Lightning remagnetization of the Vredefort impact crater: No evidence for impact-generated magnetic fields
The Vredefort impact crater in South Africa is one of the oldest and largest craters on Earth, making it a unique analog for planetary basins. Intense and randomly oriented remanent magnetization observed in surface samples at Vredefort has been attributed to impact-generated magnetic fields. This p...
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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American Geophysical Union (AGU)
2012
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| Online Access: | http://hdl.handle.net/1721.1/74217 https://orcid.org/0000-0003-3113-3415 |
| _version_ | 1826204228710825984 |
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| author | Carporzen, Laurent Weiss, Benjamin P. Gilder, Stuart A. Pommier, Anne Hart, Rodger J. |
| author2 | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences |
| author_facet | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Carporzen, Laurent Weiss, Benjamin P. Gilder, Stuart A. Pommier, Anne Hart, Rodger J. |
| author_sort | Carporzen, Laurent |
| collection | MIT |
| description | The Vredefort impact crater in South Africa is one of the oldest and largest craters on Earth, making it a unique analog for planetary basins. Intense and randomly oriented remanent magnetization observed in surface samples at Vredefort has been attributed to impact-generated magnetic fields. This possibility has major implications for extraterrestrial paleomagnetism since impact-generated fields have been proposed as a key alternative to the dynamo hypothesis for magnetization on the Moon and asteroids. Furthermore, the presence of single-domain magnetite found along shock-generated planar deformation features in Vredefort granites has been widely attributed to the 2.02 Ga impact event. An alternative hypothesis is that the unusual magnetization and/or rock magnetic properties of Vredefort rocks are the products of recent lightning strikes. Lightning and impact-generated fields can be distinguished by measuring samples collected from below the present surface. Here we present a paleomagnetic and rock magnetic study of samples from two 10 m deep vertical boreholes. We show that the magnetization at depth is consistent with a thermoremanent magnetization acquired in the local geomagnetic field following the impact, while random, intense magnetization and some of the unusual rock magnetic properties observed in surface rocks are superficial phenomena produced by lightning. Because Vredefort is the only terrestrial crater that has been proposed to contain records of impact-generated fields, this removes a key piece of evidence in support of the hypothesis that paleomagnetism of the Moon and other extraterrestrial bodies is the product of impacts rather than past core dynamos. |
| first_indexed | 2024-09-23T12:50:57Z |
| format | Article |
| id | mit-1721.1/74217 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T12:50:57Z |
| publishDate | 2012 |
| publisher | American Geophysical Union (AGU) |
| record_format | dspace |
| spelling | mit-1721.1/742172022-09-28T10:25:03Z Lightning remagnetization of the Vredefort impact crater: No evidence for impact-generated magnetic fields Carporzen, Laurent Weiss, Benjamin P. Gilder, Stuart A. Pommier, Anne Hart, Rodger J. Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Carporzen, Laurent Weiss, Benjamin P. Pommier, Anne The Vredefort impact crater in South Africa is one of the oldest and largest craters on Earth, making it a unique analog for planetary basins. Intense and randomly oriented remanent magnetization observed in surface samples at Vredefort has been attributed to impact-generated magnetic fields. This possibility has major implications for extraterrestrial paleomagnetism since impact-generated fields have been proposed as a key alternative to the dynamo hypothesis for magnetization on the Moon and asteroids. Furthermore, the presence of single-domain magnetite found along shock-generated planar deformation features in Vredefort granites has been widely attributed to the 2.02 Ga impact event. An alternative hypothesis is that the unusual magnetization and/or rock magnetic properties of Vredefort rocks are the products of recent lightning strikes. Lightning and impact-generated fields can be distinguished by measuring samples collected from below the present surface. Here we present a paleomagnetic and rock magnetic study of samples from two 10 m deep vertical boreholes. We show that the magnetization at depth is consistent with a thermoremanent magnetization acquired in the local geomagnetic field following the impact, while random, intense magnetization and some of the unusual rock magnetic properties observed in surface rocks are superficial phenomena produced by lightning. Because Vredefort is the only terrestrial crater that has been proposed to contain records of impact-generated fields, this removes a key piece of evidence in support of the hypothesis that paleomagnetism of the Moon and other extraterrestrial bodies is the product of impacts rather than past core dynamos. National Science Foundation (U.S.) (Grant EAR-0810244) 2012-10-23T17:46:22Z 2012-10-23T17:46:22Z 2012-01 2011-08 Article http://purl.org/eprint/type/JournalArticle 0148-0227 http://hdl.handle.net/1721.1/74217 Carporzen, Laurent et al. “Lightning Remagnetization of the Vredefort Impact Crater: No Evidence for Impact-generated Magnetic Fields.” Journal of Geophysical Research 117.E1 (2012). ©2012 American Geophysical Union https://orcid.org/0000-0003-3113-3415 en_US http://dx.doi.org/ 10.1029/2011je003919 Journal of Geophysical Research Planets Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Geophysical Union (AGU) MIT web domain |
| spellingShingle | Carporzen, Laurent Weiss, Benjamin P. Gilder, Stuart A. Pommier, Anne Hart, Rodger J. Lightning remagnetization of the Vredefort impact crater: No evidence for impact-generated magnetic fields |
| title | Lightning remagnetization of the Vredefort impact crater: No evidence for impact-generated magnetic fields |
| title_full | Lightning remagnetization of the Vredefort impact crater: No evidence for impact-generated magnetic fields |
| title_fullStr | Lightning remagnetization of the Vredefort impact crater: No evidence for impact-generated magnetic fields |
| title_full_unstemmed | Lightning remagnetization of the Vredefort impact crater: No evidence for impact-generated magnetic fields |
| title_short | Lightning remagnetization of the Vredefort impact crater: No evidence for impact-generated magnetic fields |
| title_sort | lightning remagnetization of the vredefort impact crater no evidence for impact generated magnetic fields |
| url | http://hdl.handle.net/1721.1/74217 https://orcid.org/0000-0003-3113-3415 |
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