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Abstract

A color magnetic-anomaly map compiled from digital data provides a synoptic view of major magnetic anomalies and corresponding geologic features of the central United States. The availability of the data in digital form allowed application of a variety of analytical techniques to enhance the anomalies and provide new interpretive information. Derivative and directional filters were applied to the data to help identify lithologic and structural boundaries. A magnetization-density ratio map was used to delineate major geophysical provinces. In addition, the data were draped over the Precambrian surface to remove the effects of basement relief.

The amplitudes and wavelengths of magnetic anomalies exhibited on the compiled maps vary considerably within the Midcontinent. Magnetic anomalies correlate well with major Precambrian and Paleozoic tectonic features and aid in delineating the features' lateral extent and associated structures. Coherent patterns of anomalies observed on the maps prove useful in delineating basement domains. Of particular interest are several linear magnetic features that may reflect continental-scale geologic features. Two northwest-trending lineaments that show remarkable linearity— the south-central and Great Lakes magnetic lineaments—coincide with several structural and lithologic boundaries in the Midcontinent and apparently express major crustal discontinuities.

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