A Regional Geophysical Analysis of the North American Midcontinent

Matt Hamilton. School of Geology and Geophysics, University of Oklahoma, Norman, OK 73019  [email protected]

New public-domain compilations of gravity and aeromagnetic data for the U. S. provide a rich database for structural studies. In this study, I have made a series of maps using these data and applied a series of digital-filtering techniques in order to better delineate anomalies and interpret regional-scale structures in the area. Techniques applied in this study include reduction to pole for magnetic data, upward continuation and subtraction to yield a residual map of gravity anomalies, and band-pass and directional filtering.

As expected, the midcontinent rift zone is the dominant feature on these maps. However, there is also significant basement texture that is not a product of the rift. This texture is partially concealed by the overwhelming anomalies associated with the midcontinent rift and related features. Directional filtering, however, allows the northeast-trending structures associated with the rift to be subdued or removed from the maps, which facilitates the study of anomalies due to basement textures resultant from other tectonic events. It appears possible that the midcontinent rift could extend further southward beneath the much younger Anadarko basin of Oklahoma and the Southern Oklahoma aulacogen. This is not a complete surprise, as previous works have suggested that the rift features may extend into Texas and New Mexico. There are also several gravity anomalies that do not appear to correlate well with known Phanerozoic geologic features and may represent previously unexplored Precambrian basins.