The PIs will conduct paleomagnetic and geochronological studies of Brunhes-age lavas from two composite volcanic sections in southwest Iceland: the Eyjafjoll and the Hengill-Grafningur- Ingolfsfjall volcanic systems, which have been mapped in detail and whose ages span the last 0.8 Ma. Improvements in the K-Ar method now permit accurate dating of tholeiitic lavas as young as 40 ka a K-Ar based timescale for these composite volcanic sections will be established. Paleomagnetism of these sections, including paleointensity determinations, will be used to describe the complete paleomagnetic vector in Iceland for the past 0.8 Ma, to determine to what extent the average Brunhes paleomagnetic field in Iceland behaved as a geocentric axial dipole (GAD), to document possible deviations for the GAD approximation, and to distinguish patterns of paleomagnetic secular variation for different periods in the Brunhes chron. From the K-Ar ages and major and trace element compositional data the PIs will document the duration, character and periodicity of volcanic processes within the neovolcanic zones of Iceland. In particular they will examine the timescale for crustal accretion at the tip of a propagating rift and within a dying rift, as analogs for spreading ridge segment evolution.
