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Mostrando recursos 1 - 20 de 12.016

  1. Annotated record of the detailed examination of Mn deposits from the 1968, R/V Mahi expeditions in the Pacific Ocean

    Andrews, James E
    This report represents the first in a projected series reporting core descriptions and their physical properties, to be made available through routine core handling procedures instituted at the Hawaii Institute of Geophysics in 1968 to keep pace with the capability to take long (120-foot) piston cores from the University of Hawaii's R/V MAHI. The data reported herein cover sediment cores collected during 1967, 1968, and 1969 in the region of the Solomon Islands and the Darvir. Rise, and along the central portion of the Murray Fracture Zone.

  2. Annotated record of the detailed examination of Mn deposits in the Mid-Atlantic Ridge during the IPOD Atlantic Site Survey near DSDP Leg 45, Site 395

    Hussong, Donald M; Fryer, Patricia B; Tuthill, J D; Wipperman, L K
    One of the main objectives of the International Phase of Ocean Drilling (IPOD) of the Deep Sea Drilling Project was to determine the geological, geochemical, and geophysical character of ocean crust formed at mid-ocean spreading ridges. A series of drill holes along the Mid-Atlantic Ridge (MAR), from near Iceland south to approximately 22°N latitude, was planned to compare the crust being generated near an anomalous ridge (Iceland) with that originating near a normal slow-spreading ridge (22°N). At the same time, a series of holes in near zero-age crust at 22 °N was planned along a "flow line" (a transect parallel...

  3. Onshore and offshore apatite fission-track dating from the southern Gulf of California

    Balestrieri, Maria Laura; Ferrari, Luca; Bonini, Marco; Duque-Trujillo, Jose; Cerca, Mariano; Moratti, Giovanna; Corti, Giacomo
    We present the results of an apatite fission-track (AFT) study on intrusive rocks in the southern Gulf of California, sampled along the eastern margin of Baja California Sur (western rift margin), as well as from islands and submerged rifted blocks within the Gulf of California, and from the conjugate Mexican margin (Nayarit state). For most of the samples U-Pb zircon and 40Ar-39Ar mineral ages were already available (Duque-Trujillo et al., 2015). Coupled with the new AFT data these ages provide a more complete information on cooling after emplacement. Our samples span a wide range of ages between 5.5±1.1 and 73.7±5.8...

  4. Tropical SSTs over the past 3.5 million years

    Herbert, Timothy D; Cleaveland Peterson, Laura; Lawrence, Kira T; Liu, Zhonghui
    Determining the timing and amplitude of tropical sea surface temperature (SST) change is an important part of solving the puzzle of the Plio-Pleistocene ice ages. Alkenone-based tropical SST records from the major ocean basins show coherent glacial-interglacial temperature changes of 1° to 3°C that align with (but slightly lead) global changes in ice volume and deep ocean temperature over the past 3.5 million years. Tropical temperatures became tightly coupled with benthic d18O and orbital forcing after 2.7 million years. We interpret the similarity of tropical SST changes, in dynamically dissimilar regions, to reflect "top-down" forcing through the atmosphere. The inception...

  5. Age models and bulk organic isotope geochemistry from Lake Superior sediment cores

    O'Beirne, Molly D; Werne, Josef P; Hecky, Robert E; Johnson, Thomas C; Katsev, Sergei; Reavie, Euan D
    The data contained herein are from eight sediment multicores and three piston sediment cores with accompanying gravity/trigger sediment cores spanning the Lake Superior basin. The multicores were sampled at high resolution encompassing the most recent ca. 200 years and the gravity-piston sediment cores are coarser resolution (ca. every 100 years) and date to ca. 10,000 years cal BP.

