Datación de lavas basáltica por 40 Ar/ 39 Ar y geología glacial de la región del lago Buenos Aires, provincia de Santa Cruz, Argentina
Lava flows ⁴⁰Ar/³⁹Ar analysis and glacial geology, Lago Buenos Aires, Santa Cruz Province. Eight basaltic lava flows and two erratic boulders in moraines east of the Andes near Lago Buenos Aires, Santa Cruz province, Argentina (46º30'-47º00' S; 70º30'-71º45' W) and one lava along...
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ftunivgeneve:oai:unige.ch:aou:unige:154345 2023-10-01T03:56:37+02:00 Datación de lavas basáltica por 40 Ar/ 39 Ar y geología glacial de la región del lago Buenos Aires, provincia de Santa Cruz, Argentina Ton-That, Thao Singer, Bradley Moerner, Nils-Axel Rabassa, Jorge 1999 https://archive-ouverte.unige.ch/unige:154345 spa spa https://archive-ouverte.unige.ch/unige:154345 unige:154345 info:eu-repo/semantics/openAccess ISSN: 1851-8249 Revista de la Asociación Geológica Argentina, vol. 54, no. 4 (1999) p. 333-352 info:eu-repo/classification/ddc/550 info:eu-repo/semantics/article Text Article scientifique info:eu-repo/semantics/publishedVersion 1999 ftunivgeneve 2023-09-07T08:05:06Z Lava flows ⁴⁰Ar/³⁹Ar analysis and glacial geology, Lago Buenos Aires, Santa Cruz Province. Eight basaltic lava flows and two erratic boulders in moraines east of the Andes near Lago Buenos Aires, Santa Cruz province, Argentina (46º30'-47º00' S; 70º30'-71º45' W) and one lava along the Río Gallegos valley (51º50' S, 70º40' W) were analysed using the ⁴⁰Ar/³⁹Ar incremental-heating technique. The ⁴⁰Ar/³⁹Ar results indicate that these samples include: (1) earliest Miocene (24.2 Ma) valley-filling lava flows, (2) late-Miocene (10.0 Ma, 7.4 Ma, and 5.0 Ma) meseta-capping lava flows, the latter two interbedded with glacial till, (3) Pleistocene lavas erupted at 1.17 Ma, 1.02 Ma, 0.76 Ma and interbedded with glacial tills, (4) a very young lava that proved difficult to date, and (5) basaltic erratic boulders that erupted at 117.5 Ma and 16.8 Ma, but which were incorporated into moraines during the late Pleistocene. These age determinations provide new constraints on the timing of Miocene and Pleistocene glacial advances of the southern Andean ice cap. The oldest Cenozoic till recognised in South America underlies a lava capping Meseta de Lago Buenos Aires whose ⁴⁰Ar/³⁹Ar isochron age of 5.04 ± 0.04 Ma is older than a previous K-Ar date by >400 k.y. Glacial till , together with outwash gravels and erratic boulders, that correspond to the greatest extent of ice in Patagonia (the so-called "Greatest Patagonian Glaciation", or GPG) are underlain by a lava dated at 1.168 ± 0.007 Ma and overlain by a lava dated at 1.016 ± 0.005 Ma. Thus the GPG occurred sometime between oxygen isotope stages 30-34. At Lago Buenos Aires, the deposition of at least twelve moraines since the GPG, including one overlain by lava dated at 0.760 ± 0.007 Ma, are consistent, in general terms, with the number and timing of glacial advances predicted by the astronomical time scale based on global marine oxygen isotope stages. Article in Journal/Newspaper Ice cap Université de Genève: Archive ouverte UNIGE Argentina Gallegos ENVELOPE(-67.150,-67.150,-68.133,-68.133) Patagonia |
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Open Polar |
collection |
Université de Genève: Archive ouverte UNIGE |
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ftunivgeneve |
language |
Spanish |
topic |
info:eu-repo/classification/ddc/550 |
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info:eu-repo/classification/ddc/550 Ton-That, Thao Singer, Bradley Moerner, Nils-Axel Rabassa, Jorge Datación de lavas basáltica por 40 Ar/ 39 Ar y geología glacial de la región del lago Buenos Aires, provincia de Santa Cruz, Argentina |
