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  • F55/B1-13 Vertical scale: 100

  • F55/B1-38 Contour interval: 5

  • 35% coverage east F55/B1-41 Contour interval: 10

  • A seismic velocity survey was carried out in Associated Freney Oilfields Nerrima No. 1 Bore by the Bureau of Mineral Resources on the 10th August 1955. The well is situated on the Nerrima Dome in the Fitzroy Basin, W.A. Some trouble was experienced with cable breaks for the shallow part of the hole, but in general it was possible to recognise the true formation break. Average measured velocities ranged from 8000 ft/sec near the top to 12,200 ft/sec for the total depth of the bore.

  • Following a gravity survey of the Perth Basin in 1951-52 (Thyer and Everingham, 1956), in which it was indicated that a sedimentary thickness of about 35,000 ft was probably present in the Perth Basin, several seismic traverses were surveyed across the Basin. This Record deals with one such reflection traverse which was surveyed between Quindalup and Donnybrook. The purposes of the survey were to find the thickness and dip of the sediments and to discover any faulting or folding within them. Results of the survey were inconclusive regarding the depth to basement but indications are that it is at least 8000 ft in the deepest part of the B,sin along this traverse. The sediments appear to be folded and faulted. There is evidence for the existence of a major fault east of the Dunsborough Fault, and the existence of the Whicher Fault was tentatively confirmed.

  • Middalya in the Carnarvon Basin, Western Australia, during October 1955 by the Bureau of Mineral resources. The object of the survey was to assist in interpreting gravity results in the region. Prior to this survey the interpretation of the geology suggested that the deepest part of the Palaeozoic basin was in the Wandagee Hill area, but gravity results indicated that a basement ridge may exist in this same area. The seismic results indicate a sedimentary thickness of at least 17,000 ft between Wandagee Hill and Middalya and possibly 24,000 ft thickness to the east of Middalya. Although no useful information was obtained in the immediate vicinity of Wandagee Hill, extrapolation of results from farther east, suggests that the basement may be as shallow as 6000 ft just west of Wandagee Hill. This would confirm the interpretation of the gravity results at this location. The seismic cross-section shows that there may be a large elevation of the basement over a region about 20 miles west of Middalya between Shot-points 90 and 113. Although there is no direct evidence of this in the gravity results, it may be related to faulting, particularly a fault four miles east of Middalya that is indicated both by surface geology and by gravity results.

  • A seismic reflection traverse was surveyed across the Perth Basin, Uestern Australia, between the townships of Rockingham and Mundijong. It was planned in order to give information regarding the depth of the Basin and its structure adjacent to the Darling Scarp. Seismic refraction traverses were surveyed to give the longitudinal velocities in the near surface granitic gneisses on the Precambrian Shield, and in the Cardup Series (Proterozoic) abutting the Darling Scarp. At least 14,000 ft of sediments are indicated in the deepest part of the Basin but there is no clear seismic evidence of what a maximum thickness might be. Seismic reflection results indicate that the sediments on the west of the Darling Scarp abut the older rocks on a plane that dips at about 60 degrees to the west and that cuts the surface some distance in front of the present position of the scarp. This suggests that the Darling Scarp at Eundijong is the surface expression of a normal fault. However, the presence of reflection alignments east of this postulated fault plane, and thus apparently arising within the granitic gneisses, is contrary to the fault hypothesis. The true nature of the tectonic features is thus unresolved. Seismic results indicate that faulting occurred within the Basin and such faulting may have completed closure of possible oil traps. Further seismic investigation of the faults and associated structures is recommended.

  • In July and August 1957 an experimental seismic survey was done in the Oodnadatta area of the Great Artesian Basin. The purposes of the survey were to find whether reflections could be recorded from beneath duricrust, a siliceous surface deposit, and whether structures mapped by surface geological methods persist with depth. Reflections were recorded from beneath the duricrust using shallow pattern holes and six geophones per trace; the sub-surface structure was mapped with reasonable accuracy. In areas where the duricrust is eroded, reflections of fair quality were obtained using a single shot-hole and six geophones per trace. A seismic reflection traverse across the Oodnadatta anticline indicated that the structure was present in a horizon which corresponds to the top of the artesian aquifer at a depth of about 1000 ft below datum (400 ft above MSL). The seismic results indicated that the anticline was of smaller relief than had been e stimated from surface mapping. There was a change from fair-quality persistent reflections at shallow depths to poor-quality less numerous reflections with sporadic dips at greater depths; this probably represents the base of the Cretaceous. The greatest depth from which Cretaceous sediments were recorded was about 2350 ft below datum. Reflection depths computed by seismic methods correspond closely with lithological boundaries, and in particular the base of the Cretaceous sediments, encountered in the Santos No. 1 bore. The results of a refraction traverse on the crest of the Oudnadatta anticline show the presence of a 'basement' refractor with a velocity of 13,900 ft/sec at a depth of about 1245 ft below datum. There is slight evidence of a refractor with a substantially higher velocity at about twice this depth. The 'basement' velocity of 13,900 ft/sec is consistent with the assumption that there is a pre-Cretaceous layer between the Cretaceous sediments and the Precambrian basement complex.

  • On 30th March 1960, a seismic velocity survey was made in the A.A.O. Timbury Hills No. 2 bore, jointly by the Bureau of Mineral Resources and Associated Australian Oilfields N.L. The bore had been drilled to a depth of 4400 ft and was surveyed to a depth of 4304 ft below the rotary table. There remains a doubt whether the breaks recorded on the well geephone were, in fact, cable breaks, particularly between 2300 and 3305 ft below the rotary table. The interpretation has boon made with the belief that true breaks wore recorded. Average and interval velocities were computed and are acceptable geologically. Sandstones, particularly cemented ones, have Renerally higher velocities than shale. The average velocity of the Mesozoic sequence is about 9800 ft/sec. A velocity of 17,980 ft/sec was measured at the bottom of the bore and corresponds to the Timbury Hills Formation of unknown age. The Moolayember Shale has a low velocity calculated as 8360 ft/sec.

  • During 1961 in the southern part of the Surat Basin a seismic party from the Bureau of Mineral Resources surveyed two main traverses by means of seismic reflection and refraction methods; the first was in an east-west direction between Yelarbon and St George and the second was in a north-south direction between Meandarra and Nome. The main purposes of the survey were to find whether the Bowen Basin Permian sediments extend as far south as the latitude of Goondiwindi and whether the Bowen Basin in Queensland and the Sydney Basin in New South Wales formed a continuous region of sedimentation during the Permian period. The east-west seismic traverse indicated a trough of sediments of greatest thickness,tabout 14,800 ft beneath Toobeah; the trough is bounded on the eastorn side at Goondiwindi by a fault down-thrown more than 7000 ft to the west and is bounded on the western side by a series of step.-faults beneath Bungunya and Talweod. The results along the north-south traverse indicated that the trough beneath Meandarra, which represents the southern extension of the Bowen Basin, continues south to Toobeah. The nature of the link, if any, between the Bowen Basin and the Sydney Basin was not established. On the eastern side of the Surat Basin, seismic results indicated that the rocks beneath the Mesozoic sediments are stratified and probably metamorphic. A shelf area between Talweod and St George has about 6000 ft of sediments above a Drobablo metamorphic 'basement'. An anticlinal structure with a dip-reversal of about 1000 ft throw was located between Goondiwindi and Toobeah.