254 



Sediments 



ited each year is the total for all normal 

 sediment and all turbidity current deposits. 

 The results, given in Table 20, are supple- 

 mented by figures for green porphyrin pig- 

 ments and hydrocarbons measured mostly 

 on other samples in the same basins 

 (Table 14). 



Results 



The rate of deposition for total sediment 

 varies throughout the region by a factor of 

 34, from 123 mg/sq cm/yr in Santa Monica 

 Basin to 3.6 on the deep-sea floor (Table 

 20). The rate for the latter is slightly more 

 than the 2.8 mg/sq cm/yr computed for the 

 same eight Atlantic Ocean cores mentioned 

 earlier, and the difference is reasonable in 

 view of the differences in distance from 

 sources of supply for the two areas. An 

 estimate of 0.073 mg/sq cm/yr by Revelle, 

 Bramlette, Arrhenius, and Goldberg (1955) 



for the nonbiogenous component of deep- 

 sea sediments in the central Pacific Ocean is 

 far lower and is also lower than other gen- 

 eral oceanic estimates made by Kuenen 

 (1950, p. 384). Rates of accumulation for 

 calcium carbonate vary by a factor of 45, 

 from 0.2 to 8.9 mg/sq cm/yr, but if the 

 deep-sea floor is excluded, calcium carbon- 

 ate varies by a factor of only 8. Organic 

 matter is deposited at rates of between 0.1 

 and 4.9 mg/sq cm/yr, a factor of 50. About 

 one-third of the organic matter is regener- 

 ated before burial to a depth of 3 meters. 



Plotted in map form (Fig. 207), the rates 

 of deposition of the various components of 

 the basin sediments given in Table 20 form 

 interesting patterns. Both normal detrital 

 and total sediments (chiefly normal detrital 

 and turbidity current deposits in nearshore 

 cores, plus some calcium carbonate and 

 organic matter) are deposited fastest in the 

 nearshore basins and formerly in those 



Table 20 



Absolute Rate of Deposition of Sediments 

 (mg/sq cm/year) 



* Data for organic matter and pheophytin is for surface of sediments: all other parameters are for sediments at depth. 



