PART ONE (February 1972)AIM:To further acquire reconnaissance reflection seismic data on an approximately 8 mile-square grid, for identifying broad regional trends within the offshore Denman Basin, presently regarded as a probably sinistrally-sheared southeastern counterpart to the Canning Basin of Western Australia.METHODS: Survey dates: 19 - 24/2/72. Energy source: 1300 cu. in. airgun array. CDP coverage: 2400%. Recording mode: 24 channel digital - Texas Instruments DFS III recorder. SP interval: 164 feet; group interval: 328 feet.RESULTS:16 lines totalling 839 miles were recorded by Party 909 of Geophysical Service International, Inc. using the M/V R.C. Dunlap, and were processed in Houston, Texas by that company. Seismic interpretation was also performed in Houston by Outback's geophysical consultant G.J. Long and Associates, Inc. Data quality varied from good to poor across what is now seen as a region of complex geology. At least 18 anomalous structural features were identified spread across the permit area, relating variously to a southwestern depositional platform, a deeply downfaulted central graben zone with at least 5500 feet of fill, and a structurally complicated truncated basement massif in the east. Three structurally closed features within the NW-SE oriented graben are seen as having promise as drillable leads, following further detailing. The seismic data available now strongly suggest the presence of additional sediments below the currently lowest mapped horizon, extending to an indeterminate depth. PART TWO (November 1972)AIM:To provide additional control lines for delineating drilling locations.METHODS: Survey dates: 1 - 17/11/72. Energy source: 1200 cu. in. airgun array. CDP coverage: 2400%. Recording mode: 24 channel digital - Texas Instruments DFS III recorder. SP interval: 109 feet; group interval: 218 feet.RESULTS:37 lines totalling 1146 miles were recorded by Party 931 of Geophysical Service International, Inc. using the M/V Eugene McDermott II, and were processed in Houston, Texas by that company. Seismic interpretation was also performed in Houston by Outback's geophysical consultant G.J. Long and Associates, Inc. The new seismic data obtained with a shorter spread length has better disclosed the shallow strata in the basin, which by their character resemble an alternating sand-shale section above the top ?Mesozoic reflector. For the same reason the new coverage now allows more continuous mapping than was available for the earlier interpretation; otherwise the data quality is similar. This interpretation differs from that of July 1972 only in details relating to the extra control lines, plus there are some modifications of the mapped horizons in the eastern and western extremities of the permit. The 3 structures of primary interest lying within the central graben are now more localised, with recent data furnishing better measures of critical components of dip (in the context of sub-unconformity stratigraphic traps). Moreover, in the vicinity of Anomaly I, seismic phenomena are observed which are of a type that has been associated with hydrocarbon (gas) occurrences elsewhere. However, the significance of these bright spots will remain purely speculative until a multi-well drilling programme is undertaken in the offshore basin. Such a programme is recommended, to test the 3 chosen leads in order of priority, which will require drilling to depths of between 2500 and 10,000 feet in order to adequately evaluate the strata identified by seismic reflections.