TREADWELL 



35 



HISTORY OF DELTAIC DEVELOPMENT 



The sequence of deltaic development in this area is rather complicated, and only a 

 condensed version can be presented. 



The oldest features now present at the surface are the stranded beach ridges, or cheniers. 

 Their age is on the order of 3000 to 5000 years (see Area 1, Fig. 5). 



A very early subdelta was present, but very little is known about it. A second subdelta 

 entered and spread over most of the area. Evidence of it has been found on the Chandeleur 

 Islands, and an isolated remnant occurs within the area 2. Following the second subdelta, river 

 flow began to shift into area 3. During this time much of area 2 was subject to marine erosion. 

 As area 3 continued to enlarge, activity also was extended into area 4, and the delta was again 

 extended an unknown distance seaward of the Chandeleur Islands. Deltaic sedimentation con- 

 tinued to about 1500 A.D. Since that time, the river has shifted to the south, and the older sub- 

 deltas have been subject to marine erosion. 



Combined with physical evidence, refuse of Indian people, such as pottery, has aided in 

 solving the developmental sequence just outlined and has been used throughout the State to help 

 affix the chronological sequence of deltas. 



f 



1^- - 



Figure 5. 



