Cook Strait Sniffer Geochemical Survey March/April 1986.

This report presents an interpretation of the geochemical SNIFFER survey data collected during 1986 in the Cook Strait offshore of NZ. Principal findings and conclusions from this survey are: 1. Elevated quantities of the light hydrocarbons are present in five sub-areas within the survey area. In all five areas, the hydrocarbons added to the water are at low levels and dry (0.3% gas wetness); and 2. Correlations between the hydrocarbons are poor, which is not considered to be indicative of a strong thermogenic origin. The presence of some ethylene in one area further suggests a non-thermogenic source. Thus, it is concluded that the anomalous hydrocarbons have a biogenic origin. Correlation of the anomalous areas with the sub-surface geology may confirm or refute this interpretation.