GEOLOGIC MAPPING OF THE MISSISSIPPI RIVER DELTA REGION AT 1:100,000 SCALE

In the post–World War II era, the Holocene Mississippi River delta complexes were first defined in work by oil companies (e.g., H. R. Gould and D. E. Frazier of Esso Production Research Company, H. N. Fisk and E. McFarlan, Jr. of Humble Oil & Refining Company, and R. J. Leblanc of Shell Oil Company); the Louisiana State University Coastal Studies Institute (especially W. G. McIntire, J. P. Morgan, J. M. Coleman, and H. H. Roberts); the U. S. Army Corps of Engineers (USACE) Waterways Experiment Station (e.g., C. R. Kolb, J. R. Van Lopik, and R. T. Saucier); and others. Their depictions of the delta complexes were very small-scale and either as vegetation, facies, or in the case of the USACE, in stack-unit format; they were not treated at larger scales as mapped polygons representative of suites of surface-geologic map units. The Louisiana state geologic map (1984) also did not depict delta-complex polygons at 1:500,000 scale, and showed marsh types in the delta plain instead. The plate depicting Quaternary geology of the Lower Mississippi Valley prepared to accompany the volume on Quaternary non-glacial geology of the conterminous United States for the Geological Society of America’s Decade of North American Geology series (1989) depicted the delta complexes, but at a scale of 1:1,100,000.

Among the Louisiana Geological Survey’s titles in its 30 × 60 minute geologic quadrangle series, begun in 2000, six sheets cover nearly the entire delta plain at 1:100,000 scale. The most-recent and final delta-plain sheets completed in the series are Black Bay and Mississippi River Delta; these show the distribution of meanderbelt, natural levee, and undifferentiated delta-plain deposits of the Plaquemines–Balize (modern), Lafourche, and St. Bernard delta complexes as polygons for the first time at this level of detail.