Ground Magnetic Observations of the Mammoth Magnetic Anomaly, Pinal County, Arizona, May 2025

This data release provides ground magnetic data collected in May 2025 at the Mammoth Magnetic Anomaly (MMA) site in Pinal County, Arizona. These data were collected to validate and characterize a large aeromagnetic anomaly observed in an airborne survey of southeastern Arizona (Scheirer et al., 2025). The geophysical fieldwork was funded by the Earth Mapping Resources Initiative. Ground survey data were collected during walking traverses using a backpack magnetometer system (G858 cesium-vapor magnetometer) and using the magnetometers in two Apple iPhones, which can acquire magnetic data below the observation floor (nominally 18,000 nT) of the G858 system. This data release includes files of the base station magnetic data and the roving magnetic data. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.