1,070 Works

Barium in Costa Rica forearc sediments

Evan A Solomon & Miriam Kastner
Barium concentrations were measured in pore fluids and sediments from the shallow forearc of the Costa Rica subduction zone to investigate the impact of progressive barite dissolution coupled to [SO4]2- depletion on the residual sediment Ba flux to the volcanic arc and mantle. At the Costa Rica subduction zone, the entire sediment section entering the trench is underthrust beneath the prism sediments of the overriding plate. Dissolved [SO4]2- concentrations measured in the reference sediment section...

Response of marine palynomorphs to Neogene climate cooling in the Iceland Sea, ODP Hole 151-907A

Michael Schreck, Marie Méheust, Ruediger Stein & Jens Matthiessen
The present study on ODP Leg 151 Hole 907A combines a detailed analysis of marine palynomorphs (dinoflagellate cysts, prasinophytes, and acritarchs) and a low-resolution alkenone-based sea-surface temperature (SST) record for the interval between 14.5 and 2.5 Ma, and allows to investigate the relationship between palynomorph assemblages and the paleoenvironmental evolution of the Iceland Sea.A high marine productivity is indicated in the Middle Miocene, and palynomorphs and SSTs both mirror the subsequent long-term Neogene climate deterioration....

Mineralogy of Hawaiian Arch sediments

Jane S Tribble, Roy H Wilkens, Rolf S Arvidson & Christopher J Busing
The mineralogy of both bulk- and clay-sized (<2 µm) fractions of sediments from Holes 842A and 842B of Ocean Drilling Program Leg 136 was determined by X-ray diffraction. The sediments consist of a combination of terrigenous (quartz, plagioclase, smectite, illite, kaolinite, and chlorite), volcaniclastic (augite, plagioclase, and volcanic glass), and diagenetic minerals (smectite, phillipsite, clinoptilolite, and opal-CT). Although biogenic silica (radiolarians and diatoms) is common in near-seafloor (<10 mbsf) sediments, biogenic calcite is rare. Variations...

Component NRM directions on four sediment cores from the Arctic Ocean

Chuang Xuang & James E T Channell
Arctic deep-sea sediments often record intervals of negative inclination of natural remanence that are tens of centimeters thick, implying magnetic excursions with durations of tens of thousand years that far exceed excursion durations estimated elsewhere, and the lack of tight age control usually provides excessive freedom in the labeling of Arctic excursions. Fortuitous variations in sedimentation rate have been invoked to explain the “amplified” excursions. Alternating field demagnetization of natural remanent magnetization (NRM) of sediment...

Water chemistry, and pigments and geochemistry of sediments from northern Victoria Land lakes

Francesca Borghini, Andrea Colacevich & Roberto Bargagli
Total concentrations of algal pigments, organic C, C, N, P and S were determined in surface sediments from the littoral zone of 21 lakes in ice-free areas of northern Victoria Land (Antarctica) with different climatic and environmental conditions. Concentrations of major ions and nutrients were also determined in water samples from the same lakes. The latter samples had extremely variable chemical compositions; however, all the lakes resulted oligotrophic. Pigment concentrations in surface sediments were comparable...

Geochemistry of altered phases, basalts and sediments of ODP Site 136-843

D Guy Waggoner
40Ar-39Ar incremental heating experiments on a relatively unaltered basalt from Site 843 yield a crystallization age of 110 ± 2 Ma for the central Pacific Ocean igneous basement near Hawaii. Previous estimates of the age of the basement inferred by indirect methods and from radiometric dates of the South Hawaiian Seamounts are too young by 20-30 m.y. Phyllosilicate alteration minerals from veins in the Site 843 basalts define a Rb/Sr isochron with an age of...

