Magnetic Anomalies of the Northern Gulf of California: Structural and Thermal Interpretations
O. Sanchez-Zamora, P. Doguin, R. W. Couch, G. E. Ness, 1991. "Magnetic Anomalies of the Northern Gulf of California: Structural and Thermal Interpretations", The Gulf and Peninsular Province of the Californias, J. Paul Dauphin, Bernd R. T. Simoneit
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Geophysical surveys in the northern Gulf of California in 1981 and 1984 (GOLFO 81, GOLFO 84) provided the magnetic data for this study. We analyze the data using frequency domain techniques to determine the depth to the tops and bottoms of magnetic sources. We assume that the bottom of the deepest sources represent the Curie-point isotherm. Our results indicate a shallow magnetic horizon with depths to source tops between 2.3 and 4.1 km below sea level; an intermediate-depth horizon between 3.6 and 6.4 km; and a deep magnetic horizon between 6.7 and 9.5 km. Our computed depths to the bottom of the magnetized crust yield an average depth of 11.5 km below sea level. Using the individual computed depths to the Curie-point isotherm, and assuming a Curie-point temperature of 580°C, we determine an average thermal gradient of 51.8°C/km. Assuming a conductivity of 2.2 W/m°C, the average computed heat flow for the central part of the northern Gulf of California is 114 mW/m2.
We also present plots of fault traces which were determined using a deconvolution method based on Werner’s (1953) simplified thin-dike assumption. The method presented automates the interpretation of magnetic profiles leading to the linearization of complex nonlinear magnetic problems. This technique identifies fault traces for the northern Gulf which are very similar to those proposed by Ness and Lyle (1991).