topic_facet |
info:eu-repo/classification/ddc/550 |
description |
Lava flows ⁴⁰Ar/³⁹Ar analysis and glacial geology, Lago Buenos Aires, Santa Cruz Province. Eight basaltic lava flows and two erratic boulders in moraines east of the Andes near Lago Buenos Aires, Santa Cruz province, Argentina (46º30'-47º00' S; 70º30'-71º45' W) and one lava along the Río Gallegos valley (51º50' S, 70º40' W) were analysed using the ⁴⁰Ar/³⁹Ar incremental-heating technique. The ⁴⁰Ar/³⁹Ar results indicate that these samples include: (1) earliest Miocene (24.2 Ma) valley-filling lava flows, (2) late-Miocene (10.0 Ma, 7.4 Ma, and 5.0 Ma) meseta-capping lava flows, the latter two interbedded with glacial till, (3) Pleistocene lavas erupted at 1.17 Ma, 1.02 Ma, 0.76 Ma and interbedded with glacial tills, (4) a very young lava that proved difficult to date, and (5) basaltic erratic boulders that erupted at 117.5 Ma and 16.8 Ma, but which were incorporated into moraines during the late Pleistocene. These age determinations provide new constraints on the timing of Miocene and Pleistocene glacial advances of the southern Andean ice cap. The oldest Cenozoic till recognised in South America underlies a lava capping Meseta de Lago Buenos Aires whose ⁴⁰Ar/³⁹Ar isochron age of 5.04 ± 0.04 Ma is older than a previous K-Ar date by >400 k.y. Glacial till , together with outwash gravels and erratic boulders, that correspond to the greatest extent of ice in Patagonia (the so-called "Greatest Patagonian Glaciation", or GPG) are underlain by a lava dated at 1.168 ± 0.007 Ma and overlain by a lava dated at 1.016 ± 0.005 Ma. Thus the GPG occurred sometime between oxygen isotope stages 30-34. At Lago Buenos Aires, the deposition of at least twelve moraines since the GPG, including one overlain by lava dated at 0.760 ± 0.007 Ma, are consistent, in general terms, with the number and timing of glacial advances predicted by the astronomical time scale based on global marine oxygen isotope stages. |
format |
Article in Journal/Newspaper |
author |
Ton-That, Thao Singer, Bradley Moerner, Nils-Axel Rabassa, Jorge |
author_facet |
Ton-That, Thao Singer, Bradley Moerner, Nils-Axel Rabassa, Jorge |
author_sort |
Ton-That, Thao |
title |
Datación de lavas basáltica por 40 Ar/ 39 Ar y geología glacial de la región del lago Buenos Aires, provincia de Santa Cruz, Argentina |
title_short |
Datación de lavas basáltica por 40 Ar/ 39 Ar y geología glacial de la región del lago Buenos Aires, provincia de Santa Cruz, Argentina |
title_full |
Datación de lavas basáltica por 40 Ar/ 39 Ar y geología glacial de la región del lago Buenos Aires, provincia de Santa Cruz, Argentina |
title_fullStr |
Datación de lavas basáltica por 40 Ar/ 39 Ar y geología glacial de la región del lago Buenos Aires, provincia de Santa Cruz, Argentina |
title_full_unstemmed |
Datación de lavas basáltica por 40 Ar/ 39 Ar y geología glacial de la región del lago Buenos Aires, provincia de Santa Cruz, Argentina |
title_sort |
datación de lavas basáltica por 40 ar/ 39 ar y geología glacial de la región del lago buenos aires, provincia de santa cruz, argentina |
publishDate |
1999 |
url |
https://archive-ouverte.unige.ch/unige:154345 |
long_lat |
ENVELOPE(-67.150,-67.150,-68.133,-68.133) |
geographic |
Argentina Gallegos Patagonia |
geographic_facet |
Argentina Gallegos Patagonia |
genre |
Ice cap |
genre_facet |
Ice cap |
op_source |
ISSN: 1851-8249 Revista de la Asociación Geológica Argentina, vol. 54, no. 4 (1999) p. 333-352 |
op_relation |
https://archive-ouverte.unige.ch/unige:154345 unige:154345 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1778526604321882112 |