A complete record of Pleistocene deposition is observed in cores from a well at the tip of the Mississippi River delta near the edge of the continental shelf. Marine Pleistocene beds under the tidelands of Louisiana are correlated with the alluvial formations at the surface and in shallow wells farther inland.
A marine transgressive wedge correlatable with the Williana Formation contains Foraminifera which suggest water as deep as 600 feet. A reef-type assemblage in the base of these beds indicates a climate warmer than at present in the northern Gulf of Mexico. Marine sediments correlatable with the Bentley Formation yielded fossils suggestive of depths of deposition as great as 400 feet. Another reef-type deposit is present in the lower part of these beds. Several depositional cycles of lesser magnitude are apparent in the upper part of the Pleistocene section. The last major transgression correlates with the Prairie Formation, and evidence for water as deep as 400 feet over the present tidelands is shown. Still another reef-type assemblage is seen in the lower part of this wedge.
The sandy section below the Williana beds does not present a means of recognizing the base of the Pleistocene, but it may be logically assumed on the basis of the thickness of overlying cyclic deposition to be near 4200 feet. This means that some of the younger beds of offshore Louisiana probably constitute the thickest Pleistocene deposits in the world, if the ages assigned to the alluvial terraces of the lower Mississippi valley are correct.