Antarctic Magnetic Anomalies and Their Gradients Differentially Reduced to the Geomagnetic Pole for Enhanced Crustal Analysis

Abstract

To facilitate geological studies of the Antarctic region south of 60 degrees S, equivalent point magnetic dipole inversion was used to produce the comprehensive airborne-to-satellite altitude ADMAP-2s magnetic anomaly model. These spherical coordinate anomaly predictions jointly match the crustal magnetic anomalies gridded at 250 km above the Earth's mean geocentric radius (mgr) from the magnetometer observations of the Swarm satellite mission and at the mgr from the Antarctic Digital Magnetic Anomaly Project's (ADMAP) second-generation magnetic anomaly compilation (ADMAP-2) of over 3.5 million line-km of aeromagnetic and shipborne survey data. The present study investigates the utility of point dipole modeling for differentially reducing the magnetic anomalies to the pole and estimating their first and second order radial (i.e., locally vertical) derivative anomalies. Where sufficiently accurate, these radially polarized magnetic anomalies and gradients help constrain the possible depths and lateral limits of the crustal magnetic anomaly sources for Antarctica and the circumjacent southern Atlantic, Indian, and Pacific oceans. For East Antarctica, the anomalies help resolve relatively ancient cratonic boundaries and related sutures and magmatic intrusions, whereas at satellite altitude, they also offer insights on variations of lithospheric heat flow.