. The basin shows a significant increase in sediment accumulation after 11 Ma, which we interpret to reflect strengthening and rerouting of the AABW from the south into Transkei Basin, as a far field effect of the start of closure of the Indonesian Throughflow.

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

    NASA Astrophysics Data System (ADS)

    Shephard, Grace E.

    2016-04-01

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

  10. Systematic removal of neutral sugars within dissolved organic matter across ocean basins

    NASA Astrophysics Data System (ADS)

    Goldberg, Stuart J.; Carlson, Craig A.; Brzezinski, Mark; Nelson, Norm B.; Siegel, David A.

    2011-09-01

    Dissolved combined neutral sugars (DCNS) support heterotrophic bacterioplankton metabolism throughout the ocean, which affects ocean carbon cycling and biogeochemistry. Variability in DCNS composition also provides information about the diagenetic state of oceanic dissolved organic matter (DOM). Here, we present results of the DCNS composition in ˜600 discrete samples from ocean basin-scale sections within the North Atlantic and South Pacific Oceans; and at the Bermuda Atlantic Time-series Study site in the Sargasso Sea. As DCNS concentrations decline with water mass age the mole percentages of glucose, mannose + xylose, and galactose change in a ratio of +2.10:-1.10:-1.00 enriching the DOM pool in glucose relative to mannose + xylose, and galactose. A new proxy is presented based on the relative change in these major sugars, diagenetic distance, which allows for comparison of the diagenetic state of DOM over broad regions of the global ocean while simultaneously quantifying progress along this pathway. In all, this inter-basin comparison suggests that there is a common diagenetic pathway for oceanic DOM.

  11. Estimating annual precipitation for the Colorado River Basin using oceanic-atmospheric oscillations

    NASA Astrophysics Data System (ADS)

    Kalra, Ajay; Ahmad, Sajjad

    2012-06-01

    Estimating long-lead time precipitation under the stress of increased climatic variability is a challenging task in the field of hydrology. A modified Support Vector Machine (SVM) based framework is proposed to estimate annual precipitation using oceanic-atmospheric oscillations. Oceanic-atmospheric oscillations, consisting of Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), and El Niño-Southern Oscillation (ENSO) for a period of 1900-2008, are used to generate annual precipitation estimates with a 1 year lead time. The SVM model is applied to 17 climate divisions encompassing the Colorado River Basin in the western United States. The overall results revealed that the annual precipitation in the Colorado River Basin is significantly influenced by oceanic-atmospheric oscillations. The long-term precipitation predictions for the Upper Colorado River Basin can be successfully obtained using a combination of PDO, NAO, and AMO indices, whereas coupling AMO and ENSO results in improved precipitation predictions for the Lower Colorado River Basin. The results also show that the SVM model provides better precipitation estimates compared to the Artificial Neural Network and Multivariate Linear Regression models. The annual precipitation estimates obtained using the modified SVM modeling framework may assist water managers in statistically understanding the hydrologic response in relation to large scale climate patterns within the Colorado River Basin.

  12. Quantity and location of groundwater recharge in the Sacramento Mountains, south-central New Mexico (USA), and their relation to the adjacent Roswell Artesian Basin

    NASA Astrophysics Data System (ADS)

    Rawling, Geoffrey C.; Newton, B. Talon

    2016-06-01

    The Sacramento Mountains and the adjacent Roswell Artesian Basin, in south-central New Mexico (USA), comprise a regional hydrologic system, wherein recharge in the mountains ultimately supplies water to the confined basin aquifer. Geologic, hydrologic, geochemical, and climatologic data were used to delineate the area of recharge in the southern Sacramento Mountains. The water-table fluctuation and chloride mass-balance methods were used to quantify recharge over a range of spatial and temporal scales. Extrapolation of the quantitative recharge estimates to the entire Sacramento Mountains region allowed comparison with previous recharge estimates for the northern Sacramento Mountains and the Roswell Artesian Basin. Recharge in the Sacramento Mountains is estimated to range from 159.86 × 106 to 209.42 × 106 m3/year. Both the location of recharge and range in estimates is consistent with previous work that suggests that ~75 % of the recharge to the confined aquifer in the Roswell Artesian Basin has moved downgradient through the Yeso Formation from distal recharge areas in the Sacramento Mountains. A smaller recharge component is derived from infiltration of streamflow beneath the major drainages that cross the Pecos Slope, but in the southern Sacramento Mountains much of this water is ultimately derived from spring discharge. Direct recharge across the Pecos Slope between the mountains and the confined basin aquifer is much smaller than either of the other two components.

  13. Quantity and location of groundwater recharge in the Sacramento Mountains, south-central New Mexico (USA), and their relation to the adjacent Roswell Artesian Basin

    NASA Astrophysics Data System (ADS)

    Rawling, Geoffrey C.; Newton, B. Talon

    2016-04-01

    The Sacramento Mountains and the adjacent Roswell Artesian Basin, in south-central New Mexico (USA), comprise a regional hydrologic system, wherein recharge in the mountains ultimately supplies water to the confined basin aquifer. Geologic, hydrologic, geochemical, and climatologic data were used to delineate the area of recharge in the southern Sacramento Mountains. The water-table fluctuation and chloride mass-balance methods were used to quantify recharge over a range of spatial and temporal scales. Extrapolation of the quantitative recharge estimates to the entire Sacramento Mountains region allowed comparison with previous recharge estimates for the northern Sacramento Mountains and the Roswell Artesian Basin. Recharge in the Sacramento Mountains is estimated to range from 159.86 × 106 to 209.42 × 106 m3/year. Both the location of recharge and range in estimates is consistent with previous work that suggests that ~75 % of the recharge to the confined aquifer in the Roswell Artesian Basin has moved downgradient through the Yeso Formation from distal recharge areas in the Sacramento Mountains. A smaller recharge component is derived from infiltration of streamflow beneath the major drainages that cross the Pecos Slope, but in the southern Sacramento Mountains much of this water is ultimately derived from spring discharge. Direct recharge across the Pecos Slope between the mountains and the confined basin aquifer is much smaller than either of the other two components.

  14. Low frequency baleen whale calls detected on ocean-bottom seismometers in the Lau basin, southwest Pacific Ocean.

    PubMed

    Brodie, Dana C; Dunn, Robert A

    2015-01-01

    Ten months of broadband seismic data, recorded on six ocean-bottom seismographs located in the Lau Basin, were examined to identify baleen whale species. As the first systematic survey of baleen whales in this part of the southwest Pacific Ocean, this study reveals the variety of species present and their temporal occurrence in and near the basin. Baleen whales produce species-specific low frequency calls that can be identified by distinct patterns in data spectrograms. By matching spectrograms with published accounts, fin, Bryde's, Antarctic blue, and New Zealand blue whale calls were identified. Probable whale sounds that could not be matched to published spectrograms, as well as non-biologic sounds that are likely of volcanogenic origin, were also recorded. Detections of fin whale calls (mid-June to mid-October) and blue whale calls (June through September) suggest that these species migrate through the region seasonally. Detections of Bryde's whale calls (primarily February to June, but also other times of the year) suggest this species resides around the basin nearly year round. The discovery of previously unpublished call types emphasizes the limited knowledge of the full call repertoires of baleen whales and the utility of using seismic survey data to enhance understanding in understudied regions. PMID:25618038

  15. Basin patterns of upper ocean warming for 1993-2009

    NASA Astrophysics Data System (ADS)

    Chang, You-Soon

    2014-06-01

    A previous study (Lyman et al., Nature 465:334-337, 2010) showed a robust warming signal of the global upper ocean (0-700 m). They examined several sources of uncertainty that contribute to differences among heat content estimations. However, their focus was limited to globally averaged estimation. This study presents the spatial pattern of the global heat content change based on observed gridded datasets (Levitus et al., Geophys Res Lett 36:L07608, 2009). The western Pacific, Atlantic, and Indian Oceans showed significant warming trends, whereas eastern Pacific and some areas of the Gulf Stream experienced negative trends during 1993-2009. Steady warming trend was obtained from the first EOF mode when El Nino and Southern Oscillation (ENSO)-related signals were removed. This result implies that the rapid increase in heat content of the upper ocean around 2000-2005 is not related to a sampling transition from XBT to Argo observations but is associated with a natural variability dominated by strong ENSO-related signals.

  16. A 4D-variational ocean data assimilation application for Santos Basin, Brazil

    NASA Astrophysics Data System (ADS)

    da Rocha Fragoso, Mauricio; de Carvalho, Gabriel Vieira; Soares, Felipe Lobo Mendes; Faller, Daiane Gracieli; de Freitas Assad, Luiz Paulo; Toste, Raquel; Sancho, Lívia Maria Barbosa; Passos, Elisa Nóbrega; Böck, Carina Stefoni; Reis, Bruna; Landau, Luiz; Arango, Hernan G.; Moore, Andrew M.

    2016-03-01

    Aiming to achieve systematic ocean forecasting for the southeastern Brazilian coast, an incremental 4D-Var data assimilation system is applied to a regional ocean model focused mainly in the Santos Basin region. This implementation is performed within the scope of The Santos Basin Ocean Observing System (or Project Azul), a pilot project designed to collect oceanographic data with enough frequency and spatial coverage so to improve regional forecasts through data assimilation. The ocean modeling and data assimilation system of Project Azul is performed with the Regional Ocean Modeling System (ROMS). The observations used in the assimilation cycles include the following: 1-day gridded, 0.1° resolution SST from POES AVHRR; 1-day gridded, 0.3° composite of the MDT SSH from AVISO; and surface and subsurface hydrographic measurements of temperature and salinity collected with gliders and ARGO floats from Project Azul and from UK Met-Office EN3 project dataset. The assimilative model results are compared to forward model results and independent observations, both from remote sensing and in situ sources. The results clearly show that 4D-Var data assimilation leads to an improvement in the skill of ocean hindcast in the studied region.

  17. Fish effects on ocean current observations in the Cariaco Basin

    NASA Astrophysics Data System (ADS)

    Virmani, Jyotika I.; Weisberg, Robert H.

    2009-03-01

    Multiple years of moored current meter observations from the Cariaco Basin show low-frequency variations along with near-inertial waves and further imply the persistent diurnal movement of fish species known to populate the basin. In agreement with short-term observations from 1979, the more recent observations with acoustic Doppler current profilers provide evidence of the multidecadal presence and behavior of these species. An unwanted corollary, however, is a bias in both the vertical and horizontal components of velocity due to the fish movements. Removal of this fish bias results in large data loss (approximately 72%); however, an interpolated, non-biased data set is developed with depth-averaged horizontal velocities comparable to the observations, demonstrating successful elimination of the bias. Further comparisons show that the interpolated data result in minimal variance density loss at low frequencies and a reduction of variance density at high frequencies such that the interpolated data in the internal wave range more closely fit the Garrett-Munk spectrum. The net result is a data set appropriate for further analysis. A mean downward velocity of 0.18 cm s-1 is a reflection of a biogenic particle flux and some residual fish contamination. The mean settling speed of particles in the Cariaco Basin is calculated, via Stokes law, to be smaller than 0.04 cm s-1. Velocity observations from acoustic current meters at depths greater than 400 m are impacted by the water clarity; therefore alternate methods should be used to make velocity measurements at depth.

  18. Insights into mantle heterogeneities: mid-ocean ridge basalt tapping an ocean island magma source in the North Fiji Basin

    NASA Astrophysics Data System (ADS)

    Brens, R., Jr.; Jenner, F. E.; Bullock, E. S.; Hauri, E. H.; Turner, S.; Rushmer, T. A.

    2015-12-01

    The North Fiji Basin (NFB), and connected Lau Basin, is located in a complex area of volcanism. The NFB is a back-arc basin (BAB) that is a result of an extinct subduction zone, incorporating the complicated geodynamics of two rotating landmasses: Fiji and the Vanuatu island arc. Collectively this makes the spreading centers of the NFB the highest producing spreading centers recorded. Here we present volatile concentrations, major, and trace element data for a previously undiscovered triple junction spreading center in the NFB. We show our enrichment samples contain some of the highest water contents yet reported from (MORB). The samples from the NFB exhibit a combination of MORB-like major chemical signatures along with high water content similar to ocean island basalts (OIB). This peculiarity in geochemistry is unlike other studied MORB or back-arc basin (to our knowledge) that is not attributed to subduction related signatures. Our results employ the use of volatiles (carbon dioxide and water) and their constraints (Nb and Ce) combined with trace element ratios to indicate a potential source for the enrichment in the North Fiji Basin. The North Fiji Basin lavas are tholeiitic with similar major element composition as averaged primitive normal MORB; with the exception of averaged K2O and P2O5, which are still within range for observed normal MORB. For a mid-ocean ridge basalt, the lavas in the NFB exhibit a large range in volatiles: H2O (0.16-0.9 wt%) and CO2 (80-359 ppm). The NFB lavas have volatile levels that exceed the range of MORB and trend toward a more enriched source. In addition, when compared to MORB, the NFB lavas are all enriched in H2O/Ce. La/Sm values in the NFB lavas range from 0.9 to 3.8 while, Gd/Yb values range from 1.2 to 2.5. The NFB lavas overlap the MORB range for both La/Sm (~1.1) and Gd/Yb (~1.3). However, they span a larger range outside of the MORB array. High La/Sm and Gd/Yb ratios (>1) are indications of deeper melting within the

  19. Decadal Variability of Tropical Cyclone Annual Frequency in Different Ocean Basins

    NASA Astrophysics Data System (ADS)

    Zhao, Y.

    2015-12-01

    Yating Zhao1, Jing Jiang1 1 School of Atmospheric Sciences, Nanjing University Nanjing 210093 China Abstract: Tropical cyclone, one of the most severe global natural disasters, causes massive casualties and economic losses every year, greatly influences the rapid development of the modern society. Using hurricane best track data from JTWC and TPC we investigate the decadal variations of TC activities. Our research indicates that the variability of TC frequency of different ocean basins (North Indian Ocean (NIO), Northwest Pacific Ocean (WP), Northeast Pacific Ocean (NEP), North Atlantic Ocean (NA) and South Hemisphere (SH)) all have significant decadal periods, and these decadal signals have something connect with the Pacific Decadal Oscillation (PDO), which acting as the background, modulating and influencing the synoptic scale weather systems. Through diagnosing the oceanic and atmospheric circulation in different stages of PDO, we find that, as the PDO signal transmits through the Pacific Ocean, the atmospheric circulation changes accordingly all over the tropical ocean. And they influence the dynamic conditions in the troposphere and promote or restrain the tropical cyclone activities in these areas. In another word, in the positive phase of PDO, there are much more (less) TC activities observed over the NEP (NA, WP, NIO, SH), which very likely due to the favorable (unfavorable) environmental factors, such as higher (lower) SST, weaker (stronger) vertical wind shear, higher (lower) relative humidity in the middle level of troposphere, and low level positive (negative) vorticity in the local area. Meanwhile, what should be noted is that the primary environmental factor could be very different in different ocean basin. Keywords: tropical cyclone, decadal variability, PDO

  20. Nd isotopic composition and REE pattern in the surface waters of the eastern Indian Ocean and its adjacent seas

    SciTech Connect

    Amakawa, Hiroshi; Alibo, D.S.; Nozaki, Yoshiyuki

    2000-05-01

    The Nd isotopic composition and dissolved rare earth elements (REEs) have been measured in the surface waters along the 1996/97 R.V. Hakuho-Maru Expedition route from Tokyo to the Southern Ocean, southwest of Australia, through the Philippine and Indonesian Archipelago, the eastern Indian Ocean, the Bay of Bengal and the South China Sea. The radiogenic {epsilon}{sub Nd} values of {minus}1.3 and {minus}1.4 were found in the Sulu Sea and near the Lombok Strait, indicating the strong influence of surrounding volcanic islands, whereas non-radiogenic {epsilon}{sub Nd} values of less than {minus}10 were found in the Southern Ocean and the Bay of Bengal suggesting Nd of continental origin. The dissolved Nd concentrations also showed a wide range of variation from 2.8 to 19.6 pmol/kg and the trivalent REE patterns exhibited characteristic features that can be grouped into each different oceanic province. The geographical distribution of dissolved Nd is different from that of atmospherically derived {sup 210}Pb, but generally resembles that of coastally derived {sup 228}Ra. This strongly suggests that fluvial and coastal input predominates over eolian input for dissolved Nd in the surface ocean. However, the riverine dissolved Nd flux appears to be relatively minor, and remobilization of Nd from coastal and shelf sediments may play an important role in the total Nd input to the ocean. By modeling the distributions of the isotopic composition and concentration of Nd together with the activity ratio of {sup 228}Ra/{sup 226}Ra in the southeastern Indian Ocean, the authors estimate a mean residence time of Nd in the surface mixed layer to be 1.5--2.6 years. The short mean residence time is comparable with, or slightly longer than that of {sup 210}Pb suggesting similar chemical reactivity.

  1. Fault-block structure and state of stress in the Earth's crust of the Gusinoozersky Basin and the adjacent territory, western Transbaikal region

    NASA Astrophysics Data System (ADS)

    Lunina, O. V.; Gladkov, A. S.

    2009-01-01

    The geological structure and tectonophysics of the Gusinoozersky Basin—a tectonotype of Mesozoic depressions in the western Transbaikal region—is discussed. New maps of the fault-block structure and state of stress in the Earth’s crust of the studied territory are presented. It is established that the Gusinoozersky Basin was formed in a transtensional regime with the leading role of extension oriented in the NW-SE direction. The transtensional conditions were caused by paths of regional tension stresses oriented obliquely to the axial line of the basin, which created a relatively small right-lateral strike-slip component of separation (in comparison with normal faulting) along the NE-trending master tectonic lines. The widespread shear stress tensors of the second order with respect to extension are related to inhomogeneities in the Earth’s crust, including those that are arising during displacement of blocks along normal faults. Folding at the basin-range boundary was brought about by gravity effects of normal faulting. The faults and blocks in the Gusinoozersky Basin remained active in the Neogene and Quaternary; however, it is suggested that their reactivation was a response to tectonic processes that occurred in the adjacent Baikal Rift Zone rather than to the effect of a local mantle source.

  2. A model of ocean basin crustal magnetization appropriate for satellite elevation anomalies

    NASA Technical Reports Server (NTRS)

    Thomas, Herman H.

    1987-01-01

    A model of ocean basin crustal magnetization measured at satellite altitudes is developed which will serve both as background to which anomalous magnetizations can be contrasted and as a beginning point for studies of tectonic modification of normal ocean crust. The model is based on published data concerned with the petrology and magnetization of the ocean crust and consists of viscous magnetization and induced magnetization estimated for individual crustal layers. Thermal remanent magnetization and chemical remanent magnetization are excluded from the model because seafloor spreading anomalies are too short in wavelength to be resolved at satellite altitudes. The exception to this generalization is found at the oceanic magnetic quiet zones where thermal remanent magnetization and chemical remanent magnetization must be considered along with viscous magnetization and induced magnetization.

  3. Upper Colorado River and Great Basin streamflow and snowpack forecasting using Pacific oceanic-atmospheric variability

    NASA Astrophysics Data System (ADS)

    Oubeidillah, Abdoul A.; Tootle, Glenn A.; Moser, Cody; Piechota, Thomas; Lamb, Kenneth

    2011-11-01

    SummaryWater managers in western U.S., including areas such as the State of Utah, are challenged with managing scarce resources and thus, rely heavily on forecasts to allocate and meet various water demands. The need for improved streamflow and snowpack forecast models in the Upper Colorado River and Great Basin is of the utmost importance. In this research, the use of oceanic and climatic variables as predictors to improve the long lead-time (three to nine months) forecast of streamflow and snowpack was investigated. Singular Value Decomposition (SVD) analysis was used to identify a region of Pacific Ocean SSTs and a region of 500 mbar geopotential height (Z 500) that were teleconnected with streamflow (and snowpack) in Upper Colorado River and Great Basin headwaters. The resulting Pacific Ocean SSTs and Z 500 regions were used to create indices that were then used as predictors in a non-parametric forecasting model. The majority of forecasts resulted in positive statistical skill, which indicated an improvement of the forecast over the climatology or no-skill forecast. The results indicated that derived indices from Pacific Ocean SSTs were better suited for long lead-time (six to nine month) forecasts of streamflow (and snowpack) while the derived indices from Z 500 improved short-lead time (3 month) forecasts. In all, the results of the forecast model indicated that incorporating Pacific oceanic-atmospheric climatic variability in forecast models can lead to improved forecasts for both streamflow and snowpack.

  4. Distinct groundwater recharge sources and geochemical evolution of two adjacent sub-basins in the lower Shule River Basin, northwest China

    NASA Astrophysics Data System (ADS)

    Wang, Liheng; Dong, Yanhui; Xie, Yueqing; Song, Fan; Wei, Yaqiang; Zhang, Jiangyi

    2016-08-01

    Based on analysis of groundwater hydrogeochemical and isotopic data, this study aims to identify the recharge sources and understand geochemical evolution of groundwater along the downstream section of the Shule River, northwest China, including two sub-basins. Groundwater samples from the Tashi sub-basin show markedly depleted stable isotopes compared to those in the Guazhou sub-basin. This difference suggests that groundwater in the Tashi sub-basin mainly originates from meltwater in the Qilian Mountains, while the groundwater in the Guazhou sub-basin may be recharged by seepage of the Shule River water. During the groundwater flow process in the Tashi sub-basin, minerals within the aquifer material (e.g., halite, calcite, dolomite, gypsum) dissolve in groundwater. Mineral dissolution leads to strongly linear relationships between Na+ and Cl- and between Mg2++ Ca2+ and SO4 2- + HCO3 -, with stoichiometry ratios of approximately 1:1 in both cases. The ion-exchange reaction plays a dominant role in hydrogeochemical evolution of groundwater in the Guazhou sub-basin and causes a good linear relationship between (Mg2++ Ca2+)-(SO4 2- + HCO3 -) and (Na++ K+)-Cl- with a slope of -0.89 and also results in positive chloroalkaline indices CAI 1 and CAI 2. The scientific results have implications for groundwater management in the downstream section of Shule River. As an important irrigation district in Hexi Corridor, groundwater in the Guazhou sub-basin should be used sustainably and rationally because its recharge source is not as abundant as expected. It is recommended that the surface water should be used efficiently and routinely, while groundwater exploitation should be limited as much as possible.

  5. Glimpses of Arctic Ocean shelf-basin interaction from submarine-borne radium sampling

    NASA Astrophysics Data System (ADS)

    Kadko, David; Aagaard, Knut

    2009-01-01

    Evidence of shelf-water transfer from temperature, salinity, and 228Ra/ 226Ra sampling from the nuclear submarine USS L. Mendel Rivers SCICEX cruise in October, 2000 demonstrates the heterogeneity of the Arctic Ocean with respect to halocline ventilation. This likely reflects both time-dependent events on the shelves and the variety of dispersal mechanisms within the ocean, including boundary currents and eddies, at least one of which was sampled in this work. Halocline waters at the 132 m sampling depth in the interior Eurasian Basin are generally not well connected to the shelves, consonant with their ventilation within the deep basins, rather than on the shelves. In the western Arctic, steep gradients in 228Ra/ 226Ra ratio and age since shelf contact are consistent with very slow exchange between the Chukchi shelf and the interior Beaufort Gyre. These are the first radium measurements from a nuclear submarine.

  6. Oceanic crust of the Grenada Basin in the Southern Lesser Antilles Arc Platform

    NASA Astrophysics Data System (ADS)

    Speed, R. C.; Walker, J. A.

    1991-03-01

    Seismic refraction data permit the southern Lesser Antilles arc and surrounding regions to be divided by the velocity of their basement. We propose that high-velocity basement of the arc platform beneath the Grenadine islands and below a part of the Tobago Trough forearc basin is oceanic and continuous and was originally connected with oceanic crust of the Grenada Basin. Low-velocity basements of the Tobago terrane and the arc platform from St. Vincent north lie south and north, respectively, of the high-velocity basement of the arc platform. An oceanic origin of this high-velocity crust in the Grenadines is argued to be more plausible than an origin as unroofed lower arc crust. The segment of probable oceanic crust in the arc platform was greatly uplifted during development of the present island arc, mainly in late Neogene time, relative to the Grenada Basin and Tobago Trough. Accepting the proposition of shallow oceanic crust in the Grenadines, early middle Eocene and possibly older pillow basalts of Mayreau, the oldest rock unit of the southern Lesser Antilles arc platform, may be an exposure of such basement. Major and minor element compositions of Mayreau Basalt are indicative of a spreading rather than arc origin. The stratigraphy of the pillow basalts indicates extrusion in an open marine environment, distant or shielded from sources of arc or continental sediment, followed by a period of pelagic sedimentation above the carbonate compensation depth. The Eocene basalt and pelagic cover formed a relatively deep floor of a marine basin in which arc-derived turbidites and pelagic sediments accumulated over the succeeding 25-30 ma. Such basalts thus indicate a probable spreading origin of the Grenada Basin and an age of cessation of spreading in the region of Mayreau in Eocene time. The configuration of the Eocene basin and the direction of spreading, however, are unknowns. Regional structural relationships imply the spreading was probably backarc, an origin also

  7. Assessing of site-related changes of tsunamis impacting closed ocean basins

    NASA Astrophysics Data System (ADS)

    Gallazzi, S.; Tinti, S.; Tonini, R.

    2009-04-01

    Tsunamis are long waves that travel across the ocean and are capable of carrying destructive energy over very long distances. Studying their propagation path and the complex way they interact with local bathymetries is of fundamental importance for predicting their impact on the coast and for hindcast analyses. This work is focussed on the influence of closed sea basins on the tsunami propagation. By closed basins we mean here any basins capable of modifying significantly the tsunami signal with respect to the surrounding open sea. Here two different methodologies are applied to two relevant examples: the Seychelles Island platform, that was impacted by the 2004 Indian Ocean megatsunami, and the Messina Strait, Italy, that was affected by several severe tsunami events, the last one taking place in 1908. In the first case, in the framework of EU- funded SCHEMA (Scenarios for Hazard-induced Emergencies Management) project, through the analysis of synthetic/real tide-gauge records of the 2004 simulated/observed tsunami, it is shown that the deep-ocean Seychelles-platform transition changes the spectral distribution of the tsunami energy with peak signal amplification of selected peaks, which is linked both to the platform bathymetric configuration and to coastal geometry of the islands. The Messina Straits is a sort of a channel connecting the Tyrrhenian sea to the Ionian sea and including some sub-basins, like the Messina harbour. To study the effect of the channel on the tsunami propagation, numerical simulations were used to force the basin along different boundaries with sinusoidal functions having different periods within the range of typical tsunami frequencies. The computed amplification curves show that the main resonance period is approximately 10 minutes all over the Straits, but reveal that the response change from place to place and identify those places that are most sensitive to tsunami attacks.

  8. A new scheme for the opening of the South Atlantic Ocean and the dissection of an Aptian salt basin

    NASA Astrophysics Data System (ADS)

    Torsvik, Trond H.; Rousse, Sonia; Labails, Cinthia; Smethurst, Mark A.

    2009-06-01

    We present a revised model for the opening of the South Atlantic Ocean founded on a remapping of the continent-ocean boundaries and Aptian salt basins, the chronology of magmatic activity in and around the ocean basin and on the timing and character of associated intraplate deformation in Africa and South America. The new plate tectonic model is internally consistent and consistent with globally balanced plate motion solutions. The model includes realistic scenarios for intraplate deformation, pre-drift extension and seafloor spreading. Within the model, Aptian salt basins preserved in the South American (Brazilian) and African (Angola, Congo, Gabon) continental shelves are reunited in their original positions as parts of a single syn-rift basin in near subtropical latitudes (10°S-27°S). The basin was dissected at around 112 Ma (Aptian-Albian boundary) when the model suggests that seafloor spreading commenced north of the Walvis Ridge-Rio Grande Rise.

  9. Assessment of Plio-Pleistocene Sea Surface Temperature Evolution Across Ocean Basins, Hemispheres, and Latitudes

    NASA Astrophysics Data System (ADS)

    Peterson, L.; Lawrence, K. T.; Mauriello, H.; Wilson, J.; Holte, L.

    2015-12-01

    New sea surface temperature (SST) records from the southern Pacific and southern Atlantic Oceans allow assessment of similarities and differences in climate evolution across ocean basins, hemispheres, and latitudes over the last 5 million years. Our high-resolution, alkenone-derived SST records from ODP Sites 1088 (South Atlantic, 41°S) and 1125 (South Pacific, 42°S) share strong structural similarities. When compared with SST records from the mid-latitudes of the northern hemisphere, these records provide compelling evidence for broadly hemispherically symmetrical open-ocean temperature evolution in both ocean basins as tropical warm pools contracted over the Plio-Pleistocene. This symmetry in temperature evolution occurs despite strong asymmetries in the development of the cryosphere over this interval, which was marked by extensive northern hemisphere ice sheet growth. Parallel SST evolution across ocean basins and hemispheres suggests that on longterm (>105 yr) timescales, many regions of the world ocean are more sensitive to the global energy budget than to local or regional climate dynamics, although important exceptions include coastal upwelling zone SSTs, high latitude SSTs, and benthic δ18O. Our analysis further reveals that throughout the last 5 Ma, temperature evolution in the extra-tropical Pacific of both hemispheres is very similar to the evolution of SST in the eastern equatorial Pacific upwelling zone, revealing tight coupling between the growth of meridional and equatorial Pacific zonal temperature gradients over this interval as both the extra-tropics and the eastern equatorial Pacific cold tongue underwent cooling. Finally, while long term temperature evolution is broadly consistent across latitudes and ocean basins throughout the entire Plio-Pleistocene, we see evidence that climate coupling on orbital timescales strengthened significantly at 2.7 Ma, at which point obliquity-band coherence emerges among diverse SST records. We attribute this

  10. Gas desorption and adsorption isotherm studies of coals in the Powder River basin, Wyoming and adjacent basins in Wyoming and North Dakota

    USGS Publications Warehouse

    Stricker, Gary D.; Flores, Romeo M.; McGarry, Dwain E.; Stillwell, Dean P.; Hoppe, Daniel J.; Stillwell, Cathy R.; Ochs, Alan M.; Ellis, Margaret S.; Osvald, Karl S.; Taylor, Sharon L.; Thorvaldson, Marjorie C.; Trippi, Michael H.; Grose, Sherry D.; Crockett, Fred J.; Shariff, Asghar J.

    2006-01-01

    The U.S. Geological Survey (USGS), in cooperation with the State Office, Reservoir Management Group (RMG), of the Bureau of Land Management (BLM) in Casper (Wyoming), investigated the coalbed methane resources (CBM) in the Powder River Basin, Wyoming and Montana, from 1999 to the present. Beginning in late 1999, the study also included the Williston Basin in Montana and North and South Dakota and Green River Basin and Big Horn Basin in Wyoming. The rapid development of CBM (referred to as coalbed natural gas by the BLM) during the early 1990s, and the lack of sufficient data for the BLM to fully assess and manage the resource in the Powder River Basin, in particular, gave impetus to the cooperative program. An integral part of the joint USGS-BLM project was the participation of 25 gas operators that entered individually into confidential agreements with the USGS, and whose cooperation was essential to the study. The arrangements were for the gas operators to drill and core coal-bed reservoirs at their cost, and for the USGS and BLM personnel to then desorb, analyze, and interpret the coal data with joint funding by the two agencies. Upon completion of analyses by the USGS, the data were to be shared with both the BLM and the gas operator that supplied the core, and then to be released or published 1 yr after the report was submitted to the operator.

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

    SciTech Connect

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

    2012-04-01

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

  12. Seasonal evolution of the upper-ocean adjacent to the South Orkney Islands, Southern Ocean: Results from a “lazy biological mooring”

    NASA Astrophysics Data System (ADS)

    Meredith, Michael P.; Nicholls, Keith W.; Renfrew, Ian A.; Boehme, Lars; Biuw, Martin; Fedak, Mike

    2011-07-01

    A serendipitous >8-month time series of hydrographic properties was obtained from the vicinity of the South Orkney Islands, Southern Ocean, by tagging a southern elephant seal ( Mirounga leonina) on Signy Island with a Conductivity-Temperature-Depth/Satellite-Relay Data Logger (CTD-SRDL) in March 2007. Such a time series (including data from the austral autumn and winter) would have been extremely difficult to obtain via other means, and it illustrates with unprecedented temporal resolution the seasonal progression of upper-ocean water mass properties and stratification at this location. Sea ice production values of around 0.15-0.4 m month -1 for April to July were inferred from the progression of salinity, with significant levels still in September (around 0.2 m month -1). However, these values presume that advective processes have negligible effect on the salinity changes observed locally; this presumption is seen to be inappropriate in this case, and it is argued that the ice production rates inferred are better considered as "smeared averages" for the region of the northwestern Weddell Sea upstream from the South Orkneys. The impact of such advective effects is illustrated by contrasting the observed hydrographic series with the output of a one-dimensional model of the upper-ocean forced with local fluxes. It is found that the difference in magnitude between local (modelled) and regional (inferred) ice production is significant, with estimates differing by around a factor of two. A halo of markedly low sea ice concentration around the South Orkneys during the austral winter offers at least a partial explanation for this, since it enabled stronger atmosphere/ocean fluxes to persist and hence stronger ice production to prevail locally compared with the upstream region. The year of data collection was an El Niño year, and it is well-established that this phenomenon can impact strongly on the surface ocean and ice field in this sector of the Southern Ocean, thus

  13. The rifting of continental and oceanic lithosphere: Observations from the Woodlark Basin

    NASA Astrophysics Data System (ADS)

    Goodliffe, Andrew Mark

    A detailed marine geophysical survey of the Woodlark Basin has given us a high resolution picture of the evolution of the Woodlark Basin. An algorithm developed for this study, which reconstructs bathymetry and magnetization grids to selected ages, has revealed many of the details of the evolution of this young ocean basin. The Woodlark Basin formed by the nucleation of spreading segments in sites of focused continental rifting. These segments, which are on the order of 100 km long, subsequently grew by propagation. Segments form in an overlapping configuration, resulting in the deformation and rotation of intervening continental lithosphere. Transform faults form some time later, cutting through continental lithosphere to join the tips of the spreading segments. Continental margins formed by nucleation of a spreading segment are distinct from those formed by propagation. Nucleation margins have concordant abyssal hill fabric, continent/ocean boundary and continental rift fabric. The continent/ocean boundary (COB) of propagation margins is discordant with abyssal hill fabric, but may be either concordant or discordant with continental rift fabric. A third type of COB, formed when there is no propagation, results in abyssal hill fabric perpendicular to the COB. Similar geometries result from a COB formed on a transform fault. Seismicity on the margins after the initiation of sea-floor spreading, and the inward curvature of abyssal fabric formed on spreading centers propagating into the continental margin, demonstrate that extension continues on the margins for up to 1 Ma. Large reorientations of the spreading center take place by propagation or synchronous reorientation. The present-day sea-floor reveals that its 500-km-long spreading center reoriented synchronously, without propagation, about 80 ka. There is no evidence of the V-shaped pseudofault geometry typical of spreading center propagation, nor of the progressive fanning of sea-floor fabric characteristic of

  14. The Eurasian and Makarov Basins target changes in the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Polyakov, I.; Padman, L.; Pnyushkov, A.; Rember, R.; Ivanov, V.; Lenn, Y. D.

    2015-12-01

    The Arctic Ocean interior is warming, and there is no indication that the rate of warming will decrease in the near future. The relative role of the interior ocean's warmth in setting net energy flux to, and the mass balance of, Arctic sea ice, however, is still under debate. Thus, quantifying this flux and understanding mechanisms for redistributing heat in the ocean interior are of particular importance. Warm (>0°C) intermediate-depth (150-900m) water of Atlantic origin (the so-called Atlantic Water, AW) is the major source of heat for the ocean interior. Ice thickness along the continental slope east of Svalbard is much less than that expected of first-year ice, suggesting that AW has a direct impact on sea ice just after entering the Arctic. However, in the Canadian Basin, far away from Fram Strait, overlying fresher and colder stable layers effectively insulate the upper mixed layer and ice from impacts of the AW heat. Even though the eastern Eurasian Basin (EEB) is separated from Fram Strait by hundreds of kilometers, the AW heat finds its ways for reaching the ice base in this part of the Arctic Ocean. A distinct process, double diffusion convection, plays an important role in vertical redistribution of AW heat in this region. Double diffusion convection is typically identified as a vertical sequence of almost-homogeneous convective layers separated by high-gradient interfaces, forming a double diffusive "staircase". The staircase structure is a consequence of the differing molecular diffusivities of heat and salt; surprisingly, even though molecular properties drive the instability, resulting net fluxes can be very large, up to several W/m2. The interaction of shear and diffusive layering can significantly alter the heat (and momentum) flux through a staircase. The existing data set are limited and further detailed process studies in the EEB targeting the unique mechanisms of oceanic heat exchange in the interior of the EEB are required.

  15. Megascopic lithologic studies of coals in the Powder River basin in Wyoming and in adjacent basins in Wyoming and North Dakota

    USGS Publications Warehouse

    Trippi, Michael H.; Stricker, Gary D.; Flores, Romeo M.; Stanton, Ronald W.; Chiehowsky, Lora A.; Moore, Timothy A.

    2010-01-01

    Between 1999 and 2007, the U.S. Geological Survey (USGS) investigated coalbed methane (CBM) resources in the Wyoming portion of the Powder River Basin. The study also included the CBM resources in the North Dakota portion of the Williston Basin of North Dakota and the Wyoming portion of the Green River Basin of Wyoming. This project involved the cooperation of the State Office, Reservoir Management Group (RMG) of the Bureau of Land Management (BLM) in Casper, Wyo., and 16 independent gas operators in the Powder River, Williston, and Green River Basins. The USGS and BLM entered into agreements with these CBM operators to supply samples for the USGS to analyze and provide the RMG with rapid, timely results of total gas desorbed, coal quality, and high-pressure methane adsorption isotherm data. This program resulted in the collection of 963 cored coal samples from 37 core holes. This report presents megascopic lithologic descriptive data collected from canister samples extracted from the 37 wells cored for this project.

  16. Detection of baleen whales on an ocean-bottom seismometer array in the Lau Basin

    NASA Astrophysics Data System (ADS)

    Brodie, D.; Dunn, R.

    2011-12-01

    Long-term deployment of ocean-bottom seismometer arrays provides a unique opportunity for identifying and tracking whales in a manner not usually possible in biological studies. Large baleen whales emit low frequency (>5Hz) sounds called 'calls' or 'songs' that can be detected on either the hydrophone or vertical channel of the instrument at distances in excess of 50 km. The calls are distinct to individual species and even geographical groups among species, and are thought to serve a variety of purposes. Distinct repeating calls can be automatically identified using matched-filter processing, and whales can be located in a manner similar to that of earthquakes. Many baleen whale species are endangered, and little is known about their geographic distribution, population dynamics, and basic behaviors. The Lau back-arc basin, a tectonically active, elongated basin bounded by volcanic shallows, lies in the southwestern Pacific Ocean between Fiji and Tonga. Although whales are known to exist around Fiji and Tonga, little is understood about the population dynamics and migration patterns throughout the basin. Twenty-nine broadband ocean-bottom seismometers deployed in the basin recorded data for approximately ten months during the years 2009-2010. To date, four species of whales have been identified in the data: Blue (one call type), Humpback (two call types, including long-lasting 'songs'), Bryde's (one call type), and Fin whales (three call types). Three as-yet-unknown call types have also been identified. After the calls were identified, idealized spectrograms of the known calls were matched against the entire data set using an auto-detection algorithm. The auto-detection output provides the number of calls and times of year when each call type was recorded. Based on the results, whales migrate seasonally through the basin with some overlapping of species. Initial results also indicate that different species of whales are more common in some parts of the basin than

  17. Widespread, Off-axis Magmatism at a Young Oceanic Rift, the Sedimented Guaymas Basin Spreading Center

    NASA Astrophysics Data System (ADS)

    Soule, S.; Lizarralde, D.; Seewald, J.; Proskurowski, G.

    2010-12-01

    A thick layer of sediment commonly blankets spreading centers within young rifted margins such as the Guaymas Basin within the Gulf of California. The shallow oceanic crust in these environments differs significantly from deep-water, unsedimented ridges in that there is little to no extrusive volcanism, and crust is accreted by the intrusion of magmatic sills into sediments. From initial observations at the seafloor and through drill holes in the S. Guaymas Basin, a model of magmatic accretion similar to that of deep-water mid-ocean ridges was proposed wherein sills are intruded at the rift axis and subsequently buried by sediments as they are rafted off axis. Seismic reflection data collected throughout the N. Guaymas basin in 2002, however, found that sills do not deepen with off-axis distance suggesting that sill intrusion to shallow levels within the sediment pile occurs throughout the basin out to 50 km from the plate boundary (spreading age of 2 Ma). This suggests that magmatic accretion within the shallow crust is active over a very wide area (10-20 times larger than at deep-water mid-ocean ridges) independent of spreading age. During a cruise to the Guaymas Basin in 2009, we collected deep-towed sidescan sonar, sub-bottom imaging, multibeam bathymetry, near-bottom photographs, and bottom water samples across the N. Guaymas Basin to test this hypothesis. Acoustic backscatter imagery revealed nearly 100 localized, acoustically bright seafloor reflectors scattered throughout the survey area. Some of these backscatter anomalies were investigated with a deep-towed camera system and found to contain authigenic carbonate, tubeworms, clams, bacterial mats, and indurated sediment outcrops. Some sites showed small thermal anomalies in near-bottom waters, methane concentrations well in excess of background, and high 3He anomalies. Where coverage overlaps, these sites correlate with the position of seismically imaged subsurface sills. In this presentation, we present

  18. Sulu-Celebes-Banda basins: a trapped piece of Cretaceous to Eocene oceanic crust

    SciTech Connect

    McCabe, R.J.; Hilde, T.W.; Cole, J.T.; Sager, W.; Lee, C.S.

    1986-07-01

    The Sulu-Celebes-Banda basin is composed of three poorly understood marginal basins located between northwest Australia and southeast Asia. Recent studies have proposed that these three basins are remnants of once-continuous ocean basin. The on-land geology of this region is complicated. However, numerous stratigraphic and paleomagnetic studies on pre-Oligocene rocks are consistent with the interpretation that older landmasses presently dissecting the basin were translated into their present position during the middle to late Tertiary. Paleomagnetic data from the Philippines suggest that the Philippine arc is a composite of Early Cretaceous to Holocene arcs that were translated clockwise and from the southeast. Paleomagnetic and stratigraphic data from Kalimantan and Sulawesi suggest that these landmasses share a common origin and that Sulawesi was rifted eastward off of Borneo during the late Tertiary. Stratigraphic studies from the Sula microcontinent, Buru, Ceram, and Timor show close correlation to the stratigraphy of northwest Australia or New Guinea. In addition, paleomagnetic studies from Timor suggest that a portion of the island was part of Australia since the early Mesozoic.

  19. Evidence that the crystalline cores of uplifts adjacent to the Powder River Basin were breached during Paleocene time

    SciTech Connect

    Merin, I.S.; Lindholm, R.C.

    1986-10-01

    Sandstones in the upper part of the Paleocene Tongue River Member of the Fort Union Formation in the Powder River basin are dominantly sublitharenite. These rocks contain abundant rock fragments of non-ferroan calcite, dolomite, chert, and foliated fine-grained metamorphic rock (phyllite). The carbonate and chert rock fragments were probably eroded from paleozoic carbonate sequences flanking the Bighorn Mountains or the Black Hills. The phyllitic rock fragments indicate that the crystalline cores of these uplifts were exposed during Paleocene time, which is earlier during the Laramide Orogeny than has been previously demonstrated.

  20. Structure of the deep oceanic lithosphere in the Northwestern Pacific ocean basin derived from active-source seismic data

    NASA Astrophysics Data System (ADS)

    Ohira, A.; Kodaira, S.; Nakamura, Y.; Fujie, G.; Arai, R.; Miura, S.

    2015-12-01

    Many seismological studies have detected the sharp seismic discontinuities in the upper mantle, some of which are interpreted the lithosphere-asthenosphere boundary (LAB). However there are few data at the old Pacific plate, in particular at ocean basin, which is critical information for understanding nature of the oceanic LAB. In 2014 we conducted an active-source refraction/reflection survey along a 1130-km-long line in southeast of the Shatsky Rise. Five ocean bottom seismometers (OBSs) were deployed and recovered by R/V Kairei of JAMSTEC. We used an airgun array with a total volume of 7,800 cubic inches with firing at intervals of 200 m. Multi-channel seismic reflection (MCS) data were also collected with a 444-channel, 6,000-m-long streamer cable. In OBS records the apparent velocity of the refraction waves from the uppermost mantle was high (< 8.6 km/sec), and considered to be caused by preferred orientation of olivine (e.g., Kodaira et al., 2014). Another remarkable feature is wide-angle reflection waves from the deep lithosphere at large (150-500 km) offsets. We applied the traveltime mapping method (Fujie et al., 2006), forward analysis (Zelt and Smith, 1992) and the amplitude modeling (Larsen and Grieger, 1998) to the OBS data. The results show that deep mantle reflectors exist at the depths from 35 to 60 km, and one possible explanation is that these reflectors correspond to patched low velocity zones around the base of the lithosphere. On MCS sections the clear and sharp Moho was imaged only at the southwestern end of the profile, but Moho was ambiguous or even not imaged in the most part of the profile. Since our seismic line covers the oceanic lithosphere with different ages that correspond to different stages of the Shatsky activity, the Moho appearance may reflect the variation of the Shatsky activity.

  1. Assessment of macroinvertebrate communities in adjacent urban stream basins, Kansas City, Missouri, metropolitan area, 2007 through 2011

    USGS Publications Warehouse

    Christensen, Eric D.; Krempa, Heather M.

    2013-01-01

    Wastewater-treatment plant discharges during base flow, which elevated specific conductance and nutrient concentrations, combined sewer overflows, and nonpoint sources likely contributed to water-quality impairment and lower aquatic-life status at the Blue River Basin sites. Releases from upstream reservoirs to the Little Blue River likely decreased specific conductance, suspended-sediment, and dissolved constituent concentrations and may have benefitted water quality and aquatic life of main-stem sites. Chloride concentrations in base-flow samples, attributable to winter road salt application, had the highest correlation with the SUII (Spearman’s ρ equals 0.87), were negatively correlated with the SCI (Spearman’s ρ equals -0.53) and several pollution sensitive Ephemeroptera plus Plecoptera plus Trichoptera abundance and percent richness metrics, and were positively correlated with pollution tolerant Oligochaeta abundance and percent richness metrics. Study results show that the easily calculated SUII and the selected modeled multimetric indices are effective for comparing urban basins and for evaluation of water quality in the Kansas City metropolitan area.

  2. Oceanic transform earthquakes with unusual mechanisms or locations - Relation to fault geometry and state of stress in the adjacent lithosphere

    NASA Technical Reports Server (NTRS)

    Wolfe, Cecily J.; Bergman, Eric A.; Solomon, Sean C.

    1993-01-01

    Results are presented of a search for transform earthquakes departing from the pattern whereby they occur on the principal transform displacement zone (PTDZ) and have strike-slip mechanisms consistent with transform-parallel motion. The search was conducted on the basis of source mechanisms and locations taken from the Harvard centroid moment tensor catalog and the bulletin of the International Seismological Center. The source mechanisms and centroid depths of 10 such earthquakes on the St. Paul's, Marathon, Owen, Heezen, Tharp, Menard, and Rivera transforms are determined from inversions of long-period body waveforms. Much of the anomalous earthquake activity on oceanic transforms is associated with complexities in the geometry of the PTDZ or the presence of large structural features that may influence slip on the fault.

  3. Ocean-Atmosphere Environments of Antarctic-Region Cold-Air Mesocyclones: Evaluation of Reanalyses for Contrasting Adjacent 10-Day Periods ("Macro-Weather") in Winter.

    NASA Astrophysics Data System (ADS)

    Carleton, A. M.; Auger, J.; Birkel, S. D.; Maasch, K. A.; Mayewski, P. A.; Claud, C.

    2015-12-01

    Mesoscale cyclones in cold-air outbreaks (mesocyclones) feature in the weather and climate of the Antarctic (e.g., Ross Sea) and sub-antarctic (Drake Passage). They adversely impact field operations, and influence snowfall, the ice-sheet mass balance, and sea-air energy fluxes. Although individual mesocyclones are poorly represented on reanalyses, these datasets robustly depict the upper-ocean and troposphere environments in which multiple mesocyclones typically form. A spatial metric of mesocyclone activity—the Meso-Cyclogenesis Potential (MCP)—used ERA-40 anomaly fields of: sea surface temperature (SST) minus marine air temperature (MAT), near-surface winds, 500 hPa air temperature, and the sea-ice edge location. MCP maps composited by teleconnection phases for 1979-2001, broadly correspond to short-period satellite "climatologies" of mesocyclones. Here, we assess 3 reanalysis datasets (CFSR, ERA-I and MERRA) for their reliably to depict MCP patterns on weekly to sub-monthly periods marked by strong regional shifts in mesocyclone activity (frequencies, track densities) occurring during a La Niña winter: June 21-30, 1999 (SE Indian Ocean) and September 1-10, 1999 (Ross Sea sector). All reanalyses depict the marked variations in upper ocean and atmosphere variables between adjacent 10-day periods. Slight differences may owe to model resolution or internal components (land surface, coupled ocean models), and/or how the observations are assimilated. For June 21-30, positive SST-MAT, southerly winds, proximity to the ice edge, and negative T500, accompany increased meso-cyclogenesis. However, for September 1-10, surface forcing does not explain frequent comma cloud "polar lows" north-east of the Ross Sea. Inclusion of the upper-level diffluence (e.g., from Z300 field) in the MCP metric, better depicts the observed mesocyclone activity. MCP patterns on these "macro-weather" time scales appear relatively insensitive to the choice of reanalysis.

  4. Upper Colorado River and Great Basin Streamflow and Snowpack Forecasting using Pacific Oceanic-Atmospheric Variability

    NASA Astrophysics Data System (ADS)

    Aziz, O. A.; Tootle, G. A.; Moser, C.; Piechota, T. C.; Lamb, K. W.; Kao, S.

    2011-12-01

    Water managers in western U.S., including areas such as the State of Utah, are challenged with managing scarce resources and thus, rely heavily on forecasts to allocate and meet various water demands. The need for improved streamflow and snowpack forecast models in the Upper Colorado River and Great Basin is of the utmost importance. In this research, the use of oceanic and climatic variables as predictors to improve the long lead-time (three to nine months) forecast of streamflow and snowpack was investigated. Singular Value Decomposition (SVD) analysis was used to identify a region of Pacific Ocean SSTs and a region of 500 mbar geopotential height (Z500) that were teleconnected with streamflow (and snowpack) in Upper Colorado River and Great Basin headwaters. The resulting Pacific Ocean SSTs and Z500 regions were used to create indices that were then used as predictors in a non-parametric forecasting model. The majority of forecasts resulted in positive statistical skill, which indicates an improvement over the climatology or no-skill forecast (i.e., ranking of events using the Weibull distribution). The results indicated that derived indices from Pacific Ocean SSTs were better suited for long lead-time (six to nine month) forecasts of streamflow (and snowpack) while the derived indices from Z500 improved short-lead time (3 month) forecasts. In all, the results of the forecast model indicated that incorporating Pacific oceanic-atmospheric climatic variability in forecast models can lead to improved forecasts for both streamflow and snowpack. This method will be applied and tested at several selected hydropower projects in the study area, and some preliminary results will be shown.

  5. Future change of the Indian Ocean basin-wide and dipole modes in the CMIP5

    NASA Astrophysics Data System (ADS)

    Chu, Jung-Eun; Ha, Kyung-Ja; Lee, June-Yi; Wang, Bin; Kim, Byeong-Hee; Chung, Chul Eddy

    2014-07-01

    The Indian Ocean sea surface temperature (SST) variability has been represented with the two dominant variability modes: the Indian Ocean basin-wide (IOBW) and dipole (IOD) modes. Here we investigate future changes of the two modes together with mean state and El Niño and Southern Oscillation (ENSO) relationship under the anthropogenic global warming using 20 coupled models that participated in the phase five of Coupled Model Intercomparison Project by comparing the historical run from 1950 to 2005 and the RCP 4.5 run from 2050 to 2099. The five best models are selected based on the evaluation of the 20 models' performances in simulating the two modes and Indian Ocean basic state for the latest 56 years. They are capable of capturing the IOBW and IOD modes in their spatial distribution, seasonal cycle, major periodicity, and relationship with ENSO to some extent. The five best models project the significant changes in the Indian Ocean mean state and variability including the two dominant modes in the latter part of twenty-first century under the anthropogenic warming scenario. First, the annual mean climatological SST displays an IOD-like pattern change over the Indian Ocean with enhanced warming in the northwestern Indian Ocean and relatively weaker warming off the Sumatra-Java coast. It is also noted that the monthly SST variance is increased over the eastern and southwestern Indian Ocean. Second, the IOBW variability on a quasi-biennial time scale will be enhanced due to the strengthening of the ENSO-IOBW mode relationship although the total variance of the IOBW mode will be significantly reduced particularly during late summer and fall. The enhanced air-sea coupling over the Indian-western Pacific climate in response to El Nino activity in the future projection makes favorable condition for a positive IOD while it tends to derive relatively cold temperature over the eastern Indian Ocean. This positive IOD-like ENSO response weakens the relationship between the

  6. Linear sea-level response to abrupt ocean warming of major West Antarctic ice basin

    NASA Astrophysics Data System (ADS)

    Mengel, M.; Feldmann, J.; Levermann, A.

    2016-01-01

    Antarctica's contribution to global sea-level rise has recently been increasing. Whether its ice discharge will become unstable and decouple from anthropogenic forcing or increase linearly with the warming of the surrounding ocean is of fundamental importance. Under unabated greenhouse-gas emissions, ocean models indicate an abrupt intrusion of warm circumpolar deep water into the cavity below West Antarctica's Filchner-Ronne ice shelf within the next two centuries. The ice basin's retrograde bed slope would allow for an unstable ice-sheet retreat, but the buttressing of the large ice shelf and the narrow glacier troughs tend to inhibit such instability. It is unclear whether future ice loss will be dominated by ice instability or anthropogenic forcing. Here we show in regional and continental-scale ice-sheet simulations, which are capable of resolving unstable grounding-line retreat, that the sea-level response of the Filchner-Ronne ice basin is not dominated by ice instability and follows the strength of the forcing quasi-linearly. We find that the ice loss reduces after each pulse of projected warm water intrusion. The long-term sea-level contribution is approximately proportional to the total shelf-ice melt. Although the local instabilities might dominate the ice loss for weak oceanic warming, we find that the upper limit of ice discharge from the region is determined by the forcing and not by the marine ice-sheet instability.

  7. Methods for Calibrating Basin-Wide Hydroacoustic Propagation in the Indian Ocean

    SciTech Connect

    Blackman, D; de Groot-Hedlin, C; Orcutt, J A; Harben, P H; Clarke, D B; Ramirez, A L

    2004-10-11

    This collaborative project was designed to test and compare methods for achieving full ocean basin propagation of hydroacoustic signals in the 5-100 Hz frequency band. Plans for a systematic calibration of the International Monitoring System (IMS) for nuclear testing were under consideration in 2000/2001. The results from this project provide information to guide such planning for future ocean basin calibration work. Several acoustic source types were tested during two sea-going experiments and most were successful at generating signals that propagated hundreds to thousands of km to be recorded at the Indian Ocean IMS hydrophone stations. Development and numerical modeling of imploding glass sphere sources was one component of this testing. The intent was to design a relatively simple-to-use source that is not subject to restrictions that can limit use of explosive charges, but whose signal is large enough to propagate 100-1000's km range. Analysis of IMS hydrophone data recording during the experiments was used to illustrate the extent of energy loss during signal propagation and to assess the accuracy with which the small acoustic sources could be located using methods typically employed for nuclear monitoring.

  8. AON observations in the Eurasian and Makarov Basins target changes in the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Polyakov, I.; Ivanov, V.; Rember, R.; Pnyushkov, A.; Alexeev, V. A.; Alkire, M. B.; Morison, J.; Ashik, I. M.

    2014-12-01

    The pan-Arctic boundary current provides the largest input of water, heat, and salt into the Arctic Ocean. Recent observations captured strong changes in the Eurasian and Makarov basins (EMB); understanding the transition requires tracing the intensity of this major subsurface transport system. Responding to urgent needs for a long-term observation system for understanding rapid high-latitude climate change, an EMB observational network is implemented as an element of the Arctic Observing Network (AON). The overarching goal of this AON program is to compile a cohesive picture of the state and transformations of water masses (particularly, Atlantic Water, AW) in the EMB. NABOS (=Nansen and Amundsen Basins Observational System) was the predecessor of this AON program. Observations provided by the program were critical for understanding the large-scale structure and temporal variability of an oceanic boundary current. Fourteen years long observations were instrumental for documenting all stages of the AW warming providing evidence for the anomalous state of the ocean in the 2000s. For example, the prevailing anticyclonic circulation in 2008-10 over the central Laptev Sea slope was documented — a deviation from the classical shallow-to-right circulation paradigm. This program naturally complements the existing AON infrastructure in a synergistic way working hand-in-hand with other elements of the AON, which is vital for interpreting and assessing polar climate change.

  9. Meiofauna assemblages of the Condor Seamount (North-East Atlantic Ocean) and adjacent deep-sea sediments

    NASA Astrophysics Data System (ADS)

    Zeppilli, Daniela; Bongiorni, Lucia; Cattaneo, Antonio; Danovaro, Roberto; Santos, Ricardo Serrão

    2013-12-01

    Seamounts are currently considered hotspots of biodiversity and biomass for macro- and megabenthic taxa, but knowledge of meiofauna is still limited. Studies have revealed the existence of highly diverse meiofauna assemblages; however most data are mainly qualitative or focused only on specific groups, thus preventing comparisons among seamounts and with other deep-sea areas. This study, conducted on Condor Seamount (Azores, North-East Atlantic Ocean), describes variation in abundance, biomass, community structure and biodiversity of benthic meiofauna from five sites located on the Condor Seamount: and one site away from the seamount. While the summit of the seamount hosted the highest alpha biodiversity, the flanks and the bases showed a rich meiofauna assemblage in terms of abundance and biomass. The observed marked differences in grain size composition of sediments reflected the oceanographic conditions impacting different sectors of the Condor seamount, and could play an important role in the spatial distribution of different meiofaunal taxa. Trophic conditions (biochemical composition of organic matter) explained 78% of the variability in the meiofauna biomass pattern while sediment grain influenced the vertical distribution of meiofauna and only partially explained meiofaunal taxa composition. This study provides a further advancement in the knowledge of meiofaunal communities of seamounts. Only a deeper understanding of the whole benthic communities (including meiofauna) will allow to elaborate effective management and conservation tools for seamount ecosystems.

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

    SciTech Connect

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

    2010-10-01

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

  11. Planktonic foraminiferal response to ocean acidification in the Santa Barbara Basin over the last century

    NASA Astrophysics Data System (ADS)

    Osborne, E.; Bizimis, M.; Cai, W. J.; Wang, Y.; Iglesias-Rodriguez, D.; Benitez-Nelson, C. R.; Holm, J. A.; Thunell, R.

    2014-12-01

    Since the onset of the industrial revolution, atmospheric CO2 concentrations have increased by more than 40% (120 ppm) due to anthropogenic activities. While nearly half of these carbon emissions remain in the atmosphere, the ocean has absorbed approximately 30% of the excess CO2. The increase in the ocean aqueous CO2 inventory has resulted in a significant change in seawater chemistry, most notably the decline of mean seawater pH (0.1 units since 1750). Some marine calcifiers, such as planktonic foraminifera, have shown an adverse response to ocean acidification exhibited as a reduction in calcification efficiency. Estimates indicate that planktonic foraminifera are responsible for up to 55% of the total open marine calcium carbonate flux and also serve as low tropic food web members making them an important constituent for chemical and biological processes in the oceans. This study utilizes morphometric (area density) and geochemical (B/Ca) analyses of planktonic foraminifera to calibrate species-specific responses to changes in modern ocean carbonate chemistry. These proxy methods have been applied to down-core records with nearly annual to sub-annual resolution to reconstruct past changes that have occured since the onset of the Industrial Revolution. The sediments used for this study were collected in the Santa Barbara Basin within the California Current System (CSS), which has been identified as a region of rapidly increasing ocean acidification due to natural upwelling processes and increasing atmospheric CO2. This study will evaluate the effect of ocean acidification on several species of planktonic foraminifera to improve our understanding of the response of these organisms to modern changes in atmospheric CO2.

  12. Crustal structure of the Wharton Basin of the eastern Indian Ocean- Geodynamic implications

    NASA Astrophysics Data System (ADS)

    Gopala Rao, D.; Krishna, K. S.; Levchenko, O. V.

