INSPISSATION OF POST-OLIGOCENE SEDIMENTS IN SOUTHERN LOUISIANA

The aggregate thickness between stratigraphic markers of post-Oligocene sediments in southern Louisiana, established from records of several thousand wells, is at least 62,000 feet.

The sediments along the Texas-Louisiana coast accumulated rapidly in rim synclines and in an area of “hinge-line” faults. Composite thicknesses are as follows: Miocene, 48,000 feet; Pliocene, 6000 feet; Pleistocene (including Recent and modern), 8000 feet. An additional 7100 feet of sediment is present in areas where no basal markers were found.

Because the unconsolidated beds in southern Louisiana reflect poorly, the geophysical data give an erroneous regional picture. Foraminiferal data and electric-log correlations together can give an adequate regional interpretation.

No valid evidence supporting the suggested regional reversal of dip or regional thinning of section can be found in any of the deep wells drilled in southern Louisiana. In spite of this, most workers in the area believe that a geosyncline of some type exists. No single center of deposition for post-Oligocene sediments can be established in a given geographic position. Each geologic subdivision possesses its own depositional axis at some unknown geographic point offshore.