Fig. 1. Location of sediment samples collected in (he Bering and Chukchi Seas. 



correspondingly low R ratio typical of a condensate. The 

 central and northern portions of the study area have significant 

 relative highs in fluorescence intensity and high R values 

 (>2.0) more typical of an oil signature (see the discussion 

 below). 



Gas Chronuitof^raphy 



Gas chromatographic analysis demonstrated that aliphatic 

 hydrocarbons are ubiquitous in sediment extracts throughout 

 the survey area. Normal alkanes were predominantly of 

 terrestrial, biological origin as evidenced by the abundance of 

 compounds with 23, 25, 27, 29, and 31 carbons (Fig. 5). The 

 lower molecular weight alkanes were only a small percentage 



of the total n-alkanes in most cases. In general, most alkanes 

 appeared to be of a biological origin, including complex 

 mixtures of normal and branched alkanes and alkenes with 15, 

 17, and 21 carbons. The presence of petroleum related n- 

 alkanes and/or UCM"s were observed in sediment extracts at 

 Stations 22. 32, 33, 45, 67, 92, and 107. In gravity cores the 

 highest concentrations were deep in the core suggesting an 

 upward migration source. A low level unresolved complex 

 mixture was observed at many locations. The geographic 

 distribution of the total unresolved complex mixture is presented 

 in Fig. 6. The co-occurrence of high fluorescence and R ratio 

 values and GC derived indicators confirms the presence of 

 microseepage at several locations. 



294 



