056 -- Preliminary paleomagnetic analysis of the Sandfell laccolith, Iceland

Paleomagnetic data can be used to determine the orientation of Earth’s magnetic field in the past. The rhyolitic Sandfell laccolith, Iceland is the cooled remains of a large body of magma that is thought to have been emplaced over a short period of time. It occurred when magma intruded between two layers creating a mushroom-shaped igneous formation beneath the surface. Due to the brief period of time in which the laccolith was emplaced, work was conducted to detect and determine significance of paleomagnetic signatures in the rock unit. These paleomagnetic signatures would indicate the usefulness of continued study of the laccolith and the best methods of testing. Prior successful studies have been conducted on this rock unit using other magnetic tests, suggesting that this unit has some consistent magnetic signature. In order to determine which method would successfully define a paleomagnetic signature, thermal demagnetization and alternating current demagnetization were applied to the same sample. The experiment consisted of taking six cores and splitting them into two groups of three. One group of samples were incrementally placed in a demagnetization oven up to 700°C. After each increment, measurements were taken using the spinning magnetometer and the Kappenbridge to test remnant magnetization and magnetic susceptibility. The other group was analyzed with the alternating field demagnetizer and the magnetic remnant was measured with the spinning magnetometer. The alternating current method had successful results suggesting it is the proper method for testing paleomagnetic signatures in the Sandfell laccolith, Iceland.