THE NEW NORTH AMERICAN MAGNETIC ANOMALY MAP

A digital magnetic anomaly database and map for the North American continent is the result of a joint effort by the Geological Survey of Canada (GSC), U. S. Geological Survey (USGS), and Consejo de Recursos Minerales of Mexico (CRM). The database and map represent a substantial upgrade from the previous compilation of magnetic anomaly data for North America, now over a decade old. This integrated, readily accessible, modern digital database of magnetic anomaly data will be a powerful tool for further evaluation of the structure, geologic processes, and tectonic evolution of the continent and may also be used to help resolve societal and scientific issues that span national boundaries. The North American magnetic anomaly map derived from the digital database provides a comprehensive magnetic view of continental-scale trends not available in individual data sets, helps link widely separated areas of outcrop, and unifies disparate geologic studies. Individual grids with a 1-km cell size from Canada, the Arctic, US, Mexico and offshore areas were combined to form the new North American magnetic anomaly grid. Anomalies with wavelengths greater than roughly 150 km created artifacts and were determined unreliable in the compilation. As a consequence, we removed anomalies with wavelengths greater than 500 km from the merged grid to reduce the effects caused by the erroneous long wavelengths but maintaining continuity of anomalies. The filtered grid was then color-shaded to form the published map. This filtered grid, the merged grid, and the correction grids are available with further processing details, along with the individual national grids, and digital survey boundary files from GSC (http://gdcinfo.agg.nrcan.gc.ca/toc.html), USGS (http://crustal.usgs.gov/namad), and CRM (http://www.coremisgm.gob.mx/inicio.html) websites.