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Magnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetism

2014-11-26Journal article Open access
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dc.contributor.authorFont, Eric
dc.contributor.authorVeiga-Pires, C.
dc.contributor.authorPozo, Manuel
dc.contributor.authorCarvallo, Claire
dc.contributor.authorDe Siqueira Neto, António Carlos
dc.contributor.authorCamps, Pierre
dc.contributor.authorFabre, Sébastien
dc.contributor.authorMirão, José
dc.date.accessioned2014-12-03T15:26:23Z
dc.date.available2014-12-03T15:26:23Z
dc.date.issued2014-11-26
dc.date.updated2014-11-25T23:23:44Z
dc.description.abstractEnvironmental 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.por
dc.description.versioninfo:eu-repo/semantics/acceptedVersion
dc.identifier.citationFont, 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.por
dc.identifier.doi10.1002/2014JB011381
dc.identifier.issn2169-9313
dc.identifier.otherAUT: CVP01371
dc.identifier.urihttp://hdl.handle.net/10400.1/5664
dc.language.isoengpor
dc.peerreviewedyespor
dc.publisherAmerican Geophysical Unionpor
dc.relation.publisherversionhttp://onlinelibrary.wiley.com/doi/10.1002/2014JB011381/pdfpor
dc.subjectSpeleothemspor
dc.subjectBioweatheringpor
dc.subjectIron oxides in speleothempor
dc.titleMagnetic fingerprint of southern Portuguese speleothems and implications for paleo- and environmental magnetismpor
dc.typejournal article
dspace.entity.typePublication
oaire.citation.endPage28por
oaire.citation.startPage1por
oaire.citation.titleJournal of Geophysical Research. Solid Earthpor
person.familyNameVeiga-Pires
person.givenNameCristina
person.identifier113325
person.identifier.ciencia-id4A1F-CEDA-E66C
person.identifier.orcid0000-0002-9323-0723
person.identifier.ridB-5144-2008
person.identifier.scopus-author-id7801372905
rcaap.rightsopenAccesspor
rcaap.typearticlepor
relation.isAuthorOfPublicationd1541efa-0eaa-48dc-aea3-a1e64aa0065a
relation.isAuthorOfPublication.latestForDiscoveryd1541efa-0eaa-48dc-aea3-a1e64aa0065a

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