Vörösmarty, Charles J; Fekete, B M; Tucker, B A
The Global River Discharge (RivDIS) data set contains monthly discharge measurements for 1018 stations located throughout the world. The period of record varies widely from station to station, with a mean of 21.5 years. These data were digitized from published UNESCO archives by Charles Voromarty, Balaze Fekete, and B.A. Tucker of the Complex Systems Research Center (CSRC) at the University of New Hampshire.
River discharge is typically measured through the use of a rating curve that relates local water level height to discharge. This rating curve is used to estimate discharge from the observed water level. The rating curves are periodically...
Sauerstoff-Isotopenuntersuchungen wurden an frischem Diatomeenopal aus der obersten Wassersäule, Diatomeen aus Kulturen, sowie an sedimentärem Diatomeenopal durchgeführt, um die Anwendbarkeit von d18O-Signalen aus marinen Diatomeen für paläozeanographische Fragestellungen zu untersuchen.
Diatomeenopal ist, besonders aus Sedimentproben, schwierig anzureichern. Physikalische und chemische Verfahren müssen mehrfach angewendet werden, um Proben zu erhalten, die den für Sauerstoff-Isotopenmessungen erforderlichen Reinheitsgrad aufweisen. Die Ausgangskonzentration an Diatomeen im Probenmaterial wirkt sich hierbei erheblich auf den Erfolg der Reinigung aus.
Verläßliche und reproduzierbare d18O-Werte können nur an sehr reinen Diatomeenproben bestimmt werden. Mittels mikroskopischer Untersuchungen (Durchlichtmikroskopie, Rasterelektronenrnikroskopie), Röntgendiffraktametrie und geochernischer Analysen am ICP-MS können z.T. Art und Menge von Verunreinigungen...
Ragueneau, Olivier; Tréguer, Paul; Leynaert, Aude; Anderson, Robert F; Brzezinski, Mark A; DeMaster, David J; Dugdale, Richard; Dymond, Jack R; Fischer, Gerhard; Francois, Roger; Heinze, Christoph; Maier-Reimer, Ernst; Martin-Jézéquel, Véronique; Nelson, David M; Quéguiner, Bernard
Due to the major role played by diatoms in the biological pump of CO2, and to the presence of silica-rich sediments in areas that play a major role in air-sea CO2 exchange (e.g. the Southern Ocean and the Equatorial Pacific), opal has a strong potential as a proxy for paleoproductivity reconstructions. However, because of spatial variations in the biogenic silica preservation, and in the degree of coupling between the marine Si and C biogeochemical cycles, paleoreconstructions are not straitghtforward. A better calibration of this proxy in the modern ocean is required, which needs a good understanding of the mechanisms that...
Goldberg, Edward D; Griffin, John J
Rates of sedimentation of pelagic sediments in the South Atlantic have been determined using the ionium/thorium methodology. Values of the order of several millimeters per thousand years for sediments were found in the deposits in the valleys of the mid-Atlantic ridge. The equatorial deposits showed higher rates of accumulation than the corresponding deposits at higher latitudes, probably reflecting the added influx of materials to the sea floor from tropical rivers through the equatorial current systems. The deposits in the ridge valleys showed marked changes in sedimentation rates at about 115,000 years ago, at which time the present rates changed from...
Kiriakoulakis, Kostas; Fisher, Elizabeth; Wolff, George A; Freiwald, André; Grehan, Anthony J; Roberts, Murray J
The lipid and organic nitrogen isotopic (delta15N) compositions of two common deep-water corals (Lophelia pertusa and Madrepora oculata) collected from selected locations of the NE Atlantic are compared to the composition of suspended particulate organic matter, in order to determine their principle food source. Initial results suggest that they may feed primarily on zooplankton. This is based on the increased abundances of mono-unsaturated fatty acids and alcohols and the different ratios of the polyunsaturated fatty acids, 22:6/20:5 of the corals when compared to those of the suspended particulate organic matter. There is enrichment in L. pertusa of mono-unsaturated fatty acids...
