High-resolution benthic foraminiferal records of the last glacial termination in the northern North Atlantic

Large oceanic changes occurred during the last transition from glacial to interglacial conditions (Termination I), which significantly affected pelagic and benthic environments. This study presents results of a quantitative investigation of benthic foraminifera at four sites distributed along a nort...

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Bibliographic Details
Main Author: Nees, Stefan
Other Authors: Hass, H. Christian, Kaminski, Michael A.
Format: Book Part
Language:unknown
Published: Grzybowski Foundation 1997
Subjects:
Online Access:http://oceanrep.geomar.de/31039/
http://oceanrep.geomar.de/31039/1/Nees%201997.pdf
Description
Summary:Large oceanic changes occurred during the last transition from glacial to interglacial conditions (Termination I), which significantly affected pelagic and benthic environments. This study presents results of a quantitative investigation of benthic foraminifera at four sites distributed along a north-south transect across the northern North Atlantic with a high temporal resolution (k 200 years). Benthic foraminifera are examined in samples (1-2 cm sampling intervals) from four long sediment cores located in the southern Fram Strait, the Greenland-Iceland-Norwegian Sea (GIN Sea), and the Rockall Plateau. The most prominent species of benthic foraminifera include Oridorsalis nnlbolzatlls, Cibicidoides wl~ellerstoufi,C assidulina spp. group, P!jrgo rotalaria, Globocassidrrliiza sllbg-lobosa and tubes of agglutinated taxa. In each core, the climatic amelioration at Termination I is recorded to have occurred in two steps. A first INDAR maximum (INDividuals Accumulation Rate = ind/cm2 ky; GIN Sea: average 3,000-6,000 ind/cm2 ky, Rockall Plateau: average 150 ind/cm2 ky) is followed by a period of lower values. A second maximum reveals slightly lower values than the older maximum. Interglacial INDAR values average 700 ind/cm2 ky for the GIN Sea and 200 ind/cm2 ky on the Rockall Plateau. This is roughly twice that of typical glacial values. Meltwater events, identified by stable isotope data and sea-surface temperature reconstructions based on planktic foraminiferal transfer functions, are marked by an increase in endobenthic and opportunistic species. A decrease of reconstructed sea-surface temperatures appears synchronous with the relative INDAR minimum that occurs between the two INDAR maxima. The results indicate a close coupling of sea-surface processes to the benthic realm ("pelagic-benthic coupling") with a longitudinally variable strength. The climate signal at the Rockall Plateau revealed by the fossil benthic foraminifera shows a lower amplitude than that of the GIN Sea. The second, younger INDAR maximum is characterized by an increased abundance of epibenthic species at all core locations, suggesting extended lateral bottom currents. In comparison with various palaeo-climatological data sets, the variability of fossil benthic foraminiferal abundances in the GIN Sea show a distinct coherence with changes of atmospheric temperatures, sea-surface temperatures and the postglacial sea level rise. The variability of the benthic foraminiferal fauna is principally in phase with climate change events.