These documents have been scanned by the GA Library. Please refer to the document for contents.

These documents have been scanned by the GA Library. Please refer to the document for contents.

Legacy product - no abstract available

The Fenton Fault, one of the major tectonic lines in the Canning and Fitzroy Basins, has always presented a major problem to geologists seeking to determine its true nature and significance. The investigation described in this report was intended to contribute towards a solution of the problem. This investigation included a seismic reflection traverse across the Fault in the area of Barnes Flow, near where previous gravity and airborne magnetic traverses had crossed it, together with refraction traverses on each side of and across the fault. The results of previous surveys are discussed, and show that the gravity meter is a most useful tool for the further investigation of the Fenton Fault. However, unless new and effective treatment of results can be devised, it is of doubtful value in investigating folding within the Fitzroy Basin, though this does not necessarily detract from its value for regional surveys. The airborne magnetometer on the other hand, is not a reasonable tool for investigating the Fault. It is concluded that the Fenton Fault at Barnes Flow is a normal fault, downthrown to the north-east, with a throw probably exceeding 10,000 feet. The thickness of the sedimentary section on the north side of the Fault near Barnes Flow probably exceeds 16,000 feet. On the south side a velocity of over 20,000 ft/sec. was recorded from a depth of 5,500 feet. This probably indicates the depth to basement at this point. On the south side of the Fault at Jurgurra Creek the sedimentary section appears to be about 7,000 feet thick. The conclusion that baaement is relatively shallow to the south of the fault could be tested by drilling. The rig used should be capable of drilling to at least 6,000 feet to ensure that the 20,000 ft/sec. refractor may be penetrated and identified.

An experimental seismic survey was conducted at Haddon Downs, South Australia, during Octobor and November.1957. The area lies within the Eromanga Sub-basin of the Great Artesian Basin, and at least 5,500 feet of Mesozoic section are known to exist there, part of which is of a marine facies. Preliminary reconnaissance work by geologists of Santos Ltd. which holds an Oil Prospecting Licence over the area, revealed some large anticlines on the surface. The Company has already completed a limited amount of gravity work which gives promise of supplying useful information on both regional and detailed subsurface structure. Two important refractors were recorded which may be useful for semi-regional mapping. A refractor of velocity 10,250 ft/sec. was recorded from a depth of about 2,700 feet, and this may represent the top of the marine Cretaceous section. The second refractor of velocity 17,000 ft/sec. and aidoroximate depth 7,250 feet may be just below the base of the Mesozoic section. Large multiple geophone arrays and pattern shots were needed to obtain good quality reflections over most of the area, except when shooting on the alluvial plains of the larger creeks. The sedimentary section was shown to be at least 8,000 feet and possibly 16,000 feet thick, The base of the Mesozoic section is interpreted as being 7,250 feet deep on the refraction traverse and 8,600 feet at the south-east end of the reflecta.on traverse. The rest of the section probably consists of Palaeozoic sediments. If so, the high velocity (17,000 ft/sec.) suggests that a dense elastic or crystalline limestone is probably present near the top of them. The structure of the Mesozoic section is subhorizontal, but there may be minor structures with dips less than 1 degree which correlate with the surface structures.

An experimental seismic survey was conducted at Surat, Queensland, on behalf of the Australisa Oil and Gas Corporation Limited during a five week period from May 28th to July 2nd. 1958. The area lies within the southeastern portion of the Great Artesian. Basin on Authority to Prospect No. 36P and, sel the evidence of numerous bores near Roma, and a few other scattered bore logs, is considered to contain sediments suitable for the generation and accumulation of hydrocarbons in possible, economic vantities. A local geological survey by the Australian Oil & Gas Corporation suggested a structure of considerable dimensions - the 'Weribone Uplift' - which, if substantiated, would provide a promising location for a stratigraphic test bore. The experimental survey conducted by the Bureaushowed that useful results could be obtained throughout the area by conventional methods of reflection and refraction shooting. The reflection shooting indicated a fairly uniform sedimentary section with generally flat-lying beds and a probable total thickness of 7,000 to 8,000 feet. The refraction work recorded several velocities: including one near 19,000 f/s which is assumed to be a basement velocity. Depths measured to this high Velocity refractor support the estimate of the thickness of sediments made from the reflection cross-section and indicate 4 south component of dip of about 40 ft. per mile across the area surveyed. Neither the reflection nor the refraction work gave any evidence for the existence of the 'Weribone Uplift'. However, the more northerly refraction traverse indicated a local component of north dip at basement depth, and a single reflection record shot along that traverse suggested a substantial thickening of the deeper sediments towards the north. Insufficient seismic work was done to estimate the northwards extent of this dip. Such limited evidence might well indicate a purely local irregularity in basement topography. On the other hand, the north dip could be extensive, and therefore structurally significant. Any further seismic work contemplated in this area should be directed, in the first instance, towards checking this possibility.

The Bureau of Mineral Resources carried out a seismic survey of four months' duration in the Carpentaria Basin, North Queensland, in the second half of 1958. The survey showed that the Carpentaria Basin deepens gradually from the south, east, and west towards the southeastern corner of the Gulf of Carpentaria. The maximum thickness of sediments measured was about 1000 metres near Rutland Plains in the north of the survey area. It was found that gravity anomalies in the area do not correlate with basement relief.

These documents have been scanned by the GA Library. Please refer to the document for contents.

These documents have been scanned by the GA Library. Please refer to the document for contents.

The R502 series of maps has been replaced by the National Topographic Map Series (NTMS). The R502 series consists of 542 map sheets and covers Australia at a scale of 1:250,000. It was compiled from aerial photography, but only about one quarter of the series was contoured. The standard sheet size is 1 degree of latitude by 1.5 degrees of longitude. Transverse Mercator map projection and Clark 1858 datum were used. Coverage of the country was completed in 1968.