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

Abstract

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.