  6. Decadal resolution record of sediment core M74/1b_944-6 (SL 163)

    Munz, Philipp; Steinke, Stephan; Böll, Anna; Lückge, Andreas; Groeneveld, Jeroen; Kucera, Michal; Schulz, Hartmut
    The Indian summer monsoon (ISM) is an important conveyor in the ocean-atmosphere coupled system on a transregional scale. Here we present a study of a sediment core from the northern Oman margin, revealing early- to mid Holocene ISM conditions on a near 20-year resolution. We assess multiple independent proxies indicative of sea surface temperatures (SST) during the upwelling season together with bottom water conditions. We use geochemical parameters, transfer functions of planktic foraminiferal assemblages and Mg/Ca paleothermometry and find evidence corroborating previous studies that upwelling intensity varies significantly in coherence to solar sunspot cycles. The dominant ~80-90-year Gleissberg cycle was...

  7. Annotated record of the detailed examination of Mn deposits from the Madcap Volcano in the Madeira-Cape Verde Abyssal plain

    Jones, E J W; Laughton, Anthony S; Hill, M N; Davies, D
    The results are discussed of a geophysical survey undertaken by R.R.S. Discovery II early in 1962 in an area centred on 29° 15'N, 25° 5'W at the western extremity of the Madeira-Cape Verde Abyssal Plain. Seismic investigations show that the sediments are underlain by an intermediate layer about 2 km in thickness of velocity 4·1-5·4 km/sec which overlies a deep layer 5·2-km thick of velocity 6·3-6·8 km/sec. Refracted arrivals on the longest seismic line give a depth of 13·2 km to the M discontinuity. Magnetic results indicate that the topography of the abyssal hills in the western part of the area...

  8. Large-scale ocean connectivity and planktonic body size

    Villarino, Ernesto; Watson, James R; Jönsson, Bror; Gasol, Josep M; Salazar, Guilhem; Acinas, Silvia G; Estrada, Marta; Massana, Ramon; Logares, Ramiro; Giner, Caterina R; Pernice, Massimo C; Olivar, M Pilar; Citores, Leire; Corell, Jon; Rodriguez-Ezpeleta, Naiara; Acuna, José Luis; Molina, Axayacatl; Gonzalez-Gordillo, Ignacio; Cozar, Andrés; Martí, Elisa; Cuesta, Jose A; Agusti, Susana; Fraile-Nuez, Eugenio; Duarte, Carlos M; Irigoien, Xabier; Chust, Guillem
    Global patterns of planktonic species diversity are in large part determined by the dispersal of propagules with ocean currents. However, the role that abundance and body size plays in determining spatial patterns of diversity remains unclear. Here, we quantified the dispersal scale and community structure - ?-diversity - for several planktonic and micro-nektonic organisms spanning a large range of body sizes, from prokaryotes to small mesopelagic fishes, collected during the Malaspina 2010 Circumnavigation Expedition. Global patterns of ?-diversity for these communities were then compared to surface ocean transit times, derived from a global circulation model. Our results reveal that ?-diversity...

  9. Reconstructed Pacific Decadal Oscillation versus Cape Bounty East Lake varve thickness

    Lapointe, François; Francus, Pierre; Lamoureux, Scott; Vuille, Mathias; Jenny, Jean-Philippe; Bradley, Raymond S; Massa, Charly
    Understanding how internal climate variability influences arctic regions is required to better forecast fu- ture global climate variations. This paper investigates an annually-laminated (varved) record from the western Canadian Arctic and finds that the varves are negatively corre- lated with both the instrumental Pacific Decadal Oscillation (PDO) during the past century and also with reconstructed PDO over the past 700 years, suggesting drier Arctic con- ditions during high-PDO phases, and vice versa. These results are in agreement with known regional teleconnections, whereby the PDO is negatively and positively correlated with summer precipitation and mean sea level pressure respec- tively. This...

  10. Annotated record of the detailed examination of Mn deposits from the Hirondelle Seamount, Eastern Equatorial Atlantic

    Jones, E J W; BouDagher-Fadel, M K; Thirlwall, Matthew F
    Phosphorites with P2O5 contents up to 33% have been recovered from the eastern Atlantic between 6°N and 9°N. Formed from the replacement of shallow-water reef limestones of Middle Eocene age, the deposits are exposed on the crests of three subsided seamounts, Lighthill, Hirondelle and Carter, at depths of 794-1246, 1161-1176 and 552-1158 m, respectively. Phosphates exposed on the sea floor are associated with high levels of acoustic backscatter recorded using a ship's echo-sounder and a 10-kHz pinger towed ?30 m above the bottom. Seabed scintillometer measurements on Carter Seamount near 9°N, 21°W revealed high ?-ray emission where phosphorites are known...

