An integrated geophysical and geological study of the deep basement structure and tectonics of the Permian basin of west Texas and southeastern New Mexico was made using gravity, magnetic, and subsurface data. Over 6,000 gravity and 13,000 magnetic readings from different sources were used to construct gravity and magnetic maps of the area. The Central Basin platform is reflected by prominent positive Bouguer gravity and magnetic anomalies. However, both the gravity and magnetic maps show an east-west trending saddle in the Central Basin platform region which must be due to a deep-seated intrabasement structure. The West Platform fault zone which separates the Central Basin platform from the Delaware basin is reflected by a steep gravity gradient. By combining gravity and abundant well data in two-dimensional computer modeling, earth models were derived for two profiles crossing the area. These earth models show that the gravity relief between the Central Basin platform and the Delaware basin is far too large (±40 mgal) to be explained simply by the thickness of the sedimentary section of the Delaware basin. These models indicate a deficiency of mass in the basement underlying

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the Delaware basin or an excess of mass under the Central Basin platform. The West Platform fault zone is basement controlled. The seismic activity recently recorded in the area may be related to these deep-seated basement structures. The geophysical and geologic similarities between the southern Oklahoma aulacogen and the Permian basin suggest that the latter may be related to a late Precambrian aulacogen.

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