Updated: Apr 30, 2021

PGCP Project 559 - Historic Data - Basement overthrust of Nagalia Basin sediments, central Australia, 1967

Information compiled by D. M. Finlayson (doug.finlayson@netspeed.com.au)

In the 1960's there were still doubts about how useful the seismic profiling techniques used for oil and gas exploration would be at determining the structure of deeper basement rocks. At that time the Australian Bureau of Mineral Resources, Geology and Geophysics (BMR) was operating two seismic profiling crews in the hunt for oil and gas within the sedimentary basins of the continent. These operations took the crews to the Amadeus and Ngalia Basins of central Australia. Experimentation was conducted to test seismic profiling techniques for penetrating basement rocks.

On the northern margin of the Ngalia Basin BMR crews demonstrated in spectacular fashion that sedimentary layering could be imaged beneath overthrust basement rocks. The image below shows quite clearly the overthrust fault (reverse fault) placing basement rocks above the sedimentary sequences of the Ngalia Basin. Explosive seismic sources were used.

This work demonstrated in 1967 that the seismic reflection profiling techniques could be used to image deep geological structures within basement rocks as well as that within sedimentary basins. Although the drilling of explosives into the ground was often more difficult when working across hard-rock terrains, the shot energy still penetrated basement rocks to give useful images. From such work BMR went on to try the technique across many other areas in Australia where basement rocks crop out.

Bibliography

Dooley, J. C., & Moss, F. J., 1988. Deep crustal reflections in Australia 1957-1973 - II. Crustal models. Geophysical Journal, 93, 239-249.

Jones, P., 1969. Ngalia Basin seismic survey, Northern Territory, 1967. Bureau of Mineral Resources, Geology and Geophysics, Australia, Record 1969/69.

Moss, F. J., & Jones, P., 1974. Ngalia Basin seismic survey, Northern Territory. Bureau of Mineral Resources, Geology and Geophysics, Australia, Record 1974/49.

Moss, F. J., & Dooley, J. C., 1988. Deep crustal reflection recordings in Australia 1957-1973 - I. Data acquisition and presentation. Geophysical Journal, 93, 229-237.