A palaeomagnetic study of the Englandsháls and Lundarháls plateau lavas in Western Iceland

Abstract

As the subaerial continuation of the Mid-Atlantic ridge, Iceland’s basaltic lavas preserve Earth’s magnetic field history for the past 16 million years. Iceland’s morphologies are formed by various glacial-interglacial intervals, leaving behind glacial shaped valleys and gorges, exposing continuous lava sequences favourable for palaeo-magnetic research. The first studies were carried out in the 1950s and ever since, a comprehensive magnetostratigraphy has been accomplished combining palaeomagentic data collected around Iceland.This project aimed to address new directional data obtained from Lundarháls and Englandsháls plateau lavas, Western Iceland, through an investigation of their magnetic polarity with relation to the current Geomagnetic Polarity Time Scale (GPTS) by Ogg (2012). A combination of fieldwork sampling and ensuing laboratory measurements obtained directional data derived from principal component analysis (PCA)using the open-source software PuffinPlot. After evaluation by carrying out Fisher statistics (see Fisher (1953)), a total of 617 from 766 samples are used for further analysis. Magnetic direction of 101 lava flows are determined, whereby their virtualgeomagnetic poles (VGP) are assumed to follow a geocentric dipole configuration.Acquired VGP positions provide a relatively continuous magnetostratigraphy. Stratigraphic logs were used to predict the number of missing lavas and correlate the sequences. The VGPs suggest three transitions towards reversed polarities, corresponding to the Mammoth subchron, Kaena subchron and the Gauss-Matuyama boundary of the GPTS. The normal polarities yield pole positions at Greenland -North Canada with excursional VGPs plotting near Japan similar to the pole pathof the transitional flows. The reversed VGPs reveal pole positions with λp= 75°S.However, due to gaps in the sample collection and the presence of excursional lava flows (λp<45°), reversed and normal VGPs do not trend around the North and South Pole.