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A new international cooperative effort (coordinated by the Geological Survey of Norway) provides the most consistent view yet of magnetic and gravity anomalies for the tectonically complex Arctic basins and surrounding continents. The compilations extend south to latitude 60° N and include new data not shown in previous compilations. Careful attention to the merging of digital data allows the new magnetic anomaly grid to be mathematically filtered to assist in the regional characterization of magnetic domains and boundaries. The frequency content, amplitudes, and patterns of regional magnetic anomalies provide a window into the tectonic character and structure of the crust above the Curie temperature of about 580° C. Continental, oceanic, and various types of transitional crust each have magnetic and gravity anomaly signatures that can be used to constrain models of the fundamental tectonic framework of the circum-Arctic and to define the location of large-scale crustal structures. Visual inspection of magnetic anomaly patterns at the broadest scales leads to the identification of 21 individual domains. In many cases, the boundaries between the magnetic domains follow horizontal gradient maxima that indicate edges of magnetic sources.
However, it is interesting to note the relative lack of through-going linear features in the magnetic data that would indicate the presence of lengthy strike-slip faults as required by some tectonic models for the opening of the Arctic basins. Definition of density domains from regional gravity data is difficult because of the large-amplitude gravity effects of variations in sediment thickness, trade-offs between crustal thickness and mean density, and different states of isostatic balance. Linear free-air gravity highs are distinctive features of the circum-Arctic region and are most plausibly related to edge-effects from the continent-to-ocean transition. Interpretating and understanding regional geophysical domains are improved with the inclusion of additional data such as regional bathymetry, an indicator of crustal buoyancy and isostatic equilibrium, and available seismic data. The geophysical subdivision of the circum-Arctic provides a framework for investigations of tectonic reconstruction, mineral and energy resource potential, and long-term climate dynamics.
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