SUBMARINE CANYONS 



OF 



SOUTHERN CALIFORNIA 



Part I, Topography, Water, and Sediments 



by 



K. O. Emery and Jobst Hiilsemann 



INTRODUCTION 



For many years submarine canyons have been known off southern 

 California and have been studied in varying degrees of detail, largely 

 by F. P. Shepard and his students and colleagues. Most of this work 

 consisted of studies on topography (Shepard and Emery, 1941), lithol- 

 ogy (Emery and Shepard, 1945), and general sediments (Cohee, 1938). 

 Hydrographic and biological work has been sketchy. Some recent studies 

 by Gorsline and Emery (1959) indicated the common presence of sandy 

 floors along the canyon axes which mark the route of turbidity currents 

 that move coarse sediment from beaches and inner shelves outward to 

 the deep basin floors (Emery, 1960a). This preliminary sampling also 

 suggested that benthic animals on the floors of the canyons differ from 

 those at the same depths outside the canyons. Differences in environ- 

 ment, such as coarse sediment, moving sediment, or abnormal water 

 conditions, may be important biological controls in the canyons. 



Thirteen of the largest submarine canyons were selected for special 

 studies of the topography, sediments, hydrography, and benthic biology. 

 Many other canyons are present in the region, some of them larger than 

 the smallest one described in this report. Among these fairly large but 

 relatively poorly known canyons are several between Mugu and Hue- 

 name Canyons, San Gabriel Canyon, Oceanside Canyon, Carlsbad Can- 

 yon, and several north and east of San Nicolas Island. These canyons 

 were omitted not because they are unimportant, but because of time 

 limitation and because the 13 canyons which were selected probably 

 cover the range of variation expected within the fields of investigation. 

 Basin slopes in the region also contain related but smaller features 

 termed sea gullies (Buffington, 1951, in press; Emery and Terry, 1956) ; 

 perhaps several thousand are present. 



