Organic Constituents 



279 



CHLOROPHYLL A 



CH^ HV— to 

 CHp CO^CH^ 

 COpCpfjHjp 

 PHEOPHYTIN A 



VINYL PHEOPORPHYRIN 



DESOXOPHYLLOERYTHRO- 

 ETIOPORPHYRIN 



PLANTS 



SEDIMENT 



INTERMEDIATE PETROLEUM 



Figure 223. Relationship of chlorophyll to pheophytin a and pheophorbide a in sediments and to porphyrins in 

 petroleum. From Orr, Emery, and Grady (1958, Fig. 16). 



contain less than 5 ppm of pheophytin. 

 Within individual basins the areal distribu- 

 tion of pheophytin is directly related to con- 

 tent of nitrogen and inversely related to 

 grain size. In vertical sections provided by 

 cores it also exhibits a very close relationship 

 to grain size, and thence to water content, 

 carbonate, and nitrogen (Fig. 224). These 

 changes are superimposed on a general de- 

 crease in concentration with depth of burial. 

 Pheophytin reaches its greatest abundance 

 in sediments found at a depth of about 600 

 meters, in contrast to nitrogen which is most 

 abundant at about 1500 meters. Its relation- 

 ship to both nitrogen and depth is so close 

 that if the contents of nitrogen and pheo- 

 phytin in a sample are known, an estimate 

 of the depth of water accurate to within a 

 few hundred meters can be formed (Fig. 

 225). The rate of deposition of pheophytin 

 in muddy sediments throughout the area of 

 Chart I ranges from more than 0.001 mg/sq 



cm/yr in the northeastern nearshore basins 

 to less than 0.00001 mg/sq cm/yr in deep- 

 sea red clays (Fig. 226, Table 20). For the 

 entire region about 280 tons of pheophytin 

 are deposited annually (Table 21), but about 

 three-fourths of it is regenerated before 

 burial to a depth of 3 meters, leaving only 

 about 70 tons annually buried to that depth 

 and still less to greater depths. 



The relationship of pheophytin to nitrogen 

 provides information about its regeneration. 

 In phytoplankton nitrogen is about 1.5 times 

 as abundant as pheophytin, at the surface 

 of the sediment in Santa Barbara Basin ni- 

 trogen is 35 times pheophytin, and at 3 

 meters it is 60 times pheophytin. Even 

 greater differences exist in some other basins; 

 for example, at 3-meters depth in a core 

 from San Clemente Basin nitrogen is 400 

 times pheophytin. It is evident that even 

 though nitrogen is lost in the water column 

 and during burial in the sediments, pheo- 



