Structural framework of the continental terrace, northwest Gulf of Mexico

Intricate detail of stratigraphy and structure, to depths of about 5000 feet (probably Miocene), is shown in Rayflex Electro-Sonic Profiler records collected on the continental shelf and the upper continental slope of the northwest Gulf of Mexico. The Rayflex Electro-Sonic Profiler is a continuous-recording, acoustic reflection surveying system which utilizes a high-intensity spark source, rather than chemical explosives. The recorded sections of the continental terrace of this area show essentially horizontally stratified deposits underlying the continental shelf (probably shelf, littoral, deltaic, lagoonal, and continental facies) changing smoothly over the shelf break into seaward-dipping continental slope deposits. The upper part of this terrace has thus formed during the late Tertiary and Quaternary by both upbuilding and outbuilding. This basic framework has been modified locally by folding and faulting, which are largely associated with salt or shale intrusion structures. The irregular topography of the upper continental slope, previously attributed to slumping, gravity tectonics, and turbidity current erosion, is shown to be controlled by these intrusive structures modified by varying amounts of contemporaneous deposition of sediment. No evidence of extensive slope erosion is shown by records of this survey.