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Datasets with PANGAEA technical keyword @ORFOISatPorosity

Mostrando recursos 1 - 20 de 4.553

  1. Alkenone analyses of sediment cores from the western Arabian Sea

    Budziak, Dörte
    Records of total organic carbon (TOC) and C37 alkenones were used as indicators for past primary productivity in the western and eastern Arabian Sea. Data from GeoB 3005, an open ocean site in the western Arabian Sea upwelling area, are compared with similar records of GeoB 3007 from the Owen Ridge, Ocean Drilling Program (ODP) Site 723 from the continental margin off Oman and MD 900963 from the eastern Arabian Sea. TOC/C37 alkenone records together with other proxies used to reconstruct upwelling intensity, indicate periods of high productivity in tune with precessional forcing all over the Arabian Sea. Based on...

  2. Alkenone analyses of sediment cores from the western Arabian Sea

    Budziak, Dörte
    Records of total organic carbon (TOC) and C37 alkenones were used as indicators for past primary productivity in the western and eastern Arabian Sea. Data from GeoB 3005, an open ocean site in the western Arabian Sea upwelling area, are compared with similar records of GeoB 3007 from the Owen Ridge, Ocean Drilling Program (ODP) Site 723 from the continental margin off Oman and MD 900963 from the eastern Arabian Sea. TOC/C37 alkenone records together with other proxies used to reconstruct upwelling intensity, indicate periods of high productivity in tune with precessional forcing all over the Arabian Sea. Based on...

  3. Geochemistry, fluxes and nitrogen isotopic composition data of traps LP1 and EBC2-1 and cores GeoB4242-4 and Geo4301-1

    Freudenthal, Tim; Neuer, Susanne; Meggers, Helge; Davenport, Robert; Wefer, Gerold
    We compare total and biogenic particle fluxes and stable nitrogen isotope ratios (d15N) at three mooring sites along a productivity gradient in the Canary Islands region with surface sediment accumulation rates and sedimentary d15N. Higher particle fluxes and sediment accumulation rates, and lower d15N were observed in the upwelling influenced eastern boundary region (EBC) compared to the oligotrophic sites north of Gran Canaria [European Station for Time-Series in the Ocean, Canary Islands (ESTOC]] and north of La Palma (LP). The impact of organic matter degradation and lateral particle advection on sediment accumulation was quantified with respect to the multi-year flux...

  4. Geochemistry, fluxes and nitrogen isotopic composition data of traps LP1 and EBC2-1 and cores GeoB4242-4 and Geo4301-1

    Freudenthal, Tim; Neuer, Susanne; Meggers, Helge; Davenport, Robert; Wefer, Gerold
    We compare total and biogenic particle fluxes and stable nitrogen isotope ratios (d15N) at three mooring sites along a productivity gradient in the Canary Islands region with surface sediment accumulation rates and sedimentary d15N. Higher particle fluxes and sediment accumulation rates, and lower d15N were observed in the upwelling influenced eastern boundary region (EBC) compared to the oligotrophic sites north of Gran Canaria [European Station for Time-Series in the Ocean, Canary Islands (ESTOC]] and north of La Palma (LP). The impact of organic matter degradation and lateral particle advection on sediment accumulation was quantified with respect to the multi-year flux...

  5. Geochemistry and soil characteristics of sediment core GeoB4234

    Freudenthal, Tim; Wagner, Thomas; Wenzhöfer, Frank; Zabel, Matthias; Wefer, Gerold
    Stable isotopes of sedimentary nitrogen and organic carbon are widely used as proxy variables for biogeochemical parameters and processes in the water column. In order to investigate alterations of the primary isotopic signal by sedimentary diagenetic processes, we determined concentrations and isotopic compositions of inorganic nitrogen (IN), organic nitrogen (ON), total nitrogen (TN), and total organic carbon (TOC) on one short core recovered from sediments of the eastern subtropical Atlantic, between the Canary Islands and the Moroccan coast. Changes with depth in concentration and isotopic composition of the different fractions were related to early diagenetic conditions indicated by pore water...

