An oil seep at Leask Bay, Stewart Island, New Zealand

Chemical analysis of a recently discovered oil seep on Stewart Island, New Zealand, shows the oil to be natural, mature, and closely comparable with condensate from Kawau‐1A, Great South Basin. The seep appears to be associated with a substantial fault cutting the local diorite. Such a fault would act as a migration conduit from the sedimentary sequence offshore. The implication is that hydrocarbons generated deep in the Great South Basin may have migrated westwards into the shallow basin margin; future exploration therefore should look for trapping in such a position.