704 



ARRHENIUS 



[chap. 25 



F. Organic Matter 



At the low rate of deposition characteristic of pelagic sediments, and under 

 the oxidizing conditions usually prevailing at the deep-ocean floor, most of the 



Fig. 31. Carbon and nitrogen concentrations as a function of depth in a pelagic clay 

 sequence (Sw 55, 11° 20'N, 127° 37'W; 4916 m). (From Arrhenius, 1952.) 



EN (//mole/I.) NH3 (/zmole/l.) NO3 (//mole/I.) NO3 (mole % of EN) 



Qgpip^ 3500 3500 50 100 150 200 10 20 30 40 50 



cm 



200 



400 



600 



800 



(a) 



(b) 



(c) 



(d) 



Fig. 32. Distribution of nitrogen between ammonia and nitrate in interstitial solution of 

 core Capricorn 38 BP (South Pacific, 14° 16'S, 119° ll'W; 3400 m). (From Arrhenius 

 and Rotschi, 1953.) 



organic matter is oxidized soon after deposition. The oxidation probably is 

 accomplished mainly by bacteria and mud-eating animals concentrated in the 

 surface layer of the sediment (cf. Section 5, and ZoBell, 1946, p. 91). In pelagic 

 sequences far from any terrestrial source of organic matter, the concentration 