    2012-12-01

    Multichannel seismic reflection, magnetic and bathymetric data along seven northwest-southeast regional profiles across the Wharton Basin (WB), eastern Indian Ocean between lat.18N to 14N and 98E to 112E collected as part of Trans Indian Ocean Geotraverse (TIOG) project studies together with earlier published data have been analyzed to interpret crustal structure. Varied geomorphic and crust features identified include; Investigator Ridge System (IRS), Abandoned Spreading Ridge System (ASRS), Western Plains (WP) and Eastern Plains (EP) from west to east. The N-S trending IRS and faults and prominent trough parallel to it and sediments are seismically imaged. The NNE-SSW trending ASRS, >100 km wide is segmented by four NW-SE Fracture Zones: between 108°E and 104E; 106E and 102E, 103.5E and 101E and 103E and 99.5E offsetting the ridge axis. Axial graben and associated magnetic low of it in the north and highs in the south and lack of geomorphic expression in further south imply varied spread rates. Absence of linear magnetic anomalies points to probable spreading during late Cretaceous Magnetic Quite Period. The WP is flanked by the dense tectonic elements and deformed sediments in between. Seismic images of the EP and plains have revealed numerous grabens bounded by vertical faults extend from basement through the sediments in the east, limited mostly to basement in west and turbidities along axial parts. Sediments, up to 0.8 S thick consisting of five seismic sequences carpet Cretaceous oceanic basement. Their acoustic character, stratal and on-lap pattern have revealed deformation of pelagic sediments of ASRS (in northeast), WP and EP during Paleogene and extension subsequently. The basin's crust, thus, depicts 1) north-south structural trends of IRS in east compared to northeast-southwest of WB. 2) Ocean crust is Mesozoic-Cretaceous in age, 3) northwest-southeast compression in contrast to east-west of the Central Indian Ocean Basin. 4) Most of the faults

  13. Characterization of surface-water resources in the Great Basin National Park area and their susceptibility to ground-water withdrawals in adjacent valleys, White Pine County, Nevada

    USGS Publications Warehouse

    Elliott, Peggy E.; Beck, David A.; Prudic, David E.

    2006-01-01

    Eight drainage basins and one spring within the Great Basin National Park area were monitored continually from October 2002 to September 2004 to quantify stream discharge and assess the natural variability in flow. Mean annual discharge for the stream drainages ranged from 0 cubic feet per second at Decathon Canyon to 9.08 cubic feet per second at Baker Creek. Seasonal variability in streamflow generally was uniform throughout the network. Minimum and maximum mean monthly discharges occurred in February and June, respectively, at all but one of the perennial streamflow sites. Synoptic-discharge, specific-conductance, and water- and air-temperature measurements were collected during the spring, summer, and autumn of 2003 along selected reaches of Strawberry, Shingle, Lehman, Baker, and Snake Creeks, and Big Wash to determine areas where surface-water resources would be susceptible to ground-water withdrawals in adjacent valleys. Comparison of streamflow and water-property data to the geology along each stream indicated areas where surface-water resources likely or potentially would be susceptible to ground-water withdrawals. These areas consist of reaches where streams (1) are in contact with permeable rocks or sediments, or (2) receive water from either spring discharge or ground-water inflow.

  14. More than one way to stretch: A tectonic model for extension along the plume track of the Yellowstone hotspot and adjacent Basin and Range Province

    USGS Publications Warehouse

    Parsons, T.; Thompson, G.A.; Smith, R.P.

    1998-01-01

    The eastern Snake River Plain of southern Idaho poses a paradoxical problem because it is nearly aseismic and unfaulted although it appears to be actively extending in a SW-NE direction continuously with the adjacent block-faulted Basin and Range Province. The plain represents the 100-km-wide track of the Yellowstone hotspot during the last ???16-17 m.y., and its crust has been heavily intruded by mafic magma, some of which has erupted to the surface as extensive basalt flows. Outside the plain's distinct topographic boundaries is a transition zone 30-100 km wide that has variable expression of normal faulting and magmatic activity as compared with the surrounding Basin and Range Province. Many models for the evolution of the Snake River Plain have as an integral component the suggestion that the crust of the plain became strong enough through basaltic intrusion to resist extensional deformation. However, both the boundaries of the plain and its transition zone lack any evidence of zones of strike slip or other accommodation that would allow the plain to remain intact while the Basin and Range Province extended around it; instead, the plain is coupled to its surroundings and extending with them. We estimate strain rates for the northern Basin and Range Province from various lines of evidence and show that these strains would far exceed the elastic limit of any rocks coupled to the Basin and Range; thus, if the plain is extending along with its surroundings, as the geologic evidence indicates, it must be doing so by a nearly aseismic process. Evidence of the process is provided by volcanic rift zones, indicators of subsurface dikes, which trend across the plain perpendicular to its axis. We suggest that variable magmatic strain accommodation, by emplacement and inflation of dikes perpendicular to the least principal stress in the elastic crust, allows the crust of the plain to extend nearly aseismically. Dike injection releases accumulated elastic strain but

  15. Changes in Nematode Communities in Different Physiographic Sites of the Condor Seamount (North-East Atlantic Ocean) and Adjacent Sediments

    PubMed Central

    Zeppilli, Daniela; Bongiorni, Lucia; Serrão Santos, Ricardo; Vanreusel, Ann

    2014-01-01

    Several seamounts are known as ‘oases’ of high abundances and biomass and hotspots of biodiversity in contrast to the surrounding deep-sea environments. Recent studies have indicated that each single seamount can exhibit a high intricate habitat turnover. Information on alpha and beta diversity of single seamount is needed in order to fully understand seamounts contribution to regional and global biodiversity. However, while most of the seamount research has been focused on summits, studies considering the whole seamount structure are still rather poor. In the present study we analysed abundance, biomass and diversity of nematodes collected in distinct physiographic sites and surrounding sediments of the Condor Seamount (Azores, North-East Atlantic Ocean). Our study revealed higher nematode biomass in the seamount bases and values 10 times higher in the Condor sediments than in the far-field site. Although biodiversity indices did not showed significant differences comparing seamount sites and far-field sites, significant differences were observed in term of nematode composition. The Condor summit harboured a completely different nematode community when compared to the other seamount sites, with a high number of exclusive species and important differences in term of nematode trophic diversity. The oceanographic conditions observed around the Condor Seamount and the associated sediment mixing, together with the high quality of food resources available in seamount base could explain the observed patterns. Our results support the hypothesis that seamounts maintain high biodiversity through heightened beta diversity and showed that not only summits but also seamount bases can support rich benthic community in terms of standing stocks and diversity. Furthermore functional diversity of nematodes strongly depends on environmental conditions link to the local setting and seamount structure. This finding should be considered in future studies on seamounts, especially in

  16. Changes in nematode communities in different physiographic sites of the condor seamount (north-East atlantic ocean) and adjacent sediments.

    PubMed

    Zeppilli, Daniela; Bongiorni, Lucia; Serrão Santos, Ricardo; Vanreusel, Ann

    2014-01-01

    Several seamounts are known as 'oases' of high abundances and biomass and hotspots of biodiversity in contrast to the surrounding deep-sea environments. Recent studies have indicated that each single seamount can exhibit a high intricate habitat turnover. Information on alpha and beta diversity of single seamount is needed in order to fully understand seamounts contribution to regional and global biodiversity. However, while most of the seamount research has been focused on summits, studies considering the whole seamount structure are still rather poor. In the present study we analysed abundance, biomass and diversity of nematodes collected in distinct physiographic sites and surrounding sediments of the Condor Seamount (Azores, North-East Atlantic Ocean). Our study revealed higher nematode biomass in the seamount bases and values 10 times higher in the Condor sediments than in the far-field site. Although biodiversity indices did not showed significant differences comparing seamount sites and far-field sites, significant differences were observed in term of nematode composition. The Condor summit harboured a completely different nematode community when compared to the other seamount sites, with a high number of exclusive species and important differences in term of nematode trophic diversity. The oceanographic conditions observed around the Condor Seamount and the associated sediment mixing, together with the high quality of food resources available in seamount base could explain the observed patterns. Our results support the hypothesis that seamounts maintain high biodiversity through heightened beta diversity and showed that not only summits but also seamount bases can support rich benthic community in terms of standing stocks and diversity. Furthermore functional diversity of nematodes strongly depends on environmental conditions link to the local setting and seamount structure. This finding should be considered in future studies on seamounts, especially in

  17. Subsurface geology and porosity distribution, Madison Limestone and underlying formations, Powder River basin, northeastern Wyoming and southeastern Montana and adjacent areas

    USGS Publications Warehouse

    Peterson, James A.

    1978-01-01

    To evaluate the Madison Limestone and associated rocks as potential sources for water supplies in the Powder River Basin and adjacent areas, an understanding of the geologic framework of these units, their lithologic facies patterns, the distribution of porosity zones, and the relation between porosity development and stratigraphic facies is necessary. Regionally the Madison is mainly a fossiliferous limestone. However, in broad areas of the eastern Rocky Mountains and western Great Plains, dolomite is a dominant constituent and in places the Madison is almost entirely dolomite. Within these areas maximum porosity development is found and it seems to be related to the coarser crystalline dolomite facies. The porosity development is associated with tabular and fairly continuous crystalline dolomite beds separated by non-porous limestones. The maximum porosity development in the Bighorn Dolomite, as in the Madison, is directly associated with the occurrence of a more coarsely crystalline sucrosic dolomite facies. Well data indicate, however, that where the Bighorn is present in the deeper parts of the Powder River Basin, it may be dominated by a finer crystalline dolomite facies of low porosity. The 'Winnipeg Sandstone' is a clean, generally well-sorted, medium-grained sandstone. It shows good porosity development in parts of the northern Powder River Basin and northwestern South Dakota. Because the sandstone is silica-cemented and quartzitic in areas of deep burial, good porosity is expected only where it is no deeper than a few thousand feet. The Flathead Sandstone is a predominantly quartzose, slightly feldspathic sandstone, commonly cemented with iron oxide. Like the 'Winnipeg Sandstone,' it too is silica-cemented and quartzitic in many places so that its porosity is poor in areas of deep burial. Illustrations in this report show the thickness, percent dolomite, and porosity-feet for the Bighorn Dolomite and the Madison Limestone and its subdivisions. The

  18. Backarc basin evolution and cordilleran orogenesis: Insights from new ocean-bottom seismograph refraction profiling in Bransfield Strait, Antarctica

    NASA Astrophysics Data System (ADS)

    Barker, Daniel H. N.; Christeson, Gail L.; Austin, James A., Jr.; Dalziel, Ian W. D.

    2003-02-01

    Bransfield Strait, a backarc basin off the northwestern Antarctic Peninsula, is a modern analog for Cretaceous basins inverted in the compressional tectonic regime that initiated the Andean Cordillera. Eight new refraction ocean-bottom seismograph profiles in the strait demonstrate that crustal thickness in the deep central basin increases from northeast to southwest, from ˜10 km to ˜14 16 km. This confirms multichannel seismic interpretation of upper crustal structures suggesting that the Bransfield basin is opening by northeast to southwest rift propagation within arc crust of the Antarctic Peninsula, a process also recorded in the obducted Cretaceous Rocas Verdes basin of the southernmost Andes. Thinning is most prominent along the axis of the strait, where the crust is ˜9 11 km thick. In contrast, thicknesses beneath the Antarctic Peninsula margin and the inactive South Shetland Islands pedestal are ˜18 km and ˜24 km, respectively. Seismic velocities and thicknesses suggest that new oceanic crust is not yet being generated. Extension is focused along the northwest margin, imparting the physiographic asymmetry to the strait. Comparing the Bransfield basin with the inverted Rocas Verdes basin and intraoceanic counterparts in the western Pacific suggests that rift propagation and trench-side focusing of extension may be fundamental features of young backarc basins. Resultant asymmetry may facilitate observed obduction of backarc basin floor and arc rocks onto continental margins during compressional orogenesis.

  19. The Mohorovicic discontinuity in ocean basins: Some observations from seismic data

    NASA Astrophysics Data System (ADS)

    Mutter, J. C.; Carton, Hélène D.

    2013-12-01

    Since the late 1970s studies of the oceanic crust using airgun sources and towed hydrophone arrays have been conducted in a wide range of ocean basin settings including mid-ocean ridges and old oceanic crust. The very earliest studies were performed at the fast-spreading East Pacific Rise (EPR) and revealed a very distinct almost continuous vertical incidence reflection event at a depth corresponding to the crust-mantle transition as inferred from seismic refraction studies. This suggested that the transition was quite sharp in comparison to the source wavelength. That Moho was observed very close to or even exactly beneath the ridge crest implied that it was formed at essentially zero age. Since then, many experiments using progressively improving airgun arrays and streamer systems have expanded these observations. Here we review the literature presenting studies of “normal” oceanic crust produced at mid-ocean ridges with the objective of assessing the age of formation of Moho and the nature of variability of Moho signature in multi-channel seismic data. Moho is observed as a consistent feature for all spreading rates but appears quite variable, being very distinct in some areas, complex in form in others and absent in many regions (as much as 40%). Although fast-spread crust is associated with the strongest, simplest and most laterally continuous Moho images we see significant variability at almost all spreading rates and ages. Where Moho is absent from vertical incidence data this cannot be fully explained by the effect of scattering or attenuation in the crustal section above. Moho can be observed at zero age in only a small number of areas at or near Overlapping Spreading Centers on the EPR. After three decades of marine seismic studies many fundamental questions remain concerning the nature of the Moho that will require targeted experiments to solve.

  20. Deep Circulation in the Lau Basin of the South Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Speer, K.; Thurnherr, A.

    2006-12-01

    The Lau Basin is a semi-enclosed basin in the tropical South Pacific, located approximately 1500 km north of New Zealand. Below 1000m it is largely closed to the east, south and west by the Lau and the Tonga Ridges, respectively. The Zephyr Shoal at 15S blocks the northern edge of the Lau Basin below 2000m almost completely. The East Lau Spreading Center (ELSC), which form the "bull's eye" of the Lau Basin Integrated Study Sites (ISS), runs approximately parallel to the Tonga Ridge in the Lau Basin between 19S and 23S. Its depth is shallowest (2000m) near its southern end and deepens northward to about 2800m. There are currently 11 neutrally buoyant floats drifting in the Lau Basin at 1700m, near the depth of the hydrothermal plumes known at the time of deployment. The floats, which were deployed during three R2K cruises in 2004/05, return to the surface every 3 4 weeks in order to transmit their positions and temperature data back to shore via a network of satellites. The data are made available in near real-time on the web. In contrast to current-meter data, which become available only after mooring recovery and which, because of their Eulerian nature, are not very well suited for studying dispersal near topography, the float data yield timely, cost-effective and directly usable information about dispersal in the deep ocean. The available float data currently span 261 drift cycles and cover a good portion of the Lau Basin. Between April 2004 and June 2006, the mean meridional velocity at 1700m was 3.2 ± 1.1 mm/s to the north, while the zonal flow was indistinguishable from zero. Individual float-cycle-averaged velocities, on the other hand, are randomly distributed and associated with speeds up to 9 cm/s. These observations imply that on timescales of months to years horizontal dispersal in the deep interior of the Lau Basin is primarily eddy diffusive, while the observed northward mean flow becomes important on longer timescales. As a consequence, larval

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  2. Tien Shan, Pamir, and Tibet: History and geodynamics of phanerozoic oceanic basins

    NASA Astrophysics Data System (ADS)

    Burtman, V. S.

    2010-09-01

    Geological and biogeographical data on the paleooceanic basins of the Tien Shan and High Asia are summarized. The oceanic crustal rocks in the Tien Shan, Pamir, and Tibet belong to the Tethian and Turkestan-Paleoasian systems of paleooceanic basins. The tectonic evolution of these systems in the Phanerozoic was not coeval and unidirectional. The sialic blocks of the future Tien Shan, Pamir, and Tibet were incorporated into the Eurasian continent during several stages. In the Late Ordovician and Silurian several microcontinents were preliminarily combined into the Kazakh-Kyrgyz continent as a composite aggregation. The territories of the Tien Shan and Tarim became a part of Eurasia after the closure of the Turkestan, Ural, and Paleotethian oceans in the Late Carboniferous and Early Permian. The territories of the Pamir, Karakorum, Kunlun, and most of Tibet attached to the Eurasian continent in the Triassic. The Lhasa and Kohistan blocks were incorporated into Eurasia in the Cretaceous, whereas Hindustan was docked to Eurasia in the Paleogene.

  3. Mode of opening of an oceanic pull-apart: The 20°N Basin along the Owen Fracture Zone (NW Indian Ocean)

    NASA Astrophysics Data System (ADS)

    Rodriguez, Mathieu; Chamot-Rooke, Nicolas; Fournier, Marc; Huchon, Philippe; Delescluse, Matthias

    2013-09-01

    basins are common features observed at releasing bends along major strike-slip faults. The formation and structural evolution of such basins have mostly been investigated in the continental domain and by sandbox laboratory experiments or numerical models. Here we present recently acquired multibeam bathymetry, 3.5 kHz echo sounder, and seismic profiles across the 20°N pull-apart Basin along the India-Arabia transform boundary, known as the Owen Fracture Zone (OFZ). Using nearby oceanic drilling (Deep Sea Drilling Project 222), we constrain the structural evolution of the basin since opening some 3 Myr ago. The 20°N Basin is large (90 km long and 35 km wide) despite limited transcurrent motion (~10 km). The first stage involved the formation of a step over along the OFZ and the subsequent isolation of a subsiding half graben. Extension and subsidence were further partitioned over three distinct subbasins separated by complex sets of transverse faults. The size of the basin was enhanced by gravity-driven collapse. The 20°N Basin has been a catchment for Indus turbidites since its opening, which provide a good record of syn-sedimentary deformation. The deformation related to the subsidence of the half graben mimics rollover structures commonly encountered in salt tectonics, suggesting that subsidence was accommodated by one or several décollement layers at depth. Despite a different rheological context, the subsurface structure of the nascent oceanic 20°N Basin is very similar to the more mature continental Dead Sea Basin along the Levant Fault, which also displays subbasins separated by transverse faults.

  4. Ancient drainage basin of the Tharsis region, Mars: Potential source for outflow channel systems and putative oceans or paleolakes

    USGS Publications Warehouse

    Dohm, J.M.; Ferris, J.C.; Baker, V.R.; Anderson, R.C.; Hare, T.M.; Strom, R.G.; Barlow, N.G.; Tanaka, K.L.; Klemaszewski, J.E.; Scott, D.H.

    2001-01-01

    Paleotopographic reconstructions based on a synthesis of published geologic information and high-resolution topography, including topographic profiles, reveal the potential existence of an enormous drainage basin/aquifer system in the eastern part of the Tharsis region during the Noachian Period. Large topographic highs formed the margin of the gigantic drainage basin. Subsequently, lavas, sediments, and volatiles partly infilled the basin, resulting in an enormous and productive regional aquifer. The stacked sequences of water-bearing strata were then deformed locally and, in places, exposed by magmatic-driven uplifts, tectonic deformation, and erosion. This basin model provides a potential source of water necessary to carve the large outflow channel systems of the Tharsis and surrounding regions and to contribute to the formation of putative northern-plains ocean(s) and/or paleolakes. Copyright 2001 by the American Geophysical Union.

  5. A zonally averaged, three-basin ocean circulation model for climate studies

    SciTech Connect

    Hovine, S.; Fichefet, T.

    1994-09-01

    A two-dimensional, three-basin ocean model suitable for long-term climate studies is developed. The model is based on the zonally averaged form of the primitive equations written in spherical coordinates. The east-west density difference which arises upon averaging the momentum equations is taken to be proportional to the meridional density gradient. Lateral exchanges of heat and salt between the basins are explicitly resolved. Moreover, the model includes bottom topography and has representations of the Arctic Ocean and of the Weddell and Ross seas. Under realistic restoring boundary conditions, the model reproduces the global conveyor belt: deep water is formed in the Atlantic between 60 and 70{degree}N at a rate of about 17 Sv (1 Sv=10{sup 6} m{sup 3}S{sup {minus}1}) and in the vicinity of the Antarctic continent, while the Indian and Pacific basins show broad upwelling. Superimposed on this thermohaline circulation are vigorous wind-driven cells in the upper thermocline. The simulated temperature and salinity fields and the computed meridional heat transport compare reasonably well with the observational estimates. When mixed boundary conditions i.e., a restoring condition no sea-surface temperature and flux condition on sea-surface salinity are applied, the model exhibits an irregular behavior before reaching a steady state characterized by self-sustained oscillations of 8.5-y period. The conveyor-belt circulation always results at this stage. A series of perturbation experiments illustrates the ability of the model to reproduce different steady-state circulations under mixed boundary conditions. Finally, the model sensitivity to various factors is examined. This sensitivity study reveals that the bottom topography and the presence of a submarine meridional ridge in the zone of the Drake passage play a crucial role in determining the properties of the model bottom-water masses. The importance of the seasonality of the surface forcing is also stressed.

  6. Benthic macrofaunal production for a typical shelf-slope-basin region in the western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Lin, Heshan; Wang, Jianjun; Liu, Kun; He, Xuebao; Lin, Junhui; Huang, Yaqin; Zhang, Shuyi; Mou, Jianfeng; Zheng, Chengxing; Wang, Yu

    2016-02-01

    Secondary production by macrofaunal communities in the western Arctic Ocean were quantified during the 4th and 5th Chinese Arctic Scientific Expeditions. The total production and P/B ratio for each sector ranged from 3.8 (±7.9) to 615.6 (±635.5) kJ m-2 yr-1 and 0.5 (± 0.2) to 0.7 (± 0.2) yr-1, respectively. The shallow shelves in the western Arctic Ocean exhibited particularly high production (178.7-615.6 kJ m-2 yr-1), particularly in the two "hotspots" - the southern and northeastern (around Barrow Canyon) Chukchi Sea. Benthic macrofaunal production decreased sharply with depth and latitude along a shelf-slope-basin transect, with values of 17.0-269.8 kJ m-2 yr-1 in slope regions and 3.8-10.1 kJ m-2 yr-1 in basins. Redundancy analysis indicated that hydrological characteristics (depth, bottom temperature and salinity) and granulometric parameters (mean particle size, % sand and % clay) show significant positive/negative correlations with total production. These correlations revealed that the dominant factors influencing benthic production are the habitat type and food supply from the overlying water column. In the Arctic, the extreme environmental conditions and low temperature constrain macrofaunal metabolic processes, such that food and energy are primarily used to increase body mass rather than for reproduction. Hence, energy turnover is relatively low at high latitudes. These data further our understanding of benthic production processes and ecosystem dynamics in the context of rapid climate change in the western Arctic Ocean.

  7. Isotope composition of iron delivered to the oceans by intertropical rivers: The Amazon River Basin case

    NASA Astrophysics Data System (ADS)

    Poitrasson, F.; Vieira, L. C.; Seyler, P.; dos Santos Pinheiro, G. M.; Mulholland, D. S.; Ferreira Lima, B. A.; Bonnet, M.; Martinez, J.; Prunier, J.

    2011-12-01

    Riverborne iron is a notable source for this biogeochemically key element to the oceans. Recent investigations have shown that its isotopic composition may vary significantly in oceanic waters. Hence, a proper understanding of the Fe cycle at the surface of the Earth requires a good characterization of the isotopic composition of its various reservoirs. However, as the database growths, it appears that the isotope composition of the riverborne Fe delivered to the oceans may be more varied than initially thought, in agreement with inferences from soil studies from different climatic contexts. It is therefore important to compare major rivers from different latitudes. We focused our attention on the Amazon River and its tributaries that represent ca. 20% of the freshwater delivered to the oceans by world rivers. Preliminary experiments suggest that water filtration may induce biases in stable Fe isotope composition. Therefore, we worked first on bulk waters, sampled during multidisciplinary field campaigns on the Amazon River and its tributaries, including the Solimoes, Negro, Madeira and Tapajos Rivers. Besides a complete sample physical-chemical characterization, Fe isotope determinations were conduced after water sample mineralization, iron purification and MC-ICP-MS analysis. Our first results reveal that most bulk water samples cluster close to the continental crust value (0.1% δ57FeIRMM-14) with an overall range of 0.2%. This is consistent with the restricted range found in lateritic soils elsewhere that represent 80% of the Amazon basin surface. Only black water rivers flowing over the podzols of the northern portion of the Amazon basin tend to show lighter isotopic compositions, down to -0.18%. However, sediment analyses suggest that this light Fe isotopic is lost through sedimentation on the river bed, thereby leading the waters to have Fe isotope compositions remaining close to that of the continental crust. This constant isotopic signature holds whatever

  8. Stratigraphic and structural framework of the western edge of Canada Basin, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Hutchinson, D. R.; Mosher, D. C.; Shimeld, J.; Chian, D.; Lebedeva-Ivanova, N. N.; Evangelatos, J.; Jackson, R.

    2012-12-01

    Seismic reflection and refraction data collected in joint two-icebreaker expeditions by the U.S. and Canada between 2008 and 2011 reveal how the western edge of the Canada Basin has evolved through rifting and post rifting history. Our observations suggest that the western margin of Canada Basin (along Northwind Ridge [NR} and the northern Chukchi Borderland [CB]) is a mix of highly stretched continental and transitional crust with unique attributes that reflect local influences of NR, CB, and Alpha Ridge with the extension that formed Canada Basin. The reflection character of basement and refraction velocities indicate that the regions adjacent to NR and north-northwest of CB are probably underlain by a high-velocity (7.2-7.5 km/s) layer that may be serpentinized mantle or a transitional, intruded lower continental crust. Between these two regions, north of CB, is an area underlain by highly stretched continental crust (lower crust with velocities less than 6.7 km/s). Dredge samples collected from near NR recovered basaltic rocks. The area north and northeast of CB also contains discontinuous, segmented, bright reflections at the base of the postrift Canada Basin sediments consistent with the kind of reflections seen in magmatically intruded regions. These bright reflections may indicate a postrift magmatic pulse associated with Alpha Ridge. On top of Northwind Ridge, the stratigraphic units above basement are truncated and eroded and tilt towards Canada basin. The relationship between these units and the deepest units in Canada Basin is speculative, but they are interpreted to represent prerift or synrift deposits that were faulted during the formation of NR. Similar truncated, eroded, and tilted deposits occur along the northern part of the CB and southern Alpha Ridge and can be traced both continuously and discontinuously into Canada Basin where they unconformably underlie the younger deposits that lap onto them. The postrift depositional patterns inferred from

  9. Geodynamic evolution of ophiolites from Albania and Greece (Dinaric-Hellenic belt): one, two, or more oceanic basins?

    NASA Astrophysics Data System (ADS)

    Bortolotti, Valerio; Chiari, Marco; Marroni, Michele; Pandolfi, Luca; Principi, Gianfranco; Saccani, Emilio

    2013-04-01

    All the geological constraints for an exhaustive reconstruction of the Triassic to Tertiary tectonic history of the southern Dinaric-Hellenic belt can be found in Albania and Greece. This article aims to schematically reconstruct this long tectonic evolution primarily based on a detailed analysis of the tectonic setting, the stratigraphy, the geochemistry, and the age of the ophiolites. In contrast to what was previously reported in the literature, we propose a new subdivision on a regional scale of the ophiolite complexes cropping out in Albania and Greece. This new subdivision includes six types of ophiolite occurrences, each corresponding to different tectonic units derived from a single obducted sheet. These units are represented by: (1) sub-ophiolite mélange, (2) Triassic ocean-floor ophiolites, (3) metamorphic soles, (4) Jurassic fore-arc ophiolites, (5) Jurassic intra-oceanic-arc ophiolites, and (6) Jurassic back-arc basin ophiolites. The overall features of these ophiolites are coherent with the existence of a single, though composite, oceanic basin located east of the Adria/Pelagonian continental margin. This oceanic basin was originated during the Middle Triassic and was subsequently (Early Jurassic) affected by an east-dipping intra-oceanic subduction. This subduction was responsible for the birth of intra-oceanic-arc and back-arc oceanic basins separated by a continental volcanic arc during the Early to Middle Jurassic. From the uppermost Middle Jurassic to the Early Cretaceous, an obduction developed, during which the ophiolites were thrust westwards firstly onto the neighboring oceanic lithosphere and then onto the Adria margin.

  10. Formation and variability of the Lofoten basin vortex in a high-resolution ocean model

    NASA Astrophysics Data System (ADS)

    Volkov, Denis L.; Kubryakov, Arseny A.; Lumpkin, Rick

    2015-11-01

    The Lofoten Basin of the Norwegian Sea is characterized by a local maximum of eddy kinetic energy and it is an important transit region for the warm and saline Atlantic waters on their way towards the Arctic Ocean. Eddies are generated by the Norwegian Atlantic Current and propagate anticlockwise around the center of the basin. In situ and satellite observations have discovered a rather small (with a radius of a few tens of km), but strong quasi-permanent anticyclonic vortex that resides in the center of the Lofoten Basin near 3°E, 69.8°N. The objective of this paper is to understand how and why the vortex is formed and to investigate what processes support its stability and drive its variability. To achieve this objective, we have conducted three high-resolution numerical experiments with the mean horizontal grid spacing of 18 km, 9 km, and 4 km. The Lofoten Vortex did not form in the 18-km experiment. The most realistic (compared to available observations) simulation of the vortex is provided by the 4-km experiment, which better reproduces eddy variability in the region. The experiments thus provide experimental evidence of the importance of eddies in the formation and stability of the vortex. We demonstrate how anticyclonic eddies, that are usually stronger and more numerous in the basin than cyclonic eddies, contribute to the intensification of the Lofoten Vortex. The Lofoten Vortex itself is not stationary and drifts cyclonically within the area bounded by approximately the 3250 m isobath. The analysis of the barotropic vorticity budget in the 4-km experiment shows that the advection of the relative vorticity gradient by eddies is the main mechanism that drives the variability of the Lofoten Vortex. The direct impact of wind/buoyancy forcing is found to be small to negligible.

  11. Water Resources of the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah - Draft Report

    USGS Publications Warehouse

    Welch, Alan H., (Edited By); Bright, Daniel J.

    2007-01-01

    Summary of Major Findings This report summarizes results of a water-resources study for White Pine County, Nevada, and adjacent areas in east-central Nevada and western Utah. The Basin and Range carbonate-rock aquifer system (BARCAS) study was initiated in December 2004 through Federal legislation (Section 131 of the Lincoln County Conservation, Recreation, and Development Act of 2004) directing the Secretary of the Interior to complete a water-resources study through the U.S. Geological Survey, Desert Research Institute, and State of Utah. The study was designed as a regional water-resource assessment, with particular emphasis on summarizing the hydrogeologic framework and hydrologic processes that influence ground-water resources. The study area includes 13 hydrographic areas that cover most of White Pine County; in this report however, results for the northern and central parts of Little Smoky Valley were combined and presented as one hydrographic area. Hydrographic areas are the basic geographic units used by the State of Nevada and Utah and local agencies for water-resource planning and management, and are commonly defined on the basis of surface-water drainage areas. Hydrographic areas were further divided into subbasins that are separated by areas where bedrock is at or near the land surface. Subbasins represent subdivisions used in this study for estimating recharge, discharge, and water budget. Hydrographic areas represent the subdivision used for reporting summed and tabulated subbasin estimates.

  12. Water Resources of the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah

    USGS Publications Warehouse

    Welch, Alan H., (Edited By); Bright, Daniel J.; Knochenmus, Lari A.

    2008-01-01

    INTRODUCTION This report summarizes results of a water-resources study for White Pine County, Nevada, and adjacent areas in east-central Nevada and western Utah. The Basin and Range carbonate-rock aquifer system (BARCAS) study was initiated in December 2004 through Federal legislation (Section 301(e) of the Lincoln County Conservation, Recreation, and Development Act of 2004; PL108-424) directing the Secretary of the Interior to complete a water-resources study through the U.S. Geological Survey, Desert Research Institute, and State of Utah. The study was designed as a regional water-resource assessment, with particular emphasis on summarizing the hydrogeologic framework and hydrologic processes that influence ground-water resources. The study area includes 13 hydrographic areas that cover most of White Pine County; in this report however, results for the northern and central parts of Little Smoky Valley were combined and presented as one hydrographic area. Hydrographic areas are the basic geographic units used by the State of Nevada and Utah and local agencies for water-resource planning and management, and are commonly defined on the basis of surface-water drainage areas. Hydrographic areas were further divided into subbasins that are separated by areas where bedrock is at or near the land surface. Subbasins are the subdivisions used in this study for estimating recharge, discharge, and water budget. Hydrographic areas are the subdivision used for reporting summed and tabulated subbasin estimates.

  13. Petrogenesis and structure of oceanic crust in the Lau back-arc basin

    NASA Astrophysics Data System (ADS)

    Eason, Deborah E.; Dunn, Robert A.

    2015-11-01

    Oceanic crust formed along spreading centers in the Lau back-arc basin exhibits a dramatic change in structure and composition with proximity to the nearby Tofua Arc. Results from recent seismic studies in the basin indicate that crust formed near the Tofua Arc is abnormally thick (8-9 km) and compositionally stratified, with a thick low-velocity (3.4-4.5 km/s) upper crust and an abnormally high-velocity (7.2-7.4+ km/s) lower crust (Arai and Dunn, 2014). Lava samples from this area show arc-like compositional enrichments and tend to be more vesicular and differentiated than typical mid-ocean ridge basalts, with an average MgO of ∼3.8 wt.%. We propose that slab-derived water entrained in the near-arc ridge system not only enhances mantle melting, as commonly proposed to explain high crustal production in back-arc environments, but also affects magmatic differentiation and crustal accretion processes. We present a petrologic model of Lau back-arc crustal formation that successfully predicts the unusual crustal stratification imaged in the near-arc regions of the Lau basin, as well as the highly fractionated basaltic andesites and andesites that erupt there. Results from phase equilibria modeling using MELTS indicate that the high water contents found in near-arc parental melts can lead to crystallization of an unusually mafic, high velocity cumulate layer. Best-fit model runs contain initial water contents of ∼0.5-1.0 wt.% H2O in the parental melts, and successfully reproduce geochemical trends of the erupted lavas while crystallizing a cumulate assemblage with calculated seismic velocities consistent with those observed in the near-arc lower crust. Modeled residual melts are also lower density than their dry equivalents, which aids in melt segregation from the cumulate layer. Low-density, water-rich residual melts can lead to the eruption of vesicular lavas that are unusually evolved for an oceanic spreading center.

  14. Do manganese nodules grow or dissolve after burial? Results from the Central Indian Ocean Basin

    NASA Astrophysics Data System (ADS)

    Pattan, J. N.; Parthiban, G.

    2007-07-01

    Fifty buried manganese nodules at different depth intervals were recovered in 12 sediment cores from the Central Indian Ocean Basin (CIOB). A maximum of 15 buried nodules were encountered in one sediment core (AAS-22/GC-07) and the deepest nodule was recovered at 5.50 m below seafloor in core AAS-04/GC-5A. Approximately 80% of the buried nodules are small in size (˜2 cm diameter) in contrast to the Atlantic Ocean and Peru Basin (Pacific Ocean) where the majority of the buried nodules are large, ˜8 cm and >6 cm, respectively. Buried nodule size decreases with core depth and this distribution appears to be similar to the phenomenon of "Brazil Nut Effect". Buried nodules exhibit both smooth and rough surface textures and are ellipsoidal, elongated, rounded, sub rounded, irregular and polynucleated. Buried nodules from siliceous ooze are enriched in Mn, Cu, Ni, Zn, Mo, Ga, V and Rb whereas those from red clay are enriched in Fe, Co, Ti, U, Th, Y, Cr, Nb and Rare Earth Elements (REE). Buried nodules from siliceous ooze suggest their formation under hydrogenetic, early digenetic and diagenetic processes whereas those from red clay are of hydrogenetic origin. REE are enriched more than 1.5 times in buried nodules from red clay compared to siliceous ooze. However, the mode of incorporation of REE into buried nodules from both sedimentary environments is by a single authigenic phase consisting of Fe-Ti-P. Shale-normalized REE patterns and Ce anomalies suggest that nodules from siliceous ooze formed under more oxidizing conditions than those from red clay. Nodules buried at depths between 1.5 and 2.5 m are diagenetic (Mn/Fe ratio 10-15), formed in highly oxic environments (large positive Ce anomalies) and record aeolian dust (high Eu anomalies). Chemical composition, surface texture and morphology of buried nodules are similar to those of surface nodules from the same basin. Furthermore, buried nodule compositions do not exhibit any distinct patterns within the core depth

  15. Transformation of Atlantic Water in the Nansen Basin of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Ivanov, Vladimir; Aksenov, Yevgeny

    2015-04-01

    The joint analysis of recent hydrographic observations and high resolution numerical modelling is presented for the segment of the boundary current between Fram Strait and the Lomonosov Ridge in the Nansen Basin of the Arctic Ocean. The process of the Fram Strait branch of Atlantic Water (FAW) transformation on this route is in the focus of this study. Two specific regions are distinguished, where fast transformation of FAW occurs. The first region is located between northern Svalbard and Franz Joseph Land. This is the place where eastward flow of warm and salty FAW encounters pack ice, which moves towards Fram Strait. Intensive ocean-ice-air interaction leads to rapid heat and salt loss from the upper part of FAW, resulting in formation of surface mixed layer and isolation of the warm FAW core from further direct contact with atmosphere. The second crucial region of FAW transformation is located around Severnaya Zemlya Archipelago. In this region deep warm core of FAW rapidly loses heat and salt as a result of intensive vertical and lateral mixing with the Barents Sea AW branch (BAW), which enters the Nansen Basin through St.Anna Trough, submerges the warm core of FAW and pushes it seaward. Dense water, originating on the north-western shelf of the Laptev Sea, cascades down continental slope and also contributes to cooling and freshening of FAW on its way along the Laptev Sea continental margin. The end product of the transformation process in the Laptev Sea is a new water mass, which includes FAW, BAW and shelf water fractions. This water occupies the depth range 200-1000 m. It is characterised by the positive temperature and by the absence of local maxima on salinity vertical profile. Sitting on the continental slope makes this water mass quite mobile and therefore - the major candidate to reach Canadian Basin. This perspective is less likely for the original FAW. In the Laptev Sea this water is detached off the continental margin and is likely to recirculate

  16. Contribution of allochthonous organic carbon across the Serrano River Basin and the adjacent fjord system in Southern Chilean Patagonia: Insights from the combined use of stable isotope and fatty acid biomarkers

    NASA Astrophysics Data System (ADS)

    Lafon, Alejandra; Silva, Nelson; Vargas, Cristian A.

    2014-12-01

    Chilean Patagonia is characterized by an irregular geography involving many islands, peninsulas, channels, sounds and fjords, that prevent direct interaction between oceanic water masses and freshwater river discharges at the head of the continental fjords. In this paper, we evaluate the potential sources and composition of organic matter along the Serrano River basin and the adjacent channels and fjords in Southern Chilean Patagonia (51-52°S), as well as their importance for marine planktonic organisms. In spring of 2009, evidence of C:N ratio, δ13C, δ15N and fatty acids composition in particulate organic carbon (POC), surface sediment, soil, plankton, and vegetal tissue, as well some physical and chemical characteristics (i.e. salinity, dissolved oxygen, NO3-, NH4+, PO4-3, Si(OH)4), were measured in samples collected during the CIMAR 14 Fiordos oceanographic cruise. Significant differences in δ13C-POC were found between the terrestrial and marine environments but not within fjord stations. Along the fjord region, the high C:N ratio and depleted δ13C values in POC samples suggest that particulate organic matter (POM) in the upper level of the water column (0-10 m depth) is supported by different sources. Terrestrial organic carbon exported by rivers may constitute a significant subsidy, up to 70% based on two end-member mixing model, to the fjord ecosystem. Furthermore, terrestrial carbon might account for a significant percentage of the zooplankton body carbon, estimated both by using isotopic (∼24-61%) and fatty acid analysis (∼14-61%). Isotopic analyses in marine sediment samples suggest that POC seems to be decoupled from terrestrial-influenced surface sources at the fjord stations, and the contribution of surrounding vegetation seemingly unimportant for carbon export to the benthos. Local hydrographic and geomorphological characteristics might determine the presence of oceanographic frontal zones, which in turn might explain differences in carbon

  17. Oxygenation of a Cryogenian ocean (Nanhua Basin, South China) revealed by pyrite Fe isotope compositions

    NASA Astrophysics Data System (ADS)

    Zhang, Feifei; Zhu, Xiangkun; Yan, Bin; Kendall, Brian; Peng, Xi; Li, Jin; Algeo, Thomas J.; Romaniello, Stephen

    2015-11-01

    The nature of ocean redox chemistry between the Cryogenian Sturtian and Marinoan glaciations (ca. 663-654 Ma) is important for understanding the relationship between environmental conditions and the subsequent emergence and expansion of early animals. The Cryogenian-to-Ediacaran stratigraphic succession of the Nanhua Basin in South China provides a nearly complete sedimentary record of the Cryogenian, including a continuous record of interglacial sedimentation. Here, we present a high-resolution pyrite Fe isotope record for a ∼120-m-long drill-core (ZK105) through Sturtian glacial diamictites and the overlying interglacial sediments in the Nanhua Basin to explore changes in marine chemistry during the late Cryogenian. Our pyrite Fe isotope profile exhibits significant stratigraphic variation: Interval I, comprising middle to upper Tiesi'ao diamictites (correlative with the Sturtian glaciation), is characterized by light, modern seawater-like Fe isotope compositions; Interval II, comprising uppermost Tiesi'ao diamictites and the basal organic-rich Datangpo Formation, is characterized by an abrupt shift to heavier Fe isotope compositions; and Interval III, comprising organic-poor grey shales in the middle Datangpo Formation, is characterized by the return of lighter, seawater-like Fe isotope compositions. We infer that Interval I pyrite was deposited in a predominantly anoxic glacial Nanhua Basin through reaction of dissolved Fe2+ and H2S mediated by microbial sulfate reduction (MSR). The shift to heavier pyrite Fe isotope values in Interval II is interpreted as partial oxidation of ferrous iron to ferric iron and subsequent near-quantitative reduction and transformation of Fe-oxyhydroxides to pyrite through coupling with oxidation of organic matter in the local diagenetic environment. In Interval III, near-quantitative oxidation of ferrous iron to Fe-oxyhydroxides followed by near-quantitative reduction and conversion to pyrite in the local diagenetic environment

  18. Placing Absolute Timing on Basin Incision Adjacent to the Colorado Front Range: Results from Meteoric and in Situ 10BE Dating

    NASA Astrophysics Data System (ADS)

    Duehnforth, M.; Anderson, R. S.; Ward, D.

    2010-12-01

    A sequence of six levels of gravel-capped surfaces, mapped as Pliocene to Holocene in age, are cut into Cretaceous shale in the northwestern part of the Denver Basin immediately adjacent to the Colorado Front Range (CFR). The existing relative age constraints and terrace correlations suggest that the incision of the Denver Basin occurred at a steady and uniform rate of 0.1 mm yr-1 since the Pliocene. As absolute ages in this landscape are rare, they have the potential to test the reliability of the existing chronology, and to illuminate the detailed history of incision. We explore the timing of basin incision and the variability of geomorphic process rates through time by dating the three highest surfaces at the northwestern edge of the Denver Basin using both in situ and meteoric 10Be concentrations. As the tectonic conditions have not changed since the Pliocene, much of the variability of generation and abandonment of alluvial surfaces likely reflects the influence of glacial-interglacial climate variations. We selected Gunbarrel Hill (mapped as pre-Rocky Flats (Pliocene)), Table Mountain (mapped as Rocky Flats (early Pleistocene)), and the Pioneer surface (mapped as Verdos (Pleistocene, ~640 ka)) as sample locations. We took two amalgamated clast samples on the Gunbarrel Hill surface, and dated depth profiles using meteoric and in situ 10Be on the Table Mountain and Pioneer surfaces. In addition, we measured the in situ 10Be concentrations of 6 boulder samples from the Table Mountain surface. We find that all three surfaces are significantly younger than expected and that in situ and meteoric age measurements largely agree with each other. The samples from the pre-Rocky Flats site (Gunbarrel Hill) show ages of 250 and 310 ka, ignoring post-depositional surface erosion. The ages of the Table Mountain and Pioneer sites fall within the 120 to 150 ka window. These absolute ages overlap with the timing of the penultimate glaciation during marine isotope stage (MIS) 6

  19. The newfoundland basin - Ocean-continent boundary and Mesozoic seafloor spreading history

    NASA Technical Reports Server (NTRS)

    Sullivan, K. D.

    1983-01-01

    It is pointed out that over the past 15 years there has been considerable progress in the refinement of predrift fits and seafloor spreading models of the North Atlantic. With the widespread acceptance of these basic models has come increasing interest in resolution of specific paleogeographic and kinematic problems. Two such problems are the initial position of Iberia with respect to North America and the geometry and chronology of early (pre-80 m.y.) relative motions between these two plates. The present investigation is concerned with geophysical data from numerous Bedford Institute/Dalhousie University cruises to the Newfoundland Basin which were undrtaken to determine the location of the ocean-continent boundary (OCB) and the Mesozoic spreading history on the western side. From the examination of magnetic data in the Newfoundland Basin, the OCB east of the Grand Banks is defined as the seaward limit of the 'smooth' magnetic domain which characterizes the surrounding continental shelves. A substantial improvement in Iberia-North America paleographic reconstructions is achieved.

  20. Seismic stratigraphy and sediment thickness of the Nansen Basin, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Engen, Øyvind; Gjengedal, Jakob Andreas; Faleide, Jan Inge; Kristoffersen, Yngve; Eldholm, Olav

    2009-03-01

    A Norwegian expedition to the western Nansen Basin, Yermak Plateau and the Hinlopen margin in 2001 acquired about 1100 km of 2-D multichannel seismic profiles and 50 wide-angle sonobuoy record sections. Analysis of these data establishes a regional seismic stratigraphic framework for the western Nansen Basin integrating previously published stratigraphic schemes. P-wave velocities and sediment thickness were derived within 7-8 per cent uncertainty from 2-D seismic ray tracing models of each sonobuoy section. Sediment thickness reaches 2 km in the studied area and increases towards the depocentre of the giant Franz-Victoria fan on the Barents-Kara continental margin. High-relief oceanic crystalline crust with 3.7 km s-1 average near-top velocity is infilled by four seismic sediment units with typical velocities 2.4, 2.2, 2.0 and 1.8 km s-1. A prominent regional seismic horizon between units 2 and 3 is tentatively correlated by basement onlap and sedimentation rates to a Miocene (~10 Ma) palaeoceanographic event, possibly the opening of the Fram Strait. The youngest unit is correlated to prograding sequences on the margin and to the onset of major slope failure caused by intensified glacio-fluvial drainage and ice sheet erosion during Northern Hemisphere glaciations (2.6-0.01 Ma).

  1. Breaking into the Plate: Seismic and Hydroacoustic Analysis of a 7.6 Mw Oceanic Fracture Zone Earthquake Adjacent to the Central Indian Ridge Plate Boundary

    NASA Astrophysics Data System (ADS)

    Bohnenstiehl, D. R.; Tolstoy, M.; Chapp, E.

    2003-12-01

    Where oceanic spreading segments are offset laterally from one another, the differential motion of the plates is accommodated by strike-slip motion along ridge-perpendicular transform faults. Off-axis from the ridge-transform intersection, no differential motion is require, and the fracture zone trace is thought to be inactive except where reactivated by intra-plate stresses. On 15 July 2003, an earthquake with a magnitude of 7.6 Mw occurred near the northern Central Indian Ridge (CIR), the divergent boundary separating the Somalian plate from the Indian and Australian plates. The size of this event places it within the 99th quantile of magnitude for shallow (< 40 km depth) strike-slip events (null axis plunge >45 deg) within the global Harvard CMT catalog. The earthquake's epicenter is near 2.5 deg S, 68.33 deg E, where the CIR is marked by a series of short (<100 km long) right-stepping transforms that offset the northwest trending spreading segments (20 mm/yr). Seismic signals associated with the mainshock and its largest aftershocks were recorded well by land-based seismic networks. Regional seismic phases (Pn, Sn), as well oceanic T-waves, where also recorded at an IMS hydroacoustic station to the north of the Diego Garcia atoll. T-wave signals recorded at Diego Garcia were cross correlated to determine accurate travel time differences. These traveltime differences were used in a plane wave fitting inversion to determine the horizontal slowness components and estimate the back azimuth to the epicenter. Aftershock locations are derived using the azimuthal information and Pn-T traveltime differences. Together, the seismically- and hydroacoustically-derived epicenters show a linear band of aftershocks extending more than 200 km along the off-axis trace of a right stepping transform. We interpret these aftershock events as delineating the length of the mainshock rupture. As the well-constrain hypocenter of the mainshock lies near the western edge of this

  2. Fate of copper complexes in hydrothermally altered deep-sea sediments from the Central Indian Ocean Basin.

    PubMed

    Chakraborty, Parthasarathi; Sander, Sylvia G; Jayachandran, Saranya; Nath, B Nagender; Nagaraju, G; Chennuri, Kartheek; Vudamala, Krushna; Lathika, N; Mascarenhas-Pereira, Maria Brenda L

    2014-11-01

    The current study aims to understand the speciation and fate of Cu complexes in hydrothermally altered sediments from the Central Indian Ocean Basin and assess the probable impacts of deep-sea mining on speciation of Cu complexes and assess the Cu flux from this sediment to the water column in this area. This study suggests that most of the Cu was strongly associated with different binding sites in Fe-oxide phases of the hydrothermally altered sediments with stabilities higher than that of Cu-EDTA complexes. The speciation of Cu indicates that hydrothermally influenced deep-sea sediments from Central Indian Ocean Basin may not significantly contribute to the global Cu flux. However, increasing lability of Cu-sediment complexes with increasing depth of sediment may increase bioavailability and Cu flux to the global ocean during deep-sea mining. PMID:25108489

  3. Characterization of the Hosgri Fault Zone and adjacent structures in the offshore Santa Maria Basin, south-central California: Chapter CC of Evolution of sedimentary basins/onshore oil and gas investigations - Santa Maria province

    USGS Publications Warehouse

    Willingham, C. Richard; Rietman, Jan D.; Heck, Ronald G.; Lettis, William R.

    2013-01-01

    The Hosgri Fault Zone trends subparallel to the south-central California coast for 110 km from north of Point Estero to south of Purisima Point and forms the eastern margin of the present offshore Santa Maria Basin. Knowledge of the attributes of the Hosgri Fault Zone is important for petroleum development, seismic engineering, and environmental planning in the region. Because it lies offshore along its entire reach, our characterizations of the Hosgri Fault Zone and adjacent structures are primarily based on the analysis of over 10,000 km of common-depth-point marine seismic reflection data collected from a 5,000-km2 area of the central and eastern parts of the offshore Santa Maria Basin. We describe and illustrate the along-strike and downdip geometry of the Hosgri Fault Zone over its entire length and provide examples of interpreted seismic reflection records and a map of the structural trends of the fault zone and adjacent structures in the eastern offshore Santa Maria Basin. The seismic data are integrated with offshore well and seafloor geologic data to describe the age and seismic appearance of offshore geologic units and marker horizons. We develop a basin-wide seismic velocity model for depth conversions and map three major unconformities along the eastern offshore Santa Maria Basin. Accompanying plates include maps that are also presented as figures in the report. Appendix A provides microfossil data from selected wells and appendix B includes uninterpreted copies of the annotated seismic record sections illustrated in the chapter. Features of the Hosgri Fault Zone documented in this investigation are suggestive of both lateral and reverse slip. Characteristics indicative of lateral slip include (1) the linear to curvilinear character of the mapped trace of the fault zone, (2) changes in structural trend along and across the fault zone that diminish in magnitude toward the ends of the fault zone, (3) localized compressional and extensional structures

  4. Gulf of Aden: Structure and evolution of a young ocean basin and continental margin

    SciTech Connect

    Cochran, J.R.

    1981-01-10

    New marine geophysical data are used to describe the structure and history of the Gulf of Aden. Magnetic anomaly data shows seafloor spreading magnetic anomalies of Sheba Ridge from the axial anomaly to anomaly 5 (10 m.y. B.P.) between the Owen fracture zone and 45 /sup 0/E and to anomaly 2' (3 m.y. B.P.) or anomaly 3 (4 m.y. B.P.) west of 45 /sup 0/E. The data does not support the two episodes of seafloor spreading recently proposed. Landward of the seafloor spreading magnetic anomalies is a magnetic quiet zone of uncorrelatable anomalies. The magnetic quiet zone boundary is also a structural boundary effectively marking the edge of Sheba Ridge, with deeper basement lacking a significant topographic gradient found on the landward side. A magnetic quiet zone is found not only where Sheba Ridge splits continental lithosphere but also on East Sheba Ridge where the ridge splits the old oceanic lithosphre of the Owen and Somali basins. There the position occupied by the continental margin within the gulf is marked by nonmagnetic ridge complexes that stretch from the continents to the Owen fracture zone. The magnetic quiet zone boundary is not an isochron in either the Gulf of Aden or the Red Sea, suggesting that significant horizontal motions can occur prior to the initiation of seafloor spreading. The offset on the Dead Sea Rift is used to estimate that from 80 to 160 km of opening, amounting to between 65% and 200% extension of the initial rift valley, occurred in the Gulf of Aden and Red Sea prior to the establishment of a mid-ocean ridge. It is suggested that the development of a new ocean basin occurs in two stages. The first involves diffuse extension over an area perhaps 10 km wide in a rift valley environment without an organized spreading center. This is followed by concentration of the extension at a single axis and the beginning of true seafloor spreading.

  5. Sedimentology of cores recovered from the Canada Basin of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Edwards, B. D.; Saint-Ange, F.; Pohlman, J.; Higgins, J.; Mosher, D. C.; Lorenson, T. D.; Hart, P.

    2011-12-01

    Researchers from the United States and Canada are collaborating to understand the tectonic and sedimentary history of the Arctic Ocean between Canada and Alaska. As part of this on-going study, a joint US-Canadian ice breaker expedition operated in parts of the Canada Basin during August 2010. Occasional interruptions of the seismic data acquisition provided the ship time to collect gravity and piston cores at five sites-of-opportunity throughout the basin. High-resolution multibeam bathymetry and chirp sub-bottom profiler data collected immediately prior to coring reveal the fine-scale morphology of each site. Core photographs, X-ray radiographs, and physical property data support the following descriptions. Two piston cores were collected from the Beaufort Sea continental margin in a region of known bottom simulating reflectors (BSRs). Site 1 (2538 m water depth): This core recovered 5.72 m of gas-charged, gray sticky clay and silty-clay from an approximately 1100 m diameter, 130 m high conical mound overlying the crest of a buried anticline. Gas hydrate recovered in the core catcher combined with cracks and voids, methane and other hydrocarbon gasses, pyrite concretions, chemosynthetic clams, carbonate nodules, and soft carbonate masses indicate the likely upward migration of deep-seated fluids. Site 2 (1157 m water depth): This core, positioned 40 km upslope from the gas hydrate core, recovered 3 m of gray sticky silty clay and clayey silt near the base of an erosional scarp. Some voids and fracturing are apparent but carbonate masses and pyrite concretions are absent. Site 3 (3070 m water depth): This core from the top of a seamount discovered in 2009 in the north-central part of the Canada Basin recovered 4.94 m of sediment. More than 3 m of dark brown to yellowish brown, massive interbedded silty clays with sands and matrix-supported gravels (ice rafted debris [IRD]) occur in abrupt contact with underlying reddish yellow to brownish yellow silty clay and

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

    USGS Publications Warehouse

    Henry, Christopher S.; Colgan, Joseph P.

    2011-01-01

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

  7. Application of the Basin Characterization Model to Estimate In-Place Recharge and Runoff Potential in the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah

    USGS Publications Warehouse

    Flint, Alan L.; Flint, Lorraine E.

    2007-01-01

    A regional-scale water-balance model was used to estimate recharge and runoff potential and support U.S. Geological Survey efforts to develop a better understanding of water availability for the Basin and Range carbonate-rock aquifer system (BARCAS) study in White Pine County, Nevada, and adjacent areas in Nevada and Utah. The water-balance model, or Basin Characterization Model (BCM), was used to estimate regional ground-water recharge for the 13 hydrographic areas in the study area. The BCM calculates recharge by using a distributed-parameter, water-balance method and monthly climatic boundary conditions. The BCM requires geographic information system coverages of soil, geology, and topographic information with monthly time-varying climatic conditions of air temperature and precipitation. Potential evapotranspiration, snow accumulation, and snowmelt are distributed spatially with process models. When combined with surface properties of soil-water storage and saturated hydraulic conductivity of bedrock and alluvium, the potential water available for in-place recharge and runoff is calculated using monthly time steps using a grid scale of 866 feet (270 meters). The BCM was used with monthly climatic inputs from 1970 to 2004, and results were averaged to provide an estimate of the average annual recharge for the BARCAS study area. The model estimates 526,000 acre-feet of potential in-place recharge and approximately 398,000 acre-feet of potential runoff. Assuming 15 percent of the runoff becomes recharge, the model estimates average annual ground-water recharge for the BARCAS area of about 586,000 acre-feet. When precipitation is extrapolated to the long-term climatic record (1895-2006), average annual recharge is estimated to be 530,000 acre-feet, or about 9 percent less than the recharge estimated for 1970-2004.

  8. Basin-scale controls on the molybdenum-isotope composition of seawater during Oceanic Anoxic Event 2 (Late Cretaceous)

    NASA Astrophysics Data System (ADS)

    Dickson, Alexander J.; Jenkyns, Hugh C.; Porcelli, Donald; van den Boorn, Sander; Idiz, Erdem

    2016-04-01

    It is well established that the burial of organic carbon in marine sediments increased dramatically at a global scale at the Cenomanian-Turonian boundary (Oceanic Anoxic Event 2: OAE-2, ∼94 Myr ago, Late Cretaceous). Many localities containing chemostratigraphic expressions of this event are not, however, enriched in organic carbon, and point to a heterogeneous set of oceanographic and environmental processes operating in different ocean basins. These processes are difficult to reconstruct because of the uneven geographical distribution of sites recording OAE-2, thus limiting our understanding of the causes and palaeoceanographic consequences of the environmental changes that occurred at this time. A new, highly resolved molybdenum-isotope dataset is presented from the Cape Verde Basin (southern proto-North Atlantic Ocean) and a lower resolution record from the Tarfaya Basin, Morocco. The new data reveal periodic oscillations in the Mo-isotope composition of proto-North Atlantic Ocean sediments, from which coupled changes in the dissolved sulphide concentration and Mo inventories of the basin seawater can be inferred. The cyclic variations in sedimentary Mo-isotope compositions can be hypothetically linked to regional changes in the depth of the chemocline, and in the rate of seawater exchange between basinal waters and global seawater. The new data suggest that a global seawater Mo-isotope composition of ∼1.2‰ was reached very soon after the onset of OAE-2, implying a rapid expansion of marine deoxygenation coeval with, or slightly preceding, enhanced global rates of organic-carbon burial. During OAE-2, the modelled flux of Mo into anoxic sediments is likely to have been ∼60-125 times greater than at the present day, although the spatial extent of anoxia is unlikely to have been greater than 10% of the total seafloor.

  9. Estuarine fish communities respond to climate variability over both river and ocean basins.

    PubMed

    Feyrer, Frederick; Cloern, James E; Brown, Larry R; Fish, Maxfield A; Hieb, Kathryn A; Baxter, Randall D

    2015-10-01

    Estuaries are dynamic environments at the land-sea interface that are strongly affected by interannual climate variability. Ocean-atmosphere processes propagate into estuaries from the sea, and atmospheric processes over land propagate into estuaries from watersheds. We examined the effects of these two separate climate-driven processes on pelagic and demersal fish community structure along the salinity gradient in the San Francisco Estuary, California, USA. A 33-year data set (1980-2012) on pelagic and demersal fishes spanning the freshwater to marine regions of the estuary suggested the existence of five estuarine salinity fish guilds: limnetic (salinity = 0-1), oligohaline (salinity = 1-12), mesohaline (salinity = 6-19), polyhaline (salinity = 19-28), and euhaline (salinity = 29-32). Climatic effects propagating from the adjacent Pacific Ocean, indexed by the North Pacific Gyre Oscillation (NPGO), affected demersal and pelagic fish community structure in the euhaline and polyhaline guilds. Climatic effects propagating over land, indexed as freshwater outflow from the watershed (OUT), affected demersal and pelagic fish community structure in the oligohaline, mesohaline, polyhaline, and euhaline guilds. The effects of OUT propagated further down the estuary salinity gradient than the effects of NPGO that propagated up the estuary salinity gradient, exemplifying the role of variable freshwater outflow as an important driver of biotic communities in river-dominated estuaries. These results illustrate how unique sources of climate variability interact to drive biotic communities and, therefore, that climate change is likely to be an important driver in shaping the future trajectory of biotic communities in estuaries and other transitional habitats. PMID:25966973

  10. Pseudorhabdosynochus species (Monogenoidea, Diplectanidae) parasitizing groupers (Serranidae, Epinephelinae, Epinephelini) in the western Atlantic Ocean and adjacent waters, with descriptions of 13 new species.

