ABSTRACT

Gravimetric and magnetometric investigations of the Ouachita structural belt in central Texas show that gravity minima correspond to a tectonic zone containing unmetamorphosed to weakly metamorphosed sedimentary rocks and gravity maxima correspond to a tectonic zone containing thoroughly altered low to medium grade metamorphic rocks. The boundary between these two zones can be estimated within 5 miles on the basis of gravity anomalies. The two zones appear to be separated by low-angle thrust faults with a calculated minimum displacement of 12 miles. It may be possible to locate the boundary between the structural belt and the foreland on the basis of anomalies in the earth's magnetic field. Estimates of the maximum thickness of the sedimentary prism based on gravity and magnetic anomalies are compatible with thickness determined from drilling. Gravity anomalies in the Marathon Basin are aberrant with respect to the rest of the structural belt.