A reconnaissance marine reflection seismic survey was conducted hi Exmouth Gulf and the open coastal waters along the west coast of Western Australia from Frazer Island to Bernier Island (see Fig. 1).
The survey was a two-boat operation. The survey in the Exmouth Gulf area was controlled by a Lorac radio navigational system, and along the west coast positioning was determined by sextant angle measurements to shore beacons and landmarks. All shots were recorded on magnetic tapes which were processed into variable area record sections.
The following maps were constructed:
(i) On a Horizon "A" within the Upper Cretaceous Korojon Calcarenite (Exmouth Gulf area only);
(ii) On a Horizon "B" near the Basal Cretaceous unconformity;
(iii) On pre-Cretaceous structure;
(iv) Time interval between Horizons "A" and "B" (Exmouth Gulf area only);
(v) Depth of water.
The Exmouth marine survey indicated that Exmouth Gulf is essentially synclinal in character in the Cretaceous and Tertiary sediments. Several major pra-Cretaceous fault trends which had already been mapped on land with the seismograph were followed beneath the Gulf. The pre-Cretaceous axis of the Cape Range Anticline was located both to the north and to the south of the surface expression of the structure. The chain of islands to the north-east of the Ca.pe Range are aligned on a structural trend.
To the south of-Point Maud, the Cuvier marine survey provided a much-needed tie between the Rough Range-Cape Range area and the structurally complex area around the Salt Marsh. Some structural leads were found in this southern area and the trend of major faults was established.
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