Gravity and magnetic anomalies show small departures from the expected values of the earth’s gravity and magnetic fields caused by variations in the density and magnetisation of the rocks within the crust. The gravity map shows contour values as Bouger anomaly onshore, and free-air anomaly offshore. The magnetic map shows countours displayed as total field anomaly.
These anomalies are used to determine concealed geological structure, including: the depth and extent of sedimentary basins, depth to magnetic basement, and location of concealed igneous bodies. On the broadest scale, they help to convey an understanding of the regional configuration of the Earth’s crust and upper mantle.