    PubMed

    Kritsky, Delane C; Bakenhaster, Micah D; Adams, Douglas H

    2015-01-01

    Seventeen of twenty-three species of groupers collected from the western Atlantic Ocean and adjacent waters were infected with 19 identified species (13 new) of Pseudorhabdosynochus Yamaguti, 1958 (Dactylogyridea, Diplectanidae); specimens of the Spanish flag Gonioplectrus hispanus, coney Cephalopholis fulva, marbled grouper Dermatolepis inermis, mutton hamlet Alphestes afer, and misty grouper Hyporthodus mystacinus were not infected; the yellowmouth grouper Mycteroperca interstitialis and yellowfin grouper Mycteroperca venenosa were infected with unidentified species of Pseudorhabdosynochus; the Atlantic creolefish Paranthias furcifer was infected with an unidentified species of Diplectanidae that could not be accommodated in Pseudorhabdosynochus. The following species of Pseudorhabdosynochus are described or redescribed based entirely or in part on new collections: Pseudorhabdosynochus americanus (Price, 1937) Kritsky & Beverley-Burton, 1986 from Atlantic goliath grouper Epinephelus itajara; Pseudorhabdosynochus yucatanensis Vidal-Martínez, Aguirre-Macedo & Mendoza-Franco, 1997 and Pseudorhabdosynochus justinella n. sp. from red grouper Epinephelus morio; Pseudorhabdosynochus kritskyi Dyer, Williams & Bunkley-Williams, 1995 from gag Mycteroperca microlepis; Pseudorhabdosynochus capurroi Vidal-Martínez & Mendoza-Franco, 1998 from black grouper Mycteroperca bonaci; Pseudorhabdosynochus hyphessometochus n. sp. from Mycteroperca interstitialis; Pseudorhabdosynochus sulamericanus Santos, Buchmann & Gibson, 2000 from snowy grouper Hyporthodus niveatus and Warsaw grouper Hyporthodus nigritus (new host record); Pseudorhabdosynochus firmicoleatus n. sp. from yellowedge grouper Hyporthodus flavolimbatus and snowy grouper H. niveatus; Pseudorhabdosynochus mcmichaeli n. sp., Pseudorhabdosynochus contubernalis n. sp., and Pseudorhabdosynochus vascellum n. sp. from scamp Mycteroperca phenax; Pseudorhabdosynochus meganmarieae n. sp. from graysby Cephalopholis cruentata

  11. Pseudorhabdosynochus species (Monogenoidea, Diplectanidae) parasitizing groupers (Serranidae, Epinephelinae, Epinephelini) in the western Atlantic Ocean and adjacent waters, with descriptions of 13 new species

    PubMed Central

    Kritsky, Delane C.; Bakenhaster, Micah D.; Adams, Douglas H.

    2015-01-01

    Seventeen of twenty-three species of groupers collected from the western Atlantic Ocean and adjacent waters were infected with 19 identified species (13 new) of Pseudorhabdosynochus Yamaguti, 1958 (Dactylogyridea, Diplectanidae); specimens of the Spanish flag Gonioplectrus hispanus, coney Cephalopholis fulva, marbled grouper Dermatolepis inermis, mutton hamlet Alphestes afer, and misty grouper Hyporthodus mystacinus were not infected; the yellowmouth grouper Mycteroperca interstitialis and yellowfin grouper Mycteroperca venenosa were infected with unidentified species of Pseudorhabdosynochus; the Atlantic creolefish Paranthias furcifer was infected with an unidentified species of Diplectanidae that could not be accommodated in Pseudorhabdosynochus. The following species of Pseudorhabdosynochus are described or redescribed based entirely or in part on new collections: Pseudorhabdosynochus americanus (Price, 1937) Kritsky & Beverley-Burton, 1986 from Atlantic goliath grouper Epinephelus itajara; Pseudorhabdosynochus yucatanensis Vidal-Martínez, Aguirre-Macedo & Mendoza-Franco, 1997 and Pseudorhabdosynochus justinella n. sp. from red grouper Epinephelus morio; Pseudorhabdosynochus kritskyi Dyer, Williams & Bunkley-Williams, 1995 from gag Mycteroperca microlepis; Pseudorhabdosynochus capurroi Vidal-Martínez & Mendoza-Franco, 1998 from black grouper Mycteroperca bonaci; Pseudorhabdosynochus hyphessometochus n. sp. from Mycteroperca interstitialis; Pseudorhabdosynochus sulamericanus Santos, Buchmann & Gibson, 2000 from snowy grouper Hyporthodus niveatus and Warsaw grouper Hyporthodus nigritus (new host record); Pseudorhabdosynochus firmicoleatus n. sp. from yellowedge grouper Hyporthodus flavolimbatus and snowy grouper H. niveatus; Pseudorhabdosynochus mcmichaeli n. sp., Pseudorhabdosynochus contubernalis n. sp., and Pseudorhabdosynochus vascellum n. sp. from scamp Mycteroperca phenax; Pseudorhabdosynochus meganmarieae n. sp. from graysby Cephalopholis cruentata

  12. The Cretaceous Sverdrup Basin, Nunavut, Canada: A Boreal Ocean under Greenhouse Conditions

    NASA Astrophysics Data System (ADS)

    Schröder-Adams, Claudia J.; Herrle, Jens O.; Pugh, Adam T.; Andrews, Julie; Galloway, Jennifer

    2013-04-01

    The Arctic Boreal Sea and its paleoceanographic and paleoecological response to the Cretaceous Greenhouse climate remain enigmatic. This study takes a multi-fossil approach coupled with carbon isotope stratigraphy and geochemistry to address large-scale stratigraphic correlations, water column structure and paleoproductivity changes by comparing distal and proximal sedimentary records exposed on Ellef Ringnes and Axel Heiberg islands respectively, part of the Sverdrup Basin, Nunavut, Canada. A newly established carbon isotope record documents several δ13Corg excursions that tie well to precisely dated European carbon isotope records bringing an unprecedented stratigraphic accuracy to the Boreal Sea strata. This framework also allows for refinement of new and existing biostratigraphic data. Several OAEs are recognized including a prominent OAE 2 straddling the Cenomanian/Turonian boundary. This documents high latitude increased carbon burial during the Cenomanian/Turonian temperature maximum independent of different lithologies that mark this interval in our studied localities. As temperature cooled again primary productivity and carbon flux decreased and slight bottom oxygenation returned in the upper Santonian, where rare benthic foraminifera are observed. The Boreal Ocean is almost devoid of carbonate as it is predicted for a future Arctic Ocean under increasing levels of atmospheric greenhouse gases. Contrasting to distal basin settings benthic agglutinated foraminifera thrived in shelf areas where watermass stratification was disrupted. Changes in dinocyst assemblages responded to regressive/transgressive cycles that have not been previously recognized within the thick lithologically indistinct shale interval of the Upper Cenomanian to Campanian Kanguk Formation. Regressions triggered radiations in radiolarian assemblages due to reduced oxygen minimum zones (OMZ) and fertile shelf settings. In contrast, transgressive phases provided increased rates of organic

  13. Structure and variability of the boundary current in the Eurasian Basin of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Pnyushkov, Andrey V.; Polyakov, Igor V.; Ivanov, Vladimir V.; Aksenov, Yevgeny; Coward, Andrew C.; Janout, Markus; Rabe, Benjamin

    2015-07-01

    The Arctic Circumpolar Boundary Current (ACBC) transports a vast amount of mass and heat around cyclonic gyres of the deep basins, acting as a narrow, topographically-controlled flow, confined to the continental margins. Current observations during 2002-2011 at seven moorings along the major Atlantic Water (AW) pathway, complemented by an extensive collection of measured temperatures and salinities as well as results of state-of-the-art numerical modeling, have been used to examine the spatial structure and temporal variability of the ACBC within the Eurasian Basin (EB). These observations and modeling results suggest a gradual, six-fold decrease of boundary current speed (from 24 to 4 cm/s) on the route between Fram Strait and the Lomonosov Ridge, accompanied by a transformation of the vertical flow structure from mainly barotropic in Fram Strait to baroclinic between the area north of Spitsbergen and the central Laptev Sea continental slope. The relative role of density-driven currents in maintaining AW circulation increases with the progression of the ACBC eastward from Fram Strait, so that baroclinic ACBC forcing dominates over the barotropic in the eastern EB. Mooring records have revealed that waters within the AW and the cold halocline layers circulate in roughly the same direction in the eastern EB. The seasonal signal, meanwhile, is the most powerful mode of variability in the EB, contributing up to ~70% of the total variability in currents (resolved by moorings records) within the eastern EB. Seasonal signal amplitudes for current speed and AW temperature both decrease with the eastward progression of AW flow from source regions, and demonstrate strong interannual modulation. In the 2000s, the state of the EB (e.g., circulation pattern, thermohaline conditions, and freshwater balance) experienced remarkable changes. Results showing anomalous circulation patterns for an extended period of 30 months in 2008-2010 for the eastern EB, and a two-core AW

  14. Observational validation of the diffusive convection flux laws in the Amundsen Basin, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Guthrie, John D.; Fer, Ilker; Morison, James

    2015-12-01

    The low levels of mechanically driven mixing in many regions of the Arctic Ocean make double diffusive convection virtually the only mechanism for moving heat up from the core of Atlantic Water towards the surface. In an attempt to quantify double diffusive heat fluxes in the Arctic Ocean, a temperature microstructure experiment was performed as a part of the North Pole Environmental Observatory (NPEO) 2013 field season from the drifting ice station Barneo located in the Amundsen Basin near the Lomonosov Ridge (89.5°N, 75°W). A diffusive convective thermohaline staircase was present between 150 and 250 m in nearly all of the profiles. Typical vertical heat fluxes across the high-gradient interfaces were consistently small, O(10-1) W m-2. Our experiment was designed to resolve the staircase and differed from earlier Arctic studies that utilized inadequate instrumentation or sampling. Our measured fluxes from temperature microstructure agree well with the laboratory derived flux laws compared to previous studies, which could find agreement only to within a factor of two to four. Correlations between measured and parameterized heat fluxes are slightly higher when using the more recent Flanagan et al. [2013] laboratory derivation than the more commonly used derivation presented in Kelley [1990]. Nusselt versus Rayleigh number scaling reveals the convective exponent, η, to be closer to 0.29 as predicted by recent numerical simulations of single-component convection rather than the canonical 1/3 assumed for double diffusion. However, the exponent appears to be sensitive to how convective layer height is defined.

  15. Active deformation in the frontal part of the Northern Apennines: insights from the lower Metauro River basin area (northern Marche, Italy) and adjacent Adriatic off-shore

    NASA Astrophysics Data System (ADS)

    Di Bucci, D.; Mazzoli, S.; Nesci, O.; Savelli, D.; Tramontana, M.; De Donatis, M.; Borraccini, F.

    2003-09-01

    An integration of seismological data with geological and geomorphological information aided by seismic interpretation was performed to characterise the Quaternary tectonic evolution of the Metauro River basin area (northern Marche) and adjacent off-shore sector of the external Northern Apennines. On-shore, along the Adriatic coast, the youngest age of thrusting and folding post-dates the Early-Middle Pliocene, while Pleistocene deposits appear to be, at least in part, not involved in the deformation. Recent (i.e. post-thrusting) tectonic structures have been recognised both in pre-Quaternary substratum rocks and in Upper Quaternary continental deposits (Upper Pleistocene terrace alluvium, Upper Pleistocene-Holocene slope deposits). These faults are all compatible with a WSW-ENE oriented extension. In the Metauro River basin area, preserved flights of stream terraces have been categorised according to the presence or absence of alluvial suites in relationship to each terrace level. Here, based on both the heights above the valley floor and the areal distribution of stream terraces, a generalised vertical tectonic uplift can be inferred, particularly during the Middle-Late Pleistocene. Moreover, the along-valley distribution of stream terraces provides further constraints on the age of thrusting and folding. In fact, the reconstructed terrace-levels are substantially parallel, and no evidence for any significant deformation by fold activity has been recognised. Local deformation displayed by both terrace surfaces and alluvial/slope-waste deposits suggests, instead, the intervening of some minor differential movements associated with the generalised uplift and/or to Middle-Late Pleistocene normal faulting. Their occurrence appears anyhow to be unrelated with the pattern of folds and associated thrusts. The present-day seismic activity of the study area was considered by analysing 83 seismic events that occurred from 1987 to 2000. The epicentre distribution is very

  16. The architecture of an incipient oceanic basin: a tentative reconstruction of the Jurassic Liguria-Piemonte basin along the Northern Apennines-Alpine Corsica transect

    NASA Astrophysics Data System (ADS)

    Marroni, Michele; Pandolfi, Luca

    2007-11-01

    In this paper, a scenario for the early evolution of the Jurassic oceanic Liguria-Piemonte basin is sketched. For this purpose, four selected examples of ophiolite sequences from the Northern Apennines and Corsica are described and analyzed. In the External Ligurian units (Northern Apennines), the ocean-continent transition of the Adria plate was characterized by a basement made up of subcontinental mantle and lower continental crust, covered by extensional allochthons of upper crust. Both, the basement rocks and the extensional allochthons are cut by basaltic dikes and covered by basalts and pelagic deposits. The conjugate ocean-continent transition of the Corsica margin, represented by the Balagne nappe (Corsica), was composed of mantle peridotites and gabbros covered by basaltic flows and minor breccias, that in addition include continent-derived clasts. By contrast, the innermost (i.e., closest to the ocean) preserved area observed in the Internal Ligurian (Northern Apennines) and Inzecca (Corsica) units consists of former morphological highs of mantle peridotites and gabbros, bordered by small basins where the basement is covered by a volcano-sedimentary complex, characterized by ophiolitic breccias and cherts interlayered with basaltic flows. The overall picture resulting from our reconstructions suggests an asymmetric architecture for the Liguria-Piemonte basin with a central area bounded by two different transition zones toward the continental margins. This architecture can be interpreted as the result of a rifting process whose development includes a final stage characterized by passive, asymmetric extension of the lithosphere along an east-dipping detachment fault system.

  17. The relative timing of Lunar Magma Ocean solidification and the Late Heavy Bombardment inferred from highly degraded impact basin structures

    NASA Astrophysics Data System (ADS)

    Kamata, Shunichi; Sugita, Seiji; Abe, Yutaka; Ishihara, Yoshiaki; Harada, Yuji; Morota, Tomokatsu; Namiki, Noriyuki; Iwata, Takahiro; Hanada, Hideo; Araki, Hiroshi; Matsumoto, Koji; Tajika, Eiichi; Kuramoto, Kiyoshi; Nimmo, Francis

    2015-04-01

    The solidification of the Lunar Magma Ocean (LMO) and formation of impact basins are important events that took place on the early Moon. The relative timing of these events, however, is poorly constrained. The aim of this study is to constrain the formation ages of old impact basins based on inferences of their thermal state. Most proposed basins formed before Pre-Nectarian (PN) 5 stage do not exhibit clear concentric features in either topography or gravity, suggesting substantial viscous lateral flow in the crust. Recent geodetic measurements reveal that the lunar crust is thinner than previously estimated, indicating that an extremely high crustal temperature is required for lateral flow to occur. In this study, we calculate lunar thermal evolution and viscoelastic deformation of basins and investigate the thermal state at the time of basin formation using recent crustal thickness models. We find that a Moho temperature >1300-1400 K at the time of basin formation is required for substantial viscous relaxation of topography to occur; the implied elastic thickness at the time of loading is <30 km. Such a high temperature can be maintained only for a short time (i.e., <50 Myr for most conditions) after solidification of the LMO or after mantle overturn if it took place; relaxed impact basins forming ⩾150 Myr later than LMO solidification are unlikely. This result is in conflict with an intensive Late Heavy Bombardment (LHB) model, which assumes that most impact basins were formed at ∼3.9 Ga, since it requires LMO solidification time much later than previous theoretical estimates. Either the LHB was moderate, or the majority of proposed early PN basins were not in fact formed by impacts.

  18. Geology of the Eel River basin and adjacent region: implications for late Cenozoic tectonics of the southern Cascadia subduction zone and Mendocino triple junction

    USGS Publications Warehouse

    Clarke, S.H., Jr.

    1992-01-01

    Two upper Cenozoic depositional sequences of principally marine strata about 4000m thick overlie accreted basement terranes of the Central and Coastal belts of the Franciscan Complex in the onshore-offshore Eel River basin of northwestern California. The older depositional sequence is early to middle Miocene in age and represents slope basin and slope-blanket deposition, whereas the younger sequence, late Miocene to middle Pleistocene in age, consists largely of forearc basin deposits. -from Author

  19. Possible Origin of High-Amplitude Reflection Packages (HARPs) in the Canada Basin, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Lebedeva-Ivanova, Nina; Hutchinson, Deborah; Shimeld, John; Chian, Deping; Hart, Patrick; Jackson, Ruth; Saltus, Richard; Mosher, David

    2013-04-01

    The Canada Basin (CB) of the Arctic Ocean is a semi-enclosed ocean basin surrounded by the Alaskan and Canadian margins to the south and east, the Alpha-Mendeleev Large Igneous Province (AMLIP) to the north and the subsided continental Chukchi Borderland (ChB) to the west. During 2007-2011, US-Canada expeditions collected ~15,000 km multichannel seismic data and sonobuoy reflection and refraction seismic data with average spacing of ~80 km mostly over the CB and AMLIP. High-amplitude reflective packages (HARPs) underlie the mostly flat-lying sediments of CB. Although HARPs are discontinuous in the central CB, they become more continuous toward ChB and AMLIP. HARPs are often the most reflective events in the seismic section, exceeding even the seafloor reflection. Only rarely are reflections seen beneath HARPs. Where best developed, HARPs are ~100-300 ms TWTT, consisting of several high-amplitude wavelets with a pronounced narrow frequency band within the limits of ~10-30 Hz. This character of HARPs is consistent with patterns produced by constructive interference of thin beds (Widess, 1973). Forward modeling of sonobuoy data, synthetic tests, and frequency analysis of the tuning effect suggest that HARPs are composed of a series of alternating high- and low-velocity layers. The high-velocity layers are ~100-200 m thick with P-velocities of ~3.5-4.5 km/s. The low-velocity layers are about half as thick with velocities of ~2-3 km/s. A broad range of possible interpretations of rock composition exists from these velocities, e.g. sandstone and interbedded shale (Prince Patrick Island, Harrison and Brent, 2005); or tholeiitic basalts flows and sediments (Voring volcanic margin, Olanke and Eldholm, 1994); or sills and sediments (Newfoundland margin, Peron-Pinvidic et all, 2010). HARP can be associated with several origins. In the central and southern CB, where oceanic spreading is interpreted, HARPs are discontinuous among high-relief, but otherwise low

  20. Mooring-Based Observations of Boundary Current in the Nansen Basin of the Arctic Ocean: Vertical Structure and Variability

    NASA Astrophysics Data System (ADS)

    Pnyushkov, A.; Polyakov, I.

    2010-12-01

    The pan-Arctic Boundary Current (BC) provides the largest input of water, heat, and salt into the Polar Basins. Recent mooring-based observations at several locations along the continental slope of the Arctic Ocean’s Eurasian Basin showed a transformation of the BC from a mostly barotropic flow in Fram Strait to a jet-like baroclinic current northeast of Svalbard, and the reemergence of the barotropic structure of the flow further along in the eastern Eurasian Basin. The speed maximum of the baroclinic jet-like BC segment coincides with the Atlantic Water core at an intermediate depth (~200-370 m). Strongly amplified current events with corresponding changes in T and S are associated with eddies which are an integral part of the BC. Vertical velocity shear of tidal/inertial oscillations is an important contributor to mixing in the BC region. This new information is critically important to understand the ocean's role in the arctic climate system.

  1. Intracontinental accommodation of oceanic transform shear and the transtensional opening of Cenozoic deep basins at the northeastern edge of Antarctica

    NASA Astrophysics Data System (ADS)

    Storti, F.; Rossetti, F.; Storti, F.

    2003-04-01

    The development of extensional basins is commonly explained as induced by the kinematics of tectonic plates (lithospheric stretching and flexure, strike-slip-related basins) and by the density imbalances produced by oceanic ridges, continental margins and plateau uplifts. Strike-slip-related basins are commonly associated to transform plate boundaries, to obliquely-converging plate boundaries where deformation is fully partitioned into dip-slip and strike-slip faulting, and to intraplate strike-slip deformation belts transferring displacement from convergent plate boundaries to the plate interiors. The occurrence of strike-slip deformation belts that are significantly active in intraplate regions is possibly uncommon in divergent plate boundaries, that are generally believed to be dominated by sea floor spreading and passive margin development. Plate tectonics theory does not predict any strike-slip movement along fracture zones once they pass outboard of their associated ridge segments and away from the plate boundary. In this contribution we illustrate the Cenozoic geodynamic framework at the northeastern edge of the Antarctic plate, where we believe there is strong evidence for the occurrence of post-rift strike-slip deformation belts including both the intraridge (transform) and out-of-ridge segments of fracture zones, and their collinear onshore strike-slip fault systems. These impressively long strike-slip belts transfer differential spreading at the constructional plate boundary into the plate interior, where residual horizontal displacement is accommodated in a lithosphere-scale horsetail array of transtensional basins. Deep basins originated also along the main traces of these intraplate strike-slip belts, both in oceanic and continental crust. Basin opening to accommodate displacement associated to intraplate strike-slip deformation belts dissecting passive margins provides an additional geodynamic scenario for explaining the occurrence of important

  2. Structure of a Young Oceanic Basin: Results of the Encens-Sheba Cruise in the Eastern Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Leroy, S.; Fournier, M.; Gente, P.; Al-Kathiri, A.; Bellahsen, N.; Beslier, M.; Blais, A.; d'Acremont, E.; Mercouriev, S.; Patriat, P.; Perrot, J.

    2001-12-01

    The Encens-Sheba cruise was carried out in July 2000 aboard R/V Marion Dufresne in the eastern part of the Gulf of Aden. It produced a complete swath bathymetry, gravity and magnetic data set between southern Oman (Dhofar) and Yemen in the north and Socotra island in the south, and between Alula-Fartak fracture zone in the west and the Socotra fracture zone in the east. The new data set shows a complete section of a young oceanic basin from conjugate passive continental margins up to the oceanic spreading center. On the conjugate passive margins, single channel seismic data have been also collected. The two conjugate margins are steep, narrow and asymmetric. Titled blocks, horsts and grabens bounded by faults dipping towards the ocean or the continent compose the northern margin, whereas a deep basin near the continental slope in the vicinity of the continent-ocean transition characterizes the southern margin. The two margins are divided by transfer faults in 3 major segments. The continent-ocean transition is marked by a negative gradient of the free-air gravity anomalies. The present Sheba ridge is divided by discontinuities in 3 segments from 20 to 100 km long. The central part of the 100-km-long western segment is characterized by an axial uplift reflecting a large magmatic activity. The two other shorter segments display axial valley more classical for a slow spreading ridge (1.1cm/a). Although the magnetic anomalies show a complex history of oceanic accretion, the evolution of the segmentation can be followed. Indeed, the segmentation of the conjugate passive margins seems to be correlated with the location of early traces of identifiable Sheba ridge offset. The oldest anomalies are identified as an5C-an5D. The Gulf of Aden in this area thus opened 16-17Ma ago, which is significantly older than the 12-13 Ma suggested by previous studies.

  3. Foraminifera fauna of the Tethys Ocean Basin from the Aalenian - Bajocian boundary from Bakony Mountain (Hungary)

    NASA Astrophysics Data System (ADS)

    Zsiborás, Gábor; Görög, Ágnes

    2014-05-01

    The Middle Jurassic foraminiferal fauna of the Tethys Ocean Basin is hardly known. It is especially true for the Aalenian- early Bajocian, from when only BARBIERI (1964) published some forms from Sicily. Thus the aim of our study was to give a detailed systematic description of the foraminiferal fauna and microfacies analyses of Tű zköves Gorge of Bakonycsernye, Bakony Mountains, Western Hungary. The studied succession is near to the classic Jurassic locality - which become famous by the pioneering ammonite work of GéCZY. According to the recent study of GALáCZ & EVANICS, ammonites indicate Concavum (Aalenian), Discites and Ovale (Bajocian) zones. Seventeen samples were collected from the 3.5 m thick sequence of Ammonitico Rosso type reddish and greenish grey marl with limestone nodules. For the microfacies studies thin sections were made. To extract the microfossils, each sample was dissolved in concentrated acetic acid. The layers were rich in macrofossils: the most abundant were Bositra shells and ammonites. The microfauna consist of foraminifers, ostracods, radiolarians, Echinodermata parts and rhyncholits. The preservation of the foraminiferal fauna is relatively poor. 36 taxa, 29 genera and 27 species were identified, for the paleoecological evaluation quantitative analysis and classifying into morphogroups were made. Throughout the studied succession, the foraminiferal fauna is relative monotonous, poor and low diversity in species. All these taxa have wide stratigraphical distribution, significant Aalenian or Bajocian species have not been found. At the Aalenian-Bajocian transition the foraminiferal fauna showed an impoverishment. The most abundant genus was Spirillina, its amount is more than 90% in some samples. In suborder Lagenina the most frequent genera were Lenticulina, Dentalina and Nodosaria, moreover, Vaginulina, Eoguttulina, Ramulina and Bullopora could have been found. Agglutinated forms and Paalzowella were subordinated. Porcelaneous

  4. Seismic structure of the crust and uppermost mantle of South America and surrounding oceanic basins

    USGS Publications Warehouse

    Chulick, Gary S.; Detweiler, Shane; Mooney, Walter D.

    2013-01-01

    We present a new set of contour maps of the seismic structure of South America and the surrounding ocean basins. These maps include new data, helping to constrain crustal thickness, whole-crustal average P-wave and S-wave velocity, and the seismic velocity of the uppermost mantle (Pn and Sn). We find that: (1) The weighted average thickness of the crust under South America is 38.17 km (standard deviation, s.d. ±8.7 km), which is ∼1 km thinner than the global average of 39.2 km (s.d. ±8.5 km) for continental crust. (2) Histograms of whole-crustal P-wave velocities for the South American crust are bi-modal, with the lower peak occurring for crust that appears to be missing a high-velocity (6.9–7.3 km/s) lower crustal layer. (3) The average P-wave velocity of the crystalline crust (Pcc) is 6.47 km/s (s.d. ±0.25 km/s). This is essentially identical to the global average of 6.45 km/s. (4) The average Pn velocity beneath South America is 8.00 km/s (s.d. ±0.23 km/s), slightly lower than the global average of 8.07 km/s. (5) A region across northern Chile and northeast Argentina has anomalously low P- and S-wave velocities in the crust. Geographically, this corresponds to the shallowly-subducted portion of the Nazca plate (the Pampean flat slab first described by Isacks et al., 1968), which is also a region of crustal extension. (6) The thick crust of the Brazilian craton appears to extend into Venezuela and Colombia. (7) The crust in the Amazon basin and along the western edge of the Brazilian craton may be thinned by extension. (8) The average crustal P-wave velocity under the eastern Pacific seafloor is higher than under the western Atlantic seafloor, most likely due to the thicker sediment layer on the older Atlantic seafloor.

  5. Spatial extent and degree of oxygen depletion in the deep proto-North Atlantic basin during Oceanic Anoxic Event 2

    NASA Astrophysics Data System (ADS)

    van Helmond, Niels A. G. M.; Ruvalcaba Baroni, Itzel; Sluijs, Appy; Sinninghe Damsté, Jaap S.; Slomp, Caroline P.

    2014-11-01

    organic matter burial due to widespread ocean anoxia across the Cenomanian/Turonian boundary event (˜94 Ma) resulted in a major perturbation of the global carbon cycle: the so-called Oceanic Anoxic Event 2 (OAE2). The characteristics and spatial distribution of the OAE2 deposits that formed in the deep basin of the proto-North Atlantic remain poorly described, however. Here we present proxy data of redox sensitive (trace) elements (e.g., Mo, Fe/Al, Corg/Ptot, and Mn) for OAE2 sediments from five Deep Sea Drilling Project and Ocean Drilling Program sites located in the deep proto-North Atlantic basin. Our results highlight that bottom waters in the entire deep proto-North Atlantic were anoxic during most of OAE2. Furthermore, regressions of Mo with total organic carbon content (TOC), previously shown to document the degree of water mass restriction, confirm that the water circulation in the proto-North Atlantic basin was severely restricted during OAE2. Comparison of these values to Mo/TOC ratios in the present-day Black Sea suggests a renewal frequency of the deep proto-North Atlantic water mass of between 0.5 and 4 ka, compared to a maximum of ˜200 years for the present-day northern Atlantic. The Plenus Cold Event, a cooler episode during the early stages of OAE2 hypothesized to be caused by declining pCO2 due to extensive burial of organic matter, appears to have led to temporary re-oxygenation of the bottom water in the deep proto-North Atlantic basin during OAE2.

  6. Geochemistry of rare and minor elements in sediments from Brazil Basin of Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Vvedenskaya, Irina; Dubinin, Alexander

    2010-05-01

    This paper reviews the features of the rare and minor elements in the sediment samples recovered from the Brazil Basin at the location of the Station No. 1537 in the Atlantic Ocean during the 18th cruise of the Research Vessel "Akademik Sergey Vavilov". The depth of the sediment column is 470 cm. The sediments are represented by the oxidized miopelagic clay (0-305 cm) which are underlain by the thin bedded Ethmodiscus diatom oozes (305-470 cm). The brown miopelagic clay (0.09-1.25% СаСО3, 0.05-0.28% Сorganic) predominately consist of the clay minerals (91-97%). The top section sediments also include some terrigenous clastic sandy-silt minerals (1-5%), diatoms (up to 2%), manganese micronodules (approx. 1%), occasional spicules, radiolarian, coccoliths and marine fossil fragments. The transition to the lower diatom oozes is associated with the lens-shape structures and increase in the content of diatoms in clay. The age of sediments at the station No. 1537 is Late Pleistocene. Presence of thin bedded Ethmodiscus oozes is an indirect evidence of re-deposition of the sediments in the central part of the Brazil Basin The chemical composition has been analyzed on 37 core samples recovered from the column. These core samples have been used to define the content of the chemical composition as well as the rare and minor elements. The manganese content in the top section of the miopelagic clay varies insignificantly and value is close 0.46%. The rare and minor elements content in the miopelagic clay is quite stable. The sharp increase in manganese content (to 1.16%) as well as in that of the minor elements such as Co, Cu, Ni, Mo and Tl are observed at the 305-308 cm horizon which corresponds to the bottom of the miopelagic clay. Than, the manganese content decreases to reach its minimum value (0.20%) immediately below this horizon. With further depth increase, the content of manganese starts rising again reaces its maximum value of 2.31% at the 405-407 cm horizon. The

  7. Hydrothermal signature in ferromanganese oxide coatings on pumice from the Central Indian Ocean Basin

    NASA Astrophysics Data System (ADS)

    Kalangutkar, Niyati G.; Iyer, Sridhar D.; Mascarenhas-Pereira, Maria B. L.; Nath, B. Nagender

    2015-06-01

    Mineralogical and elemental analyses of 20 ferromanganese (FeMn)-coated pumice samples from the Central Indian Ocean Basin (CIOB) indicate that todorokite is the major mineral phase, whereas vernadite occurs only rarely. Based on major, trace and rare earth elements (REEs) as well as Ce anomalies, the sources of the FeMn oxides were identified to be either hydrogenous, hydrothermal-plume fallout, diagenetic or a combination of these. Plots of Fe/Mn vs. Ce or Co reveal a distinct demarcation of the diagenetic, hydrogenous and plume fallout samples. Five samples are interpreted to be of hydrothermal origin because these show negative Ce anomalies and low Co/Zn ratios (0.5 to 1.1), and are masked by diagenesis. The relative contributions of hydrogenous, hydrothermal and diagenetic inputs were assessed in terms of ternary mixing patterns using REE mass balance equations. Furthermore, the hypothetical Ce anomaly (Ce/Ce*) was calculated using ternary mixing calculations for hydrogenous, hydrothermal and diagenetic end-members to ascertain the input to FeMn oxides on the pumice samples. This revealed a distinction between hydrogenous and hydrothermal components but diagenetic and plume fallout components could not be distinguished because this scheme comprises a three end-member calculation. A conservative estimate indicates the hydrothermal component to vary between 24% and 72%. The growth rates of the oxides, as estimated from published empirical methods, range between 3 and 47 mm/106 years. Fe/Mn ratios yielded a maximum age of 5-7 Ma and a minimum of 0.04-0.1 Ma. This suggests that the commencement of accretion of the FeMn oxides generally precedes the age of the Krakatau 1883 eruption, which is commonly considered as being the prime source of pumice to the CIOB. This is the first evidence of hydrothermal influence in the formation of FeMn oxides on CIOB pumice.

  8. Primary particulate matter from ocean-going engines in the Southern California Air Basin.

    PubMed

    Agrawal, Harshit; Eden, Rudy; Zhang, Xinqiu; Fine, Philip M; Katzenstein, Aaron; Miller, J Wayne; Ospital, Jean; Teffera, Solomon; Cocker, David R

    2009-07-15

    The impact of primary fine particulate matter (PM2.5) from ship emissions within the Southern California Air Basin is quantified by comparing in-stack vanadium (V) and nickel (Ni) measurements from in-use ocean-going vessels (OGVs) with ambient measurements made at 10 monitoring stations throughout Southern California. V and Ni are demonstrated as robust markers for the combustion of heavy fuel oil in OGVs, and ambient measurements of fine particulate V and Ni within Southern California are shown to decrease inversely with increased distance from the ports of Los Angeles and Long Beach (ports). High levels of V and Ni were observed from in-stack emission measurements conducted on the propulsion engines of two different in-use OGVs. The in-stack V and Ni emission rates (g/h) normalized by the V and Ni contents in the fuel tested correlates with the stack total PM emission rates (g/h). The normalized emission rates are used to estimate the primary PM2.5 contributions from OGVs at 10 monitoring locations within Southern California. Primary PM2.5 contributions from OGVs were found to range from 8.8% of the total PM2.5 at the monitoring location closest to the port (West Long Beach) to 1.4% of the total PM2.5 at the monitoring location 80 km inland (Rubidoux). The calculated OGV contributions to ambient PM2.5 measurements at the 10 monitoring sites agree well with estimates developed using an emission inventory based regional model. Results of this analysis will be useful in determining the impacts of primary particulate emissions from OGVs upon worldwide communities downwind of port operations. PMID:19708372

  9. Three Plate Reconstruction in the Eastern Indian Ocean: New Constraints on Wharton and Australian-Antarctic basins

    NASA Astrophysics Data System (ADS)

    Jacob, J.; Dyment, J.

    2012-12-01

    Understanding the continuous seismicity and repeated occurrence of major earthquakes in Sumatra and the neighboring area requires detailed constrains on the subducting plate. In this study we analyze the past plate kinematics evolution of the Wharton basin, eastern Indian Ocean through a three plate reconstruction involving Australia (AUS), Antarctica (ANT), and India (IND). We compile marine magnetic identifications in the Australian-Antarctic Basin [1,2], the Crozet and Central Indian basins (Yatheesh et al, in prep.) and the Wharton Basin [3]. The Wharton Basin is characterized by an extinct spreading center dated by anomaly 18 (38 Ma). The southern flank of the basin exhibits a continuous sequence of anomalies 20n (42 Ma) to 34n (84 Ma), whereas the northern flank lacks some of the older anomalies because a significant part has been subducted in the Sunda Trench. The three-plate reconstructions have provided set of rotation parameters describing the evolution of IND-AUS. Using these parameters, we have reconstructed the missing isochrons of the northern flank and the detailed geometry of the subducted part of the Wharton basin. Such an exercise provides useful constraints on the age and structure of the plate in subduction under Indonesia. As a byproduct, the three plate reconstruction provided set of rotation parameters for AUS-ANT as well, which constrains the conjugate fit between the basins. Previous studies [1,2,4,5] have achieved such a fit on the base of ill-defined fracture zones. We consider the well-defined fracture zones from the Crozet, Central Indian, and Wharton basins, but avoid using the poor fracture zone imprints from the Australian-Antarctic Basin. As a result from this approach, we conclude that the relative motion of AUS with respect to ANT initially followed a north-south direction, then changed to northwest-southeast at anomaly 32ny, and reverted to northeast southwest at anomaly 24no prior to the establishment of the Southeast Indian

  10. Basin-scale estimates of pelagic and coral reef calcification in the Red Sea and Western Indian Ocean.

    PubMed

    Steiner, Zvi; Erez, Jonathan; Shemesh, Aldo; Yam, Ruth; Katz, Amitai; Lazar, Boaz

    2014-11-18

    Basin-scale calcification rates are highly important in assessments of the global oceanic carbon cycle. Traditionally, such estimates were based on rates of sedimentation measured with sediment traps or in deep sea cores. Here we estimated CaCO3 precipitation rates in the surface water of the Red Sea from total alkalinity depletion along their axial flow using the water flux in the straits of Bab el Mandeb. The relative contribution of coral reefs and open sea plankton were calculated by fitting a Rayleigh distillation model to the increase in the strontium to calcium ratio. We estimate the net amount of CaCO3 precipitated in the Red Sea to be 7.3 ± 0.4·10(10) kg·y(-1) of which 80 ± 5% is by pelagic calcareous plankton and 20 ± 5% is by the flourishing coastal coral reefs. This estimate for pelagic calcification rate is up to 40% higher than published sedimentary CaCO3 accumulation rates for the region. The calcification rate of the Gulf of Aden was estimated by the Rayleigh model to be ∼1/2 of the Red Sea, and in the northwestern Indian Ocean, it was smaller than our detection limit. The results of this study suggest that variations of major ions on a basin scale may potentially help in assessing long-term effects of ocean acidification on carbonate deposition by marine organisms. PMID:25368148

  11. Basin-scale estimates of pelagic and coral reef calcification in the Red Sea and Western Indian Ocean

    PubMed Central

    Steiner, Zvi; Erez, Jonathan; Shemesh, Aldo; Yam, Ruth; Katz, Amitai; Lazar, Boaz

    2014-01-01

    Basin-scale calcification rates are highly important in assessments of the global oceanic carbon cycle. Traditionally, such estimates were based on rates of sedimentation measured with sediment traps or in deep sea cores. Here we estimated CaCO3 precipitation rates in the surface water of the Red Sea from total alkalinity depletion along their axial flow using the water flux in the straits of Bab el Mandeb. The relative contribution of coral reefs and open sea plankton were calculated by fitting a Rayleigh distillation model to the increase in the strontium to calcium ratio. We estimate the net amount of CaCO3 precipitated in the Red Sea to be 7.3 ± 0.4·1010 kg·y−1 of which 80 ± 5% is by pelagic calcareous plankton and 20 ± 5% is by the flourishing coastal coral reefs. This estimate for pelagic calcification rate is up to 40% higher than published sedimentary CaCO3 accumulation rates for the region. The calcification rate of the Gulf of Aden was estimated by the Rayleigh model to be ∼1/2 of the Red Sea, and in the northwestern Indian Ocean, it was smaller than our detection limit. The results of this study suggest that variations of major ions on a basin scale may potentially help in assessing long-term effects of ocean acidification on carbonate deposition by marine organisms. PMID:25368148

  12. Using Pacific and Atlantic Ocean Climate Variability for Improving Streamflow Estimates in the Rio Grande River Basin

    NASA Astrophysics Data System (ADS)

    Kalra, A.; Ahmad, S.

    2013-12-01

    Over the years, hydrologist and climatologist have been engaged in developing relationship between oceanic-atmospheric oscillations and hydroclimatology within a region. Several modes of oceanic-atmospheric climate phenomena are available that have periodicity ranging from annual-to decadal-to multidecadal and can provide predictive information that can be used to improve forecast lead time of hydrologic variables. The most commonly understood and studied oceanic-atmospheric oscillations representing the variability in sea surface temperatures (SSTs) are the Pacific Decadal Oscillation, El Niño-Southern Oscillation, and Atlantic Multidecadal Oscillation. Although, these climate patterns are indicative of SST variability, spatial bias is introduced as these oscillations represent specific predetermined regions. The exploitation of entire Pacific and Atlantic Ocean SST eliminates the ocean or region specific bias impacting the hydroclimatology. With this motivation, we propose a time lagged analyses between the Pacific Ocean and Atlantic Ocean SSTs and 500 mbar geopotential height (Z500) values with spring-summer streamflow volume for improving the forecast lead time. Singular Value Decomposition (SVD) statistical technique is used to identify coupled regions of SST/Z500 and six unimpaired streamflow gages in Rio Grande River Basin, located in the western United States, for a 63-year period (1949-2011). The significant SST/ Z500 regions are utilized as predictors in non-parametric model to develop continuous exceedance probability forecasts for 3-6 months lead times. The SST/Z500 1st mode temporal expansion series explained 90% of the variability in streamflow. Additionally, the results indicated improved streamflow forecasts using only significant SST/Z500 regions compared to using predefine climate indices. The improved skill found over basic climatology forecasts will be useful to water managers when trying to predict and manage expected streamflow volumes

  13. The record of India-Asia collision preserved in Tethyan ocean basin sediments.

    NASA Astrophysics Data System (ADS)

    Najman, Yani; Jenks, Dan; Godin, Laurent; Boudagher-Fadel, Marcelle; Bown, Paul; Horstwood, Matt; Garzanti, Eduardo; Bracialli, Laura; Millar, Ian

    2015-04-01

    The timing of India-Asia collision is critical to the understanding of crustal deformation processes, since, for example, it impacts on calculations regarding the amount of convergence that needs to be accommodated by various mechanisms. In this research we use sediments originally deposited in the Tethyan ocean basin and now preserved in the Himalayan orogeny to constrain the timing of collision. In the NW Himalaya, a number of workers have proposed a ca 55-50 Ma age for collision along the Indus suture zone which separates India from the Kohistan-Ladakh Intraoceanic Island arc (KLA) to the north. This is based on a number of factors including the age of youngest marine sediments in the Indus suture (e.g. Green et al. 2008), age of eclogites indicative of onset of Indian continental subduction (e.g. de Sigoyer et al. 2000), and first evidence of detritus from north of the suture zone deposited on the Indian plate (e.g. Clift et al. 2002). Such evidence can be interpreted as documenting the age of India-Asia collision if one takes the KLA to have collided with the Asian plate prior to its collision with India (e.g. Petterson 2010 and refs therein). However, an increasing number of workers propose that the KLA collided with Asia subsequent to its earlier collision with India, dated variously at 85 Ma (Chatterjee et al. 2013), 61 Ma (Khan et al. 2009) and 50 Ma (Bouilhol et al. 2013). This, plus the questioning of earlier provenance work (Clift et al. 2002) regarding the validity of their data for constraining timing of earliest arrival of material north of the suture deposited on the Indian plate (Henderson et al. 2011) suggests that the time is right for a reappraisal of this topic. We use a provenance-based approach here, using combined U-Pb and Hf on detrital zircons from Tethyan ocean basin sediments, along with petrography and biostratigraphy, to identify first arrival of material from north of the Indian plate to arrive on the Indian continent, to constrain

  14. A paleomagnetic and relative paleointensity record from the Argentine Basin (western South Atlantic Ocean) for the last ~125 kyrs

    NASA Astrophysics Data System (ADS)

    Heil, C. W., Jr.; Stoner, J. S.; St-Onge, G.; King, J. W.

    2015-12-01

    The paucity of paleomagnetic records from the western South Atlantic Ocean presents a significant gap in our understanding of the spatial variations in geomagnetic field dynamics as they relate to the occurrence of geomagnetic excursions and changes in field strength. As such, high quality records from this region can help build upon Holocene observations and extend the geographic and temporal data coverage for spherical harmonic models. To that end, we present paleomagnetic directional (inclination) and strength (relative paleointensity) records from two cores from the Argentine Basin (RC11-49 and RC16-88). Although the cores were collected more than 40 years ago, the sediments appear to hold a stable remanence and reliable magnetic directions, as evidenced by their reproducibility between the two cores that are separated by ~25 km. The records show evidence of 4 excursional features in the uppermost 16-m of the sediments from the basin. A comparison of the relative paleointensity records from these cores to the South Atlantic Paleointensity Stack (SAPIS) (Stoner et al., 2002) and the relative paleointensity record from ODP Site 1089 (Stoner et al., 2003) indicate that the sediments reliably record relative changes in geomagnetic field intensity and suggests that the longest record (RC11-49) spans the last ~125 kyrs. Our results indicate that the sediments of the Argentine Basin are an important sedimentary archive of geomagnetic field behavior and strength at least through the Holocene and Late Pleistocene and highlight the need for further studies of cores within the basin.

  15. Aalenian foraminiferal fauna and microfacies analyses of the Tethys Ocean Basin from the Transdanubian Range (Hungary)

    NASA Astrophysics Data System (ADS)

    Zsiborás, Gábor; Görög, Ágnes

    2016-04-01

    The early Middle Jurassic foraminiferal fauna of the Tethys Ocean Basin is hardly known. It is especially true for the Aalenian from when only Monaco et al. (1994) published some forms from Valdorbia Section, Central Italy and Wernli (1988) from Domuz Dag, Turkey. Thus the aim of our study was to give a detailed systematic description of the foraminiferal fauna and microfacies analyses of Nagy-Pisznice Section of Lábatlan and T?zköves Gorge of Bakonycsernye from the Transdanubian Range. According to several studies of Géczy} and others, the ammonite fauna indicate all Aalenian (Opalinum, Murchisonae, Concavum) biozones in both successions. 6 samples from T?zköves Gorge, 13 samples from Nagy-Pisznice were collected. Both sequences are about 3 metres thick Ammonitico Rosso type reddish grey limestone with flaser beds and nodules (Tölgyhát Limestone Formation). For the microfacies studies thin sections were made. The dominant microfacies is bioclastic wackestone predominated {Bositra} shells. To extract the microfossils, each sample was dissolved in glacial acetic acid. The microfauna consist of foraminifers, calcispheres, juvenile ammonites, ostracods, radiolarians, microgastropods and fragments of echinoderms. Throughout the Nagy-Pisznice succession, the composition of the foraminiferal fauna is relatively uniform and moderately divers. Most specimens belong to Suborder Lagenina with 60-80{%} abundance. The Suborder Spirillinina are also frequent with 20-35{%} abundance. Agglutinants are subordinated and Suborder Miliolina is absent. The most abundant genus is {Lenticulina}, its amount is more than 50{%} in some samples. {Astacolus}, {Marginulina}, {Dentalina}, {Nodosaria}, {Paralingulina} and Epistominidae are also frequent. {Eoguttulina} and {Paalzowella} are scarce. Spirillinids are represented by {Spirillina}, {Turrispirillina}, and {Coronipora} genera. The taxonomic composition of the foraminiferal fauna of T?zköves Gorge is similar to the aforesaid

  16. Role of colloidal material in the removal of 234Th in the Canada basin of the Arctic Ocean

    USGS Publications Warehouse

    Baskaran, M.; Swarzenski, P.W.; Porcelli, D.

    2003-01-01

    The phase partitioning of 234Th between dissolved ( 200m, general equilibrium existed between total 234Th and 238U. The inventory of SPM and the specific activity of particulate 234Th in the Canada Basin was about an order of magnitude higher than the profile reported for the Alpha Ridge ice camp station. This higher concentration of SPM in the southwestern Canada Basin is likely derived from ice-rafted sedimentary particles. Inventories of nutrients, and dissolved organic carbon and nitrogen in the upper 100 m of the Canada Basin are comparable to the other estimates for the central Arctic Ocean. Comparison of the mass concentrations of colloidal and filter-retained particulate matter as well as the activity of 234Th in these phases indicates that only a very small component of the colloidal material is actively involved in Th scavenging. Lower values of the conditional partition coefficient between the colloidal and dissolved phase indicate that the Arctic colloids are less reactive than colloidal material from other regions. The conditional partition coefficient between the filter-retained and dissolved phases (Kf) is generally higher than that for other regions, which is attributed to the higher complexation capacity of glacio-marine sedimentary particles in these waters. The 234Th-derived export of POC for the shelf and deep Canada Basin ranges between 5.6 and 6.5 mmol m-2 d-1, and is in agreement with other estimates reported for the central Arctic Ocean and Beaufort Sea. ?? 2003 Elsevier Ltd. All rights reserved.

  17. Oceanic response to Pliensbachian and Toarcian magmatic events: Implications from an organic-rich basinal succession in the NW Tethys

    NASA Astrophysics Data System (ADS)

    Neumeister, S.; Gratzer, R.; Algeo, T. J.; Bechtel, A.; Gawlick, H.-J.; Newton, R. J.; Sachsenhofer, R. F.

    2015-03-01

    The Bächental bituminous marls (Bächentaler Bitumenmergel) belonging to the Sachrang Member of the Lower Jurassic Middle Allgäu Formation were investigated using a multidisciplinary approach to determine environmental controls on the formation of organic-rich deposits in a semi-restricted basin of the NW Tethys during the Early Jurassic. The marls are subdivided into three units on the basis of mineralogical composition, source-rock parameters, redox conditions, salinity variations, and diagenetic processes. Redox proxies (e.g., pristane/phytane ratio; aryl isoprenoids; bioturbation; ternary plot of iron, total organic carbon, and sulphur) indicate varying suboxic to euxinic conditions during deposition of the Bächental section. Redox variations were mainly controlled by sea-level fluctuations with the tectonically complex bathymetry of the Bächental basin determining watermass exchange with the Tethys Ocean. Accordingly, strongest anoxia and highest total organic carbon content (up to 13%) occur in the middle part of the profile (upper tenuicostatum and lower falciferum zones), coincident with an increase in surface-water productivity during a period of relative sea-level lowstand that induced salinity stratification in a stagnant basin setting. This level corresponds to the time interval of the lower Toarcian oceanic anoxic event (T-OAE). However, the absence of the widely observed lower Toarcian negative carbon isotope excursion in the study section questions its unrestricted use as a global chemostratigraphic marker. Stratigraphic correlation of the thermally immature Bächental bituminous marls with the Posidonia Shale of SW Germany on the basis of C27/C29 sterane ratio profiles and ammonite data suggests that deposition of organic matter-rich sediments in isolated basins in the Alpine realm commenced earlier (late Pliensbachian margaritatus Zone) than in regionally proximal epicontinental seas (early Toarcian tenuicostatum Zone). The late Pliensbachian

  18. Seismic structure of the extended continental crust in the Yamato Basin, Japan Sea, from ocean bottom seismometer survey

    NASA Astrophysics Data System (ADS)

    Nakahigashi, Kazuo; Shinohara, Masanao; Yamada, Tomoaki; Uehira, Kenji; Mochizuki, Kimihiro; Kanazawa, Toshihiko

    2013-05-01

    We present the result of a seismic experiment conducted using ocean bottom seismometers and an airgun in the Yamato Basin, of the Japan Sea. The Japan Sea is one of the most well-studied back-arc basins in the western Pacific. The Japan Sea is believed to have been formed by back-arc opening. However, the timing and formation processes of the opening of individual basins in and around the Japan Sea are not clear. To reveal the crustal structure of the Yamato Basin it is important to consider the formation process of the Japan Sea. Therefore, we conducted a seismic survey and estimated the P-wave seismic velocity structure beneath the 170-km profile using a 2-D ray-tracing method. A layer with a P-wave velocity of 3.4-4.0 km/s underlies the sedimentary sections, which is thought to consist of a sill-and-sediment complex. The upper crust below the profile varies greatly in thickness. The thickness of the upper crust is 3.5 km in the thinnest part and 7 km in the thickest part. The thickness of the lower crust is approximately 8 km and is relatively constant over the profile. The total thickness of the crust is approximately 15 km including the sedimentary layer. The distribution of P-wave velocities and the thickness indicate that the crust in the Yamato Basin is neither a typical continental nor a typical oceanic crust. From the point of view of seismic velocity, the obtained structure is more similar to a continental crust than to an oceanic crust. The large lateral thickness variation in the upper crust and the uniform thickness of the lower crust suggest that the crust in the study area was formed by rifting/extension of continental crust during the opening of the Japan Sea. The margins of the continent or of island arcs can be divided into two types: volcanic rifted margins and non-volcanic rifted margins. Volcanic rifted margins are normally classified by the presence of a high-velocity body in the lower crust. At the volcanic rifted margin, the high

  19. New deep ocean Iravadiidae of the genus Ceratia (Caenogastropoda: Truncatelloidea) from an underwater canyon and adjacent regions of
    the southwestern Atlantic (northeastern Brazil).

    PubMed

    Lima, Silvio Felipe B; Júnior, Ivan Cardoso L; Guimarães, Carmen Regina P; Dominguez, José Maria L

    2016-01-01

    Previous studies on the mollusks from Brazilian underwater canyons have addressed the record and description of new species of aplacophorans, bivalves, scaphopods and/or gastropods (Leal & Simone 2000; Absalão 2010; Corrêa et al. 2014). Leal & Simone (2000) described a new bathyal gastropod of the family Pseudococculinidae collected from the continental slope and Doce River Canyon (960 m) off the state of Espírito Santo (southeastern Brazil). Absalão (2010) reported a number of species of gastropods, bivalves and scaphopods from Campos Basin off the state of Rio de Janeiro (southeastern Brazil). It is likely that some of these species reported by Absalão (2010) were collected from underwater canyons in the northern portion of the Campos Basin. Corrêa et al. (2014) recorded two species of aplacophorans of the genus Falcidens Salvini-Plawen, 1968 obtained from the continental slope and underwater canyons of Campos Basin. Certainly more species of mollusks were studied from Brazilian underwater canyons, but not duly mentioned in publications (i.e., the region of canyons may have been referred to as the continental slope or deep sea). PMID:27395545

  20. Mapping the hydraulic connection between a coalbed and adjacent aquifer: example of the coal-seam gas resource area, north Galilee Basin, Australia

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenjiao; Mariethoz, Gregoire; Schrank, Christoph; Cox, Malcolm; Timms, Wendy

    2016-07-01

    Coal-seam gas production requires groundwater extraction from coal-bearing formations to reduce the hydraulic pressure and improve gas recovery. In layered sedimentary basins, the coalbeds are often separated from freshwater aquifers by low-permeability aquitards. However, hydraulic connection between the coalbed and aquifers is possible due to the heterogeneity in the aquitard such as the existence of conductive faults or sandy channel deposits. For coal-seam gas extraction operations, it is desirable to identify areas in a basin where the probability of hydraulic connection between the coalbed and aquifers is low in order to avoid unnecessary loss of groundwater from aquifers and gas production problems. A connection indicator, the groundwater age indictor (GAI), is proposed, to quantify the degree of hydraulic connection. The spatial distribution of GAI can indicate the optimum positions for gas/water extraction in the coalbed. Depressurizing the coalbed at locations with a low GAI would result in little or no interaction with the aquifer when compared to the other positions. The concept of GAI is validated on synthetic cases and is then applied to the north Galilee Basin, Australia, to assess the degree of hydraulic connection between the Aramac Coal Measure and the water-bearing formations in the Great Artesian Basin, which are separated by an aquitard, the Betts Creek Beds. It is found that the GAI is higher in the western part of the basin, indicating a higher risk to depressurization of the coalbed in this region due to the strong hydraulic connection between the coalbed and the overlying aquifer.

  1. Geology of the Eel River basin and adjacent region: Implications for late Cenozoic tectonics of the southern Cascadia subduction zone and Mendocino triple junction

    SciTech Connect

    Clarke, S.H. Jr. )

    1992-02-01

    Two upper Cenozoic depositional sequences of principally marine strata about 4,000 m thick overlie accreted basement terranes of the Central and Coastal belts of the Franciscan Complex in the onshore-offshore Eel River basin of northwestern California. The older depositional sequence is early to middle Miocene in age and represents slope basin and slope-blanket deposition, whereas the younger sequence, later Miocene to middle Pleistocene in age, consists largely of forearc basin deposits. Youthful tectonic activity related to Gorda-North American plate convergence indicates an active Cascadia subduction zone and strong partial coupling between these plates. Structures of the northeastern margin of the Eel River basin are principally north-northwest-trending, east-northeast-dipping thrust and reverse faults that form imbricate thrust fans. The Coastal belt fault, the early Tertiary accretionary suture between the Franciscan Central and Coastal belts, can be traced from Arcata Bay northward offshore to the southern Oregon border. It is tentatively extended farther northward based on aeromagnetic data to an offshore position west of Cape Blanco. Thereafter, it may coincide with the offshore Fulmar fault. The Cascadia subduction zone (CSZ) does not join the Mendocino transform fault at the commonly depicted offshore location of the Mendocino triple junction (MTJ). Instead, the CSZ extends southeastward around the southern Eel River basin and shoreward along Mendocino Canyon to join the Petrolia shear zone. Similarly, the Mendocino fault may extend shoreward via Mattole Canyon and join the Cooskie shear zone. These two shear zones intersect onshore north of the King Range, and the area of their intersection is the probable location of the MTJ.

  2. Baseline Monitoring of the Western Arctic Ocean Estimates 20% of Canadian Basin Surface Waters Are Undersaturated with Respect to Aragonite

    PubMed Central

    Robbins, Lisa L.; Wynn, Jonathan G.; Lisle, John T.; Yates, Kimberly K.; Knorr, Paul O.; Byrne, Robert H.; Liu, Xuewu; Patsavas, Mark C.; Azetsu-Scott, Kumiko; Takahashi, Taro

    2013-01-01

    Marine surface waters are being acidified due to uptake of anthropogenic carbon dioxide, resulting in surface ocean areas of undersaturation with respect to carbonate minerals, including aragonite. In the Arctic Ocean, acidification is expected to occur at an accelerated rate with respect to the global oceans, but a paucity of baseline data has limited our understanding of the extent of Arctic undersaturation and of regional variations in rates and causes. The lack of data has also hindered refinement of models aimed at projecting future trends of ocean acidification. Here, based on more than 34,000 data records collected in 2010 and 2011, we establish a baseline of inorganic carbon data (pH, total alkalinity, dissolved inorganic carbon, partial pressure of carbon dioxide, and aragonite saturation index) for the western Arctic Ocean. This data set documents aragonite undersaturation in ∼20% of the surface waters of the combined Canada and Makarov basins, an area characterized by recent acceleration of sea ice loss. Conservative tracer studies using stable oxygen isotopic data from 307 sites show that while the entire surface of this area receives abundant freshwater from meteoric sources, freshwater from sea ice melt is most closely linked to the areas of carbonate mineral undersaturation. These data link the Arctic Ocean’s largest area of aragonite undersaturation to sea ice melt and atmospheric CO2 absorption in areas of low buffering capacity. Some relatively supersaturated areas can be linked to localized biological activity. Collectively, these observations can be used to project trends of ocean acidification in higher latitude marine surface waters where inorganic carbon chemistry is largely influenced by sea ice meltwater. PMID:24040074

  3. Baseline monitoring of the western Arctic Ocean estimates 20% of Canadian Basin surface waters are undersaturated with respect to aragonite

    USGS Publications Warehouse

    Robbins, Lisa L.; Wynn, Jonathan G.; Lisle, John T.; Yates, Kimberly K.; Knorr, Paul O.; Byrne, Robert H.; Liu, Xuewu; Patsava, Mark C.; Azetsu-Scott, Kumiko; Takahashi, Taro

    2013-01-01

    Marine surface waters are being acidified due to uptake of anthropogenic carbon dioxide, resulting in surface ocean areas of undersaturation with respect to carbonate minerals, including aragonite. In the Arctic Ocean, acidification is expected to occur at an accelerated rate with respect to the global oceans, but a paucity of baseline data has limited our understanding of the extent of Arctic undersaturation and of regional variations in rates and causes. The lack of data has also hindered refinement of models aimed at projecting future trends of ocean acidification. Here, based on more than 34,000 data records collected in 2010 and 2011, we establish a baseline of inorganic carbon data (pH, total alkalinity, dissolved inorganic carbon, partial pressure of carbon dioxide, and aragonite saturation index) for the western Arctic Ocean. This data set documents aragonite undersaturation in ~20% of the surface waters of the combined Canada and Makarov basins, an area characterized by recent acceleration of sea ice loss. Conservative tracer studies using stable oxygen isotopic data from 307 sites show that while the entire surface of this area receives abundant freshwater from meteoric sources, freshwater from sea ice melt is most closely linked to the areas of carbonate mineral undersaturation. These data link the Arctic Ocean’s largest area of aragonite undersaturation to sea ice melt and atmospheric CO2 absorption in areas of low buffering capacity. Some relatively supersaturated areas can be linked to localized biological activity. Collectively, these observations can be used to project trends of ocean acidification in higher latitude marine surface waters where inorganic carbon chemistry is largely influenced by sea ice meltwater.

