PRICE 



27 



properly dynamic environments defined by topographic (bathymetric), physical, and geological 

 data. Using the slopes of the continental shelf taken from profile studies, the outlines of the 

 submerged deltaic plains, reef platforms, and other obstacles, I have drawn major longitudinal 

 zones. The transverse energy zones are not shown on these maps but have been inditated 

 (without boundary lines) on Fig. 13. 



The shoreface is the narrow belt between the ramp and the shoreline. I have determined 

 the height of the shoreface roughly at different points. The ramp zone passes almost entirely 

 across the front of the deltaic plains. In places there is an inner and outer ramp. New ramps 

 are being cut at the shoreline on very recently submerged deltaic masses, with the older, more 

 prominent ramp on the offshore slope. Apparently there must be breakers along the outer sub- 

 merged edges of deltaic shoals with a shoreface where the edge of the shoal is less than about 

 12 feet deep. I am sure that in storms there would be a line of breakers in such places, and 

 we have indicated the outer ramp to show that this is the case, as on shoals off Atchafalaya 

 Bay. The camber zone is shown along the shoulder of the deltaic north shelf but not on the 

 west and east shelves in the broad, supposedly down-warped areas off Florida and Texas. 



In regard to the "down- warp" of the western shelf, zones of strong folding buckle the 

 Cretaceous and early Tertiary strata only 60 miles inland. Off shore from the Rio Grande 

 delta there are submerged mountains shown by the war-time soundings. One mountain top 

 stands about 3,800 feet above the adjacent bottom. Its flanks slope several hundred feet per 

 mile. Thus, this western shelf lies between areas of considerable diastrophism and is 

 apparently a down-warped shelf as its broadly bowed profile suggests. 



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Figure 16. 



