Anomalous Remanent Magnetization of Some Klamath River Andesites

摘要

A section of the Western Cascade series of Tertiary volcanics with anomalous remanent magnetization directions was sampled. Five anomalous flows and three stable flows are studied in detail. The direction and intensity of the natural remanent magnetization (NRM) is measured before and after demagnetization experiments. The direction of the NRM vectors in the anomalous flows is almost horizontal in contrast to the usual sixty degree magnetic inclinations of the adjacent stable flows. The declinations of contiguous anomalous flows alternate between approximately twenty and two hundred degrees. The declinations, plus or minus 180 degrees, are consistent with the series as a whole. A study of the mineralogy shows that all the anomalous flows are slightly altered (propylitized) and that four of the five flows have a well-developed flow structure. Different mineral parameters were examined and plotted against variations in the magnetic properties of the flows, but the exact mechansim of the formation of the anomalous magnetic directions remains unknown. (Author)