Cause of graded bedding similar to that present in the TOTO sediments is discussed 

 by Kuenen (1953) and Kuenen and Menard (1952), and lithologic features of this nature 

 are suspected to be the result of deposition by turbidity currents of high density. Such 

 processes are of short temporal duration, and the velocity attained by the turbid flow is 

 dependent upon the density of the flow and the slope gradient over which it is passing. 

 As the turbidity current decreases in velocity, the coarser and gradually the finer and 

 finer particles are deposited; hence, vertical grading results. Graded beds of this 

 nature and the suspected mode of deposition have been designated by Kuenen (1957) as 

 "turbidites," and this nomenclature will be used herein. 



Turbidites do not generally occur at the same depth level in all cores, or are they 

 of the same vertical thickness. Since all cores except those preceded by the number 

 61 were taken with the same instrument and following the same method, differentially 

 induced compaction through variation in sampling procedure or instrument type is not 

 suspected for the lack of correlation between turbidites from one core to another. To 

 account for the lack of horizontal continuity, extensive sheet-like turbidity currents 

 are not theorized. Instead, localized turbidity flows within the many gullies trending 

 at right angles to the bank edges and incising the channel walls are more likely. High 

 velocity restricted flows of this nature are discussed by Ericson et al (1961), and such 

 localized transporting phenomena which have originated througfTslLmfiping on the upper 

 walls or bank edges best explain the discontinuous, variable distribution of the turbidites. 

 Rusnak and Nesteroff (1962) discussed the TOTO turbidites in detail and concluded that 

 70 to 90 percent of the channel deposits have been produced by turbidity currents. 



It is stated in a Technical Report by the University of Miami (1958) that density 

 (turbidity) currents created by instability of sediments on the edge of the banks may 

 contribute material to the floor of the TOTO. Many of the cores in the near-flank 

 area were collected from within the gullies and displayed no features suggestive of 

 turbidity current deposition. Consequently, it is expected that the turbidity currents 

 originating on the banks above the near-flank area flow with sufficient velocity down- 

 slope to prohibit deposition in this area. On the other hand, turbidity flows may be 

 originating near the base of the flanks and flowing outward into the channel, thereby 

 accounting for the absence of turbidities in the near-flank sediments. 



Particle Size : Silt-sized particles are the dominant size fraction in the axial 

 sediments; however, compared to the near-flank area, there is a decrease in percentage 

 of silts, a slight increase in sands (generally explained by the coarse turbidite layers 

 present), and a fairly large increase in lutites (Table III). Average particle size distri- 

 bution in the axial area is 17 percent sand, 49 percent silt, and 34 percent lutite. 



Sorting values are higher in these sediments as a result of an increase in sand and 

 lutite. Over 75 percent of the samples analyzed are poorly sorted, and the bulk of 

 the remaining samples show average sorting. Sorting values in the turbidites are 

 generally high. Rusnak and Nesteroff (1962) discussed sorting coefficients and ex- 

 plained the poor sorting in the turbidites as relating to the small size of the channel 

 which limits the distance over which sorting can occur and to the hydraulic behavior 

 of the variety of biological debris in the turbidity current flow. 



26 