  6. Geochemistry and soil characteristics of sediment core GeoB4234

    Freudenthal, Tim; Wagner, Thomas; Wenzhöfer, Frank; Zabel, Matthias; Wefer, Gerold
    Stable isotopes of sedimentary nitrogen and organic carbon are widely used as proxy variables for biogeochemical parameters and processes in the water column. In order to investigate alterations of the primary isotopic signal by sedimentary diagenetic processes, we determined concentrations and isotopic compositions of inorganic nitrogen (IN), organic nitrogen (ON), total nitrogen (TN), and total organic carbon (TOC) on one short core recovered from sediments of the eastern subtropical Atlantic, between the Canary Islands and the Moroccan coast. Changes with depth in concentration and isotopic composition of the different fractions were related to early diagenetic conditions indicated by pore water...

  7. Alkenone and foraminifera records from sediment samples off Namibia

    Mollenhauer, Gesine; Eglinton, Timothy I; Ohkouchi, Naohiko; Schneider, Ralph R; Müller, Peter J; Grootes, Pieter Meiert; Rullkötter, Jürgen
    Radiocarbon stratigraphy is an essential tool for high resolution paleoceanographic studies. Age models based on radiocarbon ages of foraminifera are commonly applied to a wide range of geochemical studies, including the investigation of temporal leads and lags. The critical assumption is that temporal coupling between foraminifera and other sediment constituents, including specific molecular organic compounds (biomarkers) of marine phytoplankton, e.g. alkenones, is maintained in the sediments. To test this critical assumption in the Benguela upwelling area, we have determined radiocarbon ages of total C37-C39 alkenones in 20 samples from two gravity cores and three multicorer cores. The cores were retrieved from...

  8. Alkenone and foraminifera records from sediment samples off Namibia

    Mollenhauer, Gesine; Eglinton, Timothy I; Ohkouchi, Naohiko; Schneider, Ralph R; Müller, Peter J; Grootes, Pieter Meiert; Rullkötter, Jürgen
    Radiocarbon stratigraphy is an essential tool for high resolution paleoceanographic studies. Age models based on radiocarbon ages of foraminifera are commonly applied to a wide range of geochemical studies, including the investigation of temporal leads and lags. The critical assumption is that temporal coupling between foraminifera and other sediment constituents, including specific molecular organic compounds (biomarkers) of marine phytoplankton, e.g. alkenones, is maintained in the sediments. To test this critical assumption in the Benguela upwelling area, we have determined radiocarbon ages of total C37-C39 alkenones in 20 samples from two gravity cores and three multicorer cores. The cores were retrieved from...

  9. Long time-series benthic observation at station DYFAMED

    Guidi-Guilvard, Laurence D
    In 1990, a benthic component to the DYFAMED (dynamics of fluxes in the Mediterranean) program, the DYFAMED-BENTHOS survey, was established to investigate the possible coupling of benthic to pelagic processes at a permanent station in >2700 m water depth, 52 km off Nice, France. Surface sediment was first sampled at different periods of the year to assess the importance of the biological compartment (particularly metazoan meiofauna) and its relation to seasonally varying particulate matter input to the sea floor (estimated by measuring surface sediment particle size and porosity, as well as chloroplastic pigments, organic carbon, nitrogen and calcium carbonate contents). Beginning in...

  10. Oxygen microprofiles and porewater chemistry in sediments of the Skagerrak

    Bakker, Joop F; Helder, Wim
    Sediment porewater oxygen profiles were measured with micro and needle electrodes in sediment cores of 27 stations in the Skagerrak (northeastern North Sea). Oxygen penetration depth ranged from 3 to 20 mm depth. Fluxes estimated from the oxygen gradients varied from 3 to 18 mmol m**-2 d**-1. Oxygen penetration and flux depend on water depth, but possibly more on the hydrological conditions, related to the import of fresh organic matter by primary production in the water column. Oxygen fluxes were not related to the total organic carbon (TOC) content of the sediments. Stations in the eastern part of the Skagerrak...

