World Digital Magnetic Anomaly Map (WDMAM) v.2.1 and the magnetic signature of geological provinces

The World Digital Magnetic Anomaly Map is prepared under the auspices of IAGA and the CGMW (Commission for the Geological Map of the World) of UNESCO. A first version was released in 2007 (Korhonen et al., 2007), and a second one in 2015 (Dyment et al., 2015; Lesur et al., 2016) with the mandate to update the version 2.0 using the same methodology when the availability of new data would make it necessary. The present version 2.1, compiled at 5 km interval, at 5 km altitude above the continents and at sea-level over the oceans, includes new datasets: (1) the complete digital aeromagnetic map of Brasil made available by ANP; (2) an improved version of the aeromagnetic map of Russia prepared by V-SEGEI; (3) the second version of the Antarctic Digital Magnetic Anomaly maP (ADMAP; Golynsky et al., 2018) which results from a remarkable international effort during and after the Second International Polar Year; (4) a new map of the Caribbean plate and Gulf of Mexico resulting from the compilation and re-processing of existing marine and aeromagnetic data in the area (Garcia and Dyment, EPSL, 2021, 2022); (5) the updated Magnetic Anomaly Map of Eastern Asia prepared by the CCOP (MAMEA; Ishihara and Uchida, 2021); and (6) a new marine magnetic anomaly data compilation prepared by T. Ishihara and coworkers. The new map will be presented and its improvements over the previous version discussed.

We try to characterize the magnetic signature of the different geological provinces at global scale by comparing WDMAM v.2.1 and the Geological Map of the World (Bouysse et al., 2014, CGMW). The latitudinal and directional dependences of the magnetic anomaly amplitude and shape prevent a direct global comparison. Instead, we examine the distribution of magnetic anomaly amplitudes within the geological provinces continent by continent. We build an histogram of the magnetic anomaly amplitudes for each type of geological province within each studied continent. The histograms resemble normal distributions from which we determine the average amplitude and its standard deviation. The latter reflects how wide is the range of amplitudes in the distribution: a small standard deviation means a narrow distribution and low amplitudes, a large one a wide distribution and high amplitudes. On land, our first investigation suggests that cratons exhibit stronger magnetic anomalies, whereas regions covered by a significant thickness of sediments present weaker anomalies. At sea, large igneous provinces show stronger anomalies, whereas continental platforms and the oceanic crust show similar amplitudes.