  4. Oceanic source strength of carbon monoxide on the basis of basin-wide observations in the Atlantic.

    PubMed

    Park, Keyhong; Rhee, Tae Siek

    2016-01-01

    We measured the carbon monoxide (CO) concentrations in the marine boundary layer and the surface waters of the Atlantic Ocean from 50°N to 50°S during the UK Atlantic Meridional Transect expedition (AMT-7) in October 1998, covering the open ocean and coastal regions. Throughout the cruise track, atmospheric CO concentrations continually decreased southwards in the northern hemisphere with sporadic low and high concentrations encountered. South of the intertropical convergence zone (ITCZ) atmospheric CO was enhanced by ∼10 ppb compared to north of the ITCZ due likely to biomass burning emissions prevailing in the tropical continents. The remainder of the southern hemisphere remains nearly invariable except for the vicinity of Rio de la Plata. The surface seawater was supersaturated everywhere along the track and its saturation anomaly oscillated up to 90, exhibiting a typical diurnal cycle. The maximal dissolved CO concentration in the diurnal cycle appeared 2-5 hours behind the local maximum of solar insolation in the open ocean and the time lag further increased in the coastal region. The global ocean flux of CO to the atmosphere was estimated to be 14 Tg(CO) a(-1) within the range of 4-24 Tg(CO) a(-1). This is within uncertainty almost identical to what was estimated on the basis of the basin-wide observations in the Pacific and the Atlantic, but more than ∼4 times lower than the values appeared in the Intergovernmental Panel on Climate Change (IPCC) reports. PMID:26648555

  5. Arctic-HYCOS: a Large Sample observing system for estimating freshwater fluxes in the drainage basin of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Pietroniro, Al; Korhonen, Johanna; Looser, Ulrich; Hardardóttir, Jórunn; Johnsrud, Morten; Vuglinsky, Valery; Gustafsson, David; Lins, Harry F.; Conaway, Jeffrey S.; Lammers, Richard; Stewart, Bruce; Abrate, Tommaso; Pilon, Paul; Sighomnou, Daniel; Arheimer, Berit

    2015-04-01

    The Arctic region is an important regulating component of the global climate system, and is also experiencing a considerable change during recent decades. More than 10% of world's river-runoff flows to the Arctic Ocean and there is evidence of changes in its fresh-water balance. However, about 30% of the Arctic basin is still ungauged, with differing monitoring practices and data availability from the countries in the region. A consistent system for monitoring and sharing of hydrological information throughout the Arctic region is thus of highest interest for further studies and monitoring of the freshwater flux to the Arctic Ocean. The purpose of the Arctic-HYCOS project is to allow for collection and sharing of hydrological data. Preliminary 616 stations were identified with long-term daily discharge data available, and around 250 of these already provide online available data in near real time. This large sample will be used in the following scientific analysis: 1) to evaluate freshwater flux to the Arctic Ocean and Seas, 2) to monitor changes and enhance understanding of the hydrological regime and 3) to estimate flows in ungauged regions and develop models for enhanced hydrological prediction in the Arctic region. The project is intended as a component of the WMO (World Meteorological Organization) WHYCOS (World Hydrological Cycle Observing System) initiative, covering the area of the expansive transnational Arctic basin with participation from Canada, Denmark, Finland, Iceland, Norway, Russian Federation, Sweden and United States of America. The overall objective is to regularly collect, manage and share high quality data from a defined basic network of hydrological stations in the Arctic basin. The project focus on collecting data on discharge and possibly sediment transport and temperature. Data should be provisional in near-real time if available, whereas time-series of historical data should be provided once quality assurance has been completed. The

  6. The record of India-Asia collision preserved in Tethyan ocean basin sediments.

    NASA Astrophysics Data System (ADS)

    Najman, Yani; Jenks, Dan; Godin, Laurent; Boudagher-Fadel, Marcelle; Bown, Paul; Horstwood, Matt; Garzanti, Eduardo; Bracialli, Laura; Millar, Ian

    2015-04-01

    The timing of India-Asia collision is critical to the understanding of crustal deformation processes, since, for example, it impacts on calculations regarding the amount of convergence that needs to be accommodated by various mechanisms. In this research we use sediments originally deposited in the Tethyan ocean basin and now preserved in the Himalayan orogeny to constrain the timing of collision. In the NW Himalaya, a number of workers have proposed a ca 55-50 Ma age for collision along the Indus suture zone which separates India from the Kohistan-Ladakh Intraoceanic Island arc (KLA) to the north. This is based on a number of factors including the age of youngest marine sediments in the Indus suture (e.g. Green et al. 2008), age of eclogites indicative of onset of Indian continental subduction (e.g. de Sigoyer et al. 2000), and first evidence of detritus from north of the suture zone deposited on the Indian plate (e.g. Clift et al. 2002). Such evidence can be interpreted as documenting the age of India-Asia collision if one takes the KLA to have collided with the Asian plate prior to its collision with India (e.g. Petterson 2010 and refs therein). However, an increasing number of workers propose that the KLA collided with Asia subsequent to its earlier collision with India, dated variously at 85 Ma (Chatterjee et al. 2013), 61 Ma (Khan et al. 2009) and 50 Ma (Bouilhol et al. 2013). This, plus the questioning of earlier provenance work (Clift et al. 2002) regarding the validity of their data for constraining timing of earliest arrival of material north of the suture deposited on the Indian plate (Henderson et al. 2011) suggests that the time is right for a reappraisal of this topic. We use a provenance-based approach here, using combined U-Pb and Hf on detrital zircons from Tethyan ocean basin sediments, along with petrography and biostratigraphy, to identify first arrival of material from north of the Indian plate to arrive on the Indian continent, to constrain

  7. Variation of ocean sediment thickness with crustal age

    NASA Astrophysics Data System (ADS)

    Olson, Peter; Reynolds, Evan; Hinnov, Linda; Goswami, Arghya

    2016-04-01

    Global ocean sediment thickness and present-day ocean sediment accumulation rates are analyzed with respect to the age of the underlying ocean crust. Trends in average sediment thickness and present-day accumulation rate are well fit by cubic polynomials in crustal age for the global ocean and for individual ocean basins. Sediment thickness and accumulation rates are larger in the North and South Atlantic and Indian Oceans compared to the Pacific Ocean, primarily because the anomalous sediment accumulations that followed continental rifting and collision in the Atlantic and Indian Ocean basins are missing in the Pacific Ocean. Modern ocean sediment accumulation rates, extrapolated into the past assuming steady state conditions, account within uncertainties for the global average sediment thickness on 0-65 Ma (Cenozoic age) ocean crust, while the profile of anomalously thick sediments on older (Mesozoic age) ocean crust is well fit by adding localized, diffusive sediment transport from a steady state source referenced to the adjacent continental margin. Apart from a distinct 0-5 Ma (Quaternary age) sediment pulse, deviations in average sediment thickness from this simple model are generally small and are uncorrelated across ocean basins.

  8. Estimation of groundwater use for a groundwater-flow model of the Lake Michigan Basin and adjacent areas, 1864-2005

    USGS Publications Warehouse

    Buchwald, Cheryl A.; Luukkonen, Carol L.; Rachol, Cynthia M.

    2010-01-01

    The U.S. Geological Survey, at the request of Congress, is assessing the availability and use of the Nation's water resources to help characterize how much water is available now, how water availability is changing, and how much water can be expected to be available in the future. The Great Lakes Basin Pilot project of the U.S. Geological Survey national assessment of water availability and use focused on the Great Lakes Basin and included detailed studies of the processes governing water availability in the Great Lakes Basin. One of these studies included the development of a groundwater-flow model of the Lake Michigan Basin. This report describes the compilation and estimation of the groundwater withdrawals in those areas in Wisconsin, Michigan, Indiana, and Illinois that were needed for the Lake Michigan Basin study groundwater-flow model. These data were aggregated for 12 model time intervals spanning 1864 to 2005 and were summarized by model area, model subregion, category of water use, aquifer system, aquifer type, and hydrogeologic unit model layer. The types and availability of information on groundwater withdrawals vary considerably among states because water-use programs often differ in the types of data collected and in the methods and frequency of data collection. As a consequence, the methods used to estimate and verify the data also vary. Additionally, because of the different sources of data and different terminologies applied for the purposes of this report, the water-use data published in this report may differ from water-use data presented in other reports. These data represent only a partial estimate of groundwater use in each state because estimates were compiled only for areas in Wisconsin, Michigan, Indiana, and Illinois within the Lake Michigan Basin model area. Groundwater-withdrawal data were compiled for both nearfield and farfield model areas in Wisconsin and Illinois, whereas these data were compiled primarily for the nearfield model

  9. New data on mammoth fauna mammals in the central Lena River basin (Yakutia, Lenskie Stolby National Nature Park and adjacent areas)

    NASA Astrophysics Data System (ADS)

    Boeskorov, G. G.; Nogovitsyn, P. R.; Mashchenko, E. N.; Belolyubsky, I. N.; Stepanov, A. D.; Plotnikov, V. V.; Protopopov, A. V.; Shchelchkova, M. V.; van der Plicht, J.; Solomonov, N. G.

    2016-07-01

    This paper considers the data on new findings of mammoth fauna remains in the Middle Lena basin used to specify the species composition of large Late Neopleistocene mammals represented by eleven species. The obtained range of radiocarbon dates made it possible to state that mass burials of Pleistocene mammal remains were formed in the region during the Karginsk Interstadial (24 000-55 000 years ago).

  10. Oceanic provinces and basin-scale connectivity derived from a hydrodynamical network help designing marine reserves in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    López, Cristóbal; Rossi, Vincent; Ser-Giacomi, Enrico; Hernandez-Garcia, Emilio

    2014-05-01

    Larval dispersal and marine connectivity have been identified as crucial factors for structuring marine population and thus to design Marine Protected Areas (MPAs). Focusing on larval dispersal by ocean currents, we propose a new approach coupling Lagrangian modeling and network theory which characterizes marine connectivity in the whole Mediterranean basin. Larvae of different Pelagic Larval Duration are modeled as passive tracers advected in a simulated oceanic surface flow from which a network of connected areas can be constructed. Hydrodynamical 'coherent' provinces extracted from this network are delimited by frontiers which match mesoscale oceanographic features. By examining the repeated occurrence of such boundaries, we identify the relevant scales of larval dispersal across the entire seascape. We finally used these hydrodynamical units to define connectivity metrics for a few selected MPAs in the Mediterranean sea and we discuss our results for future allocations of MPA. The characterization of marine connectivity and its geographic structure at basin-scale has ecological and managerial implications, especially considering the growing interests for offshore MPAs.

  11. Basin-scale transport of hydrothermal dissolved metals across the South Pacific Ocean.

    PubMed

    Resing, Joseph A; Sedwick, Peter N; German, Christopher R; Jenkins, William J; Moffett, James W; Sohst, Bettina M; Tagliabue, Alessandro

    2015-07-01

    Hydrothermal venting along mid-ocean ridges exerts an important control on the chemical composition of sea water by serving as a major source or sink for a number of trace elements in the ocean. Of these, iron has received considerable attention because of its role as an essential and often limiting nutrient for primary production in regions of the ocean that are of critical importance for the global carbon cycle. It has been thought that most of the dissolved iron discharged by hydrothermal vents is lost from solution close to ridge-axis sources and is thus of limited importance for ocean biogeochemistry. This long-standing view is challenged by recent studies which suggest that stabilization of hydrothermal dissolved iron may facilitate its long-range oceanic transport. Such transport has been subsequently inferred from spatially limited oceanographic observations. Here we report data from the US GEOTRACES Eastern Pacific Zonal Transect (EPZT) that demonstrate lateral transport of hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise (SEPR) several thousand kilometres westward across the South Pacific Ocean. Dissolved iron exhibits nearly conservative (that is, no loss from solution during transport and mixing) behaviour in this hydrothermal plume, implying a greater longevity in the deep ocean than previously assumed. Based on our observations, we estimate a global hydrothermal dissolved iron input of three to four gigamoles per year to the ocean interior, which is more than fourfold higher than previous estimates. Complementary simulations with a global-scale ocean biogeochemical model suggest that the observed transport of hydrothermal dissolved iron requires some means of physicochemical stabilization and indicate that hydrothermally derived iron sustains a large fraction of Southern Ocean export production. PMID:26156374

  12. Basin-scale transport of hydrothermal dissolved metals across the South Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Resing, Joseph A.; Sedwick, Peter N.; German, Christopher R.; Jenkins, William J.; Moffett, James W.; Sohst, Bettina M.; Tagliabue, Alessandro

    2015-07-01

    Hydrothermal venting along mid-ocean ridges exerts an important control on the chemical composition of sea water by serving as a major source or sink for a number of trace elements in the ocean. Of these, iron has received considerable attention because of its role as an essential and often limiting nutrient for primary production in regions of the ocean that are of critical importance for the global carbon cycle. It has been thought that most of the dissolved iron discharged by hydrothermal vents is lost from solution close to ridge-axis sources and is thus of limited importance for ocean biogeochemistry. This long-standing view is challenged by recent studies which suggest that stabilization of hydrothermal dissolved iron may facilitate its long-range oceanic transport. Such transport has been subsequently inferred from spatially limited oceanographic observations. Here we report data from the US GEOTRACES Eastern Pacific Zonal Transect (EPZT) that demonstrate lateral transport of hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise (SEPR) several thousand kilometres westward across the South Pacific Ocean. Dissolved iron exhibits nearly conservative (that is, no loss from solution during transport and mixing) behaviour in this hydrothermal plume, implying a greater longevity in the deep ocean than previously assumed. Based on our observations, we estimate a global hydrothermal dissolved iron input of three to four gigamoles per year to the ocean interior, which is more than fourfold higher than previous estimates. Complementary simulations with a global-scale ocean biogeochemical model suggest that the observed transport of hydrothermal dissolved iron requires some means of physicochemical stabilization and indicate that hydrothermally derived iron sustains a large fraction of Southern Ocean export production.

  13. Observation of oceanic heat flux to the sea ice using ice-tethered moorings: Canada Basin, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Ha, Ho Kyung; Yae Son, Eun; Park, Jae Hun; Cole, Sylvia; Park, Keyhong; Sul La, Hyoung

    2016-04-01

    It is important to figure out the physical mechanisms (e.g. shear, turbulence) below the sea ice, because of its direct influence on oceanic heat flux that is closely related to sea ice melt. A short-term (3.5 days) mooring was conducted in August 2014 to measure the vertical profiles of velocity, salinity and temperature within the sea-ice boundary layer. The mooring package consisted of an acoustic Doppler current profiler (ADCP) and 3 MicroCats. A long-term mooring of an ice-tethered profiler with modular acoustic velocity sensor (MAVS) was conducted to acquire vertical profiles of salinity, temperature, pressure and velocity in the marginal ice zone. The mooring data was analyzed to examine the role of the Pacific Summer Water (PSW) as a heat source, which can provide oceanic heat to the overlying layer. The ADCP data showed distinctive upper-velocity fields induced by entrainment of the sea ice. It appeared up to about 15 m depth during the entire observation period. Periodical components of MAVS data were extracted through wavelet transform. Since sea ice extent is relatively low in summer, the wind forcing could be effectively delivered in the form of a near 12 hours period oscillation to the 60 m depth where the PSW was occupying. Even in winter, while the sea surface was fully covered with the sea ice, near 12 hours period oscillation was appeared at 60 m depth. In September and January, strong 12 hours period oscillation appeared up to a deeper layer, which is deeper than 150 m depth where the wind forcing is hard to reach. The relationship between the heat flux and the oscillation strength will be discussed during the presentation.

  14. Simulation of ocean variability in the last 40 years with a high-resolution Mediterranean basin model

    NASA Astrophysics Data System (ADS)

    An, B. W.; Vichi, M.; Oddo, P.; Mattia, G.; Zavatarelli, M.

    2009-04-01

    The Mediterranean Sea high-resolution model developed at INGV was run for the period 1958 - 2001 forced by the ECMWF ERA40 atmospheric forcing functions. The model is the NEMO primitive equation model with the Mediterranean Forecasting System (MFS) grid at 1/16 degree horizontal resolution and 72 vertical levels, optimized for long-term simulations in the framework of the EU FP6 project SESAME. The open boundary data in the Atlantic box are derived from global ocean analyses produced in the framework of the EU FP5 ENACT project and forced with the same ERA40 atmospheric data. The presentation focuses on the analysis of the simulated ocean variability in the last 40 years with emphasis on the reproduction of climatological features and biases with respect to the observations. In this work, we focused on dense water formation processes in the Eastern Mediterranean Sea in related to the larger scale climatic conditions. Eastern Mediterranean Transient (hereafter EMT) was captured and evaluated by the deep and intermediate water mass pathway and the amount of their formation rate. Analysis of the main driving mechanism of this EMT was also studied. During the pre-EMT period, about 0.2 Sv of intermediate water formed in the Levantine basin at depth around 300 m and about 0.1 Sv of the deep water formed in the Ionian basin. However, during EMT, the intermediate water and the deep water paths were modified in the Eastern Mediterranean Sea because of the deep water and the intermediate water formed only in the Aegean Sea. From our results, we conclude that the general driving mechanism of EMT is mainly affected by the atmospheric forcing and the locations of dense water formation are affected by the freshwater budget. Our results demonstrate the model skills in capturing the major climatic state and variability in the basin, which will allow us to use this model for studying the impacts on marine biogeochemistry as planned in the SESAME project.

  15. Seismic reflection and refraction data acquired in Canada Basin, Northwind Ridge and Northwind Basin, Arctic Ocean in 1988, 1992 and 1993

    USGS Publications Warehouse

    Grantz, Arthur; Hart, Patrick E.; May, Steven D.

    2004-01-01

    Seismic reflection and refraction data were collected in generally ice-covered waters of the Canada Basin and the eastern part of the Chukchi Continental Borderland of the Amerasia Basin, Arctic Ocean, during the late summers of 1988, 1992, and 1993. The data were acquired from a Polar class icebreaker, the U.S. Coast Guard Cutter Polar Star, using a seismic reflection system designed by the U.S. Geological Survey (USGS). The northernmost data extend to 78? 48' N latitude. In 1988, 155 km of reflection data were acquired with a prototype system consisting of a single 195 cubic inch air gun seismic source and a two-channel hydrophone streamer with a 150-m active section. In 1992 and 1993, 500 and 1,900 km, respectively, of seismic reflection profile data were acquired with an improved six air gun, 674 to 1303 cubic inch tuned seismic source array and the same two-channel streamer. In 1993, a 12-channel streamer with a 150-m active section was used to record five of the reflection lines and one line was acquired using a three air gun, 3,000 cubic inch source. All data were recorded with a DFS-V digital seismic recorder. Processed sections feature high quality vertical incidence images to more than 6 km of sub-bottom penetration in the Canada Basin. Refraction data were acquired with U.S. Navy sonobuoys recorded simultaneously with the seismic reflection profiles. In 1988 eight refraction profiles were recorded with the single air gun, and in 1992 and 1993 a total of 47 refraction profiles were recorded with the six air gun array. The sonobuoy refraction records, with offsets up to 35 km, provide acoustic velocity information to complement the short-offset reflection data. The report includes trackline maps showing the location of the data, as well as both digital data files (SEG-Y) and images of all of the profiles.

  16. Constructing mid-ocean ridge flat-topped volcanoes: First evidence from AUV mapping in the Woodlark Basin

    NASA Astrophysics Data System (ADS)

    Devey, C. W.; Petersen, S.; Hannington, M.; Klaucke, I.; Lackschewitz, K. S.; Mahlke, J.; Rothenbeck, M.; Sticklus, J.

    2010-12-01

    The style of volcanic activity at many of the global spreading axes is dominated or at least strongly influenced by the construction of circular volcanoes with a flat, sometimes cratered, summit plateau. Such volcanoes are an important constituent of the upper oceanic crust in many ocean basins and so knowledge of their formation process and the rock types which constitute them is important for understanding the rheology and hydrology of the upper crust on a regional to ocean basin scale. Based on previous ship-mounted multibeam sonar cartography, deep-towed side-scan sonar and submersible investigations, a range of models for their formation has been proposed varying from construction above ring-dykes, with the central crater being either a product of this eruption style or of later caldera collapse, to successive eruptions of ever-smaller sheet flows ("pancake-stack"). Here we present the results of the first high resolution (<1m) mapping of such volcanoes using an autonomous underwater vehicle (AUV). The maps, combined with visual ground truthing, clearly show that the summit plateau was generated by lavas flowing laterally from a central lava lake. In the case of cratered volcanoes, this lake has drained (fully or partially) post-eruption, volcanoes with no crater (which are in the majority) appear to have retained the lake, which is now solidified. The solidified lake will form a massive, doleritic plug whose seismic, mechanical and hydrological characteristics will differ greatly (both at the axis itself and during crustal ageing) from those of pillow or sheet lava flows, with important consequences for bulk crustal properties both at the ridge axis and in older crust.

  17. Coupled ocean-atmosphere model system for studies of interannual-to-decadal climate variability over the North Pacific Basin and precipitation over the Southwestern United States

    SciTech Connect

    Lai, Chung-Chieng A.

    1997-10-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The ultimate objective of this research project is to make understanding and predicting regional climate easier. The long-term goals of this project are (1) to construct a coupled ocean-atmosphere model (COAM) system, (2) use it to explore the interannual-to-decadal climate variability over the North Pacific Basin, and (3) determine climate effects on the precipitation over the Southwestern United States. During this project life, three major tasks were completed: (1) Mesoscale ocean and atmospheric model; (2) global-coupled ocean and atmospheric modeling: completed the coupling of LANL POP global ocean model with NCAR CCM2+ global atmospheric model; and (3) global nested-grid ocean modeling: designed the boundary interface for the nested-grid ocean models.

  18. Aerosol transport over the Andes from the Amazon Basin to the remote Pacific Ocean: A multiyear CALIOP assessment

    NASA Astrophysics Data System (ADS)

    Bourgeois, Quentin; Ekman, Annica M. L.; Krejci, Radovan

    2015-08-01

    Six years (2007-2012) of data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite instrument were used to investigate the vertical distribution and transport of aerosols over the tropical South American continent and the southeast Pacific Ocean. The multiyear aerosol extinction assessment indicates that aerosols, mainly biomass burning particles emitted during the dry season in the Amazon Basin, are lifted in significant amounts over the Andes. The aerosols are mainly transported in the planetary boundary layer between the surface and 2 km altitude with an aerosol extinction maximum near the surface. During the transport toward the Andes, the aerosol extinction decreases at a rate of 0.02 km-1 per kilometer of altitude likely due to dilution and deposition processes. Aerosols reaching the top of the Andes, at altitudes typically between 4 and 5 km, are entrained into the free troposphere (FT) over the southeast Pacific Ocean. A comparison between CALIOP observations and ERA-Interim reanalysis data indicates that during their long-range transport over the tropical Pacific Ocean, these aerosols are slowly transported toward the marine boundary layer by the large-scale subsidence at a rate of 0.4 cm s-1. The observed vertical/horizontal transport ratio is 0.7-0.8 m km-1. Continental aerosols linked to transport over the Andes can be traced on average over 4000 km away from the continent indicating an aerosol residence time of 8-9 days in the FT over the Pacific Ocean. The FT aerosol optical depth (AOD) above the Pacific Ocean near South American coast accounts on average for 6% and 25% of the total AOD during the season of low and high biomass burning, respectively. This result shows that, during the biomass burning season, continental aerosols largely influence the AOD over the remote southeast Pacific Ocean. Overall, FT AOD decrease exponentially with the distance to continental sources at a rate of about 10% per degree of longitude over the

  19. 137Cs, 239+240Pu and 240Pu/239Pu atom ratios in the surface waters of the western North Pacific Ocean, eastern Indian Ocean and their adjacent seas.

    PubMed

    Yamada, Masatoshi; Zheng, Jian; Wang, Zhong-Liang

    2006-07-31

    Surface seawater samples were collected along the track of the R/V Hakuho-Maru cruise (KH-96-5) from Tokyo to the Southern Ocean. The (137)Cs activities were determined for the surface waters in the western North Pacific Ocean, the Sulu and Indonesian Seas, the eastern Indian Ocean, the Bay of Bengal, the Andaman Sea, and the South China Sea. The (137)Cs activities showed a wide variation with values ranging from 1.1 Bq m(-3) in the Antarctic Circumpolar Region of the Southern Ocean to 3 Bq m(-3) in the western North Pacific Ocean and the South China Sea. The latitudinal distributions of (137)Cs activity were not reflective of that of the integrated deposition density of atmospheric global fallout. The removal rates of (137)Cs from the surface waters were roughly estimated from the two data sets of Miyake et al. [Miyake Y, Saruhashi K, Sugimura Y, Kanazawa T, Hirose K. Contents of (137)Cs, plutonium and americium isotopes in the Southern Ocean waters. Pap Meteorol Geophys 1988;39:95-113] and this study to be 0.016 yr(-1) in the Sulu and Indonesian Seas, 0.033 yr(-1) in the Bay of Bengal and Andaman Sea, and 0.029 yr(-1) in the South China Sea. These values were much lower than that in the coastal surface water of the western Northwest Pacific Ocean. This was likely due to less horizontal and vertical mixing of water masses and less scavenging. (239+240)Pu activities and (240)Pu/(239)Pu atom ratios were also determined for the surface waters in the western North Pacific Ocean, the Sulu and Indonesian Seas and the South China Sea. The (240)Pu/(239)Pu atom ratios ranged from 0.199+/-0.026 to 0.248+/-0.027 on average, and were significantly higher than the global stratospheric fallout ratio of 0.18. The contributions of the North Pacific Proving Grounds close-in fallout Pu were estimated to be 20% for the western North Pacific Ocean, 39% for the Sulu and Indonesian Seas and 42% for the South China Sea by using the two end-member mixing model. The higher (240)Pu/(239)Pu

  20. Phylogeographic Structure in Penguin Ticks across an Ocean Basin Indicates Allopatric Divergence and Rare Trans-Oceanic Dispersal.

    PubMed

    Moon, Katherine L; Banks, Sam C; Fraser, Ceridwen I

    2015-01-01

    The association of ticks (Acarina) and seabirds provides an intriguing system for assessing the influence of long-distance dispersal on the evolution of parasitic species. Recent research has focused on host-parasite evolutionary relationships and dispersal capacity of ticks parasitising flighted seabirds. Evolutionary research on the ticks of non-flighted seabirds is, in contrast, scarce. We conducted the first phylogeographic investigation of a hard tick species (Ixodes eudyptidis) that parasitises the Little Blue Penguin (Eudyptula minor). Using one nuclear (28S) and two mitochondrial (COI and 16S) markers, we assessed genetic diversity among several populations in Australia and a single population on the South Island of New Zealand. Our results reveal two deeply divergent lineages, possibly representing different species: one comprising all New Zealand samples and some from Australia, and the other representing all other samples from Australian sites. No significant population differentiation was observed among any Australian sites from within each major clade, even those separated by hundreds of kilometres of coastline. In contrast, the New Zealand population was significantly different to all samples from Australia. Our phylogenetic results suggest that the New Zealand and Australian populations are effectively isolated from each other; although rare long-distance dispersal events must occur, these are insufficient to maintain trans-Tasman gene flow. Despite the evidence for limited dispersal of penguin ticks between Australia and New Zealand, we found no evidence to suggest that ticks are unable to disperse shorter distances at sea with their hosts, with no pattern of population differentiation found among Australian sites. Our results suggest that terrestrial seabird parasites may be quite capable of short-distance movements, but only sporadic longer-distance (trans-oceanic) dispersal. PMID:26083353

  1. Phylogeographic Structure in Penguin Ticks across an Ocean Basin Indicates Allopatric Divergence and Rare Trans-Oceanic Dispersal

    PubMed Central

    Moon, Katherine L.; Banks, Sam C.; Fraser, Ceridwen I.

    2015-01-01

    The association of ticks (Acarina) and seabirds provides an intriguing system for assessing the influence of long-distance dispersal on the evolution of parasitic species. Recent research has focused on host-parasite evolutionary relationships and dispersal capacity of ticks parasitising flighted seabirds. Evolutionary research on the ticks of non-flighted seabirds is, in contrast, scarce. We conducted the first phylogeographic investigation of a hard tick species (Ixodes eudyptidis) that parasitises the Little Blue Penguin (Eudyptula minor). Using one nuclear (28S) and two mitochondrial (COI and 16S) markers, we assessed genetic diversity among several populations in Australia and a single population on the South Island of New Zealand. Our results reveal two deeply divergent lineages, possibly representing different species: one comprising all New Zealand samples and some from Australia, and the other representing all other samples from Australian sites. No significant population differentiation was observed among any Australian sites from within each major clade, even those separated by hundreds of kilometres of coastline. In contrast, the New Zealand population was significantly different to all samples from Australia. Our phylogenetic results suggest that the New Zealand and Australian populations are effectively isolated from each other; although rare long-distance dispersal events must occur, these are insufficient to maintain trans-Tasman gene flow. Despite the evidence for limited dispersal of penguin ticks between Australia and New Zealand, we found no evidence to suggest that ticks are unable to disperse shorter distances at sea with their hosts, with no pattern of population differentiation found among Australian sites. Our results suggest that terrestrial seabird parasites may be quite capable of short-distance movements, but only sporadic longer-distance (trans-oceanic) dispersal. PMID:26083353

  2. Current-controlled, abyssal microtopography and sedimentation in Mozambique Basin, southwest Indian Ocean

    USGS Publications Warehouse

    Kolla, V.; Eittreim, S.; Sullivan, L.; Kostecki, J.A.; Burckle, L.H.

    1980-01-01

    The Antarctic Bottom Water (AABW) activity and the variations in the abundance and grain size of the terrigenous sediments, derived from Africa and Madagascar land masses, are reflected in different types of microtopography in the Mozambique Basin. In southerly areas, where the sediment supply is much less, the bottom-current activity has resulted in the presence of manganese nodules, a thin veneer of sediments, and the absence of sediment waves. Farther north, along the marginal areas of the basin where the fine-grained sediments from the Africa-Madagascar source have been supplied in abundance, wavy bedforms have been generated by AABW. Wavy bedforms do not exist even in the northerly areas if coarse-grained, turbidite sediments are present on the sea floor. The continuation of acoustic reflectors from the zone of turbidites in the central areas of the basin into the zone of sediment waves along the margins, and the lithology and structures in sediment cores from these zones suggest that the turbidity-current-fed, fine-grained sediments were deposited as wavy bedforms by AABW flow. Thus, sediment waves formed readily during Pleistocene times. The enrichment of quartz and displaced Antarctic diatoms, and the relatively low kaolinite/chlorite ratios in the sediments, the north-pointing current lineations on the sea floor, the lack of any perceptible sedimentary fill in the troughs of waves, and the dense nepheloid layer in the westerly areas of the Mozambique Basin, attest to the current-controlled sedimentation and generation of wavy bedforms during Holocene time also. The formation of sediment waves in the Mozambique Basin can be modeled after a fluvial antidune mechanism. This model envisages that internal waves, focussed on a benthic boundary layer cap, have been locked in phase with sediment waves in the presence of an 8-10 cm/sec current in the Mozambique Basin. A density contrast of 2??10-6 g/cm3 appears to exist at the tops of benthic boundary layers in the

  3. Coupling of regional atmospheric-ocean models for climate applications in the Mediterranean basin by using CORDEX-compliant simulations

    NASA Astrophysics Data System (ADS)

    Jimenez-Guerrero, Pedro; Montávez, Juan P.; Lorente-Plazas, Raquel

    2013-04-01

    Nowadays, most regional climate models (RCMs) are essentially composed of an atmospheric component coupled to a land surface scheme and driven over ocean areas by prescribed sea surface temperature (SST). Although such a RCM can be sufficient for many applications, there are cases (like in the Mediterranean basin) in which fine scale feedbacks associated with air-sea interactions can substantially influence the spatial and temporal structure of regional climates. Therefore, in this work we present the first testing phase of the application of a coupled atmospheric-ocean regional climate model (AORCM) for the Mediterranean basin under the framework of the CORWES project. CORWES is a Spanish consortium of research groups using the Weather Research and Forecasting (WRF) model to contribute to the Coordinated Regional Climate Downscaling Experiment (CORDEX). We use WRF and ROMS models as the atmospheric and oceanic component, respectively. Coupling between WRF and ROMS is achieved in the following way: on a prescribed interval of 2 h, WRF sends wind stress, surface heat and water fluxes to ROMS time-averaged over the previous two hours. One hour later, and also with a prescribed interval of 2 h, ROMS sends time-averaged SST to WRF. Here, we mainly focus on the performance of the coupled system in reproducing the ocean surface temperatures. To separate effects of the coupling on SST, additional uncoupled atmospheric simulations are also done in parallel. The case study covers the years 2001-2005 and is described below. The resolution of the domain used is 12 km. The number of vertical levels is 30 for WRF. The ROMS domain, with 32 vertical levels, is slightly smaller than WRF innermost nest and has a higher resolution of 4 km. The lateral atmospheric boundary conditions for WRF are taken from ERA-Interim reanalysis. The lateral oceanic boundary conditions for ROMS come from the downscaling of the Simple Ocean Data Assimilation analysis (SODA) by an uncoupled nested ROMS

  4. Water-level data for the Albuquerque Basin and adjacent areas, central New Mexico, period of record through September 30, 2014

    USGS Publications Warehouse

    Beman, Joseph E.

    2015-01-01

    An initial network of wells was established by the U.S. Geological Survey (USGS) in cooperation with the City of Albuquerque from April 1982 through September 1983 to monitor changes in groundwater levels throughout the basin. This network consisted of 6 wells with analog-to-digital recorders and 27 wells where water levels were measured monthly in 1983. The network currently (2014) consists of 125 wells and piezometers. (A piezometer is a specialized well open to a specific depth in the aquifer, often of small diameter and nested with other piezometers open to different depths.) The USGS, in cooperation with the Albuquerque Bernalillo County Water Utility Authority, currently (2014) measures and reports water levels from the 125 wells and piezometers in the network; this report presents water-level data collected by USGS personnel at those 125 sites through water year 2014 (October 1, 2013, to September 30, 2014).

  5. Patterns of deep-water coral diversity in the Caribbean Basin and adjacent southern waters: an approach based on records from the R/V Pillsbury expeditions.

    PubMed

    Hernández-Ávila, Iván

    2014-01-01

    The diversity of deep-water corals in the Caribbean Sea was studied using records from oceanographic expeditions performed by the R/V Pillsbury. Sampled stations were sorted according to broad depth ranges and ecoregions and were analyzed in terms of species accumulation curves, variance in the species composition and contributions to alpha, beta and gamma diversity. According to the analysis of species accumulation curves using the Chao2 estimator, more diversity occurs on the continental slope (200-2000 m depth) than on the upper continental shelf (60-200 m depth). In addition to the effect of depth sampling, differences in species composition related to depth ranges were detected. However, the differences between ecoregions are dependent on depth ranges, there were fewer differences among ecoregions on the continental slope than on the upper continental shelf. Indicator species for distinctness of ecoregions were, in general, Alcyonaria and Antipatharia for the upper continental shelf, but also the scleractinians Madracis myriabilis and Cladocora debilis. In the continental slope, the alcyonarian Placogorgia and the scleractinians Stephanocyathus and Fungiacyathus were important for the distinction of ecoregions. Beta diversity was the most important component of gamma diversity in the Caribbean Basin. The contribution of ecoregions to alpha, beta and gamma diversity differed with depth range. On the upper continental shelf, the Southern Caribbean ecoregion contributed substantially to all components of diversity. In contrast, the northern ecoregions contributed substantially to the diversity of the Continental Slope. Strategies for the conservation of deep-water coral diversity in the Caribbean Basin must consider the variation between ecoregions and depth ranges. PMID:24671156

  6. Patterns of Deep-Water Coral Diversity in the Caribbean Basin and Adjacent Southern Waters: An Approach based on Records from the R/V Pillsbury Expeditions

    PubMed Central

    Hernández-Ávila, Iván

    2014-01-01

    The diversity of deep-water corals in the Caribbean Sea was studied using records from oceanographic expeditions performed by the R/V Pillsbury. Sampled stations were sorted according to broad depth ranges and ecoregions and were analyzed in terms of species accumulation curves, variance in the species composition and contributions to alpha, beta and gamma diversity. According to the analysis of species accumulation curves using the Chao2 estimator, more diversity occurs on the continental slope (200–2000 m depth) than on the upper continental shelf (60–200 m depth). In addition to the effect of depth sampling, differences in species composition related to depth ranges were detected. However, the differences between ecoregions are dependent on depth ranges, there were fewer differences among ecoregions on the continental slope than on the upper continental shelf. Indicator species for distinctness of ecoregions were, in general, Alcyonaria and Antipatharia for the upper continental shelf, but also the scleractinians Madracis myriabilis and Cladocora debilis. In the continental slope, the alcyonarian Placogorgia and the scleractinians Stephanocyathus and Fungiacyathus were important for the distinction of ecoregions. Beta diversity was the most important component of gamma diversity in the Caribbean Basin. The contribution of ecoregions to alpha, beta and gamma diversity differed with depth range. On the upper continental shelf, the Southern Caribbean ecoregion contributed substantially to all components of diversity. In contrast, the northern ecoregions contributed substantially to the diversity of the Continental Slope. Strategies for the conservation of deep-water coral diversity in the Caribbean Basin must consider the variation between ecoregions and depth ranges. PMID:24671156

  7. Geology, Geochemistry and Re-Os systematics of manganese deposits from the Santa Rosalía Basin and adjacent areas in Baja California Sur, México

    NASA Astrophysics Data System (ADS)

    Del Rio Salas, R.; Ruiz, J.; Ochoa-Landín, L.; Noriega, O.; Barra, F.; Meza-Figueroa, D.; Paz-Moreno, F.

    2008-06-01

    The manganese ores in the Santa Rosalía region, western Mexico, are mainly stratiform horizons or mantos, constrained to the initial stages of sedimentary cycles of the Miocene Boléo Formation. The manganese mineralization is generally restricted to isolated paleo-basins and related to NW-SE faults formed during the early stages of the opening of the Gulf of California. Jasper, Fe, and Mn oxides associated to the NW-SE structures may represent feeder zones for the mineralized system. The manganese oxide minerals include pyrolusite, cryptomelane, todorokite, hollandite, jacobsite, and pyrochroite. Trace elements in the manganese ores indicate a hydrothermal origin for the deposits of the Santa Rosalía area. Rare earth elements (REE) patterns obtained for manganese minerals from the Lucifer and El Gavilán deposits also support a hydrothermal origin, whereas the middle REE enrichment observed in samples from the Boléo district indicates mixing between hydrothermal and hydrogenous sources. Osmium and rhenium concentrations of the manganese minerals range between 33-173 ppt and 0.14-89 ppb, respectively. The initial 187Os/188Os ratios in the manganese oxides from Lucifer and the Boléo district range between 0.43 to 0.51 and 0.70 to 0.74, respectively. These ratios are different from seawater at 7 Ma (0.84-0.89), which suggests important contributions of osmium from underlying rocks such as the Miocene volcanic rocks and the Cretaceous quartz-monzonite basement. Field evidence, manganese oxide mineralogy coupled with major and trace element geochemistry and Re-Os systematics support a hydrothermal origin for the manganese deposits from the Santa Rosalía region. The ore deposition style indicates an exhalative-intraformational environment restricted to isolated basins in a diagenetic stage related to the initial evolution of the Gulf of California.

  8. Geochemical characteristics of basaltic rocks from the Nain ophiolite (Central Iran); constraints on mantle wedge source evolution in an oceanic back arc basin and a geodynamical model

    NASA Astrophysics Data System (ADS)

    Ghazi, Javad Mehdipour; Moazzen, Mohssen; Rahgoshay, Mohammad; Shafaii Moghadam, Hadi

    2012-10-01

    The Nain ophiolitic complex is situated at the north west of the Central Iran Micro-continent (CIM) block. The basaltic rocks of this complex consist of both mantle and crustal suites and include pegmatitic and isotropic gabbros, gabbroic-dibasic dykes, dyke swarm complex and pillow lavas. The chondrite-normalized rare earth element (REE) patterns of most of these rocks show LREE depletion and the primary mantle-normalized incompatible elements indicate depletion in HFSEs (Nb, Ta) and enrichment in LILEs. The rocks show characters of island arc tholeiite/mid-ocean ridge basalt magma types. Whole rock chemistry of the rocks shows that they are originated in an oceanic back arc basin, and subsequently have been enriched by slab-derived fluids. Abundances of HFSE and HREE in most of the basaltic samples, suggest a slow subduction rate. Opening of Nain-Baft Ocean, which was probably a marginal basin, occurred during Lower Jurassic. After generation of an inter-oceanic island arc in the Nain-Baft Ocean during the Late Jurassic, a second rifting phase started within the inter-ocean island arc during Late Cretaceous (Cenomanian-Senonian). The inter-ocean island arc was developed and formed an oceanic back arc basin, the site of generation of most of the Nain ophiolitic rocks. The Nain-Baft Ocean finally closed in Maastrichtian. According to the new tectono-magmatic evolution model proposed here, the arc volcanic-like magmas were produced at the early stage (producing gabbros, gabbroic-diabasic dykes and dyke swarm complex) and then MORB-like basalts (producing pillow lavas) were generated at the later stage of evolution of the Nain ophiolitic complex.

  9. Triple seismic source, double research ship, single ambitious goal: integrated imaging of young oceanic crust in the Panama Basin

    NASA Astrophysics Data System (ADS)

    Wilson, Dean; Peirce, Christine; Hobbs, Richard; Gregory, Emma

    2016-04-01

    Understanding geothermal heat and mass fluxes through the seafloor is fundamental to the study of the Earth's energy budget. Using geophysical, geological and physical oceanography data we are exploring the interaction between the young oceanic crust and the ocean in the Panama Basin. We acquired a unique geophysical dataset that will allow us to build a comprehensive model of young oceanic crust from the Costa Rica Ridge axis to ODP borehole 504B. Data were collected over two 35 x 35 km2 3D grid areas, one each at the ridge axis and the borehole, and along three 330 km long 2D profiles orientated in the spreading direction, connecting the two grids. In addition to the 4.5 km long multichannel streamer and 75 ocean-bottom seismographs (OBS), we also deployed 12 magnetotelluric (MT) stations and collected underway swath bathymetry, gravity and magnetic data. For the long 2D profiles we used two research vessels operating synchronously. The RRS James Cook towed a high frequency GI-gun array (120 Hz) to image the sediments, and a medium frequency Bolt-gun array (50 Hz) for shallow-to-mid-crustal imaging. The R/V Sonne followed the Cook, 9 km astern and towed a third seismic source; a low frequency, large volume G-gun array (30 Hz) for whole crustal and upper mantle imaging at large offsets. Two bespoke vertical hydrophone arrays recorded real far field signatures that have enabled us to develop inverse source filters and match filters. Here we present the seismic reflection image, forward and inverse velocity-depth models and a density model along the primary 330 km north-south profile, from ridge axis to 6 Ma crust. By incorporating wide-angle streamer data from our two-ship, synthetic aperture acquisition together with traditional wide-angle OBS data we are able to constrain the structure of the upper oceanic crust. The results show a long-wavelength trend of increasing seismic velocity and density with age, and a correlation between velocity structure and basement

  10. Synchronous oceanic spreading and continental rifting in West Antarctica

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  11. Onset and demise of Cretaceous oceanic anoxic events: The coupling of surface and bottom oceanic processes in two pelagic basins of the western Tethys

    NASA Astrophysics Data System (ADS)

    Gambacorta, G.; Bersezio, R.; Weissert, H.; Erba, E.

    2016-06-01

    The upper Albian-lower Turonian pelagic successions of the Tethys record processes acting during the onset, core, and recovery from perturbed conditions across oceanic anoxic event (OAE) 1d, OAE 2, and the mid-Cenomanian event I (MCE I) relative to intervening intervals. Five sections from Umbria-Marche and Belluno Basins (Italy) were analyzed at high resolution to assess processes in surface and deep waters. Recurrent facies stacking patterns (SP) and their associations record periods of bottom current activity coupled with surface changes in trophic level. Climate changes appear to have been influential on deep circulation dynamics. Under greenhouse conditions, vigorous bottom currents were arguably induced by warm and dense saline deep waters originated on tropical shelves in the Tethys and/or proto-Atlantic Ocean. Tractive facies postdating intermittent anoxia during OAE 1d and in the interval bracketed by MCE I and OAE 2 are indicative of feeble bottom currents, though capable of disrupting stratification and replenish deep water with oxygen. The major warming at the onset of OAE 2 might have enhanced the formation of warm salty waters, possibly producing local hiatuses at the base of the Bonarelli Level and winnowing at the seafloor. Hiatuses detected at the top of the Bonarelli Level possibly resulted from most effective bottom currents during the early Turonian thermal maximum. Times of minimal sediment displacement correlate with cooler climatic conditions and testify a different mechanism of deep water formation, as further suggested by a color change to reddish lithologies of the post-OAE 1d and post-OAE 2 intervals.

  12. Megafaunal community structure of Andaman seamounts including the Back-arc Basin--a quantitative exploration from the Indian Ocean.

    PubMed

    Sautya, Sabyasachi; Ingole, Baban; Ray, Durbar; Stöhr, Sabine; Samudrala, Kiranmai; Raju, K A Kamesh; Mudholkar, Abhay

    2011-01-01

    Species rich benthic communities have been reported from some seamounts, predominantly from the Atlantic and Pacific Oceans, but the fauna and habitats on Indian Ocean seamounts are still poorly known. This study focuses on two seamounts, a submarine volcano (cratered seamount--CSM) and a non-volcano (SM2) in the Andaman Back-arc Basin (ABB), and the basin itself. The main purpose was to explore and generate regional biodiversity data from summit and flank (upper slope) of the Andaman seamounts for comparison with other seamounts worldwide. We also investigated how substratum types affect the megafaunal community structure along the ABB. Underwater video recordings from TeleVision guided Gripper (TVG) lowerings were used to describe the benthic community structure along the ABB and both seamounts. We found 13 varieties of substratum in the study area. The CSM has hard substratum, such as boulders and cobbles, whereas the SM2 was dominated by cobbles and fine sediment. The highest abundance of megabenthic communities was recorded on the flank of the CSM. Species richness and diversity were higher at the flank of the CSM than other are of ABB. Non-metric multi-dimensional scaling (nMDS) analysis of substratum types showed 50% similarity between the flanks of both seamounts, because both sites have a component of cobbles mixed with fine sediments in their substratum. Further, nMDS of faunal abundance revealed two groups, each restricted to one of the seamounts, suggesting faunal distinctness between them. The sessile fauna corals and poriferans showed a significant positive relation with cobbles and fine sediments substratum, while the mobile categories echinoderms and arthropods showed a significant positive relation with fine sediments only. PMID:21297959

  13. Megafaunal Community Structure of Andaman Seamounts Including the Back-Arc Basin – A Quantitative Exploration from the Indian Ocean

    PubMed Central

    Sautya, Sabyasachi; Ingole, Baban; Ray, Durbar; Stöhr, Sabine; Samudrala, Kiranmai; Raju, K. A. Kamesh; Mudholkar, Abhay

    2011-01-01

    Species rich benthic communities have been reported from some seamounts, predominantly from the Atlantic and Pacific Oceans, but the fauna and habitats on Indian Ocean seamounts are still poorly known. This study focuses on two seamounts, a submarine volcano (cratered seamount – CSM) and a non-volcano (SM2) in the Andaman Back–arc Basin (ABB), and the basin itself. The main purpose was to explore and generate regional biodiversity data from summit and flank (upper slope) of the Andaman seamounts for comparison with other seamounts worldwide. We also investigated how substratum types affect the megafaunal community structure along the ABB. Underwater video recordings from TeleVision guided Gripper (TVG) lowerings were used to describe the benthic community structure along the ABB and both seamounts. We found 13 varieties of substratum in the study area. The CSM has hard substratum, such as boulders and cobbles, whereas the SM2 was dominated by cobbles and fine sediment. The highest abundance of megabenthic communities was recorded on the flank of the CSM. Species richness and diversity were higher at the flank of the CSM than other are of ABB. Non-metric multi-dimensional scaling (nMDS) analysis of substratum types showed 50% similarity between the flanks of both seamounts, because both sites have a component of cobbles mixed with fine sediments in their substratum. Further, nMDS of faunal abundance revealed two groups, each restricted to one of the seamounts, suggesting faunal distinctness between them. The sessile fauna corals and poriferans showed a significant positive relation with cobbles and fine sediments substratum, while the mobile categories echinoderms and arthropods showed a significant positive relation with fine sediments only. PMID:21297959

  14. Monthly satellite-derived phytoplankton pigment distribution for the North Atlantic Ocean basin

    NASA Astrophysics Data System (ADS)

    Esaias, W. E.; Feldman, G. C.; McClain, C. R.; Elrod, J. A.

    Surface phytoplankton distributions have been derived from Coastal Zone Color Scanner (CZCS) with an accuracy of from 35% in open oceans to within a factor of 2 generally [Gordon et al., 1983; Brown et al., 1985]. The remotely sensed pigment fields have been used to quantify spatial and temporal variability of plankton biomass on scales of days [McClain et al., 1984, 1986; Walsh et al., 1986] to years [Feldman, 1986; Abbott and Zion, 1985; Banse and McClain, 1986; Barale et al., 1986; D. K. Clark, National Oceanic and Atmospheric Administration/National Environmental Satellite Data and Information Service (NOAA/NESDIS), Suitland, Md.; personal communication]. Efforts to relate these fields to areal primary productivity [Eppley, 1985; Piatt, 1986] are very promising. These findings form the basis of current plans to investigate the carbon flux within the oceans on a global scale over the next decade (see the article “The Global Ocean Flux Study (GOFS): Status of the U.S. GOFS Program” by P. Brewer et al., this issue), as well as a multitude of regional process-oriented field studies.

  15. The Taili-Yiwulüshan metamorphic core complex corridor: Diachronous exhumation and relationships to the adjacent basins based on new 40Ar/39Ar and (U-Th-Sm)/He mineral ages

    NASA Astrophysics Data System (ADS)

    Liang, Chenyue; Neubauer, Franz; Liu, Yongjiang; Genser, Johann; Dunkl, István; Heberer, Bianca; Jin, Wei; Zeng, Zuoxun; Li, Weimin; Wen, Quanbo; Li, Jing

    2015-04-01

    The Xingcheng-Taili ductile shear zone (western Liaoning Province in China) formed during latest Jurassic to Early Cretaceous crustal extension of the eastern North China craton, and exhumed low to medium metamorphic grade Archean, Upper Triassic and Upper Jurassic granitic rocks. The Mesozoic Yiwulüshan metamorphic core complex (Yiwulüshan MCC) is dominated by a NNE-SSW elongated dome with a left-lateral shear zone, which is located in the northeastern part of Xingcheng-Taili ductile shear zone, and combine as Taili-Yiwulüshan metamorphic core complex corridor. To the east, it is bounded by the NNE-trending Cretaceous to Eocene Liaohe basin (the northern extension of the Bohai Bay basin), and to the west by the Cretaceous-aged Fuxin-Yixian basin, which could potentially interpreted as supra-detachment basins. Here, we present results from a multi-method thermochronological study and coupled with structural investigations and sections of adjacent supra-detachment basins, which constrain the timing of regional deformation as well as the cooling history and exhumation processes of the low- to middle-grade metamorphic complex in the Taili-Yiwulüshan MCC corridor, in order to understand the mode of lithospheric scale reactivation, extension and thinning of the North China craton. The new40Ar/39Ar muscovite, biotite, K-feldspar and (U-Th)/He apatite ages from granitic rocks help constrain the thermal evolution during its exhumation. The thermochronologic studies have shown at least three stages of exhumation and cooling from late Jurassic to Eocene in Xingcheng-Taili shear zone should be distinguished, e.g., ~ 150-130 Ma, 130-115 Ma and 115-52 Ma, respectively. Diachronous onset and subsequent parallel cooling and exhumation characterize the early thermal history. The Yiwulüshan MCC has a similar exhumation history from 135 to 97 Ma with a similar cooling history. The development of Taili-Yiwulüshan MCC corridor is associated with synkinematic emplacement

  16. Stratigraphy, sedimentology and petrology of neogene rocks in the Deschutes Basin, Central Oregon: a record of continental-margin volcanism and its influence on fluvial sedimentation in an arc-adjacent basin

    SciTech Connect

    Smith, G.A.

    1986-07-01

    Neogene rocks of the Deschutes basin include the middle Miocene Columbia River Basalt Group and Simtustus Formation, and late Miocene to early Pliocene Deschutes Formation. Assignment of Prineville chemical-type flows to the Grande Ronde Basalt of the Columbia River Basalt Group is based on correlation of these lavas from their type area through the Deschutes basin and onto the Columbia Plateau, where they have been previously mapped as Grande Ronde Basalt. Simtustus Formation is a newly defined unit intercalated with and conformable upon these basalts, and is unconformably overlain by Deschutes Formation. Burial of mature topography by middle Miocene basalts raised local base levels and initiated aggradation by low-gradient streams within the basin represented by the tuffaceous sandstones and mudstones of the Simtustus Formation. These sediments are enriched in pyroclastic constituents relative to contemporaneous Western Cascades volcanics, reflecting preferential incorporation of easily eroded and more widespread pyroclastic debris in distal sedimentary sequences compared to epiclastic contributions from lavas. The abundance of basalts, combined with the paucity of hydrous minerals and FeO and TiO/sub 2/ enrichment in intermediate lavas, characterizes early High Cascade volcanics as atypical for convergent-margin arcs. These petrologic characteristics are consistent with high-level fractionation in an extensional regime. Extension culminated in the development of an intra-arc graben, which ended Deschutes Formation deposition by structurally isolating the basin from the High Cascade source area.

  17. Compression of oceanic lithosphere - An analysis of intraplate deformation in the Central Indian Basin

    NASA Technical Reports Server (NTRS)

    Zuber, Maria T.

    1987-01-01

    The development of intraplate structure in the Central Indian Basin is examined using models in which deformation is due to flexural buckling and the hydrodynamic growth of instabilities. Comparison of the models reveal that in a strong viscous lithosphere, deformation of the layer occurs by flexural folding at a wavelength which corresponds to the flexural buckling theory; in a lithosphere of intermediate strength, the layer deforms by folding characterized by thickening which localizes beneath topographic heights; and in a relatively weak lithosphere, the layer incurs an even greater amount of localized thickening and deforms in the symmetric or pinch-and-swell mode by inverse boudinage. It is noted that the models in which the layer folds either flexurally or with periodic thickening correspond with observed depth distribution of seismicity in the Central Indian Basin and with experimental rock rheological data.

  18. A mid-Permian chert event: widespread deposition of biogenic siliceous sediments in coastal, island arc and oceanic basins

    USGS Publications Warehouse

    Murchey, B.L.; Jones, D.L.

    1992-01-01

    Radiolarian and conodont of Permian siliceous rocks from twenty-three areas in teh the circum-Pacific and Mediterranean regions reveal a widespread Permian Chert Event during the middle Leonardian to Wordian. Radiolarian- and (or) sponge spicule-rich siliceous sediments accumulated beneath high productivity zones in coastal, island arc and oceanic basins. Most of these deposits now crop out in fault-bounded accreted terranes. Biogenic siliceous sediments did not accumulate in terranes lying beneath infertile waters including the marine sequences in terranes of northern and central Alaska. The Permian Chert Event is coeval with major phosphorite deposition along the western margin of Pangea (Phosphoria Formation and related deposits). A well-known analogue for this event is middle Miocene deposition of biogenic siliceous sediments beneath high productivity zones in many parts of the Pacific and concurrent deposition of phosphatic as well as siliceous sediments in basins along the coast of California. Interrelated factors associated with both the Miocene and Permian depositional events include plate reorientations, small sea-level rises and cool polar waters. ?? 1992.

  19. On estimating the basin-scale ocean circulation from satellite altimetry. Part 1: Straightforward spherical harmonic expansion

    NASA Technical Reports Server (NTRS)

    Tai, Chang-Kou

    1988-01-01

    Direct estimation of the absolute dynamic topography from satellite altimetry has been confined to the largest scales (basically the basin-scale) owing to the fact that the signal-to-noise ratio is more unfavorable everywhere else. But even for the largest scales, the results are contaminated by the orbit error and geoid uncertainties. Recently a more accurate Earth gravity model (GEM-T1) became available, providing the opportunity to examine the whole question of direct estimation under a more critical limelight. It is found that our knowledge of the Earth's gravity field has indeed improved a great deal. However, it is not yet possible to claim definitively that our knowledge of the ocean circulation has improved through direct estimation. Yet, the improvement in the gravity model has come to the point that it is no longer possible to attribute the discrepancy at the basin scales between altimetric and hydrographic results as mostly due to geoid uncertainties. A substantial part of the difference must be due to other factors; i.e., the orbit error, or the uncertainty of the hydrographically derived dynamic topography.

  20. Promiscuous Speciation with Gene Flow in Silverside Fish Genus Odontesthes (Atheriniformes, Atherinopsidae) from South Western Atlantic Ocean Basins

    PubMed Central

    García, Graciela; Ríos, Néstor; Gutiérrez, Verónica; Varela, Jorge Guerra; Bouza Fernández, Carmen; Pardo, Belén Gómez; Portela, Paulino Martínez

    2014-01-01

    The present paper integrates phylogenetic and population genetics analyses based on mitochondrial and nuclear molecular markers in silversides, genus Odontesthes, from a non-sampled area in the SW Atlantic Ocean to address species discrimination and to define Managements Units for sustainable conservation. All phylogenetic analyses based on the COI mitochondrial gene were consistent to support the monophyly of the genus Odontesthes and to include O. argentinensis, O. perugiae-humensis and some O. bonariensis haplotypes in a basal polytomy conforming a major derivative clade. Microsatellites data revealed somewhat higher genetic variability values in the O. argentinensis-perugia populations than in O. bonariensis and O. perugia-humensis taxa. Contrasting population genetics structuring emerged from mitochondrial and microsatellites analyses in these taxa. Whereas mitochondrial data supported two major groups (O. argentinensis-perugia-humensis vs. O. bonariensis-perugiae-humensis populations), microsatellite data detected three major genetic entities represented by O. bonariensis, O. perugiae-humensis and an admixture of populations belonging to O. argentinensis-perugiae respectively. Therefore, the star COI polytomy in the tree topology involving these taxa could be interpreted by several hypothetic scenarios such as the existence of shared ancestral polymorphisms, incomplete lineage sorting in a radiating speciation process and/or reticulation events. Present findings support that promiscuous and recent contact between incipient species sharing asymmetric gene flow exchanges, blurs taxa boundaries yielding complicated taxonomy and Management Units delimitation in silverside genus Odontesthes from SW Atlantic Ocean basins. PMID:25126842

  1. Late Aptian (Cretaceous) paleoceanography of the South Atlantic Ocean inferred from dinocyst communities of the Sergipe Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Carvalho, Marcelo de A.; Bengtson, Peter; Lana, Cecília C.

    2016-01-01

    The late Aptian (Early Cretaceous) is a crucial time interval for understanding the paleoceanographic changes in the Southern Hemisphere. Oceanographic changes in the emerging South Atlantic Ocean during this interval are reflected in the stratigraphic distribution of dinoflagellate communities recorded in the Muribeca and Riachuelo formations of the Sergipe Basin in northeastern Brazil. The Subtilisphaera community, in the lower and middle parts of the section, appears to be related to the Subtilisphaera Ecozone and suggests the onset of Tethyan influence in the central South Atlantic, in a restricted to inner-neritic environment. The succeeding Spiniferites community, in the middle part of the section, represents the first significant transgression, probably of eustatic origin. The Cyclonephelium-Exochosphaeridium community, in the upper part of the section, appears to be related to an oceanic event characterized by intermittent dysoxic-anoxic conditions. The uppermost part of the section is dominated by the Spiniferites community, related to a progressive regional transgression and culminating in an open-marine, fully Tethyan environment in the central part of the widening South Atlantic.

  2. Multi-decadal increases in dissolved organic carbon and alkalinity flux from the Mackenzie drainage basin to the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Tank, Suzanne E.; Striegl, Robert G.; McClelland, James W.; Kokelj, Steven V.

    2016-05-01

    Riverine exports of organic and inorganic carbon (OC, IC) to oceans are intricately linked to processes occurring on land. Across high latitudes, thawing permafrost, alteration of hydrologic flow paths, and changes in vegetation may all affect this flux, with subsequent implications for regional and global carbon (C) budgets. Using a unique, multi-decadal dataset of continuous discharge coupled with water chemistry measurements for the Mackenzie River, we show major increases in dissolved OC (DOC) and IC (as alkalinity) fluxes since the early 1970s, for a watershed that covers 1.8 M km2 of northwestern Canada, and provides substantial inputs of freshwater and biogeochemical constituents to the Arctic Ocean. Over a 39-year period of record, DOC flux at the Mackenzie mouth increased by 39.3% (44.5 ± 22.6 Gmol), while alkalinity flux increased by 12.5% (61.5 ± 60.1 Gmol). Isotopic analyses and substantial increases in sulfate flux indicate that increases in alkalinity are driven by accelerating sulfide oxidation, a process that liberates IC from rock and soils in the absence of CO2 consumption. Seasonal and sub-catchment trends suggest that permafrost thaw plays an important role in the observed increases in DOC and alkalinity: sub-catchment increases for all constituents are confined to northern, permafrost-affected regions, while observed increases in autumn to winter are consistent with documented landscape-scale changes that have resulted from changing thaw dynamics. This increase in DOC and sulfide-derived alkalinity represents a substantial intensification of land-to-ocean C mobilization, at a level that is significant within the regional C budget. The change we observe, for example, is similar to current and projected future rates of CO2 consumption by weathering in the Mackenzie basin.

  3. Microbial community transcriptional networks are conserved in three domains at ocean basin scales

    PubMed Central

    Aylward, Frank O.; Eppley, John M.; Chavez, Francisco P.; Scholin, Christopher A.; DeLong, Edward F.