  11. Oxygen microprofiles and porewater chemistry in sediments of the Skagerrak

    Bakker, Joop F; Helder, Wim
    Sediment porewater oxygen profiles were measured with micro and needle electrodes in sediment cores of 27 stations in the Skagerrak (northeastern North Sea). Oxygen penetration depth ranged from 3 to 20 mm depth. Fluxes estimated from the oxygen gradients varied from 3 to 18 mmol m**-2 d**-1. Oxygen penetration and flux depend on water depth, but possibly more on the hydrological conditions, related to the import of fresh organic matter by primary production in the water column. Oxygen fluxes were not related to the total organic carbon (TOC) content of the sediments. Stations in the eastern part of the Skagerrak...

  12. Benthic oxygen flixes on the Washington shelf and slope

    Archer, David E; Devol, Alan H
    Benthic oxygen fluxes calculated from in situ microelectrode profiles arc compared with benthic flux chamber O2 uptake measurements on a transect of eight stations across the continental shelf and three stations on the slope of Washington State. Station depths ranged from 40 to 630 m and bottom-water oxygen concentrations were 127-38 µM. The fluxes measured by the two methods were similar on the slope, but on the shelf, the chamber flux exceeded the microelectrode flux by as much as a factor of 3-4. We attribute this difference to pore-water irrigation, a process which apparently accounts for the oxidation of a...

  13. Benthic oxygen flixes on the Washington shelf and slope

    Archer, David E; Devol, Alan H
    Benthic oxygen fluxes calculated from in situ microelectrode profiles arc compared with benthic flux chamber O2 uptake measurements on a transect of eight stations across the continental shelf and three stations on the slope of Washington State. Station depths ranged from 40 to 630 m and bottom-water oxygen concentrations were 127-38 µM. The fluxes measured by the two methods were similar on the slope, but on the shelf, the chamber flux exceeded the microelectrode flux by as much as a factor of 3-4. We attribute this difference to pore-water irrigation, a process which apparently accounts for the oxidation of a...

  14. Mineralogical and chemical investigation of biogenic siliceous Antarctic deep-ses sediments

    Bohrmann, Gerhard; Abelmann, Andrea; Gersonde, Rainer; Kuhn, Gerhard
    The formation of marine opal-CT nodules or layers as early diagenetic deposits has been documented only in Antarctic deep-sea sediments. In contrast, porcellanites and cherts in land sections and Deep Sea Drilling Project and Ocean Drilling Program drill sites are usually found in sediment sections of Miocene age and older. During R.V. Polarstem cruises ANT-IX/3 and 4, young porcellanites were recovered for the first time in contact with their host sediment in two cores from the Atlantic sector of the southern ocean. Chemical and mineralogical studies of these deposits and their surrounding sediments have increased knowledge about very early chert...

  15. Mineralogical and chemical investigation of biogenic siliceous Antarctic deep-ses sediments

    Bohrmann, Gerhard; Abelmann, Andrea; Gersonde, Rainer; Kuhn, Gerhard
    The formation of marine opal-CT nodules or layers as early diagenetic deposits has been documented only in Antarctic deep-sea sediments. In contrast, porcellanites and cherts in land sections and Deep Sea Drilling Project and Ocean Drilling Program drill sites are usually found in sediment sections of Miocene age and older. During R.V. Polarstem cruises ANT-IX/3 and 4, young porcellanites were recovered for the first time in contact with their host sediment in two cores from the Atlantic sector of the southern ocean. Chemical and mineralogical studies of these deposits and their surrounding sediments have increased knowledge about very early chert...

