Akustostratigraphie im äquatorialen Ostatlantik : zur Entwicklung der Tiefenwasserzirkulation der letzten 3.5 Millionen Jahre
To reconstruct the deep-water circulation for the last 3.5 Ma from deep-sea sediments of the eastern equatorial Atlantic, sea floor morphology, sub-bottom reflectors and the echo character have been mapped on the basis of 3.5 kHz records and sediment cores. Physical properties of sediments and synth...
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Bornträger
1986
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Online Access: | https://oceanrep.geomar.de/id/eprint/34086/ https://oceanrep.geomar.de/id/eprint/34086/1/20160930142327.pdf |
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ftoceanrep:oai:oceanrep.geomar.de:34086 2023-05-15T14:06:46+02:00 Akustostratigraphie im äquatorialen Ostatlantik : zur Entwicklung der Tiefenwasserzirkulation der letzten 3.5 Millionen Jahre Mienert, Jürgen 1986-10 text https://oceanrep.geomar.de/id/eprint/34086/ https://oceanrep.geomar.de/id/eprint/34086/1/20160930142327.pdf de ger Bornträger https://oceanrep.geomar.de/id/eprint/34086/1/20160930142327.pdf Mienert, J. (1986) Akustostratigraphie im äquatorialen Ostatlantik : zur Entwicklung der Tiefenwasserzirkulation der letzten 3.5 Millionen Jahre. Meteor Forschungsergebnisse: Reihe C, Geologie und Geophysik, 40 . pp. 19-86. info:eu-repo/semantics/restrictedAccess Article PeerReviewed 1986 ftoceanrep 2023-04-07T15:27:48Z To reconstruct the deep-water circulation for the last 3.5 Ma from deep-sea sediments of the eastern equatorial Atlantic, sea floor morphology, sub-bottom reflectors and the echo character have been mapped on the basis of 3.5 kHz records and sediment cores. Physical properties of sediments and synthetic seismograms derived from them enable us to decipher reflector sequences in environments of pelagic, currentresuspended and turbidity sedimentation. The individual reflectors originate from carbonate dissolution, hiatuses, coarse sand layers and interferences. Those which are related to carbonate dissolution and hiatuses provide evidence of water-mass boundaries by their distribution. Five phases of different deep-water circulation can be seen in the record of the last 3.5 Ma, and these are related to climate history: 1. Between 3.7 Ma and 2.2 Ma a strong deep-water circulation indicates a northward flow of bottom water below 4200 m (AABW = Antarctic - Bottom Water) and a southward flow of deep-water above 4200 m (NADW = North-Atlantic Deep Water). 2. Between 1.6 and 1.4 Ma a southward flow of bottom water below 4500 m and a diminished southward flow above 4500 m can be detected. This water-mass geometry can be interpreted by an expansion of the NADW-masses and a displacement of the AABW-masses during the same time. 3. Since 1.4 Ma a northward flow of a bottom-water current developed again. This current flow created a leeside sediment ridge in the southern part of the Kane Gap and furrows in the northern part of it. 4. Beetween 400,000 and 200,000 yrs B. P. the oceanic and atmospheric circulation increased. The strengthened oceanic circulation caused an increase in carbonate dissolution, which is documented by a traceable reflector from 2800 m to 4500 m water depth. At the same time an increase of the atmospheric circulation caused a drastic rise in the pelagic sediment accumulation (> 100%) through an intensification of upwelling. This runs parallel with a higher oceanic productivity in the northern equatorial ... Article in Journal/Newspaper Antarc* Antarctic NADW North Atlantic Deep Water North Atlantic OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Antarctic Kane ENVELOPE(-63.038,-63.038,-73.952,-73.952) |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
German |
description |
