Comparación de dos métodos de determinación de la paleointensidad absoluta en coladas miocenas, pleistocenas e históricas de Lanzarote (Islas Canarias, España)

Abstract

A paleomagnetic, rock-magnetic and paleointensity study has been carried out on 16 Miocene, Pleistoceneand historical basaltic lava flows from Lanzarote (Canary Islands, Spain) with two main goals: (i) tocompare paleointensity results obtained with two different techniques (Thellier-type and multispecimen)and (ii) to obtain new paleointensity data. Rock-magnetic experiments on selected samples from eachsite were carried out to find out the carriers of remanence and to determine their thermal stability andgrain size. Paleomagnetic analysis generally showed a single component although in one site no consistentresults could be obtained; so that a characteristic component could be determined in 15 flows, all displayingnormal-polarity. Thellier-type paleointensity determinations were performed with the Coe (1967) methodbetween room temperature and 581° C on small specimens. After heating, samples were left cooling downnaturally during several hours. Multispecimen paleointensity determinations were carried out using themethod of Dekkers and Böhnel (2006). A set of eight experiments was performed at a temperature of 450° Cusing laboratory fields from 10 to 80 μT, with increments of 10 μT. A very good agreement between resultsobtained with both methods was observed in five sites. However an extreme discrepancy was observed intwo cases (LZ9 and TM1).