Number Page 



13 The relationship of glacial advance and retreat to continental shelf 

 exposurs and sedimentation during the Late Quarternary 25 



14 Location of major buried river channels formed during the Wisconsin 



gl acial period 15 



15 The position of major delta lobes on the gulf coast during the 

 previous 25,000 years. (A) Late Wisconsin, 25,000 - 20,000 yr B. P. 

 (B) Late Wisconsin, 15,000 yr B. P. (C) Early Holocene, 12,000 - 



10,000 yr B. P. (D) Present, 5,000 - 1,000 yr B. P 17 



If) Deltaic lobes of Mississippi River deltas 18 



17 Satellite image of the Mississippi Delta Region showing delta lobes of 



different ages 19 



13 Six subdeltas of the modern Mississippi Balize Delta recognized from 

 maps and sediment analysis. Dates indicate year of crevasse 

 opening 20 



19 Plan view and cross sections through A-A' and B-B' of environments of 

 deposition in a crevasse 21 



20 Sequential development of Cubits Gap subdelta 22 



21 Linear, areal , and volume growth curves for the Cubits Gao 



subdelta 23 



22 Composite subaerial growth curve, Mississippi River subdeltas. Total 

 subaerial land determined from averages at 10-yr intervals 24 



23 The accelerating wetland loss rate in the Mississippi Delta 24 



24 Conputerized re-creation of the west side of Barataria Bay showing the 

 change in wetlands between 1945 (a) and 1980 (b). Black is open 



water; marshes are shown as varying shades of grey 25 



25 Environmental succession of an idealized delta cycle 29 



26 Mineral content of marsh soils in Mississippi delta hydrologic units, 

 arranged in order of increasing age 30 



27 Marsh soil salinity and percent fresh marsh in Mississippi delta 

 marshes by hydrologic unit, arranged in order of increasing age. Soil 

 salinity is a mean for the whole basin weighted by ares of each marsh 



zone. The fresh marsh is percent of total marsh area 30 



28 Marsh edge length :area ratio and total marsh edge length for delta 

 hydrologic units. The units are arranged in order of increasing 



age 31 



29 Net primary production and fishery yield of Mississippi River Deltaic 

 Plain hydrologic units. Production calculated from average production 

 of each habitat type and its area in the hydrologic unit. Shrimp data 

 from Barrett and Gillespie (1975). Basins are, in order of increasing 

 aye: I - Pontchartrain-Lake Borgne, II - Balize, III -Barataria, IV - 

 Terrebonne, V - Atchafalaya , VI -Vermilion 31 



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