G.J. Long and Associates, at the request of Outback Oil NL, has undertaken a review of seismic and magnetic data recently obtained from the offshore portion of OEL 33. The amount of data available for study is limited, with the spacing of seismic lines in the area ranging upwards from a distance of 25 miles apart.Three seismic horizons were picked for mapping and structural interpretation. At the shallowest, locally discontinuous, possibly Cretaceous reflecting horizon level, a seaward projection is seen of the trough which has been recognised onshore in the vicinity of Mallabie 1. Underlying this and the pre - Tertiary unconformity, a strong top ?Cambrian reflecting horizon is correlative over approximately two-thirds of the offshore licence area. The topography of this level is rugged due to fault activity, but records from the northern end of lines in OEL 33 suggest that a thicker post-Cambrian section is present there than at locations further offshore. Mapping of a third, distinctive high-velocity refractor event, possibly the top of basement, allows sufficient areal control to indicate that sediments may be from 6200 to 10,000 feet thick within the offshore extension of the trough observed in onshore, near coastal stratigraphic wells .It is recommended that drilling be undertaken preferably at the deepest known point in this trough (SP 75, line F), or alternatively at the corresponding deepest location onshore, for the purpose of gaining stratigraphic information to guide the direction of future geophysical work aimed at structural targets.