Resultados paleomagnéticos y características magnéticas de la secuencia Neógena de coladas basálticas de La Rajita (La Gomera, Islas Canarias)

Abstract

Rock-magnetic, microscopy and paleomagnetic results from the Neogene La Rajita sequence (11 lava flows and a dyke) from La Gomera (Canary Islands, Spain) are presented. Thermomagnetic curves allow distinguishing three types of samples: (i) Magnetite as the only carrier of remanence (type H); (ii) a main phase with TC = 450ºC and magnetite (type M); (iii) a phase with TC =120 to 200ºC and a phase with TC = 400ºC (type L). Hysteresis parameters suggest pseudo single-domain behaviour on most samples. Paleomagnetic experiments reveal only a single paleomagnetic component with reverse- polarity direction. The mean direction of the whole sequence is D = 188.2º, I = -35.4º (k=47; α95 = 6.4º) and the calculated paleomagnetic pole yields a longitude λ =150.7º and a latitude Φ = 78.8º (k=59; A95 = 5.7º). Secular variation is analysed through the scatter of virtual geomagnetic poles (VGP). VGP angular scatter SB = 5.9º, with confidence limits Sup=8.0º and Slow= 4.6º. This scatter is clearly smaller than the average for this latitude obtained for the last 5 My. The studied lava flows were probably emitted in a relatively short time interval.