    2015-01-01

    Planktonic microbial communities in the ocean are typically dominated by several cosmopolitan clades of Bacteria, Archaea, and Eukarya characterized by their ribosomal RNA gene phylogenies and genomic features. Although the environments these communities inhabit range from coastal to open ocean waters, how the biological dynamics vary between such disparate habitats is not well known. To gain insight into the differential activities of microbial populations inhabiting different oceanic provinces we compared the daily metatranscriptome profiles of related microbial populations inhabiting surface waters of both a coastal California upwelling region (CC) as well as the oligotrophic North Pacific Subtropical Gyre (NPSG). Transcriptional networks revealed that the dominant photoautotrophic microbes in each environment (Ostreococcus in CC, Prochlorococcus in NPSG) were central determinants of overall community transcriptome dynamics. Furthermore, heterotrophic bacterial clades common to both ecosystems (SAR11, SAR116, SAR86, SAR406, and Roseobacter) displayed conserved, genome-wide inter- and intrataxon transcriptional patterns and diel cycles. Populations of SAR11 and SAR86 clades in particular exhibited tightly coordinated transcriptional patterns in both coastal and pelagic ecosystems, suggesting that specific biological interactions between these groups are widespread in nature. Our results identify common diurnally oscillating behaviors among diverse planktonic microbial species regardless of habitat, suggesting that highly conserved temporally phased biotic interactions are ubiquitous among planktonic microbial communities worldwide. PMID:25775583

  4. Microbial community transcriptional networks are conserved in three domains at ocean basin scales

    NASA Astrophysics Data System (ADS)

    Aylward, Frank O.; Eppley, John M.; Smith, Jason M.; Chavez, Francisco P.; Scholin, Christopher A.; DeLong, Edward F.

    2015-04-01

    Planktonic microbial communities in the ocean are typically dominated by several cosmopolitan clades of Bacteria, Archaea, and Eukarya characterized by their ribosomal RNA gene phylogenies and genomic features. Although the environments these communities inhabit range from coastal to open ocean waters, how the biological dynamics vary between such disparate habitats is not well known. To gain insight into the differential activities of microbial populations inhabiting different oceanic provinces we compared the daily metatranscriptome profiles of related microbial populations inhabiting surface waters of both a coastal California upwelling region (CC) as well as the oligotrophic North Pacific Subtropical Gyre (NPSG). Transcriptional networks revealed that the dominant photoautotrophic microbes in each environment (Ostreococcus in CC, Prochlorococcus in NPSG) were central determinants of overall community transcriptome dynamics. Furthermore, heterotrophic bacterial clades common to both ecosystems (SAR11, SAR116, SAR86, SAR406, and Roseobacter) displayed conserved, genome-wide inter- and intrataxon transcriptional patterns and diel cycles. Populations of SAR11 and SAR86 clades in particular exhibited tightly coordinated transcriptional patterns in both coastal and pelagic ecosystems, suggesting that specific biological interactions between these groups are widespread in nature. Our results identify common diurnally oscillating behaviors among diverse planktonic microbial species regardless of habitat, suggesting that highly conserved temporally phased biotic interactions are ubiquitous among planktonic microbial communities worldwide.

  5. Sonobuoy-based velocity functions for sediment thickness calculation in the deep Canada Basin of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Lebedeva-Ivanova, N. N.; Hart, P. E.; Chian, D.; Shimeld, J.; Lizarralde, D.; Hutchinson, D. R.; Mosher, D. C.

    2012-12-01

    The deep Canada Basin, which occupies much of the western (Amerasian) Arctic Ocean, is one of the most unexplored and difficult areas on Earth for marine seismic acquisition due to permanent sea ice cover. It extends northward from the Alaskan and Canadian margins for ~500 km and is characterized by a remarkably flat sea floor at 3.6-3.8 km below sea level (bsl) and covers ~500,000 km^2. A set of 143 sonobuoy records were collected during 2007-2010 over the Canada Basin by US-Canada collaborative expeditions. The sonobuoys were deployed along short streamer multi-channel seismic (MCS) lines for estimating seismic velocities in the sediments. A spatial coverage of sonobuoys at every ~80 km on MCS lines provides data for robust average empirical time-depth conversion functions.Sediments are nearly sub-horizontal and sub-parallel, mostly undisturbed with maximum two-way travel time (TWTT)thicknesses of ~5 s, but not greater than ~2.5-3.0 s TWTT closer to the Alpha Ridge and the Chukchi Borderland. Semblance velocity analysis has been applied to the sonobuoy records to determine sediment thickness and depth using the Dix equation. Assuming flat-lying sediments, the normal-moveout (NMO) velocity is approximately equal to the root-mean-square (RMS) average velocity from the sea surface to the reflection horizon. A dip of 5 degrees effects velocity less than 0.5%. Semblance velocity analyses were completed for 128 of 143 sonobuoy records in the deep Canada Basin; 25 records were excluded from later analysis due to bad quality or location on the slope. Results were also converted to interval velocities and depths.The RMS velocities were consistently picked from clear high-coherency events to yield only increasing interval velocities.Picking stopped at or above the bright reflection interpreted as basement on the MCS. Velocities were not picked on dipping reflections surfaces, along the margins where the seafloor was dipping, nor for sedimentary horizons characterized by

  6. Diagenesis in Okavango fan and adjacent dune deposits with implications for the record of palaeo-environmental change in Makgadikgadi Okavango Zambezi basin, northern Botswana

    NASA Astrophysics Data System (ADS)

    Ringrose, Susan; Huntsman-Mapila, Philippa; Downey, William; Coetzee, Stephan; Fey, Martin; Vanderpost, Cornelis; Vink, Bernard; Kemosidile, Thebe; Kolokose, Dikitso

    2008-11-01

    This work considers the spatial distribution and ages of western MOZ basin siliclastic sediments prior to providing insights into the diagenesis of degraded dune and alluvial fan sands. Previously published and new TL/OSL ages imply that extensive over-washing of dune sands took place at least 100 ka ago while ages on Okavango floodplains imply that the fan was formed ca. 40 ka and has since undergone periods of higher and lower flood regimes. Sediment analyses indicate that both dune and fan sands contain a diagenetic matrix of clay-enhanced amorphous silica (CEAS) which bonds weakly formed aggregates. The time of formation of diagenetic matrix products is inconclusive but may have been accelerated during or shortly after events dated using OSL/TL techniques. Hence earlier dune over-washing may have led to greater porewater of an acidic to near neutral nature which in turn promoted smectite formation and silicic acid precipitation > 100 000 years ago. The relatively abundant CEAS matrix in floodplain sands implies more recent semi-continuous flood events again of an acidic-near neutral nature leading to the formation of smectite. In this case the floodplain sediments are dated as having been deposited around 40 and 11 ka, when porewater content may have accelerated clay formation and silica dissolution. The dual nature of the CEAS in the islands reflects a changing environment from smectite-dominated flooding events to sepiolite-dominated desiccation events. Flooding may also correspond to TL/OSL ages over the past 40 000 years which contributed to accelerated CEAS formation. The sepiolite is associated with a Ca-rich matrix implying desiccation which may relate to drying events over the 40 000 year period or to riparian tree root pumping and selective salt accumulation. This work shows that sedimentation in incipient rifts is complex and rarely explained totally in terms of primary depositional events. The implications of different stages of sand diagenesis may

  7. Influence of SST from Pacific and Atlantic Ocean and atmospheric circulation in the precipitation regime of basin from Brazilian SIN

    NASA Astrophysics Data System (ADS)

    Custodio, M. D.; Ramos, C. G.; Madeira, P.; de Macedo, A. L.

    2013-12-01

    The South American climate presents tropical, subtropical and extratropical features because of its territorial extension, being influenced by a variety of dynamical systems with different spatial and temporal scales which result in different climatic regimes in their subregions. Furthermore, the precipitation regime in South America is influenced by low-frequency phenomena as El Niño-Southern Oscillation (ENSO), the Atlantic dipole and the Madden Julian Oscilation (MJO), in other words, is directly influenced by variations of the Sea Surface Temperature (SST). Due to the importance of the precipitation for many sectors including the planning of productive activities, such as agriculture, livestock and hydropower energy, many studies about climate variations in Brazil have tried to determine and explain the mechanisms that affect the precipitation regime. However, because of complexity of the climate system, and consequently of their impacts on the global precipitation regime, its interactions are not totally understood and therefore misrepresented in numerical models used to forecast climate. The precipitation pattern over hydrographic basin which form the Brasilian National Interconnected System (Sistema Interligado Nacional-SIN) are not yet known and therefore the climate forecast of these regions still presents considerable failure that need to be corrected due to its economic importance. In this context, the purpose here is to determine the precipitation patterns on the Brazilian SIN, based on SST and circulation observed data. In a second phase a forecast climate model for these regions will be produced. In this first moment 30 years (1983 to 2012) of SST over Pacific and Atlantic Ocean were analyzed, along with wind in 850 and 200 hPa and precipitation observed data. The precipitation patterns were analyzed through statistical analyses for interannual (ENSO) and intraseasonal (MJO) anomalies for these variables over the SIN basin. Subsequently, these

  8. The thermal environment of Cascadia Basin

    NASA Astrophysics Data System (ADS)

    Johnson, H. Paul; Hautala, Susan L.; Bjorklund, Tor A.

    2012-07-01

    Located adjacent to the NE Pacific convergent boundary, Cascadia Basin has a global impact well beyond its small geographic size. Composed of young oceanic crust formed at the Juan de Fuca Ridge, igneous rocks underlying the basin are partially insulated from cooling of their initial heat of formation by a thick layer of pelagic and turbidite sediments derived from the adjacent North American margin. The igneous seafloor is eventually consumed at the Cascadia subduction zone, where interactions between the approaching oceanic crust and the North American continental margin are partially controlled by the thermal environment. Within Cascadia Basin, basement topographic relief varies dramatically, and sediments have a wide range of thickness and physical properties. This variation produces regional differences in heat flow and basement temperatures for seafloor even of similar age. Previous studies proposed a north-south thermal gradient within Cascadia Basin, with high geothermal flux and crustal temperatures measured in the heavily sedimented northern portion near Vancouver Island and lower than average heat flux and basement temperatures predicted for the central and southern portions of the basin. If confirmed, this prediction has implications for processes associated with the Cascadia subduction zone, including the location of the "locked zone" of the megathrust fault. Although existing archival geophysical data in the central and southern basin are sparse, nonuniformly distributed, and derived from a wide range of historical sources, a substantial N-S geothermal gradient appears to be confirmed by our present compilation of combined water column and heat flow measurements.

  9. R/V Sonne Cruise SO199 CHRISP: New Insights Into the Geodynamic History of northern Wharton Basin (South-East Indian Ocean)

    NASA Astrophysics Data System (ADS)

    Werner, R.; Hoernle, K.; Hauff, F.; Heydolph, K.; Barckhausen, U.; Scientific Party, S.

    2008-12-01

    The morphology of the northern Wharton Basin (South-East Indian Ocean) is dominated by the Investigator Ridge, a ~1800 km long, N-S striking fracture zone and a huge (~1800 x 600 km) submarine volcanic province of unknown origin which includes Cocos/Keeling Islands, Muirfield Seamount, Vening Meinesz Seamounts, Christmas Island, and many unnamed seamounts further south and east. From August 3 through September 22, 2008, RV Sonne cruise SO199 CHRISP (short for Christmas Island Seamount Province) conducted extensive multi-beam mapping and the first systematic hard rock sampling of these features. Age and geochemical data from samples obtained on cruise SO199 aim to contribute to the ongoing debates (1) on the origin of the enriched composition of the Indian Mantle Domain and (2) on the origin of intraplate volcanism in the northern Wharton Basin. Mapping of ~1300 km of the Investigator Ridge revealed a steep west-facing scarp along most of the fracture zone, suggesting recent reactivation related to the presently diffuse but developing new plate boundary between the eastern (Australian) and the western (Indian) parts of the Indo-Australian Plate. Faulted sediments and north-south oriented ravines and asymmetric tops of seamounts adjacent to the ridge imply left-lateral reactivation of older seafloor fractures, consistent with the regional tectonic picture in which Australia is continuing to move northwards whereas India has been stuck since colliding with Asia. The multi- beam data also suggest that the largest intraplate earthquake ever recorded (on June 18, 2000 near the Cocos/Keeling Islands; mag. 7.8) may be related to a reactivated fracture zone just west of the Investigator Ridge. Sampling along the ridge at ~100km intervals yielded a spectacular array of rock types (e.g., lavas, sheeted dikes, mafic and felsic intrusives, layered cumulates, serpentinites), representing a full cross section through the ocean crust into the upper mantle. Particularly surprising

  10. Phase locking of convectively coupled equatorial atmospheric Kelvin waves over Indian Ocean basin

    NASA Astrophysics Data System (ADS)

    Baranowski, Dariusz; Flatau, Maria; Flatau, Piotr; Matthews, Adrian

    2015-04-01

    The properties of convectively coupled Kelvin waves in the Indian Ocean and their propagation over the Maritime Continent are studied. It is shown that Kelvin waves are longitude - diurnal cycle phase locked over the Maritime Continent, Africa and the Indian Ocean. Thus, it is shown that they tend to propagate over definite areas during specific times of the day. Over the Maritime Continent, longitude-diurnal cycle phase locking is such that it agrees with mean, local diurnal cycle of convection. The strength of the longitude-diurnal cycle phase locking differs between 'non-blocked' Kelvin waves, which make successful transition over the Maritime Continent, and 'blocked' waves that terminated within it. It is shown that a specific combination of Kelvin wave phase speed and time of the day at which a wave approaches the Maritime Continent influence the chance of successful transition into the Western Pacific. Kelvin waves that maintain phase speed of 10 to 11 degrees per day over the central-eastern Indian Ocean and arrive at 90E between 9UTC and 18UTC have the highest chance of being 'non-blocked' by the Maritime Continent. The distance between the islands of Sumatra and Borneo agrees with the distance travelled by an average convectively coupled Kelvin wave in one day. This suggests that the Maritime Continent may act as a 'filter' for Kelvin waves favoring successful propagation of those waves for which propagation is in phase with the local diurnal cycle of precipitation. The AmPm index, a simple measure of local diurnal cycle for propagating disturbances, is introduced and shown to be useful metric depicting key characteristics of the convection associated with propagating Kelvin waves.

  11. Model basin test of ocean wave responses for a 40-MW OTEC pilot plant

    NASA Astrophysics Data System (ADS)

    George, J. F.; Richards, D.

    1982-02-01

    A 1/30th-scale model of a floating 40-MW OTEC pilot plant has been subjected to wave conditions that the prototype would experience as a plant moored off Puerto Rico or Hawaii, or as a cruising plantship in the South Atlantic Ocean east of Brazil. The model, in its unmodified baseline configuration, survived the design wave conditions for the three sites, with more than adequate stability margins. A modified configuration was also tested to reduce the possibility of taking on 'green water' which was a concern at the Puerto Rico and Hawaii sites. Additional data were obtained on seawater system parameters, cold water pipe motions, and mooring forces.

  12. Using oceanic-atmospheric oscillations for long lead-time streamflow forecasting in the Upper Colorado River Basin

    NASA Astrophysics Data System (ADS)

    Kalra, A.; Ahmad, S.

    2007-12-01

    In the recent past, oceanic-atmospheric oscillations have been used successfully for long lead-time streamflow forecasting. Herein, we present a data-driven model, Support Vector Machine (SVM) for the long lead-time streamflow forecast incorporating oceanic-atmospheric oscillations. The SVM is based on Statistical Learning Theory that uses a hypothesis space of linear functions based on Kernel approach and can be used to predict a quantity forward in time based on training that uses past data. The principal strength of SVM lies in minimizing the empirical classification error and maximizing the geometric margin by solving inverse problems. The SVMs are considered superior to the Artificial Neural Networks (ANNs) due to the tendency of formulating a quadratic optimization problem which ensures a global optimum that is found missing in the traditional ANN approach. The SVM model was applied to four unimpaired gages in the Upper Colorado River Basin (UCRB). The streamflow data for the selected gages was used from 1906¡§C2004. Annual oceanic-atmospheric indexes comprising of Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), and El Nino-Southern Oscillations (ENSO) for a period of 1906¡§C2001 were used to generate streamflow volumes for three years ahead. The SVM model was trained with 86 years of data (1906¡§C1991) and tested for 10 years of data (1992-2001). The testing criteria used for the model effectiveness was based on correlation coefficient r, root means square error (RMSE) and nash sutcliffe efficiency coefficient e. Predictions during the testing phase showed a good agreement with measured streamflow volumes for the selected gages in UCRB. Rigorous sensitivity analysis was performed to evaluate the effect of individual oscillation. The results indicated a strong signal for NAO and ENSO indexes as compared to PDO and AMO indexes for the long lead-time streamflow forecast. The oceanic

  13. Basin-scale population genetic structure of the planktonic copepod Calanus finmarchicus in the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Unal, Ebru; Bucklin, Ann

    2010-10-01

    differentiation among area populations within gyres was reduced. Analysis of additional genes, higher resolution sampling, and comparisons across different years are needed to resolve the spatial limits and number of distinct C. finmarchicus populations across the N. Atlantic Ocean basin.

  14. The break-up of continents and the formation of new ocean basins.

    PubMed

    Minshull, T A

    2002-12-15

    Rifted continental margins are the product of stretching, thinning and ultimate break-up of a continental plate into smaller fragments, and the rocks lying beneath them store a record of this rifting process. Earth scientists can read this record by careful sampling and with remote geophysical techniques. These experimental studies have been complemented by theoretical analyses of continental extension and associated magmatism. Some rifted margins show evidence for extensive volcanic activity and uplift during rifting; at these margins, the record of the final stages of rifting is removed by erosion and obscured by the thick volcanic cover. Other margins were underwater throughout their formation and showed rather little volcanic activity; here the ongoing deposition of sediment provides a clearer record. During the last decade, vast areas of exhumed mantle rocks have been discovered at such margins between continental and oceanic crust. This observation conflicts with the well-established idea that the mantle melts to produce new crust when it is brought close to the Earth's surface. In contrast to the steeply dipping faults commonly seen in zones of extension within continental interiors, faults with very shallow dips play a key role in the deformation immediately preceding continental break-up. Future progress in the study of continental break-up will depend on studies of pairs of margins which were once joined and on the development of computer models which can handle rigorously the complex transition from distributed continental deformation to sea-floor spreading focused at a mid-ocean ridge. PMID:12626269

  15. Coherence between Great Basin precipitation and low frequency Pacific Ocean variability in CMIP5

    NASA Astrophysics Data System (ADS)

    Smith, K.; Strong, C.; Wang, S.

    2013-12-01

    Precipitation over the northern Wasatch Range of the Great Basin provides water for millions of people, and observations indicate its sensitivity to Pacific sea surface temperature (SST) modes including a 3-7 year El Nino-like pattern and a multidecadal pattern in the north Pacific resembling the Pacific Decadal Oscillation (PDO). We assessed the fidelity of this precipitation-SST connectivity for models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) by using historical (1900-2005) monthly model output. Coherence analyses at various lags indicated that the observed precipitation-SST connectivity was best captured by the NCAR Community Climate System Model (CCSM). We show how these results are being used to incorporate low-frequency variations in a nonstationary daily stochastic weather generator suitable for hydrology and ecosystem impact studies out to the year 2100.

  16. The Santa Barbara Channel - Santa Maria Basin Study: A model for Coastal Ocean Observing Systems

    NASA Astrophysics Data System (ADS)

    Winant, C. D.

    2002-12-01

    The need to anticipate the potential impact of oil exploration and production activities on coastal resources, and the information needs of agencies charged with responding to coastal emergencies motivated the development of the oil-spill response system for the Santa Barbara Channel (SBC) and the Santa Maria Basin (SMB), along the California coast, between Ventura and Morro Bay. In the Santa Barbara Channel (SBC), moorings and drifter trajectories document a persistent cyclonic circulation with a typical re-circulation period between three and five days. In the spring currents near the mainland are weaker than near the Channel Islands and the overall flow is toward the southeast. Trajectories document the possibility for water parcels to leave the channel through the inter-island passes. In the late fall and winter, a poleward flow with velocities often exceeding 0.5 m/s is confined within 20 km of the mainland. Between these two seasons, the cyclonic tendency is enhanced although most of the drifters eventually migrate westward. The trajectories of drifters released at the same time from sites only 20 km apart can be remarkably different. In the Santa Maria Basin (SMB), the direction and amplitude of the flow is strongly depth dependent. Near the surface, moorings and drifters show the flow to be equatorward except during late fall and early winter when the surface flow is poleward. Beneath the surface layer the flow is poleward except in March and April, right after the spring transition. The observations provide a basis on which several data assimilating model of the circulation are based. The models reproduce all the major observed features of the circulation, including individual drifter trajectories. With little effort these models could be used to maintain an operational predictive capability with real predictive skills over periods of a few days.

  17. Mechanisms of low-flux intraplate volcanic fields - Basin and Range and Northwest Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Valentine, G.; Hirano, N.

    2009-05-01

    Many fields of small-volume, scattered volcanoes that typically have alkaline affinities occur in intraplate settings. The underlying mechanisms of these intraplate volcanoes are enigmatic; they often do not correlate with anomalous heat sources or upwelling mantle (as in hot spots, mid-ocean ridges, and active continental rifts), or with fluids introduced by actively-subducting lithosphere. We compare the characteristics of two low volume-flux intraplate volcanic fields, one in a continental setting that is characterized by slow extension (western U.S.A.), and the other on the floor of the northwest Pacific Ocean in a region of plate flexure. The comparison supports an interpretation that the fundamental driving mechanism for low magma-flux volcanic fields, which episodically erupt scattered, small-volume volcanoes over millions of years, is regional-scale deformation of compositionally-heterogeneous upper mantle. Deformation serves to mechanically focus partial melts that might be present due to locally-depressed solidus temperatures caused by slightly higher volatile contents, creating sufficient melt buoyancy to trigger magma ascent via magma-driven fractures (dikes). The key role of deformation in collecting magmas and triggering dike ascent and eruption, without influx of new material or heat into the source region, supports the definition of such systems as tectonically-controlled, and is likely applicable at other low-flux, diffuse volcanic fields. Differences in the degree of fractionation and wall-rock contamination in the two fields is related to vertical variations in principal-stress orientation that may cause stalling of ascending dikes.

  18. Divergence and phylogeny of Firmicutes from the Cuatro Ciénegas Basin, Mexico: a window to an ancient ocean.

    PubMed

    Moreno-Letelier, Alejandra; Olmedo-Alvarez, Gabriela; Eguiarte, Luis E; Souza, Valeria

    2012-07-01

    The Cuatro Ciénegas Basin (CCB) has been identified as a center of endemism for many life-forms. Nearly half the bacterial species found in the spring systems have their closest relatives in the ocean. This raises the question of whether the high diversity observed today is the product of an adaptive radiation similar to that of the Galapagos Islands or whether the bacterial groups are "survivors" of an ancient sea, which would be of interest for astrobiology. To help answer this question, we focused on Firmicutes from Cuatro Ciénegas (mainly Bacillus and Exiguobacterium). We reconstructed the phylogenetic relationships of Firmicutes with 28 housekeeping genes and dated the resulting tree using geological events as calibration points. Our results show that marine Bacillus diverged from other Bacillus strains 838 Ma, while Bacillus from Cuatro Ciénegas have divergence dates that range from 770 to 202 Ma. The members of Exiguobacterium from the CCB conform to a much younger group that diverged from the Andes strain 60 Ma and from the one in Yellowstone 183 Ma. Therefore, the diversity of Firmicutes in Cuatro Ciénegas is not the product of a recent radiation but the product of the isolation of lineages from an ancient ocean. Hence, Cuatro Ciénegas is not a Galapagos Archipelago for bacteria but is more like an astrobiological "time machine" in which bacterial lineages survived in an oligotrophic environment that may be very similar to that of the Precambrian. Key Words: Firmicutes-Cuatro Ciénegas-Precambrian-Molecular dating-Western Interior Seaway. PMID:22920517

  19. Divergence and Phylogeny of Firmicutes from the Cuatro Ciénegas Basin, Mexico: A Window to an Ancient Ocean

    PubMed Central

    Moreno-Letelier, Alejandra; Olmedo-Alvarez, Gabriela; Eguiarte, Luis E.

    2012-01-01

    Abstract The Cuatro Ciénegas Basin (CCB) has been identified as a center of endemism for many life-forms. Nearly half the bacterial species found in the spring systems have their closest relatives in the ocean. This raises the question of whether the high diversity observed today is the product of an adaptive radiation similar to that of the Galapagos Islands or whether the bacterial groups are “survivors” of an ancient sea, which would be of interest for astrobiology. To help answer this question, we focused on Firmicutes from Cuatro Ciénegas (mainly Bacillus and Exiguobacterium). We reconstructed the phylogenetic relationships of Firmicutes with 28 housekeeping genes and dated the resulting tree using geological events as calibration points. Our results show that marine Bacillus diverged from other Bacillus strains 838 Ma, while Bacillus from Cuatro Ciénegas have divergence dates that range from 770 to 202 Ma. The members of Exiguobacterium from the CCB conform to a much younger group that diverged from the Andes strain 60 Ma and from the one in Yellowstone 183 Ma. Therefore, the diversity of Firmicutes in Cuatro Ciénegas is not the product of a recent radiation but the product of the isolation of lineages from an ancient ocean. Hence, Cuatro Ciénegas is not a Galapagos Archipelago for bacteria but is more like an astrobiological “time machine” in which bacterial lineages survived in an oligotrophic environment that may be very similar to that of the Precambrian. Key Words: Firmicutes—Cuatro Ciénegas—Precambrian—Molecular dating—Western Interior Seaway. Astrobiology 12, 674–684. PMID:22920517

  20. Oceanic Anoxic Event 1b: insights and new data from the Poggio le Guaine section (Umbria-Marche Basin)

    NASA Astrophysics Data System (ADS)

    Sabatino, Nadia; Sprovieri, Mario; Coccioni, Rodolfo; Salvagio Manta, Daniela; Gardin, Silvia; Baudin, François

    2015-04-01

    The upper Aptian to lower Albian interval (~114-109 Ma) represents a crucial period during Earth's history, with a major evolution in the nature of mid-Cretaceous tectonics, sea level, climate, and marine plankton communities. Interestingly, it also includes multiple prominent black shale horizons that are the sedimentary expression of oceanic anoxic event (OAE) 1b. An high-resolution planktonic foraminiferal and calcareous nannofossil biostratigraphy in combination with an integrated study of multiple geochemical proxies (δ13Ccarb, δ13Corg, TOC, HI, CaCO3, trace elements/Al ratios) of the late Aptian-early Albian OAE 1b has been performed on the pelagic sedimentary sequence of Poggio le Guaine (Umbria-Marche Basin, central Italy). A comparison of the newly collected stable isotope carbon curve with the records from the Vocontian Basin (SE France), DSDP Site 545 and Hole 1049C provided a reliable and precise identification of the four main prominent black shale levels (113/Jacob, Kilian, Urbino/Paquier and Leenhardt) that definitively punctuate the OAE 1b. The studied record shows an increase in the marine organic carbon accumulation rate, in particular in the 113/Jacob and Urbino/Paquier levels. In the other black shales, TOC values are < 1%, with evidence of degraded marine organic matter. Completely anoxic conditions were never established during the sediment deposition, although evidence of oxygen depletion at the bottom of the basin is clearly documented by the distribution pattern of redox-sensitive trace metals. The results suggest an increase in organic carbon burial rates during the OAE 1b due to the effect of enhanced surface productivity, as supported by a major increase in Ba/Al, and reduced bottom water ventilation. Noteworthy, the Kilian and Urbino/Paquier levels from the PLG section are characterized by the absence of correlative shifts in δ13Ccarb and δ13Corg. The increase in the δ13Corg, values in these levels is explained by an increase in

  1. Optimum interpolation analysis of basin-scale ¹³⁷Cs transport in surface seawater in the North Pacific Ocean.

    PubMed

    Inomata, Y; Aoyama, M; Tsumune, D; Motoi, T; Nakano, H

    2012-12-01

    ¹³⁷Cs is one of the conservative tracers applied to the study of oceanic circulation processes on decadal time scales. To investigate the spatial distribution and the temporal variation of ¹³⁷Cs concentrations in surface seawater in the North Pacific Ocean after 1957, a technique for optimum interpolation (OI) was applied to understand the behaviour of ¹³⁷Cs that revealed the basin-scale circulation of Cs ¹³⁷Cs in surface seawater in the North Pacific Ocean: ¹³⁷Cs deposited in the western North Pacific Ocean from global fallout (late 1950s and early 1960s) and from local fallout (transported from the Bikini and Enewetak Atolls during the late 1950s) was further transported eastward with the Kuroshio and North Pacific Currents within several years of deposition and was accumulated in the eastern North Pacific Ocean until 1967. Subsequently, ¹³⁷Cs concentrations in the eastern North Pacific Ocean decreased due to southward transport. Less radioactively contaminated seawater was also transported northward, upstream of the North Equatorial Current in the western North Pacific Ocean in the 1970s, indicating seawater re-circulation in the North Pacific Gyre. PMID:23117411

  2. U-Pb ages on single detrital zircon grains from the Witwatersrand Basin, South Africa: Constraints on the age of sedimentation and on the evolution of granites adjacent to the basin

    SciTech Connect

    Robb, L.J. ); Davis, D.W.; Kamo, S.L. )

    1990-05-01

    U-Pb ages of single detrital zircon grains from various stratigraphic horizons in the Dominion and Witwatersrand sequences provide constraints on the maximum age of sedimentation as well as indicating the pattern of age distribution in the (granitoid) source area providing detritus into the basin. Zircon ages in the Dominion sediments range from 3,191-3,105 Ma with a geometric mean ({bar X}) t 3,153 Ma. Those from the lower Witwatersrand sediments (West Rand Group) range from 3,305-3,044 Ma with {bar X} = 3,097 Ma, and zircons in the upper Witwatersrand sediments (Central Rand Group) are between 3,207-2,894 Ma old with {bar X} = 3,053 Ma. Ages of detrital zircons generally decrease upward in the stratigraphic record, and <3,000 Ma old zircons are only found in the Central Rand Group. This trend implies that younger granites may have formed at some time subsequent to lower Witwatersrand deposition, or that continued erosion of the hinterland resulted in the unroofing of successively younger granites. The wide spread of zircon ages (411 Ma) evident in the data set indicates that granites formed virtually continuously between circa 3,300-2.900 Ma in the Witwatersrand source area. Of the zircon ages 45% fall within 30 m.y. of the geometric mean of the total data set, suggesting that a major crust-forming event occurred at 3,073 {plus minus} 30 Ma. Granitoids in the source area can be divided into (i) pre-Dominion basement; (ii) Dominion granites, whose emplacement coincided with the extrusion of Dominion volcanics, and (iii) Randian granites, which were emplaced synchronously with Witwatersrand deposition. This sequence of events supports recent tectonic models that view the Witwatersrand sequence as having been deposited in a foreland basin.

  3. Availability of free oxygen in deep bottom water of some Archean-Early Paleoproterozoic ocean basins as derived from iron formation facies analyses

    NASA Astrophysics Data System (ADS)

    Beukes, N. J.; Smith, A.

    2013-12-01

    Archean to Early Paleoproterozoic ocean basins are commonly, although not exclusively, depicted as rather static systems; either permanently stratified with shallow mixed oxygenated water overlying anoxic deep water or with a totally anoxic water column. The anoxic water columns are considered enriched in dissolved ferrous iron derived from hydrothermal plume activity. These sourced deposition of iron formations through precipitation of mainly ferrihydrite via reaction with free oxygen in the stratified model or anaerobic iron oxidizing photoautotrophs in the anoxic model. However, both these models face a simple basic problem if detailed facies reconstructions of deepwater microbanded iron formations (MIFs) are considered. In such MIFs it is common that the deepest water and most distal facies is hematite rich followed shoreward by magnetite, iron silicate and siderite facies iron formation. Examples of such facies relations are known from jaspilitic iron formation of the ~3,2 Ga Fig Tree Group (Barberton Mountainland), ~ 2,95 Ga iron formations of the Witwatersrand-Mozaan basin and the ~2,5 Ga Kuruman Iron Formation, Transvaal Supergroup, South Africa. Facies relations of these MIFs with associated siliciclastics or carbonates also indicate that the upper water columns of the basins, down to below wave base, were depleted in iron favoring anoxic-oxic stratification rather than total anoxia. In the MIFs it can be shown that hematite in the distal facies represents the earliest formed diagenetic mineral; most likely crystallized from primary ferrihydrite. The problem is one of how ferrihydrite could have been preserved on the ocean floor if it was in direct contact with reducing ferrous deep bottom water. Rather dissolved ferrous iron would have reacted with ferrihydrite to form diagenetic magnetite. This dilemma is resolved if in the area of deepwater hematite MIF deposition, the anoxic ferrous iron enriched plume was detached from the basin floor due to buoyancy

  4. The Hurst Exponent as an Indicator of the Behaviour of a Model Monopile in an Ocean Wave Testing Basin

    NASA Astrophysics Data System (ADS)

    Pakrashi, Vikram; O'Shea, Richard; Jaksic, Vesna; Murphy, Jimmy

    2015-07-01

    With the importance of renewable energy well-established worldwide, and targets of such energy quantified in many cases, there exists a considerable interest in the assessment of wind and wave devices. While the individual components of these devices are often relatively well understood and the aspects of energy generation well researched, there seems to be a gap in the understanding of these devices as a whole and especially in the field of their dynamic responses under operational conditions. The mathematical modelling and estimation of their dynamic responses are more evolved but research directed towards testing of these devices still requires significant attention. Model-free indicators of the dynamic responses of these devices are important since it reflects the as-deployed behaviour of the devices when the exposure conditions are scaled reasonably correctly, along with the structural dimensions. This paper demonstrates how the Hurst exponent of the dynamic responses of a monopile exposed to different exposure conditions in an ocean wave basin can be used as a model-free indicator of various responses. The scaled model is exposed to Froude scaled waves and tested under different exposure conditions. The analysis and interpretation is carried out in a model-free and output-only environment, with only some preliminary ideas regarding the input of the system. The analysis indicates how the Hurst exponent can be an interesting descriptor to compare and contrast various scenarios of dynamic response conditions.

  5. Plagioclase-peridotites recording the incipient stage of oceanic basin formation: new constraints from the Nain ophiolites (central Iran)

    NASA Astrophysics Data System (ADS)

    Pirnia Naeini, Tahmineh; Arai, Shoji; Saccani, Emilio

    2016-04-01

    spinel; (2) Al, Ca decrease and Cr, Ti increase in pyroxenes and pargasite; (3) slight overall increase in the concentration of rare earth elements and most trace elements in pyroxenes and pargasite, except for Eu and Sr for which a slight decrease is observed. The pointed variations all support the subsolidus origin of the plagioclases, since they took place at constant Mg#s of pyroxenes and coexisting olivines. The magmatic and metamorphic events that affected the Nain peridotites correspond well to the expected geodynamics of a short-lived oceanic basin. Melting was a result of peridotites upwelling (up to the plagioclase-facies) in the early stages of the ocean spreading. Cooling and the subsequent recrystallization in the spinel-facies correspond to the early ceasing of spreading and magmatism in the ocean. Reconditioning of the peridotites in the plagioclase-facies is likely related to the ocean closure and Nain ophiolite emplacement. Based on the short-lived and subduction-related character deduced from the ubiquitous occurrence of amphiboles in the peridotites, we strongly suggest a back-arc setting for the Nain Mesozoic Ocean.

  6. Ocean Basin Evolution and Global-Scale Plate Reorganization Events Since Pangea Breakup

    NASA Astrophysics Data System (ADS)

    Müller, R. Dietmar; Seton, Maria; Zahirovic, Sabin; Williams, Simon E.; Matthews, Kara J.; Wright, Nicky M.; Shephard, Grace E.; Maloney, Kayla T.; Barnett-Moore, Nicholas; Hosseinpour, Maral; Bower, Dan J.; Cannon, John

    2016-06-01

    We present a revised global plate motion model with continuously closing plate boundaries ranging from the Triassic at 230 Ma to the present day, assess differences among alternative absolute plate motion models, and review global tectonic events. Relatively high mean absolute plate motion rates of approximately 9–10 cm yr‑1 between 140 and 120 Ma may be related to transient plate motion accelerations driven by the successive emplacement of a sequence of large igneous provinces during that time. An event at ˜100 Ma is most clearly expressed in the Indian Ocean and may reflect the initiation of Andean-style subduction along southern continental Eurasia, whereas an acceleration at ˜80 Ma of mean rates from 6 to 8 cm yr‑1 reflects the initial northward acceleration of India and simultaneous speedups of plates in the Pacific. An event at ˜50 Ma expressed in relative, and some absolute, plate motion changes around the globe and in a reduction of global mean plate speeds from about 6 to 4–5 cm yr‑1 indicates that an increase in collisional forces (such as the India–Eurasia collision) and ridge subduction events in the Pacific (such as the Izanagi–Pacific Ridge) play a significant role in modulating plate velocities.

  7. Long Lead-Time Forecasting of Snowpack and Precipitation in the Upper Snake River Basin using Pacific Oceanic-Atmospheric Variability

    NASA Astrophysics Data System (ADS)

    Anderson, S.; Tootle, G.; Parkinson, S.; Holbrook, P.; Blestrud, D.

    2012-12-01

    Water managers and planners in the western United States are challenged with managing resources for various uses, including hydropower. Hydropower is especially important throughout the Upper Snake River Basin, where a series of hydropower projects provide a low cost renewable energy source to the region. These hydropower projects include several dams that are managed by Idaho Power Company (IPC). Planners and managers rely heavily on forecasts of snowpack and precipitation to plan for hydropower availability and the need for other generation sources. There is a pressing need for improved snowpack and precipitation forecast models in the Upper Snake River Basin. This research investigates the ability of Pacific oceanic-atmospheric data and climatic variables to provide skillful long lead-time (three to nine months) forecasts of snowpack and precipitation, and examines the benefits of segregating the warm and cold phases of the Pacific Decadal Oscillation (PDO) to reduce the temperature variability within the target dataset. Singular value decomposition (SVD) was used to identify regions of Pacific Ocean sea surface temperatures (SST) and 500mbar geopotential heights (Z500) for various lead times (three, six, and nine months) that were teleconnected with snowpack and precipitation stations in Upper Snake River Basin headwaters. The identified Pacific Ocean SST and Z500 regions were used to create indices that became predictors in a non-parametric forecasting model. The majority of forecasts resulted in positive statistical skill, which indicated an improvement of the forecast over the climatology forecast (no-skill forecast). The results from the forecasts models indicated that derived indices from the SVD analysis resulted in improved forecast skill when compared to forecasts using established climate indices. Segregation of the cold phase PDO years resulted in the identification of different regions in the Pacific Ocean and vastly improved skill for the nine month

  8. Vertical scales and dynamics of eddies in the Arctic Ocean's Canada Basin

    NASA Astrophysics Data System (ADS)

    Zhao, Mengnan; Timmermans, Mary-Louise

    2015-12-01

    A decade of moored measurements from the Arctic Ocean's northwestern Beaufort Gyre (collected as a component of the Beaufort Gyre Exploration Project) are analyzed to examine the range of mesoscale eddies over the water column and the dynamical processes that set eddy vertical scales. A total of 58 eddies were identified in the moored record, all anticyclones with azimuthal velocities ranging from 10 to 43 cm/s. These are divided into three classes based on core depths. Shallow eddies (core depths around 120 m) are shown to be vertically confined by the strong stratification of the halocline; typical thicknesses are around 100 m. Deep eddies (core depths around 1200 m) are much taller (thicknesses around 1300 m) owing to the weaker stratification at depth, consistent with a previous study. Eddies centered around mid-depths all have two cores (vertically aligned and separated in depth) characterized by velocity maxima and anomalous temperature and salinity properties. One core is located at the base of the halocline (around 200 m depth) and the other at the depth of the Atlantic Water layer (around 400 m depth). These double-core eddies have vertical scales between those of the shallow and deep eddies. The strongly decreasing stratification in their depth range motivates a derivation for the quasi-geostrophic adjustment of a nonuniformly stratified water column to a potential vorticity anomaly. The result aids in interpreting the dynamics and origins of the double-core eddies, providing insight into transport across a major water mass front separating Canadian and Eurasian Water.

  9. Basin-wide runup measurements of the 26 December 2004 Indian Ocean tsunami

    NASA Astrophysics Data System (ADS)

    Borrero, J. C.; Fritz, H. M.; Kong, L. S.; Synolakis, C. E.; Okal, E. A.

    2006-12-01

    We summarize the findings and observations from all field surveys we know of conducted in the aftermath of the horrific tsunami of 26 December 2004. They represent an unprecedented undertaking by both local and international scientists working side by side in at least 15 countries. This was the first tsunami with transoceanic impact, since the start of comprehensive post-event surveys with modern equipment in the early 1990s. The death toll included citizens from many other countries not directly hit by the tsunami, giving it the grim distinction of being the first universal natural disaster of modern times.Basic conclusions from the surveys are: (i) tsunami numerical models must continue to be improved through testing with benchmark laboratory data, instrumental tsunameter recordings, and field inundation measurements. Specific emphasis needs to be given to landslide initial conditions and to sediment layers, a problem identified almost ten years earlier; (ii) the forces on structures need to be better understood, particularly in the presence of debris; (iii) early warning can work only with efficient emergency preparedness (as implemented in the Pacific Ocean), through a synergy of deployment of direct detection instruments, and preparation of inundation maps; (iv) shortcomings in population and emergency response underscore the urgent need for a worldwide educational effort on tsunami hazard mitigation, as further demonstrated during tsunamis in 2006(Tonga, Kythira, Java); (v) in an era of global citizenship, simply educating the local populations is not enough. All visitors to shorelines must know precursors of a tsunami attack and how to evacuate to high ground.

  10. Paleoceanographic Changes in the Lagonegro Basin (Southern Italy) during the Late Triassic Linked to Oceanic Rifting in the Western Tethyan Region

    NASA Astrophysics Data System (ADS)

    Casacci, M.; Algeo, T. J.; Bertinelli, A.; Rigo, M.

    2015-12-01

    The Lagonegro Basin was part of the southwestern branch of the western Tethys, an actively spreading young ocean during the Late Triassic (Ciarapica and Passeri, 2002, 2005). The sedimentary environment was a deepening-upward basin, bordered to the north by the Apenninic and Apulian carbonate platforms. Paleoseismic activity is evidenced by frequent debris flows on the basin margins (Passeri et al., 2005). The Lagonegro succession is characterized by Permian to Miocene formations deposited in shallow to deep basinal environments. The Upper Triassic is comprised of deep-marine sediments belonging to the Calcari con Selce ("Cherty Limestone") Formation of late Ladinian to late Norian-early Rhaetian age and the Scisti Silicei ("Siliceous Shale") Formation of late Norian-early Rhaetian to Late Jurassic age. The "Transitional Interval" between these two formations is gradational over a 20- to 40-m interval (Miconnet, 1983). The Transitional Interval was investigated in three sections (Pignola-Abriola, Monte Volturino, and Madonna del Sirino) in the Southern Apennines (southern Italy), representing a proximal-to-distal transect across the Lagonegro Basin. The transition from mainly calcareous to mainly siliceous sedimentation may have been influenced by rapid, post-rift subsidence of the Lagonegro Basin. It also coincided with a shift to warmer or more humid conditions around the Norian/Rhaetian boundary, as reflected in a pronounced increase in the chemical index of alteration (CIA), a weathering proxy (Young and Nesbitt, 1998). Redox proxies indicate mainly oxic conditions in the deep basin, although organic-rich shale beds are present at multiple levels in the otherwise organic-poor succession. The abruptness of the transitions between organic-poor and -rich sediment layers suggests major changes in paleoceanographic conditions, possibly related to switches from lagoonal circulation (linked to a net negative water balance) to estuarine circulation (linked to a net

  11. Spatial and seasonal responses of precipitation in the Ganges and Brahmaputra river basins to ENSO and Indian Ocean dipole modes: implications for flooding and drought

    NASA Astrophysics Data System (ADS)

    Pervez, M. S.; Henebry, G. M.

    2014-02-01

    We evaluated the spatial and temporal responses of precipitation in the basins as modulated by the El Niño Southern Oscillation (ENSO) and Indian Ocean (IO) dipole modes using observed precipitation records at 43 stations across the Ganges and Brahmaputra basins from 1982 to 2010. Daily observed precipitation records were extracted from Global Surface Summary of the Day dataset and spatial and monthly anomalies were computed. The anomalies were averaged for the years influenced by climate modes combinations. Occurrences of El Niño alone significantly reduced (60% and 88% of baseline in the Ganges and Brahmaputra basins, respectively) precipitation during the monsoon months in the northwestern and central Ganges basin and across the Brahmaputra basin. In contrast, co-occurrence of La Niña and a positive IO dipole mode significantly enhanced (135% and 160% of baseline, respectively) precipitation across both basins. During the co-occurrence of neutral phases in both climate modes (occurring 13 out of 28 yr), precipitation remained below average to average in the agriculturally extensive areas of Haryana, Uttar Pradesh, Bihar, eastern Nepal, and the Rajshahi district in Bangladesh in the Ganges basin and northern Bangladesh, Meghalaya, Assam, and Arunachal Pradesh in the Brahmaputra basin. This pattern implies that a regular water deficit is likely in these areas with implications for the agriculture sector due to its reliance on consistent rainfall for successful production. Major flooding and drought occurred as a consequence of the interactive effects of the ENSO and IO dipole modes, with the sole exception of extreme precipitation and flooding during El Niño events. This observational analysis will facilitate well informed decision making in minimizing natural hazard risks and climate impacts on agriculture, and supports development of strategies ensuring optimized use of water resources in best management practice under changing climate.

  12. Identification of a genetic marker that discriminates ocean-type and stream-type chinook salmon in the Columbia River basin

    USGS Publications Warehouse

    Rasmussen, C.; Ostberg, C.O.; Clifton, D.R.; Holloway, J.L.; Rodriguez, R.J.

    2003-01-01

    A marker based on randomly amplified polymorphic DNA (RAPD), OT-38, was discovered that nonlethally discriminates between stream-type and ocean-type populations of chinook salmon Oncorhynchus tshawytscha in the Columbia River basin, including the threatened fall-run (ocean-type) and spring-run (stream-type) Snake River populations. This marker was developed by amplifying chinook salmon genomic DNA with a single RAPD primer, sequencing the termini of the polymorphic products, and designing primer pairs for allele-specific amplification. It was used to assay 18-80 individuals from several wild and hatchery populations differing in year-class, freshwater life history, and location along the Columbia River OT-38 unambiguously distinguished ocean-type from stream-type populations in 93.1% of the chinook salmon sampled.

  13. Seismic velocity structure at Deep Sea Drilling Project site 504B, Panama Basin: Evidence for thin oceanic crust

    NASA Astrophysics Data System (ADS)

    Collins, John A.; Purdy, Michael G.; Brocher, Thomas M.

    1989-07-01

    We present an analysis of wide-angle reflection/refraction data collected in the immediate vicinity of Deep Sea Drilling Project hole 504B in the Panama Basin, currently the deepest drill hole (1.288 km) into oceanic crust. The data were acquired with a 1785 inch3 air gun array and fixed-gain sonobuoy receivers and consist of four intersecting profiles shot along three different azimuths. Near-normal-incidence, multichannel seismic (MCS) reflection data were acquired simultaneously. Observed P and S wave arrivals out to maximum ranges of 30 km provide constraints on the velocity structure of the middle and lower crust and on total crustal thickness. Comparison of the travel times and amplitudes of the P and S wave arrivals on all four profiles revealed important similarities which were modeled using the reflectivity synthetic seismogram method. Forward modeling shows that in contrast to standard oceanic velocity models, a velocity-depth profile that better explains the observed data is characterized by high-velocity gradients (up to 0.6 km/s/km) in the middle crust, a 1.8-km-thick low-velocity zone (Vp = 7.1-6.7 km/s) immediately above Moho, and a total crustal thickness of only 5 km. Interpretation of the high-velocity gradients in the middle crust is constrained by the observation of P wave amplitude focusing at ranges of 16-19 km. Although not as well developed in comparison to the P wave arrivals, S wave arrivals show similar focusing. Total crustal thickness is constrained by the combined interpretation of a P wave, wide-angle reflection event observed at a range of 16-28 km and an MCS reflection event with a crustal travel time of 1.4-1.5 s. Although these events cannot be directly correlated, their travel times are consistent with the assumption that both have a common origin. Amplitude modeling of the wide-angle event demonstrates that these events are generated at the Moho.

  14. Population genetic data of a model symbiotic cnidarian system reveal remarkable symbiotic specificity and vectored introductions across ocean basins.

    PubMed

    Thornhill, Daniel J; Xiang, Yu; Pettay, D Tye; Zhong, Min; Santos, Scott R

    2013-09-01

    The Aiptasia-Symbiodinium symbiosis is a promising model for experimental studies of cnidarian-dinoflagellate associations, yet relatively little is known regarding the genetic diversity of either symbiotic partner. To address this, we collected Aiptasia from 16 localities throughout the world and examined the genetic diversity of both anemones and their endosymbionts. Based on newly developed SCAR markers, Aiptasia consisted of two genetically distinct populations: one Aiptasia lineage from Florida and a second network of Aiptasia genotypes found at other localities. These populations did not conform to the distributions of described Aiptasia species, suggesting that taxonomic re-evaluation is needed in the light of molecular genetics. Associations with Symbiodinium further demonstrated the distinctions among Aiptasia populations. According to 18S RFLP, ITS2-DGGE and microsatellite flanker region sequencing, Florida anemones engaged in diverse symbioses predominantly with members of Symbiodinium Clades A and B, but also C, whereas anemones from elsewhere harboured only S. minutum within Clade B. Symbiodinium minutum apparently does not form a stable symbiosis with other hosts, which implies a highly specific symbiosis. Fine-scale differences among S. minutum populations were quantified using six microsatellite loci. Populations of S. minutum had low genotypic diversity and high clonality (R = 0.14). Furthermore, minimal population structure was observed among regions and ocean basins, due to allele and genotype sharing. The lack of genetic structure and low genotypic diversity suggest recent vectoring of Aiptasia and S. minutum across localities. This first ever molecular-genetic study of a globally distributed cnidarian and its Symbiodinium assemblages reveals host-symbiont specificity and widely distributed populations in an important model system. PMID:23980764

  15. The role of gateways in the evolution of temperature and salinity of semi-enclosed basins: An oceanic box model for the Miocene Mediterranean Sea and Paratethys

    NASA Astrophysics Data System (ADS)

    Karami, M. P.; de Leeuw, A.; Krijgsman, W.; Meijer, P. Th.; Wortel, M. J. R.

    2011-10-01

    Marine gateways are important for semi-enclosed basins as they control exchange flows and influence water circulation. During much of the Early and Middle Miocene (~ 23-13 Ma), the Paratethys (of which at present only the Black Sea and Caspian Sea remain) and the Mediterranean Sea were connected to both the Atlantic and Indian Oceans. The gateways to the Indian Ocean were closed ultimately in the Middle Miocene. Here, we apply an oceanic 4-box model to determine the temperature, salinity and exchange flows for the Paratethys and the Mediterranean Sea before and after closure of the Indian Ocean gateways. Our analysis forms a novel way of linking tectonics, climate and basin evolution. We investigate whether changes observed in the geological record of Paratethys are caused by changes in gateway configuration or in climate. We mainly focus on Paratethys which, because of the availability of a large variety of geological studies, presents an outstanding opportunity for studying the evolution of semi-enclosed basins and the impact of gateway closure. Moreover, Paratethys is considered to have played an important role in the evolution of Eurasian climate. Our analysis explores various values of the model parameters such as net evaporation and surface heat flux. Our main conclusions are: (1) Paratethys became more responsive to climate change after closure, (2) closure of the gateways to the Indian Ocean probably caused cooling of Paratethys and, in particular, accounted for the enigmatic Mid-Burdigalian cooling in Paratethys, (3) closure induced a change in salinity of Paratethys which is dependent on the net evaporation and size of the gateway connecting Paratethys to the Mediterranean, (4) Paratethys is sensitive to closure of both the gateway between Paratethys and the Indian Ocean, and the gateway between the Mediterranean Sea and the Indian Ocean, (5) Paratethys is influenced by the water properties of the Mediterranean Sea, (6) the water properties of Paratethys

  16. Structural studies near Pevek, Russia: implications for formation of the East Siberian Shelf and Makarov Basin of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Miller, E. L.; Verzhbitsky, V. E.

    2009-09-01

    and magnetic data for the offshore Siberian Shelf reveals a widespread, seismically mappable basement-sedimentary cover contact that deepens northward towards the edge of the shelf with few other significant basins. Various ages have been assigned to the oldest strata above the unconformity, ranging from Cretaceous (Albian - 112-100 Ma) to Tertiary (Paleocene-Eocene - ~60-50 Ma). The period of uplift and erosion documented along the Arctic coast of Russia at this longitude could represent the landward equivalent of the (yet undrilled) offshore basement-sedimentary cover contact, thus overlying sedimentary sequences could be as old as early Late Cretaceous. Although quite speculative, these conclusions suggest that land-based geologic, structural, petrologic and geochronologic studies could provide useful constraints to help resolve the plate tectonic history of the Arctic Ocean.

  17. Adjacent segment disease.

    PubMed

    Virk, Sohrab S; Niedermeier, Steven; Yu, Elizabeth; Khan, Safdar N

    2014-08-01

    EDUCATIONAL OBJECTIVES As a result of reading this article, physicians should be able to: 1. Understand the forces that predispose adjacent cervical segments to degeneration. 2. Understand the challenges of radiographic evaluation in the diagnosis of cervical and lumbar adjacent segment disease. 3. Describe the changes in biomechanical forces applied to adjacent segments of lumbar vertebrae with fusion. 4. Know the risk factors for adjacent segment disease in spinal fusion. Adjacent segment disease (ASD) is a broad term encompassing many complications of spinal fusion, including listhesis, instability, herniated nucleus pulposus, stenosis, hypertrophic facet arthritis, scoliosis, and vertebral compression fracture. The area of the cervical spine where most fusions occur (C3-C7) is adjacent to a highly mobile upper cervical region, and this contributes to the biomechanical stress put on the adjacent cervical segments postfusion. Studies have shown that after fusion surgery, there is increased load on adjacent segments. Definitive treatment of ASD is a topic of continuing research, but in general, treatment choices are dictated by patient age and degree of debilitation. Investigators have also studied the risk factors associated with spinal fusion that may predispose certain patients to ASD postfusion, and these data are invaluable for properly counseling patients considering spinal fusion surgery. Biomechanical studies have confirmed the added stress on adjacent segments in the cervical and lumbar spine. The diagnosis of cervical ASD is complicated given the imprecise correlation of radiographic and clinical findings. Although radiological and clinical diagnoses do not always correlate, radiographs and clinical examination dictate how a patient with prolonged pain is treated. Options for both cervical and lumbar spine ASD include fusion and/or decompression. Current studies are encouraging regarding the adoption of arthroplasty in spinal surgery, but more long

  18. Circulation and transformation of Atlantic water in the Eurasian Basin and the contribution of the Fram Strait inflow branch to the Arctic Ocean heat budget

    NASA Astrophysics Data System (ADS)

    Rudels, Bert; Korhonen, Meri; Schauer, Ursula; Pisarev, Sergey; Rabe, Benjamin; Wisotzki, Andreas

    2015-03-01

    The inflows of Atlantic water from the Nordic Seas to the Arctic Ocean through Fram Strait and over the Barents Sea are examined and their pathways and transformations in the Eurasian Basin are described based primarily on hydrographic observations from two cruises with RV Polarstern in 2007 and 2011. The contrast between the high salinity Atlantic water core in the Nansen Basin and the lower Atlantic water salinity in the Amundsen Basin, combined with a salinity minimum below the Atlantic layer, suggest that the Fram Strait branch mainly remains in the Nansen Basin, while the Barents Sea branch continues along the continental slope, enters the Amundsen Basin and provides most of the Atlantic water in the Makarov and Canada basins. To examine the consequences of such a circulation pattern recently published estimates of the in- and outflows of volume and liquid freshwater through the Barents Sea, Bering Strait and the Canadian Arctic Archipelago as well as river runoff, net precipitation and ice export are reviewed and added together. To achieve volume and freshwater balances net outflows through Fram Strait of 2.3 Sv and 100 mSv respectively are required. This is reasonably close to the recently reported Fram Strait transport estimates. The net outflows are separated into two parts, upper layer transports, less dense than the entering Atlantic water, and lower layer transports, as dense as or denser than the Atlantic water. The largest net volume outflow occurs in the lower layer, 1.65 Sv, while the liquid freshwater is almost exclusively exported in the 0.64 Sv net outflow in upper layer, leading to unrealistically low salinities in the upper layer compared with observations. Atlantic water is north of Svalbard transformed into less saline surface water through melting of sea ice, which can supply the necessary higher salinity (halocline) water to the upper layer. 1.23 Sv of halocline water of salinity 34.2 must be added to obtain a more realistic salinity of 33

  19. The southwestern Nansen Basin: Crustal stretching and sea floor spreading

    NASA Astrophysics Data System (ADS)

    Berglar, Kai; Ehrhardt, Axel; Damm, Volkmar; Heyde, Ingo; Schreckenberger, Bernd; Barckhausen, Udo

    2014-05-01

    New geophysical data were collected in August/September 2013 north of Svalbard in the zone from the North Barents shelf towards the oceanic Nansen Basin. We acquired 1056 km of multi-channel seismic data, 2658 km of magnetic data and more than 5000 km of gravity, bathymetric and sediment echosounder data. In the east of the working area, the transition from the Yermak Plateau to the Nansen Basin is characterized by block faulting and well developed syn-rift basins. A large crustal block located about 80 km east of the Yermak Plateau and 120 km north of the slope of the Barents shelf indicates extensive rifting and east-west directed crustal stretching and the absence of oceanic crust in that area. A different picture is found north of Kvitoya Island, in the western part of the working area. There, the slope of the Barents shelf is very steep and a distinct continent-ocean-boundary seems to be located directly at the foot of the slope where we interpret oceanic crust characterized by irregular topography based on the multi-channel seismic data. This will be tested by an analysis of the gravity and magnetic data which is currently work in progress. The combination of east-west-directed continental stretching east of the Yermak Plateau and adjacent oceanic crust to the west points to an opening of the southwesternmost part of the Nansen Basin prior to the spreading of the Gakkel Ridge, possibly related to the opening of the Amerasian Basin.

  20. Assessment of the hindcast, nowcast and forecast capabilities of the Mercator-Ocean high resolution ocean forecasting system in the Global and Atlantic and Mediterranean basins.

    NASA Astrophysics Data System (ADS)

    Lellouche, Jean-Michel; Tranchant, Benoît.; Bourdallé-Badie, Romain; Le Galloudec, Olivier; Greiner, Eric; Benkiran, Mounir; Derval, Corine; Testut, Charles-Emmanuel

    2010-05-01

    In the framework of the European project GMES/MyOcean, Mercator-Ocean has been designing a hierarchy of ocean analysis and forecasting systems based on numerical models of the ocean and data assimilation methods. Since April 2008, Mercator-Ocean runs an Atlantic and Mediterranean system at 1/12° between 20°S and 80°N. Since a few months, a global system, with the same horizontal and vertical resolution (50 levels on the vertical with a surface refinement), runs also in an operational mode. These two systems are eddy resolving. The ocean and sea ice models are based on the NEMO code. The data assimilation algorithm is a reduced order Kalman filter using 3D multivariate modal decomposition of the forecast error covariance. The system assimilates conjointly altimeter data, SST and in situ observations (temperature and salinity profiles, including ARGO data) in order to provide the initial conditions required for numerical ocean prediction. The main characteristics of the assimilation system are (i) the background error covariances calculated from a free oceanic simulation, (ii) the adaptive error variance, (iii) the use of the localization technique and (iv) the use of the IAU (Incremental Analysis Update) procedure where analysis increments are inserted at every time step over the same period as the data assimilation window. The real time operation of these systems produce each week realistic 3-dimensional oceanic conditions (temperature, salinity, currents,…) two weeks back in time (hindcast and nowcast) and a one or two weeks forecast, driven at the surface by atmospheric conditions from the European Center for Medium Range Weather Forecast (ECMWF). Moreover, the Atlantic and Mediterranean system is operated daily to produce 7 days ocean forecasts with daily updates of the ECMWF atmospheric forcing. A new version of the regional system is planned to replace soon the actual one with many improvements concerning the ocean model and the assimilation scheme

  1. Multi-channel seismic reflection measurements in the Eurasian Basin, Arctic Ocean, from U.S. ice station Fram-IV

    NASA Astrophysics Data System (ADS)

    Kristoffersen, Yngve; Husebye, Eystein S.

