Earth’s Magnetic Field record from the Middle to Upper Pleistocene lava-flows of La Garrotxa Volcanic Field (NE Iberian Peninsula)

The monogenetic Quaternary La Garrotxa Volcanic Field is located in the North-East of the Iberian Peninsula and was active from the Middle Pleistocene to the Early Holocene, thus, being the youngest known volcanic activity in the Iberian Peninsula. It forms part of the Catalan Volcanic Zone (Girona, NE Iberian Peninsula), one of the alkaline volcanic provinces of the European rift system.

The main goal of this work was to obtain a reliable full-vector record of the Earth’s Magnetic Field (EMF) recorded by 247 kya to 16 kya lava-flows in La Garrotxa Volcanic Field. With this purpose, fifteen basaltic lava-flows with known absolute and/or relative ages from previous studies, were selected and sampled. Paleomagnetic and paleointensity experiments were performed on these samples at the University of Burgos and the CCiTUB - Geo3BCN-CSIC (Spain). For paleomagnetic experiments, thermal and alternating field progressive demagnetizations were applied to obtain the Characteristic Remanent Magnetization direction of each lava-flow. Paleointensity values were obtained by applying the Thellier-Coe method, including in some cases a low temperature demagnetization pre-treatment to compare the outcome with and without pre-treatment. Also, rock-magnetic experiments have been carried out with a Variable Field Translation Balance to assess the suitability of the obtained determinations. This study represents the most continuous record of the EMF features evolution in La Garrotxa Volcanic Field so far.