Mesozoic seafloor spreading in the southern Weddell Sea
A re-evaluation of Weddell Sea magnetic anomaly data, in the light of satellite gravity maps, provides important constraints on plate kinematics prior to chron C34 (83 Ma). Although M-series anomalies are difficult to identify, the evidence favours younger ages than previously suggested, based on th...
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Geological Society of London
1996
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ftnerc:oai:nora.nerc.ac.uk:515196 2023-05-15T13:25:25+02:00 Mesozoic seafloor spreading in the southern Weddell Sea Livermore, R. A. Hunter, R. J. Storey, B.C. King, E.C. Livermore, R.A. 1996 http://nora.nerc.ac.uk/id/eprint/515196/ https://doi.org/10.1144/GSL.SP.1996.108.01.17 unknown Geological Society of London Livermore, R. A.; Hunter, R. J. 1996 Mesozoic seafloor spreading in the southern Weddell Sea. In: Storey, B.C.; King, E.C. orcid:0000-0003-3793-3915 Livermore, R.A., (eds.) Weddell Sea tectonics and Gondwana break-up. London, Geological Society of London, 227-241. (Geological Society special publication, 108, 108). Publication - Book Section PeerReviewed 1996 ftnerc https://doi.org/10.1144/GSL.SP.1996.108.01.17 2023-02-04T19:43:55Z A re-evaluation of Weddell Sea magnetic anomaly data, in the light of satellite gravity maps, provides important constraints on plate kinematics prior to chron C34 (83 Ma). Although M-series anomalies are difficult to identify, the evidence favours younger ages than previously suggested, based on the assumption that these anomalies formed at the South America-Antarctica plate boundary. Geosat-derived free-air gravity maps show a distinct anomaly, ‘Anomaly-T’, associated with the southern termination of a herring-bone pattern of flow lines. The associated magnetic anomaly has been identified previously as anomaly M20, on the basis of a model of very slow spreading, but is interpreted here as an edge-effect, associated with an abrupt decline in spreading rate which occurred between M4 (126 Ma) and M0 (118 Ma), and which induced the fine segmentation pattern to the north. Although anomalies are present to the south of Anomaly-T, they are of reduced amplitude, and are difficult to correlate over distances of more than c. 100 km. Nevertheless, they appear to strike approximately W-E, sub-parallel to the younger anomalies to the north, and show a resemblance to anomalies M4–M12, modelled at a rate of 15 km Ma−1. Flow-line modelling, based on published rotations for the Southwest Indian Ridge and southern Mid-Atlantic Ridge, gives a reasonable fit to the observed trends of Weddell Sea gravity ridges. Two alternative models for the M-series reconstruction of Africa and Antarctica are employed, corresponding to the two M2 fits suggested by Bergh. Although it is not possible to reject either of the models, the tighter fit of the two gives slightly better agreement with Weddell Sea trends. In both models, a drop in rates occurs at M0 time. Anomalies farther south correspond with previously identified features, such as the Orion, Explora and Andenes anomalies, and the Polarstern Bank, all characterized by magnetic anomaly highs, attributed to excess volcanism during early break-up. Book Part Andenes Antarc* Antarctica Weddell Sea Natural Environment Research Council: NERC Open Research Archive Weddell Sea Indian Weddell Mid-Atlantic Ridge Orion ENVELOPE(-59.800,-59.800,-62.438,-62.438) Geological Society, London, Special Publications 108 1 227 241 |
institution |
Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
unknown |
description |
A re-evaluation of Weddell Sea magnetic anomaly data, in the light of satellite gravity maps, provides important constraints on plate kinematics prior to chron C34 (83 Ma). Although M-series anomalies are difficult to identify, the evidence favours younger ages than previously suggested, based on the assumption that these anomalies formed at the South America-Antarctica plate boundary. Geosat-derived free-air gravity maps show a distinct anomaly, ‘Anomaly-T’, associated with the southern termination of a herring-bone pattern of flow lines. The associated magnetic anomaly has been identified previously as anomaly M20, on the basis of a model of very slow spreading, but is interpreted here as an edge-effect, associated with an abrupt decline in spreading rate which occurred between M4 (126 Ma) and M0 (118 Ma), and which induced the fine segmentation pattern to the north. Although anomalies are present to the south of Anomaly-T, they are of reduced amplitude, and are difficult to correlate over distances of more than c. 100 km. Nevertheless, they appear to strike approximately W-E, sub-parallel to the younger anomalies to the north, and show a resemblance to anomalies M4–M12, modelled at a rate of 15 km Ma−1. Flow-line modelling, based on published rotations for the Southwest Indian Ridge and southern Mid-Atlantic Ridge, gives a reasonable fit to the observed trends of Weddell Sea gravity ridges. Two alternative models for the M-series reconstruction of Africa and Antarctica are employed, corresponding to the two M2 fits suggested by Bergh. Although it is not possible to reject either of the models, the tighter fit of the two gives slightly better agreement with Weddell Sea trends. In both models, a drop in rates occurs at M0 time. Anomalies farther south correspond with previously identified features, such as the Orion, Explora and Andenes anomalies, and the Polarstern Bank, all characterized by magnetic anomaly highs, attributed to excess volcanism during early break-up. |
author2 |
Storey, B.C. King, E.C. Livermore, R.A. |
format |
Book Part |
author |
Livermore, R. A. Hunter, R. J. |
spellingShingle |
Livermore, R. A. Hunter, R. J. Mesozoic seafloor spreading in the southern Weddell Sea |
author_facet |
Livermore, R. A. Hunter, R. J. |
author_sort |
Livermore, R. A. |
title |
Mesozoic seafloor spreading in the southern Weddell Sea |
title_short |
Mesozoic seafloor spreading in the southern Weddell Sea |
title_full |
Mesozoic seafloor spreading in the southern Weddell Sea |
title_fullStr |
Mesozoic seafloor spreading in the southern Weddell Sea |
title_full_unstemmed |
Mesozoic seafloor spreading in the southern Weddell Sea |
title_sort |
mesozoic seafloor spreading in the southern weddell sea |
publisher |
Geological Society of London |
publishDate |
1996 |
url |
http://nora.nerc.ac.uk/id/eprint/515196/ https://doi.org/10.1144/GSL.SP.1996.108.01.17 |
long_lat |
ENVELOPE(-59.800,-59.800,-62.438,-62.438) |
geographic |
Weddell Sea Indian Weddell Mid-Atlantic Ridge Orion |
geographic_facet |
Weddell Sea Indian Weddell Mid-Atlantic Ridge Orion |
genre |
Andenes Antarc* Antarctica Weddell Sea |
genre_facet |
Andenes Antarc* Antarctica Weddell Sea |
op_relation |
Livermore, R. A.; Hunter, R. J. 1996 Mesozoic seafloor spreading in the southern Weddell Sea. In: Storey, B.C.; King, E.C. orcid:0000-0003-3793-3915 Livermore, R.A., (eds.) Weddell Sea tectonics and Gondwana break-up. London, Geological Society of London, 227-241. (Geological Society special publication, 108, 108). |
op_doi |
https://doi.org/10.1144/GSL.SP.1996.108.01.17 |
container_title |
Geological Society, London, Special Publications |
container_volume |
108 |
container_issue |
1 |
container_start_page |
227 |
op_container_end_page |
241 |
_version_ |
1766385144104484864 |