--> ABSTRACT: Geophysical Evidence for Late-Middle Proterozoic Extension in the Precambrian Basement of the Permian Basin Region, by K. C. Miller and G. R. Keller; #91019 (1996)

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Geophysical Evidence for Late-Middle Proterozoic Extension in the Precambrian Basement of the Permian Basin Region

K. C. Miller and G. R. Keller

Integration of geophysical data with petrologic and geochemical data from the Precambrian basement of the Permian Basin suggests that the basement has been affected by an ~ 1100 Ma extensional event. Gravity modeling, seismic data, and well data shows that the Central Basin Platform, and adjacent parts of the Midland and Delaware Basins are underlain by layered mafic rocks, the Pecos mafic intrusive suite. In 1984, 4.5 km of these rocks were drilled by the North American Royalties #1 Nellie well. Pervasive seismic layering within what would be considered the Precambrian basement can be correlated to compositional variations in the intrusion with a synthetic seismogram made from well log data. Gravity modeling of the 300-km long N-S trending gravity anomaly associated with the Central Basin Platform suggests that the suite takes the form of a 3-10 km thick sill with a dike-like keel. We interpret the Pecos mafic intrusive suite to represent the core of an ~ 1100 Ma rift that may be associated either with extension in the foreland of the Grenville orogeny or with hot-spot-related extension that formed the Midcontinent rift. if this interpretation is correct, petroleum exploration targets in the form of erosional remnants of rift sediments may still lie within the basement. Seismic layering within the basement observed in both the Palo Duro and Tucumcari Basins may represent such erosional remnants. Additional geochemical and geochronologic studies of well cuttings from basement rocks in these regions are necessary in order to fully test the extension hypoth sis.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California