Allemand, Lake Salvador, Lake Cataouatche, and Little Lake) are also portions of the gulf which 

 were cut-off from the gulf by the formation of the St. Bernard, Lafourche, and present Mississippi 

 Deltas. In summary, constructional processes of sedimentation have created these lakes. In 

 contrast, major destructional processes created the coastal bays described below. 



PART II. DESCRIPTION OF COASTAL BAYS, SOUNDS, 

 TRANSGRESSrVE BARRIER ISLANDS AND OFFSHORE SHOALS 



Coastal Bays 



The origin of the coastal, shallow water bays and sounds of southeast Louisiana was very 

 different from the origin of the inland lakes. These coastal water bodies were developed during 

 the past few thousands years as gulf waters transgressed over the abandoned, subsiding deltas. 

 They are the products of nature's destructional forces. The compaction of delta sediments, 

 following delta abandonment, caused the shorelines of Louisiana to move inland for about 50 mi 

 over the Teche Delta, 35 mi over the St. Bernard Delta, and about 15-20 mi over the Lafourche 

 Delta. Transgressions of the seas upon abandoned deltas are a perfectly natural geological process 

 that has occurred all over the world for millions of years. 



Coastal Barrier Islands 



Coastal barrier islands are very common features in the world. Unfortunately, there is a great 

 deal of confusion in the geological literature on barriers. It is very important to recognize that 

 there are two basic types of barrier islands. One group, such as Galveston Island and Matagorda 

 Island of the Texas coast, are "constructional features." This type of barrier is fed by longshore 

 transport of sand and over a long period of geological time grows seaward by the process of 

 "shoreface accretion." The second type of barrier island, such as the ones along the Louisiana coast 

 shown on Figure 2, are the products of destructional processes. The Isles Dernieres and the 

 Timbalier and East Timbalier Islands have been moving inland and westward since the Lafourche 

 Delta was abandoned. Grand Island is moving northeast because of local eastward longshore 

 currents along the west margin of the present Mississippi Delta. The Chandeleur Islands have been 

 moving westward over the St. Bernard Delta. 



Offshore Shoals and Sounds 



There is a very significant relationship between the presence of nearshore shoals and sounds 

 off the Louisiana coast and the abandoned deltaic plains. Recent sediment research during the 

 early 1950's revealed that these broad sandy shoals and sounds are submarine topographic features 

 which mark the former seaward portions of the Teche and St. Bernard Deltas. The bottom 

 sediments within much of the shoal areas consist of transgressive marine sands and silts overlying 

 organic-rich deltaic plain sediments. The south Louisiana deltaic plains and the adjacent shoals 

 mark the results of a major battle between river power and ocean power. As will be demonstrated 

 in the next part of this paper, while the mighty Mississippi River constructed about 14,000 mi 2 of 

 new land in the gulf waters, the gulf has in turn reclaimed about 7,000 mi 2 of coastal marshlands 

 according to the basic principles of deltaic sedimentation. 



PART III - SIGNIFICANT PAPERS ON THE 

 MISSISSIPPI RT^ER DELTAIC PLAIN COMPLEX 



On the basis of 48 years of experience studying the geology of my native land, I have selected 

 37 papers on the geology of the Mississippi River Deltaic Plain Complex which I consider to be 