    1985-04-01

    We present the first multi-channel seismic reflection data ever collected from the Eurasian Basin of the Arctic Ocean. The 200 km data set was acquired by a 20 channel sonobuoy array deployed at U.S. ice drift station FRAM-IV and operated for 34 days about 370 km north of Svalbard in April-May 1982. Cross array drift and ice floe rotation which may constitute the most serious obstacle to the advantage of multi-channel data acquisition did only occur to a minor degree during the experiment and render most of the data set suitable for processing using common mid-point binning. A 0.7-1.4 s (two-way traveltime) thick sedimentary section has been deposited over oceanic crust of mid-Oligocene age below the Barents Abyssal Plain. In the deepest part, sediments are infilling topographic lows which indicate predominantly turbidite deposition. Erosional truncations are only locally present in the central part of the section. Conformable bedforms deposited over gentle basement highs indicate a relatively stable bottom current regime since mid-Oligocene time. Thus the establishment of a deep water connection between the Arctic Ocean and lower latitude water masses appear to have had only minor effect on Eurasian Basin bottom current circulation. Extensive submarine slide scars on the north slope of Yermak Plateau show that mass waste have been a sediment source to the Barents Abyssal Plain.

  2. Tectonic and geodynamic setting of oil and gas basins of the Soviet Union

    SciTech Connect

    Khain, V.E.; Sokolov, B.A. ); Kleshchev, K.A.; Shein, V.S. )

    1991-02-01

    Within the territory of the Soviet Union and its off-shore economic zone are about 70 sedimentary basins containing oil and gas. The basins include almost all basin types described in present-day plate-tectonic classifications, namely (1) intracontinental and pericontinental rifts, suprarift syneclises, and zones of pericratonic downwarps; (2) ancient passive margins of continents with adjacent overthrust fold system; (3) modern passive margins of continents; (4) zones of convergence of lithospheric plates (i.e., zones of subduction of oceanic plates below continental plates); and (5) zones of collision of continental lithospheric plates. So, far, the only type of basin not identified within the territory of the Soviet Union is the pull-apart basin. The location and distribution of oil and gas deposits in the section of a basin, prevailing types of traps, and scale of potential resources are all features influenced by the geodynamic type of the basin.

  3. Evidence for Thin Oceanic Crust on the Extinct Aegir Ridge, Norwegian Basin, N.E. Atlantic Derived from Satellite Gravity Inversion

    NASA Astrophysics Data System (ADS)

    Greenhalgh, E. E.; Kusznir, N. J.

    2006-12-01

    Satellite gravity inversion incorporating a lithosphere thermal gravity correction has been used to map crustal thickness and lithosphere thinning factor for the N.E. Atlantic. The inversion of gravity data to determine crustal thickness incorporates a lithosphere thermal gravity anomaly correction for both oceanic and continental margin lithosphere. Predicted crustal thicknesses in the Norwegian Basin are between 7 and 4 km on the extinct Aegir oceanic ridge which ceased sea-floor spreading in the Oligocene. Crustal thickness estimates do not include a correction for sediment thickness and are upper bounds. Crustal thicknesses determined by gravity inversion for the Aegir Ridge are consistent with recent estimates derived using refraction seismology by Breivik et al. (2006). Failure to incorporate a lithosphere thermal gravity anomaly correction produces an over-estimate of crustal thickness. Oceanic crustal thicknesses within the Norwegian Basin are predicted by the gravity inversion to increase to 9-10 km eastwards towards the Norwegian (Moere) and westwards towards the Jan Mayen micro-continent, consistent with volcanic margin continental breakup at the end of the Palaeocene. The observation (from gravity inversion and seismic refraction studies) of thin oceanic crust produced by the Aegir ocean ridge in the Oligocene has implications for the temporal evolution of asthenosphere temperature under the N.E. Atlantic during the Tertiary. Thin Oligocene oceanic crust may imply cool (normal) asthenosphere temperatures during the Oligocene in contrast to elevated asthenosphere temperatures in the Palaeocene and Miocene-Recent as indicated by volcanic margin formation and the formation of Iceland respectively. Gravity inversion also predicts a region of thin oceanic crust to the west of the northern part of the Jan Mayen micro-continent and to the east of the thicker oceanic crust currently being formed at the Kolbeinsey Ridge. Thicker crust (c.f. ocean basins) is

  4. What role does crustal heterogeneity play on continental break-up; the interplay of a foldbelt, rift system and ocean basin in the South Atlantic

    NASA Astrophysics Data System (ADS)

    Paton, Douglas; Mortimer, Estelle; Hodgson, Neil

    2015-04-01

    Although extensively studied, two key questions remain unanswered regarding the evolution of the southern South Atlantic. Firstly, where is the Cape Foldbelt (CFB) in offshore South Africa? The CFB is part of the broader Gonwanian Orogeny that prior to South Atlantic rifting continued into the Ventana Foldbelt of Argentina but to date its location in the offshore part of South Africa remains enigmatic. Secondly, the conjugate rift basin to South Africa is the Colorado Basin in Argentina but why does it trend east-west despite its perpendicular orientation to the Atlantic spreading ridge? Current plate models and structural understands cannot explain these fundamental questions. We use newly acquired deep reflection seismic data in the Orange Basin, South Africa, to develop a new structural model for the southern South Atlantic. We characterise the geometry of the Cape Foldbelt onshore and for the first time correlate it into the offshore. We show that it has a north-south trend immediately to the north of the Cape Peninsula but then has a syntaxis (Garies syntaxis) that results in a change to an east-west orientation. This forms the missing jigsaw piece of the Atlantic reconstruction as this is directly beside the restored Colorado Basin. When considered within the pre-break up structural configuration our observations imply that prior to the main phase of Atlantic rifting in the Mezosoic there was significant variation in crustal geometry incorporating the Orange Basin of South Africa, the Colorado Basin and the Gariep Belt of Namibia. These faults were active during Gondwana rifting, but the Colorado rift failed resulting in the present day location of the South Atlantic. Not only do our results improve our understanding of the evolution of the South Atlantic ocean, they highlight the importance of differentiating between early rift evolution and strain localisation during the subsequent rift phase prior to seafloor spreading.

  5. Spatial and seasonal responses of precipitation in the Ganges and Brahmaputra river basins to ENSO and Indian Ocean dipole modes: implications for flooding and drought

    USGS Publications Warehouse

    Pervez, Md Shahriar; Henebry, Geoffry M.

    2015-01-01

    We evaluated the spatial and seasonal responses of precipitation in the Ganges and Brahmaputra basins as modulated by the El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) modes using Global Precipitation Climatology Centre (GPCC) full data reanalysis of monthly global land-surface precipitation data from 1901 to 2010 with a spatial resolution of 0.5° × 0.5°. The GPCC monthly total precipitation climatology targeting the period 1951–2000 was used to compute gridded monthly anomalies for the entire time period. The gridded monthly anomalies were averaged for the years influenced by combinations of climate modes. Occurrences of El Niño alone significantly reduce (88% of the long-term average (LTA)) precipitation during the monsoon months in the western and southeastern Ganges Basin. In contrast, occurrences of La Niña and co-occurrences of La Niña and negative IOD events significantly enhance (110 and 109% of LTA in the Ganges and Brahmaputra Basin, respectively) precipitation across both basins. When El Niño co-occurs with positive IOD events, the impacts of El Niño on the basins' precipitation diminishes. When there is no active ENSO or IOD events (occurring in 41 out of 110 years), precipitation remains below average (95% of LTA) in the agriculturally intensive areas of Haryana, Uttar Pradesh, Rajasthan, Madhya Pradesh, and Western Nepal in the Ganges Basin, whereas precipitation remains average to above average (104% of LTA) across the Brahmaputra Basin. This pattern implies that a regular water deficit is likely, especially in the Ganges Basin, with implications for the agriculture sector due to its reliance on consistent rainfall for successful production. Historically, major droughts occurred during El Niño and co-occurrences of El Niño and positive IOD events, while major flooding occurred during La Niña and co-occurrences of La Niña and negative IOD events in the basins. This observational analysis will facilitate well

  6. Spatial and seasonal responses of precipitation in the Ganges and Brahmaputra river basins to ENSO and Indian Ocean dipole modes: implications for flooding and drought

    NASA Astrophysics Data System (ADS)

    Pervez, M. S.; Henebry, G. M.

    2015-01-01

    We evaluated the spatial and seasonal responses of precipitation in the Ganges and Brahmaputra basins as modulated by the El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) modes using Global Precipitation Climatology Centre (GPCC) full data reanalysis of monthly global land-surface precipitation data from 1901 to 2010 with a spatial resolution of 0.5° × 0.5°. The GPCC monthly total precipitation climatology targeting the period 1951-2000 was used to compute gridded monthly anomalies for the entire time period. The gridded monthly anomalies were averaged for the years influenced by combinations of climate modes. Occurrences of El Niño alone significantly reduce (88% of the long-term average (LTA)) precipitation during the monsoon months in the western and southeastern Ganges Basin. In contrast, occurrences of La Niña and co-occurrences of La Niña and negative IOD events significantly enhance (110 and 109% of LTA in the Ganges and Brahmaputra Basin, respectively) precipitation across both basins. When El Niño co-occurs with positive IOD events, the impacts of El Niño on the basins' precipitation diminishes. When there is no active ENSO or IOD events (occurring in 41 out of 110 years), precipitation remains below average (95% of LTA) in the agriculturally intensive areas of Haryana, Uttar Pradesh, Rajasthan, Madhya Pradesh, and Western Nepal in the Ganges Basin, whereas precipitation remains average to above average (104% of LTA) across the Brahmaputra Basin. This pattern implies that a regular water deficit is likely, especially in the Ganges Basin, with implications for the agriculture sector due to its reliance on consistent rainfall for successful production. Historically, major droughts occurred during El Niño and co-occurrences of El Niño and positive IOD events, while major flooding occurred during La Niña and co-occurrences of La Niña and negative IOD events in the basins. This observational analysis will facilitate well

  7. Iron and humic-type fluorescent dissolved organic matter in the Chukchi Sea and Canada Basin of the western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Nakayama, Yuta; Fujita, Satoshi; Kuma, Kenshi; Shimada, Koji

    2011-07-01

    The concentrations of dissolved Fe ([D-Fe]), total dissolvable Fe ([T-Fe]), humic-type fluorescence intensity (humic F intensity) as humic-type fluorescent dissolved organic matter, and nutrients were vertically determined in the shelf, slope, and basin regions (Chukchi Sea and Canada Basin) of the western Arctic Ocean during 1-27 September 2008. In all stations, the remarkably high [D-Fe] and humic F intensity were found at depths between 25 and 200 m with the subsurface maxima of [D-Fe] (1.0-3.2 nM) and humic F intensity (4-5 quinine sulfate units) in the upper halocline layer (upper HL), being associated with a prominent nutrient maximum. The high [D-Fe] and humic F intensity within the upper HL are probably attributed to the Fe(III) complexation with natural organic ligands, such as marine dissolved humic substances, resulting from main processes of the brine rejection during sea ice formation and interactions with sediments on the shelves. However, subsurface maxima (10-50 nM) of [T-Fe] were found in the lower halocline layer, beneath the upper HL, of all slope and basin regions and are mainly attributed to the resuspension of sedimentary particles in the shelf region. The finding of subsurface iron maxima in the halocline water of all regions may be the first confirmation for the lateral iron transport into the halocline layer from the shelves to the Arctic Basin.

  8. Mid-1980s distribution of tritium, 3He, 14C and 39Ar in the Greenland/Norwegian seas and the Nansen basin of the Arctic ocean

    SciTech Connect

    Schlosser, P.; Bonisch, G.; Kromer, B.; Loosli, H.H.; Buehler, R.

    1995-12-31

    The distributions of tritium/3He, 14C and 39Ar observed in the period between 1985 and 1987 in the Greenland/Norwegian Seas and the Nansen Basin of the Arctic Ocean are presented. The data are used to outline aspects of the large-scale circulation and the exchange of deep water between the Greenland/Norwegian Seas and the Nansen Basin. Additionally, semi-quantitative estimates of mean ages of the main water masses found in these regions are obtained. Apparent tritium/3He ages of the upper waters (depth <500m) vary from close to zero in the Norwegian Current to about 15 years at the lower boundary of the Arctic halocline. The deep waters (>1,500m depth) of the Greenland/ Norwegian Seas show apparent tritium/3He ages between about 17 years in the Greenland Sea and 30 years in the Norwegian Sea.

  9. Geochemical characteristics of the Permian basins and their provenances across the Solonker Suture Zone: Assessment of net crustal growth during the closure of the Palaeo-Asian Ocean

    NASA Astrophysics Data System (ADS)

    Eizenhöfer, Paul R.; Zhao, Guochun; Zhang, Jian; Han, Yigui; Hou, Wenzhu; Liu, Dongxing; Wang, Bo

    2015-05-01

    The Solonker Suture Zone is commonly recognised as the location of the Late Permian to Early Triassic closure of the Palaeo-Asian Ocean in the southeastern segment of the Central Asian Orogenic Belt. However, the absence of typical suture-related features, as a consequence of uncommon collisional geometries, gave it a cryptic nature. Thus, the tectonic setting, which led to suturing, still remains enigmatic. A geochemical characterisation of Permian sedimentary and volcanic rocks across the suture was carried out. Supplemented with Hf and Nd isotopic analyses, this approach enables not only a better definition of such regional suture, but also estimates on the long-controversial issue of net crustal growth in accretionary tectonic environments. The results indicate short sedimentary transport distances between the arc basins and their provenances, of which the studied volcanic rocks were a major contributor. Similar enrichment and depletion patterns with respect to N-MORB and average continental crust further corroborate a close source-sediment relationship. Immobile element provenance analyses indicate that the active continental northern margin of the North China Craton was a major source for arc basins to the south of the Solonker Suture Zone. To its north, arc basins are interpreted to be sourced by a more complex mixture of provenances, e.g., the Baolidao volcanic arc suite and the heterogenous Precambrian basement of southern Mongolia. An overall collisional tectonic setting across the suture is recognised. The geochemical signature of sedimentary rocks to the south of the suture points at an active continental arc setting, whereas the bimodal geochemical distribution of the samples to the north shows a contemporaneous active oceanic island arc as well as a passive margin environment. These features favour a double-sided subduction of the Palaeo-Asian Ocean beneath the North China Craton and the Mongolian Arcs throughout the Palaeozoic, including back

  10. Large-scale temperature and salinity changes in the upper Canadian Basin of the Arctic Ocean at a time of a drastic Arctic Oscillation inversion

    NASA Astrophysics Data System (ADS)

    Bourgain, P.; Gascard, J. C.; Shi, J.; Zhao, J.

    2013-04-01

    Between 2008 and 2010, the Arctic Oscillation index over Arctic regions shifted from positive values corresponding to more cyclonic conditions prevailing during the 4th International Polar Year (IPY) period (2007-2008) to extremely negative values corresponding to strong anticyclonic conditions in 2010. In this context, we investigated the recent large-scale evolution of the upper western Arctic Ocean, based on temperature and salinity summertime observations collected during icebreaker campaigns and from ice-tethered profilers (ITPs) drifting across the region in 2008 and 2010. Particularly, we focused on (1) the freshwater content which was extensively studied during previous years, (2) the near-surface temperature maximum due to incoming solar radiation, and (3) the water masses advected from the Pacific Ocean into the Arctic Ocean. The observations revealed a freshwater content change in the Canadian Basin during this time period. South of 80° N, the freshwater content increased, while north of 80° N, less freshening occurred in 2010 compared to 2008. This was more likely due to the strong anticyclonicity characteristic of a low AO index mode that enhanced both a wind-generated Ekman pumping in the Beaufort Gyre and a possible diversion of the Siberian River runoff toward the Eurasian Basin at the same time. The near-surface temperature maximum due to incoming solar radiation was almost 1 °C colder in the southern Canada Basin (south of 75° N) in 2010 compared to 2008, which contrasted with the positive trend observed during previous years. This was more likely due to higher summer sea ice concentration in 2010 compared to 2008 in that region, and surface albedo feedback reflecting more sun radiation back in space. The Pacific water (PaW) was also subjected to strong spatial and temporal variability between 2008 and 2010. In the Canada Basin, both summer and winter PaW signatures were stronger between 75° N and 80° N. This was more likely due to a strong

  11. Baseline monitoring of the Western Arctic Ocean estimates 20% of the Canadian Basin surface waters are undersaturated with respect to aragonite

    USGS Publications Warehouse

    Robbins, Lisa L.; Wynn, Jonathan G.; Lisle, John T.; Yates, Kimberly K.; Knorr, Paul O.; Byrne, Robert H.; Liu, Xuewu; Patsavas, Mark C.; Azetsu-Scott, Kumiko; Takahashi, Taro

    2013-01-01

    Marine surface waters are being acidified due to uptake of anthropogenic carbon dioxide, resulting in surface ocean areas of undersaturation with respect to carbonate minerals, including aragonite. In the Arctic Ocean, acidification is expected to occur at an accelerated rate with respect to the global oceans, but a paucity of baseline data has limited our understanding of the extent of Arctic undersaturation and of regional variations in rates and causes. The lack of data has also hindered refinement of models aimed at projecting future trends of ocean acidification. Here, based on more than 34,000 data records collected in 2010 and 2011, we establish a baseline of inorganic carbon data (pH, total alkalinity, dissolved inorganic carbon, partial pressure of carbon dioxide, and aragonite saturation index) for the western Arctic Ocean. This data set documents aragonite undersaturation in ~20% of the surface waters of the combined Canada and Makarov basins, an area characterized by recent acceleration of sea ice loss. Conservative tracer studies using stable oxygen isotopic data from 307 sites show that while the entire surface of this area receives abundant freshwater from meteoric sources, freshwater from sea ice melt is most closely linked to the areas of carbonate mineral undersaturation. These data link the Arctic Ocean’s largest area of aragonite undersaturation to sea ice melt and atmospheric CO2 absorption in areas of low buffering capacity. Some relatively supersaturated areas can be linked to localized biological activity. Collectively, these observations can be used to project trends of ocean acidification in higher latitude marine surface waters where inorganic carbon chemistry is largely influenced by sea ice meltwater.

  12. Protactinium-231 and thorium-230 abundances and high scavenging rates in the western arctic ocean

    PubMed

    Edmonds; Moran; Hoff; Smith; Edwards

    1998-04-17

    The Canadian Basin of the Arctic Ocean, largely ice covered and isolated from deep contact with the more dynamic Eurasian Basin by the Lomonosov Ridge, has historically been considered an area of low productivity and particle flux and sluggish circulation. High-sensitivity mass-spectrometric measurements of the naturally occurring radionuclides protactinium-231 and thorium-230 in the deep Canada Basin and on the adjacent shelf indicate high particle fluxes and scavenging rates in this region. The thorium-232 data suggest that offshore advection of particulate material from the shelves contributes to scavenging of reactive materials in areas of permanent ice cover. PMID:9545211

  13. Mooring-based long-term observation of oceanographic condition in the Chukchi Ses and Canada Basin of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Kikuchi, Takashi; Itoh, Motoyo; Nishino, Shigeto; Watanabe, Eiji

    2015-04-01

    Changes of the Arctic Ocean environment are well known as one of the most remarkable evidences of global warming, attracting social and public attentions as well as scientists'. However, to illustrate on-going changes and predict future condition of the Arctic marine environment, we still do not have enough knowledge of Arctic sea ice and marine environment. In particular, lack of observation data in winter, e.g., under sea ice, still remains a key issue for precise understanding of seasonal cycle on oceanographic condition in the Arctic Ocean. Mooring-based observation is one of the most useful methods to collect year-long data in the Arctic Ocean. We have been conducting long-term monitoring using mooring system in the Pacific sector of the Arctic Ocean. Volume, heat, and freshwater fluxes through Barrow Canyon where is a major conduit of Pacific-origin water-masses into the Canada Basin have been observed since 2000. We show from an analysis of the mooring results that volume flux through Barrow Canyon was about 60 % of Bering Strait volume flux. Averaged heat flux ranges from 0.9 to 3.07 TW, which could melt 88,000 to 300,000 km2 of 1m thick ice in the Canada Basin, which likely contributed to sea ice retreat in the Pacific sector of the Arctic Ocean. In winter, we found inter-annual variability in salinity related to coastal polynya activity in the Chukchi Sea. In collaboration with Distributed Biological Observatory (DBO) project, which is one of the tasks of Sustaining Arctic Observing Network (SAON), we also initiated year-long mooring observation in the Hope Valley of the southern Chukchi Sea since 2012. Interestingly, winter oceanographic conditions in the Hope Valley are greatly different between in 2012-2013 and in 2013-2014. We speculate that differences of sea ice freeze-up and coastal polynya activity in the southern Chukchi Sea cause significant difference of winter oceanographic condition. It suggests that recent sea ice reduction in the Pacific

  14. Dansgaard-Oeschger Cycles and the California Current System: Planktonic foraminiferal response to rapid climate change in Santa Barbara Basin, Ocean Drilling Program Hole 893A

    NASA Astrophysics Data System (ADS)

    Hendy, Ingrid L.; Kennett, James P.

    2000-02-01

    High-resolution planktonic foraminiferal census data from Santa Barbara Basin (Ocean Drilling Program hole 893A) demonstrate major assemblage switches between 25 and 60 ka that were associated with Dansgaard-Oeschger cycles. Stadials dominated by Neogloboquadrina pachyderma (sinistral), and Globigerinoides glutinata suggest a strong subpolar California Current influence, while interstadials marked by abundant N. pachyderma (dextral) and G. bulloides indicate a relative increase in subtropical countercurrent influence. Modern analog technique and transfer function (F-20RSC) temperature reconstructions support δ18O evidence of large rapid (70 years or less) sea surface temperature shifts (3° to 5°C) between stadials and interstadials. Changes in the vertical temperature gradient and water column structure (thermocline depth) are recorded by planktonic faunal oscillations suggest bimodal stability in the organization of North Pacific surface ocean circulation. Santa Barbara Basin surface water demonstrates the rapid response of the California Current System to reorganization of North Pacific atmospheric circulation during rapid climate change. Supporting assemblage data are, available on diskette or via Anonymous FTP from Kosmos.agu.org, Directory APEND (username = anonymous, Password = guest). Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009 or by phone at 800-966-2481; $5.00. Payment must accompany order.

  15. Discussion of the Ionian and Levantine Seas, NATO workshop on atmospheric and oceanic circulation in the Mediterranean Basin

    SciTech Connect

    Hopkins, T.S.

    1984-01-01

    The gross features and distinctiveness of its thermohaline circulation are described for the Ionian and Levantine Seas of the eastern Mediterranean. The paper also discusses the significance of the thermohaline coupling with neighboring Mediterranean basins. 22 refs. (ACR)

  16. Evidence of different ocean responses to atmospheric pressurevariations in the Atlantic, Indian and Pacific Basins as deduced fromERS-2 altimetric data

    NASA Astrophysics Data System (ADS)

    Gómez-Enri, J.; Villares, P.; Bruno, M.; Catalán, M.

    2004-02-01

    . The exponential increase in the use of altimeter data in oceanographic studies in the past two decades has improved the knowledge of the processes that govern the interaction between the ocean and the atmosphere. One of these processes is the response of the ocean to atmospheric pressure variations, which has been deeply analysed in the past. That response is based on the isostatic assumption used to establish a standard correction for altimetric purposes, the Inverse Barometer Correction (IBC). As a general rule, the ocean goes up/down 1cm when the atmospheric pressure goes down/up 1mbar. However, in light of recent works in some oceanic regions, discrepancies arise when the real response is compared to the hypothetical one. It is important to quantify this discrepancy, in order to improve the accuracy of the correction, which is one of the most significant geophysical corrections applied to altimeter records. Some aspects of this response remain unclear, such as the real space-temporal scales where IBC can be applied, the influence of wind, non-isostatic atmospheric pressure-driven signals, and the effect of aliasing from high frequency signals. This paper is an attempt to gain insight into this phenomenon. The data used are the residuals obtained between sea surface heights from the ERS-2 altimeter and the outputs of a global barotropic ocean model. Significant departures from the hypothetical isostatic response in all data series (spatial and temporal domain) have been found, especially in the case of altimeter records. By applying the collinear track method, we observe that the estimated Atlantic Ocean response is quite similar to the one deduced from the isostatic assumption at all latitudinal bands. Nonetheless, the Indian and Pacific Oceans show important departures from the hypothetical value at low latitudes. Results obtained with the crossover track method show important deviations at low latitudes in the three basins. In order to understand why the

  17. A study of biases in simulation of the Indian Ocean basin mode and its capacitor effect in CMIP3/CMIP5 models

    NASA Astrophysics Data System (ADS)

    Tao, Weichen; Huang, Gang; Hu, Kaiming; Gong, Hainan; Wen, Guanhuan; Liu, Lin

    2016-01-01

    Based on 15 Coupled Model Intercomparison Project (CMIP) phase 3 (CMIP3) and 32 CMIP phase 5 (CMIP5) models, a detailed diagnosis was carried out to understand what compose the biases in simulation of the Indian Ocean basin mode (IOBM) and its capacitor effect. Cloud-radiation-SST (CRS) feedback and wind-evaporation-SST (WES) feedback are the two major atmospheric processes for SST changes. Most CMIP models simulate a stronger CRS feedback and a weaker WES feedback. During boreal fall of the El Niño/Southern Oscillation developing year and the following spring, there are weak biases of suppressed rainfall anomalies over the Maritime Continent and anomalous anticyclone over South Indian Ocean. Most CMIP models simulate reasonable short wave radiation (SWR) and weaker latent heat flux (LHF) anomalies. This leads to a weak bias of atmospheric processes. During winter, however, the rainfall anomalies are stronger due to west bias, and the anomalous anticyclone is comparable to observations. As such, most models simulate stronger SWR and reasonable LHF anomalies, leading to a strong bias of atmospheric processes. The thermocline feedback is stronger in most models. Though there is a deep bias of climatology thermocline, most models capture reasonable sea surface height-induced SST anomalies. Therefore, the effect of oceanic processes offset the weak bias of atmospheric processes in spring, and the tropical Indian Ocean warming persists into summer. However, anomalous northwest Pacific (NWP) anticyclone is weaker due to weak and west bias of the capacitor effect. The unrealistic western Pacific SST anomalies in models favor the westward extension of Rossby wave from the Pacific, weakening the effect of Kelvin wave from the Indian Ocean. Moreover, the western Pacific warming forces the NWP anticyclone move farther north than observations, suggesting a major forcing from the Pacific. Compared to CMIP3, CMIP5 models simulate the feedbacks more realistically and display

  18. Significance of Nain-Baft ophiolitic belt (Iran): Short-lived, transtensional Cretaceous back-arc oceanic basins over the Tethyan subduction zone

    NASA Astrophysics Data System (ADS)

    Moghadam, Hadi Shafaii; Whitechurch, Hubert; Rahgoshay, Mohamad; Monsef, Iman

    2009-12-01

    Four dismembered massifs belonging to the Nain-Baft ophiolitic belt (Central Iran) stretch in a NW-SE direction parallel to the fossil active margin of the Iranian Continental Block (Sanandaj-Sirjan Zone). They are separated by huge transcurrent faults. The Nain, Dehshir, Shahr-e-Babak and Baft massifs are composed of associated slices of harzburgites, small bodies of gabbros and dike swarm complexes, accompanied by various extrusives from basaltic-andesitic lava flows and breccias to dacites and rhyolites. Trace element geochemistry of these lavas displays calc-alkaline and arc-tholeiite signatures, suggesting a back-arc origin for these ophiolites. This is in accordance with the position of these massifs, to the North of the Mesozoic Magmatic Arc crosscutting the Sanadaj-Sirjan Zone. Conventional K-Ar datings on amphibole within amphibolite and gabbros deliver ages between 93 Ma and 67 Ma. These ages are in good agreement with the stratigraphic age of the conformably Cenomanian to Maastrichtian sedimentary cover of the extrusives. The closure of these back-arc basins occurred in the Middle Paleocene as testified by the presence of neritic limestones, sealing all the tectonic contacts. The general geological setting of the Nain-Baft belt suggests that these massifs generated in a transtensional small back-arc basins separated by transcurrent faults. These short-lived transtensional basins result from the oblique subduction of the Tethyan Ocean under the Iranian Continental Block.

  19. The Detrital White Mica 40Ar/39Ar Record of the Katawaz Remnant Ocean Basin, Pakistan, and Tectonic Implications for the Himalayan Source Region

    NASA Astrophysics Data System (ADS)

    Zhuang, G.; Najman, Y.; Wijbrans, J. R.; Millar, I.; Carter, A.

    2014-12-01

    The Paleogene-Neogene sedimentary rocks in the Katawaz remnant ocean basin, Pakistan were thought to be a product of a fan-deltaic system, analogous to the modern Indus River and delta. A preliminary detrital zircon U-Pb study (Carter et al 2010) supported materials derived from the nascent western Himalaya and associated magmatic arc but that study was based on too few samples to fully characterize the whole series. Moreover, the chronology in the Katawaz basin was previously not well constrained, which impedes accurate comparison to other Himalaya foreland records. Here, we present a densely sampled study of detrital white mica 40Ar/39Ar. This study aims to: (1) constrain sedimentary ages of major lithostratigraphic units, (2) understand the exhumation history of the source region, and (3) reconstruct the paleodrainage system in NW Himalayan foreland. New 40Ar/39Ar data, together with a complementary study of detrital zircon U-Pb, constrain the sand-rich, fluvial-dominated Shaigalu Member to span from <34-36 Ma (basal sample) to <22 Ma (uppermost sample). The basal Shaigalu Member demonstrates similarity of ages of detrital zircon U-Pb and detrital white mica 40Ar/39Ar; both are characterized by a dominant peak of ca. 37 Ma. The dominant 37 Ma peak of detrital white mica 40Ar/39Ar ages has also been identified in the late Eocene Balakot Formation (Najman et al. 2001), the oldest terrestrial unit in the Himalayan peripheral foreland basin, and which is Himalayan-derived. We interpret the similarity in youngest age peak (37 Ma) between U-Pb and 40Ar/39Ar as a signal of rapid exhumation related to a rising western Himalaya. Our new 40Ar/39Ar data also reveal that sediment sources changed through time, as demonstrated by the disappearance of the 37 Ma population up-section and re-occurrence at the top. This could be related to either migration of the drainage system and/or changes in sediment sources. Finally, our study indicates that the latest Eocene rapid

  20. Intracontinental accommodation of oceanic transform shear: an alternative geodynamic scenario for explaining seismicity, magmatism, and basin opening in passive margin environments

    NASA Astrophysics Data System (ADS)

    Salvini, F.; Storti, F.

    2003-04-01

    In the last years it has been recognised that one of the basic principles of Plate Tectonics i.e. the localisation of plate interactions at their boundaries whereas internal regions remain virtually undeformed, is an oversimplified assumption. Geological, geophysical and geodetic data indicate that plate interiors are associated to a much higher level of neotectonic activity than hitherto realised. Lithosphere buckle folding and intraplate strike-slip faulting during plate convergence, density imbalances produced by oceanic ridges, continental margins and plateau uplifts, and flexural unloading of the lithosphere, are geodynamic processes commonly used to explain the occurrence of significant deformations far from plate boundaries. In this contribution we propose that important intraplate deformations can be produced in passive margin environments by the post-rift activity of strike-slip deformation belts transferring differential spreading at constructional plate boundaries into the plate interiors. This despite the plate tectonics theory does not predict any strike-slip movement along fracture zones once they pass outboard of their associated ridge segments and away from the plate boundary. We illustrate the Cenozoic geodynamic framework at the northeastern edge of the Antarctic plate, where we believe there is strong evidence for the occurrence of post-rift strike-slip deformation belts including both the intraridge (transform) and out-of-ridge segments of fracture zones, and their collinear onshore strike-slip fault systems. Deep basins originated along the main traces of these impressively long strike-slip belts, where strong earthquakes have been recorded, including the 1998 Balleny event (8.2 Mw), which is one of the larger intraplate earthquake ever detected. The residual horizontal displacement at the tip of these intraplate strike-slip belts is accommodated by a lithosphere-scale horsetail array of transtensional basins, where subcrustal magmatism has

  1. A History of Warming Sea Surface Temperature and Ocean Acidification Recorded by Planktonic Foraminifera Geochemistry from the Santa Barbara Basin, California

    NASA Astrophysics Data System (ADS)

    Osborne, E.; Thunell, R.; Bizimis, M.; Buckley, W. P., Jr.; benitez-Nelson, C. R.; Chartier, C. J.

    2015-12-01

    The geochemistry of foraminiferal shells has been widely used to reconstruct past conditions of the ocean and climate. Since the onset of the Industrial Revolution, anthropogenically produced CO2 has resulted in an increase in global temperatures and a decline in the mean pH of the world's oceans. The California Current System is a particularly susceptible region to ocean acidification due to natural upwelling processes that also cause a reduction in seawater pH. The trace element concentration of magnesium and boron in planktonic foraminiferal shells are used here as proxies for temperature and carbonate ion concentration ([CO32-]), respectively. Newly developed calibrations relating Mg/Ca ratios to temperature (R2 0.91) and B/Ca ratios to [CO32-] (R2 0.84) for the surface-mixed layer species Globogerina bulloides were generated using material collected in the Santa Barbara Basin sediment trap time-series. Using these empirical relationships, temperature and [CO32-] are reconstructed using a 0.5 meter long multi-core collected within the basin. 210Pb activities were used to determine a sedimentation rate for the core to estimate ages for core samples (sedimentation rate: 0.341 cm/yr). A spike in 137Cs activity is used as a tie-point to the year 1965 coinciding with the peak of nuclear bomb testing. Our down-core record extends through the mid-19th century to create a history of rising sea surface temperatures and declining [CO32-] as a result of anthropogenic CO2 emissions.

  2. Mesoscale activity in the Comoros Basin from satellite altimetry and a high-resolution ocean circulation model

    NASA Astrophysics Data System (ADS)

    Collins, C.; Hermes, J. C.; Reason, C. J. C.

    2014-08-01

    Recently it has been shown that anticyclonic eddies are generated in the Comoros Basin contesting the long-held notion of a single large anticyclonic cell, the Comoros Gyre. Limited knowledge exists about the mesoscale activity within the basin, a potential key source of variability for the Mozambique Channel and subsequently the Agulhas Current. In this paper an automated eddy tracking scheme, applied to satellite altimetry data and a high-resolution model simulation, is used to determine the characteristics of the anticyclonic eddies generated in the Comoros Basin. The generation and characteristics of cyclonic eddies are also investigated. The eddy tracking scheme revealed that anticyclonic eddies are primarily generated west of the tip of Madagascar due to barotropic instabilities whereas cyclonic eddies are mainly generated along the northwest coast of Madagascar as a result of baroclinic instabilities. Anticyclonic eddies, with a mean lifespan of about 3 months, reside in the basin for half their lifespan before propagating into the Mozambique Channel. On the other hand, the majority of cyclonic eddies, with a similar mean lifespan, dissipate within the basin. Initially, the anticyclones, with translation speeds of 6-8 km d-1 and mean radii of 80-100 km, follow the trajectory of the North East Madagascar Current and turn south upon reaching the African coast. The cyclonic eddies tend to be smaller (˜60 km) and have slower translation speeds (2.5-3.5 km d-1) than their anticyclonic counterparts.

  3. Timing of flysch sedimentation in the Ouachita remnant ocean basin: Constraints from U-Pb ages of zircon in subaqueous tuff deposits

    NASA Astrophysics Data System (ADS)

    Shaulis, B. J.; Lapen, T. J.; Casey, J. F.; Staszyc, A.; Newberry, A. S.

    2012-12-01

    New U-Pb ages of zircon from subaqueous tuff in the oldest flysch units deposited in the Ouachita-Marathon remnant ocean basin constrain the absolute timing of orogenic flysch deposition. Zircons from five tuffaceous units distributed throughout the Mississippian Stanley Group in the Ouachita region define its absolute age range and depositional rates (Shaulis et al., 2012, in press). From the lowermost to the uppermost tuff unit analyzed, the weighted averages for the youngest age population range from 328.5 ± 2.7 Ma to 320.7 ± 2.5 Ma. Combined with conodont biostratigraphy, these new zircon ages show sedimentation rates remained low (1-40 m/Ma.) from the end of the Devonian until ~323 Ma. After 323 Ma sedimentation rates increase rapidly to 300-1400 m/Ma and remain high through the deposition of the Pennsylvanian Atoka Formation. The Tesnus Formation (Stanley Group equivalent) in the Marathon region is just 1850 m thick compared to a thickness of ~3000 m for the Stanley Group. The tuffaceous units have only been identified in a single outcrop, but well data from across the region suggest the volcanic units could cover a large area. New U-Pb zircon ages of three tuff units in the Tesnus Formation (320.2 ± 1.7 Ma, 321.5 ± 3.1 Ma, and 321.9 ± 1.7 Ma, lowermost to uppermost) suggest that these tuffs are equivalent to the Mud Creek and Chickasaw Creek tuffs in the Stanley Group. Compared to the Mud Creek and Chickasaw Creek tuffs in the Stanley Group which are separated by nearly 2000 m of sediment, the Tesnus tuffs occur over a much smaller 20 m interval. Based on these proposed tuff correlations, the onset of rapid flysch sedimentation began in the Ouachita region during deposition of the Mud Creek and Chickasaw Creek tuffs (323 Ma) but had not yet begun in the Marathon region during deposition of the age equivalent Tesnus tuffs, where sedimentation rates appear low. This, and dominantly westward paleo-flow indicators (Johnson, 1968), are consistent with a

  4. Two stage melt-rock interaction in the lower oceanic crust of the Parece Vela basin (Philippine sea), evidence from the primitive troctolites from the Godzilla Megamullion

    NASA Astrophysics Data System (ADS)

    Sanfilippo, A.; Dick, H. J.; Ohara, Y.

    2011-12-01

    Godzilla Megamullion is a giant oceanic core complex exposed in an extinct slow- to intermediate-spreading segment of the Parece Vela Basin (Philippine sea) [1; 2]. It exposes lower crust and mantle rocks on the sea-floor, offering a unique opportunity to unravel the architecture and the composition of the lower oceanic lithosphere of an extinct back arc basin. Here we present data on primitive troctolites and associated olivine-gabbros from the breakaway area of the Godzilla Megamullion. On the basis of the olivine/plagioclase volume ratio, the troctolites are subdivided into Ol-troctolites (Ol/Pl >1) and Pl-troctolites (Ol/Pl<1), which show evident textural differences. Ol-troctolites have rounded to polygonal olivine, subhedral plagioclase, and poikilitic clinopyroxene. This texture suggests chemical disequilibrium between the olivine and a melt crystallizing plagioclase and clinopyroxene. We interpret these rocks as reaction products of a dunite matrix with transient basaltic melts [e.g. 3; 4]. Pl-troctolites have euhedral plagioclase and poikilitic olivine and clinopyroxene. Irregular shapes and inverse zoning of the plagioclase chadacrysts within the olivine indicate disequilibrium between existing plagioclase and an olivine-clinopyroxene saturated melt. The occurrence of plagioclase chadacrysts within clinopyroxene ranging from irregular to euhedral in shape suggests crystallization of new lower-Na plagioclase with the clinopyroxene. Olivine oikocrysts in the Pl-troctolites have low-NiO olivine in equilibrium with a high-MgO melt. The Pl-troctolites, then, may be the product of reaction between a plagioclase cumulate and a basaltic melt produced by mixing the high-MgO melt residual to the formation of the Ol-troctolites with new magma. The effect of melt-rock reaction in the Pl- and Ol- troctolites explains the sharp decrease in plagioclase An with respect to Mg# in clinopyroxene and olivine. Furthermore, the melt is shifted towards lower Na, which is

  5. Quaternary history of sea ice and paleoclimate in the Amerasia Basin, Arctic Ocean, as recorded in the cyclical strata of Northwind Ridge

    USGS Publications Warehouse

    Phillips, R.L.; Grantz, A.

    1997-01-01

    The 19 middle-early Pleistocene to Holocene bipartite lithostratigraphic cycles observed in high-resolution piston cores from Northwind Ridge in the Amerasia Basin of the Arctic Ocean, provide a detailed record of alternating glacial and interglacial climatic and oceanographic conditions and of correlative changes in the character and thickness of the sea-ice cover in the Amerasia Basin. Glacial conditions in each cycle are represented by gray pelagic muds that are suboxic, laminated, and essentially lacking in microfossils, macrofossils, trace fossils, and generally in glacial erratics. Interglacial conditions are represented by ochre pelagic muds that are oxic and bioturbated and contain rare to abundant microfossils and abundant glacial erratics. The synglacial laminated gray muds were deposited when the central Amerasia Basin was covered by a floating sheet of sea ice of sufficient thickness and continuity to reduce downwelling solar irradiance and oxygen to levels that precluded photosynthesis, maintenance of a biota, and strong oxidation of the pelagic sediment. Except during the early part of 3 of the 19 synglacial episodes, when it was periodically breached by erratic-bearing glacial icebergs, the floating Arctic Ocean sea-ice sheet was sufficiently thick to block the circulation of icebergs over Northwind Ridge and presumably other areas of the central Arctic Ocean. Interglacial conditions were initiated by abrupt thinning and breakup of the floating sea-ice sheet at the close of glacial time, which permitted surges of glacial erratic-laden ice-bergs to reach Northwind Ridge and the central Arctic Ocean, where they circulated freely and deposited numerous, and relatively thick, erratic clast-rich beds. Breakup of the successive synglacial sea-ice sheets initiated deposition of the interglacial ochre mud units under conditions that allowed sunlight and increased amounts of oxygen to enter the water column, resulting in photosynthesis and biologic

  6. Sedimentation in forearc basins, trenches, and collision zones of the western Pacific: A summary of results from the Ocean Drilling Program

    NASA Astrophysics Data System (ADS)

    Underwood, Michael B.; Ballance, Peter F.; Clift, Peter D.; Hiscott, Richard N.; Marsaglia, Kathleen M.; Pickering, Kevin T.; Reid, R. Pamela

    The comprehensive strategy pursued by the Ocean Drilling Program in the western Pacific Ocean resulted in significant improvements in our understanding of arc-related geologic processes and products. Many types of depositional environments were examined, including intraoceanic forearc basins, backarc basins, trenches, and ridge-trench collision zones. Most of the ODP sites were chosen to address tectonic, geochemical, or hydrologic objectives, but a wealth of new sedimentologic information was generated at the same time. We now have a better appreciation of how intraoceanic forearcs are affected by diverse depositional processes (e.g., debris flows, turbidity currents, and vertical settling of tephra, hemipelagic mud, and pelagic ooze). Detailed turbidite stratigraphy deduced from FMS borehole imagery shows that the Izu-Bonin forearc basin is characterized by a noncyclic basin-plain style of sedimentation, rather than a channelized submarine fan or a channelized slope apron. Detrital modes for volcaniclastic sands in the Izu-Bonin forearc are consistent with an undissected-arc provenance; subdivisions of volcanic texture and glass type provide additional details and support the idea of extensive subaerial production and mixing of epiclastic detritus. Evolution of the Tonga forearc has been affected by a complicated interplay of tectonic subsidence, eustacy, and arc volcanism. Stratigraphic evolution of the Nankai accretionary prism produced a classic upward-coarsening and upward-thickening mega-cycle representative of transition from abyssal hemipelagites to trench turbidites. Turbidite sands within the outer trench-wedge facies display indicators of northwest-directed paleoflow; those flows probably experienced a phase of upslope movement onto the outer wall and deflection back toward the Nankai trench axis. Sand petrography and clay mineralogy collectively support a mixed detrital provenance for the Nankai trench wedge; the main source area is located in the Izu

  7. Diagnosing isopycnal diffusivity in an eddying, idealized midlatitude ocean basin via Lagrangian, in Situ, Global, High-Performance Particle Tracking (LIGHT)

    DOE PAGESBeta

    Wolfram, Phillip J.; Ringler, Todd D.; Maltrud, Mathew E.; Jacobsen, Douglas W.; Petersen, Mark R.

    2015-08-01

    Isopycnal diffusivity due to stirring by mesoscale eddies in an idealized, wind-forced, eddying, midlatitude ocean basin is computed using Lagrangian, in Situ, Global, High-Performance Particle Tracking (LIGHT). Simulation is performed via LIGHT within the Model for Prediction across Scales Ocean (MPAS-O). Simulations are performed at 4-, 8-, 16-, and 32-km resolution, where the first Rossby radius of deformation (RRD) is approximately 30 km. Scalar and tensor diffusivities are estimated at each resolution based on 30 ensemble members using particle cluster statistics. Each ensemble member is composed of 303 665 particles distributed across five potential density surfaces. Diffusivity dependence upon modelmore » resolution, velocity spatial scale, and buoyancy surface is quantified and compared with mixing length theory. The spatial structure of diffusivity ranges over approximately two orders of magnitude with values of O(105) m2 s–1 in the region of western boundary current separation to O(103) m2 s–1 in the eastern region of the basin. Dominant mixing occurs at scales twice the size of the first RRD. Model resolution at scales finer than the RRD is necessary to obtain sufficient model fidelity at scales between one and four RRD to accurately represent mixing. Mixing length scaling with eddy kinetic energy and the Lagrangian time scale yield mixing efficiencies that typically range between 0.4 and 0.8. In conclusion, a reduced mixing length in the eastern region of the domain relative to the west suggests there are different mixing regimes outside the baroclinic jet region.« less

  8. Diagnosing isopycnal diffusivity in an eddying, idealized midlatitude ocean basin via Lagrangian, in Situ, Global, High-Performance Particle Tracking (LIGHT)

    SciTech Connect

    Wolfram, Phillip J.; Ringler, Todd D.; Maltrud, Mathew E.; Jacobsen, Douglas W.; Petersen, Mark R.

    2015-08-01

    Isopycnal diffusivity due to stirring by mesoscale eddies in an idealized, wind-forced, eddying, midlatitude ocean basin is computed using Lagrangian, in Situ, Global, High-Performance Particle Tracking (LIGHT). Simulation is performed via LIGHT within the Model for Prediction across Scales Ocean (MPAS-O). Simulations are performed at 4-, 8-, 16-, and 32-km resolution, where the first Rossby radius of deformation (RRD) is approximately 30 km. Scalar and tensor diffusivities are estimated at each resolution based on 30 ensemble members using particle cluster statistics. Each ensemble member is composed of 303 665 particles distributed across five potential density surfaces. Diffusivity dependence upon model resolution, velocity spatial scale, and buoyancy surface is quantified and compared with mixing length theory. The spatial structure of diffusivity ranges over approximately two orders of magnitude with values of O(105) m2 s–1 in the region of western boundary current separation to O(103) m2 s–1 in the eastern region of the basin. Dominant mixing occurs at scales twice the size of the first RRD. Model resolution at scales finer than the RRD is necessary to obtain sufficient model fidelity at scales between one and four RRD to accurately represent mixing. Mixing length scaling with eddy kinetic energy and the Lagrangian time scale yield mixing efficiencies that typically range between 0.4 and 0.8. In conclusion, a reduced mixing length in the eastern region of the domain relative to the west suggests there are different mixing regimes outside the baroclinic jet region.

  9. Basin-wide modification of dynamical and biogeochemical processes by the positive phase of the Indian Ocean dipole during the SeaWiFS era

    NASA Astrophysics Data System (ADS)

    Wiggert, Jerry D.; Vialard, Jérôme; Behrenfeld, Michael J.

    Characterizing how the Indian Ocean dipole (IOD) modifies typical basin-wide dynamical variability has been vigorously pursued over the past decade. Along with this dynamic response, a clear biological impact has been revealed in the ocean color data acquired by remote sensing platforms such as Sea-viewing Wide Field-of-View Sensor (SeaWiFS). The signature feature illustrating IOD alteration of typical spatiotemporal chlorophyll variability is the phytoplankton bloom that first appears in September along the eastern boundary of the IO in tropical waters that are normally highly oligotrophic. Positive chlorophyll anomalies (CLa) are also apparent in the southeastern Bay of Bengal, while negative anomalies are observed over much of the Arabian Sea. Moreover, in situ measurements obtained by the R/V Suroit as part of the Cirene cruise during the 2006/2007 IOD reveal anomalous subsurface biochemical distributions in the southern tropical IO that are not reflected in SeaWiFS data. Despite the clear basin-wide influence of IOD events on biological variability, the accompanying influence on biogeochemical cycling that must occur has received little attention. Here, the dynamical signatures apparent in remote sensing fields for the two positive-phase IODs of the SeaWiFS era are used to illuminate how these events are similar or distinct. A corresponding comparison of IOD-engendered surface CLa is performed, with the dynamical fields providing the framework for interpreting the mechanisms underlying the biological response. Then, results from a newly developed net primary production algorithm are presented that provide the first characterization of how biogeochemical fluxes throughout the IO are altered by IOD occurrence

  10. Trace-element budgets in the Ohio/Sunbury shales of Kentucky: Constraints on ocean circulation and primary productivity in the Devonian-Mississippian Appalachian Basin

    USGS Publications Warehouse

    Perkins, R.B.; Piper, D.Z.; Mason, C.E.

    2008-01-01

    The hydrography of the Appalachian Basin in late Devonian-early Mississippian time is modeled based on the geochemistry of black shales and constrained by others' paleogeographic reconstructions. The model supports a robust exchange of basin bottom water with the open ocean, with residence times of less than forty years during deposition of the Cleveland Shale Member of the Ohio Shale. This is counter to previous interpretations of these carbon-rich units having accumulated under a stratified and stagnant water column, i.e., with a strongly restricted bottom bottom-water circulation. A robust circulation of bottom waters is further consistent with the palaeoclimatology, whereby eastern trade-winds drove upwelling and arid conditions limited terrestrial inputs of siliciclastic sediment, fresh waters, and riverine nutrients. The model suggests that primary productivity was high (~ 2??g C m- 2 d- 1), although no higher than in select locations in the ocean today. The flux of organic carbon settling through the water column and its deposition on the sea floor was similar to fluxes found in modern marine environments. Calculations based on the average accumulation rate of the marine fraction of Ni suggest the flux of organic carbon settling out of the water column was approximately 9% of primary productivity, versus an accumulation rate (burial) of organic carbon of 0.5% of primary productivity. Trace-element ratios of V:Mo and Cr:Mo in the marine sediment fraction indicate that bottom waters shifted from predominantly anoxic (sulfate reducing) during deposition of the Huron Shale Member of the Ohio Shale to predominantly suboxic (nitrate reducing) during deposition of the Cleveland Shale Member and the Sunbury Shale, but with anoxic conditions occurring intermittently throughout this period. ?? 2008 Elsevier B.V.

  11. Geologic tie-points across the Arctic Ocean: Insight into the paleogeography and configuration of the Arctic before the opening of the Amerasia Basin

    NASA Astrophysics Data System (ADS)

    Miller, E. L.; Gottlieb, E. S.; Meisling, K. E.; Brumley, K. J.; O'Brien, T.

    2013-12-01

    Relevant data are compiled and synthesized with the goal of establishing spatial and temporal connections between rifted and displaced continental fragments in order to provide insight into the pre-rift paleogeography of the Arctic and the plate kinematic history that led to its present-day geology. Prior to the opening of the Atlantic Ocean, Eurasia, Greenland and Canada formed part of Pangea, characterized by a once continuous paleo-Pacific facing northwestern continental margin. Formation of the Amerasia Basin by a multi-stage and poorly understood history of rifting in the Cretaceous resulted in the displacement of continental fragments towards the paleo-Pacific margin, forming the Amerasia Basin in its wake. Basement rock ages from Chukotka and western Arctic Alaska are Neoproterozoic in age and are overlain by sedimentary successions that have Baltica-affinity sources, based on U-Pb detrital zircon (DZ) geochronology. Younger Triassic and Jurassic strata DZ indicate pre-rift ties between Chukotka and the Taimyr/polar Ural portion of Eurasia while coeval strata of the North Slope Alaska are derived from Laurentia. Two important sediment-source divides provide additional information on geological reconstructions: The lower Paleozoic Caledonide suture between Laurentia and Eurasia remained a source of sediment throughout the late Paleozoic and early Mesozoic. Its rifted remains are inferred to underlie the Chukchi Borderland and likely continue across northern Alaska, but has not been identified with certainty on the ground. In the Triassic, Ural-Taimyr sediment sources were separated from Laurentia/Caledonide sources by topographic highs, one of which has been identified as the Chukchi high that bounds the offshore Hanna trough of Alaska on its western side. The kinematic opening history of the Amerasia Basin of the Arctic has eluded us because the basin lacks magnetic anomalies and there are conflicting constraints on its age(s) and direction(s) of rifting

  12. Ocean Drilling Simulation Activity.

    ERIC Educational Resources Information Center

    Telese, James A.; Jordan, Kathy

    The Ocean Drilling Project brings together scientists and governments from 20 countries to explore the earth's structure and history as it is revealed beneath the oceans' basins. Scientific expeditions examine rock and sediment cores obtained from the ocean floor to learn about the earth's basic processes. The series of activities in this…

  13. Trends of pH decrease in the Mediterranean Sea through high frequency observational data: indication of ocean acidification in the basin

    NASA Astrophysics Data System (ADS)

    Flecha, Susana; Pérez, Fiz F.; García-Lafuente, Jesús; Sammartino, Simone; Ríos, Aida. F.; Huertas, I. Emma

    2015-11-01

    A significant fraction of anthropogenic carbon dioxide (CO2) released to the atmosphere is absorbed by the oceans, leading to a range of chemical changes and causing ocean acidification (OA). Assessing the impact of OA on marine ecosystems requires the accurate detection of the rate of seawater pH change. This work reports the results of nearly 3 years of continuous pH measurements in the Mediterranean Sea at the Strait of Gibraltar GIFT time series station. We document a remarkable decreasing annual trend of -0.0044 ± 0.00006 in the Mediterranean pH, which can be interpreted as an indicator of acidification in the basin based on high frequency records. Modeling pH data of the Mediterranean outflow allowed to discriminate between the pH values of its two main constituent water masses, the Levantine Intermediate Water (LIW) and the Western Mediterranean Deep Water (WMDW). Both water masses also exhibited a decline in pH with time, particularly the WMDW, which can be related to their different biogeochemical nature and processes occurring during transit time from formation sites to the Strait of Gibraltar.

  14. Trends of pH decrease in the Mediterranean Sea through high frequency observational data: indication of ocean acidification in the basin

    PubMed Central

    Flecha, Susana; Pérez, Fiz F.; García-Lafuente, Jesús; Sammartino, Simone; Ríos, Aida. F.; Huertas, I. Emma

    2015-01-01

    A significant fraction of anthropogenic carbon dioxide (CO2) released to the atmosphere is absorbed by the oceans, leading to a range of chemical changes and causing ocean acidification (OA). Assessing the impact of OA on marine ecosystems requires the accurate detection of the rate of seawater pH change. This work reports the results of nearly 3 years of continuous pH measurements in the Mediterranean Sea at the Strait of Gibraltar GIFT time series station. We document a remarkable decreasing annual trend of −0.0044 ± 0.00006 in the Mediterranean pH, which can be interpreted as an indicator of acidification in the basin based on high frequency records. Modeling pH data of the Mediterranean outflow allowed to discriminate between the pH values of its two main constituent water masses, the Levantine Intermediate Water (LIW) and the Western Mediterranean Deep Water (WMDW). Both water masses also exhibited a decline in pH with time, particularly the WMDW, which can be related to their different biogeochemical nature and processes occurring during transit time from formation sites to the Strait of Gibraltar. PMID:26608196

  15. Trends of pH decrease in the Mediterranean Sea through high frequency observational data: indication of ocean acidification in the basin.

    PubMed

    Flecha, Susana; Pérez, Fiz F; García-Lafuente, Jesús; Sammartino, Simone; Ríos, Aida F; Huertas, I Emma

    2015-01-01

    A significant fraction of anthropogenic carbon dioxide (CO2) released to the atmosphere is absorbed by the oceans, leading to a range of chemical changes and causing ocean acidification (OA). Assessing the impact of OA on marine ecosystems requires the accurate detection of the rate of seawater pH change. This work reports the results of nearly 3 years of continuous pH measurements in the Mediterranean Sea at the Strait of Gibraltar GIFT time series station. We document a remarkable decreasing annual trend of -0.0044 ± 0.00006 in the Mediterranean pH, which can be interpreted as an indicator of acidification in the basin based on high frequency records. Modeling pH data of the Mediterranean outflow allowed to discriminate between the pH values of its two main constituent water masses, the Levantine Intermediate Water (LIW) and the Western Mediterranean Deep Water (WMDW). Both water masses also exhibited a decline in pH with time, particularly the WMDW, which can be related to their different biogeochemical nature and processes occurring during transit time from formation sites to the Strait of Gibraltar. PMID:26608196

  16. Effects of Human Alterations on Global River Basins and their Associated Coastal Zones: focus on River-dominated Ocean Margins (RiOMars)

    NASA Astrophysics Data System (ADS)

    Dürr, H. H.; Van Cappellen, P.; Meybeck, M.; Laruelle, G. G.; Mayorga, E.; Hartmann, J.; Maavara, T.; Bouwman, L.; Seitzinger, S.

    2013-12-01

    Coastal systems connected to large rivers, mostly major delta systems or river-dominated ocean margins (RiOMars), make up <1% of the worldwide shoreline. Yet, they comprise 28% of the exorheic terrestrial river basins area, and host 26.4% of the population connected via rivers to coastal systems (Dürr et al. 2011). These systems receive 41.6% of the discharge delivered to oceans. 25.7% of the suspended sediment load is processed, with comparable amounts for the total nitrogen (N) and phosphorus (P) loads. The filter function for incoming riverine nutrients (N, P, C, Si) in these coastal environments is very different from other near-shore environments such as macro-tidal estuaries, lagoons or fjords. In this type, the major biogeochemical transformation of incoming river fluxes takes place in a plume on the continental margins (RiOMars). This effect is even more pronounced at high flow stages when the highest volumes of water and material are delivered. The filtering efficiency of delta systems is highest during low flows, and some of the systems may be influenced by tides when ebb and flood might flow through different channels, creating a braided network of streams and many islands (Dürr et al. 2011). Here, we discuss controls on the different nutrient forms delivered to different coastal environments, and how they are assessed (Global-NEWS and other approaches), with a special focus on large deltas and RiOMars. Drivers and impacts of global change will be explored through the Millenium Assessment Scenarios and how the fluxes to these different coastal systems might change. An increasing role is also played by aquaculture in different coastal types as a non-insignificant source of nutrients. World-wide distribution of coastal types and their related river basins (Dürr et al. 2011). Characteristics of types of near-shore coastal areas and their associated river basins Greenland and Antarctica excepted. Data from Dürr et al. (2011) and the Global-NEWS program

  17. Slab-derived water and the petrogenesis of distinct zones of oceanic crust along spreading centers in the Lau back-arc basin

    NASA Astrophysics Data System (ADS)

    Eason, Deborah; Dunn, Robert

    2014-05-01

    Back-arc basin crust formed along the Eastern Lau Spreading Center (ELSC) exhibits dramatic and abrupt changes in magmatic processes and crustal formation with proximity to the nearby Tofua Arc. Systematic variations in seafloor morphology, crustal thickness, seismic properties, and lava composition reflect a decreasing 'subduction influence' with increasing distance from the arc. Results from seismic tomography indicate that the crust that forms near the arc is abnormally thick and compositionally stratified, with a thick low-velocity upper crust and an abnormally high-velocity lower crust. As the ridge moves away from the arc, there is a step-like transition in crustal properties towards crustal velocities and thicknesses more typical of oceanic crust produced at mid-ocean ridges. Likewise, lava compositions exhibit abrupt changes in slab-derived volatiles and trace element enrichments, with silicic, arc-like compositions at the Valu Fa Ridge and southern half of the ELSC, located near the arc, and relatively depleted basalts along the northern ELSC, which is located further from the arc. We attribute the observed changes in the physical and chemical makeup of the crust to excess mantle melting coupled with higher degrees of crustal differentiation near the arc due to higher mantle water contents. We propose a model for the formation of the arc-proximal layered crust whereby water-rich basaltic melts stall and differentiate in the lower crust. High-pressure crystallization concentrates water in the residual melts, decreasing their viscosity and density. Eventually the lighter, more felsic residual melts are extracted from the lower crust, leaving behind a dense, mafic cumulate layer, and go on to produce a silica-rich, porous volcanic layer. We present results of thermodynamic modeling of phase equilibria and develop a petrological model for the formation of this unusual "hydrous" form of oceanic crust.

  18. The Southern Ocean: Source and sink?

    NASA Astrophysics Data System (ADS)

    Strugnell, J. M.; Cherel, Y.; Cooke, I. R.; Gleadall, I. G.; Hochberg, F. G.; Ibáñez, C. M.; Jorgensen, E.; Laptikhovsky, V. V.; Linse, K.; Norman, M.; Vecchione, M.; Voight, J. R.; Allcock, A. L.