  11. Annotated record of the detailed examination of Mn deposits from DSDP Leg 72 (Holes 515, 515A, 515B, 516A, 516F, 517, 518)

    Barker, Peter F; Carlson, Richard L; Johnson, David A
    DSDP Leg 72 of the Glomar Challenger addressed paleoceanographic objectives in the southwestern Atlantic. It was planned to extend the observations and interpretations from the Leg 39 report in order to btain a complete deposition record of pelagic sedimentation on the Rio Grande Rise, down to and including the underlying volcanic basement.

  12. Annotated record of the detailed examination of Mn deposits from DSDP Leg 71 (Holes 511, 512, 513, 514)

    Ludwig, Wolfgang; Krasheninnikov, Valery A; Wise, Sherwood W
    The high-latitude South Atlantic Ocean and the adjacent Antarctic Ocean have throughout Mesozoic and Cenozoic time undergone pronounced geographic alterations that have produced a change from a temperate marine climate in the late Mesozoic and Paleogene to a frigid ocean in the Neogene. DSDP Leg 71 was the first of five legs designed to study late Mesozoic and Cenozoic paleoenvironments through the history of sedimentation at the eastern end of the Falkland Plateau, the effect of the plateau as a barrier between water masses during the early opening of the South Atlantic, and the evolution of the Antarctic Convergence.

  13. Annotated record of the detailed examination of Mn deposits at the mouth of the Gulf of California during an IPOD Site Survey prior to DSDP Leg 65

    Lewis, B T R; Snydsman, W E; McClain, J S; Holmes, M L; Lister, C R B
    During an IPOD site survey at the mouth of the Gulf of California, an axial valley about 50 km long and 600 meters deep was found on the East Pacific Rise (EPR) south of the Tamayo Fracture Zone. Magnetic anomalies along the axis of the rise change character from the axial valley to normal sections of the EPR, and off-axis anomalies tend to meander slightly with age, probably indicating that the axial injection zone wanders slightly with time. Along the Baja California margin the magnetic lineations cut across the bathymetric expression of the margin, suggesting that the original rifting of...

  14. Analysis of Manganese deposits from the South China Sea

    Zhang, Z G; Du, Y S; Wu, C H; Fang, N Q; Yang, S X; Liu, J; Song, C B
    In the northern South China Sea, the accumulation of enormous quantities of terrigenous sediment during Cenozoic rendered well-developed polymetallic nodules very rare. In this study, we analyzed a polymetallic nodule from the northwestern continental margin of the South China Sea using microscopic mineralogical observation, electron probes, X-ray diffraction (XRD), ICP-MS, and Be isotope dating. We found the nodule's shell layers rich in different types of microstructures, including columnar, laminar, stack-like, petal-like, and porphyritic structures. The major mineral components of the nodule are MnO2. Unlike nodules from the eastern Pacific basin, this nodule has high contents in Fe, Si, Al, and...

  15. Mean TerraSAR-X backscatter and in-situ measurements of near surface soil moisture and temperature including vegetation survey in August 2015 on central Yamal (Vaskiny Dachi CALM site)

    Widhalm, Barbara; Bartsch, Annett; Leibman, Marina O; Khomutov, Artem V
    The active layer above the permafrost, which seasonally thaws during summer, is an important parameter for monitoring the state of permafrost. Its thickness is typically measured locally, but a range of methods which utilize information from satellite data exist. Mostly, the normalized difference vegetation index (NDVI) obtained from optical satellite data is used as a proxy. The applicability has been demonstrated mostly for shallow depths of active-layer thickness (ALT) below approximately 70 cm. Some permafrost areas including central Yamal are, however, characterized by larger ALT. Surface properties including vegetation structure are also represented by microwave backscatter intensity. So far, the...

