Rate of Deposition 



255 



ii7°i2r 



DETRITAL- 

 -o ^^\ NORMAL 



, ^^■^•X TOTAL ORGANIC 

 <,^ ^^ "^"^ "MATTER 



Figure 207. Rates of deposition in mg/sq cm/yr of the major constituents in basin sediments. The rates are based on 

 radiocarbon ages of cores at localities indicated by circles, except for Los Angeles and Ventura Basins on land where 

 the rates are based on the thickness of all post-Miocene strata. Contours have been drawn independently of basin 

 boundaries but of course refer only to the basin, continental slope, and deep-sea sediments. Total sediment includes 

 normal detrital grains, turbidity current deposits, calcium carbonate, and organic matter at the surface. 



basins now on land because of their near- 

 ness to the chief source of sediments — the 

 Transverse Ranges (Santa Ynez, Santa 

 Monica, San Gabriel, and San Bernardino 

 Mountains). At greater distances from 

 shore the rate for normal detrital and for 

 total sediment diminishes, except for minor 

 erratic variations. Calcium carbonate is 

 also being deposited most rapidly in near- 

 shore basins, probably partly because of in- 

 clusion of reworked calcium carbonate from 

 shelf areas and because of greater produc- 

 tivity of surface waters near Santa Barbara 



Basin. On the deep-sea floor the rate of de- 

 position of calcium carbonate, or rather the 

 rate of its accumulation, is low because of 

 solution in the corrosive deep oceanic waters 

 before it can become safely buried. Organic 

 matter is being deposited much faster in the 

 nearshore basins of rapid burial than in off- 

 shore basins and on the deep-sea floor where 

 it becomes oxidized before burial. Again 

 high productivity near Santa Barbara Basin 

 is probably partly responsible for high values 

 there. 



The lapsed time for deposition of the 