    2011-03-01

    Many members of the benthic fauna of the Antarctic continental shelf share close phylogenetic relationships to the deep-sea fauna adjacent to Antarctica and in other ocean basins. It has been suggested that connections between the Southern Ocean and the deep sea have been facilitated by the presence of a deep Antarctic continental shelf coupled with submerging Antarctic bottom water and emerging circumpolar deep water. These conditions may have allowed 'polar submergence', whereby shallow Southern Ocean fauna have colonised the deep sea and 'polar emergence', whereby deep-sea fauna colonised the shallow Southern Ocean. A recent molecular study showed that a lineage of deep-sea and Southern Ocean octopuses with a uniserial sucker arrangement on their arms appear to have arisen via polar submergence. A distantly related clade of octopuses with a biserial sucker arrangement on their arms (historically placed in the genus Benthoctopus) is also present in the deep-sea basins of the world and the Southern Ocean. To date their evolutionary history has not been examined. The present study investigated the origins of this group using 3133 base pairs (bp) of nucleotide data from five mitochondrial genes (12S rRNA, 16S rRNA, cytochrome c oxidase subunit I, cytochrome c oxidase subunit III, cytochrome b) and the nuclear gene rhodopsin from at least 18 species (and 7 outgroup taxa). Bayesian relaxed clock analyses showed that Benthoctopus species with a high-latitude distribution in the Southern Hemisphere represent a paraphyletic group comprised of three independent clades. The results suggest that the Benthoctopus clade originated in relatively shallow Northern Hemisphere waters. Benthoctopus species distributed in the Southern Ocean are representative of polar emergence and occur at shallower depths than non-polar Benthoctopus species.

  19. Climate and ocean variability during the past 1000 years in Pescadero basin, southern Gulf of California, Mexico.

    NASA Astrophysics Data System (ADS)

    Tenorio, Alejandra; Pérez-Cruz, Ligia; Roy, Debajyoti; Rodriguez, Alejandro; Vilaclara-Fatjó, Gloria

    2013-04-01

    We analyzed a laminated sedimentary sequence, box core C-2 (30.5 cm length); it was recovered in the eastern part of Pescadero Basin at 670 m depth collected aboard of the R/V "El Puma". Pescadero Basin is one of a series of deep tectonically active basins developed in the Gulf of California from south to north, which are characterized by their distinct climatic, oceanographic and geologic conditions. The purpose for this study is to contribute to the understanding of the paleoceanographic variability during 1000 years in the southern Gulf of California, using geochemical data, X- ray fluorescence and Corg analyses. The Core C-2 is characterized by silty clay sediments with visible laminated structure throughout the core. The preliminary chronology for core C-2 was obtained with the isotopic 210Pb dating method, based on this we estimated a sedimentation rate of 27 mm/yr for the first 5 cm. The data were extrapolated to the base of the core (30.5 cm); according to this the C-2 core covers the period from 900 to 2003 years EC. The geochemical proxies suggest three main changes in sedimentary sequence, considering Al, K, Fe, Si as terrigenous proxies, Ti as precipitation proxy , Zr/Al ratio as aeolian supply proxy and Corg as productivity proxy. At the bottom of the core, low values of Al, K, Si and Fe suggest a decrease in terrigenous input, low values of Ti concentration are associated with reduction in precipitation and high values of the Zr/Al ratio are shown increase aeolian supply. In this context, the proportion of aeolian sediments in the terrigenous record indicates dry conditions.In the middle of the core, high values Al, K, Si and Fe are interpreted to reflect increased terrigenous input, Ti high values suggest an increase in precipitation, low values of Corg reflect diminish in productivity. Also, within the period it is possible to recognize an episode with an abrupt decrease of terrigenous input, but aeolian supply is greater, it suggested a multi

  20. Evidence for an important tectonostratigraphic seismic marker across Canada Basin and southern Alpha Ridge of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Shimeld, J.; Chian, D.; Jackson, R.; Hutchinson, D. R.; Mosher, D. C.; Wade, J.; Chapman, B.

    2010-12-01

    Using a modern ice-strengthened seismic acquisition system, more than 12,000 km of high quality 16-channel, vertical incidence seismic reflection and wide-angle sonobuoy data, along with single- and multibeam bathymetric soundings and gravimetric profiles have been acquired across Canada Basin and the southern flank of Alpha Ridge. These datasets are being used to determine the crustal types, rifting processes, subsidence history, and sedimentary sequences of this poorly known region. More than a dozen regional seismostratigraphic units are identified, exceeding ~6.5 km in total sediment thickness in the south, thinning northward toward Alpha Ridge. The oldest regionally mappable unit is informally named “bisque” and is characterized by high-amplitude, continuous, parallel and subparallel internal reflections. The bisque unit averages ~600 m thick, with significant local variability. Along southern Alpha Ridge, the base of the bisque unit is marked by a prominent angular unconformity which can be traced southwards into Canada Basin before becoming obscured by thick overlying units. Though affected by faulting and compaction drape, the bisque unit appears to be concordant with the topography of the underlying acoustic basement. It is also spatially and temporally associated with large structures that are interpreted to be volcanic edifices. Most of the 129 available sonobuoy records show clear wide-angle refractions/reflections from sedimentary and upper and lower crustal layers, which can be ray-traced and velocity modeled using constraints from coincident reflection profiles. Slight ray angle dependent anisotropy is found to best describe these observed data, and is used for conversion between two-way travel time and vertical depth domains. Two distinct features are identified for the bisque layer: 1) a wide-angle reflection observed on nearly all sonobuoy data; and 2) S waves (named PsP), doubly converted at the bisque layer. P-wave refractors from bisque

  1. Petrography of volcaniclastic rocks in intra-arc volcano-bounded to fault-bounded basins of the Rosario segment of the Lower Cretaceous Alisitos oceanic arc, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Marsaglia, K. M.; Barone, M.; Critelli, S.; Busby, C.; Fackler-Adams, B.

    2016-05-01

    The Rosario segment of the Early Cretaceous Alisitos oceanic magmatic arc in Baja California displays a record of arc-axis sedimentation and volcanism that is well preserved in outcrops within a southern volcano-bounded and a northern fault-bounded basin that flanked an intervening subaerial edifice. This record includes volcanic and volcaniclastic rocks that range from felsic to mafic in composition. Volcaniclastic/tuffaceous sandstone samples from two previously published measured sections are mainly composed of volcanic clasts with moderate plagioclase content. Locally quartz and/or potassium feldspar are present in trace to moderate amounts. The proportions of volcanic lithic types exhibiting vitric, microlitic, lathwork, and felsitic textures are highly variable with no distinct stratigraphic trends, likely as a function of the mixed styles of eruption and magma compositions that produced pyroclasts, as well as erosion-produced epiclastic debris. The volcaniclastic fill of the basins is consistent with an oceanic arc setting, except for the relatively high felsitic volcanic lithic content, likely associated with subaerial, as opposed to the more common submarine felsic magmatism associated with arc extension in oceanic settings. There are no major differences in compositional modes of tuff and sandstone between the fault-bounded and volcano-bounded basin strata, even though they exhibit distinctly different volcaniclastic facies. This suggests that proximal arc-axis basins of varying types around a single major subaerial edifice provide a faithful record of volcanic trends in the arc segment, regardless of variation in transport and depositional processes.

  2. A simple estimation of equatorial Pacific response from windstress to untangle Indian Ocean Dipole and Basin influences on El Niño

    NASA Astrophysics Data System (ADS)

    Izumo, T.; Vialard, J.; Dayan, H.; Lengaigne, M.; Suresh, I.

    2016-04-01

    Sea Surface Temperature (SST) anomalies that develop in spring in the central Pacific are crucial to the El Niño Southern Oscillation (ENSO) development. Here we use a linear, continuously stratified, ocean model, and its impulse response to a typical ENSO wind pattern, to derive a simple equation that relates those SST anomalies to the low frequency evolution of zonal wind stress anomalies τ x over the preceding months. We show that SST anomalies can be approximated as a "causal" filter of τ x , τ x (t - t 1) - c τ x (t - t 2), where t1 is ~1-2 months, t2 - t1 is ~6 months and c ranges between 0 and 1 depending on τ x location (i.e. SST anomalies are approximately proportional to the wind stress anomalies 1-2 months earlier minus a fraction of the wind stress anomalies 7-8 months earlier). The first term represents the fast oceanic response, while the second one represents the delayed negative feedback associated with wave reflection at both boundaries. This simple approach is then applied to assess the relative influence of the Indian Ocean Dipole (IOD) and of the Indian Ocean Basin-wide warming/cooling (IOB) in favouring the phase transition of ENSO. In agreement with previous studies, Atmospheric General Circulation Model experiments indicate that the equatorial Pacific wind responses to the IOD eastern and (IOB-related) western poles tend to cancel out during autumn. The abrupt demise of the IOD eastern pole thus favours an abrupt development of the IOB-cooling-forced westerly wind anomalies in the western Pacific in winter-spring (vice versa for an IOB warming). As expected from the simple SST equation above, the faster wind change fostered by the IOD enhances the central Pacific SST response as compared to the sole IOB influence. The IOD thereby enhances the IOB tendency to favour ENSO phase transition. As the IOD is more independent of ENSO than the IOB, this external influence could contribute to enhanced ENSO predictability.

  3. Dubinectes infirmus, a new species of deep-water Munnopsidae (Crustacea, Isopoda, Asellota) from the Argentine Basin, South Atlantic Ocean

    PubMed Central

    Malyutina, Marina; Brandt, Angelika

    2011-01-01

    Abstract Dubinectes infirmus sp. n., Munnopsidae, is described from the Argentine Basin, southwest Atlantic, at depths between 4586–4607 m. The new species is distinguished by a narrow rim of the pleotelson posterior margin which is not raising over its dorsal surface; article 3 of the antennula is subequal in length to article 2; distomedial lobes of male pleopod 1 are of same size as distolateral lobes; stylet of male pleopod 2 is subequal in length to protopod; uropod exopod is more than a half of endopod length. Some generic characters which are weakly pronounced in the new species or have different state are defined more precisely in the revised diagnosis of Dubinectes. The modified diagnosis of the genus, a key to the species of Dubinectes as well as the distribution of the genus are presented. PMID:22207784

  4. Response to memorandum by Rowley and Dixon regarding U.S. Geological Survey report titled "Characterization of Surface-Water Resources in the Great Basin National Park Area and Their Susceptibility to Ground-Water Withdrawals in Adjacent Valleys, White Pine County, Nevada"

    USGS Publications Warehouse

    Prudic, David E.

    2006-01-01

    Applications pending for permanent permits to pump large quantities of ground water in Spring and Snake Valleys adjacent to Great Basin National Park (the Park) prompted the National Park Service to request a study by the U.S. Geological Survey to evaluate the susceptibility of the Park's surface-water resources to pumping. The result of this study was published as U.S. Geological Survey Scientific Investigations Report 2006-5099 'Characterization of Surface-Water Resources in the Great Basin National Park Area and Their Susceptibility to Ground-Water Withdrawals in Adjacent Valleys, White Pine County, Nevada,' by P.E. Elliott, D.A. Beck, and D.E. Prudic. That report identified areas within the Park where surface-water resources are susceptible to ground-water pumping; results from the study showed that three streams and several springs near the eastern edge of the Park were susceptible. However, most of the Park's surface-water resources likely would not be affected by pumping because of either low-permeability rocks or because ground water is sufficiently deep as to not be directly in contact with the streambeds. A memorandum sent by Peter D. Rowley and Gary L. Dixon, Consulting Geologists, to the Southern Nevada Water Authority (SNWA) on June 29, 2006 was critical of the report. The memorandum by Rowley and Dixon was made available to the National Park Service, the U.S. Geological Survey, and the public during the Nevada State Engineer's 'Evidentiary Exchange' process for the recent hearing on applications for ground-water permits by SNWA in Spring Valley adjacent to Great Basin National Park. The U.S. Geological Survey was asked by the National Park Service to assess the validity of the concerns and comments contained in the Rowley and Dixon memorandum. An Administrative Letter Report responding to Rowley and Dixon's concerns and comments was released to the National Park Service on October 30, 2006. The National Park Service subsequently requested that the

  5. Coincidence or not? Interconnected gas/fluid migration and ocean-atmosphere oscillations in the Levant Basin

    NASA Astrophysics Data System (ADS)

    Lazar, Michael; Lang, Guy; Schattner, Uri

    2016-08-01

    A growing number of studies on shallow marine gas/fluid systems from across the globe indicate their abundance throughout geological epochs. However, these episodic events have not been fully integrated into the fundamental concepts of continental margin development, which are thought to be dictated by three elements: tectonics, sedimentation and eustasy. The current study focuses on the passive sector of the Levant Basin on the eastern Mediterranean continental margin where these elements are well constrained, in order to isolate the contribution of gas/fluid systems. Single-channel, multichannel and 3D seismic reflection data are interpreted in terms of variance, chaos, envelope and sweetness attributes. Correlation with the Romi-1 borehole and sequence boundaries constrains interpretation of seismic stratigraphy. Results show a variety of fluid- or gas-related features such as seafloor and subsurface pockmarks, volumes of acoustic blanking, bright spots, conic pinnacle mounds, gas chimneys and high sweetness zones that represent possible secondary reservoirs. It is suggested that gas/fluid migrate upwards along lithological conduits such as falling-stage systems tracts and sequence boundaries during both highstands and lowstands. In all, 13 mid-late Pleistocene sequence boundaries are accompanied by independent evidence of 13 eustatic sea-level drops. Whether this connection is coincidental or not requires further research. These findings fill gaps between previously reported sporadic appearances throughout the Levant Basin and margin and throughout geological time from the Messinian until the present day, and create a unified framework for understanding the system as a whole. Repetitive appearance of these features suggests that their role in the morphodynamics of continental margins is more important than previously thought and thus may constitute one of the key elements of continental margin development.

  6. Coincidence or not? Interconnected gas/fluid migration and ocean-atmosphere oscillations in the Levant Basin

    NASA Astrophysics Data System (ADS)

    Lazar, Michael; Lang, Guy; Schattner, Uri

    2016-03-01

    A growing number of studies on shallow marine gas/fluid systems from across the globe indicate their abundance throughout geological epochs. However, these episodic events have not been fully integrated into the fundamental concepts of continental margin development, which are thought to be dictated by three elements: tectonics, sedimentation and eustasy. The current study focuses on the passive sector of the Levant Basin on the eastern Mediterranean continental margin where these elements are well constrained, in order to isolate the contribution of gas/fluid systems. Single-channel, multichannel and 3D seismic reflection data are interpreted in terms of variance, chaos, envelope and sweetness attributes. Correlation with the Romi-1 borehole and sequence boundaries constrains interpretation of seismic stratigraphy. Results show a variety of fluid- or gas-related features such as seafloor and subsurface pockmarks, volumes of acoustic blanking, bright spots, conic pinnacle mounds, gas chimneys and high sweetness zones that represent possible secondary reservoirs. It is suggested that gas/fluid migrate upwards along lithological conduits such as falling-stage systems tracts and sequence boundaries during both highstands and lowstands. In all, 13 mid-late Pleistocene sequence boundaries are accompanied by independent evidence of 13 eustatic sea-level drops. Whether this connection is coincidental or not requires further research. These findings fill gaps between previously reported sporadic appearances throughout the Levant Basin and margin and throughout geological time from the Messinian until the present day, and create a unified framework for understanding the system as a whole. Repetitive appearance of these features suggests that their role in the morphodynamics of continental margins is more important than previously thought and thus may constitute one of the key elements of continental margin development.

  7. Late Mesozoic and Cenozoic thermotectonic evolution of the central Brooks Range and adjacent North Slope foreland basin, Alaska: Including fission track results from the Trans-Alaska Crustal Transect (TACT)

    USGS Publications Warehouse

    O'Sullivan, P. B.; Murphy, J.M.; Blythe, A.E.

    1997-01-01

    Apatite fission track data are used to evaluate the thermal and tectonic history of the central Brooks Range and the North Slope foreland basin in northern Alaska along the northern leg of the Trans-Alaska Crustal Transect (TACT). Fission track analyses of the detrital apatite grains in most sedimentary units resolve the timing of structures and denudation within the Brooks Range, ranging in scale from the entire mountain range to relatively small-scale folds and faults. Interpretation of the results indicates that rocks exposed within the central Brooks Range cooled rapidly from paleotemperatures 110?? to 50??C during discrete episodes at ???100??5 Ma, ???60??4 Ma, and ???24??3 Ma, probably in response to kilometer-scale denudation. North of the mountain front, rocks in the southern half of the foreland basin were exposed to maximum paleotemperatures 110??C in the Late Cretaceous to early Paleocene as a result of burial by Upper Jurassic and Cretaceous sedimentary rocks. Rapid cooling from these elevated paleotemperatures also occurred due to distinct episodes of kilometer-scale denudation at ???60??4 Ma, 46??3 Ma, 35??2 Ma, and ???24??3 Ma. Combined, the apatite analyses indicate that rocks exposed along the TACT line through the central Brooks Range and foreland basin experienced episodic rapid cooling throughout the Late Cretaceous and Cenozoic in response to at least three distinct kilometer-scale denudation events. Future models explaining orogenic events in northern Alaska must consider these new constraints from fission track thermochronology. Copyright 1997 by the American Geophysical Union.

  8. Seismic velocities within the sedimentary succession of the Canada Basin and southern Alpha-Mendeleev Ridge, Arctic Ocean: evidence for accelerated porosity reduction?

    NASA Astrophysics Data System (ADS)

    Shimeld, John; Li, Qingmou; Chian, Deping; Lebedeva-Ivanova, Nina; Jackson, Ruth; Mosher, David; Hutchinson, Deborah

    2016-01-01

    The Canada Basin and the southern Alpha-Mendeleev ridge complex underlie a significant proportion of the Arctic Ocean, but the geology of this undrilled and mostly ice-covered frontier is poorly known. New information is encoded in seismic wide-angle reflections and refractions recorded with expendable sonobuoys between 2007 and 2011. Velocity-depth samples within the sedimentary succession are extracted from published analyses for 142 of these records obtained at irregularly spaced stations across an area of 1.9E + 06 km2. The samples are modelled at regional, subregional and station-specific scales using an exponential function of inverse velocity versus depth with regionally representative parameters determined through numerical regression. With this approach, smooth, non-oscillatory velocity-depth profiles can be generated for any desired location in the study area, even where the measurement density is low. Practical application is demonstrated with a map of sedimentary thickness, derived from seismic reflection horizons interpreted in the time domain and depth converted using the velocity-depth profiles for each seismic trace. A thickness of 12-13 km is present beneath both the upper Mackenzie fan and the middle slope off of Alaska, but the sedimentary prism thins more gradually outboard of the latter region. Mapping of the observed-to-predicted velocities reveals coherent geospatial trends associated with five subregions: the Mackenzie fan; the continental slopes beyond the Mackenzie fan; the abyssal plain; the southwestern Canada Basin; and, the Alpha-Mendeleev magnetic domain. Comparison of the subregional velocity-depth models with published borehole data, and interpretation of the station-specific best-fitting model parameters, suggests that sandstone is not a predominant lithology in any of the five subregions. However, the bulk sand-to-shale ratio likely increases towards the Mackenzie fan, and the model for this subregion compares favourably with

  9. Intermediate crust (IC); its construction at continent edges, distinctive epeirogenic behaviour and identification as sedimentary basins within continents: new light on pre-oceanic plate motions

    NASA Astrophysics Data System (ADS)

    Osmaston, Miles F.

    2014-05-01

    Introduction. The plate tectonics paradigm currently posits that the Earth has only two kinds of crust - continental and oceanic - and that the former may be stretched to form sedimentary basins or the latter may be modified by arc or collision until it looks continental. But global analysis of the dynamics of actual plate motions for the past 150 Ma indicates [1 - 3] that continental tectospheres must be immensely thicker and rheologically stiffer than previously thought; almost certainly too thick to be stretched with the forces available. In the extreme case of cratons, these tectospheric keels evidently extend to 600 km or more [2, 3]. This thick-plate behaviour is attributable, not to cooling but to a petrological 'stiffening' effect, associated with a loss of water-weakening of the mineral crystals, which also applies to the hitherto supposedly mobile LVZ below MORs [4, 5]. The corresponding thick-plate version of the mid-ocean ridge (MOR) process [6 - 8], replacing the divergent mantle flow model, has a deep, narrow wall-accreting axial crack which not only provides the seismic anisotropy beneath the flanks but also brings two outstanding additional benefits:- (i) why, at medium to fast spreading rates, MOR axes become straight and orthogonally segmented [6], (ii) not being driven by body forces, it can achieve the sudden jumps of axis, spreading-rate and direction widely present in the ocean-floor record. Furthermore, as we will illustrate, the crack walls push themselves apart at depth by a thermodynamic mechanism, so the plates are not being pulled apart. So the presence of this process at a continental edge would not imply the application of extensional force to the margin. Intermediate Crust (IC). In seeking to resolve the paradox that superficially extensional structures are often seen at margins we will first consider how this MOR process would be affected by the heavy concurrent sedimentation to be expected when splitting a mature continent. I reason

  10. Marine redox conditions in the middle Proterozoic ocean and isotopic constraints on authigenic carbonate formation: Insights from the Chuanlinggou Formation, Yanshan Basin, North China

    NASA Astrophysics Data System (ADS)

    Li, Chao; Planavsky, Noah J.; Love, Gordon D.; Reinhard, Christopher T.; Hardisty, Dalton; Feng, Lianjun; Bates, Steven M.; Huang, Jing; Zhang, Qirui; Chu, Xuelei; Lyons, Timothy W.

    2015-02-01

    To improve our understanding of ocean chemistry and biogeochemical cycling following the termination of large-scale Paleoproterozoic iron formation (IF) deposition (∼1.85 billion years ago [Ga]), we conducted a Fe-S-C-Mo geochemical study of the ∼1.65 Ga Chuanlinggou Formation, Yanshan Basin, North China. Despite the cessation of IF deposition, our results suggest the presence of anoxic but non-euxinic (ferruginous) conditions persisted below the surface mixed layer for the deepest portion of the continental rifting basin and that this pattern is apparently independent of the local organic carbon content. However, our paired S-isotope data of carbonate-associated sulfate and pyrite suggest presence of sulfate in pore fluids, which is not consistent with insufficient sulfate for bacterial sulfate reduction in the water column. Despite evidence for deposition under anoxic conditions, sedimentary molybdenum (Mo) concentrations are mostly not enriched relative to average continental crust. This relationship is consistent with the notion that sulfide-dominated conditions in the water column and/or the sediments are required for Mo enrichment and validates past assertions that Mo enrichment patterns in ancient shales track both the local presence and global distribution of euxinia specifically. In addition, we identified extensive diagenetic carbonate precipitation in the upper Chuanlinggou Formation with only moderately negative δ13C values (-3.4 ± 1.4‰). We propose, with support from a numerical model, that these diagenetic carbon isotope values were most likely derived from precipitation of carbonates dominantly in the methanic zone within the sediments. Diagenetic carbonate precipitation in the methanic zone is likely to have been more extensive in the Proterozoic than the Phanerozoic due to porewater oxidant limitation.

  11. Intermediate crust (IC); its construction at continent edges, distinctive epeirogenic behaviour and identification as sedimentary basins within continents: new light on pre-oceanic plate motions

    NASA Astrophysics Data System (ADS)

    Osmaston, Miles F.

    2014-05-01

    Introduction. The plate tectonics paradigm currently posits that the Earth has only two kinds of crust - continental and oceanic - and that the former may be stretched to form sedimentary basins or the latter may be modified by arc or collision until it looks continental. But global analysis of the dynamics of actual plate motions for the past 150 Ma indicates [1 - 3] that continental tectospheres must be immensely thicker and rheologically stiffer than previously thought; almost certainly too thick to be stretched with the forces available. In the extreme case of cratons, these tectospheric keels evidently extend to 600 km or more [2, 3]. This thick-plate behaviour is attributable, not to cooling but to a petrological 'stiffening' effect, associated with a loss of water-weakening of the mineral crystals, which also applies to the hitherto supposedly mobile LVZ below MORs [4, 5]. The corresponding thick-plate version of the mid-ocean ridge (MOR) process [6 - 8], replacing the divergent mantle flow model, has a deep, narrow wall-accreting axial crack which not only provides the seismic anisotropy beneath the flanks but also brings two outstanding additional benefits:- (i) why, at medium to fast spreading rates, MOR axes become straight and orthogonally segmented [6], (ii) not being driven by body forces, it can achieve the sudden jumps of axis, spreading-rate and direction widely present in the ocean-floor record. Furthermore, as we will illustrate, the crack walls push themselves apart at depth by a thermodynamic mechanism, so the plates are not being pulled apart. So the presence of this process at a continental edge would not imply the application of extensional force to the margin. Intermediate Crust (IC). In seeking to resolve the paradox that superficially extensional structures are often seen at margins we will first consider how this MOR process would be affected by the heavy concurrent sedimentation to be expected when splitting a mature continent. I reason

  12. Can the South China Sea tell us anything about Canada Basin?

    NASA Astrophysics Data System (ADS)

    Stephenson, Randell; Li, Lu

    2016-04-01

    The Canada Basin (a sub-basin within the Amerasia Basin) and the South China Sea both preserve oceanic spreading centres and adjacent passive continental margins characterised by broad continent-ocean transition zones with hyper-extended continental crust. There are indications that hyper-extension in the South China Sea occurred mainly as a result of flow within a weak lower crustal layer and that it occurred both before and after plate break-up and the onset of ocean lithosphere formation at the sea-floor spreading axis. Available geophysical data from Canada Basin permit similar inferences. Both basins are about the same size and the oceanic segment in both is about the same size. Seafloor spreading in the South China Sea took place in the Cenozoic whereas in Canada Basin it is widely believed to have occurred during the Cretaceous. Widespread magmatism expressed as the High Arctic Large Igneous Province (HALIP) may or may not have played an intrinsic, linked, role in Canada Basin formation. No similar LIP is associated with the South China Sea although one mechanism proposed to have driven its formation is ascribed to mantle plume activity in its northernmost part. More conventionally the mechanism of opening of the South China Sea is considered to be "passive" rather than "active", related to plate reconfigurations in the southeast Asia region linked or not linked to the nearby collision of India and Eurasia and/or subduction of a "proto-South China Sea". The driving mechanism for opening of Canada Basin is poorly discussed in the literature but is generally ascribed to paleo-tectonic plate reconfigurations and subduction in the northern Pacific (Eurasia-North America plates) region in the Mesozoic. Can the South China Sea tell us anything about Canada Basin in terms of the pre-existing lithosphere of each and the geodynamic processes leading to its hyper-extension and eventual break-up?

  13. The Arctic Ocean and climate: A Perspective

    NASA Astrophysics Data System (ADS)

    Aagaard, K.; Carmack, E. C.

    The most likely effects of the Arctic Ocean on global climate are through the surface heat balance and the thermohaline circulation. The former is intimately related to the stratification of the Arctic Ocean, while the latter may be significantly controlled by outflow from the Arctic Ocean into the major convective regions to the south. Evaluating these issues adequately requires detailed knowledge of the density structure and circulation of the Arctic Ocean and of their variability. New long time series of temperature and salinity (T/S) from the Canadian Basin show a grainy T/S structure, probably on a horizontal scale of a few tens of kilometers. The temperature field is particularly inhomogeneous, since for cold water it is not greatly constrained by buoyancy forces. The simultaneous velocity time series show that the grainy T/S structure results from a complex eddy field, often with vertically or horizontally paired counter-rotating eddies drifting with a slow larger-scale flow. The ocean is therefore not well mixed on these scales. Finally, we note that the ventilation of the interior Arctic Ocean from the adjacent shelves appears to be highly variable on an interannual basis, and indeed may not be robust on longer time scales. In particular we note the absence, or near-absence, of deep ventilation of the Canadian Basin during the last 500 years. Based on the 14C model of Macdonald et al. [1993], however, we hypothesize that these same waters were ventilated prior to that time and that the deep convective shutdown about 500 years ago coincided with the end of the whale-hunting Thule culture. We further suggest that the two events had a common cause, viz., the increase of sea ice over the continental shelves during summer.

  14. Great Basin paleontological database

    USGS Publications Warehouse

    Zhang, N.; Blodgett, R.B.; Hofstra, A.H.

    2008-01-01

    The U.S. Geological Survey has constructed a paleontological database for the Great Basin physiographic province that can be served over the World Wide Web for data entry, queries, displays, and retrievals. It is similar to the web-database solution that we constructed for Alaskan paleontological data (www.alaskafossil.org). The first phase of this effort was to compile a paleontological bibliography for Nevada and portions of adjacent states in the Great Basin that has recently been completed. In addition, we are also compiling paleontological reports (Known as E&R reports) of the U.S. Geological Survey, which are another extensive source of l,egacy data for this region. Initial population of the database benefited from a recently published conodont data set and is otherwise focused on Devonian and Mississippian localities because strata of this age host important sedimentary exhalative (sedex) Au, Zn, and barite resources and enormons Carlin-type An deposits. In addition, these strata are the most important petroleum source rocks in the region, and record the transition from extension to contraction associated with the Antler orogeny, the Alamo meteorite impact, and biotic crises associated with global oceanic anoxic events. The finished product will provide an invaluable tool for future geologic mapping, paleontological research, and mineral resource investigations in the Great Basin, making paleontological data acquired over nearly the past 150 yr readily available over the World Wide Web. A description of the structure of the database and the web interface developed for this effort are provided herein. This database is being used ws a model for a National Paleontological Database (which we am currently developing for the U.S. Geological Survey) as well as for other paleontological databases now being developed in other parts of the globe. ?? 2008 Geological Society of America.

  15. The recent extreme hydrological events in the Western Amazon Basin: The role of the Pacific and Atlantic Oceans

    NASA Astrophysics Data System (ADS)

    Espinoza, J.; Ronchail, J.; Guyot, J.; Santini, W.; Lavado, W.; Ore-Hybam Observatory

    2013-05-01

    The Peruvian Amazonas River, the main western tributary of the Amazon basin, has a huge drainage (750 000 km2, 50% of which lies in the Andes) and a mean discharge estimated in 32 000 m3/s, which correspond to 15% of the Amazon discharge at the estuary. Recently, in a context of significant discharge diminution during the low-water season (1970-2012), severe hydrological events, as intense droughts and floods, have been reported in the Peruvian Amazonas River. As they have not been always observed in other regions of the Amazon basin and because they have strong impacts on vulnerable riverside residents, we shall focus on the origin and the predictability of the western Amazon extremes, providing a review of the main findings about the climate features during recent extreme hydrological events in western Amazon. While the lowest discharge value was observed in September 2010 (8 300 m3/s) at the hydrological Tamshiyacu station (near to Iquitos city), a rapid transition toward a high discharge was noticed in April 2011 (45 000 m3/s). Finally, in April 2012, during the on going high waters period, the Amazonas River is experimenting its historical highest discharge (55 000 m3/s). Our work is based on several datasets including in-situ discharge and rainfall information from ORE-HYBAM observatory. Extreme droughts (1995, 2005 and 2010) are generally associated with positive SST anomalies in the tropical North Atlantic and weak trade winds and water vapor transport toward the western Amazon, which, in association with increased subsidence over central and southern Amazon, explain the lack of rainfall and very low discharge values. But, in 1998, toward the end of the 1997-98 El Niño event, the drought has been more likely related to an anomalous divergence of water vapor in the western Amazon that is characteristic of a warm event in the Pacific. The years with a rapid transition form low waters to very high floods (e.g. September 2010 to April 2011) are characterized

  16. A new species of Afropinnotheres Manning, 1993 (Crustacea, Brachyura, Pinnotheridae) from southwestern India, the first record of the genus from the Indian Ocean, with a review of the Pinnotheridae of India and adjacent seas.

    PubMed

    Ng, Peter K L; Kumar, Appukuttannair Biju

    2015-01-01

    A new species of pinnotherid crab of the genus Afropinnotheres Manning, 1993, is described from the brown mussel, Perna perna (Linnaeus, 1758), in southwestern India. This is the first record of the genus from the western Indian Ocean, the other four species been recorded from the eastern Atlantic. The new species can be distinguished from all congeners in  possessing a more rounded male carapace, form of the chela, relatively longer ambulatory legs which have no natatory setae, presence of dense pubescence on the male ambulatory legs, and the shape of the male and female telsons. The Indian Pinnotheridae is also reviewed and the taxonomy of the species reappraised. The taxonomy of Pinnaxodes Heller, 1865, and Holothuriophilus Nauck, 1880, is also discussed, in the context of their similarity to Afropinnotheres. PMID:25947734

  17. Heat flow distribution and thermal structure of the Philippine Sea Plate and its adjacent areas

    NASA Astrophysics Data System (ADS)

    Wang, Q.; Chen, C.; Liang, Q.; Sun, S.

    2013-12-01

    Research on the present geothermal state is an important way to understand the lithospheric geodynamics. We studied the heat flow (HF) distribution and the geothermal structure of the Philippine Sea Plate (PSP) and its adjacent area (100°E~155°E, 5°S~45°N) surrounded by the East China Sea, South China Sea and the West Pacific Ocean, which is aimed to provide thermal constraints for the dynamic mechanism and tectonic evolution of the PSP. Based on the observed seafloor HF data of the study area with the latest release of CRUST1.0 crustal layered model, the lithospheric geotherm was calculated using 1D steady-state heat conduction equation. However, the obtained numerous geotherms derived from the extrapolation through heat conduction equation strongly depended on the accuracy of the measured HF data, which is limited, unevenly distributed and easily affected by local factors. Therefore, as a meaningful comparison, the temperature distributions at 25 km and 50 km depth inferred from the upper mantle shear wave velocities structure (S2.9EA) are inverted. The HF distribution shows relatively high values in Ryuku Trench and nearby Izu-Boning Trench, where the crust thicken and the mantle uplift obviously as typical transition zones. The Mariana Trench located in the east (southeast) part and the Philippine Trench in the southwest both are with low HF, which is also illustrated in the upper mantle gravity map after temperature correction. The Central Basin Ridge is with unquestionable high HF, being perpendicular to which the value decreasing. The calculated temperature maps (at depth of 25 km and 50 km) by the two methods both present that the temperature in PSP is higher than that in the Western Pacific Ocean and the west Philippine Basin is lower than the east one, which consists well with the crust age. The west half parts both of the Philippine Basin and Parece Vela Basin show low temperature, but high value in Ryuku Trench, Nankai Through, Shikoku Basin, Amami

  18. Regional comparison of syn- and post-rift sequences in salt and salt-free basins offshore Brazil and Angola/Namibia, South Atlantic

    NASA Astrophysics Data System (ADS)

    Strozyk, Frank; Back, Stefan; Kukla, Peter

    2015-04-01

    The large South Atlantic basins offshore South America and Africa record a highly variable syn- to post-breakup tectono-stratigraphic development. The present-day diversity in the structural and sedimentary architecture of the conjugate margins offshore southern Brazil, Namibia and Angola reflects variations in the interplay of a number of controlling factors, of which the most important are i) the structural configuration of each margin segment at the time of break-up, ii) the post break-up geodynamic history including tectonics and magmatism, and iii) variations in the type, quantity and distribution of sediment input to the respective margin segment. Particularly the basins around the Rio Grande Rise - Walvis Ridge volcanic complex show a pronounced tectono-stratigraphic asymmetry both along the respective continental margin and across the Atlantic. Only a few attempts exist to establish a regional tectono-stratigraphic correlation framework across the South Atlantic Ocean, mainly because of the lack of data across entire margin segments and limited resolution of basin wide geophysics. Still unresolved issues particularly concern the explanation of the basin-specific geological evolution of respective margin segments along the same continental margin, as well as the correlation of conjugate basins and margin segments across the Atlantic Ocean. In our study we present interpretations and first-pass restorations of regional 2D seismic-reflectivity data from the large basins offshore Brazil (Pelotas Basin, Santos Basin, Campos Basin, Espirito Santo Basin), and offshore Namibia and Angola (Walvis Basin, Namibe Basin, Benguela Basin, Kwanza Basin), which represent four adjacent pairs of conjugate basins on both sides of the South Atlantic. Results are used to document and compare on a basin-scale the contrasting styles of rift and post-rift settings during and after the continental breakup.

  19. Distributions of C22-C30 even-carbon-number n-alkanes in Ocean Anoxic Event 1 samples from the Basque-Cantabrian Basin.

    PubMed

    Chaler, R; Dorronsoro, C; Grimalt, J O; Agirrezabala, L M; Fernández-Mendiola, P A; García-Mondejar, J; Gómez-Pérez, I; López-Horgue, M

    2005-05-01

    The Ocean Anoxic Event 1 (OAE-1) in central sites of the Basque-Cantabrian Basin exhibits very reducing depositional conditions of sedimentation. These sedimentation events have left a distinct mixture of hydrocarbons that are represented by C22-C30 n-alkanes with a predominance of the even-carbon-number homologues, high relative proportions of squalane and C16-C24 n-alkylcyclopentanes predominated by n-undecyl-, n-tridecyl- and n-pentadecylcyclopentane. Other minor compounds encompass a series of C18-C21 n-alkylcyclohexanes and C18-C24 dimethyl n-alkylcyclohexanes maximized by the even-carbon-number homologues as well as iso- and anteiso-alkanes. This unusual distribution of n-alkanes in this environment provides a new case for comparison with previously reported hypersaline and phosphorite sedimentary deposits where the occurrence of similar n-alkane distributions was reported. In the present case, these major n-alkanes and squalane are indicative of transformation under strong reducing conditions. In contrast, the occurrence of the alkylcyclopentanes, irrespective of the presence of even-carbon-number n-alkanes or squalane, suggests that reductive cyclization of fatty acids is less dependent on strong reducing conditions. PMID:15776255

  20. Relative contributions of the Tibetan Plateau thermal forcing and the Indian Ocean Sea surface temperature basin mode to the interannual variability of the East Asian summer monsoon

    NASA Astrophysics Data System (ADS)

    Hu, Jun; Duan, Anmin

    2015-11-01

    Investigating the relationships among different factors impacting the East Asian summer monsoon (EASM) is urgent for improving its predictability. In the present study, two factors, the Tibetan Plateau (TP) atmospheric thermal forcing and the Indian Ocean sea surface temperature basin mode (IOBM), are selected to compare their relative contributions to the interannual variability of the EASM. Both statistical methods and numerical experiments are used to separate and compare their respective influences under realistic circumstances. The results indicate that the IOBM mainly drives an anticyclonic anomaly over the northwestern Pacific in the lower troposphere, which is consistent with the dominant mode of the EASM circulation system. Meanwhile, influences from the TP thermal forcing are primarily on the anticyclonic anomaly over the TP in the upper troposphere, together with the enhanced southwesterly over southern China and a northerly anomaly over northern China in the lower troposphere. Moreover, the TP thermal forcing seems to play a more important role than the IOBM in affecting the main rainfall belt of the EASM, which extends from the middle and lower reaches of the Yangtze River to Japan. Such a rainfall pattern anomaly is directly related to the anomalous northerly over northern China and the resultant stronger moisture convergence over the main rainfall belt region when a strong TP thermal forcing occurs. In addition, the IOBM can increase the precipitation over the southeastern TP during its positive phase and hence enhance the in situ atmospheric heat source to a certain degree.

  1. Genetic structure of populations of whale sharks among ocean basins and evidence for their historic rise and recent decline.

    PubMed

    Vignaud, Thomas M; Maynard, Jeffrey A; Leblois, Raphael; Meekan, Mark G; Vázquez-Juárez, Ricardo; Ramírez-Macías, Dení; Pierce, Simon J; Rowat, David; Berumen, Michael L; Beeravolu, Champak; Baksay, Sandra; Planes, Serge

    2014-05-01

    This study presents genetic evidence that whale sharks, Rhincodon typus, are comprised of at least two populations that rarely mix and is the first to document a population expansion. Relatively high genetic structure is found when comparing sharks from the Gulf of Mexico with sharks from the Indo-Pacific. If mixing occurs between the Indian and Atlantic Oceans, it is not sufficient to counter genetic drift. This suggests whale sharks are not all part of a single global metapopulation. The significant population expansion we found was indicated by both microsatellite and mitochondrial DNA. The expansion may have happened during the Holocene, when tropical species could expand their range due to sea-level rise, eliminating dispersal barriers and increasing plankton productivity. However, the historic trend of population increase may have reversed recently. Declines in genetic diversity are found for 6 consecutive years at Ningaloo Reef in Australia. The declines in genetic diversity being seen now in Australia may be due to commercial-scale harvesting of whale sharks and collision with boats in past decades in other countries in the Indo-Pacific. The study findings have implications for models of population connectivity for whale sharks and advocate for continued focus on effective protection of the world's largest fish at multiple spatial scales. PMID:24750370

  2. Anaerobic Oxidation of Methane at a Marine Methane Seep in a Forearc Sediment Basin off Sumatra, Indian Ocean

    PubMed Central

    Siegert, Michael; Krüger, Martin; Teichert, Barbara; Wiedicke, Michael; Schippers, Axel

    2011-01-01

    A cold methane seep was discovered in a forearc sediment basin off the island Sumatra, exhibiting a methane-seep adapted microbial community. A defined seep center of activity, like in mud volcanoes, was not discovered. The seep area was rather characterized by a patchy distribution of active spots. The relevance of anaerobic oxidation of methane (AOM) was reflected by 13C-depleted isotopic signatures of dissolved inorganic carbon. The anaerobic conversion of methane to CO2 was confirmed in a 13C-labeling experiment. Methane fueled a vital microbial community with cell numbers of up to 4 × 109 cells cm−3 sediment. The microbial community was analyzed by total cell counting, catalyzed reporter deposition–fluorescence in situ hybridization (CARD–FISH), quantitative real-time PCR (qPCR), and denaturing gradient gel electrophoresis (DGGE). CARD–FISH cell counts and qPCR measurements showed the presence of Bacteria and Archaea, but only small numbers of Eukarya. The archaeal community comprised largely members of ANME-1 and ANME-2. Furthermore, members of the Crenarchaeota were frequently detected in the DGGE analysis. Three major bacterial phylogenetic groups (δ-Proteobacteria, candidate division OP9, and Anaerolineaceae) were abundant across the study area. Several of these sequences were closely related to the genus Desulfococcus of the family Desulfobacteraceae, which is in good agreement with previously described AOM sites. In conclusion, the majority of the microbial community at the seep consisted of AOM-related microorganisms, while the relevance of higher hydrocarbons as microbial substrates was negligible. PMID:22207865

  3. Geological and environmental controls on the change of eruptive style (phreatomagmatic to Strombolian-effusive) of Late Pleistocene El Caracol tuff cone and its comparison with adjacent volcanoes around the Zacapu basin (Michoacán, México)

    NASA Astrophysics Data System (ADS)

    Kshirsagar, Pooja; Siebe, Claus; Guilbaud, Marie Noëlle; Salinas, Sergio

    2016-05-01

    The 28,300 year BP (cal 32,300 BP) El Caracol tuff cone complex is one of the few phreatomagmatic volcanoes in the scoria-cone dominated Plio-Quaternary Michoacán-Guanajuato Volcanic Field (MGVF). It displays a shallow circular crater of ~ 1 km in diameter that is filled with several meter-thick lava flows and is located between two NE-SW trending normal faults dipping NW. It lies directly on top of Pliocene lavas of the San Lorenzo shield volcano that forms part of a tectonic horst (topographic high) separating the Zacapu lake basin (1980 m) in the south from the Río Angulo river valley (1760 m) to the north. Detailed study of the tephra sequence indicates that the eruption occurred in two stages: 1) Weak phreatomagmatic, in which about 0.1-0.5 km3 dense rock equivalent (DRE) of magma was issued within ~ 1 to 3 months at the rate of 4-40 m3/s, and 2) purely magmatic (Strombolian-effusive) during which the vent shifted slightly its position toward the NW, forming a small scoria cone (~ 100 m high) on the crater rim of the tuff cone. From this scoria cone lava flows were issued, first into the tuff cone crater occupying its bottom, and subsequently toward the NW, down the outer flank of the tuff cone and into the plain, where they reached a distance of ~ 3.5 km. During this stage ~ 0.6 km3 DRE of magma was produced at the rate of ~ 4 m3/s in a period of ~ 5 months. Although El Caracol displays many features that are characteristic for a phreatomagmatic vent, its morphology, types of deposits, and its complex process of formation makes it strikingly different from the more typical case of the ~ 21,000 year BP (cal 25,300 BP) Alberca de Guadalupe maar volcano, situated not far at the SE margin of the Zacapu basin. The latter was solely phreatomagmatic during the course of its eruption and is formed in its entirety by surge and fallout breccias consisting largely of xenolithic material. In contrast, at El Caracol the hydrogeological environment (namely the low

  4. Subduction initiation at oceanic detachment faults: a mechanism to generate extensive ophiolite belts

    NASA Astrophysics Data System (ADS)

    Maffione, Marco; Thieulot, Cedric; van Hinsbergen, Douwe; Morris, Antony; Plumper, oliver; Spakman, Wim

    2015-04-01

    One of the least understood processes of plate tectonics is the nucleation of new subduction zones and the formation of ophiolites by subsequent upper plate extension. Subduction initiation within ocean basins is thought to occur along weakness zones such as transform faults, fracture zones, and mid-ocean ridges. Detachment faults, which cut across oceanic lithosphere immediately adjacent to slow-spreading mid-ocean ridges may yields ideal rheological conditions for subduction initiation due to their pervasive serpentinization. We numerically test this hypothesis by modeling the inversion of an ocean basin cut by a serpentinized detachment fault adjacent to an active spreading center. The results of our models consistently show that the serpentinized fault effectively localizes deformation, assisting subduction initiation upon compression. Subsequent reactivation of the pre-existing spreading center preserved in the forearc above the nascent subduction zone provides an efficient mechanism for the formation of supra-subduction zone ophiolites. Application of our model of subduction initiation to the ~700 km-long ophiolite belt spanning from Albania to Greece is then discussed.

  5. Event sedimentation in low-latitude deep-water carbonate basins, Anegada passage, northeast Caribbean

    USGS Publications Warehouse

    Chaytor, Jason D.; ten Brink, Uri S.

    2015-01-01

    The Virgin Islands and Whiting basins in the Northeast Caribbean are deep, structurally controlled depocentres partially bound by shallow-water carbonate platforms. Closed basins such as these are thought to document earthquake and hurricane events through the accumulation of event layers such as debris flow and turbidity current deposits and the internal deformation of deposited material. Event layers in the Virgin Islands and Whiting basins are predominantly thin and discontinuous, containing varying amounts of reef- and slope-derived material. Three turbidites/sandy intervals in the upper 2 m of sediment in the eastern Virgin Islands Basin were deposited between ca. 2000 and 13 600 years ago, but do not extend across the basin. In the central and western Virgin Islands Basin, a structureless clay-rich interval is interpreted to be a unifite. Within the Whiting Basin, several discontinuous turbidites and other sand-rich intervals are primarily deposited in base of slope fans. The youngest of these turbidites is ca. 2600 years old. Sediment accumulation in these basins is low (−1) for basin adjacent to carbonate platform, possibly due to limited sediment input during highstand sea-level conditions, sediment trapping and/or cohesive basin walls. We find no evidence of recent sediment transport (turbidites or debris flows) or sediment deformation that can be attributed to the ca. M7.2 1867 Virgin Islands earthquake whose epicentre was located on the north wall of the Virgin Islands Basin or to recent hurricanes that have impacted the region. The lack of significant appreciable pebble or greater size carbonate material in any of the available cores suggests that submarine landslide and basin-wide blocky debris flows have not been a significant mechanism of basin margin modification in the last several thousand years. Thus, basins such as those described here may be poor recorders of past natural hazards, but may provide a long-term record of past oceanographic

  6. Seafloor seismicity, Antarctic ice-sounds, cetacean vocalizations and long-term ambient sound in the Indian Ocean basin

    NASA Astrophysics Data System (ADS)

    Royer, J.-Y.; Chateau, R.; Dziak, R. P.; Bohnenstiehl, D. R.

    2015-08-01

    This paper presents the results from the Deflo-hydroacoustic experiment in the Southern Indian Ocean using three autonomous underwater hydrophones, complemented by two permanent hydroacoustic stations. The array monitored for 14 months, from November 2006 to December 2007, a 3000 × 3000 km wide area, encompassing large segments of the three Indian spreading ridges that meet at the Indian Triple Junction. A catalogue of 11 105 acoustic events is derived from the recorded data, of which 55 per cent are located from three hydrophones, 38 per cent from 4, 6 per cent from five and less than 1 per cent by six hydrophones. From a comparison with land-based seismic catalogues, the smallest detected earthquakes are mb 2.6 in size, the range of recorded magnitudes is about twice that of land-based networks and the number of detected events is 5-16 times larger. Seismicity patterns vary between the three spreading ridges, with activity mainly focused on transform faults along the fast spreading Southeast Indian Ridge and more evenly distributed along spreading segments and transforms on the slow spreading Central and ultra-slow spreading Southwest Indian ridges; the Central Indian Ridge is the most active of the three with an average of 1.9 events/100 km/month. Along the Sunda Trench, acoustic events mostly radiate from the inner wall of the trench and show a 200-km-long seismic gap between 2 °S and the Equator. The array also detected more than 3600 cryogenic events, with different seasonal trends observed for events from the Antarctic margin, compared to those from drifting icebergs at lower (up to 50°S) latitudes. Vocalizations of five species and subspecies of large baleen whales were also observed and exhibit clear seasonal variability. On the three autonomous hydrophones, whale vocalizations dominate sound levels in the 20-30 and 100 Hz frequency bands, whereas earthquakes and ice tremor are a dominant source of ambient sound at frequencies <20 Hz.

  7. Record of Late Quaternary Glacial/Interglacial Variability in the Amerasian Basin (Arctic Ocean) with Improved Stratigraphy

    NASA Astrophysics Data System (ADS)

    Bazhenova, E.; Frederichs, T.; Wollenburg, J.; Stein, R. H.; Vogt, C. M.; Krylov, A.; Kostygov, S.

    2011-12-01

    Piston core TN062 0550, located 13 km offshore of Eureka, California (40.866 deg. N, 124.572 deg. W, 550 m water depth), contains a continuous high-resolution climate record of the past 7,300 yr. Deposition occurred at nearly constant sedimentation rates averaging 94 cm/kyr based on 14C AMS dating of planktonic foraminifers. Pollen and marine ecosystem proxies (diatoms, silicoflagellates, wt. percent biogenic silica) studied at 50-70 yr sample resolution show a stepwise development of the climate/ oceanographic system off northernmost California. The relative contributions of Sequoia sempervirens (coastal redwood) pollen, a proxy for coastal fog associated with offshore upwelling, and biogenic silica concentrations (a proxy for siliceous export productivity) increase (two fold and three fold, respectively) in successive steps at ~5,000 yr BP and from ~2,400 to 2,000 yr BP. These increases are interpreted to reflect a progressive intensification of spring upwelling based on modern observations of the California Current system. At 5,000 yr BP diatom assemblages change from an assorted mixture of warm, temperate, and cool-water taxa to a low diversity temperate-oceanic assemblage dominated by Thalassionema spp. At ~2,400 yr BP the diatom assemblage transitions to a mixture of nearshore upwelling taxa and taxa associated with the central North Pacific Gyre. Silicoflagellate assemblages undergo a similar increase in the representation of modern seasonal proxies at ~3,000 yr BP that may reflect intensified ENSO variability. A two-fold increase in the relative contributions of Quercus (oak) and riparian Alnus (alder) pollen between ~3,800 and 2,000 yr BP likely signals a period of enhanced fluvial runoff associated with increased winter precipitation. Given the present day association of the Eel River system with the northwestern half of the western US winter precipitation dipole, these pollen data suggest that the ~3,800 and 2,000 yr interval was dominated by protracted

  8. Distribution of foraminifera and calcareous nannoplankton in quaternary sediments of the Eastern Angola Basin in response to climatic and oceanic fluctuations

    NASA Astrophysics Data System (ADS)

    Zachariasse, W. J.; Schmidt, R. R.; Van Leeuwen, R. J. W.

    The impact of the Zaire River on the oceanic environment is clearly illustrated in the surface sediments by anomalously high carbonate dissolution rates over a large area off the river mouth. This anomaly results from the high supply of terrestrial organic matter brought into the Angola Basin by the outflowing river water. Carbonate dissolution indices demonstrate that downcore fluctuations in carbonate content are strongly controlled by carbonate dissolution processes. In the deep water cores variations in the rate of dissolution follow from changes in the position of the CCD. Variations in carbonate dissolution in the shallow cores are of local origin, and are linked to differences in the flux of land-derived organic matter. Associations of planktonic Foraminifera in the cored sediments of the eastern Angola Basin consist of tropical-subtropical and transitional-subantarctic species. The latter are considered as "southern intruders" brought northward by the Benguela Current and are potentially useful for deciphering changes in surface-water circulation during the Quaternary. Unfortunately, in almost all cores the planktonic foraminiferal signal in the "cold" periods has been obliterated by dissolution. The compositional pattern (in core T78-46) indicates that the Benguela Current had a stronger influence during the last glacial than it has today. High joint percentages of Epistominella exigua and Osangularia? umbonifera (in core T78-45) during the Holocene and Emian I document periods in which bottom waters were made up of an admixture of North Atlantic Deep Water and Antarctic Bottom Water just as they are today. Recurrent peak frequencies of Uvigerina peregrina may reflect intermittent stages of oxygen-poor bottom water. A distinct drop in radiolarian numbers across the W-X and Y-Z zonal boundaries is attributed to a periodically increased discharge of river water, which lowered primary productivity due to the short residence time and high turbidity of the

  9. Tectonic development, sedimentation and paleoceanography of the Scan Basin (southern Scotia Sea, Antarctica)

    NASA Astrophysics Data System (ADS)

    Pérez, Lara F.; Lodolo, Emanuele; Maldonado, Andrés; Hernández-Molina, F. Javier; Bohoyo, Fernando; Galindo-Zaldívar, Jesús; Lobo, F. José; Burca, Mihai

    2014-12-01

    The N-S trending Scan Basin is the easternmost deep basin north of the South Scotia Ridge, which is a geologically complex structural elevation that hosts the strike-slip boundary between the Scotia and Antarctic plates. We characterized the main morpho-structural features of the basin by analyzing the available multichannel seismic reflection profiles. The reconstruction of the seismo-stratigraphy reveals the growth patterns of the Scan Basin. Seismic data and gravity modeling support the interpretation that the basin is mainly floored by oceanic crust, however its northern and southern provinces exhibit different seismic attributes. Stratigraphic calibrations with adjacent regions together with the distribution of sedimentary units indicate that this basin was formed by rifting processes and subsequent spreading accretion from the Oligocene to the Miocene. This age attribution suggests that the Scan Basin might be one of the oldest oceanic basins of the southern Scotia Sea-possibly coeval with the Eocene-Oligocene opening of the Drake Passage. The basin is the most direct connection between the Weddell Sea and the Scotia Sea, whereas the stratigraphic features reveal the occurrence of major paleoceanographic changes. The initial phases of the evolution were influenced by mass-transport and turbidite processes of sediment supply from the nearby continental margins of the eastern tip of the Antarctic Peninsula. From the Middle Miocene to the Present-day, the eastward motion of the basin due to plate tectonic and the connection with the Weddell Sea through gateways enabled instauration of the overflow of Weddell Sea Deep Water (WSDW) into the Scan Basin. The WSDW forced the northward migration of the Circumpolar Deep Water (CDW) and became progressively dominant, controlling depositional patterns. The results that we report here should prove essential for understanding the formation of the Scotia Sea, the beginning of the Scotia Arc fragmentation, and the increasing

  10. Deglacial 14C plateau suites recalibrated by Suigetsu atmospheric 14C record - Revised 14C reservoir ages from three ocean basins corroborate extreme surface water variations

    NASA Astrophysics Data System (ADS)

    Sarnthein, M.; Balmer, S.; Grootes, P. M.

    2013-12-01

    widely assumed constant planktic Δ14C age of 400 yr. (3) Suites of deglacial planktic Δ14C ages are closely reproducible in 14C records measured on neighbor core sites. (4) Apparent deep-water 14C ventilation ages (benthic Δ14C), obtained from the sum of planktic Δ14C and coeval benthic-planktic Δ14C age differences, vary from an equivalent of <1000 to 5000 yr in LGM and deglacial ocean basins.

  11. Crustal structures across Canada Basin and southern Alpha Ridge of the Arctic Ocean from P- and S-wave sonobuoy wide-angle studies

    NASA Astrophysics Data System (ADS)

    Chian, D.; Shimeld, J.; Jackson, R.; Hutchinson, D. R.; Mosher, D. C.

    2010-12-01

    During 2007-2009, a total of 127 expendable sonobuoys (SB) were deployed across Canada Basin and southern Alpha Ridge to record wide-angle reflections and refractions from more than 10,000 km of inline, short-offset seismic reflection surveying. Most of the SB data show clear wide-angle refractions/reflections from various sedimentary and crustal layers at offsets up to 35 km. Source-receiver offsets are calculated using direct water waves. Subsequent processing includes compensation for spherical divergence and attenuation, despiking, filtering, deconvolution, and NMO correction. During wide-angle modeling, inline reflection data are converted to depth using velocity models/interpretations, iteratively updated based on wide-angle raytracing. Slight ray angle dependent anisotropy is found to best describe observed data, and is used for time-depth conversions. Clear deep refractions from upper, middle and lower crusts are recorded by most SB. Across southern Canada Basin, a regionally consistent velocity structure exists: velocities of ~4.5 km/s overlie a sub-basement layer of 5.5-5.8 km/s at depths of 12-13 km which, in turn, overlie a lower crust of 6.7-7.2 km/s. This structure is intersected by a central gravity low (previously interpreted to be an extinct spreading center), west of which the basement and sub-basement layers are consistently shallower by >1 km than the eastern side. Further northward, significant velocity variations exist. For example, the southern Alpha Ridge has a lower crust of 6.0-6.6 km/s or 6.8-7.0 km/s. Volcanic intrusions, inferred from high basement velocities of ~5.7 km/s at unusually shallow depths (~5 km), exist at discrete locations along southern Alpha Ridge. Between Northwind Ridge and Alpha Ridge, a typical continent-type crustal structure is observed. PmP is occasionally observed, modeling of which results in a Moho depth of 12-15 km. Velocities of 4.2-4.5 km/s in the northern study area are associated with a regional

  12. Study of satellite geoid and gravity anomaly data of conjugate regions of Bay of Bengal and Enderby Basin new constraints on early evolution of the eastern Indian Ocean

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    Timing for breakup of the Indian plate from eastern Gondwanaland and evolution of the lithosphere in the Bay of Bengal still remain debated because of lack of confident identification of seafloor spreading magnetic anomalies and fracture zones. Satellite geoid and gravity data of the two conjugate regions, Bay of Bengal (BOB) and Enderby Basin (EB), are coupled with ship-borne data for investigation of early evolution of the eastern Indian Ocean, particularly the lithosphere formed earlier to seafloor magnetic anomaly 34. The magnetic anomaly 34 is identified with greater confidence in north and northwestern periphery of the EB and in the distal Bengal Fan region. In BOB no correlatable magnetic anomaly related to M-sequence is identified, therefore EB holds the key for understanding of the breakups that had occurred between eastern margin of India and east Antarctica. Recent identifications of pairs of M-sequence anomalies (from M9N to M2) and extinct ridge segment in the eastern Enderby Basin suggest that formation of the lithosphere in the BOB was no earlier than anomaly M2. High-resolution geoid and gravity data of the BOB reveal the presence of prominent tectonic features such as Sunda trench, Ninetyeast and 85°E ridges, etc. Geoidal gradient of the BOB trends in WSW-ENE direction and does not follow the direction of the plate motion as expected, instead it trends in the resultant direction between the plate motion direction and geoidal low lying south of Sri Lanka. While in the EB the geoidal gradients trend in N-S to NW-SE following the general trends of the plate motion directions. Two prominent NW-SE trending fracture zones and five isolated NE-SW elongated structural rises are observed in residual geoidal and free-air gravity anomaly data between eastern margin of India and the 85°E Ridge. The rises are associated with low gravity anomalies and are oriented in orthogonal to the fracture zones trend. We interpret these structures as extinct ridge

  13. Hydrologic and water-quality conditions in the lower Apalachicola-Chattahoochee-Flint and parts of the Aucilla-Suwannee-Ochlockonee River basins in Georgia and adjacent parts of Florida and Alabama during drought conditions, July 2011

    USGS Publications Warehouse

    Gordon, Debbie W.; Peck, Michael F.; Painter, Jaime A.

    2012-01-01

    As part of the U.S. Department of the Interior sustainable water strategy, WaterSMART, the U.S. Geological Survey documented hydrologic and water-quality conditions in the lower Apalachicola-Chattahoochee-Flint and western and central Aucilla-Suwannee-Ochlockonee River basins in Alabama, Florida, and Georgia during low-flow conditions in July 2011. Moderate-drought conditions prevailed in this area during early 2011 and worsened to exceptional by June, with cumulative rainfall departures from the 1981-2010 climate normals registering deficits ranging from 17 to 27 inches. As a result, groundwater levels and stream discharges measured below median daily levels throughout most of 2011. Water-quality field properties including temperature, dissolved oxygen, specific conductance, and pH were measured at selected surface-water sites. Record-low groundwater levels measured in 12 of 43 surficial aquifer wells and 128 of 312 Upper Floridan aquifer wells during July 2011 underscored the severity of drought conditions in the study area. Most wells recorded groundwater levels below the median daily statistic, and 7 surficial aquifer wells were dry. Groundwater-level measurements taken in July 2011 were used to determine the potentiometric surface of the Upper Floridan aquifer. Groundwater generally flows to the south and toward streams except in reaches where streams discharge to the aquifer. The degree of connection between the Upper Floridan aquifer and streams decreases east of the Flint River where thick overburden hydraulically separates the aquifer from stream interaction. Hydraulic separation of the Upper Floridan aquifer from streams located east of the Flint River is shown by stream-stage altitudes that differ from groundwater levels measured in close proximity to streams. Most streams located in the study area during 2011 exhibited below normal flows (streamflows less than the 25th percentile), substantiating the severity of drought conditions that year. Streamflow

  14. Phylogeny and biogeography of exacum (gentianaceae): a disjunctive distribution in the Indian ocean basin resulted from long distance dispersal and extensive radiation.