Ash layer characteristics and major element oxide content of glasses from ODP Sites 162-982 and 162-985

Hans-Joachim Wallrabe-Adams & Reinhard Werner
The Cenozoic volcanic activity on Iceland has been recorded in North Atlantic sediments drilled during several Ocean Drilling Program (ODP)/Deep Sea Drilling Project legs (Legs 104, 151, 152, 162, and 163). Leg 162 (North Atlantic-Arctic Gateways II) recovered ash layers at Sites 982, 985, and 907 (Jansen, Raymo, Blum, et al., 1996, doi:10.2973/odp.proc.ir.162.1996). The revisited Site 907 was first drilled during Leg 151, and the ash from this site has been described in detail by...

Porewater concentrations, pH, single cell number, anaerobic oxidation of methane (AOM) rate, sulfate reduction (SR) rate of samples during METEOR cruise M76/3b at the REGAB cold seep site from the West African margin in 2008

Petra Pop Ristova, Frank Wenzhöfer, Alban Ramette, Matthias Zabel, David Fischer, Sabine Kasten & Antje Boetius
The giant pockmark REGAB (West African margin, 3160 m water depth) is an active methane-emitting cold seep ecosystem, where the energy derived from microbially mediated oxidation of methane supports high biomass and diversity of chemosynthetic communities. Bare sediments interspersed with heterogeneous chemosynthetic assemblages of mytilid mussels, vesicomyid clams and siboglinid tubeworms form a complex seep ecosystem. To better understand if benthic bacterial communities reflect the patchy distribution of chemosynthetic fauna, all major chemosynthetic habitats at...

Bedform measurements from the San Francisco Bay Coastal System

Patrick L Barnard, Li H Erikson, Edwin Elias & Peter Dartnell
The morphology of ~45,000 bedforms from 13 multibeam bathymetry surveys was used as a proxy for identifying net bedload sediment transport directions and pathways throughout the San Francisco Bay estuary and adjacent outer coast. The spatially-averaged shape asymmetry of the bedforms reveals distinct pathways of ebb and flood transport. Additionally, the region-wide, ebb-oriented asymmetry of 5% suggests net seaward-directed transport within the estuarine-coastal system, with significant seaward asymmetry at the mouth of San Francisco Bay...

Late Cenozoic eolian dust accumulation in the eastern equatorial Pacific Ocean

Steven A Hovan
Sediments recovered during Ocean Drilling Program (ODP) Leg 138 in the eastern equatorial Pacific Ocean were analyzed for variations in eolian accumulation rate and mean grain-size. Latitudinal and temporal patterns of these parameters showed important changes in the intensity of atmospheric circulation and eolian flux associated with the intertropical convergence zone (ITCZ) and suggested that eolian input parameters could be used to define its paleoposition through time. Modern atmospheric circulation in the equatorial region is...

Soil characteristics and Collembola and Acari abundance in control and warming plots at Abisco Research Station

Stef Bokhorst, Gareth K Phoenix, Jarle W Bjerke, Terry V Callaghan, F Huyer-Brugman & Matty P Berg
Extreme weather events can have negative impacts on species survival and community structure when surpassing lethal thresholds. Extreme winter warming events in the Arctic rapidly melt snow and expose ecosystems to unseasonably warm air (2-10 °C for 2-14 days), but returning to cold winter climate exposes the ecosystem to lower temperatures by the loss of insulating snow. Soil animals, which play an integral part in soil processes, may be very susceptible to such events depending...

Geochemistry and minerals at DSDP Leg 81 Holes

Jean Louis Joron, Henri Bougault, R C Maury, Marcel Bohn & Alain Desprairies
The Leg 81 basalts, drilled either from the margins ("dipping reflectors" sequence: Holes 552, 553A, and 554A) or from the "continental" side (Hole 555) of the Rockall Plateau microcontinent, are strongly light rare-earth element (LREE) depleted oceanic tholeiites. The basalts from the four holes are almost similar. Most of their primary characteristics have been preserved, although they have suffered alteration by seawater. From the petrological and mineralogical points of view, they resemble deep-ocean-floor basalts but...

