GRAVITY AND AEROMAGNETIC DATA ANALYSIS, CENTRAL NORTH SLOPE, ALASKA – HISTORICAL PERSPECTIVE AND CONTEMPORARY IMPLICATIONS

Gravity and aeromagnetic data reveal information about both deep and shallow crustal structure of the central North Slope, Alaska. Even the limited resolution, public-domain data lead to useful conclusions. Regional gravity and aeromagnetic data reflect remarkable heterogeneity in the density and magnetic properties of the pre-Carboniferous basement. Historically, this heterogeneity has created challenges for the application of geophysical data, particularly gravity data, to interpretation of basin structure for hydrocarbon exploration. The central North Slope pre-Carboniferous basement consists of two distinct geophysical domains. To the southwest, the basement is dense, highly magnetic, and may have played a fundamental role as a buttress to basement involvement in Brooks Range thrusting. This geophysical domain is part of a much larger feature that extends to the north and west and may represent a Devonian(?) failed rift. To the northeast, the central North Slope basement consists of lower density, moderately magnetic rocks with several discrete regions (intrusions?) of more magnetic rocks. A conjugate set of geophysical trends, northwest-southeast and southwest-northeast, may reflect faults that formed as a crustal response to tectonic compression in this domain. High-resolution gravity and aeromagnetic data, where available, were filtered mathematically to provide detailed maps of shallow fault and fold structure. These maps provide useful complementary information for regional structural interpretation, particularly in combination with detailed seismic profile interpretation. Future challenges include collection of high-resolution geophysical data for the entire North Slope and additional deep crustal information from seismic, drilling, and other complementary methods.