Paleomagnetic and rock magnetic properties of Jurassic quiet zone basalts, Hole 801C

Abstract

The paleomagnetic and rock magnetic properties of 51 Jurassic basalts from ODP Hole 801C have been examined. Magnetic properties vary with lithologic composition. For the entire column, the Jurassic basalts have an average initial NRM intensity of approximately 1.24 A/m and average median destructive fields (MDF) of 8.31 mT. These values and the mean Koenigsberger ratio of 1.7 are very similar to results obtained for Jurassic basalts from the Atlantic (DSDP Leg 76). The similarities suggest that the basalts of both sites and their remanence characteristics are representative of Jurassic oceanic crust. The most profound discovery in these samples was the presence of 5 inclination zones, each showing consistent positive (or negative) polarity opposite the overlying and underlying polarity bands. These represent a record of change in polarity of the Earth's magnetic field and it is asserted that the rapid change in polarity during the Jurassic is the probable reason behind the origin of the Jurassic Quiet Zone. -from Authors