HR: 09:45h
AN: GP31A-08    [Abstracts]
TI: Circum-Arctic Magnetic Anomalies – Challenges of Compilation and the Value of Regional Interpretation in a Frontier Area
AU: * Saltus, R W
EM: saltus@usgs.gov
AF: U.S. Geological Survey, Mail Stop 964 Box 25046, Denver, CO 80225-0046, United States
AU: Gaina, C
EM: Carmen.Gaina@ngo.no
AF: Geological Survey of Norway, Leiv Erikssons vei 39, Trondheim, N-7491, Norway
AU: Brown, P J
EM: pbrown@usgs.gov
AF: U.S. Geological Survey, Mail Stop 964 Box 25046, Denver, CO 80225-0046, United States
AB: Important societal issues are driving increased attention to polar regions. The arctic, in particular, is the focus of scientific studies relating to climate change as well as resource exploration and territorial claims. The news and entertainment media are picking up on polar themes and driving interest within popular culture. Part of the attraction and mystique of the ends of the Earth lies in their relative inaccessibility and harsh environment. These same attributes make it difficult to conduct even basic scientific investigation, and therefore, the arctic remains a scientific frontier in many respects. Delineation of a robust tectonic framework for the top of the world is an essential prerequisite to resource assessment. The difficulty of making direct geologic observations beneath ice and sea requires remote measurement. Regional magnetic anomaly mapping provides important constraining information for the development of tectonic models for this structurally complex region. In addition to the obvious logistical challenges to detailed magnetic field measurement in the high arctic, noise and instability in the magnetic field itself at high latitudes presents difficulties. Nevertheless, regional magnetic anomaly data have been collected over the past 50 years for much of the arctic. The available surveys are diverse in vintage and survey design; the amplitude and frequency content of measured anomalies are widely variable. Availability of metadata and other documentation are also inconsistent for these surveys. This leads to significant challenges in constructing accurate regional magnetic anomaly maps. Preliminary maps from a new international cooperation effort (CAMP-GM, under the direction of Carmen Gaina, Geological Survey of Norway) provide the most consistent view yet of magnetic anomalies for the tectonically complex arctic basins and surrounding continents. Careful attention to digital compilation details allows the new grids 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. Continental, oceanic, and various types of transitional crust each have a distinctive magnetic anomaly signature that can be used to define a fundamental tectonic framework of the circum-arctic. Interpretation can be extended by including additional data such as regional bathymetry (an indicator of crustal buoyancy and isostatic equilibrium) and free air gravity (an independent indicator of crustal density balance and composition). Used together with magnetic domains these data reveal a composite geodynamic subdivision of the arctic. This subdivision provides a framework for investigations of mineral and energy resource potential, tectonic reconstruction, and long-term climate dynamics.
DE: 0905 Continental structures (8109, 8110)
DE: 0925 Magnetic and electrical methods (5109)
DE: 1517 Magnetic anomalies: modeling and interpretation
DE: 8038 Regional crustal structure
DE: 8110 Continental tectonics: general (0905)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting