A Late-Quaternary full-vector geomagnetic record from El Golfo section, El Hierro, Canary Islands

Abstract

Regional full-vector palaeosecular variation (PSV) curves are essential to further our understanding of geodynamo operation. Such curves typically lack palaeointensity information (with palaeodirectional being much more common), particularly for periods before the Holocene. Notably low palaeointensity values have been reported for significant portions of the Late Quaternary. Here, we present full-vector palaeomagnetic from the El Golfo section on El Hierro (Canary Islands, Spain), spanning the age range between ∼120 and ∼450 ka, to substantiate these reported low palaeointensity values for the Canary Islands. We sampled 28 flows (mostly alkaline oceanic basalts of the shield building stage) along the Camino de Jinama, a few kilometres to the south of a section studied by Széréméta et al. for PSV. In line with their results, we observe an easterly declination deviation of ∼14° for the middle and lower part of our section. We relate this to undersampling of the complete PSV spectrum; rotation of El Hierro since ∼500 ka is deemed unlikely. Attempts to date the flows with the 40Ar/39Ar method on a multicollector instrument were unsuccessful due to the presence of copious amounts of methane in the extracted gases. Stratigraphic correlation to Széréméta et al.’s section lends support to ages (technically of very low quality) obtained for the sites reported on here. Importantly, we add palaeointensity information in the present study, for the first time on El Hierro. Three different palaeointensity protocols were utilized, IZZI-Thellier, multispecimen, and pseudo-Thellier, to provide an additional consistency check and to increase the success rate. After applying strict selection criteria, reliable palaeointensities could be obtained for 18 flows, a success rate of ∼64 per cent. If more than one protocol yielded results for the same flow, the obtained intensities were often within error of each other, testifying to their robustness. Flows with a common true mean direction tend to produce similar intensity values as well; this testifies to the presumed under-sampling of PSV within the section. Obtained palaeointensity values typically range between ∼20 and ∼35 μT, distinctly lower than the present-day field value of ∼39 μT and lower than the average intensity during the Brunhes Chron. The determinations are in line with other rather low values obtained elsewhere for this particular time span.