146 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



80* 75' 



Fig. 10.11. Physiographic provinces, Atlantic Ocean. Reproduced from Heezen et a/., 1959. 



The Atlantic continental shelf is most probably constructional and due 

 to sedimentation influenced by fluctuating sea level during the Pleisto- 

 cene. Although certain early writers during a vigorous controvery ( 1930- 

 1940) contended that the canyons are due to subaerial erosion, and 

 therefore that the Atlantic coast has subsided 5000-10,000 feet subse- 

 quently, the theory is generally held today that the canyons are due to 



submarine slumping, mud flows, and turbidity currents. See discussion 

 in Chapter 32 of submarine canyons off the California coast. 



Appalachian Epeirogeny 



Following the Appalachian orogeny in the late Paleozoic and the 

 Palisades orogeny in the late Triassic, a long period of erosion set in and 