  16. An inventory of active rock glaciers in the northern Tien Shan of China compiled using satellite SAR interferometry

    Wang, Xiaowen; Liu, Lin; Zhao, Lin; Wu, Tonghua; Li, Zhongqin; Liu, Guoxiang
    Rock glaciers are widespread in the Tien Shan. However, rock glaciers in the Chinese part of the Tien Shan have not been systematically investigated for more than two decades. In this study, we propose a new method that combines SAR interferometry and optical images from Google Earth to map active rock glaciers (ARGs) in the Northern Tien Shan (NTS) of China. We compiled an inventory that includes 261 ARGs and quantitative information about their locations, geomorphic parameters, and down-slope velocities. Our inventory shows that most of the ARGs are moraine-derived (69 %) and facing northeast (56 %). The altitude distribution...

  17. Recent changes in glacier mass balance and equilibrium line altitude and the impact of climatic change on King George Island, Antarctic Peninsula

    Falk, Ulrike; López, Damián; Silva-Busso, Adrian A
    The South Shetland Islands are located at the northern tip of the Antarctic Peninsula (AP) which is among the fastest warming regions on Earth. Surface air temperature increases (about 3 K in 50 years) are concurrent with retreating glacier fronts, an increase in melt areas, ice surface lowering and rapid break-up and disintegration of ice shelves. Observed surface air temperature lapse rates show a high variability during winter months (standard deviations up to 1.0 K/100 m), and a distinct spatial heterogeneity reflecting the impact of synoptic weather patterns especially during winter glacial mass accumulation periods. The over the past decades...

  18. Compilation of detailed examination of Mn deposits from the North tip of the Baja peninsula prior to DSDP Leg 64

    Curray, Joseph R; Moore, David G; Kelts, Kerry; Einsele, Gerhard
    he three-site Leg 64 Deep Sea Drilling transect at the tip of the Peninsula of Baja California straddled the transition from continental to oceanic crust. The outer site, 474, penetrated mainly mud turbidites and bottomed in "middle" Pliocene oceanic crust about 3 m.y. old. Two sites on the lower continental slope penetrated hemipelagic muddy sediments, a thin section of low-oxygen, phosphoritic, and glauconitic sediments, and a metamorphic cobble conglomerate; one of the sites, 476, bottomed in deeply weathered granite. The oldest marine sediments at this site are early Pliocene, about 4.5 m.y. old. Depth indicators in these holes suggest that...

  19. (Tables 1-2, page 195) Chemical composition of ferromanganese crusts and associated smectites from the Gulf of Aden

    Cann, Joe R
    Fragments of a hydrothermal deposit, partly moulded on pieces of basalt lava, were dredged from the edge of the median valley in the centre of the Gulf of Aden. The deposit consists of two main components, manganese oxide in the form of spongy brown to hard black lumps and coatings, and friable green massive smectite. There are smaller amounts of an iron-oxide component, and mixed manganese-oxide-smectite material. Contents of the less mobile trace elements in the smectite are too low for it to have formed by alteration of basalt glass, and it is interpreted as a direct precipitate from hydrothermal...

  20. Chemical composition of ferromanganese crusts recovered in the South China Sea during the SO49 Cruise of R/V Sonne

    Bao, G; Li, Q
    Five ferromanganese crusts and 6 ferromanganese nodules samples collected by the Joint Chinese-West Germany Geophysical Investigation Team in May-June, 1987 during the SO49 cruise of the R/V Sonne. They were analyzed for their rare earth element contents by means of X-Ray fluorescent spectrometry. On the basis of study of 15 rare earth elements detected, the relationship among rare earth element concentration, source,, as well as distribution pattern and associated elements was discussed in detail. Results show that 1) The average concentration of rare earth elements in South China Sea ferromanganese crusts and nodules was 1. 625 g/kg and 2. 167...

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