Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism
Autor(a) principal: | |
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Data de Publicação: | 2014 |
Outros Autores: | , , , , , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/10400.1/5664 |
Resumo: | Environmental magnetism of speleothems is still in its early stage of development. Here we report on our investigation of the environmental and paleomagnetic information that has been recorded in speleothems, and what are the factors that control its preservation and reliability. To address these issues, we used a multidisciplinary approach, including rock magnetism, petrography, scanning electron microscopy, stable carbon and oxygen isotope compositions, and major and trace element concentrations. We applied this to a set of samples from different stages of speleothem evolution: present-day dripwater (glass plates), a weathered stalactite, a fresh stalagmite, cave sediments, and terra rossa soils. These samples come from the Penico and Excentricas caves, located in two distinct aquifers of the Algarve region, South Portugal. Our results show that the main magnetic carriers of the speleothems under study are primary (detrital) and consist of maghemite (and magnetite?). Similarities in coercivity and temperature dependence of the studied set of samples suggest that iron oxides are inherited from the terra rossa soils that cap the cave and were transported to the speleothems by dripwater. Hence, they represent a regional environmental signature. Interestingly, a stable and probably detrital remanent magnetization could be isolated in the fresh stalagmite, whereas the weathered stalactite yielded chaotic magnetic directions and very low remanent intensities. We propose that these low intensities can be the result from(i) different remanence acquisition mechanisms between stalagmite and stalactite and/or (ii) iron dissolution by fungal activity. We also suggest that magnetic properties and color and the content in detrital elements in the fresh speleothem inform about environmental processes acting on the interface of rock (soil)-atmosphere, while oxygen isotope composition and alkaline-earth element concentrations inform about calcite-water interaction processes. These results provide a better understanding of how environmental information is recorded in speleothems and what the factors are that control the reliability of the paleomagnetic and paleo-environmental signal. |
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Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetismSpeleothemsBioweatheringIron oxides in speleothemEnvironmental magnetism of speleothems is still in its early stage of development. Here we report on our investigation of the environmental and paleomagnetic information that has been recorded in speleothems, and what are the factors that control its preservation and reliability. To address these issues, we used a multidisciplinary approach, including rock magnetism, petrography, scanning electron microscopy, stable carbon and oxygen isotope compositions, and major and trace element concentrations. We applied this to a set of samples from different stages of speleothem evolution: present-day dripwater (glass plates), a weathered stalactite, a fresh stalagmite, cave sediments, and terra rossa soils. These samples come from the Penico and Excentricas caves, located in two distinct aquifers of the Algarve region, South Portugal. Our results show that the main magnetic carriers of the speleothems under study are primary (detrital) and consist of maghemite (and magnetite?). Similarities in coercivity and temperature dependence of the studied set of samples suggest that iron oxides are inherited from the terra rossa soils that cap the cave and were transported to the speleothems by dripwater. Hence, they represent a regional environmental signature. Interestingly, a stable and probably detrital remanent magnetization could be isolated in the fresh stalagmite, whereas the weathered stalactite yielded chaotic magnetic directions and very low remanent intensities. We propose that these low intensities can be the result from(i) different remanence acquisition mechanisms between stalagmite and stalactite and/or (ii) iron dissolution by fungal activity. We also suggest that magnetic properties and color and the content in detrital elements in the fresh speleothem inform about environmental processes acting on the interface of rock (soil)-atmosphere, while oxygen isotope composition and alkaline-earth element concentrations inform about calcite-water interaction processes. These results provide a better understanding of how environmental information is recorded in speleothems and what the factors are that control the reliability of the paleomagnetic and paleo-environmental signal.American Geophysical UnionSapientiaFont, EricVeiga-Pires, C.Pozo, ManuelCarvallo, ClaireDe Siqueira Neto, António CarlosCamps, PierreFabre, SébastienMirão, José2014-12-03T15:26:23Z2014-11-262014-11-25T23:23:44Z2014-11-26T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articleapplication/pdfhttp://hdl.handle.net/10400.1/5664engFont, Eric; Veiga-Pires, Cristina; Pozo, Manuel; Carvallo, Claire; de Siqueira Neto, António Carlos; Camps, Pierre; Fabre, Sébastien; Mirão, José. Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism, Journal of Geophysical Research: Solid Earth, na, n/a-n/a, 2014.2169-9313AUT: CVP0137110.1002/2014JB011381info:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2023-07-24T10:16:54Zoai:sapientia.ualg.pt:10400.1/5664Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T19:58:39.824572Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism |
