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Bentische Foraminiferen im Boreas-Becken, Grönlandsee: Verbreitung und paläo-ozeanographische Rekonstruktionen für die letzten 450.000 Jahre = Benthic Foraminifera in the Boreas Basin, Greenland Sea: distribution and paleoceanographic recon structions of the last 450,000 years
Magnus, S. (2000). Bentische Foraminiferen im Boreas-Becken, Grönlandsee: Verbreitung und paläo-ozeanographische Rekonstruktionen für die letzten 450.000 Jahre = Benthic Foraminifera in the Boreas Basin, Greenland Sea: distribution and paleoceanographic recon structions of the last 450,000 years. Ber. Polarforsch. Meeresforsch. 373: 1-137
In: Berichte zur Polar- und Meeresforschung = Reports on Polar and Marine Research. Alfred-Wegener-Institut für Polar- und Meeresforschung: Bremerhaven. ISSN 1618-3193, more
Peer reviewed article  

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Document type: Review

Keyword
    Marine

Author  Top 
  • Magnus, S.

Abstract
    The taphocoenosis of benthic Foraminifera in the grain fraction 125- 2,000 µm has been examined in three long sediment cores from different regions of the Boreas Basin. Dating is based on oxygen isotopes stratigraphy. The northern basin core was dated to stage seven by the Urrh-method. Older sediments of this core were dated by correlation ofbiostratigraphic results. Thirty-nine known species were identified and three groups of species were defined. The most important species in the Boreas Basin during the last 450,000 years are Cibicidoides wuellerstorfi, Oridorsalis umbonatus, Pyrgo rotalaria, Triloculina tricarinata, Cribrostomoides subglobosum, and agglutinated tubular species, which are typically preserved as fossil fragments. Bucella frigida, Cassidulina teretis, Cassidulina reniforme, Cibicides lobatulus, Nonion labradoricum, and Elphidiae are considered the most important allochthonous species of the deep sea sediments (>2,400 m). The development and distribution of benthic Foraminifera associations in the deep sea are mainly controlled by the following factors a) Primary production and transport to the seafloor: Atlantic surface-water masses influence primary production (phytoplankton), which partly serves as food for the benthos. Additionally, allochthonous foraminiferal species (e.g. shelf Elphidiae) and food particles reach deep sea sediments through ice drift or during melting periods. b) Bottom-water masses and dissolution of bottom- water: the distribution of C. wuellerstorfi is mainly related to interglacial phases but also to those glacial phases, during which thermohaline convection supplied the bottom water masses with small amounts of organic carbon. c) Bottom-water current and lateral sediment transport: shelf sediments and food particles are deposited by advective lateral transport to the deep seafloor. The amount of deposition is controlled by bottom-water currents. Bottom-water circulation, which is mainly driven by deep sea convection, can be further enhanced by seafloor topography.Benthic species associations provide a sensitive record of climatic changes. The sediments investigated include seven glacial and five interglacial stages. In the whole Boreas Basin the glacial stages differ from the interglacial stages by their respective species association and by a higher foraminiferal density. The association of benthic Foraminifera is used as an indicator of Atlantic surface-water masses, according to the following classification. Species association and foraminiferal density indicate, that for the last 450,000 years the effect of Atlantic surface-water masses has been stronger in the south-eastern part of the Boreas Basin in comparison to the south-western and northern regions. In contrast to the other parts, the south-western region of the Boreas Basin is characterized by a higher population density in glacial sediments. Species associations in glacial and interglacial stages are similar in this region. It seems that the varying pack ice edge drove a local convection system. Other findings in the south-western basin indicate sedimentation events such as gravitational down slope transport. The varying time intervals of the maximum accumulation rates of the benthic Foraminifera C. teretis can be explained by cyclic down slope transport. A typical "Atlantic fauna" is defined in the Boreas Basin from the comparison of benthic Foraminifera with lithofacial results. This" Atlantic fauna" is characterized by high productivity . Species association in relation to age indicate that the influence of an intensive thermohaline circulation began earlier in the south-western portion of the Boreas Basin than in the south-eastern and northern parts of the basin.

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