SEISMIC REFLECTIONS FROM LAYERING WITHIN THE PRE‐CAMBRIAN BASEMENT COMPLEX, OKLAHOMA

Abstract

Reflections from within the pre‐Cambrian basement complex were recorded in the vicinity of the Wichita Mountains in southwestern Oklahoma. The reflections, of good quality and persistence, depict a section in excess of 20,000 ft of igneous rocks that appears like a seismic section of sedimentary formations. A well in the area drilled 4,000 ft of this pre‐Cambrian section, encountering alternating layers of silicic and gabbroic igneous rocks exhibiting high contrast in density. Pre‐Cambrian outcrops of much of the Wichita Mountains, comprising comparable types of rocks, display sheet‐like, gently dipping layers, some of which persist for several miles. The seismic reflections are thus produced by the igneous layers of differential acoustic properties. An abrupt change of direction of dip occurring at about mid‐depth of the seismic section precludes the possibility that the seismic events are multiple reflections.