To reconstruct the deep-water circulation for the last 3.5 Ma from deep-sea sediments of the eastern equatorial Atlantic, sea floor morphology, sub-bottom reflectors and the echo character have been mapped on the basis of 3.5 kHz records and sediment cores. Physical properties of sediments and synthetic seismograms derived from them enable us to decipher reflector sequences in environments of pelagic, currentresuspended and turbidity sedimentation. The individual reflectors originate from carbonate dissolution, hiatuses, coarse sand layers and interferences. Those which are related to carbonate dissolution and hiatuses provide evidence of water-mass boundaries by their distribution. Five phases of different deep-water circulation can be seen in the record of the last 3.5 Ma, and these are related to climate history: 1. Between 3.7 Ma and 2.2 Ma a strong deep-water circulation indicates a northward flow of bottom water below 4200 m (AABW = Antarctic - Bottom Water) and a southward flow of deep-water above 4200 m (NADW = North-Atlantic Deep Water). 2. Between 1.6 and 1.4 Ma a southward flow of bottom water below 4500 m and a diminished southward flow above 4500 m can be detected. This water-mass geometry can be interpreted by an expansion of the NADW-masses and a displacement of the AABW-masses during the same time. 3. Since 1.4 Ma a northward flow of a bottom-water current developed again. This current flow created a leeside sediment ridge in the southern part of the Kane Gap and furrows in the northern part of it. 4. Beetween 400,000 and 200,000 yrs B. P. the oceanic and atmospheric circulation increased. The strengthened oceanic circulation caused an increase in carbonate dissolution, which is documented by a traceable reflector from 2800 m to 4500 m water depth. At the same time an increase of the atmospheric circulation caused a drastic rise in the pelagic sediment accumulation (> 100%) through an intensification of upwelling. This runs parallel with a higher oceanic productivity in the northern equatorial ... |
format |
Article in Journal/Newspaper |
author |
Mienert, Jürgen |
spellingShingle |
Mienert, Jürgen Akustostratigraphie im äquatorialen Ostatlantik : zur Entwicklung der Tiefenwasserzirkulation der letzten 3.5 Millionen Jahre |
author_facet |
Mienert, Jürgen |
author_sort |
Mienert, Jürgen |
title |
Akustostratigraphie im äquatorialen Ostatlantik : zur Entwicklung der Tiefenwasserzirkulation der letzten 3.5 Millionen Jahre |
title_short |
Akustostratigraphie im äquatorialen Ostatlantik : zur Entwicklung der Tiefenwasserzirkulation der letzten 3.5 Millionen Jahre |
title_full |
Akustostratigraphie im äquatorialen Ostatlantik : zur Entwicklung der Tiefenwasserzirkulation der letzten 3.5 Millionen Jahre |
title_fullStr |
Akustostratigraphie im äquatorialen Ostatlantik : zur Entwicklung der Tiefenwasserzirkulation der letzten 3.5 Millionen Jahre |
title_full_unstemmed |
Akustostratigraphie im äquatorialen Ostatlantik : zur Entwicklung der Tiefenwasserzirkulation der letzten 3.5 Millionen Jahre |
title_sort |
akustostratigraphie im äquatorialen ostatlantik : zur entwicklung der tiefenwasserzirkulation der letzten 3.5 millionen jahre |
publisher |
Bornträger |
publishDate |
1986 |
url |
https://oceanrep.geomar.de/id/eprint/34086/ https://oceanrep.geomar.de/id/eprint/34086/1/20160930142327.pdf |
long_lat |
ENVELOPE(-63.038,-63.038,-73.952,-73.952) |
geographic |
Antarctic Kane |
geographic_facet |
Antarctic Kane |
genre |
Antarc* Antarctic NADW North Atlantic Deep Water North Atlantic |
genre_facet |
Antarc* Antarctic NADW North Atlantic Deep Water North Atlantic |
op_relation |
https://oceanrep.geomar.de/id/eprint/34086/1/20160930142327.pdf Mienert, J. (1986) Akustostratigraphie im äquatorialen Ostatlantik : zur Entwicklung der Tiefenwasserzirkulation der letzten 3.5 Millionen Jahre. Meteor Forschungsergebnisse: Reihe C, Geologie und Geophysik, 40 . pp. 19-86. |
op_rights |
info:eu-repo/semantics/restrictedAccess |
_version_ |
1766278814514544640 |