A new method of comparing extended hopane distributions

Variations in extended hopane distributions are now routinely applied in assessing anoxia in ancient marine sediments and for oil-source correlation studies. Current parameters based on the extended hopanes focus on the predominance of the C-35 17 alpha homologues (22S + R isomers), and thus reveal little information on the overall distribution. We present here a new method of characterising extended hopane distributions, using a combination of a C-31:C-33:C-35 ternary diagram, and a hopane odd/even predominance parameter (HOEP). This allows the distinction of virtually all extended hopane distributions. The ternary figure is particularly useful in characterising large numbers of distributions and for correlation purposes. The application of this figure to a set of North Sea data, reveals the existence of a continuum of extended hopane distributions.