Characterizing the Geomagnetic Field at High Southern Latitudes: Evidence From the Antarctic Peninsula
Due to a dearth of data from high-latitude paleomagnetic sites, it is not currently clear if the geocentric axial dipole (GAD) hypothesis accurately describes the long-term behavior of the geomagnetic field at high latitudes. Here we present new paleomagnetic and paleointensity data from the James R...
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ftdartmouthcoll:oai:digitalcommons.dartmouth.edu:staff_other-1001 2023-07-16T03:54:04+02:00 Characterizing the Geomagnetic Field at High Southern Latitudes: Evidence From the Antarctic Peninsula Biasi, Joseph Kirschvink, Joseph Fu, Roger 2021-01-01T08:00:00Z application/pdf https://digitalcommons.dartmouth.edu/staff_other/3 https://digitalcommons.dartmouth.edu/context/staff_other/article/1001/viewcontent/Biasi_2021_High_Southern_Latitudes.pdf unknown Dartmouth Digital Commons https://digitalcommons.dartmouth.edu/staff_other/3 https://digitalcommons.dartmouth.edu/context/staff_other/article/1001/viewcontent/Biasi_2021_High_Southern_Latitudes.pdf Other Staff Materials antarctica paleomagnetism volcano geomagnetic james ross reversal stratigraphy Geology Geophysics and Seismology Other Earth Sciences Volcanology text 2021 ftdartmouthcoll 2023-06-28T10:42:19Z Due to a dearth of data from high-latitude paleomagnetic sites, it is not currently clear if the geocentric axial dipole (GAD) hypothesis accurately describes the long-term behavior of the geomagnetic field at high latitudes. Here we present new paleomagnetic and paleointensity data from the James Ross Island (JRI) volcanic group, located on the Antarctic Peninsula. This data set addresses a notable lack of data from the 60°–70°S latitude bin and includes 251 samples from 31 sites, spanning 0.99–6.8 Ma in age. We also include positive fold, conglomerate, and baked contact tests. Paleointensity data from three methods (Thellier- Thellier, pseudo-Thellier, and Tsunakawa-Shaw) were collected from all sites. The Thellier-Thellier method had low yields and produced unreliable data, likely due to sample alteration during heating. Results from the Tsunakawa-Shaw and pseudo-Thellier methods were more consistent, and we found a bimodal distribution of paleointensity estimates. Most sites yielded either <15 μT or >40 μT, which together span a range of estimates from long-term geomagnetic field models, but do not favor any model in particular. Alternating-field demagnetization of these samples, when combined with preexisting data, yields a revised paleomagnetic pole of −87.5°, 025°, α95 = 3.6° for the Antarctic Peninsula over the last ∼5 Ma, which suggests that the current data set is sufficiently large to “average out” secular variation. Finally, the C2r/C2n transition was probably found at a site on JRI, and further geochronological and paleomagnetic study of these units could refine the age of this reversal. Text Antarc* Antarctic Antarctic Peninsula Antarctica James Ross Island Ross Island Dartmouth Digital Commons (Dartmouth College) Antarctic Antarctic Peninsula Ross Island The Antarctic |
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Dartmouth Digital Commons (Dartmouth College) |
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antarctica paleomagnetism volcano geomagnetic james ross reversal stratigraphy Geology Geophysics and Seismology Other Earth Sciences Volcanology |
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antarctica paleomagnetism volcano geomagnetic james ross reversal stratigraphy Geology Geophysics and Seismology Other Earth Sciences Volcanology Biasi, Joseph Kirschvink, Joseph Fu, Roger Characterizing the Geomagnetic Field at High Southern Latitudes: Evidence From the Antarctic Peninsula |
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antarctica paleomagnetism volcano geomagnetic james ross reversal stratigraphy Geology Geophysics and Seismology Other Earth Sciences Volcanology |
description |
Due to a dearth of data from high-latitude paleomagnetic sites, it is not currently clear if the geocentric axial dipole (GAD) hypothesis accurately describes the long-term behavior of the geomagnetic field at high latitudes. Here we present new paleomagnetic and paleointensity data from the James Ross Island (JRI) volcanic group, located on the Antarctic Peninsula. This data set addresses a notable lack of data from the 60°–70°S latitude bin and includes 251 samples from 31 sites, spanning 0.99–6.8 Ma in age. We also include positive fold, conglomerate, and baked contact tests. Paleointensity data from three methods (Thellier- Thellier, pseudo-Thellier, and Tsunakawa-Shaw) were collected from all sites. The Thellier-Thellier method had low yields and produced unreliable data, likely due to sample alteration during heating. Results from the Tsunakawa-Shaw and pseudo-Thellier methods were more consistent, and we found a bimodal distribution of paleointensity estimates. Most sites yielded either <15 μT or >40 μT, which together span a range of estimates from long-term geomagnetic field models, but do not favor any model in particular. Alternating-field demagnetization of these samples, when combined with preexisting data, yields a revised paleomagnetic pole of −87.5°, 025°, α95 = 3.6° for the Antarctic Peninsula over the last ∼5 Ma, which suggests that the current data set is sufficiently large to “average out” secular variation. Finally, the C2r/C2n transition was probably found at a site on JRI, and further geochronological and paleomagnetic study of these units could refine the age of this reversal. |
format |
Text |
author |
Biasi, Joseph Kirschvink, Joseph Fu, Roger |
author_facet |
Biasi, Joseph Kirschvink, Joseph Fu, Roger |
author_sort |
Biasi, Joseph |
title |
Characterizing the Geomagnetic Field at High Southern Latitudes: Evidence From the Antarctic Peninsula |
title_short |
Characterizing the Geomagnetic Field at High Southern Latitudes: Evidence From the Antarctic Peninsula |
title_full |
Characterizing the Geomagnetic Field at High Southern Latitudes: Evidence From the Antarctic Peninsula |
title_fullStr |
Characterizing the Geomagnetic Field at High Southern Latitudes: Evidence From the Antarctic Peninsula |
title_full_unstemmed |
Characterizing the Geomagnetic Field at High Southern Latitudes: Evidence From the Antarctic Peninsula |
title_sort |
characterizing the geomagnetic field at high southern latitudes: evidence from the antarctic peninsula |
publisher |
Dartmouth Digital Commons |
publishDate |
2021 |
url |
https://digitalcommons.dartmouth.edu/staff_other/3 https://digitalcommons.dartmouth.edu/context/staff_other/article/1001/viewcontent/Biasi_2021_High_Southern_Latitudes.pdf |
geographic |
Antarctic Antarctic Peninsula Ross Island The Antarctic |
geographic_facet |
Antarctic Antarctic Peninsula Ross Island The Antarctic |
genre |
Antarc* Antarctic Antarctic Peninsula Antarctica James Ross Island Ross Island |
genre_facet |
Antarc* Antarctic Antarctic Peninsula Antarctica James Ross Island Ross Island |
op_source |
Other Staff Materials |
op_relation |
https://digitalcommons.dartmouth.edu/staff_other/3 https://digitalcommons.dartmouth.edu/context/staff_other/article/1001/viewcontent/Biasi_2021_High_Southern_Latitudes.pdf |
_version_ |
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