246 



HEEZEN AND MENARD 



[chap. 12 



California, known as the continental borderland, might be considered a highly 

 fractured marginal ])lateaii. Here, basins adjacent to shore in the continental 

 margin arc being filled by turbidity currents while the outer basins receive only 

 IK'lagic sediments. The ancient Los Angeles basin is com])letely filled and the 

 modern basins lying seaward of it are rapidly filling (Gorsline and Emery, 





kj 

 kl 



•vi 



03 



SCALE IN NAUTICAL MILES 



Fig. 13. Ten topographic profiles east of Cape Hatteras, Vii'ginia, and the Blake Plateau. 

 The sequence of profiles showTi in this figure ilkistrates the transition from the 

 typical continental shelf, continental slope, continental rise profiles of the north- 

 eastern United States to the more complex profiles across the Blake Plateau and 

 marginal basin of the southeastern United States. Note the well-developed marginal 

 escarpment and outer ridge on the lower three profiles. (After Heezen et al., 1959.) 



1959). It can be safely predicted that if tectonic activity in the area diminishes, 

 sedimentation will eventually completely fill the offshore basins of the con- 

 tinental borderland one by one and produce a shelf-like feature which may 

 eventually resemble a marginal plateau very similar to the Blake Plateau. The 

 analogy seems rather good M^hen one compares the deeper structure revealed by 

 results of seismic-refraction A\oi-k on the Blake Plateau with the modern to])o- 



