Table 2

Abundances and isotopic compositions of kerogens and individual compounds. Biomarker ratios were measured according to published methods (7, 15). Numbers in subscript refer to the number of carbon atoms in the biomarker.

Mam1Roy1Roy2Roy5Roy3
Depth (m)665.4679.4681.9696.9718.2
Acyclic hydrocarbons*
Pristane/phytane1.2 (0.1) 1.31.31.01.3
Pristane/n-C17 0.2 (0.1)0.30.40.50.3
Phytane/n-C18 0.1 (0.1)0.20.30.50.2
Hopanes(ppm)§ 23030075110
C27Ts/(C27Ts+C27Tm)| 0.59 (0.01)0.570.590.560.58
C29Ts/C29 | 0.23 (0.04)0.240.160.200.25
(C27Ts+C27Ts)/C29 |, 1.3 (0.40)1.10.571.01.82
C29/C30 1.3 (0.20)1.32.11.40.9
C30/C31 1.1 (0.16)1.41.51.31.5
2α-Methylhopane index,# 14 (1.4)12171212
Steranes/Hopanes|,,** 0.79 (0.20)0.952.60.611.1
Steranes (ppm)§ 180280190120
Dia- /Regular |,,TF2-164 0.58 (0.10)0.911.330.770.87
C2920S/(20S+20R)| 0.53 (0.04)0.640.770.630.57
C29αββ/(ααα+αββ)| 0.54 (0.02)0.580.630.610.57
C27/(C27+C28+C29) 0.52 (0.03)0.540.570.500.55
C28/(C27+C28+C29) 0.21 (0.04)0.190.200.200.20
C29/(C27+C28+C29) 0.28 (0.04)0.280.230.300.25
TA-I/(TA-I+TA-II)|,‡‡ 0.920.940.96>0.900.96
Carbon isotopes (δ13C per mil PDB)
Kerogen−46.8†† −39.5−39.6−41.1
n-C17−26.2TF2-166 −26.2−26.0−27.0
n-C18−26.5−26.1−27.4−26.3
Pristane−28.8−29.4−29.8−28.9
Phytane−29.6−29.5−30.1−27.8
  • * Ratios measured using GC-FID peak areas.

  • The value in parentheses is the maximum error of the particular ratio obtained in a series of repeat measurements.

  • C27Ts = 18α(H)-22,29,30-trisnorneohopane; C27Tm = 17α(H)-22,29,30-trisnorhopane; C29Ts = 18α(H)-30-norneohopane; C29 = 17α,21β(H)-30-norhopane; C30 = 17α,21β(H)-hopane; C31 = 22S + 22R 17β,21α(H)-29-homohopane; 2αMeC31 = 2α-methyl-17α,21β(H)-hopane.

  • § Estimated concentration of hopanes (C27Ts, C27Tm, C29Ts, C29, C30, C31, 2α-MeC31) and steranes (C27 to C29 20S + 20R 13β,17α(H)-diasteranes and C27 to C29 20S + 20R 5α,14α,17α(H) and 5α,14β,17β(H)-regular steranes) in the saturated fraction of the bitumen. D4-20R-5α,14α,17α(H)-cholestane was used as internal standard.

  • | Indicates a parameter primarily controlled by degree of thermal maturation.

  • Indicates a parameter primarily controlled by organic matter sources.

  • # The 2α-MeC31/(2αMeC31+C30) is expressed as a percent.

  • ** Ratio measured using hopanes C27Ts, C27Tm, C29Ts, C29, C30, C31 and the C27 to C29 dia- and regular steranes.

  • Ratio measured using C27 to C29 20S + 20R 13β,17α(H)-diasteranes and C27 to C29 20S + 20R 5α,14α,17α(H) and 5α,14β,17β(H)-regular steranes.

  • ‡‡ Triaromatic-sterane ratios measured using SIR m/z 231 as defined in (7).

  • †† Carbon isotope data measured by combustion of isolated kerogens (4).

  • Analytical errors for GC-C-IRMS are within 0.4 per mil.