K-Ar geochronology and palaeomagnetism of volcanic rocks in the Lesser Antilles island arc
K-Ar age determinations, mainly whole rock, with some corroboration from mineral separates, are presented for lava flows, domes, minor intrusives and blocks in tuffs from 95 localities in the Lesser Antilles. Together with the much smaller number of previously published data, these show a distinctio...
Published in: | Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences |
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crroyalsociety:10.1098/rsta.1979.0040 2024-06-23T07:55:17+00:00 K-Ar geochronology and palaeomagnetism of volcanic rocks in the Lesser Antilles island arc 1979 http://dx.doi.org/10.1098/rsta.1979.0040 https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.1979.0040 en eng The Royal Society https://royalsociety.org/journals/ethics-policies/data-sharing-mining/ Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences volume 291, issue 1383, page 485-528 ISSN 0080-4614 2054-0272 journal-article 1979 crroyalsociety https://doi.org/10.1098/rsta.1979.0040 2024-06-04T06:22:43Z K-Ar age determinations, mainly whole rock, with some corroboration from mineral separates, are presented for lava flows, domes, minor intrusives and blocks in tuffs from 95 localities in the Lesser Antilles. Together with the much smaller number of previously published data, these show a distinction between a range 38-10 million years (Ma) in the outer arc (Limestone Caribbees) and less than 7.7 Ma in the inner arc (Volcanic Caribbees). From southern Martinique southwards, the two arcs are superposed, and the whole range is fragmentarily represented. The observed age ranges in the outer and inner arcs fit between discontinuities in sea floor spreading in the North Atlantic at ca. 38 and ca. 9 Ma and a causal connection between spreading change and relocation of arc volcanicity is suggested. Palaeomagnetic directions at 108 localities in ten of the islands fall into normal ( N = 56, k = 13.8, D = 359°, I = + 22°, pole position 229° E, 89° N with drjr = 3°, d X = 6°) and reversed groups ( N = 41, k = 14.1, D = 178°, I = -22°, pole position 18° E, 88° S with d xjr = 3°, dx = 6°) plus six sites of intermediate polarity and five sites indeterminate. The mean dipole axis is within 2° of the present rotation axis and is likely to be identical with it with a probability of 99%. The data are generally in accord with the established geomagnetic polarity time scale, but there is some suggestion of a normal polarity event at ca. 1.18 Ma within the Matuyama Reversed Epoch. The palaeomagnetic data relate mainly to be past 10 Ma and suggest that within that time the Lesser Antilles have not changed their latitude or geographic orientation, and that the geomagnetic field has averaged that of a centred axial dipole. The few older palaeomagnetic data are consistent with these same conclusions (though with less certainty) back to ca. 20 Ma ago. There is no evidence for oroclinal bending of the arc since then. Article in Journal/Newspaper North Atlantic The Royal Society Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences 291 1383 485 528 |
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The Royal Society |
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crroyalsociety |
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English |
description |
K-Ar age determinations, mainly whole rock, with some corroboration from mineral separates, are presented for lava flows, domes, minor intrusives and blocks in tuffs from 95 localities in the Lesser Antilles. Together with the much smaller number of previously published data, these show a distinction between a range 38-10 million years (Ma) in the outer arc (Limestone Caribbees) and less than 7.7 Ma in the inner arc (Volcanic Caribbees). From southern Martinique southwards, the two arcs are superposed, and the whole range is fragmentarily represented. The observed age ranges in the outer and inner arcs fit between discontinuities in sea floor spreading in the North Atlantic at ca. 38 and ca. 9 Ma and a causal connection between spreading change and relocation of arc volcanicity is suggested. Palaeomagnetic directions at 108 localities in ten of the islands fall into normal ( N = 56, k = 13.8, D = 359°, I = + 22°, pole position 229° E, 89° N with drjr = 3°, d X = 6°) and reversed groups ( N = 41, k = 14.1, D = 178°, I = -22°, pole position 18° E, 88° S with d xjr = 3°, dx = 6°) plus six sites of intermediate polarity and five sites indeterminate. The mean dipole axis is within 2° of the present rotation axis and is likely to be identical with it with a probability of 99%. The data are generally in accord with the established geomagnetic polarity time scale, but there is some suggestion of a normal polarity event at ca. 1.18 Ma within the Matuyama Reversed Epoch. The palaeomagnetic data relate mainly to be past 10 Ma and suggest that within that time the Lesser Antilles have not changed their latitude or geographic orientation, and that the geomagnetic field has averaged that of a centred axial dipole. The few older palaeomagnetic data are consistent with these same conclusions (though with less certainty) back to ca. 20 Ma ago. There is no evidence for oroclinal bending of the arc since then. |
format |
Article in Journal/Newspaper |
title |
K-Ar geochronology and palaeomagnetism of volcanic rocks in the Lesser Antilles island arc |
spellingShingle |
K-Ar geochronology and palaeomagnetism of volcanic rocks in the Lesser Antilles island arc |
title_short |
K-Ar geochronology and palaeomagnetism of volcanic rocks in the Lesser Antilles island arc |
title_full |
K-Ar geochronology and palaeomagnetism of volcanic rocks in the Lesser Antilles island arc |
title_fullStr |
K-Ar geochronology and palaeomagnetism of volcanic rocks in the Lesser Antilles island arc |
title_full_unstemmed |
K-Ar geochronology and palaeomagnetism of volcanic rocks in the Lesser Antilles island arc |
title_sort |
k-ar geochronology and palaeomagnetism of volcanic rocks in the lesser antilles island arc |
publisher |
The Royal Society |
publishDate |
1979 |
url |
http://dx.doi.org/10.1098/rsta.1979.0040 https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.1979.0040 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences volume 291, issue 1383, page 485-528 ISSN 0080-4614 2054-0272 |
op_rights |
https://royalsociety.org/journals/ethics-policies/data-sharing-mining/ |
op_doi |
https://doi.org/10.1098/rsta.1979.0040 |
container_title |
Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences |
container_volume |
291 |
container_issue |
1383 |
container_start_page |
485 |
op_container_end_page |
528 |
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1802647809971716096 |