200million barrel onshore poss 50 plus bagger, page-20

Stewart Island seeps

Alternative suggestions have been offered for the origin of
the Leask and Horseshoe Bay oil stains: biodegraded engine
fuel (Gibbons & Jackson 1980) and a natural seep from a
similar source to Kawau condensate (Cook 1982).

As for the condensate from Kawau-IA, there is no clear correlation with any potential source-rock sample, but the biomarker and isotopic characteristics could be consistent with an origin from mid-Cretaceous coaly units. The stains are slightly isotopically lighter than the Kawau condensate, as might be expected if they originate from the same source horizon (in different kitchen areas) but have retained a slightly greater proportion of higher plant derived waxy «-alkanes, as observed in gas chromatograms (Cook 1982).