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

• Published in: Studia geophysica et geodaetica 2010-10, Vol.54 (4), p.547-560
• Main Authors: Caccavari, Anna, Calvo-Rathert, Manuel, Goguitchaichvili, Avto, Soler, Vicente, Reyes, Bertha Aguilar
• Format: Article
• Language: English
• Subjects: Atmospheric Sciences; Earth and Environmental Science; Earth Sciences; Geophysics/Geodesy; Islands; Latitude; Lava; Lava flows; Magnetic studies; Magnetism; Neogene; Paleoclimate science; Paleomagnetism; Rocks; Structural Geology
• ISSN: 0039-3169; 1573-1626
• DOI: 10.1007/s11200-010-0033-7

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 Curie-temperature 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; α 95 = 6.4°) and the calculated paleomagnetic pole yields a longitude λ= 150.7° and a latitude ϕ= 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.