Diapiric features of the offshore Bonaparte Gulf Basin, Northwest Australian Shelf

Abstract

Offshore reconnaissance seismic sparker surveys shot during the mid-sixties in the Bonaparte Gulf Basin on the Northwest Australian Shelf, outlined a number of diapiric features in the southern part of the Basin. Early aeromagnetic and marine gravity programmes were run on too wide a grid to give clear indications of the nature of the intrusives. Later, more sophisticated seismic equipment was used to map the plugs and it became possible to date the age of the movement of the intrusives in several cases. A wildcat well, Sandpiper No. 1 was subsequently drilled on the crest of one of the features; it entered massive salt at a fairly shallow depth, as did another well, Pelican Island No. 1, a hundred miles to the south. Hypotheses involving salt migration toward the Basin margins are put forward to explain the Wickham Gravity High, uplift at the SW Basin Margin Fault and the Petrel Structure. The salt is dated as "probably Devonian" with salt flowage probably continuous from at least Upper Permian time.