54 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 27 



some kind of sediment analysis was made for 176. In 16 samples two 

 different kinds of sediment were noted; these were separated and ana- 

 lyzed individually. 



Texture 



Textural analyses were made by a combination of standard pipette 

 procedure for fine ( < 62 micron) fractions and settling tube for the 

 coarse fractions. Percentages of gravel, sand, silt, and clay are reported 

 in the Appendix, along with median diameter and Trask sorting co- 

 efficient. The Trask coefficient was used so that results would be com- 

 parable with those of the many other analyses of sediments in the region 

 (Emery, 1960a). 



A comparison of the median diameters of samples from within 10 

 meters of the floor of the canyons with those of samples from higher 

 on the walls is given in the top panel of Figure 20. The frequency curves 

 show that the sediment from the axes is only slightly coarser than that 

 from the walls. Clean coarse, even gravelly, sediment is present in many 

 samples from the canyon floors, but other coarse sediment occurs high 

 on the canyon walls and atop the adjacent shelf. Fine green silty clay is 

 common on the canyon walls but it also is interbedded with clean sands 

 along the canyon axes. The average median diameter of the 95 axial 

 samples is 69 microns and for the 60 wall samples it is 40 microns. A 

 similar average median diameter of 70 microns was obtained by Cohee 

 ( 1938) for 29 small dredge samples mostly from the walls of Hueneme, 

 Mugu, Dume, Newport, and Coronado canyons. 



The sorting coefficients for axial and wall samples exhibit even 

 smaller differences than do median diameters, so no distinction was made 

 on most panels of Figure 20 for the two sources of sediments. Sorting 

 coefficients for all canyon sediments average about 2.5 but in a general 

 way the sorting coefficients are lower for sediments having median diam- 

 eters coarser than 50 microns than for finer sediments: about 1.8 versus 

 3.2. 