    PubMed

    Yuan, Yong-Ming; Wohlhauser, Sébastien; Möller, Michael; Klackenberg, Jens; Callmander, Martin; Küpfer, Philippe

    2005-02-01

    Disjunctive distributions across paleotropical regions in the Indian Ocean Basin (IOB) often invoke dispersal/vicariance debates. Exacum (Gentianaceae, tribe Exaceae) species are spread around the IOB, in Africa, Madagascar, Socotra, the Arabian peninsula, Sri Lanka, India, the Himalayas, mainland Southeast Asia including southern China and Malaysia, and northern Australia. The distribution of this genus was suggested to be a typical example of vicariance resulting from the breakup of the Gondwanan supercontinent. The molecular phylogeny of Exacum is in principle congruent with morphological conclusions and shows a pattern that resembles a vicariance scenario with rapid divergence among lineages, but our molecular dating analysis demonstrates that the radiation is too recent to be associated with the Gondwanan continental breakup. We used our dating analysis to test the results of DIVA and found that the program predicted impossible vicariance events. Ancestral area reconstruction suggests that Exacum originated in Madagascar, and divergence dating suggests its origin was not before the Eocene. The Madagascan progenitor, the most recent common ancestor of Exacum, colonized Sri Lanka and southern India via long-distance dispersals. This colonizer underwent an extensive range expansion and spread to Socotra-Arabia, northern India, and mainland Southeast Asia in the northern IOB when it was warm and humid in these regions. This widespread common ancestor retreated subsequently from most parts of these regions and survived in isolation in Socotra-Arabia, southern India-Sri Lanka, and perhaps mainland Southeast Asia, possibly as a consequence of drastic climatic changes, particularly the spreading drought during the Neogene. Secondary diversification from these surviving centers and Madagascar resulted in the extant main lineages of the genus. The vicariance-like pattern shown by the phylogeny appears to have resulted from long-distance dispersals followed by extensive

  15. Evidence For Decadal and Century Scale Climate and Oceanic Variability in the Guaymas Basin, Gulf of California, Over the Last Millenium

    NASA Astrophysics Data System (ADS)

    Pineda, L.; Ravelo, A. C.; Aiello, I. W.; Stewart, Z.; Sauthoff, W.

    2015-12-01

    Linda Pineda1Ana Christina Ravelo2Ivano Aiello3Zach Stewart2Wilson Sauthoff2 Earth and Planetary Sciences Department, UCSC Ocean Sciences Department, UCSC Moss Landing Marine Lab Natural climate change affects coastal water resources, human land use, and marine biological productivity. In particular, the seasonal migration of the Intertropical Convergence Zone (ITCZ) is influenced by changes in global-scale temperature and pressure gradients and is responsible for spatial changes in summertime rainfall in Mesoamerica impacting regional water resources and the strength of upwelling. In October 2014, aboard the Research Vessel El Puma, a 3.9 meter long core (G14-P12) was recovered from the Northeast flank of the Guaymas Basin in the Gulf of California within the oxygen minimum zone (27˚52.11'N, 111˚41.51'W, water depth of 677m) to investigate changes in seasonal upwelling and Central Mexico rainfall over the last ~1000 years. The age model was developed using Pb210, C14 and lamination counting. The time interval includes the Little Ice Age and the Medieval Warm Period. Biological productivity and precipitation proxy records were produced using an X-Ray Fluorescence (XRF) core-scanner and a color line scanner to generate a record of bulk chemistry and color reflectance. The records indicate marked decadal and centennial scale variability in the lithologic composition of the sediment superimposed on millimeter-scale variability that reflects the presence of seasonally laminated sediments. Nitrogen isotopic and nitrogen weight % measurements were used, in combination with the scanned data, to interpret changes in nitrate utilization and biological productivity. These new records will have broad implications on the link between regional coastal environmental conditions in the Gulf of California and global climate change.

  16. The Cretaceous-Paleogene boundary unit in the Gulf of Mexico: Large-scale oceanic basin response to the Chicxulub impact

    NASA Astrophysics Data System (ADS)

    Sanford, J. C.; Gulick, S. P.; Snedden, J.

    2013-12-01

    the lower slope of the Florida Platform, providing further evidence of massive sediment redistribution. Log character of the boundary deposit varies significantly, suggesting changes in both depositional style (e.g, mass flow deposit, collapsed platform block, etc.) and sediment source (e.g., Yucatán Platform, Florida Platform, Texas coast, etc.). Reinvestigation of the classic K-Pg boundary deposits in DSDP Leg 77 cores reveals evidence of several sequences of debris flows and/or turbidites with possibly unique sediment sources, furthering our understanding of small-scale sedimentary processes of impact-related deposition. Generally, evidence supports the theory that the Chicxulub impact was a source of extreme allogenic energy that drastically altered the Gulf Mexico at the start of the Cenozoic. Seismogenic ground roll and multiple episodes of tsunami, erosion, platform collapse, and remobilized sediment effectively overwhelmed and resurfaced the basin's existing depositional systems within a matter of weeks to months. Such processes resulted in the nearly ubiquitous and often extremely thick K-Pg boundary unit in the Gulf. These results yield insight into the near-field effects of a massive bolide impact in a passive marine setting and the ability of such an impact to instantaneously restructure an oceanic basin and its depositional systems.

  17. Tectonic history of the Illinois basin

    SciTech Connect

    Kolata, D.R.; Nelson, J.W. )

    1990-05-01

    The Illinois basin began as a failed rift that developed during breakup of a supercontinent approximately 550 Ma. A rift basin in the southernmost part of the present Illinois basin subsided rapidly and filled with about 3,000 m of probable Early and Middle Cambrian sediments. By the Late Cambrian, the rift-bounding faults became inactive and a broad relatively slowly subsiding embayment, extending well beyond the rift and open to the Iapetus Ocean, persisted through most of the Paleozoic Era. Widespread deformation swept through the proto-Illinois basin beginning in the latest Mississippian, continuing to the end of the Paleozoic Era. Uplift of basement fault blocks resulted in the formation of many major folds and faults. The timing of deformation and location of these structures in the forelands of the Ouachita and Alleghanian orogenic belts suggest that much of the deformation resulted from continental collision between North America and Gondwana. The associated compressional stress reactivated the ancient rift-bounding faults, upthrusting the northern edge of a crustal block approximately 1,000 m within the rift. Concurrently, dikes (radiometrically dated as Early Permian), sills, and explosion breccias formed in or adjacent to the reactivated rift. Subsequent extensional stress, probably associated with breakup of Pangea, caused the crustal block within the rift to sink back to near its original position. High-angle, northeast- to east-west-trending normal faults, with as much as 1,000 m of displacement, formed in the southern part of the basin. These faults displace some of the northwest trending Early Permian dikes. Structural closure of the southern end of the Illinois basin was caused by uplift of the Pascola arch sometime between the Late Pennsylvanian and Late Cretaceous.

  18. Seismic sequence stratigraphy of the Lower Congo, Kwanza, and Benguela Basins, offshore Angola, Africa

    NASA Astrophysics Data System (ADS)

    Schollnberger, Elle Marie

    2001-07-01

    Sequences are recognized throughout the geologic record. The Angolan margin provides an excellent opportunity to examine the factors that control the deposition and preservation of sediments in sequences, as well as the factors that create the erosion or non-deposition along sequence boundaries. The Angolan sequences can be compared to global sequence charts and used to investigate the effects of local events versus global events on the area's sequences. Using seismic sequence stratigraphic principles, a 2D regional seismic data set covering three basins offshore Angola, the Lower Congo, Kwanza, and Benguela Basins, was interpreted. Sequences and their unconformities were correlated within each basin as well as between basins. Major sequences could be interpreted throughout and between the three basins with a high degree of confidence. Additional sequences within these major sequences were interpreted within a basin, but could not be correlated to the adjacent basin with a high degree of confidence. Detailed interpretation of the sequence stratigraphic significance of each reflector was performed on three profiles, one for each basin. Chronostratigraphic charts were constructed using the detailed interpretation of the profiles. Within the interpreted sequence stratigraphic framework, the timing and mechanics of the formation of salt structures was examined. The Angolan basins contain a variety of salt tectonic features. The reflectors of strata adjacent to the salt features were used to determine the timing and mechanics of the salt structure formation. This study accomplished several objectives. The tectonic evolution of the Angolan margin was reviewed. This study established a sequence stratigraphic framework for Angola. The process of deposition and preservation of sediments as depositional sequences was examined. The sequences were compared with the global sequence charts as well as with eustatic, tectonic, and oceanic circulation events. The formation of the

  19. Ocean-to-Ocean Dissimilarities of Salty Subtropical Surface Water

    NASA Astrophysics Data System (ADS)

    Gordon, A. L.

    2014-12-01

    Each ocean basin displays its own 'personality', reflecting its degree of isolation or connectivity to the global ocean, its place in the interocean exchange network and associated ocean overturning circulation systems, as well as regional circulation and air-sea exchange patterns. While dissimilarities are most notable in the northern hemisphere (the salty North Atlantic vs the fresher North Pacific; as well as the salty Arabian and the fresher Bay of Bengal, a miniature Atlantic/Pacific analog?) far removed from the grand equalizing interocean link of the circum-Antarctic belt, and where large continental blocks impose contrasting forcing, the southern hemisphere ocean basins also display differences. Ocean to ocean dissimilarities are evident in the dry subtropical climate belt, marked by deserts on land and salty surface ocean water. The subtropical sea surface salinity maximum (SSS-max) patterns of 5 the subtropical regimes (the North and South Atlantic, North and South Pacific, and the southern Indian Ocean) display significant dissimilarities in their relative position within their ocean basin, in the structure and seasonality of the SSS-max pattern. The near synoptic coverage of Aquarius and Argo profilers are further defining interannual variability. The South Atlantic SSS-max is pressed against the western boundary, whereas in the other regimes the SSS-max falls within the eastern half of the ocean basin, though the western South Pacific displays a secondary SSS-max. For further details see: A. Gordon, C. Giulivi, J. Busecke, F. Bingham, submitted to the SPURS Oceanography special issue.

  20. Seismic refraction profile in coral sea basin.

    PubMed

    Shor, G G

    1967-11-17

    A refraction profile near the south edge of Coral Sea Basin shows sediments, "second layer," and oceanic crust all thicker than normal for an oceanic station; normal mantle lies at a depth of 19 kilometers. PMID:17753600

  1. The Cretaceous oceanic events (anoxia and hiatus) within a sequence stratigraphic framework

    SciTech Connect

    Jacquin, T.; Magniez-Jannin, F.; Ponsot, C. ); De Graciansky, P. ); Vail, P.R. )

    1991-03-01

    The authors revision of the stratigraphy and organic geochemistry of the North and South Atlantic DSDP boreholes has demonstrated the large range of occurrences and settings of the Cretaceous black shales during the so-called Oceanic Anoxic Events. No simple model has yet been found to explain the exact timing of the anoxic layers and stratigraphic gaps associated with these three particular events. Sequence stratigraphic analyses of outcrop sections in the Western Interior basin (Black Hills area), in the Paris basin, and in the Southeast basin of France provide data to precisely date the timing of the anoxia and oceanic gaps and to show their relationship to long and short term changes of relative sea level. The Oceanic Anoxic Events correspond to periods of severe starvation events where several depositional sequences, and more particularly their maximum flooding surfaces, are merged. Three strongly condensed stratigraphic periods are recognized in the deep Atlantic ocean: event E1 a during the early Aptian, event E1b during the late Aptian-early Albian, and event E2 from the late Cenomanian to the middle Turonian. They coincide on the adjacent landmass with the overall backstepping of the depositional environments due to the overall rapid rising of relative sea level.

  2. The Design and Analysis of Salmonid Tagging Studies in the Columbia Basin; Volume XII; A Multinomial Model for Estimating Ocean Survival from Salmonid Coded Wire-Tag Data.

    SciTech Connect

    Ryding, Kristen E.; Skalski, John R.

    1999-06-01

    The purpose of this report is to illustrate the development of a stochastic model using coded wire-tag (CWT) release and age-at-return data, in order to regress first year ocean survival probabilities against coastal ocean conditions and climate covariates.

  3. Deep crustal structure of the Adare and Northern Basins, Ross Sea, Antarctica, from sonobuoy data

    NASA Astrophysics Data System (ADS)

    Selvans, M. M.; Stock, J. M.; Clayton, R. W.; Cande, S.; Granot, R.

    2014-11-01

    Extension associated with ultraslow seafloor spreading within the Adare Basin, in oceanic crust just north of the continental shelf in the Ross Sea, Antarctica, extended south into the Northern Basin. Magnetic and gravity anomaly data suggest continuity of crustal structure across the continental shelf break that separates the Adare and Northern Basins. We use sonobuoy refraction data and multi-channel seismic (MCS) reflection data collected during research cruise NBP0701, including 71 new sonobuoy records, to provide constraints on crustal structure in the Adare and Northern Basins. Adjacent 1D sonobuoy profiles along several MCS lines reveal deep crustal structure in the vicinity of the continental shelf break, and agree with additional sonobuoy data that document fast crustal velocities (6000-8000 m/s) at shallow depths (1-6 km below sea level) from the Adare Basin to the continental shelf, a structure consistent with that of other ultraslow-spread crust. Our determination of crustal structure in the Northern Basin only extends through sedimentary rock to the basement rock, and so cannot help to distinguish between different hypotheses for formation of the basin.

  4. Geological Structure and History of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Petrov, Oleg; Morozov, Andrey; Shokalsky, Sergey; Sobolev, Nikolay; Kashubin, Sergey; Pospelov, Igor; Tolmacheva, Tatiana; Petrov, Eugeny

    2016-04-01

    New data on geological structure of the deep-water part of the Arctic Basin have been integrated in the joint project of Arctic states - the Atlas of maps of the Circumpolar Arctic. Geological (CGS, 2009) and potential field (NGS, 2009) maps were published as part of the Atlas; tectonic (Russia) and mineral resources (Norway) maps are being completed. The Arctic basement map is one of supplements to the tectonic map. It shows the Eurasian basin with oceanic crust and submerged margins of adjacent continents: the Barents-Kara, Amerasian ("Amerasian basin") and the Canada-Greenland. These margins are characterized by strained and thinned crust with the upper crust layer, almost extinct in places (South Barents and Makarov basins). In the Central Arctic elevations, seismic studies and investigation of seabed rock samples resulted in the identification of a craton with the Early Precambrian crust (near-polar part of the Lomonosov Ridge - Alpha-Mendeleev Rise). Its basement presumably consists of gneiss granite (2.6-2.2 Ga), and the cover is composed of Proterozoic quartzite sandstone and dolomite overlain with unconformity and break in sedimentation by Devonian-Triassic limestone with fauna and terrigenous rocks. The old crust is surrounded by accretion belts of Timanides and Grenvillides. Folded belts with the Late Precambrian crust are reworked by Caledonian-Ellesmerian and the Late Mesozoic movements. Structures of the South Anuy - Angayucham ophiolite suture reworked in the Early Cretaceous are separated from Mesozoides proper of the Pacific - Verkhoyansk-Kolyma and Koryak-Kamchatka belts. The complicated modern ensemble of structures of the basement and the continental frame of the Arctic Ocean was formed as a result of the conjugate evolution and interaction of the three major oceans of the Earth: Paleoasian, Paleoatlantic and Paleopacific.

  5. Deep structure in rifted crust at the ocean-continent margin in the northwestern Ross Sea

    NASA Astrophysics Data System (ADS)

    Selvans, M. M.; Clayton, R. W.; Stock, J. M.; Cande, S. C.; Davey, F. J.

    2010-12-01

    The Ross Sea contains several deep sedimentary basins which formed as a result of distributed extension in continental crust during Cenozoic and Cretaceous time. These basins contain sedimentary sequences that are laterally extensive across multiple basins, which in the western Ross Sea represent infill from erosion of the Transantarctic Mountains. The Northern Basin lies in the northwestern Ross Sea, and borders oceanic crust that includes the Adare Trough spreading center, active from 43 to 26 Ma. This area provides an ideal location to study the mechanisms by which strain localized in a spreading center is transferred to adjacent continental crust. Refraction seismic records from 74 sonobuoys with 20 to 30 km of offset were obtained in the Northern and Adare Basins during research cruise NBP0701; they complement the ~2,700 km of multi-channel seismic (MCS) data, by probing the deeper velocity structure of the crust and by providing direct detection of layer velocities. We use standard techniques including linear moveout and conversion of the data into τ-p space (intercept time and slowness) to determine layer depths and velocities; we also construct a finite difference model of each sonobuoy in order to recognize converted phases, confidently tie the refracted arrivals to the reflections from which they originate (which are then tied to the shallower MCS data), and constrain layers’ s-wave velocities. In further support of the hypothesis that volcanic intrusions contributed significantly to the process of extension in the Northern Basin, high crustal velocities do not appreciably deepen when moving from the Adare Basin into the Northern Basin, as would be expected when moving from oceanic to continental crust. We consistently detect high crustal velocities at only a few kilometers depth into the crust, implying that processes such as compaction and erosion of sediment layers and volcanic intrusion have a significant effect on crustal structure.

  6. Hydrocarbon provinces and productive trends in Libya and adjacent areas

    SciTech Connect

    Missallati, A.A. Ltd., Tripoli )

    1988-08-01

    According to the age of major reservoirs, hydrocarbon occurrences in Libya and adjacent areas can be grouped into six major systems which, according to their geographic locations, can be classified into two major hydrocarbon provinces: (1) Sirte-Pelagian basins province, with major reservoirs ranging from middle-late Mesozoic to early Tertiary, and (2) Murzog-Ghadames basins province, with major reservoirs ranging from early Paleozoic to early Mesozoic. In the Sirte-Pelagian basins province, hydrocarbons have been trapped in structural highs or in stratigraphic wedge-out against structural highs and in carbonate buildups. Here, hydrocarbon generation is characterized by the combined effect of abundant structural relief and reservoir development in the same hydrocarbon systems of the same age, providing an excellent example of hydrocarbon traps in sedimentary basins that have undergone extensive tensional fracturing in a shallow marine environment. In the Murzog-Ghadames basins province, hydrocarbons have been trapped mainly in structural highs controlled by paleostructural trends as basement arches which acted as focal points for oil migration and accumulation.

  7. Knowledge of marine fish trematodes of Atlantic and Eastern Pacific Oceans.

    PubMed

    Bray, Rodney A; Diaz, Pablo E; Cribb, Thomas H

    2016-03-01

    A brief summary of the early history of the study of Atlantic Ocean marine fish digeneans is followed by a discussion of the occurrence and distribution of these worms in the Atlantic Ocean and adjacent Eastern Pacific Ocean, using the Provinces of the 'Marine Ecoregions' delimited by Spalding et al. (Bioscience 57:573-583, 2007). The discussion is based on a database of 9,880 records of 1,274 species in 430 genera and 45 families. 8,633 of these records are from the Atlantic Ocean, including 1,125 species in 384 genera and 45 families. About 1,000 species are endemic to the Atlantic Ocean Basin. The most species-rich families in the Atlantic Ocean are the Opecoelidae Ozaki, 1925, Hemiuridae Looss, 1899 and Bucephalidae Poche, 1907, and the most wide-spread the Opecoelidae, Hemiuridae, Acanthocolpidae Lühe, 1906, Lepocreadiidae Odhner, 1905 and Lecithasteridae Odhner, 1905. A total of 109 species are shared by the Atlantic Ocean and the Eastern Pacific, made up of cosmopolitan, circum-boreal, trans-Panama Isthmus and Magellanic species. The lack of genetic evaluation of identifications is emphasised and the scope for much more work is stressed. PMID:26898586

  8. Bransfield Basin and Cordilleran Orogenesis

    NASA Astrophysics Data System (ADS)

    Dalziel, I. W.; Austin, J. A.; Barker, D. H.; Christensen, G. L.

    2003-12-01

    Tectonic uplift of the Andean Cordillera was initiated in the mid-Cretaceous with inversion of a composite marginal basin along 7500 km of the continental margin of South America, from Peru to Tierra del Fuego and the North Scotia Ridge. In the southernmost Andes, from 50-56 degrees S, the quasi-oceanic floor of this basin is preserved in the obducted ophiolitic rocks of the Rocas Verdes (Green Rocks) basin. We suggest that the basin beneath Bransfield Strait, 61-64 degrees S, separating the South Shetland Islands from the Antarctic Peninsula, constitutes a modern analog for the Rocas Verdes basin. Marine geophysical studies of Bransfield basin have been undertaken over the past 12 years by the Institute for Geophysics, University of Texas at Austin, under the auspices of the Ocean Sciences Division and United States Antarctic Program, National Science Foundation. These studies have elucidated the structure and evolution of Bransfield basin for comparison with the Rocas Verdes basin, with a view to eventual forward modeling of the evolution of a hypothetical cordilleran orogen by compression and inversion of the basin. These are the processes that can be observed in the tectonic transformation of the Rocas Verdes basin into the southernmost Andean cordillera, as South America moved rapidly westward in an Atlantic-Indian ocean hot-spot reference frame during the mid-Cretaceous. Multi-channel reflection seismic data from the Bransfield basin reveal an asymmetric structural architecture characterized by steeply-dipping normal faults flanking the South Shetlands island arc and gently dipping listric normal faults along the Antarctic Peninsula margin. Normal fault polarity reversals appear to be related to distributed loci of magmatic activity within the basin. This architecture is remarkably similar to that deduced from field structural studies of the Rocas Verdes basin. Notably, the oceanward-dipping, low angle normal faults along the Antarctic Peninsula margin

  9. How subaerial salt extrusions influence water quality in adjacent aquifers

    NASA Astrophysics Data System (ADS)

    Mehdizadeh, Razieh; Zarei, Mehdi; Raeisi, Ezzat

    2015-12-01

    Brines supplied from salt extrusions cause significant groundwater salinization in arid and semi-arid regions where salt rock is exposed to dissolution by episodic rainfalls. Here we focus on 62 of the 122 diapirs of Hormuz salt emergent in the southern Iran. To consider managing the degradation effect that salt extrusions have on the quality of adjoining aquifers, it is first necessary to understand how they influence adjacent water resources. We evaluate here the impacts that these diapirs have on adjacent aquifers based on investigating their geomorphologies, geologies, hydrologies and hydrogeologies. The results indicate that 28/62 (45%) of our sample of salt diapirs have no significant impact on the quality of groundwater in adjoining aquifers (namely Type N), while the remaining 34/62 (55%) degrade nearby groundwater quality. We offer simple conceptual models that account for how brines flowing from each of these types of salt extrusions contaminate adjacent aquifers. We identify three main mechanisms that lead to contamination: surface impact (Type A), subsurface intrusion (Type B) and indirect infiltration (Type C). A combination of all these mechanisms degrades the water quality in nearby aquifers in 19/62 (31%) of the salt diapirs studied. Having characterized the mechanism(s) by which each diapir affects the adjacent aquifer, we suggest a few possible remediation strategies to be considered. For instance, engineering the surface runoff of diapirs Types A and C into nearby evaporation basins would improve groundwater quality.

  10. Modeling ocean circulation

    SciTech Connect

    Semtner, A.J.

    1995-09-08

    Ocean numerical models have become quite realistic over the past several years as a result of improved methods, faster computers, and global data sets. Models now treat basin-scale to global domains while retaining the fine spatial scales that are important for modeling the transport of heat, salt, and other properties over vast distances. Simulations are reproducing observed satellite results on the energetics of strong currents and are properly showing diverse aspects of thermodynamic and dynamic ocean responses ranging from deep-water production of El Nino. Now models can represent not only currents but also the consequences for climate, biology, and geo-chemistry over time spans for months to decades. However, much remains to be understood from models about ocean circulation on longer time scales, including the evolution of the dominant water masses, the predictability of climate, and the ocean`s influence on global change. 34 refs., 6 figs.

  11. Whole water column distribution and carbon isotopic composition of bulk particulate organic carbon, cholesterol and brassicasterol from the Cape Basin to the northern Weddell Gyre in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Cavagna, A.-J.; Dehairs, F.; Woule-Ebongué, V.; Bouillon, S.; Planchon, F.; Delille, B.; Bouloubassi, I.

    2012-02-01

    The combination of concentrations and δ13C signatures of Particulate Organic Carbon (POC) and sterols provides a powerful approach to study ecological and environmental changes both in the modern and ancient ocean, but its application has so far been restricted to the surface area. We applied this tool to study the biogeochemical changes in the modern ocean water column during the BONUS-GoodHope survey (Feb-Mar 2008) from Cape Basin to the northern part of the Weddell Gyre. Cholesterol and brassicasterol were chosen as ideal biomarkers of the heterotrophic and autotrophic carbon pools, respectively, because of their ubiquitous and relatively refractory nature. We document depth distributions of concentrations (relative to bulk POC) and δ13C signatures of cholesterol and brassicasterol from the Cape Basin to the northern Weddell Gyre combined with CO2 aq. surface concentration variation. While relationships between surface water CO2 aq. and δ13C of bulk POC and biomarkers have been previously established for surface waters, our data show that these remain valid in deeper waters, suggesting that δ13C signatures of certain biomarkers could be developed as proxies for surface water CO2 aq. Our data suggest a key role of zooplankton fecal aggregates in carbon export for this part of the Southern Ocean. We observed a general increase in sterol δ13C signatures with depth, which is likely related to a combination of particle size effects, selective feeding on larger cells by zooplankton, and growth rate related effects Additionally, in the southern part of the transect south of the Polar Front (PF), the release of sea-ice algae is hypothesized to influence the isotopic signature of sterols in the open ocean. Overall, combined use of δ13C and concentrations measurements of both bulk organic C and specific sterol markers throughout the water column shows the promising potential of analyzing δ13C signatures of individual marine sterols to explore the recent history of

  12. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

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

  13. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

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

  14. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

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

  15. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

  16. CLOUD PEAK PRIMITIVE AREA AND ADJACENT AREAS, WYOMING.

    USGS Publications Warehouse

    Kiilsgaard, Thor H.; Patten, Lowell L.

    1984-01-01

    The results of a mineral survey of the Cloud Peak Primitive Area and adjacent areas in Wyoming indicated little promise for the occurrence of mineral resources. There are some prospect workings, particularly in the northern part of the area, but in none of them were there indications that ore had been mined. Samples from the workings, from nearby rocks and sediments from streams that drain the area did not yield any metal values of significance. The crystalline rocks that underlie the area do not contain oil and gas or coal, products that are extracted from the younger rocks that underlie basins on both sides of the study area.

  17. Ejecta from Ocean Impacts

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.

    2003-01-01

    Numerical simulations of deep-ocean impact provide some limits on the size of a projectile that will not mix with the ocean floor during a deep-ocean impact. For a vertical impact at asteroidal velocities (approx. 20 km/s), mixing is only likely when the projectile diameter is greater than 112 of the water depth. For oblique impacts, even larger projectiles will not mix with ocean floor silicates. Given the typical water depths of 4 to 5 km in deep-ocean basins, asteroidal projectiles with diameters as large as 2 or 3 km may commonly produce silicate ejecta that is composed only of meteoritic materials and seawater salts. However, the compressed water column beneath the projectile can still disrupt and shock metamorphose the ocean floor. Therefore, production of a separate, terrestrial ejecta component is not ruled out in the most extreme case. With increasing projectile size (or energy) relative to water depths, there must be a gradation between oceanic impacts and more conventional continental impacts. Given that 60% of the Earth's surface is covered by oceanic lithosphere and 500 m projectiles impact the Earth on 10(exp 5) y timescales, there must be hundreds of oceanic impact deposits in the sediment record awaiting discovery.

  18. Oceanic Plateaus

    NASA Astrophysics Data System (ADS)

    Kerr, A. C.

    2003-12-01

    Although the existence of large continental flood basalt provinces has been known for some considerable time, e.g., Holmes (1918), the recognition that similar flood basalt provinces also exist below the oceans is relatively recent. In the early 1970s increasing amounts of evidence from seismic reflection and refraction studies revealed that the crust in several large portions of the ocean floor is significantly thicker than "normal" oceanic crust, which is 6-7 km thick. One of the first areas of such over-thickened crust to be identified was the Caribbean plate ( Edgar et al., 1971) which Donnelly (1973) proposed to be an "oceanic flood basalt province". The term oceanic plateau was coined by Kroenke (1974), and was prompted by the discovery of a large area of thickened crust (>30 km) in the western Pacific known as the Ontong Java plateau (OJP). As our knowledge of the ocean basins has improved over the last 25 years, many more oceanic plateaus have been identified ( Figure 1). Coffin and Eldholm (1992) introduced the term "large igneous provinces" (LIPs) as a generic term encompassing oceanic plateaus, continental flood basalt provinces, and those provinces which form at the continent-ocean boundary (volcanic rifted margins). (22K)Figure 1. Map showing all major oceanic plateaus, and other large igneous provinces discussed in the text (after Saunders et al., 1992). LIPs are generally believed to be formed by decompression melting of upwelling hotter mantle, known as mantle plumes. Although ideas about hotpots and mantle plumes have been around for almost 40 years (Wilson, 1963), it is only in the past 15 years that LIPs have become the focus of major research. One of the main reasons for the increased research activity into LIPs is the realization that significant proportions of these LIPs erupted over a relatively short time, often less than 2-3 Myr (see review in Coffin, 1994). This has important implications for mantle processes and source regions ( Hart et

  19. The deep Ionian Basin revisited

    NASA Astrophysics Data System (ADS)

    Tugend, Julie; Chamot-Rooke, Nicolas; Arsenikos, Stavros; Frizon de Lamotte, Dominique; Blanpied, Christian

    2016-04-01

    The deep Eastern Mediterranean Basins (Ionian and Herodotus) are characterized by thick sedimentary sequences overlying an extremely thinned basement evidenced from different geophysical methods. Yet, the nature of the crust (continental or oceanic) and the timing of the extreme crustal and lithosphere thinning in the different sub-basins remain highly controversial, casting doubts on the tectonic setting related to the formation of this segment of the North Gondwana paleo-margin. We focus on the Ionian Basin located at the western termination of the Eastern Mediterranean with the aim of identifying, characterizing and mapping the deepest sedimentary sequences. We present tentative age correlations relying on calibrations and observations from the surrounding margins and basins (Malta shelf and Escarpment, Cyrenaica margin, Sirte Basin, Apulian Platform). Two-ship deep refraction seismic data (Expanding Spread Profiles from the PASIPHAE cruise) combined with reprocessed reflection data (from the ARCHIMEDE survey) enabled us to present a homogeneous seismic stratigraphy across the basin and to investigate the velocity structure of its basement. Based on our results, and on a review of geological and geophysical observations, we suggest an Upper Triassic-Early Dogger age for the formation of the deep Ionian Basin. The nature of the underlying basement remains uncertain, both highly-thinned continental and slow-spreading type oceanic crust being compatible with the available constraints. The narrow size and relatively short-lived evolution of the Ionian Basin lead us to suggest that it is more likely the remnant of an immature oceanic basin than of a stable oceanic domain. Eventually, upscaling these results at the scale of the Eastern Mediterranean Basins highlights the complex interaction observed between two propagating oceans: The Central Atlantic and Neo-Tethys.

  20. Asynchronous responses of fish assemblages to climate-driven ocean regime shifts between the upper and deep layer in the Ulleung basin of the East Sea from 1986 to 2010

    NASA Astrophysics Data System (ADS)

    Jung, Sukgeun

    2014-03-01

    Past studies suggested that a basin-wide regime shift occurred in 1988-1989, impacting marine ecosystem and fish assemblages in the western North Pacific. However, the detailed mechanisms involved in this phenomenon are still yet unclear. In the Ulleung basin of the East Sea, filefish, anchovy and sardine dominated the commercial fish catches in 1986-1992, but thereafter common squid comprised > 60% of the total catch in 1993-2010. To illuminate the mechanisms causing this dramatic shift in dominant fisheries species, I related changes in depth-specific oceanographic conditions from 0 to 500 m to inter-annual changes in the fish assemblage structure from 1986 to 2010. In the upper layer of 50-100 m depths, water temperature suddenly increased in 1987-1989, and consequently warm-water epi-pelagic species (anchovy, chub mackerel, and common squid) became dominant, while sardine, relatively cold-water epi-pelagic species, nearly disappeared. An annual index of the volume transport by the Korea Strait Bottom Cold Water, originating from the deep water of the Ulleung Basin, displayed a sudden intensification in 1992-1993, accompanied by decreased water temperature and increased water density in the deep water and replacement of dominant bentho-pelagic species from filefish, warm-water species, to herring and cod, cold-water species. The results suggest that climate-driven oceanic changes and the subsequent ecological impacts can occur asynchronously, often with time lags of several years, between the upper and the deep layer, and between epi-pelagic and deepwater fish assemblages.

  1. Environmental Conditions in a Carpathian Deep Sea Basin During the Period Preceding Oceanic Anoxic Event 2 - A Case Study from the Skole Nappe

    NASA Astrophysics Data System (ADS)

    Bąk, Krzysztof; Bąk, Marta; Górny, Zbigniew; Wolska, Anna

    2015-01-01

    Hemipelagic green clayey shales and thin muddy turbidites accumulated in a deep sea environment below the CCD in the Skole Basin, a part of the Outer Carpathian realm, during the Middle Cenomanian. The hemipelagites contain numerous radiolarians, associated with deep-water agglutinated foraminifera. These sediments accumulated under mesotrophic conditions with limited oxygen concentration. Short-term periodic anoxia also occurred during that time. Muddy turbidity currents caused deposition of siliciclastic and biogenic material, including calcareous foramini-fers and numerous sponge spicules. The preservation and diversity of the spicules suggests that they originate from disarticulation of moderately diversified sponge assemblages, which lived predominantly in the neritic-bathyal zone. Analyses of radiolarian ecological groups and pellets reflect the water column properties during the sedimentation of green shales. At that time, surface and also intermediate waters were oxygenated enough and sufficiently rich in nutri-ents to enable plankton production. Numerous, uncompacted pellets with nearly pristine radiolarian skeletons inside show that pelletization was the main factor of radiolarian flux into the deep basin floor. Partly dissolved skeletons indicate that waters in the Skole Basin were undersaturated in relation to silica content. Oxygen content might have been depleted in the deeper part of the water column causing periodic anoxic conditions which prevent rapid bacterial degra-dation of the pellets during their fall to the sea floor.

  2. 15 CFR 922.154 - Consultation with the State of Washington, affected Indian tribes, and adjacent county governments.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Washington, affected Indian tribes, and adjacent county governments. 922.154 Section 922.154 Commerce and... ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE OCEAN AND COASTAL RESOURCE MANAGEMENT NATIONAL MARINE... of Washington, affected Indian tribes, and adjacent county governments. (a) The Director...

  3. 15 CFR 922.154 - Consultation with the State of Washington, affected Indian tribes, and adjacent county governments.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Washington, affected Indian tribes, and adjacent county governments. 922.154 Section 922.154 Commerce and... ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE OCEAN AND COASTAL RESOURCE MANAGEMENT NATIONAL MARINE... of Washington, affected Indian tribes, and adjacent county governments. (a) The Director...

  4. 15 CFR 922.154 - Consultation with the State of Washington, affected Indian tribes, and adjacent county governments.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Washington, affected Indian tribes, and adjacent county governments. 922.154 Section 922.154 Commerce and... ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE OCEAN AND COASTAL RESOURCE MANAGEMENT NATIONAL MARINE... of Washington, affected Indian tribes, and adjacent county governments. (a) The Director...

  5. 15 CFR 922.154 - Consultation with the State of Washington, affected Indian tribes, and adjacent county governments.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Washington, affected Indian tribes, and adjacent county governments. 922.154 Section 922.154 Commerce and... ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE OCEAN AND COASTAL RESOURCE MANAGEMENT NATIONAL MARINE... of Washington, affected Indian tribes, and adjacent county governments. (a) The Director...

  6. 15 CFR 922.154 - Consultation with the State of Washington, affected Indian tribes, and adjacent county governments.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Washington, affected Indian tribes, and adjacent county governments. 922.154 Section 922.154 Commerce and... ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE OCEAN AND COASTAL RESOURCE MANAGEMENT NATIONAL MARINE... of Washington, affected Indian tribes, and adjacent county governments. (a) The Director...

  7. Assessment of undiscovered oil and gas resources of the East Coast Mesozoic basins of the Piedmont, Blue Ridge Thrust Belt, Atlantic Coastal Plain, and New England Provinces, 2011

    USGS Publications Warehouse

    Milici, Robert C.; Coleman, James L., Jr.; Rowan, Elisabeth L.; Cook, Troy A.; Charpentier, Ronald R.; Kirschbaum, Mark A.; Klett, Timothy R.; Pollastro, Richard M.; Schenk, Christopher J.

    2012-01-01

    During the early opening of the Atlantic Ocean in the Mesozoic Era, numerous extensional basins formed along the eastern margin of the North American continent from Florida northward to New England and parts of adjacent Canada. The basins extend generally from the offshore Atlantic continental margin westward beneath the Atlantic Coastal Plain to the Appalachian Mountains. Using a geology-based assessment method, the U.S. Geological Survey estimated a mean undiscovered natural gas resource of 3,860 billion cubic feet and a mean undiscovered natural gas liquids resource of 135 million barrels in continuous accumulations within five of the East Coast Mesozoic basins: the Deep River, Dan River-Danville, and Richmond basins, which are within the Piedmont Province of North Carolina and Virginia; the Taylorsville basin, which is almost entirely within the Atlantic Coastal Plain Province of Virginia and Maryland; and the southern part of the Newark basin (herein referred to as the South Newark basin), which is within the Blue Ridge Thrust Belt Province of New Jersey. The provinces, which contain these extensional basins, extend across parts of Georgia, South Carolina, North Carolina, Virginia, Maryland, Delaware, Pennsylvania, New Jersey, New York, Connecticut, and Massachusetts.

  8. Albuquerque Basin seismic network

    USGS Publications Warehouse

    Jaksha, Lawrence H.; Locke, Jerry; Thompson, J.B.; Garcia, Alvin

    1977-01-01

    The U.S. Geological Survey has recently completed the installation of a seismic network around the Albuquerque Basin in New Mexico. The network consists of two seismometer arrays, a thirteen-station array monitoring an area of approximately 28,000 km 2 and an eight-element array monitoring the area immediately adjacent to the Albuquerque Seismological Laboratory. This report describes the instrumentation deployed in the network.

  9. Transport of branched tetraether lipids from the Tagus River basin to the coastal ocean of the Portuguese margin: consequences for the interpretation of the MBT'/CBT paleothermometer

    NASA Astrophysics Data System (ADS)

    Zell, C.; Kim, J.-H.; Balsinha, M.; Dorhout, D.; Fernandes, C.; Baas, M.; Sinninghe Damsté, J. S.

    2014-10-01

    Branched glycerol dialkyl glycerol tetraethers (brGDGTs), which are thought to be transported from soil to marine sediment by rivers, have been used to reconstruct the mean annual air temperature (MAAT) and soil pH of the drainage basin using the methylation index of branched tetraethers (MBT, recently refined as MBT') and cyclization index of branched tetraethers (CBT) from coastal marine sediment records. In this study, we trace the brGDGTs from source to sink in the Tagus River basin, the longest river system on the Iberian Peninsula, by determining their concentration and distribution in soils, river suspended particulate matter (SPM), riverbank sediments, marine SPM, and marine surface sediments. The concentrations of brGDGTs in river SPM were substantially higher and their distributions were different compared to those of the drainage basin soils. This indicates that brGDGTs are mainly produced in the river itself. In the marine environment, the brGDGT concentrations rapidly decreased with increasing distance from the Tagus estuary. At the same time, the brGDGT distributions in marine sediments also changed, indicating that marine in situ production also takes place. These results show that there are various problems that complicate the use of the MBT'/CBT for paleoreconstructions using coastal marine sediments in the vicinity of a river. However, if the majority of brGDGTs are produced in the river, it might be possible to reconstruct the environmental (temperature and pH) conditions of the river water using appropriate aquatic calibrations, provided that marine core locations are chosen in such a way that the brGDGTs in their sediments are predominantly derived from riverine in situ production.

  10. Transport of branched tetraether lipids from the Tagus River basin to the coastal ocean of the Portuguese margin: consequences for the interpretation of the MBT'/CBT paleothermometer

    NASA Astrophysics Data System (ADS)

    Zell, C.; Kim, J.-H.; Balsinha, M.; Dorhout, D.; Fernandes, C.; Baas, M.; Sinninghe Damsté, J. S.

    2014-03-01

    Branched glycerol dialkyl glycerol tetraethers (brGDGTs), which are transported from soil to marine sediment by rivers, have been used to reconstruct the mean annual air temperature (MAAT) and soil pH of the drainage basin using the methylation index of branched tetraethers (MBT, recently refined as MBT') and cyclization index of branched tetraethers (CBT) from coastal marine sediment records. In this study we are tracing the brGDGTs from source to sink in the Tagus River basin, the longest river system on the Iberian Peninsula, by determining their concentration and distribution in soils, river suspended particulate matter (SPM), riverbank sediments, marine SPM, and marine surface sediments. The concentrations of brGDGTs in river SPM were substantially higher and their distributions were different compared to those of the drainage basin soils. This indicates that brGDGTs are mainly produced in the river itself. In the marine environment, the brGDGT concentrations rapidly decreased with increasing distance from the Tagus estuary. At the same time, the brGDGT distributions in marine sediments also changed, indicating that marine in-situ production also takes place. These results show that there are various problems that complicate the use of the MBT'/CBT for paleoreconstructions using coastal marine sediments in the vicinity of a river. However, if the majority of brGDGTs are produced in the river, it might be possible to reconstruct the environmental (temperature and pH) conditions of the river water using appropriate aquatic calibrations, provided that marine core locations are chosen in such a way that the brGDGTs in their sediments are predominantly derived from riverine in-situ production.

  11. Transport of branched tetraether lipids from the Tagus River basin to the coastal ocean of the Portuguese margin: Consequences for the interpretation of the MBT'/CBT paleothermometer

    NASA Astrophysics Data System (ADS)

    Zell, Claudia; Kim, Jung-Hyun; Balinsha, Maria; Dorhout, Denise; Santos Fernandez, Cten; Baas, Marianne; Sinninghe Damsté, Jaap S.

    2014-05-01

    Branched glycerol dialkyl glycerol tetraethers (brGDGTs), which are transported from soil to marine sediment by rivers, have been used to reconstruct the mean annual air temperature(MAAT) and soil pH of the drainage basin using the methylation index of branched tetraethers(MBT, recently refined as MBT') and cyclization index of branched tetraethers (CBT) from coastal marine sediment records. In this study we are tracing the brGDGTs from source to sink in the Tagus River basin, the longest river system on the Iberian Peninsula, by determining their concentration and distribution in soils, river suspended particulate matter (SPM), riverbank sediments, marine SPM, and marine surface sediments. The concentrations of brGDGTs in river SPM were substantially higher and their distributions were different compared to those of the drainage basin soils. This indicates that brGDGTs are mainly produced in the river itself. In the marine environment, the brGDGT concentrations rapidly decreased with increasing distance from the Tagus estuary. At the same time, the brGDGT distributions in marine sediments also changed,indicating that marine in-situ production also takes place. These results show that there are various problems that complicate the use of the MBT'/CBT for paleoreconstructions using coastal marine sediments in the vicinity of a river. However, if the majority of brGDGTs are produced in the river, it might be possible to reconstruct the environmental (temperature and pH) conditions of the river water using appropriate aquatic calibrations, provided that marine core locations are chosen in such a way that the brGDGTs in their sediments are predominantly derived from riverine in-situ production.

  12. The crustal structure of central East Greenland-II: From the Precambrian shield to the recent mid-oceanic ridges

    NASA Astrophysics Data System (ADS)

    Schmidt-Aursch, Mechita C.; Jokat, Wilfried

    2005-02-01

    We present a 3-D crustal model of the East Greenland Fjord Region between 69°N and 74°N. The model covers the Precambrian shield and the Caledonian orogenic belt, the adjoining Devonian and Mesozoic basins, the continent-ocean transition and the Cenozoic oceanic areas as far as the Kolbeinsey and the Mohns mid-oceanic ridges. Existing seismic models of the crustal structure are extrapolated into adjacent areas using 3-D gravity modelling. For this purpose, we compile a new regional-scale Bouguer anomaly map. The Precambrian shield, west of the Caledonian orogen (approximately west of 32°W), shows a mean thickness of 35 km with only small-scale undulations. This thickness is at the lower limit of the global range in shield thickness. The Caledonian orogen exhibits a pronounced mountain root with overall crustal thicknesses up to 51 km. Beside the Urals, the East Greenland Caledonides are one of the two Palaeozoic mountain belts where a crustal root has preserved to the present day. Continuation of the crustal model to the east, beyond the continent-ocean transition, yielded thicknesses of the crystalline oceanic crust from 9 km near the Kolbeinsey Ridge to 3 km west of the Mohns Ridge. Differences in the thermal structures of the old continental and the young oceanic lithosphere are responsible for the low-density mantle beneath the oceanic crust, which is also demonstrated by 3-D gravity modelling.

  13. Ocean Cooling Pattern at the Last Glacial Maximum

    DOE PAGESBeta

    Zhuang, Kelin; Giardino, John R.

    2012-01-01

    Ocean temperature and ocean heat content change are analyzed based on four PMIP3 model results at the Last Glacial Maximum relative to the prehistorical run. Ocean cooling mostly occurs in the upper 1000 m depth and varies spatially in the tropical and temperate zones. The Atlantic Ocean experiences greater cooling than the rest of the ocean basins. Ocean cooling is closely related to the weakening of meridional overturning circulation and enhanced intrusion of Antarctic Bottom Water into the North Atlantic.

  14. Structural geology of cuttings and cores recovered from below the Kumano forearc basin, Nankai accretionary margin of Japan: Expedition 319 of the Integrated Ocean Drilling Program (IODP)

    NASA Astrophysics Data System (ADS)

    Hayman, N. W.; Byrne, T. B.; Huftile, G.; McNeill, L. C.; Kanamatsu, T.; Saffer, D.; Araki, E.; Eguchi, N. O.; Toczko, S.; Takahashi, K.; Scientists, E.

    2009-12-01

    The geologic materials below the Kumano Basin provide critical information for understanding the geologic evolution of Japan’s Nankai margin and its earthquake hazards. Riser-based drilling at IODP Site C0009 recovered these geologic materials in cuttings from 704-1604 mbsf, and in ~70 m of core from 1510-1594 mbsf. The >4-mm size fraction of cuttings from 1332-1482 mbsf contains abundant vein structures in moderately consolidated, coarse-siltstones. Vein structures are <1 mm-wide granular rearrangements, possibly paleoseismites, and are mostly restricted to the late Miocene section below a significant unconformity at ~1300 mbsf. At Site C0002, close to the southeastern edge of the forearc basin, vein structures were also localized to a narrow depth interval in a slightly younger (Pliocene age) section. The cored interval at Site C0009 is from below a prominent unconformity at ~1360 mbsf and comprises finely (~10 cm-scale) interbedded, unmetamorphosed, and moderately cohesive silt- and sandstone. Bedding in the cored interval generally dips NNW in logging data and increases in dip from ~20° to ~ 60° with depth in both the FMI and the core data. A set of dominantly thrust-sense shear zones cuts and locally imbricates bedding, with dips <20° to >40°. The shear zones are 1-2 cm-wide, exhibit granular rather than cataclastic (fracture-dominated) microstructures, and though dark in appearance and bright in tomographic images (and thus likely higher density than the surrounding core), they are mineralogically similar to the surrounding material. The shear zones may have formed during tectonically induced dewatering and consolidation. In many places the shear zones define the center of a gradient in stretched and folded sedimentary structures. Younger faults also appear dark relative to the surrounding core, but are <1-mm wide, with a range of geometries and cross cutting relationships; there are likely at least two generations of these thin faults. The youngest

  15. Control of sedimentation by active tectonics, glaciation and contourite-depositing currents in Endurance Basin, South Georgia

    NASA Astrophysics Data System (ADS)

    Owen, Matthew J.; Day, Simon J.; Leat, Philip T.; Tate, Alex J.; Martin, Tara J.

    2014-12-01

    Endurance Basin is an elongate broadly WNW-ESE trending basin located on the northern margin of the Scotia Sea, adjacent to the southern margin of the South Georgia micro-continent. Bathymetric and TOPAS sub-bottom profile data acquired in 2010 by the British research ship RRS James Clark Ross map this basin and its sedimentology for the first time. Endurance Basin contains a number of sub-basins and a substantial glaciogenic fan. The northern margin of Endurance Basin is formed by a series of steep slopes and intervening troughs. These are interpreted as a left-stepping en echelon array of oblique, strike-slip faults whilst the sub-basins are separated by compressional dip-slip faults. It appears that South Georgia is moving NW with respect to the basin. We interpret five seismic facies from TOPAS data, which are associated with distinct sedimentologies. The most striking units in the basin fill are: substantial contourite drifts located in the NW of the basin and on its southern margin; and two distinct mass transport deposits that pond in the centre of the basin. Combined with the known regional oceanographic setting, the contourites provide evidence of broadly eastward flowing bottom currents, entering the basin from at least two locations. Although landslide scars are present on the steep northern basin margin, the imaged mass transport deposits are interpreted to have been sourced from the glaciogenic fan, located in the SE of the basin, and from a contourite unit located on the basin's southern margin. Sediments from these events are transported at least 40 km. The contourite drift sequence is at least 100 m thick in the west of the basin and may contain a palaeoenvironmental archive of Antarctic Circumpolar Current (ACC) flow and the climate of South Georgia extending to the Pliocene. Such an archive would allow the reconstruction of ACC flow through the Pleistocene glaciations and provide a means of linking ocean circulation and climate records in the sub

  16. Neodymium isotopes and concentrations in Caribbean seawater: Tracing water mass mixing and continental input in a semi-enclosed ocean basin

    NASA Astrophysics Data System (ADS)

    Osborne, Anne H.; Haley, Brian A.; Hathorne, Ed C.; Flögel, Sascha; Frank, Martin

    2014-11-01

    We present the first full water column Nd isotope (εNd) and concentration data for Caribbean seawater, as well as for stations close to the Orinoco River mouth and in the Florida Straits. The surface inflow into the southeastern Caribbean via the Guyana Current is characterized by an εNd signature of -10.9, which is a consequence of the mixing of relatively unradiogenic εNd signatures (-13.6) supplied by the Orinoco River with contributions from the Amazon River (∼-10). Despite the proximity to land, sub-surface and intermediate waters within the Caribbean largely retain the εNd signatures of their source water masses in the Atlantic. In contrast, the deep waters of the Caribbean show εNd signatures at least 3 εNd units more radiogenic than the inflowing Upper North Atlantic Deep Water (UNADW). A εNd shift from -13 to -9.7 can be explained by addition of radiogenic Nd to the deep Caribbean through weathering inputs from land. However, in order to balance such large shifts in εNd with at the same time modest increases in Nd concentrations, Nd must also be removed from seawater within the basin. It is suggested that the long residence time of deep waters in the Caribbean allows significant interaction of seawater with sinking particles and seafloor sediments resulting in more radiogenic values. These findings have implications for the use of εNd as a proxy for paleocirculation in restricted basins, in which the residence times of the deep waters are long.

  17. The Cretaceous-Paleogene boundary deposit in the Gulf of Mexico: Large-scale oceanic basin response to the Chicxulub impact

    NASA Astrophysics Data System (ADS)

    Sanford, Jason C.; Snedden, John W.; Gulick, Sean P. S.

    2016-03-01

    Hydrocarbon exploration in the last decade has yielded sufficient data to evaluate the Gulf of Mexico basin response to the Chicxulub asteroid impact. Given its passive marine setting and proximity to the impact structure on the Yucatán Peninsula, the gulf is the premier locale in which to study the near-field geologic effect of a bolide impact. We mapped a thick (decimeter- to hectometer-scale) deposit of carbonate debris at the Cretaceous-Paleogene boundary that is ubiquitous in the gulf and readily identifiable on borehole and seismic data. We interpret deposits seen in seismic and borehole data in the deepwater gulf to be predominately muddy debrites with minor turbidites based on cores in the southeastern gulf. Mapping of the deposit in the northern Gulf of Mexico reveals that the impact redistributed roughly 1.05 × 105 km3 of sediment therein and over 1.98 × 105 km3 gulfwide. Deposit distribution suggests that the majority of sediment derived from coastal and shallow-water environments throughout the gulf via seismic and megatsunamic processes initiated by the impact. The Texas shelf and northern margin of the Florida Platform were significant sources of sediment, while the central and southern Florida Platform underwent more localized platform collapse. The crustal structure of the ancestral gulf influenced postimpact deposition both directly and indirectly through its control on salt distribution in the Louann Salt Basin. Nevertheless, impact-generated deposition overwhelmed virtually all topography and depositional systems at the start of the Cenozoic, blanketing the gulf with carbonate debris within days.

  18. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 1 2014-10-01 2014-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR...-managing agencies on adjacent lands (both public and private)....

  19. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 1 2013-10-01 2013-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR...-managing agencies on adjacent lands (both public and private)....

  20. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of off-road vehicle use on Reclamation lands will...

  1. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 1 2012-10-01 2011-10-01 true Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR...-managing agencies on adjacent lands (both public and private)....

  2. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of...

  3. Deposition of organic carbon-rich sediments in narrow marine basins and open-marine upwelling environments - New results from the ocean drilling program

    SciTech Connect

    Stein, R. )

    1988-08-01

    Detailed sedimentological and organic geochemical investigations have been performed on Neogene sediments from ODP site 645 (Baffin Bay), ODP site 658 (upwelling area of northwest Africa), and ODP site 679 (upwelling area off Peru). The study is mainly based on (1) data derived from total organic carbon and nitrogen analyses, Rock-Eval pyrolysis, and kerogen microscopy (2) sedimentation rates, and (3) x-ray diffraction analyses. The main objective of this study was to point out the most important factors controlling the accumulation of organic carbon in the different sedimentary environments, such as supply of terrigenous organic matter, productivity of marine organic matter, and preservation of organic matter. These new results from the investigation of ODP sediments are compared with DSDP data from the Mesozoic Atlantic Ocean to characterize the depositional environments of Mesozoic black shales.

  4. The Design and Analysis of Salmonid Tagging Studies in the Columbia Basin : Volume XVII : Effects of Ocean Covariates and Release Timing on First Ocean-Year Survival of Fall Chinook Salmon from Oregon and Washington Coastal Hatcheries.

    SciTech Connect

    Burgess, Caitlin; Skalski, John R.

    2001-05-01

    Effects of oceanographic conditions, as well as effects of release-timing and release-size, on first ocean-year survival of subyearling fall chinook salmon were investigated by analyzing CWT release and recovery data from Oregon and Washington coastal hatcheries. Age-class strength was estimated using a multinomial probability likelihood which estimated first-year survival as a proportional hazards regression against ocean and release covariates. Weight-at-release and release-month were found to significantly effect first year survival (p < 0.05) and ocean effects were therefore estimated after adjusting for weight-at-release. Negative survival trend was modeled for sea surface temperature (SST) during 11 months of the year over the study period (1970-1992). Statistically significant negative survival trends (p < 0.05) were found for SST during April, June, November and December. Strong pairwise correlations (r > 0.6) between SST in April/June, April/November and April/December suggest the significant relationships were due to one underlying process. At higher latitudes (45{sup o} and 48{sup o}N), summer upwelling (June-August) showed positive survival trend with survival and fall (September-November) downwelling showed positive trend with survival, indicating early fall transition improved survival. At 45{sup o} and 48{sup o}, during spring, alternating survival trends with upwelling were observed between March and May, with negative trend occurring in March and May, and positive trend with survival occurring in April. In January, two distinct scenarios of improved survival were linked to upwelling conditions, indicated by (1) a significant linear model effect (p < 0.05) showing improved survival with increasing upwelling, and (2) significant bowl-shaped curvature (p < 0.05) of survival with upwelling. The interpretation of the effects is that there was (1) significantly improved survival when downwelling conditions shifted to upwelling conditions in January (i

  5. Discovery of a Late Devonian magmatic arc in the southern Lancangjiang zone, western Yunnan: Geochemical and zircon U-Pb geochronological constraints on the evolution of Tethyan ocean basins in SW China

    NASA Astrophysics Data System (ADS)

    Nie, Xiaomei; Feng, Qinglai; Metcalfe, Ian; Baxter, Alan T.; Liu, Guichun

    2016-03-01

    The Tibetan Plateau and western Yunnan are known to have formed by the amalgamation of Gondwana-derived continental blocks and arc terranes as a result of Tethyan subduction followed by continental collisions during the Paleozoic, Mesozoic and Cenozoic. The Devonian and the southern Lancangjiang zone, western Yunnan is a critical period and key region for studying the transformation between the "Proto-Tethyan" and Paleo-Tethyan oceanic systems. New geochemical data and LA-ICPMS U-Pb zircon ages of the Late Devonian volcanogenic sediments from the southern Lancangjiang zone in western Yunnan, SW China, are presented. The studied sedimentary rocks of the Nanguang Formation are volcaniclastic rocks with high volcanic lithic content (55-65%, mostly andesite, dacite, with some rhyolite and tuffs). Whole rock geochemistry, zircon trace elements and detrital modal analyses indicate derivation from a subduction-related magmatic arc. Three tuff samples yield Late Devonian weighted mean 206Pb/238U ages of 378 ± 4 Ma, 366 ± 5 Ma and 382 ± 8 Ma, suggesting a Late Devonian depositional age. 104 zircon U-Pb analyses on 104 zircon grains from two sandstone samples present extremely tight age clusters, mostly ranging from 380 Ma to 360 Ma. This indicates a single Late Devonian igneous source. A short transport distance and a high rate of denudation and deposition within an arc-related basin are considered likely for the tuffs and volcaniclastic rocks in this study. This implies the presence of an as yet unidentified Late Devonian magmatic arc in the southern Lancangjiang zone. The cryptic Late Devonian arc is likely to represent either a continuation of Late Ordovician-Late Silurian "Proto-Tethyan" subduction or the initial stage of the Paleo-Tethyan Lincang Arc and indicates that subduction of the Changning-Menglian ocean beneath the Simao/Indochina Block occurred in the Late Devonian.

  6. Potiguar basin: geologic model and habitat of oil of a Brazilian equatorial basin

    SciTech Connect

    Falkenhein, F.U.; Barros, R.M.; Da Costa, I.G.; Cainelli, C.

    1984-04-01

    The Potiguar basin integrates the eastern part of the Brazilian equatorial Atlantic-type margin. The rifting stage of this basin occurred during the Neocomian and Aptian. The drifting stage and sea-floor spreading began in the Late Albian. The rifting stage clearly was intracratonic during the Neocomian and is recognized as a mosaic of half-grabens trending mostly northeast-southwest and filled with syntectonic lacustrine siliciclastics. The half-graben pattern exhibits rotation of beds into the major fault zone, and the preserved uplifted margins display either paleostructures of paleogeomorphic features with hydrocarbons. A regional pre-Aptian unconformity preceded the Aptian proto-oceanic rifting stage which was characterized by syntectonic fluvio-deltaic sediments. The Aptian tectonics were represented by reactivation of former lineaments superimposed by predominant east-west normal faulting. Structural highs during this stage are so far the most prolific oil accumulations. The most important source beds and reservoir rocks are both Neocomian and Aptian sediments. Geochemistry and hydrodynamics have shown that hydrocarbon migration was driven through fracture or fault zones in both Aptian or Albian plays. Lithofacies maps support this interpretation because pools occur whenever adjacent downthrown blocks present a high shale content.

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

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

    The iSIMM project is using state-of-the art seismic techniques with long-offset and wide-angle data, to image the crust formed on volcanic continental margins in parallel with developing and testing new quantitative models of rifted margin formation, incorporating heterogeneous stretching, the effects of melt generation and emplacement and varying thermal anomalies in the mantle. During June-July 2002, we used RRS Discovery to acquire wide angle and normal incidence seismic data on the Faroes Shelf and adjacent continental margin, Hatton-Rockall Basin, Hatton Bank and the adjacent oceanic crust using OBS and MCS. In August 2002, WesternGeco's Topaz used three single-sensor, Q-Marine streamers, 12km plus two 4km, to overshoot the wide-angle profiles on the Faroes Shelf and adjacent continental margin. In the Faroes region we deployed 85 4-component ocean bottom seismometers (OBS) and 5 vertical arrays along a 350km-long profile extending from the Faroes-Shetland Channel across the Faroes Shelf and continental margin into the oceanic crus