Is Magnetic Secular Variation Recorded in the Ocean Crust: Analysis of Deep Towed Magnetic Anomalies Measured on Cruises Tow Two II and Seven Tow

摘要

Deeply towed maring magnetometer profiles over anomalies 10 and 9 in the Gulf of Alaska, and number 10 off California, were studied for correlation of short wavelength (short period) features. It is proposed that part of the (dipole) secular variation spectrum is recorded with some fidelity during sea floor spreading. Statistical and model studies suggest that topographic effects are not significant in the data analyzed. Agreement between profiles degenerates at periods shorter than 100000 years (wavelengths less than 4 km) and coherence tests suggest that a linear system related the earth's field and ocean crust magnetization only at periods longer than this. One striking observation is that the polarity transitions to anomaly 10 are very sharp but the anomaly 9 transition is broad and cannot easily be located in the deep magnetometer profiles. (Author)