Wendler, Jens E; Gräfe, Kai-Uwe; Willems, Helmut
A transect from the bathyal to proximal shelf facies of the Boreal Realm was investigated to compare spatial and temporal distribution changes of calcareous dinoflagellate cysts (c-dinocysts) throughout the mid-Cenomanian in order to gain information on the ecology of these organisms. Pithonelloideae dominated the cyst assemblages to more than 95% on the shelf, a prevalence that can be observed throughout most of the Upper Cretaceous. The affinity of this group with the dinoflagellates, which is still controversially discussed, can be confirmed, based on evidence from morphological features and distribution patterns. The consistent prevalence of Pithonella sphaerica and P. ovalis in...
High-resolution Holocene pollen profiles from lakes Großer Krebssee and Felchowsee, in the Lower Oder valley, north-eastern Germany, are presented. The Großer Krebssee profile includes a Late-glacial sequence. These investigations have been carried out in the context of a programme of archaeological excavation. AMS radiocarbon dates (26 in all) based on pollen concentrates have been used to provide a chronology for the pollen records. Holocene forest history and human impact are reconstructed for contrasting landscapes, namely, the Neuenhagener Oderinsel in the Lower Oderbruch (Großer Krebssee profile) and the more fertile Uckermärker Hügelland (Felchowsee profile) that lies immediately to the north. Both...
A high-resolution Late Pleistocene and Middle to Late Holocene pollen profile of regional significance is presented. The coring site is located in a mire between two lakes. Ober- and Unter-Ückersee, in Brandenburg, north-eastern Germany. The study was carried out in an archaeological context. It provides information about the history of vegetation, climate and human impact in the Ücker river valley and the surrounding hills, the Uckermärker Hügelland. Hence, it is an important contribution for the reconstruction of the past vegetation of this area of Brandenburg. Seven AMS 14C-dates based on pollen concentrates provide a chronology for the middle Holocene part...
Balsam, William L; McCoy, F M J
To assess the regional effects of glaciation on sedimentation in the Atlantic Ocean we compare sediment types, distributions, and rates between Recent (core top) and last glacial maximum (LGM: ~18,000 years B.P.) stratigraphic levels. Based upon smear slides and carbonate analyses in 178 cores we find that glacial age carbonate content is generally lower than Recent. During both the Recent and LGM, carbonate content shows an east/west asymmetry with western basins exhibiting lower carbonate values. Input of ice-rafted detritus into the North Atlantic during LGM time interrupts this topographic control on carbonate distribution considerably farther south than at present; in...
Gingele, Franz; Leipe, Thomas
Surface samples and nine cores from the western Baltic Sea and marginal water bodies were investigated for clay mineral composition. The clay mineral assemblages of recent sediments are rather homogeneous. Variations result mainly from the erosion of different glacial source deposits. High percentages of illite and low kaolinite/chlorite and quartz/feldspar ratios are characteristic for this glacial source. Advection of kaolinite-rich suspensions from the North Sea is believed to account for higher kaolinite/chlorite ratios in the Mecklenburg Bight. A contribution of the rivers Trave and Oder to the western Baltic Sea is indicated by increased smectite values in marginal water bodies....
Meier, K J Sebastian; Willems, Helmut
The distribution of calcareous dinoflagellate cysts in surface sediments from the Mediterranean Sea was quantitatively analysed. The samples contain 11 cyst species and the vegetative coccoid Thoracosphaera heimii. Cyst abundance increases towards the deeper parts of the basins and is generally higher in the eastern Mediterranean Sea. Three major distribution characteristics exist: (1) different assemblages in oceanic and neritic regions, (2) little agreement with the associations of areas studied so far like the Atlantic Ocean, and (3) a unique oceanic assemblage in the eastern Mediterranean Sea. A gradual change in cyst assemblages from the western to the eastern Mediterranean Sea...
Pirrung, Michael; Fütterer, Dieter K; Grobe, Hannes; Matthiessen, Jens; Niessen, Frank
Magnetic susceptibility and ice-rafted debris of surface sediments in the Nordic Seas were investigated to reconstruct source areas and recent transport pathways of magnetic minerals. From the distribution of magnetic susceptibility and ice-rafted debris and published data on petrographic tracers for iceberg drift, we reconstructed a counter-clockwise iceberg drift pattern during cooler phases in the Holocene, which is similar to conceptual and numerical models for Weichselian iceberg drift. The release of basaltic debris at Scoresby Sund played a significant role for the magnetic signature of stadial/interstadial events during isotope stage 3 recorded in sediment cores of the Nordic Seas.