  16. Mineralogical and chemical investigation of biogenic siliceous Antarctic deep-ses sediments

    Bohrmann, Gerhard; Abelmann, Andrea; Gersonde, Rainer; Kuhn, Gerhard
    The formation of marine opal-CT nodules or layers as early diagenetic deposits has been documented only in Antarctic deep-sea sediments. In contrast, porcellanites and cherts in land sections and Deep Sea Drilling Project and Ocean Drilling Program drill sites are usually found in sediment sections of Miocene age and older. During R.V. Polarstem cruises ANT-IX/3 and 4, young porcellanites were recovered for the first time in contact with their host sediment in two cores from the Atlantic sector of the southern ocean. Chemical and mineralogical studies of these deposits and their surrounding sediments have increased knowledge about very early chert...

  17. Sedimentology and geochemistry of the Iberian margin

    Thomson, John; Nixon, S; Summerhayes, Colin P; Schönfeld, Joachim; Zahn, Rainer; Grootes, Pieter Meiert
    The Portuguese margin is well-suited for studies of the contrasts in North Atlantic circulation during glacial and interglacial times because of its rapid sediment accumulation rate. This paper reports a (230Thexcess)0-based study of sediment accumulation over the past 140 ky, a period which includes the last two glacial/interglacial transitions, in two cores at 2.4 and 3.5 km water depth on a slope transect at 40°N. Although the independently-determined mean sediment accumulation fluxes over the past 140 ky are unequivocally high with means of 13.2 and 10.5 g cm**-2 ky**-1 in the two cores, conventional application of the (230Thexcess)0 method yields...

  18. Sedimentology and geochemistry of the Iberian margin

    Thomson, John; Nixon, S; Summerhayes, Colin P; Schönfeld, Joachim; Zahn, Rainer; Grootes, Pieter Meiert
    The Portuguese margin is well-suited for studies of the contrasts in North Atlantic circulation during glacial and interglacial times because of its rapid sediment accumulation rate. This paper reports a (230Thexcess)0-based study of sediment accumulation over the past 140 ky, a period which includes the last two glacial/interglacial transitions, in two cores at 2.4 and 3.5 km water depth on a slope transect at 40°N. Although the independently-determined mean sediment accumulation fluxes over the past 140 ky are unequivocally high with means of 13.2 and 10.5 g cm**-2 ky**-1 in the two cores, conventional application of the (230Thexcess)0 method yields...

  19. Physical properties of ODP Leg 178 sites

    Volpi, Valentina; Camerlenghi, Angelo; Moerz, Tobias; Corubolo, P; Rebesco, Michele; Tinivella, Umberta
    We have reanalyzed the porosity, bulk density, and seismic velocity information collected from continental rise Sites 1095, 1096, and 1101 during the drilling of Ocean Drilling Program (ODP) Leg 178 (Fig. F1). The purpose is to provide a comprehensive composite digital set of data readily available for future studies aimed at well-seismic correlation. The work originates from the occurrence of overlapping sets of physical parameters and acoustic velocity collected by different methods (downhole logging, core logging, laboratory determination, and derivation from seismic data) and from different holes at the same site. These data do not always provide the same information...

  20. Physical properties of ODP Leg 178 sites

    Volpi, Valentina; Camerlenghi, Angelo; Moerz, Tobias; Corubolo, P; Rebesco, Michele; Tinivella, Umberta
    We have reanalyzed the porosity, bulk density, and seismic velocity information collected from continental rise Sites 1095, 1096, and 1101 during the drilling of Ocean Drilling Program (ODP) Leg 178 (Fig. F1). The purpose is to provide a comprehensive composite digital set of data readily available for future studies aimed at well-seismic correlation. The work originates from the occurrence of overlapping sets of physical parameters and acoustic velocity collected by different methods (downhole logging, core logging, laboratory determination, and derivation from seismic data) and from different holes at the same site. These data do not always provide the same information...

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