Dill 



bottom placement of instruments in acoustic test ranges or the tacti- 

 cal use of these areas as acoustic screens for hiding submarines. 

 I'm reasonably certain that little is being done to improve the capa- 

 bility of acoustic equipment to differentiate natural occurring objects 

 on the terraces and those that may be lost or placed in these areas. 



We have only begun to investigate the nature of the deeply- sub- 

 merged terraces on the continental slope. Their origin is compli- 

 cated because they were formed during the geologic past when environ- 

 mental conditions were different from those existing today. Little is 

 known about the time necessary for them to formi or their distribution 

 throughout the world. 



A preliminary review of the existing literature indicates, in addi- 

 tion to Southern California, that deeply submerged terraces occur in 

 the Carribean, along the Atlantic coast, off Baja California, Mexico, 

 in the straits of Florida, and off the Oregon coast. A well -developed 

 terrace is indicated in sub-bottom profiles off the relatively unstable 

 insular slope of Japan. 



The acoustic reflections from the rocky cliffs, coarse shelly 

 sands, and cobble areas associated with the terraces must be very 

 different from those of the intervening soft muds separating the ter- 

 races. This difference has to be considered in any type of ASW or 

 lost instrument search employing acoustic sound sources. Consider- 

 able research remains to be done before we can determine how these 

 sea-floor features affect acoustic search and whether or not they 

 could be utilized tactically by the fleet or as underwater construction 

 and installation sites. 



ACKNOWLEDGEMENTS 



The writer wishes to thank John A. Beagles, Bruce C. Heezen, 

 and R. F. Busby for their assistance and discussion during and 

 before the field work. Edwin C. Buffington, Edwin L. Hamilton, 

 and E. C. LaFond critically read the manuscript and gave many 

 helpful suggestions. 



BIBLIOGRAPHY 



Buffington, E. C and Moore, D. G. , 1963, Geophysical evidence on 

 the origin of gullied submarine slopes, San Clemente, Califor- 

 nia. Jour. Geol. , V. 71 (3), 356-370. 



Busby, R. F. , 1962, Submarine geology of the Tongue of the Ocean, 

 Bahamas. Tech. Report 108, U. S. Naval Oceanographic 

 Office, Wash. D. C. , 84 p. 



Curray, J. R. , 1960, Sediments and history of Holocene Transgres- 

 sion, Continental Shelf, Northwest Gulf of Mexico, in Recent 

 Sediments, Northwest Gulf of Mexico. Am. Assoc. Petrol. 

 Geol. P. 221-381. 



115 



