1,700 cm -1 ; (Figure 6). The elemental analyses of 



the resins confirm this tendency toward oxidation over time (oxygen 



levels in March 1978 were 5.4 % ; in June 1980, 7 %). 



31 03-78 



22-11-78 



20 06-79 



17-01-80 



24-06-80 



3400 3000 



1700 



1100 



700 



cm 



1600 



Station 5 - FIGURE 6. Infra-red spectrometry of the resins. 



The distribution of saturated hydrocarbons determined by gas 

 phase chromatography (Fig. 7) demonstrates the evolution which led to 

 the degradation of the n-alkanes (5.99 % to 3.33 %) to n-C30 (Table 1). 

 It should be noted that by March 31, 1978, this degradation appears to 

 have begun. Thus there was an increase in the ratios of pristane/n-Cl7 

 and phytane/n-Cl8 (Table 1). The isoprenoids degraded less easily than 

 the n-alkanes (TISSOT and al . ) , but by June 1980 these compounds could 

 no longer be detected. As degradation advanced, the contribution of the 

 biogenic hydrocarbons increased, and n-alkanes of odd carbon numbers 

 between n-C25 and n-C35 -- characteristic of the cuticle waxes of higher 

 plants (Eglington and Hamilton - 1963) — appeared, confirming the ter- 

 restrial contribution to the contents of organic matter in the sediments. 



Moreover, the disappearance of the n-paraffins points up a relative 

 enrichment in the unresolved complex mixture of the isoalkane and cyclo- 

 alkane compounds, and generally in the compounds around n-C30 . It was 

 possible to demonstrate these last compounds by GPC/MS by measuring 

 the masses : m/e 217 being characteristic of the tetracyclic 



117 



