L051 Palm Valley-Hermannsburg seismic survey, NT, 1961

Brief description

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.

Lineage

Maintenance and Update Frequency: asNeeded

Statement: Following a request in March 1961 by Magellan Petroleum Corporation, it was decided that the Bureau of Mineral Resources' No. 2 seismic party would, on completion of the Amadeus Basin survey, conduct a short survey over the Palm Valley Anticline. The objectives of this survey were as follows: (a) to test the applicability of the seismic method in the area, (b) to confirm the anticlinal structure at depth, (c) to determine the thickness of the Pertnjarra-Mareenie interval, (d) to determine the total depth of sediments. It was found that along the proposed reflection traverse in the Finke River bed, which cut through the surface expression of the anticline: (a) shot holes were difficult to drill in the gravel and would not stay open, (b) movement of vehicles was difficult in the deep, loose sand, (c) seismic records from a small pattern of shallow holes were noisy and showed no reflected energy. It was decided to move the traverse out of the river bed to the plains north of the outcrops and to record: (a) a reflection traverse perpendicular to the strike, (b) a refraction depth probe along the strike. Good reflections were obtained, and therefore a velocity survey was recorded on the traverse along strike. A high-velocity refractor (17,800 ft/sec) in the Pertnjarra series prevented any useful deeper information being obtained by refraction with offsets up to 6 miles. In the remainder of the time available, one mile of reflection traverse was shot in the bed of the River Finke south of the crest of the anticline. Single shots at a depth of 40 feet were used in shet holes in bedrock exposed as sandstone ledges at the edge of the canyon. The records obtained were of sufficient quality to prove the anticlinal structure at depth.