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Indiana University Studies 



to it. It more likely has been for the most part an epiconti- 

 nental sea, which has from time to time subsided perhaps 

 in response to the load of land waste from the interior plains. 

 The embayment has been gradually crowded more and more 

 toward the gulf basin until the ultimate result has been to 

 extend the land out into the gulf. This has been the work 

 of the master stream of the great interior of the United 

 States. It would appear that this delta building, which has 

 resulted in extending the land seaward, has been slowed down 

 from time to time by depression of the lower part of the 

 area. Data at hand show that the Mississippi valley is filled 

 with Pleistocene and post-Pleistocene material to a depth of 

 about 250 feet below the present valley surface at the junction 

 of the Ohio with the Mississippi, and that farther south the 

 filling is to be measured in hundreds of feet, probably not 

 less than 900 or 1,000 feet in the region of New Orleans. It 

 would appear that for the most part, if not altogether, the 

 depression has l^een confined to the immediate axis of the 

 embayment and that it has there been fairly sharp. Streams 

 paralleling the Mississippi River on either side do not seem 

 to have filled valleys. Pearl River in Mississippi is an in- 

 stance. This stream does not appear to have any more valley 

 alluvium above its bed-rock floor than it is itself capable of 

 moving. 



The present delta of the Mississippi River begins near 

 the mouth of Red River. Here occurs the branching off of 

 the first distributary. This position is 315 milec by channel 

 from the mouth of the river, and has an elevation of approxi- 

 mately 50 feet AT. The channel could be shortened by 100 

 miles by eliminating all the crooks and oxbows. The stream 

 channel, however, is no more winding than it normally should 

 be. The head of the present delta is some 125 miles north of 

 the gulf, in a straight line. It is conceivable that this posi- 

 tion was in no very remote past the sea-level mouth of the 

 ^Mississippi River. Lyell^" in discussing the convergence of 

 the deltas of the Red River and the Mississippi, says in part: 

 'The date of the junction of the Red River and the Missis- 

 sippi would, in all likelihood, have been known, if America 

 had not been so recently discovered." It is quite certain that 

 the present delta is the work of continual deposition of ma- 



1" Charles Lyell, Principles of Geology, 1873. P. 482. 



