2 ALLAN HANCOCK PAaFIC EXPEDITIONS VOL. 27 



ACKNOWLEDGMENTS 



Most of the field work was accomplished between December 1959 

 and May 1960 (Stations 6776 to 7055) through the aid of National 

 Science Foundation Grant G-9060. A few samples collected during 1961 

 and 1962 were by-products of an additional National Science Founda- 

 tion Grant G-12329. Many of the data for Santa Monica, Redondo, 

 and San Pedro Canyons were collected during short cruises extending 

 back to 1951 ; most of these cruises were financed by Captain Allan 

 Hancock, but some were part of a contract for studies of Santa Monica 

 Bay for Hyperion Engineers, Incorporated. Appreciation is due J. R. 

 Grady for his careful analyses for nutrients in the waters and to many 

 other students of the Department of Geology who participated in 

 the ship work during class or special field trips. All field measurements 

 were made aboard the Allan Hancock Foundation's research vessel 

 VELERO IV. 



TOPOGRAPHY 



Methods 



The 13 submarine canyons of this study occur along the mainland 

 and off islands and banks (Fig. 1). For each of them 6 to 13 sounding 

 lines were run at right angles to the canyon axis, as shown by naviga- 

 tional charts, and at approximately equal intervals along it. The lines are 

 long enough to show the relationship between the sides of the canyons 

 and the adjacent mainland or island shelf, basin slope, or basin floor. 

 Soundings were made with the Precision Depth Recorder (Luskin, 

 Heezen, Ewing, and Landisman, 1954) attached to an Edo echo 

 sounder. Instrumental error is less than 1 part in 3000, so the chief 

 error in depth results from variation of the speed of sound in sea water 

 and the reflection of sound from areas of the bottom within the sound 

 cone and shallower than the point directly beneath the ship. The pro- 

 files are based upon soundings uncorrected for sound velocity. Since the 

 echo sounder is calibrated for a sound velocity in sea water of 1463 

 meters per second and the actual sound velocity for these depths is about 

 1.2 per cent faster (Emery, 1960b), the profiles are about 1.2 per cent 

 too shallow. More important, however, is the effect of echoes from the 

 sides of the narrow canyons; these often obscure the echoes from the 

 narrow bottom. Comparison of wire depths for samples taken in the 

 canyons with simultaneous echo soundings corrected for sound velocity 

 show that some of the echo soundings are as much as 50 meters too 



