Organic Constituents 



283 



WAVE NUMBER -CM-I 



5000 3000 2000 1500 1200 1000 900 800 700 650 



TIinilllllllllUil'liHIippMMIi M M M M MM i I 'I |iiii|iMi|nii i i n i |i ii i|ii i|| i i ii | iii 1 1 1 1 1 1 1 1 1 i 1 1 i i i i | i i i i i [ i i i i | i i i n | i i ii i 



6 7 8 9 10 II 12 



WAVE LENGTH — MICRONS 



Figure 227. Infrared spectra for paraffin-naphthene, aromatic, and asphaltic fractions of samples of organic matter 

 present between 418 and 478 cm in Santa Barbara Basin and of Pliocene crude oil from Los Angeles Basin. From 

 Orr and Emery (1956a, Fig. 2). 



present as it is in petroleum (Oakwood, 

 Shriver, Fall, McAleer, and Wunz, 1952) and 

 in chromatographic fractions from Recent 

 sediments of the Gulf of Mexico (Smith, 

 1954), but it could not be measured, owing 

 to the small size of the hydrocarbon frac- 

 tions. The elemental composition, molecu- 

 lar weight, spectra, waxy nature, and the 

 degree of rotation indicate that the paraffin- 

 naphthene fractions are largely straight 

 chains 15 to 30 carbon atoms long. 



Data on the depth distribution of hydro- 

 carbons are provided by three to five sam- 

 ples in cores from four basins (Table 27), 



some of which are presented in Figure 228. 

 Total extract decreases with depth in all four 

 basins, indicating the loss of less resistant 

 organic materials during the course of burial 

 if steady-state conditions existed throughout 

 the period of deposition. The paraffin- 

 naphthene fraction decreases with depth in 

 Santa Barbara and Tanner Basins, the two 

 basins in which it is most abundant. It pre- 

 sents only an irregular depth variation in the 

 other two basins, although conceivably if 

 hydrocarbons could have been run on a very 

 thin surface layer of sediment, they would 

 have been found quite abundant there. The 