title |
Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism |
spellingShingle |
Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism Font, Eric Speleothems Bioweathering Iron oxides in speleothem |
title_short |
Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism |
title_full |
Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism |
title_fullStr |
Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism |
title_full_unstemmed |
Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism |
title_sort |
Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism |
author |
Font, Eric |
author_facet |
Font, Eric Veiga-Pires, C. Pozo, Manuel Carvallo, Claire De Siqueira Neto, António Carlos Camps, Pierre Fabre, Sébastien Mirão, José |
author_role |
author |
author2 |
Veiga-Pires, C. Pozo, Manuel Carvallo, Claire De Siqueira Neto, António Carlos Camps, Pierre Fabre, Sébastien Mirão, José |
author2_role |
author author author author author author author |
dc.contributor.none.fl_str_mv |
Sapientia |
dc.contributor.author.fl_str_mv |
Font, Eric Veiga-Pires, C. Pozo, Manuel Carvallo, Claire De Siqueira Neto, António Carlos Camps, Pierre Fabre, Sébastien Mirão, José |
dc.subject.por.fl_str_mv |
Speleothems Bioweathering Iron oxides in speleothem |
topic |
Speleothems Bioweathering Iron oxides in speleothem |
description |
Environmental magnetism of speleothems is still in its early stage of development. Here we report on our investigation of the environmental and paleomagnetic information that has been recorded in speleothems, and what are the factors that control its preservation and reliability. To address these issues, we used a multidisciplinary approach, including rock magnetism, petrography, scanning electron microscopy, stable carbon and oxygen isotope compositions, and major and trace element concentrations. We applied this to a set of samples from different stages of speleothem evolution: present-day dripwater (glass plates), a weathered stalactite, a fresh stalagmite, cave sediments, and terra rossa soils. These samples come from the Penico and Excentricas caves, located in two distinct aquifers of the Algarve region, South Portugal. Our results show that the main magnetic carriers of the speleothems under study are primary (detrital) and consist of maghemite (and magnetite?). Similarities in coercivity and temperature dependence of the studied set of samples suggest that iron oxides are inherited from the terra rossa soils that cap the cave and were transported to the speleothems by dripwater. Hence, they represent a regional environmental signature. Interestingly, a stable and probably detrital remanent magnetization could be isolated in the fresh stalagmite, whereas the weathered stalactite yielded chaotic magnetic directions and very low remanent intensities. We propose that these low intensities can be the result from(i) different remanence acquisition mechanisms between stalagmite and stalactite and/or (ii) iron dissolution by fungal activity. We also suggest that magnetic properties and color and the content in detrital elements in the fresh speleothem inform about environmental processes acting on the interface of rock (soil)-atmosphere, while oxygen isotope composition and alkaline-earth element concentrations inform about calcite-water interaction processes. These results provide a better understanding of how environmental information is recorded in speleothems and what the factors are that control the reliability of the paleomagnetic and paleo-environmental signal. |
publishDate |
2014 |
dc.date.none.fl_str_mv |
2014-12-03T15:26:23Z 2014-11-26 2014-11-25T23:23:44Z 2014-11-26T00:00:00Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10400.1/5664 |
url |
http://hdl.handle.net/10400.1/5664 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
Font, Eric; Veiga-Pires, Cristina; Pozo, Manuel; Carvallo, Claire; de Siqueira Neto, António Carlos; Camps, Pierre; Fabre, Sébastien; Mirão, José. Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism, Journal of Geophysical Research: Solid Earth, na, n/a-n/a, 2014. 2169-9313 AUT: CVP01371 10.1002/2014JB011381 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf |
dc.publisher.none.fl_str_mv |
American Geophysical Union |
publisher.none.fl_str_mv |
American Geophysical Union |
dc.source.none.fl_str_mv |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
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