A paleomagnetic and rock-magnetic study of a neogene lava flow sequence in La Gomera (Canary Islands, Spain)

Abstract

We present rock-magnetic and paleomagnetic results obtained on samples belonging to a Neogene sequence of 11 successive lava flows and a dyke from La Gomera (Canary Islands, Spain). Analysis of thermomagnetic curves allows to distinguish three types of samples: (i) Type H samples with low-Ti titanomagnetite as the only carrier of remanence; (ii) type M samples with a main intermediate Curie-temperature phase (T C = 450C) and low-Ti titanomagnetite; (iii) type L curves with a low Curietemperature phase (T C = 120 to 200C) and an intermediate Curie-temperature phase (T C = 400C). Analysis of hysteresis parameters suggests that the grain size of most studied samples corresponds to pseudo single-domain particles, which can be also interpreted as a mixture of single-domain and multi-domain particles. Paleomagnetic experiments reveal only a single paleomagnetic component. Characteristic remanence of all studied lava flows and the dyke shows reverse polarity. The mean direction of the whole sequence is D = 188.2, I = 35.4 (k = 46.9;  95 = 6.4º) and the calculated paleomagnetic pole yields a longitude  = 150.7 and a latitude  = 78.8 (k = 59.4; A 95 = 5.7). Secular variation is analysed through the scatter of virtual geomagnetic poles (VGP). A VGP angular scatter S B = 5.9 with an upper confidence limit S up = 8.0 and a lower confidence limit S low = 4.6 are obtained. This scatter is clearly smaller than the average for this latitude obtained for the last 5 Ma. The studied lava flows were probably emitted in a relatively short time interval. K e y w o r d s : secular variation, VGP angular scatter, thermomagnetic curves, hysteresis parameters A. Caccavari et al. 548 Stud. Geophys. Geod., 54 (2010)

An integrated palaeomagnetic, palaeointensity and 40Ar/39Ar investigation on a Miocene polarity transition recorded in a lava sequence in la Gomera, Canary Islands

“…Although many palaeomagnetic studies have been performed in the Canary Islands (e.g. Carracedo & Soler 1995;Valet et al 1999;Tauxe et al 2000;Leonhardt et al 2002;Singer et al 2002;Guillou et al , 2013, palaeomagnetic data from La Gomera are still sparse (Abdel Monen et al 1971;Glen et al 2003;Caccavari et al 2010). This study is focused on a 9.7 Ma (Glen et al 2003) lava sequence located in La Gomera Island that belongs to the Canarian archipelago.…”