Palaeomagnetism of the Cretaceous Pirgua Subgroup (Argentina) and the age of the opening of the South Atlantic

Palaeomagnetic data for the Cretaceous Pirgua Subgroup from 14 different time units of basalts and red beds exposed in the north‐western part of Argentina (25° 45′ S 65° 50′ W) are given. After cleaning all the units show normally polarized magnetic remanence and yield a palaeomagnetic pole at 222°...

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Publicado: 1977
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00168009_v51_n1_p47_Valencio
http://hdl.handle.net/20.500.12110/paper_00168009_v51_n1_p47_Valencio
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling paper:paper_00168009_v51_n1_p47_Valencio2023-06-08T14:38:55Z Palaeomagnetism of the Cretaceous Pirgua Subgroup (Argentina) and the age of the opening of the South Atlantic Palaeomagnetic data for the Cretaceous Pirgua Subgroup from 14 different time units of basalts and red beds exposed in the north‐western part of Argentina (25° 45′ S 65° 50′ W) are given. After cleaning all the units show normally polarized magnetic remanence and yield a palaeomagnetic pole at 222° E 85° S (dΦ= 7°, dχ= 10°). The palaeomagnetic poles for the Pirgua Subgroup (Early to Late Cretaceous, 114–77 Myr), for the Vulcanitas Cerro Rumipalla Formation (Early Cretaceous,<118 Myr, Valencio & Vilas) and for the Poços de Caldas Alkaline Complex (Late Cretaceous, 75 Myr, Opdyke & McDonald) form a ‘time‐group’ reflecting a quasi‐static interval (mean pole position, 220° E 85° S, α95= 6°) and define a westward polar wander in Early Cretaceous time for South America. Comparison of the positions of the Cretaceous palaeomagnetic poles for South America with those for Africa suggests that the separation of South America and Africa occurred in late Early Cretaceous time, after the effusion of the Serra Geral basalts. The K‐Ar ages of basalts of the Pirgua Subgroup (114 ± 5; 98 ± 1 and 77 ± 1 Myr) fix points of reference for three periods of normal polarity within the Cretaceous palaeomagnetic polarity column. Copyright © 1977, Wiley Blackwell. All rights reserved 1977 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00168009_v51_n1_p47_Valencio http://hdl.handle.net/20.500.12110/paper_00168009_v51_n1_p47_Valencio
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
description Palaeomagnetic data for the Cretaceous Pirgua Subgroup from 14 different time units of basalts and red beds exposed in the north‐western part of Argentina (25° 45′ S 65° 50′ W) are given. After cleaning all the units show normally polarized magnetic remanence and yield a palaeomagnetic pole at 222° E 85° S (dΦ= 7°, dχ= 10°). The palaeomagnetic poles for the Pirgua Subgroup (Early to Late Cretaceous, 114–77 Myr), for the Vulcanitas Cerro Rumipalla Formation (Early Cretaceous,<118 Myr, Valencio & Vilas) and for the Poços de Caldas Alkaline Complex (Late Cretaceous, 75 Myr, Opdyke & McDonald) form a ‘time‐group’ reflecting a quasi‐static interval (mean pole position, 220° E 85° S, α95= 6°) and define a westward polar wander in Early Cretaceous time for South America. Comparison of the positions of the Cretaceous palaeomagnetic poles for South America with those for Africa suggests that the separation of South America and Africa occurred in late Early Cretaceous time, after the effusion of the Serra Geral basalts. The K‐Ar ages of basalts of the Pirgua Subgroup (114 ± 5; 98 ± 1 and 77 ± 1 Myr) fix points of reference for three periods of normal polarity within the Cretaceous palaeomagnetic polarity column. Copyright © 1977, Wiley Blackwell. All rights reserved
title Palaeomagnetism of the Cretaceous Pirgua Subgroup (Argentina) and the age of the opening of the South Atlantic
spellingShingle Palaeomagnetism of the Cretaceous Pirgua Subgroup (Argentina) and the age of the opening of the South Atlantic
title_short Palaeomagnetism of the Cretaceous Pirgua Subgroup (Argentina) and the age of the opening of the South Atlantic
title_full Palaeomagnetism of the Cretaceous Pirgua Subgroup (Argentina) and the age of the opening of the South Atlantic
title_fullStr Palaeomagnetism of the Cretaceous Pirgua Subgroup (Argentina) and the age of the opening of the South Atlantic
title_full_unstemmed Palaeomagnetism of the Cretaceous Pirgua Subgroup (Argentina) and the age of the opening of the South Atlantic
title_sort palaeomagnetism of the cretaceous pirgua subgroup (argentina) and the age of the opening of the south atlantic
publishDate 1977
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00168009_v51_n1_p47_Valencio
http://hdl.handle.net/20.500.12110/paper_00168009_v51_n1_p47_Valencio
_version_ 1768542488167972864

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