Aeromagnetic map of the Stockton 1:100,000-scale quadrangle, California

The accompanying aeromagnetic map is part of the San Francisco Bay area National Geologic Mapping Project and is intended to promote further understanding of the geology in the Stockton 1:100,000-scale quadrangle, California, by serving as a basis for geophysical interpretations and by supporting geological mapping, mineral resource investigations, and topical studies. Local spatial variations in the Earth's magnetic field (evident as anomalies on aeromagnetic maps) reflect the distribution of magnetic minerals, primarily magnetite, in the underlying rocks. The volume content of magnetic minerals often can be related to rock type, and abrupt spatial changes in the amount of magnetic minerals commonly mark lithologic boundaries.