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  • 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.

  • A seismic velocity survey of the APM Development Pty Limited No. 1 bore at Rosedale, Victoria, was made by the Geophysical Branch of the Bureau on the 3rd May 1960 using a TIC three-component well geophone. Measurements were taken with the geophone suspended in the well at selected intervals down to 5500 ft. It was apparent that signals reached the geophone by transmission along the cable by which it was suspended, and these interfered with the signals reaching the geophone along a path directly through the ground. This made interpretation difficult; however, by careful inspection of both the vertical and horizontal components of the signals received by the geophone at each depth, an interpretation has been made that yields a series of velocity/depth determinations. The average vertical velocity increases from 5000 ft/sec at the surface to 8930 ft/sec at a depth of 5500 ft. The average velocity in the Tertiary (0-2159 ft below datum) was computed to be 6420 ft/sec; the -werage velocity in the Mesozoic rocks penetrated (2159-5314 ft below datum) was 12,180 ft/sec. Two reflection spreads laid out and recorded in the vicinity of the bore showed the presence of reflectors at depths estimated to be in excess of 7700ft.

  • Towa.:ccis the end of 1960 , the Bureau. of Mineral Resources, Geology and Geophysics made a brief seismic survey in the Winton area of Queensland to resolve an apparent contradiction between the interpretations of gravity and aeromagnetic results previously obtained in the area. Gravity and aeromagnetic results both suggested the occurrence of a large fault or fault zone about 20 miles north-west of Winton, but the gravity and aeromagnetic interpretations differed regarding the direction of throw of the fault. A nine-mile seismic reflection traverse was surveyed across the supposed fault. The seismic results indicate the presence of a large fault or monoclinal fold with dowthrown side nouth-wast as suggested by the gravity values and also a smaller fault or monocline about two miles south-east with downthrown side south-east. The variations in thckness of Mesozoic rocks caused by these features were insufficient to explain the observed Bouguer gravity anomaly values, but the seismic results left open the possibilitues that there may be a considerable thickness of pre-Mesozoic sedimemts north-west of the main monocline or fault. It is postulated that the steep gravity gradient observed may be due to a large fault whose main movement took place in pre-Mesozoic times. Indications are that there is 5000 to 6000 ft of Mesozoic sediments in tha area.

  • Between February and April 1961 the Bureau of Mineral Resources, Geology and Geophysics made a seismic survey in the Rosedale area of the Latrobe Valley, partly at the request of the State Electricity Commission of Victoria to provide more information about the brown coal measures in this area, and partly in order to test the Bureau's latest seismic recording equipment. One traverse, combining both reflection and refraction profiling techniques, was run south from the A.P.M. No.1 bore at Rosedale as far as Merrimans Creek, and a second traverse was run west from the bore as far as Toongabbie. Results show that the maximum thickness of the Tertiary sequence is about 3000 ft and that it thins gradually to 1000 ft at Toongabbie and rapidly to about 750 ft on the Baragwanath Anticline. It is shown that early Tertiary deposits were laid over the whole area but have been uplifted and partly eroded in late Tertiary or post-Tertiary times in the Toongabbie and Baragwanath areas, but the main syncline sank and accumulated thick Tertiary sediments. Results show alao that on the northern flank of the Baragwanath Anticline where crossed by the seismic lines the Tertiary and Jurassic sediments are steeply folded but not necessarily faulted. No positive information was obtained below 4500 ft but long refraction shots suggest that a high-velocity basement does not exist at a depth less than 12,000 ft.

  • Between August and December 1960 a seismic party from the Bureau of Mineral Resources carried out a reconnaissance seismic survey, using reflection and refraction techniques, across the Murray Basin. Traverses were placed at selected localities at Carrathool, Hay, Maude, Balranald, Wentworth, Merbein, Lake Victoria, and Loxton. In general, the results show that the Basin, at least along the line of traverse, consists of essentially undisturbed sediments above a high-velocity basement. The thickness of Basin sediments ranges from about 900 ft at Carrathool to 2200 ft at Lake Victoria and Merbein. Most of the sediments are of Tertiary age, with Mesozoic at Loxton and Wentworth and perhaps at other traverses in the western part of the Basin. The seismic velocity in the sediments has a typical value of about 6000 to 7000 ft/sec, while the velocity in the basement ranges from 15,750 ft/sec (at Hay) up to 20,000 ft/sec (at Lake Victoria). The geological nature of basement is not known, but it is considered that it definitely marks the floor of the Tertiary (or Tertiary - Mesozoic) basin. Refraction velocities alone are of doubtful value in identifying the floor, as it is known that crystalline basement, metamorphosed sediments, or unmetamorphosed sediments such as limestone, may have velocities within this range.

  • 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.

  • The Bureau of Mineral Resources Seismic Party No. 2 conducted a survey from 15th May to 25th August 1961 in the Amadeus Basin. Reflection and refraction traverses were shot at intervals, along or near the Alice Springs/Port Augusta railway line, from Polhill in the north to Finke in the south. In broad terms the object of the survey was to obtain across the Amadeus Basin a north-south seismic cross-section that would aid in investigating the stratigraphic cross-section and structural relations especially on the southern margin of the Basin. Access and drilling problems caused the progress of the survey to be slow. The statistics of the operation are included in three appendices. During the course of the seismic survey, the Bureau also made gravity surveys covering the area; gravity-meter readings were made along all seismic traverses.

  • Seismic refraction velocities were measured in the Archaean or crystalline basement rocks at Mount Davies (SA) and Giles (WA) where the rocks are near the surface. Refraction velocities were measured in the Proterozoic outcrops of the Rawlinson Range and Lake Hopkins. Refraction velocities were measured in the Palaeozoic and Mesozoic rocks at Lake Christopher, and in the Mesozoic rocks at Iragana Turnoff. Those velocities were used as a basis for a suggested correlation between refractors recorded at traverses between Signpost and Mount Beadell. Reflection tecniques, as tried 9 yielded fair reflections at Mount Beadell, and doubtful reflection alignments at trig. point NMF 19. It is likely that the sedimentary basin shows an increasing thickness of sediments from Signpost to Mount Beadell, At Mount Beadoll there is at least 6000 ft of apparently post-Proterozoic sediments. The thickness and degree of metamorphism of Proterozoic ratio below this have not been determined. Present evidence suggests an area of uplift under Lake Breaden.

  • The Bureau of Mineral Resources'No. 2 seismic party conducted a Survey over the Palm Valley Anticline 80 miles west of Alice Springs, from 2nd November to 22nd November 1961. The seismic reflection method showed (a) the anticlinal structure existed at depth and (b) at the northern end of the main north-south traverse in the Missionary Plains north-dipping reflections were recorded from about 2500-ft depth. A shallow refractor was recorded in which the velocity Was 17,800 ft/sec. This refractor, which could not be positively identified, prevented, any useful deeper refraction information being recorded.

  • The Undilla Basin, in north-western Queensland, is a small sedimentary basin containing Cambrian limestones which adjoin the widespread but undated CamoowJal Dolomite to the West. In the latter part of 1961 the Bureau of Mineral Resources, Geology and Geophysics did a brief reconnaissance seismic survey lasting about seven weeks in the Undilla Basin. This Record describes briefly the work done and results obtained. The occurrence of limestone near the surface throughout the basin presented difficult problems in the application of the reflection and refraction seismic methods but some progress was made towards the solution of these problems.