Physical ocanography and nutrients during L'Atalante cruise EBENE

Gérard Eldin & Martine Rodier
This paper presents physical and nutrient results from the Etude du Broutage en Zone Equatoriale cruise, conducted in the equatorial Pacific along the 180° meridian from 8°S to 8°N. Cold conditions of the El Niño-Southern Oscillation cycle were evident during the cruise (October-November 1996), and the equatorial upwelling was in its far western extension. Along the sampled section the nutrient-enriched area was asymmetric around the equator, and a zone of high remineralization was found from...

Surface water properties, phytoplankton composition and photosynthesis rates of Amundsen Sea sites

Anne-Carlijn Alderkamp, Matthew M Mills, Gert L van Dijken, Patrick Laan, Charles-Edouard Thuróczy, Loes J A Gerringa, Hein J W de Baar, Christopher D Payne, Ronald J W Visser, Anita G J Buma & Kevin R Arrigo
The phytoplankton community composition and productivity in waters of the Amundsen Sea and surrounding sea ice zone were characterized with respect to iron (Fe) input from melting glaciers. High Fe input from glaciers such as the Pine Island Glacier, and the Dotson and Crosson ice shelves resulted in dense phytoplankton blooms in surface waters of Pine Island Bay, Pine Island Polynya, and Amundsen Polynya. Phytoplankton biomass distribution was the opposite of the distribution of dissolved...

Distribution of heavy minerals in sediment cores MSSTS-1 and DVDP-12

Kerstin Polozek
This study encompasses an investigation of the heavy mineral composition of early Oligocene-Quaternary glacial and glaciomarine sediment sequences from the Victoria Land Basin and the fjords of the South Victoria Land, Ross Sea, Antarctica. The sediment cores used were recovered during different international drilling campaigns (DVDP- 12, CIROS-2, MSSTS-l, CRP-l, CRP-212A). The main objectives were to identify possible source rocks and to unravel the provenance regions of different heavy minerals and mineral groups. Moreover, with...

Elemental and mineral composition of DSDP Leg 84 Holes

Jacques Bourgois, Alain Desmet, Jean Tournon & Jean Aubouin
Ultramafic rocks were recovered from the lower parts of holes at four sites (567, 566, 569, 570) drilled on Leg 84. These sites are on the landward slope of the Middle America Trench off Guatemala. Harzburgites, cumulative texture peridotites, gabbros, dolerites, and amphibolite facies rocks were recognized by pétrologie and geochemical analysis (Xray fluorescence, microprobe). Some of these rocks belong to an ophiolitic sequence. They form the basement of the landward slope of the Guatemala...

Geochemistry, mineralogy, and 40K-40Ar radiometric dating of DSDP Leg 84 basalts - Guatemala Trench

Herve Bellon, R C Maury, Jean Louis Joron, Jacques Bourgois & Jean Aubouin
Geochemical (atomic absorption, neutron activation analyses), mineralogical (microprobe), and radiometric (40K - 40Ar) data are presented for five basalts from the Guatemala Trench area (Deep Sea Drilling Project, Leg 84). Strong geochemical and mineralogical differences distinguish two types among these basalts: (1) One basalt (Sample 567A-19,CC), recovered below Upper Cretaceous limestone has the following characteristics: it is quartz normative and has low TiO2, content, as well as low amounts of Cr, Ni and other transition...

Core characteristics and events detected in ice cores from Svalbard

Okitsugu Watanabe, Hideaki Motoyama, Makoto Igarashi, Kokichi Kamiyama, Sumito Matoba, Kumiko Goto-Azuma, Hideki Narita & Takao Kameda
Ice coring and snow cover observations have been carried out at 3 sites in Nordaustlandet, Svalbard since 1995. The results of stratigraphic analyses, and chemical and d18O analyses from Vestfonna and Austfonna cores are presented here. The results from these sites show that most of the chemical constituents contained in the initial snow cover still remained in the ice cores, although re-distribution of them by melt water percolation had occurred. Anthropogenic increases in trace metals,...

