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 C-13 contents of individual extractable n-alkanes (C-16-C29) can be modelled quantitatively and interpreted as indicating contributions from at least five distinct sources. These appear to be cyanobacterial (C-16-C18, deltaC-13 = -37 parts per thousand vs PDB), phytoplanktonic (C-16-C23, delta = -32 parts per thousand), chemoautotrophic bacterial (C20-C29, delta = -38 parts per thousand), phytoplanktonic or heterotrophic bacterial (C20-C29 delta = -30 parts per thousand), and vascular plants (C23-C29, delta = -29 parts per thousand). Hydrous pyrolysis of related kerogens yields large quantities of additional n-alkanes with different and much more uniform delta 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.