Müller, German; Stoffers, Peter
The origin and modes of transportation and deposition of inorganic sedimentary material of the Black Sea were studied in approximately 60 piston, gravity, and Kasten cores.
The investigation showed that the sediment derived from the north and northwest (especially from the Danube) has a low calcite-dolomite ratio and a high quartz-feldspar ratio. Rock fragments are generally not abundant; garnet is the principal heavy mineral and illite is the predominant clay mineral. This sedimentary material differs markedly from that carried by Anatolian rivers, which is characterized by a high calcite-dolomite ratio and a low quartz-feldspar ratio. Rock fragments are abundant; pyroxene...
Huang, Yongsong; Dupont, Lydie M; Sarnthein, Michael; Hayes, John M; Eglinton, Geoffrey
Mapping the abundance of 13C in leaf-wax components in surface sediments recovered from the seafloor off northwest Africa (0-35°N) reveals a clear pattern of delta13C distribution, indicating systematic changes in the proportions of terrestrial C3 and C4 plant input. At 20°N latitude, we find that isotopically enriched products characteristic of C4 plants account for more than 50% of the terrigenous inputs. This signal extends westward beneath the path of the dust-laden Sahara Air Layer (SAL). High C4 contributions, apparently carried by January trade winds, also extend far into the Gulf of Guinea. Similar distributions are obtained if summed pollen counts...
SKAGEX Members; Dahlin, Hans; Dubra, Juozas; Dybern, Bernt I; Fennel, Wolfgang; Fogelqvist, Elisabet; Foyn, Lars; Gaul, Horst; Hansen, Hans Peter; Hernroth, Lars; Johannessen, Ola M; Krol, Tadeusz; Lange, Wolfgang; Lindahl, Odd; Slaczka, Wojciech; Talpsepp, Lembit; Vitautas, A
Al-Sabouni, Nadia; Kucera, Michal; Schmidt, Daniela N
Species distribution patterns in planktonic foraminiferal assemblages are fundamental to the understanding of the determinants of their ecology. Until now, data used to identify such distribution patterns was mainly acquired using the standard >150 µm sieve size. However, given that assemblage shell size-range in planktonic foraminifera is not constant, this data acquisition practice could introduce artefacts in the distributional data. Here, we investigated the link between assemblage shell size-range and diversity in Recent planktonic foraminifera by analysing multiple sieve-size fractions in 12 samples spanning all bioprovinces of the Atlantic Ocean. Using five diversity indices covering various aspects of community structure,...
Egger, Hans; Brückl, Ewald
23 layers of altered volcanic ash (bentonites) originating from the North Atlantic Igneous Province have been recorded in early Eocene deposits of the Austrian Alps, about 1,900 km away from the source area. The Austrian bentonites are distal equivalents of the ''main ash-phase'' in Denmark and the North Sea basin. We have calculated the total eruption volume of this series as 21,000 km**3, which occurred in 600,000 years. The most powerful single eruption of this series took place 54.0 million years ago (Ma) and ejected ca. 1,200 km**3 of ash material, which makes it one of the largest basaltic pyroclastic...
Kuhnt, Wolfgang; Kaminski, Michael A; Moullade, Michel
The stratigraphic and biogeographic distribution of more than 170 species of deep-water agglutinated benthic foraminifers (DWAF) from the North Atlantic and adjacent marginal seas has been compared with paleoenvironmental data (e.g. paleobathymetry, oxygenation of the bottom waters, amount of terrigenous input and substrate disturbance). Six general types of assemblages, in which deep water agglutinated taxa occur, are defined from the Turonian to Maastrichtian times:
1. High latitude slope assemblages
2. Low to mid latitude slope assemblages
3. Flysch-type assemblages
4. Deep water limestone assemblages (,,Scaglia,,-type)
5. Abyssal mixed calcareous-agglutinated assemblages
6. Abyssal purely agglutinated assemblages
Latitudinal differences in faunal composition are observed, the most important of which...
Fimpel, Hans P; Gass, Manfred E; Müller, Hans Gerhard