Partial resolution of sources of n-alkanes in the saline portion of the Parachute Creek Member, Green River Formation (Piceance Creek Basin, Colorado)

Systematic variations in the ¹³C contents of individual extractable n-alkanes (C₁₆-C₂₉) can be modelled quantitatively and interpreted as indicating contributions from at least five distinct sources. These appear to be cyanobacterial (C₁₆-C₁₈, δ¹³C = - 37 0 00 vs PDB), phytoplanktonic C₁₆-C₂₃, δ = -32 0 00), chemoautotrophic bacterial (C₂₀-C₂₉, δ = -38 0 00), phytoplanktonic or heterotrophic bacterial (C₂₀-C₂₉, δ = -30‰), and vascular plants (C₂₃-C₂₉, δ = -29‰). Hydrous pyrolysis of related kerogens yields large quantities of additional n-alkanes with different and much more uniform δ values. The latter materials are apparently derived from the thermolysis of aliphatic biopolymers whose presence in the Green River Oil Shale has been recognized visually.