Geochemistry of frost flowers and snow obtained near Ahlmann summit, Vestfonna ice cap

Emilie Beaudon & John C Moore
The chemistry of snow and ice cores from Svalbard is influenced by variations in local sea ice margin and distance to open water. Snow pits sampled at two summits of Vestfonna ice cap (Nordaustlandet, Svalbard), exhibit spatially heterogeneous soluble ions concentrations despite similar accumulation rates, reflecting the importance of small-scale weather patterns on this island ice cap. The snow pack on the western summit shows higher average values of marine ions and a winter snow...

Part of the global DOC versus AOU (dissolved organic carbon/apparent oxygen utilization) data compilation, Indian Ocean

María Dolores Doval & Dennis A Hansell
Samples for total organic carbon (TOC) analysis were collected on WOCE Line P15S (0° to 67°S along 170°W) and from 53° to 67°S along 170°E in the western South Pacific, and on Line I8 (5°N to 43°S along 80°/90°E) in the central Indian Ocean. TOC concentrations in the upper ocean varied greatly between the regions studied. Highest surface TOC concentrations (81-85 µM C and 68-73 µM C) were observed in the warmest waters (>27°C) of...

Part of the global DOC versus AOU (dissolved organic carbon/apparent oxygen utilization) data compilation, Pacific Ocean

Edward T Peltzer & N A Hayward
Total organic carbon (TOC) was analyzed on four transects along 140°W in 1992 using a high temperature combustion/discrete injection (HTC/DI) analyzer. For two of the transects, the analyses were conducted on-board ship. Mixed-layer concentrations of organic carbon varied from about 80 µM C at either end of the transect (12°N and 12°S) to about 60 µM C at the equator. Total organic carbon concentrations decreased rapidly below the mixed-layer to about 38-40 µM C at...

Part of the global DOC versus AOU (dissolved organic carbon/apparent oxygen utilization) data compilation, Arabian Sea

Dennis A Hansell & Edward T Peltzer
Concentrations of total organic carbon (TOC) were determined on samples collected during six cruises in the northern Arabian Sea during the 1995 US JGOFS Arabian Sea Process Study. Total organic carbon concentrations and integrated stocks in the upper ocean varied both spatially and seasonally. Highest mixed-layer TOC concentrations (80-100 µM C) were observed near the coast when upwelling was not active, while upwelling tended to reduce local concentrations. In the open ocean, highest mixed-layer TOC...

Cadmium analytical results from sediment and foraminifera shells

Edward A Boyle & Yair Rosenthal
There has been a major contradiction between benthic foraminiferal Cd/Ca and d13C data concerning the labile nutrient chemistry of the Southern Ocean during the Last Glacial Maximum (LGM). Cd data indicates that LGM South Atlantic nutrient concentrations were as low as they are today, indicative of a persistent influx of nutrient-depleted North Atlantic Deep Water (NADW). d13C data indicates that LGM South Atlantic nutrient concentrations were much higher than at present (even higher than anywhere...

Magnetic properties and heavy metals at DSDP Hole 83-504B

Hajimu Kinoshita, Toshio Furuta & Hodaka Kawahata
We report measurements of magnetic intensity, inclination, initial susceptibility, Koenigsberger's ratio, saturation magnetization, and Curie temperatures of 68 basalt samples from the Leg 83 section of Hole 504B. As in the upper part of the hole, reversely magnetized units predominate. Intensities of natural remanent magnetization vary widely, but the range of variation is an order of magnitude less than in the upper part of the hole. This and the other properties measured indicate that the...

Oxygen and carbon isotope composition of Globoquadrina venezuelana and Oridorsalis umbonatus at DSDP Leg 85 Holes

Edith Vincent & John S Killingley
Oxygen and carbon isotope stratigraphies are given for the planktonic foraminifer Globoquadrina venezuelana (a deep-dwelling species) at three DSDP sites located along a north-south transect at approximately 133°W across the Pacific equatorial high-productivity zone. The records obtained at Sites 573 and 574 encompass the lower Miocene. At Site 575 the record includes the middle Miocene and extends into the lowermost lower Miocene. The time resolution of the planktonic foraminifer isotope record varies from 50,000 to...

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